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WP5–Action5.3–Finalreport Thermalandgeomorphicpermafrost responsetopresentandfutureclimate changeintheEuropeanAlps Editors: AndreasKellererͲPirklbauer,GerhardKarlLieb, PhilippeSchoeneich,PhilipDelineandPaoloPogliotti Graz,2011 WP5–Action5.3–Finalreport Thermalandgeomorphicpermafrost responsetopresentandfutureclimate changeintheEuropeanAlps Citationreference KellererͲPirklbauer A., Lieb G.K., Schoeneich P., Deline P., Pogliotti P. eds (2011). Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,177pp. Downladableon:www.permanetͲalpinespace.eu Editors Andreas KellererͲPirklbauer and Gerhard Karl Lieb, Institute of Geography and Regional Science, UniversityofGraz,Austria(IGRS) PhilippeSchoeneich,InstitutdeGéographieAlpine,UniversitédeGrenoble,France(IGAͲPACTE) PhilipDeline,EDYTEM,UniversitédeSavoie,France(EDYTEM) Paolo Pogliotti, Regional Agency for the Environmental Protection of the Aosta Valley, Italy (ARPA VdA) Projectreference The PermaNET – Permafrost long term monitoring network (2008Ͳ2011) project is part of the EuropeanTerritorialCooperationandcoͲfundedbytheEuropeanRegionalDevelopmentFund(ERDF) inthescopeoftheAlpineSpaceProgrammewww.alpineͲspace.eu PermaNET–Permafrostresponsetoclimatechange Authors Baroni,Carlo Bodin,Xavier Cagnati,Anselmo Carollo,Federico Coviello,Velio Cremonese,Edoardo Crepaz,Andrea Dall’Amico,Matteo Defendi,Valentina Deline,Philip Drenkelfluss,Anja Galuppo,Anna Gruber,Stephan KellererͲPirklbauer, Andreas Kemna,Andreas Klee,Alexander Krainer,Karl Krautblatter,Michael Kroisleinter,Christine Krysiecki,JeanͲMichel LeRoux,Olivier UniversityofPisa(Italy) UniversityJosephFourier,Grenoble(France) RegionalAgencyfortheEnvironmentalProtectionofVeneto(Italy) E.P.C.EuropeanProjectConsultingS.r.l.(Italy) NationalCenterforScientificResearchEDYTEM,Grenoble(France) RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) RegionalAgencyfortheEnvironmentalProtectionofVeneto(Italy) MountainͲeeringsrl(Italy) RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) NationalCenterforScientificResearchEDYTEM,Grenoble(France) UniversityofBonn(Germany) RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) UniversityofZurich(Switzerland) UniversityofGraz(Austria) UniversityofBonn(Germany) CentralInstituteforMeteorologyandGeodynamics(Austria) UniversityofInnsbruck(Austria) UniversityofBonn(Germany) CentralInstituteforMeteorologyandGeodynamics(Austria) UniversityJosephFourier,Grenoble(France) Associationpourledéveloppementdelarecherchesurlesglissementsdeterrain (France) Lieb,GerhardKarl UniversityofGraz(Austria) Lorier,Lionel Associationpourledéveloppementdelarecherchesurlesglissementsdeterrain (France) Magnabosco,Laura RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) Magnin,Florence NationalCenterforScientificResearchEDYTEM,Grenoble(France) Mair,Volkmar AutomousProvinceofBolzano(Italy) Malet,Emmanuel NationalCenterforScientificResearchEDYTEM,Grenoble(France) Marinoni,Francesco Freelancer(Italy) MorradiCella,Umberto RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) Noetzli,Jeanette UniversityofZurich(Switzerland) Pogliotti,Paolo RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) Ravanel,Ludovic NationalCenterforScientificResearchEDYTEM,Grenoble(France) Reisenhofer,Stefan CentralInstituteforMeteorologyandGeodynamics(Austria) Riedl,Claudia CentralInstituteforMeteorologyandGeodynamics(Austria) Rigon,Riccardo UniversityofTrento(Italy) Schoeneich,Philippe UniversityJosephFourier,Grenoble(France) Schöner,Wolfgang CentralInstituteforMeteorologyandGeodynamics(Austria) Seppi,Roberto UniversityofPavia(Italy) Vallon,Michel UniversityJosephFourier,Grenoble(France) Zampedri,Giorgio GeologicalSurvey,AutonomousProvinceofTrento(Italy) Zischg,Andreas AbenisAlpinexpertGmbH/srl(Italy) Zumiani,Matteo Geologist(Italy) ADRAͲAssociationpourladiffusiondelarecherchealpine 14bisav.MarieͲReynoard, FͲ38100Grenoble ISBN978Ͳ2Ͳ903095Ͳ58Ͳ1 Contentsandlistforchapterpublications 1.PermafrostResponsetoClimateChange SchoeneichP.,LiebG.K.,KellererͲPirklbauerA.,DelineP.,PogliottiP.(2011).Chapter1:Permafrost Response to Climate Change. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.4Ͳ15. 2.ClimateChangeintheEuropeanAlps KroisleitnerCh.,ReisenhoferS.,SchönerW.(2011).Chapter2:ClimateChangeintheEuropeanAlps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNET project, final report of Action 5.3. OnͲline publicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.16Ͳ27. 3.CasestudiesintheEuropeanAlps 3.1Overviewoncasestudies KellererͲPirklbauerA,LiebG.K.(2011).Chapter3.1:CasestudiesintheEuropeanAlps–Overviewon case studies. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.28Ͳ34. 3.2Hochreichart,EasternAustrianAlps KellererͲPirklbauerA(2011).Chapter3.2:CasestudiesintheEuropeanAlps–Hochreichart,Eastern AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.35Ͳ44. 3.3DösenValley,CentralAustrianAlps KellererͲPirklbauerA(2011).Chapter3.3:CasestudiesintheEuropeanAlps–DösenValley,Central AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.45Ͳ58. 3.4HoherSonnblick,CentralAustrianAlps Klee A, Riedl C. (2011). Chapter 3.4: Case studies in the European Alps – Hoher Sonnblick, Central AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.59Ͳ65. 1 PermaNET–Permafrostresponsetoclimatechange 3.5RockGlacierHochebenkar,WesternAustrianAlps Krainer K. (2011). Chapter 3.5: Case studies in the European Alps – Rock Glacier Hochebenkar, Western Austrian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost responsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreport ofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.66Ͳ76. 3.6RockGlacierLaurichard,NorthernFrenchAlps SchoeneichP.,BodinX.,KrysieckiJ.ͲM.(2011).Chapter3.6:CasestudiesintheEuropeanAlps–Rock Glacier Laurichard, Northern French Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.77Ͳ86. 3.7RockGlacierBellecombes,NorthernFrenchAlps SchoeneichP.,KrysieckiJ.ͲM.,LeRouxO.,LorierL.,VallonM.(2011).Chapter3.7:Casestudiesinthe European Alps – Rock Glacier Bellecombes, Northern French Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the EuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ 58Ͳ1,p.87Ͳ96. 3.8AiguilleduMidi,MontBlancmassif,FrenchAlps DelineP.,CremoneseE.,DrenkelflussA.,GruberS.,KemnaA.,KrautblatterM.,MagninF.,MaletE., MorradiCellaU.,NoetzliJ.,PogliottiP.,RavanelL.(2011).Chapter3.8:CasestudiesintheEuropean Alps–AiguilleduMidi,MontBlancmassif,FrenchAlps.InKellererͲPirklbauerA.etal.(eds):Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.97Ͳ108. 3.9RockfallsintheMontBlancmassif, DelineP.,RavanelL.(2011).Chapter3.9:CasestudiesintheEuropeanAlps–RockfallsintheMont Blanc massif, FrenchͲItalian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.109Ͳ118. 3.10CimeBianchePass,ItalianAlps PogliottiP,CremoneseE.,MorradiCellaU.(2011).Chapter3.10:CasestudiesintheEuropeanAlps– Cime Bianche Pass, Italian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.119Ͳ128. 3.11Maroccarorockglacier,ValdiGenova,ItalianAlps SeppiR.,BaroniC.CartonA.,Dall’AmicoM.,RigonR.,ZampedriG.,ZumianiM.(2011).Chapter3.11: CasestudiesintheEuropeanAlps–Maroccarorockglacier,ValdiGenova,ItalianAlps.InKellererͲ PirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponsetopresentandfutureclimate changeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN 978Ͳ2Ͳ903095Ͳ58Ͳ1,p.129Ͳ139. 2 3.12Amolarockglacier,Vald’Amola,ItalianAlps SeppiR.,BaroniC.CartonA.,Dall’AmicoM.,RigonR.,ZampedriG.,ZumianiM.(2011).Chapter3.12: Case studies in the European Alps – Amola rock glacier, Val d’Amola, Italian Alps. In KellererͲ PirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponsetopresentandfutureclimate changeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.ISBN978Ͳ2Ͳ903095Ͳ58Ͳ1, p.140Ͳ150. 3.13PizBoèrockglacier,Dolomites,EasternItalianAlps A. Crepaz A., Cagnati A., Galuppo A., Carollo F., Marinoni F., Magnabosco L., Defendi V. (2011). Chapter 3.13: Case studies in the European Alps – Piz Boè rock glacier, Dolomites, Eastern Italian Alps.InKellererͲPirklbauerA.etal.(eds):Thermal andgeomorphicpermafrostresponsetopresent andfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲline publicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.151Ͳ158. 3.14UpperSuldenValley,OrtlerMountains,ItalianAlps Zischg A., Mair V. (2011). Chapter 3.14: Case studies in the European Alps – Upper Sulden Valley, Ortler Mountains, Italian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.159Ͳ169. 4.SynthesisofCaseStudies LiebG.K.,KellererͲPirklbauerA.(2011).Chapter4:Synthesisofcasestudies.InKellererͲPirklbauerA. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNET project, final report of Action 5.3. OnͲline publication ISBN 978Ͳ2Ͳ 903095Ͳ58Ͳ1,p.170Ͳ177. 3 PermaNET–Permafrostresponsetoclimatechange 1. PermafrostResponsetoClimateChange Citationreference SchoeneichP.,LiebG.K.,KellererͲPirklbauerA.,DelineP.,PogliottiP.(2011).Chapter1:Permafrost Response to Climate Change. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.4Ͳ15. Authors Coordination:PhilippeSchoeneich Involvedprojectpartnersandcontributors: Ͳ Institut de Géographie Alpine, Université de Grenoble, France (IGAͲPACTE) – Philippe Schoeneich Ͳ Institute of Geography and Regional Science, University of Graz, Austria (IGRS) – Andreas KellererͲPirklbauer,GerhardKarlLieb Ͳ EDYTEM,UniversitédeSavoie,France(EDYTEM)–PhilipDeline Ͳ Regional Agency for the Environmental Protection of the Aosta Valley, Italy (ARPA VdA) – PaoloPogliotti Content Summary 1. Introduction 2. Thermalpermafrostresponse 3. Geomorphicpermafrostresponse 4. Finalremarks References 4 PermaNETͲPermafrostResponsetoClimateChange Summary Permafrost is defined as subsurface material that remains below 0°C also during the summer. Thuspermafrostisathermalphenomenonwhosecharacteristicslargelydependontheclimatic conditions. This means that a changing climate also affects the thermal regime of the underground. The interactions between the atmosphere and the surface as well as the subsurfacetemperaturesyetarehighlycomplexdependingonseveralenvironmentalfactorslike e.g. the substrate itself (coarseͲgrained blocky material, fineͲgrained material, bedrock), the character of the relief (e.g. depression vs. ridge), the exposure relative to the sun or the snow cover characteristics (onset and disappearance date, length of snow cover period, thickness, dynamics). In this chapter the occurrence types of frost and their altitudinal distribution is described first. Thenpermafrostreactionstoclimatechangearediscussedundertwoaspects–thethermaland thegeomorphiconeaccordingtothealreadyexistingknowledge. Mainthermalreactionsare:(a)increasinggroundtemperatureandhencepermafrostwarming, (b) thawing of permafrost leading to reduction in its spatial extent, active layer thickening and changing groundͲwater circulation, (c) changes in the number of freezeͲthaw cycles and magnitudeoffreezingandthawingperiods. Maingeomorphicreactionsare:(a)changesintherateofrockglacierdisplacement,(b)changes in the displacement mode of rock glaciers, (c) changes in solifluction rates, (d) changes in cryogenicweathering,(e)changesinthevolumeandextentofunstablematerials,(f)changesin frequency and magnitude of mass movement events, and (g) surface instabilities caused by thermokarstprocesses/meltingofpermafrostice.Someofthesegeomorphicreactionsarealso truefornonͲpermafrostperiglacialareas,meaningalpineandsubalpineenvironmentsatlower elevations. Summingupitisshownherequitewellthatongoingclimatechangehasanumberofcomplex influencesonthegroundtemperaturebutalsogroundstabilityonthemountainpermafrostof theEuropeanAlps. 5 PermaNET–Permafrostresponsetoclimatechange 1. Introduction Permafrost is an effect of frost and negative temperatures and results from a negative energy balance at the ground surface. The energy balance mainly depends on the direct incoming solar radiationandonthesensibleheatflux.ThusitisencounteredintheAlpsathighelevations,where airtemperature(controllingthesensibleheatflux)islow.Permafrostismoreextensiveandoccursat lower altitudes on north facing than on south facing slopes, because of a reduced incoming solar radiationduetoslopeangleandshadowingeffects. 1.1Theoccurrencetypesoffrost Permafrostisnottheonlyeffectoffrost.FrostoccursatallaltitudinallevelsintheAlps,withvarious intensityandduration.Oneusuallydistinguishesthefollowingoccurrencesoffrost: x DiurnalfreezeͲthawcyclesconsistofthefreezingandsubsequentthawingofmaterialduring anightͲdaycycleorseveralconsecutivedaysorweeks.Theyaredrivenbyairtemperature cycles. Climatologists define frost days (FD) as days where the minimum temperature is negative, and ice days (ID) as days where the maximum temperature remains below zero, henceinducingfreezeconditionsoveratatleastoneday.FreezeͲthawdays(FTD)aredefined asdayswithnegativeminimumandpositivemaximumtemperature.Insoilandrock,freezeͲ thaw cycles have to be distinguished according to their duration, intensity and penetration depth. Diurnal frost is usually of moderate intensity and has a limited penetration depth, whereas periods of consecutive very cold ice days have the highest penetration depth and intensity. FreezeͲthaw cycles induce frost shattering of rocks and are the main controlling factor of debris production. To be efficient, the frost must have a minimal intensity and duration. Diurnal frost cycles have only a limited impact. Cycles of several days reaching temperaturesofͲ5°Candlessareconsideredtobemostefficient. x SeasonalfrostdefinesmaterialthatexperiencesoneannualfreezeͲthawcycle,ofaduration of at least several weeks up to several months, but with a total thawing during the warm season.Frostdurationanddepthdependmoreonthemeantemperaturethanonindividual cycles.Seasonalfrostinducesgeomorphicprocesseslikesolifluctionandsimilarshallowsoil creepingphenomena. x Permafrostisdefinedformallyasasubsurfacematerial(rock,debrisorsoil)thatremainsata temperature below zero during the whole year. It consists of two parts: the surface layer, called active layer that thaws seasonally and refreezes during the cold season, and the permafrostsensustrictuthatremainsconstantlybelowzero.Fromtheclimaticpointofview, permafrostoccurswheretheannualheatbalanceisnegative.Duetosomecharacteristicsof thesurfacelayers(knownasthethermaloffset),thisdoesnotoccuratthe0°Cisotherm,but at a mean annual air temperature of Ͳ1 to Ͳ2°C. Permafrost is usually subdivided into continuous,discontinuous,sporadicandisolatedpermafrost,accordingtothepercentageof theareacoveredbypermafrost.Theusualthresholdsarethefollowingonesbutpartlyvary betweenauthors(cf.French2007): o o o o isolated:lessthan10%ofthesurfaceaffectedbypermafrost sporadic:between10and50%ofthesurfaceaffectedbypermafrost discontinuous:between50and90%ofthesurfaceaffectedbypermafrost continuous:morethan90%ofthesurfaceaffectedbypermafrost. Furthermore,someauthorsdistinguish: o coldpermafrost,withameangroundtemperaturebelowͲ1°C o temperateorwarmpermafrost,withagroundtemperaturecloseto0°C(typicallyͲ 0.1toͲ0.2°C). 6 PermaNETͲPermafrostResponsetoClimateChange Thispointraisesthequestionofthemeltingpointtemperatureinpermafrost,especiallyin aniceͲdebrismixture. 1.2Altitudinaldistribution The various occurrences of frost show an altitudinal distribution, controlled by the altitudinal gradientsofthecontrollingclimatefactors. x DiurnalfreezeͲthawcyclesoccurinwinteratlowaltitudes,inspringandautumnat middle altitudes and in summer at high altitudes. Their maximal frequency is observed at middle altitudes.IntensityanddurationofthefreezeͲthawcyclesincreasewithaltitude. x Seasonal frost occurs at middle altitudes and its duration and penetration depth increase withaltitude.Itpassestopermafrostathighaltitudes. x Permafrost occurs sporadically at middle altitudes. At high altitudes discontinuous permafrostoccurs,withaprogressivetransitiontomorecontinuouscoveragewithincreasing altitude. Thisaltitudinaldistributionoffrostoccurrencesisassociatedwithanaltitudinaldistributionoffrost relatedprocessesandlandforms: x FrostshatteringandtalusproductionarerelatedtofreezeͲthawcycles. x Shallowsolifluctionprocessesarerelatedtoseasonalfrost. x Deepcreepprocesses(rockglaciers)arerelatedtopermafrost. This altitudinal morphoͲclimatic distribution has been described by several authors, especially Chardon(1984,1989)whodistinguishesthefollowingbelts: x The infraͲperiglacial belt is concerned by freezeͲthaw cycles and seasonal frost, and processesaredominatedbytalusproductionandsolifluction. x The periglacial belt sensu stricto is concerned by discontinuous permafrost, and processes aredominatedbysolifluctionandrockglaciers. x ThesupraͲperiglacialbeltisconcernedbycontinuouspermafrost.IntheAlpsitcoversmainly rockfacesandprocessesaredominatedbyepisodicrockfallsandglaciers. 2. Thermalpermafrostresponse Climatewarminginducesanincreaseofairtemperature,henceanincreaseofthesensibleheatflux. Thus the energy balance should become less negative. A general warming ofground temperatures canthereforebeexpected. However, climate warming will will most probably neither change solar radiation nor altitudinal gradients, so that the overall altitudinal distribution of frost types and effects will remain, but is expectedtoshifttowardshigheraltitudes. Heat transfers from both solar radiation and heat flux to the ground are influenced by the snow cover. Thus the evolution of the ground temperature will not only depend on the evolution of the temperature, but also on the amount and type of winter precipitation and subsequently of the distribution,durationandthicknessofthewintersnowcover. 7 PermaNET–Permafrostresponsetoclimatechange 2.1Migrationofpermafrostbelts Temperaturechangeswillaffectallphenomenarelatedtofrost:diurnalfreezeͲthawcycles,seasonal frost as well as permafrost. In general, a climate warming should induce a migration of all climate relatedlimitsandbeltstowardshigheraltitudes.Thefollowingmainchangescanbeexpected: x ConcerningfreezeͲthawcycles: o Lowerfrequencyandintensityatmiddlealtitudes o Migrationofmaximalfrequencyandintensitytowardshigheraltitudes o Seasonalshiftofcyclefrequencytowardsearlier/laterseason o Increaseoffrequencyathighaltitudes x Concerningseasonalfrost: o Decreaseoffrequencyanddepthatmiddlealtitudes o Decreaseofdepthanddurationathigheraltitudes o Replacementofpermafrostbyseasonalfrostatthelowerpermafrostlimit x Concerningpermafrost: o Disappearanceofsporadicpermafrostatmiddlealtitudes o Migrationofthelowerpermafrostlimittowardshigheraltitudes o Replacementofcontinuousbydiscontinuouspermafrost Fig. 1 Ͳ Processes which may occur within permafrost shown as a process of degradation (from Dobinski2011). 8 PermaNETͲPermafrostResponsetoClimateChange 2.2Changesinthermalprofilesoftheground TemperaturechangeswillaffectpermafrostmainlybythefollowingprocessesvisualisedalsoinFig. 1:(a)thickeningoftheactivelayer,(b)warmingofthepermafrosttemperature,(c)reductionofthe permafrostthickness,and(d)decreaseoftheicecontent. Increaseofactivelayerthickness Thefirsteffectof climate warmingwillbe theincreaseoftheactivelayer thickness. Thisresponds directly to interannual variations. It depends both on the thermal state acquired during the precedingwinterandonthesummertemperature. On rock glaciers there is often a strong contrast between the coarse blocky active layer and the underlying iceͲrich and finer grained permafrost. In such cases, an increase of the active layer will inducealossoficeatthepermafrosttableandageneralloweringofthesurface. Ifthethawingofpermafrostgetsdeeperthantheseasonalfrostdepth,thisseasonalfreezingwillnot beabletorefreezetheentirethawedlayer,andatalik(=unfrozenlayer)willremainduringwinter between the seasonally frozen surface layer and the residual deeper permafrost. This situation occurs when the permafrost warms up, and stops to be cooled from the surface. It can be transitional (after a particularly warm year) or permanent (inactivation of permafrost). Such situationsarelikelytooccurinthefutureatthelowerlimitsofdiscontinuouspermafrost. Warmingofthepermafrost Due to a low thermal conductivity of the ground, the heat transfer towards depth is very slow, especially in iceͲrich permafrost. It therefore can take years to propagate through the profile. The permafrosttemperatureisthereforeexpectedtoreactrathertodecadaltrendsthantointerannual variations. Thedownprofilepropagationofheatwavescanalreadybeinterpretedfromsomeboreholeprofiles, where the minimal temperature is registered at a greater depth than the ZAA (zero annual amplitude).Withtime,areductionofthecoolingfromthesurfacewillalsoallowawarmingfromthe bottomupwards,duetothegeothermalheatflux. Theroleofthesnowcover All above mentioned evolutions postulate a linear response of ground temperature to air temperature. However, ground surface temperature monitoring series show that the link is not straightforward. The snow cover plays an important role through its insulation capacity, and can inducesignificantdeviationsfromtheairtemperaturetrends. The onset and thickness of the snow cover in early winter plays the major role: in November to January,thedaysaretheshortestandthedirectradiationataminimum,whereasairtemperatures reachalreadyverylowvalues.Ifthereisnosnowcover,thesoilwilldrasticallycooldown.Ashallow snow cover may even increase the heat loss. On the contrary, an early and thick snow cover will preventthesoilfromcoolingand“keep”theaccumulatedheatoftheprevioussummerandautumn. The snow cover history in early winter will thus largely determine the winter ground surface temperature, and the winter equilibrium temperature (WEqT), i.e. the mean ground surface temperatureinFebruaryandMarch.Onareasofseasonalfrost,itwilldeterminethefreezingorno freezingofthesoil,aswellasthefrostdepth. 9 PermaNET–Permafrostresponsetoclimatechange The thickness of the snow cover during the winter has of course also a great importance. A thick cover (at least ca. 0.8Ͳ1 m) insulates the ground from air temperature variations, and keeps the thermal state acquired during autumn and early winter. A shallow or discontinuous (through wind deflation)snowcoverallowsacontinuedcoolingofthegroundduringthewholewinter. Thedurationofthesnowcoverinspringhasaninverseeffectthaninearlywinter.Alatesnowmelt preventsthesoilfromthedirectsolarradiation,inaperiodwhereitisatamaximum,andprotectsit fromthesensibleheatflux.Onthecontrary,anearlysnowmeltwillallowanearlierwarmingofthe soil.Thus,thewintercoolingeffectofashallowsnowcovercanbecompensatedbyanearliersnow melt. Theeffectofthesnowcoveriswellvisibleontheinterannualtemperaturevariability.Itcaninduce significant departures from the atmospheric temperature variations, e.g. cooling during rather moderate winters, or warming despite of cool winters. Its real influence on middle to long term temperaturetrendsremainsanopenquestion.Temperaturerecordsinboreholesatca10mdepth showadistinctwarmingtrendfrom1987to1994,andthenastabilisation(PERMOS2009),butno realcooling,unlikethesurfacetemperatures. Thethermalevolutionofpermafrost,andmoregenerallyofgroundtemperatures,willthusdepend on both air temperature and snow cover. Most climate models predict an increase of winter precipitations.Ifthisoccursassnowfall,itcanhavevariouseffects,dependingonitsseasonality: x Earlysnowfallswouldincreasewarming x Athickhighwintersnowcoverwillratherincreasewarming x Alatesnowmeltwouldpreventgroundfromwarming. Thesnowcoveronlyimpactsareasofmoderateslopeswhere athicksnowcovercandevelopand stayduringwinter.Onsteeprockfacesthesnowcoverhasnoinfluence. 2.3Ratesofchange Asmentionedabove,theheattransfertowardsdepthisveryslow,especiallyiniceͲrichpermafrost. It therefore can take years to propagate through the profile. The permafrost temperature is therefore rather expected to react to decadal trends than to interannual variations. Model calculations show that it takes decades to reach a new equilibrium at depths of 20 to 30 m. In bedrock,theheatpropagationcanbemuchfaster. Theroleoficecontent The propagation of temperature changes into the soil is strongly dependent from the ice content. Due to the high amount of latent heat needed to melt ice, high ice content strongly reduces the thermalconductivityoftheground.Onedimensionalheattransfermodelsshowthatanicecontent of 60% almost totally blocks the propagation of seasonal temperature variations, and that the meltingoftheicebodymayneedseveraldecades. Fromthethermalpointofview,iceͲrichpermafrostisthereforelesssensitivetoclimatechangethan “dry”permafrost.Ontheotherhand,thehighicecontentcanleadtosubsidenceandthermokarst phenomena,duetovolumeloss.InflatterrainthethawingoficeͲrichpermafrostthereforeleadsto greaterdisturbanceanddamagethanthethawingof“dry”permafrost. 10 PermaNETͲPermafrostResponsetoClimateChange 3. Geomorphicpermafrostresponse Climate change will affect both spatial distribution and intensity of frost related processes. As mentionedabove,thermaleffectsoffrostshowaclearaltitudinaldistribution.Thus,thefrostrelated geomorphicprocessesandlandformsshouldmigratetohigheraltitudes,togetherwiththeirdriving climate parameters. This however will mainly happen through changes in magnitude (intensity, duration,frequency)oftheseprocesses.Inadditiontothealtitudinalshift,someparticularoreven so far unknown phenomena may occur, due to transient states of ground conditions that are not usuallyobservedunderclimaticallystableconditions. 3.1Frostshatteringanddebrisproduction FrostshatteringanddebrisproductionarecontrolledbyfreezeͲthawcycles,anditisusuallyadmitted thatthemaximaldebrisproductionoccursataltitudesofmaximalcyclefrequency,correspondingto spring and autumn cycles. This altitudinal range has been defined as the talus window (Hales & Roering2005). Thetaluswindowisthusexpectedtomovetowardshigheraltitudes.Somestudiesalreadyshowa decrease of talus production in the upper subalpine belt (Arquès 2005, Corona 2007), as well as a decreaseofthetorrentialactivityontalussuppliedtorrents(Garitte2006).Thisevolutioncouldlead to an overall decrease of geomorphic activity in middle altitudes, and favour the reͲvegetation of screeslopes. Ontheupperend,thenormalstateofhighaltitudinalrockwallsinthecontinuouspermafrostbeltis ahighstabilityofrockfaces,withonlylimitedsporadicdebrissupplyfromoccasionalrockfalls.These slopes where freezeͲthaw cycles were yet limited to the summer season could experience an increaseoftalusproduction.Departurezonesofrockfallsarefrequentlyconcentratedinthelower partsofthecontinuouspermafrostbelt.Bothrockfallsanddebrisproductionareclearlyrelatedto warm periods during summer months, inducing a deepening of the heat penetration in rock faces (Deline&Ravanel2011). Regardingdebrisproductionfromcliffsandrockfaces,climatewarmingwillinducesignificanteffects ontwodifferentaltitudinallevels: x Thetaluswindowcanbeexpectedtoshifttowardshigheraltitudes.Asaconsequence,talus productionshoulddecreaseinthelowerparts,andincreasein theupperpartsofthebelt. Thisbeltischaracterizedbyaregularproductionofsmalldebris. x Anewbeltofincreaseddebrisproductionisdevelopingatthelowerlimitofthecontinuous permafrost belt. This belt is characterized by a sporadic production of coarse debris, up to large or even very large rockfalls. Due to often high and steep slopes, these processes can impactzonessituatedfarlowerdownslope. Indirecteffectsonotherprocessescanbeexpected: x Rockglaciersareusuallysituatedintheupperpartofthetaluswindow.Anincreaseofthe talusproductionatthislevelcouldthereforeinduceanincreaseofthedebrissupplytorock glaciers. On a much longer time scale, the increase in volume of some talus bodies could induce the formation of new rock glaciers. However, fast climate warming and hence permafrostdegradationwillmaketheformationofnewrockglaciersmoredifficult. x Accumulationzonesofglaciersareoftensituatedatthefootofhighaltituderockwalls.An increase of sporadic debris supply from these rock walls will induce an increase of debris coveranddebriscontentoftheglaciers,andconsequentlyanincreaseoftheextentofdebris coveronglaciers.ThisimpactthedynamicoftheseglaciersasforinstancetheMiageGlacier 11 PermaNET–Permafrostresponsetoclimatechange inItaly(Deline&Orombelli2005)orthePasterzeGlacierinAustria(KellererͲPirklbaueretal. 2008). 3.2Solifluctionandseasonalfrost Solifluction phenomena are related to seasonal frost and need a sufficient frost depth in order to allow a waterͲsaturated thawed layer to form in spring over a still frozen impermeable soil. After complete thawing, the soil drains and solifluction processes stop. A decrease of the seasonal frost depthwillthereforeinduceashorteningoftheactivityperiodandhenceadecreaseofmovement rates.ForamoredetailedclassificationofsolifluctiontypesrefertoMatsuoka(2001). Inaddition,someprocesseslikeboundedsolifluctionareconnectedwithfinegrainedsoilsandwith thepresenceofavegetationcover.Theupwardsmigrationofsuchphenomenawilldependonthe presenceoffinegrainedmaterialandonthedevelopmentofalpinemeadows.Solifluctionprocesses areverydifficulttostudyandonlyfewlongͲtermmonitoringsitesareknownintheAlps(e.g.Stingl etal.2010).Ingeneral,thereisalackofdataonseasonalfrostandonrelatedprocesses. 3.3Rockglaciers ThemostprominentfeaturesofAlpinepermafrostarerockglaciers.Theyarealsothemostmobile ones.Thepossibleevolutionscenariosofrockglacierdynamicsaretherefore acentralconcernfor Alpine mountain regions. Displacement time series and reconstructions of a dozen of rock glaciers throughouttheAlps,indicatedifferenttypesofbehaviouratvarioustimescales. Attheinterannualtimescale(Delaloyeetal.2008,Bodinetal.2009,KellererͲPirklbauer&Lieb2011): x Mostrockglaciersshowinterannualvelocityvariations,andthusreacttoclimatevariability. x These velocity variations are best correlated with a 12 month running mean of the ground surfacetemperature. x Thevelocityvariationsshowatimelagofca1yeartowardsairandgroundtemperature. x Thesevariationsarereversiblewithwarmingleadingtoavelocityincreaseandcoolingtoa velocitydecrease.Thevelocityratesremainintherangeof0.1toafewm/yͲ1). Some rock glaciers have shown a distinct change in dynamic behaviour during the last decades or years,withastrongincreaseofvelocitiesonpartsorthewholeoftherockglacier(e.g.Avianetal. 2005). Several types of behaviours can be distinguished (see PermaNET report 6.2 for study cases andmoredetail): x Strong acceleration with opening of crevasses. The velocities increase by an order of magnitude,uptoseveralm.yͲ1.Crevassesshowthatthedeformationratesexceedtheflow capacityoftheice. x Ruptureanddislocationofthelowerpartoftherockglacier.Inthesecases,adistinctrupture withascarpappearsintherockglacierandseparatesthelower,fastpart,fromtheupper, “normal”movingpart. x Total collapse of the lower part. Only one case is known yet, where the lower part totally collapsedintoamudflow(Krysieckietal.2008). x Extremeaccelerationoftherockglacier.Onecaseisknown,withvelocitiesofseveraltensof m.yͲ1(Delaloyeetal.2010). All these evolutions are apparently not reversible, but observation times are not yet sufficient to knowtheendofthestory.Theacceleratedlowerpartstendtodislocate,whereastheupperparts possiblyformanewrockglacierfront.Severalquestionsarise: 12 PermaNETͲPermafrostResponsetoClimateChange x Interannual variations are hard to explain. One possible explanation could be a higher plasticityoficewithhighertemperature.However,themaindeformationratesoccurinthe basallayerofrockglaciers,asshownbythefewexistinginclinometerprofiles.Thethermal conductivityoficeͲrockmixturesisverylow,anditisunlikelythatinterannualtemperature variationsreachthebottomoftheiceͲrichbody.Anotherexplanationcouldbeanincreased presenceofinterstitialwater,facilitatinginternalmovementsbetweenicegrains. x The very high velocity increase observed on accelerating rock glaciers (some authors even talkabout“surging”rockglaciers)impliesachangeofdisplacementmode.Rockglaciersare usuallyconsideredtomoveatthesamewayascoldbasedglaciers,bydeformationoficeand shearofthebasalicelayer.Velocitiesofseveralm/yͲ1andevenmoreseemtoindicatethe onsetofabasalsliding.Thiswouldmeanthattheserockglaciershavechangedfroma“cold glacier” to a “temperate glacier” displacement mode. The latter point is crucial for future development,andhastoberelatedtothequestionofthemeltingpointtemperature. x Theconditionsthatleadarockglaciertoaccelerateornotareunknownyet.Thepresenceof aconvexslopeseemstobenecessaryfortheonsetofstrongaccelerationsofthelowerpart (e.g.Avianetal.2005).Thetotalcollapseoccurredonarockglaciermadeoffinematerial, andispossiblyunlikelytohappenonacoarseblockyrockglacier. Fromtheseconsiderations,thefollowingmostprobableevolutionscenarioscanbeproposed: x Interannualvariationswillcontinue.Velocityincreasesareexpectedtohappenmainlyafter very hot summers associated with snow rich winters. Such episodes may occur more frequentlyandonanincreasingnumberofrockglaciers. x Strongaccelerationsarelikelytooccuronanincreasingnumberofrockglaciers. x Acceleration episodes are a transient state, and will last only as long as the ice content is sufficient to allow creeping. After ice loss is sufficient and the permafrost is no longer supersaturatedwithice,movementsshouldslowdownandstop. x Total collapse or extreme accelerations will possibly remain exceptional cases, but a better knowledgeisrequestedinordertobeabletoevaluatetheirprobability. 3.4Thermokarstphenomena If permafrost is supersaturated in ice, the melting of ice due to permafrost degradation induced a volume loss of the substrate affected which leads to instabilities at the surface and finally to settlementofthesurface.Theseprocessescanespeciallybeobservedinareaswithlowinclinations wheretheycreateamoreruggedtopographythanithasexistedbefore.Ifthereisanimpermeable layerbeneath(e.g.thepermafrosttableitself)thermokarstlakesmaygetformed. Settlementprocessesdonotonlylowerthesurfaceandchangeitstopographybutarealsoofspecial significance for buildings and other infrastructures because they create the need to adapt the constructionsinordertoavoiddamage. 4. Finalremarks Table1givesanoverviewofthethermalandgeomorphicreactionsofpermafrosttoclimatechange astheycanbeexpectedaccordingtoconsiderationsgiveninthepreviousparagraphs.Thechanges listedinthetableservedasguidelinesforcarryingoutthecasestudiesinChapter3andinterpreting theresultswhicharesummarizedinChapter4. 13 PermaNET–Permafrostresponsetoclimatechange Table1ͲPossiblethermalandgeomorphicpermafrostreactionsrelevantforPermaNET. Possiblethermalpermafrostreactions Increasinggroundtemperature(inbedrock,fineandcoarsesediments)andhencepermafrostwarming Thawingofpermafrostwiththreeeffects:(1)reductioninthespatialextentofpermafrost,(2)activelayerthickening,and (3)increasinggroundͲwatercirculationandpressure ChangesinthenumberoffreezeͲthawcyclesandmagnitude(durationandintensity)offreezingandthawingperiods Possiblegeomorphicpermafrostreactions Changesintherateofrockglacierdisplacement(verticallyandhorizontally) Changesindisplacementmodeofrockglaciers(initiationofbasalsliding,collapse) Changesinsolifluctionrates* Changesincryogenicweathering(freezeͲthawcycles,icesegregation)* Changesinthevolumeandextentofunstable/unconsolidatedmaterials Changesinfrequencyandmagnitudeofmassmovementevents(e.g.rockfall,rockslide,debrisflow)* Surfaceinstabilitiescausedbythermokarstprocesses/meltingofpermafrostice* *notstrictlyrelatedtoonlypermafrostbuttoperiglacialenvironmentsingeneral Monitoring of permafrost temperature is performed on three different kinds of permafrost sites primarilyusingminiaturetemperaturedataloggers(MTD)orthermistorͲchainslocatedinboreholes (fromveryshallowtodeep): x x x Permafrostandactivelayerinbedrock(fromnearͲverticalrockwallstoflatmorphologies) Permafrostandactivelayerinfinegrainedmaterial(ratherflatmorphology) Permafrost and active layer in coarse grained and blocky material (scree slopes, rock glaciers; fromsteepslopestoratherflatmorphologies) Climate conditions at permafrost sites are monitored by meteorological stations. Monitoring of dynamic conditions in permafrost environments is carried out by geodetic, photogrammetric, terrestrial laserscanning (LiDAR or TLS), differential SAR interferometry (DINSAR) and DGPS techniquesaswellasvisualobservationsandcalculations.Thismonitoringfocuseson: x x x Massmovement(e.g.rockfall)frequencyandmagnitude Rateofrockglacierdisplacement(verticallyandhorizontally) Physicalweathering(freezeͲthawcycles) TosumupAction5.3usesawiderangeofmethodsintheassessmentofthethermalanddynamic reaction scenarios of different permafrost typologies. Research in this action is carried out in two steps: (i) Establishment of the relationship between measured climate data and observed thermal and geomorphic permafrost reactions (Table 1) using available datasets collected during the last years and decades (cf. Chapter 3). (ii) Combining the established relationships with data from the climatescenariofortheyear2050presentedinChapter2formsthebasisforestimationsoffuture changesinpermafrostdistribution(verticallyandhorizontally),intheactivelayerthicknessorinthe ratesofrockglacierdisplacement. References: Arquès S., 2005: Géodynamique et biodiversité des versants asylvatiques du massif de la Grande Chartreuse. Evolutionliéeauréchauffementclimatiqueetproblèmedegestion.ThèseUniversitéJosephFourier, Grenoble. AvianM.,KaufmannV.&LiebG.K.,2005:RecentandHolocenedynamicsofarockglaciersystem:Theexample ofHinteresLangtalkar(CentralAlps,Austria).NorwegianJournalofGeography,59,149Ͳ156. 14 PermaNETͲPermafrostResponsetoClimateChange BodinX.,ThibertE.,FabreD.,RiboliniA,SchoeneichP.,FrancouB.,Reynaudl.&FortM.,2009:Twodecadesof responses (1986–2006) to climate by the Laurichard rock glacier, French Alps. Permafrost and PeriglacialProcesses,20,331Ͳ344. ChardonM.,1984:Montagneethautemontagnealpine,critèresetlimitesmorphologiquesremarquablesen hautemontagne.RevuedeGéographieAlpine72(2Ͳ4):213Ͳ224. ChardonM.,1989:Essaid'approchedelaspécificitédesmilieuxdelamontagnealpine.RevuedeGéographie Alpine77(1Ͳ3):15Ͳ18. Corona C., 2007: Evolution biostasique du paysage, géodynamique nivéoͲpériglaciaire et fluctuations climatiquesrécentesdanslahautevalléedelaRomanche(AlpesduNord,France).ThèseUniversité JosephFourier,Grenoble. DelineP.&OrombelliG.,2005:GlacierfluctuationsinthewesternAlpsduringtheNeoglacial,asindicatedby theMiagemorainicamphitheatre(MontBlancmassif,Italy).Boreas,34:456–467. Deline P. & Ravanel L. (2011). Chapter 3.9: Case studies in the European Alps – Rockfalls in the Mont Blanc massif,FrenchͲItalianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrost responsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportof Action5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1. Delaloye R., Perruchoud E., Avian M., Kaufmann V., Bodin X., Hausmann H., Ikeda A., Kääb A., KellererͲ PirklbauerA.,KrainerK.LambielC.,MihajlovicD.,StaubB.,RoerI.,ThibertE,.2008:Recentinterannual variations of rockglacier creep in the European Alps. 9th International Conference on Permafrost, Fairbanks,UniversityofAlaska:343–348. DelaloyeR.,MORARDS.,AbbetD.,HilbichC.,2010.TheSlumpoftheGrabenguferRockGlacier(SwissAlps). 3rdEuropeanConferenceonPermafrost(EUCOPIII),Svalbard,Norway:157. DobinskiW.,2011:Permafrost.EarthͲScienceReviews108:158–169. FrenchHM.,2007:ThePeriglacialEnvironment.3rdedition.WestSussex:JohnWileyandSons,458pp. Garitte G., 2006: Les torrents de la vallée de la Clarée (Htes Alpes, France). Approche géographique et contribution à la gestion du risque torrentiel dans une vallée de montagne. Thèse Université scientifiqueettechniquedeLille. Hales TC, Roering JJ., 2005: ClimateͲcontrolled variations in scree production, Southern Alps, New Zealand. Geology33:701Ͳ704. KellererͲPirklbauerA.&LiebG.K.,2011:Recentrockglaciervelocitybehaviourandrelatednaturalhazardsin the Hohe Tauern Range, central Austria. PermaNET Project Report Ͳ Contribution of IGRS to Action 6.2/Group1–Rockglacier. KellererͲPirklbauerA.,LiebG.K.,AvianM.&GspurningJ.2008:TheresponseofpartiallydebrisͲcoveredvalley glacierstoclimatechange:TheExampleofthePasterzeGlacier(Austria)intheperiod1964to2006. GeografiskaAnnaler,90A(4):269Ͳ285. Krysiecki,J.M.,Bodin,X.,Schoeneich,P.,2008.CollapseoftheBérardRockGlacier(SouthernFrenchAlps).9th InternationalConferenceonPermafrost,Fairbanks,UniversityofAlaska:153–154. Matsuoka N., 2001: Solifluction rates, processes and landforms: a global review. Earth Science Reviews, 55, 107Ͳ134. PERMOS 2009: Permafrost in Switzerland 2004/2005 and 2005/2006. Nötzli J., Naegeli B., Vonder Mühll D. (eds). Glaciological Report Permafrost N° 6/7, Cryospheric Commission of the Swiss Academy of Sciences. Stingl, H., Garleff, K., Höfner, T., Huwe, B., Jaesche, P., John, B. and Veit, H., 2010: Grundfragen des alpinen Periglazials Ͳ Ergebnisse, Probleme und Perspektiven periglazialmorphologischer Untersuchungen im Langzeitprojekt„GlorerHütte“inderSüdlichenGlocknerͲ/NördlichenSchobergruppe(SüdlicheHohe Tauern,Osttirol).SalzburgerGeographischeArbeiten,15Ͳ42. 15 2. TemperatureChangeintheEuropeanAlps Citationreference KroisleitnerCh.,ReisenhoferS.,SchönerW.(2011).Chapter2:ClimateChangeintheEuropeanAlps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNET project, final report of Action 5.3. OnͲline publicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.16Ͳ27. Authors Coordination:ChristineKroisleitner Involvedprojectpartnersandcontributors: Ͳ Central Institute for Meteorology and Geodynamics (ZAMG) – Christine Kroisleinter, Stefan Reisenhofer,WolfgangSchöner Content Summaryfordecisionmakers 1. Temperaturechangeintherecentpast 2. Projectedtemperaturechangeuntil2050 References 16 PermaNET–ClimateChangeintheEuropeanAlps Summary TheairtemperatureintheEuropeanAlpshasincreasedbyabout2°Csincethelate19thcentury. The warming was particularly pronounced since the beginning of the 1980s. The temperature increasewasassociatedwithdegradationoftheAlpinepermafrost.Thispapersummarizesthe observedchangesofairtemperatureandusesresultsfromclimatemodelsimulationstoderive future scenarios of air temperature in the Alps for the period 2021Ͳ2050. In order to provide morerelevantinformationonthermalresponseofpermafrostthepaperusesanempiricalmodel torelateairtemperaturedatatonumberoffrostdays,numberoficedaysandnumberoffreezeͲ thaw days for the Alps at altitudes above 1800m a.s.l. for both the present climate (reference period 1961Ͳ90) and for a future climate 2021Ͳ2050. The model results show that highest numbersoffreezeͲthawdaysaresimulatedforaltitudesof1800ma.s.l.(evenhighervaluesare modeled for lower elevations) with about 100 days per year and decreasing number of freezeͲ thawdayswithincreasingelevation.Moreover,themodelshowsthatthenumberoffreezeͲthaw dayswillgenerallyincreaseforaltitudesabove1800ma.s.l.byvaluesup to4daysayearuntil 2021Ͳ2050,thusincreasingtheweatheringatallelevationsabove1800ma.s.l. 17 PermaNET–Permafrostresponsetoclimatechange 1. Temperaturechangeintherecentpast The Alps as one of the major topographic forms in Europe influences the atmospheric circulation overawiderangeofscales.Theconsequencesofthisfactareavarietyofdifferentclimates,from maritimetocontinentalandfromlowlandtomountainous.InaclimateanalysisoftheGreaterAlpine Region(GAR)Brunettietal.(2009)highlightedanaverageGARwarmingtrendofabout1.3°Cover thecommonperiodcoveredbyalltheclimatevariables(1886Ͳ2005),1.4°CforthereferenceIPCCͲ period(1906Ͳ2005)whichisawarmingabouttwiceaslargeastheglobaltrendreferredtobyIPCC (2007). Furthermore, Brunetti et al. (2009) found out, that for the GAR region the majority of the warmestyearsintheperiod1774Ͳ2005weremeasuredinthepast15to20years.Themostextreme summerwasfoundfor2003,whereasthemostextremesummercoldeventhappenedin1816after thevolcaniceruptionsofTambora.Itisworthnoticingthatthe2003summertemperaturewas4.2 standarddeviationsabovethecorresponding2003summernormalvalue,butthe1816coldextreme was only 2.6 standard deviations lower than the summer normal value corresponding to summer 1816. The20thcenturyclimateinEuropevariednotonlyintime,butalsofromlocationtolocation.1900to 1940, the mean annual air temperature (MAAT) increased in western and northern Europe, while mostoftheremainingpartofthecontinentexperiencedonlysmallchanges.From1940to1975was aperiodofcoolinginthearctic,butincontinentalEuropejustthenorthernpartwasaffectedbythis trend.TheeasternpartofEuropeexperiencedaslightwarmingduringthattimeandthesouthern part kept nearly constant. In the period 1975Ͳ2000 widespread climate warming in Europe was recorded. GenerallytheSouthͲWestofEuropeand Scandinaviaweremostaffected,butseasonally therewerelargeregionaldeviationsfromthisannualtrend.Inwinterthetemperatureinnorthern andwesternEuropewasincreasing,whereasinspringthetemperatureroseespeciallyinthecentral andsouthͲwesternparts.SummertemperatureswerecharacterizedbyanincreasealloverEurope, mostpronouncedinthesouthernpart.Autumn’stemperaturewasmainlycharacterizedbyitsspatial variability(Harrisetal.,2009). Climatechangeinthepast250yearsintheAlpshasbeenextensivelystudiedintheprojectHISTALP (Auer et al., 2007). The HISTALP database covers the Greater Alpine Region (GAR) with monthly homogenised records of temperature, pressure, precipitation, sunshine and cloudiness for times datingbackto1760fortemperatureand1800forprecipitation.ThelongͲtermwarmingtrendvisible intheseasonalandannualmeantemperaturetimeseriesofGARcouldnotbeconfirmedforother climateparameters,likeprecipitation,forwhichAueretal.(2005)detectedtwoantagonistictrends, awettingtrendintheNorthͲwestoftheAlps(sincethe1860s)andadryingtrendintheSouthͲeast (since 1800). Remarkably, even the highest mountain observatories within the Alps such as Sonnblick,JungfraujochandZugspitzeshowthesametemperaturetrendsasMunich,Vienna,Milano orSarajevo.TheglobalmeantemperatureseriesshowonlyhalfofthelongͲtermwarmingoftheAlps sincethemidͲ19thcentury. 2. Projectedtemperaturechangesuntil2050 2.1Introduction Asinthepast,theAlpswillalsoinfuturebeexposedtoastrongerwarmingthantheearthingeneral. AccordingtotheIPCC(2007)scenarios,thetemperatureforwholeEuropewillrisefor3.3°,whereas theAlpswillhavetofaceatemperatureriseof3.9°Cuntiltheendofthe21stcentury(Figure1).In the highͲmountainareas above1500ma.s.l.the warmingfromclimatemodelprojectionscouldbe evenhigher(4.2°C;EEAReportNo.8,2009). 18 PermaNET–ClimateChangeintheEuropeanAlps Fig.1–Temperatureanomaly1860to2100fortheGreaterAlpineRegion(GAR)relativetotheWMO normal period 1961Ͳ1990 derived from the IPCCͲAR4 AOGCM Multimodel Ensemble (anthropogenic andnaturalforcingpriorto2001,anthropogenicforcingonlyfrom2001Ͳ2100).Thegreenlineshows measuredtemperatureanomaliesfromtheHISTALPͲproject.(Source:Schöneretal.,2011). 2.2 Experimentaldesign Althoughpermafrostinthehighmountainareasisnotverywellknownyet,itisobviousthatthereis arelationshiptoclimaticelements.However,ifthisrelationshipwouldbeeasytodescribe,itwould have been done decades ago. The relationship of nearͲsurface permafrost temperatures and air temperature is strongly affected by snow thickness and duration, which are themselves driven by atmospheric conditions (Harris et al., 2009). This investigation does not focus on change in the permafrostͲdistribution, but on the change in atmospheric frostͲbehaviour. The presence of frost above the earth’s surface is crucial for the existence of permafrost, but furthermore for the developmentandconservationofasnowcover. The core of this investigation is the comparison of frostͲ, iceͲ, and freezeͲthaw days between the climateperiods1961Ͳ90and2021Ͳ2050.Adaybecomesclassifiedasfrostday(FD),whenthedaily minimum temperature is below zero. If also the daily maximum temperature is below the freezing point, the day is classified as ice day (ID). The difference between ice days and frost days, which meansalldayswithadailyminimumtemperaturebelow0°Candadailymaximumabovethislimit, get classified as freezeͲthaw days (FTD). It is obvious from future climate scenarios, that frost frequencywillgetless. Accordingtotheclimatictrend,severalAlpineregionsexperiencedadecreaseinfrostfrequency(FF) and an extension of the frostͲfree season (Auer et al. 2005). In Austria observations indicate, that duringthe20thcenturyareductionofthefrostseasonby17daysintheflateasternregion(Vienna) and by 22 days in the high Alpine region around the mountain peak station of Sonnblick (3100m a.s.l.)hashappened. 19 PermaNET–Permafrostresponsetoclimatechange Incanbeassumed,thatinawarmerclimatetheintensityoffrostweatheringchanges,causedbythe spreading of the freezeͲthawͲcyclesͲzone to higher altitudes. How this change could happen in an A1B climate scenario was investigated for the high mountainous zone of the entire Alps above 1800ma.s.l. 2.3 Empiricalapproachtoestimatefrostdays,icedaysandfreezeͲthawdays Auer et al. (2005) found an empirical relationship of a tangens hyperbolicus function to estimate frostfrequency(FF)frommonthlymeanairtemperature.FFisdefinedbythenumberoffrostdays dividedbythenumberofdayswithintheconsideredmonth.ThetanhͲfunctionwascalculatedusing temperature data from 363 climate stations in Austria including the high alpine station Sonnblick (3105 m a.s.l.). Auer et al. (2005) calculated at least 66% FF (20.5 FD) for January in Austria for all stations.InApriltheFFcoveredawidespectrum,from100%(30FD)atthemountainpeakstation Sonnblicktonearlynofrostinthelowlands.InJulyonlyatthemountainstationSonnblickfrostdays were registered. Hence, without taking into account highͲelevation mountain stations it would be impossibletoreceiverobustcoefficientsforthemodel.Overall,thetanhͲmodelwasabletoexplain abound55%ofthethevarianceofFFdatafromairtemperaturedata.Validationofthemodelwith datafromtheentireGARshowedthatthereisalmostnodifferenceintheperformanceifthemodels arecalibratedonAustriandataorondatafortheentireGAR(seeAueretal.,2005,fordetails). IncontrarytoAueretal.(2005)inourstudyweused30Ͳyearsclimatenormals(1961Ͳ90)torelate annualfrostdaystoannualairtemperaturemeans,whichsignificantlyincreasedtheperformanceof statistical relationships. This approach is motivated from the aim of this study to compare present mean climate with a future climate mean scenario for both frost days and ice days. Consequently, the frequency of ice days (as the number of ice days divided by the number of days within the consideredmonth)wererelatedinasamemannertomeanannualairtemperatureusingatanhͲfit forthereferenceperiod1961Ͳ90.ThestatisticsofthederivedtanhͲmodelsareshowninTables1and 2.InafinalstepthefreezeͲthawdayswerecalculatedfromthedifferencebetweenicedaysandfrost days. Table1–Statisticalmodel(generalmodel,coefficientsandgoodnessoffit)inordertocomputeannualfrostday frequency(f(x))fromannualairtemperature(x)forthereferenceperiod1961Ͳ90 Generalmodel Coefficients (with95%confidencebounds) Goodnessoffit SSE:3530 f(x)=50+(50*tanh(a*x+b)) a=Ͳ0.09316(Ͳ0.0947,Ͳ0.09163) RͲsquare:0.9847 b=0.3437(0.3328,0.3546) AdjustedRͲsquare:0.9847 RMSE:2.77 20 PermaNET–ClimateChangeintheEuropeanAlps MeanAnnualAiremperature(°C) Fig.2–RatiofrostdaystototaldaysversusmeanannualairtemperatureinAustriausingdatafrom 363climatestationsinAustriafortheperiod1961Ͳ90.TheredlineisatanhͲfit.Statisticalmeasures ofthefitareshowninTable1. MeanAnnualAiremperature(°C) Fig.3–RatioicedaystototaldaysversusmeanannualairtemperatureinAustriausingdatafrom 363climatestationsinAustriafortheperiod1961Ͳ90.TheredlineisatanhͲfit.Statisticalmeasures ofthefitareshowninTable2. 21 PermaNET–Permafrostresponsetoclimatechange Table2–Statisticalmodel(generalmodel,coefficientsandgoodnessoffit)inordertocomputeannualiceday frequency(f(x))fromannualairtemperature(x)forthereferenceperiod1961Ͳ90 Generalmodel Coefficients (with95%confidencebounds) Goodnessoffit SSE:1323 f(x)=50+(50*tanh(a*x+b)) a=Ͳ0.1248(Ͳ0.1259,Ͳ0.1236) RͲsquare:0.9951 b=Ͳ0.3573(Ͳ0.3638,Ͳ0.3507) AdjustedRͲsquare:0.995 RMSE:1.696 2.4 Empiricalapproachtoestimatefrostdays,icedaysandfreezeͲthawdaysfortheentireAlps WeusedthespatiallyhighͲresolutiontemperatureclimatologyofHiebletal.(2009)tocomputethe number of frost days, the number of ice days and the number of freezeͲthaw days for the Alpine region for both the present climate and the future climate 2021Ͳ2050. However, our study was restrictedtotheAlpineareaabove1800ma.s.l.asthezonemostrelevantforpermafrost.Inafirst stepthe~1kmresolutionGARmonthlytemperatureclimatology(1961Ͳ90)wasdownscaledusingthe ~30mͲresolution ASTER GDEM for the high mountain area of the Alps. The temperatureͲgrid was recalculatedaccordingtotheapproachofHiebletal.(2009),whichheusedforthedevelopmentof the~1kmspatialresolutionGARͲclimatologybasedon1961Ͳ1990climatenormals.TheworkofHiebl etal.(2009)isbasedonastationnetworkof1,726climatestationsfortheGreaterAlpineRegion, whichwerecarefullyqualitycheckedandhomogenized. AccordingtoHiebletal.(2009)weusedseveralgeographicalvariablestocomputeairtemperature bymeansofamultilinearregressionapproach: x x x x x Thelongitudinalgradientstakeintoaccounttheunderlyingoceanictocontinentaltransition, which occurs from the western to the eastern edge of the GAR. However, the variance of temperatureexplainedfromlongitudeislimitedto1%oftheannualvariance. On the contrary to this small amount, latitude explained 19% of the variance of annual air temperature by mainly capturing the effect of the SouthͲNorth solar radiation gradient on temperature. Asexpected,thelargestpartoftemperaturevariancecouldbeexplainedbyelevation.The verticalregressionmodelexplainsasmuchas69%ofthetemperaturevariancefortheyearly averages,althoughduringwinterduetostableatmosphericlayeringthevaluedecreasesto around45%. For considering different temperature behaviours at low altitude areas and high altitude areasHiebletal.(2009)introduceda3verticallayersͲmodel.Thelowestlayerrangesfrom 600minthesouthernpartsupto800minthewesternpartsoftheGAR.Thehighelevation layersverticalextentbeginsat1800ma.s.l.Betweenthetwolayersthetemperatureswere simplyinterpolated.Inourstudyweusedonlythehighest(above1800ma.s.l.)layer. Slopes got implemented in the model by using an analysis of Auer & Böhm (2003) which systematicallyanalyseddatafrom85Austriansiteswithdetailedsitedescription.Theyfound 22 PermaNET–ClimateChangeintheEuropeanAlps x monthly deviations from the mean for NorthͲ and SouthͲfacing slopes ranging from Ͳ0.2 to 1.0°C. Maritimeinfluencewastakenintoaccountbyestablishingatopographicallyweightedfield of distances from the coast. Hiebl et al. (2009) found a surprisingly strong dependency of temperature on distance from the coast. At a yearly average the distance to the coast variableexplained41%ofthetemperaturevariance. The 30year highͲalpine monthly mean temperatures were calculated from the following regression equation: t01=9.412932+Ͳ0.190362*[lon_1]+Ͳ0.035543*[lat_1]+Ͳ0.005002*[DEM]+Ͳ0.003347*[coast] [lon_1]Ælongitude [lat_1]Ælatitude [DEM]Ædigitalelevationmodel [coast]Æcoastdistancegrid As shown by Hiebl et al. (2009), considering longitude, latitude and the distance from the coasts besides elevation reduced the average monthly standard error to 0.79°C per month. Furthermore Hiebl et al. (2009) used the GTOPO30ͲDEM with a spatial resolution of 30 arc seconds, which corresponds to about 1km. GTOPO30 has a root mean square error of about 18m. Applied on monthlylapseratemodels,theDEMinaccuracyleadstoatemperatureerrorof0.09°Conaverage. In this study we used the empirical temperature model of Hiebl et al. (2009) but replaced the GTOPO30ͲDEMbytheASTERGDEM,thusrefiningthespatialresolutionoftemperaturegridto1arc second (~30m). Compared to GTOPO, with an error of surface elevation of about 18m, the ASTER GDEM has an overall root mean square error of 10.87m. The error of surface elevation can be assumedtobeapproximately20mataconfidencelevelof95%. Based on the refined climatology (climate normal 1961Ͳ90) of annual air temperature and the empiricalmodelsforfrostdays(Tab.1andFig.2)andforicedays(Tab.2andFig.3)30mͲrasterdata ofclimatenormals(referenceperiod1961Ͳ90)offrostdaysandicedaysfortheAlpineregionwere computed. 2.5 Estimationoffuturefrost,iceandfreezeͲthawͲcyclesdaysscenariosfortheperiod2021Ͳ2050 For projecting the temperature of the Alps for the future period 2021Ͳ2050 we used the regional climate model experiment of Hollweg et al. (2008) which dynamically downscaled the ECHAM5Ͳ MPIOMͲA1B scenario (Röckner et al., 2003) by means of the regional climate model CLM. The performance of this CLM model run for the GAR was extensively tested in Schöner et al. (2011). Particularly,itwasshownbySchöneretal.(2011)thatcomparedtoanensemblessimulationforthe Alpineregion(usedfromthePRUDENCEensembles;seeFreietal.,2006)theusedCLMsimulation shows a temperature change which lies close to the ensembles median. The spatial pattern of the temperaturechangefor2021Ͳ2050relativeto1976Ͳ2007derivedfromtheCLMsimulationisshown inFigure4.ThespatialresolutionoftheCLMgridis18x18km. 23 PermaNET–Permafrostresponsetoclimatechange Fig. 4 Ͳ Change of seasonal mean temperature (left: winter season, right: summer season) for the GreaterAlpineRegionfor2021Ͳ2050relativeto1976Ͳ2007(fromSchöneretal.,2011,sourceforCLM data:Hollwegetal.,2008). The spatial distributions of the number of frost days, the number of ice days and the number of freezeͲthawdaysfortheclimatereferenceperiod1961Ͳ90fortheregionoftheEuropeanAlpswith elevationshigher1800ma.s.l.areshowninFigures5,6and7.ThehighestnumberoffreezeͲthaw dayswerecomputedforlowestelevationscloseto1800ma.s.l.Withhigherelevationsthenumber offreezeͲthawdaysdecreasesfromabout100daysat1800ma.s.l.tolessthan15daysathighest elevationsoftheAlps.Changesinthenumberoffrostdays,thenumberoficedaysandthenumber offreezeͲthawdaysaredisplayedinFigures8,9and10fortheperiod2021Ͳ2050relativeto1961Ͳ90 based on the temperature change from the CLM simulations. Temperature increase will generally increasethenumberoffreezeͲthawdaysbynumbersupto4daysperyear,thusincreasingalsothe frostweathering. Acknowledgements.–ThedigitalelevationmodelwascontributedbyMETIandNASAtotheGlobal EarthObservationSytemofSystems(GEOSS)andwasdownloadedfromtheEarthRemoteSensing DataAnalysisCenter(ERDSAC)ofJapanandNASA`sLandProcessDistributedActiveArchiveCenter (LP DAAC) http://asterweb.jpl.nasa.gov/gdem.asp. Climate model results of CLM regional climate model were provided by Deutsches Klimarechenzentrum within the frame of the project AnpassungsstrategienandenKlimawandelfürÖsterreichsWasserwirtschaft. 24 PermaNET–ClimateChangeintheEuropeanAlps Fig.5–Frostdays(1961Ͳ90)intheAlpsforthesubregionwithelevationabove1800ma.s.l. Fig.6–Icedays(1961Ͳ90)intheAlpsforthesubregionwithelevationabove1800ma.s.l. Fig.7–FreezeͲthawdays(1961Ͳ90)intheAlpsforthesubregionwithelevationsabove1800ma.s.l. 25 PermaNET–Permafrostresponsetoclimatechange Fig. 8 – Estimated difference in frost days between 1961Ͳ90 and 2021Ͳ2050 for the subregion with elevationsabove1800ma.s.l. Fig. 9 – Estimated difference in ice days between 1961Ͳ90 and 2021Ͳ2050 for the subregion with elevationsabove1800ma.s.l. Fig.10–EstimateddifferenceinfreezeͲthawdaysbetween1961Ͳ90and2021Ͳ2050forthesubregion withelevationsabove1800ma.s.l. 26 PermaNET–ClimateChangeintheEuropeanAlps References: ASTER GDEM Validation Team, 2009: METI/ERSDAC, NASA/LPDAAC, USGS/EROS, (2009): ASTER GlobalDEMValidationSummaryReport,June2009 Auer I. & Böhm R., 2003: Jahresmittel der Lufttemperatur. Hydrologischer Atlas Österreichs. ÖsterreichischerKunstͲundKulturverlag,Vienna,MapSheet1.6. AuerI.,MatullaC.,BöhmR.,UngersböckM.,MaugeriM.,NanniR.,PastorelliR.,2005:Sensitivityof frostoccurrencetotemperaturevariabilityintheEuropeanAlps.Int.JournalofClimatology, 25,1749Ͳ1766. AuerI.,BöhmR.,JurkovicA.,LipaW.,OrlikA.,PotzmannR.,SchönerW.,UngersböckM.,MatullaCh., BriffaK.,JonesP.,EfthymiadisD.,BrunettiM.,NanniT.,MaugeriM.,MercalliL.,MestreO., MoisselinJ.ͲM.,BegertM.,MüllerͲWestermeierG.,KvetonV.,BochnicekO.,StastnyP.,Lapin M.,SzalaiS.,SzentimreyT.,CegnarT.,DolinarM.,GajicͲCapkaM.,ZaninovicK.,MajstorovicZ. & Nieplova E. 2007: HISTALP – Historical instrumental climatological surface time series of theGreaterAlpineRegion1760Ͳ2003.InternationalJournalofClimatology,27,17Ͳ46. BrunettiM.,LentiniG.,MaugeriM.,NanniR.,AuerI.,BöhmR.,SchönerW.,2009:Climatevariability andchangeintheGreaterAlpineRegionoverthelasttwocenturiesbasedonmultiͲvariable analysis.Int.JournalofClimatology,Vol.29,Issue15,2197Ͳ2225DOI:10.1002/joc.1857 EEA Report No. 8, 2009: Regional climate change and adaptation. The Alps facing the challenge of changingwaterresources.EuropeanEnvironmentAgency,Copenhagen,143pp. FreiC.,SchöllR.,FukutomeS.,SchmidliJ.,VidaleP.L.,2006:Futurechangeofprecipitationextremes inEurope:Intercomparisonofscenariosfromregionalclimatemodels.JournalofGeophysical Research,111:D06105 Harris C., Arenson L. U., Christiansen H. H., Etzelmüller B., Frauenfelder R., Gruber S., Haeberli W., Hauck C., Hölzle M., Humlum O., Isaksen K., Kääb A., KernͲLütschg A.M., Lehning M., MatsoukaN.,MuronJ.B.,MötzliJ.,PhilipsM.,RossN.,SeppäläM.,SpringmanS.M.,Vonder Mühll D., 2009: Permafrost and climate in Europe: Monitoring and modelling thermal, geomorphologicalandgeotechnicalresponses.EarthͲScienceReviews,92,117Ͳ171. HieblJ.,AuerI.,BöhmR.,SchönerW.,MaugeriM.,LentiniG.,SpinoniJ.,BrunettiM.,NanniT.,Tadiđ PerēecM.,BihariZ.,DolinarM.,MüllerͲWestermeierG.,2009:AhighͲresolution1961Ͳ1990 monthlytemperatureclimatologyfortheGreaterAlpineRegion.MeteorologischeZeitschrift, 18,507Ͳ530. HollwegH.D.,BöhmU.,FastI.,HennemuthB.,KeulerK.,KeupͲThielE.,LautenschlagerM.,Legutke S., Radtke K., Rockel B., Schubert M., Will A., Woldt M., Wunram C., 2008: Ensemble simulations over Europe with the regional climate model CLM forced with IPCC AR4 Global Scenarios.M&DTechnicalReport,3,2008. IPCC,2007:ClimateChange2007:ThePhysicalScienceBasis.ContributionfromtheWorkingGroupI to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. CambridgeUniversityPress:Cambridge,UnitedKingdomandNewYork,NY,USA,996pp. RöcknerE.,Bäuml G.,BonaventuraL., BrokopfR.,Esch M., Giorgetta M.,Hagemann S.,KirchnerI., Kornblueh L., Manzini E., Rhodin A., Schlese U., Schulzweida U., Tompkins A., 2003: The atmospheric general circulation model ECHAMͲ5, Part I: Model description. MaxͲ PlanckͲ InstitutfürMeteorologie,Report349. Schöner W., Böhm R., Haslinger K., 2011: Klimaänderung in Österreich – hydrologisch relevante Klimaelemente.Österr.WasserͲundAbfallwirtschaft1Ͳ2/2011,11Ͳ20 27 3. CasestudiesintheEuropeanAlps 3.1 Overviewoncasestudies Citationreference KellererͲPirklbauerA,LiebG.K.(2011).Chapter3.1:CasestudiesintheEuropeanAlps–Overviewon case studies. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.28Ͳ34. Authors Coordination:AndreasKellererͲPirklbauer Involvedprojectpartnersandcontributors: Ͳ Institute of Geography and Regional Science, University of Graz, Austria (IGRS) – Andreas KellererͲPirklbauer,GerhardKarlLieb Content Summary 1. Theregionaldistributionofthecasestudies 2. Projectpartnersandresearchactivities 3. Structureofthecasestudies References 28 PermafrostResponsetoClimateChange Summary Thecasestudiesprovideinformationrelevantofthereactionsofpermafrosttoclimatechange from study sites which are distributed between 47°22’ and 44°59’N and between 06°10’ and 14°41’E,respectively,coveringagreatpartoftheAlpineArc.Fromaspatialpointofview,the results thus can be considered sufficiently representative for the entire Alps. The methodology usedcoversabroadspectrumoftechniquesmakingtheresultswellreliable. Alltheactivitieswerecarriedoutbyscientificinstitutionswhicharewellprovidedwithbestlocal field experience and in many cases with regional actor networks. All the case studies have a similarconceptualstructurebeginningwithashortpresentationofthesite,thengivingconcise informationonthemethodsusedandtheresultselaborated. Eachcasestudyfinallyprovidessomeassumptionsonthefuturedevelopmentofpermafrostin therespectiveareatakingintoaccounttheclimatescenariopresentedinChapter2. 29 PermaNET–Permafrostresponsetoclimatechange 1. Theregionaldistributionofthecasestudies Theassessmentofthermalanddynamicreactionscenariosofdifferentpermafrostsitesiscarriedout at13siteswithintheEuropeanAlps.Figures1and2depictthelocationofthestudysiteswithinthe AlpineArcaswellasvisualimpressionsofthestudysites.Table1givesanoverviewforeachofthese study sites. The study sites are distributed between 47°22’ and 44°59’ N and between 6°10’ and 14°41’ E, respectively, with Hochreichart (A) being the northernmost and easternmost and Bellecombes (F) the westernmost and southernmost site. Thus the sites cover a great part of the AlpineArcwiththeexceptionoftheSwissAlps(whicharemissingduethecompositionoftheproject staff).ThesitesalsocoverthemostimportantgeologicalunitsoftheAlps(e.g.metamorphicrocksof theCentralZoneoftheEasternAlpsandlimestonesoftheSouthernAlpsaswellasgranitesofthe CentralMassivesoftheWesternAlps).Thus,intermsofthegeographicaldistribution,theresultscan beconsideredsufficientlyrepresentativefortheentireAlps. Fig.1–Locationofthe13PermaNETstudysitesrelevantfortheassessmentofthermalanddynamic reactionscenariosofdifferentpermafrostsitesintheEuropeanAlps. 2. Projectpartnersandresearchactivities Table 1 gives an overview on the study sites containing for each one its name, country, location, elevation, studied landform and processes, research initiation, type of permafrost monitoring site and the institution which has responsibly coordinated the documentation of the respective case study. All persons involved in elaborating the case studies are kindly acknowledged and listed in Table2.Informationontherelevanceofthecharacterofthedifferentpermafrostmonitoringsitesas wellaslandformsandprocessesisgiveninChapter4. 30 PermafrostResponsetoClimateChange Fig.2–Visualimpressionsof9ofthe13PermaNETstudysitesrelevantfortheassessmentofthermal and dynamic reaction scenarios. The numbers in brackets refer to the numbers in Fig. 1. The study sitesrangefromjustbelow2000ma.s.l.(studysiteHochreichart)toabout4000ma.s.l.(studysites intheAiguilleduMidì).Allphotographsprovidedbytheauthors. 31 PermaNET–Permafrostresponsetoclimatechange Table 1 – Overview of the study sites investigated in order to assess the thermal and dynamic reaction of permafrost to climate change in the Alps within action 5.3 of the project PermaNET. The different types of permafrost monitoring sites are: PFͲbedrock=Permafrost in bedrock (from nearͲvertical rockwalls to flat morphologies);PFͲfine=PermafrostinfineͲgrainedmaterial(flatmorphology);PFͲcoarse=PermafrostincoarseͲ grained and blocky material (scree slopes, rock glaciers; from slopes to rather flat morphologies). Project partners and collaborators: ARPA VdA=Regional Agency for the Environmental Protection of Valle d'Aosta, Aosta,Italy;ARPAV=EnvironmentProtectionRegionalAgencyofVeneto;UIBK=InstituteofGeology,University of Innsbruck, Innsbruck, Austria; IGRS=Institute of Geography and Regional Science, University of Graz, Graz, Austria; ZAMG=Central Institute for Meteorology and Geodynamics, Vienna, and Regional Office for Salzburg andUpperAustria,Salzburg,Austria;IGAͲPACTE=InstitutdeGéographieAlpine,UniversityofGrenoble,France; EDYTEM=EDYTEMLab,UniversitédeSavoie;UniPavia=EarthScienceDepartment,UniversityofPavia,Pavia, Italy;Abenis=AbenisAlpinexpertGmbh/srl,Bozen/Bolzano,Italy. Nameofstudysite (codeseeFig.1) Con. Latitude Longitude Elevation range/ max. (ma.s.l.) Hochreichart(1) A 47°22’N 14°41’E 1920Ͳ2415 DösenValley(2) A 46°59’N 13°17’E 2400Ͳ3000 rock glacier, 1995 rockwall HoherSonnblick(3) A 47°03’N 12°57’E 3105 bedrock, detritus 2007 A 46°50’ 11°01’ 2360Ͳ2840 rockglacier 1938 PFͲcoarse UIBK F 45°56’N 06°24’E 2450Ͳ2630 rockglacier 1979 PFͲcoarse IGAͲPACTE F 44°59’N 06°10’E 2600Ͳ2800 rockglacier 2007 PFͲcoarse IGAͲPACTE F 45°53’N 06°53’E 3840 nearͲvertical rockwalls 2005 PFͲbedrock EDYTEM F 45°50’N 06°52’E 3000Ͳ4000 2006 PFͲbedrock EDYTEM OuterHocheben Cirque(4) Combe du Laurichard(5) Bellecombes(6) Aiguille du Midì* (Mont Blanc Massif) (7) MontBlancMassif (othersitesas*)(8) Cime Bianche Pass (9) ValdiGenova(10) Vald’Amola(11) I 45°55’N 07°41’E 3100 I I 46°13’N 46°12’N 10°34’E 10°42’E PizBoè(12) I 46°30’N Upper Sulden Valley I (13) 46°30’N Main studied landform or process rock glacier, rock wall, detritus ReͲ search initiaͲ tion Permafrost monitoring site Coordinator’ sinstitution 2004 PFͲbedrock PFͲcoarse IGRS 2750Ͳ2860 2330Ͳ2480 nearͲvertical rockwalls bedrock, detritus rockglacier rockglacier 2001 2001 11°50’E 2900Ͳ2950 rockglacier 2005 10°37’E 2600Ͳ3150 detritus 1992 32 2005 PFͲbedrock PFͲfine PFͲcoarse PFͲbedrock PFͲcoarse PFͲbedrock PFͲcoarse PFͲcoarse PFͲcoarse PFͲcoarse PFͲbedrock PFͲcoarse PFͲfine IGRS ZAMG ARPAVdA UniPavia UniPavia ARPAV Abenis Alpinexpert PermafrostResponsetoClimateChange Table2–PersonsinvolvedinelaboratingthecasestudiesofAction5.3andtheiraffiliations. Name Baroni,Carlo Bodin,Xavier Cagnati,Anselmo Carollo,Federico Coviello,Velio Cremonese, Edoardo Crepaz,Andrea Dall’Amico,Matteo Defendi,Valentina Deline,Philip Casestudy (Chapter) UniversityofPisa(Italy) 3.11.,3.12. UniversityJosephFourier,Grenoble(France) 3.6. RegionalAgencyfortheEnvironmentalProtectionofVeneto(Italy) 3.13. E.P.C.EuropeanProjectConsultingS.r.l.(Italy) 3.13. NationalCenterforScientificResearchEDYTEM,Grenoble(France) 3.8. RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) 3.8.,3.10. Institution RegionalAgencyfortheEnvironmentalProtectionofVeneto(Italy) MountainͲeeringsrl(Italy) RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) NationalCenterforScientificResearchEDYTEM,Grenoble(France) Drenkelfluss,Anja Galuppo,Anna Gruber,Stephan KellererͲPirklbauer, Andreas UniversityofBonn(Germany) RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) UniversityofZurich(Switzerland) UniversityofGraz(Austria) 3.13. 3.11.,3.12. 3.13. editor, 3.8., 3.9. 3.8. 3.13. 3.8. editor,3.2,3.3 Kemna,Andreas Klee,Alexander Krainer,Karl Krautblatter, Michael Krysiecki,JeanͲ Michel LeRoux,Olivier UniversityofBonn(Germany) CentralInstituteforMeteorologyandGeodynamics(Austria) UniversityofInnsbruck(Austria) UniversityofBonn(Germany) 3.8. 3.4. 3.5. 3.8. UniversityJosephFourier,Grenoble(France) 3.6. Lieb,GerhardKarl Lorier,Lionel UniversityofGraz(Austria) editor,3.2,3.3 Association pour le développement de la recherche sur les glissements de 3.7. terrain(France) Magnabosco,Laura Magnin,Florence Mair,Volkmar Malet,Emmanuel Marinoni, Francesco MorradiCella, Umberto Noetzli,Jeanette Pogliotti,Paolo RegioneVeneto,DirezioneGeologiaeGeorisorse,ServizioGeologico(Italy) NationalCenterforScientificResearchEDYTEM,Grenoble(France) AutomousProvinceofBolzano(Italy) NationalCenterforScientificResearchEDYTEM,Grenoble(France) Freelancer(Italy) Association pour le développement de la recherche sur les glissements de 3.7. terrain(France) 3.13. 3.8. 3.14. 3.8. 3.13. RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) 3.8.,3.10. UniversityofZurich(Switzerland) 3.8. RegionalAgencyfortheEnvironmentalProtectionoftheAostaValley(Italy) editor, 3.8., 3.10. Ravanel,Ludovic NationalCenterforScientificResearchEDYTEM,Grenoble(France) 3.8.,3.9. Riedl,Claudia CentralInstituteforMeteorologyandGeodynamics(Austria) 3.4. Rigon,Riccardo UniversityofTrento(Italy) 3.11.,3.12. Schöner,Wolfgang CentralInstituteforMeteorologyandGeodynamics(Austria) editor, 3.6., 3.7. Seppi,Roberto UniversityofPavia(Italy) 3.11. Vallon,Michel UniversityJosephFourier,Grenoble(France) 3.7. Zampedri,Giorgio GeologicalSurvey,AutonomousProvinceofTrento(Italy) 3.11.,3.12. Zischg,Andreas AbenisAlpinexpertGmbH/srl(Italy) 3.14. Zumiani,Matteo Geologist(Italy) 3.11.,3.12. 33 PermaNET–Permafrostresponsetoclimatechange 3. Structureofthecasestudies Inordertofacilitatethecomparisonbetweenthedifferentcasestudiesallofthemusemoreorless thesamestructureasfollows: x Summary x Short introduction into the case study site and the relevant landform (in most cases with detailedmapsandphotographs) x Methodology (in most cases a set of different methods has been used, see discussion in Chapter4) x Recentthermaland/orgeomorphicevolutionoftherelevantlandform(s)(inmostcaseswith graphs,forthecoveredtimespansseediscussioninChapter4) x Assumptionsonpossiblefuturethermal/geomorphicresponseofthislandformtopredicted climatechange(takingintoaccounttheclimatescenariopresentedinChapter2) x Referencelist. 34 3. CasestudiesintheEuropeanAlps 3.2 Hochreichart,EasternAustrianAlps Citationreference KellererͲPirklbauerA(2011).Chapter3.2:CasestudiesintheEuropeanAlps–Hochreichart,Eastern AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.35Ͳ44. Authors Coordination:AndreasKellererͲPirklbauer Involvedprojectpartnersandcontributors: Ͳ Institute of Geography and Regional Science, University of Graz, Austria (IGRS) – Andreas KellererͲPirklbauer Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 35 PermaNET–CasestudiesintheEuropeanAlps Summary Knowledge regarding marginal permafrost zones in the European Alps is fairly limited. A permafrost research project in the Seckauer Tauern, focusing particularly on the Mt. HochreichartͲReichart Cirque area (47°22’N, 14°41’E), Austria, was initiated in 2004 by the author.Since2006,theresearchactivitieswerecarriedoutwithintheprojectsALPCHANGEand PermaNET. Based on geomorphic mapping, numerical permafrost modelling, multiͲannual measurementsofthebottomtemperatureofthesnowcover(BTS),continuousmeasurementsof groundsurface,neargroundsurfaceandairtemperaturesbyminiaturetemperaturedataloggers (MTD), geoelectrics and optical snowͲcover monitoring by a remote digital camera (RDC) the existence of permafrost was proven. Patches of permafrost are strongly related to elevation, aspect,grainsizeofthesediments,andcharacteristicsofwintersnowcover.Therefore,thestudy site is the most easterly evidence of existing permafrost found in the entire European Alps at 14°41’Einelevationsaslowas1900masl.Predictingclimatewarmingwillsubstantiallyinfluence the permafrost distribution and geomorphic dynamics in the study area HochreichartͲReichart Cirque.By2050,permafrostwillbealmostcompletelythawedapartfromfewhighͲelevatedsites where the substrate material (coarseͲblocky material) and topoclimatic conditions (radiation, snowcover)stillallowsmallpatchesofpermafrost. 36 PermafrostResponsetoClimateChange 1. Introductionandstudyarea Mountain permafrost is a widespread phenomenon in alpine regions in the European Alps. For instance,some2000km²or4%oftheAustrianAlpsareunderlainbypermafrost(Lieb1998).Upto recent times most research on permafrost issues in Austria focused on the central and highest sectionoftheAustrianAlps.Bycontrast,knowledgeconcerningmarginalpermafrostzonesisfairly limitedsofar. ToincreaseknowledgeabouttheeasternmostlimitofpermafrostintheEuropeanAlps,aresearch projectfocusingontheSeckauerTauernMountains(14°30’Eto15°00’E)andparticularlyontheMt. Hochreichart area (47°22’N, 14°41’E) was initiated in 2004 by the author (Fig. 1). First permafrost resultswerepublishedinKellererͲPirklbauer(2005).Theresearchactivitieswerecontinuedbetween 2006and2010withintheprojectALPCHANGEandsince2008withinPermaNET. Fig.1–LocationofthestudyregionSeckauerTauernMountainsandthestudyareaMt.Hochreichart TheSeckauerTauernMountainsaretheeasternmostmountainsoftheTauernRangewhichcovers almost9,500km²inAustriaandItaly.TheSeckauerTauerhaveaspatialextentof626km²andits highest peak is Mt. Geierhaupt reaching 2417 m asl (KellererͲPirklbauer 2008). Research in the SeckauerTauernMountainsfocusesspatiallyonthesummitareaofMt.Hochreichart (2416masl) andthenorthͲeastfacingReichartCirque. The study area covers about 1 km² in total, ranging in elevation from about 1800 to 2416 m asl. Bedrock is predominantly quartzite and gneiss. The Reichart Cirque is covered by a large relict polymorphicrockglacierwithaverticalextentofc.450mrangingfromabout1500maslto1950m aslattheuppermostpartoftherootingzone(Fig.2A). Thehigherelevationsofthestudyareawereexposedtointensiveperiglacialweatheringduringthe cold periods in the Pleistocene causing the formation of coarseͲgrained autochthonous blockfields (mountainͲtopdetritus)andrectilinearslopeswithsolifluctionlandforms,partlywithmaterialsorting byfrostaction(Fig2B).According toownairtemperature measurementsbetweenSept. 2008and August2009,themeanannualairtemperature(MAAT)atthesummitat2416masl(AT1)isͲ1.4°C,in thecirqueat1920masl(AT2)isabout+2.2°C,revealingameanlapserateof0.0072°C/m. 37 PermaNET–CasestudiesintheEuropeanAlps Fig. 2 – (A) Mt. Hochreichart (2416 m asl) and Reichart Cirque with the uppermost part of a polymorphic quasiͲrelict (i.e. contains small patches of permafrost) rock glacier. Locations of the miniaturetemperaturedataloggers/MTDwheregroundsurfacetemperature(GST,blackdots)andair temperature (AT, grey dots) are measured and the profile where geoelectrical measurements were carried out in 2008 (blue and white line) are indicated. (B) Summit of Hochreichart with coarseͲ grainedautochthonousblockfieldswithmaterialsortingbyfrostaction(notethevegetationpatchin frontoftheperson).PhotographsbyA.KellererͲPirklbauer(A)22.09.2007and(B)22.08.2007. Fig. 3 – The study area HochreichartͲReichart Cirque: The distribution of the modelled potential discontinuous permafrost, areas of rock glacier depositis, location of air (AT) and ground surface temperature(GST)measurementsites,andthelocationofthegeoelectricprofileareindicated. 38 PermafrostResponsetoClimateChange 2. Permafrostindicatorsandrecentthermalevolution 2.1Methods Since2004asuiteofmethodshasbeenappliedsuchasgeomorphicmapping,numericalpermafrost modelling, multiͲannual measurements of the bottom temperature of the snow cover (BTS), continuousmeasurementsofgroundsurface,neargroundsurfaceandairtemperaturesbyminiature temperaturedataloggers(MTD),geoelectricsandopticalsnowͲcovermonitoringbyaremotedigital camera(RDC). Thespatialdistributionofpotentialdiscontinuouspermafrostinthestudyareawasmodelledbyan adaptation of the program PERMAKART (Keller 1992), using GIS ArcView and ArcInfo. Details and resultsofthismodellingapproachwerepublishedinKellererͲPirklbauer(2005). MTDswereusedatninelocationsduringdifferentperiods.Theresultsfromthreesites(Fig.1)with groundsurfacetemperature(GST)measurementsloggedat1hintervalarepresentedhere.Theused loggers are produced by GeoPrecision, Model MͲLog1 with PT1000 temperature sensors (accuracy +/Ͳ0.05°C, range Ͳ40 to +100°C, calibration drift <0.01°C/yr). Data of continuous measurements of groundsurfacetemperatureatthethreesitesGST1toGST3wereavailableforthe47Ͳmonthperiod 09.10.2006 to 21.09.2010. At site GST3 malfunction of the logger caused a data gap between 18.05.2007and12.08.2007.InordertoallowcomparisonbetweenthesitesaswellasallowingfullͲ year data analysis, the three fullͲyear periods 01.11.2006Ͳ31.10.2007, 01.11.2007Ͳ31.10.2008 and 01.11.2008Ͳ31.10.2009,wereanalysed.AtGST3,onlythesecondandthirdyearwasconsidered.The dataanalysisfocusedonfrostday(FD),iceday(ID),freezeͲthawday(FTD)andfrostͲfreeday(FFD).A day got classified as FD, when the daily minimum temperature is below zero. If also the daily maximum temperature is among the freezing point, the day got classified as ice day ID. The differencebetweenicedaysandfrostdays,whichmeansalldayswithadailyminimumtemperature below 0°C and a daily maximum above this limit, got classified as FTD. Finally, a day with positive minimumtemperaturegotclassifiedasFFD. BTSwasmeasuredatReichartCirqueannuallybetweenwinter2004and2009usingathermocouple probePT100(1/3DINclassB)fixedtothebottomofa3mlongsteelrod(SystemKRONEIS,Vienna). BTSisknowntobeagoodindicatoroftheoccurrenceorabsenceofpermafrost.ThemeasuredBTS valuesindicate:BTS>Ͳ2°C:permafrostunlikely;BTSͲ2toͲ3°C:permafrostpossible;BTS<Ͳ3°C: permafrostprobable(Haeberli1973).However,theinterpretationofmeasuredBTSvaluesshouldbe madeverycarefullyandinterannualvariationatagivensitemightvarysubstantialfromoneyearto thenext. In order to verify the temperature data and to extend the spatial knowledge about permafrost distribution beyond point information, a geoelectrical survey was carried out at the end of August 2008 by applying the electrical resistivity tomography (ERT) method along a 120 m long profile coveringtheupperpartoftherootingzoneofa(moreͲorͲless)relictrockglacierandthetalusslope above.ForthissurveythetwoͲdimensional(2D)electricalsurveyswasperformedusingtheWennerͲ Alfaconfigurationwith2.5mspacingandanLGMͲLippmann4ͲPunktlighthpresistivityͲmeter.The ERTmeasurementswerecarriedoutbyB.Kühnast(KNGeoelektrik)jointlywithE.Niesner(University ofLeoben)(KellererͲPirklbauer&Kühnast2009). Finally, a RDC system was set up at a nearby mountain (Feistererhorn 2081m asl.) to monitor the snowcoverdynamicsinthecirqueandsummitareofMt.Hochreichart.ThecorepartsoftheRDC system are a standard handͲheld digital camera (Nikon Coolpix), a remote control, a water proof casingwithatransparentopening,a12V/25Ahbatteryandsolarpanelswithachargecontroller. 2.2Resultsoncurrentpermafrostdistribution 39 PermaNET–CasestudiesintheEuropeanAlps Permafrostmodelling Permafrostdistributionaccordingtothisthechosenmodellingapproachrevealedthatpermafrostis verylikelyatnorthͲfacingaspectsathighestelevations,butnotoccurringataltitudesbelow2270m asl.Accordingtothismodelresult,theentireReichartCirqueispermafrostfree(Fig.3). Thermalregimebasedonminiaturetemperaturedatalogger ResultsofthecontinuousmeasurementsofgroundsurfacetemperatureatthethreesitesGST1to GST3 are shown in Fig. 4. The mean values for the three year period at the highest site (GST1, FD 235)forFDis15dayshighercomparedtothesite116mlowerinelevation(GST2,FD220).ForID, thedifferenceismoresubstantialwith19days,whereasthenumberofFTDisslightlyhigheratthe lowerofthetwosites.Thelowestofthethreesites(GST3)experiencessubstantiallylessFDbutonly slightlylessFTDcomparedtoGST2.Regardinginterannualvariations,thenumberofFDatallthree sitesisrelativelystable,whereasthenumberofIDaswellasofFTDvariesabitmore. Fig.4–ThermalregimeatthethreesitesGST1toGST3betweenNov.2006andOctober2009.Numberoffrost days(includingicedays),icedays,freezeͲthawdaysandfrostͲfree.Resultsofsingleyearsandthemeanforthe entireperiodareshown. Fig.5showsthemeanannualgroundsurfacetemperature(MAGST)aswellastheelevationofthe computedͲzerodegreeisothermbasedonalapserateof0.0065°C/m.Thisgraphclearlydepictsthat theMAGSTvaluesatsiteGST1andGST2areallnegativeindicatingpermafrost,whereasatthelow elevation site GST3 the temperature at the ground surface is at around +2°C. However, GST3 is locatedoncoarseͲgrainedblockymaterialintherootingzoneofarockglacier.Duetothethermal behaviourofsoilmaterial(inparticularcoarseͲgrainedblockymaterialwithopenvoidsinbetween), thetemperatureatthegroundsurface(i.e.MAGST)iswarmercomparedtothetemperatureatthe topofpermafrost(TTOP), possiblyuptoseveraldegrees(“thermaloffset”;Smithand Riseborough 2002). Therefore, despite the fact that positive MAGST are measured at the surface, permafrost mightstillexistintheground. The diagram showing the computedͲzero degree isotherm for the three sites indicates that in general, the lowest computed zeroͲdegree isotherm was calculated for site GST3, whereas the highestcomputedzeroͲdegreeisothermwascalculatedforthehighestsiteGST1.Explanationforthis isthedifferentbufferingeffectofthewintersnowcover.AtsiteGST1,snowcoverisofsubstantially less importance (summit site, small local depression) compared to site GST3 (footͲslope position, rootingzoneofrockglacierwithmoreefficientsnowaccumulationandlonglyingsnowcover).This clearly highlights the importance of snow influencing the thermal regime of the ground (cf. “nival offset”;SmithandRiseborough2002) 40 PermafrostResponsetoClimateChange Fig.5 –Meanannualgroundsurfacetemperature(MAGST)andcomputedzeroͲdegreeisotherm(usingalapse rateof0.0065°C/m)atthethreesites.Resultsofsingleyearsandtheentireperiodareshown. Figure 6 shows the results of two BTSͲcampaigns in the Reichart cirque. The maps show that the general pattern is the same, but BTS values in 2008 were cooler. In 2008 more measurement locations were within the possible (Ͳ2 to Ͳ3°C) and probable (< Ͳ3°C) permafrost classes. BTS measurementsindicatethatpatchypermafrostprobablyexistsinthecirqueattwodifferenttypesof topographicalpositions:(i)anorthtonorthͲeastfacingfootslope,and(ii)atthefootofasteepnorth to northͲwest facing rockface at elevations as low as 1850 m asl. According to this method, the uppermostpartoftherockglacierincludingtherootzonearepresumablyunderlainbypatchesof permafrost. Fig. 6 – BTS measurements in late winter 2007 and 2008 in the Reichart Cirque. The measurements in 2008 indicate substantial cooler ground temperatures. Note the pronounced morphology of the relict rock glacier (Orthophotographkindlyprovidedby©GISSteiermark). Geoelectricalmeasurements TheERTresults(Fig.7)indicateanactivelayerof2to4munderlainbyapermafrostbodyalong3/4 oftheentireprofilewithresistivityvaluesbetween50to100kOhm.mandextendingtoadepthof 10to15m.Thepermafrostbodyissubstantiallythickeratthelowerpartoftheprofile(rockglacier; first50mofprofile)comparedtomostoftheupperpart(talusslope).Focusingonthetalusslope, thepermafrostbodyisthickestonthecentralsectionoftheprofile(~5Ͳ6mthickness).Incontrast,at 41 PermaNET–CasestudiesintheEuropeanAlps thelowerpartofthetalusslopethepermafrostbodyismostlikelyverythin(lessthan1m)whereas attheuppermostpartpermafrostisabsent. Fig.7 –Electricalresistivitytomography(ERT)ofthe120mlongprofilemeasuredintheReichartCirque(see Fig.2forlocation).MeasurementscarriedoutbyKNGeoelektrik 2.3Summaryofcurrentpermafrostdistribution Based on the permafrost research carried out so far, one can conclude that the existence of permafrostisproveninthestudyareaMt.Hochreichart.Themountainpermafrostoccursaspatches inthelowerpartsasforinstanceintherootingzoneoftheofapseudoͲrelictrockglacierwherethe substrat consists of coarseͲgrained sediments. This cooling effect of coarse blocks has been recognised since decades (cf. Gruber & Hoelzle 2008).In higher elevations, permafrost is more widespread affecting the entire summit area. MAGST near 0°C at elevations higher ca. 2300 m asl indicatethatpermafrostisthinandingeneralwarm.Theredistributionofsnowandcharacteristics of the winter snow cover as well as the type of substrat (bedrock, fine material, coarseͲgrained blockymaterial)arethedominantlocalfactorforpresenceorabsenceofpermafrost. Fig.8depictsthesnowcoversituationinthestudyareaMt.HochreichartinNovember2006,2007, 2008and2009basedontheownRDCsystem.Thesefourimagesexemplarilyshowthatsnowcover variessubstantiallyfromyeartoyearduringsimilarperiods.Earlysnowfallinautumnproducinga protectingsnowcoverinhibitsgroundcooling.Incontrast,longlyingsnow(e.g.footslopepositionin cirque)inhibitsgroundwarminginspring.Regardingsubstrat,siteswithratherthicklayers(several meters) of coarseͲgrained blocky material in the uppermost part of the Reichart Cirque (talus and rooting zone of the rock glacier) are more likely underlain by permafrost as shown by the ERT measurements.Summarising,thissiteisthemosteasterlyevidenceofexistingpermafrostfoundin theentireEuropeanAlpsat14°41’Eatelevationsaslowas1900masl. 42 PermafrostResponsetoClimateChange Fig.8–SnowcoverdistributioninthecirqueandinthesummitareaofMt.HochreichartinNovember2006, 2007,2008and2009.cf.Fig.2. 3. Possiblefuturethermalresponsetopredictedclimatechange As presented above, permafrost in the study area HochreichartͲReichart Cirque is restricted to the highestelevationsandtolocations,wherethesnowcoverregimeand/orthecharacteristicsofthe substrat material is favourable for permafrost existence. Climate change with the predicted temperatureincreasefortheGreaterAlpineRegion(GAR)byusingtherelativelyoptimisticCLMA1B scenarioindicatesatemperatureincreaseofaround2°Cby2050(seeChapter2.) The estimates for frost day (FD), ice day (ID) and (FTD) for the periods 1961Ͳ1990 and 2021Ͳ2050 basedonairtemperaturedatarevealforthestudyareaHochreichartͲReichartCirquethefollowing results:ThenumberofFDwilldecreaseby13to14daysperyear.Forthesummitarea,thiswould mean207Ͳ227FDinsteadof221Ͳ240FDhenceareductionofFDbyupto6.3%.ThenumberofIDwill decrease also by some 13 to 14 days per year, which means 127Ͳ147 ID instead of 141Ͳ160. In relativenumber,thisisalmost10%.Incontrast,thenumberofFTDwillpresumablyremainmoreor lessatthesamelevelwithasmallincreaseby0.1to2daysperyear. ThepredictedwarmingbasedontheCLMA1BscenariocausingthemodelledchangesinFD,IDand FTDwillseverelyinfluencethepermafrostdistributionandgeomorphicdynamicsinthestudyarea HochreichartͲReichart Cirque. By 2050, permafrost in the study area will be restricted to few high elevated locations in the summit area where the substrat and the snow cover conditions will still allow the existence of permafrost. In contrast, permafrost in the cirque will be completely thawed despitethefactoflargeareasofcoarseͲgrainedsediments. 43 PermaNET–CasestudiesintheEuropeanAlps Acknowledgements. – This study was partly carried out within the framework of the projects ALPCHANGE,financedbytheAustrianScienceFund(FWF)throughprojectno.FWFP18304ͲN10,and PermaNET.ThePermaNETprojectispartoftheEuropeanTerritorialCooperationandcoͲfundedby the European Regional Development Fund (ERDF) in the scope of the Alpine Space Programme www.alpinespace.eu References: Gruber S. & Hoelzle M., 2008: The cooling effect of coarse blocks revisited: a modeling study of a purely conductive mechanism. Proceedings of the Ninth International Conference on Permafrost(NICOP),UniversityofAlaska,Fairbanks,June29–July3,2008,557Ͳ561. Haeberli W., 1973: Die BasisͲTemperatur der winterlichen Schneedecke als möglicher Indikator für die Verbreitung von Permafrost in den Alpen. Zeitschrift für Gletscherkunde und Glazialgeologie,9,221Ͳ227. KellerF.,1992:AutomatedmappingofmountainpermafrostusingtheprogramPERMAKARTwithin the Geographical Information System ARC/INFO. Permafrost and Periglacial Processes, 3, 133Ͳ138. KellererͲPirklbauerA.,2005:Alpinepermafrostoccurrenceatitsspatiallimits:Firstresultsfromthe easternmarginoftheEuropeanAlps,Austria.NorskGeografiskTidsskriftͲNorwegianJournal ofGeography,59,184Ͳ193. KellererͲPirklbauerA.,2008:Aspectsofglacial,paraglacialandperiglacialprocessesandlandformsof theTauernRange,Austria.UnpublishedPhDͲThesis,UniversityofGraz,200p. KellererͲPirklbauer A. & Kühnast B., 2009: Permafrost at its limits: The most easterly evidence of existing permafrost in the European Alps as indicated by ground temperature and geoelectricalmeasurements.GeophysicalResearchAbstracts11:EGU2009Ͳ2779. Lieb G.K., 1998: HighͲmountain permafrost in the Austrian Alps (Europe). Proceedings of the 7th International Permafrost Conference (Yellowknife, 23–27 June 1998), Collection Nordicana 57,663–668.Centred’étudesnordiques,UniversitéLaval,Québec. Smith M.W. & Riseborough D.W., 2002: Climate and the limits of permafrost: a zonal analysis. PermafrostandPeriglacialProcesses,13,1Ͳ15. 44 3. CasestudiesintheEuropeanAlps 3.3 DösenValley,CentralAustrianAlps Citationreference KellererͲPirklbauerA(2011).Chapter3.3:CasestudiesintheEuropeanAlps–DösenValley,Central AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.45Ͳ58. Authors Coordination:AndreasKellererͲPirklbauer Involvedprojectpartnersandcontributors: Ͳ Institute of Geography and Regional Science, University of Graz, Austria (IGRS) – Andreas KellererͲPirklbauer Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 45 PermaNET–CasestudiesintheEuropeanAlps Summary Permafrost research in the Dösen Valley (46°59’N and 13°17’E), Hohe Tauern Range, Central Austriawasinitiatedinthe1990s.Sincethen,anumberofdifferentmethodshavebeenapplied to understand permafrost distribution and rock glacier dynamics. Results show that at present permafrost exists at permafrost favourable sites (northͲexposed, well sheltered, coarseͲblocky material) at elevations down to 2200 m asl. In contrast, on southͲexposed slopes covered by coarseͲblockymaterialthelowerlimitisataround2600masl.Localconditionssuchassubstrate material(i.e.fine/coarsesediments,thick/thinsediments,bedrock)andtopoclimaticconditions (radiation sheltered, timing and characteristics of snow cover) alter the general pattern of decreasing ground surface temperature with increasing elevation substantially and makes the permafrostdistributionpatterninthestudyareacomplex.Rockglaciervelocitiesseemtoreact quickerafteracoolperiodwithdeceleration.Incontrast,rockglaciersseemtoneedmoretime to react after warmer periods with movement acceleration indicating the inertia of the rock glaciersystemtowardsgroundwarmingandvelocitychanges.By2050,southͲfacingslopesnot coveredbycoarseͲblockymaterialwillbepermafrostfree.OnlythehighestnorthͲfacingslopes willstillbeinfluencedbywidespreadpermafrost.Theroleofsubstratematerialandsnowcover dynamics will be even more important for the remaining permafrost than today. Temperature increasewilleventuallyleadtoinactivationofallpresentlyactiverockglaciersinthestudyarea. 46 PermafrostResponsetoClimateChange 1. Introductionandstudyarea PermafrostresearchintheHoheTauernRangeinCentralAustriawasinitiatedinthe1990s.Oneof themainstudyareasforpermafrostresearchistheDösenValleynearMallnitz(Fig.1A).Sincethen, differentmethodshavebeenappliedinordertounderstandpermafrostdistributionandrockglacier dynamicsinthisvalley(Table1).Presentpermafrostresearchinthisstudyareaiscarriedoutwithin the framework of the projects ALPCHANGE (2006Ͳ2010), PermaNET (2008Ͳ2011) and permAfrost (2010Ͳ2012)byresearchersfromtheUniversityofGraz,theGrazUniversityofTechnologyaswellas theUniversityofLeoben. Table1–AppliedmethodsandpublicationsatthestudyareaDösenValley Method Geodeticsurveys Photogrammetricsurveys Geophysical campaigns (seismics, geomagnetics andgeoradar/GPR) Geomorphologicalmappingandobservations Meteorologicalmonitoring Monitoring of snow cover dynamics in the rootingzonebyautomaticdigitalcameras Groundtemperaturemonitoring NearͲsurfacegroundtemperaturemonitoring Relativedatingofrockglaciersurface initiated/carriedout 1995 1954 Publications Buck&Kaufmann2008 Delaloyeetal.2008 1994 Kaufmann & Ladstädter 2007 Kaufmann etal.2007 1994 2006 2006 KellererͲPirklbauer2008 KellererͲPirklbaueretal.2008a,2008b 1995 (continuoussince2006) 1995 (continuoussince2006) 2007 Kenyi&Kaufmann2003 Kienast&Kaufmann2004 Lieb1991,1996,1998 Schmöller&Fruhwirth1996 The study area is situated in the Ankogel Mountains at the inner part of the glacially shaped, EͲW trendingDösenValleyataboutN46°59´andE13°17.Theelevationofthestudyarearangesbetween 2270maslatthecirquethresholdneartheArthurͲvonͲSchmidHuttoslightlymorethan3000masl atthenearbySäuleckpeak.Thispartofthevalleyischaracterisedbyanumberofrockglaciersand distinctterminalmorainesinrelatively flatparts,acirquefloorwithatarn lake,slopescoveredby coarse debris and steep rock faces partly acting as debris supply areas for the rock glaciers. Geologically, the study area is located within the central gneiss complex of the Hochalm/Ankogel area with predominantly westͲdipping biotite gneiss (Lieb 1996). (Fig. 1B). The moraines were presumablyformedduringtheEgesenͲmaximumadvanceandarethusofearlyYoungerDryas(YD) age(Lieb1996).InAustria,theearlyYDis10BeͲdatedtoaround12.3–12.4ka(Kerschner&IvyͲOchs 2007).Atpresent,onlysomeperennialsnowpatchesarefoundinthestudyarea. TheninerockglaciersintheDösenValleydepictedinFig.1Bpredominantlyconsistofgraniticgneiss (Kaufmannetal.2007)andwereformedafterdeglaciationintheLateglacialandHoloceneperiod. Accordingtothe“RockGlacierInventoryofCentralandEasternAustria”(Liebetal.2010,KellererͲ Pirklbaueretal.2010),threeoftheserockglaciers(mo236,mo239.1,mo239.2)areconsideredtobe relictandsixareregardedasintactstillcontainingpermafrost(mo237,mo237.1,mo238,mo238.1, mo238.2, mo239). Previous permafrost research – including velocity measurements – focused particularlyontherockglaciermo238(fordetailsseeLieb1996orKaufmannetal.2007).Thisrock glacierischaracterisedbyanaltitudinalrangeof2355Ͳ2650masl,alengthof950m,awidthof250 m and an area of 0.19 km². The rock glacier is an active monomorphic tongueͲshaped rock glacier situatedattheendoftheinnerDoesenvalleywithpresentmeansurfacevelocityratesofaround15Ͳ 25cmperyear(Fig.2). 47 PermaNET–CasestudiesintheEuropeanAlps According to air temperature measurements by the own meteorological station located at the surface of rock glacier mo238 (for location see Fig. 1) in the 4Ͳyears period September 2006 to August 2010, the mean annual air temperature (MAAT) at the 2603 m asl is Ͳ1.7°C. The coldest monthisJanuarywithamonthlyvalueofuptoͲ11.8°CwhereasthewarmestmonthisAugustwitha monthlymeanvalueofupto7.8°C. Fig. 1 – Study area Dösen Valley and its location within Austria. The distribution of rock glaciers, terminal moraines of Late Glacial age (Younger Dryas), modelled potential discontinuous permafrost, location of the meteorological station (MS) as well as the location of six miniature temperature datalogger (MTD) used for ground surface temperature (GST) measurements are indicated. Code of the rock glacier is according to the “RockGlacierInventoryofCentralandEasternAustria”(Liebetal.2010,KellererͲPirklbaueretal.2010). Fig.2–ThestudyareaDösenValleywithfourintactrockglaciers:(A)viewtowardsE,(B)viewtowardsSE. Note the widespread steep rock faces acting as debris supply areas, the perennial snow fields, the flowing structureoftherockglaciersandwidespreadvegetation(indicatorforabsenceofalpinepermafrost).Locations ofthesixminiaturetemperaturedataloggers/MTDwheregroundsurfacetemperature(GST)ismeasuredand the site of the meteorological station (MS) are indicated. Code of the rock glacier is according to the “Rock GlacierInventoryofCentralandEasternAustria”(Liebetal.2010,KellererͲPirklbaueretal.2010).Photographs byA.KellererͲPirklbauer. 48 PermafrostResponsetoClimateChange In this paper, the present situation and the evolution of the ground surface temperature in the recentpast(2006Ͳ2010)anditssignificanceforpermafrostdistributionarehighlighted.Furthermore, theresultsoftherockglaciermonitoringprogramfortheperiod1954to2010anditsrelationshipto climaticconditionsandclimatechangearediscussed. 2. Permafrostindicatorsandrecentthermalevolution 2.1Methods Since1994asuiteofmethodshasbeenappliedaslistedaboveinTable1.Inthispaper,resultsbased onnumericalpermafrostmodelling,climatemonitoringbyusingameteorologicalstationaswellas continuous measurements of ground surface temperature by using miniature temperature dataloggers(MTD)andphotogrammetricandgeodeticrockglacierdisplacementmeasurementsare presented. Thespatialdistributionofpotentialdiscontinuouspermafrostinthestudyareawasmodelledbyan adaptationoftheprogramPERMAKART(Keller1992)usingGISArcViewandArcInfo.Forthissimple modellingapproach,theempiricalvaluesofthelowerlimitofdiscontinuouspermafrostforcentral Austriawereused(Lieb1998). Themeteorologicalstationhasbeeninstalledin2006atonelargeblockonthesurfaceoftherock glaciermo238withintheALPCHANGEproject.Atthisstation,climatedataincludingairtemperature, airhumidity,windspeed,winddirectionandglobalradiationarecontinuouslyloggedanddataare availablefortheperiod01.09.2006to17.08.2010. MTDs were used at a total of 11 locations during different periods. The results from six sites with groundsurfacetemperature(GST)measurementsloggedat1hintervalarepresentedhere(Figs.1& 2).TheusedloggersareproducedbyGeoPrecision,ModelMͲLog1withPT1000temperaturesensors (accuracy +/Ͳ0.05°C, range Ͳ40 to +100°C, calibration drift <0.01°C/yr). At each of the six sites, the temperaturesensorisshelteredfromdirectsolarradiationbyaplatyrock.SitesGST1andGST2are locatedoncoarseͲblockyslopes.GST2islocatedbetweenalargeboulderandbedrock. All three sites form a vertical profile on southͲfacing slopes. In contrast, sites GST4 to GST6 are locatedonthesurfaceofthemainactiverockglacierinthevalley(mo238)andfromaverticalprofile on northͲfacing slopes. Data of continuous measurements of ground surface temperature at the threesitesGST1ͲGST4andGST6wereavailableforthec.48Ͳmonthperiod01.09.2006to17.08.2010. AtsiteGST5thetimeseriesendson05.09.2009.Toallowcomparisonbetweenthesixsitesaswellas to allow fullͲyear data analysis, the four fullͲyear periods 01.09.2006Ͳ31.08.2007, 01.09.2007Ͳ 31.08.2008, 01.09.2008Ͳ31.08.2009 and 01.09.2009Ͳ17.08.2010 were analysed. Furthermore, the zeroͲdegree isotherm was computed for each site using a vertical temperature gradient of 0.0065°C/m.Table2summariseskeyparametersofthesixGSTsites. Temperaturedata(airandground)analysesfocusedonfrostday(FD),iceday(ID),freezeͲthawday (FTD) and frostͲfree day (FFD). A day got classified as FD, when the daily minimum temperature is belowzero.Ifalsothedailymaximumtemperatureisamongthefreezingpoint,thedaygotclassified as ice day ID. The difference between ice days and frost days, which means all days with a daily minimumtemperaturebelow0°Candadailymaximumabovethislimit,gotclassifiedasFTD.Finally, adaywithpositiveminimumtemperaturegotclassifiedasFFD. 49 PermaNET–CasestudiesintheEuropeanAlps Table 2 – Summary of the sites where ground surface temperature (GST) is monitored by using miniature temperature dataloggers (MTD). Location of the GSTͲsites in indicated in Figs. 1 and 2. The elevation of the computed zeroͲdegree isotherm was computed by using a vertical temperature gradient of 0.0065°C/m. MAGST=meanannualgroundsurfacetemperature. GSTͲsite Exposition Elevation Dataperiod (masl) MAGST(°C) Computed zeroͲdegree isotherm (masl) GST1 South 2489 4years:1.09.2006to17.08.2010 2.0 2797 GST2 South 2586 4years:1.09.2006to17.08.2010 1.2 2771 GST3 South 3002 4years:1.09.2006to17.08.2010 Ͳ2.6 2602 GST4 North 2626 4years:1.09.2006to17.08.2010 Ͳ0.9 2488 GST5 North 2501 3years:1.09.2006to05.09.2009 Ͳ1.5 2270 GST6 North 2407 4years:1.09.2006to17.08.2010 Ͳ1.3 2207 Surface displacement measurements of the rock glacier mo238 is carried out since 1954 by using aerialphotogrammetryandsince1995byusingterrestrialgeodeticsurvey(Kaufmann&Ladstädter 2007,Kaufmannetal.2007).Thegeodeticmeasurementsusingatotalstationareannuallycarried out in the middle of August following a proven scheme. Since 1995, the measurements were repeatedapartfrom2003duetolackoffunding.TheannualcampaignsareledbyV.Kaufmann,TU Graz. In addition to the geodetic measurements satellite based radar interferometry (Kenyi & Kaufmann 2003) and photogrammetric displacement measurements based on aerial photographs (1954,1969,1975,1983,1993,1997and1998)werecarriedout(Kaufmannetal.2007,Kaufmann& Ladstädter2007)previously. Finally,aRDCsystemwassetupinSeptember2006inordertomonitorthesnowcoverdynamicsat therootingzoneoftherockglaciermo238.ThecorepartsoftheRDCsystemareastandardhandͲ held digital camera (Nikon Coolpix), a remote control, a water proof casing with a transparent opening,a12V/25Ahbatteryandsolarpanelswithachargecontroller. 2.2Resultsoncurrentpermafrostdistribution Permafrostmodelling The lower limit of potential discontinuous permafrost according to the chosen regional permafrost modellingapproachindicatespermafrostonslopesbetween2500masl(northͲfacing)and2900m asl.(southͲfacing)andonfootslopepositionsbetween2410masl(northͲfacing)and2690m(southͲ facing).Themodellingresultsshowthatonlythelargeintactrockglaciermo238aswellasthetwo smaller ones slightly to the west (mo238.1 and mo238.1) as well as the southͲfacing rock glacier mo237.1arepredominantlyinpermafrostareaswhichisinaccordancetothefreshappearanceof thefourrockglaciers(Fig.2). Airtemperatureregimebasedonthemeteorologicalstation Themeteorologicalstationislocatedat2603maslintheupperpartoftherockglacier(Figs.1&2). Results from this station show, that the number of frost days (FD), ice days (ID), freezeͲthaw days (FTD)andfrostͲfreedays(FFD)wasrelativelystableinthe4yearperiod2006to2010(Fig.3).The meanvalueofFDis246meaningthatduring2/3oftheyearfrostoccursat2600masl.inthestudy area. In contrast, the mean annual air temperature values indicate a substantially warmer year 50 PermafrostResponsetoClimateChange 2006/07,twocomparableyears2007/08and2008/09andasubstantiallycooleryear2009/10(Fig.3) yieldingameanvalueofͲ1.7°C.TheelevationofthezeroͲdegreeisothermis2340masl.ifusinga verticallapserateof0.0065°C/m. Fig.3–Airtemperatureregimeatthemeteorologicalstationattherockglaciermo238.(A)Numberoffrost days(includingicedays),icedays,freezeͲthawdaysandfrostͲfree;(B)meanannualairtemperature(MAAT); bothforthesingleyearsandthemeanoftheentire4Ͳyearsperiod. Groundthermalregimebasedonminiaturetemperaturedatalogger ResultsofthecontinuousmeasurementsofgroundsurfacetemperatureatthesixsitesGST1toGST6 areshowninFigs.4and5.Fig.4showsthenumberoffrostdays(includingicedays),icedays,freezeͲ thawdaysandfrostͲfreedays.Ingeneral,thelowestvaluesinFDandIDweremeasuredinwinter 2006/07. In contrast, the highest values of FTD were measured generally in winter 2006/07 apart fromthesnowrichsiteGST5.Atallsixsites,thenumberofFFDwasagainhighestinwinter2006/07, atsiteGST1theFFDvaluewasevenhigherthantheFDvalue. ThemeanvalueofFDislowestatthesouthexposedsiteGST1withonly198days,followedbyGST2 with208days.Incontrast,atsiteGST3at3000masl,themeanvalueofFDdaysisalmost270.The FDvalueforthenorthexposedsitesGST4toGST6isquitesimilaratallthreesiteswith237to245. Regardinginterannualvariation,thenumberofFDduringthefouryearperiodvariedonlyby15days betweenthehighestandcoldestsiteGST3.Incontrast,atsouthexposedandwarmersiteGST1the numberofFDvariedduringthesameperiodby60days(168FDin2006/07vs.228FDin2007/08). Considering the fact that the winter 2006/07 was exceptionally warm and the winter 2007/08 was relatively“normal”,these resultssupposethatpermafrostsitesatlowerlocationinthestudyarea DösenValleyaremoresusceptibletoclimatewarming. Regardingicedays,thelowestIDvaluesareagainfoundatthesouthfacingsitesGST1andGST2with about 170 days. The coldest site with the highest number of ID is site GST5 with 234 days. This maximuminIDatthissiteisattributedtolocaltopoclimaticconditions(smalldepressiononnorth facing slope favouring ground cooling) and long snow cover duration (delay in ground warming in springtomidsummer).SimilarIDvaluesarefoundatthehighestsiteGST3andthetwonorthfacing sites GST4 and GST6. The interannual variation of the number of ID during the four year measurementperiodvariedsubstantiallyby36(GST4)to73days(GST1). ThemeanvalueofthefreezeͲthawdaysisgenerallylowrangingfrombetween11atthesnowrich siteGST5to37atthewarmsiteGST2,but50atthehighestsiteGST3.AtsiteGST5,theFTDvalue was even only five in the winter 2007/08 related to the longͲlasting snow cover at this site. In contrast, at site GST3 the number of FTD value reached 70 in the warm winter 2006/07. The differences in the number of FTD at the sites alsoindicate that frost weathering caused by freezeͲ 51 PermaNET–CasestudiesintheEuropeanAlps thawactionisimportantatthesouthͲexposedsitesGST1,GST2andinparticularGST3.Incontrast,at thecoolerandsnowrichersitesthisweatheringprocessislessactiveatpresentclimateconditions. Finally,frostͲfreedaysishighestatthewarmsitesGST1andGST2,comparableatthethreenorthͲ exposedsitesGST4toGST6andsubstantiallylowestatsiteGST3. Fig.4–GroundthermalRegimeatthesixsitesGST1toGST6betweenSeptember2006andAugust2010with numberoffrostdays(includingicedays),icedays,freezeͲthawdaysandfrostͲfreedays.Resultsofsingleyears andthemeanfortheentireperiodareshown. Fig.5showsthemeanannualgroundsurfacetemperature(MAGST)aswellastheelevationofthe computedͲzero degree isotherm based on a lapse rate of 0.0065°C/m for all six sites. Results are shownforthesinglemeasurementyearsbetween2006and2010aswellasthemeanoftheentire period. Results show that the northͲfacing slopes are cooler than the southͲfacing slopes at comparableelevation.OnthesouthͲexposedslopes,theverticaltemperaturegradientforthefour yearperiodis0.0082°C/m(betweenGST1undGST2)und0.0091°C/m(betweenGST2undGST3).In contrast, on the northͲexposed slopes the situation is more complex due to local topoclimatic conditions also influencing the characteristics of the winter snow cover (duration, thickness). A negativegradientofͲ0.0048°C/mwascalculatedbetweenthesitesGST4andGST5,whereasaslight positivegradientof0.0021°C/mwascalculatedbetweenthesitesGST5andGST6 Fig.5clearlydepictsthattheMAGSTatsitesGST1andGST2arepositivewithmeanvaluesof+1.2°C (GST2) to +2.0°C (GST1) indicating absence of permafrost. However, site GST1 is located on blocky material.Duetothethermalbehaviourofsoilmaterial(inparticularcoarseͲgrainedblockymaterial with open voids in between; Gruber & Hoelzle 2008), the temperature at the ground surface (i.e. MAGST) is warmer compared to the temperature at the top of permafrost (TTOP), possibly up to several degrees (“thermal offset”; Smith and Riseborough 2002). Therefore, despite the fact that positiveMAGSTaremeasuredatthesurface,permafrostmightstillexistinthegroundatoraround thesiteGST1.Incontrast,theMAGSTvaluesattheotherfoursitesGST3toGST6areclearlynegative 52 PermafrostResponsetoClimateChange (apartfrom2006/07atsiteGST6)withmeanvaluesofͲ0.9°CatsiteGST4toͲ2.6°Catthe3000ͲmͲ siteGST3indicatingatthesefoursitespresenceofpermafrost. Fig.5–Meanannualgroundsurfacetemperature(MAGST)andcomputedzeroͲdegreeisotherm(usingalapse rateof0.0065°C/m)atthesixsitesGST1toGST6.Resultsofsingleyearsandthemeanfortheentireperiodare shown.TheelevationrangeofthecomputedzeroͲdegreeisothermduringthefouryearsisindicated. ThediagramshowingthecomputedͲzerodegreeisothermforthesixsitesindicatesthatthelowest computedzeroͲdegreeisothermwascalculatedforthenorthͲfacingandlowelevatedsiteGST6with a mean value of 2207 m asl. In contrast, the highest computed zeroͲdegree isotherms were calculatedforthetwosouthͲfacingsitesGST1(2797masl)andGST2(2771 masl).Explanationfor thisisthelocaltopoclimaticconditionandthebufferingeffectofthewintersnowcoveratagiven site. At sites GST1, GST2, GST3 and GST6) snow cover is of minor importance (wind exposed sites with little/minor snow cover) compared to sites GST4 and GST5 (footͲslope position with more efficientsnowaccumulationandlonglyingsnowcover).Thisalsohighlightstheimportanceofsnow influencingthethermalregimeoftheground(“nivaloffset”;SmithandRiseborough2002).Basedon thecalculations,thezerodegreeisothermatthegroundsurfaceonnorthͲexposedslopesislocated between about 2200 and 2500 m asl, on southͲfacing slopes between 2600 and 2800 m asl. The computedͲzero degree isotherm varied during the four years between 177 m (GST4) and 472 m (GST6) indicating substantial interannual changes. Single years such as the warm winter 2006/07 causeasubstantiallyincreaseofthisisothermby80to260m. Summarising, one might expect permafrost in the study area on northͲexposed slopes covered by coarseͲblocky material at elevations of 2200Ͳ2300 m asl, on southͲexposed slopes at 2600Ͳ2750 m asl. Rockglacierkinematic Active rock glaciers are creeping phenomena of continuous or discontinuous permafrost. Their movement mode is strongly related to climatic conditions and as a consequence to ground temperatures(Kääbetal.2007).Fig.6depictstheevolutionofthemeanannualhorizontalsurface velocity at the Dösen rock glacier mo238 between 1954 and 2010 based on geodetic and photogrammetric measurements. Note that the mean annual values in the period before 1995 are generally lower compared to the years after 1995 indicating generally lower displacement rates in theperiod1954to1995.However,singleyearswithdisplacementratescomparabletothevaluesof 53 PermaNET–CasestudiesintheEuropeanAlps the postͲ1995 period are conceivable. Furthermore, note the maximum in the movement rates between 2002 and 2004, the following deceleration until 2008 followed by a remarkable new acceleration during the last two measurement yeas. This movement pattern over the last 1.5 decadescorrelateswithothermonitoredrockglaciersintheHoheTauernRange(KellererͲPirklbauer & Lieb 2011) and in the entire Alpine Arc (Delaloye et al. 2008). This circumstance confirms the assumption that climatic conditions and changes in the European Alps are the dominant steering factorsforrockglaciermovement. Fig.6–Changeofmeanannualhorizontalsurfacevelocity(cmaͲ1)attheDösenrockglaciermo238between 1954and2010basedongeodeticandphotogrammetricmeasurements.Meanof11measurementpoints(Pt. 10Ͳ17,21Ͳ23).DatasourceKaufmannetal.(2007)andunpublisheddata. Relationshipbetweenrockglacierkinematicandclimate Theownmeteorologicalstationattherockglaciermo238wasusedtocollectairtemperaturedata fortheperiodOctober2006toAugust2010.Meanmonthlyairtemperaturedatawerecalculatedfor theperiodJanuary1990toSeptember2006fortheDösensitebyapplyingcorrelationanalysiswith theairtemperaturedatafromthemeteorologicalobservatorySonnblick,about24kmWNWofthe DösenValley.Fig.7depictstherelationshipbetweenthegeodeticmeasurementsatmo238andthe mean annual air temperature/MAAT (running 12Ͳmont mean). This graph shows that the warm MAATvaluesattheendof1994/beginningof1995causedanincreaseinsurfacedisplacementinthe years1997to1999.Incontrast,thecoolerMAATvaluesbetweenendof1996andmid1997caused lower velocities in 1999Ͳ2000. The MAAT values in the period 1999 to 2004 were generally high causingasteadyincreaseofthevelocityratespeakingin2003Ͳ2004.Thiswaspreviouslyexplained byconstantwarmingandanincreaseofliquidwaterinthepermafrostbodyoftherockglacier(Buck &Kaufmann2008).Accordingtotheseauthors,therockglaciervelocityexperiencedinthisperioda selfͲreinforcingdynamicleadingtoafurtherincreaseinvelocity.The MAAT valuesdecreasedafter 2004causingrockglacierdecelerationuntil2007Ͳ2008.TheextremeincreaseoftheMAATbetween early2007tomidof2008causedanewaccelerationintheperiod2008to2010. 54 PermafrostResponsetoClimateChange Fig.7–Meanannualairtemperature/MAAT(running12Ͳmonthmean)andhorizontalsurfacevelocitiesatthe Dösenrockglaciermo238duringtheperiod1990to2010.DatasourceofvelocityvaluesKaufmannetal.(2007) andunpublisheddata.Data 2.3Summaryofcurrentpermafrostdistributionanddynamics Basedonthepermafrostresearchcarriedoutsofar,wecanconcludethatpermafrostinthestudy areaDösenValleyexistsatextremesites(northͲexposedslopes,wellshelteredfromsolarradiation, andcoarseͲblockymaterial)atelevationsdownto2200masl.Incontrast,onsouthͲexposedslopes coveredbycoarseͲblockymaterialthelowerlimitisataround2600masl.Animportantroleplays thewintersnowcoverinthelocalpermafrostdistributionparticularlyatsuchcoarseͲblockysites.On theonehand,snowpoorsitesinradiationshelteredlocations(suchasGST6)allowefficientground coolinginautumnaccompaniedbymoderatewarminginspring.Ontheotherhand,snowrichsites atfootslopepositionsinradiationshelteredlocations(suchasGST5)reduceefficientgroundcooling butshelterthegroundfromwarminginspringandevensummer. OnslopesnotcoveredbycoarseͲblockymaterial,thelowerlimitofpermafrostissubstantiallyhigher at elevations of between 2500 m asl. (northͲfacing) to 2900 m asl. (southͲfacing). At footslope positions influenced by long lasting snow, the permafrost limit seems to be at around 2400 m asl (northͲfacing) to 2700 m asl (southͲfacing). These results clearly show that local conditions influencingsolarradiation,degreeofgroundcooling,thermalregimeofthegroundsurfaceandnear groundsurfaceaswellaswintersnowcoverconditionshaveamajorimpactonthedistributionof permafrost in the study area. This impact alters the general pattern of decreasing ground surface temperaturewithincreasingelevationsubstantiallyandmakesthepermafrostdistributionpatternin the study area (and at comparable sites in the neighbouring area) complex at elevations between 2200mand2900masl. The behaviour of the monitored rock glacier mo238 in the inner Dösen Valley is in accordance to othermonitoredrockglaciersintheHoheTauernRangeandtheentireAlpineArc.Duringthelast1.5 decades,twopeaksofhighsurfacedisplacementratesweredetectedat2003Ͳ2004and2008Ͳ2010 withratesexceeding30cmperyear.Therockglaciervelocitypatternindicatesthattherockglacier mo238reactsquickerafteracoolperiodwithdeceleration.Incontrast,therockglacierneedsmore timetoreacttowarmerperiodswithaccelerationofthemovementindicatingtheinertiaoftherock glaciersystemtowardsgroundwarmingandvelocitychanges. 55 PermaNET–CasestudiesintheEuropeanAlps 3. Possiblefuturethermalresponsetopredictedclimatechange Aspresentedabove,permafrostinthestudyareaDösenValleyplaysanimportantroleandcovers presumably about 1/3 of the area above 2270 m asl. Besides the sole existence of permafrost in bedrock and in slope deposits, permafrost in the study area is also important for geomorphic periglacialprocessessuchascreepingoftheactiverockglaciers(inparticularrockglaciermo238)or rockfallscausedbyfrostweatheringobservedfrequentlyduringeachfieldcampaign. Climate change with the predicted temperature increase for the Greater Alpine Region (GAR) by usingtherelativelyoptimisticCLMA1Bscenarioindicatesatemperatureincreaseofaround2°Cby 2050 (see Chapter 3). The air temperature at the meteorological station in the study area Dösen Valleywouldbeslightlypositivewitharound+0.3°C.Ifusingalapserateof0.0065°C/mandtheair temperatureincreaseof+2°C,theelevationofthezeroͲdegreeisothermwouldshiftbyabout310m frompresently2340maslto2650maslcausingsubstantialpermafrostdegradationinthebedrock (fasterreaction)andintheintactrockglaciers(slowerreactionwithalongertimelag). The estimates for frost day (FD), ice day (ID) and (FTD) for the periods 1961Ͳ1990 and 2021Ͳ2050 based on air temperature data reveal for the study area Dösen Valley the following results: The numberofFDwilldecreaseby14to15daysperyear.Forthesummitarea,thiswouldmean246Ͳ266 FDinsteadof261Ͳ280FD.Fortheelevationaroundtheactiverockglaciermo238(2350Ͳ2650,this wouldyield226Ͳ246FDinsteadof241Ͳ260FD,henceareductionofFDbyupto5.7%.Thenumberof IDwilldecreasealsobysome15to16daysperyear,henceareductionfrom201Ͳ220to185Ͳ205ID inthesummitareasand,respectively,from161Ͳ180to145Ͳ165atelevationsataround2350to2650 masl,henceareductionofIDbyupto10%.Incontrast,thenumberofFTDwillpresumablyincrease slightlyby0.1to2daysperyear.Intheperiod1961Ͳ1990,thenumberofFTDinthesummitareasis about 70Ͳ80, at elevations at around 2350 to 2650 m asl about 80Ͳ90. Based on the own air temperaturemeasurementsatthemeteorologicalstationat2603maslatthesurfaceofmo238,the mean number of FD during the four year period September 2006 to August 2010 was 246. Furthermore, 165 ID and 82 FTD were measured. This suggests that the modelling results for the standardperiod1961Ͳ1990appliedfortheGARareinaccordancewiththemeasurementsof2006Ͳ 2010attheDösenValley.However,onehastokeepinmindthatMAATatthenearbymeteorological observatorySonnblickwasaboutͲ1.3°Ccoolerduringthenormalperiod1961Ͳ1990comparedtothe periodSeptember2006toAugust2010.ThisdifferenceintheMAATvaluesduringthetwoperiods certainly influences the number of FD, ID and FTD. Therefore, this circumstance clearly shows that comparinglocaldatawithregionalmodellingresultsisnottrivial. Regarding rock glacier velocity and climatic conditions in the Dösen Valley, one can expect that an increase of ground temperatures in the active rock glaciers will cause permafrost warming and eventuallypartialthawingofthepermafrost.Thiswillleadtoanincreaseofliquidwaterintherock glacierwhichitselfmightincreasethemobilityandhencesurfacevelocityoftherockglacier.Further permafrost warming and thawing will lead to increasing friction within the rock glacier due to ice loss, to complete permafrost degradation and finally to the formation of an inactive or even relict rockglacierwithlittletonopermafrostice. Thepredictedclimatechangeuntil2050willsubstantiallydecreasethearealextentofpermafrostin thestudyareaDösenValleyaccompainedbydestabilisationofbedrockandslopedepositsaswellas changes in frost weathering conditions and consequently rock fall activity. SouthͲfacing slopes not covered by coarseͲblocky material will be permafrost free in the entire study area and only the highest northͲfacing slopes will still be influenced by widespread permafrost. The role of substrate material (coarse, fine, bedrock) and snow cover dynamics will be even more important for the remainingpermafrostthantoday.Furthermore,temperatureincreasewillpresumablycausefirstan increaseofthecreepvelocitiesofcurrentlymovingrockglacier.Inalaterstage,however,thiswill leadtoinactivationofallpresentlyactiverockglaciersinthestudyareaDösenValley. 56 PermafrostResponsetoClimateChange Acknowledgements. – This study was mainly carried out within the framework of the projects ALPCHANGE,financedbytheAustrianScienceFund(FWF)throughprojectno.FWFP18304ͲN10,and PermaNET.ThePermaNETprojectispartoftheEuropeanTerritorialCooperationandcoͲfundedby the European Regional Development Fund (ERDF) in the scope of the Alpine Space Programme www.alpinespace.eu. 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KellererͲPirklbauer A., 2008: The SchmidtͲhammer as a Relative Age Dating Tool for Rock Glacier Surfaces: Examples from Northern and Central Europe. Proceedings of the Ninth International Conference on Permafrost(NICOP),UniversityofAlaska,Fairbanks,June29–July3,2008,913Ͳ918. KellererͲPirklbauerA.&LiebG.K.,2011:Recentrockglaciervelocitybehaviourandrelatednaturalhazardsin the Hohe Tauern Range, central Austria. PermaNET Project Report Ͳ Contribution of IGRS to Action 6.2/Group1–Rockglacier. KellererͲPirklbauer A., Avian M., Lieb G.K. & Rieckh M., 2008a: Temperatures in Alpine Rockwalls during the Warm Winter 2006/2007 in Austria and their Significance for Mountain Permafrost: Preliminary Results. Extended Abstracts, Ninth International Conference on Permafrost (NICOP), University of Alaska,Fairbanks,June29–July3,2008,131Ͳ132. KellererͲPirklbauerA.,AvianM.,LiebG.K.&PilzA.,2008b:AutomaticDigitalPhotographyforMonitoringSnow Cover Distribution, Redistribution and Duration in alpine Areas (Hinteres Langtal Cirque, Austria). GeophysicalResearchAbstracts10:EGU2008ͲAͲ11359. KellererͲPirklbauerA.,LiebG.K.&KleinferchnerH.,2010:Anewrockglacierinventoryattheeasternmarginof theEuropeanAlps.GeophysicalResearchAbstracts12:EGU2010Ͳ13110. Kenyi L.M. & Kaufmann V., 2003: Measuring rock glacier surface deformation using SAR interferometry. Proceedingsofthe8thInternationalConferenceonPermafrost,Zurich,Switzerland,537Ͳ541. 57 PermaNET–CasestudiesintheEuropeanAlps Kerschner H. & IvyͲOchs S., 2007: Palaeoclimate from glaciers: Examples from the Eastern Alps during the AlpineLateglacialandearlyHolocene.GlobalandPlanetaryChange,60,58Ͳ71. Kienast G. & Kaufmann V., 2004: Geodetic measurements on glaciers and rock glaciers in the Hohe Tauern National Park (Austria). Proceedings, 4th ICA Mountain Cartography Workshop, 30 September Ͳ 2 October 2004, Vall de Núria, Catalonia, Spain, Monografies tècniques 8, Institut Cartogràfic de Catalunya,Barcelona,101Ͳ108. LiebG.K.,1991:DiehorizontaleundvertikaleVerteilungderBlockgletscherindenHohenTauern(Österreich). ZeitschriftfürGeomorphologieN.F.,35,345Ͳ365. Lieb G.K., 1996: Permafrost und Blockgletscher in den östlichen österreichischen Alpen. Arbeiten aus dem InstitutfürGeographiederKarlͲFranzensͲUniversitätGraz,33,9Ͳ125. LiebG.K.,1998:HighͲmountainpermafrostintheAustrianAlps(Europe).Proceedingsofthe7thInternational ConferenceonPermafrost,Yellowknife,663Ͳ668. LiebG.K.,KellererͲPirklbauerA.&KleinferchnerH.,2010:BlockgletscherinventarvonZentralundOstösterreich erstelltimRahmendesProjektesPermaNET.InstitutsfürGeographieundRaumforschung,Graz SchmöllerR.&FruhwirthR.K.,1996:KomplexgeophysikalischeUntersuchungaufdemDösenerBlockgletscher (Hohe Tauern, Österreich). Arbeiten aus dem Institut für Geographie der KarlͲFranzensͲUniversität Graz,33,165Ͳ190. SmithM.W.&RiseboroughD.W.,2002:Climateandthelimitsofpermafrost:azonalanalysis.Permafrostand PeriglacialProcesses,13,1Ͳ15. 58 3. CasestudiesintheEuropeanAlps 3.4 HoherSonnblick,CentralAustria Citationreference Klee A, Riedl C. (2011). Chapter 3.4: Case studies in the European Alps – Hoher Sonnblick, Central AustrianAlps.InKellererͲPirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponseto presentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3. OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.59Ͳ65. Authors Coordination:AlexanderKlee Involvedprojectpartnersandcontributors: Ͳ CentralInstituteforMeteorologyandGeodynamics(ZAMG)–AlexanderKlee,ClaudiaRiedl Content Summary 1. Introductionandstudyarea 2. Measurementsandresults 3. Possiblefuturethermalresponsetopredictedclimatechange References 59 PermaNET–CasestudiesintheEuropeanAlps Summary Climate change in the Alps is not only related to the retreat of glaciers, but rather to the permafrost distribution. Indices for the permafrost retreat in the higher mountain area, e. g. erosion, frost shattering or instabilities of the infrastructure are observable. The relevance of permafrostlongͲtermmonitoringiswidelyspread.Theknowledgeaboutpermafrostinteraction, influencesonpermafrostandthetemporalbehaviourofpermafrostisveryimportantforseveral kindsofinfrastructure,e.g.cablelifts,liftstationsormountainhuts.Furthermorethisknowledge is the basis for measuring the drinking water reservoirs of permafrost in the higher mountain areas,itsqualityanditsusageforthefuture.DetaileddataabouttheglacierͲretreatisavailable. But the permafrost distribution Ͳ including its thickness and spatial dimension Ͳ is largely unknown. On the top of Hoher Sonnblick (3.105 m asl) in the Hohe Tauern (Austria) three boreholeshavebeeninstalledtomeasurerocktemperaturesdownto20munderthesurface. Thisdataabouttemperature,geophysicalandgeodeticalmeasurements(availablesince2007)is a first approach for the documentation of permafrost behaviour in the Alps. Furthermore the summit region of Hoher Sonnblick will be modelled with the aim to compute the behaviour of permafrostinthefuturewithdifferentscenariosinclimatechange. 60 PermafrostResponsetoClimateChange 1. Introductionandstudyarea ThetopofHoherSonnblick(3.105ma.s.l.)islocatedintherangeoftheEasternAlpsintheregionof HoheTauern(Austria).NeighbouringmountainsofHoherSonnblickreachsimilarelevationsofabout 3.000ma.s.l..ThenorthslopeofHoherSonnblickischaracterizedbyaverydeepandsteepnorth face. To the south the slope is moderate with about 30° down to the upper margin of the glacier Goldbergkees.Fig.1showsthesummitareaofHoherSonnblick. InthevicinityofHoherSonnblickarethreeglaciers.Thelargestglacierisofthethreeistheglacier Goldbergkees.ThetwosmalleronesareKleinfleißkeesandPilatuskeesbothwithoutatypicalglacier tongue.Glaciericeoccurrencedowntoabout2.500ma.s.l..Therockintheregionconsistsmainlyof biotitͲgneiss(Exner,1964).Thethicknessofthedebrislayermantlingthebedrockinthesummitarea (wherethethreeboreholesweredrilled;Fig.1)isupto2m. Fig. 1 – The summit of Hoher Sonnblick (3105 m a.s.l.) with the location of the three boreholes. To the right Zittelhausandtothelefttheobservatorium.ThesummitinthebackgroundisMt.Hocharn(3254ma.s.l.) The observatory was built at the end of 19th century and a mountain hut, the Zittelhaus, is also locatedontopofthesummit.In2001astudyobservedthatfissuringofthecrestdemandsforthe necessity of a geological stabilization of the steep north face to protect the observatory. This reͲ development was done from 2003 to 2007. The main reason for the fissuring is the change in meteorological conditions in the 20th century. Higher temperatures and more liquid precipitation advance the physical weathering process of the rock. Higher temperature contrasts causes frost shattering,whichismoreactivethaninpasttimes. 61 PermaNET–CasestudiesintheEuropeanAlps Climatologicalmeasurements,especiallyoftemperature,startedin1886.Actually,eachyearcounts 310 freezing days (daily minimum below 0° C) and 239 ice days (daily maximum below 0° C). All valuesrefertotheperiodbetween1971and2000.Uptonowanunbrokentemperaturerowexists. Next to temperature measurements and measurements of other meteorological parameters, the Sonnblickobservatoryisacentreofseveralscientificactivities.E.g.measurementsinatmospheric chemistry,snowchemicalmeasurements,massbalancemeasurementsofthesurroundingglaciers, avalanche reports, of course the permafrost longͲterm monitoring since 2007 and many more researchactivitiesactuallytakeplaceatHoherSonnblick. 2. Measurementsandresults Tomeasurethebehaviourofpermafrostandtheinfluencesofclimatechangeforpermafrostontop ofHoherSonnblick,three20mdeepboreholesweredrilledon14thand15thSeptember2005.At theendofAugust2006theboreholeswereequippedwithtemperaturesensorsindifferentdepths (Fig. 2). Additionally, a 10 m deep borehole next to borehole 2 was drilled and equipped with extensometers. Daily actualized measurements of temperature data and extensometer data are availableonlineatwww.sonnblick.net.Allboreholesarelocatedonthesouthernslope(seeFig.1). Themeanslopebetweenborehole1and3is27°andthetotalelevationdifferenceis34m.Borehole 1isdirectlylocatedtotheSonnblickobservatory,borehole3isadjacenttoacontinuoussnowfield andborehole2islocatedinbetween. Not only measurements in the boreholes are available. In October 2006 35 miniature temperature datalogger/MTD(20ofthetypeUTLͲ1andUTLͲ2and15ofthetypeHOBOTidbiT)wereinstalledto measure the basic temperature of the snow cover in wintertime and the ground surface temperatures during summer. The 20 logger of type UTLͲ1 and UTLͲ2 were installed on moderate slope on the southern side of the summit. In the steep north face, the 15 HOBO TidbiTs were installed. Furthermore, the air temperature change in the past since 1886 is also available. Fig. 3 shows an example of temporal variability of the temperature with increasing depth for the hydrological year in 2008. Measurements of the boreholes show that the summerly temperature amplitudeisobservabledownto15mwithadelayofabout6to7months. Thecoolingfromthewinterseasoniseffectiveto5mwithadelayofabout4months.Thethickness oftheactivelayerinsummertimewasaboutinborehole1in20081mand70cmin2009.Inthe boreholes2and3theactivelayerislessthan1m.There,theactivelayerwasabout60cmin2008. In 2009 there are no data available for borehole 2 and 3. Naturally, in the upper layers of the boreholesthedifferencesbetweensummerandwinterseasonsarelargerthanindeeperlevels.Itis also interesting to compare yearly average temperatures as it is done in Fig. 4. On the xͲaxis the temperature is assigned and on the yͲaxis the depth of the borehole. The figure shows the temperature of borehole 1 in 2008 (blue line) and in 2009 (red line). Down to about9mthetemperatureprofilein2008ismuchwarmerthanin2009.In3mthereisadifference of0.7°C.Inautumn2009thesummitregionwassnowlessorwithonlyathinsnowcoverforalong timewhichcausedthesedifferences. 62 PermafrostResponsetoClimateChange Fig. 2 Ͳ Construction of measurement chain in the boreholes with depths of the temperature sensors and geophones.Additionally,theentranceofoneboreholeisshown. 63 PermaNET–CasestudiesintheEuropeanAlps Fig 3 – Temporal temperature variability with increasing depth for borehole 1 during the hydrological year 2007/2008. Fig.4–Meantemperaturesofborehole1in2008(blueline)and2009(redline). 64 PermafrostResponsetoClimateChange Inwinter2008/09anearlyandthicksnowcoverexistedsothecoldnesscouldnotpenetrateintothe ground. This fact causes the higher mean temperature in the upper layers in 2009. Another fact is illustrated in Fig. 4. Below 10 m the temperature of the years 2008 and 2009 are similar. One explanationcouldbethatthepenetrationdepthofseasonallytemperatureonlyreachesadepthof 15m.ThisbehaviourisalsoillustratedinFig.3.Below15mtherearenearlynotemporalfluctuations andbetween10and15mthefluctuationsareverysmall. Asitwasmentionedabove,nexttoborehole2isanothermoreshallowborehole,whichwasdrilled down to 10 m and is equipped with extensometers. Measurements show that in autumn the extensometersmeasurenegativevalues,whichcanbeidentifiedwithcompression.Notenoughdata are available yet for late spring and summer, but a first guess would be stretching with positive values.Thishypothesiswillbetestedinsummer2011,whenwinterseasonisgone. 3. Possiblefuturethermalresponsetopredictedclimatechange Because measurements exist only since 2007 it is not possible to make statements concerning permafrostretreatinthepastclimatewarmingatSonnblickuntilnow.Butwiththehelpofclimate models which are able to compute temperature development in the future with different assumptions, it is achievable to produce possible future scenarios. As it is described in section 3.1, above1.800ma.s.l.iceandfrostdayswillbereducedbyabout14daysperyearbetween2021and 2050 and also freezeͲthaw days will increase about 3 to 5 days per year in this timeͲperiod (the referenceintervalis1961to1990).ActuallyonHoherSonnblick310freezingdayswillbereducedto 296and239icedayswillbereducedtoabout225dayswithdailymaximumbelow0°C.Underthese scenariospermafrostinhighermountainareaswillretreat.Especiallyupperrocklayerswillreactfast to the warming of the air. In deep layers, where the temperature change during one year is not observable,warmingwillbeslower.TheincreaseoffreezeͲthawdayswillbenefitweathering,frost shattering and fissuring. In regions with permafrost existence higher activity in rockfall will affect humaninfrastructure,mountainclimbersandchangeofthelandscape. Acknowledgement.ThisworkwaspartlygrantedbytheprojectPermafrostinAustriabytheAustrian AcademyofScience. References: ExnerCh.,1964.ErläuterungenzurgeologischenKartederSonnblickgruppe1:50.000.Geol.B.ͲA.168 S.,Vienna. 65 PermaNET–Permafrostresponsetoclimatechange 3. CasestudiesintheEuropeanAlps 3.5 RockGlacierHochebenkar,WesternAustria Citationreference Krainer K. (2011). Chapter 3.5: Case studies in the European Alps – Rock Glacier Hochebenkar, Western Austrian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost responsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreport ofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.66Ͳ76. Authors Coordination:KarlKrainer Involvedprojectpartnersandcontributors: Ͳ InstituteofGeologyandPaleontology,UniversityofInnsbruck(UIBK)–KarlKrainer Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentgeomorphicevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 66 PermafrostResponsetoClimateChange Summary Rock glacier Hochebenkar is a tongueͲshaped active rock glacier located in a small Northwest facingcirqueintheÖtztalAlps(Austria;46°50´14´´N,11°00´46´´E).Morphologyandhighsurface flowvelocitiesindicatethattherockglaciercontainsamassiveicecoreandthuspointtoaglacial origin.Duringwinter,thetemperatureatthebaseofthesnowcover(BTS)issignificantlylower ontherockglacierthanonpermafrostͲfreegroundadjacenttotherockglacier.Dischargeofthe rockglacierischaracterizedbystrongseasonalanddiurnalvariationsandisstronglycontrolled by the local weather conditions, particularly the amount of snow and rainfall events. Water temperature of the rock glacier springs remains constantly low, mostly below 1°C during the entire melt season. During the last decades changes in the velocity of the rock glacier show a closecorrelationwithchangesinthemeanannualairtemperatureofnearbyweatherstations. The strong decrease in thickness in the lowermost, steep part of the rock glacier is caused by increasedmeltingoficeandindicatesthepresenceofamassiveicecore.Ifincreasedmeltingwill continueduringthenextdecadesflowvelocitywilldecreaseandtheactiverockglacierwillpass intoaninactiveone. 67 PermaNET–Permafrostresponsetoclimatechange 1. Introductionandstudyarea PermafrostiswidespreadintheAlpswhichisdocumentedbythelargenumberofrockglaciersthat havebeenmappedintheeasternpartoftheAlps,particularlyinthecentralmountainranges(e.g. ÖtztalandStubaiAlps).AspermafrosttemperaturesintheAlpsarejustslightlybelow0°Candthe frozencoreofrockglaciersisthin,rarelyexceeding25m,permafrostintheAlps,particularlyactive and inactive rock glaciers, are very sensitive to climate change. Studies on Alpine permafrost, particularly on active rock glaciers, advanced rapidly during the last two decades (see summary by Haeberlietal.2006).IntheAustrianAlpsseveralrockglaciershavebeenstudiedindetailinrecent years (e.g. Lieb, 1986, 1987, 1991, 1996; Lieb & Slupetzky 1993; Kaufmann, 1996a, b, Kaufmann & Ladstädter2002,2003,KellererͲPirklbauer2007,2008,Bergeretal.2004,Krainer&Mostler,2000, 2001,2002,2004,2006,Kraineretal.2002,2007,Hausmannetal.,2007). Hochebenkar rock glacier is located in Äußeres Hochebenkar, a Northwest oriented cirque in the southernÖtztalAlps,about4.3kmSSWofObergurgl,Ötztal(Tyrol,Austria).AlthoughHochebenkar rock glacier has been studied concerning flow velocities for more than 70 years (see below), only littleinformationisavailableaboutcomposition,thickness,hydrologyandthermalconditions. Fig.1–RockglacierHochebenkarwithlocationofsprings,gaugingstationsandtemperatureloggers (fromAbermannetal.2011). 68 PermafrostResponsetoClimateChange Hochebenkarrockglacieristongueshapedandextendsfromanaltitudeof2840m(rootingzone)to 2360m (front). The maximum length of this active, NWͲfacing rock glacier is 1550m. The width rangesfrom160mnearthefrontto335minthemiddleandupto470mintheupperpart.Therock glaciercoversanareaof0.4km²,thedrainageareacomprises1km². ThesurfacelayeriscoarseͲgrainedwithvaryinggrainsizeandlocallywelldevelopedtransverseand longitudinalfurrowsandridges.Adepressionisdevelopedinthewesternpartoftherootingzone. The front is steep and bare of vegetation. The highest peaks surrounding the rock glacier are Hangerer(3021m)ontheeasternsideandtheHochebenkammwithitshighestpointat3149mon the southern side, separated by the Hochebenscharte (2895m). The debris of the rock glacier is derivedfromthesteeprockwallsoftheHochebenkamm. Bedrockin thedrainageareaoftherockglacieris composedofparagneissandmicaschistsofthe ÖtztalͲStubaicomplex.AtHochebenkammthebedrockiscutbynumeroussteepfaultsalongwhich highamountsofdebrisareproducedbyfrostweathering,particularlyduringbreakͲupinspringand earlysummer. TheaimofthiscasestudycontributionistopresentsomepreliminarydataonthedynamicsofRock GlacierHochebenkar,oneofthelargestandmostactiverockglaciersoftheAustrianAlps. Fig.2:Viewtothesteep,activefrontofHochebenkarrockglacier(viewtowardsSW) 69 PermaNET–Permafrostresponsetoclimatechange 2. Permafrostindicatorsandrecentgeomorphicevolution 2.1Previousstudies Hochebenkar rock glacier is one of the largest and most active rock glaciers in the Austrian Alps, whichalsoshowstheworldwidelongestrecordofflowvelocities.Pillewizerstartedtomeasureflow velocitieson Hochebenkarrockglacier in1938.Sincethattime,i.e.overaperiodofmorethan70 years,flowvelocitiesonthisrockglacierhavebeenmeasuredbyterrestrialphotogrammetry,since 1951 by terrestrial geodetic methods (Theodolite) and since 2008 by differential GPS (Pillewizer 1938, 1957; Vietoris 1958, 1972; Haeberli & Patzelt 1982; Kaufmann 1996; Schneider & Schneider 2001;Kaufmann&Ladstädter2002,2003;Ladstädter&Kaufmann2005).Haeberli&Patzelt(1982) measured thebasaltemperaturesofthewintersnowcoverin February1975,1976and 1977,and the water temperature of rock glacier springs during summer. They also carried out refractionͲ seismicmeasurementsalong11transectsonfrozenandunfrozenground. 2.2Rockglacierdynamicsandthermalregime DuringthelastyearsintensiveinvestigationshavebeencarriedoutonHochebenkarrockglacierto study the dynamics. These investigations include field mapping of the bedrock and sediments and geomorphologic features, grainͲsize analysis of the debris layer, BTS measurements, hydrology, georadarandflowvelocitymeasurements(detailsinAbermannetal.2011). Fig.3:GrainͲsizedistributionofthreesitesonHochebenkarrockglacier.Greenbars:coarseͲgrained, bluebars:mediumͲgrained,redbars:fineͲgrined. 70 PermafrostResponsetoClimateChange Grainsizeofrockglacier ThesurfacedebrislayerofHochebenkarrockglacieriscoarseͲgrainedwithanaveragegrainsize(aͲ axis)measuring35cmonfinergrainedareasand58cmoncoarsergrainedareasinthemiddlepart (Fig.3).Locallyblocksuptoafewmindiameteroccuronthesurface.Similarvaluesarerecorded from other rock glaciers composed ofdebris derived from gneisses and schists (Berger et al. 2004, KrainerandMostler2001,2004). The coarseͲgrained debris layer has a maximum thickness of 1.5m and is underlain by debris containinghigheramountsofsandandsilt(Fig.4)displayingpoortoverypoorsortingwithvaluesof 2.96Ͳ3.23Phi (inclusive graphic standard deviation after Folk & Ward, 1957). Similar values have been reported from other rock glaciers (Barsch et al. 1979, Giardino & Vick 1987, Haeberli 1985, Krainer&Mostler2000,2004,Bergeretal.2004)andtills. Fig.4:CumulativecurvesoftwosamplestakenatthesteepfrontofHochebenkarrockglacier.Both samplesshowasimilartrendindicatingpoorsorting. Thermalregimeofground BTSmeasurementsperformedbyHaeberli&Patzelt(1982)inFebruary1975,1976and1977yielded meanvaluesrangingbetweenͲ4.8andͲ7°C.SimilartemperatureswererecordedinMarch2010. Duringwinter2006/2007eighttemperatureloggerswereinstalledwhichrecordedthetemperature atthebaseofthesnowcoveratanintervaloftwohours.Resultsshowthatthetemperatureatthe base of the snow cover on permafrostͲfree ground near the gauging station remained constantly between 0 and Ͳ1°C from November until May. From December until April temperatures varied betweenͲ3andͲ4°Cat thewesternmarginandbetweenͲ2andͲ4°Catthe eastern marginofthe rockglacier.BTStemperaturesweresignificantlydeeperinthecentralpartoftherockglacierranging betweenͲ5andͲ9.3°Cwithonlyminorvariations.Thedeepesttemperature(Ͳ9.9°C)wasobservedin earlyJanuary.SnowmeltstartedduringthefirsthalfofMay. 71 PermaNET–Permafrostresponsetoclimatechange SimilarBTStemperaturepatternswererecordedonotheractiverockglaciersintheÖtztalandStubai Alps (Ölgrube rock glacier – Berger et al. 2004, Reichenkar rock glacier – Krainer & Mostler 2000, Sulzkarrockglacier–Krainer&Mostler2004)andSchoberMountains(Krainer&Mostler2001). Thermalregime,dischargeandelectricalconductivityofwatersprings Water temperature of the rock glacier springs remained almost continuously <1°C during summer. Even after heavy thunderstorms in summer with rather “warm” rainfall causing peak floods in dischargeoftherockglacierthewatertemperaturedidnotchange. AtHochebenkarrockglaciermostofthemeltwater isreleasedfromspringsatthefront(Fig.1).A minoramount(ca.30%) ofmeltwaterisreleasedfromtwospringsontheeasternsideoftherock glacieratanaltitudeof2575m(Fig.1).About95mdownstreamagaugingstationwasinstalledin spring2007atanaltitudeof2555minordertorecordthewaterdepthversustimeduringthemelt season.Waterdepthofthemeltwaterstreamiscontinuouslyrecordedbyapressuretransducerat intervalsof1hour. The discharge of the rock glacier is mainly controlled by water derived from snowmelt, summer thunderstorms and/or snowfall during summer and thus displays pronounced seasonal and diurnal variationsindischarge.Runoffin2009startedduringAprildisplayingfloodswithmaximumflowpeak duringMayandJunecausedbyfairweatherperiodswithintensemeltingofsnowandice(Fig.5).A rapid decline in discharge was recorded a few hours after influx of cold air which sometimes was accompanied by snowfall. ShortͲterm floods with peakflows >100l/s are triggered by summer thunderstorms with heavy rainfall. From July until September discharge decreased and was interruptedbysinglepeakflowscausedbyrainfallevents. Fig. 5 – Hydrograph (water heights, blue line) of the meltwater stream released from Hochebenkar rockglacier(springsattheeasternsideoftherockglacier)fortheperiodApriltoSeptember2009. Redlineindicateswatertemperatureatthegaugingstation(locationseeFig.1). Thevaluesforelectricalconductivityofthewaterdischargedfromtherockglaciervarysignificantly overtheseason.AtHochebenkarrockglaciersignificantlyhighervaluesofelectricalconductivityare recordedatthetwospringsontheeasternsidethanatthemainspringatthefront. 72 PermafrostResponsetoClimateChange AtspringswhichoccuratthebaseofthesteepfrontelectricalconductivityisextremelylowinMay andJune(20Ͳ30µS/cm)andincreasesslightlyreachingvaluesof40µS/cmbytheendofAugustand 60µS/cm at the beginning of October. The water temperature at these springs ranges from 0.6 to 1.4°C. At the two springs on the eastern side of the rock glacier the values of electrical conductivity are significantly higher with 100Ͳ200µS/cm in June, increasing to 400µS/cm during August and to 570µS/cmduringSeptember.Watertemperatureisverylowwith0.2Ͳ0.4°C.Theseasonalvariation inelectricalconductivityresultsfromthedifferentmixingratiooflowmineralizedprecipitationand highermineralizedgroundwater(Krainer&Mostler2001,2002,Kraineretal.2007). Rockglacierdynamics Fortheperiod1938Ͳ1953Pillewizer(1957)documentedamaximumflowvelocityintheupperpart (profile B) of 75cm/a, and 85 cm/a for the period 1953Ͳ1955. Profile 2 yielded flow velocities of 1.61mfortheperiod1951Ͳ1952,1.84mfortheperiod1952Ͳ1953and1.53mfortheperiod1953Ͳ 1955(Pillewizer1957,Vietoris1958). Significantly higher flow velocities (average 3.9m/a, maximum6.6 m/a) were recorded between 1954 and 1972, whereas between 1973 and 1995 flow velocities were lower (average 1.15m/a, maximum2m/a).Flowvelocitiesagainincreasedsince1995reachingthehighestvaluesin2003,and thendecreasedagain(seeAbermannetal.2011). Recentmorphologicalchanges From1936to1997thefrontoftherockglacieradvancedfor165m(Schneider&Schneider2001). AccordingtoKaufmann(1996)thefrontofHochebenkarrockglacieradvancedfor148mduring50 years,indicatingameanflowvelocityof3m/aforthatperiod.Thelowermostprofile1yieldedthe highestflowvelocitiesof3.57m/a(1953Ͳ1955)whichincreasedto5m/a(Vietoris1972).Since1995 asignificantdecreaseinthicknesswasobservedinthelowermost,steeppartoftherockglacier. 2.3DiscussionandConclusion Morphologyanddebrispropertiesoftheactivelayerareverysimilartootherrockglacierscomposed ofdebrisderivedfrommetamorphicrocks,particularlygneissandschist(Bergeretal.2004;Krainer &Mostler2000,2001,2004).BasedongrainͲsizeofthesurfacelayerHochebenkarrockglacierisa typicalboulderrockglacieraccordingtoIkedaandMatsuoka(2006).Temperaturesatthebaseofthe wintersnowcover(BTS)aretypicalforactiverockglaciersandsimilartothoserecordedfromother activerockglaciersintheAustrianAlps(Bergeretal.2004;Krainer&Mostler2000,2001,2004).The pronounced seasonal and diurnal variations in discharge are strongly controlled by the weather conditions.Waterreleasedattherockglacierspringsismainlyderivedfromsnowmeltandsummer rainfall,subordinatelyfrommeltingofpermafrosticeandgroundwater.Floodpeaksarecausedby intensivesnowmeltonwarm,sunnydaysduringlatespringandearlysummerandbyrainfallevents. Thewatertemperatureoftherockglacierspringswhichremainspermanentlybelow1.5°C,mostly below1°C,indicatesthatthewaterflowsthroughtherockglacierindirectcontactwithpermafrost ice(Krainer&Mostler2002,Kraineretal.2007).Extremelyhighvaluesoftheelectricalconductivity at the spring on the eastern side of the rock glacier indicate a much longer residence time of the watercomparedtothewaterreleasedatthespringsatthesteepfrontwhichischaracterizedbyvery lowvaluesindicatingthattheresidencetimeisshortandthatthewaterisderivedfrommeltingof iceandsnowandrainfall. 73 PermaNET–Permafrostresponsetoclimatechange Thedepressionintherootingzoneandthepronounceddecreaseinthicknessinthelowermostpart duringthelastyearsindicatemeltingofmassiveiceandwesuggestthatHochebenkarrockglacier has a glacial origin similar to Reichenkar rock glacier (Krainer & Mostler 2000, Krainer et al. 2002, Hausmann et al. 2007). High iceͲcontent is also indicated by annual flow velocities which are significantly higher than those of most other active rock glaciers with typical values of 0.1Ͳ1m. Schneider & Schneider (2001) showed that the variations in flow velocity correlate with the mean annual air temperature values. Higher flow rates during warmer periods are probably caused by higher amounts of meltwater within the rock glacier and near the base, probably also to slightly highericetemperatures. Hochebenkar rock glacier most likely developed from a debrisͲcovered cirque glacier due to the inefficiencyofsedimenttransferfromglaciericetomeltwater,amodelproposedbyShroderetal. (2000)basedonstudiesintheNangaParbatHimalaya. 3. Possiblefuturethermalresponsetopredictedclimatechange In high alpine mountain environments permafrost is warm (Ͳ2 to 0°C) and thus highly sensitive to temperaturechanges.WhereaswarmingofpermafrostwasobservedinthenorthernpartsofEurope of 0.5Ͳ1°C during the period 1998Ͳ2008, no clear warming trend was recorded in the Alps for this periodduetohighannualvariationsresultingparticularlyfromvaryingthicknessesofthesnowcover (GärtnerͲRoer et al. 2011). However, field observations show that many rock glaciers in the Alps alreadyreactedonthewarmingtrendduringthelastdecade.AsmostrockglaciersintheAlpsare located near the lower boundary of discontinuous permafrost, which is thin and rather “warm”, theserockglaciersareexpectedtoreactmorerapidlytoevenslighttemperaturechangescompared torockglaciersofcolderregions. AtHochebenkarrockglacierasignificantdecreaseinthicknesswasobservedduringthelast15years in the steep lower part indicating increased melting of permafrost ice. This already resulted in a decrease of flow rates. If the trend of global warming will continue, melting of permafrost ice will continue, particularly in the lower part of the rock glacier which is close to the lower limit of permafrost,resultinginadecreaseinflowvelocity. Butevenintheupperpartoftherockglacierincreasedmeltingofpermafrosticeisexpected.Thus Hochebenkarrockglacierwilltransformfromahighlyactiverockglacierintoaninactiverockglacier duringthenextdecades.Asaconsequence,vegetationwillstarttogrowonthefineͲgrained,steep frontalpartoftherockglacier,whichisstillbareofvegetation. Changes of total rock glacier discharge will depend on changes of annual precipitation. Increased melting of permafrost ice will slightly increase the amount of meltwater derived from ice, which constitutes only a small part (<10%) of the total discharge. Warming will change the discharge patternofrockglaciers:themeltingseasonwillstartearlier(inAprilinsteadofearlyMay),andsnow is expected to melt more rapidly within a shorter period during May and June causing high peak flows.Thesepeakflowsmaybeoverprintedbysinglerainfalleventsresultinginextremepeakflows. Heightofpeakflowandlengthofthepeakflowperiodwilldependonthesnowheightswhichalso maychange.SuchadischargepatternwithonsetofthemeltperiodinAprilandextremepeakflows due to intensive snowmelt during May and early June was already recorded in the extreme warm summerof2003.LowdischargeisexpectedforJulyuntiltheendofthemeltperiod,interruptedby singlepeakflowscausedbyrainfallevents. Acknowledgements:MonitoringofHochebenkarrockglacierisfundedbytheAustrianAcademyof Sciences(project“ImpactofClimateChangeonAlpinePermafrost”). 74 PermafrostResponsetoClimateChange References: Abermann,J.,Fischer,A.,Krainer,K.,Nickus,U.,Schneider,H.,&Span,N.,2011:Resultsofrecentresearchon RockGlacierÄußeresHochebenkar.ZeitschriftfürGletscherkundeundGlazialgeologie(submitted). BarschD.,FierzH.&HaeberliW.,1979:Shallowcoredrillingandboreholemeasurementsinpermafrostofan activerockglacierneartheGrubengletscher,Wallis,SwissAlps.ArcticandAlpineResearch,11,215Ͳ 228. BergerJ.,KrainerK.&MostlerW.,2004:Dynamicsofanactiverockglacier(ÖtztalAlps,Austria).Quaternary Research,62,233Ͳ242. FolkR.L.&WardW.C.,1957:BrazosRiverBar:Astudyinthesignificanceofgrainsoilparameters.Journalof SedimentaryPetrology,27,3Ͳ26. GärtnerͲRoerI.,ChristiansenH.H.,EtzelmüllerB.,FarbotH.,GruberS.,IsaksenK.,KellererͲPirklbauerA.,Krainer K.&NoetzliJ.,2011:Permafrost.In:T.Voigt&H.M.Füssel(eds),Impactsofclimatechangeonsnow, ice,andpermafrostinEurope:Observedtrends,futureprojections,andsocioeconomicrelevance:66Ͳ 76. Giardino J.R. & Vick S.G., 1987: Geologic engeneering aspects of rock glaciers. Rock Glaciers, Allen & Unwin, London,265Ͳ287. Haeberli W., 1985: Creep of mountain permafrost: Internal structures and flow of alpine rock glaciers. MitteilungenderVersuchsanstaltfürWasserbau,HydrologieundGlaziologieETHZürich,77,1Ͳ142. Haeberli W. & Patzelt G., 1982: Permafrostkartierung im Gebiet der HochebenkarͲBlockgletscher, Obergurgl, ÖtztalerAlpen,ZeitschriftfürGletscherkundeundGlazialgeologie,18,127Ͳ150. Haeberli W., Hallet B., Arenson L., Elconin R., Humlum O., Kääb A., Kaufmann V., Ladanyi B., Matsuoka N., SpringmanS.&VonderMühllD.,2006:PermafrostCreepandRockGlacierDynamics.Permafrostand PeriglacialProcesses,17,189Ͳ214. HausmannH.,KrainerK.,BrücklE.&MostlerW.,2007:InternalStructureandIceContentofReichenkarRock Glacier (Stubai Alps, Austria) Assessed by Geophysical Investigations. Permafrost and Periglacial Processes,18,351Ͳ367. Ikeda A. & Matsuoka N., 2006: Pebbly versus boulder rock glaciers: Morphology, structure and processes. – Geomorphology,73,279Ͳ296. KaufmannV.,1996a:DerDösenerBlockgletscher–StudienkartenundBewegungsmessungen.Arb.Inst.Geogr. Univ.Graz,33,141Ͳ162. KaufmannV.,1996b:GeomorphometricmonitoringofactiverockglaciersintheAustrianAlps.4th International SymposiumonHighMountainRemoteSensingCartography.Karlstad,Kiruna,Tromso,August19Ͳ29, 1996,97Ͳ113. Kaufmann V. & Ladstädter R., 2002: SpatioͲtemporal analysis of the dynamic behaviour of the Hochebenkar rockglaciers(OetztalAlps,Austria)bymeansofdigitalphotogrammetricmethods.GrazerSchriftender GeographieundRaumforschung,37,119Ͳ140. Kaufmann V. & Ladstädter R., 2003: Quantitative analysis of rock glacier creep by means of digital photogrammetry using multiͲtemporal aerial photographs: two case studies in the Austrian Alps. Proceedingsofthe8th InternationalConferenceonPermafrost,21Ͳ25July2003,Zurich,Switzerland,1, 525Ͳ530. KellererͲPirklbauer A. 2007: Lithology and the distribution of rock glaciers: Niedere Tauern Range, Styria, Austria.Z.Gemorph.N.F.,51/2,17Ͳ38. KellererͲPirklbauer A., 2008: The SchmidtͲhammer as a Relative Age Dating Tool for Rock Glacier Surfaces: Examples from Northern and Central Europe. Proceedings of the Ninth International Conference on Permafrost(NICOP),UniversityofAlaska,Fairbanks,June29–July3,2008,913Ͳ918. 75 PermaNET–Permafrostresponsetoclimatechange Krainer K. & Mostler W., 2000: Reichenkar Rock Glacier: a Glacier Derived DebrisͲIce System in the Western StubaiAlps,Austria.PermafrostandPeriglacialProcesses,11,267Ͳ275. KrainerK.&MostlerW.,2001:DeraktiveBlockgletscherimHinterenLangtalKar,Gößnitztal(Schobergruppe, NationalparkHoheTauern,Österreich).Wiss.Mitt.NationalparkHoheTauern,6,139Ͳ168. Krainer K. & Mostler W., 2002: Hydrology of Active Rock Glaciers: Examples from the Austrian Alps. Arctic, Antarctic,andAlpineResearch,34,142Ͳ149. Krainer K. & Mostler W., 2004: Aufbau und Entstehung des aktiven Blockgletschers im Sulzkar, westliche StubaierAlpen.Geo.Alp,1,37Ͳ55. KrainerK.&MostlerW.,2006:FlowVelocitiesofActiveRockGlaciersintheAustrianAlps.GeografiskaAnnaler, 88A,267Ͳ280. Krainer K., Mostler W. & Span N., 2002: A glacierͲderived, iceͲcored rock glacier in the Western Stubai Alps (Austria): Evidence from ice exposures and ground penetrating radar investigation. Zeitschrift für GletscherkundeundGlazialgeologie,38,21Ͳ34. Krainer K., Mostler W. & Spötl C., 2007: Discharge from active rock glaciers, Austrian Alps: a stable isotope approach.AustrianJournalofEarthSciences,100,102Ͳ112. LadstädterR.&KaufmannV.,2005:StudyingthemovementoftheOuterHochebenkarrockglacier:Aerialvs. groundͲbased photogrammetric methods. Second European Conference on Permafrost, Potsdam, Germany,TerraNostra2005(2),97. LiebG.K.,1986:DieBlockgletscherderöstlichenSchobergruppe(HoheTauern,Kärnten).Arb.Inst.Geogr.Univ. Graz,27,123Ͳ132. Lieb G.K., 1987: Zur spätglazialen GletscherͲ und Blockgletscehrgeschichte im Vergleich zwischen den Hohen undNiederenTauern.Mitt.Österr.Geogr.Ges.,129,5Ͳ27. LiebG.K.,1991:DiehorizontaleundvertikaleVerteilungderBlockgletscherindenHohenTauern(Österreich). Z.Geomorph.N.F.,35,345Ͳ365. LiebG.K.,1996:PermafrostundBlockgletscherindenöstlichenösterreichischenAlpen.Arb.Inst.Geogr.Univ. Graz,33,9Ͳ125. LiebG.K.&SlupetzkyH.,1993:DerTauernfelckͲBlockgletscherimHollersbachtal(Venedigergruppe,Salzburg, Österreich).Wiss.Mitt.NationalparkHoheTauern,1,138Ͳ146. Pillewizer W., 1938: Photogrammetrische Gletscheruntersuchungen im Sommer 1938. Zeitschrift der GesellschaftfürErdkunde,1938(9/19),367Ͳ372. PillewizerW.,1957:UntersuchungenanBlockströmenderÖtztalerAlpen.GeomorphologischeAbhandlungen desGeographischenInstitutesderFUBerlin(OttoͲMaullͲFestschrift),5,37Ͳ50. SchneiderB.&SchneiderH.,2001:Zur60jährigenMessreihederkurzfristigenGeschwindigkeitsschwankungen amBlockgletscherimÄusserenHochebenkar,ÖtztalerAlpen,Tirol.ZeitschriftfürGletscherkundeund Glazialgeologie,37(1),1Ͳ33. ShroderJ.F.,BishopM.P.,CoplandL.&SloanV.F.,2000.DebrisͲcoveredglaciersandrockglaciersintheNanga ParbatHimalaya,Pakistan.GeografiskaAnnaler,82:17Ͳ31. VietorisL.,1958:DerBlockgletscherdesäußerenHochebenkares.GurglerBerichte,1,41Ͳ45. Vietoris L., 1972: Über die Blockgletscher des Äußeren Hochebenkars. Zeitschrift für Gletscherkunde und Glazialgeologie,8,169Ͳ188. 76 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.6 RockGlacierLaurichard,NorthernFrenchAlps Citationreference SchoeneichP.,BodinX.,KrysieckiJ.ͲM.(2011).Chapter3.6:CasestudiesintheEuropeanAlps–Rock Glacier Laurichard, Northern French Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.77Ͳ86. Authors Coordination:PhilippeSchoeneich Involvedprojectpartnersandcontributors: Ͳ Institut de Géographie Alpine, Université de Grenoble, France (IGAͲPACTE) – Philippe Schoeneich,XavierBodin,JeanͲMichelKrysiecki Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentgeomorphicandthermalevolution 3. Possiblefuturethermalanddynamicresponsetopredictedclimatechange References 77 PermaNET–CasestudiesintheEuropeanAlps Summary The Laurichard rock glacier in the French Alps is monitored for surface displacements and repeated geoelectrical soundings and tomographies since the 1980’s. The 25 years velocity record,togetherwiththerepeatedgeoelectricalsurveysandgroundsurfacetemperaturerecord, allows to draw some essential conclusions on the influence of climate on the behaviour and evolutionofrockglaciers.Rockglaciersreacttoclimateandshowinterannualvelocityvariations. Theirreactiontimeisthusmuchshorterthanpreviouslyassumed.Velocityvariationsarelinked to temperature variations– an increase in temperature induces an increase in velocity. The air temperature only partly explains the observed ground surface temperature and velocity variations. The ground surface temperature shows the best link with velocity variations,with a time lag of around one year. The snow cover explains most of the difference between air temperatureandgroundsurfacetemperature,andthusappearsasthemaindrivingfactorboth for ground surface temperatures and for velocity variations. Thus, the evolution of the permafrost will not onlydepend on the air temperature, but will be strongly influenced by the evolutionofthesnowcover,especiallyitsearlyorlateonsetinautumn.Alateonsetofthesnow covercanatleastpartiallycompensateariseinairtemperature. 78 PermafrostResponsetoClimateChange 1. Introductionandstudyarea TheLaurichardrockglacierRGL1issituatedinthegraniticCombeynotmassifonaNorthfacingslope. Itisawelldevelopedboulderyrockglacierwithdistinctcompressionridgesandasteepfrontaland lateralslope(Fig.1).TheRGL1extendsfromtherootingzone(2650ma.s.l.)atthecontactwiththe rockfaceto2450ma.s.l.atitsfrontandisadvancingontoHoloceneglacialandperiglacialdeposits. Itis490mlong,between80and200mwide,andhasanapparentthickness(basedonthevertical heightofthesidesandfront)of20Ͳ30m.Therockglacierhasathreesteppedlongitudinalprofile, with moderate slopes in the upper part, a steep median part, and again a moderate slope in the frontalpart.Itdisplaysmorphologicalfeaturestypicalofanactivelandform:longitudinalridgesinthe centralsteeppartandasuccessionoftransverseridgesandfurrowsinthecompressivepartofthe tongue(Table1). Fig.1–TheLaurichardrockglacier.PhotographbyX.Bodin. Table1–CharacteristicsoftheLaurichardrockglacier Method Latitude Longitude Elevation[ma.s.l.] Slope Aspect Typeofrockglacier Evidenceofpermafrost Evidenceofmovement Typologyofmovement Meanvelocityrange Changeinvelocity Yearoffirstdata initiated/carriedout N45.0181° E06.3997° 2440Ͳ2650m Variable:moderateontopandtoe,steep(50%)inmiddlepart North talus;lobatetotongueshaped;active Observationofgroundice,groundsurfacetemperature,geoelectric Aerialphotograph,geodetic,Lidar Velocitiychanges From0.3to1.6m/yr 20%increase2000Ͳ2004,decrease2004Ͳ2006 (1979)1985 79 PermaNET–CasestudiesintheEuropeanAlps 2. Permafrostindicatorsandrecentgeomorphicandthermalevolution 2.1Methods Movements havebeen measuredsince1979andregularlyrepeatedsince1985.Thusitrepresents oneofthelongestdisplacementmeasurementrecordonarockglacierintheAlps.Classicalgeodetic measurementsaremadeundersupervisionoftheParcNationaldesEcrinsonatransverseandona longitudinallineofpoints,withaclassicaltotalstation.Thesurveywascarriedouteverytwotothree yearsfrom1979to1999andsubsequentlyeveryyear.Fourmarkedblockswereaddedattheupper end part of the longitudinal profile in 1999. Annual velocity (downslope, vertical and horizontal), actual vertical change after removing total displacement of the block downslope and variation in interͲblockdistancecanbecalculatedfromthesedata(Bodinetal.2009).Measuredvelocitiesrange from0.2to1.6m/a.Thehighestvelocitiesaremeasuredinthesteepmedianpart(Fig.2).Compared toothersurveyedrockglaciers,itcanbeconsideredasaratherfastmovingrockglacier. Fig.2–DownslopemeanannualsurfacevelocitiesoftheLaurichardrockglacieralonglongitudinal profile line L (1986Ͳ2006 or 2000Ͳ06). Grey band represents one standard deviation for each measurementlocation(fromBodinetal.2009). Geophysical investigations have been repeated regularly since 1986. In total 12 vertical electrical soundings(VES)andsixelectricalresistivitytomography(ERT)profileshavebeenundertakenonthe rockglaciertoinvestigateitsinternalstructure:twoVESin1986(Francou&Reynaud,1992),fiveVES in 1998 (V. Jomelli & D. Fabre, unpublished work), four VES and two ERT in 2004, and one VES in 2006. All of the VES were carried out using the Schlumberger configuration and the results were interpretedwithtwoorthreeͲlayeredresistivitymodels,whereasapoleͲdipoleconfigurationproved tobethebestforERT.ThetwoERTprofilesweremeasuredagainin2007and2009.Theserepeated measurementsallowsomeinterpretationsontheevolutionoftheicecontent. Ground surface temperature (GST) measurements have been performed on the Laurichard rock glaciersince2003,withsevenUTLminidataloggersburiedjustbelowtheblockysurfacetoprotect themfromdirectsolarradiation.OneloggerisplacedoutsidetherockglacierinanonͲpermafrost area,whereasthesixothersaredistributedoverthesurfaceofthelandform.Anautomatedweather stationhasbeeninstalledin2004besidetherockglacier.Meteorologicaldatafromnearbystations canbeusedinaddition 80 PermafrostResponsetoClimateChange 2.2Rockglaciervelocityvariation OneofthetypicalcaractristicsoftheLaurichardrockglacierRGL1aresignificantvelocityvariations all over the 25 years observation period. The rock glacier showed an increasing trend in flow velocitiesfrom1985to1999,oscillationsaroundahighvelocityratefrom2000to2004,adecrease from2004to2006,andagainamoderateincreasesince2007.Previousto2000,thevelocitychanges aremoredifficulttointerpret,duetothenonͲannualmeasurements.Meanvelocitiesonperiodsof2 to3yearsdonotshowsignificantchanges,butthemeasurementintervalinducesasmoothingofthe valuesthatpossiblyhidesmoresignificantinterannualvariations. Thevelocitychangescanbecomparedtothemeanannualairtemperature(MAAT)usingthenearby station of MonêtierͲlesͲBains (MeteoͲFrance), using a 12 month running mean (Fig. 3). The overall picture shows a correspondence between the increasing temperature trend and the increasing velocitytrendfrom1985to1999,thehighlevelofbothtemperatureandvelocitybetween2000and 2004, and the decrease in both temperature and velocity since 2004. This shows at least that a generaldependenceofvelocityontemperatureseemstoexist.Whenlookingondetails,however, thecorrespondenceappearstobelessevident.Before2000strongtemperaturevariationsarenot expressedinthevelocitychanges,butasmentionnedabove,thiscouldbepartlyduetoasmoothing ofthevelocitycurvebythemeasurementinterval.Between2000and2004,somevelocityvariations appeartobeinvertedcomparedtotemperaturevariations.Thiscouldindicateeitheratimelagor theinfluenceofotherparameters. Fig.3–MeansurfacevelocityoftheLaurichardrockglacier(RGL1)and1ʍrange(greyband)from 1986Ͳ2006 (based on points L1ͲL3, L5ͲL8, L10ͲL12), and 12Ͳmonths running mean air temperature anomaly(relativetothe1960Ͳ91average)attheMonêtierstation(MeteoFrancedata)(fromBodin etal.2009). Since2000velocityvariationscanbecomparedonanannualbasiswithgroundsurfacetemperature records(usingadatasetfromValaisfortheperiodbefore2004).Thevelocitychangesshowagood correspondence with the MAGST (mean annual ground surface temperature), averaged over the previous 12 months. This shows that creep rates are strongly dependent on ground surface temperatures,whichappearasthemaincontrollingfactorwithatimelagintheorderof1year(Fig. 4). 81 PermaNET–CasestudiesintheEuropeanAlps Fig. 4 – Ground surface temperatures and rock glacier movement, 2000Ͳ06: mean surface velocity (profileL)oftheLaurichardrockglacier(RGL1),andgroundsurfacetemperaturesonRGL1(2003Ͳ06, 12Ͳmonthsrunningmean,averageoffourdataloggers)andintheValaisregion(2000Ͳ06,12Ͳmonths runningmean;westernSwissAlps;about2500ma.s.l.,datafromDelaloyeetal.,2008)(fromBodinet al.2009). 2.3Evolutionofgroundsurfacetemperature Ground surface temperatures (GST) show some deviations from the air temperature. The main controllingfactorforgroundsurfacetemperatureappearstobethesnowcoverthickness,especially inautumnandearlywinter.ThisiswelldemonstratedbytheGSTmeasurementseriesperformedat Laurichardsince2003(fig.5,Schoeneichetal.2010). Anearlyandsufficientlythicksnowcoverprotectsthegroundsurfacefromcoolingduringthecold andshortdaysofNovemberͲDecember,whereasalateorshallowsnowcoverallowsastrongcooling oftheground.Whenthesubsequentsnowcoveristhickenough,itsinsulationeffectpreservesthe “thermal memory” during the whole winter, as is shown by the winter equilibrium temperatures (WeqT)measuredinMarch. Thus the ground surface can experience an average cooling even in warm years, if the snow cover onsetislate,and/orifthesnowcoverremainsthin.Ontheotherhand,thecumulativeeffectofan early snow rich winter preceded or followed by a hot summer is most efficient for inducing a warmingofthegroundsurface. 2.4Evolutionoficecontentandstate Repeated vertical electric soundings (VES) and electrical resistivity tomography (ERT) profiles show an evolution of apparent resistivities measured on the rock glacier body. All data show the typical profile expected on rock glaciers, with a moderately resistant surface layer corresponding to the blockyactivelayer,ahighresistivemainlayercorrespondingtothepermafrostbody,andabasalless resistivelayer.Thediscussionwillthusfocusondifferenceswithtime. FoursuccessiveVESwereperformedonthetongue(1986,1998,2004,2006)andthreeattheroot (1986, 1998, 2004). The accuracy of relocation of the 1986 sites is judged to be about 5m for the lower one and 10m for the upper one. There was a general decrease in the maximum apparent resistivity (ramax) at the VES sounding sites located at the root and on the tongue from 1986 to 2004Ͳ06(Fig.6).Attheroot(foraninterͲelectrodespacingAB/2=50m),ramaxdecreasedby35Ͳ50% from8.105ɏ.min1986to3Ͳ4.105ɏ.m18yearslater.Atthetongue,ramaxdecreasedby20Ͳ50%cent from5.104ɏ.min1986(AB/2=30m)to1.5Ͳ4.104ɏ.min2004(AB/2=20m). 82 PermafrostResponsetoClimateChange Figure 5 – Ground surface temperatures measured on 5 locations on the Laurichard rock glacier (2003Ͳ2009,runningmeanofthe12previousmonths).LA1isoutsideoftherockglacier,theothers areonit.Theeffectofthesnowpoorwinters2004/05and2005/06isclearlyvisible,aswellasthe cumulativeeffectofthehotsummer2006andthesnowrichwinter2006/07. Fig. 6 – (a)Measured and modelled resistivity at the root (black curves and dots) and tongue (grey curves and dots) of the Laurichard rock glacier in 1986 and 2004; (b) inverted models for the root (top)andtongue(bottom)in1986and2004(fromBodinetal.2009). 83 PermaNET–CasestudiesintheEuropeanAlps Therelativelylargevariationsinresistivityovertheperiod1998Ͳ2006suggestthatitmaybedifficult todistinguishresistivitychangesduetolongͲtermmodificationofthepermafrost(e.g.athickening oftheactivelayer,anincreaseingroundtemperature,adecreaseinicecontent)fromthoserelating to seasonal changes in ground properties (e.g. differing water contents during the sounding campaigns in the active layer and/or within the icy layer), and/or localised changes in the internal structure related to permafrost deformation. Despite these limitations, the diachronic VES measurementscanbeinterpretedusinginversionmodelstodepicthypotheticalverticalchangesin structurescomposedofhomogeneoushorizontallayers(Figure6b).Takingintoaccounttheinfinity ofsolutionsandthewellͲestablishedelectricalpropertiesofsimilargroundmaterials(Fabre&Evin 1990,Hauck2001,Delaloye2004),changesattherootcanbeinterpretedasbeingduetothickening oftheactivelayerfrom1Ͳ2mto2Ͳ3mwithnonoticeablemodificationoftheicylayer.Incontrast, thoseatthetonguecouldrepresentathickeningoftheactivelayerandalowericecontent,and/ora thinningoftheicylayer.Theseresultsarelessreliable,however,duetostronglateralvariationsof theinternalstructurewhicharenotidealforlayeredmodelling. 2.5LessonsfromtheLaurichardcase The 25 years velocity record, together with the repeated geoelectrical surveys and ground surface temperature record allows to draw some essential conclusions on the influence of climate on the behaviourandevolutionofrockglaciers. x Rockglaciersreacttoclimateandshowinterannualvelocityvariations.Theirreactiontimeis thusmuchshorterthanpreviouslyassumed. x Velocityvariationsarelinkedtotemperaturevariations–anincreaseintemperatureinduces anincreaseinvelocity. x The air temperature only partly explains the observed ground surface temperature and velocityvariations. x Thegroundsurfacetemperatureshowsthebestlinkwithvelocityvariations,withatimelag ofaround1year. x Thesnowcoverexplainsmostofthedifferencebetweenairtemperatureandgroundsurface temperature, and thus appears as the main driving factor both for ground surface temperatureandforvelocityvariations. Thus, the evolution of the permafrost will not only depend on the air temperature, but will be stronglyinfluencedbytheevolutionofthesnowcover,especiallyitsearlyorlateonsetinautumn.A lateonsetofthesnowcovercanatleastpartiallycompensateariseinairtemperature. Severalopenquestionsremain,however.Themainquestionmaybehowtoexplaintheveryrapid response ofvelocity to ground surface temperature. The rock glacier movement takes place in the permafrostbodyandmainlyatitsbase.Thethermalconductivityofthepermafrostislowandthe surfacetemperaturevariationsneedtimetodiffusethroughtheprofileandarestronglyattenuated with depth. It seems unlikely that the temperature variations alone are sufficient to induce strong velocity variations. Another factor could be the presence of liquid water percolating through the permafrost body or at its base. This would mean that the velocity variations are controlled by the amount of available liquid water. This would imply a permafrost temperature close to the melting point. Asimilarquestionarisesconcerningtheresistivitymeasurementsontherockglaciertongue.Thelow resistivity measured in the VES are considered as typical for ice poor permafrost, and ERT profiles suggest a discontinuous and ice poor permafrost body. Such interpretations however are 84 PermafrostResponsetoClimateChange inconsistentwiththehighvelocityratesmeasuredonthetongue,whichimplyanicesupersaturated permafrostbody.Theexplanationcouldbethepresenceofliquidwaterin“temperate”permafrost. This means that the evolution of rock glacier permafrost with rising temperature could be characterizedbyanincreaseofthepermafrosttemperaturetovaluesclosetothemeltingpoint,and anincreaseofinterstitialliquidwaterduringthemeltingseason. 3. Possiblefuturethermalanddynamicresponsetopredictedclimatechange TheresultsfromtheLaurichardrockglacierandformothersimilarcasesshowthat(i)thedynamic response of rock glaciers will strongly depend on the thermal evolution of the permafrost and (ii) thatthethermalresponsewilldependonthetemperatureevolutionaswellasontheevolutionof winterprecipitationandsnowcoveronsetandduration. Forgroundsurfacetemperature,thedirectinfluenceofthesnowcoveronsetdateandthicknessis welldocumentedatLaurichard,andshowsastronginterannualvariability.Notemperatureprofileis availableatLaurichard,butotherexistinglongtimeseriesshowanoverallwarmingtrendatca10m depth(Permosreports).Sothemostprobablescenarioofthermalresponsecouldbethefollowing: x Warmingtemperatureswillinduceageneralwarmingtrendofthepermafrost. x Astronginterannualvariabilitywillcontinuetoexist,andcoolingperiodsofonetoseveral yearswillcontinuetohappen. x The interannual variability depends mainly on the snow cover. Increased winter precipitationscouldinduceastrongerwarmingofgroundsurfacetemperature,especiallyif increasedprecipitationmeansearlieronsetofthesnowcover. x Anearliersnowmeltduetowarmerspringtemperatureswouldinduceawarmingofground surfacetemperatures. x The thermal effect of increased amounts of melting water due to increased winter precipitationisunknown. The dynamic response of the rock glacier depends on the ice content, temperature and state. The followingresponsescanbededucedfromtheobservations: x Thedecreaseobservedinelectricalresistivitywillpossiblycontinue,reflectingthepresence of increasing amounts of water within the iceͲrock mixture. The amount of ice in the rock glacierbodyisstillhigh,however,andshouldremainsoforalongtime. x Interannual velocity variations will continue to occur, in relation to ground surface temperaturevariations.Velocityincreasesareexpectedespeciallyafterverywarmsummers associatedwithsnowrichwinters. x ThegeomorphologicalsettingsoftheLaurichardrockglacierarenotfavourabletoastrong acceleration, and a destabilization of the rock glacier is not expected. Due to its already relativelyhighmeanvelocity,thispointhoweverneedstobemonitored. Acknowledgements. – The study of the Laurichard rock glacier was supported by the Fondation MAIF. The annual displacement measurements are performed by the Parc National des Ecrins. We thankDenisFabreandAdrianoRiboliniforallowingtheuseofgeophysicialdata. 85 PermaNET–CasestudiesintheEuropeanAlps References: BodinX.,2007:Géodynamiquedupergélisoldemontagne:fonctionnement,distributionetévolution récente. L’exemple du massif du Combeynot (Hautes Alpes). PhD thesis, University of ParisͲ DiderotParis7.272pp. BodinX.,ThibertE.,FabreD.,RiboliniA,SchoeneichP.,FrancouB.,Reynaudl.&FortM.,2009:Two decades of responses (1986–2006) to climate by the Laurichard rock glacier, French Alps. PermafrostandPeriglacialProcesses,20,331Ͳ344. DelaloyeR.,2004:Contributionàl’étudedupergélisoldemontagneenzonemarginale.PhDthesis, UniversitédeFribourg.260pp. Delaloye,R., Perruchoud, E.,Avian, M.,Kaufmann, V.,Bodin,X.,Ikeda,A., Hausmann,H.,Kääb,A., KellererͲPirklbauer,A.,Krainer,K.,Lambiel,C.,Mihajlovic,D.,Staub,B.,Roer,I.andThibert, E.,2008:RecentInterannualVariationsofRockglaciersCreepintheEuropeanAlps.In:Kane, D.L. and Hinkel, K.M. (eds), Proceedings, Ninth International Conference on Permafrost (NICOP),UniversityofAlaska,Fairbanks,343Ͳ348. Fabre D. & Evin M., 1990: Prospection électrique des milieux à très forte résistivité: le cas du pergélisolalpin.6èmeCongrèsInternationaldeAIGI,Rotterdam. FrancouB.&ReynaudL.,1992:Tenyearsofsurficialvelocitiesonarockglacier(Laurichard,French Alps).PermafrostandPeriglacialProcesses3:209–213. HauckC.,2001:Geophysicalmethodsfordetectingpermafrostinhighmountains.PhDthesis,VAW, Zürich.204pp. Schoeneich P., Bodin X., Krysiecki J.ͲM., Deline P. & Ravanel L., 2010: Permafrost in France. Report N°1.PermaFrancenetwork,Grenoble,InstitutdeGéographieAlpine. 86 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.6 RockGlacierBellecombes,NorthernFrenchAlps Citationreference SchoeneichP.,KrysieckiJ.ͲM.,LeRouxO.,LorierL.,VallonM.(2011).Chapter3.7:Casestudiesinthe European Alps – Rock Glacier Bellecombes, Northern French Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the EuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ 58Ͳ1,p.87Ͳ96. Authors Coordination:PhilippeSchoeneich Involvedprojectpartnersandcontributors: Ͳ Institut de Géographie Alpine, Université de Grenoble, France (IGAͲPACTE) – Philippe Schoeneich,JeanͲMichelKrysiecki Ͳ Association pour le développement de la recherche sur les glissements de terrain, France (ADRGT)–LionelLorier,OlivierLeRoux Ͳ Laboratoire de Glaciologie et de Géophysique del'Environnement, Université de Grenoble, France(LGGE)–MichelVallon Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentgeomorphicandthermalevolution 3. Possiblefuturethermalanddynamicresponsetopredictedclimatechange References 87 PermaNET–CasestudiesintheEuropeanAlps Summary TherockglacierBellecombesisashallowslowmovingrockglacier.However,surfacemovements associated with settlement due to ice melting are sufficient to induce strong disturbance to a chairliftstationbuiltonitssurface.Twoboreholesweredrilledthroughtherockglacier,revealing atotalthicknessofca9.50m,butwithaveryiceͲrichlayer,6Ͳ7mthick,lyingdirectlyonbedrock. The temperature profiles show a very stable and constant temperature of the iceͲrich layer around Ͳ0.2°C, with almost no seasonal variation. The ground surface temperature shows cold winterequilibriumtemperatures(downtoͲ4°C)andstrongseasonalvariationslimitedtotheiceͲ poorblockysurfacelayer.Thetemperatureprofilearisesthequestionofthestatusoftheice:the icetemperature,verycloseto0°C,couldindicatethattheiceisatthemeltingpointtemperature. On the other hand, very high electrical resistivity values indicate low liquid water content, and velocities show that no basal sliding is occurring so far. The question of the melting point temperature of an iceͲrock mixture could be crucial for the future dynamic behavior of rock glaciers like Bellecombes. More knowledge is needed on the physics of iceͲrock mixtures. One dimensional modelling was run with different scenarios. Results show that the very iceͲrich permafrost body seems to be very stable under present day conditions, and a strong warming wouldbenecessarytoinducesignificantchangesiniceͲcontentandtemperature. 88 PermafrostResponsetoClimateChange 1. Introductionandstudyarea TheBellecombesrockglacierissituatedontheskiresortLesDeuxAlpes,intheEcrinsmassif,French Alps(Table1).Itisashallow,topographicallysmoothrockglacier.It developsonaNorth oriented slopefromca2800to2600ma.s.l.Thetwolastpylonsandtheupperstationofachairliftarebuilt ontherockglacier.Duringconstructionwork,anicelayerof2Ͳ4mthicknesswasremovedunderthe future chair lift station. Despite this, the chairlift station is subjected to settling movements, indicatingthatthereisstillicebelowit. The site has therefore been monitored since 2007 for ground surface temperature and surface displacements. It has become a reference test site for various geophysical methods (geoelectrical sounding and tomography, refraction and reflexion seismics, surface waves, seismic ground noise, georadar).Twoboreholesweredrilledinautumn2009throughtherockglacierdowntothebedrock andequippedwithsensorchainsfortemperatureprofilemonitoring. Fig.1–TheBellecombesrockglacier.PhotographbyPhilippeSchoeneich. Table1–CharacteristicsoftheBellecombesrockglacier Method Latitude Longitude Elevation[ma.s.l.] Slope Aspect Typeofrockglacier Evidenceofpermafrost Evidenceofmovement Typologyofmovement Meanvelocityrange Changeinvelocity Yearoffirstdata initiated/carriedout N44.99° E06.16° 2710m moderate North talus;lobatetotongueshaped;active Observation of ground ice, ground surface temperature, borehole profile Aerialphotograph,DGPS Veryslowmovement From0.03to0.10m/yr Nosignificantchange 2007 2. Permafrostindicatorsandrecentgeomorphicandthermalevolution 2.1Groundsurfacetemperatures Ground surface temperatures are monitored since 2007 with 4 UTLͲ1 mini data loggers (3 on the rockglaciersurface,1outsideoftherockglacierinnonͲpermafrostterrain).Inaddition,severalBTSͲ mappingcampaignswereperformedinlatewinter,inordertomapthegroundsurfacetemperature distributionduringwinterequilibriumconditions. 89 PermaNET–CasestudiesintheEuropeanAlps Fig.2–OrthophotooftheBellcombesrockglacier,andpositionofmonitoringdevices. Theresultsshow: x A generally low winter equilibrium temperature on the rock glacier surface, with values as lowasͲ4toͲ5°C. x A strong temperature contrast with the nonͲpermafrost area surrounding the rock glacier, whereonlyslightlynegativetemperaturesarerecorded.Thiscontrastappearsontheloggers aswellasontheBTSͲmaps. x TheBTSͲmappingshowsanalmostperfectmatchbetweenlowgroundsurfacetemperature andgeomorphologicalextentoftherockglacier(fig.3). Theseresultsclearlyindicatethepresenceofpermafrostontheentireareaoftherockglacier. 90 PermafrostResponsetoClimateChange Fig.3–Groundsurfacetemperaturedistributionatwinterequilibrium,fromBTSͲmappinginMarch 2009(left)andsnowcoverthickness(right).Theleftmapshowsdistinctlimitsofthepermafrostzone, consistentwiththegeomorphologicallimitsoftherockglacier. 2.2Rockglaciervelocity ThesurfacedisplacementsaremeasuredwithDGPSon32pointsdistributedoverthesurfaceofthe rockglacier.Theannualdisplacementvaluesareverylowonmostofthepoints,intheorderofafew cm/a, at the accuracy limit of the measurement method. In addition to horizontal displacements, verticalsettlementsareobservedatthechairliftstationandonthepylons.Thesemovements,inthe orderofseveralmillimeters,aresufficienttoneedperiodiccablealignments. 2.3Icecontentandstratigraphy Verticalresistivitysoudings(VES)andelectricalresisitivitytomography(ERT)wereperformedin2007 and 2009 on four profiles across the rock glacier. No significant changes have been observed between2007and2009.AllERTprofilesshowveryhighresistivityvalues,typicalofhighicecontent. Thishighicecontentwassubsequentlyconfirmedbytwoboreholes. Bothdestructiveboreholesshowasimilarstratigraphy(fig.4): x Ontop,2.1mofdrydebris,correspondingtotheblockyactivelayer. x 7.5m of very iceͲrich material. From the interpretation of the penetration logs and of the cuttings, this layer can be subdivided on borehole SD1 into an upper iceͲrock mixture and andaloweralmostpureicelayer,whereasinboreholeSD2thewholelayerismadeofaniceͲ rockmixture. x Bedrock was reached in both boreholes at ca 9.5m depth. The iceͲrich layer lies in both boreholesdirectlyonthebedrock. 91 PermaNET–CasestudiesintheEuropeanAlps Fig.4–BoreholestratigraphyofthetwoboreholesatBellecombesrockglacier. The boreholes confirmed the presence of very high ice content, as deduced from the ERT profiles. However,thethicknessinterpretedfromtheERTprovedtobelargelyoverestimated,duetothevery highresistivityvalues.ThisknowndrawbackoftheERTmethodlimitsitsuseforthedeterminationof the thickness of permafrost bodies. Combined tests of several geophysical methods on the same profiles show that only the georadar can possibly help to determine the real thickness of the permafrostbody. 2.4Temperatureprofiles Thetwoboreholeswereequippedwiththermistorchains(PT100sensors)connectedtoaloggerfor temperatureprofilemonitoring.TheresultsofboreholeSD1areshowninfig.5.Theinfluenceofthe icecontentonthetemperaturevariationsappearsveryobviously: x Strongseasonaltemperaturevariationsoccurwithinthe2mthickactivelayerwithalmostno icecontent. x The seasonal temperature variations are drastically attenuated at ca. 2m depth, at the boundarywiththeiceͲrichlayer. x Thezeroannualamplitudecanbesetatthetransitionfromfrozendebristomassiveice. 92 PermafrostResponsetoClimateChange Fig.5–TemperatureprofileofboreholeSD1andevolutionfromNovember2009toJuly2011. x In the iceͲrich layer, as well as in the bedrock below, temperature variations are almost absentorlimitedtoarangeof±0.1°C. ThetemperatureoftheiceͲrichlayerisveryconstantandstable: x TheabsolutevalueisaroundͲ0.2°C,veryclosetothemeltingpoint. x Itshowsnotrendtowardsdepth,buttheprofileisveryshort(ca13mtotaldepth). x Variationsarelimitedtoaverynarrowrange. 2.5LessonsfromtheBellecombescase The investigations on the Bellecombes rock glacier show the limits of geophysical methods for the determinationoficebodythicknessandgeometry.Themostfavourablegeophysicalmethodusedin permafrost, geoelectrical tomography (ERT), proves to strongly overestimate the thickness of the permafrostbodyincaseofaveryhighicecontentinducingveryhighresistivityvalues.Thispointis verycritical,astheknowledgeofthethicknessiscrucialforacorrectmanagementofgeotechnical problemsliketheoneofthechairliftstation.Sofar,boreholesremainthebestmethodtoassessthe stratigraphyofpermafrostbodies. The most interesting aspect of the Bellecombes study case is the temperature profile of the boreholes.Thevery“warm”temperaturesregisteredinthepermafrostbodycontrastwiththelow winter equilibrium temperatures registered on the surface. Moreover, the values very close to 0°C andtheirconstancywithdepthandstabilityintimeraisethequestionofthestatusoftheice: x Theconstancyoftemperatureintimeanddepthsuggeststhattheicecouldbeatthemelting pointtemperature,similarto“temperate”glaciers. x However the values are still negative, and the consistency of the values on both sensor chainsseemtoindicatethattheyarereliableandnotduetoalackofaccuracy. Actually the physics of iceͲrock mixtures is poorly known, and the value of the melting point temperatureinsuchamaterialisunknown.Itcouldbeslightlybelowzero,intherangemeasuredin theBellecombesboreholes.Ontheotherhand,theveryhighresistivityvaluesindicatetheabsence of liquid water in the ice body, and the very low displacement rates indicate that no basal sliding occurs,likeitwouldbeexpectedincaseof“temperate”basalice.Thequestionremainsopenand needsfurtherinvestigations. 93 PermaNET–CasestudiesintheEuropeanAlps 3. Possiblefuturethermalanddynamicresponsetopredictedclimatechange Theknowledgeofthestratigraphyandofthegeophysicalpropertiesoftherockglacierbodyallowed thecalibrationofathermaldiffusionmodel.Themodelwasrunforvarioustemperatureevolution scenarios.Themodelusedisaonedimensionalmodelthatcalculatestemperatureandicecontentat a spacing of 0.2m, and for time slices of 0.01 days. It uses as input the mean monthly air temperatureandageothermalfluxof0.05watt.mͲ2. Fig.6–LogofboreholeSD1andmodelsettingsforstructureandicecontent. The ice content was estimated from the cuttings and the drilling progression graph, according to figure6.Themodelcharacteristicsweresetwiththevaluesoftable2. Table2–Intrinsicvaluesusedformodelcalculations Thermalconductivity Specificmass Kw.mͲ1.°CͲ1 Ukg.mͲ3 Snow 0.20 300 Ice 2.10 900 Debris 0.50 1800 Bedrock 2.50 2600 Massicheat CpJ.kgͲ1.°CͲ1 2009 2009 900 900 Themodelneedstosetameanairtemperatureaswellasprecipitation,andusesaclimaticscenario todrivethemodel.Toavoiduncertaintiesrelatedtoaltitudinalgradientextrapolations,initialvalues were taken from the meteorological station of SaintͲSorlin, situated ca 20 km North of the site, at almost exactly the same altitude and a similar situation in the Alpine range: the mean annual air temperature during the years 2006Ͳ2009 is Ͳ0.35°C, and the mean precipitation during the last 35 years is between 1 and 2m per year. For the variability, the history of deviations against mean temperature and precipitation values measured at the station Chamonix from October 1959 to September1994wastransferred. Themodelwasrunforvariousscenarios.Themainresultsarethefollowingones: 94 PermafrostResponsetoClimateChange x Allscenarioswithameanannualairtemperature<Ͳ3°Candprecipitation>1mperyearlead tothepersistenceofthesnowcoverandtotheformationofaglacier.Intheseconditions, the ground ice volume doesn’t change and its temperature rises to the melting point. The permafrostunderthepermanentsnowbecomestemperate. x WithameanairtemperatureofͲ0.5°Candaprecipitationof1mperyear,nothinghappens within the first ten years. The snow cover, with a mean thikness of 1m in high winter preventsthesoilfromcooling,andthehighicecontentabsorbstheheatflux.Underpresent conditions,thepermafrostandicebodyseemstobestable. x Totesttheeffectofastrongandbrutalwarming,awarmingof5°Cwassetfromthesecond model year, leading to a mean annual air temperature of 4.5°C. After three years, the ice volumehasnotyetchanged,buthastotallydisappearedafter20years.Thiscorrespondsto themeltingof150to200kg/m2/year.Thethermalequilibriumhoweverisstillnotreached after30years,andthetemperatrureat20Ͳ30mdepthisstillcloseto0°C(figure7).Inthis simulation,thewintersnowcoverisoftenverythin(0to1.5mdependingontheyear). Fig7–BoreholeSD1.Left:initialstate,year1(MAATͲ0.5°C).Right:monthlygeothermsofyear32,10 yearsaftertotaldisappearanceofgroundice,31yearsaftersuddenwarmingof5°C. Theresultsshowthat: x The high ice content totally explains the damping of seasonal variations at the activeͲ layer/iceͲrich body transition. The latent heat transfer due to ice melting/freezing absorbs almostthetotalheatflux. x Thesiteisstableunderpresentdayconditions. x In case of a progressive temperature rise, the heat flux increase would be almost totally absorbedbylatentheatduringthefirstdecade,andneithericetemperaturewouldrisenor significanticevolumelosswouldoccur. 95 PermaNET–CasestudiesintheEuropeanAlps x Significant changes would occur only after several decades or in case of a very strong warming. Thus,veryiceͲrichpermafrostcouldshowahighresistancetoclimatechange.However,themodel run considered a melting point at 0°C and does not take into account the effect of possible melt waterflows. Acknowledgements. – The study of the Bellecombes Rockglacier was supported by the Fondation MAIF.TheboreholeswerecoͲfinancedbytheRegionRhôneͲAlpesthroughtheCIBLE2008program. TheskiresortDeuxͲAlpesfacilitatedtheworkandprovidedhelpforlogistics. References: Lorier L. et al., 2010: Analyse des risques induits par la dégradation du permafrost alpin. Rapport final,projetFondationMAIF.ADRGT,Gières. Schoeneich P., Bodin X., Krysiecki J.ͲM., Deline P. & Ravanel L., 2010: Permafrost in France. Report N°1.PermaFrancenetwork,Grenoble,InstitutdeGéographieAlpine. 96 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.8 AiguilleduMidi,MontBlancMassif,FrenchAlps Citationreference DelineP.,CremoneseE.,DrenkelflussA.,GruberS.,KemnaA.,KrautblatterM.,MagninF.,MaletE., MorradiCellaU.,NoetzliJ.,PogliottiP.,RavanelL.(2011).Chapter3.8:CasestudiesintheEuropean Alps–AiguilleduMidi,MontBlancmassif,FrenchAlps.InKellererͲPirklbauerA.etal.(eds):Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.97Ͳ108. Authors Coordination:PhilipDeline Involvedprojectpartnersandcontributors: Ͳ EDYTEM, Université de Savoie, France (EDYTEM) – Philip Deline, Velio Coviello, Florence Magnin,EmmanuelMalet,LudovicRavanel Ͳ Regional Agency for the Environmental Protection of the Aosta Valley, Italy (ARPA VdA) – EdoardoCremonese,UmbertoMorradiCella,PaoloPogliotti Ͳ UniversityofBonn–AnjaDrenkelfluss,AndreasKemna,MichaelKrautblatter Ͳ UniversityofZurich–StephanGruber,JeanetteNoetzli Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 97 PermaNET–CasestudiesintheEuropeanAlps Summary WedevelopinvestigationsattheAiguilleduMidi(3842ma.s.l),whererockwallsareofdiverse aspectsandslopeangles,andgalleriesareaccessibleyearͲround.Intheframeworkoftheproject PermaNET,wemonitortherockthermalregime(i)with9sensorswithonetothreethermistors installeduptoadepthof55cm;(ii)withthree10mdeepboreholesequippedwiththermistor chains; and (iii) by using Electrical Resistivity Tomography (ERT), based on the temperatureͲ resistivityrelationshipofthelocalgranite.Thesemeasurementswerecompletedbytwomobile automatic weather stations. Combined with a 3DͲhighͲresolution DEM made using longͲ and shortͲrange Terrestrial Laser Scanning (for rockwalls and galleries, respectively), these data will be used for physicallyͲbased model validation or construction of statistical models of rock temperature distributionandevolution intherockwalls.Thesitestartedtobeinstrumentedin 2005,andsomemethodsarestillexperimental.Herewefocusonthethermalmonitoringdevice installedonthesiteandpresentsomefirstresults. 98 PermafrostResponsetoClimateChange 1. Introductionandstudyarea Starting off in the framework of the EU coͲfunded FrenchͲItalian PERMAdataROC project and presentlyunderdevelopmentwithintheprojectPermaNET,ourinvestigationsattheAiguilleduMidi (N45°52',E6°53')beganinNovember2005.Wechoosethissite(Fig.1)becauseof(i)itselevation (3842m a.s.l.), (ii) its steep rockwalls characterized by differents aspects, slope angles, rock structures,andsnowcovers,and(iii)itsaccessibilitythroughouttheyearfromChamonixbyacable car from 1955 – half a million tourists visit the site each year; rockwalls of the Piton central are accessiblebyabseilingfromtheupperterrace,andgalleriesallowtopenetrateintotherockmass whichisrareinhighmountainareas,andlede.g.toobserveasignificantcirculationofwaterduring thehotSummerof2003,forthefirsttimesincetheopeningofthesite.AiguilleduMidihasbecome amajorsiteforthestudyofrockwallpermafrostintheAlps. A B C D Fig.1 TheAiguilleduMidi(3842ma.s.l.):(A)viewfromtheeast.Atthecenter:Pitoncentral;ontheright: Pitonnord,withthecablecarstation.(B)westside(1000ͲmͲhigh).Atitsbottom:GlacierdesBossonsetGlacier Rond;ontheleft,intheshadow:northsideofthegroupoftheAiguilleduMidi,mainlyglaciated.(C)underthe pylon:subverticalnorthwestsideofthePitoncentral(100ͲmͲhigh).(D)Southeastside(200ͲmͲhigh).Ontheleft: beginningoftheArêtedesCosmiques;ontheright:PilastresudͲest.PhotographsbyP.DelineandS.Gruber(A, C,D:11.10.2005;B:30.09.2007) 99 PermaNET–CasestudiesintheEuropeanAlps The group of the Aiguille du Midi, at the western end of the Aiguilles de Chamonix, develops asymmetricallyover2kmbetweentheColduMidiandtheColduPlan(Fig.2).Itformsarockyscarp whose west face and north face (which is glaciated on its upper half) are towering the Glacier des Bossons (by 1000 m) and the Glacier des Pélerins (by 1350 m) respectively (Fig. 1B). However, the back of this scarp is occupied by the western basin of Glacier du Géant, separated from west and northfacesbytherockyArêtedesCosmiquesandthesummitoftheAiguilleduMidi. ThebulkoftherockisgraniteofMontBlanc,amassiverockwithagrainedfaciesthatcontributesto thesteepnessoftheAiguilledu Midifaces–50°forthenorthface,57Ͳ58°forthesoutheast(only 200mhigh)andwestsides.Manyrockwallswithinthesefacesaresubvertical,asthenorthfaceof thePitoncentral(Fig.1C)orthePilastresudͲest(Fig.1D),becauseofthesubverticaldipofthetwo mainfamiliesoffaultswhosedensenetworkcutsacrosstheMontBlancmassif.Becauseofadense secondary fracturing unevenly distributed very massive rockwalls alternate with very densely fracturedones(Fig.1D).OurstudyfocusesonthesummitoftheAiguilleduMidi,between3740and 3842ma.s.l.,heretermed“AiguilleduMidi”. Fig.2GroupoftheAiguilleduMidi.TheinstrumentedsiteisthepeaklabelledAig duMidi.Detailofthemap Mont Blanc n°1 NordͲAiguille du Midi (IGN, 1952) at 1:10000 (contour interval: 10 m). This extract is 4 km large. le 2. Permafrostindicatorsandrecentthermalevolution 2.1Methods Rocktemperaturemonitoring TherocksurfacetemperatureismeasuredeveryhouroverallfacesofthePitoncentralsince2005by severalminiͲdataloggerswiththermistorsplacedatdepthsof3,10,30and55cmbelowthesurface. Three 10m deep boreholes have also been drilled in September 2009 (Fig. 3), normal to the rock 100 PermafrostResponsetoClimateChange surface of: (i) the northwest face (borehole at 3738m a.s.l.), a vertical rockwall in a very massive granite;snowcanonlyaccumulateonasmall2mwideterrace;(ii)thesoutheastface(boreholeat 3745ma.s.l.),a55°slopeangleinahighlyfracturedareasnowcoveredduringapartoftheyear;and (iii)thenortheastface(boreholeat3753ma.s.l.),witha65°slopeangleinaveryfracturedcouloir, wheresnowoccursoveralargepartoftheyearduetotheconcavetopography.Theseboreholesare located well below the cable car infrastructure level in order to minimize its thermal influence on rock temperature. They are equipped with 10m long chains of 15 thermistors that measure rock temperatureevery3hourssinceDecember2009onthenorthwestandsoutheastfaces,sinceApril 2010onthenortheastface. Fig.3 Drillingofa10mdeepboreholeinthesoutheastfaceofPitoncentralinSeptember2009.Photograph byP.Deline17.09.2009 Electricalresistivitytomography Electrical Resistivity Tomography (ERT) is increasingly being used as a nonͲinvasive imaging tool in alpine permafrost studies (Krautblatter & Hauck, 2007; Krautblatter et al., 2010). Key objectives of thismethodare(i)themappingoftemperaturedistributionsinsidetherocktoinferthepresenceof permafrost, and (ii) the delineation of fracture zones given their influencing role on permafrost dynamics and stability. For the first purpose a preliminary relationship between temperature and resistivity of the rock has been established in laboratory. The imaging of fractures, however, is a notoriously difficult task using conventional ERT approaches which rely on smoothnessͲconstraint regularization.AttheAiguilleduMidi,weinvestigateregularizationschemesforimprovedfracture delineationbymeansofnumericalsimulationsandapplicationtofielddata. 101 PermaNET–CasestudiesintheEuropeanAlps Since2008,fourERTsurveyswereconductedatthesite.Eachonecomprisedtheacquisitionofmore than 10,000normal and reciprocal dipoleͲdipole data over three different arrays of altogether 144 electrodes. The electrodes of twoarrays could be placed to almost surround the Piton central and the Piton nord in a horizontal plane, offering a favourable tomographic coverage. A vertical northͲ southtransectacrossthePitoncentralwasinstalledbyabseilingonthenearverticalnorthandsouth faces.TheERTdatawereinvertedusingisotropicsmoothing,anisotropicsmoothing,andafocussing regularization scheme based on the soͲcalled minimumͲgradient support (MGS), and employing a finiteͲelementgridwhichcapturestheirregulargeometryoftherockaswellastheelectrodelayout. Airtemperaturemonitoring AirtemperatureandrelativehumidityaremeasuredonsouthandnorthfacesbythemeanofminiͲ dataloggersplacedinsideradiationshields.Onthesouthface,meteorologicalparameters(incoming andoutgoingsolarradiationinbothshortwaveandlongwavebands,windspeedanddirection)were measuredduringnearly4years(December2006toOctober2010)byanautomaticweatherstation adaptedandinstalleddirectlyontherockwall. TerrestrialLaserScanning A DEM is necessary (i) to accurately represent the rock volume, (ii) as a basis for a geological structureanalysis,(iii)torefinethemodelingofrocktemperaturedistribution,and(iv)tostudythe water flow into the rock mass. A highͲresolution DEM was made using longͲ and shortͲrange TerrestrialLaserScanning–forrockwallsandgalleries,respectively(Fig.4). Fig. 4 Triangulated Irregular Network (TIN) model of the rockwalls of the Pitons nord (left) and central, obtainedbylongͲrangeterrestriallaserscanning. 102 PermafrostResponsetoClimateChange 2.2 Preliminaryresultsaboutrocktemperature All the subͲsurface data are collected mainly for initialization, calibration and validation of rock temperature and permafrost distribution models. However their statistical analysis allows quantifyingthegreatspatialvariabilityofsubͲsurfacetemperaturesinsuchcomplexmorphologies. Preliminaryresults(Table1;Fig.5)showthat:(i)themeanannualgroundsurfacetemperaturecan varyofmorethan6°Cwithinfewmetersofdistance,dependingontheaspect;(ii)freezeͲthawcycles on southern aspect are nearly twice as frequent than in the north but markedly shallower; (iii) a significantthermalͲoffsetprobablyexistsdespitethecompactrockmassandtheabsenceofground covers(e.g.debris,snow)onsouthfaces. Fig.5–MeandailyrocktemperatureonthesouthandnorthfacesofthePitonCentralforthehydrologicalyear 2008Ͳ09atthreedifferentdepthsbelowthesurface. Table 1 – Rock temperature 55cm below the surface on south and north faces of the Piton Central of the Aiguille du Midi for 2007Ͳ08, 2008Ͳ09, and 2009Ͳ10 hydrological years. MAGT: mean annual ground temperature;MAX/MINabs:absolutelywarmestandcoldesttemperature;DateMAX/MINabs:occurrencedate of MAX/MINabs; ȴTavg/max/min: mean, maximal and minimal amplitude of daily temperatures; ZCD: Zero Crossing Days, i.e. number of days per year where the 0°CͲisotherm is crossed; MAX/MINday: warmest and coldestmeandailytemperature;DateMAX/MINday:occurrencedateofMAX/MINday;DBZ:DaysBelowZero, i.e.numberofdayswithmaximumtemperaturebelow0°C. 103 PermaNET–CasestudiesintheEuropeanAlps Deeper borehole thermistor chains show a very sharp contrast between the three surveyed faces (Fig.6). A time lag of approximately half a year between minimal and maximal air temperature periods (JanuaryͲFebruary, and July, respectively) and minimal and maximal rock temperature periodsatadepthof10m(JuneͲJuly,andDecemberͲJanuary,respectively;Fig.7).In2010,theactive layerthicknessvariedfrom1.80minthenorthwestfaceto5.20minthesoutheastface. While anisotropic smoothing can be adjusted such as to allow a correct interpretation of the ERT image, inversion with MGSͲbased regularization provides most convincing results in terms of resolvingsharpstructuralfeaturesassociatedwithlithologicalchangessuchasfractures,butatthe sametimepreservingsmoothchanges typicaloftemperaturevariationsintherock.LowͲresistivity zonescouldbedelineatedatthePitonnord,whichseemtocoincidewithwaterͲcontainingfractures causedbyartificialheatsupply;continuationofthesefracturesoutsidetheheatedgalleryindicates permafrost conditions. At the Piton central, resistivity values were below 200000:m in October 2010,whichisquitereasonablewithrespecttothetemperaturerange(Fig.8). Meteorologicaldataontherockwallshowthat:(i)thepeakofSWradiationoccursduringthewinter (>1300W/m2)givingstrongdailytemperatureamplitudesatrocksurface(upto30°C);(ii)thereisa clear prevalence of upslope winds with speeds ranging from 4 to 9m/s; (iii) the mean annual air temperature isaroundͲ7°Conaverage(Table2),with5to6°Cofdailyamplitudeandanabsolute temperaturerangebetweenͲ25to+12°C. Fig.6 Plotsofrocktemperaturefromthesurfaceto10mdepthfortheperiod18.12.2009to21.01.2011at thenorthwestandsoutheastfaces,and13/04/2009to21/01/2011atthenortheastfaceoftheAiguilleduMidi (continuednextpage) 104 PermafrostResponsetoClimateChange Fig.6continued 105 PermaNET–CasestudiesintheEuropeanAlps Fig.7Timelagbetweenairtemperatureand10mdeeprockatthesoutheast,northeastandnorthwestfaces ofthePitoncentraloftheAiguilleduMidi. Fig.8 Electrical resistivity tomography in a horizontal plane at the Piton central of the Aiguille du Midi on 22.10.2010.Blackdotsareelectrodelocations;blue/green:unfrozen;yellow:transitionfromunfrozentofrozen; red:frozen;resistivityisintherange102.Ͳ105.0:m.Reliableresultsareonlyinsidethearcthatisenclosedby the48electrodes. 106 PermafrostResponsetoClimateChange Table2–AirTemperatureonthesouthface(A)andnorthface(B)ofthePitonCentraloftheAiguilleduMidifor 2007Ͳ08, 2008Ͳ09and 2009Ͳ10hydrological years.Meanannual air temperature(MAAT), frost days (FD), ice days(ID)andfreezeͲthawdays(FTD)calculatedassuggestedinchapter2.Onthenorthface,hydrologicalyear 2007Ͳ08istheonlyonewithoutmissingdata. (A) South face 2007-08 2008-09 2009-10 Mean (B) North face 2007-08 MAAT (°C) -6.77 -6.85 -7.33 -6.98 -7.53 FD (d) 352 336 335 341 353 ID (d) 246 241 249 245 275 FTD (d) 106 95 86 96 77 2.3 Outlook Aiguille du Midi is the most elevated Alpine site to study permafrost in rockwalls. During the next yearsnumericalmodellingofthetransient3Dsubsurfacetemperaturefields,combiningadistributed energybalancemodelwitha3Dheatconductionscheme,willbeaccomplished(Noetzlietal.,2007; Delineetal.,2009).Severalstatisticalmodelsofdistributionofsurfacetemperaturesoftherockwalls begantobedevelopedfortheMontBlancmassif,butcomparingtemperaturedataattheAiguilledu Midi with one of these models shows some discrepancies: whereas the Piton central north face modeledtemperatureisintherangeofͲ7°toͲ13°C(Fig.9),itsmonitoredaveragetemperatureisca. Ͳ6°C(Table1). Fig.9 ModeleddistributionofrocksurfacemeanannualtemperatureintheMontBlancmassif(Frenchside) with the model TEBAL (view from the west; image draping: E. Ployon). The temperature is in the range Ͳ1°C (darkorange)toͲ13°C(darkblue);groupoftheAiguilleduMidi(northandwestsides)isdelimited. 107 PermaNET–CasestudiesintheEuropeanAlps The combination of process understanding, statistical analyses and/or modelling (e.g. numerical modelling of water flow in rock fractures) will help to improve our understanding of the characteristics of the mountain permafrost degradation. Secondly, we are interested in how a reduction in the uncertainty of data, process understanding and models may contribute to our predictive skill of corresponding effects. This longͲterm monitoring and modelling approach at Aiguille du Midi will be a strong support to take into account future thermal response of rockwall permafrosttopredictedclimatechangeinthenext50yearsanditsgeomorphicconsequences. 3. Possiblefuturethermalresponsetopredictedclimatechange Assuggestedinchapter2,frostdays,icedaysandfreezeͲthawdayshavebeencomputedusingthe availableairtemperaturedatasetofthesouthfaceofAiguilleduMidi(Table2A).Referringtomaps andpredictionsinchapter2,theairtemperaturemeasurementsconductedonbothsouthandnorth facesoftheAiguilleduMidifrom2007to2010areinaccordancewiththemeansoftheperiod1961Ͳ 1990fortheGreatAlpineRegion(GAR).ThatisanumberofIDintherange241Ͳ260andanumberof FDgreaterthan320.OnlythenumberofFTDisabovethemeaninthemeasurements(96vs.70/80 of the mean 1961Ͳ1990), probably because the sensor is placed on a south near vertical rockwall wheredailytemperaturevariationsareverystrong,especiallyduringwinter. Thepredictionsfortheperiod2021Ͳ2050inthestudyareaareadecreaseofIDrangingfromͲ13/Ͳ16 daysperyearthatmeans232Ͳ229IDinsteadof245,andadecreaseofFDrangingfromͲ14/Ͳ15days peryearthatmeans326FDinsteadof341.Applyingthesescenariostothedataofthenorthface (Table2B)thenumberofIDcouldfalltoabout260daysperyearthatmeansconditionsmoresimilar to those observed today on the south faces. These changes could lead to a doubling of the active layerthicknessofthenorthexposedrockwallsoftheAlpsinthefuture,withaconsequentlyincrease ofinstabilitiesandrockfallevents. Acknowledgements.–CompagnieduMontBlanc,especiallyE.Desvaux,areacknowledgedfortheir assistance to our study at Aiguille du Midi. Participation of Chamonix Alpine guides M. Arizzi, L. Collignon,andS.Frendo,andEDYTEMcolleaguesP.PaccardandM.LeRoy,totheSeptember2009 drillingwascrucialforitssuccess.ManythanksareduetoR.Bölhert,S.Jaillet,A.Rabatel,B.Sadier, S.Verleysdonkfortheirhelpandcontributions. References: DelineP.,BölhertR.,CovielloV.,CremoneseE.,GruberS.,KrautblatterM.,JailletS.,MaletE.,MorradiCellaU., NoetzliJ.,PogliottiP.,RabatelA.,RavanelL.,SadierB.,VerleysdonkS.,2009:L’AiguilleduMidi(massif du Mont Blanc): un site remarquable pour l’étude du permafrost des parois d’altitude. Collection EDYTEM,8–CahierdeGéographie,135Ͳ146. KrautblatterM.,Hauck,C.,2007:Electricalresistivitytomographymonitoringofpermafrostinsolidrockwalls. JournalofGeophysicalResearch,112,F02S20,doi:10.1029/2006JF000546. KrautblatterM.,VerleysdonkS.,FloresͲOrozcoA.,KemnaA.,2010:TemperatureͲcalibratedimagingofseasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/AustrianAlps).JournalofGeophysicalResearch,115,F02003. NoetzliJ.,GruberS.,2009:TransientthermaleffectsinAlpinepermafrost.TheCryosphere,3,85Ͳ99. NoetzliJ.,GruberS.,KohlT.,SalzmannN.,HaeberliW.,2007:ThreeͲdimensionaldistributionandevolutionof permafrost temperatures in idealized highͲmountain topography. Journal of Geophysical Research, 112,F02S13.doi:10.1029/2006JF000545: 108 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.9 RockfallsintheMontBlancmassif,FrenchͲItalianAlps Citationreference DelineP.,RavanelL.(2011).Chapter3.9:CasestudiesintheEuropeanAlps–RockfallsintheMont Blanc massif, FrenchͲItalian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.109Ͳ118. Authors Coordination:PhilipDeline Involvedprojectpartnersandcontributors: Ͳ EDYTEM,UniversitédeSavoie,France(EDYTEM)–PhilipDeline,LudovicRavanel Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 109 PermaNET–CasestudiesintheEuropeanAlps Summary The frequency and volumes of rockfalls as well as their triggering factors remain poorly understoodduetoalackofsystematicobservations.IntheframeworkoftheprojectPermaNET, this study case analyses inventories of rockfalls acquired in the whole Mont Blanc massif by innovative methods in order to characterize the link between climate and rockfalls, and to emphasizetheroleofpermafrost.Intwosectorsofthemassif,thecomparisonofphotographs takensincetheendoftheLittleIceAgeallowedtheidentificationof50rockfalls.Inmostcases these rockfalls occurred during the hottest periods. On another time scale, a network of local observersallowedthedocumentationofthe139rockfallsthatoccurredin2007,2008and2009 in the central area of the Mont Blanc massif. Furthermore, the analyses of a satellite image allowed the identification of 182 rockfalls in the whole massif at the end of the 2003 summer heat wave. For most of those rockfalls, the permafrost degradation seems to be the main triggeringfactor. 110 PermafrostResponsetoClimateChange 1. Introductionandstudyarea Arockfallcorrespondstothesuddencollapseofarockmassfromasteeprockwall,withavolume exceeding 100m3. In the last two decades, many rockfalls and rock avalanches (volume > 0.1Ͳ 1×106m3) occurred from permafrost affected rockwalls throughout the world (Noetzli et al. 2003). Rockfalls generally occur in hard rocks along preͲexisting fractures. In high mountains, three major factors–possiblycombined–cantriggerrockfalls:(i)glacialdebuttressingduetoglacialretreat,(ii) seismic activity, and (iii) permafrost degradation, generating physical changes of the potential interstitialice(Gruber&Haeberli2007). Thecharacterizationofrockfalleventsandtheunderstandingoftheirevolutionareprerequisitesto anyresponseofmanagement.However,dataonrockfallsathighelevationarerareanditisdifficult tointerpretnonͲrepresentativedata(fewisolatedexamples). Started in the framework of the EU coͲfunded FrenchͲItalian PERMAdataROC project, our investigations are presently carried out within the project PermaNET. In this context, we systematicallycollectandprocesshistoricalandcurrentdataonrockfalls(Ravanel2010)inorderto bettercharacterizethisprocess(triggeringconditions,frequency,andvolumes). ThefirstaimofthisstudycaseistoshowthecorrelationexistingbetweenrockfallsintheMontBlanc massifandglobalwarming.Thesecondoneistohighlighttheprobablycrucialroleofthepermafrost degradationontherockfalltrigger. 2. Permafrostindicatorsandrecentthermalevolution 2.1Methods PhotoͲcomparisonapproach Written and oral evidences of rockfalls are not sufficient to accurately reconstruct the recent rockwallmorphodynamics.ThephotoͲinterpretationofaseriesofphotographsisthereforethemost appropriate method. We focus on two areas of the Mont Blanc massif with a rich existing documentation:theWestfaceofthePetitDru(3730ma.s.l.)andthenorthsideoftheAiguillesde Chamonix(3842ma.s.l.fortheAiguilleduMidi).TheproximityofthesepeakswithChamonix,their morphologyandtheirsymbolismallowarichiconographysincetheendoftheLittleIceAge(LIA). Thefirststepconsistsinsettingupdocumentarycorpus,whichisverytimeconsuming.Nearly400 photographsofthetwostudiedareashavebeengatheredbutonlyafewdozencouldfinallybeused. Photographs are compared and interpreted in different steps: (i) delineation of the rockfall scars (Fig.1),(ii)determinationoftheperiodscharacterizedbymorphologicalandcolourchangescaused by rockfalls – it was often necessary to diversify and crossͲcheck information sources in order to precisedatesofcollapse–,and(iii)estimationoftheinvolvedvolumes.50rockfallsoccurredinthe twoareasduringtheperiodfromthe endof theLIAto2009,involvingrock volumesrangingfrom 500to265000m3(Fig.2;Ravanel&Deline2008,2011). Networkofobservers,SPOTͲ5imageandGISanalysis BesidestheinventoriesofpostͲLIArockfalls,itisimportanttocharacterizecurrentrockfalls.Onlya structured network of observation coupled with fieldwork can allow a near completeness of the inventoryofthecurrentrockfalls. 111 PermaNET–CasestudiesintheEuropeanAlps Fig.1 Comparisonbetweenphotographsof1862and2009ofthewestfaceoftheGrandsCharmozandthe Aiguille du Grépon, and of the north face of the Rognon des Grands Charmoz. Yellow ellipses indicate areas affectedbyrockfallsbetweenthetwodates(Ravanel&Deline2011,slightlymodified). The network consists of dozens of guides, hut keepers and mountaineers. Initiated in 2005, this observernetworkbecamefullyoperationalin2007.FocusedonthecentralpartoftheMontBlanc massif, the inventory is carried out with reporting forms, indicating the main characteristics of the rockfallsandtheconditionsoftheaffectedrockwall.Animportantfieldworkisconductedeveryfall inordertocheckandtocompletethereportedobservations. Meanwhile, in order to compare the data obtained by the network with the exceptional morphodynamicsofthethreemonth2003summerheatwave,the2003rockfallsweresurveyedon thebaseofsupraglacialdepositsthroughtheanalysisofaSPOTͲ5imageoftheentiremassiftakenat theendoftheheatwave(23.08.200,10:50GMT). Characteristicsofeachcollapsearedeterminedusingseveralmethods.Altitudeofscars,slopeangle and orientation of the affected rockwalls, and the deposit areas are calculated in a GIS. Because directmeasurementsofthescarvolumeswerenotpossible,theareaofthedepositswasmultiplied withanestimateoftheirthicknessesinordertoassessthecollapsedvolumes.Geologicalparameters arederivedfromgeologicalmaps,andthepossiblepresenceofpermafrostwasdeterminedfroma modelofmeanannualgroundsurfacetemperature. Thenetworkofobserversallowedthedocumentationof45rockfallsin2007,22in2008and72in 2009(Fig.3),involvingrockvolumesrangingfrom100to33000m3(Delineetal.2008,Ravaneletal. 2010, Ravanel & Deline in press). Furthermore, the analysis of the SPOTͲ5 image allowed the identificationof182rockfallsinthewholemassifattheendofthe2003summerheatwave(Fig.4; Ravaneletal.2011). 112 PermafrostResponsetoClimateChange Fig.2Locationofthe8scarsofthemain(outlines)andsecondary(stars)rockfallsatthewestfaceoftheDrus. 113 PermaNET–CasestudiesintheEuropeanAlps Fig. 3 Rockfalls occurred in the Mont Blanc massif in 2007 (red dots), 2008 (yellow dots) and 2009 (green dots). 2.2 Linkbetweenclimateandrockfalls Todealwiththerelationshipsbetweenrockfallsandglobalwarming,wecomparedtheoccurrenceof rockfalls at the Drus and the Aiguilles of Chamonix with available climate data – local and reconstructed for the Alps. At the Drus, the climatic factor – especially the thermal one – seems important in the triggering of rockfalls which occurred after the end of the LIA, as shown by their occurrence during the hottest periods (Fig. 5; Ravanel & Deline 2008). The climate control is also demonstrated by the analysis of the 42 rockfalls documented on the north side of the Aiguilles de Chamonix during the same period, with a very strong correlation between rockfalls and hottest periods.70%oftherockfallsoccurredduringthepasttwodecades,whichwerecharacterizedbyan acceleration of the global warming. Heat wave periods are particularly prone to rockfalls: the maximum rockfall frequency occurred during the 2003 summer heat wave (Ravanel & Deline in press). 114 PermafrostResponsetoClimateChange Fig.4 Locationofthe182rockfallsthatoccurredduringthehotsummer2003onthepanchromaticSPOTͲ5 satelliteimage051/257ofthe23.08.2003(Ravaneletal.2011,slightlymodified). 115 PermaNET–CasestudiesintheEuropeanAlps Fig.5ChangesinChamonixmeansummertemperature,volumeandelevationofdocumentedrockfallsinthe west face of the Drus (a fiveͲyear filter has been applied to remove interannual noise). Dotted quadrilaterals representthedifferentrockfalls. There is also correspondence between the 2003, 2007, 2008 and 2009 rockfalls and climatic conditions of those years – in particular with temperatures (Fig. 6). 139 rockfalls have been documentedbetween2007and2009inthecentralareaoftheMontBlancmassif,53ofthembeing preciselydated(38%).Amongthem,51rockfalls(96%)occurredbetweenJuneandSeptember,i.e. duringthehottestmonthsoftheyear.The2003summerheatwave,withapositiveMeanDailyAir Temperature (MDAT) located at very high elevation, has generated extremely active morphodynamics. In the area covered by the network of observers, with 152 rockfalls reported in 2003outofthe182observed,2003hasbeenquiteexceptionalintermsofrockfalloccurrence.Some intensestormsduringsummer2003mayhavecausedhighfluidpressureinfracturesthattriggered rockfalls,butthisfactorremainsdifficulttoassess.Finally,itisworthytonotethat38(72%)ofthe 53preciselydatedrockfallsof2007,2008and2009occurredafteraperiodofMDATwarmingofat leasttwodays(Ravanel2010). 2.3 Theprobableroleofpermafrost The role of climate – especially the one of the thermal factor – has been demonstrated by the analysis of the rockfalls documented in the Mont Blanc massif. This relation can only be fully explained by temperatureͲdependent factors: permafrost degradation, glacial debuttressing and evolutionofice/snowcoveronrockwalls(cryosphericfactors).Thetwolastfactorsmayonlyexplain a little part of the rockfalls. Furthermore, it is sometimes difficult to distinguish between rockfalls linked to glacial debuttressing or to ice/snow cover retreat, and rockfalls due to permafrost degradation,asbothfactorsareoftencloselyrelatedandfavouredbysummertemperatures. Secondly, topographic factors are highlighting the importance of permafrost in rockfall triggering. The average rockwalls elevation in the Mont Blanc massif is around 3000m a.s.l., whereas the averageelevationofrockfallscarsof2003and2007Ͳ2009is3335ma.s.l.Althoughrockwallsarevery commonbelow3000ma.s.l.,theyareaffectedbyveryfewcollapses.Themostaffectedaltitudinal beltis3200Ͳ3600ma.s.l.,whichcorrespondstoareasof“warm”permafrost(closeto0°C,withfast degradation).Moreover,observationsareconsistentwithpermafrostdistributionanditsevolution: (i)thehotterthesummer,thehigherthescarelevations;(ii)asharpcontrastinthescarelevations between north and south faces. Rockfalls occur more frequently in context of pillars, spurs and ridges,particularlyaffectedbypermafrostdegradation. 116 PermafrostResponsetoClimateChange Fig.6 MeandailyairtemperatureattheAiguilleduMidi(3842ma.s.l.)anddailytotalrainfallatChamonix for the year 2009. Arrows indicate the days when one or several collapses occurred, with the value of temperatureandrainfallforthesedays. Finally,thepermafrostdegradationappearstobethemostlikelytriggeringfactorforseveralother reasons(Ravanel2010): x x x x x Almostalloftherecordedrockfalls(98%)occurredinpossibleorprobablemodelledpermafrost; Rockfallsoccurprimarilyduringsummertime,whichispronetopermafrostdegradation; Massiveicewasobservedinatleast22scarsofthe2007Ͳ2009rockfalls; Summer 2003 rockfalls were unusually numerous and could mainly be explained only by permafrostdegradation(Gruberetal.2004); For the largest identified rockfalls (e.g. June 2005 at the Drus), the formation of a deep thaw corridorinthepermafrostmayhavepredisposedrockwallstocollapse. WhenrockfallsinhighͲAlpinesteeprockwallsareconsideredindividually,the roleofpermafrostin their triggering is difficult to establish. On the other hand, this role in the Mont Blanc massif is strongly supported by the analysis of: (i) the 50 surveyed rockfalls (ranging in volume from 500 to 265000m3) at the west face of the Drus and on the north side of the Aiguilles of Chamonix since 1862;(ii) the182surveyedrockfalls(ranginginvolumefrom100to65000m3)inthewholeMont Blancmassifattheendofthe2003summerheatwave;and(iii)the139surveyedrockfallsbetween 2007and2009inthecentralpartofthemassif(ranginginvolumefrom100to33000m3). 117 PermaNET–CasestudiesintheEuropeanAlps 3. Possiblefuturethermalresponsetopredictedclimatechange Withintheglobalwarmingpredictionforthe21thcentury,rockfallsfromhighͲAlpinesteeprockwalls areexpectedtooccurmorefrequently,withvolumesthatarelikelytoincrease.Thefrequencythatis currently increasing should maintain the same trend in the next decades, due to the deepening of theactivelayerasthetemperatureriseabove1800ma.s.l.intheAlpsforthe21thcenturywillbe higher by nearly 1°C than the global one, as reported in chapter 2. Moreover, heat advection by triggeringofwatercirculationatdepthalongthawcorridorswouldincreasethecollapsedvolumes. Acknowledgements. – Alpine guides and hut keepers from Chamonix and Courmayeur who are involvedintherockfallinventoryoftheMontBlancmassifsince2005arekindlyacknowledged. References: DelineP.,KirkbrideM.,RavanelL.,RavelloM.,2008:TheTréͲlaͲTêterockfallontotheglacierdelaLexBlanche (MontͲBlancmassif,Italy)inSeptember2008.GeografiaFisicaeDinamicaQuaternaria,31,251Ͳ254. GruberS.,HoelzleM.,Haeberli,W.,2004:PermafrostthawanddestabilizationofAlpinerockwallsinthehot summerof2003.GeophysicalResearchLetter,31.L13504.doi:10.1029/2004GL020051. GruberS.,HaeberliW.,2007:PermafrostinsteepbedrockslopesanditstemperatureͲrelateddestabilization followingclimatechange.JournalofGeophysicalResearch,112.F02S18.doi:10.1029/2006JF000547. NoetzliJ.,HoelzleM.,HaeberliW.,2003:MountainpermafrostandrecentAlpinerockͲfallevents:aGISͲbased approachtodeterminecriticalfactors.Proceedingsofthe8thInternationalConferenceonPermafrost, Zurich,Switzerland,827Ͳ832. Ravanel L., 2010: Caractérisation, facteurs et dynamiques des écroulements rocheux dans les parois à permafrost du massif du Mont Blanc. Thèse de Doctorat, Université de Savoie, Le Bourget du Lac, France,322pp. RavanelL.,DelineP.,2008:LafaceouestdesDrus(massifduMontͲBlanc):évolutiondel’instabilitéd’uneparoi rocheusedanslahautemontagnealpinedepuislafinduPetitAgeGlaciaire.Géomorphologie,4,261Ͳ 272. RavanelL.,DelineP.,2011:ClimateinfluenceonrockfallsinhighͲAlpinesteeprockwalls:thenorthsideofthe AiguillesdeChamonix(MontBlancmassif)sincetheendoftheLittleIceAge.TheHolocene,21,357Ͳ 365. Ravanel L., Deline P., in press: On the trigger of rockfalls in high alpine mountain. A study of the rockfalls occurredin2009intheMontBlancmassif.ProceedingsoftheRockSlopeStabilityConference,Paris, France. RavanelL.,AllignolF.,DelineP.,GruberS.,RavelloM.,2010:RockfallsintheMontBlancMassifin2007and 2008.Landslides,7,493Ͳ501. RavanelL.,AllignolF.,DelineP.,2011:LesécroulementsrocheuxdanslemassifduMontBlancpendantl’été caniculairede2003.ActesduColloque2009delaSSGm,Olivone,Suisse,245Ͳ261. 118 3. CasestudiesintheEuropeanAlps 3.10 CimeBianchePass,ItalianAlps Citationreference PogliottiP,CremoneseE.,MorradiCellaU.(2011).Chapter3.10:CasestudiesintheEuropeanAlps– Cime Bianche Pass, Italian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.119Ͳ128. Authors Coordination:PaoloPogliotti Involvedprojectpartnersandcontributors: Ͳ Regional Agency for the Environmental Protection of the Aosta Valley, Italy (ARPA VdA) – PaoloPogliotti,EdoardoCremonese,UmbertoMorradiCella Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange Reference 119 PermafrostResponsetoClimateChange Summary Cime Bianche Pass (45°55'N 7°41'E) is located at the head of the Valtournenche Valley in the northeasterncorneroftheAostaValleyRegion(Italy)atanelevationof3100ma.s.l.Twoboreholes ofdifferentdepth(6and41m)drilled30mapartindifferentmorphologicalconditionshavebeen realized in 2005 and instrumented in 2006. The active layer thickness reflects the different snowͲ coverconditionsofthetwoboreholes:inthedeepboreholeitisalmosttwicethevalueobservedin theshallowone.Thetemperatureprofilesofthedeepboreholeallowtoidentifythedepthofzero annual amplitude (ZAA) at ca. 17m. The mean permafrost temperature is about Ͳ1.36°C in this depth. In the next future a probable decrease in the number of ID/year will strongly affect the ground thermal regime leading to a thickening of the active layer, increasing water pressure and permafrost degradation in the study area. All these changes will probably affect the spatial distributionofthehydroͲgeologicalriskinsucharegion. 120 PermafrostResponsetoClimateChange 1.Introductionandstudyarea Cime Bianche Pass (45°55'N 7°41'E) is located at the head of the Valtournenche Valley in the northeast corner of the Aosta Valley Region at an elevation of 3100m a.s.l. (Fig. 1). The site is characterized by bare fractured bedrock locally mantled by shallow coarseͲdebris deposits. The lithologyismainlyconsistingofgarnetiferousmicaschistsandcalcschistsbelongingtotheupperpart of the ZermattͲSaas ophiolite complex (Dal Piaz et al. 1992). Several gelifluction lobes, terracettes andsortedpolygonsoccuronthedeposits. A B Fig.1–Studyarea:(A)localizationofthestudyarea.(B)Siteoverviewandinstruments;intheforegrounda GSTͲgridarea(fencedbytheyellowflags)andinthebackgroundfromrighttoleft:boreholesdataloggers,GSTͲ grid datalogger, automatic weather station and related dataloggers. SkiͲlifts of the BreuilͲCervinia ValtournencheZermattresortarevisibleinthebackground. 121 PermafrostResponsetoClimateChange Thelocalclimatecanbedefinedasslightlycontinentalwithmeanprecipitationaround1000mm/a (meanoftheperiod1931Ͳ1996attheLakeGoilletweatherstation,2540ma.s.l.,1.5kmfar,Fig.1AͲ left).Themeanairtemperature(derivedfromPlateauRosàweatherstation(3480ma.s.l.,2kmfar, Fig.1AͲright)isaboutͲ3.2°Cfortheperiod1951Ͳ2000(Mercallietal.2003).Themeanmonthlyair temperaturesoverthesameperiodgivepositivevaluesonlyfromJunetoSeptember.Februaryisthe coldestmonthandJulyisthehottestone.ThesiteisverywindyandmainlyinfluencedbynortheastͲ northwestairmasses.Thecombinedeffectofirregularmorphologyandstrongwindactionleadtoa highvariabilityofsnowcoverthicknesswithinfewmeters. Thepermafrostmonitoringisperformedby: x Two boreholes of different depth (6 and 41m) drilled 30m apart in different morphological conditions (Fig. 1A). The shallow borehole (SH) is drilled on a convex coarseͲdebris landͲform highlysubjecttowinderosionwhichusuallyavoidstheformationofthicksnowcovers.Onthe other hand the deep borehole (DP) is located in a depression where the snow tends to accumulate,assuringasnowthicknessalwaysgreaterandmoredurablethanthoseobservedin SH. Temperature measurements in the borehole started in January 2005 for the SH and in August2008forDP. x A small GSTͲgrid area equipped with the purpose to quantify the spatial variability of surface temperatureinasmallarea.Thegridhasanextensionof40x10mandisactivesinceJanuary 2005.TheGSTismeasuredat5nodes:4atthegridcornersand1inthecentreofthearea.In each node the ground temperature is measured 2 and 30cm below the surface with hourly frequency.Thesurfaceischaracterizedbycoarseblockymaterialslightlypendingandirregular whichgivesgreatvariabilityofsnowcoveramongthenodes(Fig.1B). The site is equipped with an automatic weather station for the measurement of snowͲdepth, air temperature and relative humidity, wind speed and direction as well as radiation. The site is accessibleallovertheyear,bycablecarandskiinwinterandbyoffͲroadvehicleduringsummer. 2.Permafrostindicatorsandrecentthermalevolution 2.1Meteorologicalrecords Airtemperatureandsnowdeptharetheparametersthatmainlyaffectthegroundthermalregimein permafrost environments (Zhang 2005). On the study site both parameters are measured in correspondenceoftheSHborehole. The Fig. 2A shows monthly air temperature anomalies calculated comparing the monthly means measured at Cime Bianche Pass with longͲterm monthly means (1951Ͳ1998) derived from the Plateau Rosà meteorological station. An extrapolation method based on monthly lapse rates was usedtoshiftͲdownthelongͲtermdatasetfromtheelevationofPlateauRosàtoCimeBianchePass. TheFig.2BshowsthemeansnowdepthoftheperiodNovember15thͲJune15thovertheboreholeSH for3availablehydrologicalyears. 2.2ActiveLayerThickness The active layer thickness reflects the different snowͲcover conditions of the two boreholes. The combinedeffectofmorphologyandwindleadstothicksnowcoverabovetheDPboreholeandathin snow cover above the SH. These morphological differences strongly affect the ground thermal regime:itfollowsthatthethicknessoftheactivelayer(ALT),definedasthemaximumdepthofthe 0°CͲisotherm, in the deep borehole is almost twice the one observed in the shallow one. Table 1 summarizesthevaluesofALTofsomeyearsobtainedbylinearinterpolationamongthemeasured temperaturesatdifferentdepths. 122 PermafrostResponsetoClimateChange A B Fig.2–(A):monthlyairtemperaturesfrom2006to2009comparedwithalongtermmean(1951Ͳ1998)derived fromPlateauRosaobservations.Theverticallinesgivethestandarddeviationofthelongtermmonthlymeans. Red lines are the monthly means measured at Cime Bianche Pass. (B) mean seasonal snow depth above the boreholeSHcalculatedovertheperiodNovember15thͲJune15th. 123 PermafrostResponsetoClimateChange A B Fig.3–Maximumdailygroundtemperaturevs.timeintheSH(A)andDP(B)boreholes.Theblacklineisthe 0°CͲisotherm.NotethatyͲaxeshavedifferentranges. 124 PermafrostResponsetoClimateChange Table1–Valuesofthemaximumactivelayerthickness(ALT)inthetwoboreholesatCimeBianchePassand dayoftheyearinwhichthevaluehasbeenreached. ActiveLayerThickness(ALT)(m) Shallow Deep Borehole Borehole 3.12 Ͳ 2.36 Ͳ 1.9 3.9 2.8 4.85 Hydrological Year 2005/2006 2006/2007 2007/2008 2008/2009 OccurrencedayofmaximumALT Shallow Deep Borehole Borehole th October7 Ͳ th October11 Ͳ September30th September27th th th October22 October17 Comparingthecontourplotsofbothboreholes(Fig.3)withthesnowͲdepthmeasuresofFig.2B,a goodcorrelationbetweenthemeanseasonalsnowdepthandtheactivelayerthicknesscanbeseen. The difference in the active layer thickness from 2008 to 2009 in both boreholes shows the same behaviour: 2009 maximum depth has an increase of about 1m compared to 2008, due to the exceptionalsnowfallsofthewinterseason2008/09whichleadtoimportantsnowcoverthroughout thewinteronbothboreholes. 2.3PermafrostTemperature Thetemperatureprofilesofthedeepboreholeallowtoidentifythedepthofzeroannualamplitude (ZAA)ataround17m.ThemeanpermafrosttemperatureatthisdepthisaboutͲ1.36°C(Fig.4A).The thermalͲoffset,definedinaccordancetoRomanovsky&Osterkamp(1995)asthedifferencebetween TTOP (mean annual permafrost surface temperature) and MAGST (mean annual ground surface temperature), seems quite variable from year to year. The available values for both boreholes are reportedinTable2. Table 2 – Values of thermalͲoffset in the boreholes. MAGST is calculated using the node at Ͳ2cm from the groundsurface.TTOPiscalculatedatthedepthofALT(Table1)bylinearinterpolationamongthemeanannual temperaturesofthefirstnodeaboveandfirstnodebelowtheALTvalue. ShallowBorehole Hydro.Year DeepBorehole MAGST (°C) TTOP (°C) ThͲOffset (°C) MAGST (°C) TTOP (°C) ThͲOffset (°C)㩷 '08Ͳ'09 Ͳ0.05 Ͳ0.73 Ͳ0.67 Ͳ0.01 Ͳ0.81 Ͳ0.8 '09Ͳ'10 Ͳ1.1 Ͳ1.24 Ͳ0.14 Ͳ1.17 Ͳ1.23 Ͳ0.05 Fig.4showstheboreholetemperatureprofilesatspecificdaysoftheyear.Meandailytemperature profileof1stAprilarerepresentativeofgroundtemperaturesattheendofthewinterseasonwhile thoseof1stOctoberarerepresentativeofgroundtemperaturesattheendofthehydrologicalyear neartheoccurrenceofthemaximumALT. The effect of different snow amount during the winter season is clearly reflected in the 1st April profiles of borehole SH. The profiles differ very much from each other with the colder ones corresponding to the less snowy years. The great differences at the end of the winter are systematically levelled during the spring/summer period, indeed the 1st October profiles differ less from each other. From the beginning of the measures the hydrological year 2007/08 shows the coldestgroundtemperatureprofilesandshallowerALT(Table1).Thisresultsfromacombinationof 125 PermafrostResponsetoClimateChange scarce snow accumulation and summer air temperature around the mean (Fig. 2). In contrast the seasonswhichshowwarmergroundtemperatureprofilesanddeeperALTarethosewithabundant snowduringthewinterandairtemperatureabovethemeanduringthewinterͲsummerperiod.This ismainlytrueforthehydrologicalyear2008/09whilein2005/06thequitecoldgroundtemperature profile of April is completely overhung by the extremely warm spring/summer 2006. All these considerationssuggestthatevenifwinterconditionsarestronglyfavourabletogroundcoolingthey are often not enough to restrain the effect of very hot springͲsummer conditions on ground temperatures. A B Fig.4–GroundtemperatureprofilesovertheSH(A)andDP(B)boreholesatspecificdaysattheendofwinter andsummerseasons. 126 PermafrostResponsetoClimateChange 3.Possiblefuturethermalresponsetopredictedclimatechange As suggested in chapter 2, frost days (FD), ice days (ID) and freezeͲthaw days (FTD) have been computed using the air temperature dataset of the Cime Bianche Pass over the available years of observation(Table3). Table3–Frostdays(FD),IceDays(ID)andFreezeͲThawDays(FTD)occurrenceattheCimeBianchesiteduring the available hydrological years (October 1stͲNovember 30th). The last column reports the mean value of the period. 2006/07 2007/08 2008/09 2009/10 Mean MAAT (°C) Ͳ1.73 Ͳ3.01 Ͳ3.4 Ͳ3.75 Ͳ2.97 FD 275 284 275 282 279 ID 149 202 198 201 187.5 FTD 126 82 77 81 91.5 Referringtothemapsandpredictionsofchapter2,theairtemperaturemeasurementsconductedat Cime Bianche Pass from 2006 to 2010 are in accordance with the means of the period 1961Ͳ1990 computed for the Great Alpine Region (GAR). That is a number of ID in the range of 261Ͳ280, a numberofFDintherangeof181Ͳ200andanumberofFTDintherangeof80Ͳ90.Thepredictionfor the period 2021Ͳ2050 in the study area are a decrease of ID ranging from Ͳ15/Ͳ16 days/year that means172IDinsteadof187andadecreaseofFDrangingfromͲ15/Ͳ16days/yearthatmeans264FD insteadof279. Comparing the data of Table 3 and plots of Figure 3 year by year, it is evident that the air temperature is not the only factor controlling the ground temperatures. In fact, as already highlighted,thesnowcoverplaysakeyrole.Despitethis,lookingatthehydrologicalyear2006/07a clear correlation between warmer air temperature and deeper ALT exists. Looking at table 3 it is interesting to note that the number of ID is the most affected value by this anomalous winter. ProbablyafuturedecreaseinthenumberofID/yearwillstronglyaffectthegroundthermalregime leadingtoathickeningoftheALT,increasingwaterpressureandpermafrostdegradation.Allthese changeswillprobablyaffectthespatialdistributionofthehydrogeologicalriskinsucharegion. References: Dal Piaz G. et al., 1992: Le Alpi dal Monte Bianco al Lago Maggiore. Guide Geologiche Regionali a cura della SocietàGeologicaItaliana,3/II,211pp. MercalliL.,CastellanoC.,CatBerroD.,DiNapoliG.,MontuschiS.,MortaraG.,RattiM.&GuindaniN.,2003: AtlanteClimaticodellaValled'Aosta.EditionsSMS,405pp. ZhangT.,2005:Influenceoftheseasonalsnowcoveronthegroundthermalregime:anoverview.Reviewof Geophysics,43:RG4002. 127 PermafrostResponsetoClimateChange RomanovskyV.E.&OsterkampT.E.,1995:Interannualvariationsofthethermalregimeoftheactivelayerand nearͲsurfacepermafrostinnorthernAlaska.PermafrostandPeriglacialProcesses,6,313Ͳ335. 128 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.11 Maroccarorockglacier,ValdiGenova,ItalianAlps Citationreference SeppiR.,BaroniC.CartonA.,Dall’AmicoM.,RigonR.,ZampedriG.,ZumianiM.(2011).Chapter3.11: CasestudiesintheEuropeanAlps–Maroccarorockglacier,ValdiGenova,ItalianAlps.InKellererͲ PirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponsetopresentandfutureclimate changeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲlinepublicationISBN 978Ͳ2Ͳ903095Ͳ58Ͳ1,p.129Ͳ139. Authors Coordination:RobertoSeppi Involvedprojectpartnersandcontributors: Ͳ UniversityofPavia–RobertoSeppi Ͳ UniversityofPisa–CarloBaroni Ͳ MountainͲeeringsrl–MatteoDall’Amico Ͳ UniversityofTrento–RiccardoRigon Ͳ GeologicalSurvey,AutonomousProvinceofTrento–GiorgioZampedri Ͳ Geologist–MatteoZumiani Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalandgeomorphicevolution 3. Possiblefuturethermalandgeomorphicresponsetopredictedclimatechange References 129 PermaNET–CasestudiesintheEuropeanAlps Summary In2001westartedatopographicstudyonanactiverockglacier(namedMaroccarorockglacier, acronym MaRG, coordinates: 46° 13’ 06” N, 10° 34’ 34” E) located in the AdamelloͲPresanella massif(CentralItalianAlps).Since2004,alsothenearͲsurfacegroundtemperaturewasmeasured usingaminiaturedatalogger.Ourdatashowthatineightyears(2001Ͳ2009)MaRGhasmoved downslope with average velocities ranging from 0.02 to 0.21m/year. The velocity reaches a maximuminthemiddleandthelowerpartoftherockglacier,anddecreasestowardstheupper sector,wherethesurveyedbouldersarealmoststationary.Aconsiderabledifferentvelocityfrom year to year has been observed, but no clear trends seem to emerge from the mean annual displacement rate. On the rock glacier the evolution of the ground temperature since 2004 is directlyassociatedwiththeairtemperatureandthesnowconditions,intermsofthicknessand durationofthesnowpack.Thegroundhaswarmedsignificantlybothin2007,afteraverymild and little snowy winter, and in 2009, after a cold but exceptionally snowy winter. The displacement rate of MaRG seems to rapidly react to the ground temperature variations, apparently without any time delay. The exceptionally snowy winter 2008/09 seems to have playedasignificantroleonthedisplacementrate,causingagroundtemperatureincreaseand, probably,anincreaseinvelocity,whichreacheditsmaximuminthatyear. 130 PermafrostResponsetoClimateChange 1. Introductionandstudyarea IntheAdamelloͲPresanellaGroup(CentralItalianAlps),anactiverockglacier(MaRG)locatedinVal Genova has been selected for carrying out multitemporal topographic surveys (Fig. 1). The measurements aim at studying its surface displacement rate and its dynamic behaviour. The displacement rates of the rock glacier are compared with the nearͲsurface thermal regime of the ground and with the major climatic parameters, in order to investigate the potential relationships betweenitsdynamic behaviourandthelocalclimaticconditions.Thisrockglacierisincludedinan inventory published by Baroni et al. (2004), in which it has the number 41 and is also briefly described. Fig.1–GeographicalsettingofthestudyareawithrockglacierMaRGandautomaticweatherstations(AWS) The topographic measurements started in 2001 and have been repeated in late summer of the followingyears(2002,2004,2006,2007,2008and2009).Ontherockglaciersurface,amonitoring networkof25largebouldersmarkedwithsteelboltshasbeenestablishedandalasertheodolitehas beenusedforperformingthesurveys.FormonitoringthenearͲsurfacetemperatureoftheground,a miniaturetemperaturedatalogger(UTL1,accuracy:±0,25°C;Hoelzleetal.1999)hasbeenplacedin 2004 few centimetres below the surface, in a place were fineͲgrained material outcrops. Detailed meteorologicaldata(i.e.airtemperatureandsnowthickness)coveringthefullmonitoringperiodare available from two highͲaltitude automatic weather stations (AWS) located near the studied rock glacier(CimaPresena,3015ma.s.l.,andCapannaPresena,2730ma.sl.). MaRGisatongueͲshaperockglacier,about280mlongand100mwide.Itfacessouthwestandits lowerpart(topedgeofthefrontalslope)reachesanaltitudeof2760ma.s.l.(Fig.2).Thesurfaceof MaRGdoesn’tdisplaythetypicalmorphologicalfeaturesofactiverockglaciers,suchaslongitudinal and transversal ridges, furrows and hollows. MaRG is composed of talus material coming from the shatteredrockwallssituatedabove,andnofieldevidencesofLittleIceAgeglaciationarepresentin 131 PermaNET–CasestudiesintheEuropeanAlps its rooting area. It is almost completely covered by large and very angular boulders (from few decimetrestosomemetersindiameter),andfineͲgrainedrockmaterialoutcropsonlyonthesteep frontalandlateralslopes.AccordingtothedefinitiongivenbyBarsch(1996),MaRGcanbedefinedas atalusrockglacier. Fig. 2 – General view of MaRG. The elevation at the front is about 2760m a.s.l., the highest peaks in the backgroundreachelevationsofabout3000ma.s.l.PhotographybyR.Seppi(21.08.2009) On this rock glacier, BTS measurements carried out in late March 2003 recorded very cold temperatures,consistentwiththepresenceofafrozencoreintothedebrisdeposit.TheBTSvalues rangedbetweenͲ2.1°CandͲ6.1°C(averagevalueof23measurementpoints:Ͳ4.2°C)andtheaverage thicknessofthesnowpackwas230cm.Thetemperatureofaspringemergingfromthebottomof thefrontalslopeisalsoundermeasurementssince2004.Thewatertemperaturemeasuredduring thelatesummerseasonisconstantlybelow1°C,indicatingfurthermorethepresenceofpermafrost intherockglacier. 2. Permafrostindicatorsandrecentthermalandgeomorphicevolution Fig. 3 shows the total horizontal displacement of MaRG in the full period of measurements (2001Ͳ 2009).Onthisrockglacier,thetotaldisplacementrangesbetween0.12m(boulder19)and1.67m (boulder2),correspondingtoavelocityof0.02and0.21m/year,respectively(Table1).Thesurveyed boulders moved along the maximum gradient of the slope in a rather homogeneous pattern. The velocity reaches a maximum in the middle and the lower part of the landform, and decreases towardstheuppersector,wheretheslowestboulders(18,19and20)arelocated.Afterthesecond survey(2002)theboulder3felldownfromthefrontalslope. 132 PermafrostResponsetoClimateChange The mean displacement of MaRG in all the measurement intervals is shown in Fig. 7 (top graph), where all the surveyed boulders of the rock glacier have been taken into account. The average velocity is significantly variable from year to year, ranging from a minimum of 0.08m/year (2007Ͳ 2008) to a maximum of 0.17m/year (2008Ͳ2009). No clear trends seems to emerge from the evolution of the mean annual displacement. The interannual variability of the velocity and an acceleratingtrendhavebeenrecentlyreportedforseveralrockglaciersintheEuropeanAlps(Roeret al.2005,Delaloyeetal.2008,PERMOS2009,Bodinetal.2009). Table 1 – Horizontal displacements of MaRG. The first six columns show the displacement for each period of measurements,thecolumnseventhetotaldisplacement,andthecolumneighttheannualdisplacementrate. (*)Measurementperiodoftwoyears;(**)Thebouldernumber3fellfromthefrontalslopeafter2002. Boulder ID Horizontaldisplacement(m) 2001Ͳ09 total horizontal displacement (m) 2001Ͳ09 horizontal displacement rate (m/yr) 2001Ͳ02 2002Ͳ04(*) 2004Ͳ06(*) 2006Ͳ07 2007Ͳ08 2008Ͳ09 01 0.16 43.2 27.6 0.21 0.08 0.22 1.38 0.17 02 0.21 51.9 34.1 0.24 0.11 0.25 1.67 0.21 03(**) 0.20 . . . . . . . 04 0.18 47.4 29.7 0.20 0.11 0.24 1.50 0.19 05 0.17 43.6 26.2 0.17 0.12 0.23 1.38 0.17 06 0.17 46.6 26.5 0.20 0.09 0.25 1.44 0.18 07 0.16 44.2 25.3 0.18 0.08 0.23 1.34 0.17 08 0.15 35.9 22.0 0.12 0.10 0.18 1.13 0.14 09 0.11 25.9 14.6 0.06 0.06 0.12 0.77 0.10 10 0.17 46.7 24.9 0.18 0.10 0.24 1.41 0.18 11 0.16 45.0 22.9 0.17 0.08 0.21 1.31 0.16 12 0.15 37.1 20.8 0.14 0.08 0.19 1.13 0.14 13 0.16 40.9 23.9 0.16 0.08 0.21 1.26 0.16 14 0.13 27.2 16.3 0.07 0.08 0.15 0.87 0.11 15 0.15 34.0 19.2 0.11 0.08 0.19 1.05 0.13 16 0.13 30.6 16.4 0.11 0.06 0.17 0.94 0.12 17 0.08 12.6 5.4 0.07 0.0 0.07 0.39 0.05 18 0.08 5.6 4.4 0.0 0.04 0.04 0.22 0.03 19 0.07 2.0 1.8 0.01 0.0 0.03 0.12 0.02 20 0.08 Ͳ0.5 2.1 0.02 0.0 0.04 0.14 0.02 21 0.05 10.8 8.3 0.06 0.0 0.07 0.35 0.04 22 0.09 19.9 10.6 0.11 0.02 0.09 0.61 0.08 23 0.12 29.7 14.3 0.12 0.06 0.15 0.88 0.11 24 0.15 38.0 20.6 0.16 0.08 0.19 1.17 0.15 25 0.10 21.2 9.0 0.10 0.01 0.10 0.61 0.08 ThenearͲsurfacetemperatureofthegroundrecordedonMaRGfromAugust2004toAugust2009is showninFig.4(bottomgraph).Inthisfigurethegroundtemperature(dailymean)isassociatedto theairtemperature(centralgraph)andtothethicknessofthesnowcover(topgraph),recordedat two meteorological stations located about 1 km from the rock glacier (Cima Presena AWS and CapannaPresenaAWS). Focusing on the ground thermal regime during winter, the coldest temperatures were recorded in the 2004Ͳ2005 and 2005Ͳ2006 winter seasons. During the first winter, the ground reached a minimumtemperatureofaboutͲ10°CinlateFebruary,andastrongwarmingfollowedinMarchdue 133 PermaNET–CasestudiesintheEuropeanAlps to an early starting of the snow melt. In the winter of 2005Ͳ2006, the ground cooled very quickly towardsthe minimumvaluesofaboutͲ8°C.Thestrongcooling ofthegroundinthese twowinters maybeduetothecombinedeffectofcoldairtemperatureandrelativelythinsnowpackinautumn andearlywinter.Inthetwofollowingwinters,thegroundtemperaturewaswarmerandreacheda phaseofwinterequilibriumtemperature(WEqT)ofaboutͲ5°C.Thewinter2006Ͳ2007wasverymild and the snowpack was relatively thin until mid winter, while the following winter was colder and snowier. Fig.3–Totalhorizontaldisplacement(2001Ͳ2009)ofMaRG. Fig.4–Topandmiddlegraphs:snowthicknessandairtemperatureatCapannaPresenaautomaticweather station; bottom graph: ground nearͲsurface temperature from August 2004 to August 2009 for MaRG. For locationoftemperaturedataloggerrefertoFig.3. 134 PermafrostResponsetoClimateChange Withrespecttothepreviousyears,thegroundtemperaturewascomparativelywarmerduringthe 2008Ͳ2009winterseason,andreachedarelativelyshortWEqTofaboutͲ4°C.Althoughinthiswinter theairtemperaturewasnotparticularlymildcomparedtotheprecedingones,thesnowpackalready reached a significant thickness in autumn and early winter, preventing the cooling of the ground. Moreover, the snowpack further thickened in the following winter months. This underlines the strongcontrolofthesnowcoveronthewintertemperatureofthegroundand,consequently,onthe meanannualgroundtemperature. The Ground Freezing Index (GFI), computed as the cumulative value of the negative daily mean groundtemperaturesbetween1stOctoberand30thJune,isshowninFig.5.Thelowestvalueswere recorded in the winter 2005Ͳ2006 and 2007Ͳ2008 (Ͳ1197°Cͼday and Ͳ1052°Cͼday, respectively). DespiteathinandlateͲappearedsnowcoverinwinter2006Ͳ2007,theGFIwaslessnegativethanthe previousandthefollowingwinter,probablybecauseoftherelativelyhighairtemperature(seeCima PresenaAWSinFig.4).ThehighestGFI(Ͳ471°CͼDay)sincethebeginningofthemeasurementswas recordedinwinter2008Ͳ2009,whenaverythicksnowpackwaspresentontherockglaciersincethe middleofautumn. Fig.5–Annualgroundfreezingindex(GFI)atMaRGfrom2004to2009. TheeffectofthesnowcoveronthegroundtemperaturecanbeobservedinFig.6.Inthegraph,the evolutionofthemeanannualairtemperature(MAAT)atCimaPresenaAWSandtheevolutionofthe mean annual ground temperature at MaRG are compared on the same period of time. The temperaturesaredisplayedas12Ͳmonthsrunningmeans,andthedateonthexͲaxiscorrespondsto the end of the period used for the calculation. The mean ground temperature on MaRG ranged between0°CandͲ2°Cintheperiodofmeasurements(mid2005tomid2009),reachingthehighest valuesin2007andin2009.Thefirstwarmingphase(2007)occurredafterawinterseasonthatwas verymildandwithlittlesnow,whilethesecond(2009)followedanexceptionallysnowywinterwith relativelycoldairtemperature.Onthisrockglacier,theevolutionofthegroundtemperatureseems tobewellcorrelatedwiththeMAAT,atleastuntil2008.Infact,thestrongwarmingoftheground observedin2009ismoreduetoaneffectofthethicksnowcoverofthepreviouswinterthantoa correspondingwarmingintheairtemperature. 135 PermaNET–CasestudiesintheEuropeanAlps Fig.6–EvolutionofthemeanannualairtemperatureatCimaPresenaautomaticweatherstation(topgraph) andofthenearͲsurfacegroundtemperatureatMaRg(bottomgraph).Allthetemperaturesaredisplayedas12Ͳ monthsrunningmeans,andthedateonthexͲaxiscorrespondstotheendoftheperiodusedforthecalculation. InFig.7alltheobservationscarriedoutonMaRGaresummarized.Thetopgraphshowsthemean annualdisplacementsince2001andhasbeendescribedabove.Theintermediategraphshowsthe mean annual nearͲsurface temperature of the ground, and the bottom graph reports the mean annualairtemperatureatCimaPresenaAWS.Inordertoemphasizethecontributionofthewinter seasons,thevaluesofthemeanannualtemperature(bothforthegroundandfortheair)havebeen calculatedtakingintoaccountanannualbasisextendingfromthe15thAugustofthepreviousyearto the14thAugustofthefollowingyear.Forthisreason,anextremelywarmsummerlike2003isnotas wellvisibleinthedatarecordasamildwinterlike2006Ͳ2007. Fig.7–MeandisplacementofMaRG(topgraph)comparedwiththemeanannualgroundtemperature(middle graph)andthemeanannualairtemperatureatCimaPresenaautomaticweatherstation(bottomgraph). 136 PermafrostResponsetoClimateChange Fig. 8 – Potential change of frost, ice and freezeͲthaw days for 2020Ͳ2050, as proposed in chapter 2. The locationofMaRGisshown. 137 PermaNET–CasestudiesintheEuropeanAlps The displacement of the MaRG seems to react rapidly to the ground temperature variations, apparently without any time delay. In the last three years, indeed, higher ground temperatures correspondratherwellwithhigherdisplacementvelocities,asclarifiede.g.intheyear2006Ͳ2007.In thisyear,therockglacierhasmovedfasterthaninthepreviousandinthefollowingyears,inclose relationwiththehighermeantemperatureofthegroundthatwasslightlyabove0°C.Inthelastyear of measurements (2008Ͳ2009) MaRG reached the highest velocity since the beginning of the observations.Thisaccelerationcorrespondswithameangroundtemperaturethatapproachedagain 0°C,buttheeffectseemstobeamplifiedbythesnowcover.Infact,theexceptionallysnowywinter of2008Ͳ2009couldhaveplayedaroleindeterminingthedisplacementrate,probablybecauseofthe longmeltingphaseofthesnowcoverassociatedtothelongzerocurtainphaseofthegroundthat characterizedMaRG(fromearlyMaytolateJuly;seeFig.4,bottomgraph).Thelongmeltingphase couldhaveinducedaprolongedinfiltrationofmeltwaterintotheactivelayerand,possibly,intothe frozencoreoftherockglacier,causingtheobservedacceleration.Asimilareffecthasrecentlybeen observedanddescribedbyIkedaetal.(2008)onarockglacieroftheSwissAlps. 3. Possible future thermal and geomorphic response to predicted climate change Accordingtotheanalysesinchapter2,somespeculationsonthefutureevolutionofMaRGcanbe done.IntheareawhereMaRGislocated,themodelledaveragenumberoffrostdaysintheperiod 1961Ͳ1990rangesbetween280and300peryear,andthepredictedchangefor2021Ͳ2050showsa decreaseof15/16days/year.Inthesameareaandthesameperiod,theaveragenumberoficedays is between 201 and 220 per year, with a predicted decrease of 17/19 days/year for 2021Ͳ2050. RegardingtheaveragenumberoffreezeͲthawdays,ithasbeenmodelledasrangingbetween70and 80peryearinthe30Ͳyearreferenceperiod,andanincreaseof3/4days/yearispredictedfor2021Ͳ 2050.InFig.8thelocationofMaRG(whitedot)onthemapsofthepredictedchangeinfrost,iceand freezeͲthaw days is displayed. Some changes in the dynamic response of MaRG to climate change canbeexpected,becauseofthecloserelationshipbetweenitsbehaviourandtheclimaticvariables. However, an assessment of its future evolution should carefully take into account the future evolution of the precipitation (amount and distribution) and not only the predicted rise in air temperature. Acknowledgements. – Mauro Degasperi and Franco Crippa (Geological Survey, Autonomous ProvinceofTrento)conductedthetopographicsurveysandprocessedtheroughtopographicdata. FieldcollaborationwasprovidedbyLucaCarturan,StefanoFontanaandDavideTagliavini.Thiswork waspartlyfundedbythePRIN2008project“ClimateChangeeffectsonglaciers,onglacierͲderived waterresourceandonpermafrost:QuantificationoftheongoingvariationsintheItalianAlps”. References: Baroni C., CartonA. & SeppiR.,2004:Distribution and behaviour of rock glaciers in the AdamelloͲPresanella Massif(ItalianAlps).PermafrostandPeriglacialProcesses,15,243Ͳ259. Barsch D., 1996: Rockglaciers: Indicators for the Present and Former geoecology in High Mountain Environments.Springer,Berlin,331pp. 138 PermafrostResponsetoClimateChange Bodin X., Thibert E., Fabre D. Ribolini A., Schoeneich P, Francou B., Louis Reynaud L. & Fort M., 2009: Two DecadesofResponses(1986–2006)toClimatebytheLaurichardRockGlacier,FrenchAlps.Permafrost andPeriglacialProcesses,20,331Ͳ344. Delaloye R., Perruchoud E., Avian M., Kaufmann V., Bodin X., Ikeda A., Hausmann H., Kääb A., KellererͲ Pirklbauer A., Krainer K., Lambiel C., Mihajlovic D., Staub B., Roer I. & Thibert E., 2008: Recent interannualvariationsofrockglacierscreepintheEuropeanAlps.Proceedingsofthe9thInternational ConferenceonPermafrost(NICOP),UniversityofAlaska,Fairbanks,June29ͲJuly3,2008,343Ͳ348. Haeberli W., Hallet B., Arenson L., Elconin R., Humlum O., Kaab A., Kaufmann V., Ladanyi B., Matsuoka N., SpringmanS.&VonderMühllD.,2006:Permafrostcreepandrockglacierdynamics.Permafrostand PeriglacialProcesses,17,189Ͳ214. Hoelzle M., Wegmann M. & Krummenacher B., 1999: Miniature temperature dataloggers for mapping and monitoringofpermafrostinhighmountainareas:firstexperiencefromtheSwissAlps.Permafrostand PeriglacialProcesses,10,113Ͳ124. KääbA.,FrauenfelderR.&RoerI.,2007:Ontheresponseofrockglaciercreeptosurfacetemperatureincrease. GlobalandPlanetaryChange,56,172Ͳ187. IkedaA.,MatsuokaN.&KääbA.,2008:Fastdeformationofperenniallyfrozendebrisinawarmrockglacierin theSwissAlps:Aneffectofliquidwater.JournalofGeophysicalResearch113,F01021. PERMOS, 2009: Permafrost in Switzerland 2004/2005 and 2005/2006. Noetzli, J., Naegeli, B., and Vonder Muehll,D.(eds.),GlaciologicalReportPermafrostNo.6/7oftheCryosphericCommissionoftheSwiss AcademyofSciences,100pp. Roer I., Kääb A. & Dikau R., 2005: Rockglacier acceleration in the Turtmann valley (Swiss Alps) – probable controls.NorwegianJournalofGeography,59,157Ͳ163. 139 PermaNET–CasestudiesintheEuropeanAlps 3. CasestudiesintheEuropeanAlps 3.12 Amolarockglacier,Vald’Amola,ItalianAlps Citationreference SeppiR.,BaroniC.CartonA.,Dall’AmicoM.,RigonR.,ZampedriG.,ZumianiM.(2011).Chapter3.12: Case studies in the European Alps – Amola rock glacier, Val d’Amola, Italian Alps. In KellererͲ PirklbauerA.etal.(eds):Thermalandgeomorphicpermafrostresponsetopresentandfutureclimate changeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.ISBN978Ͳ2Ͳ903095Ͳ58Ͳ1, p.140Ͳ150. Authors Coordination:RobertoSeppi Involvedprojectpartnersandcontributors: Ͳ UniversityofPavia–RobertoSeppi Ͳ UniversityofPisa–CarloBaroni Ͳ MountainͲeeringsrl–MatteoDall’Amico Ͳ UniversityofTrento–RiccardoRigon Ͳ GeologicalSurvey,AutonomousProvinceofTrento–GiorgioZampedri Ͳ Geologist–MatteoZumiani Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalandgeomorphicevolution 3. Possiblefuturethermalandgeomorphicresponsetopredictedclimatechange References 140 PermafrostResponsetoClimateChange Summary Topographic measurements are in progress since 2001 on a glacierͲderived, active rock glacier (namedAmolarockglacier,acronymAmRG,coordinates:46°12’09”N,10°42’46”E)locatedin theAdamelloͲPresanellagroup,CentralItalianAlps.Inaddition,dataonthegroundtemperature measured few centimetres below the surface are available since 2004. The displacement data showthatsomeareasoftherockglaciercurrently(2001Ͳ2009)movewithvelocitiesrangingfrom 10 to 20cm/year, while other sectors can be defined as “dynamically inactive”. The average velocityissignificantlyvariablefromyeartoyear,rangingfromaminimumof0.06m/year(2007Ͳ 2008)toamaximumof0.13m/year(2006Ͳ2007),andaslowingtrendhasbeenrecordedinthe lasttwoyears.In2006Ͳ2007ahigherrateofdisplacementseemstoberelatedtoariseinthe mean air temperature that probably caused a corresponding rise in the ground temperature. However,inthelastyearofmeasurements(2008Ͳ2009),anincreaseinthegroundtemperature causedbythelargeamountofsnowoftheprecedingwinter,didnotresultinacorresponding increaseofthedisplacementrate.Thedynamicbehaviourofthisrockglacierreactsveryfastto theexternalforcing,anditsresponseseemstobemodulatedbytheamountandevolutionofthe snowduringwinter,duetoitseffectonthegroundtemperature.Thus,notonlythetemperature but also the projected changes in the amount and distribution of precipitation, especially as snow,shouldbetakenintoaccountinassessingtheresponseofthislandformtofutureclimate change. 141 PermaNET–CasestudiesintheEuropeanAlps 1. Introductionandstudyarea Activerockglaciersoriginatefromthecreepofperenniallyfrozendebris(i.e.permafrost)andmove downslope with typical velocities ranging from few cm to more than 1m per year. The surface displacementofactiverockglaciersismarkedlyvariablefromyeartoyear,andintheEuropeanAlps arecentspeedingͲuptrendhasbeenunderlinedonsomelandforms(Roeretal.2005,Haeberlietal. 2006,Delaloyeetal.2008,PERMOS2009).Theinterannualvariabilityofthesurfacevelocityseems toberelatedtotheclimaticfactorsinfluencinggroundsurfacetemperatureofthedeposits,suchas theairtemperature,thethicknessanddurationofthewintersnowcoverandtheprocessesofwater infiltration(Kääbetal.2007,Ikedaetal.2008;Bodinetal.2009) In 2001 we choose an active rock glacier located in Val d’Amola for performing topographic measurements,inordertostudyitssurfacedisplacementrateandthepotentialvelocityvariations (Fig.1).Thisrockglacierisoneoftheactivelandformsincludedintherockglacierinventoryofthe AdamelloͲPresanella massif (Baroni et al. 2004), where it has the number 51 and is also briefly described. The measurements have been carried out using a laser theodolite and after the first survey have been repeated in the late summer/early autumn of the following years (2002, 2004, 2006,2007,2008,2009).ThesurveyswereconductedeveryyearbetweenearlySeptemberandmid October.Onthesurfaceoftherockglacier,amonitoringnetworkof25largebouldersmarkedwith steelboltshasbeenestablished. Fig.1–GeographicalsettingofthestudyareawithrockglacierAmRGandautomaticweatherstations(AWS) In 2004 we also started to measure the temperature of the ground few centimetres below the surface, using a miniature temperature data logger (UTL1, accuracy: ±0,25°C; Hoelzle et al. 1999) placedinfineͲgraineddebrisonthelowerpartoftherockglacier.Thedataloggerhadamalfunction in 2006 and stopped to collect data between March and August 2006. In order to compare the groundtemperaturewiththeairtemperatureandtheevolutionofthewintersnowcover,weused 142 PermafrostResponsetoClimateChange themeteorologicaldataoftwohighͲaltitudeautomaticweatherstations/AWS(CimaPresenaAWS, 3015ma.s.l.,andCapannaPresenaAWS,2730ma.sl.)locatedabout10kmfromtherockglacier. AmRG is a tongueͲshape rock glacier located in a north facing glacial cirque, between an upper altitudeof2480ma.s.l.andaloweraltitudeof2360ma.s.l.(topedgeofthefrontalslope)(Fig.2).It isabout530mlongand250mwideandshowsadistinctivesetoflongitudinalandtransversalridges onitssurface.Initsintermediateanduppersector,awidehollowlocatedbetweentwoelongated longitudinalridgesispresent,whilethecompressiveridgescanbemainlyobservedinitslowerarea. TherockglaciersurfaceismostlycomposedofmatrixͲfree,largeandveryangulargraniteboulders (uptosomemetersindiameter),whilethefineͲgrainedmaterialfrequentlyoutcropsnotonlyonthe lateralandfrontalslopes,butalsoonthetopofthelongitudinalandtransverseridges.Intherooting area of the rock glacier, snow patches are present over the whole summer only in the most favourableyears(i.e.withalargeamountsofsnowduringtheprecedingwinter). Fig. 2 – General view of AmRG. The elevation at the front is about 2300m a.s.l., the highest peaks in the backgroundreachelevationsofabout2700ma.s.l.PhotographybyR.Seppi(26.09.2009). Fieldevidences,confirmedbyhistoricalmaps,showthatacirqueglacierwaspresentintherooting area of the rock glacier during and after the Little Ice Age. This little glacier is still reported in a 1:75.000mapof1903,whileinmorerecentmaps(e.g1:25.000mapof1973)thecirqueisindicated withoutaglacier.Thematerialcomposingthisrockglacierisprobablyofdifferentorigin,butglacial till seems prevailing. Therefore, this landform is developing from glacial deposits and thus can be defined,accordingtothedefinitionofBarsch(1996),asadebrisrockglacier. 143 PermaNET–CasestudiesintheEuropeanAlps SeveralspringsemergeatthebaseofthefrontalslopeofMaRG.Besidetheotherinvestigations,in 2004westartedtomeasurethetemperatureofthewater,inordertogetadditionalinformationon thepresenceofafrozencorewithintherockglacier.Thewatertemperaturewasmeasuredseveral times during summer using a handͲheld thermometer and continuously from early August to late September2004usingdataloggers(HoboH8Temp,accuracy:±0,4°C). 2. Permafrostindicatorsandrecentthermalandgeomorhicevolution The water temperature that was monitored continuously in late summer 2004 showed very cold values (below 1°C). Therefore, this data support the presence of permafrost in the rock glacier (Fig.3). Fig. 3 – Water temperature of a spring (SLC7) emerging from AmRG continuously measured between August andSeptember2004.ThelocationofthespringisindicatedinFig.4. The total displacement (2001Ͳ2009) of AmRG ranges between 0.05m (boulder 9) and 1.60m (boulder 15), corresponding to a velocity of 0.01 and 0.20m/year, respectively (Fig. 4 and Tab. 1). Thefrontalareaofthisrockglaciershowsaverydifferentbehaviour,withanactivesector(boulders 1to6)closetoasectorthatcanberegardedasdynamicallyinactive(boulders7to11).Similarly,the rightsideoftherockglacier(boulders12to20)ismoreactivethanthemiddleandtheleftsectors (boulders21to25).Thesurveyedboulderslocatedonthelongitudinalridgemovetowardthecentre ofthelandform,whereawidehollowispresent. The meandisplacementofAmRGinallintervalof measurementsisshowninFigure8(topgraph), where all the surveyed points have been taken into account. The average velocity is significantly variable from year to year, ranging from a minimum of 0,06m/year (2007Ͳ2008) to a maximum of 0,13m/year(2006Ͳ2007).Aslowingtrendseemstoemergeinthelasttwoyearsofmeasurements. ThenearͲsurfacetemperatureofthegroundrecordedonAmRGfromAugust2004toAugust2009is showninFig.5(bottomgraph).Inthisgraph,thegroundtemperature(dailymean)isassociatedto theairtemperature(centralgraph)andtothethicknessofthesnowcover(topgraph). 144 PermafrostResponsetoClimateChange Table 1 – Horizontal displacement of AmRG. The first six columns show the displacement for each period of measurements, the column seven the total displacement, and the column eight the displacement rate. (*) Measurementperiodoftwoyears. Boulder ID Horizontaldisplacement(m) 2001Ͳ09 total horizontal displacement (m) 2001Ͳ09 horizontal displacement rate (m/yr) 2001Ͳ02 2002Ͳ04(*) 2004Ͳ06(*) 2006Ͳ07 2007Ͳ08 2008Ͳ09 01 0.13 40.42 17.83 0.17 0.09 0.10 1.08 0.13 02 0.13 39.59 9.61 0.12 0.08 0.10 0.93 0.12 03 0.15 39.05 13.58 0.14 0.06 0.09 0.97 0.12 04 0.12 34.71 12.50 0.12 0.08 0.06 0.85 0.11 05 0.06 19.33 6.74 0.08 0.06 0.11 0.57 0.07 06 0.05 9.10 3.70 0.07 0.02 0.01 0.28 0.03 07 0.02 10.55 0.00 0.09 0.01 0.00 0.16 0.02 08 0.04 6.08 0.00 0.06 0.00 0.01 0.13 0.02 09 0.04 3.23 0.00 0.07 0.00 0.01 0.05 0.01 10 0.04 14.80 0.87 0.06 0.00 0.06 0.32 0.04 11 0.02 0.00 5.90 0.08 0.00 0.00 0.08 0.01 12 0.07 25.56 10.75 0.13 0.04 0.10 0.71 0.09 13 0.13 36.30 25.13 0.21 0.11 0.17 1.23 0.15 14 0.11 36.44 23.37 0.22 0.13 0.25 1.30 0.16 15 0.16 39.15 39.09 0.36 0.19 0.10 1.60 0.20 16 0.04 15.26 6.88 0.13 0.02 0.00 0.39 0.05 17 0.07 24.13 17.22 0.21 0.05 0.02 0.76 0.10 18 0.04 18.79 5.97 0.16 0.02 0.04 0.51 0.06 19 0.15 32.93 31.83 0.34 0.18 0.00 1.31 0.16 20 0.07 24.89 10.23 0.07 0.05 0.14 0.69 0.09 21 0.08 19.96 8.94 0.13 0.05 0.03 0.58 0.07 22 0.04 12.59 4.91 0.05 0.02 0.07 0.36 0.04 23 0.06 23.01 5.15 0.06 0.05 0.07 0.53 0.07 24 0.04 15.25 0.03 0.10 0.04 0.00 0.29 0.04 25 0.04 13.15 0.00 0.09 0.03 0.00 0.28 0.03 Focusing on the winters the coldest temperatures were recorded in the 2004Ͳ2005 and 2005Ͳ2006 seasons.Duringbothwinters,thegroundreachedtemperaturesbelowͲ10°C.Thestrongcoolingof thegroundmaybeduetothecombinedeffectofcoldairtemperatureandrelativelythinsnowpack in autumn and early winter. In the two following winters (2006Ͳ2007 and 2007Ͳ2008), the ground temperaturewaswarmer,withamarkedphaseofWEqT(WinterEquilibriumTemperature)ofabout Ͳ5°C. The winter 2006Ͳ2007 was very mild and the snowpack was relatively thin until mid winter, whilethefollowingwinter(2007Ͳ2008)wascolderandsnowier. Thehighestwintertemperatureswererecordedduringthe2008Ͳ2009seasonandreachedaWEqT phaseofaboutͲ3°C.Thiswasmainlyduetothepresenceofaverythicksnowcover,whichappeared early in autumn and further increased in the following winter months. The snow, with its thermal insulatingeffect,preventedthecoolingofthegroundalreadyinthefirstpartofthewinter,whilethe air temperature was not particularly mild compared to the preceding winters. This underlines the strongcontrolofthesnowcoveronthewintertemperatureofthegroundand,consequently,onthe meanannualgroundtemperature. 145 PermaNET–CasestudiesintheEuropeanAlps Fig.4–Totalhorizontaldisplacement(2001Ͳ2009)ofAmRG.ThelocationofthespringmentionedinFig.3is indicated. Fig.5–Topandmiddlegraphs:snowthicknessandairtemperatureatCapannaPresenaautomaticweather station;bottomgraph:groundnearͲsurfacetemperaturefromAugust2004toAugust2009forAmRG.Thelack ofdatainthefirsthalfof2006wasduetoadataloggerfailure.Forlocationoftemperaturedataloggersee Fig.4. 146 PermafrostResponsetoClimateChange Fig.6–Annualgroundfreezingindex(GFI)atAmRGfrom2004to2009.Nodatawereavailableforthe2005Ͳ 2006period. Fig.7–EvolutionofthemeanannualairtemperatureatCimaPresenaautomaticweatherstation(topgraph) andof the nearͲsurfaceground temperature at AmRG (bottom graph). All the temperatures are displayed as 12Ͳmonths running means, and the date on the xͲaxis corresponds to the end of the period used for the calculation. ThecoolingofthegroundduringthewinterseasonisalsohighlightedbytheGroundFreezingIndex (GFI),calculatedasthecumulativevalueofthenegativedailymeangroundtemperaturesbetween 1stOctoberand30thJune(Fig.6).Thecoldestwinter(Ͳ1020°Cͼday)wasrecordedin2004Ͳ2005dueto acombinationofverycoldairtemperatureandrelativelythinsnowcover.Theindexwasalsovery 147 PermaNET–CasestudiesintheEuropeanAlps low in the winter 2007Ͳ2008 (Ͳ972°Cͼday), as a result of the strong cooling of the ground at the beginningofthewinterduetocoldairtemperatureduringautumnandearlywinter.AveryhighGFI value (Ͳ360°Cͼday) was recorded in 2008Ͳ2009, mainly due to the very thick snow cover of that winter. TheroleofthewintersnowcoveronthegroundtemperaturecanalsobeobservedinFig.7,where theevolutionofthemeanannualairtemperature(MAAT)atCimaPresenaAWSandtheevolutionof theMAGSTarecomparedonthesameperiodoftime.Thetemperaturesaredisplayedas12Ͳmonths running means, and the date on the xͲaxis corresponds to the end of the period used for the calculation.Groundtemperaturedataaremissingin2006and2007becauseofthefailureofthedata logger.Forexample,astrongwarmingofthegroundin2009(temperaturesabove1°C)andaclear separationbetweenthetemperaturetrendsofsoilandaircanbeobserved.Thisisduemoretothe effect of the thick snow cover of the previous winter than to a corresponding warming of the air temperature. Finally,inFig.8themeanannualdisplacementrateiscomparedwiththemeanannualtemperature of the ground and the air. In order to emphasize the role of the winter seasons, the values of the mean annual temperature (both for the ground and for the air) have been calculated taking into accountanannualbasisextendingfromthe15thAugustofthepreviousyeartothe14thAugustofthe followingyear.Forthisreason,anextremelywarmsummerlike2003isnotaswellperceptibleinthe datarecordasamildwinterlike2006Ͳ2007.Thegroundtemperaturedataaremissingfor2005Ͳ2006 and2006Ͳ2007. Fig.8–MeandisplacementofAmRG(topgraph)comparedwiththemeanannualgroundtemperature(middle graph)andthemeanannualairtemperatureatCimaPresenaautomaticweatherstation(bottomgraph). In 2006Ͳ2007, an increase in the displacement rate corresponds quite well with a higher air temperaturecomparedtotheprecedingyear.Inthefollowingyear,thedisplacementratedecreased considerably, in good agreement with a lower air temperature. In the last year of measurements (2008Ͳ2009),thedisplacementratewasonlyslightlyhigherandthemeanairtemperaturesomewhat lowerthanintheprecedingyear.Inthesameyear,asignificantincreaseinthegroundtemperature duetothelargeamountofsnow(seeabove)wasrecorded,butthisdoesnotseemtohaveresulted inanincreaseofthedisplacementrate. 148 PermafrostResponsetoClimateChange Fig. 9 – Potential change of frost, ice and freezeͲthaw days for 2020Ͳ2050, as proposed in chapter 2. The locationofAmRGisshown. 149 PermaNET–CasestudiesintheEuropeanAlps 3. Possible future thermal and geomorphic response to predicted climate change FutureevolutionandgeomorphicresponseofAmRGtoclimatechangearedifficulttohypothesize. As reported in chapter 2, not only changes in the temperature for the end of the 21st century (a warmingof4.2°Cinthealpineareasabove1800ma.s.l.),butalsosignificantchangesinthenumber offrost,iceandfreezeͲthawdaysfortheperiod2021Ͳ2050canbeexpected.Accordingtothis,inthe areawhereAmRGislocated,weexpectadecreaseinthefrostdaysof15/16days/year,adecreasein theicedaysof15/19days/yearandaslightincreaseinthefreezeͲthawdaysof0/4days/year(Fig.9). As highlighted above, the dynamic response of AmRG seems to be related to the changes in the amountandevolutionofthesnowduringwinter,duetoitseffectonthegroundtemperature.Thus alsothefuturechangesintheamountanddistributionofprecipitations,especiallyassnow,should betakenintoaccountinassessingtheresponseofthislandformtofutureclimatechange. Acknowledgements. – Mauro Degasperi and Franco Crippa (Geological Survey, Autonomous ProvinceofTrento)conductedthetopographicsurveysandprocessedtheroughtopographicdata. FieldcollaborationwasprovidedbyLucaCarturan,StefanoFontanaandAndreaPaoli.Thisworkwas partlyfundedbythePRIN2008project“ClimateChangeeffectsonglaciers,onglacierͲderivedwater resourceandonpermafrost.QuantificationoftheongoingvariationsintheItalianAlps”. References: Baroni C., CartonA. & SeppiR.,2004:Distribution and behaviour of rock glaciers in the AdamelloͲPresanella Massif(ItalianAlps).PermafrostandPeriglacialProcesses,15,243Ͳ259. Barsch D., 1996: Rockglaciers: Indicators for the Present and Former geoecology in High Mountain Environments.Springer,Berlin,331pp. Bodin X., Thibert E., Fabre D. Ribolini A., Schoeneich P, Francou B., Louis Reynaud L. & Fort M., 2009: Two DecadesofResponses(1986–2006)toClimatebytheLaurichardRockGlacier,FrenchAlps.Permafrost andPeriglacialProcesses,20,331Ͳ344. Delaloye R., Perruchoud E., Avian M., Kaufmann V., Bodin X., Ikeda A., Hausmann H., Kääb A., KellererͲ Pirklbauer A., Krainer K., Lambiel C., Mihajlovic D., Staub B., Roer I. & Thibert E., 2008: Recent interannualvariationsofrockglacierscreepintheEuropeanAlps.Proceedingsofthe9thInternational ConferenceonPermafrost(NICOP),UniversityofAlaska,Fairbanks,June29–July3,2008,343Ͳ348. Haeberli W., Hallet B., Arenson L., Elconin R., Humlum O., Kaab A., Kaufmann V., Ladanyi B., Matsuoka N., SpringmanS.&VonderMühllD.,2006:Permafrostcreepandrockglacierdynamics.Permafrostand PeriglacialProcesses,17,189Ͳ214. Hoelzle M., Wegmann M. & Krummenacher B., 1999: Miniature temperature dataloggers for mapping and monitoringofpermafrostinhighmountainareas:firstexperiencefromtheSwissAlps.Permafrostand PeriglacialProcesses,10,113Ͳ124. KääbA.,FrauenfelderR.&RoerI.,2007:Ontheresponseofrockglaciercreeptosurfacetemperatureincrease. GlobalandPlanetaryChange,56,172Ͳ187. IkedaA.,MatsuokaN.&KääbA.,2008:Fastdeformationofperenniallyfrozendebrisinawarmrockglacierin theSwissAlps:Aneffectofliquidwater.JournalofGeophysicalResearch113,F01021. PERMOS, 2009: Permafrost in Switzerland 2004/2005 and 2005/2006. Noetzli, J., Naegeli, B., and Vonder Muehll,D.(eds.),GlaciologicalReportPermafrostNo.6/7oftheCryosphericCommissionoftheSwiss AcademyofSciences,100pp. Roer I., Kääb A. & Dikau R., 2005: Rockglacier acceleration in the Turtmann valley (Swiss Alps) – probable controls.NorwegianJournalofGeography,59,157Ͳ163. 150 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.13 PizBoèrockglacier,Dolomites,EasternItalianAlps Citationreference A. Crepaz A., Cagnati A., Galuppo A., Carollo F., Marinoni F., Magnabosco L., Defendi V. (2011). Chapter 3.13: Case studies in the European Alps – Piz Boè rock glacier, Dolomites, Eastern Italian Alps.InKellererͲPirklbauerA.etal.(eds):Thermal andgeomorphicpermafrostresponsetopresent andfutureclimatechangeintheEuropeanAlps.PermaNETproject,finalreportofAction5.3.OnͲline publicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.151Ͳ158. Authors Coordination:AndreaCrepaz Involvedprojectpartnersandcontributors: Ͳ RegionalAgencyfortheEnvironmentalProtectionofVeneto,Italy(ARPAV)–AndreaCrepaz, AnselmoCagnati Ͳ Regione Veneto, Direzione Geologia e Georisorse, Servizio Geologico (GeoVE) – Anna Galuppo,LauraMagnabosco,ValentinaDefendi Ͳ E.P.C.EuropeanProjectConsultingS.r.l.–FedericoCarollo Ͳ Freelancer–FrancescoMarinoni Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 151 PermaNET–CasestudiesintheEuropeanAlps Summary Recently,ARPAVincollaborationwithGeoVEstartedtomonitortheperiglacialenvironmentof Piz Boè (46.51° N, 11.83° E), in Veneto region, at an altitude of 2900m a.s.l. In the past, some preliminarygeoelectricalandgeoseismicsurveyswerecarriedoutontherockglacier,butonlyin the framework of the PermaNET project the characteristics of the permafrost are extensively studied. Continuous GST (Ground surface temperature) measurements were carried out in the winter 2009/2010; a 30m deep borehole was drilled in Dolomite bedrock and an automatic weatherstationwasinstalledinsummer2010.Laterweplannedtocarryoutasecondelectrical resistivity tomography (ERT) campaign (first one in 2005) on the rock glacier. In this report we presentthefirstresultsonthecomparisonofERTmeasurementscarriedoutin2005and2010. Thedatacomparisondoesnotshowsignificantchangesinthestructureoftheicecoveredwith debrisduringthelastfiveyears.Inparticular,itseemsthatthecoveredicedidneithermodifyits consistencenoritsextent.Duetotheshortmonitoringtimeandthelackofotherexperimental dataonthePizBoèsite,itisverydifficulttoexplainitsfuturebehaviour.ARPAVmanagesalsoa broad weather station network on Veneto mountain region, so the highest station data (Ra Vales) was used to make some analysis of the last years. For the next century climate models estimate a dramatic increase of air temperature. This condition will directly influence the thickness,theextensionandthedisplacementoftherockglacieratPizBoè. 152 PermafrostResponsetoClimateChange 1. Introductionandstudyarea The Piz Boè site is located in the NorthͲEast of Italy (46.51°N, 11.83°E; Fig. 1), on the border of Veneto region, at 2900m a.s.l. on the Sella Group, near Piz Boè peak (Fig 2). The Sella Group represents one of the most important massifs of the Dolomites. Its base is constituted by the “DolomiadelloSciliar”Formation(LadinianͲLowerCarnian).ThethicknessofthisnonͲstratifiedcoral reef varies from 300 to 600m. The top of the massif is made up by “Dolomia Principale” (Norian). Thegeologicalboundarybetweenthetwoabovementionedformationsisveryclearandmarkedby layersofmarlsandclaysofthe“RaiblFormation” (Carnian).Thewhite/cleargreyDolomiaPrincipale Formationiswellstratifiedanditsthicknessreachesitsmaximum(300Ͳ350m)atPizBoè,whereitis covered by the most recent “Calcari di Dachstein” (Lias), nodular limestones of the “Rosso Ammonitico”Formation(Jurassic)and“MarnedelPuez”Formation(LowerCretaceous). Fig.1–GeographicalsettingofVenetoregionandPizBoèintheDolomites,EasternItalianAlps AtNorthͲEastofthepeakPizBoètherewasaglacier,listedin1980’scampaignsurveywithabouta surface of 0.04km2. Nowadays the glaciated area is very limited (about 0.014km2), but a debris coveredglacier(insomemapsitisconsideredarockglacier)hasbeenformedbelowtheglacier.At the bottom of the debris there is a small shallow lake (Lech Dlacé, Fig. 3), which is completely coveredbysnowandiceithemostpartoftheyearover(NovembertoJune). 153 PermaNET–CasestudiesintheEuropeanAlps Fig.2–SellaGroupandPizBoè(3151ma.s.l.)fromEast(Livinallongo).Locationofthestudysiteisindicated withanarrow.PhotographbyBrunoRenon(ARPAV)(30.07.2008). Boreholeand weatherstation Dataloggers 2005/2010 2010WͲE Spring Fig.3–ViewtowardsSouthͲWestofthelakeLechDlacéandtherockglacierofPizBoèwiththelocationofthe borehole and the weather station, dataloggers, ERT profiles and the spring. Elevation of the lake is 2833m a.s.l.,elevationofthepeakinthebackground(PizBoè)is3151ma.s.l.NotethewidespreadappearanceoflateͲ lyingsnowpatches.PhotographbyBrunoRenon(ARPAV)(30.07.2008). 154 PermafrostResponsetoClimateChange 2. Permafrostindicatorsandrecentthermalevolution 2.1Methods InJuly2010aboreholewasdrilledintothebedrockdowntoadepthof30mandathermistorchain of16sensors(at0.02,0.3,0.6,1.0,1.5,2.0,3.0,3.5,4.5,5.5,10.0,15.0,20.0,25.0,30.0mfromthe surface)wasplacedtomeasurethegroundtemperatures.InSeptember2010aweatherstationwas installedatthelocationindicatedinfig.3;itmeasuesairtemperature,relativehumidity,snowpack height,winddirectionandvelocity,incomingandoutcoming(shortwaveandlongwave)radiation. DuringSummer2010watersampleswerecollectedfromthespringcomingoutfromtherockglacier andfromtheLechDlacéwithatemporalresolutionofabout15days,inordertoevaluatechemical compositionanditsrelativeseasonalchanges;watertemperaturesweremeasuredaswell. SinceOctober2009twodataloggers(HoboProV2U23Ͳ001,OnsetComputerCorp.),loggingevery30 minutes, have been placed near Piz Boè rock glacier in order to measure the ground surface temperature.Thefirstonewasputontherockglacierfrontandthesecondoneoutsideoftherock glacier,belowthefront,wheretheweatherstationwasplannedtobeinstalledinSeptember2010 (see Fig. 3 for location). They were recovered in the melting season in July 2010. At the end of October,onedataloggerwasreplacedinthesameprevioussite,afewcentimetersbelowthesurface oftherockglacier,whiletheotherone,outsideoftherockglacier,wasmovedabout30mtowards SouthͲEast. Duringthesummer2005adetailedtopographicsurveywascarriedoutandinthesummer2010a LaserScannersurveywasperformedbyIRPICNR. The study area was furthermore investigated on 01.09.2010 by performing an electrical resistivity profile (ERT) of 124 m, using the device electrode WennerͲSchlumberger with a distance between the electrodes equal to 4m and maximum depth of exploration of 25m. The inversion of geoelectricaltomographicdatawasperformedusingthemethodproposedbyLaBrequeetal.(1996), using a finite element algorithm based on the concept of reverse OCAM'S (Oldenburg, 1994) and implementedinsoftwarePROFILER(Binely,2003).Theconfigurationwascomparabletotheoneof theERTcampaignon04.08.2005,thelengthofwhichwas141m. 2.2Resultsoncurrentpermafrostexistence Fig.4showsthemeasuredtemperaturesduringtheperiod09.10.2009and02.07.2010alsodepicting somesignificantevents.On22ndOctoberthefirstsnowfalloccurred(about5Ͳ10cmoffreshsnow), meltingthefollowingdays.ThenextsignificantsnowfalloccurredatthebeginningofNovemberwith about 50Ͳ60cm of fresh snow; this part of snow pack remained all the winter, even though at the endofNovembertheairtemperatureincreasedwithfreezinglevelatabout3200Ͳ3500m.Duringall thewinter,groundsurfacetemperaturesremainedataboutͲ4toͲ2°C.InFebruary,Marchandpart of April GST was about Ͳ4°C in both sites (winter equilibrium temperature – WeqT). At the end of April on the rock glacier zero curtain was reached, while on the monitoring site temperatures remainedbelow0°C,excepton29thAprilwhentemperaturesincreasedupto0°C.On17thMay2010 asnowpitwasdugonthemonitoringsiteandabottomtemperatureofsnowcover(BTS)ofͲ1.5°C wasmeasured(dataloggervalueswerearoundͲ1.7°C).Zerocurtainonthebedrockstartedon11th June, while on the rock glacier snow was already completely melted; at the beginning of July the dataloggeronthebedrockwasburiedinameltingicelayer. Thesetemperatureresultsindicatethepossiblepresenceofpermafrostonthebedrockandonthe debris, where in 2005 ERT measurements were performed, as well. In summer 2010, the ERT measurementswererepeatedalongthesamesectionandtheinvestigationwasextendedtoanew orthogonalWͲEorientedtransect,alongthemaximumslopegradient.Inthisworkwecomparethe profilescarriedoutin2005and2010alongthesamesection. 155 PermaNET–CasestudiesintheEuropeanAlps 12.0 10.0 Bedrock Rock glacier 22/10 5/10 cm Fresh snow 8.0 02-03/11 Snow Height 50/60 cm 6.0 GST (°C) 17.05 Snow pit (Snow Height 240 cm) 4.0 2.0 0.0 -2.0 -4.0 Zero curtain on the bedrock 21/06/2010 06/06/2010 22/05/2010 07/05/2010 22/04/2010 07/04/2010 23/03/2010 08/03/2010 21/02/2010 06/02/2010 22/01/2010 07/01/2010 23/12/2009 08/12/2009 23/11/2009 08/11/2009 24/10/2009 09/10/2009 -6.0 Date Fig.4–Evolutionofthegroundsurfacetemperaturebetween09.10.2009and02.07.2010.InredGSTfromthe rockglacier,inbluefromthesiteoftheplannedborehole. The twoͲdimensional model obtained by inversion of apparent resistivity data (Fig. 5) returns the actualdistributionofvaluesofresistivityinthesubsurface;itishighlightedbothbyisolinesandby colour scale. The first contour has been traced to a value of 5*104ɏ*m. The second isoline is 1*105ɏ*m, while the subsequent ones are placed at intervals of 2*105ɏ*m up to the value of 1*106ɏ*m;forhigherresistivitythespacingbetweentheisoresistivelinesishigher. Highest resistivity values (above 1.5*106 ɏ*m) might be related to massive ice; values between 1*105ɏ*m and 1.5*106ɏ*m should correspond to ice mixed with boulders, while lower values (5*104ɏ*m<ʌ<1*105ɏ*m)mightdetecttheactivelayer. Comparingthetwoprofileswe can makethefollowingobservations.The geometryof thebodyat veryhighresistivityissimilarinthetwosections.At2940maltitudea.s.l.,thewidthoftheanomaly resistive(ʌ>1.5x106ɏ*m)isapproximatelyequalto99m.Thesurfacemateriallayer(about2mof boulders mixed to fine grained debris) shows more or less the same thickness in both profiles (ʌ<5*104). Thethicknessoftherockglacierismoreorlessthesame,greaterthan23minbothcases.Inboth profiles the maximum depth of investigation was not sufficient to achieve resistence values attributabletothebedrock.Theanalysisofthetwosectionsalsoshowsthelimiteddifferencesinthe pattern of deeper sections; in the section of the 2005 isoresistive lines remain open on values ranging from 1.5 to 5*106ɏ*m, while in the section of 2010 they reach values close to 2*106ɏ*m.Thesedifferencesarenotsignificantbecausetheslightdiscrepancyinthepositioningof two profiles on the ground and high difference of resistivity on surface layer, which may affect, in part,theresultsofthereverseprocesses. The section of 2005 showed a difference in the resistive body, with two anomalies at very high resistivity(ʌ>4x106ɏ*m),separatedbyastripwithslightlylowerresistivity(ʌ=1.5x106ɏ*m).The 156 PermafrostResponsetoClimateChange section of 2010 shows these two anomalies, too, but their separation is more weakened. Also this differencecanbeexplainedinpartwiththeconsiderationslistedabove. Wecanconcludethatthesetwoprofilesareverysimilarandthattheslightdifferencesaremainly attributabletothemethoduncertainty. Altitude(m) 2005 Altitude(m) Distance(m) 2010 Distance(m) Resistivity(ohm*m) Fig.5–Resultsoftheelectricaltomography(ERT)campaignson04.08.2005and01.09.2010. 3. Possiblefuturethermalresponsetopredictedclimatechange ThePizBoèrockglacierismonitoredsince2005.From2005to2010noairtemperaturesdataare available because the weather station was not installed before September 2010. However, time series of both air temperature (until 2009) and snow height is available for Ra Vales station, at 2615ma.s.l.,about19kmtotheEastͲNorthͲEastofPizBoè. Takingintoaccountthelasttenyears(Table1);thefirstperiod(2000Ͳ2005)seemstobecolderthan thelastone(2005Ͳ2010).MAATwassignificantloweralltheyears,whileitincreasedinthelastfive years, when values were above 0°C in 2006, 2007 and 2008. The number of frost and ice days decreased in the last years. Snow cover duration is similar during these two periods. A little difference can be observed in June; in the last three years snow cover duration was longer in the earlysummer,whilein2000Ͳ2005someyearswerecharacterizedbyatotalabsenceofsnowcover. Winter snow height was not so high in 2005Ͳ2008, while in the last two years snow amount was higher. 157 PermaNET–CasestudiesintheEuropeanAlps Table 1 – Different temperature derived parameters from the meteorological station Ra Vales (2615m a.s.l.) 19km to the EastͲNorthͲEast of Biz Poè (DSC=days with snow cover; MAAT=mean annual air temperature; JJA=JuneͲJulyͲAugust). RaVales 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Frostdays 221 239 238 225 233 229 218 202 215 211 247 Icedays 141 140 131 137 134 133 110 104 120 138 157 Freeze/Thawdays 80 99 107 88 99 96 108 98 95 73 90 DaysofSnowcover 173 255 265 240 166 248 207 231 247 235 266 0 30 17 0 30 1 12 6 22 20 23 MAAT Ͳ0.38 Ͳ0.89 Ͳ0.30 Ͳ0.14 Ͳ0.97 Ͳ1.46 0.10 0.94 0.51 Ͳ0.06 Ͳ2.13 JJAMeanAirTemp 6.10 6.28 6.55 9.08 5.95 5.66 5.99 6.94 7.26 7.23 6.36 JuneDSC Summermeantemperature(JJA)seemstoincreaseduringthelasttenyearswithapeakin2003;this veryhotsummercertainlyinfluencedthemeltingoftheseasonalsnowpackandoftheiceaswell. Thelastyear(2010)wasthecoldestoneofthelasteleven,withaverylongsnowcoverduration;this mighthavesignificantlyinfluencedERTprofileofthe2010.Thismeteorologicalbehaviouralloweda quasiͲsteadysituationforthedebriscoveredglacierofPizBoèinthelastfiveyears. Climate models show a dramatic air temperatures increase for the next century (see chapter 2), especially at high altitudes, and this will certainly influence covered ice. In the next decades, accordingtoSRESA1B,frostandicedayswilldecreasebyabout14Ͳ15days.Coveredicewilllikely meltquicklyduringthenextdecadesandthedisplacementoficewillincrease.Themoreimportant factors that will determine the velocity of melting and displacement, will be the summer temperaturesandsnowcoverdurationintheearlysummer.DuringthenextyearsARPAVisgoingto investigatethefutureevolutionofpermafrostatPizBoè. Acknowledgements.–TheauthorsthankAbuZeidNasserforhisworkduringfieldcampaign. References: BinelyA.,2003:2Dinversionofapparentresistivitydatausing“Profiler”.InstituteofEnvironmental andNaturalSciences,LancasterUniversity,LANCASTER,UK.6pp. LaBreque D.J., Miletto M., Daily W., Ramirez A., Owen E., 1996: The effects of noise on Occam’s inversionofresistivitytomographydata.Geophysics,61,538Ͳ548. OldenburgD.,L.Y.,1994:Inversionofinducedpolarizationdata.Geophysics,59,9:1327. 158 PermafrostResponsetoClimateChange 3. CasestudiesintheEuropeanAlps 3.14 UpperSuldenValley,OrtlerMountains,ItalianAlps Citationreference Zischg A., Mair V. (2011). Chapter 3.14: Case studies in the European Alps – Upper Sulden Valley, Ortler Mountains, Italian Alps. In KellererͲPirklbauer A. et al. (eds): Thermal and geomorphic permafrostresponsetopresentandfutureclimatechangeintheEuropeanAlps.PermaNETproject, finalreportofAction5.3.OnͲlinepublicationISBN978Ͳ2Ͳ903095Ͳ58Ͳ1,p.159Ͳ169. Authors Coordination:AndreasZischg Involvedprojectpartnersandcontributors: Ͳ AbenisAlpinexpertGmbH/srl–AndreasZischg Ͳ Automous Province of Bolzano Ͳ South Tyrol, Office for Geology and Building Materials Testing(GeoLAB)–VolkmarMair Content Summary 1. Introductionandstudyarea 2. Permafrostindicatorsandrecentthermalandgeomorphicevolution 3. Possiblefuturethermalresponsetopredictedclimatechange References 159 PermaNET–CasestudiesintheEuropeanAlps Summary ThecasestudyfromtheUpperSuldenValley(46°29’37.87’’N,10°36’57.31’’E),OrtlerMountains, ItalianAlps,showedthegeomorphicresponseofflatorgentlyinclinedareascoveredbydebrisin a highͲmountain ski resort outside of rock glaciers. The subsidence of the surface due to the melting of the ground ice lies in a dimension of 4m in 11 years (1996Ͳ2006). The measured surface subsidence is accompanied with geomorphic signs such as thermokarst phenomena or with increasing surface temperatures. In steeper areas, geomorphic signs of slope movements arefoundinareaswithprobablepresenceofpermafrost.Thesubsidenceofsurfaceisrelevant forskiinfrastructuresandmustbehandledwithsometechnicaleffort.Inthevicinityofthepillar no.12oftheskiliftMadritschjoch,mostprobablythegroundicehasmeltedtotally.Therefore, thesubsidenceprocessofthesurfacenearthepillarisfinished.However,thiscanbeconcluded onlyforthisspecificlocationinthestudyarea.Inotherareaswheregroundiceisstillpresent, thedegradationprocesswillcontinuewiththeexpectedincreaseoftemperatures. 160 PermafrostResponsetoClimateChange 1. Introductionandstudyarea Thestudyareaissituatedintheskiresort"SuldenͲMadritsch"intheUpperSuldenValley,community of Stilfs/Stelvio, Autonomous Province of Bozen/Bolzano (46°29’37.87’’N, 10°36’57.31’’E, Figs. 1, 2 and3).ThestudyareaissituatedintheOrtlermountainrangeneartheStilfserjochpass.Theextent of the study area is about 5km2. The area is mostly free of vegetation and is partially covered by debris. One small rock glacier is situated in the study area. During the period between 1805 and 1850,partsoftheareawerecoveredbyasmallglacier. Intheearly1990s,ateamoftheUniversityofMunichbeganitsfirstpermafrostinvestigationsinthis area(Stötter1994).In1992firstmeasurementsofthetemperaturesatthebottomofthesnowcover (BTS), topographic surveys and geophysical measurements (seismics) for mapping the permafrost distribution had been made. Since 2004, the BTS measurements have been repeated in the years 2004,2006,2007,2008and2009.BTSmeasurementswerecarriedoutatmorethan1100pointsin thestudyarea.Since2006,devicesformeasuringthegroundsurfacetemperatures(UTLdataloggers) wereinstalledon10locationsinthestudyarea. Fig.1–LocationofthestudyareaUpperSuldenValley. Fig. 2 – Overview of the study area Upper Sulden Valley. Photograph taken from the upper station of the "Madritschjoch"skiliftlocatedat3150ma.s.l.PhotographbyA.Zischg(09.03.2007).Thestudyareaistheski resortintheforegroundofthepicture. 161 PermaNET–CasestudiesintheEuropeanAlps Fig.3–OverviewofthestudyareaUpperSuldenValley.Theblacklinesindicatethelocationofthechairsliftsof theMadritschskiresort.Orthoimage2008. Fig.4.–OverviewofthestudyareaUpperSuldenValley.HillshadeoftheairͲborneLidarͲDEM2006.Thered circleshowsthelocationofthepillarno.12oftheskilift"Madritschjoch"mentionedinthetext.Thegreendots showthelocationoftheGSTmeasurementdevices(UTLdataloggers). 162 PermafrostResponsetoClimateChange 2. Permafrostindicatorsandrecentthermalandgeomorphicevolution Themeasurementsofthetemperaturesatthebottomofthesnowcoverin1992and1996showed the main areas with probable presence of permafrost. Geophysical measurements (seismic refraction)andtheconstructionoftheskiliftsprovedtheexistenceofcompacticelensesinthearea aroundthepillarno.12oftheskilift“Madritschjoch”.InAugust1992,massiveicewasfoundduring thefoundationofthispillar(Fig.5). Fig.5–Excavationworksforthefoundationofthepillarno.12oftheskilift"Madritschjoch"inAugust1992. PhotographbyM.Maukisch.Source:Stötteretal.(2003).Groundicewasobservedintheconstructionsiteand underthemoraineattheleftoftheconstructionsite. Thefirstmeasurementsofthetemperaturesatthebottomofthesnowcover(BTS)intheareawere carriedoutin1992and1996bymeansofmobiledevicesinthemonthsFebruaryandMarch.Since 2004,themeasurementshavebeenrepeated.Duringthewinterhalfyearsbetween2004and2008 themeasurementshavebeenrepeatedonlyinthepartswhereasnowdepthofatminimum60cm wasexistent(Figs.6and7,Table1). Table1–SummaryofthefiveBTSͲmeasurementcampaignsinthestudyareaUpperSuldenValley. Year Measurement date/period NumberofBTSͲ measurements Probable permafrost(n) Possible permafrost(n) Nopermafrost(n) 1992 March1992 371 227 58 34 1996 March1996 24.02.,03.03., 16.03.,07.04. 25.04. 09.03.,27.03., 29.03. 06.03.,07.03. 184 157 19 8 70 27 9 34 51 4 6 38 249 133 51 65 2004 2006 2007 2008 Allyears 236 73 37 89 1161 621 180 268 163 PermaNET–CasestudiesintheEuropeanAlps Fig.6–ResultsoftheassessmentofpermafrostexistenceusingBTSmeasurementsin1992,1996and2004. 164 PermafrostResponsetoClimateChange Fig.6–ResultsoftheassessmentofpermafrostexistenceusingBTSmeasurementsin2007,2008andallyears. 165 PermaNET–CasestudiesintheEuropeanAlps Since 2006, the ground surface temperatures (GST) have been monitored continuously by 10 miniature temperature dataloggers situated in different parts of the study area (UTL datalogger, logginginterval1hour,forlocationsseeFig.4). ThecomparisonoftheBTSmeasurementsofthedifferentyearsshowedanincreaseoftemperatures at the bottom of the snow cover in the area near the mentioned pillar no. 12 of the ski lift “Madritschjoch”. The GST measurements in this area showed a high interannual variability. Despite this fact the followingpatternscouldbefound:TheupperpartoftheslopeoftheHintereSchöntaufpeakshows constantly negative temperatures (ca. Ͳ6°C) over all observed periods. The lowest parts of the hill betweenthebottomandtheupperstationoftheskilift“Madritschjoch”showedanincreaseofthe temperaturesovertheyears. In the years before the construction of the ski lift, topographic surveys had been made. These measurementshavebeenrepeatedregularlysincetheconstructionoftheskilift.Inthistimeperiod between1992and2004,thesurfaceoftheareasinthealignmentoftheskilift“Madritschjoch”that are covered by debris were supposed to subsidence processes. In the vicinity of pillar no. 12, the surfacesaggedfor4m(topographicsurveysbytheskiresortoperator).Thissubsidence ofsurface was due to the melting of ground ice. In the vicinity of pillar no. 12 geomorphologic evidences for surfacesubsidencehavebeenobserved(Fig.7). Fig.7–Photographofsubsidenceprocessesinthevicinityofpillarno.12oftheskilift"Madritschjoch"inJuly 2006.PhotographbyA.Zischg. The foundation of the pillar moved sideward and disarranged the position of the pillar no. 12. Therefore,thepillarhadtobeadjustedseveraltimessince1992untilthefoundationofthepillarwas reͲconstructed by means of a deeper foundation reaching the bedrock under the debris cover (Fig.8). 166 PermafrostResponsetoClimateChange Fig. 8 – Photograph of the reͲadjustment of the position of the pillar no. 12 of the ski lift "Madritschjoch". PhotographbyA.Zischg. During the construction of the ski lift, the ridge of debris material alongside the skilift (Fig. 9) had beengrabbedslightlywithanexcavator.In1996,theridgeshowedanoutcropofmassiveiceonits lateral part exposed towards the ski lift. The slope was nearly vertical. In the meantime the ridge slumpeddown.Theslopeexposedtowardsthealignmentoftheskiliftisrecontouredandflattened. Theoutcropoficedisappeared. Fig.9–Photographofthedebrisridgealongtheskilift"Madritschjoch"inJuly2006.PhotographbyA.Zischg. Theredarrowshowsthelocationwithoftheobservedslopedeformation. 167 PermaNET–CasestudiesintheEuropeanAlps Inthesteeperpartsoftheareascoveredwithdebris,someevidencesforslopemovementscouldbe observed(Fig.10).Theevidencesformovingdownwardsoftheslopeweremorefrequentlyinthe areasthatareshowingwarmergroundtemperaturesofthemeasurementsduringthelastyears.The geomorphicsignsforslopemovementsinthisareawereobservedforthefirsttimein2006. Fig. 10 – Photograph of evidences for slope movements in the active layer of the southͲwestern slope of the peakHintereSchöntaufspitzeintheskiresortSuldenͲMadritschinJuly2007.PhotographbyA.Zischg. 3. Possiblefuturethermalresponsetopredictedclimatechange Theobservationsofthesurfacesubsidencearerelevantfortheinfrastructureoftheskiresort.With sometechnicalefforts,theproblemforthestabilityofthefoundationofapillaroftheskiliftdueto thisgeomorphicphenomenonofsubsidencecouldbehandled.Thephenomenonhasacceleratedin the years from 2000 to 2007. In the vicinity of the pillar no. 12 most probably the ground ice has beenmeltedtotally.Therefore,thefurthersubsidenceofthesurfacenearbyofthepillarisfinished. However,thiscanbeconcludedonlyforthisspecificlocationinthestudyarea.Inotherareaswhere groundiceisstillpresent,thedegradationprocesswillcontinuewiththeincreaseoftemperatures. AftertheanalysesprovidedinChapter2,thenumberoffrostdaysintheMadritschskiresortislikely to decrease for 15 days and the number of ice days will decrease for 17Ͳ19 days. The freezeͲthaw days will increase about 3Ͳ4 days. This will have consequences for a further continuation of the permafrostdegradationprocess.The monitoringofthe permafrostdegradationin thisareawillbe continued.Incaseofabeginningsubsidenceprocessinotherpartsofthestudyarea,thecourseof thiseventwillbeobserved. 168 PermafrostResponsetoClimateChange References: Stötter J., 1994: Veränderungen der Kryosphäre in Vergangenheit und Zukunft sowie Folgeerscheinungen – Untersuchungen in ausgewählten Hochgebirgsräumen im Vinschgau (Südtirol). Habilitationsschrift, München. Stötter J., Fuchs S., Keiler M., Zischg A., 2003: Oberes Suldental. Eine Hochgebirgsregion im Zeichen des Klimawandels. In: E. Steinicke (ed.): Geographischer Exkursionsführer Europaregion Tirol, Südtirol, Trentino. Spezialexkursionen in Südtirol. Innsbrucker Geographische Studien Band 33/3, 239Ͳ281, Innsbruck 169 PermafrostResponsetoClimateChange 4. Synthesis Citationreference LiebG.K.,KellererͲPirklbauerA.(2011).Chapter4:Synthesisofcasestudies.InKellererͲPirklbauerA. et al. (eds): Thermal and geomorphic permafrost response to present and future climate change in the European Alps. PermaNET project, final report of Action 5.3. OnͲline publication ISBN 978Ͳ2Ͳ 903095Ͳ58Ͳ1,p.170Ͳ177. Authors Coordination:GerhardKarlLieb Involvedprojectpartnersandcontributors: Ͳ InstituteofGeographyandRegionalScience,UniversityofGraz,Austria(IGRS)–GerhardKarl Lieb,AndreasKellererͲPirklbauer Ͳ Institut de Géographie Alpine, Université de Grenoble, France (IGAͲPACTE) – Philippe Schoeneich Ͳ EDYTEM,UniversitédeSavoie,France(EDYTEM)–PhilipDeline Ͳ Regional Agency for the Environmental Protection of the Aosta Valley, Italy (ARPA VdA) – PaoloPogliotti Content Summary 1. Casestudies:Methodsandoverallresults 2. Thermalpermafrostreactioninthepastandfuture 3. Geomorphicpermafrostreactioninthepastandfuture References 170 PermafrostResponsetoClimateChange Summary In the framework of Action 5.3 of the PermNET projects investigations on the thermal and permafrostresponsetoclimatechangewerecarriedoutin13testsitesdistributednearlyallover the Alps. This research work was based on a great variety of methods ranging from geomorphological mapping over monitoring of ground surface temperature to borholes thus makingtheresultswellreliable.Nearlyallhypothesisestablishedintheinitialphaseofthework could be verified and quantified in at least one of the case studies. From this the following conclusionscanbedrawn: Thermalpermafrostreactions An increase in ground temperatures and hence permafrost warming as a response to climate warmingcanalreadybeobservedandwillcontinueinthefuture.However,thereisalsoastrong control of snow cover to the thermal regime of the ground thus complicating the relationship betweenclimatewarmingandpermafrostwarmingordegradation.Air,groundandpermafrost temperaturesaswellassnowcovershouldbemonitoredatasmuchlocationsaspossible. There is already a lot of evidence of thawing of permafrost in the Alps which leads and will increasingly lead to a reduced spatial extent of permafrost and to active layer thickening. However, little is yet not known about the assumed increasing ground water circulation and pressurewhichshouldbeonefocusoffutureresearch. Inspecificaltitudinalbeltsthenumberoffreeze/thawcyclesaswellasthedurationandintensity offreezingandthawingperiodswillchangesignificantly.Thusthesubsequentprocesseslikerock fallswillshifttohigheraltitudesaffectingareaswhicharenotyetpronetotheseprocesses.From thisitisadvisabletomonitorthethermalregimeofthegroundatmanysites. Geomorphicpermafrostreactions Rockglaciersreactwithasurprisinglyshorttimelagonairandgroundtemperaturevariations.It canbeassumedthatmostrockglacierswillcreepfasterinthenextyearstodecadesandthen will become climatically inactive due to permafrost degradation. The surface velocity of rock glaciers should be monitored at least at the sites in which infrastructure is placed on rock glaciers. Thedisplacementmodeofrockglaciersalreadychangesandwillcontinuetochangesignificantly inthenextdecades.Especiallysurfaceloweringcanbeobservedatseveralsitesduetomelting ofthepermafrostice.In thefuturecollapseoficerichrock glacierswilloccurmorefrequently thus endangering infrastructure. Damage can only be avoided if the internal structure of the permafrostusinggeophysicaltechniquesiswellknown. Volumeandextentofdestabilizedmaterialsincreaseasaresponsetoactivelayerthickeningand decreasingpermafrostextent.Thusthedispositiontogravitativeprocessesincreasesmakingthe reevaluationofexistinghazardprotectingmeasuresnecessary. Increasing frequency and magnitude of mass movement events are clearly evident. A further increaseispossible,ashiftofrockfallscarstohigherelevationsevenveryprobable.Monitoring andmodellingofthesesprocesseswillhelptoreducethehazard. The melting of ice in thawͲsensitive permafrost makes surfaces instable thus leading to subsidenceinflatareasorongentleslopesandtodifferenterosionalprocessesonsteepslopes. The consequence is damage of infrastructure if the internal structure of the permafrost is not known. 171 PermafrostResponsetoClimateChange 1. Casestudies:Methodsandoverallresults In the 13 case studies of Action 5.3 high mountain permafrost has been investigated by a great methodologicalvariety(Tab.1)comprisingnearlyalltechniqueswhichareavailable.Thustheresults are well reliable, particularly since all the case studies also provide similar evidences from other study sites situated within and without the Alps (see the respective references). According to the thematic aspect of Action 5.3 ground surface temperatures (GST) play a crucial role and thus have been used in all of the case studies. GST is the key parameter in giving information on how the warming of the atmosphere is coupled with the thermal regime of the ground. GST can be easily measuredbycheapandtoughequipment(miniaturedataloggerMDL).Thereforethissimplebutin terms of its relevance for understanding thermal (and subsequently geomorphic) changes in permafrostareasveryefficientmethodcanberecommendedforevenmorewidespreadusageinthe future. Table1–OverviewofpermafrostrelatedmethodsusedinmorethanoneofthecasestudiesofAction 5.3 (Abbreviations: BTS = Basic temperature of winter snow cover, ERT = electrical resistivity tomography,GPR=groundpenetratingradar,GST=groundsurfacetemperature,MDL=miniature datalogger,TLS=terrestriallaserscanning).Annotations:*Modellingofpermafrostdistributionwas thetaskofAction5.1inthePermaNETproject.**Atthestudysiteswhichwerenotequippedwith automaticweatherstationsmeteorologicaldatafromstationsinthevicinityhavebeenused.***In somestudysitesmeasurementstakeplaceinshallowboreholes (downto depthsof+/Ͳ1m)which areincludedinthiscategory.****OnlytheseBTSsitesarelistedwherespecialBTScampaignswere carriedout(andBTSvalueswerenotjusttakenfromGSTmeasurements). Method Geomorphologicalmapping Continuousphotographic documentation Numericalpermafrostmodelling* Automaticweatherstation GSTlogging(usingMTD) BTSmeasurement**** Spring(water)temperature measurement Dischargemeasurementand chemicalanalysisofwater Geodeticmeasurement PhotogrammetryandTLS Geophysicalsoundings(inmost casesgeoelectrics/ERTorGPR) Borehole Casestudy(chapter) 3.2.,3.3.,3.5.,3.7. Gainedinformation Geomorphologyofstudyareas 3.2.,3.3.,3.8. Snowcover,rockfallevents 3.2.,3.3. 3.2.,3.3.,3.6.,3.8.,3.9.,3.10., 3.13. Spatialdistributionofpermafrost Atmosphericconditions** GSTandnearGST***(evidenceof permafrost) 3.2.,3.3.,3.5.,3.7.,3.11.,3.14. BTS(evidenceofpermafrost) Watertemperature(evidenceof 3.3.,3.5.,3.11.,3.12.,3.13. permafrost) Runoffandchemicalpropertiesof 3.5.,3.13. water 3.3.,3.5.,3.6.,3.7.,3.11.,3.12. Displacementofsurface 3.3.,3.5.,3.8.,3.13. Displacementofsurface 3.2.,3.3.,3.5.,3.6.,3.7.,3.8.,3.13., Internalstructureand 3.14. temperatureofpermafrost Internalstructureand 3.4,3.7,3.8.,3.10.,3.13. temperatureofpermafrost allcasestudies Summarizingtheresultspresentedinthecasestudiesithastobementionedthatwithrespecttothe aimofidentifyingandquantifyingtheresponseofhighmountainpermafrosttoclimatechangeone problemremainsunsolved–itisthelackoflongtermdataconcerningpermafrost.Mostofthesites werenotestablishedbeforearound2005andthereise.g.noGSTrecordlongerthan10yearsinany studysite(withtheexceptionofSonnblickwherethemeteorologicalobservatoryprovidesalsoGST 172 PermafrostResponsetoClimateChange datawhichhavenotbeenconsideredinChapter3.4.).Thuswearefarawayfromhavingsufficient informationonlongtermthermalreactionofpermafrost–astatementwhichcanonlyleadtothe conclusion that is absolutely necessary to establish a long term monitoring network as it was the mainobjectiveofthePermaNETproject. The only aspect showing a record of a few decades for at least some sites (the longest one at Hochebenkar since 1938, cf. Chapter 3.5.) is the surface velocity of rock glaciers. Natural scientists becameawareofcreepingrockmassesalongtimebeforetheywererecognisedasbeingthemost striking features of high mountain permafrost. The results of the existing geodetic and photogrammetric measurements which are presented and discussed especially at the examples of Doesenrockglacier(Chapter3.3.)andLaurichardrockglacier(Chapter3.6.)clearlyrevealsignificant geomorphodynamicchangesoverthelastdecadeswhichcanonlybeexplainedwithchangesinthe thermalregimeofthepermafrost. Inordertoprovideacloserlooktothe“overallresults”itishelpfultodistinguishbetweendifferent typesofpermafrostenvironmentswhichhavebeeninvestigatedinthestudysites(Tab.2).Mostof the work has been done on active rock glaciers which have become the most important object of permafrostresearchinhighmountains.Thustheprocessestakingplaceinrockglaciersystemsare understoodincreasinglywellalthough,ofcourse,alotquestionsstillremainsopen.However,there are still fewer permafrost investigations outside of rock glaciers leading to a relative lack of information on the other environment types which is regrettable due to the fact that most of the infrastructure–mainlyfortouristicpurposes–isbuiltintheseenvironmentandnotonrockglaciers whoseunfavourableconditionsforconstructionworkisinthemeantimewellknowntotechnicians leadingthemtoavoidrockglaciersurfaceswhereverpossible. Table 2 – Overview of permafrost environments investigated by the case studies of Action 5.3 (Annotations: Some of the case studies refer to different types of permafrost environments, in the tableonlythemostsignificantonesareindicated). Typeofpermafrostenvironment Casestudy(chapter) Activerockglacier 3.3.,3.5.,3.6.,3.7.,3.11.,3.12., 3.13. Slope 3.2.,3.3.,3.10.,3.14. Rockwall 3.8.,3.9. Summitandridge 3.2.,3.4.,3.8.,3.9. Annotations Debrisortalusderivedrock glacierswhichareatleastpartly active,boulderysurface Slopesoutsideofactiverock glaciers,mostlycoveredbyglacial orperiglacialsediments Steeprockfaceswithlittleorno coveragebysediments,snowor ice Summitareasmostlyconsistingof heavilyweatheredbedrock,partly withmountaintopdetritus The general thermal reaction of permafrost to climate change can be described in the way that permafrosttemperaturesincrease,activelayersthickenandpermafrostthusbecomesmoreprone todegradation.Basedonthisthemainstatementsonthefourenvironmentaltypesderivedfromthe resultsofthecasestudiescanbesummarizedasfollows: x Active rock glaciers react surprisingly fast on annual or seasonal temperature variations in thewaythatwarmerconditionsresultinhighersurfacevelocities.Thisisduetothefactthat deformationratesincreasewithtemperatureaswellastothepresenceofmoreliquidwater intherockglaciersystem. 173 PermafrostResponsetoClimateChange x Onslopestheactivelayerthickeninganddegradationofpermafrostleadstodestabilization ofsedimentswhichthenarepronetoerosionalprocessesofdifferentkind(especiallydebris flows)whentheinclinationishigh.Inflatterterrainfrostsettlingandsubsequentsubsidence ofthesurfaceisthemostimportantprocessasfaraspermafrostisthawͲsensitve. x Rock walls free of sediments or cryospheric cover are directly coupled to atmospheric changes which therefore have direct consequences on the thermal regime and thus geomorphic processes inrock faces. Depending on the rock type and its properties (strata, fracturing,clefts)rockfallsofincreasingfrequencyandmagnitudearelikelytooccur. x On summits and ridges the conditions are similar to that in rock walls. Regardless of the existenceofmountaintopdetritusthetendencyofsummitsandridgestocollapseisgiven. 2. Thermalpermafrostreactioninthepastandfuture 2.1Increasinggroundtemperatureandpermafrostwarming Theentireevidenceavailablesofar–notonlyfromthecasestudiesofAction5.3butalsofromthe literature(Harrisetal.2003)–clearlyshowsthattherisingairtemperaturescausesanincreaseof GSTsundviaheatfluxtothegroundanincreaseofpermafrosttemperatures.Asrecordedinthecase studiesallmeasuredpermafrosttemperaturesarequitecloseto0°C(e.g.Ͳ1.02°Casmeanvaluefor the period 2008Ͳ10 at the permafrost table in the deep borehole at Cime Bianche Pass, calculated fromTable2inChapter3.10.).Thismeansthatonlyaslightfurtherincreaseintemperaturewould be sufficient to induce permafrost degradation in vast areas currently underlain by permafrost. A modelapproachonthisaspectisdiscussedinChapter3.7. Ontheotherhandmanyofthecasestudieshaveshownthatthereisobviouslynolinearcorrelation between rising air temperatures and rising permafrost temperatures. Instead of this the characteristics of the substrate as well as the snow cover play a crucial role for the temperature regime in the ground. Especially the latter aspect has been elaborated intensively in all the case studies where high resolution GST measurements using MDL have been carried out. So the conclusionthat“theevolutionofthepermafrostwillnotonlydependontheairtemperature,butwill bestronglyinfluencedbytheevolutionofthesnowcover,especiallyitsearlyorlateonsetinautumn. Alateonsetofthesnowcovercanatleastpartiallycompensateariseinairtemperature”(Chapter 3.6.)canbeappliedtoallthecasestudiesandfinallycanbeconsideredasarulevalidfortheentire Alps.Yetthishastobequalifiedbythefactthattherearehardlyany(andwithinAction5.3noneat all)longtermdataseriesofpermafrosttemperatureavailablesofar. 2.2Thawingofpermafrostwithdifferenteffects ThawingofpermafrostintheAlpswhichhasalreadybeenprovenbyalotofevidenceisassumedto createthefollowingeffects.(i)Thespatialextentofpermafrostisreduced:Thisfactcane.g.beseen attheSuldenValleystudysite(Chapter3.14.)wherethepillarofaskiliftwasoriginallyplacedona buried body of massive ice which in the meantime has disappeared so that the pillar could be reconstructedontheunderlyingbedrock.Unfortunately,duetothelackofknowledgeonprevious permafrostdistribution,thecompletedegradationofpermafrostinrecentyearscanundoubtedlybe provenonlyinalimitednumberofcases.However,thenowavailableinformationontheexistence of permafrost not only at specific sites – as documented e.g. within Action 5.3 – but also for the entire Alps will provide the possibility to observe the (probably accelerated) future degradation processindetail.(ii)Activelayerthickeninghasbeendetectedinsomeofthestudysites,e.g.well documentedbyrepeatedgeoelectricalsoundingsonLaurichardrockglacier(Chapter3.6.).However, alsothisstatementcontainssomeuncertaintiesbecauseofthelackoflongtermdataavailability.It hastobekeptinmindthattheinterannualvariabilityoftheactivelayerdepthisveryhighdepending 174 PermafrostResponsetoClimateChange especiallyonthebeginning,durationandthicknessofthewintersnowcover.Thiscane.g.beseenin the respective graphs from Cime Bianche Pass (Chapter 3.10.) in which the active layer thickness shows a great temporal variation but not yet a trend to increase. (iii) Increasing ground water circulation and pressure has been worked out as a possible contribution to increasing rates of permafrost creep on rock glaciers at several study sites (e.g. Doesen Valley, Chapter 3.3., and Hochebenkar, Chapter 3.5.). However, there is not yet any unambiguous proof for this assumption becauseatleastinthecasestudiesinvestigatedinAction5.3therewasnospecificresearchonthe hydrologicalsystemwithinpermafrostbodies. Summarizingfromtheconsiderationsongroundtemperatures,permafrostwarmingandpermafrost thawing given in this and the previous subchapter the conclusion can be drawn that the thermal regime of permafrost should be monitored more intensively in the future. This means that measurementsofGSTandtemperaturesindifferentdepths(inboreholes)havetobecarriedoutat moresitesthantodayand–aboveall–overlongerperiodsthanithashappeneduntilnow.Afurther focus of future research should be the investigation of the existence, dynamics and significance of liquidwaterinpermafrostareas. 2.3Changesinthenumberoffreeze/thawcyclesandmagnitudeoffreezingandthawingperiods The basic information on this topic is given in Chapter 2 providing data on the numbers of freeze days, ice days and freezeͲthaw days for the entire Alpine Arc. The analysis is based on the period 1961Ͳ90 and the difference in the number of these days to the period 2021Ͳ2050 is given. E.g. consideringthenumberoffrostdaysadecreaseof9Ͳ18daysperyearbetweentheperiods1961Ͳ90 and 2021Ͳ2050 is expected. The change of freeze/thaw days which are of specific relevance for geomorphicprocesses(e.g.frostweathering,rockfallactivity)isestimatedbetweenͲ4and+5days peryear.Thisdoesnotseemtobeahighvalue,yetonemustkeepinmindthealtitudinalshiftof temperature beltsupwards.Asithasbeenpointed oute.g.in thestudyarea MontBlanc (Chapter 3.9.)thesubsequentprocesseslikerockfallswillaffecthigheraltitudeswhicharenotyetproneto theseprocesses.Inanycasealsofromthispointofviewitisadvisabletomonitorthethermalregime ofthegroundatasmanysitesaspossible. 3. Geomorphicpermafrostreactioninthepastandfuture 3.1Changesintherateofrockglacierdisplacement Allthe7casestudiesonrockglaciers(Tab.2)haverevealedthefactthatthedynamicsofrockglacier creepstronglydependsontemperaturevariations.Themeasuredsurfacevelocitiesonrockglaciers react on air temperature and especially on GST variations within a surprisingly short time lag. According to the Action 5.3 studies this time ranges between less than one and a few years. As reported e. g. from Doesen rock glacier (Chapter 3.3.) interannual temperature variations of 1Ͳ2°C can result in velocity changes of approx. +/Ͳ20%. The conclusion for the evidence available on surface velocity changes on rock glaciers can be taken from Chapter 3.6.: “Rock glaciers react to climate and show interannual velocity variations. Their reaction time is thus much shorter than previously assumed. Velocity variations are linked to temperature variations: an increase in temperature induces an increase in velocity. The air temperature only partly explains the observed groundsurfacetemperatureandvelocityvariations.Thegroundsurfacetemperatureshowsthebest linkwithvelocityvariations,withatimelagofaround1year.Thesnowcoverexplainsmostofthe differencebetweenairtemperatureandgroundsurfacetemperature,andthusappearsasthemain drivingfactorbothforgroundsurfacetemperatureandforvelocityvariations”. Forthenearfuture(nextyearstodecades)itcanbeassumedthatmostrockglacierwillshowatrend to faster surface velocities although there will be subordinate periods of reduced dynamics as a 175 PermafrostResponsetoClimateChange consequencesofcolderyears.Afterthisphaseofincreaseddynamicspermafrostdegradationwith meltingoftheicewillreducetheicecontentofrockglaciersuntilthesubstrateisnotsupersaturated iniceanymore.Giventhissituationtherockglacierwillfallintothestatusofaclimaticallyinactive one,i.e.themovementwillstopandtheremainingicewillslowlymeltaway.Dependingonthesize andelevationoftherockglacierthiswillprobablylastseveraldecadestocenturies. Verticaldisplacementonrockglaciersurfacesmaybeduetothedynamicbehaviourofrockglaciers (areaswithextendingorcompressing“flow”).However,ifthereisanetloweringoftheentirerock glaciersurfacetherecanbenodoubtthatthereisaniceloss.Suchasituationise.g.describedfor HochebenkarrockglacierinChapter3.5.,butitalsoappliese.g.toDoesenrockglacier(Kaufmann& Ladstädter2007;Kaufmannetal.2007).Ithastobeexpectedthatasurfaceloweringduetomeltingof the ice will occur on most of the alpine rock glaciers in the first phase of acceleration due to permafrostwarmingaswellasinthesecondphaseoficedisappearance. Themeasurementofsurfacedisplacementsonrockglaciersshouldbecontinuedwhereitisalready carried out in order to achieve long term data series. Furthermore such monitoring should be establishedatthefewsiteswhereinfrastructureisplacedonthesurfaceofrockglaciers. 3.2Changesindisplacementmodeofrockglaciers The displacement mode of rock glaciers already changes as it has been described considering the verticalsurfacechangesintheprevioussubchapter.Thesealreadyongoingprocesseswillcontinuein thenextdecadesaccompanyingtheaccelerationandsubsequentlythedeactivationofrockglaciers. Withregardtotheaccelerationbasalslidingofrockglacierscanbetakenintoaccount(Hausmannet al.2007)asaconsequenceofachanginghydrologicalsystem.However,asalreadymentionedabove noempiricalfindingsonthisaspectareavailableinAction5.3. Thusstatementsonlyonsurfaceloweringarepossiblewhichcanbeobservedatseveralsitesdueto melting of the permafrost ice. In the future collapse processes on ice rich rock glaciers will occur more frequently creating thermokarst structures which can already be observed on several alpine rock glaciers (e.g. Murfreit Rock Glacier, Italy; Krainer & Mussner 2010), but not on the ones investigatedinAction5.3.Collapseofcoursecancausedamagetoinfrastructurewhichcanonlybe avoidediftheinternalstructureofthepermafrostusinggeophysicaltechniquesiswellknown. 3.3Changesinsolifluctionratesandcryogenicweathering NoempiricalevidencehasbeenprovidedonthesetwotopicsbythecasestudiesofAction5.3. 3.4Changesinvolumeandextentofunstable/unconsolidatedmaterials As it has been shown e.g. in the Sulden Valley study site (Chapter 3.14.) volume and extent of destabilized materials increase as a response to active layer thickening and decreasing permafrost extent. Because more loose material is present meteorological events like heavy rainfalls can mobilize these sediments. Thus the disposition to gravitative and erosional processes has already increasedatmanylocationsandwillfurtherincreaseinthefutureaffectingmoreandlargerareas.In many cases these changes will certainly make the reͲevaluation of existing hazard protecting measuresnecessary. 176 PermafrostResponsetoClimateChange 3.5Changesinfrequencyandmagnitudeofmassmovementevents This aspect has been highlighted in much detail by the Mont Blanc study in Chapter 3.9. even at differenttimescales.Theresultsundoubtedlyrevealthattheincreasingfrequencyandmagnitudeof massmovementeventscanonlybecausedbypermafrostdegradation.Thustheconclusionscanbe taken from this chapter: “… rockfalls from highͲAlpine steep rockwalls are expected to occur more frequently,withvolumesthatarelikelytoincrease.Thefrequencythatiscurrentlyincreasingshould maintain the same trend in the next decades, due to the deepening of the active layer as the temperaturerise…intheAlpsforthe21thcenturywillbehigherbynearly1°Cthantheglobalone…. Moreover, heat advection by triggering of water circulation at depth along thaw corridors would increase the collapsed volumes”. Furthermore for purposes one must be aware of the fact that rockfallscarswillshifttohigherelevations.Thereforemoreinitiativesofmonitoringandmodellingof thesesprocessesshouldbecarriedoutinordertoprovideknowledgeforreducingrockfallhazards. 3.6Surfaceinstabilitiescausedbythermokarstprocesses/meltingofpermafrostice Surfaceinstabilitiesareofspecialsignificanceinpermafrostareaswhereinfrastructure–intheAlps in most cases constructions and edifices for touristic needs – is present. Thus the most striking examplesofAction5.3aretheMadritschskiingareainSuldenValley(Chapter3.13)aswellasthe observatoryandtouristhutonthesummitofHoherSonnblick(thoughChapter3.4.doesnotprovide muchinformationonthisaspect).MeltingoficeinthawͲsensitivepermafrost(intheAlpinecontext permafrost supersaturated with ice) makes surfaces instable thus leading to subsidence (ground settling) in flat areas or on gentle slopes. Additionally different erosional processes may occur on steepslopes due tothesameprocess.Theconsequenceisdamagetoinfrastructureif the internal structure of the permafrost is not sufficiently known and thus measures to avoid such problems cannotbetakenintime. Acknowledgements.ThePermaNETprojectispartoftheEuropeanTerritorialCooperationandcoͲ funded by the European Regional Development Fund (ERDF) in the scope of the Alpine Space Programmewww.alpinespace.eu References: Harris C., Vonder Muhll D., Isaksen K., Haeberli W., Sollid J.L., King L., Holmlund P., Dramis F., GuglielminM.&PalaciosD.,2003:WarmingpermafrostinEuropeanmountains.Globaland PlanetaryChange,39,215Ͳ225.doi:10.1016/j.gloplacha.2003.04.001. Hausmann H., Krainer K., Brückl E. & Mostler W. 2007: Internal Structure and Ice Content of Reichenkar Rock Glacier (Stubai Alps, Austria) Assessed by Geophysical Investigations. PermafrostandPeriglac.Process.18:351Ͳ367. KaufmannV.&LadstädterR.,2007:Mappingofthe3DsurfacemotionfieldofDoesenrockglacier (Ankogel group, Austria) and its spatioͲtemporal change (1954Ͳ1998) by means of digital photogrammetry.GrazerSchriftenderGeographieundRaumforschung43:127Ͳ144. Kaufmann V., Ladstädter R. & Kienast G., 2007: 10 years of monitoring of the Doesen rock glacier (Ankogelgroup,Austria)–Areviewoftheresearchactivitiesforthetimeperiod1995Ͳ2005. Proceedings,5thMountainCartographyWorkshop,29MarchͲ1April2006,Bohinj,Slovenia, 129Ͳ144. Krainer K. & Mussner L., 2010: Blockgletscher und Naturgefahren: Der aktive Blockgletscher 'Murfreit'indernördlichenSellagruppe,Dolomiten.Geo.Alp,7:p.99. 177
