* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Heinrich Event - EdShare - University of Southampton
Fred Singer wikipedia , lookup
Climatic Research Unit email controversy wikipedia , lookup
Effects of global warming on human health wikipedia , lookup
Climate resilience wikipedia , lookup
Global warming hiatus wikipedia , lookup
Climate change denial wikipedia , lookup
Economics of global warming wikipedia , lookup
Climate change in the Arctic wikipedia , lookup
Michael E. Mann wikipedia , lookup
Climate engineering wikipedia , lookup
Climate change adaptation wikipedia , lookup
Politics of global warming wikipedia , lookup
Global warming wikipedia , lookup
Climate sensitivity wikipedia , lookup
Climatic Research Unit documents wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Climate change and agriculture wikipedia , lookup
Citizens' Climate Lobby wikipedia , lookup
Climate governance wikipedia , lookup
Sea level rise wikipedia , lookup
Solar radiation management wikipedia , lookup
General circulation model wikipedia , lookup
Media coverage of global warming wikipedia , lookup
Climate change in the United States wikipedia , lookup
Climate change feedback wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Effects of global warming wikipedia , lookup
Climate change and poverty wikipedia , lookup
Public opinion on global warming wikipedia , lookup
Global Energy and Water Cycle Experiment wikipedia , lookup
Climate change, industry and society wikipedia , lookup
Physical impacts of climate change wikipedia , lookup
Effects of global warming on humans wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
Sea level, meltwater pulses, the overturning circulation, and climate Eelco J Rohling With thanks to Jenny Stanford, Mark Siddall, Bob Marsh Stable O isotope records from Greenland (example here is GISP2) through the last glacial cycle show strong climate variability Reproduced by permission of American Geophysical Union: Rahmstorf, S., Timing of abrupt climate change: A precise clock, Geophys. Res. Lett., 30(10), 1510, 21 May 2003. Copyright [2003] American geophysical Union. The “Dansgaard-Oeschger cycle” warm = interstadial; cold = stadial Large (order 10°C) temperature shifts Warming events within time-span of a decade or possibly less Also sharp coolings, after a more gradual onset of cooling ©Niels Bohr Institutet CH4 synchronisation Antarctica Greenland How related to climate variability in high southern latitudes? Reprinted by permission from Macmillan Publishers Ltd: Asynchrony of Antarctic and Greenland climate change during the last glacial period. Blunier, T; Chappellaz, J; Schwander, J; Daellenbach, A; Stauffer, B; Stocker, T F; Raynaud, D; Jouzel, J; Clausen, H B; Hammer, C U; Johnson, S J., Nature, v. 394, no. 6695, p. 739-743. Copyright (1998) Not under CC licence Frequent and “Square-wave” Type fluctuations (DO-events of order 10+oC) Fewer and temporally more Symmetrical fluctuations (A-events of order 3oC) • Timing relationship: bipolar see-saw • 1100 y integration of –ve northern record giving southern record [CH4] in air bubbles within all Ice cores follows DO-style Variability = synchronisation criterion! Most discussed explanations focus on the North Atlantic overturning component of the global ocean conveyor Courtesy of LDEO North Atlantic overturning thought to be sensitive to fresh-water fluxes into the N Atlantic (order 0.1 Sv) In a bi-stable regime, surpassing of forcing thresholds would result in rapid circulation change Reprinted by permission from Macmillan Publishers Ltd: Ocean circulation and climate during the past 120,000 years, Rahmstorf, S., Nature, vl. 419, no. 6903, p. 207-214. Copyright (2002). Not under CC Licence Models suggest that collapse of the overturn would shut down northward heat transport, causing abrupt cooling over N Atlantic sector (Note: in records, the warmings are the really sharp events!) Link to article with figure that Demonstates the cold nothern Hemisphere that would result from overturn shutdown (Figure 3) Link to article: Global Climatic Impacts of a Collapse of the Atlantic Thermohaline Circulation., Vellinga, M; Wood, R, A., Climatic Change. Vol. 54, no. 3, p251. Copyright (2002). Strongest cases for freshwater dilution concept : “Heinrich Events” in coldest extreme DO stadials Widespread IRD deposition - massive iceberg input. Durations: 550-900 years (Rohling et al., 2003) or 250-750 years (Hemming, 2004). Max. associated meltwater input into N Atlantic equivalent to 15 m sea-level rise (Hemming, 2004). Reproduced by permission of American Geophysical Union: Hemming, S.R., Heinrich events: Massive Llate Pleistocene detritus layers of the North Atlantic and their global climate imprint. Reviews of Geophysics, v. 42, no. 1, [np]. March 2004. Copyright [2004] American Geophysical Union. Concepts of what the world may have looked like: Schematic overturning in N Atlantic: DO interstadial DO stadial “Heinrich Events” Reprinted by permission from Macmillan Publishers Ltd: Ocean circulation and climate during the past 120,000 years, Rahmstorf, S., Nature. v. 419, no. 6903, p. 207-214. Copyright (2002). Not under CC Licence Reproduced by permission of American Geophysical Union: Rahmstorf, S., Alley, R., Stochastic resonance in glacial climate Eos, Transactions, American Geophysical Union, v. 83, no.12, pp.129-135, 19 Mar 2002. Copyright [2002] American Geophysical Union. Heinrich Event = interval of high ice-berg discharge into N Atlantic (IRD deposits and light surface-water δ18O anomalies) BUT: Greenland ice-core data show changes of order 10°C or more…. No model gets even close to that. Link to article with figure that Demonstates the cold nothern Hemisphere that would result from overturn shutdown (Figure 3) Link to article: Global Climatic Impacts of a Collapse of the Atlantic Thermohaline Circulation., Vellinga, M; Wood, R, A., Climatic Change. Vol. 54, no. 3, p251. Copyright (2002). Courtesy of The Russian Journal of Earth Sciences: Raspopov, O. M., Dergachev, A.V., Kolström, T., Kuzmin, A.V., Lopatin, E.V., Lisitsyna, O.V., (2007), Long-term solar activity variations as a stimulator of abrupt climate change, Russ. J. Earth Sci., 9, ES3002, Seager & Battista (2006) review data and simulations from coupled GCMs (GFDL, Hadley Centre), and find: “In the North Atlantic region, therefore, there is sufficient agreement ... that changes in the THC were likely involved in abrupt climate changes. …., changes in the THC, even shutdowns - at least as represented in GCMs - cannot explain the magnitude of the cooling around the North Atlantic…. …., even on its own home turf, the THC theory falls short of being able to offer a complete explanation of abrupt climate changes, unless all existing coupled GCMs are significantly in error ….” Did the THC slow down? Consider the last two big events: H1 and Younger Dryas YD H1 IRD 13C Reproduced by permission of American Geophysical Union: Stanford, J.D., Rohling, E.J., Hunter, S.H., Roberts, A.P., Rasmussen, S.O.,Bard, E., McManus, J. and Fairbanks, R.G., Timing of meltwater pulse 1a and climate responses to meltwater injections. Paleoceanography, 21, (4), PA4103. 9 December 2006. Copyright [2006] American Geophysical Union. SST Pa/Th Pa scavenged/ settles slower than Th, so if much lateral advection, then Pa depleted (low ratio). If less lateral advection, then ratio increases Reprinted by permission from Macmillan Publishers Ltd: Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes. McManus, J F; Francois, R; Gherardi, J M; Keigwin, L D; Brown-Leger, S., Nature, v.428, no.6985, p.834-837, Copyright (2004). Not under CC licence Widespread light benthic 13C and marked shift in Pa/Th ratios (GGC-5) suggest strongly reduced NADW flow starting with the IRD event of H1. Similar, but less pronounced for YD. At same time of reduced NADW, strong surface (SST) cooling. Q: Is Pa/Th reconstruction supported by other rate-sensitive proxies? Yes - new record of magnetic grainsize from Eirik Drift core TTR-451 strong signal similarity to Pa/Th in GGC-5. Both show gradual slowdown over 2kyr or more, and sharp recovery (vs. abrupt collapse in models) YD H1 Reproduced by permission of American Geophysical Union: Stanford, J.D., Rohling, E.J., Hunter, S.H., Roberts, A.P., Rasmussen, S.O.,Bard, E., McManus, J. and Fairbanks, R.G., Timing of meltwater pulse 1a and climate responses to meltwater injections. Paleoceanography, 21, (4), PA4103. 9 December 2006. Copyright [2006] American Geophysical Union. Q: Is Pa/Th reconstruction supported by other rate-sensitive proxies? Yes - new record of magnetic grainsize from Eirik Drift core TTR-451 strong signal similarity to Pa/Th in GGC-5. Both show gradual slowdown over 2kyr or more, and sharp recovery (vs. abrupt collapse in models) YD Q: Is freshwater driving these things at all ? i.e., how is it related to documented large freshwater fluxes (sea level change) ? H1 Reproduced by permission of American Geophysical Union: Stanford, J.D., Rohling, E.J., Hunter, S.H., Roberts, A.P., Rasmussen, S.O.,Bard, E., McManus, J. and Fairbanks, R.G., Timing of meltwater pulse 1a and climate responses to meltwater injections. Paleoceanography, 21, (4), PA4103. 9 December 2006. Copyright [2006] American Geophysical Union. Courtesy of AGU: Stanford, J.D., Rohling, E.J., Hunter, S.H., Roberts, A.P., Rasmussen, S.O., Bard, E., McManus, J. and Fairbanks, R.G. (2006) Timing of meltwater pulse 1a and climate responses to meltwater injections. Paleoceanography, 21, (4), PA4103. Barbados sea-level data (new datings) Rate of sea-level change THC intensity proxies Heavy line: GRIP on new GICC05 timescale Comparison layer-counted GICC05 timescale with Barbados sea-level record shows: ... the ~20m magnitude mwp-1a did NOT coincide with Bölling warming (even when pushing the confidence limits, they are 300 years separated) Instead, melt input started during Bölling (…warming caused melting…!), and the massive peak meltwater flux coincides with abrupt (but rather unimpressive) 200y Older Dryas cooling event Strong indications of local freshwater dilution in Nordic Seas during H events (Lekens et al., 2006) Is this (location) what controls the THC, rather than sheer magnitude and rate of input? Caption: Distribution of 18O anomalies in the Nordic Seas during Heinrich events and between 33 and 35 cal kyr B.P. measured on N. pachyderma (s). No corrections made for global ice volume and temperature effects. Reproduced by permisson of American Geophysical Union: Lekens, W.A.H., Sejrup, H.P., Haflidason, H., Knies, J., Richter, T., Meltwater and ice rafting in the southern Norwegian Sea between 20 and 40 calendar kyr B.P.; implications for Fennoscandian Heinrich events Paleoceanography, v. 21, no. 3, PA3013. 9 September 2006. Copyright [2006] American Geophysical Union. Strong indications of local freshwater dilution in Nordic Seas during H events (Lekens et al., 2006) Is this (location) what controls the THC, rather than sheer magnitude and rate of input? Moore (2005) and Tarasov & Peltier (2005) ascribe YD to a relatively small surface (iceberg) meltwater flux into Nordic Seas (from Arctic). Also, Jennings et al. (2006) a detected YD meltwater signal on SE Greenland shelf. Caption: Distribution of 18O anomalies in the Nordic Seas during Heinrich events and between 33 and 35 cal kyr B.P. measured on N. pachyderma (s). No corrections made for global ice volume and temperature effects. Reproduced by permisson of American Geophysical Union: Lekens, W.A.H., Sejrup, H.P., Haflidason, H., Knies, J., Richter, T., Meltwater and ice rafting in the southern Norwegian Sea between 20 and 40 calendar kyr B.P.; implications for Fennoscandian Heinrich events Paleoceanography, v. 21, no. 3, PA3013. 9 September 2006. Copyright [2006] American Geophysical Union. So how do H events in general relate to global sea-level variations? CH4 synchronisation Antarctica Greenland First: consider climate variability in high southern latitudes: Frequent and “square-wave” type fluctuations (DO-events of order 10+°C) Fewer and temporally more symmetrical fluctuations (A-events of order 3°C) of order 3°C) • Timing relationship; bipolar see-saw • 1100 y integration of -ve northern record giving southern record [CH4] in air bubbles within all ice cores follows DO-style variability Reprinted by permission of Macmillan Publishers Ltd: Asynchrony of Antarctic and Greenland climate change during the last glacial period. Blunier, T; Chappellaz, J; Schwander, J; Daellenbach, A; Stauffer, B; Stocker, T F; Raynaud, D; Jouzel, J; Clausen, H B; Hammer, C U; Johnson, S J., Nature, v. 394, no. 6695, p. 739-743. Copyright (1998) Not under CC licence Greenland-Antarctic phase relationships confirmed, by analyses of both types of signals within a single sample set from a sediment core taken from 3150 m waterdepth off Portugal (MD952042). Benthic δ18O signal ~identical in SW Pacific core MD972120 off New Zealand (~1200 m depth) Surface foraminiferal δ18O: DO-style signal Bottom-dwelling foraminiferal δ18O: AA-style signal From: Pahnke, K., Zahn, R., Elderfield, H., Schulz, M., (2003) 340,000-year centennial-scale marine record of Southern Hemisphere climatic oscillation Science, v. 301, no. 5635, p. 948-952, Reprinted with permission from AAAS. This figure may be used for non-commercial classroom purposes only. Any other uses requires the prior written permission from AAAS. Structure so prevalent that it is even preserved in the 57-record stack of Lisiecki and Raymo (2005) Use of coral-reef data allows first estimate of sea-level (ice volume) component in the benthic δ18O signals High amplitude shifts with timing that looks like AA climate variability ! From: Shackleton, N J., (2000) The 100,000-year ice-age cycle identified and found to lag temperature, carbon dioxide, and orbital eccentricity. Science. v. 289, no. 5486, p. 1897-1902. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS. International Glaciological Society: A numerical investigation of ice-lobe permafrost interaction around the southern Laurentide ice sheet. Cutler, Paul M; MacAyeal, Douglas R; Mickelson, David M; Parizek, Byron R; Colgan, Patrick M, Journal of Glaciology, vol.46, no.153, pp.311-325, Copyright (2000). Independent validation from the Red Sea sea-level calibration Why is the Red Sea sensitive to sea level? • highly evaporative (2.06 m/yr) • very limited catchment for run off • very limited communication with open ocean: narrow (20km) and shallow (137m) strait • at 137 m, depth of the sill is very close to the glacial/ interglacial sea-level range Small strait limits water exchange. Any reduction in the strait profile further reduces the exchange. That: • increases residence time of water in basin • extends exposure to high evaporation • consequently enhances salinity and 18O in the basin. Link to article (Figure 1) Map of Red Sea bathymetry and surrounding topography. Note the small surface area of the Red Sea rainfall catchment marked by the bold dashed line From: Understanding the Red Sea response to sea level. Siddall, Mark; Smeed, David A; Hemleben, Christoph; Rohling, Eelco J; Schmelzer, Ina; Peltier, William R .Earth and Planetary Science Letters, v. 225, no. 3-4, p. 421-434, So, Red Sea 18O records predominantly reflect sea-level change (dominant cause of change in the strait profile) How to quantitatively express this influence? • develop a realistic model for the hydraulic control of exchange transport through the Strait • couple this to a basin representation which includes algorithms for calculating 18Owater and 18Ocalcite • develop the relationship between changes in sea-level and change in 18Ocalcite • transform planktonic foraminiferal 18O records from central Red Sea to sea-level change records Link to article figure (7) The changing Δsalinity/Δδ18Oseawater with respect to sea level. Shows strong negative trend between salinity/oxygen, which Allows oxygen to be used as a proxy for measuring past sealevels. From: Understanding the Red Sea response to sea level. Siddall, Mark; Smeed, David A; Hemleben, Christoph; Rohling, Eelco J; Schmelzer, Ina; Peltier, William R .Earth and Planetary Science Letters, v. 225, no. 3-4, p. 421-434, 2 sigma confidence limit for sea-level variations inferred from oxygen isotopes is ±12m (based on ± 2ºC uncertainty in temperature, changes in evaporation between 2.8m y-1 and 1.4m y-1, and changes in relative humidity between 60% and 80%, the modern seasonal extremes). Relationship sea-level and millennial-scale climate changes during last glacial cycle Sea-level record based on central Red Sea planktonic O-isotope data shows: Large changes (order 30 m), in agreement with maximum amplitudes suggested by coral data Antarctic-type rhythm of change, very similar to deepsea benthic O-isotope data Reprinted by permission of Macmillan Publishers Ltd: Sea-level fluctuations during the last glacial cycle. Siddall, M; Rohling, E J; Almogi-Labin, A; Hemleben, C; Meischner, D; Schmelzer, I; Smeed, D A., Nature, v. 423 ,no. 6942, p. 853-858, Copyright (2003) not under CC licence. Relationship sea-level and millennial-scale climate changes during last glacial cycle -40 24m 35m 40m 47m -37 -38 -60 -70 -39 -80 -40 -90 -100 f A1 A2 b -50 H4 12 -60 A3 -41 A4 -42 error bars: ± 1 : 3 pt. (~500y) mov. avg. -40 88 H5 H6? -36 -38 14 14 12 -70 -40 -80 -42 -90 f -100 Southern Ocean IRD & 18O shifts sea level (m below present) 23m 30m -50 -30 Reprinted by permission of Macmillan Publishers Ltd: Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets Rohling, Eelco J; Marsh, Robert; Wells, Neil C; Siddall, Mark; Edwards, Neil R Nature, v. 430, no. 7003, p. 1016-1021, Copyright (2004) Not under CC Licence 24m 32m 17m 32m a c 53°S 41°S 35000 -44 SA3 GISP2 18O (‰ VSMOW) sea level (m below present) -30 BYRD 18O (‰ VSMOW) In terms of sea level, we find large-amplitude shifts, of similar order to those derived from deconvolved deep-sea δ18O records (Cutler et al., 2003). Typically ~ 30 m in roughly 2kyr. SA4 SA5 -0.9‰ -0.5‰ -0.7‰ 40000 45000 50000 -0.5‰ 55000 -0.5‰ 60000 65000 age (cal yr BP) to the GISP2 age model of Blunier et al (1998) Note ~coincidence of major rises (which last ~1500 y) with periods marked by H-events in N Atlantic, and IRD and light surface-water δ18O in Southern Ocean (S.O. data after Kanfoush et al., 2000) Note: co-registered signals in Iberian Margin core MD95-2042 (Shackleton et al., 2000) demonstrate clearly that THC collapses of H events (negative benthic 13C spikes) occupy final phase of sea-level rise (shifts to light benthic 18O) But: was there sea-level rise before H1 as well? Reproduced by permission of American Geophysical Union: Shackleton, N.J., Hall, M.A., Vincent, E., Phase relationships between millennial-scale events 64,00024,000 years ago Paleoceanography, v. 15, no. 6, p. 565-569. 25 July 2000. Copyright [2000] American Geophysical Union. Looks like it: roughly 20m in roughly 2 kyr Reprinted by permission of Macmillan Publishers Ltd: Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets Rohling, Eelco J; Marsh, Robert; Wells, Neil C; Siddall, Mark; Edwards, Neil R. Nature, v. 430, no. 7003, p. 1016-1021, Copyright (2004) Not under CC Licence Hemming (2004) calculates that H events may explain a maximum of 15m sea-level rise (but some would argue only 1-2m; Roche et al., 2004). Then: Q: Where might pre-HE sea-level rises originate from? A component from Antarctica (e.g. Kanfoush et al., 2000; Rohling et al., 2004)? But note: changes in general too large to explain as AA variability !! New evidence shows melt-water release from the southern margin of the Laurentide ice sheet, following an AA-style timing ! Hill et al. (2006): melt-signal from southern Laurentide margin (via Mississippi) agrees more with AA climate rhythm than D-O rhythm (hard relative timing constraint, based on palaeomagnetic Laschamp event) Reproduced by permission of American Geophysical Union: Hill, H.W., Flower, B.P., Quinn, T.M., Hollander, D.J., Guilderson, T.P., Laurentide ice sheet meltwater and abrupt climate change during the last glaciation. Paleoceanography, v. 21, no. 1, 9 pp. 18 February 2006. Copyright [2006] American Geophysical Union. My speculation: Observed: AA climate changes are very similar to atmospheric CO2 changes (Siegenthaler et al., 2005) Might AA climate signal/rhythm be a (CO2 related?) “global” background climate signal, and the sharp D-O variability in the North a superimposed pattern? From: Urs S., Stocker, T.F., Monnin, E., Lüthi, D., Schwander, J., Stauffer, B., Raynaud, D., Barnola, J-M., Fischer, H., Masson-Delmotte, V., Jouzel, J., (2005) Stable Carbon Cycle–Climate Relationship During the Late Pleistocene. Science v 310, p 1313-1317. Reprinted with permission from AAAS. These figures may be used for non-commerical, classroom purposes only. Any other uses requires the prior written permission from AAAS. Conclusions • AA climate & CO2 signal represents the underlying “global” climate variability • Global ice-volume fluctuations seem to be closely tied to this AA climate (and global CO2) rhythm • Ice volume reductions at S Laurentide margin seem to have followed the (AAtype) rhythm • We cannot exclude that there may have been AA melt contributions • Speculation: maybe ice-sheet melting (summer) globally (?) related to an underlying (CO2 related?) global climate signal, as recorded in AA. • In Northern Hemisphere, the abrupt D-O style variability may be a superimposed, winter-dominated signal (for seasonal idea, see: Rohling et al., 2003; Denton et al., 2005; Seager and Battisti, 2006) • THC rather insensitive to plain bulk and rate of meltwater additions • THC may be more sensitive to (much smaller) freshwater input targeted into the critical Nordic Seas Copyright statement • This resource was created by the University of Southampton and released as an open educational resource through the 'C-change in GEES' project exploring the open licensing of climate change and sustainability resources in the Geography, Earth and Environmental Sciences. The C-change in GEES project was funded by HEFCE as part of the JISC/HE Academy UKOER programme and coordinated by the GEES Subject Centre. • This resource is licensed under the terms of the Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales license (http://creativecommons.org/licenses/by-nc-sa/2.0/uk/). • However the resource, where specified below, contains other 3rd party materials under their own licenses. The licenses and attributions are outlined below: • The University of Southampton and the National Oceanography Centre, Southampton and its logos are registered trade marks of the University. The University reserves all rights to these items beyond their inclusion in these CC resources. • The JISC logo, the C-change logo and the logo of the Higher Education Academy Subject Centre for the Geography, Earth and Environmental Sciences are licensed under the terms of the Creative Commons Attribution -non-commercial-No Derivative Works 2.0 UK England & Wales license. All reproductions must comply with the terms of that license. • All content reproduced from copyrighted material of the American Geophysical Union (AGU) are subject to the terms and conditi ons as published at: http://www.agu.org/pubs/authors/usage_permissions.shtml AGU content may be reproduced and modified for non-commercial and classroom use only. Any other use requires the prror written permission from AGU. • All content reproduced from the American Association for the Advancement of Science (AAAS) may be reproduced for non commercial classroom purposes only, any other uses requires the prior written permission from AAAS. • All content reproduced from Macmillan Publishers Ltd remains the copyright of Macmillan Publishers Ltd. Reproduction of copyrighted material is permitted for noncommercial personal and/or classroom use only. Any other use requires the prior written permission of Macmillan Publishers Ltd