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Geomorphological Observations of Permafrost and Ground-Ice Degradation on
Deception and Livingston Islands, Maritime Antarctica
Gonçalo Vieira
Centre of Geographical Studies, University of Lisbon, Portugal
Jerónimo López-Martínez
Autonomous University of Madrid, Spain
Enrique Serrano
Department of Geography, University of Valladolid, Spain
Miguel Ramos
Department of Physics, University of Alcalá de Henares, Spain
Stephan Gruber
Department of Geography, University of Zurich, Switzerland
Christian Hauck
University of Karlsruhe, Germany
Juan José Blanco
Department of Physics, University of Alcalá de Henares, Spain
Abstract
The Antarctic Peninsula is experiencing one of the fastest increases in mean annual air temperatures (ca. 2.5ºC in
the last 50 years) on Earth. If the observed warming trend continues as indicated by climate models, the region
could suffer widespread permafrost degradation. This paper presents field observations of geomorphological features
linked to permafrost and ground-ice degradation at two study areas: northwest Hurd Peninsula (Livingston Island) and
Deception Island along the Antarctic Peninsula. These observations include thermokarst features, debris flows, activelayer detachment slides, and rockfalls. The processes observed may be linked not only to an increase in temperature, but
also to increased rainfall, which can trigger debris flows and other processes. On Deception Island some thermokarst
features may be related to anomalous geothermal heat flux from volcanic activity.
Keywords: active layer; Antarctic; debris flow; permafrost; thermokarst.
Introduction
The Antarctic Peninsula is experiencing the strongest
warming signal in the Southern Hemisphere, with mean
annual air temperatures (MAAT) increasing ca. 3ºC since
1951 (Marshall et al. 2002, Meredith & King 2005, Turner
et al. 2005). However, the region of strongest warming is
limited in area, with the highest increases near Faraday/
Vernadsky Stations and lesser increases near the northern
tip of the Peninsula and the Orcadas Islands (King &
Comiso 2003, Turner et al. 2007). Global Climate Model
(GCM) projections for 2001–2100 suggest that the strongest
warming will extend into the Antarctic continent, with values
even greater than those expected on the Antarctic Peninsula
(Chapman & Walsh 2007).
The strong atmospheric warming in the Antarctic Peninsula
region has had a substantial effect on glaciers in the last few
decades, especially on ice-shelves along the eastern coast
(Scambos et al. 2003). The collapse of Larsen-B in 2002 is
the most well-known example, but the retreat of mountain
and outlet glaciers has been also reported. On Livingston
Island (Hurd Peninsula) glaciers have been retreating and
equilibrium-line elevations increasing (Ximenis et al. 1999,
Molina et al. 2007).
Permafrost is central to the carbon cycle and to the climate
system, especially due to CH4 and CO2 release following
permafrost degradation in organic-rich sediments (Anisimov
et al. 1997, Osterkamp 2003). The active-layer thickness and
dynamics are also important factors in polar ecology. Since
most exchanges of energy, moisture, and gases between
the atmospheric and terrestrial systems occur through the
active layer, its thickening has important ramifications on
geomorphic, hydrologic and biological processes (Nelson
& Anisimov 1993). Furthermore, permafrost degradation
can cause terrain instability and increase geomorphological
hazards and damage to infrastructures. According to the
International Panel on Climate Change (IPCC), regions
underlain by permafrost have been reduced in extent, and
a warming of the ground has been observed in many areas
(Anisimov et al 2001, Lemke et al 2007). Permafrost is,
therefore, recognized by the (World Climate Research
Programme/World Meteorological Organization (WCRP/
WMO) as a key element of the Earth System in which
research efforts should focus. However, compared with the
Arctic, very little is known about the distribution, thickness,
and properties of permafrost in Antarctica. The scarcity of
data on Antarctic permafrost is reflected in the last IPCC
1839
1840 Ninth International Conference on Permafrost
D E C E P TI O N
ISLAN D
0
3 km
Figure 1. Location of Deception and Livingston Islands in the
Antarctic.
report (Lemke et al. 2007) where it is not even mentioned.
The main problem is the limited network of boreholes for
monitoring permafrost temperatures and the paucity of
active-layer monitoring sites. Turner et al. (2007) mention
a reduction in permafrost extent in the Antarctic Peninsula
region.
In general, increasing air temperatures will have a direct
influence on ground-temperature regimes and, therefore,
on permafrost and ground ice. A major consequence of
warming of the lower atmosphere is an increase in activelayer thickness, which induces permafrost degradation
and amplifies the rates of geomorphic processes. As a
consequence, thermokarst features are prone to occur in icerich and unconsolidated sediments, active-layer detachment
slides and debris flows on sloping ground, and an increase in
rockfall activity may occur in rocky terrain.
The northerly location of the Antarctic Peninsula region
and the oceanic setting result in a milder and moister
climate than in the interior of the Antarctic continent. The
northern Antarctic Peninsula is roughly located between the
MAAT isotherms of -1 to -8ºC at sea level and, therefore,
the northern tip of the Peninsula and especially the South
Shetland islands are close to the environmental limits of
permafrost occurrence (Bockheim 1995). If the observed
warming trend continues, as indicated by climate models,
the region might suffer widespread permafrost degradation.
Monitoring of ground temperatures is essential for assessing
the reaction of permafrost to global change, but in remote areas
the drilling and maintenance of boreholes is problematic.
Geomorphological surveying enables identification of the
processes related to permafrost degradation and provides
important information for assessing the influence of climate
change on ground temperatures. However, other techniques
are needed, such as geophysical surveying, monitoring of
active-layer depths, micrometeorological measurements,
and modelling to achieve a more complete overview of the
response of permafrost to regional warming.
This paper joins together inputs from two groups
researching in the South Shetlands. The group of the
Autónoma de Madrid and Valladolid universities (i.e.,
Serrano & López-Martínez 2000, Smellie et al. 2002,
Serrano 2003) has been focusing on geomorphological
surveying and mapping of the periglacial processes in the
South Shetlands (Fig. 1). The group at the universities of
Alcalá de Henares, Lisbon, Zurich, and Karlsruhe (Ramos
& Vieira 2003, Vieira & Ramos 2003, Ramos et al. 2007,
Hauck et al. 2007) has been monitoring ground temperatures
and modelling spatial distribution of permafrost. In this paper
a synthesis of observations on geomorphic processes that are
seemingly related to permafrost and ground-ice degradation
from Hurd Peninsula (Livingston Island) and Deception
Island is presented. The next step is a geomorphological and
climatological monitoring programme, which is planned to
start in 2008–09.
Climate of the South Shetlands
The climate of the South Shetlands is cold-oceanic at sea
level with frequent summer rainfalls and a moderate annual
temperature range. Mean annual air temperatures are close
to -2ºC at sea level and average relative humidity is very
high, ranging from 80 to 90% (Simonov 1977, RakusaSusczewski 1993). The weather conditions are dominated by
the influence of the polar frontal systems, and atmospheric
circulation is variable, with the possibility of winter rainfall
occurring as far south as Rothera Station (Turner et al.
2007). Temperature data from Hurd Peninsula recorded by
our group for the period of 2003–05 at 20 m a.s.l. show
values comparable to those at Arctowski Station on King
George Island. From April to November average daily
temperatures stay generally below 0ºC and from December
to March temperatures are generally slightly above 0ºC. Two
contrasting seasons in terms of freezing and thawing are,
therefore, defined. At 275 m a.s.l. on Reina Sofia Hill the
recorded mean annual air temperatures were of ca. -4.2ºC.
This corresponds to a lapse rate of -0.8 ºC/100 m and to a
freezing season that is about one month longer than at sea
level. The climate on Deception Island is similar to Hurd
Peninsula.
Geomorphological Setting and Permafrost
Distribution
Deception Island
Deception Island is an active stratovolcano with a large
collapsed caldera; the most recent eruptions occurred in
1967, 1969, and 1970 (Smellie et al. 2002). In some places
there are fumaroles and ground temperature anomalies from
continued volcanic activity. Mean annual air temperature at
sea level is close to -2ºC. The volcano rim rises to 539 m a.s.l.
at Mount Pond, and the island is glaciated to a large extent.
As a result of recent eruptions, the island has been covered
by volcanic ash and debris, and many of the glaciers remain
ash-covered today. Pyroclastic deposits covered snow, and
buried snow is still present at some sites. The pyroclastic
deposits are very porous and insulating, and give rise to a
thin active layer, which varies from 30 to 90 cm in thickness.
Vieira et al. 1841 Figure 2. Thermokarst bumpy terrain in Deception Island (arrow).
Figure 3. Thermokarst hollows in Deception Island.
On lower valley slopes, exposures of fossil snow (buriedice) with perennially frozen ice-cemented volcanic debris on
top can be observed, testifying to post-eruption aggradation
of permafrost. At these sites, ice-cemented permafrost also
occurs under the buried-ice layer.
Buried-ice is widespread on Deception Island, especially
along the lower slopes, and ice-cemented permafrost occurs
down to sea level. Geophysical surveying and trenches show
that the permafrost inside the caldera thins near sea level and
is absent on beaches near the shore.
limit between continuous and discontinuous permafrost in
bedrock is probably located between these two altitudinal
limits, 115 and 275 m a.s.l. However, it is possible that at 115
m the active layer is thicker than 1 m. At 35 m a.s.l. ground
temperature data indicate that permafrost may be absent in
bedrock, or that the active layer is thicker than 2.3 m.
Ice-cored sediments are widely distributed on Hurd
Peninsula and occur down to sea level. These are likely
of glacigenic origin, but in several cases still show active
deformation giving origin to rockglaciers, mostly of the
protalus or moraine-derived types.
Hurd Peninsula (Livingston Island)
Hurd Peninsula is comprised of mountainous terrain
and is located on the southern coast of Livingston Island.
About 90% of the island is glaciated, with ice-free areas
occurring at low altitude, generally on small peninsulas with
rugged relief. Our study focused on ice-free areas of the
northwestern part of Hurd Peninsula in the vicinity of the
Spanish Antarctic Station Juan Carlos I. The bedrock is a
low-grade metamorphic turbidite sequence with alternating
layers of quartzite and shales; conglomerates and breccias
occur in some areas (Miers Bluff Formation). Dolerite dykes
and quartz veins are frequent (Arche et al., 1992), with the
surficial lithology being very heterogeneous (Pallàs 1996).
The geological setting on Hurd Peninsula is substantially
different to that of Deception Island. On the former, bedrock
outcrops are prevalent, with only a thin cover of diamictite.
Therefore, studying permafrost distribution is much more
complex than at Deception, since frozen bedrock is very
difficult to identify without a good network of boreholes.
Observations from boreholes and geophysical surveying
(Electrical Resistivity Tomography and Refraction Seismics
Tomography) will allow a first insight into permafrost
distribution, and a dense network of boreholes is planned for
installation in 2007/08.
The observations indicate that continuous permafrost is
present in diamictite and bedrock at least at 275 m a.s.l. At 115
m a.s.l. permafrost probably occurs only at some locations
and seems to be controlled by late-lying snow patches. At this
altitude in diamictite deposits, during summer, the ground
thaws at least down to 1 m depth. On Hurd Peninsula, the
Permafrost and Ground-Ice Degradation
Features
Thermokarst
Thermokarst features have been observed at different sites
on Deception Island. Two types of features occur, including
thermokarst bumpy terrain and thermokarst hollows.
Bumpy terrain consists on a series of depressions with a
small depth/width ratio that cover the terrain continuously
(Fig. 2). They appear on the upper parts of the slopes inside
the caldera. Preliminary observations suggest that they are
more frequent on slopes below 100–150 m a.s.l.
Bumpy terrain is related to the thaw of buried-ice derived
from buried snow patches. It is not yet clear if the depressions
are solely the consequence of atmospheric warming or if they
relate to a dynamic situation mainly induced by the thinning
of the insulating layer of pyroclastic material being eroded.
The thinning of the sedimentary cover, which is stronger in
upper sector of the slopes, induces a decrease of the thermal
insulation of the buried-ice layer, allowing for thawing. On
the lower slope, the sedimentary cover is thickest due to the
accumulation of material transported from upslope. There, a
permafrost layer above the buried-ice layer can be observed
which is probably linked to an increasing insulation effect
due to sediment accretion.
Thermokarst hollows are features of decimetric to metric
size and occur isolated or in small groups (Fig. 3). Their
depth/width ratio is larger than the bumpy terrain, but
they were not studied in detail yet. They appear in flat or
1842 Ninth International Conference on Permafrost
Figure 4. Debris-flow tracks in a talus slope on Hurd Peninsula
(Livingston Island).
Figure 6. Debris flow tracks in Deception Island.
Figure 5. Debris flows depositing over the surface of the Las Palmas
Glacier in Hurd Peninsula (Livingston Island).
gentle sloping terrain. No trenches were excavated, nor was
geophysical surveying conducted in these features. They are
probably related to localized degradation of massive ice.
Their origin is not clear yet, since they can result from a
climatic influence, but may also relate to changes in ground
heat flux due to the volcanic activity. Geophysical surveying
of these thermokarst hollows will be conducted in 2007/08.
Debris flows
Sub-aerial present-day debris-flow activity is a geomorphic
process that has been poorly analysed in the literature for
maritime Antarctica. Recent debris-flow tracks and deposits
have been observed at several sites both on Livingston
(Vieira & Ramos 2003) and Deception Islands (Figs. 4, 5, 6).
Debris-flow activity is initiated by the saturation of surface
unconsolidated material that flows along a channel in the
slope, reworking the slope material.
In several mountain regions in the northern hemisphere
an increase or altitudinal change in debris-flow activity
has been linked to permafrost degradation (Jomelli et al.
2004). In maritime Antarctica, the widespread distribution
of permafrost, together with the mountainous terrain and
its proximity to the climatic limits of permafrost, a similar
consequence of increasing air temperatures is to be expected.
Figure 7. Active layer detachment slide on Deception Island.
However, rainfall episodes may also be a triggering
mechanism for debris flows. The lack of monitoring data does
not allow us to precisely define the origin of the debris-flow
activity and, therefore, in 2008/09 a monitoring programme
for debris-flows will be implemented.
On Deception Island debris-flow tracks are widespread, at
least in the inner slopes of the caldera. These are erosional
slopes built up of volcanoclastic material. The debris
flows form on the upper parts of the slopes and seem to be
related to permafrost degradation, since this area is also at
a similar geomorphological setting to the bumpy terrain
features. The tracks are tens to a few hundred metres long.
The predominantly gravely grain-size of the slope material
and moderate slope angle limit the downslope movement of
the flow; therefore, the debris generally does not contribute
significantly to the valley floors. In the 2007/08 campaign
a systematical mapping of the debris-flow tracks will
be conducted in order to detect their spatial pattern and
controlling factors.
On Hurd Peninsula several debris-flow tracks have been
Vieira et al. 1843 observed and one of them is known to have occurred in late
spring. Debris flows on Hurd affect mainly talus slopes and
lateral moraines. Due to the steep slope angles and slope
length they reach more than a hundred metres in length and
have been observed being deposited on top of glaciers (Fig.
5).
Active-layer detachment slides
Active-layer detachment slides form from the presence of
an impermeable frozen layer at depth. Several small slides of
metric dimension have been observed affecting the surface of
the ice-cored moraine of the Argentine lobe of Hurd glacier
in January 2000 and are related to the degradation of the icerich till on the very steep inner slope of the moraine. Other
ice-cored moraines near sea level have been detected using
electrical resistivity tomography and refraction seismics
tomography and they can be subject to these processes of
degradation in the near future if the current climate trend
continues.
On Deception Island small detachment slides were also
found on steep slopes. The mass movements were under 40
m2 in area (Fig. 7).
Rockfalls
Rockfalls in the mountain permafrost zone have been
pointed out as a consequence of permafrost degradation,
especially relating to the melting of ice filling rock wall
fractures (Davies et al. 2001, Kaab et al. 2005, Gruber &
Haeberli 2007). Rockfalls occur on both Hurd Peninsula and
Deception Island; however, without proper monitoring it is
difficult to access the influence of permafrost degradation on
their origin.
Conclusions
The South Shetland Islands are a privileged area to study
climate change and its effects on landscape dynamics.
Permafrost is widespread and occurs down to sea level. On
Deception Island permafrost is continuous throughout most
of the area, but on the Hurd Peninsula continuous permafrost
likely occurs only above ca. 150 m a.s.l. In the same area
discontinuous and sporadic permafrost exist down to sea
level, especially in the form of ice-cored moraines and rock
glaciers. The mean annual air temperatures at sea level are
close to -2ºC, positioning the archipelago near the climatic
limit of permafrost. This fact, together with the warming that
affects the Antarctic Peninsula region should be responsible
for permafrost degradation.
This paper describes landforms and geomorphic processes
related to permafrost and ground-ice degradation that seem
to result from climate change. Where ground-ice occurs,
thermokarst hollows, bumpy terrain, and active-layer
detachment slides have been found. The first occurs on flat
or gentle sloping ground and the latter on moderate to steep
slopes. Debris-flow activity was observed to be widespread
on slopes of both. Their genesis has still to be assessed, since
they can be linked either to ground warming or to heavy
rainfall events. On Deception Island heat flux anomalies
caused by volcanic activity can also generate permafrost
degradation features. These anomalies are of small areal
extent and their locations are known.
The observations presented here are preliminary and
constitute a starting point for a new approach that will
emphasize monitoring of geomorphological activity in order
to detect the influence of climate change on present-day
processes. Another interesting issue to be analysed is the
control of changing geothermal heat fluxes on permafrost
degradation in Deception Island and to assess on the
possibility of using permafrost degradation features as
indicators of changes in volcanic activity.
Acknowledgments
This study was conducted as part of the project
PERMAMODEL within the Spanish Antarctic Program
CICyT (CGL2004-20896-E/ANT). This research is included
in the IPY project ANTPAS – Antarctic and Sub-Antarctic
Permafrost, Soils and Periglacial Processes. G. Vieira was
funded by the Fundo de Apoio à Comunidade Científica
(FCT) and Fundação Calouste Gulbenkian.
References
Anisimov., O. A., Shiklomanov., N. I. & Nelson, F.E. 1997.
Global warming and active layer thickness: results
from transient general circulation models. Global and
Planetary Change 15: 61-67.
Arche, A., López-Martínez, J. & Martínez de Pisón, E.
1992. Sedimentology of the Miers Bluff Formation,
Livingston Island, South Shetland Islands, in Recent
Progress in Antarctic Earth Science, edited by Y.
Yoshida et al., 357-362, Terrapub., Tokyo.
Bockheim, J.G. 1995. Permafrost distribution in Southern
circumpolar region and its relation to the environment:
a review and recommendations for further research.
Permafrost and Periglacial Processes 6, 27-45.
Chapman, W.L. & Walsh, J.E. 2007. A synthesis of Antarctic
temperatures. Journal of Climate 20(16): 4096-4117.
Davies, M.C.R., Hamza, O. & Harris, C. 2001. The effect
of rise in mean annual temperature on the stability
of rock slopes containing ice-filled discontinuities.
Permafrost and Periglacial Processes 12: 137-144
Gruber, S. & Haeberli, W. 2007. Permafrost in steep bedrock
slopes and its temperature-related destabilization
following climate change. Journal of Geophysical
Research 112.
Hauck, C., Vieira, G., Gruber, S., Blanco, J. & Ramos, M.
2007. Geophysical identification of permafrost in
Livingston Island, Maritime Antarctica. Journal of
Geophysical Research 112.
Jomelli, V., Pech, V.P., Chochillon, C. & Brunstein, D. 2004.
Geomorphic Variations of Debris Flows and Recent
Climatic Change in the French Alps. Climatic Change
64(1–2): 67-102.
1844 Ninth International Conference on Permafrost
Kaab, A., Reynolds, J.M. & Haeberli, W. 2005. Glaciers
and permafrost hazards in high mountains. In: U.M.
Huber, H.K.M. Bugmann, & M.A. Reasoner (eds.).
Global Change and Mountain Regions – An overview
of current knowledge: 225-234.
King, J.C. & Comiso, J.C. 2003. The spatial coherence of
interannual temperature variations in the Antarctic
Peninsula. Geophysical Research Letters 30(2):
1040.
Lemke, P., Ren, J., Alley, R.B., Allison, I., Carrasco, J., Flato,
G., Fujii, Y., Kaser, G., Mote, P., Thomas, R.H. & T.
Zhang, 2007: Observations: Changes in Snow, Ice and
Frozen Ground. In: S. Solomon, D. Qin, M. Manning,
Z. Chen, M. Marquis, K.B. Averyt, M. Tignor & H.L.
Miller (eds.) Climate Change 2007: The Physical
Science Basis. Contribution of Working Group I to the
Fourth Assessment Report of the Intergovernmental
Panel on Climate Change. Cambridge, UK & New
York, NY: Cambridge University Press.
Marshall, G.J., Lagun, V. & Lachlan-Cope, T.A. 2002.
Changes in Antarctic Peninsula tropospheric
temperatures from 1956 to 1999: A synthesis of
observations and reanalysis data. International
Journal of Climatology 22: 291–310.
Meredith, M.P. & King, J.C. 2005. Rapid climate change in
the ocean west of the Antarctic Peninsula during the
second half of the 20th century. Geophysical Research
Letters 32.
Molina, C.; Navarro, F.J.; Calvet, J. García-sellés, D. &
Lapazaran, J.J. 2007. Hurd Peninsula glaciers,
Livingston Island, Antarctica, as indicators of
regional warming: Ice-volume changes during the
period 1956–2000. Annals of Glaciology 46: 43-49.
Nelson, F.E. & Anisimov, O.A. 1993. Permafrost zonation
in Russia under anthropogenic climate change.
Permafrost and Periglacial Processes 4(2): 137-148.
Osterkamp, T.E. 2003. Establishing Long-term permafrost
observatories for active-layer and permafrost
investigations in Alaska: 1977-2002. Permafrost and
Periglacial Processes 14: 331-342.
Pallàs, R. 1996. Geologia de l’Illa de Livingston (Shetland
del Sud, Antàrtida). Del Mesozoic al Present. PhD
thesis, Universitat de Barcelona.
Ramos, M. & Vieira, G. 2003. Active layer and permafrost
monitoring in Livingston Island, Antarctic. First
results from 2000 and 2001. In: M. Phillips, S.M.
Springman & L.U. Arenson (eds.), Permafrost.
Proceedings of the Eight International Conference
on Permafrost, 21-25 July 2003, Zurich, Switzerland:
929-933.
Rakusa-Susczewski, S. 1993. The maritime Antarctic coastal
ecosystem of Admiralty Bay. Department of Antarctic
Biology. Polish Academy of Sciences, Warsaw.
Scambos, T.A., Hulbe, C. & Fahnestock, M.A. 2003. Climateinduced ice shelf disintegration in the Antarctic
Peninsula. Antarctic Research Series 79: 79-92.
Serrano, E. 2003. Paisaje natural y pisos geoecologicos en
las áreas libres de hielo de la Antártida Marítima (Islas
Shetland del Sur). Boletín de la A.G.E. 35: 5-32.
Serrano, E. & López-Martínez, J. 2000. Rock glaciers in
the South Shetland Islands, Western Antarctica,
Geomorphology 35: 145-162.
Smellie, J.L., López-Martínez, J. et al. 2002. Geology and
geomorphology of Deception Island. BAS Geomap
Series Sheets 6-A and 6-B, 1:25 000. Cambridge:
British Antarctic Survey.
Simonov, I.M. 1977. Physical geographic description of
Fildes Peninsula (South Shetland Islands). Polar
Geography 1: 223-242.
Turner, J., Colwell, S.R., Marshall, G.J., Lachlan-Cope,
T.A., Carleton, A.M., Jones, P.D., Lagun, V., Reid,
P.A. & Iagovkina, S. 2005. Antarctic climate change
during the last 50 years. International Journal of
Climatology 25: 279-294.
Turner, J., Overland, J.E. & Walsh, J.E. 2007. An Arctic
and Antarctic perspective on recent climate change
International Journal of Climatology 27(3): 277293.
Ximenis, L., Calvet, J., Enrique, J., Corbera, J., Fernández de
Gamboa, C. & Furdada, G. 1999. The measurement
of ice velocity, mass balance and thinning-rate on
Johnsons Glacier, Livingston Island, South Shetland
Islands, Antarctica. Acta Geologica Hispanica 34(4):
403-409.
Vieira, G. & Ramos, M. 2003. Geographic factors and
geocryological activity in Livingston Island, Antarctic.
Preliminary results. In: M. Phillips, S.M. Springman
& L.U. Arenson (eds.), Permafrost. Proceedings of
the Eight International Conference on Permafrost,
21–25 July 2003, Zurich, Switzerland: 1183-1188.