Glacier response to climate change

Climate change on the Antarctic Peninsula | Glacier fluctuations on James Ross Island | Glacier modelling experiments | Summary and conclusions | Further reading |

Modelled glacier response to centennial temperature and precipitation trends on the Antarctic Peninsula

This article is a summary of the following paper:

Davies, B.J., Golledge, N.R., Glasser, N.F., Carrivick, J.L., Ligtenberg, S.R.M., Barrand, N.E., van den Broeke, M.R,. Hambrey, M.J., and Smellie, J.L., 2014. Modelled glacier response to centennial temperature and precipitation trends on the Antarctic Peninsula. Nature Climate Change. DOI: 10.1038/nclimate2369

Read the Press Release.

Climate change on the Antarctic Peninsula

It’s getting snowier on the Antarctic Peninsula. Glaciers are thickening in their accumulation centres, but are melting more and thinning in their lower portions. Snowfall is forecast to continue to increase over the next couple of decades, so what does this mean for glaciers on the Antarctic Peninsula? Will the increase in snow offset glacier melt?

We studied this phenomenon on James Ross Island, northern Antarctic Peninsula. Here, summer temperatures can reach above 0°C and glaciers are melting strongly. In 1995 AD, Prince Gustav Ice Shelf collapsed, which resulted in glacier acceleration, recession and thinning, which continues to this day.

We carried out extensive fieldwork on James Ross Island to map and analyse the changes to a glacier, which is currently 4km long, over the past 10,000 years. We used a combination of glacier and climate modelling, glacial geology and ice-core data. We found that small glaciers that end on land around the Antarctic Peninsula are highly vulnerable to slight changes in air temperature. Over the next few decades, they will be smaller than at any point during the last 10,000 years. Just small increases in air temperature increased melting so much that even large amounts of extra snowfall could not prevent glacier recession. These small glaciers around the Antarctic Peninsula are likely to contribute most to rising sea levels over the coming decades, because they can respond quickly to climate change.

James Ross Island on the NE Antarctic Peninsula. James Ross Isand ice core is denoted by a green star. The study area is Ulu Peninsula, denoted by the red box.

James Ross Island on the NE Antarctic Peninsula. James Ross Isand ice core is denoted by a green star. The study area is Ulu Peninsula, denoted by the red box.

Glacier fluctuations on James Ross Island

James Ross Island is well studied, being reasonably accessible by ship. There is a high resolution ice core, taken in 2007 AD, available from the summit of the Mount Haddington Ice Cap. The Ulu Peninsula is one of the largest ice-free areas in the region, which makes it ideal for glacial geological studies of past ice-sheet extent. Here, a large boulder train extends from Glacier IJR45 towards Brandy Bay, where it aligns with a large moraine. This moraine overlies reworked marine sediments with shells, which have been dated to ~5000 years ago. Because the shells are underneath the moraine, this suggests that the readvance that deposited the boulder train and the moraine occurred AFTER ~5000 years ago.

Ulu Peninsula on James Ross Island, showing modern glaciers, published areas, and glacial geomorphology. The reconstructed maximum Holocene extent is also shown. The model domain, line A-B, is shown in plan and profile view.

Ulu Peninsula on James Ross Island, showing modern glaciers, published areas, and glacial geomorphology. The reconstructed maximum Holocene extent is also shown. The model domain, line A-B, is shown in plan and profile view. Published radiocarbon (circles) and cosmogenic nuclide ages (diamonds) are shown.

The ice-core temperature records from Mulvaney et al. (2012) tell us that the air temperatures on James Ross Island 5000 years ago were about 0.5°C warmer than today. Prince Gustav Ice Shelf was absent from ~6000 to 2000 years ago, during this relatively warm period. Ice shelf absence is usually indicative of strong surface melt.

James Ross Island ice core temperature record over the last 14,000 years.

James Ross Island ice core temperature record over the last 14,000 years. Location is shown by a green star on the map of James Ross Island.

Warm air usually carries more water, so a readvance may have occurred because there may have been more precipitation at this time. People have therefore hypothesised that the glacier readvanced during a period that was WARMER but WETTER than today, in response to increased snowfall. This behaviour is contrary to that observed today, with glacier recession during a period of warming and ice-shelf collapse. This readvance is therefore a good analogue for future glacier behaviour in this sensitive region.

Glacier modelling experiments

We used a computer numerical model to test these hypotheses of glacier behaviour. The glacier flowline model was calibrated and tested using the temperature and precipitation ice-core record over the last 160 years. The glacier flowline model (along line A-B in the Ulu Peninsula map) was calibrated and tested using the temperature and precipitation ice-core record over the last 160 years. The modelled glacier replicated rates of recession from 1970 AD to present, and finished in 2006 with a similar geometry and velocity to the observed glacier in 2006 AD, thus increasing confidence in our model.

Results of the dynamic calibration. (a) air temperature and (b) precipitation from the ice core record. (c) Glacier length. (d) Glacier volume. (e) Glacier area.

Results of the dynamic calibration. (a) air temperature and (b) precipitation from the ice core record. (c) Glacier length. (d) Glacier volume. (e) Glacier area.

Sensitivity experiments

We conducted a number of sensitivity experiments on the glacier model, including precipitation (snowfall), temperature, how easily snow and ice melt (snow and ice degree day factors), and how much the glacier ice deforms and slides (flow enhancement coefficient, sliding factor). The results are shown in the plots below. You can see that for a small decrease in temperature there is a very large increase in glacier length and volume, but there are only small changes for a +20% to -20% change in precipitation, degree day factors or the ice deformation factor.

Sensitivity experiments for Glacier IJR45 on Ulu Peninsula, James Ross Island.

Sensitivity experiments for Glacier IJR45 on Ulu Peninsula, James Ross Island.

The profiles below show just how different the length changes are between temperature and precipitation sensitivity experiments.

Change in glacier profile following temperature and precipitation perturbations.

Change in glacier profile following temperature and precipitation perturbations.

Holocene simulations

The next stage was to use the Holocene climate record to drive the glacier through the last 10,000 years. Snowfall data are unavailable for this length of time. At first, we kept precipitation constant at modern values (0.65 m per year). This resulted in a fairly stable glacier for most of the Holocene, with a small retreat from 6000-2000 years ago, when Prince Gustav Ice Shelf was absent, and a large readvance out to the bay and Brandy Bay Moraine in the last millennium.

To test the hypothesis that it was a warmer but WETTER climate that forced a readvance 5000 years ago, we varied precipitation with temperature. We varied it by 5%, 7.3%, 15%, 20% and 100%, so that for every 1°C of warming, it became 5%, 7.3% (etc.) wetter. We were feeding the glacier during warm periods and starving it during cool periods.

Simulations of glacier length change over the last 10,000 years, driven by the James Ross Island ice core temperature record.

Simulations of glacier length change over the last 10,000 years, driven by the James Ross Island ice core temperature record.

You can see from the figure (b) above that all this did was successively dampen the glacier’s response to cooling and warming. The readvance occurred at the same time, but was smaller according to amount of precipitation was reduced by. You can see this happening in profile view in the animation below.

These modelling experiments show that the glaciers on Ulu Peninsula remained largely stable for most of the Holocene, with likely recession during the period of ice-shelf collapse (6000-2000 years ago), and a large readvance during climatic cooling 1500-300 years ago, when the ice-shelf reformed. The glacier then receded rapidly in response to warming temperatures. The ice shelf collapsed again in 1995 AD, and the glacier continues to retreat today. This modelled behaviour is therefore more in line with current glacier observations.

We surmise that the readvance occurred during the Neoglacial, or “Little Ice Age” period, and not during the warmer period ~5000 years ago. Evidence for this is patchy, and there are few terrestrial records of ice advance at this time. Our study is the first to convincingly show glacier advance during a period of strong cooling during the last millennium. This research also suggests that, rather than being more extensive during warm periods in the past, glacier minima similar to present have occurred multiple times during the last 10,000 years.

Future simulations

To assess the significance of these findings within the context of future climate change, we performed simulations from 1980 to 2200 AD, with climate outputs from regional climate models. All four scenarios used predict temperature rises over the region for the next two hundred years, but projections of snowfall vary.

All four experiments predicted a strong decrease in glacier volume over the next two centuries. Glacier volume reaches minima not experienced at any point in the last 10,000 years within the next century, and the glacier has almost disappeared after 200 years.

Simulations of air temperature (c), precipitation (d) and glacier volume (e) over the next 200 years.

Simulations of air temperature (c), precipitation (d) and glacier volume (e) over the next 200 years.

Summary and conclusions

Glacier IJR45 is typical of many of the small, land-terminating glaciers peripheral to the Antarctic Peninsula, where surface melting is strongly controlled by air temperature and the length of the melt season. Both of these are projected to increase over coming decades, and summer melting will become increasingly important. These glaciers will therefore contribute significantly to sea level rise over coming decades to centuries. These processes are likely to be representative of regional glaciers.

Our main conclusions are:

  • Glacier modelling, spanning a range of past, present and future time intervals, shows that Glacier IJR45 has a high sensitivity to temperature and is less sensitive to precipitation.
  • Glacier advance during past and future warm periods is unlikely. Increases in precipitation on the Antarctic Peninsula will not offset glacier melting and recession.
  • The most recent advance of the glacier likely occurred during the last millennium, peaking at ~300 years ago, during a period of strong cooling.
  • The currently observed trends of glacier melting, thinning and recession around the Antarctic Peninsula will continue over coming decades to centuries, with glacier minima not experienced at any time over the last 10,000 years occurring within the next century.

Citation:

Please read the original article and cite as:

Davies, B.J., Golledge, N.R., Glasser, N.F., Carrivick, J.L., Ligtenberg, S.R.M., Barrand, N.E., van den Broeke, M.R,. Hambrey, M.J., and Smellie, J.L., 2014. Modelled glacier response to centennial temperature and precipitation trends on the Antarctic Peninsula. Nature Climate Change. DOI: 10.1038/nclimate2369

Further reading

Coverage in the news

Ice stream initiation on the northern Antarctic Peninsula

Please see the following work:

Glasser, N.F., B.J. Davies, J.L. Carrivick, A. Ròdes, M.J. Hambrey, J.L. Smellie and E. Domack (2014). Ice-stream initiation, duration and thinning on James Ross Island, northern Antarctic Peninsula. Quaternary Science Reviews 86, 78-88.

Download the Glasser et al. 2014 Preprint. The following is a shorter, simpler version of the paper.

Reconstructing ice stream changes in Antarctica | Why study ancient, long-gone ice streams? | Prince Gustav Ice Stream | Living on James Ross Island | What did we find? | Dynamic ice-sheet change | Further reading | References | Comments |

Reconstructing ice stream changes in Antarctica

Map of the Antarctic Peninsula, after Davies et al., 2012 (Quaternary Science Reviews)

Map of the Antarctic Peninsula, after Davies et al., 2012 (Quaternary Science Reviews). James Ross Island is located at the northern tip of the Antarctic Peninsula. Inset shows predominant ocean currents.

Antarctica is an area that is changing very rapidly. Ice streams are thinning, receding and shrinking. How will these ice streams change in the future?

If we want to understand this, we must look to the past; specifically, to another recent period of rapid climatic change. The Last Glacial-Interglacial Transition, a time of rapid warming not dissimilar to the present day, is particularly relevant.

Our work from James Ross Island, northern Antarctic Peninsula, reveals how the Antarctic Peninsula Ice Sheet changed during the Last Glacial-Interglacial Tranistion, from a thicker, cold, slow-moving ice sheet at around 18,000 years ago to a thinner, warmer, more dynamic ice sheet drained by fast-flowing ice streams after 12,000 years ago.

Why study ancient, long-gone ice streams?

Schematic figure of geomorphology on the continental shelf around the Antarctic Peninsula. From Davies et al., 2012.

Ice streams around the Antarctic Peninsula at the Last Glacial Maximum. Red lines schematically indicate mega scale glacial lineations. After Davies et al., 2012

Ice streams around Antarctica are undergoing rapid change. In recent centuries, the Siple Coast ice streams have had rapid and dynamic fluctuations in flow, including stopping flowing, whilst Pine Island Glacier is currently accelerating, thinning and receding. Predicting the wider future response of the Antarctic Ice Sheet to change requires a detailed understanding of the ice streams that dominate its dynamics.

We know that, at the Last Glacial Maximum (about 18,000 years ago), the Antarctic Peninsula Ice Sheet was drained by ice streams (see map to the right). Much of our evidence of these ice streams comes from the marine geological record; from swath bathymetry images of the sea floor, providing images of moraines and mega-scale glacial lineations, and from radiocarbon ages from microfossils from marine muds. However, these data provide only a snapshot of ice-stream behaviour during deglaciation, and don’t provide information on ice-stream initiation and dynamics.

Prince Gustav Ice Stream

In order to understand how ice streams begin, we must look to the terrestrial record. A three-person team (Neil Glasser, Bethan Davies and Jonathan Carrivick) therefore spent seven weeks on Ulu Peninsula, James Ross Island, on the Antarctic Peninsula, camping in a tiny tent, carrying around huge sacks of rocks, trying to decipher a complicated story from fragmentary evidence left behind. Ulu Peninsula is one of the largest ice-free areas of the Antarctic Peninsula, so it’s ideal for our kind of glacial geology. We wanted to use cosmogenic nuclide dating of boulders (surface exposure age dating) to define the evolution of Last Glacial Maximum ice in Prince Gustav Channel, the region between Trinity Peninsula (northern Antarctic Peninsula) and James Ross Island.

Several lines of evidence, including mega-scale glacial lineations (which are mapped on the figure below), suggest that, during the Last Glacial Maximum, Prince Gustav Channel was occupied by an ice stream, Prince Gustav Ice Stream, which flowed north and south around James Ross island, with an ice divide halfway along Prince Gustav Channel. Marine radiocarbon ages document the final recession of this ice stream, but cannot tell us whether it was a short-lived feature, or a more permanent feature of the Antarctic Peninsula Ice Sheet during the last glaciation.

James Ross Island, northern Antarctic Peninsula. Red indicates granite bedrock, the source of granite boulders on James Ross Island. Ulu Peninsula is shown by the red box.

James Ross Island, northern Antarctic Peninsula. Red indicates granite bedrock, the source of granite boulders on James Ross Island. Ulu Peninsula is shown by the red box. From Glasser et al., 2014

Living on James Ross Island

There is no way around it: if you want to collect high-quality cosmogenic nuclide samples, you have to spend time on the ground. You need to go there, count pebbles to determine sediment transport histories, sketch landforms like moraines, collect samples for particle size analysis, and mark geomorphological features like ridges and breaks in slope in great detail on your map. We were joined by Alan Hill, our mountain safety expert whose job it was to stop the clumsy scientists setting fire to their tent, getting lost in a blizzard or cutting off their foot while sampling a hard granite boulder with a hammer and chisel. We were completely cut off from society, with only a radio link to the main British research station, Rothera, 330 miles to the south by direct flight (which, I hasten to add, wasn’t possible as the ski planes couldn’t land on our rocky ground). We were dropped off, and picked up, by ship. Until our uplift date, some seven weeks hence, we were on our own.

You can use Google Maps to explore James Ross Island for yourself. Ulu Peninsula is the large ice-free peninsula projecting north of the island. If you zoom in on Ulu Peninsula, you will be able to see the flat-topped hills (basalt volcanic floods), with small, cold-based ice domes and small cirque glaciers.

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What did we find?

By sampling granite boulders derived from the nearby mainland Antarctic Peninsula, we were able to reconstruct ice-sheet behaviour through the last glacial cycle. Those granite boulders situated on tops of the ‘mesas’ (a flat-topped hill; that was a hike that day I can tell you!) proved to have been exposed at the Earth’s surface for over 17,700 years. This indicates that the earliest ice-sheet thinning occurred just after the Last Glacial Maximum.

We also found a drift rich in granite erratics around the margins of Prince Gustav Channel. We interpreted this drift, rich in exotic pebbles and boulders, as representing the lateral margins of Prince Gustav Ice Stream, impinging on Ulu Peninsula. Boulders associated with this drift proved to have exposure ages of around 12,000 years in the north to 6,000 years in the south of the study region. One boulder, associated with a lateral moraine from Prince Gustav Ice Stream, had a height of 144 m above sea level and an exposure age of 7,600 years.

Ulu Peninsula on James Ross Island. Glacial drift rich in granite erratics from the mainland Antarctic Peninsula is denoted by cross-hatching. Our cosmogenic nuclide ages are marked with green triangles and stars.

Ulu Peninsula on James Ross Island. Glacial drift rich in granite erratics from the mainland Antarctic Peninsula is denoted by cross-hatching. Our cosmogenic nuclide ages are marked with green triangles and stars. From Glasser et al., 2014

These exposure ages told us that, at the Last Glacial Maximum, Ulu Peninsula was overwhelmed by a  large ice sheet that originated on Trinity Peninsula. This thick, colm, slow-moving Antarctic Peninsula Ice Sheet deposited granite boulders all across James Ross Island and on nearby Seymour Island. When it became warmer in the Early Holocene (with temperatures recorded in the Mount Haddington Ice Core, see figure below), the ice sheet began to thin and recede from the continental shelf edge. This surface lowering was coincident with a dynamic change with the onset of Prince Gustav Ice Stream, which occurred after 12,000 years ago but before 18,000 years ago. The ice surface lowered in excess of 230 m during this time. The ice stream continued to impinge on the edges of Ulu Peninsula until 7,000 years ago, after which time it shrank back away from the study area. Local ice from the Mount Haddington Ice Cap remained on the inner parts of Ulu Peninsula until around 6,000 years ago.

Ice sheet thinning occurred during a period of rapid warming (from the Mount Haddington ice core) and rapid regional sea level rise.

Ice sheet thinning occurred during a period of rapid warming (from the Mount Haddington ice core) and rapid regional sea level rise. From Glasser et al., 2014.

Dynamic ice-sheet change

These results indicate that a dynamic change occurred during deglaciation, with the ice sheet switching from a thicker, cold-based style of glaciation at the Last Glacial Maximum to a warm-based, thinner, more dynamic ice sheet with ice streaming and a lower surface profile. This occurred during a period of rapid sea level rise and warming recorded in the Mount Haddington Ice Core. Oxygen isotope data from marine sediments indicate that ice streaming and rapid deglaciation also occurred from 13,000 to 12,000 years ago on the western Antarctic Peninsula, suggesting that ice-stream response was synchronous on both the western and eastern Antarctic Peninsula. This region-wide recession was coincident with increased upwelling of Circumpolar Deep Water onto the continental shelf edge – something we are again seeing around the Antarctic’s marine margins.

The Antarctic Peninsula Ice Sheet is a dynamic environment, sensitive to small changes in oceanic and atmospheric circulation. Our results have important implications for future ice dynamics, as temperatures approach those last seen during the Early Holocene and Mid-Holocene Climatic Optimum – both periods of rapid ice-sheet change. And it’s projected to get even warmer than that.

Further Reading

Subpolar landsystems of James Ross Island

This page is a shortened and simplified version of the paper by Davies et al. 2013, published by the Geological Society of London. It discusses a semi-arid subpolar landsystem and its paraglacial modification on James Ross Island, northeast Antarctic Peninsula.

Glacial landsystems | | Methods | Sediment-landform assemblages | Processes of landscape evolution | Glacial-paraglacial-periglacial interactions | Character and behaviour of the LGM ice sheet | Conclusions | Full citation | References | Comments

Glacial Landsystems

A landsystems approach encourages looking at the whole of a landscape to understand how it formed. A landsystems approach means understanding the landforms around, how they were formed (process-form relationships), through analysing both the sediments and the landforms. A series of sediment-landform assemblages make up a landsystem. Landsystems use modern landscapes to understand geomorphological processes, and characterise the terrain with repeated patterns of these sediment-landform assemblages 1,2.

Polar deserts were widespread during the time of the last glaciation, and are present today, both in the Arctic and the Antarctic. However, geomorphological processes are poorly understood in polar deserts, and the interrelationship between glacial, periglacial and paraglacial processes is poorly understood. The ‘paraglacial period’ responds to that period of readjustment from glacial to non-glacial conditions, with the reworking and relaxation of glacial sediments and landforms, such as steep, debris-mantled cliffs and large fluvial systems3. The ‘Periglacial environment’ refers to environments where the ground remains frozen for more than two years in a row, typically with the upper metre of so of the ground thawing in the summer season.

James Ross Island

James Ross Island is located on the northern Antarctic Peninsula. It lies east of the Trinity Peninsula mountains on the Antarctic Peninsula, and these mountains shield the island from precipitation. This is one of the reasons why the island has large ice-free areas. You can use the Google Map below to explore the ice-free portions of James Ross Island.

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Geological timescale

Geological timescale

The Ulu Peninsula on James Ross Island is relatively accessible, and is one of the largest ice-free regions in the northern Antarctic Peninsula. It therefore provides an ideal opportunity to investigate palaeo- and modern geomorphological and sedimentological processes. This holistic study presents a new conceptual landsystem model for James Ross Island. The aim of this work4 is to provide a modern analogue to aid the interpretation and understanding of ancient polar deserts, and through interrogation of this, to present new data regarding the character and behaviour of the Antarctic Peninsula Ice Sheet through the Last Glacial Maximum and Holocene Epoch.

Study area characteristics

Climate

James Ross Island (NE Antarctic Peninsula) has a cold, polar-continental climate5, and it is strongly influenced by the large mountains on Trinity Peninsula. These mountains form a barrier to the relatively warm, moist air on the western Antarctic Peninsula6,7. James Ross Island is separated from Trinity Peninsula by the deep Prince Gustav Channel, which is 4-8 km wide and 450-1200 m deep8. Mean annual air temperatures are around -7°C, and can reach up to +8°C in January, with more than 200 positive degree days and 100 freeze-thaw days per year9,10. It is a semi-arid environment, with precipitation estimates ranging from 200 to 500 mm per year11,12.  However, strong winds and dry air result in the removal of snow by snow drift and sublimation. Snow and ice melt is restricted to the short summer season, with strong temperature fluctuations each night and day.

Geology

Geological map of James Ross Island, NE Antarctic Peninsula, showing the Ulu Peninsula study area (box).

Geological map of James Ross Island, NE Antarctic Peninsula, showing the Ulu Peninsula study area (box).

Trinity Peninsula, northern Antarctic Peninsula, is made up of hard igneous and metamorphic rocks, including granites, granodiorite, quartz monazite and gabbro13-15. James Ross Island, in comparison, comprises Late Cretaceous sedimentary strata, which occasionally bears fossils, overlain by the Neogene James Ross Island Volcanic Group13-19. You can read more about volcanoes on James Ross Island on the Cambridge Volcanology Group website and on our Subglacial Volcanoes page.

Glacial history

During glaciations throughout the Quaternary, James Ross Island was overwhelmed by ice sheets from Trinity Peninsula, which deposited numerous granitic erratics across the island14,20,21. Glacial drift, drumlins and moraines have been described from Ulu Peninsula22-26.  Prince Gustav Ice Stream developed during the Last Glacial Maximum (LGM), diverting ice flow north and south around the island27,28. This ice shrank back from the continental shelf edge around 18,000 years ago, with recession to the inner continental shelf between 17,500 and 9100 years ago20,21,29. Mean ages from cosmogenic nuclide dating of boulders on Cape Lachman indicate that the ice sheet had disappeared from northern James Ross Island by around 8,000 years ago20.

Methods

Geomorphological mapping was achieved through the visual interpretation of satellite images and aerial photographs, and through an intensive field campaign that covered 200 km2 on Ulu Peninsula from January to March 2011. Glaciological structures, sediments and landforms were identified on remotely sensed images and in the field according to standard procedures, using previously defined criteria30-35.

Sediments were characterised quantitatively through the collection of numerous samples of 50 pebbles. Stone lithologies were identified, and pebbles were measured for shape-roundness data36,37.

Sediment-landform assemblages

As a result of these analyses, six sediment-landform assemblages were identified, and they are summarised in the table below. They represent landforms dating from the Neogene to the present day, under a range of different environmental conditions.

Assemblage Principle land elements Age of formation Interpretation
Glacier snow and ice Glacier ice (cirque, tidewater, valley, dome); snow patches Holocene to present day Contemporary glaciation. Small cold-based cirque and plateau glaciers dominate.
Glacigenic Erratic-poor drift; erratic-rich drift in coastal regions and cols and passes; moraine fragments LGM James Ross Island overwhelmed by Antarctic Peninsula Ice Sheet. Erratic-rich drift from the margins of Prince Gustav Ice Stream.
Boulder train Boulder train, Brandy Bay moraine, IJR-45 Glacier moraine Mid-Holocene Readvance of IJR-45 to form a marine-terminating glacier in Brandy Bay
Ice-cored moraine Ice-cored moraines in front of cirque glaciers Late Holocene Late-Holocene readvance of small glaciers
Paraglacial Scree slopes, boulder lags on beaches, ventifacts, spits and beaches, marine terraces, rivers and streams, mass movements Holocene to present Paraglacial reworking of glacigenic sediments and landforms
Periglacial Rock glaciers, nivation hollows, protalus ramparts, freeze-thaw shattering, solifluction, mesas, blockfields Holocene to present Periglaciation of James Ross Island, with a deep permafrost and a seasonal active layer.

Glacier snow and ice assemblage

Ulu Peninsula, James Ross Island, with the glaciers analysed in this study. ASTER image from 2009.

Ulu Peninsula, James Ross Island, with the glaciers analysed in this study. ASTER image from 2009.

James Ross Island has numerous small cirque, valley, tidewater and plateau dome glaciers. Most of these are receding38,39, but the land-terminating glaciers have only small rates of recession. 100-200 m of recession has occurred since the most recent readvance, when prominent ice-cored moraines were formed39. Davies Dome and IJR-45 Glacier (also known as Whisky Glacier) are thinning40. Glacier surfaces are layered and supraglacial debris is common. Most of the small glaciers are free of crevasses.

Perennial snow banks lie in the lee of hill slopes, and feed small streams on positive degree days. These snow banks are sometimes associated with protalus ramparts and nivation hollows.

The small cirque glaciers have little evidence of modern thrusting, and are passively downwasting and receding, with a negative mass balance39. Some of the glaciers have become detached from their plateau accumulation areas, which has further encouraged ice stagnation.

San Jose and Lachman Glacier, Ulu Peninsula. Land-terminating mountain glacier on James Ross Island with prominent ice-cored moraines.

San Jose and Lachman Glacier, Ulu Peninsula. Land-terminating mountain glacier on James Ross Island with prominent ice-cored moraines.

Glacigenic assemblage

Ulu Peninsula is covered with a superficial drift sheet dominated by basalt pebbles and occasional erratics, which together form an armoured surface that overlies sand. In some coastal areas, this drift sheet is overprinted by marine terraces. Three principal glacial drifts are identified, and they are summarised in the table below.

Land element Sediments Landforms Process and interpretation Age
Erratic-poor drift Basalt pebble-cobble gravel; in paces with local sandstone and siltstone Smooth, flat surfaces. Widespread across Ulu Peninsula. Deposition beneath a cold-based, slow-moving ice sheet LGM
Erratic-rich coastal drift Abundant erratics. Found along western coast of Ulu Peninsula. Constructional ridges, moraine fragments, smooth slopes. Deposition beneath a fast-flowing ice stream. Lateral moraines. LGM
Erratic-rich patchy drift in cols and passes Numerous erratic boulders on a basalt pebble-cobble gravel Occasional moraine fragments; streamlined bedrock ridges Deposition beneath wet-based ice sheet; sheet flow. LGM

Erratic-poor drift

Geomorphological map of Ulu Peninsula, James Ross Island, northern Antarctic Peninsula

Geomorphological map of Ulu Peninsula, James Ross Island, northern Antarctic Peninsula

A erratic-poor drift is widespread across Ulu Peninsula, and comprises unlithified (loose, not rock-like) subangular basalt pebbles and cobbles forming a lag on the surface, which frequent basalt boulders and rare granite erratic boulders. It is typically more than 90% basalt. Boulders can be faceted and striated. Periglacial stone stripes or patterned ground are often well developed on this surface.

Drift sheets such as these are often found in deglaciated Antarctic regions, including the Dry Valleys41, where they are inferred to have been deposited by cold-based ice (see Glacial Thermal Regime). The climate of the Dry Valleys is probably comparable with the climate on James Ross Island during the Last Glacial Maximum. Silt, clay and fine materials are typically absent. This erratic-poor drift is interpreted as being deposited by slow-moving, cold-based ice during the Last Glacial Maximum.

Erratic-rich drift

In some coastal regions adjacent to Prince Gustav Channel, such as Lewis Hill, there are drift sheets comprising poorly compacted, unsorted sandy boulder gravel with high percentages of Trinity Peninsula erratics and increased silt content in the matrix. These erratic-rich sediments are associated with constructional ridges and moraine fragments, such as at Kaa Bluff. Erratic-rich drift also occurs patchily in cols and passes, such as Baloo Col and San José Pass.

San Jose Pass, where there is an accumulation of Trinity Peninsula erratics

San Jose Pass, where there is an accumulation of Trinity Peninsula erratics

During the LGM, Prince Gustav Ice Stream flowed northwards along the north-western coast of James Ross Island28,42, and impinged upon its coastal regions, resulting in the formation of lateral moraines and the erratic-rich drift.

Patches of erratic-rich drift also occur in cols and passes. The large accumulations of erratics indicate enhanced deposition and wet-based subglacial conditions. As ice flowed over the passes, it became focussed and compressional stresses increased. Pressure melting point was reached, allowing subglacial deposition and resulting in the erratic-rich sandy boulder gravels and further erosion of the cols43. Both ice deformation and frictional sliding can increase basal ice temperatures44. These patches of erratic-rich drift are therefore interpreted to be a result of changes in the subglacial thermal regime of the ice sheet during LGM glaciation, which can create mosaics of selective erosion and deposition45,46.

Boulder train assemblage

The Boulder train assemblage comprises the boulder train and glacial drift, and the Brandy Bay Moraine. It also includes the IJR-45 Glacier Moraine. These features are associated with a mid-Holocene readvance of IJR-45, dated to ~5,000 years ago24.

Boulder train and glacial drift

A train of large (7-10 m across) boulders of hyaloclastite and diamictite stretches from the western side of IJR-45 Glacier Moraine to a low ridge flanking Brandy Bay. The sediments associated with this boulder train are a sandy boulder gravel, with rare granite boulders. The surficial sediments are similar to the LGM erratic-poor drift. They are stratigraphically younger than (i.e. lie on top of) the coastal erratic-rich drift. The large, intact hyaloclastite boulders are perched on, rather than lodged in, the surficial sediments. These friable boulders would not survive subglacial transport or reworking, and it is likely that they were transported supraglacially by a mid-Holocene readvance of IJR-45 Glacier. The boulder train was probably formed by marginal dumping. Rapid (possibly cold-based) recession may have protected these boulders.

Brandy Bay Moraine

The ridge bounding the SW coastline of Brandy Bay is ~30 m high with a rounded, undulating crest. It is ~3.5 km long and up to 0.7 km wide. It declines in elevation seaward (east to west). The surficial sediments are a basalt pebble-cobble lag with a fine silt matrix buried beneath the cobble armour. There are rare granite boulders, increasing in number seawards. Hyaloclastite boulders decrease in size and number seawards, and weathering and degradation of the boulders increases.

This ridge has previously been interpreted as a moraine24, and we name it ‘Brandy Bay Moraine’.  Drumlins have been reported in association with this moraine22, but here they are interpreted as remnants of a formerly thicker drift sheet, that has since been dissected by ephemeral streams and periglacial slope processes.

The basalt drift and rare granite erratics were derived from reworking of LGM drift sheets,  and the hyaloclastite boulders can be traced to source at Lookalike Peaks.

The photographs below illustrate the various facies of the Boulder Train Assemblage.

IJR-45 Glacier Moraine

IJR-45 Glacier Moraine is up to 1 km wide, with low slope angles until the edge of the moraine, where it drops off sharply. The glacier trunk has clean ice and ice with a thin debris cover. The lateral-frontal complex (closest to the current ice margin) comprises a chaotic assemblage of small, sharp-crested ridges 1-3 m high and up to 1 m wide, often with lines of boulders on their crests. Ice scars are often visible. This region of ice-cored moraine extends ~50 m from the glacier snout.

The next 50-160 m are characterised by increasingly degraded down-wasting back scars of ice, with exposed stratified white and blue ice and small, sharp-crested ridges 1-3 m high. There are numerous small perched ponds.

From 160-400 m from the glacier snout, there are subdued, crescent-shaped scars, circular niches and ridges with no ice visible. There are numerous large hyaloclastite boulders, weathering and downwasting in situ. From 400-1000 m from the glacier snout, the ridges widen and flatten downslope into a 100 m wide ridge, sometimes with small 5 m high ridges and isolated mounds. Stone stripes and patterned ground are well developed. From 1000 m to the edge of the moraine, the moraine is characterised by smooth, steep slopes with loose scree, frost-shattered boulders, well-developed stone stripes, drained lakes and subdued ridges.

IJR-45 Glacier Moraine is characterised by five different zones, ranging from fresh, actively back-wasting ice scars in the frontal-lateral complex, grading outwards to increasingly smoother slopes, more uniform and compacted sediments, and increasing weathering, disintegration of hyaloclastite boulders, and periglacial development. These features suggest that the outer parts of the moraine have an older age than the other smaller ice-cored moraines on Ulu Peninsula.

Ice-cored moraine assemblage

Ice-cored moraines in front of small cirque glaciers and abandoned cirques are the youngest landforms on Ulu Peninsula. They date from a readvance of small glaciers in the last 1000 years39. The cirques have steep backwalls, a rounded, over-deepened basin, and some are occupied by small glaciers or occasionally by lakes.

The ice-cored moraines have multiple sharp-crested ridges, numerous small lakes and ponds, and surficial sediments ranging from sandy boulder gravel through to openwork basalt boulders and diamicton. Exposures show stratified ice (layered blue, white, bubble-poor and bubble-rich ice), sometimes with debris in.

These hummocky moraines are primarily composed of stratified glacier ice. The stratified ice contains basal ice (with debris) and surface ice (white, bubble-rich). Ice with laminated debris is formed though the attenuation by ice creep47,48.

The debris on the moraines is mostly basalt, primarily derived from rockfall from the headwalls onto the glacier surface. The terminal moraines contain more rounded pebbles (occasionally striated), indicating greater distances of subglacial transport, whilst the high lateral moraines contain very angular pebbles, indicating a higher input of supraglacial material.

Paraglacial assemblage

Paraglacial processes, meaning processes which are involved in the readjustment of a landscape from glacial to non-glacial conditions, are strongly apparent on James Ross Island. Here, they include fluvial and marine transportation of sediments, relaxation of steep slopes, mass movements, and aeolian (wind-blown) processes. On Ulu Peninsula, paraglacial sediments and landforms overprint the glaciological story.

Marine terraces and raised beaches

Below 30 m above sea level on Ulu Peninsula, there are smooth, flat slopes, an absence of large boulders and more rounded pebbles. In some places there is a series of flat terraces with rounded pebbles.  These are marine terraces, formed during and after deglaciation, following isostatic uplift of the land.

Spits and modern beaches

Northern James Ross Island is fringed with beaches, some with sandy spits. On some of the beaches there are large numbers of erratic boulders. These spits were formed by the reworking of glacial and fluvial sediments in the littoral zone (wave-washed zone on the beach). Littoral longshore currents transported formerly deposited glacial and fluvial material along the beach. Glacially transported boulders are left behind as a lag on the beach. Unstable steep slopes behind beaches are subjected to solifluction and over-steepening, and erosion of these cliffs may also contribute erratic boulders.

Rivers and streams

Ephemeral (temporary, seasonal) streams and braided streams on Ulu Peninsula typically have multiple channels, with an active river width of up to 100 m. There are incised stream cuts, small islands, point bars and longitudinal mid-channel bars49. The pebbles are typically rounded and clast-supported, and incision is typically around 1-2 m.

These small streams are fed by perennial snowfields and small glaciers, and their discharge varies considerably during the day/night (diurnal) cycle, and on weekly and monthly timescales. On warm days, with increased melt, they are capable of winnowing glacial sediments and incising Cretaceous bedrock.

The photographs below show a number of paraglacial phenomenon on Ulu Peninsula, James Ross Island.

Aeolian sediments and landforms

Glacial drifts on Ulu Peninsula are frequently covered by a basalt pebble-cobble armour, commonly only 1-2 pebbles thick, with sand beneath. Accumulations of sand are also found on snowfields. Many of the boulders have smooth, plano-concave sides, and red staining is common on many granite boulders.

The lag of pebbles is due to winnowing by strong winds. These winds remove fines from the surface, leaving behind only those protected underneath the pebble-cobble armour. The dry, unvegetated climate makes the island susceptible to aeolian deflation like this, and strong katabatic winds exacerbate the process.

The boulders with smooth plano-concave and convex sides are ventifacts, moulded by the wind and sand-blasted into new shapes. They are typical of recently deglaciated, periglacial environments, where there is a large availability of unburied boulders, strong winds and readily available sand50. In some places, the wind has created beautiful shapes and curved on the boulders.

The red staining on the boulders is a red desert varnish, enriched in iron. Iron oxides are leached out of the rock and deposited on the surface as a varnish51.  Well-developed desert varnish occurs in semi-arid, sheltered areas, away from wind abrasion.

Scree slopes

Scree slopes are common beneath the steep basalt cliffs, and are an important input into moraines, rock glaciers and protalus ramparts. The pebbles from scree slopes are more angular than those from the glacigenic drifts and are similar to the high lateral moraines on small cirque glaciers.

The steep basalt cliffs contain vertically jointed hyaloclastite deltaic deposits, which are particularly susceptible to rock weathering and scree slope formation. After recession of the glacier ice, fracturing occurs due to stress release. The exposure of the cliffs to the air makes them vulnerable to freeze-thaw activity in the periglacial climate. This has resulted in rapid readjustment and the formation of new scree slopes.

Large scale mass movements

Large-scale mass movements are evident on Ulu Peninsula were the James Ross Island Volcanic Group rests on gently inclined, poorly consolidated Cretaceous mudstone. These large-scale mass movements involve volcanic blocks many tens of metres high (the full thickness of the local volcanic sequence), and a few hundred metres long, forming enormous jumbled heaps.

These large scale mass movements are controlled by gravity acting on steep-fronted brittle rock masses (delta margins), resting on soft, ductile, Cretaceous sediments. They are geologically controlled, with the upper surface of the Cretaceous muds representing a slip-surface (décollment surface) on which the volcanic blocks can slide. Instability probably occurred after the removal of surrounding ice, and many of the mass movements may span several interglacial periods.

Periglacial assemblage

Periglacial and paraglacial processes are intertwined on James Ross Island, and massive ground ice and glacier ice underlie many of the landforms. The active layer here is approximately 1 m thick52-54.

Rock glaciers

Rock glaciers are lobate or tongue-shaped landforms comprising a mixture of rock and ice, typically with a furrowed form, ridges, ponds, and a steep terminus and sides. They can be derived from scree slopes (talus-derived) or glacier-derived. Glacier-derived rock glaciers form part of a continuum with, and can evolve from, ice-cored moraines55,56.

There are six rock glaciers near Lachman Crags alone. Some are located near the end of ice-cored moraines, and merge with these moraines12,26,57. The rock glaciers are distinguished from ice-cored moraines by evidence for down-slope movement, including arcuate ridges and furrows. Rates of flow have been measured at ~0.2 m per year58.

Protalus ramparts

Protalus ramparts on James Ross Island are curved, flat features on steep slopes, found in association with scree and perennial snow banks. They have a sharp break in slope on their down-slope side, where the talus rests at the angle of repose. Numerous protalus ramparts are found on Ulu Peninsula, along Johnson Mesa, the western slopes of Lachman Crags and below Davies Dome mesa. They form by pebbles rolling down the snow banks. A mesa is a high, flat mountain; in this case, flood basalt deltas form flat-topped mountains.

Slope processes

Solifluction lobes are apparent on many moderate and low-gradient debris-mantled slopes on the island. Many boulders on these slopes are ‘ploughing’ into the sediment, with a keel at the down-slope edge.

Alluvial fans and valley-fills are also important on James Ross Island, with streams, snow avalanches, debris flows and solifluction resulting in gentle fan-shaped sediment accumulations in many valleys. Some of this valley fill has been dissected by rivers and streams, with sorted material being deposited downstream. Rock streams (sensu59) were seen in small valleys, with coarse rock debris forming a linear deposit with a down-slope alignment. They typically have a single thread down the valley axis.

The photographs below show a series of periglacial features on Ulu Peninsula, James Ross Island.

Frost creep is one of the main components of solifluction, with melting ice lenses within the sediment providing water, which reduces the internal friction and cohesion within the regolith. The sediments are slowly deformed through freeze-thaw activity under the influence of gravity, and slide downslope in a series of lobes.

Unvegetated slopes with thick glacial drifts are susceptible to erosion by slope failure, debris flows, tributary streams and surface wash, resulting in gullying, slope-foot debris cones and valley floor deposits3.

Freeze-thaw sediments and landforms

Evidence for modification of surface sediments by freeze-thaw includes frost-shattered boulders, nivation hollows and nivation processes, sorted stone polygons and stripes (sometimes vegetated by lichens and mosses), and surface cracks. Nivation hollows are common, and are related to small, late-lying snow patches. Shattered boulders occur through mechanical weathering induced through freezing and thawing in a periglacial environment60.

Sorted polygons (cf. 61) comprise hexagonal cells of sand and fine to coarse gravel, surrounded by angular coarse gravel and boulders. Pattern widths are 0.4-4 m. They are particularly prevalent in areas with abundant water, such as near streams and snow banks. Stone stripes with alternating coarse and fine sediment are well developed on some slopes. Weathering and down-slope transportation of basalt cobbles on Cretaceous sandstone bedrock has resulted in some striking black stone stripes. Patterned ground overprints most landforms on James Ross Island.

Polygons on the ground surface may form through the development of vertical ice wedges in the ground. Sorted polygons and stone stripes both form through diurnal needle-ice growth. Freezing and thawing of needle ice results in creep on sloping surfaces61. Networks of cracks are interpreted as being the product of the fissuring of seasonally frozen ground.

The availability of water may be a limiting factor in the freeze-thaw cycles that form these features, which are generally more common near streams, nivation hollows and snow patches. More liquid water is present downslope of snow banks, resulting in ice wedge growth and more well-developed polygons and stripes.

Mesas and blockfields

Frost heave turns boulders over on a blockfield on the Ulu Peninsula, James Ross Island

Frost heave turns boulders over on a blockfield on the Ulu Peninsula, James Ross Island

The surface of Lachman Crags mesa (400 m high) is smooth and flat, with stone stripes and stone polygons across its surface. The surficial sediments are mostly basalt clasts, with rare, well-embedded, rounded granite boulders. Above 380 m, the sediments form a blockfield of large, angular basalt boulders, which are not faceted nor striated, and many are subvertical as a result of frost upheaval.

Blockfields develop under periglacial conditions on level or gently undulating relief. They form as a result of in situ weathering of bedrock, with limited downslope movement of blocks62,63. The blockfields on James Ross Island have developed on the Neogene basalt plateaux, where there is abundant periglacial frost action. The presence of granites suggests that at some point, the high mesas may have been overridden by ice from the Antarctic Peninsula.

Processes of landscape evolution in a semi-arid polar environment

Using the glaciological, geological and geomorphological studies undertaken on James Ross Island, we present a new landsystems model for landscape evolution, which will aid the interpretation of past, present and future glacierised and glaciated environments (note: glacierised means currently with glaciers; glaciated means it once had glaciers but doesn’t any more).

A key feature of this new model is the multi-temporal approach. Six sediment-landform assemblages were described and interpreted in the above sections, and they mark a change from landscape dominance by large-scale glaciation during the LGM and Mid- and Late-Holocene glacier readvances, and paraglacial and periglacial processes throughout the Holocene and into the present day.

Landsystem model of landscape processes on James Ross Island

Landsystem model of landscape processes on James Ross Island

The polar desert landsystem on Ulu Peninsula is strongly controlled by the geology; basalt flood-delta mesas dominate the landscape, while being underlain by softer Cretaceous marine deposits; a basalt pebble-cobble gravel covers most land surfaces. The large scale mass movements are predicated by the presence of basalt deltas, likely to be uncommon in other polar environments, although similar features have been noted elsewhere (e.g., Skye).

The landscape was overprinted by ice from the Antarctic Peninsula during the LGM. This ice sheet, and previous incarnations, has sculpted and moulded Ulu Peninsula. Variations in its thermal regime and ice-stream activity have resulted in differences in the glacial drift. Following deglaciation, paraglacial and periglacial processes immediately began to modify the landscape.

Glacial-paraglacial-periglacial interactions

A latitudinal transect from northern Chile through to the Dry Valleys of Antarctica highlights the changing dominance of different processes, driven primarily by the availability of water.  Meltwater is increasingly available important at more northerly latitudes (i.e., closer to the equator). The fast-flowing, temperate glaciers of the Northern Patagonian Icefield produce large volumes of meltwater, which rapidly rework and remove fines generated subglacially. Subglacial landforms are rare, because after glacier recession they are removed by proglacial meltwater32, but there are large glaciofluvial ice-contact landforms. The meltwater also facilitates basal sliding and enables glaciers to flow quickly, resulting in abundant ice-scoured bedrock.

Latitudinal transect demonstrating the importance of modern processes and the abundance of different products across a latitudinal transect from northern Chile to the Dry Valleys

Latitudinal transect demonstrating the importance of modern processes and the abundance of different products across a latitudinal transect from northern Chile to the Dry Valleys

In contrast, the sediment-landform assemblage near Tierra del Fuego, southern Chile (53°S), is dominated by abundant subglacial till, flutes, drumlins and moraines, deposited by temperate glaciers with reduced proglacial meltwater, which aids the preservation of these landforms. There is discontinuous permafrost only, resulting in fewer rock glaciers, protalus ramparts, frost-shattered boulders or stone polygons than on James Ross Island. Aeolian processes are also comparatively less important; ventifacts and pebble-cobble lags are more important in Antarctica because of the faster, sand-bearing winds, less vegetation and less fine-grained, muddy, sticky surficial sediment than in temperate regions.

On James Ross Island, freeze-thaw and fluvial activity have far greater importance than the colder, drier Dry Valleys (cf. 64-66), which significantly aids the development of patterned ground and solifluction landforms. The prevalence of moisture-driven periglacial processes on Ulu Peninsula contrasts sharply with their absence in more southerly, colder parts of Antarctica. In contrast, the glacigenic assemblage on James Ross Island more closely resembles the cold-based glacial sediment-landforms assemblages recognised in East Antarctica43,67-69, perhaps indicating similarities between climate during the LGM on James Ross Island and the climate in East Antarctica today.

Some paraglacial processes, such as glacio-isostatic adjustment and marine terrace formation, and relaxation of rock walls, occur throughout the transect, although marine terraces are more prevalent in regions close to the sea and at sea level.

The scope for landscape modification at the intersection of a paraglacial-periglacial-glacial landsystem is of great importance.  Ground ice is prevalent on James Ross Island today, in the form of permafrost, rock glaciers, buried glacier ice and ice-cored moraines. However, despite the wealth of research on glacial and periglacial processes, there are relatively few papers that discuss the actions of one set of processes upon the other.

The presence of permafrost beneath cold-based ice on James Ross Island during the LGM may have facilitated forward movement, as high porewater pressures beneath subglacial permafrost can reduce the shear strength of unfrozen substrate. This may also help initiate large scale mass movements. Proglacial permafrost can also reduce effective stress by over-pressurising groundwater70. Entrainment of debris occurs through the transmission of basal shear stress from the glacier bed into the frozen subglacial sediment71.

Character and behaviour of the LGM ice sheet on Ulu Peninsula

Artist’s impression of the northern part of the Antarctic Peninsula Ice Sheet at maximum Pleistocene ice thickness, reconstructed using information derived from glaciovolcanic rocks.

Artist’s impression of the northern part of the Antarctic Peninsula Ice Sheet at maximum Pleistocene ice thickness, reconstructed using information derived from glaciovolcanic rocks.

The basal thermal regime of ice sheets represents important empirical data required for numerical ice-sheet models. The subglacial thermal regime on Ulu Peninsula comprised four principal types: a wet-based ice stream, warm-based sheet flow, cold-based sheet flow and cold-based plateau ice caps. Each leaves a distinctive sediment-landform assemblage behind in the geological record. There is evidence of frozen-bed patches with slow sheet flow. Marine geological evidence has been taken to suggest that there was cold-based ice on Antarctic Peninsula mountains during the LGM72,73. The mesas may have harboured ice domes during the LGM period, if they were above the height of the LGM ice sheet. Ice streaming and rapid basal sliding may have been encouraged by slippery marine sediments in Prince Gustav Channel.

The table below summaries some of the key features and inferred thermal regimes of different glacial drifts found on Ulu Peninsula.

Glacial drift Characteristics Inferred thermal regime
Erratic-poor glacial drift Sandy boulder gravel, found widely across Ulu Peninsula Cold-based sheet flow
Erratic-poor glacial drift On mesas and around Davies Dome. Smooth and flat, no landforms Cold-based plateau ice cap
Erratic-rich drift (in cols and passes) Sandy boulder gravel in cols and passes with Trinity Peninsula erratics. Warm-based sheet flow
Erratic-rich drift (in coastal regions) Sandy boulder gravel, up to 50% erratics, associated with moraine fragments Ice stream (warm-based streaming flow)

The glacial sandy boulder gravel that characterises James Ross Island today is significantly different to the Neogene diamictite logged in many places across the island19,74,75. Similar contrasts have been noted in the Dry Valleys, where pebble gravels deposited by cold-based glaciers differ from the Neogene Sirius Group diamictons68. This is indicative of changing climatic regimes, with diamicton, silt and clay forming only under the warmer conditions of the Neogene (cf. 76,77). Warmer atmospheric temperatures encouraged basal sliding, erosion, transportation and deposition under a wet-based ice sheet, with abundant production of fines through glacial abrasion, producing diamictites (note: a diamictite is a lithified diamicton). Abrasion under cold-based glaciers is insufficient to produce the large quantities of fines needed for subglacial till formation, which is associated with warm-based glaciers above the pressure melting point. As well as warmer atmospheric temperatures, geothermal heating may also have  helped Neogene glaciers reach pressure melting point.

This study has shown that cold-based ice sheets are capably of entraining and moving subglacial sediments, and supports a new and emerging paradigm of sheet flow in high latitude regions. The old paradigm suggested that ice sheets comprised a patchwork of cold-based ice on mountain tops, with little or no erosion or deposition, surrounded by highly active warm-based ice that typically occupied valleys78,79. New and emerging research suggests that this is an oversimplification, and that sheet flow is more complex. Although cold-based glaciers are weak erosional and depositional agents compared with warm-based glaciers, their thermal regime and their beds is more subtle than previously thought43,80.

The ice sheet that overwhelmed James Ross Island during the LGM was a composite of ice streaming in the trough of Prince Gustav Channel, which impinged on the coastal margins of Ulu Peninsula. Sheet flow occurred on the main part of the peninsula, with both warm- and cold-based ice flowing across the island, and cold-based and stationary ice domes on high plateaux blockfields. The lateral margins of Prince Gustav Ice Stream were likely to have been dominated by warm-based sheet flow; the evidence for this includes moraine fragments and enhanced deposition of erratics.

Conclusions

This holistic and systematic study of Ulu Peninsula on James Ross Island has used detailed sedimentary descriptions, clast lithology, shape-roundness data and geomorphology mapped from both remotely sensed images and in the field to discriminate six sediment-landform assemblages and thus to present the first landsystem model from a semi-arid polar environment from the Antarctic Peninsula.

The conceptual model emphasises the interrelationship and importance of glacial, periglacial and paraglacial processes. We identified, (1) a glacier snow and ice assemblage; (2) a glacigenic assemblage; (3) a boulder train assemblage; (4) an ice-cored moraine assemblage; (5) the paraglacial assemblage; and (6) a periglacial assemblage. Analysis of these assemblages provides a detailed understanding of landscape evolution on James Ross Island. Analysis of these assemblages provides a detailed understanding of landscape evolution on James Ross Island.

Sediments and landforms were deposited during LGM glaciation and during mid- and Late-Holocene glacier readvances. They were subsequently reworked and deposited by periglacial and paraglacial processes, throughout the Holocene and into the present day. Crucially, when compared with other landsystem models, we find that the availability of meltwater encourages strong landform modification by periglacial processes. These processes would have been similarly important during Late Pleistocene glaciation in the Northern Hemisphere. Therefore, the landsystem model presented here is a modern analogue to be used in the interpretation of past glaciated environments.

This paper presented new information regarding the thermal regime of the Antarctic Peninsula Ice Sheet during LGM glaciation. The data and the model for the interplay between cold-based, warm-based and streaming ice challenges the theory that cold-based glaciers do not erode or deposit. Finally, this paper presented important new data regarding the thermal regime and character and behaviour of the Antarctic Peninsula Ice Sheet during the LGM, which will aid reconstructions of the LGM ice sheet in the northern Antarctic Peninsula.

Further reading

Citation

Please cite the paper as:

Davies, B.J., Glasser, N.F., Carrivick, J.L., Hambrey, M.J., Smellie, J.L. and Nývlt, D., 2013. Landscape evolution and ice-sheet behaviour in a semi-arid polar environment: James Ross Island, NE Antarctic Peninsula. In: M.J. Hambrey et al. (Editors), Antarctic Palaeoenvironments and Earth Surface Processes. Geological Society of London, Special Publications, volume 381, London, pp. 1-43.

The full paper can be downloaded from the link above. Please email the authors if you cannot access this publication.

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Ice-cored moraines, James Ross Island

The Little Ice Age on James Ross Island | Methods | Moraine morphology and sedimentology | Glacier extent, surface and volume changesy | Interpretation | Summary and conclusions | References | Comments |

This is a shortened and simplified version of the Carrivick et al. 2012 article in Journal of Glaciology. 

The Late Holocene on James Ross Island

The Little Ice Age moraines on James Ross Island

Cirque glacier with large ice-cored moraines, viewed from Hambrey Mesa, James Ross Island

Although the Antarctic Peninsula is a region of rapid warming, the spatial and temporal pattern in this warming is complex[1]. The wide range of glacial types across the Antarctic Peninsula has resulted in a range of responses[2].

The response of land-terminating glaciers across the Antarctic Peninsula is particularly interesting, because land-terminating glaciers respond in a linear fashion to changes in temperature and precipitation.

Land-terminating glaciers on James Ross Island and nearby land have been observed to be shrinking[2-4], and this has resulted in several campaigns to monitor long-term glacier mass balance in the region[5, 6]. Studies of glaciers are limited to either a short temporal scale (era of satellite observations) or are limited to small numbers of glaciers (field-based measurements).

Aims and Objectives

It is important to characterise the centennial-scale behaviour of small land-terminating glaciers in this region, in order to understand these short-term variations. This study of glaciers on James Ross Island provides a longer-term view and broader perspective of glacier character and behaviour on the northern Antarctic Peninsula during the Late Holocene, a time possibly synchronous with the northern Hemisphere’s Little Ice Age.

Over a 7-week field season in January-March 2011, Jonathan Carrivick, Bethan Davies and Neil Glasser investigated prominent moraines in front of small land-terminating glaciers.  Our objectives were,

  1. Holistic geological descriptions of the topography, sedimentology and geomorphology of the prominent ice-cored moraines;
  2. Interpretation of the character and behaviour of those glaciers while they were at this relatively advanced position, and;
  3. Quantification of the geometric changes to these glaciers during the Late Holocene.

Study Site

Geological map of James Ross Island, NE Antarctic Peninsula, showing the Ulu Peninsula study area (box).

James Ross Island is on the NE tip of the Antarctic Peninsula, and the Ulu Peninsula on James Ross Island is one of the largest ice-free areas in Antarctica. The Ulu Peninsula comprises large areas of Cretaceous sandstone and mudstone, overlain by multiple layers of basalt and hyaloclastite.

Radiocarbon dates on organic remains on James Ross Island suggest that the Ulu Peninsula became ice-free following the Last Glacial Maximum by around 7500 years ago, with a glacial readvance that finished around 4700 years ago. Ulu Peninsula has several small cirque glaciers with pronounced ice-cored moraines, which relate to a more recent glacier readvance.

Methods

Ulu Peninsula, James Ross Island, with the glaciers analysed in this study. ASTER image from 2009.

We investigated six glaciers on Ulu Peninsula: Unnamed Glacier, Triangular Glacier, IJR-45, Alpha Glacier and San José Glacier. A differential GPS (dGPS) Leica GPS500 was used in realtime kinematic mode for topographical surveys and to precisely determine the location and elevation of glacier margins, glacier snout positions and moraine crests. Glaciological structures were mapped from aerial photographs (taken in 2006); structures mapped include stratification, crevasses, streams and supraglacial debris. The landscape position of the moraines, their surface character, planform and longitudinal profile was mapped in the field using dGPS. Sedimentological analysis of sections of sediment and ice provided information on depositional history, style and environment.

Late Holocene glacier extent was interpolated from the mapped innermost moraine crests in a Geographical Information System (GIS). This gave a minimum height for the moraines and a palaeo ice-surface elevation.

Moraine morphology and sedimentology

The Little Ice Age moraines on James Ross Island

San Jose and Lachman Glacier, Ulu Peninsula. Land-terminating mountain glacier on James Ross Island with prominent ice-cored moraines.

The moraines in front of the glaciers were typically 25-40m higher in elevation than the modern glacier surface, and all the moraines are ice-cored.

Most of the moraines have multiple crests, particularly near the glacier snout, and all have a hummocky topography and slides sloping at 30° to 40°. The moraines have a complex topography, with a hummocky ridge crest, shallow surface depressions (some with ponded lakes) and numerous surficial mass movements. Sediment thickness over the ice core varies from 1-2 m.

Glacier ice exposed in the ice-cored moraines is well bedded with layers of clean white bubbly ice, ice with debris content (dispersed, laminated and stratified), and clear, massive, bubble-free blue ice with large crystals with dispersed (occasional) cobbles, pebbles or small boulders. The layers dip at 40° down glacier.

Ice cored moraines, San Jose glacier

At the terminal moraines, rounded and striated boulders can be found. In contrast, the lateral moraines are formed of angular material that is very similar in composition to the scree slopes surrounding the glacier.

The form of the moraines mirrors the glaciological structures mapped (especially the stratification).

Glaciological features (mostly stratification) and moraine morphology for San Jose and Lachman glaciers

Glacier extent, surface and volume changes

Reconstructed LIA extent and amount of surface lowering

All six of the glaciers investigated have undergone significant decreases in glacier extent and elevation since their maximum (when they deposited these moraines). The decrease is a function of snout recession and ice-margin surface lowering to within the lateral moraine margins. Glacier snout retreat varies between 75 m at Triangular Glacier to 130 m at San José Glacier.

Long profiles of glaciers, showing surface lowering.

Surface lowering decreases in magnitude with increasing altitude up to the maximum elevation of the moraine crests. There is a distinct east-west gradient in surface lowering across the glaciers, with greater surface lowering on the western parts of the glaciers relative to the eastern parts. This difference can be up to 20 m, as on Unnamed and Triangular glaciers. The pattern is least pronounced on IJR-45.

Triangular, Unnamed and  San José glaciers have lost 20-30% of their surface area since their most recent maximum, while IJR-45 and Alpha Glacier have receded by 12-15%. The land-terminating glaciers have had a volume reduction of 0.01-0.03 km3, with a combined total of 0.1 km3. Westward-facing glaciers (Unnamed, Triangular and Lachman) have lost less volume for their relative area than San José, Alpha and IJR-45.

Interpretation

Past behaviour

The glacier ice exposed in the moraine is interpreted as basal glacier ice formed by adfreezing near the glacial margin[7-9]. The basal ice facies becomes interbedded with the clear blue basal ice by shearing and thrusting. This produces stacked basal, englacial, supraglacial and proglacial ice[7]. Debris laminations were formed through the attenuation of debris and interstitial ice (the ice frozen around the debris) at the boundary with clean glacier ice. Folding occurs due to ice creep, particularly around larger obstacles.

Subglacial and englacial thrusting has therefore entrained sediment, which melts out at the surface to bury the ice core and produce the present-day surface sediment veneer. Shearing and thrusting of basal ice is commonly associated with polythermal glaciers[10-12]. These processes produce the arcuate belts of aligned ridges and superimposed minor moraine ridges. The orientation of the thrusting closely mirrors the angle of dip and dip direction observed in the stratified glacier ice in the moraines; this closely controls moraine morphology and surface slopes, and also moraine height, width and character.

The sediment drape, particularly at the terminal moraines, has melted out from the debris within the ice-cored moraines. Once the ice core has melted, there will be little geomorphological expression of the moraine. They therefore have a limited preservation potential. This may explain the lack of other prominent moraines on Ulu Peninsula. Sediment redistribution by mass flows and mass movements during melting further limits preservation potential[13]. These processes have been observed in other high-latitude environments[14, 15].

These are ‘controlled moraines’; i.e., the moraine morphology is controlled by englacial structures[15]. The moraine form is specifically controlled by stratification[16], which is produced by marginal shear and by the melt out of debris-rich basal ice[17].

We therefore conclude that these moraines record the advance of polythermal glaciers, because the englacial and proglacial thrusting and stacking and thick deformed basal ice is indicative of a compressive regime near the snout of the glacier[11, 12, 15].

Past glacier extent and volume changes

All glaciers have retreated, and retreat is most evident at the glacier snouts, although retreat is also observed at the lateral margins. The magnitude of surface lowering decreases with altitude, and it is therefore likely to have been driven by air temperature.

The evolution of surface lowering and the observed east-west gradients reflects the importance of wind-blown snow. Enhanced accumulation on the eastern parts is a product of orographically enhanced snow drifting by the prevailing westerly/southwesterly winds, which are typical of this region. A change in the dominance of controlling factors could be a cause and a symptom of a changing mass balance.

The glaciers previously were thicker, more extensive and had a convex long-profile. They now have an asymmetric surface morphology and a linear slope long profile, and an absence of modern, active moraines or crevasses. These factors would imply a modern negative mass balance. Finally, the present lack of dynamism or movement is due to glacier stagnation and a transition to a cold-based thermal regime, as reported for other glaciers on James Ross Island [cf. 12]. We therefore surmise that there has been a transition from a polythermal to a cold-based glacier thermal regime.

Rate of glaciological change

There are no absolute dates available for the age of these moraines. Dating them is difficult due to the lack of organic matter for radiocarbon dating, and because of the difficulties in cosmogenic nuclide dating of basalt boulders of such a young age. However, the moraines are much younger and fresher than the moraine in Brandy Bay, dated to 4500 years old by radiocarbon dating[18, 19]. These moraines are most likely to date from a Neoglacial readvance 700-1000 years ago, broadly synchronous with the early stages of a Little Ice Age, which has been postulated but undated for James Ross Island[20] and from around the Antarctic Peninsula[21, 22]. This would produce mean snout recession rates of 0.17-0.1 meters per annum (m a-1), mean surface lowering of 0.03-0.02 m a0.02 m a-1 and mean areal decline of 0.03% m a-1. These rates are much lower than those calculated for the glaciers of James Ross Island from 1995 onwards[2, 23]. Recent work has shown a mean annual surface lowering of 0.79 m a-1 of IJR-45m a-1 between 1979-2006[5].

Summary and conclusions

In summary, the combined topographical, sedimentological and geomorphological measurements and observations of glaciers on Ulu Peninsula, James Ross Island describe the first meso-scale changes in the character and behaviour of land-terminating glaciers in the Antarctic Peninsula region. They have retreated 75-120 m each, and glacier surfaces have lowered 9-23 m on average since a Late Holocene readvance. These changes are relatively uniform across the glaciers, but there is a west-east gradient in these changes that may be due to wind-blown snow.

Lachman and San Jose glaciers

These Late-Holocene moraines are ice-cored, and reflect the importance of thrusting and shearing when the moraines were formed. The composition of the moraines and the ice surface reconstructed from them indicates that the glaciers were polythermal during the Late Holocene, and that the glaciers were more dynamic than at present. The glaciers are now cold based, and down wasting in situ. Comparison of reconstructed past glacier dynamics with the present glaciers permits speculation that glacier shrinkage, caused by warming temperatures, resulted in a transition from a polythermal to a cold-based thermal regime. Land-terminating glaciers on James Ross Island are now cooler despite a warmer climate.

Was the Little Ice Age a global phenomenon? Increasing evidence of a LIA in Antarctica seems to suggest it was so.

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Citation

Please refer to the original article and cite as:Jonathan L. CARRIVICK, Bethan J. DAVIES, Neil F. GLASSER, Daniel NÝVLT, Michael J. HAMBREY, 2012. Late Holocene changes in character and behaviour of land-terminating glaciers on James Ross Island, Antarctica. Journal of Glaciology 58 (212).

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14.          Hambrey, M.J., Huddart, D., Bennett, M.R., and Glasser, N.F., 1997. Genesis of ‘hummocky moraines’ by thrusting in glacier ice: evidence from Svalbard and Britain. Journal of the Geological Society, London, 1997. 154: p. 623-632.

15.          Evans, D.J.A., 2009. Controlled moraines: origins, characteristics and palaeoglaciological implications. Quaternary Science Reviews, 2009. 28(3-4): p. 183-208.

16.          Hambrey, M.J. and Lawson, W., 2000. Structural styles and deformation fields in glaciers: a review, in Deformation of Glacial Materials, A.J. Maltman, B. Hubbard, and M.J. Hambrey, Editors. Geological Society of London, Special Publication: London. p. 59-83.

17.          Ó Cofaigh, C., Evans, D.J.A., and England, J.H., 2003. Ice-marginal terrestrial landsystems: sub-polar glacier margins of the Canadian and Greenland High Arctic, in Glacier Landsystems, D.J.A. Evans, Editor. Hodder Arnold: London. p. 44-64.

18.          Hjort, C., Ingólfsson, Ó., Möller, P., and Lirio, J.M., 1997. Holocene glacial history and sea-level changes on James Ross Island, Antarctic Peninsula. Journal of Quaternary Science, 1997. 12: p. 259-273.

19.          Björck, S., Olsson, S., Ellis-Evans, C., Håkansson, H., Humlum, O., and de Lirio, J.M., 1996. Late Holocene palaeoclimatic records from lake sediments on James Ross Island, Antarctica. Palaeogeography, Palaeoclimatology, Palaeoecology, 1996. 121(3-4): p. 195-220.

20.          Strelin, J.A., Sone, T., Mori, J., Torielli, C.A., and Nakamura, E., 2006. New data related to Holocene landform development and climatic change from James Ross Island, Antarctic Peninsula, in Antarctica: contributuins to global Earth sciences. Proceedings of the IX International Symposium of Antarctic Earth Sciences, Potsdam, 2003, D.K. Fütterer, et al., Editors. Springer-Verlag: New York. p. 455-460.

21.          Domack, E.W., Leventer, A., Dunbar, G.B., Taylor, F., Brachfeld, S., Sjunneskog, C., and Party, O.L.S., 2001. Chronology of the Palmer Deep site, Antarctic Peninsula: A Holocene palaeoenvironmental reference for the circum-Antarctic. The Holocene, 2001. 11(1): p. 1-9.

22.          Bentley, M.J., Hodgson, D.A., Smith, J.A., Ó Cofaigh, C., Domack, E.W., Larter, R.D., Roberts, S.J., Brachfeld, S., Leventer, A., Hjort, C., Hillenbrand, C.-D., and Evans, J., 2009. Mechanisms of Holocene palaeoenvironmental change in the Antarctic Peninsula region. Holocene, 2009. 19(1): p. 51-69.

23.          Skvarca, P. and De Angelis, H., 2003. Impact assessment of regional climatic warming on glaciers and ice shelves of the northeastern Antarctic Peninsula, in Antarctic Peninsula climate variability: historical and palaeoenvironmental perspectives, E.W. Domack, et al., Editors. American Geophysical Union, Antarctic Research Series, Volume 79: Washington, D.C. p. 69-78.

Periglacial environments

Introduction to periglacial environments | James Ross Island | Patriot Hills, Ellsworth Mountains | Vestfold Hills, East Antarctica | Terra Nova Bay, Northern Victoria Land | References | Comments |

Introduction  to periglacial environments

Periglacial, Paraglacial and Permafrost

Periglacial environments are those that are in a cold climate, typically near glacierised regions. Permafrost environments are those where the ground is frozen for more than two years in a row[1]. In contrast, paraglacial processes, landforms and landscapes are those that are directly conditioned by former glaciation and deglaciation[2].

Antarctic environments and landscapes are conditioned by both periglacial and paraglacial processes, with landforms related to frozen ground, and with the redistribution of glacigenic sediments by fluvial, coastal and aeolian processes. Rock wall relaxation following the removal of buttressing glaciers is also a common paraglacial process in Antarctica.

The periglacial environment is a cold climate, frequently marginal to the glacial environment, and is characteristically subject to intense cycles of freezing and thawing of superficial sediments. Permafrost commonly occurs within this periglacial environment. However, processes that involve the freezing, unfreezing, and movement of water are considered to be periglacial; processes associated with the presence of perennially frozen ground are permafrost. Permafrost is therefore closely associated with the periglacial environment, and usually permafrost processes take place within a periglacial environment[1].

Periglacial environments in Antarctica

Most of the ice-free ground in Antarctica is underlain by frozen ground[3]. Rock glaciers are common in sub-Antarctic islands and coastal areas[4], in the Transantarctic Mountains and in the McMurdo Dry Valleys[5].

Climate change is likely to result in changes in periglacial areas, such as large hydrological changes, increased methane release to the atmosphere, changes in vegetation composition, and increases in dissolved material to rivers and oceans[3]. Slope instability is likely to increase under a warming climate, and processes involving changing wind regimes, freeze-thaw cycles and related landforms will also be affected.

We will now look at a few case studies of Antarctic periglacial and permafrost environments. Antarctic periglacial environments are very variable, and the processes and landforms active are dependent on the amount of seasonal meltwater available.

James Ross Island

Climate

Geological map of James Ross Island, NE Antarctic Peninsula

James Ross Island has a cold, polar-continental climate, with mean annual temperatures of -7°C and summer highs reaching +8°C in January[4]. It has a semi-arid climate, with precipitation (mainly as snow) between 200 and 500 mm per annum (water equivalent)[4, 6].

During the Last Glacial Maximum, James Ross Island was covered by ice, with the Prince Gustav Ice Stream depositing glacial erratics on the north-western parts of the island[7].

Paraglacial landforms

Paraglacial processes are well developed on James Ross Island. Here, mass wasting of rock walls, movement on debris-mantled slopes, wind processes and some limited fluvial (stream) transportation dominate sediment transfers, which are limited to the short summer season. Paraglacial sediments and landforms overprint older glacial landforms, and understanding these is important for unravelling the glacial stratigraphy.

The principle paraglacial landforms include marine terraces and raised beaches, which are well developed here. There is a prominent marine limit at 30 m on Brandy Bay[14]. Coastal processes rework exposed glacial sediments, re-depositing them in spits and modern beaches. The windy climate results in finer grained material being removed from surficial sediments; these aeolian processes result in cobble-boulder armour overlying finer grained sediments across the Ulu Peninsula. Scree slopes are common, and provide input for rock glaciers, protalus ramparts and glaciers. Freeze-thaw weathering, over-steepening and rock-slope relaxation following the removal of buttressing ice masses encourages scree to form. Finally, James Ross Island is characterised by large-scale mass movements, where volcanic rocks resting on sloping soft Cretaceous sediments become detached from their rock walls and slip downslope.

Periglacial landforms

Periglacial landforms are well developed on James Ross Island[8-13], facilitated by relatively warm summer temperatures, which allow melting and surface water. These observations are based on fieldwork to the Ulu Peninsula in January to February 2011.

Rock glaciers are a common feature on James Ross Island. Some of these are located at the end of an ice-cored moraines, in front of stagnating glacier ice[4, 11, 15, 16]. Other rock glaciers form beneath steep cliffs, where active scree slopes result in abundant rock debris being available. This scree, combined with perennial snow banks, also results in the development of protalus ramparts. Protalus ramparts here are curved, relatively flat features. They form by stones rolling down snow banks, and accumulating at their base.

Slope processes are very active on James Ross Island, and there are solifluction lobes on many of the medium- to low-gradient slopes. Some of these have boulders ploughing into the sediment. Alluvial fans and valleys fills are major sediment sinks on the island. These periglacial slope processes are controlled by freeze-thaw activity, rock weathering, frost heave and thaw consolidation. Surficial sediments are saturated as the frozen permafrost table inhibits water draining away and being absorbed into the soil. Frost creep is also important, with the slow downslope gravitational deformation of surficial sediments through freeze-thaw activity[cf. 17].

Finally, freeze-thaw weathering results in frost-shattered boulders, snow hollows, sorted stone polygons and stripes, and surface cracks. The sorted polygons [cf. 18] comprise sand and fine to coarse gravel, surrounded by angular coarse gravel and cobbles.  These polygons are formed by the development of vertical ice wedges in the ground, or through regular needle ice-growth[18-20].

Patriot Hills, Ellsworth Mountains

The Patriot Hills are located in the Ellsworth Mountains (80°S), 50 km inland from the Ronne Ice Shelf grounding line[5]. There are seven deglaciated valleys, and two glacierised (ice-filled) valleys. This is a dry, windy area, with strong southerly katabatic winds. The mean annual temperature is -28°C, and the summer high temperatures are around -15°C.

The periglacial landforms here comprise rock glacier-like landforms, slightly creeping debris slopes, and rock falls[5]. The rock glacier-like landforms has a lobed shape, abrupt fronts and sides, and a relatively flat top. This extends 400 m downslope from the cirque above as a tongue of rock debris. It is arcuate with small ridges on the downslope upper surface. It is connected with ice-cored moraines. Although this is very like a rock glacier, the lack of information available on the internal structure means that it is difficult to interpret it as such[5].

This area is far colder than James Ross Island, and the lack of meltwater available means that periglacial landforms are less well developed.

Vestfold Hills, East Antarctica

Vestfold Hills is a 200 km2 oasis in East Antarctica, and is the third largest ice-free area in Antarctica after the Dry Valleys in southern Victoria Land and the Bunger Hills of Wilkes Land[21].  There is a cool periglacial climate with a mean annual temperature of -10.2°C. Rainfall is very rare, and precipitation is light, making this a semi-arid environment. Snow and ice melts from December to February, resulting in limited surface water being available.

Surficial sediments comprise thin mantles and scattered erratic boulders as isolated patches, ridges of glacial deposits and filled valleys[21]. The lack of surficial sediments here is a result of low volumes of debris in glacier ice, and paraglacial processes that transport material downslope into sediment sinks in the valley floors. Ice-cored moraines have a poor preservation  potential, with meltwater rapidly redistributing sediments via mass movements and debris flows[21].

Terra Nova Bay, Northern Victoria Land

This is an ice-marginal, high-latitude periglacial environment, characterised by cold, arid and windy conditions[22]. In these environments again, freeze-thaw and solifluction processes are limited because of the lack of moisture and the shallow active layer (depth that seasonally thaws and refreezes). The main processes here are mass wasting through rock disintegration and gravitationally-driven mass movements. Wind erosion, however, is significant, eroding the rocks into various shapes with tafoni and honeycomb weathering.

Go to top or jump to Subglacial Volcanoes.

References


1.            Dobinski, W., 2011. Permafrost. Earth-Science Reviews, 108(3-4): 158-169.

2.            Ballantyne, C.K., 2002. Paraglacial geomorphology. Quaternary Science Reviews, 21(18-19): 1935-2017.

3.            Guglielmin, M., 2012. Advances in permafrost and periglacial research in Antarctica: a review. Geomorphology, 155-156: 1-6.

4.            Strelin, J.A. and T. Sone, 1998. Rock glaciers on James Ross Island, Antarctica. Permafrost – Seventh International Conference (Proceedings), 55: 1027-1033.

5.            Vieira, R., S. Hinata, K.K. da Rosa, S. Zilberstein, and J.C. Simoes, 2012. Periglacial features in Patriot Hills, Ellsworth Mountains, Antarctica. Geomorphology, 155-156: 96-101.

6.            van Lipzig, N.P.M., J.C. King, T.A. Lachlan-Cope, and M.R. van den Broeke, 2004. Precipitation, sublimation and snow drift in the Antarctic Peninsula region from a regional atmospheric model. Journal of Geophysical Research, 109: D24106.

7.            Johnson, J.S., M.J. Bentley, S.J. Roberts, S.A. Binney, and S.P.H.T. Freeman, 2011. Holocene deglacial history of the north east Antarctic Peninsula – a review and new chronological constraints. Quaternary Science Reviews, 30: 3791-3802.

8.            Lundqvist, J., M. Lillieskold, and K. Ostmark, 1995. Glacial and periglacial deposits of the Tumbledown Cliffs area, James Ross Island, West Antarctica. Geomorphology, 11: 205-214.

9.            Ermolin, E., H. De Angelis, and P. Skvarca, 2002. Mapping of permafrost on Vega Island, Antarctic Peninsula, using satellite images and aerial photography. Annals of Glaciology, 34: 184-188.

10.          Ermolin, E., H. de Angelis, P. Skvarca, and F. Rau, 2004. Ground ice in permafrost on Seymour (Marambio) and Vega Islands, Antarctic Peninsula. Annals of Glaciology, 39: 373-378.

11.          Strelin, J.A., T. Sone, J. Mori, C.A. Torielli, and E. Nakamura, New data related to Holocene landform development and climatic change from James Ross Island, Antarctic Peninsula, in Antarctica: contributuins to global Earth sciences. Proceedings of the IX International Symposium of Antarctic Earth Sciences, Potsdam, 2003, D.K. Fütterer, et al., Editors. 2006, Springer-Verlag: New York. 455-460.

12.          Fukui, K., T. Sone, J.A. Strelin, C.A. Torielli, and J. Mori, 2007. Ground penetrating radar sounding on an active rock glacier on James Ross Island, Antarctic Peninsula region. Polish Polar Research, 28(1): 13-22.

13.          Fukui, K., T. Sone, J.A. Strelin, C.A. Torielli, J. Mori, and Y. Fujii, 2008. Dynamics and GPR stratigraphy of a polar rock glacier on James Ross Island, Antarctic Peninsula. Journal of Glaciology, 54: 445-451.

14.          Hjort, C., Ó. Ingólfsson, P. Möller, and J.M. Lirio, 1997. Holocene glacial history and sea-level changes on James Ross Island, Antarctic Peninsula. Journal of Quaternary Science, 12: 259-273.

15.          Strelin, J.A. and E.C. Malagnino, Geomorfologìa de la Isla James Ross, in Geologia de la Isla James Ross. 1992, Instituto Antàrctico Argentino: Buenos Aires. 7-36.

16.          Strelin, J.A., C.A. Torielli, T. Sone, K. Fukui, and J. Mori, 2007. Particularidades geneticas de glaciares de roca la Isla James Ross, Peninsula Antartica. Revista de la Asociacion Argentina, 62(4): 627-634.

17.          Harris, C., Periglacial Landforms: Slope Deposits and Forms, in Encyclopedia of Quaternary Science, A.E. Scott, Editor. 2007, Elsevier: Oxford. 2207-2217.

18.          Ballantyne, C.K., Periglacial Landforms: Patterned Ground, in Encyclopedia of Quaternary Science, A.E. Scott, Editor. 2007, Elsevier: Oxford. 2182-2191.

19.          Harry, D.G., Ground ice and permafrost, in Advances in periglacial geomorphology, M.J. Clark, Editor. 1988, Wiley-Interscience: Chichester. 113-150.

20.          Harry, D.G. and J.S. Gozdzik, 1988. Ice wedges: Growth, thaw transformation, and palaeoenvironmental significance. Journal of Quaternary Science, 3(1): 39-55.

21.          Fitzsimons, S.J., 1996. Paraglacial redistribution of glacial sediments in the Vestfold Hills, East Antarctica. Geomorphology, 15(2): 93-108.

22.          French, H.M. and M. Guglielmin, 1999. Observations on the ice-marginal, periglacial geomorphology of Terra Nova Bay, Northern Victoria Land, Antarctica. Permafrost and Periglacial Processes, 10: 331-347.

James Ross Island fieldwork photographs

Photographs from glacial geological fieldwork on James Ross Island in February to March 2011 (to Brandy Bay region) and 2012 (to Terrapin Hill). James Ross Island photographs by Bethan Davies.

Article by Bethan Davies.

Antarctic terrestrial landforms

Glacial Landforms

There is a huge variety of glacial landforms recognised in the geological record. However, they are difficult to see in Antarctica, because they are usually buried beneath ice.

On a few small islands around the Antarctic Peninsula, however, you can see evidence of past glaciations through glacier sediments and landforms.

The contrast between landforms being made by different processes is clear around the Antarctic Peninsula. Small islands and ice-free areas, such as James Ross Island, are characterised by small moraines made by polythermal glaciers. However, on the continental shelf, there are large landforms generated by ice streams at the Last Glacial Maximum (LGM). The next section contrasts these different environments and their landforms.

James Ross Island

Geological map of James Ross Island, NE Antarctic Peninsula

Some of our examples of glacial landforms come from James Ross Island, which is located on the northeast tip of the Antarctic Peninsula, at about 64°S (see map below)[1].

The area was glaciated during the Last Glacial Maximum, with cosmogenic nuclide exposure ages indicating recession of the main glacier ice around 11,000 to 9500 years ago[2] (see ice sheet evolution).

The landscape is now characterised by permafrost (see Periglaciation)[3, 4], with small cold and polythermal glaciers, and periglacial landforms, such as rock glaciers[5], protalus ramparts, patterned ground, snow patches and small ephemeral streams.

The most obvious glacier landforms on James Ross Island are ice-cored moraines around small glaciers on Ulu Peninsula. These glaciers are surrounded by sharp-crested moraines with a core of glacier ice. The glacier ice is stratified with blue and white, bubble-rich ice and debris-rich bands, suggesting that it is basal glacier ice.

The crests of the moraines range from sharp-crested to chaotic, with the ice wasting and melting in situ. The buried glacier ice means that water cannot drain away, and many small frozen and unfrozen lakes and ponds are impounded on the moraines.

You can see many more examples of glacial landforms on the Glaciers Online photoglossary.

References


1.            British Antarctic Survey, Antarctic Sound and James Ross Island, Northern Antarctic Peninsula, in Series BAS (UKAHT) Sheets 3A and 3B, 1:250000. 2010, United Kingdom Antarctic Heritage Trust: Cambridge.

2.            Johnson, J.S., Bentley, M.J., Roberts, S.J., Binney, S.A., and Freeman, S.P.H.T., 2011. Holocene deglacial history of the north east Antarctic Peninsula – a review and new chronological constraints. Quaternary Science Reviews, 2011. 30(27-28), 3791-3802

3.            Fukuda, M., Strelin, J.A., Shimokawa, K., Takahashi, N., Sone, T., and Trombott, D., 1992. Permafrost occurrence of Seymour Island and James Ross Island, Antarctic Peninsula region, in Recent progress in Antarctic Earth Sciences, N. Yoshida, K. Kaminuma, and K. Shiraishi, Editors. Terra Scientific Publishing Company (TERRAPUB): Tokyo. p. 745-750.

4.            Lundqvist, J., Lillieskold, M., and Ostmark, K., 1995. Glacial and periglacial deposits of the Tumbledown Cliffs area, James Ross Island, West Antarctica. Geomorphology, 1995. 11: p. 205-214.

5.            Fukui, K., Sone, T., Strelin, J.A., Torielli, C.A., Mori, J., and Fujii, Y., 2008. Dynamics and GPR stratigraphy of a polar rock glacier on James Ross Island, Antarctic Peninsula. Journal of Glaciology, 2008. 54: p. 445-451.

6.            Davies, B.J., Hambrey, M.J., Smellie, J.L., Carrivick, J.L., and Glasser, N.F., 2012. Antarctic Peninsula Ice Sheet evolution during the Cenozoic Era. Quaternary Science Reviews, 2012. 31(0): p. 30-66.

7.            Graham, A.G.C., Larter, R.D., Gohl, K., Hillenbrand, C.-D., Smith, J.A., and Kuhn, G., 2009. Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control. Quaternary Science Reviews, 2009. 28(25-26): p. 2774-2793.