The East Antarctic Ice Sheet today
The East Antarctic Ice Sheet is the largest of Antarctica’s ice sheets, and has a very different behaviour to its counterparts. Its dynamics and geography are distinctive, and the East Antarctic Ice Sheet behemoth warrants a closer look in its own right.
The total volume of ice in the Antarctic Ice Sheet today is 27 million km3, which is equivalent to 58 m of global sea level (i.e., if all the ice in Antarctica melted, sea levels would rise by 58 metres). The Antarctic Ice Sheet is usually divided into three ice sheets: The Antarctic Peninsula Ice Sheet, the West Antarctic Ice Sheet, and the East Antarctic Ice Sheet. The East Antarctic Ice Sheet makes up the majority of the Antarctic Ice Sheet, and has a global sea level equivalent of 53 m 1. 19 of these metres would be from glacier ice grounded below present sea level. The South Pole is found in East Antarctica. It lies at 2835 m above sea level.
Because the bulk of the ice sheet rests on bedrock high above current sea level, the East Antarctic Ice Sheet is more stable than its neighbours. However, the East Antarctic Ice Sheet has received less scientific attention than its more headline-grabbing neighbours. Its extent at the Last Glacial Maximum is comparatively poorly resolved, and its dynamics and the interior’s geomorphology is less well understood. In part, this is because this high, cold, windy place is still inaccessible, as well as huge.
Ice flow in East Antarctica
The East Antarctic Ice Sheet has a complex configuration, with ice velocity being slow near the ice divide, but feeding out into a number of ice streams. Many of these ice streams end in ice shelves, floating glacier ice that is no longer in contact with the bed. Many of these ice shelves receive snow and ice in their own right, from freezing sea water below or from snow falling on them from above. One of the largest ice streams in East Antarctica is the Lambert Glacier System, which drains around 16% of the ice sheet by area 2.
Topography of the East Antarctic Ice Sheet
Mountains hidden under the ice
The East Antarctic Ice Sheet may look smooth and flat, but the ice sheet covers whole mountain ranges. The Bed Elevation figure shows these mountains, which have beautiful valleys carved into them. Some of these valleys have a geomorphological signature that indicates that they were initially incised by rivers. The Gamburtsev Mountains are under 3 km thick ice in East Antarctica, and they can be seen and visualised by aerogeophysical surveys flown over the East Antarctic Ice Sheet. These mountains are located in the central East Antarctic Plate, and are around 400 km wide. Ice thickness varies considerably over these mountains, from 1-3 km thick 2. Other important features of East Antarctica include Dome C, which is a lowland area, and Ridge B, which rests over regions of high bedrock topography.
The Transantarctic Mountains
The East Antarctic Ice Sheet is bounded by the Transantartic Mountains, which are around 4 km high and are visible as nunataks, poking up out the top of the ice sheet. This 2000 km long mountain range divides the East and West Antarctic ice sheets 2. The East Antarctic Ice Sheet also contains the enigmatic Dry Valleys, a region with so little precipitation that the region has been ice free for millions of years.
In the Google May below, you can explore the Byrd Glacier, which flows through the Transantarctic Mountains into the giant Ross Ice Shelf. Byrd Glacier is a major ice stream, and you can see the convergent flow as it is channelled through a valley in the mountain range.
View Byrd Glacier in a larger map
Prince Charles Mountains
Another mountain range is the Prince Charles Mountains, located near the Lambert Glacier. These mountains are important geologically, as they contain sediments deposited millions of years ago by the first Antarctic ice sheets. The mountains reach elevations of 3228 m, and the mountain range is 260 km long. They were only discovered in the late 1940s.
The photographs below are from the Prince Charles Mountains, taken by Professor Michael Hambrey during fieldwork there.
Another way in which scientists can analyse the rocks hidden underneath the East Antarctic Ice Sheet is by looking at mineral grains washed up in sediment drifts on the continental slope, in deep sea water. These mineral grains were eroded by the ice sheet, transported to its edge, and then released into the open as icebergs calved off the edge of the massive ice sheet. Analysis of these sediments help scientists analyse the evolution of the Lambert Glacier system over the last 34 million years 3. Over millions of years, this ice stream incised the trough by 1.6-2.5 km.
Subglacial lakes underneath East Antarctica
Although much of the East Antarctic Ice Sheet is very cold, and above pressure melting point, in some places, the ice is so thick that it does reach this magic temperature. In some of the deep troughs, where ice is over 3.5 km thick, pressure melting point is reached 2. This means that there is water underneath the ice sheet. The East Antarctic Ice Sheet therefore hides a huge number of subglacial lakes, the largest being Subglacial Lake Vostok 4.
The Dry Valleys of East Antarctica
The Dry Valleys of East Antarctica are in Southern Victoria Land, near McMurdo Station. This is the largest ice-free part of Antarctica, with glaciers limited by the extremely low precipitation they receive. These glaciers receive only 10 mm of water through precipitation per year, and mean annual air temperature is around -19.8°C. These cold-based glaciers move very little and very slowly, and some of the ice in the Dry Valleys is thought to be millions of years old.
These photographs of the Dry Valleys are credit Professor Michael Hambrey.
You can use the Google Map below to explore the Dry Valleys of East Antarctica by yourself.
View Larger Map
Climate of the East Antarctic Ice Sheet
The East Antarctic Ice Sheet is very cold. Temperatures as low as -85°C have been recorded at Dome C 5. It is also dry, receiving very little annual precipitation and far less than the Antarctic Peninsula Ice Sheet6. East Antarctica is so cold, high and dry, that it creates its own climate 7.
Surface mass balance
The surface mass balance of the East Antarctic Ice Sheet is shown in this figure, from Van den Broeke et al., 2011. Surface mass balance is the sum of accumulation (snow, rain) and melting (by sublimation and run off). This can be calculated using measurements from satellites8. This figure is the average surface mass balance from 1989-2009. This figure shows that the Antarctic Peninsula, West Antarctic Ice Sheet and the coastal regions of the East Antarctic Ice Sheet are significantly wetter than the ice sheet interior. Peak values of 3000 kg per metre per year of accumulation are experienced in the western Antarctic Peninsula, but the interior of the East Antarctic Ice Sheet receives less than 50 kg per metre per year.
Although there has been rapid ice sheet thinning observed in West Antarctica and on the Antarctic Peninsula, so far, this has not been observed around East Antarctica 9. In fact, parts of the East Antarctic Ice Sheet are thickening, especially deep in the interior, which contrasts strongly with the observed rapid thinning of the West Antarctic Ice Sheet 10. Shepherd et al. indicate that the East Antarctic Ice Sheet gained 14 ± 43 gigatonnes between 1992 and 2011 11. This is because precipitation in the interior increases under a generally warmer global climate 7.
Although most of the glaciers in this region are close to mass balance (input = output), some of the glaciers of the East Antarctic Ice Sheet are thinning and receding. These glaciers include Totten Glacier, the largest discharger of ice within the ice sheet 7. Moscow University Ice Shelf and most glaciers in Wilkes Land are also thinning. These glaciers are grounded well below sea level.
The East Antarctic Ice Sheet is currently cooling slightly 12, probably as a result of changes in the circumpolar vortex. This results in falling pressure over Marie Byrd Land and northerly flow anomalies 6. The warming over the Antarctic Peninsula and West Antarctica and cooling over East Antarctica is also related to changes in regional sea surface temperatures, broader changes in atmospheric circulation and changes in sea ice13.
Some models predict that continued climate change will actually result in increased snowfall around East Antarctica. A recent numerical ice sheet model projected climate change and snow fall in East Antarctica until AD2500 14. However, this increased snowfall increased ice discharge around the continent, meaning that it had little effect in mitigating global sea level rise caused by the melting of other glaciers and ice caps, and global ocean thermal expansion. Generally, dynamically driven ice loss as a result of increased snowfall was around 30-60% of the mass gain. Indeed, the authors reported a 1.25 m global sea level contribution from the East Antarctic Ice Sheet by 2500 under the strongest warming scenarios 14.
To learn more about the East Antarctic Ice Sheet, you can read:
1. Fretwell, L.O., H. D. Pritchard, D. G. Vaughan, J. L. Bamber, N. E. Barrand, R. Bell, C. Bianchi, R. G. Bingham, D. D. Blankenship, G. Casassa, G. Catania, D. Callens, H. Conway, A. J. Cook, H. F. J. Corr, D. Damaske, V. Damm, F. Ferraccioli, R. Forsberg, S. Fujita, P. Gogineni, J. A. Griggs, R. C. A. Hindmarsh, P. Holmlund, J. W. Holt, R. W. Jacobel, A. Jenkins, W. Jokat, T. Jordan, E. C. King, J. Kohler, W. Krabill, M. Riger-Kusk, K. A. Langley, G. Leitchenkov, C. Leuschen, B. P. Luyendyk, K. Matsuoka, Y. Nogi, O. A. Nost, S. V. Popov, E. Rignot, D. M. Rippin, A. Riviera, J. Roberts, N. Ross, M. J. Siegert, A. M. Smith, D. Steinhage, M. Studinger, B. Sun, B. K. Tinto, B. C. Welch, D. A. Young, C. Xiangbin & Zirizzotti, A. Bedmap2: improved ice bed, surface and thickness datasets for Antarctica. The Cryosphere 7, 375-393 (2013).
2. Siegert, M.J. Antarctic subglacial topography and ice-sheet evolution. Earth Surface Processes and Landforms 33, 646-660 (2008).
3. Thomson, S.N., Reiners, P.W., Hemming, S.R. & Gehrels, G.E. The contribution of glacial erosion to shaping the hidden landscape of East Antarctica. Nature Geosci 6, 203-207 (2013).
4. Siegert, M.J., Carter, S., Tabacco, I., Popov, S. & Blankenship, D.D. A revised inventory of Antarctic subglacial lakes. Antarctic Science 17, 453-460 (2005).
5. Allison, I., Wendler, G. & Radok, U. Climatology of the East Antarctic ice sheet (100°E to 140°E) derived from automatic weather stations. Journal of Geophysical Research: Atmospheres 98, 8815-8823 (1993).
6. van den Broeke, M.R. & van Lipzig, N.P.M. Changes in Antarctic temperature, wind and precipitation in response to the Antarctic Oscillation. Annals of Glaciology 39, 119-126 (2004).
7. Rignot, E. Changes in ice dynamics and mass balance of the Antarctic ice sheet. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364, 1637-1655 (2006).
9. Pritchard, H.D., Arthern, R.J., Vaughan, D.G. & Edwards, L.A. Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets. Nature 461, 971-975 (2009).
10. Davis, C.H., Li, Y., McConnell, J.R., Frey, M.M. & Hanna, E. Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise. Science 308, 1898-1901 (2005).
11. Shepherd, A., Ivins, E.R., A, G., Barletta, V.R., Bentley, M.J., Bettadpur, S., Briggs, K.H., Bromwich, D.H., Forsberg, R., Galin, N., Horwath, M., Jacobs, S., Joughin, I., King, M.A., Lenaerts, J.T.M., Li, J., Ligtenberg, S.R.M., Luckman, A., Luthcke, S.B., McMillan, M., Meister, R., Milne, G., Mouginot, J., Muir, A., Nicolas, J.P., Paden, J., Payne, A.J., Pritchard, H., Rignot, E., Rott, H., Sørensen, L.S., Scambos, T.A., Scheuchl, B., Schrama, E.J.O., Smith, B., Sundal, A.V., van Angelen, J.H., van de Berg, W.J., van den Broeke, M.R., Vaughan, D.G., Velicogna, I., Wahr, J., Whitehouse, P.L., Wingham, D.J., Yi, D., Young, D. & Zwally, H.J. A Reconciled Estimate of Ice-Sheet Mass Balance. Science 338, 1183-1189 (2012).
12. Turner, J., Colwell, S.R., Marshall, G.J., Lachlan-Cope, T.A., Carelton, A.M., Jones, P.D., Lagun, V., Reid, P.A. & Iagovkina, S. Antarctic climate change during the last 50 years. International Journal of Climatology 25, 279-294 (2005).
13. Steig, E.J., Schneider, D.P., Rutherford, S.D., Mann, M.E., Comiso, J.C. & Shindell, D.T. Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature 457, 459-462 (2009).
14. Winkelmann, R., Levermann, A., Martin, M.A. & Frieler, K. Increased future ice discharge from Antarctica owing to higher snowfall. Nature 492, 239-243 (2012).