Tag Archives: Thwaites Glacier

Changing Antarctica

Antarctica is a vast ice sheet. The continent is larger than the United States of America, and has enough ice to raise global sea levels by ~58 m if it all melted. It is extremely cold, with very little surface melt.

However, it is changing rapidly. Parts of West Antarctica are grounded well below sea level, which can act to destabliise the ice sheet. Warm ocean currents are able to melt ice shelves from below, and cause a retreat of the grounding line of tidewater glaciers. These articles outline how Antarctica is changing.

West Antarctic Ice Sheet

These pages cover information on the West Antarctic Ice Sheet. This is the part of Antarctica west of the Transantarctic Mountains. It is characterised by a bed that is largely below sea level. The two largest ice streams draining the West Antarctic Ice Sheet are Pine Island Glacier and Thwaites Glacier.

Other relevant articles:

Landsat Image Mosaic of the West Antarctic Ice Sheet

Thwaites Glacier

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Thwaites Glacier, Antarctica, is of particular concern to scientists. Here, warm water is pushed up onto the continental shelf, where it flows along the bottom until it reaches the floating ice shelf in front of Thwaites Glacier.

Thwaites Glacier today is rapidly losing mass in response to changing atmospheric and oceanic conditions.

Thwaites Glacier
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What is the ice volume of Thwaites Glacier?

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Thwaites Glacier in West Antarctica is currently the focus of a major scientific campaign. Why is Thwaites Glacier of so much interest, however? How much ice is there, and how much would sea levels rise if it all melted?

Thwaites Glacier is roughly the size of UK (176 x103 km2). The glacier terminus is nearly 120 km wide, and the bed of the glacier reaches to >1000 m below sea level. Pine Island Glacier and Thwaites Glacier together account for 3% of grounded ice-sheet area, but they receive 7% of Antarctica’s snowfall1.

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Antarctica

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This page focuses on introducing the Antarctic Ice Sheet. Antarctica is actually composed of three ice sheets: the Antarctic Peninsula, the West Antarctic Ice Sheet, and the East Antarctic Ice Sheet.

You may also be interested in reading about the Patagonian Ice Sheet or the British-Irish Ice Sheet.

Antarctica StoryMap Series

You can learn more about Antarctica in the Antarctica StoryMap Series, a collection of four StoryMap Collections that explore Antarctica, it’s ecology and wildlife, how it is impacted by climate change and People in Antarctica.

Antarctica StoryMap Series

Freely available talks about Antarctica

This introductory lecture (21 minutes) introduces Antarctica, climate change and geopolitics with Dr Bethan Davies and Professor Klaus Dodds. This video is suitable for A-Level and post-16 students. You can also learn more about territorial claims in Antarctica in this excellent ESRI StoryMap.

Here, you can watch a more advanced lecture (1 hr) given by Dr Bethan Davies on climate change and her research in Antarctica. This video is suitable for undergraduate or postgraduate students or researchers.

West Antarctic Ice Sheet

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Introduction | Topography | Oceanography | Ice streams and ice shelves | References | Comments |

Introduction

Landsat Image Mosaic of Antarctica, showing the different ice sheets of Antarctica

The West Antarctic Ice Sheet (the WAIS) is capable of rapid change as it is a marine ice sheet and therefore could be unstable. It has the potential to raise global sea level by 3.3 m[1] over a matter of centuries. The Transantarctic Mountains divide the West Antarctic Ice Sheet from the East Antarctic Ice Sheet[2]. West Antarctica is approximately 97% ice-covered, and is 1.97 x 106 km2 in area. The West Antarctic Ice Sheet flows into the Bellingshausen, Weddell, Amundsen and Ross seas.

There are principally three sectors of the ice sheet, which flow northeast-ward into the Weddell Sea, westward into the Ross Ice Shelf and northward into the Amundsen/Bellingshausen seas. The highest elevations reached are 3000 m above sea level[2], occurring at the divides between these sectors. The size of the West Antarctic Ice Sheet is limited, despite its high average snow falls, by the faster speeds of its ice streams.

Topography

Images of the Amundsen Sea Embayment, showing: Landsat image (LIMA); BEDMAP bed elevation (from Lythe et al., 2001); and ice velocity (from Rignot et al. 2011)

The West Antarctic Ice Sheet is, in places, over 2000 m thick, with the geological floor well below sea level. The marine basins are variable, with both rough mountainous terrain and flat, deep oceanic basins[2], with a maximum depth of 2555 m below present sea level.

During past interglacials, the West Antarctic Ice Sheet has been completely removed[3], which is one of the arguments supporting a Marine Ice Sheet Instability hypothesis. During past glacials, the West Antarctic Ice Sheet extended to the continental shelf edge[4-6], drained by numerous ice streams[7, 8], such as the Pine Island and Thwaites ice streams, which flow out into the Amundsen Sea. In the four-panel figure opposite, you can see these two ice streams clearly. They are grounded below sea level and drain a large proportion of the West Antarctic Ice Sheet.

In the map below, showing ice thicknesses across the Antarctic continent, you can see that the West Antarctic Ice Sheet has ice thicknesses of up to 2000 m, but that it is largely grounded below sea level. The maximum altitude of the ice surface is less than 2000 m above sea level. The West Antarctic Ice Sheet is divided from the East Antarctic Ice Sheet by the large Transantarctic Mountains.

The BEDMAP 2 dataset shows how ice thickness across the Antarctic continent is variable, with thin ice over the mountains and thick ice over East Antarctica. The cross section shows how the West Antarctic Ice Sheet is grounded below sea level.

The BEDMAP 2 dataset (Fretwell et al. 2013) shows how ice thickness across the Antarctic continent is variable, with thin ice over the mountains and thick ice over East Antarctica. The cross section shows how the West Antarctic Ice Sheet is grounded below sea level.

Oceanography

Simplified schematic map of ocean currents of the Southern Ocean.

West Antarctica is surrounded by a strong clockwise circumpolar circulation. These currents play a significant role in the global thermohaline circulation, and are one of the reasons why Antarctica is so cold.

At shallower depths, Circumpolar Deep Water can move across the continental shelf and reach the underside of ice shelves[2], which it can rapidly melt due to its relatively warm temperatures.

Ice streams and ice shelves

Simplified cartoon of a tributary glacier feeding into an ice shelf, showing the grounding line (where the glacier begins to float).

The West Antarctic Ice Sheet is drained by several large ice streams. The basal sediments of West Antarctica comprise soft marine sediments. Combined with geothermal heating at the base, this is sufficient to allow glaciers to slide rapidly: see Glacial Processes. This ice flow is partly constrained by buttressing ice shelves. The ice streams flow from an inland reservoir of ice towards the ocean, passing over a grounding line and, in places, into an ice shelf. Nearly all the precipitation received in West Antarctica eventually passes through these ice streams[2].

Further reading

To learn more about the West Antarctic Ice Sheet, you can read:

Go to top or jump to Antarctic Peninsula Ice Sheet.

References

1.            Bamber, J.L., Riva, R.E.M., Vermeersen, B.L.A., and Le Brocq, A.M., 2009. Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice Sheet. Science, 2009. 324(5929): p. 901-903.

2.            Bindschadler, R., 2006. The environment and evolution of the West Antarctic ice sheet: setting the stage. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2006. 364(1844): p. 1583-1605.

3.            Scherer, R.P., Aldahan, A., Tulaczyk, S., Possnert, G., Engelhardt, H., and Kamb, B., 1998. Pleistocene Collapse of the West Antarctic Ice Sheet. Science, 1998. 281(5373): p. 82-85.

4.            Bentley, M.J. and Anderson, J.B., 1998. Glacial and marine geological evidence for the ice sheet configuration in the Weddell Sea-Antarctic Peninsula region during the Last Glacial Maximum. Antarctic Science, 1998. 10(3): p. 309-325.

5.            Lowe, A.L. and Anderson, J.B., 2002. Reconstruction of the West Antarctic ice sheet in Pine Island Bay during the Last Glacial Maximum and its subsequent retreat history. Quaternary Science Reviews, 2002. 21(16-17): p. 1879-1897.

6.            Anderson, J.B., Shipp, S.S., Lowe, A.L., Wellner, J.S., and Mosola, A.B., 2002. The Antarctic Ice Sheet during the Last Glacial Maximum and its subsequent retreat history: a review. Quaternary Science Reviews, 2002. 21(1-3): p. 49-70.

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.

8.            Livingstone, S.J., O Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., and Jamieson, S.S.R., 2012. Antarctic palaeo-ice streams. Earth-Science Reviews, 2012. 111(1-2): p. 90-128.

Go to top or jump to Antarctic Peninsula Ice Sheet.