The West Antarctic Ice Sheet (WAIS) blankets the continent of Antarctica west of the Transantarctic Mountains, covering the area called "Lesser Antarctica". The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea. It is estimated that it contains seven million cubic miles of ice. It has been suggested that Geographic Realms be merged into this article or section. ... Categories: Antarctica geography stubs | Geography of Antarctica | Ross Dependency ... An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²). The only current ice sheets are Antarctic and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of Canada... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... Ross Ice Shelf in 1997 Ross Ice Shelf with Royal Society Range in the background, 1999 (NOAA) The Ross Ice Shelf (81°30′S 175°00′W) is the largest ice shelf of Antarctica (an area of half a million square kilometres, and about 800 km across: about the size... The calving of A-38 off Ronne ice shelf The Filchner-Ronne ice shelf is in Antarctica bordering the Weddell Sea. ... The Amundsen Sea, named for Norwegian polar explorer Roald Amundsen, is an arm of the Southern Ocean off Marie Byrd Land in western Antarctica. ...

Description

The weight of Antarctica's ice is so enormous that it has literally pressed the continent two thirds of a mile into the earth. Under the massive forces of their own weight, the ice sheets deform and drag themselves outward. The interior ice flows slowly over rough bedrock. Bedrock is the native consolidated rock underlying the Earths surface. ...

Away from the interior, the ice is channelled into anomalously fast-flowing ice streams, transporting ice from the center of the continent to the sea. These streams are separated by slow-flowing ice ridges. The inter-stream ridges are frozen to the bed while the bed beneath the ice streams consists of water-saturated clay. The clay was deposited before the ice sheet occupied the region, when much of West Antarctica was a marine seaway. The rapid ice-stream flow is due to the water-saturated clay. An Ice stream is a region of an ice sheet that moves significantly faster than the surrounding ice. ... Quaternary clay in Estonia. ...

When ice streams finally reach the coast and push out across the ocean, they pass over rocky terrain, anchoring themselves to the irregular rocks to form a hinge. The ice will continue to grow outward onto the water. The result is a large, floating shelf of ice affixed to the continent. [1]

Potential collapse of the WAIS

In January 2006, in a UK government-commissioned report, the head of the British Antarctic Survey, Chris Rapley, warned that this huge west Antarctic ice sheet may be starting to disintegrate, an event that could raise sea levels by 16 feet. [Estimates by others have ranged from 20 to 50 feet.] Rapley said a previous Intergovernmental Panel on Climate Change report playing down worries about the ice sheet's stability should be revised. "The last IPCC report characterized Antarctica as a slumbering giant in terms of climate change," he wrote. "I would say it is now an awakened giant. There is real concern." [2] BAS headquarters The British Antarctic Survey (BAS), formerly the Falkland Islands Dependencies Survey (FIDS), is an institute of the Natural Environment Research Council, and has, for the last fifty years, undertaken the majority of Britains scientific research on and around the Antarctic continent. ...

Rapley said, "Parts of the Antarctic ice sheet that rest on bedrock below sea level have begun to discharge ice fast enough to make a significant contribution to sea level rise. Understanding the reason for this change is urgent in order to be able to predict how much ice may ultimately be discharged and over what timescale. Current computer models do not include the effect of liquid water on ice sheet sliding and flow, and so provide only conservative estimates of future behaviour." [3]

Jim Hansen, a senior NASA scientist who is a leading climate adviser to the US government, said the results were deeply worrying. “Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid,” he said. [4]

Indications that climate change may be affecting the west Antarctic ice sheet comes from three glaciers, including Pine Island and Thwaites. Data reveal they are losing more ice - mainly through the calving of icebergs - than is being replaced by snowfall. According to a preliminary analysis, the difference between the mass lost and mass replaced is about 60%. The melting of these three glaciers alone is contributing an estimated one-tenth of an inch per year to the rise in the worldwide sea level. [5]

External links

• U.S. West Antarctic Ice Sheet Initiative
• U.S. National Snow and Ice Data Center Antarctic News
• U.S. National Science Foundation: Antactic Science Section
• British Antarctic Survey: About Antarctica