The West Antarctic Ice Sheet (WAIS) blankets the Antarctic continent west of the Transantarctic Mountains. 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.
The interior ice flows slowly over rough bedrock. Downstream, the ice is channelled into anomalously fast-flowing ice streams , which 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 the West Antarcitc was a marine seaway. The rapid ice-stream flow is due to the water-saturated clay.
It has been suggested that its marine nature and dissection by ice streams makes the WAIS vulnerable to rapid retreat due to climate warming. Several decades of research, primarily by the American-led West Antarctic Ice Sheet Initiative and by glaciologists at the British Antarctic Survey and other British institutions, has sought to evaluate the liklihood of WAIS collapse. Were the ice sheet to collapse completely (an unlikely event), its 3.2 million km2 of ice would contribute about 5 meters to global sea level.
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