Antarctic warming behind ice shelf collapse
April 6th, 2009 by Jim JustThe big news over the weekend was the collapse of the ice bridge which pinned the Wilkins Ice Shelf in place since the beginning of recorded history.
The context of that event is the warming of Antarctia.
Antarctic ice is melting far faster than believed possible. Updated scientific modeling on global warming projects up to one-third of all Antarctic sea ice is likely to melt by the end of the century and that ice melts in the Antarctic Peninsula and Western Ice Shelf will be greater and more rapid than expected, contributing significantly to dangerous sea level rises.
Ice shelves float on the water, so breakages will not directly raise sea levels. But when ice shelves break up, the glaciers and landed ice behind them then slide towards the ocean more rapidly, thus raising sea levels.
The West Antarctic Ice Sheet (WAIS) is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level. The WAIS rests on bedrock as deep as two kilometers underwater. The collapse of ice shelves provides exit routes for ice from further inland.
Joseph Romm sees this as a potentially catastrophic feedback loop:
The warmer it gets, the more unstable WAIS outlet glaciers will become. Since so much of the ice sheet is grounded underwater, rising sea levels may have the effect of lifting the sheets, allowing more – and increasingly warmer – water underneath, leading to further bottom melting, more ice shelf disintegration, accelerated glacial flow, and further sea level rise, and so on and on, another vicious cycle. The combination of global warming and accelerating sea level rise from Greenland could be the trigger for catastrophic collapse in the WAIS.
You can see the ice bridge and how it pins the Wilkins ice sheet together on this map.
