If the West Antarctica ice sheet collapses, sea levels could rise more than expected

Ice Melt Could Increase Sea Level Risks
AP
Feb. 7, 2009

...a report in Friday's edition of the journal Science warns that factors not previously considered could one day boost that increase to up to 21 feet in some areas.

The study did not list a time frame for such a dramatic change. But co-author Peter Clark, a geoscientist at Oregon State University, stressed that they "aren't suggesting that a collapse of the West Antarctic Ice Sheet is imminent."

The most recent International Panel on Climate Change report estimated sea level rise of up to 3 feet by the end of this century...

Earlier research has focused on melting ice adding water to the oceans and on thermal expansion of sea water in a warmer climate over long periods of time...

--When an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it. That means sea levels could fall near Antarctica and rise more than expected in the northern hemisphere.

--Antarctic bedrock that currently sits under the weight of the ice sheet will rebound from the weight, pushing some water out into the ocean.

--The melting of the West Antarctic ice sheet will cause the Earth's rotation axis to shift, potentially moving water northward.

"The net effect of all of these processes is that if the West Antarctic ice sheet collapses, the rise in sea levels around many coastal regions will be as much as 25 per cent more than expected," Mitrovica said in a statement.