4um: Massive ice shelf collapsing off Antarctica

Title: Massive ice shelf collapsing off Antarctica
Source: http://www.news.com/
URL Source: http://www.news.com/2300-11395_3-6235636-1.html
Published: Mar 26, 2008
Author: http://www.news.com/
Post Date: 2008-03-26 12:01:20 by robin
Keywords: None
Views: 1219
Comments: 12

Scientists are citing "rapid climate change in a fast-warming region of Antarctica" as the cause of an initial collapse of the Wilkins Ice Shelf. The damage got started at the end of February when an iceberg dropped off and triggered the "runaway disintegration" of a 160-square-mile portion of the 5,282-square-mile shelf.

The ice shelf, which scientists speculate has floated in the Antarctic region for hundreds of years, is succumbing to recent rises in temperature in the area--an average of 0.9 degree Fahrenheit every 10 years for the last 50 years.

This series of pictures that show the beginning of the breakup were taken by NASA's Moderate Resolution Imaging Spectroradiometer sensor, which flies on its Earth Observing System Aqua and Terra satellites.

News of the disturbing collapse of a Manhattan-sized piece of western Antarctic ice was mildly reassuring in one way: the chunk itself wouldn't immediately start to melt, or unleash pent-up glaciers into the sea.

"Scientists said they are not concerned about a rise in sea level from the latest event, but say it's a sign of worsening global warming," reported the Associated Press.

As Dylan noted in his post, Antarctic ice shelves are "the leading edges of land-based glaciers." The shelves act like dams -- and we all know what happens when a dam breaks. In 1995 and 2002, when vast portions of the Larsen B ice shelf broke off and disintegrated, glaciers soon surged towards the sea.

But researchers say that the Wilkins Ice Shelf -- the larger sheet from which the now-fallen piece detached -- already floats in the ocean, with few glaciers flowing into it. When it collapses -- its lifespan is optimistically pegged at 15 years -- no glaciers will be released.

So that's reassuring. Or is it?

As the BBC reported last month, the British Antarctic Survey recently found "the clearest evidence yet" of glacial instabilities in West Antarctica, where three "rivers of ice" have accelerated their seaward course.

"If there is a feedback mechanism to make the ice sheet unstable, it will be most unstable in this region," said BAS researcher David Vaughan.

Could the disintegrating Wilkins Ice Shelf be part of such a feedback mechanism? Or is it a vast, icy canary in the coal mine of Earth? I'll ask the BAS and let you know.

My suggestion was it's time to build a boat. But the second article I posted said we still have time.

The ice caps on Greenland and Antartica have enough ice to raise worldwide sea levels by something like 170 feet.