msnbc.com
updated 7/11/2008 1:28:22 PM ET 2008-07-11T17:28:22

New satellite images show that an Antarctic ice shelf continues to disintegrate — and even more surprising is that it's happening during the Southern Hemisphere's winter.

Experts warned last March, at the end of the Antarctic summer, that the Wilkins Ice Shelf was disintegrating more quickly, but they expected that the winter cold would put the trend in a temporary deep freeze.

At 6,000 square miles in size, Wilkins "is the most recent in a long, and growing, list of ice shelves on the Antarctic Peninsula that are responding to the rapid warming that has occurred in this area over the last 50 years," David Vaughan of the British Antarctic Survey said in a statement released by the European Space Agency as it revealed the satellite images late Thursday.

"Current events are showing that we were being too conservative, when we made the prediction in the early 1990s that Wilkins Ice Shelf would be lost within 30 years," he added. "The truth is it is going more quickly than we guessed."

Warmer water melting ice?
Ted Scambos, an expert with the U.S. National Snow and Ice Data Center, said warm sea water appears to be "reaching the underside of the Wilkins Ice Shelf and thinning it rapidly —  and perhaps reaching the surface, or at least mixing with surface waters."

Video: Ice shelf's demise "The scale of rifting in the newly removed areas seems larger, and the pieces are moving out as large bergs and not toppled, finely-divided ice melange," he added.

Scambos noted that "the persistently low sea ice cover in the area" could also be contributing to the breakup.

The satellite images, taken between May 30 and July 9, show how a piece of the shelf that connects to Charcot Island off Antarctica had narrowed to about 1.7 miles wide. By July 8, a fracture that could sever the ice bridge was visible.

"Since the connection to the island ... helps to stabilize the ice shelf, it is likely the breakup of the bridge will put the remainder of the ice shelf at risk," the European Space Agency said.

The breakup of ice shelves doesn't raise sea levels because that ice is already on top of sea waters, but their disintegration does speed up the process of glacial ice sliding into the seas from land areas on Antarctica and Arctic areas like Greenland. And that process does raise sea levels.

Other shelves have collapsed
The Wilkins Ice Shelf, a broad plate on the Antarctic Peninsula across from the tip of South America, is connected to the Charcot and Latady islands. It had been stable for most of the last century before it began retreating in the 1990s.

Other Antarctic ice shelves to collapse over the last 30 years are Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and Jones.

In Argentina, just north of Wilkins, an inland glacier last week began calving even though it, too, is in the dead of winter.

Perito Moreno, an Argentine glacier that draws tourists from around the world, even saw the collapse Wednesday of an ice tunnel that forms and disintegrates every four or five years.

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