Image: Wilkins Ice Shelf calving
ESA via AFP-Getty Images
This European Space Agency satellite image shows icebergs calving from the Wilkins Ice Shelf on the Antarctic Peninsula. An ice bridge, which effectively formed a barrier pinning back the ice, collapsed on April 5.
msnbc.com news services
updated 4/29/2009 11:56:19 AM ET 2009-04-29T15:56:19

New satellite images from the European Space Agency show massive amounts of ice are breaking away from an ice shelf on the western side of the Antarctic Peninsula, researchers said Wednesday.

The Wilkins Ice Shelf had been stable for most of the last century, but began retreating in the 1990s. Researchers believe it was held in place by an ice bridge linking Charcot Island to the Antarctic mainland.

But the 127-square-mile bridge lost two large chunks last year and then shattered completely on April 5.

"As a consequence of the collapse, the rifts, which had already featured along the northern ice front, widened and new cracks formed as the ice adjusted," the European Space Agency said in a statement Wednesday.

The first icebergs started to break away on Friday, and since then some 270 square miles of ice have already dropped into the sea, according to the satellite data. That's nearly the size of New York City and much more is expected to break off.

"There is little doubt that these changes are the result of atmospheric warming," said David Vaughan of the British Antarctic Survey.

"The retreat of Wilkins Ice Shelf is the latest and the largest of its kind," he said, adding that "eight separate ice shelves along the Antarctic Peninsula have shown signs of retreat over the last few decades."

Strong warming on peninsula
Average temperatures in the Antarctic Peninsula have risen by 3.8 degrees Fahrenheit over the past 50 years — higher than the average global rise, according to studies.

The loss of ice shelves — which are ice floating on the sea and linked to the coast — does not raise sea levels significantly because the ice is floating and already mostly submerged by the ocean.

But the big worry is that their loss will allow ice sheets on land to move faster, adding extra water to the seas.

Wilkins has almost no pent-up glaciers behind it, but ice shelves further south hold back vast volumes of ice.

The Wilkins shelf, which is the size of Jamaica, lost 14 percent of its mass last year, according to scientists.

Antarctic ice shelves to break up abruptly include the Larsen A in 1995 and the Larsen B in 2002.

Breakup to continue for weeks
Over the next several weeks, scientists estimate the Wilkins shelf will lose some 1,300 square miles — a piece larger than the state of Rhode Island.

Video: Arctic adventures One researcher said, however, that it was unclear how the situation would evolve.

"We are not sure if a new stable ice front will now form between Latady Island, Petrie Ice Rises and Dorsey Island," said Angelika Humbert of Germany's Muenster University Institute of Geophysics.

But even more ice could break off "if the connection to Latady Island is lost," she said, "though we have no indication that this will happen in the near future."

In the meantime, researchers said the quality and frequency of the ESA satellite images have allowed them to analyze the Wilkins shelf breakup far more effectively than any previous event.

"For the first time, I think, we can really begin to see the processes that have brought about the demise of the ice shelf," Vaughan said.

The Associated Press and Reuters contributed to this report.

Video: Changes in Wilkins Ice Bridge

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