April 28, 2009

Massive Antarctic Peninsula Ice Bridge Collapses

A segment of an Antarctic ice shelf about the size of New York City has fallen into the sea this month following an ice bridge collapse, scientists said Tuesday.

Satellite images depict the collapse of an ice bridge that previously connected Charcot Island to Antarctica.

The ice bridge apparently collapsed on April 5, removing about 330 sq km of ice, according to the European Space Agency.

"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 in the days that followed," said the ESA.

"On 24 April, the satellite data showed that the first icebergs had started to break away from the fragile ice shelf. A very rough estimate suggests that, so far, about 700 sq km of ice has been lost from the Wilkins Ice Shelf."

Angelika Humbert, glaciologist at the Institute of Geophysics at the University of Muenster in Germany, said the recent collapse represents the latest of about 10 shelves in the region to begin their retreat.

Although the ice bridge fell quickly, the discharge of ice is expected to continue for weeks.

Humbert told Reuters that she believes Wilkins could lose 800 to 3,000 sq kms after the ice bridge collapse. The Wilkins shelf has already shrunk by about a third from its original 16,000 sq kms when first spotted decades ago.

The UN Climate Panel has linked such activity to global warming. Temperatures on the Peninsula have increased by 5.4 degrees Fahrenheit this century.

Nine shelves have receded or collapsed around the Antarctic Peninsula in the past 50 years.

"The retreat of Wilkins Ice Shelf is the latest and the largest of its kind," said David Vaughan from the British Antarctic Survey.

"Eight separate ice shelves along the Antarctic Peninsula have shown signs of retreat over the last few decades. There is little doubt that these changes are the result of atmospheric warming on the Antarctic Peninsula, which has been the most rapid in the Southern Hemisphere."

"The changes to Wilkins Ice Shelf provide a fabulous natural laboratory that will allow us to understand how ice shelves respond to climate change and what the future will hold for the rest of Antarctica," he added.

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


Image 2: The figure displays the Envisat Advanced Synthetic Aperture Radar (ASAR) image from 27 April 2009 superimposed on an image from 24 April 2009. The margins of the collapsed ice bridge that formerly connected Charcot and Latady Islands are outlined in white. The demise of the ice bridge led to a destabilisation of the northern ice front of the Wilkins Ice Shelf, where the first icebergs calved off on 20 April 2009 (area denoted in red). Credits: ESA (Annotations by A. Humbert, Mnster University)


On the Net: