13,680 sq km of Antarctic ice collapses

The scientists at the US National Snow and Ice Data Center (NSIDC) at the University of Colorado, USA, have based their calculation on the satellite imagery received by it.

The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwest Antarctic Peninsula, about 1,600 kilometers south of South America.

In the past 50 years, the western Antarctic Peninsula has experienced the biggest temperature increase on Earth, rising by 0.5 degree Celsius per decade.

NSIDC Lead Scientist Ted Scambos, who first spotted the disintegration in March, said, "We believe the Wilkins has been in place for at least a few hundred years. But warm air and exposure to ocean waves are causing a break-up." Satellite images, scientists say, indicate that the Wilkins began its collapse on February 28 and a large iceberg, 41 by 2.5 kilometers, fell away from the ice shelf's southwestern front, triggering a runaway disintegration of 405 square kilometers of the shelf interior.

The edge of the shelf crumbled into the sky-blue pattern of exposed deep glacial ice that has become characteristic of climate-induced ice shelf break-ups such as the Larsen B in 2002. A narrow beam of intact ice, just 6 kilometers wide was protecting the remaining shelf from further breakup as of March 23, they said.

Scientists track ice shelves and study collapses carefully because some of them hold back glaciers, which if unleashed, can accelerate and raise sea level.

Scambos said, "The Wilkins disintegration won't raise sea level because it already floats in the ocean, and few glaciers flow into it.

However, the collapse underscores that the Wilkins region has experienced an intense melt season. Regional sea ice has all but vanished, leaving the ice shelf exposed to the action of waves."

With Antarctica's summer melt season drawing to a close, scientists do not expect the Wilkins to further disintegrate in the next several months. "This unusual show is over for this season," Scambos said.

Images from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and data from ICESat showed that the ice shelf was in a state of collapse since March. Scambos then alerted colleagues around the world, seeking to ensure that every means of gathering information was focused on the break-up.

British Antarctic Survey (BAS) mounted an overflight of the crumbling shelf, collecting video footage and other observations. BAS glaciologist David Vaughan said of the ice shelf, which is supported by a single strip of ice strung between two islands.

"Wilkins is the largest ice shelf on West Antarctica yet to be threatened. This shelf is hanging by a thread."

Associate Professor Cheng-Chien Liu at Taiwan's National Cheng-Kung University (NCKU) also responded, requesting high-resolution colour satellite images of the area from Taiwan's Formosat-2 satellite, operated by the National Space Organization.