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Antarctic Ice Shelf Disintegration Underscores a Warming World

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Satellite imagery from the National Snow and Ice Data Center at the University of Colorado at Boulder reveals that a 13,680 square kilometer (5,282 square mile) ice shelf has begun to collapse because of rapid climate change in a fast-warming region of Antarctica.

 

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The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwest Antarctic Peninsula, about 1,000 miles 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 (0.9 degree Fahrenheit) 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 indicate that the Wilkins began its collapse on February 28; data revealed that a large iceberg, 41 by 2.5 kilometers (25.5 by 1.5 miles), fell away from the ice shelf's southwestern front, triggering a runaway disintegration of 405 square kilometers (160 square miles) of the shelf interior (Figure 1). 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 (3.7 miles) was protecting the remaining shelf from further breakup as of March 23 (Figure 2).

 

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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. "But come January, we'll be watching to see if the Wilkins continues to fall apart."

 

Real-time collaboration

Images from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and data from ICESat showed that the ice shelf was in a state of collapse in 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 color satellite images of the area from Taiwan's Formosat-2 satellite (Figure 3), operated by the National Space Organization. Cheng-Chien Liu said, "It looks as if something is slicing the ice shelf piece by piece on an incredible scale, kilometers long but only a few hundred meters in width."

 

South American scientists also got involved. Andrés Rivera and Gino Cassasa at the Laboratorio de Glaciología y Cambio Climático at the Centro de Estudios Científicos in Chile (CECS), acquired images of the Wilkins from the ASTER instrument, aboard NASA's Terra satellite.

 

The combined efforts of these international teams have begun to provide observational data that will improve scientific understanding of the mechanisms behind ice shelf collapse. Scambos said, "The Wilkins is an example of an event we don't see very often. But it's a key process in being able to predict how sea level will change in the future."

 

More information

The Wilkins is one of a string of ice shelves that have collapsed in the West Antarctic Peninsula in the past thirty years. The Larsen B became the most well-known of these, disappearing in just over thirty days in 2002. The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones Ice Shelf collapses also underscore the unprecedented warming in this region of Antarctica.

 

Watch the Movie

 

http://nsidc.org/news/images/20080325_wilk...imation_low.mov

 

Stephanie Renfrow, NSIDC: srenfrow@nsidc.org or +1 303 492-1497 (se habla Español)

Athena Dinar, BAS: amdi@bas.ac.uk or +44 (0)1223 221414

Cheng-Chien Liu, NCKU: ccliu88@mail.ncku.eduspam or +886-6-2757575 X65422

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Guest Jocelyne Landeau-Constantin

The European Space Agency (ESA) reported on Friday that the Wilkins Shelf, an enormous Antarctic ice shelf half the size of Scotland, could break away from the continent very soon.

 

According to reports, only a thin strip of ice connects it to the Charcot Island, and cracks are expanding rapidly. This is the largest shelf of ice so far to have disintegrated in the Antarctic.

 

In February 2008, the shelf lost 425 square kilometres (164 square miles) of ice, followed by a loss of another 62 square miles in May 2008.

 

"During the last year the ice shelf has lost about 1800 square kilometers (694 square miles), or about 14 percent of its size," said Angelika Humbert from the Institute of Geophysics at University of Münster in Germany. Scientists say that the shelf, if it detaches from the mainland, won't cause an increase in sea levels, as it is already floating.

 

Most scientists believe that the incident is further evidence of global warming. Average temperatures in the Antarctic peninsula have increased by about 2.5 degrees Celsius (3.8 degrees Fahrenheit) in the past fifty years.

 

http://www.esa.int/esaCP/SEMD07EH1TF_index_0.html

 

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The island visible in the upper left of the image is Charcot Island. The Wilkins Ice Shelf is connected to these by an ice bridge which is approximately 100 km long and only few km wide. Should the ice bridge break up due to increasing temperatures in the Antarctic spring, this would remove the stabilising factor that has been keeping the ice sheet grounded to the peninsula.

 

 

The above animation is comprised of images acquired by Envisat’s Advanced Synthetic Aperture Radar (ASAR). The ice bridge is visible as a narrow strip in the image centre.

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