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Antarctic ice shelf collapsing
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NewsByte on 26 March, 2008 03:33:50
 
By DHARAM SHOURIE
New York, March 26: A huge chunk of ice measuring 13,680 square km or about
seven times the size of Manhattan island has begun to collapse because of
climate change in the fast-warming region of Antarctica.
The scientists at the US National Snow and Ice Data Centre (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 km south of South America.
In the past 50 years, the western Antarctic Peninsula has experienced the
biggest temperature increase on earth, rising by 0.5º 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 km, fell away from the ice
shelf’s southwestern front, triggering a runaway disintegration of 405 square
km 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 km
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.
Mr 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," Mr 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.
Mr 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 Organisation.
Mr Liu said, "It looks as if something is slicing the ice shelf piece by piece
on an incredible scale, km long but only a few hundred meters in width." (PTI)