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Source: ONE News -
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An ice bridge which had apparently held a vast Antarctic ice
shelf in place during recorded history has shattered and could
herald a wider collapse linked to global warming, a leading
scientist said.
"It's amazing how the ice has ruptured. Two days ago it was
intact," David Vaughan, a glaciologist with the British Antarctic
Survey, told Reuters of a satellite image of the Wilkins Ice Shelf
on the Antarctic Peninsula.
The satellite picture, from the European Space Agency (ESA), showed
that a 40 km long strip of ice believed to pin the Wilkins Ice
Shelf in place had splintered at its narrowest point, about 500
metres wide.
"We've waited a long time to see this," he said.
The Wilkins, now the size of Jamaica or the US state of
Connecticut, is one of 10 shelves to have shrunk or collapsed in
recent years on the Antarctic Peninsula, where temperatures have
risen in recent decades apparently because of global warming.
The ESA picture showed a jumble of huge flat-topped icebergs in the
sea where the ice bridge had been on Friday, pinning the Wilkins to
the coast and running northwest to Charcot Islandt.
"Charcot Island will be a real island for the first time in
history," Vaughan said.
Vaughan, who landed on the flat-topped ice bridge on the Wilkins in
January in a ski-equipped plane with other scientists and two
Reuters reporters, said change in Antarctica was rarely so
dramatic. It was the first - and last - visit to the area.
The loss of the ice bridge, jutting about 20 metres out of the
water and which was almost 100 km wide in 1950, may now allow ocean
currents to wash away far more of the Wilkins shelf.
"My feeling is that we will lose more of the ice, but there will be
a remnant to the south," said Vaughan. Ice shelves float on the
water, formed by ice spilling off Antarctica, and can be hundreds
of metres thick.
Nine other shelves have receded or collapsed around the Antarctic
Peninsula in the past 50 years, often abruptly like the Larsen A in
1995 or the Larsen B in 2002 further north.
Disappear from map
Cores of sediments on the seabed indicate that some of these ice
shelves had been in place for at least 10,000 years. Vaughan said
an ice shelf would take many hundreds of years to form.
In January, the remaining ice bridge had been surrounded by
icebergs the size of shopping malls, many of them trapped in sea
ice. A few seals were visible lolling on sea ice in the low
Antarctic sunshine.
On that visit, Vaughan put up a GPS satellite monitoring device and
predicted the ice bridge would break within weeks. The plane left
quickly, in case the ice was unstable on a part of the world about
to disappear from the map.
Temperatures on the Antarctic Peninsula have risen by up to about 3
Celsius in the past 50 years, the fastest rate of warming in the
Southern Hemisphere.
"We believe the warming on the Antarctic Peninsla is related to
global climate change, though the links are not entirely clear,"
Vaughan said. Antarctica's response to warming will go a long way
to deciding the pace of global sea level rise.
About 175 nations have been meeting in Bonn, Germany, since March
29 as part of a push to agree by the end of 2009 a new UN treaty to
combat climate change. The talks end on April 8.
The loss of ice shelves does not affect sea levels - floating ice
contracts as it melts and so does not raise ocean levels. But their
loss can allow glaciers on land to slide more rapidly towards the
sea, adding water to the oceans.
The Wilkins does not have much ice pent up behind it. But bigger
ice shelves to the south on the frozen continent, where no major
warming has been detected, hold back far more ice.
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