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- (ENN) -- A large section of an ice shelf
on the Antarctic Peninsula has broken away -- a possible result of global
warming, say scientists at the University of Colorado-based National Snow
and Ice Data Center.
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- Recent satellite images show that a section
about 40 kilometers long and five kilometers wide broke off, according
to Ted Scambos, a research associate at the Cooperative Institute for Research
in Environmental Sciences, a joint institute of CU-Boulder and the National
Oceanic and Atmospheric Administration.
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- NSIDC researchers spotted the event within
a few days of its occurrence in late February after analyzing images obtained
with a radiometer aboard a polar-orbiting NOAA satellite.
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- A second image from March 23 confirmed
the disintegrated area of ice, about 200 square kilometers in size, on
a shelf known as the Larsen B Ice Shelf.
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- "The February 26 image shows that
much of the ice was already gone," said Scambos. "The March 23
image made it crystal clear that a significant portion of the ice shelf
had broken off."
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- In Rapid Retreat
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- The satellite pictures appear to confirm
earlier studies by the British Antarctic Survey that predicted the 12,000-square-kilometer
ice shelf was nearing its stability limit. Researchers believe it has retreated
too far to be able to brace itself against the rocky peninsulas and islands
that flank it.
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- If the model is correct, the ice shelf
will continue to crumble rapidly beginning early next year, said Scambos.
Although no more reduction is expected until summer begins again in Antarctica
in late December, "This may be the beginning of the end for the Larsen
Ice Shelf," said Scambos.
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- Antarctic Peninsula ice shelves have
been in rapid retreat for the last few decades, apparently in response
to a regional climate warming of 4.5 degrees F since the 1940s. Although
the rate of warming is several times that of the global average, the exact
cause of the warming is not known.
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- "The warming trend appears to be
related to a reduction in sea ice," said Scambos. "The question
now is what is causing the reduction. At this point we do not have enough
evidence to find a smoking gun."
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- About two-thirds of the 12,000-square-kilometer
ice sheet is now threatening to break off, he said. The other one-third
is nestled in bays that are expected to protect it from breaking off.
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- "This is the biggest ice shelf yet
to be threatened," Scambos said. "The total size of the Larsen
B Ice Shelf is more than all the previous ice that has been lost from Antarctic
ice sheets in the past two decades."
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- 'Speed of the final breakup was unprecedented'
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- In early 1995, a smaller ice shelf area,
called the Larsen A, completely disintegrated during a single storm after
years of gradually shrinking. "The speed of the final breakup was
unprecedented, and followed several of the warmest summers on record for
this portion of the Antarctic." he said.
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- A much smaller ice shelf, the Wordie,
disappeared in the late 1980s. Currently the Larsen B is the northernmost
ice shelf in Antarctica, and therefore "on the front line of the warming
trend," said Scambos.
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- Ice shelves, thick plates of floating
ice surrounding portions of Greenland and Antarctica, are fed by glaciers
and snowfall. Reaching up to 800 meters in thickness in some cases, the
largest ice shelf is the Ross Ice Shelf, which is larger than the state
of Texas. The Larsen Ice Shelf is roughly the size of Connecticut.
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More On Ice Shelf...
- British predictions that a massive ice
shelf at the bottom of the world was in danger of breaking up were confirmed
yesterday by photographs from space.
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- The satellite pictures of one of earth's
most desolate regions showed that 4,000 square miles, about the size of
Oxfordshire, was in danger of disintegrating into the sea.
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- Environmentalists immediately blamed
global warming for steadily rising temperatures which have caused dramatic
changes in Antarctica.In February the British Antarctic Survey predicted
from computer research that the ice shelf was in danger.
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- The latest satellite pictures show that
a huge section 25 miles long and three miles wide had broken off what is
known as the Larsen B Ice Shelf. There are fears that with the loss of
this huge slice of ice, the rest of the ice shelf will continue to break
up.
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- "This is the biggest ice shelf to
be threatened,' Antarctic researcher Ted Scambos said yesterday.
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- The massive chunk of ice fell away from
the east side of the peninsula, which reaches towards South America.
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- 'The on-going ice shelf collapse is consistent
with what we see from the effects of increased greenhouse gases,' said
Bill Budd, a meteorlogy professor at Australia's Anterctic Co-operative
Research Centre.
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- He predicts significant degradation starting
in the 21st century and continuing for the next 500 years, by which time
there will have been near total loss of Antarctica's ice shelves.
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- In January, 1995, the Larsen A ice shelf
to the north, measuring 48 miles by 32 miles and 600ft thick, collapsed
completely during a storm. Ice shelves, thick plates of floating ice fed
by glaciers and snowfall, cover 1.5million square miles.
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- Despite the concerns for the ice shelves,
scientists say they doubt whether the phenomenon will have any significant
effect on ocean levels. At the British Antarctic Survey headquarters in
Cambridge, a spokeswoman said: "The world is not in any danger.' 'Ice
shelves are floating like the ice in a gin and tonic,' she said. - Source:
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