Large Antarctic Ice
Shelf Disintegrating
By Environmental News Network Staff
(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.
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.
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.
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.
"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."
In Rapid Retreat
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.
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.
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.
"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."
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.
"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."
'Speed of the final breakup was unprecedented'
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.
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.
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.


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.
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.
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.
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.
"This is the biggest ice shelf to be threatened,' Antarctic researcher Ted Scambos said yesterday.
The massive chunk of ice fell away from the east side of the peninsula, which reaches towards South America.
'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.
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.
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.
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:

Sightings HomePage