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Experts Studying Meaning Of Ice Shelf Collapse - 2002-03-21

Earlier this month, a 3,300-square-kilometer Antarctic ice shelf melted and collapsed into the sea. Experts are studying what the phenomenon means.

Experts do not know for sure whether the huge ice melt is proof of global warming or simply caused by a regional increase in temperatures. But the disappearance of an ice plate located off the tip of the South Pole peninsula sure got their attention.

Known as the Larsen B ice shelf, the structure collapsed into fragments and floated away or submerged into the ocean. Lara Hansen is senior climate scientist for the environmental group, World Wildlife Fund.

"Events like this allow the general public to see events that as scientists we see are going on," he said. "Having an ice shelf the size of the U.S. state of Rhode Island melt is not something people expect to have happen everyday. It's certainly not something the scientists who are watching expected. And it's not what I expected. But it did in fact happen."

Experts say disappearance of the Larsen B ice shelf all began with an unusual warming trend in the region that started about 50 years ago. In the Antarctic Peninsula, the warming trend amounted to an average temperature increase of about 2.5 degrees Celsius.

"As a consequence of that warming, ice shelves, which are floating pieces of ice that border the land on one end and are out to sea on the other end, have been gradually disintegrating because summertime temperatures on the ice exceed the melting point. And it appears that pond water appears on the shelves that slips down through crevices and fragments the larger ice sheet."

Michael Oppenheimer teaches geophysics at Princeton University in New Jersey. "What is surprising and disturbing about this finding is how quickly this huge mass of ice, about this size of Rhode Island, disintegrated in barely more than a month," he said.

And all of a sudden, a structure that had been around for about 10,000 years was gone.

Scientists say the melting of Larsen B will not result in the rise of global sea levels, because the ice was already floating. But Professor Oppenheimer says Larsen B provides some interesting warnings for more massive ice shelves to the south of Larsen B.

"Those ice shelves around west Antarctica are bordering massive amounts of ice that sit on land," he said. "And there's long been a concern that if the ice shelves that sit on land disintegrate, that change could allow the land born ice to speed up and accelerate into the ocean, which would significantly raise the global sea level. In fact, if the whole of west Antarctica collapsed into the sea, global sea level would rise five meters, which would destroy coastal civilization as we know it."

Because temperatures to the south of Larsen are much colder, scientists say future disintegration of ice shelves would take tens of thousands of years.

But they add, if the melting of Larsen B was caused by global warming, it serves as an example of how efforts to contain greenhouse gas emissions today can affect the environment tens of thousands of years into the future.