Scientists Warn of Possible Collapse of Massive Ice Sheet

Scientists Warn of Possible Collapse of Massive Ice Sheet

WASHINGTON (July 23, 1998 4:10 p.m. EDT http://www.nandotimes.com) - A melting Antarctic glacier could lead to the collapse of the West Antarctic Ice Sheet, causing global sea levels to rise up to 20 feet, researchers said on Thursday.

Radar images from satellite observations between 1992 and 1996 of Pine Island glacier in West Antarctica showed the glacier is shrinking.

"It is important because it could lead to a collapse of the West Antarctic Ice Sheet (WAIS)," said Eric Rignot, a radar scientist at the Jet Propulsion Laboratory in California, who led the study. "We are seeing a glacier melt in the heart of Antarctica."

Antarctica, the fifth-largest continent, is almost completely covered with ice. About 90 percent of the world's glacial ice is in Antarctica.

But scientists say this data from remote and stormy West Antarctica could be the first real evidence that some of these massive glaciers might actually be rapidly retreating.

"The continuing retreat of Pine Island glacier could be a symptom of the WAIS disintegration," said Craig Lingle, a glaciologist at the University of Alaska in Fairbanks, who is familiar with the study.

If the WAIS did collapse it would push sea levels up throughout the world, with regions near sea level experiencing more flooding and faster erosion, Lingle said.

Pine Island glacier is important because it is really a fast-moving ice stream, taking accumulated snow from the interior of the WAIS and spitting it into the ocean in the form of ice, he added.

But if the bottom of a glacier melts at a faster rate than snow collects on the surface, more ice belched into the ocean causes sea levels to rise, he explained in a telephone interview.

"There is no other example of anything in West Antarctica that is retreating that fast," Lingle said. "This is the farthest south this phenomena has been observed."

In the study, published in the journal Science, Rignot speculated warmer ocean waters were causing Pine Island's rapid bottom melting.

"This is one of the most sensitive ice sheets to climatic change. For many, many years we have neglected the importance of bottom melting," Rignot said in a telephone interview.

Richard Alley, a glaciologist at Penn State University, said if the glacier retreated too far it would allow too much ice to escape from the WAIS, causing a collapse.

"It would make a hole in the side of the ice sheet and the remaining ice would drain through that hole," he added. "This is the disaster scenario."

"If world sea levels went up six meters (20 feet) there would be problems for all coastal areas," Lingle said.

Alley agreed the consequences of a WAIS ice collapse would be severe. But this study only showed the collapse was possible, not that it would occur, he pointed out in a telephone interview.

"We are not saying it will probably happen but it is possible and if it does it will affect a lot of people," he said.

By MICHAEL KAHN, Reuters