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Antarctic ice potentially unstable.

Antarctic ice potentially unstable

Recent changes in western Antarctica have led glaciologists to suspect they know far too little about the stability of the ice sheet there, including the odds of its collapsing into the ocean in the next few centuries -- a catastrophic event that could raise global sea levels by 6 meters. A report issued last month, based on a workshop attended by 32 scientists, calls for more ice-sheet research to help define the hazard.

Glaciologists have assumed that ice sheets do not undergo rapid changes in behavior. But an ongoing study along the Antarctic coast near the Ross ice shelf has revealed a dramatically different beast, says workshop organizer Robert Bindschadler of the NASA Goddard Space Flight Center in Green-belt, Md. The project examines large streams of glacial ice that flow down from the mountains and onto the floating ice shelf. To their surprise, investigators found that the movement of one stream has slowed markedly over the past decade. But even with this 20 percent reduction in speed, the stream carries ice to the coast about 40 percent faster than ice accumulates up at the stream's source. These observations "indicate possible instability and spur an urgent effort to understand the coupled system [of ice, air, ocean and rock] so as to predict its future behavior," the workshop scientists state in their report.

In recent years, scientists have focused much attention on whether the predicted global warming will increase melting in the Antarctic or even cause an ice-sheet collagpse. Some researchers announced last year that they believed the ice sheet would not melt as quickly as previously expected, and they predicted it would remain stable for at least the next century. These assumptions led to estimates that the global ocean level will rise only about one-third as rapidly as earlier calculations had indicated (SN: 12/16/89, p.397).

Bindschadler, however, contends scientists donht know enough about the potential instabilities in the ice sheet to rule out collapse in the next century. Moreover, he says, experts lack sufficient Antarctic data to explain the present rate of sea level rise. With such uncertainty, "predicting [sea level] in the future is really out on thin ice," he says.
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Publication:Science News
Date:May 5, 1990
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