November 28, 2008

Scientists Able To Predict Break Rate Of Ice Shelves

Scientists have developed computer models that are useful in predicting how fast icebergs break off Antarctica and Greenland.

Researchers hope the discovery will enable them to predict rising sea levels due to global warming caused by the burning of fossil fuels.

"To predict the future of the ice sheet and to understand the past, we have to put the information into a computer," says Richard B. Alley, the Evan Pugh professor of geosciences at Pennsylvania State University. "The models we have do not currently have any way to figure out where the big ice sheets end and where the ice calves off to form icebergs."

"The problem of when things break is a really hard problem because there is so much variability," says Alley. "Anyone who has dropped a coffee cup knows this. Sometimes the coffee cup breaks and sometimes it bounces."

If all the ice in Greenland and Antarctica melted, seas would rise by more than 196 ft.

The U.N. Climate Panel foresees a global rise in sea levels by 7 to 23 inches over the course of this century.

Computer models that predict how ice sheets behave in warmer weather generally gloss over exactly how icebergs break off because researchers have failed to understand the mechanism, known as calving.

"For iceberg calving, the important variable -- the one that accounts for the largest portion of when the iceberg breaks -- is the rate at which ice shelves spread," said the study, published in the journal Science.

Researchers looked at a spectrum of factors including ice thickness, calving rate and strain rate for 20 different ice shelves.

The team's results show that the calving rate of an ice shelf is primarily determined by the rate at which the ice shelf is spreading away from the continent.

The researchers were also able to show that narrower shelves should calve more slowly than wider ones.


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