Satellite survey confirms Antarctic ice is shrinking

Published 9:00 pm Thursday, March 2, 2006

The ice sheets of Antarctica – the world’s largest reservoir of fresh water – are shrinking faster than new snow can fall, scientists reported Thursday in the first comprehensive satellite survey of the entire continent.

Researchers at the University of Colorado determined that between 2002 and 2005, Antarctica lost ice at the rate of 36 cubic miles per year, rather than growing from heavier snowfalls, as previous research had predicted. That amount of ice is equivalent to about 30 times the fresh water used by Los Angeles every year.

“It is the first time we can say that if you look at the entire ice sheet, it is losing mass,” said geophysicist Isabella Velicogna, whose findings were published online by the journal Science Thursday.

An independent research team at the Jet Propulsion Laboratory in Pasadena, Calif., reported recently that the Arctic glaciers of Greenland are melting twice as fast as five years ago, adding an extra 38 cubic miles of fresh water to the Atlantic Ocean every year.

Taken together, the findings suggest that a century of global warming has altered the seasonal balance of the world’s water cycle.

If so, experts say, increasing temperatures – the 10 warmest years on record have all occurred since 1990 – may be hastening the demise of the polar ice caps, and estimates of the pace of future sea-level rise could be too low.

By previous calculations, Antarctica’s coastal glaciers melted enough every year to raise world sea levels by two-tenths of an inch, even as new snow falling in the interior locked up the same amount in the ice cap. The result was that sea level remained essentially the same from year to year.

“A little bit of change in one of these things could throw it all out of balance, and evidently that is what is going on,” said University of Colorado geophysicist John Wahr, who helped analyze the new satellite measurements.

The shrinkage is concentrated in the West Antarctic Ice Sheet, which contains enough fresh water to raise global sea levels more than 20 feet.