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As Climate Shifts, Antarctic Ice Sheet Is Growing

Increased snowfall on the central icecap partly offsets effects of melting glaciers, researchers say.

May 20, 2005|Robert Lee Hotz | Times Staff Writer

As glaciers from Greenland to Kilimanjaro recede at record rates, the central icecap of Antarctica has been steadily growing for 11 years, partially offsetting the rise in seas from the melt waters of global warming, researchers said Thursday.

The vast East Antarctic Ice Sheet -- a 2-mile-thick wasteland larger than Australia, drier than the Sahara and as cold as a Martian spring -- increased in mass every year from 1992 to 2003 because of additional annual snowfall, an analysis of satellite radar measurements showed.

"It is an effect that has been predicted as a likely result of climate change," said David Vaughan, an independent expert on the ice sheets at the British Antarctic Survey in Cambridge, England.

In a region known for the lowest temperatures recorded on Earth, it normally is too cold for snow to form across the 2.7 million square miles of the ice sheet. Any additional annual snowfall in East Antarctica, therefore, is almost certainly attributable to warmer temperatures, four experts on Antarctica said.

"As the atmosphere warms, it should hold more moisture," said climatologist Joseph R. McConnell at the Desert Research Institute in Reno, who helped conduct the study. "In East Antarctica, that means there should be more snowfall."

The additional snowfall is enough to account for 45 billion tons of water added to the ice sheet every year, just about equal to the amount of water flowing annually into the ocean from the melting Greenland icecap, the scientists reported in research published online Thursday by the journal Science.

Rising sea level, which could swamp many coastal and island communities, is considered one of the most serious potential consequences of global warming, according to the most recent assessment by the United Nations' Intergovernmental Panel on Climate Change.

Overall, sea level is estimated to be rising by 1.8 millimeters a year worldwide because of the expansion of warming water and the added outwash from melting glaciers in Greenland, Alaska, tropical highlands and some areas of Antarctica.

Every millimeter of increased sea level corresponds to about 350 billion tons of water a year.

The growth in the East Antarctic icecap is enough to slow sea-level rise by a fraction of that -- about 0.12 millimeter a year -- the researchers reported.

All told, the fresh water locked up in the ice of East Antarctica is enough to raise the level of the oceans by about 196 feet, experts said. If it continues to grow as expected, the ice sheet could buffer some, but not all, of the effects of anticipated sea-level rise for much of the coming century, the researchers said.

"It is the only large body of ice absorbing sea level rise, not contributing to it," said Curt H. Davis, a radar mapping expert at the University of Missouri-Columbia, who led the research team.

The researchers based their conclusions on an analysis of 347 million radar altimeter measurements made by the European Space Agency's ERS-1 and ERS-2 satellites from June 1992 to May 2003.

They determined that the icecap appeared to be thickening at the rate of 1.8 centimeters every year. The ice is thinning in West Antarctica and other regions of the continent.

"The changes in the ice look like those expected for a warming world," said glaciologist Richard Alley at Pennsylvania State University. "The new result in no way disproves global warming; if anything, the new result supports global warming."

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