ANTARCTICA: As glaciers from Greenland to Kilimanjaro recede at record rates, the central ice cap of Antarctica has steadily grown for the past 11 years, partially offsetting rising seas due to the meltwaters of global warming, researchers have reported.
The vast east Antarctic ice sheet - a 3.2-km-thick (two miles) wasteland of ice larger than Australia, drier than the Sahara and as cold as a Martian spring - increased in mass every year between 1992 and 2003 due to 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," says David Vaughan, an expert on the ice sheets at the British Antarctic Survey in Cambridge.
In a region known for the lowest temperatures recorded on Earth, it normally is too cold to snow across the seven million square kilometres (2.7 million square miles) of the ice sheet. Any additional annual snowfall in east Antarctica, therefore, is almost certainly due to warmer temperatures, four experts on Antarctica said.
"As the atmosphere warms, it should hold more moisture," says climatologist Joseph R McConnell at the Desert Research Institute in Reno, Nevada, who helped conduct the study. "In east Antarctica, that means there should be more snowfall."
The additional snowfall is enough to account for an extra 45 billion tonnes of water added to the ice sheet every year, just about equal to the annual amount of water flowing into the ocean from the melting Greenland ice cap, the scientists reported in research published online 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 UN Intergovernmental Panel on Climate Change.
Overall, sea level is believed to be rising worldwide at an estimated rate of 1.8mm a year due to the expansion of warming water and the added outwash from melting glaciers in Greenland, Alaska, tropical highlands and elsewhere in Antarctica itself.
Every millimetre of increased sea level corresponds to about 350 billion tonnes of water a year.
The growth in the east Antarctic ice cap is enough to slow sea-level rise by about a fraction of that - 0.12 mm a year - the researchers report.
All told, the fresh water locked up in the ice of east Antarctica is enough to raise the level of the oceans by about 60m (196 ft), experts say. They believe that if it continues to grow as expected, the ice sheet could help buffer some but not all of the effects of anticipated sea-level rise for much of the coming century.
"It is the only large body of ice absorbing sea level rise, not contributing to it," says radar-mapping expert Curt H Davis 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 between June 1992 and May 2003.
They determined that the ice cap appeared to be thickening at the rate of 1.8 cm 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," says glaciologist Richard Alley at Pennsylvania State University. "The new result in no way disproves global warming; if anything, the new result supports global warming."