Antarctica Loses Ice From East as Well as West, Scientists Say
Nov. 23 (Bloomberg) -- Antarctica is losing ice from itslarger eastern side as well as the western part, an indicationthe southernmost continent may add “significantly more” torising seas, researchers in Texas said.
The eastern sheet lost ice at a rate of about 57 billionmetric tons a year from 2002 to 2009, contributing to thecontinent’s total annual average loss of about 190 billion tons,scientists at the University of Texas at Austin said in thejournal Nature Geoscience.
United Nations scientists in 2007 said most of Antarctica’scontribution to rising sea levels amid global warming comes fromthe western sheet, with the eastern part either holding steadyor gaining mass. The latest findings for East Antarctica are“surprising” because they differ from other estimates, saidglaciologist Jonathan Bamber, who wasn’t involved in the study.
“I’m surprised because other studies for slightlydifferent time periods have come up with values that are veryclose to zero,” Bamber, professor of physical geography at theUniversity of Bristol in England, said in a telephone interview.“This result really confirms that there are very substantialinconsistencies between different estimates.”
The United Nations Intergovernmental Panel on ClimateChange in 2007 said oceans will gain 18 centimeters to 59centimeters (7 inches to 23 inches) by 2100 and that uncertaintysurrounds forecasts for the amount Antarctica will contribute.Bamber said the margin of error for the latest prediction aboutEast Antarctica -- of 52 billion tons -- meant the sheet’scontribution could still be close to zero.
NASA Satellites
“The margins of error are so large that it can bedifficult to draw strong conclusions,” Bamber said, pointing toa 2008 study he co-wrote that estimated East Antarctica’s iceloss at 4 billion tons, with an error margin of 61 billion tons.The eastern sheet is about 10 times the size of the westernsheet, he said.
The University of Texas scientists used data from theNational Aeronautics and Space Administration’s Gravity Recoveryand Climate Experiment, or Grace, which measures changes ingravitational pull. NASA’s two Grace satellites were launched in2002 so prior data using the same methodology isn’t available.
The researchers’ figure for ice loss for the continent as awhole of 190 billion tons, with a margin of error of 77 billiontons, comes in at the upper end of UN estimates. The UN climatepanel in 2007 said estimates of changes in the mass of Antarcticice cover ranged from an annual gain of 50 billion tons to ayearly loss of 200 billion tons from 1993 through 2003.
Sea-Level Rise
Since 2006, Antarctica’s ice loss may be as high as 220billion tons a year, the University of Texas scientists said inthe paper.
“In contrast to previous estimates, they indicate that asa whole Antarctica may soon be contributing significantly moreto global sea-level rise,” the researchers wrote, referring totheir own estimates. They didn’t say how much the oceans mayrise as a result of melting ice.
NASA researchers last year calculated Antarctica as a wholelost 196 billion metric tons of ice in 2006, enough to raise sealevels by 0.5 millimeters (0.02 inches).
Bamber said while the current contribution to rising seasof melting ice sheets in Antarctica and Greenland isn’t“trivial,” it’s also “not absolutely catastrophic.”
Even so, “if I was in the Maldives or Bangladesh I mightnot be quite as bullish as that,” Bamber said, referring to twolow-lying nations. “If this acceleration continues at the ratewe’ve seen over the past 5 to 10 years, that’s very serious.”
Antarctica has registered the world’s lowest temperature:minus 89 degrees Celsius, or minus 128 degrees Fahrenheit, U.S.Climatic Data Center scientists say.
To contact the reporter on this story:Alex Morales in London at amorales2@bloomberg.net.
Last Updated: November 23, 2009 04:15 ESTSource: Bloomberg
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