Friday, March 3, 2006

Antarctic ice sheet melting fast: scientists


Scientists say Antarctica's mammoth ice sheet is in "significant decline", probably due to climate change.

United States researchers at the University of Colorado at Boulder say online in the journal Science that the Antarctic ice sheet is losing up to 152 cubic kilometres of ice a year.

Dr Isabella Velicogna from the University's Cooperative Institute for Research in Environmental Sciences says it is the first study to indicate the total mass balance of the Antarctic ice sheet is in significant decline.

The team calculated the ice sheet lost 152 cubic kilometres a year from April 2002 to August 2005, give or take 80 cubic kilometres.

That is equivalent to global seas rising 0.4 millimetres a year, with a margin of error of 0.2 millimetres, the researchers say.

The bulk of the loss is occurring in the West Antarctic ice sheet, Dr Velicogna says, whose team used two satellites orbiting Earth in tandem to gather data.

The satellites estimate Earth's global gravity field and variations in the gravity field over time were used to determine changes in Earth's mass distribution, necessary for estimating changes in mass of the Antarctic ice sheet.

"The changes we are seeing are probably a good indicator of the changing climatic conditions there," Dr Velicogna said.

The study seems to contradict the 2001 assessment by the Intergovernmental Panel on Climate Change (IPCC), which forecast the Antarctic ice shelf would actually gain mass in the 21st Century due to higher precipitation in a warming climate.

The US researchers say the IPCC estimate was based on sparse coverage of coastal areas, which would have affected the results.

As Earth's fifth-largest continent, Antarctica is twice the size of Australia and contains 70 per cent of Earth's fresh water resources.

The ice sheet is an average 1,981 metres thick.

Research from the British Antarctic Survey suggests melting of the West Antarctic ice sheet alone would raise global sea levels by more than six metres.

--ABC Science Online/AFP

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