Ice expanding in much of Antarctica

 Ice expanding in much of Antarctica: Eastern coast getting colder Western section remains a concern 

A composite map of Antarctica showing areas of greatest warming in red 1957-2006. The Wilkins Ice Shelf lies off the peninsula in the top left corner. credit NASA

April 18, 2009-The results of ice-core drilling and sea ice monitoring indicate there is no large-scale melting of ice over most of Antarctica, although experts are concerned at ice losses on the continent's western coast.

Antarctica has 90 per cent of the Earth's ice and 80 per cent of its fresh water, The Australian reports. Extensive melting of Antarctic ice sheets would be required to raise sea levels substantially, and ice is melting in parts of west Antarctica. The destabilization of the Wilkins ice shelf generated international headlines this month.

However, the picture is very different in east Antarctica, which includes the territory claimed by Australia.

East Antarctica is four times the size of west Antarctica and parts of it are cooling. The Scientific Committee on Antarctic Research report prepared for last week's meeting of Antarctic Treaty nations in Washington noted the South Pole had shown "significant cooling in recent decades".

Australian Antarctic Division glaciology program head Ian Allison said sea ice losses in west Antarctica over the past 30 years had been more than offset by increases in the Ross Sea region, just one sector of east Antarctica.

"Sea ice conditions have remained stable in Antarctica generally," Dr Allison said.

The melting of sea ice - fast ice and pack ice - does not cause sea levels to rise because the ice is in the water. Sea levels may rise with losses from freshwater ice sheets on the polar caps. In Antarctica, these losses are in the form of icebergs calved from ice shelves formed by glacial movements on the mainland.

Last week, federal Environment Minister Peter Garrett said experts predicted sea level rises of up to 6m from Antarctic melting by 2100, but the worst case scenario foreshadowed by the SCAR report was a 1.25m rise.

Mr Garrett insisted global warming was causing ice losses throughout Antarctica. "I don't think there's any doubt it is contributing to what we've seen both on the Wilkins shelf and more generally in Antarctica," he said.

Dr Allison said there was not any evidence of significant change in the mass of ice shelves in east Antarctica nor any indication that its ice cap was melting. "The only significant calvings in Antarctica have been in the west," he said. And he cautioned that calvings of the magnitude seen recently in west Antarctica might not be unusual.

"Ice shelves in general have episodic carvings and there can be large icebergs breaking off - I'm talking 100km or 200km long - every 10 or 20 or 50 years."

Ice core drilling in the fast ice off Australia's Davis Station in East Antarctica by the Antarctic Climate and Ecosystems Co-Operative Research Centre shows that last year, the ice had a maximum thickness of 1.89m, its densest in 10 years. The average thickness of the ice at Davis since the 1950s is 1.67m.

A paper to be published soon by the British Antarctic Survey in the journal Geophysical Research Letters is expected to confirm that over the past 30 years, the area of sea ice around the continent has expanded.

East Antarctic Ice Sheet Gains Mass and Slows Sea Level Rise, Study Finds

From 1992 to 2003, Curt Davis, MU professor of electrical and computer engineering, and his team of researchers observed 7.1 million kilometers of the ice sheet, using satellites to measure changes in elevation. They discovered that the ice sheet's interior was gaining mass by about 45 billion tons per year, which was enough to slow sea level rise by .12 millimeters per year. The interior of the ice sheet is the only large terrestrial ice body that is likely gaining mass rather than losing it, Davis said.

"Many recent studies have focused on coastal ice sheet losses and their contributions to sea level rise," Davis said. "This study suggests that the interior areas of the ice sheet also can play an important role. In particular, the East Antarctic ice sheet is the largest in the world and contains enough mass to raise sea level by more than 50 meters. Thus, only small changes in its interior can have a significant affect on sea level."

The study, funded by NASA's Cryospheric Processes Program and the National Science Foundation's Antarctic Glaciology Program, suggests that increased precipitation was the likely cause of the gain. This was based on comparisons with precipitation model predictions over the same period of time. The most recent U.N. Intergovernmental Panel on Climate Change reported that Antarctica would gain mass due to increased precipitation in a warming climate. However, the study made no direct link to global warming.

"We need more ice core measurements from East Antarctica to determine if this increased precipitation is a change from the past or part of natural variability," said Joe McConnell of the Desert Research Institute in Reno, Nev., who co-authored the study.

The researchers used satellite radar altimeters from the European Space Agency's ERS-1 and ERS-2 satellites to make 347 million elevation-change measurements between June 1992 to May 2003.

The research team found there was a strong correlation between the predicted precipitation trends and measured elevation change over the 11-year period for the ice sheet, which indicated that East Antarctica's interior was likely gaining mass due to the increased precipitation. The results, though, did not assess the overall contribution of the entire Antarctic ice sheet to sea level rise.

"Ice sheet response to climate change is a complex process that is difficult to measure and even more difficult to predict," Davis said. "The overall contribution of the Antarctic ice sheet to global sea-level change will depend on how mass changes in the ice sheet's interior balance mass changes from the coastal areas."

Source: University of Missouri