http://www.commondreams.org/headlines07/0216-03.htm

Scientists Sound Alarm Over Melting Antarctic Ice Sheets

The long-term stability of the massive ice sheets of Antarctica, which have the potential to raise sea levels by hundreds of meters, has been called into question with the discovery of fast-moving rivers of water sliding beneath their base.

Scientists analyzing satellite data were astonished to discover the size of the vast lakes and river systems flowing beneath the Antarctic ice sheets, which may lubricate the movement of these glaciers as they flow into the surrounding sea.

The discovery raises fresh questions about the speed at which sea levels might rise in a warmer world due to the rate at which parts of the ice sheets slide from the land into the ocean, scientists said at the American Association for the Advancement of Science in San Francisco.

"We've found that there are substantial subglacial lakes under ice that's moving a couple of meters per day. It's really ripping along. It's the fast-moving ice that determines how the ice sheet responds to climate change on a short timescale," said Robert Bindschadler, a Nasa scientist at the Goddard Space Flight Centre in Maryland, one of the study's co-authors...............

..............Glaciologists have known for some time that water exists under the Antarctic ice sheets - which can be hundreds of meters thick - but they were surprised to find how much water is involved and the speed at which it moves from one subglacial reservoir to another, said Helen Fricker at the Scripps Institution of Oceanography in San Diego.

"We didn't realize that the water under these ice streams was moving in such large quantities, and on such short time scales. We thought these changes took place over years and decades, but we are seeing large changes over months. The detected motions are astonishing in magnitude, dynamic nature and spatial extent," Dr Fricker said.

The West Antarctic ice sheet is the second biggest on the continent, and the rate at which ice flows from it to the Ross ice shelf, and then ultimately into the sea, is critical in assessing the likely impact of climate change on global sea levels.............