Water Found Under Antarctic Ice to Raise Sea Level Forecasts

Scientists have detected a network of lakes and rivers of rapidly moving water under the thick ice sheet of West Antarctica, a discovery that will force a revision of predictions of global sea levels as the sheet melts due to climate change.

"What we're seeing here is a lot more movement of stuff underneath the Antarctic ice sheet than we ever dreamt possible. This has been going on for a long time," said David Vaughan of the British Antarctic Survey.

The faster the water moves in the sub-glacial lakes the more quickly any melting ice from the heart of the continent will get into the open sea, causing water levels to rise. "The way we model the ice sheets to predict how they will behave in the future, how they will contribute to sea level rise in the future, doesn't take into account all of this [new work]," said Prof Vaughan.

The latest scientific report by the Intergovernmental Panel on Climate Change said that an uncertainty about how ice sheets responded to climate change was the biggest unknown in predicting sea levels around the world. "We can't make faithful predictions of what's going to happen to Antarctica unless we get this process understood," said Helen Fricker of the Scripps Institution of Oceanography at the University of California, San Diego.

Dr Fricker used satellite data to map the rise and fall of the overlying ice - which is up to 3km thick - as the lakes emptied and filled with water. "Over a period of three years from 2003 to 2006 we found regions where the elevation had changed dramatically - the first lake we found had deflated by nine metres, which we were just amazed to see," Dr Fricker said. Her results are published today in Science.

More than 145 isolated lakes have been previously reported to exist under the ice sheet. But new bodies of water have been discovered by Dr Fricker's team, ranging in size from 120 to 500 square kilometres (46 to 193 square miles), in 14 places around Antarctica and many are connected by rapidly moving water channels.

"The old paradigm was that most of the Antarctic was frozen to its bed. In a few places there was free water at the bottom and that was lubricating fast ice flow and that was all very steady, nothing changed very much," Prof Vaughan said. But this view had become out of date. "Water is not moving around in a steady trickle but filling up in one place and bursting through to another and this process is more widespread than we thought," he said.

Dr Fricker said she was surprised by the results. "We thought these changes took place over years and decades, but we are seeing large changes over months."