Glaciologists detect two more lakes beneath Antarctica

An extensive network of rapidly filling and emptying lakes has been detected beneath the snow, ice and bitter cold of Antarctica by the scientists who used NASA's Ice Cloud and land Elevation Satellite (ICESat) to map the icy surface of the southern continent.

Lasers beamed from nearly 400 miles above the Earth have detected subtle rises and falls in the surface of fast-moving ice streams on the Antarctic ice sheet, a capability that also offers scientists a magnificent view of interconnected waterways deep below that surface.

A complex network of rapidly filling and emptying lakes of ponds and rivers lies beneath at least two of West Antarctica's ice streams, the largest of which occurred under the Whillans ice stream and covered an area of 500 sq km (190 sq miles), according to a new research published in the Feb. 16 issue of Science.

After studying images from ICESat, which sends laser pulses down from space to the Antarctic surface and back, the researchers found that the lakes, some stretching across hundreds of square miles, fill and drain so dramatically that the movement can be seen by a satellite looking at the icy surface of the southern continent.

The satellite images, collected from 2003 through 2006, gave a much larger view of ice movement. Previously glaciologists had to drill deep holes in the ice to determine what was going on beneath the ice sheet, a process that inhibited them to studying only small areas at a time.

Although, more than 100 sub-glacial lakes have already been discovered in West Antarctica, but the new ones are specifically interesting because they occur below fast-moving ice.

"This exciting discovery of large lakes exchanging water under the ice sheet's surface has radically altered our view of what's happening at the base of the ice sheet and how ice moves in that environment," said Robert Bindschadler, chief scientist of the Laboratory for Hydrospheric and Biospheric Sciences at NASA's Goddard Space Flight Center, Greenbelt, Md., and co-author of the study.

The two new lakes, detected by satellite, were found under the two of the fast-moving glaciers, Whillans and Mercer Ice Streams that carry ice from the interior of the West Antarctic Ice Sheet to the floating ice sheet that covers parts of the Ross Sea.

Launched in 2003, ICESat can map changes in elevation as small as 1.5cm (0.6ins) from its orbit 645km (400 miles) above the Earth.

The ice above the lakes is moving as fast as 0.8 metres a day, “really ripping along” in the words of Bindschadler. “It's the fast-moving ice that determines how the ice sheet responds to climate change on a short timescale,” he said in a statement.

Astonished with the findings, lead author Helen Fricker of the University of California San Diego's Scripps Institution of Oceanography said they were surprised by how fast things were moving.

“We thought these changes took place over years and decades, but we are seeing large changes over months,” she said.

The findings are important for understanding how the Antarctic Ice sheet, where about 90% of the world's fresh water is locked, may respond to global warming and how much it may contribute to a worldwide rise in ocean level.

If the thick ice cap that covers Antarctica were to melt, scientists estimate it would cause a seven meter rise in sea levels. "Because climate is changing, we need to be able to predict what's going to happen to the Antarctic ice sheet," said Ms. Fricker.