Lakes Under Massive Antarctic Ice Sheet Surprise Scientists
Updated 2/16/2007 3:43 AM ET

WASHINGTON — There are 14 regions of previously undetected lakes hidden beneath parts of the massive West Antarctic Ice Sheet that are continuously dumping their contents into the surrounding sea, NASA scientists reported Thursday.

The researchers acknowledge that they don't know what role these lakes play in draining ice away from the sheet, but its collapse is one of the most extreme fears in global warming scenarios. Antarctica holds about 90% of the world's ice and 70% of its reservoir of fresh water, NASA says.

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The West Antarctic Ice Sheet contains enough ice to raise global sea levels more than 16 feet if it collapses, according to the British Antarctic Survey.

Although more than 100 subglacial lakes have been detected in Antarctica, discovery of the lakes beneath two glacial streams of ice surprised researchers, who previously thought water flowed evenly below the ice streams, says study author Robert Bindschadler of NASA's Goddard Space Flight center in Greenbelt, Md.

The lakes were detected under 2,300 feet of ice by satellite data gathered in 2003 and 2006. The satellite bounced laser measures off the same patches of ice to measure precise changes in elevation, according to a presentation made by the researchers at the American Association for the Advancement of Science meeting in San Francisco.

The lakes gave away their positions by rising and falling — by as much as 30 feet in one case. The researchers, expressing surprise at how quickly the lakes drain, think they fill until they bust, sending their contents cascading under the ice sheet.

"It's a bit like an old cartoon in which an invisible character sneaks across a sofa," says glaciologist Richard Alley of Penn State University in College Park, Pa., who was not part of the study. "You can follow the character's progress by seeing the cushion sink and then rebound under the footprints."

"This is important because this is how ice leaves the sheet and goes into the ocean, affecting sea level," says Bindschadler. A recent Intergovernmental Panel on Climate Change (IPCC) report warned that ice sheet melting could add to an already projected 7- to 23-inch rise in global sea levels by 2100.

The ice streams atop the lakes are fast-moving, daily shifting about 5 feet and dropping ice into the sea, the scientists say. They are just two of the roughly dozen ice streams feeding the edges of the West Antarctic Ice Sheet into the sea.

The sheet last melted about 125,000 years ago, during a period of temperatures rivaling today's, sending sea levels perhaps 18 feet higher, according to NASA.

Alley cautions that scientists still haven't figured out how the lakes, along with smaller subglacial lakes in Eastern Antarctica, control how ice sheets drain into the oceans, or their potential for collapse.

"We can't predict what these ice streams are going to do, based on these measurements," Bindschadler says.

Global warming melts the ice sheets, he says. "That's the easy part." However, "the hard part is the details of how it all works."

Original article: USA Today - Science
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