Buried Lakes Send Antarctica's Ice Slipping Faster Into the Sea, Study Shows
for National Geographic News
|February 21, 2007|
Like a slapstick comedian slipping on banana peels, Antarctica's ice sheets slide more quickly into the sea when they hit under-ice lakes, a new study shows.
But the finding is anything but funny, since the slippery motion could have serious implications for the way ice sheets respond to global warming.
Ice is continually sliding off Antarctica and into the sea. In ice streams, inland ice speeds into the ocean more than ten times faster than the rest of the ice sheet.
Using satellite images and elevation data, the study team found four new, large under-ice lakes right at the start of a massive ice stream in East Antarctica.
The stream currently dumps 35 billion tons (31.8 billion metric tons) of ice into the sea each year.
"We think that those subglacial lakes are the reason why these ice streams are there," said Michael Studinger, a co-author of the study and a geophysicist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.
The lakes, buried deep below the miles-thick ice sheet, appear to provide water and heat that lubricate the ice sheet, creating ice streams, the team concludes.
"This makes the lakes really important," Studinger added, "because they impact how the ice sheet responds to changes in climate."
The new study, which will appear in tomorrow's issue of the journal Nature, focused on the Recovery Glacier ice stream.
The Recovery stream, one of the world's largest, is 175 miles (280 kilometers) wide at its start and snakes its way more than 400 miles (600 kilometers) to the sea.
Despite its size, Studinger described the Recovery region as "one of the most inaccessible places on Earth."
"The only data set that existed before for this region was an over-ice traverse in 1965 to 1966," Studinger said. "And since then, no one has been there.
"It's so remote that it hasn't even been in the range of satellites until recently," he added.
But now, using two satellites called ICESat and RADARSAT, Studinger and colleagues were able to spot the lakes and see the ice moving above them.
The team identified the telltale signs of four under-ice lakes, the most prominent being the large, extremely flat patches of ice directly above each lake.
Scientists have discovered more than 140 under-ice lakes in Antarctica. But these newfound lakes are the first known in the eastern region and are among the biggest in all of Antarctica.
The ice sheet in the Recovery area generally flows toward the ocean at a rate of about 15 to 30 feet (5 to 10 meters) a year.
But where the ice runs across the newfound lakes, the researchers found it breaks up and becomes a rapidly moving ice stream.
The new study is the first to show a direct link between Antarctica's under-ice lakes and the movement of the ice streams.
"Subglacial lakes may well be influencing ice-sheet flow on a much larger scale than we had thought previously," said Martin Siegert, a glaciologist at the University of Edinburgh in Scotland who was not involved in the study.
Previous research has examined the movement and interconnectedness of under-ice lakes in an attempt to piece together Antarctica's complex dynamics and how they will affect sea levels in the face of global warming.
Last year Siegert and colleagues found that smaller under-ice lakes can "jump" from one spot to another by flowing under the ice sheet.
And a study published last week showed that a massive ice stream in West Antarctica has a series of cascading lakes below it that contributes to the flow of ice into the sea.
These subglacial systems are insulated from the atmosphere, and so they will take thousands of years to respond to today's global warming, said David Marchant, a glaciologist at Boston University.
Nonetheless, Marchant added, "the formation of some subglacial lakes could ultimately lead to accelerated rates of sea-level rise."
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