Icy manna. Sediments laden with bacteria, such as these deposits in an Antarctic ice core, may seed life in the dark waters of Lake Vostok beneath 4 kilometers of ice.

Lake Vostok: Stirred, Not Shaken

At least 76 lakes have been trapped under Antarctica's ice shield for millions of years. Vostok, the largest, is the size of Lake Ontario and plunges up to 1000 meters deep within a rugged valley. Previous radar surveys of ice layers above the lake hinted that 10 centimeters of ice melt each year at the northwestern end of the lake, where the melting temperature is lower because of pressure from the thicker overlying ice. Water then refreezes at the lake's other end. This slow circulation, researchers deduced, would replace the lake's volume every 50,000 to 100,000 years (ScienceNOW, 9 February 2000).

Recent fieldwork now hints at a faster pace. A team led by geologist Robin Bell of the Lamont-Doherty Earth Observatory at Columbia University in New York spent 33 days at Lake Vostok in December and January, flying over the lake more than 60 times. The radar images they took suggest that the melting-refreezing cycle is at least three times faster than previously thought, Bell reported here 17 January at the annual meeting of the American Association for the Advancement of Science, which publishes ScienceNOW.

The team also put two seismometers on the ice and caught a magnitude 3 earthquake. Three other relatively mild quakes have struck the region in the last century with likely magnitudes between 4 and 5, Bell notes. The seismic motions make sense, she says, because the steepness of one side of the lake suggests a restless geologic boundary. "It's not a piece of quiet old crust," Bell says. "The Earth is actively moving." This activity means that nutritious mineral-rich fluids--and possibly heat--may seep into the lake from below.

Heat and faster circulation are good news for those who hope to find an ecosystem below the ice, says ecologist John Priscu of Montana State University in Bozeman. Circulating nutrients within the lake would feed organisms, which may draw energy from hydrothermal fluids. However, it may take more than a decade for scientists to develop the sterile drilling tools needed to sample the lake without contaminating it.

Related sites
Report on Lake Vostok, from a National Science Foundation (NSF) workshop
John Priscu's Antarctic research
NSF research in Antarctica

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