Fri Jun 25, 2004
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The Antarctic interior, the coldest place on Earth, experiences only brief periods each
year with temperatures above freezing. Yet beneath miles of ice, scientists have
discovered liquid fresh water lakes. Hi, Iím Bryan Yeaton for The Weather Notebook.
At least 70 unfrozen lakes lie below the continental icecap. The largest, Lake Vostok, is
1,300 feet deep and covers an area equivalent to Lake Ontario. And, it lies 12,000 feet
below the Antarctic surface.
How can a lake survive two miles under ice at the coldest place on Earth, where
temperatures have plummeted to -129F?
First, ice is a good insulator, thus the capís bottom ice is warmer than the upper
surface. Under the pressure of two miles of ice, iceís melting point falls to about 25
degrees, rather than the usual 32 degrees.
Also, the icecapís weight causes it to slowly creep toward the ocean, and that creates
heat through friction as ice rubs against the underlying bedrock. Finally, geothermal
heat from Earthís interior continually flows toward the ice-rock interface, enough to melt
some bottom ice, but not enough to significantly impact the icecapís thickness.
Lake Vostok has been probed using NASAís ice-penetrating radar. The lake is
believed to have been isolated from the surface for perhaps 15 million years and its
dark waters may contain unique microbial life.
Researchers started drilling slowly through the ice to learn Vostokís mysteries in 1998,
but halted about 500 feet short of the liquid water to avoid any contamination. Some
believe the waters could fizz like a pop can when the pressure is relieved. Drilling will
extend another 150 feet this year while scientists debate how the final penetration
should best proceed.
Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook
receives support from the National Science Foundation, and Subaru: Driven By Whatís
A Great Under-Ice Lake in Antarctica: