The big melt.

Could part of frigid Antarctica headed for a major meltdown? That's what researchers at the Jet Propulsion Lab in California wonder after an extensive study of a melting Antarctic glacier (large river of ice) called Pine Island Glacier. "We're seeing a glacier melt in the heart of Antarctica," says radar scientist Eric Rignot.

Satellite radar images offer hard proof that between 1992 and 1996, 250-kilometer-long (155-mi) Pine Island glacier shrunk by 5 km (3 mi). And scientists finger global warming, marked by rising atmospheric temperatures, as the meltdown culprit (see SW 4/13/98). Could the dwindling glacier spell the collapse of the western half of the Antarctic Ice Sheet, causing sea levels the world over to surge by up to 6 meters (20 ft)? If so, U.S. coastal cities like New York and Miami would be plunged underwater. But researchers caution they need far more data to determine if a disaster is brewing.

If vast chunks of Antarctica do melt, it won't be the first time. The meltdown may have occurred as recently as 400,000 years ago--and global warning was also responsible. But then, global warming was part of the planet's natural heating and cooling cycle. Now, human pollutants are accelerating current global warming.

Of the three major ice floes (floating ice masses on water) of the West Antarctic Ice Sheet, Pine Island is the smallest and most likely to melt entirely. Ocean currents that lap at its ice tend to be warner than the ones that eat into the Ronne and Ross glaciers. But if all of Pine Island glacier were to melt, scientists fear the Ross and Ronne glaciers might soon thaw, too. "That's the disaster scenario," says Penn State University climatologist Richard Alley, a scientist who studies weather. If history is indeed repeating itself, man those lifeboats!