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A South Pole trek in search of global warming

Ice samples on polar trip yield clues on climate change.

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Just over 90 years after the first humans set foot at the South Pole, a team of US scientists has completed a rare cross-country trek to Antarctica's southernmost point as part of an international effort to uncover the history of climate change on Earth's most inhospitable continent.

The 775-mile route they followed would take 11 hours to cover on an interstate highway. Under polar conditions, however, the 10-member team took 27 days to make the trip. Along the route, the expedition's 14-ton sled-tugging tractors crept through deep snowdrifts, hunkered down during howling blizzards, dodged deep crevasses, and stopped to extract hundreds of core samples from the top 160 to 400 feet of the two-mile-thick mantle of ice that covers the continent.

Researchers are keenly interested in that ice cover and the climate regimes that govern its growth and shrinkage. The West Antarctic Ice Sheet is seen as a possible source of the water that raised sea levels by as much as 25 meters in a period of less than 1,000 years - probably between 14,000 and 11,000 years ago. During the past 10,000 years, the sheet has thinned by more than 2,300 feet at the coast, a process that continues today.

Understanding the links and tracking the ice's history are vital to forecasting its future behavior, particularly if the global climate's current warming trend continues, according to Paul Mayewski, a geologist at the University of Maine and the expedition's leader.

Research reported last week in the journal Science indicates that the sheet's long-term decline is expected to continue, part of a natural process that began with the end of the last ice age.

Time capsules made of ice

"In the short-term the West Antarctic Ice Sheet is generally stable," Dr. Mayewski says. The new ice cores and other data the group collected track changes that have occurred over the past 200 to 1,000 years.

By comparing these data with those from deeper core samples from elsewhere on the continent, scientists hope to find out how much of this deglaciation is part of a long-term natural process and whether the trend may be accelerating due to global warming.

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