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Mixed Signals from Antarctica
Despite Global Warming Trend, Icy Region May Be Cooling

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Taylor Glacier in Antarctica's McMurdo Dry Valleys. Photo: Richard Harris/NPR

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Jan. 21, 2002 -- The Earth's surface has warmed significantly, especially over the past few decades. Some of the most dramatic warming has been recorded in the northernmost reaches of Alaska, Canada and Siberia. But the extreme southern part of the Earth is not warming, as some had predicted. For Morning Edition, NPR's Richard Harris reports on two new studies that show a far more complicated picture of Antarctica's weather.

The first study involves one of the few places in Antarctica where there's an actual community of living things stashed away on the desolate continent -- the McMurdo Dry Valleys. The region, one of the few areas in Antarctica that isn't entirely blanketed by snow and ice, is a stark but beautiful landscape of ice-covered lakes, ephemeral streams, exposed bedrock and alpine glaciers.

But under the thick ice that covers some of the lakes, simple life forms like phytoplankton and bacteria manage to survive. A team of researchers have been studying one site in the Dry Valleys for well over a decade, with the goal of building a long-term record of its ecosystem.

That team, led by University of Illinois at Chicago researcher Peter Doran, has put years of data together to reach a startling conclusion. While the globe as a whole has been getting warmer, Doran's team, reporting in the journal Nature, has documented a sharp cooling trend in the Dry Valleys over the past 14 years.

Doran says the cooling in the region is not only reducing the flow of fresh water from the glaciers into the lakes, it's also making the lakes' surface ice thicker, so the plankton that use sunlight for energy are getting less light. If this admittedly short trend continues, Doran says, it would be tough on the life forms struggling to get by in this already harsh environment.

"The ecosystem would continue to diminish," says Doran, "and eventually it would essentially go into a deep sleep, like a freeze-dried ecosystem."

The cooling isn't limited to the Dry Valleys' lakes. A record of all Antarctic temperatures compiled by Doran and his colleagues shows an overall cooling of the continent since 1966, particularly during the summer and autumn months.

Doran attributes the cooling to unusually sunny and less stormy weather patterns. Usually, storminess helps warm parts of Antarctica by creating winds like the warm chinooks that flow off the high plateaus of the American West.

It's still unknown whether that change in the weather is linked to global climate change. And to add to the mystery, not all of Antarctica is getting colder. Temperatures have been rising sharply over the past 50 years on the long Antarctic Peninsula, which juts north toward South America. There, ice floes have been melting and some penguin populations have fled their historic breeding grounds.

But the biggest question about Antarctica isn't about local impacts of these climate trends, it's about potential global consequences -- in particular, the potential for rising sea levels.

There's enough water in the West Antarctic ice sheet to gradually raise global sea levels by a staggering 20 feet. Glacier experts are eyeing this ice warily. In the long run, global temperature changes could affect this ice, if the surrounding ocean water warms significantly. But even in the absence of ocean warming, the ice is changing. Previous studies suggested it could be in the midst of a slow-motion meltdown. Now Ian Joughin of NASA's Jet Propulsion Laboratory reports in the latest Science magazine that the ice sheet is actually growing, as snow accumulates on its surface.

But Joughin says it's too early to relax. Glaciologists are still concerned about the behavior of another part of the West Antarctic ice sheet, which appears to be sloughing off into the sea.

Meanwhile, there's a real-life reminder that weather trends can be fickle. Doran's co-author, Montana State University researcher John Priscu, hiked across the Dry Valleys' Lake Bonney last year on the spiked shoes known as crampons. He reports from Antarctica by e-mail that this summer -- underway right now in Antarctica -- the weather is so unseasonably warm he has to use a boat to get out to the ice floating on the lake.

In Depth

Richard Harris in Antarctica Last year, Richard Harris made a trip to Antarctica to see first-hand what researchers were finding out about the continent. Check out his reports.

pollution related stories Browse through NPR's archives for stories about Antarctica and global warming.

Other Resources

• Brush up on Antarctica facts at Rice University's Glacier Web site.

• Learn more about Antarctica at the McMurdo Dry Valleys Long-Term Ecological Research Web site.

• Read about the Atlas of Antarctic Research at the U.S. Geological Survey Web site.

• The United States Antarctic Resource Center has a comprehensive collection of Antarctic maps, charts, satellite images and photographs.

• Read about British research on the continent at the British Antarctic Survey Web site.

• Read about research on the West Antarctic ice sheet at NASA's West Antarctic Ice Sheet Initiative Web site.