Antarctic Dust Layers May Give Climate Hints

Antarctic Dust Layers May Give Climate Hints

Date: 30-Mar-09
Country: GERMANY
Author: Alister Doyle, Environment Correspondent

BONN - South American glaciers are a source of puzzling layers of dust in Antarctic ice, according to a study published on Sunday in Nature Geoscience that might help improve climate change forecasting.

Scientists have long thought that dust entombed in the ice was a sign that the world went through drier or windier periods during the past 70,000 years. But they could find no evidence in other parts of the world to back up that theory -- until now.

"What we've done is pin down where the dust comes from -- it comes from Patagonia" at the tip of South America, the lead author David Sugden of the University of Edinburgh told Reuters.

Patagonia's glaciers grind thousands of tonnes of dust off mountains and, when the ice was at its biggest, the dust was picked up by winds and blown southwards when some ice melted at the end of valleys in summertime.

But Sugden said that when glaciers retreated about 21,000 years ago the airborne dust supply shut off because it ended up trapped in lakes that formed at the end of the glaciers.

"Dust is only produced when the glaciers are at their peaks. This also explains why (dust) switches off so early," he said.

Release of dust at the peaks was 20-50 times more than now, when many glaciers are in retreat. The scientists, including researchers at the University of Stirling and the British Antarctic Survey, identified the dust in Antarctica by matching it against dust buried in bogs in Patagonia.

Sugden said the finding about the dust could help work in designing computer models that use earth's climate history to project the future. "It's always been a problem. None of the models can produce enough dust in Antarctica," he said.

"Now perhaps they don't need to. The dust is linked to Patagonia, not a global change," he said. The amounts of dust found on Antarctica had implied a far drier, and perhaps hotter, climate than was shown from measurements taken elsewhere.

(Editing by Louise Ireland)