Ice from ancient global warming heats debate

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By Barry Brown

TORONTO | Canadian researchers studying the Arctic´s ancient permafrost have discovered 700,000-year-old ice wedges buried in the soil that have survived earlier periods of global warming, adding complexity to predictions about the impact of contemporary climate change.

Duane Froese, an assistant professor in the Department of Earth and Atmospheric Science at the University of Alberta, found what he describes as "the oldest ice in North America" in the Klondike region of Canada's Yukon Territory about 10 feet below the surface.

Because these ice wedges were found under a layer of volcanic ash, researchers from the University of Toronto and the Geological Survey of Canada were able to use a technique known as "fission track dating" of the ash to date it at roughly 700,000 years old.

This means the ice was older than the ash and older than the previous record holder - 120,000-year-old ice wedges found in Alaska.

"The fact that this ice survived the interglacials about 120,000 and 400,000 years ago, which we think were warmer than present, really illustrates how stubborn permafrost can be in the face of climate warming," Mr. Froese said.

According to a recent article in Ambio, a journal produced by the Royal Swedish Academy of Sciences, permafrost regions occupy about 25 percent of the Northern Hemisphere, with more than 60 percent in Russia.

Warming, thawing and degradation of permafrost have already been observed, and there are fears that its shrinkage could lead to increased output of greenhouse gases and unstable structures built on what was once ice-hard ground.

Permafrost can vary from almost a mile thick in parts of Siberia to a few feet and turn up over a large region, in scattered regional patches or isolated, the magazine noted.

In Canada, permafrost can be found across half the country, in 80 percent of Alaska, 30 percent of Russia, and 20 percent to 30 percent of China and Mongolia, Mr. Froese said.

"Permafrost is the glue" that holds the Arctic together and widespread thawing could have dramatic effects on the northern environment, he said.