Wednesday, June 17, 2009

"Arctic meltdown is a threat to humanity"


I AM shocked, truly shocked," says Katey Walter, an ecologist at the University of Alaska in Fairbanks. "I was in Siberia a few weeks ago, and I am now just back in from the field in Alaska. The permafrost is melting fast all over the Arctic, lakes are forming everywhere and methane is bubbling up out of them."

The permafrost is melting fast all over the Arctic, lakes are forming everywhere and methane is bubbling out of them
Back in 2006, in a paper in Nature, Walter warned that as the permafrost in Siberia melted, growing methane emissions could accelerate climate change. But even she was not expecting such a rapid change. "Lakes in Siberia are five times bigger than when I measured them in 2006. It's unprecedented. This is a global event now, and the inertia for more permafrost melt is increasing."...

Positive feedbacks

Most of this is the result of positive feedbacks (see illustration) from lost ocean ice, says David Lawrence of the National Center for Atmospheric Research in Boulder, Colorado. His modelling studies show that during periods of rapid sea-ice loss, warming extends some 1500 kilometres inland from the ice itself. "If sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate," he says.

Changes in wind patterns may accelerate the warming even further. "Loss of summer sea ice means more heat is absorbed in the ocean, which is given back to the atmosphere in early winter, which changes the wind patterns, which favours additional sea ice loss," says James Overland, an oceanographer at the Pacific Marine Environmental Laboratory in Seattle. "The potential big deal is that we now may be having a positive feedback between atmospheric wind patterns and continued loss of sea ice."

Incidentally, the changing winds might also be to blame for some of the cold and snowy weather in North America and China in recent winters, Overland says. Unusual poleward flows of warm air over Siberia have displaced cold air southwards on either side.

Going global

The rapid warming in the Arctic means that a global temperature rise of 3 °C, likely this century, could translate into a 10 °C warming in the far north. Permafrost hundreds of metres deep will be at risk of thawing out.

This is where things go global. The Arctic is not just a reflective mirror that is cracking up. It is also a massive store of carbon and methane, locked into the frozen soils and buried in icy structures beneath the ocean bed.

A quarter of the land surface of the northern hemisphere contains permafrost, permanently frozen soil, water and rock. In places, deep permafrost that formed during the last ice age, when the sea level was much lower, extends far out under the ocean, beneath the seabed. Large areas of permafrost are already starting to melt, resulting in rapid erosion, buckled highways and pipelines, collapsing buildings and "drunken" forests.

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