Tue, Sep 13, 2011 - Page 6 News List

Arctic melting fastest in 40 years

NEW WAY AROUND THE WORLD:If current melting rates continue, the Arctic will be largely ice-free in the summer months within 30 years, 40 years earlier than predicted

The Guardian, LONDON

Arctic sea ice has melted to a level not recorded since satellite observations started in 1972 — and almost certainly not experienced for at least 8,000 years, polar scientists say.

Daily satellite sea-ice maps released by Bremen University physicists show that with a week’s more melt expected this year, the floating ice in the Arctic covered 4.24 million square kilometers on Thursday. The previous one-day minimum was 4.27 million square kilometers on Sept. 17, 2007.

The US National Snow and Ice Data Center in Colorado is expected to announce similar results in a few days.

The German researchers said that the record melt was undoubtedly because of human-induced global warming.

“The sea-ice retreat can no more be explained with the natural variability ... caused by weather,” said Georg Heygster, head of the Institute of Environmental Physics at Bremen.

“Climate models show that the reduction is related to the manmade global warming, which, due to the albedo effect, is particularly pronounced in the Arctic,” he said.

The albedo effect is related to a surface’s reflecting power — whiter sea ice reflects more of the sun’s heat back into space than darker seawater, which absorbs the sun’s heat and gets warmer.

Floating Arctic sea ice naturally melts and refreezes annually, but the speed of change has shocked scientists: It is now twice as great as it was in 1972, the Colorado center said. Arctic temperatures have risen more than twice as fast as the global average over the past half century.

Separate research suggests that Arctic ice is in a downward spiral, declining in area but also thinning. Scientists at the Polar Science Center of the University of Washington, Seattle, said last week that Arctic sea-ice volume was at its lowest ever level last year and was on course to set more records this year. Their data suggests that the volume of sea ice last month was about 8,900 cubic kilometers — half the average and 62 percent lower than the maximum covering the Arctic in 1979. The research will be published in a forthcoming issue of the Journal of Geophysical Research.

“Ice volume is now plunging faster than it did at the same time last year when the record was set,” Axel Schweiger of the Washington center said.

If current trends continue, a largely ice-free Arctic in the summer months is likely within 30 years — that is 40 years earlier than anticipated in the last Intergovernmental Panel on Climate Change assessment report. The last time the Arctic was uncontestably free of summertime ice was 125,000 years ago, at the height of the last major interglacial period.

“This stunning loss of Arctic sea ice is yet another wake-up call that climate change is here now and is having devastating effects,” Shaye Wolf, climate science director at the Center for Biological Diversity in San Francisco, told journalists.

Arctic ice plays a critical role in regulating Earth’s climate. Retreating summer sea ice is described by scientists as a measure and a driver of global warming. This year, the Northwest and Northeast passages were mostly ice free, as they have been twice since 2008. Last month, the 74,000-tonne STI Heritage tanker passed through the Northeast Passage in just eight days on its way from Houston, Texas, to Thailand. The northeast sea route, which links the Atlantic to the Pacific, is likely to become a ship operator’s favorite.

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