Arctic Could be frea of sea ice in 30 years
ARCTIC sea ice has melted to a level not recorded since satellite observations started in 1972 - and almost certainly not experienced for at least 8000 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, floating ice in the Arctic covered 4.24 million square kilometres on September 8.
The previous one-day minimum was 4.27 million square kilometres on September 17, 2007.
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The US National Snow and Ice Data Centre in Colorado is expected to announce similar results in a few days.
The German researchers said 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 man-made 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 heat and gets warmer.
Floating Arctic sea ice naturally melts and refreezes annually, but the speed of change has shocked scientists - it is twice as great as it was in 1972, according to the US data centre. Arctic temperatures have risen more than twice as fast as the global average in the past 50 years.
Separate research suggests that Arctic ice is in a downward spiral, declining in area but also thinning. Scientists at the University of Washington Polar Science Centre in Seattle said last week that Arctic sea ice volume was at its lowest ever level in 2010 and was on course to set more records this year. Their data suggests the volume of sea ice last month was about 8900 cubic kilometres - half the average and 62 per cent lower than the maximum covering the Arctic in 1979. The research will be published in 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,'' said researcher Axel Schweiger. If current trends continue, a largely ice-free Arctic in the summer is likely within 30 years - 40 years earlier than anticipated in the last Intergovernmental Panel on Climate Change assessment report.
The last time the Arctic was incontestably 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,'' said Shaye Wolf, climate science director at the Centre for Biological Diversity in San Francisco.
Arctic ice is critical in regulating Earth's climate. Scientists describe retreating summer sea ice as a measure and a driver of global warming.
This year, the north-west and north-east passages were mostly ice free, as they have been twice since 2008.
Last year tied with 2005 as the warmest year on record.
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