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NSIDC confirms Arctic sea-ice minimum Third lowest Arctic sea-ice extent continues downward trend in ice cover; little ice more than five years old now thought remaining Alan Bailey Petroleum News
The National Snow and Ice Data Center has confirmed that the 2010 Arctic sea-ice extent minimum occurred Sept. 19, a little later than the preliminary date of Sept. 10 that NSIDC scientists at first reported. At the minimum, there was open water in the Northwest Passage around the north of North America, and along the entire Northern Sea Route that runs along the northern coast of Russia.
“Two sailing expeditions, one Norwegian and one Russian, successfully navigated both passages and are nearing their goal of circumnavigating the Arctic,” NSIDC said Oct. 4.
This year’s sea ice minimum, at 1.78 million square miles, was the third lowest on record since the advent of satellite monitoring in 1979. The record minimum of 1.65 million square miles occurred in September 2007, followed by a minimum of 1.8 million square miles in September 2008 and 1.97 million miles in September 2009.
An analysis of the ice-extent minima since 1979 shows a continuing average decline rate of 11.5 percent per decade, NSIDC said.
Rapid June melt Following winter weather conditions that favored retention of ice in the Arctic Ocean, the ice extent was relatively high at the beginning of this year’s ice-melt season. But in June, with high pressure over the Arctic Ocean and unusually low pressure over Siberia, warm Arctic weather and a strong westward ice motion off the Siberian coast caused a rapid ice melt. The melt rate slowed in July as a series of low-pressure systems moved into the central Arctic Ocean, although storms helped break up the ice. August saw a return to somewhat warmer weather that persisted into the first week of September, thus causing the ice extent to drop towards its minimum, NSIDC said.
Researchers from the University of Washington also found Arctic sea water surface temperatures to be higher than normal this year, with temperatures being especially high in the Beaufort Sea, the Chukchi Sea and in the region north of the Laptev Sea, NSIDC said. The relatively warm water, a result of the ability of dark open water to absorb more solar heat than the white surface of ice, helped accelerate the melt.
“This positive feedback likely contributed to the ice loss through summer 2010, especially late in the season when surface melt had largely ceased,” NSIDC said.
And although winter wind patterns had shifted much relatively thick, multiyear ice from the Canadian Arctic coast into the Beaufort and Chukchi Seas, where the ice might be expected to survive the summer, much of this older ice had in fact melted, thus leaving almost no ice older than five years in the Arctic, NSIDC said. How much of the remaining, younger multiyear ice survives will depend on how much of that ice gets blown into the North Atlantic through the Fram Strait, and how much remaining multiyear ice melts during its transit of the Beaufort and Chukchi Seas, NSIDC said.
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