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Arctic sea ice remains near historic minimum despite freeze-up

Doug O'Harra

Plunging temperatures and the shorter days of approaching winter transformed vast reaches of the Arctic Ocean into ice during October — a freeze-up that has been 40 percent faster than average, according to the latest sea ice analysis posted by the National Snow & Ice Data Center.

It may be too little, too late.

Despite the creation of 44,360 square miles of new ice each day — adding floes nearly equal to the size of Ohio every 24 hours — the polar sea north of Alaska ended the month with the second smallest extent ever observed during the age of satellites, about 87,300 square miles larger than the all-time minimum record set in October 2007.

“Large areas of open water were still present in the Beaufort and Chukchi seas at the end of the month,” the NSIDC reported here. “The open water contributed to unusually warm conditions along the coast of Siberia and in the Beaufort and Chukchi seas.”

This late formation of ice along Alaska’s northwest coast is part of a multi-decade trend contributing to beach erosion in Kivalina, Shishmaref and other Arctic villages — forcing the communities to embark on multi-million-dollar quests to find new locations. Without the armor of sea ice fastened to land during the fall storm season, villages become vulnerable to big surf. Homes, roads, power poles and other infrastructure can all be lost.

A new study has confirmed that the erosion rate along the Beaufort Sea — Alaska’s Arctic shoreline east of Point Barrow — almost doubled over the past 30 years, increasing from about 27.9 feet per year between 1979 and 1999 to more than 47 feet per year in 2008 and 2009.

“Erosion rates of permafrost coasts along the Beaufort Sea accelerated over the past 50 years synchronously with Arctic-wide declines in sea ice extent, suggesting a causal relationship between the two,” wrote Irina Overeem of the University of Colorado Institute for Arctic and Alpine Research and five other Colorado scientists in Geophysical Research Letters.

This longer “open water season” can conspire with Arctic storms to destroy permafrost bluffs along Alaska's coast, the NSIDC added.

“Sediments comprising the coastal bluffs are locked together by permafrost — hard frozen ground with a concrete-like consistency,” the NSIDC analysis said. “As the waves lap at the permafrost, they also help to thaw it, making the ground much more vulnerable to erosion.”

Melting Arctic sea ice matters -- to everyone

It’s all part of a decades-long decline in sea ice thickness, volume and coverage that scientists attribute to a complex alchemy of climate change that includes shifts in weather patterns and ocean currents.

Why does it matter? The Earth’s ice cap plays an essential role in stabilizing the world’s climate, and its summer retreat  directly contributes to climate warming because darker open water absorbs more solar energy than the reflective white floes. The exposed ocean then stores heat that in turn and causes even swifter melt and later fall ice formation.

Summer sea ice also provides habitat necessary to maintain healthy populations of polar bears, walruses and seals. When this hunting and denning platform disappears, marine mammals must swim farther or spend time on shore, making it hard to find enough to eat or avoid predators. The United States has listed the polar bear as threatened under the Endangered Species Act due to the shrinking ice pack north of Alaska.

2011’s summer ice loss pretty much matched the record destruction seen in 2007, according to various calculations. Ice covered only about 1.78 million square miles during September — more than 40 percent lower than the monthly average recorded between 1979 and 2000 and only 120,000 square miles above the minimum seen in 2007. But this surface footprint, reported here by NSIDC, doesn’t tell the whole story.

The total volume of sea ice — size of the surface coverage plus all the ice hidden beneath — appears to have plunged to about the same unprecedented levels seen last year, according the Polar Science Center at the University of Washington. Meanwhile, a European team found that 2011 may have slipped below the record set in 2007, according to this mid-September story posted by the European Space Agency.

“In the central Arctic the proportion of old, thick sea ice has declined significantly,” according to an October report from the German research icebreaker Polarstern. “Instead, the ice cover now largely consists of thin, one-year-old floes.”

The ocean always refreezes quickly during October. But even an above average rate of new ice formation can’t overcome such huge summer losses. Each decade, the race to solidify the ice cap starts further behind.

“During the month of October, the freeze-up that begins in September kicks into high gear,” the NSIDC explains here. “The rate of freeze-up depends on several factors including the atmospheric conditions and the amount of heat in the ocean that was accumulated during the summer.

“However, each decade, the October extent has started from a lower and lower point, with the record low extent during the 1980s (1984) substantially higher than the record low extent during the 1990s (1999), which in turn is substantially higher than the record low extent during the 2000s (2007).”

Add it all up, and the winter of 2011-12 has grim prospects for rebuilding the polar ice cap.

A graphic here shows the average ice extent for October, with this graphic comparing this extent to previous years. A satellite-generated graphic posted for Nov. 2 on Cryosphere Today clearly delineates a vast triangular shaped open sea remaining north of the Bering Sea between Alaska and far eastern Siberia.

It's November, and the ocean off Alaska remains largely ice free.

Contact Doug O'Harra at doug(at)alaskadispatch.com