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Beaufort Sea ice rot and retreat continues

Doug O'Harra
The Canadian Coast Guard icebreaker Louis S. St. Laurent makes its way through the ice in Baffin Bay Jonathan Hayward/The Canadian Press photo

In what surely adds another dismal harbinger to the summer fate of the Beaufort Sea's ice pack and long-term prospects for Alaska's endangered polar bears, an international research team has discovered that sea ice didn't rebound all that much during the past winter.

A six-week scientific mission to gauge the status of the frozen pack and atmospheric conditions across uninhabited regions of the Arctic Ocean reported significantly thinner ice in the Beaufort Sea than in the past two springs, according a story posted last week by the Alfred Wegener Institute in Germany.

Measurements taken by sensors dangled over floes by the low-flying Polar 5 airplane--a twin-engine, tail-dragging Basler BT-67 specially equipped for Arctic and Antarctic research--revealed that ice was 8 to 12 inches thinner than new ice in 2010 and 2009.

"I expect that this thin one-year-old sea ice will not survive the melting period in summer," said Wegener geophysicist Stefan Hendricks.

The finding of thinner floes comes on top of a 30-year-long decline in overall extent of sea ice, especially during summer. A few weeks ago, the satellite jockeys at the National Snow and Ice Data Center found April sea ice covered the fifth smallest extent on record for that time of year, according to their latest post.

Thinner ice in spring can mean faster meltdown during summer, leading to even smaller coverage by the September minimum, when the accumulated loss eliminates important habitat for polar bears, walruses and seals. As the loss of white reflective ice gives way to the dark ocean surface, the ocean absorbs more solar energy, growing even warmer, and ultimately leading to even thinner ice the following winter. And so the process feeds on itself.

Coordinated by Wegener and University of Alberta scientists, this most recent glimpse of ice thickness along the "inner Arctic" relied on a 13-foot-long sensing device called the EM Bird. As the Polar 5 flew about 300 feet above the ice, the aircraft towed the missile-like contraption at the end of a 50-foot rope.

In temperatures that plunged to 22 degrees below zero, the airplane flew from Barrow to Inuvik near the mouth of the Mackenzie River, then made jumps along the ice-bound rim of the most northern land masses -- Resolute Bay to Eureka to Alert in Canada, then Station Nord in Greenland and finally, to Longyearbyen on Spitsbergen.

"These sites were the base stations for the measurement flights," the story reported. "The total flight time, including measurements and travel time, came to 130 hours."

The group plans to crunch the numbers and issue an estimate in a couple of weeks for just how much sea ice will shrink before it reaches its minimum extent in September.

Preliminary measurements show an accelerating  loss to first-year thickness. The winter of 2008-09 covered the Beaufort Sea with floes that measured just over 5.5 feet thick. The winter of 2009-10: Beaufort's freshman ice hit spring about five inches thinner.

By this spring, Beaufort Sea ice had shrunk another seven inches to about 4.5 feet thick. That's a foot of thickness lost to the late spring ice pack north of Alaska and northwestern Canada over just three seasons.

Along with the Polar 5, the expedition of 25 scientists and engineers deployed other craft from the European Space Agency and NASA. It's all part of a long-running effort involving American, Alaskan, German and Canadian scientists called the Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project. This spring, they also measured trace gases, aerosols and weather. At one point, three planes loaded with sensors flew directly beneath the ESA's CryoSat-2 satellite, conjuring up a unique set of data that linked cutting edge rocket science with birds-eye views of the frozen polar sea.

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