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Tuesday, August 30, 2011

Polarstern: Arctic sea ice at the North Pole half as thick as it was in 2001

North Pole sea ice half as thick as 2001

Sea ice floating near the top of the world appears to be half as thick as it was 10 years ago, according to reports from a premier German research icebreaker on a 9-week mission to survey the Arctic Ocean from one side to the other.
The 387-foot Polarstern plowed through floes at the geographic North Pole at exactly 11:42 p.m. ADT on August 21, 2011, and is now steaming south toward Canada, according to this story posted by the Alfred Wegener Institute for Polar and Marine Research.
Over the past few weeks, initial measurements of sea ice have averaged about 0.9 meters or about three feet — 1.1 meters thinner than comparable measurements taken in 2001, the last time the Polarstern visited the North Pole and a season when observed floe depth matched the long-term average.
But in what could be a disconcerting harbinger for the 2010 melt season — about to reach its low point during the next 3-4 weeks — the ice thickness measured by Polarstern scientists this summer is almost exactly the same as measurements taken in the central Arctic in 2007.
That’s the year the polar ice cap shrank to its all-time summer minimum — a dismal record that the current overall ice cap has been flirting with off-and-on for weeks.
The Arctic “is now experiencing a similarly small ice cover as the year that went down in the annals as the one with the lowest extent of sea ice since the beginning of satellite measurements in 1979,” according to chief scientist Ursula Schauer, an oceanographer from the Institute, in this story filed from the North Pole.
Sunday’s North Pole visit marked the vessel’s third visit to the home planet’s most northern point. In 1991, the Polarstern and the Swedish research icebreaker Oden became the first two conventionally driven ships to sail there. The Polarstern returned almost exactly 10 years later to the day with the U.S. Coast Guard icebreaker Healy.
But the vessel’s most startling navigational feat might have occurred in 2008, when it performed the first circumnavigation of the Arctic Ocean by traversing both the Canadian Northwest Passage and the Russian Northern Sea Route during a single 10,800-nautical-mile voyage.
One of the world’s most sophisticated and versatile research vessels, the Polarstern has conducted more than 50 separate missions since commissioned in 1982 and spends about 310 days a year at sea. Its double-hull construction allows it to bash through ice up to five feet thick while cruising at 5 knots, and can handle temperatures that descend to about -60 °F, making it capable of overwintering in the polar night. Its name means “Pole Star.”
This time, the ship is driving straight across from Franz Josef Land to the western Canadian Basin. This tracking map shows the vessel’s completed route and its current location in real time. With 55 scientists from 6 countries aboard, the goal of the latest “TransArc” mission is to document changes in water, air and ice, plus take samples from the sea floor for clues to ancient life and climate.
Trip progress was initially brisk due to the lack of thick floes, according to the story. Still, the ice did thicken somewhat as they drew further north.
“Since 9 August, the Polarstern has been sailing through dense pack ice on the route along 60° East in temperatures of around 0 °C. At first it was predominantly one-year-old sea ice, now older and consequently thicker ice floes appear.”
Visiting the North Pole itself, that mythic polar locale that dazzles the imagination and makes for whiz-bang headlines, isn’t really the point of the trip, Schauer explained.
“From a scientific point of view the North Pole is not more interesting than other places in the Arctic,” she said in statement made when the ship passed the pole. “The expected changes are rather minor here. However, the northern part of the Canadian sector of the Arctic still numbers among the least researched regions on the globe because of the dense pack ice.”
The scientists have so far struggled to find floes thick enough to conduct experiments and take measurements, according to last week’s trip report.
“It has not been easy to find a suitable ice flow to work at,” Schauer wrote. “The ice is covered by melt ponds — they look beautifully but make the flows very porous. Melt ponds are darker and thus absorb the sun’s heat stronger than the surrounding whitish ice, setting up a positive feedback loop that allows melting of even more ice.
“The ponds make the flows fragile, so when Polarstern tries to go alongside such a flow, it simply breaks in pieces. For a large ice station on Friday we had to spend 5 hours searching for a suitable flow.”
Even worse, the same warm weather that has contributed to one of the biggest meltbacks of Arctic ice on record has often enveloped the Polarstern in amorphous soup.
“Since the beginning of our research program, low-pressure systems have brought moist warm air to the central Arctic, and we have rarely seen the sun,” Schauer wrote in the report. “Fog and low clouds prevail, and the visibility is so poor that our helicopters cannot fly. This hampers an important part of our programme – the measurement of ice thickness.”
For those of us who Deutsch spreche, here is a daily blog posted by GEO Magazine in German about the latest science activity aboard the ship at the top of the world. If you can’t read it, cutting and pasting the text block into a Google translators will harvest you the gist of what’s happening. Not to mention, like any non-reader (i.e., a toddler) you can admire the pictures.
Contact Doug O'Harra at doug(at)

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