A record Arctic melt

Satellites show summer 2012 sea ice covering the Arctic Ocean shrunk to a record low

Arctic sea ice forms in the ocean, unlike glaciers and icebergs that form from land-based freshwater.
Andy Mahoney, National Snow and Ice Data Center

During the winter, frozen sea ice covers most of the Arctic Ocean. Every summer, a portion of that ice melts away. Government scientists who keep track of those losses during the warmer months now report this summer has been one for the record books.

On August 26, Arctic sea ice cover fell to 4.1 million square kilometers (about 1.6 million square miles). That’s the smallest ice cover ever observed since scientists started using satellite data in 1979 to measure the yearly melt, note researchers at the National Snow and Ice Data Center (NSIDC) in Boulder, Colo.

“The ice cover is now just so thin and weak in the springtime that large parts of it can’t survive the melt season,” Mark Serreze told Science News. He is an environmental scientist and director of the NSIDC. Melt season in the Arctic typically runs from March through September.

Arctic sea ice plays an important role in Earth’s climate. Unlike glaciers and icebergs, which form from freshwater, sea ice forms when seawater freezes. Usually covered with snow, this ice cools the area around the north pole. The bright-white surface of sea ice reflects sunlight back into space like a giant mirror. During summer, when the ice melts, the ocean’s dark waters become exposed. The result: Less light gets reflected. Seawater heats up as it now absorbs this incoming energy, warming the near-surface temperature of the Arctic Ocean even more.

Satellite data show that Arctic sea ice has hit a new low. The white area shows the extent of Arctic sea ice as of September 3. The orange line shows how much sea ice usually covers the ocean around this time of year.
National Snow and Ice Data Center

This year’s sea ice probably hasn’t reached its lowest point yet. Every year, scientists watch for the Arctic sea ice minimum, which is the day when that ice cover shrinks to its lowest. This usually happens during September, and this year’s minimum will definitely be the lowest on record.

The ice cover is not only getting smaller in area, but what remains is also getting thinner. The Arctic’s sea ice used to be 3 to 4 meters thick (about 10-13 feet). Now most of it is about half that thick.

“It’s almost like parts of the Arctic have become a giant slushee at this time of year,” says Walt Meier, a sea ice expert at NSIDC. As the ice thins, it also weakens. That may allow it to break up easier when a big storm hits. “The Arctic is becoming like a fighter with a glass jaw,” he told Science News.

As autumn hits, the water will start to refreeze. This year, there will be less sea ice to start with than in years past. So there could be even less sea ice next spring when the annual melt begins again.

“It sets us up for another world of hurt next year,” Serreze told Science News.



On September 19, the National Snow and Ice Data Center announced that falling summer Arctic sea ice values had reached a minimum value three days earlier — 3.41 million square kilometers (or about 1.32 million square miles). This is 760,000 square kilometers below the previous record low, which was set in 2007. As the sun begins to set and temperatures plummet, the Arctic sea ice will begin to rebuild.

Power Words

Arctic sea ice Ice that forms from seawater and that covers all or parts of the Arctic Ocean.

glacier A slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles.

climate Weather conditions prevailing in an area in general or over a long period of time. 

Arctic Ocean A sea that surrounds the north pole and lies within the Arctic Circle. Much of this sea is covered with ice throughout the year.

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