Warming Oceans Contributed to Record Arctic Melt

Mason Inman in San Francisco, California
for National Geographic News
December 14, 2007

Arctic sea ice shrank drastically this summer, reaching a record low, largely because warm ocean currents ate away at the base of the ice sheet, new research says.

Wind currents also played a key role, blowing sea ice south into the Atlantic Ocean, where the ice then melted, according to the research.

With more global warming in store, researchers said, the prognosis is grim for the Arctic's so-called perennial sea ice, which is the ice that survives through the summer.

At the fall meeting of the American Geophysical Union (AGU) in San Francisco, some scientists argued yesterday that the end of the perennial ice is near.

"If this trend persists, the Arctic would be ice-free [in the summer] by 2013," said Wieslaw Maslowski of the Naval Postgraduate School in Monterey, California.

Donald Perovich of the U.S. Army Corps of Engineers likened the situation to a losing football game.

"A comeback is possible," Perovich said. "But it's like the fourth quarter, and we're down by two touchdowns."

Record-Breaking Melt

The Arctic's perennial sea ice has been shrinking since the 1980s.

Before then, ice filled the whole Arctic Ocean throughout the summer, occupying an area the size of the continental United States.

But the melt this year brought it to a new low in September, melting an area larger than all of the U.S. states east of the Mississippi River.

The new record blew the old record, set in 2005, out of the water, shrinking to just three-quarters the size of that earlier low.

The ice that remains is also newer ice, which is typically not as strong as ice that's been compacted over several years, according to Jim Maslanik of the National Snow and Ice Data Center in Boulder, Colorado.

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