October 22, 2010

Warmer Arctic, Melting Sea Ice Likely Permanent: NOAA

Climate scientists at the U.S. National Oceanic and Atmospheric Administration (NOAA) reported Thursday that Arctic temperatures are on the rise again.

The sea ice extent has also fallen to one of the lowest levels on record, according to NOAA's annual Arctic report card, which was prepared this year by 69 researchers in eight countries.

"A return to previous Arctic conditions is unlikely," wrote the scientists in the report.

"Record temperatures across Canadian Arctic and Greenland, a reduced summer sea ice cover, record snow cover decreases and links to some Northern hemisphere weather support this conclusion," they said.

The 100-page report "tells a story of widespread, continued and even dramatic effects of a warming Arctic," said Jackie Richter-Menge of the Cold Regions Research and Engineering Laboratory, a U.S. Army Corps of Engineers facility in Hanover, N.H.

"This isn't just a climatological effect. It impacts the people that live there," she told The Associated Press (AP).

Climate scientists concerned about global warming look particularly to Arctic conditions because they believe that region is among the first to show the effects of the phenomenon.

Although there was a slowdown in Arctic warming in 2009, it picked up to near a record pace during the first half of 2010, with monthly measurements more than 7.2 Fahrenheit (4 degrees Celsius) above normal in parts of northern Canada, according to the report.

The researchers said last winter's brutal snowstorms in the Northeast U.S. and Mid-Atlantic states were linked to higher Arctic temperatures.

"Normally the cold air is bottled up in the Arctic," said Jim Overland of NOAA's Pacific Marine Environmental Laboratory in Seattle, WA.

However, last winter, winds that typically move from west to east across the Arctic were instead bringing the colder air south to the Mid-Atlantic, he explained.

"As we lose more sea ice it's a paradox that warming in the atmosphere can create more of these winter storms," Overland told reporters during a news briefing.

There is a strong relationship between ice cover and air temperatures, Richter-Menge said.  

When temperatures warm, the ice melts, resulting in less reflectivity and increased heat absorption within the darker surfaces below.  That, in turn, causes further melting "and on the cycle goes," she explained.

In September, the Arctic sea ice extent was the third smallest in three decades, said Don Perovich of the Army laboratory.  Furthermore, three of the smallest known ice covers have occurred during the last four years, he added.

The accumulation of winter snow on Arctic land was also the lowest since records began being kept in 1966, the report said.  Meanwhile, glaciers and ice caps in Arctic Canada are losing mass at an accelerating rate since 1987. 

Permafrost temperatures in northwest Canada, Alaska, Northern Europe and Siberia are also on the rise, the researchers reported.

Greenland experienced record-setting high air temperatures in 2010, as the largest recorded glacier area loss took place this summer at Petermann Glacier, where a slab of ice many times greater than Manhattan Island broke away.

In addition to Richter-Menge, Perovich and Overland, lead researchers for the report included Jason Box, Ohio State University; Mary-Louise Timmermans at Yale University; Mike Gill, Environment Canada; Martin Sharp, University of Alberta, Canada; Chris Derksen, Environment; and D.A. Walker, Vladimir Romanovsky and Uma Bhatt, University of Alaska-Fairbanks.


Image Caption: The ASTER instrument on NASA's Terra spacecraft captured this image of a massive iceberg from Greenland's Petermann Glacier on Aug. 12, 2010. The iceberg could eventually interfere with the flow of sea ice out of the Arctic and could ultimately be a threat to shipping. Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team


On the Net: