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Arctic ice disappearing

Sept. 20, 2007
Courtesy UC-Boulder
and World Science staff

The ex­tent of Arc­tic sea ice ap­pears to have reached a min­i­mum on Sept. 16, shat­ter­ing all pre­vi­ous lows since sat­el­lite record-keeping be­gan nearly three dec­ades ago, sci­en­tists re­ported Sept. 20.

The ar­ea cov­ered by sea ice in the Arc­tic shrunk to its low­est lev­el re­cently since sat­el­lite mea­sure­ments be­gan near­ly 30 years ago, sci­en­tists say. That resulted in the open­ing of the North­west Pas­sage – a long-sought short­cut be­tween Eu­rope and Asia that has been his­tor­i­cal­ly im­pass­a­ble. Above, an Aug. 31 sat­el­lite im­age of the Mc­Clure Strait in the Ca­na­di­an Arc­tic Archipela­go, the most di­rect route of the North­west Pas­sage. (Cour­te­sy Eu­ropean Space Agen­cy)


“The amount of ice loss this year ab­so­lutely stunned us be­cause it did­n’t just beat all pre­vi­ous records, it com­pletely shat­tered them,” said sen­ior sci­ent­ist Mark Ser­reze of the Un­ivers­ity of Col­o­rad­o at Boul­der’s Na­t­ional Snow and Ice Da­ta Cen­ter. 

Sci­en­tists have at­trib­ut­ed the van­ish­ing ice to glob­al warm­ing and said it could dis­ap­pear in sum­mers by mid-century. Ris­ing con­centra­t­ions of heat-trapping green­house gas­es in the at­mos­phere, mostly due to hu­man ac­ti­vi­ties, and strong nat­u­ral vari­abil­ity in Arc­tic sea ice have raised tem­per­a­tures from 2 to 7 de­grees Fahr­en­heit across the Arc­tic, re­search­ers say.

Arc­tic sea ice as of Sept. 16 covered about 1.59 mil­lion square miles, or 4.13 mil­lion square kilo­me­ters, ac­cord­ing to the team. Com­pared to the long-term min­i­mum av­er­age from 1979 to 2000, the new min­i­mum ex­tent was low­er by about 1 mil­lion square miles—an ar­ea about the size of Alas­ka and Tex­as com­bined, or 10 Un­ited King­doms, they re­ported.

The min­i­mum al­so breaks the pre­vi­ous min­i­mum set in Sep­tem­ber 2005 by about 460,000 square miles, an ar­ea roughly the size of Tex­as plus Cal­i­for­nia, or five Un­ited King­doms, they found. The sea ice ex­tent is the to­tal ar­ea of all Arc­tic re­gions where ice co­vers at least 15 per­cent of the ocean sur­face.

The re­search group said de­ter­min­ing the an­nu­al min­i­mum sea ice is dif­fi­cult un­til the melt sea­son has de­ci­sively ended. But the team has recorded five days of lit­tle change, and even slight gains in Arc­tic sea ice ex­tent this Sep­tem­ber, so reach­ing a low­er min­i­mum for 2007 seems un­like­ly, they re­ported.

Arc­tic sea ice gen­er­ally reaches its min­i­mum ex­tent in Sep­tem­ber and its max­i­mum in March. The re­search­ers used sat­el­lite da­ta from NASA, the Na­t­ional Oce­an­ic and At­mos­pher­ic Ad­min­is­tra­t­ion and the U.S. De­part­ment of De­fense, as well as da­ta from Ca­na­di­an sat­el­lites and weath­er ob­ser­va­to­ries.


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The extent of Arctic sea ice appears to have reached a minimum on Sept. 16, shattering all previous lows since satellite record-keeping began nearly three decades ago, scientists reported Sept. 20. “The amount of ice loss this year absolutely stunned us because it didn’t just beat all previous records, it completely shattered them,” said senior scientist Mark Serreze of from the University of Colorado at Boulder’s National Snow and Ice Data Center. Scientists have attributed the vanishing Arctic ice to global warming and said that it could disappear in summers by mid-century. Rising concentrations of heat-trapping greenhouse gases in the atmosphere, mostly due to human activities, have raised temperatures from 2 to 7 degrees Fahrenheit across the Arctic and strong natural variability in Arctic sea ice, researchers say. The Arctic sea ice extent on Sept. 16 stood at about 1.59 million square miles, or 4.13 million square kilometers, according to the team. Compared to the long-term minimum average from 1979 to 2000, the new minimum extent was lower by about 1 million square miles—an area about the size of Alaska and Texas combined, or 10 United Kingdoms, they reported. The minimum also breaks the previous minimum set on Sept. 20 and Sept. 21 of 2005 by about 460,000 square miles, an area roughly the size of Texas and California combined, or five United Kingdoms, they found. The sea ice extent is the total area of all Arctic regions where ice covers at least 15 percent of the ocean surface. The research group said determining the annual minimum sea ice is difficult until the melt season has decisively ended. But the team has recorded five days of little change, and even slight gains in Arctic sea ice extent this September, so reaching a lower minimum for 2007 seems unlikely, they reported. Arctic sea ice generally reaches its minimum extent in September and its maximum extent in March. The researchers used satellite data from NASA, the National Oceanic and Atmospheric Administration and the U.S. Department of Defense, as well as data from Canadian satellites and weather observatories for the study.