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Arctic in meltdown?

Sept. 13, 2006
Courtesy NASA
and World Science staff

Glob­al warm­ing seems to have caused rec­ord low sea ice the past two years in the Arc­tic win­ter won­der­land, known for its icy wa­ter­ways and snowy scen­er­y, NASA re­search­ers say. The melt­ing, they add, ap­pears to be harm­ing po­lar bears and other ani­mals.  

In 2005 and 2006, the win­ter ice max­i­mum was about 6 per­cent less than the av­er­age amount over the past 26 years, re­search­ers say. Click on the im­age to view a NASA an­i­ma­tion showing win­ter sea ice co­ver dur­ing its an­nu­al max­i­mum ex­tent from 1979 to 2006. The edge of the yel­low ar­e­a rep­re­sents the far­thest reach of the ice since 1979. (Cred­it: NASA)

Sci­en­tists from the agen­cy used sat­el­lite ob­ser­va­tions to re­c­ord un­u­su­al­ly warm win­tertime tem­pe­r­a­tures in the re­gion. 

The max­i­mum amount of sea ice in the Arc­tic win­ter has fall­en by six per­cent over each of the last two win­ters, they said. This com­pares to just 1.5 per­cent per de­c­ade on av­er­age an­nu­al­ly since the ear­li­est sa­t­el­lite mo­n­i­tor­ing in 1979. 

This is hap­pen­ing as sum­mer sea ice con­tin­ues a re­treat at an av­er­age of 10 per­cent per dec­ade, they added.

“This amount of Arc­tic sea ice re­duc­tion the past two con­se­c­u­tive win­ters has not ta­k­en place be­fore dur­ing the 27 years sat­el­lite da­ta has been avai­l­able,” said Jo­ey Co­mi­so, a re­search sci­entist at NASA’s God­dard Space Flight Cen­ter in Green­belt, Md. 

“In the past, sea ice re­duc­tion in win­ter was sig­ni­f­i­cant­ly low­er per de­c­ade com­pared to sum­mer sea ice... What’s re­mark­a­ble is that we’ve wit­nessed sea ice re­duc­tion at six per­cent per year over just the last two win­ters, most like­ly a re­sult of warm­ing due to green­house gas­es.”

In this image, the whole of the sea surface is made of forming sea ice. (Credit: NASA)

Most sci­entists blame glob­al warm­ing on green­house gas­es, sub­stances such as car­bon di­ox­ide emit­ted as a re­sult of hu­man ac­tiv­i­ties and that col­lect in the at­mos­phere. Last June, sci­en­tists re­port­ed that the Earth seems to have ex­per­ienced its hot­test tem­p­er­a­tures in 400 years in re­cent de­cades.

Comiso used a com­put­er sim­u­la­tion and sat­el­lite da­ta in the stu­dy, to be pub­lished in the jour­nal Ge­o­phys­i­cal Re­search Let­ters this month.

If the win­ter ice re­treat con­tin­ues, the ef­fect could be pro­found, es­pe­cial­ly for sea an­i­mals, he said. “The sea­son­al ice re­gions in the Arc­tic are among the most bi­o­log­i­cal­ly pro­duc­tive re­gions in the world,” he added. 

“For ex­am­ple, sea ice pro­vides melt-water in spring that floats be­cause of low den­si­ty. This melt-water lay­er is con­sid­ered by bi­ol­o­gists as the ide­al lay­er for phy­to­plank­ton growth.”

Phytoplankton is a key part of plank­ton, ag­gre­gates of small plant and animal or­ga­nisms that float or drift in great num­bers in water. “Plank­ton are at the bot­tom of the food web,” so if their con­cen­tra­tion goes down, ani­mals at all le­vels could suf­fer, he ar­gued.

Sci­en­tists from NASA and the Ca­na­di­an Wild­life Serv­ice al­so re­ported that the re­duc­tion in sea ice is de­priv­ing Arc­tic po­lar bears of food by short­en­ing the spring hunt­ing sea­son for fe­males. That is prob­a­bly re­spon­si­ble for an ob­served weight loss in the bears, the re­search­ers said; and the light­er the fe­males, the less they can re­pro­duce and feed their young.

Sci­en­tists have pre­vi­ously re­ported that the warm­ing might al­so be or­phan­ing wal­rus pups and forc­ing po­lar bears to can­ni­bal­ism.


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Global warming seems to have caused record low sea ice the past two years in the Arctic winter wonderland, known for its icy waterways and white snowy scenery, NASA researchers say. Scientists from the agency used satellite observations to record unusually warm wintertime temperatures in the region. The maximum amount of sea ice in the Arctic winter has fallen by six percent over each of the last two winters, they said, compared to just 1.5 percent per decade on average annually since the earliest satellite monitoring in 1979. This is happening as summer sea ice continues its retreat at an average of 10 percent per decade, they added. “This amount of Arctic sea ice reduction the past two consecutive winters has not taken place before during the 27 years satellite data has been available,” said Joey Comiso, a research scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. “In the past, sea ice reduction in winter was significantly lower per decade compared to summer sea ice retreat. What’s remarkable is that we’ve witnessed sea ice reduction at six percent per year over just the last two winters, most likely a result of warming due to greenhouse gases.” Comiso used a computer simulation and satellite data to carry out the study, to be published in the research journal Geophysical Research Letters this month. Computer simulations of the climate warming effect of greenhouse gases had predicted that winter sea ice would decline faster than summer sea ice, Cosimo said. Adding to the plight of winter sea ice, previous research has shown a trend in which the melt period lasts about 2 weeks longer per year annually due to summer sea ice decline, he added. If the winter ice retreat continues, the effect could be very profound, especially for marine animals, he continued. “The seasonal ice regions in the Arctic are among the most biologically productive regions in the world,” he said. “For example, sea ice provides melt-water in spring that floats because of low density. This melt-water layer is considered by biologists as the ideal layer for phytoplankton growth because it does not sink, and there is plenty of sunlight reaching it to enable photosynthesis. Plankton are at the bottom of the food web. If their concentration goes down, animals at all tropics level would be deprived of a basic source of food.” Most scientists blame global warming on greenhouse gases, substances such as carbon dioxide emitted as a result of human activities and that collect in the atmosphere.