Thursday, August 11, 2011

Arctic ice melt could pause in near future, then resume again

Jennifer Kay, Marika Holland, and Alexandra Jahn in University Corporation for Atmospheric Research News: Although Arctic sea ice appears fated to melt away as the climate continues to warm, the ice may temporarily stabilize or somewhat expand at times over the next few decades, new research indicates. The computer modeling study, by scientists at the National Center for Atmospheric Research, reinforces previous findings by other research teams that the level of Arctic sea ice loss observed in recent decades cannot be explained by natural causes alone, and that the ice will eventually disappear during summer if climate change continues.

But in an unexpected new result, the NCAR research team found that Arctic ice under current climate conditions is as likely to expand as it is to contract for periods of up to about a decade. “One of the results that surprised us all was the number of computer simulations that indicated a temporary halt to the loss of the ice,” says NCAR scientist Jennifer Kay, the lead author. “The computer simulations suggest that we could see a 10-year period of stable ice or even a slight increase in the extent of the ice. Even though the observed ice loss has accelerated over the last decade, the fate of sea ice over the next decade depends not only on human activity but also on climate variability that cannot be predicted.”

Kay explains that variations in atmospheric conditions such as wind patterns could, for example, temporarily halt the sea ice loss. Still, the ultimate fate of the ice in a warming world is clear. “When you start looking at longer-term trends, 50 or 60 years, there’s no escaping the loss of ice in the summer,” Kay says.

Kay and her colleagues also ran computer simulations to answer a fundamental question: why did Arctic sea ice melt far more rapidly in the late 20th century than projected by computer models? By analyzing multiple realizations of the 20th century from a single climate model, they attribute approximately half the observed decline to human emissions of greenhouse gases, and the other half to climate variability. These findings point to climate change and variability working together equally to accelerate the observed sea ice loss during the late 20th century....

Aerial view of the Chukchi Sea between Chukotka and Alaska. Shot by P199, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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