NewsFebruary 27, 2012

Warming Arctic Fueling Cold, Snowy Winters, Study Says

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Andrew Freedman

By Andrew Freedman

The blockbuster snowstorms and frigid temperatures seen in much of the northern hemisphere during the past few winters are in part the result of global warming-related Arctic sea ice loss, according to a new study published Monday. The study, published in the Proceedings of the National Academy of Sciences, finds clear links between the precipitous decline of Arctic sea ice and severe winter weather in Europe, Asia, and parts of the U.S. during the past several years.

The study adds to the growing body of evidence pointing to the widespread ramifications of melting Arctic sea ice, proving that what’s happening in the Far North is not just a concern for polar bears anymore.

This study is the first to take a comprehensive look at how Arctic sea ice loss is changing the odds of unusually heavy snows in the Midwest and eastern U.S., as well as parts of Europe and Asia. Using a combination of observational data and computer model simulations, the group of researchers from Georgia Tech, the Chinese Academy of Sciences, and Columbia University, found that sea ice loss—particularly the decline in fall sea ice cover—affects winter weather in the northern hemisphere through a complex series of interactions between the ocean and the atmosphere.

Trend in sea ice extent during January from 1979 to 2012. Credit: NSIDC.

The Arctic has been warming at about twice the rate of the rest of the globe, a trend studies show is largely due to manmade climate change. Fall sea ice cover declined by 27 percent between 1979-2010, and the five lowest sea ice extent years have all occurred during the past five years.

“On the one hand we have increased snowfall for the past four or five winters, and on the other hand we have this reduction in sea ice,” said Jiping Liu, the lead author of the study and a senior research scientist at Georgia Tech. “We found a linkage between the reduction in Arctic sea ice and the increase in winter snowfall in much of the northern continents.”

The chain of events begins during the summer sea ice melt season, when above average air temperatures and warmer waters melt highly reflective sea ice, revealing the darker ocean waters. These waters absorb much more incoming solar radiation, which increases water temperatures. This boost in water temperatures melts more sea ice, and slows the growth of new ice cover during the fall.

The warm, ice-free ocean water allows more heat and moisture to be added to the atmosphere during the fall and winter, which can alter weather patterns in favor of a “wavier” jet stream that makes more frequent dives southward, dragging Arctic air and moisture with it.

According to the study, the end result of all this is that there are increased chances of heavy snowstorms and cold air outbreaks in the Northeastern and Midwestern U.S., as well as Europe and parts of Asia. A key implication of the study is that if sea ice loss continues apace, there may be more cold and snowy winters in store for these areas.

The study sheds light on how sea ice loss may have contributed to recent snowy winters, concluding that Arctic climate change “played a critical role” in harsh winters such as the winters of 2009-10 and 2010-11, which featured the “Snowmageddon” blizzard that dumped several feet of snow in the Mid-Atlantic region, and multiple blizzards that paralyzed parts of the Northeast and Midwest.

Heavy snow fell in Rome in January, part of a deadly European cold wave.

Although the U.S. has had a much milder than normal winter this year, deadly cold and heavy snowstorms have pummeled Europe, killing hundreds, mainly due to hypothermia. The European cold wave was associated with a so-called “blocking pattern” in the atmosphere. Such patterns can lock in weather conditions for long periods of time, dumping more snow in some areas and keeping other regions mild and dry. The study also shows that sea ice loss can alter weather patterns in a way that favors the movement of Siberian cold air masses into Europe, which is what happened this winter.

The study differs from previous research in that it provides evidence that climate change-related sea ice loss can influence weather patterns in a way that is distinguishable from natural climate variability, including the Arctic Oscillation and El Nino. The researchers found that neither of these cycles can explain the observed changes in snowfall and atmospheric circulation.

Jennifer Francis, an atmospheric scientist at Rutgers University who was not involved in this study, said the findings largely fit with other investigations into the ways in which Arctic climate change is reshaping weather patterns.

“... Enhanced Arctic warming, caused by climate change, is increasing the tendency for weather patterns of all sorts to become more “stuck,” she said via email. “The cold [and] snowy winters of late have received a lot of attention, but it should be noted that at the same time other places had abnormally dry and warm conditions.”

Francis said a warming Arctic will increase the chances of extreme winters, both cold and warm. “Which areas will experience which conditions is a tough call.”

For this winter at least, many Americans are probably counting their blessings that the cold air descended on Europe, giving the U.S. a taste of the mild side of extreme winters. But if this new study is proven correct, the break from the cold may not last much longer.