Study links polar vortex chills to melting sea ice

http://phys.org/news/2014-09-links-polar-vortex-chills-sea.html

by Seth Borenstein
Sept. 2, 2014

A new study says that as the world gets warmer, parts of North America, Europe and Asia could see more frequent and stronger visits of cold air as the world gets warmer.

Researchers say that's because of shrinking ice in the seas off Russia. Less ice would let more energy go from the ocean into the air, and that would weaken the atmospheric forces that usually keep cold air trapped in the Arctic.

But at times it escapes and wanders south, bringing with it a bit of Arctic super chill.

That can happen for several reasons, and the new study suggests that one of them occurs when ice in northern seas shrinks, leaving more water uncovered.

Normally, sea ice keeps heat energy from escaping the ocean and entering the atmosphere. When there's less ice, more energy gets into the atmosphere and weakens the jet stream, the high-altitude river of air that usually keeps Arctic air from wandering south, said study co-author Jin-Ho Yoon of the Pacific Northwest National Laboratory in Richland, Washington. So the cold air escapes instead.

That happened relatively infrequently in the 1990s, but since 2000 it has happened nearly every year, according to a study published Tuesday in the journal Nature Communications. A team of scientists from South Korea and United States found that many such cold outbreaks happened a few months after unusually low sea ice levels in the Barents and Kara seas, off Russia.

The study observed historical data and then conducted computer simulations. Both approaches showed the same strong link between shrinking sea ice and cold outbreaks, according to lead author Baek-Min Kim, a research scientist at the Korea Polar Research Institute. A large portion of sea ice melting is driven by man-made climate change from the burning of fossil fuels, Kim wrote in an email.

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