Although it doesn’t seem like it on this 62 degree day in late February in Missouri, the loss of Arctic ice cover has been correlated to cold, snowy winters in the Northern Hemisphere and Europe is certainly feeling the chill. Last years’ “Snow-mageddon” may have been better example of what the U.S. can expect more of in years to come.
The Arctic’s sea ice hit a low in the summers of 2006 and 2007, and never recovered. Climate scientists recently published a study suggesting melting sea ice affects the jet stream and afflicts the North with nasty winters.
“For the past four winters, for much of the northern U.S., east Asia and Europe, we had this persistent above-normal snow cover,” Jiping Liu from Georgia Institute of Technology in Atlanta, Ga., and the Institute of Atmospheric Physics in Beijing told BBC News.
Liu led the study published recently in the Proceedings of the National Academy of Sciences.
“We don’t see a predictive relationship with any of the other factors that have been proposed, such as El Niño; but for sea ice, we do see a predictive relationship,” Liu said.
Liu’s team also explained why this happens.
When the Arctic Ocean has less ice cover in Autumn, it releases more heat and warms the atmosphere. Warmer Arctic air doesn’t sink as much, and hence doesn’t draw in warmer air from further south. That slows the jet stream. Historically, the jet stream brought warmer, wetter winters to Europe.
“It’s possible that future winters will be colder and snowier, but there are some uncertainties,” said Liu.
Other factors affect the Arctic and subsequently the northern winter. Differences in solar radiation and La Niña conditions, such as we have this year, can also bring green Christmases to the North. La Niña helps to keep the jet stream flowing from west to east across Canada, thus trapping chilly weather north of the U.S. border.
Also, the Arctic Oscillation created a low pressure system around the North Pole this year, which also helped trap the cold. The Oscillation shifted in January, but winter still seems weak in most of the U.S.
The Arctic Ocean off Tromso, Norway (Vinay Deep, Wikimedia Commons)