Scientists are discovering links between the loss of Arctic summer sea ice and changes in the polar jet stream over North America and Europe; with the likelihood of more persistent and
extreme weather in years to come.
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| The minimum extent of summer sea ice in the Arctic Ocean in 1979 and 2011. Minimum ice extent has declined by 40 percent in that time, which has further increased warming in the Arctic and begin to effect weather in the Northern Hemisphere. (Image courtesy of The Cryosphere Today/Polar Research Group, the University of Illinois at Urbana-Champaign) |
Weather patterns seem to be getting weirder during the
past few years, with endless snow storms and deep freezes. Then how about the winter of 2011/2012, with unusually warm and snowless conditions over much of North
America?
Jennifer Francis writes, “In early February this year, the jet stream
plunged unusually far southward over Europe, bringing frigid Arctic air
and snow to some areas that hadn’t seen those conditions in over half a
century. During summer, persistent weather patterns are responsible for
droughts and heat. The record heat waves in Europe and Russia in the
past several years have been linked to early snowmelt in Siberia, and a
sluggish high-pressure area caused last summer’s sweltering conditions
in the south-central U.S.“
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This graphic depicts how the drop in high-altitude winds in autumn over the past 30 years has closely tracked the decline in Arctic sea ice (dashed line). The rapid warming of the Arctic has reduced the temperature difference between the Far North and temperate regions, slowing down the jet stream and leading to more persistent, or “stuck,” weather patterns. (Jennifer Francis, based on data from the National Center for Environmental Prediction, National Center for Atmospheric Research, and National Snow and Ice Data Center) |