By Bryce Anderson
DTN Ag Meteorologist
OMAHA (DTN) -- The dramatic loss of sea ice in the Arctic Ocean due to rapid Arctic warming has altered the polar-region jet stream and helped to bring on extreme weather events of recent years, including the Midwest drought of 2012, record flooding rains of 2013, and the harsh, cold 2013-2014 winter, according to a climate-change expert at Rutgers University.
Jennifer Francis, an atmospheric research professor at Rutgers University's Institute of Marine and Coastal Sciences, said, in the past 30 years, climate change has dramatically altered the Arctic Ocean, with sea ice volume now just one-fourth of what it was in the 1980s.
These ideas were first presented in a 2012 research paper by Francis and Stephen Vavrus of the University of Wisconsin-Madison, titled "Evidence Linking Arctic Amplification to Extreme Weather in Mid-Latitudes."
"The Arctic is warming two to three times faster than the mid-latitudes," Francis said. "That difference in warming is the main driver of changes in the jet stream. Our analysis suggested that this was happening."
Francis' research indicates that the rapid rate of warming in the Arctic has reduced the air temperature difference between the far northern latitudes and locations farther south. That reduction in temperature difference, in turn, has slowed down the polar jet stream, creating a polar jet configuration that has large north-to-south waves, with the final result being weather patterns that are "stuck" for longer time periods than in the years before the sharply warmer trend in the far north.
"This winter is a wonderful example" of these extremes, said Francis. "Most of the Northern Hemisphere was much warmer than normal -- Alaska, Scandinavia, the northern Canadian Maritimes. It just so happened that the Midwest and the East (U.S. and Canada) were in the southward dips. But then, look at the winter in 2012, when we had over 3,000 high temperature records. There was a similar pattern, but in a different location."
Francis calls this jet stream re-configuration "Arctic Amplification." When the paper by her and Vavrus was first presented to the American Geophysical Union three years ago, the reaction was, in its own way, extreme. "Someone said that we had found the Holy Grail (of extreme weather); they said 'Why hasn't anyone found this before?' It really opened the door to a new way of thinking," Francis said.
The Arctic Amplification approach to understanding extreme weather has merit, according to Al Dutcher, Nebraska state climatologist. "It certainly goes along with atmospheric theory -- that if the (temperature) differential between the mid-latitudes and the polar region tends to narrow, that it will impact the strength of storm systems if the jet stream relaxes," Dutcher said.
But Dutcher sees the Arctic warming analysis as just part of a broader-scale issue. "The separation of the full impacts of different ocean components is the big question going forward -- understanding the heat content in the oceans and that distribution," he said. "The problem is -- how do oceans distribute that heat and will that modify this atmospheric pattern?"
Francis agrees that scientists have much more to do to understand what fully happens with the trends that are occurring in the Arctic. "It's a noisy climate system that we live in... scientists like to say that we are 95% confident that this pattern is real, but we need 10 more years of real-world evolution to get there," she said.
She has also had some "push-back" regarding her findings. "Most of this has been related to other studies that have not reproduced our analysis ... but nobody is saying that these views are wrong," she said.
As far as a message for farmers, Francis said that the only definite trend she can identify at this time is that more large-scale changes are likely. "We could have a cold winter -- there could be drought -- it depends on where the (jet stream) waves are located in any given year. There are a lot of people working on that," she said.
And, even though the history of this Arctic research on the climate-change-induced jet stream change is still in its nascent phase, Francis is glad to discuss its implications.
"This is a plausible hypothesis. There is evidence that supports it. The impacts are potentially huge. I feel that if I didn't focus on this issue, it would be something that I would regret," she said. "I definitely have stirred the pot."
Bryce Anderson can be reached at email@example.com
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