A new study in the journal Nature Climate Change is suggesting that Arctic sea ice loss may be a consequence of the atmospheric conditions driving colder winters in parts of North America, Europe, and Asia, rather than the cause of a series of cold snaps dating back to the polar vortex of 2013-2014.
The new study “combines observations over the past 40 years with results from climate modeling experiments,” the Washington Post reports. “Scientists found that both sources of data show that reduced regional sea ice and cold winters coincide, but that one does not necessarily cause the other.”
That finding runs counter to “numerous studies that have focused on Arctic warming and cold mid-latitude winters, in a configuration known as the ‘warm Arctic, cold continents’ pattern,” the Post notes. The previous research “generally concluded that sea ice loss at the top of the world is instigating a chain reaction throughout the atmosphere, altering the weather thousands of miles away” by producing a “wavier” jet stream more likely to keep weather patterns stuck in one place.
“Such studies do this by looking at statistical patterns, finding strong correlations between Arctic warming and unusual mid-latitude weather.”
The latest paper by atmospheric scientists from the United States and The Netherlands “finds that the same atmospheric circulation patterns that give rise to severe mid-latitude winter weather also serve to transport relatively mild air into parts of the Arctic, reducing ice cover,” the Post explains. “In other words, the pattern bringing the snow and cold to places such as DC, New York, and parts of northeast Asia is also eating away at sea ice, rather than the other way around.” Sea ice loss, the scientists wrote, is having only “a minimal influence” on severe mid-latitude winters.
“We found the direction of heat flow during cold events was predominantly from the atmosphere to the ocean, suggesting sea ice loss as a consequence, not a driver,” wrote study co-author James Screen of the University of Exeter, in an email to the Post. “We found cold events, and the circulation patterns that cause them, set up before the reduced sea ice, again pointing to sea ice loss as a consequence of circulation changes, not a driver of them. Lastly, climate model experiments with reduced sea ice showed no circulation change or cooling.”
Woods Hole Research Center atmospheric scientist Jennifer Francis said the latest research isn’t the last word on a complex issue. “While this study helps unravel the knotted web connecting Arctic change and weather patterns, it does not address a variety of factors that could explain the recent warm Arctic/cold continent patterns,” she told the Post. “When it comes to connections between the Arctic and mid-latitude weather, both chickens and eggs are still fair game.”
James Overland, an oceanographer with the U.S. National Oceanic and Atmospheric Administration (NOAA), maintained that regional ice loss could still be reinforcing “wavy” jet stream patterns. The “recent delay in freeze-up of sea ice in early winter north of Alaska and in the Barents Sea can help reinforce, not cause, a wavy jet stream pattern,” he said.
Far from being an “esoteric battle being fought in scientific journals and academic conferences,” the Post stresses, the question of correlation versus causation “is something that scientists are urgently trying to untangle, given the swift pace of Arctic climate change. The Arctic is in the throes of an extraordinary melt season, with record low Arctic-wide ice extent, and no ice at all in Alaskan waters as of early August.” That condition “could provide a test case of the hypotheses put forward that what happens in the Arctic does not stay in the Arctic.”