In Washington, Baltimore, Philadelphia, New York City, and Boston, at least five of the top 10 snow storms on record have occurred since 1990. More blockbuster storms have occurred in the past 25 years than in the hundred years prior.
Cohen, who works at Atmospheric and Environmental Research, Inc., has developed and published research that support a connection between declining Arctic ice and more severe East Coast storms.
Cohen says the melting ice, which peaks in the early fall, sets off a chain reaction that establishes “a great atmospheric background for a blockbuster snowstorm” by winter.
Here’s how it works…
When sea ice melts, Cohen says, cold winds blowing over open waters in the Arctic pick up moisture which gets deposited as snow over Eurasia in October. The process is similar to how lake effect snow forms in the Great Lakes.
Cohen says the lack of ice over the Arctic Ocean also favors the formation of high pressure over northwestern Asia and the Barents–Kara seas region which pushes the prevailing storm track farther south, which also enhances fall Eurasian snow cover.
Cohen has found that a rapid advance of snow cover in the fall over Eurasia coupled with high pressure to the north work together to destabilize the polar vortex by winter so that frigid air spills from the Arctic into the mid-latitudes.
The broken down polar vortex and transfer of frigid air from the Arctic into the North American continents is reflected by the negative phase of the Arctic Oscillation. And the overwhelming majority of major East Coast snow storms occur when the Arctic Oscillation is negative.
This past January, just prior to the Blizzard of 2016, the Arctic Oscillation was an astonishing five standard deviations below normal, according to the National Snow and Ice Data Center.
Cohen and his colleagues have documented a “statistically significant negative trend” in the Arctic Oscillation as Arctic sea ice has declined,
“Since late 1980s to early 1990s, I think [the melting ice] has contributed to blockbuster snow storms,” Cohen said.
While it is Cohen’s belief, after years of study, that melting Arctic ice from climate change and increase in big East Coast snow storms are connected, he stresses the link is not definitive and requires deeper study. As he and his colleague Jason Furtado, a professor of meteorology at the University of Oklahoma, wrote in a guest essay on this blog last year:
Clearly the frequency of extreme or historic snowfalls is increasing in the Northeast. Whether this is simply natural variability or a consequence of climate change can be answered only by more rigorous analysis and modeling studies; nonetheless, the increase in historic snowfalls is striking.