Two new studies add support to the idea that climate warming in the Arctic and melting sea ice may be increasingly laying the groundwork for blockbuster East Coast snowstorms.
It is well known that many of the fiercest East Coast storms form when a massive area of high pressure develops over Greenland, known as the Greenland Block. This feature causes the jet stream to dive south over the eastern United States, achieving a configuration that delivers cold air and establishes a path for storms to draw moisture from the Atlantic.
A study in the International Journal of Climatology published early this week documents "significant increases" in Greenland blocking "in all seasons" since 1981.
A substantial fraction of the biggest snowstorms on record to strike major East Coast cities have occurred since the 1980s.
The accelerated melting of Arctic sea ice in recent decades and an increase in Greenland blocking are probably linked, a study published in the Journal of Climate in April suggests.
Greenland blocks tend to form when an atmospheric index known as the Arctic Oscillation is negative. The Journal of Climate study finds the observed trend toward a more negative Arctic Oscillation in winter "may be partly associated to the early winter sea ice loss" in the Barents and Kara Seas region of the Arctic.
This study connecting sea ice loss in the fall with winter weather patterns that affect the mid-latitudes builds on the work of seasonal forecaster and researcher Judah Cohen, who identified a similar relationship.
"More and more studies are being published that changes in the Arctic are influencing mid-latitude weather," Cohen said in an email.
"Overall, I'd say that the case for an Arctic influence on amplified jet-stream patterns is rapidly getting stronger," added Jennifer Francis, a professor of meteorology at Rutgers University. Francis has published numerous studies that find the warming Arctic is slowing down the jet stream, making it more prone to slow or get stuck in place, which leads to features like the Greenland Block.
Cohen explained the Arctic and mid-latitude weather connection makes physical sense. "If you remove sea ice and warm the lower troposphere, that heat will likely lead to a warming not only at the surface but throughout the troposphere," he said. When the troposphere warms, it raises atmospheric pressure favoring patterns like the Greenland block to form, he noted.
He is among the first scientists to make the direct connection between climate change, sea ice loss and the recent uptick in major East Coast snowstorms.