ANCHORAGE, Alaska – What does loss of Arctic sea ice have to do with snowfall and rain in New England? Plenty, according to chemical evidence amassed by a team of scientists and described in a soon-to-be published study.
A research project analyzing precipitation in New Hampshire, part of the general U.S. Northeast region that has been blasted in recent years by episodes of the "polar vortex," links weather there to the warming Arctic.
The link comes from analysis of water isotopes in precipitation samples collected since 1968 at the Hubbard Brook Experimental Forest in New Hampshire.
The water isotopes — the varying atomic structure of the hydrogen and oxygen that make up the water — identify the precipitation that falls there during fall and winter as originating in the warming Arctic. Isotope analysis was done at the University of Alaska Anchorage's Stable Isotope Lab.
Isotopes in water molecules act like a "chemical fingerprint," said Jeff Welker, a UAA biology professor involved in the project.
Analysis by Welker, UAA postdoctoral fellow Eric Klein and their research partners at the State University of New York and other institutions parsed out the isotopes associated with the Arctic and matched them to the heavy precipitation at the New Hampshire location.
The analysis also tracked increasing incidences of Arctic-marked rain and snowfall over time with reduced Arctic sea ice — and with polar vortexes like the one that warmed Alaska but chilled the U.S. East Coast in the winter of 2013-14.
The chemical evidence backs the theory that the rapid warming of the Arctic is slowing the jet stream, causing a wavy pattern that brings warm weather to the far north and cold weather to the middle latitudes, Welker and Klein said.
"I don't think it's a smoking gun. But I think it's adding another brick to the wall supporting it," Klein said.
The Arctic-originating water molecules could not reach New Hampshire unless they were pulled by a manipulated jet stream, he said. "In order for the colder, drier source to reach this location, it necessitates some bends of the jet stream," he said.
The Arctic has been warming at twice the global rate, and a large part of that is driven by reduction in summer and fall sea ice — a phenomenon that's a self-fulfilling cycle, because reduced ice absorbs more solar warmth that reduces ice levels further.
According to an emerging theory developed by Rutgers University research professor Jennifer Francis and several other climate scientists, the amplified Arctic warming is significantly altering weather patterns much farther south.
With temperature differences between north and south smaller than in the past, and with more open water and more cloud cover sending and holding moisture in the Arctic atmosphere, weather systems are more frequently distorting the normally west-to-east jet stream into meandering loops, causing more stationary patterns and more frequent extreme events well south of the Arctic, according to the theory.
Francis, who was not involved in the isotope study, said it adds some weight to the theory. "It's certainly a completely independent type of evidence," she said.
This winter — with its extremely warm temperatures persisting in the Arctic and a strong El Niño that is behaving differently from past El Niños — is likely to be material for future study into Arctic-lower latitude links, Francis said.
"I don't see how you can have an Arctic that is 10 to 15 degrees warmer than normal in winter and not have it have an effect on the jet stream and weather farther south," she said.
The isotope analysis done for the new study is made possible by a rain- and snow-collection system set up across the nation that dates back decades, to a time when there were big concerns about acid rain, an environmental problem caused by excessive amounts of sulfur dioxide pollution in the atmosphere.
The longest U.S. records of precipitation isotopes are at the Hubbard Brook Experimental Forest, allowing scientists to examine weather events that occurred decades ago and how they relate to gradual climate change, Welker said. "This has provided us an opportunity to actually demonstrate that this is an interwoven system, and it's being recorded in the precipitation chemistry," he said.