The extraordinarily snowy winter that Europe endured in 2018 was fueled by the melting of ice in the Barents Sea, new research indicates, meaning the region could be in store for more extreme blizzards in the decades to come.

Scientists measured water vapor in Arctic Finland during the event, and found that huge amounts of moisture could be traced to the body of water, which had a surface that was 60% free of ice. The team reported the findings on April 1 in Nature Geoscience.

"Given that mean winter temperatures are warming, increased snowfall might sound counterintuitive," said Hannah Bailey, a postdoctoral research fellow at the University of Oulu in Finland and first author of the study. "But nature is complex, and what happens in the Arctic doesn't stay in the Arctic."

Researchers are only beginning to comprehend the full impacts of diminishing sea ice on phenomena such as atmospheric humidity and extreme weather. 

"The Barents Sea is a particular Arctic hotspot where a huge chunk of this loss is occurring, especially in winter," Bailey said. Since 1979, its maximum winter sea ice cover has decreased by 54%, or about 11,200 square kilometers per year. 

Although the overall average snowfall across the Northern Hemisphere has declined since this time, researchers have also observed trends of increasing snowiness across vast regions that border the Arctic Ocean, especially in Siberia and parts of northern Alaska. 

"However, a direct link between winter Barents sea-ice loss and the recent extreme snowy European winters has yet to be substantiated," Bailey and her colleagues wrote in the new study.

One reason for this is that the wintry Arctic is a challenging environment to visit and gather data from. 

"Scientists have typically relied on computers to model the link between sea ice, evaporation and snowfall," Bailey said. "What's exciting here is that we were able to directly trace that moisture through the atmosphere using its chemical 'fingerprint' as it traveled from the Arctic into Europe."  

In late 2017, Bailey's team installed an instrument in Pallas-Yllästunturi National Park that took water vapor measurements every second. The researchers examined hydrogen and oxygen isotopes, different forms of the same element that occurred in ratios that varied depending on where the water came from.

During February and March 2018, Arctic air driven over Europe brought blizzards and prolonged cold in an event nicknamed the "Beast from the East." The researchers identified three pulses of moisture from the Barents Sea during this time that corresponded to increased snowfall across the continent.  

Compared to average conditions between 1981 and 2010, the sea ice cover in the Barents Sea in March 2018 was smaller by an area about the size of Florida, Bailey says. She and her team estimate that about 140 gigatons of water evaporated from the ice-free sea surface during the Beast from the East, potentially supplying up to 88% of the fresh snow that fell over northern Europe.  

"But what's important to emphasize here is that sea ice conditions in 2018 weren't particularly exceptional," Bailey said. "Instead, they reflect a long-term declining sea ice trend that scientists have been observing across the Arctic since the late 1970s, when satellite measurements began."

She and her colleagues also analyzed satellite observations of sea ice and climate records from 1979 to 2020. They found that evaporation across the Barents Sea in March increased by about 70 kilograms per square meter of sea ice lost, while Europe's maximum March snowfall — indicative of extreme snowfall events — increased by about 1.6 millimeters per year. 

Since 1979, the vast majority of winter sea ice lost across the entire Arctic has come from the Barents Sea, and scientists have projected that the sea may face ice-free winters by the 2060s to 2080s. This means that parts of northern Europe that remain chilly enough to yield snow could see more extreme blizzards in the future. 

However, the researchers noted, "Whether or not this effect is sustainable under current and projected mean rates of warming warrants further investigation." 

According to Jeffrey Welker, a professor of biological sciences at the University of Alaska Anchorage and last author of the study, the findings ultimately reveal how a rapidly changing Arctic will lead to moisture being ferried to distant regions, "with dramatic effects on rural and urban communities, especially in winter."  

The study, "Arctic sea-ice loss fuels extreme European snowfall," published April 1 in Nature Geoscience, was authored by Hannah Bailey , Kaisa-Riikka Mustonen and Hannu Marttila, University of Oulu; Jeffrey M. Welker, University of Oulu and University of Alaska Anchorage; Eric S. Klein, University of Alaska Anchorage; Alun Hubbard, UiT the Arctic University of Norway; and Pete D. Akers, National Centre for Scientific Research.