Rainy days on track to double in the Arctic by 2100

The Arctic is the northernmost region of the Earth, encompassing the Arctic Ocean and northernmost parts of Alaska, Canada, Russia, and Greenland.

As the planet warms, more frequent and intense Arctic rainfall events are expected to encroach farther toward the center of the Arctic Ocean and inland Greenland, "which means the arrival of a new Arctic," said Tingfeng Dou, a climate scientist at the University of Chinese Academy of Sciences and lead author of the new study. The study was published today in Earth's Future, AGU's journal for interdisciplinary research on the past, present and future of our planet and its inhabitants.

"In the past, rainfall was primarily limited to the edges of the Greenland ice sheet," Dou said. "In the future, this will radically change because rainfall will expand further into inland locations and be a catalyst for further ablation of the ice sheet."

The shift to a rainier Arctic is expected to increase permafrost melt, releasing massive amounts of greenhouse gases, and to speed up the loss of sea ice cover, which will likely trigger consequences for Arctic ecology and Indigenous peoples, as well as communities around the world. (Antarctica is predicted to undergo a similar doubling of raininess by 2100 under a high-emissions scenario.)

"Even ordinary rainfall can be regarded as an extreme event in polar regions," Dou said. This is because rain-on-snow events, which occur when rain falls onto an existing snowpack and freezes into an ice crust, impact wildlife, infrastructure and local communities.

"The number of reindeer deaths caused by a single rain-on-snow event could range from several hundred to thousands," Dou said, because their food becomes trapped under an icy layer. Massive die-offs of reindeer can have local socioeconomic impacts, particularly in regions where people rely on reindeer for food, clothing and transportation.

Few studies have examined the frequency and intensity of Arctic rain, so little is known about how those factors will change in the near future. Dou and his co-authors used climate models to detail future changes in rainfall frequency and intensity under a high level of greenhouse gas emissions from 2015 to 2100.

The increasing frequency, intensity and extent of rainfall events are mainly caused by faster local warming rates, which in the Arctic are "two to three times that of the global average," said Cunde Xiao, an Earth scientist at Beijing Normal University and co-author of the study. "This is a serious cause for alarm."

They also find the onset of spring rainfall is projected to occur three months, or a season, earlier than present-day in the Chukchi Sea and the Northern Barents Sea.

"Once the transition from snow to rainfall becomes common, it will have a far-reaching impact on the Arctic ice and snow process and hydrological ecology," said Xiao. "This will also strongly amplify the warming of the Arctic, making it a major issue worthy of global attention as it can have global consequences."