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Researchers are looking ahead to a day when rain falls in the Arctic more commonly than snow, and the change may happen decades before scientists expected, a new research report warns.
We know already that the Arctic is warming three times faster than the global average. In August this year, rain fell for the first time in recorded history on the highest point of the Greenland ice sheet.
But now, researchers at the University of Manitoba’s Centre for Earth Observation Science at the University of Manitoba (UM) and the Boulder, Colorado-based National Snow and Ice Data Center (NSIDC) say the shift in Arctic precipitation from snow to rain is likely to occur decades earlier than previously predicted.
The research team also includes members from University College London, the University of Colorado Boulder, the University of Lapland, and the University of Exeter, U.K.
Projections from the latest models, published in the journal Nature Communications, show a steep increase in the rate and range of precipitation expected to fall in the Arctic, and that most of it will be rain. This shift is occurring because of rapid warming, sea ice loss, and the transport of heat in the Arctic towards the North Pole.
“There are huge ramifications of these changes, such as a reduction of snow cover, increased permafrost melt, more rain-on-snow events, and greater flooding events from increased river discharge, all of which have implications on wildlife populations and human livelihoods,” said lead researcher Michelle McCrystall.
This transition to a rain-dominated era in the Arctic is forecast to start at different times, depending on the season and region. In the fall, for instance, the new research predicts the shift will occur between 2050 and 2080, while the old models suggested a range from 2070 to 2090.
“The fact that we’re getting rainfall on the summit of Greenland right now, and that we’re maybe going to get more rainfall into the future—it kind of staggers me,” McCrystall said.
“And when we talk about this happening in 2100, it seems like such a long time away, but it’s only 80 years. That’s the next generation. And if we continue the trajectory that we’re going, a lot of issues might happen even faster than we’ve projected.”
The study warns that reduced snow cover will further exacerbate Arctic and global warming through albedo feedbacks, increased winter carbon dioxide fluxes, methane releases from soil, and thawing permafrost, affecting flood risk.
The precipitation change will also affect soil moisture and groundwater, and the underground fungal networks that support all above-ground flora. More rain-than-snow events can also be devastating to wild caribou, reindeer, and musk oxen: the rain may freeze and create layers of ice, stopping them foraging beneath the snow. Migratory birds, however, are expected to benefit from the warmer and wetter conditions.
“The issue facing us today is that the Arctic is changing so fast that wildlife might not be able to adapt,” said NSIDC Director and study co-author Mark Serreze. “It’s not just a problem for the reindeer, caribou, and musk ox, but for the people of the north that depend on them, as well.”
If average global warming stays below 1.5°C of global warming, the researchers say, some of these projected changes (specifically the transition to rainfall-dominated precipitation) may not happen in some Arctic regions. But on the current trajectory, which given current global policies could mean 3°C of warming by the end of the century, the transition probably will occur.
“The new models couldn’t be clearer—that unless global warming is stopped, the future Arctic will be wetter; once-frozen seas will be open water, rain will replace snow”, said co-author James Screen, professor (chair) in climate science at Exeter.
What this transition means for sea ice, the dominating landscape feature of the Arctic, is unknown. More rain means more fresh water at the ocean’s surface, which might aid sea ice growth, but more rainfall is associated with more heat, which would decrease the growth.
“People might say, ‘Well, what has that got to do with me?’ Well, this is going to affect you, and in actual fact, it is affecting you now,” McCrystall said.
“I think what people need to understand is, we live in a global society where everything is interconnected, and that’s true of the climate. We have a global climate. So what happens in one region will affect what happens everywhere else.”