Parts of the Arctic could become dominated by rain rather than snow during certain seasons by 2060 or 2070, according to new findings published in the journal Nature, particularly if the Earth continues to warm at its current rate. When those changes arrive, they will probably trigger consequences that affect not only local people and wildlife, but communities around the world.
Ice vanishing more rapidly could quicken sea-level rise along coastlines. Melting permafrost could release massive amounts of planet-heating gases such as methane and carbon dioxide. The “greening” of once-frozen landscapes could provide fuel for ravenous wildfires that spew more greenhouse gases into the air and further warm the atmosphere.
“What happens in the Arctic doesn’t stay in the Arctic,” Michelle McCrystall, a lead author of Tuesday’s study and a postdoctoral researcher at the University of Manitoba, said in an interview.
McCrystall and her colleagues used the most up-to-date climate models to detail how the Earth’s northernmost polar region, which has been warming much faster than the rest of the planet, will probably undergo more rapid and intense hydrological cycles in the future. This shift could be most pronounced during autumn, they found.
Warmer air temperatures, melting sea ice and the atmosphere’s increasing ability to carry moisture all point toward increased rainfall in many parts of the Arctic. In some cases, scientists are already observing the beginning of those trends, and they expect them to accelerate depending on the globe’s temperature rise.
The Arctic is not monolithic, McCrystall said. Some areas, including in Greenland, could actually see increased snowfall in coming decades, helping to stabilize fragile ice sheets but not completely offsetting mass losses. And the models that scientists use to estimate precipitation through 2100 are inherently uncertain, given the lack of data from direct observations of rainfall, snow, wind and temperatures across the vast region. “There’s no crystal ball,” she added.
Previous research shows that while snowfall may increase in the near future, precipitation will turn into rain as warming continues.
Marilena Oltmanns, a climate researcher with the United Kingdom’s National Oceanography Centre, said in an email that while scientific models tend to improve over time, projections about future shifts in snow and rain remain tricky.
“Precipitation is one of the most difficult variables for models to get right,” said Oltmanns, who was not involved in the study.
Still, Tuesday’s study suggests that rain will probably be a much more prominent feature for large swaths of the Arctic in the future as snow and ice retreat.
That shift toward a rain-dominated reality, researchers wrote, could come “approximately one or two decades earlier” than expected. Such a change could have “implications for the stability of social-ecological systems in the Arctic and the rate at which systems changes occur,” they added.
The study reflects scientists’ ongoing effort to understand the significant changes already unfolding across the Arctic, which is warming nearly three times as fast as the rest of the world.
The Arctic of inhospitable, barely accessible and icebound expanses is transforming. December’s Arctic Report Card, an effort led by the National Oceanic and Atmospheric Administration and involving 133 scientists from 15 countries, detailed how climate change has reshaped the Arctic into a place that can hit triple-digit temperatures, endure raging wildfires and suffer greater ice loss with each passing year.
In late July, polar researcher Zoe Courville gathered with several colleagues to discuss the future of research stations as Greenland’s climate deteriorates. This year its ice sheet lost more ice than it gained for the 25th year in a row.
Several engineers considered how to plan for increased temperatures, melt events and storm events over just the next several decades. Then, Courville recalled, one of the engineers asked what if it rains at the summit.
“I remember just laughing, you know, like, ‘Oh, let’s not think about rain right now,’ ” said Courville, a research engineer at the Cold Regions Research and Engineering Laboratory. “We don’t want to even have to cross that bridge yet. … Introducing liquid water into this system really does wreak havoc.”
Two weeks later, it rained on the summit of Greenland for the first time on record.
At Summit Station, buildings and runways sit on snow foundations. The aircraft are military cargo planes with skis on the bottom, which rely on solid snow or ice surfaces to land. During warmer periods, flights are delayed because the ground gets too warm and sticky.
“Now all of a sudden, if you introduce liquid water into the picture and rainfall, there are a lot of engineering questions and things that could become really problematic for us in the future if this becomes a regular occurrence,” Jennifer Mercer, a National Science Foundation program officer, said shortly after the rain event, noting that it could also affect research stations’ sewage, wastewater and underground food storage.
The rain can also cause more surface melt and runoff on the Greenland ice sheet, by changing the shaping of the snow crystals and making them darker. That leads to more sunlight absorption, which accelerates snowmelt.
Already Greenland has experienced large melting events during three separate years in the past decade. Marco Tedesco, a research professor at the Lamont-Doherty Earth Observatory at Columbia University, remembers being in Greenland during the melting event in July 2012.
“We were walking on slush and we basically had water up to our pants,” he recalled, saying the flooding was intense. “We were calling our camp ‘Little Venice’ because we had to move it so often.”
Tedesco’s own past research found that “the models were telling us there will be an increase in the snowfall” over the next 20 or 30 years, “but then this will turn into rain.”
That transition to a rain-dominated system could also lead to devastating immediate impacts, the new study warns, including “rain-on-snow” events that create a crust of ice and make it difficult for caribou and other wildlife to survive. This would imperil the people whose livelihoods depend on these animals, while more flooding could wreak havoc on roads and railways and impede some communities’ access to drinking water.
Oltmanns, the U.K. researcher, said she finds it “quite worrying” that as climate models have improved, they have tended to show that the Arctic faces more-dramatic changes rather than milder ones. “This implies that potentially rapid climate changes due to the crossing of tipping points are more likely to occur earlier than predicted by older models,” she said.
She argued that world leaders need to pursue the most ambitious aim of the Paris climate accord — to limit warming to 1.5 degrees Celsius (2.7 Fahrenheit) above preindustrial levels — because “it is more likely an overestimate than an underestimate of the warming threshold that, if crossed, can lead to irreversible damage to our planet.”
McCrystall and her co-authors underscored the same message, saying precipitation changes in the Arctic that once were expected at 2 degrees Celsius of warming “now appear possible” below 1.5 Celsius.
If anything, they suggest, the latest findings could provide yet another incentive for humans to do everything possible to remain below that threshold.
“If we can stay within this 1.5 degree world, these changes won’t happen, or won’t happen as rapidly,” they wrote. “It would be better for everybody. No two ways about it.”