Wild caribou roam the tundra in Nunavut in 2009.NATHAN DENETTE/The Canadian Press
In one scenario, the Arctic exists as we know it today: frozen, snow-covered and stable. In another, it is drenched by frequent rainfall accompanied by episodes of freezing and thawing that threaten wildlife, erode infrastructure and generally wreak havoc on northern communities.
A study led by researchers at the University of Manitoba shows that the switch from one scenario to the other is already under way across the world’s northern regions, with the most significant effects expected sooner than previously predicted.
“We know precipitation is changing … What we were able to see is that this transition to rain-dominated precipitation does occur earlier,” said Michelle McCrystall, a post-doctoral climate researcher at the University of Manitoba and the study’s lead author.
The result is in keeping with recent trends, including the first-ever rainfall recorded atop the Greenland ice sheet this past summer. However, the study drew mixed reviews from some experts who agree that profound change is coming to the region – and at a faster pace than for the rest of the world on average – but note that the timing of the change is famously difficult to predict.
In their study, published Tuesday in the journal Nature Communications, Dr. McCrystall and her colleagues analyzed the impact of a warming world on Arctic precipitation and saw that areas that are typically blanketed in snow during the fall and winter are increasingly likely to experience more rainfall, particularly in the months of September through November. Working with the same climate models used by the UN Intergovernmental Panel on Climate Change in its latest assessment, the team also found a more rapid shift to rainfall for many parts of the Arctic in the latter half of this century.
For example, some Arctic regions that would not have seen much rain until 2085 or 2090 in previous models now make the transition by 2070, Dr. McCrystall said. The shift also tends to come sooner at lower latitudes and in coastal areas, which in Canada coincide with the places where northern communities are located.
RAINY OUTLOOK
Precipitation in the Arctic in the last decade of this century will look significantly different than today based on projections using the latest available climate models. Here, a marked decrease in snowfall and an increase in rainfall is forecast for September through November during the years 2091 to 2100.
Change in type of precipitation
(millimetres per day or equivalent)
-0.9
-0.6
-0.3
0
0.3
0.6
0.9
RAIN
RUSSIA
North Pole
GREENLAND
CANADA
Diagonal lines indicate no significant change forecast.
SNOW
RUSSIA
North Pole
GREENLAND
CANADA
SOURCE: MICHELLE McCRYSTALL / NATURE COMMUNICATIONS
RAINY OUTLOOK
Precipitation in the Arctic in the last decade of this century will look significantly different than today based on projections using the latest available climate models. Here, a marked decrease in snowfall and an increase in rainfall is forecast for September through November during the years 2091 to 2100.
Change in type of precipitation
(millimetres per day or equivalent)
-0.9
-0.6
-0.3
0
0.3
0.6
0.9
RAIN
RUSSIA
North Pole
GREENLAND
CANADA
Diagonal lines indicate no significant change forecast.
SNOW
RUSSIA
North Pole
GREENLAND
CANADA
SOURCE: MICHELLE McCRYSTALL / NATURE COMMUNICATIONS
RAINY OUTLOOK
Precipitation in the Arctic in the last decade of this century will look significantly different than today based on projections using the latest available climate models. Here, a marked decrease in snowfall and an increase in rainfall is forecast for September through November during the years 2091 to 2100.
Change in type of precipitation
(millimetres per day or equivalent)
-0.9
-0.6
-0.3
0
0.3
0.6
0.9
RAIN
SNOW
Diagonal lines indicate no significant change forecast.
RUSSIA
RUSSIA
North Pole
North Pole
GREENLAND
GREENLAND
CANADA
CANADA
SOURCE: MICHELLE McCRYSTALL / NATURE COMMUNICATIONS
The results suggest those communities may have less time than anticipated to prepare for a radically different future. More rain means more water seeping into the soil and accelerating the loss of permafrost, which can in turn affect mobility on the landscape as well as the stability of buildings and roads.
Arctic rainfall on top of snow is also frequently followed by freezing periods that form a hard icy crust. In northern Scandinavia this is already a big problem for reindeer herds because the ice creates a barrier that prevents them from accessing lichen underneath the snow, a crucial winter food source.
Bruce Forbes, a research professor at the University of Lapland in Rovaniemi, Finland, and a co-author on the study, said that it has become common practice for reindeer herders in the region to supplement their animals’ diets to make up for what they can no longer acquire through natural grazing. Further east, in Russia’s Yamal Peninsula, there have been reports of mass starvation among herds, with tens of thousands of reindeer perishing.
Dr. Forbes said that compared with similar modelling studies conducted a decade ago, the new study “demonstrates that even our most pessimistic projections of a warming Arctic, with more rain during winter – falling either on bare ground or on snow – are not keeping pace with reality.”
Gavin Schmidt, a climatologist and director of NASA Goddard Institute for Space Studies in New York, said the study’s conclusions about the timing of the shift to a rain-dominated Arctic should be treated with caution because of complexities in modelling the polar climate and disagreements between the models and observations.
“These results don’t change the expected Arctic impacts given any particular temperature rise, but rather do imply that the worst impacts can be avoided if countries match their stated intentions to cut emissions by in line with the Paris agreement,” Dr. Schmidt told the Science Media Centre in Britain.
Tim Palmer, a research professor and climate modelling expert at Oxford University, said the work underscores the need for high-quality observations of precipitation in the Arctic to improve the predictive power of models for the region.
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