How heavy winter rainfall in the Arctic is threatening ecosystems. A new study from the Norwegian University of Science and Technology has found that an increase in winter rainfall across the Arctic has led to more ice on the ground. According to the researchers, the shift is so great that the ground has not been free from ice during winter since the beginning of this century.
The team of experts, which included biologists, meteorologists, and geophysicists, reviewed years of snowpack and weather data from two locations in the Arctic archipelago of Svalbard. Rain in this type of climate is especially threatening because rain falling on snow can freeze at the bottom of the snowpack, creating a layer of ice that is referred to as “basal ice.”
The ice formation can become so thick that it can swallow up and kill plants. Basal ice can also starve animals, like reindeer, which normally graze on mosses and dwarf shrubs in the snow. In addition, rain-on-snow events can saturate snowpacks to the point that they can avalanche.
The researchers explained that the amount of snow already on the ground is an important factor in basal ice formation.
“When, where and how much ice is formed is a complicated process,” said study lead author Bart Peeters. “But the main patterns are clear: basal ice forms when rain and meltwater freeze on the frozen ground, although this depends on how deep the snowpack is, if there is any snow at all, and when it starts raining.”
When there is a lot of snow on the ground and just a little rainfall, the rain can freeze into the snowpack. A large amount of rainfall, however, can penetrate throughout the entire snowpack, freezing when it hits the frozen ground below.
The experts found that the average amount of winter rain was more than twice as high on the coast than in the center of the island, which led to thicker basal ice on the coast. They also determined that winter rainfall spanned across several hundred kilometers, so the thick basal ice on the coast was also found in the center of the island.
Study co-author Brage Bremset Hansen pointed out that the most important ecological implication of large-scale rain-on-snow events is that they can simultaneously affect all of the species in the island’s overwintering animal community.
“This ultimately means that the ups and downs of populations as well as entire wildlife communities could be synchronized across large distances,” said Hansen. “In theory, the synchronization of population dynamics across large distances, caused by fluctuations in weather, will increase the long-term risk of extinction.”
Currently, however, that there is no evidence that the species that overwinter on the Svalbard tundra are at risk.
The study is published in the journal Environmental Research Letters.