As global warming intensifies, Dasher, Donner, Blitzen, and the millions of wild-living reindeer and caribou found across the Arctic Circle may find it increasingly difficult to reach the food they need to survive, according to a new study.
Warmer weather may increase the frequency of an unusual climatic condition called a rain-on-snow event, says earth system scientist Jaakko Putkonen of the University of Washington, Seattle. These events happen when winter rain percolates through snow and forms an impenetrable ice barrier over moss and lichen at the soil surface. Rain-on-snow events have been linked to die-offs of arctic grazers such as musk ox and elk since the 1970s in Canada, Greenland, Scandinavia, and Siberia.
Putkonen and his University of Washington colleague Gerard Roe, an atmospheric scientist, set out to test how the frequency of rain-on-snow events might be affected by global warming. The pair used data on winter rainfall collected during the 1980s and climate-predicting computer models to extrapolate future rain-on-snow patterns across the Northern Hemisphere.
The researchers discovered not only that the frequency and intensity of winter rainstorms might increase in arctic regions, but also that the land area affected by rain-on-snow events could grow by 40% by the 2080s. "The bottom line is that the rain will penetrate farther into the interiors of the continents, where most of the reindeer are," says Putkonen. Mass die-offs of reindeer and caribou could take a heavy toll on native peoples who herd the animals, such as Sweden's Sami and Alaska's Eskimo, warns Putkonen. The study will appear in an upcoming issue of Geophysical Research Letters.
The findings back up a body of data suggesting that "the effects of global [warming] will be seen first, and will be most pronounced, in the arctic region," says Mark Serreze, an arctic climatologist at the National Snow and Ice Data Center in Boulder, Colorado. An increase in rain on snow could reduce reindeer and caribou populations, says wildlife biologist Brad Griffith of the U.S. Geological Survey at the University of Alaska, Fairbanks. However, he says, "these animals have been successful for a long time and are very adaptable." Small populations on arctic islands might be at greater risk, he says.