Mysterious "Rain on Snow" Events Tracked in Arctic

Graeme Stemp-Morlock in Waterloo, Ontario
for National Geographic News
March 4, 2008

A few warm, springlike days might sound appealing if you live in the frigid Arctic Circle.

But a rise in temperature can spell doom for native peoples and the caribou, musk-oxen, and reindeer that they depend on in Earth's northernmost regions.

That's because a mysterious phenomenon known as "rain on snow," when sudden warm air turns northern snows to rain or slush, can cause animals to starve.

Rather than melting the snow, rain seeps through the snowpack and pools on top of the frozen soil.

When the extreme cold returns, the water freezes into an impermeable shell that prevents animals from grazing.

In October 2003 on Banks Island in Canada's Northwest Territories, a rain-on-snow event caused the deaths of more than a quarter of the musk-ox population—20,000 animals.

Some native people reported the unusual sight of musk-oxen walking onto floating sea ice in search of food, drifting to watery graves.

"When the ice layer formed, the musk-ox on the northern end of the island couldn't break through the ice to get the food," said Tom Grenfell, an atmospheric research scientist at the University of Washington who tracks rain-on-snow events.

"They starved to death or got hypothermia because they have to eat something to stay warm."

Arctic Enigma

While the results of rain-on-snow events are clear, many of the details about why and how the phenomena form remain an enigma.

Jaakko Putkonen, a research professor in the University of Washington's Department of Earth and Space Sciences, is one of a handful of scientists studying the incidents.

Continued on Next Page >>


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