STEVE INSKEEP, host:

It's MORNING EDITION from NPR News. Good morning. I'm Steve Inskeep.

LINDA WERTHEIMER, host:

And Linda Wertheimer. Scientists who study the far northern regions of the planet say they're seeing some odd things happening to the snow. They call them rain-on-snow events. Sometimes when the weather warms suddenly it rains instead of snows. The rain percolates into the snow pack and freezes into a hard sheet of ice. In the Arctic it apparently can have deadly effects. NPR's Christopher Joyce has more.

CHRISTOPHER JOYCE: It's taken years for scientists to figure out just what happened in October 2003 on Banks Island in far northern Canada. Geologist Jaakko Putkonen is one of those scientists.

Professor JAAKKO PUTKONEN (University of North Dakota): There was this huge big rain-on-snow event. And there was a huge big herd of musk oxen living there.

JOYCE: Musk oxen are pretty huge and big as well. They're shaggy and cow-like, though closer relatives to goats than oxen. But as huge and big as they are, they couldn't break through the ice sheet to browse on the plants under the snow pack.

Prof. PUTKONEN: And long story short, about 20,000 musk oxen starved to death because of this event.

JOYCE: Twenty thousand?

Prof. PUTKONEN: Yeah, it's a humongous number.

JOYCE: It wasn't until the following year, when wildlife biologists started finding the carcasses of starved musk oxen, that they realized something had gone terribly wrong out there in the snow.

Putkonen has since discovered a few anecdotal accounts of big rain-on-snow events that killed reindeer in the Arctic and Scandinavia. But he says it's hard to actually study them. Even if you put down instruments to record one, they freeze up or get snowed under.

Moreover, is it a big deal? Putkonen and his fellow rain-on-snow experts -there aren't many in this specialty yet - think it is. They suspect that a warming climate may increase the number and geographic reach of these events.

Tom Grenfell is an atmospheric scientist at the University of Washington.

Professor TOM GRENFELL (University of Washington): If the climate warms up, it doesn't just grow palm trees in sunny Fairbanks, Alaska. It creates more storms and mixes the atmosphere up a lot more.

JOYCE: Grenfell and Putkonen suspect that warmer weather and more storms could mean more rain-on-snow instead of snow-on-snow. Grenfell says that could affect people who live in the high northern latitudes.

Prof. GRENFELL: There are other places around the Arctic that have these things, like Finland and Russia, where people herd reindeer or caribou and depend for their livelihood on these things.

JOYCE: But so far no one knows if these events are increasing or not. No one has ever checked. That's what Putkonen and Grenfell are planning to do next. They've figured out what rain-on-snow looks like on a satellite image. Now they've got 30 years of images of the Arctic to look through.

Christopher Joyce, NPR News.

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