This is Scientific American 62nd Science.

I'm Julia Rosen.

Got a minute?

Last Christmas, Santa Claus must have been loading his sleigh in a t-shirt and shorts.

Temperatures at the North Pole crept up toward the freezing point when they should have been

minus 20 Fahrenheit.

The heat wave was the latest in a series that have swept over the Arctic in recent winters.

Climate change has caused steady warming in the region,

but it's also helped supercharge these extreme events,

which scientists say are tied to storms that spiral north out of the Atlantic.

This winds, they actually pick up a lot of heat and moisture.

Vladimir Alexiv, a climate scientist at the University of Alaska Fairbanks.

And the atmosphere creates all this extra moisture and heat to the Central Arctic, which results in warmer and moist the atmosphere.

Which then warms the surface.

Alexiev says the heat ferried north by these storms

helps slow the growth of sea ice in winter, causing it to be about 15 centimeters

thinner by the end of the season, and thinner ice may have a harder time

surviving the summer.

But while the impact of these storms has grown in recent decades,

the storms themselves are not happening more often, Alexiev says.

An important piece of information is that the frequency of those

storms is not changing. What's changing is the area of open water in those regions.

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