Melting Arctic Means Less Moisture in the West

Arctic sea ice is disappearing. And while that may seem a distant concern for Colorado, the loss of that ice might result in decreased precipitation and more drought in the American West.

That’s why they call it global warming.A paper this week in the journal Science by University of Colorado geographer Mark Serreze and colleagues, says that climate models are predicting a seasonally ice-free Arctic by 2100. “While this may seem extreme, September 2005 marked the lowest level of Arctic sea ice in 50 years and data point to an accelerating decline,” a summary of the paper says. “The impact of such loss could include reduced rainfall in the American West.”


Serreze told Colorado Confidential, “All the studies are saying that the sea ice matters.” Changes in Arctic ice mean changes in climate dynamics that can have wide-ranging consequences.

“Basically, if you lose the sea ice, you’re radically changing the surface conditions,” Serreze says. “What was highly reflective ice is now replaced with dark open water. The polar regions absorb more heat. So they start to evaporate more water, and there is more water vapor in the atmosphere.” This is where many storm and precipitation patterns originate.

‘If you change this pattern of heating, that changes the pattern of atmospheric circulation and the pressure gradients,” he says. Curiously, the loss of Arctic ice may mean more precipitation globally, but less precipitation locally. “Some regions get wetter, some get drier,” Serreze says.

Serreze’s conclusion is based in part on work done in 2004 by geoscientist Jacob Sewall, published in the journal Geophysical Research Letters. “The most interesting extrapolar climate response to reduced Arctic sea ice cover is a significant drying of western North America,” that paper said. Sewall and colleagues estimate about a 17 percent decline in annual precipitation in the Rockies as a result of reduced Arctic sea ice.

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Dan Whipple

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