Dust melting Rocky Mountain snow faster
DENVER ” Ranching, mining, energy exploration and other activities that raise dust in the West are helping diminish the snowpack that supplies much of the region’s water, a new study says.
Colorado scientists reported Tuesday that dust is blowing from the deserts onto the state’s snowcapped mountains, absorbing more of the sun’s warmth because of its darker color and melting the snow earlier and more quickly than in the past. That results in less water late in the summer for farmers relying on stream flows and for cities and towns.
“The snowpack 150 years ago was probably much cleaner, and by being cleaner, it lasted longer, potentially weeks longer,” said Tom Painter, a researcher with the National Snow and Ice Data Center at the University of Colorado in Boulder.
The wind-blown dust came from the Colorado Plateau, 200 miles southwest of Colorado’s San Juan Mountains, said Painter, whose study appears in the current edition of Geophysical Research Letters.
The dust-darkened snow could also be boosting the area’s temperatures. White snow reflects most of the sun’s rays while the dusty snow absorbs more of the sun’s energy, said Stephanie Renfrow, of the CU center.
In 2006, eight dust storms from northern Arizona and New Mexico covered Colorado’s San Juan Mountains with layers of orange and red grit, according to the study. Typically, there are fewer than four such dust storms in a year.
Computer water models and on-the-ground data showed that the dusty snow melted 24 to 35 days earlier last year than in dust-free years.
Global warming may be contributing to conditions creating the dust, scientists said.
Painter said the findings aren’t limited to Colorado’s San Juan Mountains.
“Around the world but particularly in the Southwest, it appears that dust emission has increased,” Painter said.
Researchers found evidence that windstorms increasingly coat Antarctica’s high peaks with dust blowing from Patagonia, where intensified sheep grazing has damaged soils, said Joseph McConnell of the Desert Research Institute based in Reno, Nev.
Grasses held most of the region’s dust in place before large-scale human settlement in the Southwest. Painter said after a century of breaking the desert crust, the dust blows freely.
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