How dust on mountain snowpack hastens runoff

How dust on mountain snowpack hastens runoff

How dust on mountain snowpack hastens runoff

News Type: State, Regional, Federal Source: Mountain West News
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“It looks apocalyptic,” says Jeff Deems, a research scientist at the University of Colorado. With “a big orange-red sky, it really does look Martian.” He’s describing dust storms — layers of windblown particles that are landing on mountain peaks and leaving them coated with a dark layer of sand and soot. As anyone who has sat in a car with black upholstery on hot summer day will attest, black objects absorb more heat than lighter ones, so by the darkening the snow, it’s melting it faster.

Deems explains that “If you put dust on the snowpack, which enhances the absorption of that solar radiation, then that just pushes on the gas pedal for snowmelt.” In a recent study looking at the Rocky Mountains of Colorado, Deems and lead author Tom Painter of NASA found that the amount of dust on mountain snowpack will control how fast rivers rise in the spring regardless of air temperature. And the more dust there is, the faster the runoff.

The problem is getting worse because there’s more dust than there used to be because of less rain with a warming climate and more land development that’s exposing bare soil. Those soil surfaces are naturally armored by crust — lichen and moss combinations that make this black armored surface. Those crusts are virtually impervious to wind erosion. They’re very strong — except when they’re crushed. Beginning back in the mid-to-late 1800s, soil started getting disturbed by people grazing animals.

Since then, Deems says, we’ve got a wide array of disturbance agents — recreational activities, oil and gas exploration and development, suburban development, dry land farming, etc. All of these activities disturb the soil crust and make the fine grain substrates available for wind transport.

Dust on the snowpack enhancing snowmelt rates in Senator Beck Basin, San Juan Mountains, CO, May 2013. Photo credit: Dr. Jeffrey Deems.