If you’ve ventured out on a hot day wearing dark clothing you know that within a short time you're soaked with sweat. Similarly, when a blanket of dust settles on snow, it acts the same way - the snow sweats or melts. The result is a rapid melting of snow. Aspen Public Radio’s Science Reporter Ellis Robinson has more.
Scientists at the Center for Snow and Avalanche Studies, have been studying the effects of dust on Colorado’s snowpack for years.
"We're routinely digging formal snow pits and doing formal snow profiles. So we're digging through the snow pack down to the ground and [...] looking for the special layers of dust."
That’s Chris Landry, one of the founders of the center. What the researchers have found is that Increased levels of dust on snow decreases reflectivity. Pure white snow reflects the suns rays but as dust darkens the snow it begins to absorb the rays instead. The result is faster snowmelting and potentially less water runoff to watersheds.
After finding the dust out in the field, Landry and his colleagues log the data as events. They collect samples from each event for chemical analysis. Looking at the chemical nature of the dust provides clues about where it might have come from. In the past year some dust events have been massive.
"We logged ten events... a couple of which were really quite major. One was an all time record event."
The term for how reflective a surface is, like the surface of a snow covered mountain draw, is albedo. A perfectly reflective surface would have an albedo of 100%, while a perfectly black surface would be zero percent. Freshly fallen snow can have an albedo close to 90%. One dust event last year decreased the snow’s reflectivity to just thirty-five percent.
"It's the difference between wearing a white shirt and a black shirt. That's not stretching the point, really."
As part of the Colorado Dust on Snow program snow scientists trek out into the high country take measurements on dust covered snowpack. Landry and the rest of the team share their dust data with watershed managers, conservation boards, and the Bureau of Reclamation, to name a few. While none of their monitoring sites are here in the Roaring Fork Valley, the data project a statewide picture of dust.
"When dust is present at those sites, it's certainly present at Independence."
The number of dust events has been increasing in recent years. The resulting impact on snowmelt is only adding to the negative effects of Colorado’s droughts.
