Dust on Snow

May's weather was slightly warmer and drier than average which, coupled with numerous layers of dust on the snowpack, has lead to a rapid depletion of the higher elevation snowpack statewide according to the USDA-Natural Resources Conservation Service (NRCS). And dust is a big deal--it makes the snow darker and dark snow melts fast. In fact, it has a much bigger effect on the snow than even global warming, says Scientist Thomas Painter of the National Snow and Ice Data Center in Boulder. In the southwest region, Chris Landry from the Center for Snow and Avalanche Studies in Silverton is also studying the effects of dust on snow.

The Colorado Plateau is the source of most of the dust that hits the Rockies. One source is the Navajo Nation’s sprawling Four Corners reservation, where steadily warming temperatures have created drought-like conditions that have killed the vegetation that held the sandy soils in place. Native plants like rice grass and purple sage have been wiped out and are replaced by foreign invasive species such as Russian thistle or tumbleweed. The non-native plants do not hold the soils together as well, further exacerbating the problem of loosening soils.

The occasional dust storm from China is a reminder, though, that this is a global problem, too. Dust blows around the world, and it falls on snow all around the world. "The Alps receive dust from the Sahara and the Taklimakan in western China, and the Gobi deposits dust into the mountain ranges in northwest China and Mongolia," Painter said. Arizona, Utah, Mongolia and the Sahara all generate dust for similar reasons: Human activities are disrupting the natural barrier that usually keeps dirt on the ground. And human disruption is only getting worse. "There's a strong sense that there's going to be intensification of the use of these semi-arid lands," Painter said. "Which means more dust, which means more dust on snow, which means more absorbed sunlight and more enhanced snowmelt."