RICHLAND, Wash. -- Soot from pollution causes winter snowpacks to warm, shrink and warm some more. This continuous cycle sends snowmelt streaming down mountains as much as a month early, a new study finds. How pollution affects a mountain range's natural water reservoirs is important for water resource managers in the western United States and Canada who plan for hydroelectricity generation, fisheries and farming.
Scientists at the Department of Energy's Pacific Northwest National Laboratory conducted the first-ever study of soot on snow in the western states at a scale that predicted impacts along mountain ranges. They found that soot warms up the snow and the air above it by up to 1.2 degrees Fahrenheit, causing snow to melt.
"If we can project the future -- how much water we'll be getting from the rivers and when -- then we can better plan for its many uses," said atmospheric scientist Yun Qian. "Snowmelt can be up to 75 percent of the water supply, in some regions. These changes can affect the water supply, as well as aggravate winter flooding and summer droughts."
The soot-snow cycle starts when soot, a byproduct of burning fossil fuels, darkens snow it lands upon, which then absorbs more of the sun's energy than clean white snow. The resulting thinner snowpack reflects less sunlight back into the atmosphere and further warms the area, continuing the snowmelt cycle.
This study revealed regional changes to the snowpack caused by soot, whereas other studies looked at the uniform changes brought by higher air temperatures due to greenhouse gases.
Previous studies have examined the effect of airborne or snowbound soot on global climate and temperatures. Qian and his colleagues at PNNL used a climate computer model to zoom in on the Rocky Mountain, Cascade, and other western United States mountain ranges. They modeled how soot from diesel engines, power plants and other sources affected snowpacks it landed on.'/>"/>
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory