Snow is an incredibly valuable resource in the North Cascade mountains. Along with nourishing the mass balance of glaciers and regulating the regional energy balance, snowmelt is an important contribution to regional watersheds. As the high elevation snow melts from Spring to Summer, it darkens, often resulting in positive feedback on albedo reduction due to increasing snow grain growth and snowpack thinning. However, another reason for snow darkening is due to the presence of light absorbing particles, such as from the deposition of wildfire-derived black carbon, as well as the growth of biological constituents, like snow algae, which are both ubiquitous in the Pacific Northwest summer. Here, we combine ground measurements of light absorbing particles like snow algae, black carbon and dust, with satellite remote sensing imagery, to document the seasonal evolution of darkening of snow in the North Cascades. We show that the snow across the stratovolcanoes of the pacific northwest (PNW) darkens each summer through a seasonal evolution that often leaves the end of summer snow/ice surface even darker than the summer before. Comparison to smoke-derived black carbon deposition output from the Navy Aerosol Analysis Prediction System (NAAPS) model shows there is a also a relationship between peaks in snow darkening and the deposition of smoke from wildfires, a trend that will likely only continue as the climate warms.
Dr. Alia Khan
Western Washington University
Presentation given at North Coast & Cascades Science Days, 2024
go.nps.gov/sciencedays
[NOCA]
28 сен 2024
