Where Deserts and Mountains Collide The Implications of Accelerated Snowmelt by Disturbed Desert Dust Thomas H. Painter Snow Optics Laboratory University of Utah

Snowmelt and Water 75% of freshwater comes from snow in the Western US Mountain snowpack provides enormous, critical reservoir capacity Early snowmelt increases growing season length, evapotranspiration, and temperatures Rate of snowmelt controls water management and yield

Photo: Chris Landry, Center for Snow and Avalanche Studies

Reflectivity = 72% Absorption = 28% Reflectivity =43% Absorption = 57% Snow Albedo Reflectivity

Impact of Dust: A Perfect Storm Dust is well timed Dust is well placed Dust is, well, darker than snow April 2009May 2009

Changes in Dust Loading Post-disturbance ~ 1850 AD Pre-disturbance From Neff et al (2008), Nature GeosciencesFrom lake sediments in the Colorado Rockies

Present Photo: McKenzie Skiles, Snow Optics Laboratory

Phoenix 2006 Future Dust Loading

albedo = 0.72 Before disturbance albedo = 0.43 After disturbance Snowmelt Modeling Senator Beck Basin Study Area, Colorado, 2006 Snow water equivalent (mm) Cleaner (before disturbance) Dirtier (after disturbance )

Informing Water Managers

Colorado River Basin May 6, 2009 MODIS-DRFS Daily sunlight absorbed by dust (W/m 2 )

Water in the Colorado River Basin STAY TUNED