Proceedings of the 12th Biennial Conference of research on the Colorado Plateau

Mountain snow cover of the Colorado River Basin (CRB) has had a fivefold increase in dust loading since Anglo settlement of the western United States in the mid-19th century.This dust deposition accelerates snowmelt by reducing albedo through surface darkening and enhanced snow grain growth.Here we present a nine-year (water years [WY] 2005[WY] -2013) ) record of dust loading and advanced snowmelt at Senator Beck Basin Study Area, San Juan Mountains, Colorado (SBBSA).Since observations of dust events began in WY 2003, a single dust-free season has not occurred.The majority of these dust events occur in the spring, which enhances the efficacy of dust-advanced snowmelt, as it coincides with increasing solar irradiance.The fewest springtime events occurred in WY 2003 (three events) and then increased through WY 2008 (nine events) before stabilizing with an average of 9±1 spring events between 2008 and 2013.The amount of dust entrained and deposited in each event is variable; therefore, the number of dust events is not a good indicator for dust loading, which exhibits greater interannual variability.End of snow season total dust concentrations range from 0.2 to 4.8 milligrams of dust per gram of snow melt water (mg/g), resulting in earlier snowmelt by 3 to 7 weeks.Results from snowmelt modeling show that the degree of advanced melt is linearly related to the amount of dust deposited each season.