Two Decades of Dust Radiative Forcing on Snow Cover Across the Great Salt Lake Basin

Abstract

Seasonal snowpacks in mountain drainages of the Great Salt Lake Basin (GSLB), western United States, are the primary surface water supply to regional agriculture, the metropolitan Wasatch Front, and the terminal Great Salt Lake. Spring dust emissions from the eastern Great Basin result in a dust-darkened GSLB snowpack, locally accelerating snowmelt relative to dust-free conditions. Such acceleration has been linked to streamflow forecasting errors in the adjacent Colorado River Basin, but snow darkening impacts within the GSLB are largely uninvestigated. To quantify the dust impact, we analyzed patterns in dust radiative forcing (RF_dust) over the MODIS record (2001–2023) using spatially and temporally complete RF_dust and fractional snow-covered area products. For validation, retrievals were cross-referenced with in situ RF_dust observations. Results showed that RF_dust was present every year and had no significant trend over the record. Spatially, RF_dust was similar across all three subbasins. Temporally, RF_dust exhibited high interannual variability (−30 to +40 Wm⁻² from record means) and has declined slightly in regions of the eastern GSLB. Controls of RF_dust may be linked to seasonal meteorology and drought conditions, but drivers remain uncertain. Further understanding of the distribution and controls of RF_dust in the GSLB during changing climate and weather patterns may allow us to predict snowmelt more accurately.