With the injection of railroads and infrastructure into the interior of the western US in the mid 1800s came substantial increases grazing, farming, and mining, and in turn a disturbance of 70% of natural ecosystems resulting in losses of soil stability and increased dust emission. Recent geochemical analysis of alpine lake sediments in southwest Colorado shows that since the 1800s settlement of the western US, dust loading to mountain environments abruptly increased by a factor of ~5 above average rates of the last 5000 years. Given present dust loading to the Rocky Mountains and its associated forcing of snowmelt and reduction of snow cover duration, it is evident that snow cover endured longer prior to the mid 1800s disturbance.

Results/Conclusions

Dust emitted from the deserts of the western US is currently shortening snow cover duration in the San Juan Mountains of Colorado by 20-35 days and affecting a spring radiative forcing of 25 – 50 W m-2 through snow albedo reduction. In this work, we present point and spatially distributed snowmelt modeling results that show the impact of disturbed soils on the snowmelt hydrology in the critical mountains of southwest Colorado. Additionally, we present an remotely sensed assessment of the interannual variability of the spatial distribution of dust radiative forcing across the Colorado Rocky Mountains for the period 2000 to 2008, corresponding to the lifetime of the NASA EOS Terra and Aqua Moderate Resolution Spectroradiometers (MODIS). These remote sensing analyses are critical to bridging the scale gap between (a) measurements of dust radiative forcing in snow that have been made by our team since 2004 and (b) the lake sediment analysis that has great temporal range but poor temporal resolution to resolve interannual variability.  We also partition the remotely sensed results into hydrologic basins for comparisons with river runoff hydrographs and snow water equivalent depletion from snow telemetry (SNOTEL) sites.