Accelerated Snow Melt in the Russian Caucasus Mountains After the Saharan Dust Outbreak in March 2018

Light absorbing particles, such as mineral dust, are a potent climate forcing agent. Many snow-covered areas are subject to dust outbreak events originating from desert regions able to significantly decrease snow albedo. Here, using a combination of Sentinel-2 imagery, in situ measurements and ensemble detailed snowpack simulations, we study the impact on snow cover duration of a major dust deposition event that occurred in the Caucasus in March 2018. This is, to the best of our knowledge, the first study using ensemble approach and Sentinel-2 imagery to quantify the impact of a dust event on the snow cover evolution. We demonstrate that the calculation of the impact is strongly affected by the snow model uncertainties but that the March 2018 dust event systematically shortened the snow cover duration inWestern Caucasus. The shortening is higher for location with higher accumulation and higher elevation (median values of 23 +/- 7 days) than for location at lower elevation (median values of 15 +/- 3 days). This is because for sites with higher location and higher accumulation, melt occurs later in the season when more incoming solar energy is available. This highlights the huge impact of a single 1- day event on snow cover duration, and consequently, on the hydrology of a large region.