Hotspots of snow cover changes in global mountain regions over 2000-2018

Quantification of snow cover changes and related phenology in global mountain areas has not been consistently addressed, despite the well-known importance of the snow in this environment. By using MODIS products from 2000 to 2018, this study reveals that around 78% of the global mountain areas are undergoing a snow decline characterized by snow cover duration decrease up to 43 days, and a snow cover area decrease up to 13%. Few areas show positive changes with snow cover duration increase up to 32 days, and snow cover area increase up to 11%, mainly during wintertime in Northern Hemisphere. Significant snow cover duration changes are related in 58% of the areas to both delayed snow onset, and earlier melt; moreover, the rate of earlier snowmelt is greater than the rate of later snow onset in the analyzed time period. Snow cover, and phenology changes are highly variable at mid-elevations, while from 4000 m upward only negative changes are detected. Air temperature is the main driver for snow onset and melt, while a combined effect of air temperature and precipitation dominates the winter season. These changes have multiple implications on water resources, ecosystem services, tourism, and energy production. The results are provided with the caveats that the short time period of the analysis (2000-2018) limit the attributions of long-term trends, and snow cover estimates are affected by uncertainties, which may be stronger in complex terrain.