Historical Occurrence of and Shift in Snow Drought Drivers in Global Mountain Ranges

Abstract

Snow droughts are a new way to understand changes in snowpack and subsequent runoff. Globally, we do not have a good understanding of the drivers of snow droughts or how those drivers have changed historically. Here, we identify what has been the dominant driver of global snow droughts in mountain ranges, how it shifted historically, and what similarities exist in similar snow types. We explore this in all global mountain ranges, ones that are highly dependent on winter precipitation for summer water, and two regional case studies in the Cascade Range and the Himalayan Mountains. We found that in both the northern and southern hemispheres, dry snow droughts (driven by precipitation) are the most common. In both the northern and southern hemisphere, more mountain ranges shifted to having temperature be the main driver of snow droughts in the historical record. In the northern hemisphere, tundra, boreal, prairie, and ice snow type areas had the most area with dry snow droughts. In the southern hemisphere, all snow types except for tundra had the most area with temperature as the main driver of snow droughts. With this global, multivariate methodology, we were able to identify common drivers and patterns of historical snow droughts that exist across similar geographical areas (i.e., northern and southern hemisphere and mountain ranges) and snow type areas. More research is needed to better understand snow droughts, their drivers, and the risk they pose regionally to food and water security.