Historical occurrence of and shift in snow drought drivers in global mountain ranges

• Global snow drought area increased between 1980–2021. • In the Northern Hemisphere, dry snow droughts occurred in 68% of the mountain area. • The main driver changed in 45% and 22% of the Northern and Southern Hem. area. • In vulnerable mountain ranges, warm snow droughts were the most common type. Snow is a critical form of water storage, but climate change is reducing snowpack and affecting water resources. Snow droughts are periods of abnormally low snowpack that are driven by low precipitation or high temperatures, or both. Globally, we do not have a good understanding of how snow drought drivers have changed over time. Here, we used a multivariate snow drought index to identify the dominant driver of snow droughts between 1980 and 2021 in all global mountain ranges and ones that are highly dependent on winter precipitation for water. We then identified whether those drivers shifted during the study period. Finally, we identified what similarities exist based on climatological areas by using snow classification types, including forest, montane, maritime, tundra, prairie, and ephemeral, as a proxy. We found that in both the Northern and Southern Hemispheres, dry snow droughts (driven by low precipitation) are the most common. Furthermore, in both the Northern and Southern Hemispheres, more mountain range area shifted to having temperature be the main driver of snow droughts in the historical record. In the Northern Hemisphere, dry snow droughts affected the largest amount of area in tundra, boreal, prairie, and ice snow types. In the Southern Hemisphere, warm snow droughts affected the largest amount of area in all snow types except for tundra. This work identified common snow drought drivers and patterns that exist across similar geographical areas (i.e., mountain ranges) and climatological areas and areas that are most vulnerable to warm and dry snow droughts.