The response of marginal snowpacks to climate warming

Marginal snowpacks are a critical part of the hydrology and ecology of temperate mountain regions. However, their sensitivity to temperature increase is uncertain due to their phenology which sits between seasonal and ephemeral snowpacks. We investigate the sensitivity and the potential response of marginal snowpacks to a warmer climate by leveraging simulated snow series under various combinations of mean winter temperature (T) and precipitation (P), and varied meteorological conditions over 21 years (01/10/2000-30/09/2021), at 24 mountain sites globally. Warmer temperatures will lead to noticeable declines in all types of snowpacks. However, marginal snowpacks are found to be more sensitive to temperature increases compared to both seasonal, and ephemeral snowpacks. According to all considered T and P combinations, 64% of marginal snowpacks would transition to ephemeral or disappear, compared to only 21% and 24% for seasonal and ephemeral snowpacks, respectively. The study reveals new insight on the impacts of a warming climate on marginal snowpacks, including: the advance of melt-out dates (−21 days) and a reduction in snowmelt contribution to runoff (−11%). Further, we estimate the global distribution of marginal snowpack based on T and P combinations from ERA5-Land reanalysis. The total area covered by marginal snowpack would decrease by 2.7% under +1 ºC, with a more significant decreases under +2 ºC (5.7%) and +3 ºC (10.5%) warming. Climate warming will impact noticeably in all snow dominated region. However, this study places marginal snowpacks at the forefront of where climate change will pose the greatest threats to mountain and montane water resources and environmental systems globally, with profound shifts even under optimistic future climate scenarios (+1 ºC).