Snow droughts enhance carbon uptake in energy-limited ecosystems but reduce it in water-limited ones

Abstract Seasonal snowpack acts as a natural water reservoir, and snowmelt provides a critical water supply for many ecosystems across the Northern Hemisphere. Snow droughts, periods of reduced winter snow accumulation, are becoming a growing threat to the functioning of these ecosystems due to ongoing global warming. Here, we demonstrate how snow droughts shift gross primary productivity (GPP) across Northern Hemisphere ecosystems. Combining dynamic global vegetation model simulations with gridded snow and multi-source GPP products, we identify positive GPP anomalies in spring and negative GPP anomalies in summer following snow drought conditions over recent decades. Overall, snow droughts reduce the annual net productivity in water-limited regions and enhance it in energy-limited regions. Further, the impact of snow droughts on GPP remains largely independent of subsequent spring and summer moisture conditions. This work advances our understanding of how declining snowpacks impact the stability of the terrestrial carbon sink under climate change.