Transitioning Climate Control on Snow and Streamflow Dynamics Over the Past 70 Years

Abstract Understanding the evolving relationships between snow and streamflow dynamics with variations in climate drivers is crucial for hydrologic predictions and the sustainability of water‐energy supply systems in cold regions. However, comprehensive hemisphere‐scale assessments are lacking. Using extensive streamflow observations from approximately 850 catchments and reanalysis data sets spanning 1950–2020, here we reveal a widespread transition from cold‐season precipitation to temperature as the dominant control of snowpack and seasonal streamflow dynamics. These transitions are most pronounced when mean cold‐season temperatures surpass −3°C for snowpack and 0°C for streamflow. Notably, these critical temperature thresholds have shown significant downward trends over time, implying more frequent transitions with persistent warming. Additionally, we observed an increase in the elevation corresponding to these transitions, suggesting that temperature is playing a more important role across broader and higher areas. These findings have significant implications for water resource management in cold regions, addressing the challenges posed by warming climates.