Dynamic Impacts of Eurasian Spring Snowmelt on Summer Heat Extremes in Northern East Asia

Eurasian spring snowmelt (ESS) significantly influences climate, yet its effects on climate extremes and their dynamic variations remains poorly understood. This study investigates the dynamic impact of ESS on summer heat extremes in Northern East Asia (NEA) during 1979–2018 and examines the underlying mechanisms driving long-range links between snowmelt and temperature anomalies. We find that ESS has a notable positive impact on NEA summer heat extremes, primarily driven by snow-hydrological effects (soil-moisture). Increased ESS drives positive local soil-moisture anomalies in summer, which cool the near-surface atmosphere, facilitating the eastward propagation of anomalous wave patterns. This process strengthens the anomalous anticyclone over NEA, amplifying summer heat extremes. We also find that the Atlantic Multidecadal Oscillation modulates this impact, with its positive phase significantly enhancing the ESS effect by altering atmospheric circulation, strengthening the coupling between spring snowmelt and summer soil moisture, and intensifying NEA heat extremes. This study underscores the critical role of ESS in driving atmospheric circulation over wide regions, and highlights the coupled impacts of multi-scale and multi-temporal climate variability.