Mechanism of Cross-Seasonal Response of Arctic Temperature to Eurasian Early Spring Snow Loss: The Critical Roles of Soil Moisture and Stationary Wave Propagation

Snow cover can significantly influence climate via modulating surface energy balance, yet its cross-seasonal impacts on Arctic temperatures remain poorly understood. Here, based on diagnostic analysis and numerical experiments, we reveal a robust linkage between reduced early spring (March-April) snow water equivalent (SWE) in northern Europe and increased May-June-July (MJJ) 2m air temperature over the East Siberian-Chukchi Sea during 1951–2022. Specifically, March-April SWE negative anomaly can persist to June and result in drier surface conditions due to reduced snowmelt. It led to elevated turbulent heat fluxes and positive geopotential height anomalies over northern Europe via snow-albedo and snow-hydrological effects during April-May-June. Hence, the eastward-propagating wave train enhanced over northern Europe and reaches South Siberia, causing cyclonic activity and enhanced precipitation. The resultant soil moisture increases persist into MJJ, favoring less sensible heat fluxes, upward wave activity flux, and wave train poleward-propagation. Finally, an anticyclonic anomaly appears over East Siberian-Chukchi Sea, enhancing anomalous descending motion, water vapor and downward longwave radiation, collectively raising near-surface temperatures. Moreover, numerical experiments successfully reproduce this cascade of mechanisms, confirming the physical pathway. Our study provides a new perspective for the studies of the snow cover climate effect, especially its impacts to the Arctic temperature variability.