Snow Cover Dynamics and Environmental Coupling Regulate Freezing Intensity Across China's Frozen Ground Regions

Abstract

Climate warming and increasingly frequent hydroclimatic extremes are altering snowfall regimes and snow cover dynamics, with important implications for frozen‐ground stability. Yet the combined effects of snow cover and environmental controls on ground thermal conditions remain poorly constrained. Using meteorological observations and remote sensing data during 2005–2024, we applied a partial least‐squares path model (PLS‐PM) to quantify how snow cover dynamics and environmental factors jointly influence ground temperature based freezing indices (FI _GT ) across China's frozen‐ground regions. Snow cover characteristics and FI _GT trends showed strong spatial heterogeneity. The insulating effect of snow varied markedly among regions and was much stronger in the permafrost regions of Northeast China than on the Qinghai‐Tibet Plateau (QTP) or in seasonally frozen ground regions. Over the past two decades, FI _GT declined across all frozen ground regions. At 0 cm depth, the rate of decline was greatest in permafrost regions of Northeast China (−25 ± 22°C·d yr ⁻¹ ), followed by seasonally frozen ground (−7 ± 10°C·d yr ⁻¹ ) and QTP permafrost (−1 ± 7°C·d yr ⁻¹ ). Shallow‐soil FI _GT was mainly controlled by climatic change, snow insulation, and soil properties, whereas deeper soil FI _GT was increasingly governed by soil mediated effects. In regions with stable snow cover, snow exerted a stronger insulating influence on surface and shallow‐soil freezing; in regions with unstable snow cover, FI _GT was more strongly constrained by climatic background and geographic setting. The findings advance understanding of frozen‐ground sensitivity to changing snow regimes and provide a scientific basis for assessing ecological and hydrological risks under continued climate warming.