Autumn snow loss over the Tibetan Plateau amplifies East Asian winter warming

Abstract

Anomalously warm winters have become increasingly frequent over East Asia in recent decades, with a marked acceleration since the mid-2010s, yet the regional drivers and feedback processes that amplify this warming beyond the global background trend remain incompletely understood. This study identifies the decline in late-autumn Tibetan Plateau snow depth (TPSD) as one contributor to these winter warm anomalies. Regression analysis of ERA5 reanalysis and observed snow depth data over 1979–2025 shows that late-autumn TPSD decline is associated with enhanced surface shortwave absorption and sensible heat flux over the Tibetan Plateau (TP), warming the mid-to-upper troposphere and inducing upper-level anticyclonic circulation anomalies over the plateau. The corresponding response over East Asia features anticyclonic anomalies over the northwestern Pacific and lower-tropospheric southerly winds that weaken the cold-air advection associated with the East Asian (EA) winter monsoon. To establish causality, we conduct a 100-member ensemble of atmospheric general circulation model sensitivity experiments in which TP snowfall is halved; wave activity flux diagnostics reveal a stationary Rossby wave train propagating eastward from the TP to the northwestern Pacific, reproducing the observed snow–warming connection. Notably, the warming response over East Asia is substantially stronger when late-autumn snow depth is shallow than when it is deep. Analysis of the CESM2 Large Ensemble further shows that members with stronger late-autumn TPSD decline exhibit enhanced TP–northwestern Pacific 300 hPa geopotential height trends consistent with the proposed mechanism, supporting its robustness under transient warming. Together, these results identify autumn TPSD reduction as an increasingly important remote forcing on EA wintertime warming, whose influence may grow further as background snow depth continues to decline.