Interdecadal Phase Shifts of Winter Asian‐Pacific Oscillation Modulate the Warm Arctic‐Cold Eurasia Pattern

Abstract Against the backdrop of global warming, warm Arctic‐cold Eurasia (WACE) has garnered extensive scientific attention. However, the drivers of its interdecadal variability remain insufficiently understood. Using reanalysis data and pre‐industrial control simulations, we demonstrate that winter Asian‐Pacific Oscillation (APO), a dominant upper‐tropospheric atmospheric mode over the Asian‐North Pacific sector, modulates the WACE variability at the interdecadal timescale. Positive APO phases tend to induce anomalous warming over the Barents‐Kara Seas (BKS) and cooling over central Asia. Information flow and Granger causality diagnostics confirm the causal effect of APO on the WACE. Physically, positive APO phases feature upper‐tropospheric warming and anticyclonic circulation anomalies over Asia, which are accompanied by cyclonic circulation anomalies over central Asia that favor local cooling. Reduced background potential vorticity gradient over the Ural‐Siberian region further facilitates persistent high‐pressure anomalies near the BKS, ultimately resulting in anomalous warming in situ.