Influence of three tropical oceans on western North Pacific anticyclone strengthening under global warming

Abstract The western North Pacific anomalous anticyclone (WNPAC) is a key atmospheric circulation system that significantly influences East Asian climate variability. Its formation and persistence result from complex interactions among the Pacific, Indian, and Atlantic Oceans. Using the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations, this study examines projected changes in WNPAC under anthropogenic warming and quantifies the seasonal contributions from the three tropical oceans. The results show a clear intensification of WNPAC in winter, spring, and summer, primarily driven by enhanced Atlantic and Pacific forcing. The Atlantic’s influence intensifies through enhanced equatorial wave activity and the development of quasi-stationary Rossby wave trains, most prominent in winter and spring. During summer, equatorial Rossby wave mechanisms dominate. The Pacific’s strongest influence emerges in summer, linked to intensified easterly winds over the western Pacific, associated with enhanced sea surface temperature gradients between the Indo-Pacific warm pool and the central-western Pacific. The Indian Ocean shows comparatively weaker changes across all seasons. These findings provide a quantitative assessment of the evolving three-ocean influence on WNPAC and underscore the increasing roles of Atlantic and Pacific variability in shaping East Asian climate under future greenhouse gas emissions.