Antarctic sea-ice loss shifts the Pacific Decadal Oscillation toward its positive phase

Antarctic sea-ice loss can influence climate far beyond the Southern Hemisphere, but its remote oceanic impacts and underlying mechanisms remain uncertain. Using two global climate models, we show that reduced Antarctic sea ice consistently triggers a positive Pacific Decadal Oscillation (PDO)–like response, characterized by sea-surface temperature (SST) cooling in the midlatitude western North Pacific and warming in the eastern and subpolar Pacific. This transient adjustment unfolds over timescales of up to ~20 years, with the pace depending on the model. Idealized zonal-wind nudging experiments reveal that an equatorward shift of the Asian westerly jet generates low sea-level pressure anomalies over the western North Pacific. These anomalies intensify cold oceanic advection from the subpolar region and suppress downward shortwave radiation, producing the SST cooling that contributes to the positive PDO-like response. In quasi-equilibrium, the tropical Pacific shifts toward either El Niño– or La Niña–like states, depending on the model and internal variability. These findings imply that Antarctic sea-ice decline can act as a cross-hemispheric driver, with the potential to shift the recent negative PDO pattern toward a positive phase over the next decade.