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

Jeong, Hyein1; Park, Hyo-Seok1; Yeh, Sang-Wook2; Chung, Eui-Seok3; Xie, Shang-Ping4

Published Mar 19, 2026 on Dryad. https://doi.org/10.5061/dryad.z8w9ghxsh

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Abstract

Antarctic sea-ice loss can influence climate far beyond the Southern Hemisphere, but its remote impacts and underlying mechanisms remain uncertain. Using two global climate models, we show that reduced Antarctic sea ice triggers a positive Pacific Decadal Oscillation (PDO)–like response, characterized by sea-surface temperature (SST) cooling in the 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. Mechanistically, this response is initiated by a strengthened Indo-Atlantic cross-equatorial SST gradient, reflecting enhanced off-equatorial Southern Hemisphere warming, that drives a southward shift of the Asian jet. Idealized zonal-wind nudging experiments confirm that this jet shift generates low sea-level pressure anomalies over the western North Pacific. These anomalies intensify cold oceanic advection from the subpolar region and reduce downward shortwave radiation, producing 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, potential to shift the recent negative PDO pattern toward a positive phase over the next decade.