<p>Antarctic sea-ice loss can influence climate far beyond the Southern Hemisphere, but its remote impacts and underlying mechanisms remain uncertain. Here we use numerical climate model experiments to show that reduced Antarctic sea ice triggers a response resembling the positive phase of the Pacific Decadal Oscillation. This pattern is characterized by sea-surface temperature cooling in the western North Pacific and warming in the eastern and subpolar Pacific. This transient adjustment unfolds over approximately 20 years. Mechanistically, the response is initiated by a strengthened interhemispheric thermal gradient that drives a southward shift of the Asian jet. Idealized experiments confirm that this jet shift generates low sea-level pressure anomalies over the western North Pacific, which intensify cold oceanic advection and reduce downward shortwave radiation. These findings imply that Antarctic sea-ice decline can act as a cross-hemispheric driver, potentially shifting the Pacific Decadal Oscillation toward a positive phase.</p>