Two contrasting atmospheric circulation patterns linked to Kuroshio Extension variability.

The influence of Kuroshio Extension (KE) variability on North Pacific atmospheric circulation has been increasingly recognized in high-resolution observations and models. While the role of fine-scale air-sea interactions has been highlighted, the dynamics underlying KE atmospheric impacts remain elusive. Here, based on observational analyses and a suite of model simulations, we report two contrasting atmospheric circulation patterns that arise from temporal variations in KE boundary forcing on the atmosphere. During the late 20th century (1979-1999), the positive KE phase, along with a northward shifted Kuroshio SST front, anchors the Pacific storm track farther poleward accompanied by an anomalous anticyclonic circulation. In contrast, during the early 21st century (2000-2022), KE variability exhibits stronger linkages with central tropical Pacific SST that drives a southward shift of the storm track with an anomalous cyclonic circulation, further amplified by enhanced Kuroshio latent heat release. Our findings suggest that accounting for decadal shifts in KE SST boundary forcing is critical for accurately representing KE downstream impacts.