Modulation of Oceanic CO ₂ Uptake by the Kuroshio Extension Bimodal States

Abstract Bimodal dynamic states of the Kuroshio Extension (KE)—stable and unstable—have been extensively studied due to the KE's critical role in climate variability. However, its influence on sea‐air CO 2 flux remains uncertain, despite the KE region being recognized as one of the principal oceanic carbon sinks globally. Utilizing observational data and a state‐of‐the‐art global ocean biogeochemistry model that assimilates both physical and biogeochemical observations, we reveal that the KE bimodal states substantially modulate sea‐air CO 2 flux. During the KE stable state, oceanic CO 2 uptake intensifies due to lateral divergence of dissolved inorganic carbon (DIC) within the mixed layer and increased surface wind speed. The DIC divergence results from the northward displacement of the DIC front associated with the northward‐shifted KE jet. Observations reveal that mesoscale warming contributes to accelerated surface winds, a feature not captured by the model.