Biogeochemistry of the Kuroshio Large Meander

The large meander of the Kuroshio western boundary current is well known to influence the local climate, fisheries, and aquaculture by greatly modulating regional heat transport, but its impacts on biogeochemical processes remain unclear. Using high-resolution numerical ocean modelling and long-term observational datasets, we show that the path of the Kuroshio determines the extent of the shallow nutricline region, where winter convective mixing replenishes nutrient availability for subsequent blooms of phytoplankton during spring. During the large meander phase, this mechanism triggers offshore phytoplankton blooms that are otherwise absent during the non-large meander phase. The large meander also modulates the spatial distributions of primary production, air-sea carbon flux, and export production. These biogeochemical impacts of the Kuroshio large meander exert bottom-up control on regional marine ecosystems that is disproportionate to the thermal effect, and therefore need to be assessed to understand the large meander's overall impacts on fisheries and aquaculture.