Nutrient Footprint from the Origin of the Kuroshio Current to the East China Sea Continental Shelf

The dynamics governing nutrient concentrations in the ocean are primarily influenced by geophysical and biogeochemical processes that regulate the introduction of these elements into seawater and their transport, dispersion, and removal. In one of the world’s most productive marine regions, the East China Sea (ECS), numerous reports have documented the relationship between biological productivity on the shelf and the nutrients primarily supplied from the subsurface waters of the Kuroshio, a powerful western boundary current. However, the mechanism behind this nutricline variation is not well understood. In this study, we trace macronutrients from the Kuroshio’s source to the ECS shelf. As the Kuroshio flows northward along the eastern coast of the Philippines to the southern Luzon Strait (LS), part of it intrudes into the South China Sea (SCS) through the strait. Due to vigorous vertical mixing and upwelling, the thermocline and nutricline are elevated in the SCS compared with those near the origin of the Kuroshio. Subsequently, at the northern LS, the SCS outflow merges with the Kuroshio’s western side. This process preconditions the upwelling of nutrient-​rich subsurface Kuroshio waters onto the ECS shelf.