How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near‐Inertial Waves and Turbulence

Abstract

Abstract The Kuroshio Current carries a large amount of nutrients in dark subsurface layer along the southern coast of Japan. However, due to lack of sufficient multidisciplinary high‐resolution observations, it has been unclear whether and how the subsurface nutrients are injected to sunlit layers on the continental shelf. In this study, using a state‐of‐the‐art tow‐yo microstructure profiler and nitrate measurements, we show that the Kuroshio flowing on the shelfbreak induces very strong turbulent dissipation rate ∼O(10 −7 W·kg −1 ) and diffusivity ∼O(10 −3 m 2 ·s −1 ) over an across frontal scale of 20–30 km. This strong turbulence could provide a diffusive nitrate flux to euphotic zone of >O(1 mmol N·m −2 ·day −1 ). As the Kuroshio steadily runs on the continental shelves along the path, the nutrient injection found in this study is a very important supply for biological production on the continental margin along the southern coast of Japan.