At the Autumn Conference of the Oceanographic Society of Japan held at the Yoshida Campus of Kyoto University from September 2023th to 9th, 24, Associate Professor Kenyo Nagai of our university received the Hidaka Paper Award of the Oceanographic Society of Japan.

【Winner】
Kenyo Nagai (Associate Professor, Department of Marine Environmental Science, Faculty of Marine Science and Technology, Tokyo University of Marine Science and Technology)

[Title of award-winning research]
Elevated turbulent and double-diffusive nutrient flux in the Kuroshio over the Izu Ridge and in the Kuroshio Extension

[Research content]
The Kuroshio Current is known to have an oligotrophic surface layer.On the other hand, the subsurface layer, where light does not reach, is a nutrient stream that transports many nutrients to the northern downstream reaches of the Kuroshio Extension and the Kuroshio-Oyashio Mixed Area.Many points remain unclear as to how these subsurface nutrients are transported to the depths where light reaches the surface and are supplied to the phytoplankton that forms the basis of marine ecosystems.Associate Professor Nagai and his colleagues deployed an autonomous lifting float capable of measuring turbulence in the Kuroshio Current, which flows over the Izu Ridge, and found that the diffusion supply of nutrients due to turbulence is active along the Kuroshio Current, which flows over the Izu Ridge, on a scale of 50 to 100 km. It was shown that it is changing.Furthermore, when the Kuroshio Current reaches the Kuroshio Extension, which is downstream, the low-salinity, low-temperature water from the north and the high-temperature, high-salinity water carried by the Kuroshio from the south form an intrusive structure on a vertical scale of about 100 m, resulting in active double diffusion. It was shown that convection and the associated supply of nutrients to the surface layer occur.

<Related links>
Oceanographic Society of Japan 2023 Autumn Conference
Oceanographic Society of Japan HP