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Tokyo University of Marine Science and Technology

Shinagawa Etchujima CampusGraduate School of Marine Science and Technology

The Graduate School of Marine Science and Technology has a doctoral course divided into a master's course and a doctoral course, and trains independent highly specialized professionals who open up cutting-edge fields.Furthermore, in collaboration with the Japan Fisheries Research and Education Agency, the Japan Agency for Marine-Earth Science and Technology, and the National Institute of Maritime, Port and Aviation Technology, we will further enhance education and research and improve the quality of graduate students. We are trying to

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[Awards and Commendations] Takasako Mio (1st year master's student) received the Young Outstanding Presentation Award at the 2025 Autumn Meeting of the Oceanographic Society of Japan.

Graduate School of Marine Science and Technology Companies / researchers Current students

At the 2025 Autumn Meeting of the Oceanographic Society of Japan, held at the Hokkaido University Hakodate Campus from September 21 to 25, 2025, graduate student Mio Takasako of our university won the Young Researcher Outstanding Presentation Award. At the Autumn Meeting of the Oceanographic Society of Japan, there were 107 research presentations by young researchers (※), of which 9 were awarded the Young Researcher Outstanding Presentation Award.
* Student members or young regular members who are under 30 years old or who have received a doctorate for less than three years as of the end of September 2025

【Winner】
Mio Takasako (1st year master's student, Department of Marine Resources and Environmental Studies, Graduate School of Marine Science and Technology)

[Title of award-winning research]
Nonlinear behavior of linearly stable and unstable baroclinic vortices.
- An attempt to interpret the end of the Kuroshio Large Meander and the quasi-periodicity of the Enshu-Nada marine heat wave -
Mio Takasako and Koji Shimada

[Details of award-winning research]
We simplified the Kuroshio Large Meander Cold Water Vortex, with horizontal spatial scales of 200-300 km, into a baroclinic vortex represented by two potential vorticity fronts and investigated its behavior when disturbances were applied. First, theoretical analysis of linear stability revealed that, within the observed range of horizontal spatial scales of the Kuroshio Large Meander Cold Water Vortex, linear instability occurs only for wavenumber 2 disturbances, while wavenumber 3 and above disturbances are stable. Next, we numerically investigated the nonlinear evolution of the linearly unstable wavenumber 2 case using the contour dynamics method. We showed that the vortex splits into two baroclinic vortices, which is one of the factors that causes the termination of the Kuroshio Large Meander. Furthermore, the spatial scales of the two baroclinic vortices after splitting are small, and they are stable even when disturbances of any wavenumber are applied. Furthermore, when a linearly stable large-amplitude disturbance of wavenumber 3 is applied, the disturbance amplitude oscillates, but the shape rotates while maintaining its wavenumber 3 state. In other words, if observed at a fixed point, the disturbance peaks (cold areas) and valleys (warm areas) are observed periodically. This behavior of vortices can be used to explain the quasi-periodicity of marine heat waves observed in the Enshu Nada Sea during the Kuroshio Large Meander period.

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<Related links>
Oceanographic Society of Japan 2025 Autumn Meeting
Oceanographic Society of Japan Young Researchers' Excellent Presentation Award

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