JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

A (Atmospheric and Hydrospheric Sciences) » A-OS Ocean Sciences & Ocean Environment

[A-OS15] [EE] Ocean Mixing Matters

Sun. May 21, 2017 10:45 AM - 12:15 PM 302 (International Conference Hall 3F)

convener:Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Louis St Laurent(Woods Hole Oceanographic Institution), Ren-Chieh Lien(University of Washington, Seattle, WA, USA), Robin Ann Robertson(University of New South Wales Canberra), Chairperson:Ren-Chieh Lien(University of Washington, Seattle, WA, USA), Chairperson:Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)

10:45 AM - 11:00 AM

[AOS15-07] How the Tokara strait cultivates the Kuroshio

*DAISUKE HASEGAWA1, Takeshi Matsuno2, Eisuke Tsutumi2, Tomoharu Senjyu2, Hirohiko Nakamura3, Toru Kobari3, Ayako Nishina3, Naoki Yoshie4, Xinyu Guo4, Miwa Nakagawa4, Takeyoshi Nagai5, Takahiro Tanaka6, Ichiro Yasuda6 (1.Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency, 2.The Research Institute for Applied Mechanics, Kyusyu University, 3.Faculty of Fisheries, Kagoshima University, 4.Center for Marine Environmental Studies, Ehime University, 5.Tokyo University of Marine Science and Technology, 6.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:Turbulence, Mixing, Topography, Nutrient, Nitrate, Flux

Previous studies have reported clear signs of vigorous turbulent mixing in the Kuroshio due to the presences of shallow and steep topographies in its path (e.g., Hasegawa et al., 2004 and 2008, Chang et al., 2016). Turbulent mixing is one of the most important processes supplying nutrients to the surface euphotic zone from the deep water; however, a quantitative understanding of the turbulent vertical nutrient flux is still limited. On November 2016, we have conducted intensive survey around the Tokara strait by drifting the T/V Kagoshima-maru with the Kuroshio's stream and passed across the shallow (∼100 m) sill while deploying a submersible ultraviolet nitrate analyzer (Deep SUNA by Satlantic) attached on a turbulence ocean microstructure profiler (TurboMAP-L by JAC). Occurrence of a flow separation and a hydraulic jump on the sill have been identified from a high resolution velocity survey. The rate of dissipation of kinetic energy reaches O(10-5 W kg-1), and the turbulent vertical nitrate flux reaches O(1 mmol m-2 day-1), which is the highest value ever reported for the open ocean.