Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

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

[A-OS18] Physical Oceanography (General)

Tue. May 22, 2018 10:45 AM - 12:15 PM 104 (1F International Conference Hall, Makuhari Messe)

convener:Eitarou Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Yoshimi Kawai(Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology), Tomoki Tozuka(東京大学大学院理学系研究科地球惑星科学専攻), Chairperson:Nishikawa Hatsumi

11:00 AM - 11:15 AM

[AOS18-08] Near-inertial and multiple-inertial internal waves trapped by negative-vorticity regions in the Subpolar Front of Japan Sea

★Invited Papers

*Yusuke Kawaguchi 1, Taku Wagawa 2, Yosuke Igeta 2 (1.Atmosphere and Ocean Research Institute, University of Tokyo , 2.Japan Sea National Fisheries Research Institute, Japan Fisheries and Education Agency )

Keywords:Japan Sea , Trapping of internal gravity waves , Relative vorticity , Overtone harmonics , Nonlinear resonance

In this study, we investigated the interaction between internal gravity waves and mesoscale features near the frontal region in the Sea of Japan. A moored ADCP current record deployed in the central pathway of meandering flow in the Japan Sea is analyzed. The data analyses showed that in a mesoscale feature of negative vorticity, massive strength of near-inertial internal waves (NIWs) were found to propagate in the upper water (<300 m). Near the critical depth, where background vorticity diminishes nearly to zero, the amplification of NIW reached > 50 cm s-1 in root-mean-square magnitude. The mid-depth NIWs were characteristically concurrent with the emergence of super-inertial oscillations, peaking at frequencies of multiple inertial (MI), i.e., double, triple, quadruple, other than the near-inertial one (see a spectral plot). The MI oscillations are considered to arise through the nonlinear resonance of NIW, which is proposed by Danioux et al. (2008). By analyzing reanalysis surface wind, it turns out that a fast-moving cyclone passing over the site would be the primary energy source for the NIW generation. In conclusion, we obtained the following picture of the kinetic energy flow in the Japan Sea –– the stormy event initially provides the energy into the oceanic surface layer, resulting in the generation of NIWs; the NIWs are trapped by anticyclonic vortices, with negative vorticity, and then transferred its energy into the MI oscillations; they ended up to mostly dissipate into turbulence.