Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

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

[A-OS04] Ocean Mixing Frontiers

Sun. May 22, 2016 1:45 PM - 3:15 PM 102 (1F)

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(Applied Physics Laboratory, University of Washington), Chair:RenChieh Lien(University of Washington, Seattle)

2:45 PM - 3:00 PM

[AOS04-05] Eikonal Simulations for Energy Transfer in the Deep-Ocean Internal Wave Field near Mixing Hotspots

*Takashi Ijichi1, Toshiyuki Hibiya1 (1.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)

Keywords:Internal Wave Spectrum, Energy Transfer, Parameterization, Turbulence, Eikonal Simulation

In the proximity of mixing hotspots in the deep ocean, the observed internal wave spectra are usually distorted from the Garrett–Munk (GM) spectrum and are characterized by the high energy level E as well as the shear/strain ratio Rω quite different from the corresponding value for the GM (Rω = 3). On the basis of the eikonal theoretical model, Ijichi and Hibiya (IH) have recently proposed the finescale parameterization of turbulent dissipation rates in the deep ocean in terms of E and Rω to reduce bias resulting from such spectral distortion. However, some simplifying assumptions are made in the theoretical model itself such as neglecting the vertical velocity associated with background internal waves and violating the WKB scale separation. To see the effect of such simplifying assumptions on the IH parameterization, this study carries out a series of eikonal simulations for energy transfer through various internal wave spectra distorted from the GM. Although the background vertical velocity as well as the strict WKB scale separation somewhat affects the calculated energy transfer rates, their parameter dependence is confirmed as expected from the IH parameterization; in other words, the calculated energy transfer rates ε follow the scaling ε ~ E2N2f with N the local buoyancy frequency and f the local inertial frequency, and exhibit strong Rω dependence quite similar to that predicted from the parameterization.