Eikonal Calculations for Energy Transfer in the Deep-Ocean Internal Wave Field near Mixing Hotspots

Abstract

n 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 a shear?strain ratio R? quite different from that of the GM spectrum. On the basis of the eikonal theoretical model, Ijichi and Hibiya (IH) recently proposed the revised finescale parameterization of turbulent dissipation rates in the distorted internal wave field, although the vertical velocity associated with background internal waves and the strict WKB scale separation, for example, were not taken into account. To see the effects of such simplifying assumptions on the revised parameterization, this study carries out a series of eikonal calculations for energy transfer through various internal wave spectra distorted from the GM. Although the background vertical velocity and the strict WKB scale separation somewhat affect the calculated energy transfer rates, their parameter dependence is confirmed as expected; the calculated energy transfer rates ε follow the basic scaling ε ? E2N2f with the local buoyancy frequency N and the local inertial frequency f and exhibit strong R? dependence quite similar to that predicted by IH.