Impacts of inertial internal wave breaking mixing parameterization on a global ocean model

Abstract

A parameterization of vertical mixing induced by fine-scale near-inertial internal waves (F-scheme) is implemented in the Parallel Ocean Program, version 2 (POP2). The F-scheme is based on the spectrum model via solving the non-traditional approximation internal wave equations and the observed internal wave spectra. The structure of the resulting dissipation and diffusivity fields and its impacts on the ocean model simulations are investigated. The diffusivity coefficient derived from F-scheme varies spatiotemporally, and is generally in consistent magnitude with observed results in the middle to high latitude ocean, and show the similar latitude dependent characteristics with the current observations, depending on the product of the horizontal and vertical components of the Coriolis parameter (f·f∼) as well as the local stratification condition. The interior mixing induced by F-scheme has some noticeable impacts on the temperature and salinity structure near the main thermocline, the meridional overturning circulation and northward heat transport as has been demonstrated in the other two OGCMs (LICOM and MOM4). The temperature and salinity structure simulated using F-scheme are statistically closer to observations, especially it improves the simulation of the Pacific Ocean, Indian Ocean and Antarctic Circumpolar Circulation. But the involved background mixing coefficients or F-scheme enlarges the temperature and salinity biases in the Atlantic Ocean, the cause is related to the pre-existing weak Antarctic Intermediate Water intrusion toward north and the inexact Atlantic Meridional Overturn Circulation simulation in the present model. F-scheme provides weak mixing in some regions, where an appropriate parameterization of turbulent mixing induced by wave-wave interaction also should be considered in the future.