An energy-bandwidth basis for the internal wave model IDEMIX

Abstract

Small-scale turbulent mixing plays an important role for the large-scale ocean circulation, but is unresolved in numerical ocean models. Since breaking internal gravity waves (IGWs) are a major source of this mixing, energetically consistent mixing parameterizations consider the internal wave energy balance. One such parameterization can be achieved with the aid of the IDEMIX (Internal Wave Dissipation, Energy and Mixing) model, which describes the generation, propagation and dissipation of internal wave energy and successfully reproduces energy and mixing estimates derived from Argo float observations. We extend the IDEMIX energy model to describe a coupled system of predictive equations for energy and bandwidth, where bandwidth is a shape parameter of the IGW energy spectrum fixing the number of excited vertical modes. The correlation between energy and bandwidth is a power law with an exponent given by the dynamical parameters. The power law agrees with energy and spectral shape estimates from finestructure observations by Argo floats. We present the coupled energy-bandwidth IDEMIX model in a stand-alone setup and preliminary results of how it affects vertical mixing and the ocean state in a global ocean model.