Pathways from Internal-Wave Driven Processes to Vortical Mode and Submesoscale Dispersion

Pathways to submesoscale lateral dispersion in the ocean’s stratified interior are examined numerically in the context of linear internal-wave-driven processes vs. those associated with nonlinear waves and vortical mode. Simulations using a fully nonlinear three-dimensional Boussinesq model are initialized with a Garrett and Munk internal-wave spectrum, which, through nonlinear interactions, small-scale dissipation and wave breaking, leads to the formation of vortical mode. Specific attention is paid to cases with strongly nonlinear waves,where turbulent mixing parameterizations are used to incorporate the impacts of incipient shear instability and/or turbulent overturns that are not resolved by the model. Results are presented for a suite of simulations ranging from a weak small-amplitude linear internal wave field without vortical mode, to weakly nonlinear and strongly nonlinear wave fields that include active vortical-mode generation. Dispersion scalings are presented as a function of key parameters for linear vs. weakly and strongly nonlinear cases. The partition of energy between internal waves and the vortical mode is also assessed in relation to the degree of nonlinearity of the wave field.