Relative dispersion and relative diffusivities in an ocean-wave coupled model of the North Sea

Abstract The study analyzes the impact of various wave-induced processes on relative dispersion and diffusivities in the North Sea using OpenDrift, a Lagrangian particle-drift model driven by a fully coupled NEMO-WAM model. The coupled model parameterizations include sea state-dependent momentum flux, energy flux, and wave-induced mixing. The study demonstrates that Eulerian currents, influenced by the interaction between the ocean and wave models, significantly enhance particle transport. Experiments conducted using drifter clusters obtained during an RV Heincke excursion further confirm the impact of wind-wave coupling. The analysis includes a comparison of results from experiments with and without wave coupling. The impact of diffusion in the Lagrangian model on relative dispersion is investigated, with the conclusion that diffusion is essential for achieving precise simulations. Furthermore, the incorporation of wind-wave-driven mixing parameters, including sea state-dependent momentum flux, energy flux, and wave-induced mixing, into the hydrodynamic model leads to elevated levels of relative dispersion and diffusivity.