Abstract
Abstract. This study focuses on how wave–current and wave–turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis–Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.
Highlights
An important application of upper ocean models is the mixing and transport of particles, which could represent e.g., suspended sediments, plastic particles, biological matter, or oil droplets (Hackett et al, 2006)
The mixing model used in our experiments is the General Ocean Turbulence Model (GOTM; for a description see Umlauf and Burchard, 2005), modified to take account of the wave effects described in the previous sections
For a particle rise velocity of 100 m day−1 and for a surface stress of roughly 0.05 N m−2, we find that DC = depths for momentum (DE) and vC/uC increases by a factor of 3 compared to the case when all particles are at the surface
Summary
An important application of upper ocean models is the mixing and transport of particles, which could represent e.g., suspended sediments, plastic particles, biological matter, or oil droplets (Hackett et al, 2006) These particles are advected by the Lagrangian current, consisting of an Eulerian component, and the wave-induced Stokes drift. The model is applied to two cases: (1) an idealized steady-state case with constant fluxes of momentum and energy, where the waves are represented by a theoretical spectrum, and (2) a specific case study where wind and wave data from the ERA Interim archive (Dee et al, 2011) are used as forcing While the former case is well-suited for studying the impact of the various wave effects, the latter case serves as a test of the model in a practical application.
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