Diffusion of Pollutants in Wind-Induced Oceanic Surface Turbulence

Pollutants such as spilled oil or chemicals have a serious impact on the ecosystem in the ocean. Accurate prediction of the spreading of spilled pollutants is crucial in risk assessment and disaster prevention. Most spill accidents happen when the weather is severe and the wind is strong. The distribution of pollutants in oceanic surface turbulence during strong wind is affected by enhanced vertical mixing through Langmuir circulation and wave breaking. In this study, the effect of wind-induced turbulence on the distribution of pollutants were quantitatively described using large eddy simulation (LES) model. There were significant differences in velocity profiles as well as turbulent diffusion, depending on the Langmuir circulation and wave breaking. Displacement and diffusion area of pollutants were 172.1 m and 4.9×10⁴ m² when the model consider Langmuir circulation and wave breaking (EXP LB), whereas they were 354 m and 1.29×10⁵ m² when the model ignores the wave-induced turbulence enhancement (EXP O). Effect of buoyancy on the distribution of pollutants was relatively small in the EXP LB. When the wind speed is stronger, the displacement of pollutants increases faster. The increase rate of the diffusion area depends on the wind speed, but is constant when the wind speed is stronger than 12 m/s.