Drift Current under the Action of Wind and Waves

Abstract

Abstract Accurate estimates of sea surface drift currents are critical to forecast ing oil spill transport and fate and the movement of objects lost at sea. The majority of existing models employ a drift factor and deflection angle, based on the local wind speed and direction, to estimate the wind induced sea surface drift vector. The effects of wind induced shear and wave induced transport are lumped together in this formulation. In the present study the conservation of momentum and turbulent kinetic energy equations are solved using an implicit finite difference scheme to predict the vertical distribution of currents, turbulent kinetic energy, and vertical eddy viscosity at one point. The model includes coupling between the wave and shear induced currents. Inputs of momentum and energy from the atmosphere to the current and turbulent energy fields are parameterized through free surface boundary conditions. The numerical model has been extensively tested against analytic solutions for wind forced shear flow and prior work on wave current interaction with very good results. The model was applied to predict the steady state surface drift currents for varying wind speeds in deep water.