Influence of Stratification and Bottom Boundary Layer on the Classical Ekman Model

Abstract

A depth understanding of the different processes of water movements produced by the wind surface stress yields a better description and improvement of the marine food chain and ecosystem. The classical Ekman model proposes a hypothetical ocean, excluding the influence of continents and the Coriolis force. It also assumes infinite depth and a constant vertical eddy viscosity. The current study aims to understand how the vertical velocity profile is affected by the variation of the eddy viscosity coefficient (kz) and the consideration of a finite depth. The study uses an ideal analytical model with the Ekman classical model as a starting point. It has been demonstrated that, for a very stratified profile, when the depth is not considered infinity, the Ekman transport tends to a direction smaller than 80°. It differs from the classical Ekman model, which proposes an approximated angle equal to 90°. Considering the modified model, it was also found that the surface current deviation is smaller than 40°, which differs from the 45° proposed by the classical model. In addition, it was determined that for ocean depths smaller than 180 m, the maximum velocity does not occur at the water surface, as in the classical model, but at deeper levels.

Keywords

• modified Ekman model
• bottom boundary layer
• stratification