A New Theory for the Generation of the Equatorial Subsurface Countercurrents

Abstract

An idealized numerical simulation of the tropical Atlantic Ocean is used to study the dynamics of an Atlantic subsurface countercurrent, the South Equatorial Undercurrent (SEUC). The particular structure of the SEUC between 28° and 10°W allows for a reformulation of the transformed Eulerian mean (TEM) equations with which the momentum balance of the SEUC can be explored. With this modified TEM framework, it is shown that between 28° and 10°W the SEUC is maintained against dissipation by the convergence of the Eliassen?Palm flux. The source of this Eliassen?Palm flux is the tropical instability waves that are generated along the shear between the Equatorial Undercurrent and the South Equatorial Current.