On the dynamics of the equatorial undercurrent

Abstract

Using three different distributions of potential vorticity, it is shown that the velocity field in the equatorial undercurrent is not necessarily unique in an inviscid ocean. The uniqueness of the velocity field is a function of both the thickness of the layer through which the undercurrent flows and the distribution of potential vorticity. For the distributions studied here there is one solution for a large layer thickness. As the layer thickness decreases, a second solution forms. These two solutions then coalesce and vanish as the layer thickness reduces further. Increased baroclinic behaviour qualitatively has the same effect as increased layer thickness. When two solutions are present, the narrower of the solutions widens as the layer thickness decreases, while the wider solution narrows.