The Ventilated Thermocline

A simple theoretical model for the oceanic thermocline and the associated field of currents is presented. The model consists of a finite but arbitrarily large number of inviscid, homogeneous fluid layers each with a different density. The dynamical balances everywhere are Sverdrupian. In regions where the Ekman pumping is negative (downward) the surface density is specified, i.e., the position of the outcrop of density interfaces is specified. This outcropping of density layers allows deep motion to be excited by the ventilation provided by Ekman pumping even in latitudes far south of the outcrop where the layer is shielded from direct influence of the wind. Analytical solutions are presented in the case where the density-outcrop lines are coincident with latitude circles. The solutions are not self-similar and important sub-domains of the solution are defined by critical potential vorticity trajectories which separate the ventilated from the unventilated regions in the lower thermocline.