Climate varialbility of the equatorial thermocline inferred from a two-moving-layer model of the ventilated thermocline

A two-moving-layer model is used to examine the structure of the equatorial thermocline and its connection with the extratropical thermocline. It is f ound that cooling (warming) in extratropics generates a low (high) potentia l vorticity anomaly and induces downward (upward) movement of the thermocli ne, and the perturbation propagates to the equatorial thermocline, inducing a downward (upward) movement of the thermocline and intensification (weake ning) of the undercurrent. Thus, surface cooling in the extratropics can in duce warming of the equatorial thermocline. In addition, the total mass flu x in the subsurface layer in the extratropics and the equatorial undercurre nt is enhanced. Although in the extratropics perturbations generated by loc alized cooling (warming) are confined within the characteristic cone, defin ed by the unperturbed trajectories of the thermocline circulation, when the se perturbations propagate into the equatorial region they are no longer co nfined by the characteristic cone in the meridional direction.