Climate variability induced by anomalous buoyancy forcing in a multilayer model of the ventilated thermocline

Climate variability induced by surface cooling in a four-moving-layer model of the ventilated thermocline is studied. The perturbations propagate with in the characteristic cones defined by streamlines in individual layers whe re the potential vorticity anomaly is created. Each time the characteristic cones cross a new outcrop line, the number of characteristic cones doubles . Thus, climate variability in a multilayer model can have very complicated structure in the horizontal plane, with anomalies of alternating sign. The vertical structure of such perturbations defines a class of dynamical ther mocline modes.