Climate variability inferred from a layered model of the ventilated thermocline

Climate variability of a layered model of the ventilated thermocline is stu died. Assuming the Ekman pumping is unchanged, cooling (heating) causes a s outhward (northward) shift of the outcrop line and thus induces a baroclini c response in the ventilated thermocline. The perturbations propagate withi n a characteristic cone downstream from the cooling (heating) region, defin ed by the two outermost characteristics streaming from the edge of the cool ing (heating) region. Changes in Ekman pumping rate induce a barotropic response that propagates westward, which is a classic result obtained from the Sverdrup relation. Ho wever, if the outcrop line is nonzonal, there can be an additional baroclin ic response, which propagates within the characteristic cone downstream fro m the source region of an Ekman pumping anomaly.