Delayed Advective Oscillation of the Atlantic Thermohaline Circulation

Abstract

A simple dynamic model is proposed to illustrate the multidecadal oscillation of the Atlantic Ocean thermohaline circulation. The proposed oscillation relies on alternating actions of positive and negative feedbacks, which are operated by a slow adjustment of the ocean circulation and the associated time delay in the advective flux response to a change in meridional density gradient. The key element of the oscillation is the time delay, which is conceptually related to the basin-crossing time of long Rossby waves in the high-latitude North Atlantic. For a sufficiently long time delay, the solution becomes unstable in some regions of model parameter space and oscillates with a period of approximately 2 times the delay time.