High-latitude salinity effects and interhemispheric thermohaline circulations

A general circulation model for the ocean is used to investigate the interaction between the global-scale thermohaline circulation and the salinity distribution. It is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing. Multiple equilibrium solutions are obtained for the same forcing by perturbing the high-latitude salinity field in an otherwise equatorially symmetric initial condition. The timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation.