Multiple Equilibrium States in Combined Thermal and Saline Circulation

摘要

Gravitational convection due to combined thermal and haline forcing in an upwindhydrostatic box model with linear frictional dynamics exhibits multiple equilibrium states. In applying such models to the ocean, the so-called Haney (1971) boundary condition has been widely used for both temperature and salinity fields. In fact, the external forcing of these two fields involves quite different physical processes and should be parameterized in quite different ways. the effect of different boundary conditions on temperature and salinity was discussed by Stommel (1961), who showed that two stable states can arise because of the difference in the Rayleigh coefficient for the two constituents. Rooth (1982) investigated the case of a three-box model, consisting of an equatorial box and two polar boxes, and suggested that a symmetric solution might be unstable and could drift toward a pole-pole mode. Welander (1986) pointed out that such a three-box model can have four stable equilibria: two symmetric and two asymmetric.