Do multiple states of the quasi-adiabatic meridional overturning circulation exist?

In the limit of weak interior mixing, the ocean can support a pole-to-pole overturning circulation on isopycnals that outcrop in both the Northern Hemisphere and a high-latitude southern circumpolar channel. This overturning cell participates in a salt-advection feedback, which counteracts the precipitation-induced surface freshening of the northern high latitudes without substantially affecting the southern high-latitude salinity. The net result is an increase in the range of isopycnals shared between the two hemispheres (but not in the pole-to-equator density difference), which strengthens the overturning circulation. However, if precipitation in the Northern Hemisphere sufficiently exceeds that in the Southern Hemisphere, the overturning cell reverses and its southern endpoint moves equatorward of the channel, avoiding the upwelling of the circumpolar channel. The reversed overturning circulation is shallower and weaker than its forward counterpart and is maintained diffusively. In a limited range of parameters, multiple equilibria are found for the same forcing configuration.