Mechanisms of thermohaline mode switching with application to warm equable climates.
(Zhang, R and Follows, M and Marshall, J), JOURNAL OF CLIMATE, vol. 15, no. 15, pp. pages, 2002.
A three-box model of haline and thermal mode overturning is developed to study thermohaline oscillations found in a number of ocean general circulation models and that might have occurred in warm equable paleo-climates. By including convective adjustment modified to represent the localized nature of deep convection, the box model shows that a steady haline mode circulation is unstable. For certain ranges of freshwater forcing/vertical diffusivity, a self-sustained oscillatory circulation is found in which haline-thermal mode switching occurs with a period of centuries to millennia. It is found that mode switching is most likely to occur in warm periods of earth’s history with, relative to the present climate, a reduced Pole-equator temperature gradient, an enhanced hydrological cycle, and somewhat smaller values of oceanic diffusivities.