Sv. Kravtsov et Wk. Dewar, MULTIPLE EQUILIBRIA AND TRANSITIONS IN A COUPLED OCEAN-ATMOSPHERE BOXMODEL, Journal of physical oceanography, 28(2), 1998, pp. 389-397
A six-box model is employed as a prototype of the coupled Atlantic oce
an-atmosphere system. Ice dynamics are excluded. Numerical integration
of this system shows that different thermohaline circulation patterns
are possible under the same forcing conditions. They consist of a glo
bal thermal mode with oceanic poleward surface flow, a global saline m
ode with equatorward surface flow, and two intermediate modes that are
combinations of the two global modes. The stability of the modern-day
-like intermediate mode to finite amplitude freshwater flux perturbati
ons in the high latitude North Atlantic (meant as a model of glacial m
elting) is explored. It is found that freshwater fluxes of the proper
inferred magnitude are close to critical and can induce a transition o
f the coupled system to a saline mode. However, paleoclimatic data arg
ues the last deglaciation was subcritical. Further, working in a reali
stic subcritical parameter regime, the box model yields an unrealistic
temperature record. This argues, in turn, that additional physics (e.
g., sea-ice effects) must be included to properly describe the fundame
ntal mechanics of the last glacial retreat.