The Effect of Indian Ocean Surface Freshwater Flux Biases On the Multi-Stable Regime of the AMOC

Abstract

It is known that global climate models (GCMs) have substantial biases in the surface freshwater flux. Using numerical bifurcation analyses on a global ocean model, we study here the effect of freshwater flux biases over the Indian Ocean on the multiple equilibrium regime of the Atlantic Meridional Overturning Circulation (AMOC). We find that a (positive) freshwater flux bias over the Indian Ocean shifts the multiple equilibrium regime to larger values of North Atlantic freshwater input but hardly affects the associated hysteresis width. The magnitude of this shift depends on the way the anomalous North Atlantic freshwater flux is compensated. The changes in bifurcation diagrams can be explained from the overall freshwater balance over the Atlantic basin.