Collapse of the Atlantic Meridional Overturning Circulation in a Strongly Eddying Ocean-Only Model

Abstract

A collapse of the Atlantic Meridional Overturning Circulation (AMOC) under a quasi-equilibrium freshwater forcing has now been found in a hierarchy of ocean-climate models and up to a fully-coupled climate model, the Community Earth System Model (CESM). However, the effects of eddies on the ocean flows are represented in a highly idealized way in the CESM and it is unknown how these affect AMOC stability. Here, we show results of the first quasi-equilibrium hosing simulation with a strongly eddying ocean-only model in which the AMOC collapses. By comparing these results to those of a companion non-eddying simulation with the same model, it is found that eddies are able to maintain a weak ((Formula presented.) 5 Sv) AMOC flow in the collapsed state. In addition, we find that the AMOC induced freshwater transport at 34 (Formula presented.) S is a reliable physics-based early warning indicator for the onset of the AMOC collapse.