Greenhouse-gas forced changes in the Atlantic meridional overturning circulation and related worldwide sea-level change

This study focuses on changes in the Atlantic Meridional Overturning Circulation (AMOC), ocean heat content (Delta OHC), and the spatial pattern of ocean dynamic sea level (Delta zeta). We analyse experiments following the FAFMIP protocol, in which AOGCMs are forced at the ocean surface with standardised heat, freshwater and momentum flux perturbations, typical of those produced by doubling CO2.

Using two new heat-flux-forced experiments, we find that the AMOC weakening is mainly caused by and linearly related to the North Atlantic heat flux perturbation, and further weakened by a positive coupled heat flux feedback. The quantitative relationships are model-dependent, but few models show significant AMOC change due to freshwater or momentum forcing, or to heat flux forcing outside the North Atlantic. AMOC decline causes warming at the South Atlantic-Southern Ocean interface.