Atlantic Meridional Overturning Circulation slowdown suppresses Atlantic Niño variability

The Atlantic Niño is the dominant mode of interannual variability in the Tropical Atlantic with significant impacts on local and remote climate patterns. Despite recent advances in understanding the mechanisms leading to weakened Atlantic Niño variability, its primary causes remain unknown. Here, we use an Earth System Model to show that the strength of the Atlantic Meridional Overturning Circulation (AMOC) modulates air-sea feedbacks in the equatorial Atlantic through both atmospheric and oceanic teleconnections. The combination of a southward shift of the Intertropical Convergence Zone and the propagation of oceanic downwelling Kelvin waves due to an AMOC weakening, generated in the subpolar North Atlantic, deepens the eastern thermocline and weakens the equatorial trade winds, leading to a decoupling in air-sea feedbacks. Finally, we show that adding the effect of meltwater in future projections reduces the upwelling feedback strength by 60 ± 6% in 2100, with potential changes in the Atlantic Niño-driven rainfall.