The tropical response to a collapse of the Atlantic Meridional Overturning Circulation

A collapse of the Atlantic Meridional Overturning Circulation (AMOC) could drive widespread changes in tropical rainfall, but the underlying physical mechanisms are poorly understood. Numerical simulations validated against hydroclimate changes during Heinrich Stadial 1(HS1) – the most recent, best-documented AMOC collapse – show a global response driven by cooling over the tropical North Atlantic. This pattern of ocean cooling is key to link changes in rainfall across the tropics with the reductions in AMOC strength. Cooling over the tropical North Atlantic drives changes over the Pacific and Indian oceans that uniquely explain the paleoclimatic evidence. A similar response is active in simulations of future greenhouse warming, but model disagreement regarding the pattern of AMOC-induced tropical cooling produces divergent rainfall predictions across the tropics. Models with responses consistent with the paleodata predict more pronounced rainfall reductions across the tropics, revealing a heightened risk of drought over vulnerable societies and ecosystems worldwide.