Influence of the atlantic meridional overturning circulation on the monsoon rainfall and carbon balance of the American tropics

We examine the response of the American Tropics to changes in Atlantic Meridional Overturning Circulation (AMOC) strength using a set of water-hosing experiments with an Earth system model that explicitly simulates the global and regional carbon cycle. We find that a moderate weakening (27%) of the AMOC, induced by a 0.1 Sv (1 Sv ≡ 10⁶ m³ s^-1) freshwater addition in the northern North Atlantic, drives small but statistically significant drying in the South American monsoon region. By contrast, a complete shutdown of the AMOC, induced by a 1.0 Sv freshwater addition, acts to considerably shift the ITCZ southward, which changes the seasonal cycle of precipitation over Amazonia. Our results indicate that AMOC weakening can have a significant impact on the terrestrial primary productivity and carbon storage of the American Tropics. Key Points AMOC changes drive precipitation change in Central and northern South America Changes in AMOC shift carbon storage and the timing of the Amazonian monsoon Decreased seasonality of rainfall changes carbon storage in the tropics