Multi-model evidence of future tropical Atlantic precipitation change modulated by AMOC decline

Abstract Projections from climate models reveal a significant inter-model spread in the anticipated changes in tropical Atlantic rainfall by the end of the 21st century, including alterations to the Intertropical Convergence Zone (ITCZ) and monsoonal regions. While existing studies have identified various sources of these uncertainties, our research uncovers, for the first time, a prominent role played by the inter-model spread in the decline of the Atlantic Meridional Overturning Circulation (AMOC). Through an examination of 30 climate model simulations for the 21st century (using the ssp5-8.5 scenario) from the CMIP6 archive, we demonstrate that models projecting a more substantial AMOC decline exhibit an equatorward shift of the ascending branch of the Atlantic Hadley circulation, resulting in a southward displacement of the ITCZ. Conversely, models projecting a relatively smaller AMOC decline depict an intensified hydrological cycle but do not indicate any displacement of the ITCZ. Our findings have crucial implications for comprehending the mechanisms driving future changes in tropical Atlantic precipitation, underscoring the central role played by the AMOC.