Dynamics of large changes in the Atlantic Meridional Overturning Circulation

The possibility of large and potentially irreversible changes in the AMOC, with potentially significant impacts on global and regional climate, are currently being debated. Whilst many studies have been conducted investigating temperature and salinity changes associated with AMOC variability, feedbacks related to the in-situ density/pressure gradient have not thus far been studied in detail. We identify and examine large changes in the AMOC on timescales up to centennial in the CMIP6 multimodel climate model ensemble (preindustrial, historical, and future climate) and historical observations. Our specific focus is on constructing budgets of in-situ density at the continental boundaries in order to understand the mechanisms leading to permanent reduction of the transbasin zonal density/pressure gradient required to maintain the AMOC. We further investigate whether and how reduction in the AMOC impacts boundary densities, and whether positive feedback loops resulting in rapid change can occur.