The impact of subpolar salinity on AMOC remains masked when forcing is weak

Atlantic Meridional Overturning Circulation (AMOC) is suggested to be in a bi-stable regime and might already be at the brink of a irreversible trajectory towards a complete shutdown–a so called tipping point. Such a tipping point requires a self-reinforcing feedback, for example one related to the upper ocean salt transport convergence to the North Atlantic subpolar gyre. We show that in Earth System Model simulations under abrupt high CO$_2$ forcing ($>$1.8 times the pre-industrial conditions), salt transport convergence is highly correlated with AMOC, indicating an active role for salinity in reinforcing AMOC decline. However, at weak or transiently increasing CO$_2$ forcing the relation is masked by internal variability in our model simulations and observationally constrained products. Our results suggest that with the present forcing levels, salinity reinforced AMOC decline is unlikely, and consequently, it is unlikely that AMOC would be close to a salt transport convergence induced tipping point.