Emulating Atlantic overturning strength for low emission scenarios: Consequences for sea-level rise along the North American east coast

In order to provide probabilistic projections of the future evolution of the Atlantic Meridional Overturning Circulation (AMOC), we calibrated a simple Stommel-type box model to emulate the output of fully coupled three-dimensional atmosphere-ocean general 5 circulation models (AOGCMs) of the Coupled Model Intercomparison Project (CMIP). Based on this calibration to idealised global warming scenarios with and without interactive atmosphere-ocean fluxes and freshwater perturbation simulations, we project the future evolution of the AMOC within the covered calibration range for the lower two Representative Concentration Pathways (RCPs) until 2100 obtained from MAGICC6. 10 For RCP3-PD with a global mean temperature median below 1.0 °C warming relative to the year 2000, we project an ensemble median weakening of up to 11% compared to 22% under RCP4.5 with a warming median up to 1.9 °C over the 21st century. Additional Greenland melt water of 10 and 20 cm of global sea-level rise equivalent further weakens the AMOC by about 4.5 and 10%, respectively. By combining our outcome 15 with a multi-model sea-level rise study we project a dynamic sea-level rise along the New York City coastline of 4 cm for the RCP3-PD and of 8 cm for the RCP4.5 scenario over the 21st century. We estimate the total steric and dynamic sea-level rise for New York City to be about 24cm till 2100 for the RCP3-PD scenario, which can hold as a lower bound for sea-level rise projections in this region.