Observed and simulated variability of the Atlantic Meridional Overturning Circulation at 41 degrees N

The Atlantic Meridional Overturning Circulation (AMOC) at 41 degrees N from a global 1/16 degrees eddying simulation is compared with ARGO-based transport estimates over the 2004-2013 period. Three different methods for calculating the modelled meridional transports are used. The first method (MOCmod) is simply based onsimulated velocity fields. The second method (MOCob) is based on the same hydrostatic and geostrophic relationships applied to ARGO observations, and the third (MOCob2) relies on the same assumptions, but does not use a reference depth of known motion. MOCmod and MOCob2 methods correctly reproduce the time-mean AMOC strength, while the MOCob result is similar to 7% weaker.