Determining the long-term nature of the Atlantic Meridional Overturning Circulation (AMOC) is crucial for understanding the recently observed slowdown in the context of climate change and for predicting future climate scenarios. Here, we present an estimate for AMOC strength over the last 119 years which is grounded in observation. Application of the Bernoulli inverse to gridded hydrography yields the general geostrophic circulation in the North Atlantic without requiring additional sea surface height information, allowing AMOC evaluation in the pre-satellite era. AMOC strength is found to oscillate with a 70-year period, and leads the Atlantic Multidecadal Oscillation (AMO) in sea surface temperature by around 10 years. We consider the dynamics of the implied AMOC/AMO coupling, and hypothesize that the low-frequency variability in both parameters is driven by large-scale density anomalies circulating in the AMOC.
Figure caption: Sea surface height from the Bernoulli inverse (a) vs satellite altimetry (b).