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. Bottom pressure observations on both sides of theAtlantic basin, combined with satellite measurements of sea level anomaliesand wind stress data, are utilized to estimate variations of the AtlanticMeridional Overturning Circulation (AMOC) at 11∘ S. Over theperiod 2013–2018, the AMOC and its components are dominated by seasonalvariability, with peak-to-peak amplitudes of 12 Sv for the upper-oceangeostrophic transport, 7 Sv for the Ekman and 14 Sv for the AMOC transport.The characteristics of the observed seasonal cycles of the AMOC and itscomponents are compared to results from an ocean general circulation model,which is known to reproduce the variability of the Western Boundary Currenton longer timescales. The observed seasonal variability of zonallyintegrated geostrophic velocity in the upper 300 m is controlled by pressurevariations at the eastern boundary, while at 500 m depth contributions fromthe western and eastern boundaries are similar. The model tends tounderestimate the seasonal pressure variability at 300 and 500 m depth,especially at the western boundary, which translates into the estimate ofthe upper-ocean geostrophic transport. In the model, seasonal AMOCvariability at 11∘ S is governed, besides the Ekman transport, bythe geostrophic transport variability in the eastern basin. The geostrophiccontribution of the western basin to the seasonal cycle of the AMOC isinstead comparably weak, as transport variability in the western basininterior related to local wind curl forcing is mainly compensated by theWestern Boundary Current. Our analyses indicate that while some of theuncertainties of our estimates result from the technical aspects of theobservational strategy or processes not being properly represented in themodel, uncertainties in the wind forcing are particularly relevant for theresulting uncertainties of AMOC estimates at 11∘ S.

Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements