What Can Hydrography Between the New England Slope, Bermuda and Africa Tell us About the Strength of the AMOC Over the Last 90 years?

The Gulf Stream is the only pathway in the subtropical North Atlantic by which warm water flows poleward. This transport of warm water and return of cold water at depth is called the Atlantic Meridional Overturning Circulation (AMOC). The dynamic method is applied to hydrocasts collected since the 1930s to estimate upper-ocean transport (0-1,000 m) between the U.S. Continental Slope and Bermuda and separately to Africa with focus on the longest directly observable timescale. Calculating transport between the Slope and Bermuda eliminates the Gulf Stream's northern and southern recirculation gyres, while calculations between the Slope and Africa remove all other recirculating geostrophic flow. The net Slope-Bermuda upper-ocean transport is estimated to be 41.1 +/- 0.4 Sv, decreasing by 2.0 +/- 0.8 Sv between 1930 and 2020. The AMOC contribution is 18.4 +/- 0.6 Sv, decreasing by 0.4 +/- 0.6 Sv between 1930 and 2020.