Arumí‐Planas, Cristina, Pérez‐Hernández, María Dolores, Pelegrí, Josep L., Vélez‐Belchí, Pedro, Emelianov, Mikhail, Caínzos, Verónica, Cana, Luis, Firing, Yvonne L., García‐Weil, Luis, Santana‐Toscano, Daniel, and Hernández‐Guerra, Alonso
The South Atlantic Ocean plays a key role in the heat exchange of the climate system, as it hosts the returning flow of the Atlantic Meridional Overturning Circulation (AMOC). To gain insights on this role, using data from three hydrographic cruises conducted in the South Atlantic Subtropical gyre at 34.5°S, 24°S, and 10°W, we identify water masses and compute absolute geostrophic circulation using inverse modeling. In the upper layers, the currents describe the South Atlantic anticyclonic gyre with the northwest flowing Benguela Current (26.3 ± 2.0 Sv at 34.5°S, and 21.2 ± 1.8 Sv at 24°S) flowing above the Mid‐Atlantic Ridge (MAR) between 22.4°S and 28.4°S (−19.2 ± 1.4 Sv), and the southward flowing Brazil Current (−16.5 ± 1.3 Sv at 34.5°S, and −7.3 ± 0.9 Sv at 24°S); the deep layers feature the southward transports of Deep Western Boundary Current (−13.9 ± 3.0 Sv at 34.5°S, and −8.7 ± 3.8 Sv at 24°S) and Deep Eastern Boundary Current (−15.1 ± 3.5 Sv at 34.5°S, and −16.3 ± 4.7 Sv at 24°S), with the interbasin west‐to‐east flow close to 24°S (7.5 ± 4.4 Sv); the abyssal waters present northward mass transports through the Argentina Basin (5.6 ± 1.1 Sv at 34.5°S, and 5.8 ± 1.5 Sv at 24°S) and Cape Basin (8.6 ± 3.5 Sv at 34.5°S–3.0 ± 0.8 Sv at 24°S) before returning southward (−2.2 ± 0.7 Sv at 24°S to −7.9 ± 3.6 Sv at 34.5°S), without any interbasin exchange across the MAR. In addition, we compute the upper AMOC strength (14.8 ± 1.0 and 17.5 ± 0.9 Sv), the equatorward heat transport (0.30 ± 0.05 and 0.80 ± 0.05 PW), and the freshwater flux (0.18 ± 0.02 and −0.07 ± 0.02 Sv) at 34.5°S and 24°S, respectively. Plain Language Summary: The location of the South Atlantic subtropical gyre plays a critical role in the Atlantic Meridional Overturning Circulation, which controls the Earth's climate system. We have examined the South Atlantic subtropical gyre's circulation between 34.5°S and 24°S and above the Mid‐Atlantic Ridge using data from three hydrographic cruises (34.5°S, 24°S, and 10°W). From these cruises, we have identified the water masses present on this region and computed their transport. Thus, we describe the path of the anticyclonic gyre and the northeast route of the Benguela Current in the upper water masses (<1,440 m depth); the southward flowing western and eastern boundary currents and an eastward interbasin flow close to 24°S above the Mid‐Atlantic Ridge in the deep water masses (those on the depth range from 1,440 to 3,800 m depth); and the northward flow of the abyssal water masses (>3,800 m depth). We have also reported the characteristic heat transport flowing northward across the subtropical South Atlantic Ocean, where evaporation dominates over precipitation. Key Points: The upper layers present the course of the anticyclonic South Atlantic subtropical gyre and the northeast route of the Benguela CurrentThe deep layers present the southward flowing boundary currents and an eastward interbasin flow close to 24°S above the Mid‐Atlantic RidgeThe heat transport flows northward across the subtropical South Atlantic Ocean, where evaporation dominates over precipitation [ABSTRACT FROM AUTHOR]