South Atlantic interbasin exchanges of mass, heat, salt and anthropogenic carbon

• Published in: Progress in Oceanography
• Main Authors: Evans, G.R., McDonagh, E.L., King, B.A., Bryden, H.L., Bakker, D.C.E., Brown, P.J., Schuster, U., Speer, K.G., van Heuven, S.M.A.C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Antarctic; Southern Ocean; The Antarctic; Drake Passage; Indian; Antarc*; North Atlantic
• Online Access: http://nora.nerc.ac.uk/id/eprint/516235/; https://nora.nerc.ac.uk/id/eprint/516235/1/Evans%20et%20al%20%282017%29%20PiO%20Accepted.pdf; https://doi.org/10.1016/j.pocean.2016.11.005

The exchange of mass, heat, salt and anthropogenic carbon (Cant) between the South Atlantic, south of 24°S, and adjacent ocean basins is estimated from hydrographic data obtained during 2008–2009 using an inverse method. Transports of anthropogenic carbon are calculated across the western (Drake Passage), eastern (30°E) and northern (24°S) boundaries. The freshwater overturning transport of 0.09 Sv is southward, consistent with an overturning circulation that exports freshwater from the North Atlantic, and consistent with a bistable Meridional Overturning Circulation (MOC), under conditions of excess freshwater perturbation. At 30°E, net eastward Antarctic Circumpolar Current (ACC) transport, south of the Subtropical Front, is compensated by a 15.9 ± 2.3 Sv westward flow along the Antarctic boundary. The region as a whole is a substantial sink for atmospheric anthropogenic carbon of 0.51 ± 0.37 Pg C yr−1, of which 0.18 ± 0.12 Pg C yr−1 accumulates and is stored within the water column. At 24°S, a 20.2 Sv meridional overturning is associated with a 0.11 Pg C yr−1 Cant overturning. The remainder is transported into the Atlantic Ocean north of 24°S (0.28 ± 0.16 Pg C yr−1) and Indian sector of Southern Ocean (1.12 ± 0.43 Pg C yr−1), having been enhanced by inflow through Drake Passage (1.07 ± 0.44 Pg C yr−1). This underlines the importance of the South Atlantic as a crucial element of the anthropogenic carbon sink in the global oceans.