South Atlantic Meridional overturning circulation in an eddy-resolving global numerical simulation

Results from an eddy-resolving 1/12° global simulation are compared to observations in order to investigate the circulation in the South Atlantic Ocean, with focus on the variability of the Atlantic meridional overturning circulation (AMOC) and the inter-basin exchanges between the Atlantic and the Pacific/Indian Oceans. The simulation represents particularly well the observed transport and vertical structure of the trans-basin AMOC near 35°S and the Antarctic Circumpolar Current (ACC) through the Drake Passage at 65°W. The upper limb of the AMOC originates from the Agulhas Leakage as well as diapycnal transformation in the southern Atlantic Ocean. Although the ACC does not directly contribute to the AMOC, it plays an important role in modifying the temperature and salinity properties in the upper limb of the AMOC. Of the 9.6 Sv northward flowing Antarctic Intermediate Water across 35°S, about 6 Sv has characteristics similar to the cold fresh water south of 45°S, whereas the remaining 3.6 Sv is similar to warm saline water east of 20°W. The modeled South Atlantic AMOC is found to exhibit a coherent variability pattern on annual and interannual time scales, similar to what was found in the North Atlantic.