Subtropical Cells and Meridional Overturning Circulation pathways in the tropical Atlantic

Pathways of Subtropical Cells (STCs) and the basin-wide meridional overturning circulation (MOC) are studied in the tropical Atlantic using a article tracking algorithm and transports from a high-resolution ocean model.16 Sv of MOC water flows to the equator from the south, primarily in the North Brazil Current.The MOC water recirculates in the tropics and after crossing the equator about half of it stays along the western boundary and
the other half loops in a cyclonic circulation northward to join the North Equatorial Current.
The STC on the Southern Hemisphere has a strength of 4 Sv. The northern STC has a strength of 1.5 Sv and is confined to the retroflection area close to the equator and contains primarily MOC water. In total, 5.5 Sv of MOC water entrains into the mixed layer in the tropical Atlantic. 2 Sv of MOC water recirculates in the southern STC and 1.5 Sv in
the northern STC. The STCs are weaker than suggested from observations, but the interior flows in the model compare well to observations. Discrepancies
in the western boundary current transports and upwelling and divergences cause the structure
to differ. It is concluded that the MOC can substantially affect the tropical circulation,
but the tropical circulation itself can also affect MOC properties because a third of its transport
upwells into the mixed layer.