The interhemispheric flow of the meridional overturning circulation (MOC) in the Atlantic interacts with the equatorial circulation and results in the northward advection of warm equatorial water. Geostrophic velocity sections reveal a meridional convergence of around 25 Sv toward the equator and Ekman transport diverges an equivalent amount away from the equator.

The result is equatorial upwelling of around 25 Sv. The geostrophic convergence is predominantly from the south and the Ekman transport is predominantly toward the north resulting in a net northwards interhemispheric transport of around 15 Sv in the upper (< 1000 m) layer. Upwelling and vertical mixing near the equator generate a cold tongue of surface water which is heated and transformed into warm surface water, adding to the northward heat flux through the equatorial band. Upper layer water is thought to flow northward through the equatorial region along three main pathways. The first pathway is in a western boundary current, the North Brazil Current (NBC) and Guiana Current. The second is through large current rings which pinch off from the NBC and translate along the western boundary. The third is via Ekman transport. Much of the upper level MOC, which crosses the equatorial band, first flows zonally in a series of zonal currents and countercurrents including vertically staked jets centered on the equator. The equatorial currents and MOC pathways vary seasonally and the partition of net northward transport in the different pathways (and depths) is only crudely known. Interannual variations in the tropical winds cause variations in equatorial currents and the resulting heat content of the water column which probably lead to interannual variations in both SST and northward heat flux.

The cold limb (> 1000 m) of the MOC contains two deep current cores flowing swiftly southward in the Deep Wester Boundary Current (DWBC). The upper NADW core is centered near 1600 m and the lower NADW core is near 4000 m. North of the equator the transport of the DBWC is two–three times larger than the net interhemispheric transport (roughly 17 Sv) of NADW. The southward transport in excess of 17 Sv is recirculated northward offshore of the DWBC in the Guiana Abyssal Gyre. DWBC water splits near the equator with portions feeding (temporarily at least) into zonal currents and countercurrents. The DWBC and deep equatorial currents vary seasonally like the upper level ones do. The equatorial band seems to act as a temporary reservoir for NADW on its way southward. Most of the lower NADW that reaches the equator passes eastward through the Romanche Fracture Zone into the eastern Atlantic, upwells into middle NADW, returns westward to the western boundary and continues southward in the DWBC. Northward flowing AABW also splits near the equator. Part turns eastward and flows through the Romanche Fracture Zone and part continues northward merging with the lower NADW recirculating in the Guiana Abyssal Gyre.