It begins when the westward moving Atlantic South Equatorial Current splits in half and flows northwestward, following the coastline of north Brazil.
Around 5°S, it merges with a northern branch of the South Equatorial Current (SEC) and increases its volume to 37 Sv, with its peak between 100m and 200m deep.
The salinity will then decrease to around 36.5 psu as the current moves northward toward the equator and into the presence of the Intertropical Convergence Zone (ITCZ).
Closer to the shore, and especially where the depth of the water is less than 400 m, the sea floor acts as the lower limit to the current.
[5] If the depth is greater than 400 meters, the thermocline acts as the lower limit, and represents the boundary of the NBC and the colder, eastward moving Atlantic North Equatorial Undercurrent (NEU).
Most rings make it to within the vicinity of the Caribbean Sea, and it is even possible for some to move into the lake, given that they are small enough to fit between the Lesser Antilles.