Why the Atlantic Equatorial Countercurrent Is Poorly Defined

The Atlantic Equatorial Countercurrent (ECC) is well-defined only in the eastern basin during January–March. For the rest of the year and across much of the central-west to eastern basins, subsurface transport consists of a single broad velocity core at 30–50 m depth without a significant eastward surface flow separating the North and South Equatorial Currents, resulting in a poorly defined ECC.