Data from the Eastropac expedition in 1967–1968 and four subsequent cruises in 1970–1973 clearly indicate two narrow, stable eastward countercurrents at approximately symmetrical positions about the equator in the subthermocline layers of the eastern equatorial Pacific Ocean. They persist throughout the year without apparent seasonal variations in intensity and position....
Tsuchiya, Mizuki. 1975. "Subsurface countercurrents in the eastern equatorial Pacific Ocean." Journal of Marine Research 33, (S). https://elischolar.library.yale.edu/journal_of_marine_research/1342