The Atlantic Equatorial Undercurrent

Recent measurements in the equatorial Atlantic from 10°W to 20°W longitude have confirmed the suspected existence of a shallow easterly undercurrent similar to the Cromwell current in the Pacific Ocean. The core of the undercurrent lies at a depth of about 60 meters, and it appears to be about 300 kilometers wide and more or less symmetrically located about the equator. At a depth of 100 meters measurements indicated an easterly current velocity of 130 cm/sec relative to a weak westerly surface drift of 10 to 20 cm/sec. Temperatures and oxygen profiles were markedly similar to those reported for the Cromwell current. The salinity profiles were different; they showed a well developed high-salinity core which was not present in the Pacific. It is suggested that the source of the high salinity is the large reservoir of very saline water lying close to the South American continent south of the equator.