Eastward flow within the South Equatorial Current in the eastern South Atlantic

Abstract

Structure of the upper 500 m of the South Equatorial Current has been investigated in the eastern tropical Atlantic between latitudes 2°S and 7°S. The vertical distribution of east-west components of geostrophic velocities along longitudes 15°W and 20°W were computed for the two main seasons using the data of Equalant I and II. The velocity distribution shows a narrow eastward-flowing current centered near 4°S. The maximum velocity of 30 to 60 cm/sec was at about 150 meters in these sections, and in one section it appeared as a narrow eastward-flowing current having a maximum velocity at the surface. Geopotential topography of the 75-decibar surface, relative to 600 decibars, indicates that the narrow eastward-flowing current turns to the southeast at about 15°W and crosses the zero meridian at 12°S. The eastward-flowing current shows somewhat higher salinity, lower temperature, and higher oxygen content at the corresponding depths than the westward-flowing mass of the South Equatorial Current. The surface water in the zone of the westward flow (northern branch of South Equatorial Current) has no, or only weakly developed, maximum salinity core. The strong maximum salinity core on both sides of this zone is of a different origin.