Two Cross-Equatorial Sections at 110°W

Abstract

Abstract A section along 110°W in the eastern Pacific from about 6°N to 6°S was occupied in March and June of 1981. Measurements consisted of absolute velocity profiles and CTD cuts. The large-scale structure of the subsurface zonal flow remained relatively invariant between these cruises. The Equatorial Undercurrent and North and South Equatorial Undercurrents appear as strong eastward flows, separated by westward currents. Away from the equator, comparison of currents estimated geostrophically with the direct observations indicate that the two techniques are in agreement within estimated errors except close to the surface. In the vicinity of the equator the geostrophic technique in general fails and the directly measured currents must be used. During March, within 3° of the equator from the surface to 700 m, the flow was more eastward by about 0.15 m s−1; than in June. In March, the flow and temperature fields were relatively symmetric about the equator. By June, strong asymmetries had developed. In the...