Low-frequency meandering of the Atlantic North Equatorial Countercurrent


  • Silvia Garzoli,

  • Philip L. Richardson


Four 19-month time series of indirect measurements of dynamic height were obtained in the tropical Atlantic along 28°W at 0°, 3°, 6°, and 9°N with three inverted echo sounders and one current meter mooring. The series were analyzed to study the time-latitude variability of the North Equatorial Countercurrent (NECC). The eastward flow associated with the NECC was present at 28°W from 3° to 9°N during most of the observed period except in March-April 1983 and April-May 1984, periods that coincided with the onset of the wind at the equator. The amplitude of the NECC's annual cycle was maximum at 6°N and was larger in 1983 than in 1984. The analysis of the time-latitude variability of differences in dynamic height shows a long-period meridional shift of the NECC. The core of the current attains its northernmost location during August-September in both years and its southernmost location during March-April in 1983 and March in 1984. The location of the core is directly related to the position of the intertropical convergence zone. From the time series of dynamic height obtained from the indirect measurements, geostrophic velocities and transports were estimated and compared with direct observations of currents and values obtained from hydrographic casts.