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Estimates of the zonal slope and seasonal transport of the Atlantic North Equatorial Countercurrent


  • James A. Carton,

  • Eli J. Katz


We use data from six inverted echo sounder moorings and the Geosat satellite altimeter to examine the seasonal variability of sea surface elevation. Monthly sea level maps are constructed using a contemporaneous subsurface temperature survey to provide a reference sea level field. The maps are then used to describe the origin and structure of the western tropical Atlantic North Equatorial Countercurrent (NECC) during a 2-year period beginning in November 1987. The data reveal a zonal current which is confined between 3°N and 9°N with a typical width of 300 km. The NECC flows strongly eastward during November and December 1986 and May 1987 through January 1988. The reappearance of the current is then delayed until August, but the current flows strongly from August until the end of our record in October 1988. Volume transport is estimated for the 2-year period from surface elevation by approximating the vertical structure of the ocean as a two-layer fluid. We find that the NECC has a maximum transport of 40×106 m3 s−1 at 38°W. This water has its origin in the retroflection of the North Brazil Current. Eastward of 38°W the NECC loses strength as water exits the current to join the currents further south.

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