North Brazil Current retroflection and transports

[1] A subset of data collected as a part of a larger program, the North Brazil Current Rings (NBCR) Experiment, is analyzed to study the variability of the transport of the North Brazil Current (NBC) and its relation with the shedding of rings. It is concluded that there is a direct relation between the latitude of penetration, the number of rings shed, and the intensity of the NBC. The data set consists of dynamic height time series derived from three inverted echo sounders and a shallow pressure gauge deployed along a section perpendicular to the South American coast between the continent and 7degreesN, and between 48degrees and 45degreesW. Velocity and hydrographic data collected during the NBCR cruises are also analyzed and used to validate the results. The 15-month mean transport of the NBC is 16 +/- 2 Sv. The 18-month mean of the retroflected southeastward flow is 22 +/- 2 Sv. Both flows display considerable variability. The retroflected southeast flow reaches its maximum value during September 1999, near the time when the climatological North Equatorial Countercurrent (NECC) reaches its maximum strength and it is minimum when the climatological NECC reverses or is not present in the basin. The mean difference between the NBC flow and the retroflected flow during August - December 1999 when the NECC is fully established is -7 Sv. The excess in the retroflected flow is due to North Atlantic water joining the retroflected flow from the South Atlantic. The combination of both flows constitutes the NECC.