Investigation of the North Brazil Current retroflection and North Equatorial Countercurrent variability

Abstract

Eight years of TOPEX/Poseidon altimeter‐derived sea height anomaly and climatological hydrographic data are used to investigate the temporal and spatial variability of the North Brazil Current (NBC) retroflection and the North Equatorial Countercurrent (NECC). The NBC retroflection exhibits a mean position of 6.6°N ± 2.0°, with a strong annual signal and year‐to‐year variability. The annual cycle of its location follows the meridional migration of the ITCZ and the strength of the wind stress curl over the equatorial Atlantic. A marked shift in the annual mean location of the NBC retroflection is observed in 1998–1999 that appears to be linked to an increase in wind stress curl during this period. The mean latitude of the NECC is estimated to be 6.0°N ± 1.3°, with a semiannual cycle showing maximum northerly locations in February and August. The baroclinic transport of the NECC varies predominantly on an annual cycle with maximum transport of 12 Sv occurring in November.