Tropical Atlantic surface current variability from 10 years of TOPEX/Poseidon altimetry

10 years of surface geostrophic currents from TOPEX/Poseidon altimetric data are used to describe the low frequency variability of the tropical Atlantic circulation through Empirical Orthogonal Function analysis. The seasonal variability clearly agrees with previous studies based on climatological data. It shows the tropical Atlantic response to seasonal fluctuations of the overlying wind system. More interesting is the capability, using altimetry, to reach for the first time on a basin scale the year-to-year variability from measurements. Abnormal events occur in 1996-1997 and in 2001 with different spatial scales regarding both large scale zonal distribution and regional variability located in the north-western basin. A first attempt to link these events to climatic indexes (El Nino-Southern Oscillation, North Atlantic Oscillation) is also evocated.