Data base The oceanic data temperature, salinity and currents were extracted from the first 19 levels of the GLORYS2V1 reanalysis product provided within the MyOcean – MERCATOR Ocean Project (www.mercator-ocean.fr ). Precipitation from the Global Precipitation Climatology Project (GPCP). Also was used the precipitation and salinity at the buoy moored at 8°N 38°W, delivered from PIRATA - Prediction and Research Moored Array in the Tropical Atlantic Project (www.pmel.noaa.gov/pirata/ ). Evaporation rate was obtained from the WHOI-OAFlux Project -Objectively Analyzed air-sea Heat Fluxex (http://oaflux.whoi.edu/index.html ). Surface currents are taken from the OSCAR current database, with 1/3 o from satellite altimetry (www.oscar.noaa.gov) . SMOS data derived Sea Surface Salinity (http://icdc.zmaw.de/las ), polar orbiting satellite based passive microwave sensor operating at L-Band (1.4 GHz), 1 x 1. Preliminary results Cross-correlation Seasonal mean salinity maps with cross-correlation (-0.7 to -0.9) between Amazon River discharge and upper ocean salinity (SMOS 2010-2012) shows strong correlation distribuition eastward at the low discharge period (SONDJF) and northward (18 o N) at the high discharge period (MAMJJA). Acknowledgements This is a contribution of the INCTAmbTropic – Brazilian National Institute of Science and Technology for Tropical Marine Environments, CNPq/FAPESB Grants: 565054/2010-4 and 8936/2011. UFPE Introduction The Amazon River releases a large freshwater plume responsible for a large part of the low Sea Surface Salinity (SSS), which heads east or north altering the surface salinity in the equatorial western Atlantic. Another factor that affects SSS is the Precipitation-Evaporation balance which is driven by the Intertropical Convergence Zone. A seasonal mapping of the influence of the the Amazon River discharge (Óbidos Station - PA) on the salinity (SMOS Salinity) is traced with correlations of -0.7 to -0.9 (10 o S−30 o N/10 o W−80 o W). The salinity at PIRATA 8 o N38 o W buoy shows that the SSS responds to the Amazon River discharge and that it is weakly correlated with regional GPCP precipitation at the area 1 o N−11 o N/30 o W−50 o W. Cross-correlation analysis allowed establishing a seasonal climatology of the Amazon River influence over the tropical Atlantic. Results are confirmed by the upper ocean salinity balance evaluated from Mercator Ocean numerical product GLORYS2V1. The equation describing Surface Layer Salinity (SLS) is given by Delcroix et al. (1996) and Bingham et al. (2010), and it is applied to the area 1 o N−11 o N/40 o W −50 o W where S 0 is the yearly average SLS, h is the mixed layer thickness (60 m), u = (u,v) is the horizontal velocity, w the vertical velocity and z the vertical coordinate, the third term, u·∇S is the horizontal advection and the last term is the seasonal variation of vertical velocity times the mean vertical gradient as the entrainment. ∂ s ∂t = S 0 E − P ( ) h − u ⋅∇S − w ∂ S ∂ z Monthly climatological salinity horizontal advection and currents (1998 – 2009) Horizontal advection of salinity is weak at the high Amazon River discharge. At the low discharge period, the salinity advection core is intensified following the NECC (North Equatorial Countercurrent). Salinity Budget The salinity budget terms were integrated to the area 1 o N−11 o N/40 o W−50 o W and for the first 60m of the SLS. The terms were spatialy averaged to show the interannual variability as the seasonal cycle. 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 0 5 10 x 10 −8 psu s −1 Horizontal Salinity Advection 1 2 3 4 5 6 7 8 9 10 11 12 0 1 2 3 4 x 10 −8 Months psu s −1 Horizontal Salinity Advection Seasonal Cycle 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 −6 −4 −2 0 2 4 x 10 −11 psu s −1 Entrainment 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 −8 −6 −4 −2 0 x 10 −6 cm s −1 E − P 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 −4 −2 0 2 4 cm s −1 E − P anomaly 1 2 3 4 5 6 7 8 9 10 11 12 −6 −4 x 10 −6 Months cm s −1 E − P cycle The salinity at PIRATA 8 o N38 o W responds to the Amazon River discharge, with a cross-correlation of -0.4 and it is weakly correlated (-0.2) with regional GPCP precipitation at the area (square area on the map). Buoy 8 o N38 o W Buoy 8 o N38 o W Discussion The preliminary results evidence that the salinity at the equatorial western Atlantic is more influenced by the Amazon River discharge than the regional precipitation. The climatology of the horizontal advection of salinity responds to the seasonality of the Amazon River discharge. At the low discharge period, the salinity advection core is intensified following the NECC. Doris Veleda 1,2 , Carlos Noriega 1,2 , Moacyr Araujo 1,2 , Fabrice Hernandez 3 , Raul Montagne 4 e-mail: doris.veleda@ufpe.br 1 Department of Oceanography - DOCEAN 2 Center for Risk Analysis and Environmental Modeling – CEERMA Federal University of Pernambuco – UFPE , Av. Arquitetura, s/n, Cidade Universitária, 50740-550, Recife-PE, Brazil 3 Institut de Recherche pour le Développement – IRD / Mercator Ocean, France 4 Federal Rural University of Pernambuco, Recife-PE, Brazil References Delcroix, T., Henin, C., Porte, V., and Arkin, P., 1996. Precipitation and Sea-surface Salinity in the Tropical Pacific, Deep-Sea Res. I, 43(7), 1123–1141. Bingham, F. M., Foltz, G. R., and McPhaden, M. J., 2010. Seasonal cycles of surface layer salinity in the Pacific Ocean, Ocean Sci., 6, 775-787, doi:10.5194/os-6-775-2010.