Variability of the North Brazil current and Amazon river plume during April-May 2010 as determined from remote sensing and in situ absortion CDOM

Abstract

The comparison of satellite ocean colour image studies and hydrographic data has shown a significant relationship between Sea Surface Salinity (SSS) and the absorption coefficient for dissolved and detritus materials from river discharge in coastal regions. Here, we use this relationship to identify the signal of the Amazon River plume. We collected water samples from the MOC2‐Equatorial oceanographic cruise (April‐May 2010) to determine the Chromophoric Dissolved Organic Matter (CDOM) gradients in the Equatorial Atlantic Ocean, in a region located from 5°S to 10°N and from 55 to 40°W. These values, together with SSS and Sea Surface Temperature (SST) data, indicate that the Amazon River plume travels long distances from the river mouth (near the Equator) until reaching these latitudes. We find, as expected, that low salinity surface waters influenced by the Amazon plume were also rich in CDOM. The temperature, salinity and CDOM distributions give us hints on the dynamics of the North Brazil Current (NBC) during the April‐May period. During early spring there is maximum Amazon River discharge but the NE winds dominate, apparently increasing the residence time of the plume near the river's mouth and slowing down the north‐westward river plume transport. During late spring and summer the Intertropical Convergence Zone moves north, so the winds turn to the SE and the northward transport of the NBC increases.This is probably the time when takes place maximum spread into the Caribbean region, before the NBC begins its retroflection in late summer