Eastward propagating surface salinity anomalies in the tropical North Atlantic

Upper ocean variations across the tropical Atlantic are strongly seasonal due to corresponding seasonality in surface forcing and continental runoff. This implies that many features in regional upper ocean state or transport anomalies may also be seasonally locked. In the boreal summer and autumn, remote sensing sea surface salinity (SSS) observations show the presence of eastward propagating anomalies concurrent with the seasonal development of fresh Amazon plume and acceleration of the eastward North Equatorial Countercurrent. Interannual variations in these eastward cross-Atlantic SSS signals are investigated in connection with their forcing by wind and circulation patterns. Satellite data show that these SSS anomalies are advected zonally across the entire Atlantic. It is suggested that they originate due to wind-induced changes in the Amazon plume areal extent, which are notorious in the North Brazil Current retroflection. Satellite SSS is instrumental for exploring such signals because in-situ observations do not always capture them due to the limitation in resolved spatial and temporal scales.