The surface salinity front in the Equatorial Atlantic Ocean

LAURA RUIZ ETCHEVERRY; NIKOLAI MAXIMENKO; OLEG MELNICHENKO

Washington

Encuentro; Ocean Salinity Science Team Meeting; 2017

NASA

The Equatorial Atlantic Ocean is a region dominated by the seasonal trade winds and InterTropical Convergence Zone (ITCZ). It is also marked by the existence of a strong sea surfacetemperature (SST) front due to the formation of the equatorial cold tongue. These features arebelieved to have strong effects on the atmospheric circulation in the region and thus climate.Little, however, is known about the salinity front, whose study became possible only with therelease of high-resolution salinity products. In this study, we use three years of sea surfacesalinity (SSS) observations from Aquarius satellite to investigate the spatial structure, temporalvariability, and driving dynamics of the frontal SSS feature in the equatorial Atlantic, itsevolution between seasons and differences between individual years. Our results show that theSSS front forms in April and amplifies in May and June. After that, the front rapidly weakensuntil it disappears in August. The front separates fresh waters in the north and salty waters in thesouth. The trigger of the SSS front is associated with the subsurface Equatorial Undercurrent(EUC) when vertical mixing translates the signature of its salty core to the surface. While theincrement of the fresh water flux might be responsible for killing the frontal feature. The verticalsection of salinity across the front indicates that the front can be traced down to ~40m,approximately the depth of the fresh water pool to the north of the Equator. Our results alsoindicate that the equatorial SSS front undergoes interannual variability. Exact physicalmechanisms generating and sustaining the SSS front and other features in the Equatorial Atlanticare under investigation. Relative contributions of salinity and temperature to the variability ofdensity gradients are discussed.