Meetings: Documents

The Surface Salinity Front in the Equatorial Atlantic Ocean
[12-Feb-18] Ruiz-Etcheverry, L., Maximenko, N.A., and Melnichenko, O.
Presented at the 2018 Ocean Sciences Meeting
The Equatorial Atlantic Ocean is a region dominated by the seasonal trade winds and Inter Tropical Convergence Zone (ITCZ). It is also marked by the existence of a strong sea surface temperature (SST) front due to the formation of the equatorial cold tongue. These features are believed 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 the release of high-resolution salinity products. In this study, we use three years of sea surface salinity (SSS) observations from Aquarius satellite to investigate the spatial structure, temporal variability, and driving dynamics of the frontal SSS feature in the equatorial Atlantic, its evolution between seasons and differences between individual years. Our results show that the SSS front forms in April and amplifies in May and June. After that, the front rapidly weakens until it disappears in August. The front separates fresh waters in the north and salty waters in the south. 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. The vertical section 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 also indicate that the equatorial SSS front undergoes interannual variability, being greatest in 2013 and weakest in 2012. Exact physical mechanisms generating and sustaining the SSS front and other features in the Equatorial Atlantic are under investigation. Relative contributions of salinity and temperature to the variability of density gradients and dynamical consequences of this variability are also discussed.