Salinity’s Role in Tropical Atlantic Instability Waves
[26-Feb-2014] Lee, T., Lagerloef, G., Kao, H-Y., McPhaden, M.J., and Willis, J.
Presented at the 2014 Ocean Sciences Meeting
Tropical Atlantic instability waves (TIWs) play an important role in the dynamics of the tropical Atlantic Ocean and related climate variability. Previous studies based on satellite-derived sea surface temperature (SST) data suggest that the signature of these waves is the strongest in the eastern-central equatorial Atlantic (around 15W). Our analysis of Aquarius sea surface salinity (SSS) indicates that these waves remain to be very energetic in the western equatorial Atlantic. In the west, the TIW-related SSS anomaly is more coherent with that of sea surface height anomaly than SST anomaly, implying a significant contribution of salinity to dynamic height in that region. The large signature of SSS variability in the west is due to the instability of the strong salinity front between the salty South Atlantic water and the fresher water associated with the spreading of the Amazon plume. An energetic analysis shows that the contribution of salinity to the perturbation potential energy (PPE) increases substantially from the east to the west. The effect of salinity on PPE includes the direct salinity influence and an indirect contribution due to the anti-correlated variability between salinity and temperature.