Impacts of The New Thermodynamic Equation of Seawater (TEOS-10) in the South Atlantic Ocean’s Water Mass Mixing and Circulation.

In 2010, a new Thermodynamic Equation of State of Seawater (TEOS-10) was developed and released to the scientific community, in order to replace the previous equation in use, EOS-80. Among the several changes carried on by this update, this study will be focusing in two aspects regarding oceanographic parameters: (1) the use of the conservative temperature, rather than the potential temperature and (2) the replacement of practice salinity for absolute salinity. This study aims to analyze the TEOS-10 impacts on the calculation of the contribution of the water masses in the South Atlantic Ocean, and also to evaluate the impact on the calculation of baroclinic velocities, which are strongly dependent on density gradients estimation. To perform these analyses, a data grid was centered on the southern portion of the Atlantic Ocean and historical hydrographic data – temperature and salinity from CTDs only – was obtained from the World Ocean Database 2009. An Optimized Analysis with Multiple Parameters (OMP) was carried out in order to calculate the mixing of the water masses. To calculate the baroclinic velocities, the Dynamic Method, or Thermal Wind Equation, was used. All analyzes were performed for both equations, EOS-80 and TEOS-10, and differences were compared and quantified. The main results indicate the differences in water mass contribution are larger for central and intermediate waters, reaching up to 10%, both positive and negative. This is consistent with the changes in T/S distributions above 1500m, the largest ones found in this set. Regarding to the baroclinic velocities, there is a wide range of variation and a remarkable difference between latitudinal and longitudinal components - the former having the greatest differences (~9%), and the latter minor impacts (~4%). Overall, these differences have a direct impact on the calculation of ocean currents transport. Therefore, a review on the ocean transport scheme and volume, using TEOS-10, is recommended.