Baroclinic Rossby Waves and the South Atlantic Meridional Overturning Circulation

The South Atlantic Meridional Overturning Circulation (SAMOC) is an ocean circulation pattern composed by geostrophic and ageostrophic currents and its subsequent transport of heat and freshwater. It impacts ocean stratification because density regulates the vertical distribution of water masses and its horizontal gradients are responsible for the geostrophic circulation. Rossby waves play a key role in large-scale circulation, controlling the western boundary currents and consequently the subtropical gyre. In a baroclinic model, they are prone to variability when changes in stratification occurs. In that way, variations of this waves mechanic energy would be, in principle, related to the SAMOC variability. These waves were identified at 11ºS, 24.5ºS and 34.5ºS in the Atlantic, Pacific and Indian oceans and significant variations in waves' amplitudes were noted among the three ocean basins. Thus, it is proposed that stratification might play an important role on this difference. Mean Brunt-Väisälä frequencies were calculated as a function of depth at these latitudes, and differences between ocean basins were observed. Traditional vertical mode decomposition was done to characterize waves vertically to relate the surface signal with the stratification in the water column. Using temperature and salinity profiles available from in-situ data and sea surface height data measured by satellite altimetry we intend to assess the role played by stratification in the amplitude of Rossby waves, comparing data from the three ocean basins at 11ºS, 24.5ºS and 34.5ºS and if there is any significant contribution of the energy transported by groups of these waves to the western boundary current at the South Atlantic Ocean. Provided that this role is explicit, it may be possible to examine how stratification had changed in the Southern Hemisphere at the aforementioned latitudes during the altimetric record and to associate this disparity with SAMOC's interannual flux variations.