Variability of the South Atlantic upper ocean circulation: a data assimilation experiment with 5 years of Topex/Poseidon altimeter observations

Elodie Garnier (1) , Jacques Verron (1) , Bernard Barnier (1)

1 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]

Dynamical interpolation of five years of TOPEX/POSEIDON altimeter data (October 1992-September 1997) is performed in the South Atlantic basin, through the use of a simple quasigeostrophic model and a simple nudging data assimilation technique. The resulting data set is analysed in order to evidence the role of mesoscale eddies on the interannual variability of the South Atlantic ocean circulations. The annual mean circulations and the eddy fields reveal some significant interannual variability in the Brazil-Malvinas confluence region and in the Aghulas Retroflection region. But this interannual variability spreads out also in large extensions of those previous regions as well as in other areas of the South Atlantic basin. In particular, significant variability shows up in the upper return branch of the subtropical gyre that is interpreted in relation with the drift of some Aghulas rings. The role of those latter rings which are crucial for the Indian-Atlantic interocean exchange processes, is further investigated in the paper, and the fate of five specific rings analysed in detail. The overall influence of topography on the circulation is clearly evidenced, especially through its interaction with eddies.

Domaines: Océanographie

Elodie Garnier, Jacques Verron, Bernard Barnier. Variability of the South Atlantic upper ocean circulation: a data assimilation experiment with 5 years of Topex/Poseidon altimeter observations. International Journal of Remote Sensing, 2003, 24 (5), pp.911-934. ⟨10.1080/01431160210154902⟩. ⟨hal-00182964⟩