Stochastic variability of oceanic flows above topography anomalies

Antoine Venaille (1) , Julien Le Sommer (2) , Jean-Marc Molines (2) , Bernard Barnier (2)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]

We describe a stochastic variability mechanism which is genuinely internal to the ocean, i.e. not due to fluctuations in atmospheric forcing. % The key ingredient is the existence of closed contours of bottom topography surrounded by a stirring region of enhanced eddy activity. This configuration leads to the formation of a robust but highly variable vortex above the topography anomaly. The vortex dynamics integrates the white noise forcing of oceanic eddies into a red noise signal for the large scale volume transport of the vortex. The strong interannual fluctuations of the transport of the Zapiola anticyclone ($\sim 100 \ Sv$) in the Argentine basin are argued to be partly due to such eddy-driven stochastic variability, on the basis of a $310$ years long simulation of a comprehensive global ocean model run driven by a repeated-year forcing.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Antoine Venaille, Julien Le Sommer, Jean-Marc Molines, Bernard Barnier. Stochastic variability of oceanic flows above topography anomalies. Geophysical Research Letters, 2011, 38 (16), pp.DOI: 10.1029/2011GL048401. ⟨hal-00577907v2⟩