Generated using V3.0 of the official AMS LATEX template–journal page layout FOR AUTHOR USE ONLY, NOT FOR SUBMISSION! Baroclinic turbulence in the ocean: analysis with primitive equation and quasi-geostrophic simulations

• Main Authors: Antoine Venaille, Geoffrey, K. Vallis, K. Shafer Smith
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Southern Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.650.9146; http://perso.ens-lyon.fr/antoine.venaille/index-en_files/vsv.pdf

This paper examines the factors determining the distribution, length scale, magnitude and structure of mesoscale oceanic eddies in an eddy-resolving primitive equation simulation of the Southern Ocean (MESO). In particular, we investigate the hypothesis that the primary source of mesoscale eddies is baroclinic instability acting locally on the mean state. Using local mean vertical profiles of shear and stratification from the MESO simulation, we integrate the forced-dissipated quasi-geostrophic equations in a doubly periodic domain at various locations. We also perform a linear stability analysis of the profiles. The scales, energy levels and structure of the eddies found in the MESO simulation are compared to those predicted by the linear analysis, as well as to the eddying structure of the quasi-geostrophic simulations,. This allows us to quantitatively estimate the role of local non-linear effects and cascade phenomena in the generation of the eddy field. We find that typically there is a modest transfer of energy (an ‘inverse cascade’) to larger scales in the horizontal, with the length scale of the resulting eddies typically comparable to or somewhat larger than the wavelength of the most unstable mode. The eddies are, however, manifestly nonlinear and in many locations the turbulence is fairly well-developed. Coherent structures also ubiquitously emerge during the non-linear evolution of the eddy field. There is a near universal tendency toward the production of grave vertical scales, with the barotropic and