Intensification of upper ocean submesoscale turbulence through Charney baroclinic instability

Type Publication
Date 2016-11
Language English
Copyright 2016 American Meteorological Society
Author(s) Capet Xavier1, Roullet Guillaume2, Klein Patrice2, Maze GuillaumeORCID3
Affiliation(s) 1 : Sorbonne Univ, UPMC, CNRS, IRD,MNHN,LOCEAN, Paris, France.
2 : Univ Brest, Lab Ocanog Phys & Spatiale, IFREMER, CNRS,IRD,IUEM, Brest, France.
Source Journal Of Physical Oceanography (0022-3670) (Amer Meteorological Soc), 2016-11 , Vol. 46 , N. 11 , P. 3365-3384
DOI 10.1175/JPO-D-16-0050.1
WOS© Times Cited 6
Abstract This study focuses on the description of an oceanic variant of the Charney baroclinic instability, arising from the joint presence of i) an equatorward buoyancy gradient that extends from the surface into the ocean interior and ii) reduced subsurface stratification, e.g., as produced by wintertime convection or subduction. We analyze forced-dissipative simulations with and without Charney baroclinic instability (C-BCI). In the former C-BCI strengthens near-surface frontal activity with important consequences in terms of turbulent statistics: increased variance of vertical vorticity and velocity, increased vertical turbulent fluxes. Energetic consequences are explored. Despite the atypical enhancement of submesoscale activity in the simulation subjected to C-BCI and contrary to several recent studies the downscale energy flux at submesoscale en route to dissipation remains modest in the flow energetic equilibration. In particular, it is modest vis a vis the global energy input to the system, the eddy kinetic energy input through conversion of available potential energy, and the classical inverse cascade of kinetic energy. Linear stability analysis suggests that the southern flank of the Gulf Stream may be conducive to oceanic Charney baroclinic instability in spring, following mode water formation and upper ocean destratification.
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