Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

Energy cascades and loss of balance in a reentrant channel forced by wind stress and buoyancy fluxes

TitleEnergy cascades and loss of balance in a reentrant channel forced by wind stress and buoyancy fluxes
Publication TypeJournal Article
Year of Publication2015
AuthorsBarkan R, Winters KB, Smith SGL
JournalJournal of Physical Oceanography
Date Published2015/01
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000347535800015
Keywordsbaroclinic; california current system; convection; instability; ocean fronts; overturning circulation; part i; southern-ocean; submesoscale transition; symmetric; vertical motion

A large fraction of the kinetic energy in the ocean is stored in the "quasigeostrophic" eddy field. This "balanced" eddy field is expected, according to geostrophic turbulence theory, to transfer energy to larger scales. In order for the general circulation to remain approximately steady, instability mechanisms leading to loss of balance (LOB) have been hypothesized to take place so that the eddy kinetic energy (EKE) may be transferred to small scales where it can be dissipated. This study examines the kinetic energy pathways in fully resolved direct numerical simulations of flow in a flat-bottomed reentrant channel, externally forced by surface buoyancy fluxes and wind stress in a configuration that resembles the Antarctic Circumpolar Current. The flow is allowed to reach a statistical steady state at which point it exhibits both a forward and an inverse energy cascade. Flow interactions with irregular bathymetry are excluded so that bottom drag is the sole mechanism available to dissipate the upscale EKE transfer. The authors show that EKE is dissipated preferentially at small scales near the surface via frontal instabilities associated with LOB and a forward energy cascade rather than by bottom drag after an inverse energy cascade. This is true both with and without forcing by the wind. These results suggest that LOB caused by frontal instabilities near the ocean surface could provide an efficient mechanism, independent of boundary effects, by which EKE is dissipated. Ageostrophic anticyclonic instability is the dominant frontal instability mechanism in these simulations. Symmetric instability is also important in a "deep convection" region, where it can be sustained by buoyancy loss.

Student Publication: