Modification of turbulent dissipation rates by a deep Southern Ocean eddy

The impact of a mesoscale eddy on the magnitude and spatial distribution of diapycnal ocean mixing is investigated using a set of hydrographic and microstructure measurements collected in the Southern Ocean. These data sampled a baroclinic, middepth eddy formed during the disintegration of a deep bo...

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Bibliographic Details
Published in:Geophysical research letters 2015-05, Vol.42 (9), p.3450-3457
Main Authors: Sheen, K. L., Brearley, J. A., Naveira Garabato, A. C., Smeed, D. A., Laurent, L. St, Meredith, M. P., Thurnherr, A. M., Waterman, S. N.
Format: Article
Language:English
Subjects:
Approximation
Boundaries
Boundary currents
Breaking
Data
Density stratification
Disintegration
Dissipation
Eddies
eddy
Eddy currents
Energy
Fluid dynamics
Heuristic
Internal waves
Marine
Mathematical analysis
Mesoscale phenomena
Microstructure
mixing
Ocean circulation
Ocean mixing
Ray tracing
Reflection
Southern Ocean
Spatial distribution
Stratification
Turbulence
turbulent dissipation
Velocity
Wave energy
Wave power
Wave reflection
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Summary:The impact of a mesoscale eddy on the magnitude and spatial distribution of diapycnal ocean mixing is investigated using a set of hydrographic and microstructure measurements collected in the Southern Ocean. These data sampled a baroclinic, middepth eddy formed during the disintegration of a deep boundary current. Turbulent dissipation is suppressed within the eddy but is elevated by up to an order of magnitude along the upper and lower eddy boundaries. A ray tracing approximation is employed as a heuristic device to elucidate how the internal wave field evolves in the ambient velocity and stratification conditions accompanying the eddy. These calculations are consistent with the observations, suggesting reflection of internal wave energy from the eddy center and enhanced breaking through critical layer processes along the eddy boundaries. These results have important implications for understanding where and how internal wave energy is dissipated in the presence of energetic deep geostrophic flows. Key Points Middepth Southern Ocean eddies impact local dissipation of internal wave energy Turbulent dissipation is enhanced on eddy periphery and suppressed in eddy core Ray tracing elucidates mechanisms by which internal waves evolve in ACC eddy
ISSN:0094-8276
1944-8007
DOI:10.1002/2015GL063216