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Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy

Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy
Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy

A 4-month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical North Atlantic. The eddy (radius ≈ 60 km) had a core of low potential vorticity between 100 and 450 m, with maximum radial velocities of 0.5 m s -1 and Rossby number ≈-0.1. Turbulent dissipation was inferred from vertical water velocities derived from the glider flight model. Dissipation was suppressed in the eddy core (ε ≈ 5 ☓ 10 -10 Wkg -1) and enhanced below it (>10 -9 Wkg -1). Elevated dissipation was coincident with quasiperiodic structures in the vertical velocity and pressure perturbations, suggesting internal waves as the drivers of dissipation. A heuristic ray-tracing approximation was used to investigate the wave–eddy interactions leading to turbulent dissipation. Ray-tracing simulations were consistent with two types of wave–eddy interactions that may induce dissipation: the trapping of near-inertial wave energy by the eddy’s relative vorticity, or the entry of an internal tide (generated at the nearby continental slope) to a critical layer in the eddy shear. The latter scenario suggests that the intense mesoscale field characterizing the western boundaries of ocean basins might act as a ‘‘leaky wall’’ controlling the propagation of internal tides into the basin’s interior.

0022-3670
1893-1914
Fernández-Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Evans, Dafydd Gwyn
4f153214-2922-459c-9a34-661c851e2286
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Vic, Clément
408e7f4a-468f-4139-90a6-3a95228ad758
Naveira-garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Fernández-Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Evans, Dafydd Gwyn
4f153214-2922-459c-9a34-661c851e2286
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Vic, Clément
408e7f4a-468f-4139-90a6-3a95228ad758
Naveira-garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6

Fernández-Castro, Bieito, Evans, Dafydd Gwyn, Frajka-Williams, Eleanor, Vic, Clément and Naveira-garabato, Alberto C. (2020) Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy. Journal of Physical Oceanography, 50 (7), 1893-1914. (doi:10.1175/JPO-D-19-0168.1).

Record type: Article

Abstract

A 4-month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical North Atlantic. The eddy (radius ≈ 60 km) had a core of low potential vorticity between 100 and 450 m, with maximum radial velocities of 0.5 m s -1 and Rossby number ≈-0.1. Turbulent dissipation was inferred from vertical water velocities derived from the glider flight model. Dissipation was suppressed in the eddy core (ε ≈ 5 ☓ 10 -10 Wkg -1) and enhanced below it (>10 -9 Wkg -1). Elevated dissipation was coincident with quasiperiodic structures in the vertical velocity and pressure perturbations, suggesting internal waves as the drivers of dissipation. A heuristic ray-tracing approximation was used to investigate the wave–eddy interactions leading to turbulent dissipation. Ray-tracing simulations were consistent with two types of wave–eddy interactions that may induce dissipation: the trapping of near-inertial wave energy by the eddy’s relative vorticity, or the entry of an internal tide (generated at the nearby continental slope) to a critical layer in the eddy shear. The latter scenario suggests that the intense mesoscale field characterizing the western boundaries of ocean basins might act as a ‘‘leaky wall’’ controlling the propagation of internal tides into the basin’s interior.

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e-pub ahead of print date: 19 March 2020
Published date: 1 July 2020

Identifiers

Local EPrints ID: 441026
URI: http://eprints.soton.ac.uk/id/eprint/441026
ISSN: 0022-3670
PURE UUID: 5b18a02d-33f6-4095-83e8-4c3528c08bb3
ORCID for Bieito Fernández-Castro: ORCID iD orcid.org/0000-0001-7797-854X
ORCID for Eleanor Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 27 May 2020 16:55
Last modified: 22 Nov 2021 03:28

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Contributors

Author: Dafydd Gwyn Evans
Author: Eleanor Frajka-Williams ORCID iD
Author: Clément Vic

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