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Generation of internal waves by eddies impinging on the western boundary of the North Atlantic

Generation of internal waves by eddies impinging on the western boundary of the North Atlantic
Generation of internal waves by eddies impinging on the western boundary of the North Atlantic

Despite the major role played by mesoscale eddies in redistributing the energy of the large-scale circulation, our understanding of their dissipation is still incomplete. This study investigates the generation of internal waves by decaying eddies in the North Atlantic western boundary. The eddy presence and decay are measured from the altimetric surface relative vorticity associated with an array of full-depth current meters extending ~100 km offshore at 26.5°N. In addition, internal waves are analysed over a topographic rise from 2-year high-frequency measurements of an Acoustic Doppler Current Profiler (ADCP), which is located 13 km offshore in 600 m deep water. Despite an apparent polarity independence of the eddy decay observed from altimetric data, the flow in the deepest 100 m is enhanced for anticyclones (25.2 cm s?1) compared with cyclones (-4.7 cm s?1). Accordingly, the internal wave field is sensitive to this polarity-dependent deep velocity. This is apparent from the eddy-modulated enhanced dissipation rate, which is obtained from a finescale parameterization and exceeds 10?9 W kg?1 for near-bottom flows greater than 8 cm s?1. The present study underlines the importance of oceanic western boundaries for removing the energy of low-mode westward-propagating eddies to higher-mode internal waves.
Circulation/Dynamics, Eddies, Internal waves, Mixing, Topographic effects
0022-3670
1067-1079
Clément, L.
597f945c-2292-4425-91dc-5178662c6ea5
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Sheen, K.L.
11fc9ce4-1a9a-4925-ae04-816e5e8660ae
Brearley, J.A.
91ab83c7-8d07-4b93-acbf-16ee4a6cdfe5
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Clément, L.
597f945c-2292-4425-91dc-5178662c6ea5
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Sheen, K.L.
11fc9ce4-1a9a-4925-ae04-816e5e8660ae
Brearley, J.A.
91ab83c7-8d07-4b93-acbf-16ee4a6cdfe5
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6

Clément, L., Frajka-Williams, E., Sheen, K.L., Brearley, J.A. and Naveira Garabato, A.C. (2016) Generation of internal waves by eddies impinging on the western boundary of the North Atlantic. Journal of Physical Oceanography, 46 (4), 1067-1079. (doi:10.1175/JPO-D-14-0241.1).

Record type: Article

Abstract


Despite the major role played by mesoscale eddies in redistributing the energy of the large-scale circulation, our understanding of their dissipation is still incomplete. This study investigates the generation of internal waves by decaying eddies in the North Atlantic western boundary. The eddy presence and decay are measured from the altimetric surface relative vorticity associated with an array of full-depth current meters extending ~100 km offshore at 26.5°N. In addition, internal waves are analysed over a topographic rise from 2-year high-frequency measurements of an Acoustic Doppler Current Profiler (ADCP), which is located 13 km offshore in 600 m deep water. Despite an apparent polarity independence of the eddy decay observed from altimetric data, the flow in the deepest 100 m is enhanced for anticyclones (25.2 cm s?1) compared with cyclones (-4.7 cm s?1). Accordingly, the internal wave field is sensitive to this polarity-dependent deep velocity. This is apparent from the eddy-modulated enhanced dissipation rate, which is obtained from a finescale parameterization and exceeds 10?9 W kg?1 for near-bottom flows greater than 8 cm s?1. The present study underlines the importance of oceanic western boundaries for removing the energy of low-mode westward-propagating eddies to higher-mode internal waves.

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e-pub ahead of print date: 2016
Published date: April 2016
Keywords: Circulation/Dynamics, Eddies, Internal waves, Mixing, Topographic effects
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 387985
URI: http://eprints.soton.ac.uk/id/eprint/387985
ISSN: 0022-3670
PURE UUID: 3660144c-bad9-4939-abf7-919dddc452cf
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 17 Feb 2016 10:02
Last modified: 17 Dec 2019 01:41

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