Toward global maps of internal tide energy sinks
Toward global maps of internal tide energy sinks
Internal tides power much of the observed small-scale turbulence in the ocean interior. To represent mixing induced by this turbulence in ocean climate models, the cascade of internal tide energy to dissipation scales must be understood and mapped. Here, we present a framework for estimating the geography of internal tide energy sinks. The mapping relies on the following ingredients: (i) a global observational climatology of stratification; (ii) maps of the generation of M
2
, S
2
and K
1
internal tides decomposed into vertical normal modes; (iii) simplified representations of the dissipation of low-mode internal tides due to wave-wave interactions, scattering by small-scale topography, interaction with critical slopes and shoaling; (iv) Lagrangian tracking of low-mode energy beams through observed stratification, including refraction and reflection. We thus obtain a global map of the column-integrated energy dissipation for each of the four considered dissipative processes, each of the three tidal constituents and each of the first five modes. Modes ≥6 are inferred to dissipate within the local water column at the employed half-degree horizontal resolution. Combining all processes, modes and constituents, we construct a map of the total internal tide energy dissipation, which compares well with observational inferences of internal wave energy dissipation. This result suggests that tides largely shape observed spatial contrasts of dissipation, and that the framework has potential in improving understanding and modelling of ocean mixing. However, sensitivity to poorly constrained parameters and simplifying assumptions entering the parameterized energy sinks calls for additional investigation. The attenuation of low-mode internal tides by wave-wave interactions needs particular attention.
Energy dissipation, Internal tides, Ocean mixing, Parameterization
52-75
de Lavergne, C.
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Falahat, S.
c98ea55e-6454-4b97-a330-4fa30beddb0a
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Roquet, F.
92998487-4f5f-42e8-8873-453e268d065e
Nycander, J.
16e86f07-b62c-4bbe-bd21-576c7ac35626
Vic, C.
408e7f4a-468f-4139-90a6-3a95228ad758
1 May 2019
de Lavergne, C.
5cd9bf80-0659-4ed5-9cc1-4d611b422759
Falahat, S.
c98ea55e-6454-4b97-a330-4fa30beddb0a
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Roquet, F.
92998487-4f5f-42e8-8873-453e268d065e
Nycander, J.
16e86f07-b62c-4bbe-bd21-576c7ac35626
Vic, C.
408e7f4a-468f-4139-90a6-3a95228ad758
de Lavergne, C., Falahat, S., Madec, G., Roquet, F., Nycander, J. and Vic, C.
(2019)
Toward global maps of internal tide energy sinks.
Ocean Modelling, 137, .
(doi:10.1016/j.ocemod.2019.03.010).
Abstract
Internal tides power much of the observed small-scale turbulence in the ocean interior. To represent mixing induced by this turbulence in ocean climate models, the cascade of internal tide energy to dissipation scales must be understood and mapped. Here, we present a framework for estimating the geography of internal tide energy sinks. The mapping relies on the following ingredients: (i) a global observational climatology of stratification; (ii) maps of the generation of M
2
, S
2
and K
1
internal tides decomposed into vertical normal modes; (iii) simplified representations of the dissipation of low-mode internal tides due to wave-wave interactions, scattering by small-scale topography, interaction with critical slopes and shoaling; (iv) Lagrangian tracking of low-mode energy beams through observed stratification, including refraction and reflection. We thus obtain a global map of the column-integrated energy dissipation for each of the four considered dissipative processes, each of the three tidal constituents and each of the first five modes. Modes ≥6 are inferred to dissipate within the local water column at the employed half-degree horizontal resolution. Combining all processes, modes and constituents, we construct a map of the total internal tide energy dissipation, which compares well with observational inferences of internal wave energy dissipation. This result suggests that tides largely shape observed spatial contrasts of dissipation, and that the framework has potential in improving understanding and modelling of ocean mixing. However, sensitivity to poorly constrained parameters and simplifying assumptions entering the parameterized energy sinks calls for additional investigation. The attenuation of low-mode internal tides by wave-wave interactions needs particular attention.
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Accepted/In Press date: 24 March 2019
e-pub ahead of print date: 1 April 2019
Published date: 1 May 2019
Keywords:
Energy dissipation, Internal tides, Ocean mixing, Parameterization
Identifiers
Local EPrints ID: 430444
URI: http://eprints.soton.ac.uk/id/eprint/430444
ISSN: 1463-5003
PURE UUID: e5be8b42-f964-41e6-a263-bb607e0e10f1
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Date deposited: 01 May 2019 16:30
Last modified: 17 Mar 2024 12:24
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Contributors
Author:
C. de Lavergne
Author:
S. Falahat
Author:
G. Madec
Author:
F. Roquet
Author:
J. Nycander
Author:
C. Vic
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