Estimation of horizontal turbulent diffusivity from deep Argo float displacements
Estimation of horizontal turbulent diffusivity from deep Argo float displacements
We use an analog method, based on displacements of Argo floats at their parking depth (nominally located around 1000 dbar) from the ANDRO dataset, to compute continuous, likely trajectories and estimate the Lagrangian dis-persion. From this, we find that the horizontal diffusivity coefficient has a median value around 500 m 2 s -1 but is highly variable in space, reaching values from 100 m 2 s -1 in the gyre interior to 40 000 m 2 s -1 in a few specific locations (in the Zapiola Gyre and in the Agulhas Current retroflection). Our analysis suggests that the closure for diffusivity is propor-tional to eddy kinetic energy (or square of turbulent velocity) rather than (absolute) turbulent velocity. It is associated with a typical turbulent time scale of 4–5.5 days, which is noticeably quite constant over the entire globe, especially away from coherent intense currents. The diffusion is anisotropic in coherent intense currents and around the equator, with a primary direction of diffusion consistent with the primary direction of horizontal velocity variance. These observationally based horizontal diffusivity estimations, and the suggested eddy kinetic energy closure, can be used for constraining, testing, and validating eddy turbulence parameterization.
Diffusion, Dispersion, In situ oceanic observations, Lagrangian circulation/transport, Mesoscale processes, Ocean
1509-1529
Sévellec, F.
01569d6c-65b0-4270-af2a-35b0a77c9140
Verdière, A. Colin De
b3372448-3b63-41da-b1c1-526157f7e627
Kolodziejczyk, N.
2fc1f1bc-e9f5-4f7a-b07e-f45f84323bc5
1 July 2022
Sévellec, F.
01569d6c-65b0-4270-af2a-35b0a77c9140
Verdière, A. Colin De
b3372448-3b63-41da-b1c1-526157f7e627
Kolodziejczyk, N.
2fc1f1bc-e9f5-4f7a-b07e-f45f84323bc5
Sévellec, F., Verdière, A. Colin De and Kolodziejczyk, N.
(2022)
Estimation of horizontal turbulent diffusivity from deep Argo float displacements.
Journal of Physical Oceanography, 52 (7), .
(doi:10.1175/JPO-D-21-0150.1).
Abstract
We use an analog method, based on displacements of Argo floats at their parking depth (nominally located around 1000 dbar) from the ANDRO dataset, to compute continuous, likely trajectories and estimate the Lagrangian dis-persion. From this, we find that the horizontal diffusivity coefficient has a median value around 500 m 2 s -1 but is highly variable in space, reaching values from 100 m 2 s -1 in the gyre interior to 40 000 m 2 s -1 in a few specific locations (in the Zapiola Gyre and in the Agulhas Current retroflection). Our analysis suggests that the closure for diffusivity is propor-tional to eddy kinetic energy (or square of turbulent velocity) rather than (absolute) turbulent velocity. It is associated with a typical turbulent time scale of 4–5.5 days, which is noticeably quite constant over the entire globe, especially away from coherent intense currents. The diffusion is anisotropic in coherent intense currents and around the equator, with a primary direction of diffusion consistent with the primary direction of horizontal velocity variance. These observationally based horizontal diffusivity estimations, and the suggested eddy kinetic energy closure, can be used for constraining, testing, and validating eddy turbulence parameterization.
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e-pub ahead of print date: 22 June 2022
Published date: 1 July 2022
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Funding Information:
Acknowledgments. This research was supported by the OceaniX project funded through the French ANR program and by the ISblue project, Interdisciplinary graduate school for the blue planet (ANR-17-EURE-0015) and co-funded by a grant from the French government under the program “Investissements d’Avenir.” The ANDRO dataset used in this study corresponds to the 2019 Release (key: 66657) and is freely available through the www.seanoe.org platform (https://doi.org/10.17882/47077).
Keywords:
Diffusion, Dispersion, In situ oceanic observations, Lagrangian circulation/transport, Mesoscale processes, Ocean
Identifiers
Local EPrints ID: 485268
URI: http://eprints.soton.ac.uk/id/eprint/485268
ISSN: 0022-3670
PURE UUID: c8853132-80fc-44eb-ac46-306d0e82eff7
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Date deposited: 01 Dec 2023 17:52
Last modified: 16 Mar 2024 22:04
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Author:
A. Colin De Verdière
Author:
N. Kolodziejczyk
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