A diagnosis of thickness fluxes in an eddy-resolving model
Output from an eddy-resolving model of the North Atlantic Ocean is used to estimate values for the thickness diffusivity κ appropriate to the Gent and McWilliams parameterization. The effect of different choices of rotational eddy fluxes on the estimated κ is discussed. Using the raw fluxes (no rota...
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ftoceanrep:oai:oceanrep.geomar.de:3394 2023-05-15T17:36:10+02:00 A diagnosis of thickness fluxes in an eddy-resolving model Eden, Carsten Greatbatch, Richard John Willebrand, Jürgen 2007 text https://oceanrep.geomar.de/id/eprint/3394/ https://oceanrep.geomar.de/id/eprint/3394/1/jpo2987.1.pdf https://doi.org/10.1175/JPO2987.1 en eng AMS (American Meteorological Society) https://oceanrep.geomar.de/id/eprint/3394/1/jpo2987.1.pdf Eden, C., Greatbatch, R. J. and Willebrand, J. (2007) A diagnosis of thickness fluxes in an eddy-resolving model. Open Access Journal of Physical Oceanography, 37 . pp. 727-742. DOI 10.1175/JPO2987.1 <https://doi.org/10.1175/JPO2987.1>. doi:10.1175/JPO2987.1 info:eu-repo/semantics/openAccess Article PeerReviewed 2007 ftoceanrep https://doi.org/10.1175/JPO2987.1 2023-04-07T14:47:34Z Output from an eddy-resolving model of the North Atlantic Ocean is used to estimate values for the thickness diffusivity κ appropriate to the Gent and McWilliams parameterization. The effect of different choices of rotational eddy fluxes on the estimated κ is discussed. Using the raw fluxes (no rotational flux removed), large negative values (exceeding −5000 m2 s−1) of κ are diagnosed locally, particularly in the Gulf Stream region and in the equatorial Atlantic. Removing a rotational flux based either on the suggestion of Marshall and Shutts or the more general theory of Medvedev and Greatbatch leads to a reduction of the negative values, but they are still present. The regions where κ < 0 correspond to regions where eddies are acting to increase, rather than decrease (as in baroclinic instability) the mean available potential energy. In the subtropical gyre, κ ranges between 500 and 2000 m2 s−1, rapidly decreasing to zero below the thermocline in all cases. Rotational fluxes and κ are also estimated using an optimization technique. In this case, |κ| can be reduced or increased by construction, but the regions where κ < 0 are still present and the optimized rotational fluxes also remain similar to a priori values given by the theoretical considerations. A previously neglected component (ν) of the bolus velocity is associated with the horizontal flux of buoyancy along, rather than across, the mean buoyancy contours. The ν component of the bolus velocity is interpreted as a streamfunction for eddy-induced advection, rather than diffusion, of mean isopycnal layer thickness, showing up when the lateral eddy fluxes cannot be described by isotropic diffusion only. All estimates show a similar large-scale pattern for ν, implying westward advection of isopycnal thickness over much of the subtropical gyre. Comparing ν with a mean streamfunction shows that it is about 10% of the mean in midlatitudes and even larger than the mean in the Tropics. Article in Journal/Newspaper North Atlantic OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Journal of Physical Oceanography 37 3 727 742 |
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Open Polar |
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OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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ftoceanrep |
language |
English |
description |
Output from an eddy-resolving model of the North Atlantic Ocean is used to estimate values for the thickness diffusivity κ appropriate to the Gent and McWilliams parameterization. The effect of different choices of rotational eddy fluxes on the estimated κ is discussed. Using the raw fluxes (no rotational flux removed), large negative values (exceeding −5000 m2 s−1) of κ are diagnosed locally, particularly in the Gulf Stream region and in the equatorial Atlantic. Removing a rotational flux based either on the suggestion of Marshall and Shutts or the more general theory of Medvedev and Greatbatch leads to a reduction of the negative values, but they are still present. The regions where κ < 0 correspond to regions where eddies are acting to increase, rather than decrease (as in baroclinic instability) the mean available potential energy. In the subtropical gyre, κ ranges between 500 and 2000 m2 s−1, rapidly decreasing to zero below the thermocline in all cases. Rotational fluxes and κ are also estimated using an optimization technique. In this case, |κ| can be reduced or increased by construction, but the regions where κ < 0 are still present and the optimized rotational fluxes also remain similar to a priori values given by the theoretical considerations. A previously neglected component (ν) of the bolus velocity is associated with the horizontal flux of buoyancy along, rather than across, the mean buoyancy contours. The ν component of the bolus velocity is interpreted as a streamfunction for eddy-induced advection, rather than diffusion, of mean isopycnal layer thickness, showing up when the lateral eddy fluxes cannot be described by isotropic diffusion only. All estimates show a similar large-scale pattern for ν, implying westward advection of isopycnal thickness over much of the subtropical gyre. Comparing ν with a mean streamfunction shows that it is about 10% of the mean in midlatitudes and even larger than the mean in the Tropics. |
format |
Article in Journal/Newspaper |
author |
Eden, Carsten Greatbatch, Richard John Willebrand, Jürgen |
spellingShingle |
Eden, Carsten Greatbatch, Richard John Willebrand, Jürgen A diagnosis of thickness fluxes in an eddy-resolving model |
author_facet |
Eden, Carsten Greatbatch, Richard John Willebrand, Jürgen |
author_sort |
Eden, Carsten |
title |
A diagnosis of thickness fluxes in an eddy-resolving model |
title_short |
A diagnosis of thickness fluxes in an eddy-resolving model |
title_full |
A diagnosis of thickness fluxes in an eddy-resolving model |
title_fullStr |
A diagnosis of thickness fluxes in an eddy-resolving model |
title_full_unstemmed |
A diagnosis of thickness fluxes in an eddy-resolving model |
title_sort |
diagnosis of thickness fluxes in an eddy-resolving model |
publisher |
AMS (American Meteorological Society) |
publishDate |
2007 |
url |
https://oceanrep.geomar.de/id/eprint/3394/ https://oceanrep.geomar.de/id/eprint/3394/1/jpo2987.1.pdf https://doi.org/10.1175/JPO2987.1 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://oceanrep.geomar.de/id/eprint/3394/1/jpo2987.1.pdf Eden, C., Greatbatch, R. J. and Willebrand, J. (2007) A diagnosis of thickness fluxes in an eddy-resolving model. Open Access Journal of Physical Oceanography, 37 . pp. 727-742. DOI 10.1175/JPO2987.1 <https://doi.org/10.1175/JPO2987.1>. doi:10.1175/JPO2987.1 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1175/JPO2987.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
37 |
container_issue |
3 |
container_start_page |
727 |
op_container_end_page |
742 |
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1766135560348368896 |