Jet Instability over Smooth, Corrugated, and Realistic Bathymetry
International audience The stability of a horizontally and vertically sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth that are characteristically shif...
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ftunivparis:oai:HAL:hal-02324024v1 2023-11-12T04:04:23+01:00 Jet Instability over Smooth, Corrugated, and Realistic Bathymetry Lacasce, J., H Escartin, Javier Chassignet, Eric Xu, Xiaobiao University of Oslo (UiO) Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) 2019-02 https://hal.science/hal-02324024 https://hal.science/hal-02324024/document https://hal.science/hal-02324024/file/LaCasce2019.pdf https://doi.org/10.1175/JPO-D-18-0129.1 en eng HAL CCSD American Meteorological Society info:eu-repo/semantics/altIdentifier/doi/10.1175/JPO-D-18-0129.1 hal-02324024 https://hal.science/hal-02324024 https://hal.science/hal-02324024/document https://hal.science/hal-02324024/file/LaCasce2019.pdf doi:10.1175/JPO-D-18-0129.1 info:eu-repo/semantics/OpenAccess ISSN: 0022-3670 EISSN: 1520-0485 Journal of Physical Oceanography https://hal.science/hal-02324024 Journal of Physical Oceanography, 2019, 49 (2), pp.585-605. ⟨10.1175/JPO-D-18-0129.1⟩ [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2019 ftunivparis https://doi.org/10.1175/JPO-D-18-0129.1 2023-10-25T16:20:48Z International audience The stability of a horizontally and vertically sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth that are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow antiparallel to topographic wave propagation) and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under bar-oclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer. A ridge with a 1-km wavelength and an amplitude of roughly 10 m is sufficient to suppress baroclinic instability. Surveys of bottom roughness from bathymetry acquired with shipboard multibeam echo sounding reveal that such heights are common beneath the Kuroshio, the Antarctic Circumpolar Current, and, to a lesser extent, the Gulf Stream. Consistent with this, vorticity and velocity cross sections from a 1/508 HYCOM simulation suggest that Gulf Stream eddies are vertically aligned, as in the linear stability calculations with strong topography. Thus, lateral instability may be more common than previously thought, owing to topography hindering vertical energy transfer. Article in Journal/Newspaper Antarc* Antarctic Université de Paris: Portail HAL Antarctic The Antarctic Journal of Physical Oceanography 49 2 585 605 |
institution |
Open Polar |
collection |
Université de Paris: Portail HAL |
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ftunivparis |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Lacasce, J., H Escartin, Javier Chassignet, Eric Xu, Xiaobiao Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
International audience The stability of a horizontally and vertically sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth that are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow antiparallel to topographic wave propagation) and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under bar-oclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer. A ridge with a 1-km wavelength and an amplitude of roughly 10 m is sufficient to suppress baroclinic instability. Surveys of bottom roughness from bathymetry acquired with shipboard multibeam echo sounding reveal that such heights are common beneath the Kuroshio, the Antarctic Circumpolar Current, and, to a lesser extent, the Gulf Stream. Consistent with this, vorticity and velocity cross sections from a 1/508 HYCOM simulation suggest that Gulf Stream eddies are vertically aligned, as in the linear stability calculations with strong topography. Thus, lateral instability may be more common than previously thought, owing to topography hindering vertical energy transfer. |
author2 |
University of Oslo (UiO) Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Lacasce, J., H Escartin, Javier Chassignet, Eric Xu, Xiaobiao |
author_facet |
Lacasce, J., H Escartin, Javier Chassignet, Eric Xu, Xiaobiao |
author_sort |
Lacasce, J., H |
title |
Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
title_short |
Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
title_full |
Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
title_fullStr |
Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
title_full_unstemmed |
Jet Instability over Smooth, Corrugated, and Realistic Bathymetry |
title_sort |
jet instability over smooth, corrugated, and realistic bathymetry |
publisher |
HAL CCSD |
publishDate |
2019 |
url |
https://hal.science/hal-02324024 https://hal.science/hal-02324024/document https://hal.science/hal-02324024/file/LaCasce2019.pdf https://doi.org/10.1175/JPO-D-18-0129.1 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
ISSN: 0022-3670 EISSN: 1520-0485 Journal of Physical Oceanography https://hal.science/hal-02324024 Journal of Physical Oceanography, 2019, 49 (2), pp.585-605. ⟨10.1175/JPO-D-18-0129.1⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1175/JPO-D-18-0129.1 hal-02324024 https://hal.science/hal-02324024 https://hal.science/hal-02324024/document https://hal.science/hal-02324024/file/LaCasce2019.pdf doi:10.1175/JPO-D-18-0129.1 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1175/JPO-D-18-0129.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
49 |
container_issue |
2 |
container_start_page |
585 |
op_container_end_page |
605 |
_version_ |
1782341602052669440 |