Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing
International audience Instability and mixing are ubiquitous processes in river plumes but their small spatial and temporal scales often limit their observation and analysis. We investigate flow instability and mixing processes in the Gironde river plume (Bay of Biscay, North-East Atlantic ocean) in...
Published in: | Frontiers in Marine Science |
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Main Authors: | , , , , |
Other Authors: | , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2021
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Subjects: | |
Online Access: | https://hal.science/hal-03414134 https://hal.science/hal-03414134/document https://hal.science/hal-03414134/file/Ayouche_2021_fmarsys.pdf https://doi.org/10.3389/fmars.2021.701773 |
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ftutoulouse3hal:oai:HAL:hal-03414134v1 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Université Toulouse III - Paul Sabatier: HAL-UPS |
op_collection_id |
ftutoulouse3hal |
language |
English |
topic |
river plumes buoyant fronts (sub)mesoscale instabilities PV mixing stratification Gironde river Bay of Biscay [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
river plumes buoyant fronts (sub)mesoscale instabilities PV mixing stratification Gironde river Bay of Biscay [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Ayouche, Adam Charria, Guillaume Carton, Xavier Ayoub, N.K. Theetten, Sébastien Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
topic_facet |
river plumes buoyant fronts (sub)mesoscale instabilities PV mixing stratification Gironde river Bay of Biscay [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
International audience Instability and mixing are ubiquitous processes in river plumes but their small spatial and temporal scales often limit their observation and analysis. We investigate flow instability and mixing processes in the Gironde river plume (Bay of Biscay, North-East Atlantic ocean) in response to air-sea fluxes, tidal currents, and winds. High-resolution numerical simulations are conducted in March (average river discharge) and in August (low discharge) to explore such processes. Two areas of the Gironde river plume (the bulge and the coastal current) experience different instabilities: barotropic, baroclinic, symmetric, and/or vertical shear instabilities. Energy conversion terms reveal the coexistence of barotropic and baroclinic instabilities in the bulge and in the coastal current during both months. These instabilities are intensified over the whole domain in August and over the inner-shelf in March. The Hoskins criterion indicates that symmetric instability exists in most parts of the plume during both periods. The evolution of the Gironde plume with the summer stratification, tidal currents and winds favors its development. During both seasons, ageostrophic flow and large Rossby numbers characterize rapidly-growing and small-scale frontal baroclinic and symmetric instabilities. The transition between these instabilities is investigated with an EKE decomposition on the modes of instability. In the frontal region of the plume, during both months, symmetric instabilities grow first followed by baroclinic and mixed ones, during wind bursts and/or high discharge events. In contrast, when the wind is weak or relaxing, baroclinic instabilities grow first followed by symmetric and then mixed ones. Their growth periods range from a few hours to a few days. Mixing at the ocean surface is analyzed via Potential Vorticity (PV) fluxes. The net injection of PV at the ocean surface occurs at submesoscale buoyant fronts of the Gironde plume during both months. Vertical mixing at these fronts has similar ... |
author2 |
Laboratoire d'Océanographie Physique et Spatiale (LOPS) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Ayouche, Adam Charria, Guillaume Carton, Xavier Ayoub, N.K. Theetten, Sébastien |
author_facet |
Ayouche, Adam Charria, Guillaume Carton, Xavier Ayoub, N.K. Theetten, Sébastien |
author_sort |
Ayouche, Adam |
title |
Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
title_short |
Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
title_full |
Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
title_fullStr |
Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
title_full_unstemmed |
Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing |
title_sort |
non-linear processes in the gironde river plume (north-east atlantic): instabilities and mixing |
publisher |
HAL CCSD |
publishDate |
2021 |
url |
https://hal.science/hal-03414134 https://hal.science/hal-03414134/document https://hal.science/hal-03414134/file/Ayouche_2021_fmarsys.pdf https://doi.org/10.3389/fmars.2021.701773 |
genre |
North East Atlantic |
genre_facet |
North East Atlantic |
op_source |
ISSN: 2296-7745 Frontiers in Marine Science https://hal.science/hal-03414134 Frontiers in Marine Science, 2021, 8, ⟨10.3389/fmars.2021.701773⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.3389/fmars.2021.701773 hal-03414134 https://hal.science/hal-03414134 https://hal.science/hal-03414134/document https://hal.science/hal-03414134/file/Ayouche_2021_fmarsys.pdf doi:10.3389/fmars.2021.701773 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.3389/fmars.2021.701773 |
container_title |
Frontiers in Marine Science |
container_volume |
8 |
_version_ |
1810465107701923840 |
spelling |
ftutoulouse3hal:oai:HAL:hal-03414134v1 2024-09-15T18:24:42+00:00 Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing Ayouche, Adam Charria, Guillaume Carton, Xavier Ayoub, N.K. Theetten, Sébastien Laboratoire d'Océanographie Physique et Spatiale (LOPS) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) 2021-06-30 https://hal.science/hal-03414134 https://hal.science/hal-03414134/document https://hal.science/hal-03414134/file/Ayouche_2021_fmarsys.pdf https://doi.org/10.3389/fmars.2021.701773 en eng HAL CCSD Frontiers Media info:eu-repo/semantics/altIdentifier/doi/10.3389/fmars.2021.701773 hal-03414134 https://hal.science/hal-03414134 https://hal.science/hal-03414134/document https://hal.science/hal-03414134/file/Ayouche_2021_fmarsys.pdf doi:10.3389/fmars.2021.701773 info:eu-repo/semantics/OpenAccess ISSN: 2296-7745 Frontiers in Marine Science https://hal.science/hal-03414134 Frontiers in Marine Science, 2021, 8, ⟨10.3389/fmars.2021.701773⟩ river plumes buoyant fronts (sub)mesoscale instabilities PV mixing stratification Gironde river Bay of Biscay [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2021 ftutoulouse3hal https://doi.org/10.3389/fmars.2021.701773 2024-06-25T00:11:19Z International audience Instability and mixing are ubiquitous processes in river plumes but their small spatial and temporal scales often limit their observation and analysis. We investigate flow instability and mixing processes in the Gironde river plume (Bay of Biscay, North-East Atlantic ocean) in response to air-sea fluxes, tidal currents, and winds. High-resolution numerical simulations are conducted in March (average river discharge) and in August (low discharge) to explore such processes. Two areas of the Gironde river plume (the bulge and the coastal current) experience different instabilities: barotropic, baroclinic, symmetric, and/or vertical shear instabilities. Energy conversion terms reveal the coexistence of barotropic and baroclinic instabilities in the bulge and in the coastal current during both months. These instabilities are intensified over the whole domain in August and over the inner-shelf in March. The Hoskins criterion indicates that symmetric instability exists in most parts of the plume during both periods. The evolution of the Gironde plume with the summer stratification, tidal currents and winds favors its development. During both seasons, ageostrophic flow and large Rossby numbers characterize rapidly-growing and small-scale frontal baroclinic and symmetric instabilities. The transition between these instabilities is investigated with an EKE decomposition on the modes of instability. In the frontal region of the plume, during both months, symmetric instabilities grow first followed by baroclinic and mixed ones, during wind bursts and/or high discharge events. In contrast, when the wind is weak or relaxing, baroclinic instabilities grow first followed by symmetric and then mixed ones. Their growth periods range from a few hours to a few days. Mixing at the ocean surface is analyzed via Potential Vorticity (PV) fluxes. The net injection of PV at the ocean surface occurs at submesoscale buoyant fronts of the Gironde plume during both months. Vertical mixing at these fronts has similar ... Article in Journal/Newspaper North East Atlantic Université Toulouse III - Paul Sabatier: HAL-UPS Frontiers in Marine Science 8 |