Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation
This study addresses the role of oceanic small-scale processes in the formation and transformation of subsurface waters that participate in the Indo-Atlantic interocean exchange.We focus on the Cape Basin dynamics, characterized by a highly non-linear turbulence.We provide qualitative and quantitati...
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ftunivbrest:oai:HAL:tel-01760721v1 2024-04-14T08:04:07+00:00 Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation Dynamiques océaniques à petite échelle dans le Bassin du Cap et leur impact sur la circulation régionale Capuano, Tonia Astrid 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) Université de Bretagne occidentale - Brest Xavier Carton Sabrina Speich 2017-12-04 https://theses.hal.science/tel-01760721 https://theses.hal.science/tel-01760721/document https://theses.hal.science/tel-01760721/file/These-2017-SML-Oceanographie_physique-CAPUANO_Tonia_Astrid.pdf fr fre HAL CCSD NNT: 2017BRES0115 tel-01760721 https://theses.hal.science/tel-01760721 https://theses.hal.science/tel-01760721/document https://theses.hal.science/tel-01760721/file/These-2017-SML-Oceanographie_physique-CAPUANO_Tonia_Astrid.pdf info:eu-repo/semantics/OpenAccess https://theses.hal.science/tel-01760721 Océanographie. Université de Bretagne occidentale - Brest, 2017. Français. ⟨NNT : 2017BRES0115⟩ Meso- and submesoscale processes Indo-Atlantic exchange Water masses dynamics Processus de méso- et sous-méso- échelle Échange Indo-Atlantique Dynamiques des masses d’eau [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/doctoralThesis Theses 2017 ftunivbrest 2024-03-21T16:27:25Z This study addresses the role of oceanic small-scale processes in the formation and transformation of subsurface waters that participate in the Indo-Atlantic interocean exchange.We focus on the Cape Basin dynamics, characterized by a highly non-linear turbulence.We provide qualitative and quantitative evidence of the direct impact that meso- and submesoscale structures, their dynamical interactions and their seasonal variability have on the local thermocline and intermediate waters. A sequence of numerical simulations, ranging from ’eddy-permitting’ to ’submesoscale resolving’, underlines the importance of an adequate vertical resolution to correctly depict the water masses properties.We point out that Agulhas eddies are mainly generated through baroclinic instabilities and are marked by a clear seasonality. This is linked to the seasonal occurrence of distinct meso-submesoscale instabilities in the upper layers: symmetric instabilities are at play during summer, while mixed-layer instabilities prevail in winter.We also found that Charney baroclinic instability connects these two submesoscale regimes and plays a major role in the seasonal formation of a newly-identified type of mode waters: Agulhas Rings Mode Water. Finally, we show that eddies of both polarity advect, stir and mix Antarctic Intermediate Water, via the mesoscale strain field producing filaments and T-S fine-scale structures.Our results suggest the existence of two dynamical regimes affecting the upper and intermediate layers of the Cape Basin. Near the surface, the submesoscale-driven frontogenesis and their enhanced energetics lead to a predominance of ageostrophic dynamics. The intermediate depths are, instead, characterised by a quasigesotrophic regime due to the prevailing mesoscale effects. Nous étudions le rôle des processus océaniques à petite échelle dans la formation et transformation des eaux de surface et intermédiaires qui participent à l’échange Indo- Atlantique à travers le Bassin du Cap. La dynamique de cette région est ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Université de Bretagne Occidentale: HAL Antarctic |
institution |
Open Polar |
collection |
Université de Bretagne Occidentale: HAL |
op_collection_id |
ftunivbrest |
language |
French |
topic |
Meso- and submesoscale processes Indo-Atlantic exchange Water masses dynamics Processus de méso- et sous-méso- échelle Échange Indo-Atlantique Dynamiques des masses d’eau [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
Meso- and submesoscale processes Indo-Atlantic exchange Water masses dynamics Processus de méso- et sous-méso- échelle Échange Indo-Atlantique Dynamiques des masses d’eau [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Capuano, Tonia Astrid Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
topic_facet |
Meso- and submesoscale processes Indo-Atlantic exchange Water masses dynamics Processus de méso- et sous-méso- échelle Échange Indo-Atlantique Dynamiques des masses d’eau [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
This study addresses the role of oceanic small-scale processes in the formation and transformation of subsurface waters that participate in the Indo-Atlantic interocean exchange.We focus on the Cape Basin dynamics, characterized by a highly non-linear turbulence.We provide qualitative and quantitative evidence of the direct impact that meso- and submesoscale structures, their dynamical interactions and their seasonal variability have on the local thermocline and intermediate waters. A sequence of numerical simulations, ranging from ’eddy-permitting’ to ’submesoscale resolving’, underlines the importance of an adequate vertical resolution to correctly depict the water masses properties.We point out that Agulhas eddies are mainly generated through baroclinic instabilities and are marked by a clear seasonality. This is linked to the seasonal occurrence of distinct meso-submesoscale instabilities in the upper layers: symmetric instabilities are at play during summer, while mixed-layer instabilities prevail in winter.We also found that Charney baroclinic instability connects these two submesoscale regimes and plays a major role in the seasonal formation of a newly-identified type of mode waters: Agulhas Rings Mode Water. Finally, we show that eddies of both polarity advect, stir and mix Antarctic Intermediate Water, via the mesoscale strain field producing filaments and T-S fine-scale structures.Our results suggest the existence of two dynamical regimes affecting the upper and intermediate layers of the Cape Basin. Near the surface, the submesoscale-driven frontogenesis and their enhanced energetics lead to a predominance of ageostrophic dynamics. The intermediate depths are, instead, characterised by a quasigesotrophic regime due to the prevailing mesoscale effects. Nous étudions le rôle des processus océaniques à petite échelle dans la formation et transformation des eaux de surface et intermédiaires qui participent à l’échange Indo- Atlantique à travers le Bassin du Cap. La dynamique de cette région est ... |
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) Université de Bretagne occidentale - Brest Xavier Carton Sabrina Speich |
format |
Doctoral or Postdoctoral Thesis |
author |
Capuano, Tonia Astrid |
author_facet |
Capuano, Tonia Astrid |
author_sort |
Capuano, Tonia Astrid |
title |
Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
title_short |
Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
title_full |
Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
title_fullStr |
Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
title_full_unstemmed |
Small-scale ocean dynamics in the Cape Basin and its impact on the regional circulation |
title_sort |
small-scale ocean dynamics in the cape basin and its impact on the regional circulation |
publisher |
HAL CCSD |
publishDate |
2017 |
url |
https://theses.hal.science/tel-01760721 https://theses.hal.science/tel-01760721/document https://theses.hal.science/tel-01760721/file/These-2017-SML-Oceanographie_physique-CAPUANO_Tonia_Astrid.pdf |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
https://theses.hal.science/tel-01760721 Océanographie. Université de Bretagne occidentale - Brest, 2017. Français. ⟨NNT : 2017BRES0115⟩ |
op_relation |
NNT: 2017BRES0115 tel-01760721 https://theses.hal.science/tel-01760721 https://theses.hal.science/tel-01760721/document https://theses.hal.science/tel-01760721/file/These-2017-SML-Oceanographie_physique-CAPUANO_Tonia_Astrid.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1796300495906668544 |