Defining Southern Ocean fronts using unsupervised classification
International audience Oceanographic fronts are transitions between thermohaline structures with different characteristics. Such transitions are ubiquitous, and their locations and properties affect how the ocean operates as part of the global climate system. In the Southern Ocean, fronts have class...
Published in: | Ocean Science |
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Main Authors: | , , , , |
Other Authors: | , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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HAL CCSD
2021
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Online Access: | https://hal.sorbonne-universite.fr/hal-03460572 https://hal.sorbonne-universite.fr/hal-03460572/document https://hal.sorbonne-universite.fr/hal-03460572/file/os-17-1545-2021.pdf https://doi.org/10.5194/os-17-1545-2021 |
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École Polytechnique, Université Paris-Saclay: HAL |
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ftepunivpsaclay |
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English |
topic |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Thomas, Simon D. A. Jones, Daniel C. Faul, Anita Mackie, Erik Pauthenet, Etienne Defining Southern Ocean fronts using unsupervised classification |
topic_facet |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
International audience Oceanographic fronts are transitions between thermohaline structures with different characteristics. Such transitions are ubiquitous, and their locations and properties affect how the ocean operates as part of the global climate system. In the Southern Ocean, fronts have classically been defined using a small number of continuous, circumpolar features in sea surface height or dynamic height. Modern observational and theoretical developments are challenging and expanding this traditional framework to accommodate a more complex view of fronts. Here, we present a complementary new approach for calculating fronts using an unsupervised classification method called Gaussian mixture modelling (GMM) and a novel inter-class parameter called the I-metric. The I-metric approach produces a probabilistic view of front location, emphasising the fact that the boundaries between water masses are not uniformly sharp across the entire Southern Ocean. The I-metric approach uses thermohaline information from a range of depth levels, making it more general than approaches that only use near-surface properties. We train the GMM using an observationally constrained state estimate in order to have more uniform spatial and temporal data coverage. The probabilistic boundaries defined by the I-metric roughly coincide with several classically defined fronts, offering a novel view of this structure. The I-metric fronts appear to be relatively sharp in the open ocean and somewhat diffuse near large topographic features, possibly highlighting the importance of topographically induced mixing. For comparison with a more localised method, we also use an edge detection approach for identifying fronts. We find a strong correlation between the edge field of the leading principal component and the zonal velocity; the edge detection method highlights the presence of jets, which are supported by thermal wind balance. This more localised method highlights the complex, multiscale structure of Southern Ocean fronts, complementing ... |
author2 |
British Antarctic Survey (BAS) Natural Environment Research Council (NERC) University of Cambridge UK (CAM) Processus et interactions de fine échelle océanique (PROTEO) Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN) Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) European Project: 637770,H2020,ERC-2014-STG,WAPITI(2015) |
format |
Article in Journal/Newspaper |
author |
Thomas, Simon D. A. Jones, Daniel C. Faul, Anita Mackie, Erik Pauthenet, Etienne |
author_facet |
Thomas, Simon D. A. Jones, Daniel C. Faul, Anita Mackie, Erik Pauthenet, Etienne |
author_sort |
Thomas, Simon D. A. |
title |
Defining Southern Ocean fronts using unsupervised classification |
title_short |
Defining Southern Ocean fronts using unsupervised classification |
title_full |
Defining Southern Ocean fronts using unsupervised classification |
title_fullStr |
Defining Southern Ocean fronts using unsupervised classification |
title_full_unstemmed |
Defining Southern Ocean fronts using unsupervised classification |
title_sort |
defining southern ocean fronts using unsupervised classification |
publisher |
HAL CCSD |
publishDate |
2021 |
url |
https://hal.sorbonne-universite.fr/hal-03460572 https://hal.sorbonne-universite.fr/hal-03460572/document https://hal.sorbonne-universite.fr/hal-03460572/file/os-17-1545-2021.pdf https://doi.org/10.5194/os-17-1545-2021 |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
ISSN: 1812-0784 EISSN: 1812-0792 Ocean Science https://hal.sorbonne-universite.fr/hal-03460572 Ocean Science, 2021, 17 (6), pp.1545 - 1562. ⟨10.5194/os-17-1545-2021⟩ |
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op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.5194/os-17-1545-2021 |
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Ocean Science |
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17 |
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6 |
container_start_page |
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1562 |
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ftepunivpsaclay:oai:HAL:hal-03460572v1 2024-05-19T07:48:53+00:00 Defining Southern Ocean fronts using unsupervised classification Thomas, Simon D. A. Jones, Daniel C. Faul, Anita Mackie, Erik Pauthenet, Etienne British Antarctic Survey (BAS) Natural Environment Research Council (NERC) University of Cambridge UK (CAM) Processus et interactions de fine échelle océanique (PROTEO) Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN) Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) European Project: 637770,H2020,ERC-2014-STG,WAPITI(2015) 2021-11-02 https://hal.sorbonne-universite.fr/hal-03460572 https://hal.sorbonne-universite.fr/hal-03460572/document https://hal.sorbonne-universite.fr/hal-03460572/file/os-17-1545-2021.pdf https://doi.org/10.5194/os-17-1545-2021 en eng HAL CCSD European Geosciences Union info:eu-repo/semantics/altIdentifier/doi/10.5194/os-17-1545-2021 info:eu-repo/grantAgreement//637770/EU/Water-mass transformation and Pathways In The Weddell Sea: uncovering the dynamics of a global climate chokepoint from In-situ measurements/WAPITI hal-03460572 https://hal.sorbonne-universite.fr/hal-03460572 https://hal.sorbonne-universite.fr/hal-03460572/document https://hal.sorbonne-universite.fr/hal-03460572/file/os-17-1545-2021.pdf doi:10.5194/os-17-1545-2021 WOS: 000714373000001 info:eu-repo/semantics/OpenAccess ISSN: 1812-0784 EISSN: 1812-0792 Ocean Science https://hal.sorbonne-universite.fr/hal-03460572 Ocean Science, 2021, 17 (6), pp.1545 - 1562. ⟨10.5194/os-17-1545-2021⟩ [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/article Journal articles 2021 ftepunivpsaclay https://doi.org/10.5194/os-17-1545-2021 2024-04-25T00:40:38Z International audience Oceanographic fronts are transitions between thermohaline structures with different characteristics. Such transitions are ubiquitous, and their locations and properties affect how the ocean operates as part of the global climate system. In the Southern Ocean, fronts have classically been defined using a small number of continuous, circumpolar features in sea surface height or dynamic height. Modern observational and theoretical developments are challenging and expanding this traditional framework to accommodate a more complex view of fronts. Here, we present a complementary new approach for calculating fronts using an unsupervised classification method called Gaussian mixture modelling (GMM) and a novel inter-class parameter called the I-metric. The I-metric approach produces a probabilistic view of front location, emphasising the fact that the boundaries between water masses are not uniformly sharp across the entire Southern Ocean. The I-metric approach uses thermohaline information from a range of depth levels, making it more general than approaches that only use near-surface properties. We train the GMM using an observationally constrained state estimate in order to have more uniform spatial and temporal data coverage. The probabilistic boundaries defined by the I-metric roughly coincide with several classically defined fronts, offering a novel view of this structure. The I-metric fronts appear to be relatively sharp in the open ocean and somewhat diffuse near large topographic features, possibly highlighting the importance of topographically induced mixing. For comparison with a more localised method, we also use an edge detection approach for identifying fronts. We find a strong correlation between the edge field of the leading principal component and the zonal velocity; the edge detection method highlights the presence of jets, which are supported by thermal wind balance. This more localised method highlights the complex, multiscale structure of Southern Ocean fronts, complementing ... Article in Journal/Newspaper Southern Ocean École Polytechnique, Université Paris-Saclay: HAL Ocean Science 17 6 1545 1562 |