An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation
International audience Hydrographic transects of the Antarctic Circumpolar Current (ACC) south of Africa are projected into baroclinic stream function space parameterized by pressure and dynamic height. This produces a two‐dimensional gravest empirical mode (GEM) that captures more than 97% of the t...
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ftunivbrest:oai:HAL:hal-00495100v1 2023-12-17T10:22:00+01:00 An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation Swart, Sebastiaan Speich, Sabrina Ansorge, Isabelle J. Lutjeharms, Johann R.E. Department of Oceanography Cape Town University of Cape Town Laboratoire de physique des océans (LPO) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) 2010 https://hal.science/hal-00495100 https://doi.org/10.1029/2009JC005299 en eng HAL CCSD Wiley-Blackwell info:eu-repo/semantics/altIdentifier/doi/10.1029/2009JC005299 hal-00495100 https://hal.science/hal-00495100 doi:10.1029/2009JC005299 ISSN: 2169-9275 EISSN: 2169-9291 Journal of Geophysical Research. Oceans https://hal.science/hal-00495100 Journal of Geophysical Research. Oceans, 2010, 115, pp.C03002. ⟨10.1029/2009JC005299⟩ [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/article Journal articles 2010 ftunivbrest https://doi.org/10.1029/2009JC005299 2023-11-21T23:37:03Z International audience Hydrographic transects of the Antarctic Circumpolar Current (ACC) south of Africa are projected into baroclinic stream function space parameterized by pressure and dynamic height. This produces a two‐dimensional gravest empirical mode (GEM) that captures more than 97% of the total density and temperature variance in the ACC domain. Weekly maps of absolute dynamic topography data, derived from satellite altimetry, are combined with the GEM to obtain a 16 year time series of temperature and salinity fields. The time series of thermohaline fields are compared with independent in situ observations. The residuals decrease sharply below the thermocline and through the entire water column the mean root‐mean‐square (RMS) error is 0.15°C, 0.02, and 0.02 kg m−3 for temperature, salinity, and density, respectively. The positions of ACC fronts are followed in time using satellite altimetry data. These locations correspond to both the observed and GEM‐based positions. The available temperature and salinity information allow one to calculate the baroclinic zonal velocity field between the surface and 2500 dbar. This is compared with velocity measurements from repeat hydrographic transects at the GoodHope line. The net accumulated transports of the ACC, derived from these different methods are within 1–3 Sv of each other. Similarly, GEM‐produced cross‐sectional velocities at 300 dbar compare closely to the observed data, with the RMS difference not exceeding 0.03 m s−1. The continuous time series of thermohaline fields, described here, are further exploited to understand the dynamic nature of the ACC fronts in the region, and which is given by Swart and Speich (2010) Article in Journal/Newspaper Antarc* Antarctic Université de Bretagne Occidentale: HAL Antarctic The Antarctic Journal of Geophysical Research 115 C3 |
institution |
Open Polar |
collection |
Université de Bretagne Occidentale: HAL |
op_collection_id |
ftunivbrest |
language |
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 Swart, Sebastiaan Speich, Sabrina Ansorge, Isabelle J. Lutjeharms, Johann R.E. An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
topic_facet |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
International audience Hydrographic transects of the Antarctic Circumpolar Current (ACC) south of Africa are projected into baroclinic stream function space parameterized by pressure and dynamic height. This produces a two‐dimensional gravest empirical mode (GEM) that captures more than 97% of the total density and temperature variance in the ACC domain. Weekly maps of absolute dynamic topography data, derived from satellite altimetry, are combined with the GEM to obtain a 16 year time series of temperature and salinity fields. The time series of thermohaline fields are compared with independent in situ observations. The residuals decrease sharply below the thermocline and through the entire water column the mean root‐mean‐square (RMS) error is 0.15°C, 0.02, and 0.02 kg m−3 for temperature, salinity, and density, respectively. The positions of ACC fronts are followed in time using satellite altimetry data. These locations correspond to both the observed and GEM‐based positions. The available temperature and salinity information allow one to calculate the baroclinic zonal velocity field between the surface and 2500 dbar. This is compared with velocity measurements from repeat hydrographic transects at the GoodHope line. The net accumulated transports of the ACC, derived from these different methods are within 1–3 Sv of each other. Similarly, GEM‐produced cross‐sectional velocities at 300 dbar compare closely to the observed data, with the RMS difference not exceeding 0.03 m s−1. The continuous time series of thermohaline fields, described here, are further exploited to understand the dynamic nature of the ACC fronts in the region, and which is given by Swart and Speich (2010) |
author2 |
Department of Oceanography Cape Town University of Cape Town Laboratoire de physique des océans (LPO) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Swart, Sebastiaan Speich, Sabrina Ansorge, Isabelle J. Lutjeharms, Johann R.E. |
author_facet |
Swart, Sebastiaan Speich, Sabrina Ansorge, Isabelle J. Lutjeharms, Johann R.E. |
author_sort |
Swart, Sebastiaan |
title |
An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
title_short |
An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
title_full |
An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
title_fullStr |
An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
title_full_unstemmed |
An altimetry‐based gravest empirical mode south of Africa: 1. Development and validation |
title_sort |
altimetry‐based gravest empirical mode south of africa: 1. development and validation |
publisher |
HAL CCSD |
publishDate |
2010 |
url |
https://hal.science/hal-00495100 https://doi.org/10.1029/2009JC005299 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
ISSN: 2169-9275 EISSN: 2169-9291 Journal of Geophysical Research. Oceans https://hal.science/hal-00495100 Journal of Geophysical Research. Oceans, 2010, 115, pp.C03002. ⟨10.1029/2009JC005299⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1029/2009JC005299 hal-00495100 https://hal.science/hal-00495100 doi:10.1029/2009JC005299 |
op_doi |
https://doi.org/10.1029/2009JC005299 |
container_title |
Journal of Geophysical Research |
container_volume |
115 |
container_issue |
C3 |
_version_ |
1785541710277771264 |