Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model
International audience A 1/6° numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Ros...
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Online Access: | https://hal.science/hal-00331150 https://hal.science/hal-00331150/document https://hal.science/hal-00331150/file/os-4-99-2008.pdf https://doi.org/10.5194/os-4-99-2008 |
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ftunivnantes:oai:HAL:hal-00331150v1 2023-05-15T17:31:36+02:00 Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model Lecointre, Albanne Penduff, Thierry Cipollini, Paolo Tailleux, Remi Barnier, Bernard Laboratoire des Écoulements Géophysiques et Industriels Grenoble (LEGI) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS) National Oceanography Centre Southampton (NOC) University of Southampton Department of Meteorology 2008-03-18 https://hal.science/hal-00331150 https://hal.science/hal-00331150/document https://hal.science/hal-00331150/file/os-4-99-2008.pdf https://doi.org/10.5194/os-4-99-2008 en eng HAL CCSD European Geosciences Union info:eu-repo/semantics/altIdentifier/doi/10.5194/os-4-99-2008 hal-00331150 https://hal.science/hal-00331150 https://hal.science/hal-00331150/document https://hal.science/hal-00331150/file/os-4-99-2008.pdf doi:10.5194/os-4-99-2008 http://creativecommons.org/licenses/by/ info:eu-repo/semantics/OpenAccess ISSN: 1812-0784 EISSN: 1812-0792 Ocean Science https://hal.science/hal-00331150 Ocean Science, 2008, 4 (1), pp.99-113. ⟨10.5194/os-4-99-2008⟩ [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2008 ftunivnantes https://doi.org/10.5194/os-4-99-2008 2023-03-01T02:21:49Z International audience A 1/6° numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Rossby waves (RW), is first assessed by comparing the simulated amplitude and zonal phase speeds of Sea Level Anomalies (SLA) against TOPEX/Poseidon-ERS satellite altimeter data. Then, the (unobserved) subsurface signature of RW phase speeds is investigated from model outputs by means of the Radon Transform which was specifically adapted to focus on first-mode baroclinic RW. The analysis is performed on observed and simulated SLA and along 9 simulated isopycnal displacements spanning the 0-3250 m depth range. Simulated RW phase speeds agree well with their observed counterparts at the surface, although with a slight slow bias. Below the surface, the simulated phase speeds exhibit a systematic deceleration with increasing depth, by a factor that appears to vary geographically. Thus, while the reduction factor is about 15-18% on average at 3250 m over the region considered, it appears to be much weaker (about 5-8%) in the eddy-active Azores Current, where westward propagating structures might be more coherent in the vertical. In the context of linear theories, these results question the often-made normal mode assumption of many WKB-based theories that the phase speed is independent of depth. Alternatively, these results could also suggest that the vertical structure of westward propagating signals may significantly depend on their degree of nonlinearity, with the degree of vertical coherence possibly increasing with the degree of nonlinearity. Article in Journal/Newspaper North Atlantic Université de Nantes: HAL-UNIV-NANTES Ocean Science 4 1 99 113 |
institution |
Open Polar |
collection |
Université de Nantes: HAL-UNIV-NANTES |
op_collection_id |
ftunivnantes |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Lecointre, Albanne Penduff, Thierry Cipollini, Paolo Tailleux, Remi Barnier, Bernard Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
International audience A 1/6° numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Rossby waves (RW), is first assessed by comparing the simulated amplitude and zonal phase speeds of Sea Level Anomalies (SLA) against TOPEX/Poseidon-ERS satellite altimeter data. Then, the (unobserved) subsurface signature of RW phase speeds is investigated from model outputs by means of the Radon Transform which was specifically adapted to focus on first-mode baroclinic RW. The analysis is performed on observed and simulated SLA and along 9 simulated isopycnal displacements spanning the 0-3250 m depth range. Simulated RW phase speeds agree well with their observed counterparts at the surface, although with a slight slow bias. Below the surface, the simulated phase speeds exhibit a systematic deceleration with increasing depth, by a factor that appears to vary geographically. Thus, while the reduction factor is about 15-18% on average at 3250 m over the region considered, it appears to be much weaker (about 5-8%) in the eddy-active Azores Current, where westward propagating structures might be more coherent in the vertical. In the context of linear theories, these results question the often-made normal mode assumption of many WKB-based theories that the phase speed is independent of depth. Alternatively, these results could also suggest that the vertical structure of westward propagating signals may significantly depend on their degree of nonlinearity, with the degree of vertical coherence possibly increasing with the degree of nonlinearity. |
author2 |
Laboratoire des Écoulements Géophysiques et Industriels Grenoble (LEGI) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS) National Oceanography Centre Southampton (NOC) University of Southampton Department of Meteorology |
format |
Article in Journal/Newspaper |
author |
Lecointre, Albanne Penduff, Thierry Cipollini, Paolo Tailleux, Remi Barnier, Bernard |
author_facet |
Lecointre, Albanne Penduff, Thierry Cipollini, Paolo Tailleux, Remi Barnier, Bernard |
author_sort |
Lecointre, Albanne |
title |
Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
title_short |
Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
title_full |
Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
title_fullStr |
Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
title_full_unstemmed |
Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model |
title_sort |
depth dependence of westward-propagating north atlantic features diagnosed from altimetry and a numerical 1/6° model |
publisher |
HAL CCSD |
publishDate |
2008 |
url |
https://hal.science/hal-00331150 https://hal.science/hal-00331150/document https://hal.science/hal-00331150/file/os-4-99-2008.pdf https://doi.org/10.5194/os-4-99-2008 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
ISSN: 1812-0784 EISSN: 1812-0792 Ocean Science https://hal.science/hal-00331150 Ocean Science, 2008, 4 (1), pp.99-113. ⟨10.5194/os-4-99-2008⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.5194/os-4-99-2008 hal-00331150 https://hal.science/hal-00331150 https://hal.science/hal-00331150/document https://hal.science/hal-00331150/file/os-4-99-2008.pdf doi:10.5194/os-4-99-2008 |
op_rights |
http://creativecommons.org/licenses/by/ info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.5194/os-4-99-2008 |
container_title |
Ocean Science |
container_volume |
4 |
container_issue |
1 |
container_start_page |
99 |
op_container_end_page |
113 |
_version_ |
1766129255315406848 |