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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ftunivnantes:oai:HAL:hal-00331135v1 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, P. Tailleux, Rémi 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 2007-11-12 https://hal.science/hal-00331135 https://hal.science/hal-00331135/document https://hal.science/hal-00331135/file/osd-4-817-2007.pdf en eng HAL CCSD European Geosciences Union hal-00331135 https://hal.science/hal-00331135 https://hal.science/hal-00331135/document https://hal.science/hal-00331135/file/osd-4-817-2007.pdf info:eu-repo/semantics/OpenAccess ISSN: 1812-0806 EISSN: 1812-0822 Ocean Science Discussions https://hal.science/hal-00331135 Ocean Science Discussions, 2007, 4 (6), pp.817-853 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2007 ftunivnantes 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. These results suggest that the often-made normal-mode assumption of many WKB-based extended theories that the phase speed is independent of depth might need to be revisited. They also suggest that the vertical structure of westward propagating signals could 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 |
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, P. Tailleux, Rémi 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. These results suggest that the often-made normal-mode assumption of many WKB-based extended theories that the phase speed is independent of depth might need to be revisited. They also suggest that the vertical structure of westward propagating signals could 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, P. Tailleux, Rémi Barnier, Bernard |
author_facet |
Lecointre, Albanne Penduff, Thierry Cipollini, P. Tailleux, Rémi 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 |
2007 |
url |
https://hal.science/hal-00331135 https://hal.science/hal-00331135/document https://hal.science/hal-00331135/file/osd-4-817-2007.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
ISSN: 1812-0806 EISSN: 1812-0822 Ocean Science Discussions https://hal.science/hal-00331135 Ocean Science Discussions, 2007, 4 (6), pp.817-853 |
op_relation |
hal-00331135 https://hal.science/hal-00331135 https://hal.science/hal-00331135/document https://hal.science/hal-00331135/file/osd-4-817-2007.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1766129255515684864 |