North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation
At multidecadal time-scales, the principal mode of variability in the North Atlantic is referred to as the AMO (Atlantic Multidecadal Oscillation). It is revealed by oceanic observations, but its origin remains unclear. Some studies describe the AMO as an oceanic mode forced by the atmosphere, while...
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ftccsdartic:oai:HAL:tel-01941078v1 2023-05-15T17:28:11+02:00 North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation Variabilité de l'Atlantique Nord dans un modèle couplé idéalisé : L'Oscillation Multidécennale Atlantique Jamet, Quentin 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) Université de Bretagne occidentale - Brest Alain Colin de Verdière 2015-11-27 https://tel.archives-ouvertes.fr/tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078/document https://tel.archives-ouvertes.fr/tel-01941078/file/These-2015-EDSM-Oceanographie_physique-JAMET_Quentin.pdf fr fre HAL CCSD NNT: 2015BRES0071 tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078/document https://tel.archives-ouvertes.fr/tel-01941078/file/These-2015-EDSM-Oceanographie_physique-JAMET_Quentin.pdf info:eu-repo/semantics/OpenAccess https://tel.archives-ouvertes.fr/tel-01941078 Océanographie. Université de Bretagne occidentale - Brest, 2015. Français. ⟨NNT : 2015BRES0071⟩ X [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/doctoralThesis Theses 2015 ftccsdartic 2021-10-17T00:42:39Z At multidecadal time-scales, the principal mode of variability in the North Atlantic is referred to as the AMO (Atlantic Multidecadal Oscillation). It is revealed by oceanic observations, but its origin remains unclear. Some studies describe the AMO as an oceanic mode forced by the atmosphere, while other studies describe the AMO as an intrinsic oceanic mode. This significant disagreement mainly results from the methods that are used by these different studies, i.e statistical analysis of observations and climate models data vs. idealized simulations and sensitivity experiments.In this PhD thesis, we focus on mechanisms that drive the low frequency North Atlantic variability in a range of simulations. Three coupled configurations of the MITgcm are integrated, with horizontal resolution of 4°, 2° and 1° (in both the ocean and the atmosphere). The idealized oceanic geometry is a flat bottom, with two meridional boundaries that delimit a small basin, comparable to the Atlantic. All these three configurations reproduce a 30-40 year variability of the Atlantic MOC (Meridional Overturning Circulation), associated with large scale Rossby waves that travel across the small basin. This variability remains in ocean-only experiments. The North Atlantic oceanic variability in these simulations is then intrinsically driven.Furthermore, increasing the horizontal resolution strengthen the ocean-atmosphere coupling, with a NAO (NorthAtlantic Oscillation) that becomes significantly correlated to the MOC two years latter at 1°. Such correlations are usually found in most climate models and observations. Some studies then infer that the oceanic variability is forced by the atmosphere.Nevertheless, our sensitivity experiments to ocean-atmosphere coupling highlight that correlations do not necessarily imply causality. These experiments provide a relatively simple and illustrating example. They show that significant lag correlations can be misleading for the identification of driving processes in the context of North Atlantic low ... Doctoral or Postdoctoral Thesis North Atlantic Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
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Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
French |
topic |
X [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
X [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Jamet, Quentin North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
topic_facet |
X [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
At multidecadal time-scales, the principal mode of variability in the North Atlantic is referred to as the AMO (Atlantic Multidecadal Oscillation). It is revealed by oceanic observations, but its origin remains unclear. Some studies describe the AMO as an oceanic mode forced by the atmosphere, while other studies describe the AMO as an intrinsic oceanic mode. This significant disagreement mainly results from the methods that are used by these different studies, i.e statistical analysis of observations and climate models data vs. idealized simulations and sensitivity experiments.In this PhD thesis, we focus on mechanisms that drive the low frequency North Atlantic variability in a range of simulations. Three coupled configurations of the MITgcm are integrated, with horizontal resolution of 4°, 2° and 1° (in both the ocean and the atmosphere). The idealized oceanic geometry is a flat bottom, with two meridional boundaries that delimit a small basin, comparable to the Atlantic. All these three configurations reproduce a 30-40 year variability of the Atlantic MOC (Meridional Overturning Circulation), associated with large scale Rossby waves that travel across the small basin. This variability remains in ocean-only experiments. The North Atlantic oceanic variability in these simulations is then intrinsically driven.Furthermore, increasing the horizontal resolution strengthen the ocean-atmosphere coupling, with a NAO (NorthAtlantic Oscillation) that becomes significantly correlated to the MOC two years latter at 1°. Such correlations are usually found in most climate models and observations. Some studies then infer that the oceanic variability is forced by the atmosphere.Nevertheless, our sensitivity experiments to ocean-atmosphere coupling highlight that correlations do not necessarily imply causality. These experiments provide a relatively simple and illustrating example. They show that significant lag correlations can be misleading for the identification of driving processes in the context of North Atlantic low ... |
author2 |
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) Université de Bretagne occidentale - Brest Alain Colin de Verdière |
format |
Doctoral or Postdoctoral Thesis |
author |
Jamet, Quentin |
author_facet |
Jamet, Quentin |
author_sort |
Jamet, Quentin |
title |
North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
title_short |
North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
title_full |
North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
title_fullStr |
North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
title_full_unstemmed |
North Atlantic variability in an idealized coupled model : the Atlantic Multidecadal Oscillation |
title_sort |
north atlantic variability in an idealized coupled model : the atlantic multidecadal oscillation |
publisher |
HAL CCSD |
publishDate |
2015 |
url |
https://tel.archives-ouvertes.fr/tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078/document https://tel.archives-ouvertes.fr/tel-01941078/file/These-2015-EDSM-Oceanographie_physique-JAMET_Quentin.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
https://tel.archives-ouvertes.fr/tel-01941078 Océanographie. Université de Bretagne occidentale - Brest, 2015. Français. ⟨NNT : 2015BRES0071⟩ |
op_relation |
NNT: 2015BRES0071 tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078 https://tel.archives-ouvertes.fr/tel-01941078/document https://tel.archives-ouvertes.fr/tel-01941078/file/These-2015-EDSM-Oceanographie_physique-JAMET_Quentin.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1766120727434493952 |