Influence of deep water formation on the variability of the meridional overturning circulation in the Atlantic Ocean

The oceanic meridional overturning circulation (MOC) and the associated poleward heat transport contribute substantially to the energy balance of present climate. One fundamental driver of the MOC is deep water formation in the North Atlantic. The objective of this study is to investigate the influe...

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Bibliographic Details
Main Author: Deshayes, Julie
Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), UPMC Université Paris VI, Pr Claude Frankignoul
Format: Doctoral or Postdoctoral Thesis
Language:French
Published: HAL CCSD 2006
Subjects:
PhD
Online Access:https://hal.science/tel-01138805
https://hal.science/tel-01138805/document
https://hal.science/tel-01138805/file/deshayes06_PhD.pdf
Description
Summary:The oceanic meridional overturning circulation (MOC) and the associated poleward heat transport contribute substantially to the energy balance of present climate. One fundamental driver of the MOC is deep water formation in the North Atlantic. The objective of this study is to investigate the influence of changes in the rate of deep water formation on the variability of the MOC in the Atlantic Ocean.First, we develop an analytic model to investigate the spectral characteristics of the response of the MOC to changes in the rate of deep water formation in the North Atlantic. This simple theoretical model reproduces qualitatively few characteristics of the variability of the MOC observed in climate models.Then a realistic simulation of the circulation in the North Atlantic from 1953 to 2003 is used to determine the mechanisms of variability associated with the formation and export of deep water in the subpolar North Atlantic. These mechanisms, which are consistent with observations, help to understand the link between changes in the rate of deep water formation and the variability of the transport in the Deep Western Boundary Current, which constitutes the deep limb of the MOC in the North Atlantic. Finally we investigate the influence of these mechanisms on the circulation in the North Atlantic. We show that the interannual to multidecadal variability of the MOC can be considered as an integration of the rate of deep water formation in the Irminger Sea. La stabilité du climat actuel est assurée par le transport méridien de chaleur de l’équateur vers les pôles, auquel contribue significativement la circulation océanique méridienne moyenne (MOC), qui transporte des masses d’eau denses formées dans l’AtlantiqueNord et l’Océan Antarctique en profondeur vers l’équateur. L’objet de cette thèse est de comprendre l’influence de la variabilité du taux de formation d’eau profonde dans l’Atlantique Nord sur la variabilité interannuelle à multi décennale de la MOC.Dans la première partie de la thèse, un modèle analytique ...