Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability

Atmospheric stochastic forcing associated with the North Atlantic Oscillation (NAO) and intrinsic ocean modes associated with the large-scale baroclinic instability of the North Atlantic Current (NAC) are recognized as two strong paradigms for the existence of the Atlantic Multidecadal Oscillation (...

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Published in:Journal of Climate
Main Authors: Arzel, Olivier, Huck, Thierry
Format: Article in Journal/Newspaper
Language:English
Published: American Meteorological Society 2020
Subjects:
Online Access:https://archimer.ifremer.fr/doc/00599/71138/69452.pdf
https://doi.org/10.1175/JCLI-D-19-0522.1
https://archimer.ifremer.fr/doc/00599/71138/
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spelling ftarchimer:oai:archimer.ifremer.fr:71138 2023-07-30T04:05:05+02:00 Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability Arzel, Olivier Huck, Thierry 2020-03 application/pdf https://archimer.ifremer.fr/doc/00599/71138/69452.pdf https://doi.org/10.1175/JCLI-D-19-0522.1 https://archimer.ifremer.fr/doc/00599/71138/ eng eng American Meteorological Society https://archimer.ifremer.fr/doc/00599/71138/69452.pdf doi:10.1175/JCLI-D-19-0522.1 https://archimer.ifremer.fr/doc/00599/71138/ info:eu-repo/semantics/openAccess restricted use Journal Of Climate (0894-8755) (American Meteorological Society), 2020-03 , Vol. 33 , N. 6 , P. 2351-2370 Instability Rossby waves Climate variability Interdecadal variability Multidecadal variability North Atlantic Oscillation text Article info:eu-repo/semantics/article 2020 ftarchimer https://doi.org/10.1175/JCLI-D-19-0522.1 2023-07-11T22:51:10Z Atmospheric stochastic forcing associated with the North Atlantic Oscillation (NAO) and intrinsic ocean modes associated with the large-scale baroclinic instability of the North Atlantic Current (NAC) are recognized as two strong paradigms for the existence of the Atlantic Multidecadal Oscillation (AMO). The degree to which each of these factors contribute to the low-frequency variability of the North Atlantic is the central question in this paper. This issue is addressed here using an ocean general circulation model run under a wide range of background conditions extending from a super-critical regime where the oceanic variability spontaneously develops in the absence of any atmospheric noise forcing to a damped regime where the variability requires some noise to appear. The answer to the question is captured by a single dimensionless number Γ measuring the ratio between the oceanic and atmospheric contributions, as inferred from the buoyancy variance budget of the western subpolar region. Using this diagnostic, about two-third of the sea surface temperature (SST) variance in the damped regime is shown to originate from atmospheric stochastic forcing whereas heat content is dominated by internal ocean dynamics. Stochastic wind-stress forcing is shown to substantially increase the role played by damped ocean modes in the variability. The thermal structure of the variability is shown to differ fundamentally between the super-critical and damped regimes, with abrupt modifications around the transition between the two regimes. Ocean circulation changes are further shown to be unimportant for setting the pattern of SST variability in the damped regime but are fundamental for a preferred timescale to emerge. Article in Journal/Newspaper north atlantic current North Atlantic North Atlantic oscillation Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Journal of Climate 33 6 2351 2370
institution Open Polar
collection Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer)
op_collection_id ftarchimer
language English
topic Instability
Rossby waves
Climate variability
Interdecadal variability
Multidecadal variability
North Atlantic Oscillation
spellingShingle Instability
Rossby waves
Climate variability
Interdecadal variability
Multidecadal variability
North Atlantic Oscillation
Arzel, Olivier
Huck, Thierry
Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
topic_facet Instability
Rossby waves
Climate variability
Interdecadal variability
Multidecadal variability
North Atlantic Oscillation
description Atmospheric stochastic forcing associated with the North Atlantic Oscillation (NAO) and intrinsic ocean modes associated with the large-scale baroclinic instability of the North Atlantic Current (NAC) are recognized as two strong paradigms for the existence of the Atlantic Multidecadal Oscillation (AMO). The degree to which each of these factors contribute to the low-frequency variability of the North Atlantic is the central question in this paper. This issue is addressed here using an ocean general circulation model run under a wide range of background conditions extending from a super-critical regime where the oceanic variability spontaneously develops in the absence of any atmospheric noise forcing to a damped regime where the variability requires some noise to appear. The answer to the question is captured by a single dimensionless number Γ measuring the ratio between the oceanic and atmospheric contributions, as inferred from the buoyancy variance budget of the western subpolar region. Using this diagnostic, about two-third of the sea surface temperature (SST) variance in the damped regime is shown to originate from atmospheric stochastic forcing whereas heat content is dominated by internal ocean dynamics. Stochastic wind-stress forcing is shown to substantially increase the role played by damped ocean modes in the variability. The thermal structure of the variability is shown to differ fundamentally between the super-critical and damped regimes, with abrupt modifications around the transition between the two regimes. Ocean circulation changes are further shown to be unimportant for setting the pattern of SST variability in the damped regime but are fundamental for a preferred timescale to emerge.
format Article in Journal/Newspaper
author Arzel, Olivier
Huck, Thierry
author_facet Arzel, Olivier
Huck, Thierry
author_sort Arzel, Olivier
title Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
title_short Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
title_full Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
title_fullStr Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
title_full_unstemmed Contributions of Atmospheric Stochastic Forcing and Intrinsic Ocean Modes to North Atlantic Ocean Interdecadal Variability
title_sort contributions of atmospheric stochastic forcing and intrinsic ocean modes to north atlantic ocean interdecadal variability
publisher American Meteorological Society
publishDate 2020
url https://archimer.ifremer.fr/doc/00599/71138/69452.pdf
https://doi.org/10.1175/JCLI-D-19-0522.1
https://archimer.ifremer.fr/doc/00599/71138/
genre north atlantic current
North Atlantic
North Atlantic oscillation
genre_facet north atlantic current
North Atlantic
North Atlantic oscillation
op_source Journal Of Climate (0894-8755) (American Meteorological Society), 2020-03 , Vol. 33 , N. 6 , P. 2351-2370
op_relation https://archimer.ifremer.fr/doc/00599/71138/69452.pdf
doi:10.1175/JCLI-D-19-0522.1
https://archimer.ifremer.fr/doc/00599/71138/
op_rights info:eu-repo/semantics/openAccess
restricted use
op_doi https://doi.org/10.1175/JCLI-D-19-0522.1
container_title Journal of Climate
container_volume 33
container_issue 6
container_start_page 2351
op_container_end_page 2370
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