Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales
This study describes the intra- to interannual variability of the Atlantic meridional overturning circulation (AMOC) and the relative dynamical contributions to the total variability in an eddy-resolving 1/128 resolution ocean model. Based on a 53-yr-long hindcast and two 4-yr-long ensembles, we ass...
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ftnerc:oai:nora.nerc.ac.uk:532749 2023-05-15T17:35:15+02:00 Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales Germe, Agathe Hirschi, Joël J.-M. Blaker, Adam T. Sinha, Bablu 2022-05-02 text http://nora.nerc.ac.uk/id/eprint/532749/ https://nora.nerc.ac.uk/id/eprint/532749/1/%5B15200485%20-%20Journal%20of%20Physical%20Oceanography%5D%20Chaotic%20Variability%20of%20the%20Atlantic%20Meridional%20Overturning%20Circulation%20at%20Subannual%20Time%20Scales.pdf https://doi.org/10.1175/JPO-D-21-0100.1 en eng https://nora.nerc.ac.uk/id/eprint/532749/1/%5B15200485%20-%20Journal%20of%20Physical%20Oceanography%5D%20Chaotic%20Variability%20of%20the%20Atlantic%20Meridional%20Overturning%20Circulation%20at%20Subannual%20Time%20Scales.pdf Germe, Agathe; Hirschi, Joël J.-M.; Blaker, Adam T. orcid:0000-0001-5454-0131 Sinha, Bablu. 2022 Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales. Journal of Physical Oceanography, 52 (5). 929-949. https://doi.org/10.1175/JPO-D-21-0100.1 <https://doi.org/10.1175/JPO-D-21-0100.1> cc_by_4 CC-BY Publication - Article PeerReviewed 2022 ftnerc https://doi.org/10.1175/JPO-D-21-0100.1 2023-02-04T19:53:22Z This study describes the intra- to interannual variability of the Atlantic meridional overturning circulation (AMOC) and the relative dynamical contributions to the total variability in an eddy-resolving 1/128 resolution ocean model. Based on a 53-yr-long hindcast and two 4-yr-long ensembles, we assess the total AMOC variability as well as the variability arising from small differences in the ocean initial state that rapidly imprints on the mesoscale eddy fields and subsequently on large-scale features. This initial-condition-dependent variability will henceforth be referred to as “chaotic” variability. We find that intra-annual AMOC fluctuations are mainly driven by the atmospheric forcing, with the chaotic variability fraction never exceeding 26% of the total variance in the whole meridional Atlantic domain. To understand the nature of the chaotic variability we decompose the AMOC (into its Ekman, geostrophic, barotropic, and residual components). The barotropic and geostrophic AMOC contributions exhibit strong, partly compensating fluctuations, which are linked to chaotic spatial variations of currents over topography. In the North Atlantic, the largest chaotic divergence of ensemble members is found around 248, 388, and 648N. At 26.58N, where the AMOC is monitored by the RAPID– MOCHA array, the chaotic fraction of the AMOC variability is 10%. This fraction is slightly overestimated with the reconstruction methodology as used in the observations (∼15%). This higher fraction of chaotic variability is due to the barotropic contribution not being completely captured by the monitoring system. We look at the strong AMOC decline observed in 2009/10 and find that the ensemble spread (our measure for chaotic variability) was not particularly large during this event. Article in Journal/Newspaper North Atlantic Natural Environment Research Council: NERC Open Research Archive Journal of Physical Oceanography 52 5 929 949 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
This study describes the intra- to interannual variability of the Atlantic meridional overturning circulation (AMOC) and the relative dynamical contributions to the total variability in an eddy-resolving 1/128 resolution ocean model. Based on a 53-yr-long hindcast and two 4-yr-long ensembles, we assess the total AMOC variability as well as the variability arising from small differences in the ocean initial state that rapidly imprints on the mesoscale eddy fields and subsequently on large-scale features. This initial-condition-dependent variability will henceforth be referred to as “chaotic” variability. We find that intra-annual AMOC fluctuations are mainly driven by the atmospheric forcing, with the chaotic variability fraction never exceeding 26% of the total variance in the whole meridional Atlantic domain. To understand the nature of the chaotic variability we decompose the AMOC (into its Ekman, geostrophic, barotropic, and residual components). The barotropic and geostrophic AMOC contributions exhibit strong, partly compensating fluctuations, which are linked to chaotic spatial variations of currents over topography. In the North Atlantic, the largest chaotic divergence of ensemble members is found around 248, 388, and 648N. At 26.58N, where the AMOC is monitored by the RAPID– MOCHA array, the chaotic fraction of the AMOC variability is 10%. This fraction is slightly overestimated with the reconstruction methodology as used in the observations (∼15%). This higher fraction of chaotic variability is due to the barotropic contribution not being completely captured by the monitoring system. We look at the strong AMOC decline observed in 2009/10 and find that the ensemble spread (our measure for chaotic variability) was not particularly large during this event. |
format |
Article in Journal/Newspaper |
author |
Germe, Agathe Hirschi, Joël J.-M. Blaker, Adam T. Sinha, Bablu |
spellingShingle |
Germe, Agathe Hirschi, Joël J.-M. Blaker, Adam T. Sinha, Bablu Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
author_facet |
Germe, Agathe Hirschi, Joël J.-M. Blaker, Adam T. Sinha, Bablu |
author_sort |
Germe, Agathe |
title |
Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
title_short |
Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
title_full |
Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
title_fullStr |
Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
title_full_unstemmed |
Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales |
title_sort |
chaotic variability of the atlantic meridional overturning circulation at subannual time scales |
publishDate |
2022 |
url |
http://nora.nerc.ac.uk/id/eprint/532749/ https://nora.nerc.ac.uk/id/eprint/532749/1/%5B15200485%20-%20Journal%20of%20Physical%20Oceanography%5D%20Chaotic%20Variability%20of%20the%20Atlantic%20Meridional%20Overturning%20Circulation%20at%20Subannual%20Time%20Scales.pdf https://doi.org/10.1175/JPO-D-21-0100.1 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://nora.nerc.ac.uk/id/eprint/532749/1/%5B15200485%20-%20Journal%20of%20Physical%20Oceanography%5D%20Chaotic%20Variability%20of%20the%20Atlantic%20Meridional%20Overturning%20Circulation%20at%20Subannual%20Time%20Scales.pdf Germe, Agathe; Hirschi, Joël J.-M.; Blaker, Adam T. orcid:0000-0001-5454-0131 Sinha, Bablu. 2022 Chaotic variability of the Atlantic meridional overturning circulation at subannual time scales. Journal of Physical Oceanography, 52 (5). 929-949. https://doi.org/10.1175/JPO-D-21-0100.1 <https://doi.org/10.1175/JPO-D-21-0100.1> |
op_rights |
cc_by_4 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1175/JPO-D-21-0100.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
52 |
container_issue |
5 |
container_start_page |
929 |
op_container_end_page |
949 |
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1766134347732090880 |