High frequency variability of the Atlantic meridional overturning circulation
We compare the variability of the Atlantic meridional overturning circulation (AMOC) as simulated by the coupled climate models of the RAPID project, which cover a wide range of resolution and complexity, and observed by the RAPID/MOCHA array at about 26° N. We analyse variability on a range of time...
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ftnerc:oai:nora.nerc.ac.uk:16698 2023-05-15T17:36:01+02:00 High frequency variability of the Atlantic meridional overturning circulation Balan Sarojini, B. Gregory, J.M. Tailleux, R. Bigg, G.R. Blaker, A.T. Cameron, D.R. Edwards, N.R. Megann, A.P. Shaffery, L.C. Sinha, B. 2011 http://nora.nerc.ac.uk/id/eprint/16698/ http://www.ocean-sci.net/7/471/2011/os-7-471-2011.pdf unknown Balan Sarojini, B.; Gregory, J.M.; Tailleux, R.; Bigg, G.R.; Blaker, A.T. orcid:0000-0001-5454-0131 Cameron, D.R.; Edwards, N.R.; Megann, A.P. orcid:0000-0003-0975-6317 Shaffery, L.C.; Sinha, B. 2011 High frequency variability of the Atlantic meridional overturning circulation. Ocean Science, 7. 471-486. https://doi.org/10.5194/os-7-471-2011 <https://doi.org/10.5194/os-7-471-2011> Earth Sciences Publication - Article PeerReviewed 2011 ftnerc https://doi.org/10.5194/os-7-471-2011 2023-02-04T19:30:39Z We compare the variability of the Atlantic meridional overturning circulation (AMOC) as simulated by the coupled climate models of the RAPID project, which cover a wide range of resolution and complexity, and observed by the RAPID/MOCHA array at about 26° N. We analyse variability on a range of timescales, from five-daily to interannual. In models of all resolutions there is substantial variability on timescales of a few days; in most AOGCMs the amplitude of the variability is of somewhat larger magnitude than that observed by the RAPID array, while the time-mean is within about 10 % of the observational estimate. The amplitude of the simulated annual cycle is similar to observations, but the shape of the annual cycle shows a spread among the models. A dynamical decomposition shows that in the models, as in observations, the AMOC is predominantly geostrophic (driven by pressure and sea-level gradients), with both geostrophic and Ekman contributions to variability, the latter being exaggerated and the former underrepresented in models. Other ageostrophic terms, neglected in the observational estimate, are small but not negligible. The time-mean of the western boundary current near the latitude of the RAPID/MOCHA array has a much wider model spread than the AMOC does, indicating large differences among models in the simulation of the wind-driven gyre circulation, and its variability is unrealistically small in the models. In many RAPID models and in models of the Coupled Model Intercomparison Project Phase 3 (CMIP3), interannual variability of the maximum of the AMOC wherever it lies, which is a commonly used model index, is similar to interannual variability in the AMOC at 26° N. Annual volume and heat transport timeseries at the same latitude are well-correlated within 15–45° N, indicating the climatic importance of the AMOC. In the RAPID and CMIP3 models, we show that the AMOC is correlated over considerable distances in latitude, but not the whole extent of the North Atlantic; consequently interannual ... Article in Journal/Newspaper North Atlantic Natural Environment Research Council: NERC Open Research Archive Ocean Science 7 4 471 486 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
topic |
Earth Sciences |
spellingShingle |
Earth Sciences Balan Sarojini, B. Gregory, J.M. Tailleux, R. Bigg, G.R. Blaker, A.T. Cameron, D.R. Edwards, N.R. Megann, A.P. Shaffery, L.C. Sinha, B. High frequency variability of the Atlantic meridional overturning circulation |
topic_facet |
Earth Sciences |
description |
We compare the variability of the Atlantic meridional overturning circulation (AMOC) as simulated by the coupled climate models of the RAPID project, which cover a wide range of resolution and complexity, and observed by the RAPID/MOCHA array at about 26° N. We analyse variability on a range of timescales, from five-daily to interannual. In models of all resolutions there is substantial variability on timescales of a few days; in most AOGCMs the amplitude of the variability is of somewhat larger magnitude than that observed by the RAPID array, while the time-mean is within about 10 % of the observational estimate. The amplitude of the simulated annual cycle is similar to observations, but the shape of the annual cycle shows a spread among the models. A dynamical decomposition shows that in the models, as in observations, the AMOC is predominantly geostrophic (driven by pressure and sea-level gradients), with both geostrophic and Ekman contributions to variability, the latter being exaggerated and the former underrepresented in models. Other ageostrophic terms, neglected in the observational estimate, are small but not negligible. The time-mean of the western boundary current near the latitude of the RAPID/MOCHA array has a much wider model spread than the AMOC does, indicating large differences among models in the simulation of the wind-driven gyre circulation, and its variability is unrealistically small in the models. In many RAPID models and in models of the Coupled Model Intercomparison Project Phase 3 (CMIP3), interannual variability of the maximum of the AMOC wherever it lies, which is a commonly used model index, is similar to interannual variability in the AMOC at 26° N. Annual volume and heat transport timeseries at the same latitude are well-correlated within 15–45° N, indicating the climatic importance of the AMOC. In the RAPID and CMIP3 models, we show that the AMOC is correlated over considerable distances in latitude, but not the whole extent of the North Atlantic; consequently interannual ... |
format |
Article in Journal/Newspaper |
author |
Balan Sarojini, B. Gregory, J.M. Tailleux, R. Bigg, G.R. Blaker, A.T. Cameron, D.R. Edwards, N.R. Megann, A.P. Shaffery, L.C. Sinha, B. |
author_facet |
Balan Sarojini, B. Gregory, J.M. Tailleux, R. Bigg, G.R. Blaker, A.T. Cameron, D.R. Edwards, N.R. Megann, A.P. Shaffery, L.C. Sinha, B. |
author_sort |
Balan Sarojini, B. |
title |
High frequency variability of the Atlantic meridional overturning circulation |
title_short |
High frequency variability of the Atlantic meridional overturning circulation |
title_full |
High frequency variability of the Atlantic meridional overturning circulation |
title_fullStr |
High frequency variability of the Atlantic meridional overturning circulation |
title_full_unstemmed |
High frequency variability of the Atlantic meridional overturning circulation |
title_sort |
high frequency variability of the atlantic meridional overturning circulation |
publishDate |
2011 |
url |
http://nora.nerc.ac.uk/id/eprint/16698/ http://www.ocean-sci.net/7/471/2011/os-7-471-2011.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
Balan Sarojini, B.; Gregory, J.M.; Tailleux, R.; Bigg, G.R.; Blaker, A.T. orcid:0000-0001-5454-0131 Cameron, D.R.; Edwards, N.R.; Megann, A.P. orcid:0000-0003-0975-6317 Shaffery, L.C.; Sinha, B. 2011 High frequency variability of the Atlantic meridional overturning circulation. Ocean Science, 7. 471-486. https://doi.org/10.5194/os-7-471-2011 <https://doi.org/10.5194/os-7-471-2011> |
op_doi |
https://doi.org/10.5194/os-7-471-2011 |
container_title |
Ocean Science |
container_volume |
7 |
container_issue |
4 |
container_start_page |
471 |
op_container_end_page |
486 |
_version_ |
1766135351546478592 |