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A new index for the Atlantic Meridional Overturning Circulation at 26°N

A new index for the Atlantic Meridional Overturning Circulation at 26°N
A new index for the Atlantic Meridional Overturning Circulation at 26°N
The Atlantic Meridional Overturning Circulation (AMOC) has received considerable attention, motivated by its major role in the global climate system. Observations of AMOC strength at 26°N made by RAPID-WATCH, provide our best current estimate of the state of the AMOC. The period 2004-2011 when RAPID AMOC is available is too short to assess decadal variability of the AMOC. In this modelling study, we define a new AMOC index (called AMOCSV ) at 26°N that combines the Florida Straits transport, the Ekman transport and the southward geostrophic Sverdrup transport. Our main hypothesis in this study is that the Upper Mid-Ocean geostrophic transport calculated using the RAPID array, is also wind-driven and can be approximated by the geostrophic Sverdrup transport at interannual and longer timescales. This index is expected to reflect variations in the AMOC at interannual / decadal time scales. This estimate of the surface branch of the AMOC can be constructed as long as reliable measurements are available for the Gulf Stream and for wind stress. To test the reliability of the AMOCSV on interannual and longer timescales, two different NEMO simulations are used: a forced and a coupled simulation. Using these simulations the AMOCSV captures a substantial fraction of the AMOC variability and is in good agreement with the AMOC transport at 26°N on both interannual and decadal timescales. These results indicate that it might be possible to extend the observation-based AMOC at 26°N back to the 1980s.
North Atlantic Ocean, Meridional overturning circulation, Climate change, Ocean models, Interannual variability, Multidecadal variability
0894-8755
6439-6455
Duchez, A.
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Hirschi, J.J.-M.
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Blaker, A.T.
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Bryden, H.L.
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de Cuevas, B.
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Atkinson, C.P.
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McCarthy, G.D.
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Frajka-Williams, E.
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Rayner, D.
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Smeed, D.
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Cunningham, S.A.
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Mizielinski, M.S.
fa1ec4c5-c7be-4205-80a9-a1dd047a6e88
Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Hirschi, J.J.-M.
c8a45006-a6e3-4319-b5f5-648e8ef98906
Blaker, A.T.
94efe8b2-c744-4e90-87d7-db19ffa41200
Bryden, H.L.
7f823946-34e8-48a3-8bd4-a72d2d749184
de Cuevas, B.
01cc697c-2832-4de6-87bf-bf9f16c1f906
Atkinson, C.P.
6f24341c-22d0-484b-8e12-7a08315a9158
McCarthy, G.D.
99241bcb-5667-469d-b7ae-4d308d516bd6
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Smeed, D.
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Cunningham, S.A.
cf4b95d7-742f-43bd-8b99-c64fe50241ae
Mizielinski, M.S.
fa1ec4c5-c7be-4205-80a9-a1dd047a6e88

Duchez, A., Hirschi, J.J.-M., Blaker, A.T., Bryden, H.L., de Cuevas, B., Atkinson, C.P., McCarthy, G.D., Frajka-Williams, E., Rayner, D., Smeed, D., Cunningham, S.A. and Mizielinski, M.S. (2014) A new index for the Atlantic Meridional Overturning Circulation at 26°N. Journal of Climate, 27 (17), 6439-6455. (doi:10.1175/JCLI-D-13-00052.1).

Record type: Article

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) has received considerable attention, motivated by its major role in the global climate system. Observations of AMOC strength at 26°N made by RAPID-WATCH, provide our best current estimate of the state of the AMOC. The period 2004-2011 when RAPID AMOC is available is too short to assess decadal variability of the AMOC. In this modelling study, we define a new AMOC index (called AMOCSV ) at 26°N that combines the Florida Straits transport, the Ekman transport and the southward geostrophic Sverdrup transport. Our main hypothesis in this study is that the Upper Mid-Ocean geostrophic transport calculated using the RAPID array, is also wind-driven and can be approximated by the geostrophic Sverdrup transport at interannual and longer timescales. This index is expected to reflect variations in the AMOC at interannual / decadal time scales. This estimate of the surface branch of the AMOC can be constructed as long as reliable measurements are available for the Gulf Stream and for wind stress. To test the reliability of the AMOCSV on interannual and longer timescales, two different NEMO simulations are used: a forced and a coupled simulation. Using these simulations the AMOCSV captures a substantial fraction of the AMOC variability and is in good agreement with the AMOC transport at 26°N on both interannual and decadal timescales. These results indicate that it might be possible to extend the observation-based AMOC at 26°N back to the 1980s.

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More information

Accepted/In Press date: June 2014
Published date: 1 September 2014
Keywords: North Atlantic Ocean, Meridional overturning circulation, Climate change, Ocean models, Interannual variability, Multidecadal variability
Organisations: Marine Systems Modelling, Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 365713
URI: http://eprints.soton.ac.uk/id/eprint/365713
ISSN: 0894-8755
PURE UUID: 89eecd6b-1bdf-4994-9f7d-fe4a93d59bbc
ORCID for H.L. Bryden: ORCID iD orcid.org/0000-0002-8216-6359
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

Catalogue record

Date deposited: 13 Jun 2014 09:38
Last modified: 08 Oct 2019 00:53

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