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Seasonal to interannual variability in density around the Canary Islands and their influence on the Atlantic meridional overturning circulation at 26°N

Seasonal to interannual variability in density around the Canary Islands and their influence on the Atlantic meridional overturning circulation at 26°N
Seasonal to interannual variability in density around the Canary Islands and their influence on the Atlantic meridional overturning circulation at 26°N
The meridional interior flow obtained from the RAPID array is determined by horizontal density fluctuations at the eastern and western boundary of 26°N. The physical causes of these density variations are responsible for fluctuations in the Atlantic Meridional Overturning Circulation (AMOC) and through it, the meridional heat transport of the Atlantic. In this modelling study, a high resolution ocean model is used to investigate the source and origin of the AMOC variability associated with the density fluctuations at the eastern boundary. The AMOC in the model is in good agreement with the RAPID observations and appears to adequately represent the smaller scale features of variability around the Canary Islands. In this paper, we identify a robust relationship between the density structure south of the Canary Islands, the local wind stress curl (WSC) around these islands and the AMOC using an empirical orthogonal functions analysis, wavelet transform and wavelet coherence. We find that the deep density fluctuations at the eastern boundary of 26°N arise from the pumping effect of the spatial pattern of WSC south of the islands. These deep density fluctuations drive the AMOC both on seasonal and interannual timescales, through their influence on the basinwide tilt of the thermocline. At seasonal timescales, the density fluctuations south of the islands are driven by the WSC and directly influence the AMOC. At interannual timescales, a significant coherence is found between the density fluctuation and the southward UMO transport although the origin of these density fluctuations is not explained by the direct pumping caused by the WSC.
Physical oceanography, Atlantic Meridional Overturning Circulation (AMOC), Canary Islands, Seasonal / interannual variability, density fluctuations, Wind Stress Curl (WSC)
0148-0227
1843-1860
Duchez, Aurélie
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Castro, Natalia
50ef2a6a-4d12-4a4f-8ad5-5a7c35bf5d12
Hirschi, Joël
c8a45006-a6e3-4319-b5f5-648e8ef98906
Coward, Andrew
53b78140-2e65-476a-b287-e8384a65224b
Duchez, Aurélie
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Frajka-Williams, Eleanor
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Castro, Natalia
50ef2a6a-4d12-4a4f-8ad5-5a7c35bf5d12
Hirschi, Joël
c8a45006-a6e3-4319-b5f5-648e8ef98906
Coward, Andrew
53b78140-2e65-476a-b287-e8384a65224b

Duchez, Aurélie, Frajka-Williams, Eleanor, Castro, Natalia, Hirschi, Joël and Coward, Andrew (2014) Seasonal to interannual variability in density around the Canary Islands and their influence on the Atlantic meridional overturning circulation at 26°N. Journal of Geophysical Research, 119 (3), 1843-1860. (doi:10.1002/2013JC009416).

Record type: Article

Abstract

The meridional interior flow obtained from the RAPID array is determined by horizontal density fluctuations at the eastern and western boundary of 26°N. The physical causes of these density variations are responsible for fluctuations in the Atlantic Meridional Overturning Circulation (AMOC) and through it, the meridional heat transport of the Atlantic. In this modelling study, a high resolution ocean model is used to investigate the source and origin of the AMOC variability associated with the density fluctuations at the eastern boundary. The AMOC in the model is in good agreement with the RAPID observations and appears to adequately represent the smaller scale features of variability around the Canary Islands. In this paper, we identify a robust relationship between the density structure south of the Canary Islands, the local wind stress curl (WSC) around these islands and the AMOC using an empirical orthogonal functions analysis, wavelet transform and wavelet coherence. We find that the deep density fluctuations at the eastern boundary of 26°N arise from the pumping effect of the spatial pattern of WSC south of the islands. These deep density fluctuations drive the AMOC both on seasonal and interannual timescales, through their influence on the basinwide tilt of the thermocline. At seasonal timescales, the density fluctuations south of the islands are driven by the WSC and directly influence the AMOC. At interannual timescales, a significant coherence is found between the density fluctuation and the southward UMO transport although the origin of these density fluctuations is not explained by the direct pumping caused by the WSC.

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Accepted/In Press date: February 2014
Published date: March 2014
Keywords: Physical oceanography, Atlantic Meridional Overturning Circulation (AMOC), Canary Islands, Seasonal / interannual variability, density fluctuations, Wind Stress Curl (WSC)
Organisations: Marine Systems Modelling, Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 362284
URI: http://eprints.soton.ac.uk/id/eprint/362284
ISSN: 0148-0227
PURE UUID: 6014b6c3-4ce2-401a-9d9d-8bdb9b63d7db
ORCID for Eleanor Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 19 Feb 2014 11:46
Last modified: 15 Mar 2024 03:35

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Contributors

Author: Aurélie Duchez
Author: Eleanor Frajka-Williams ORCID iD
Author: Natalia Castro
Author: Joël Hirschi
Author: Andrew Coward

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