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Compensation between meridional flow components of the AMOC at 26°N

Compensation between meridional flow components of the AMOC at 26°N
Compensation between meridional flow components of the AMOC at 26°N
From ten years of observations of the Atlantic meridional overturning circulation at 26° N (MOC, 2004–2014), we revisit the question of flow compensation between components of the circulation. Contrasting with early results from the observations, transport variations of the Florida Current (FC) and upper mid-ocean transports (UMO, top 1000 m east of the Bahamas) are now found to compensate on sub-annual timescales. A deep baroclinic response to wind-forcing (Ekman transport) is also found in the lower North Atlantic Deep Water (LNADW, 3000–5000 m) transport. The observed compensation between the FC and UMO transports is associated with horizontal circulation and means that their individual variability does not project onto the MOC. In contrast, covariability between Ekman and the LNADW transports does contribute to overturning. On longer timescales, the southward UMO transport has continued to strengthen, resulting in a continued decline of the MOC. Most of this interannual variability of the MOC can be traced to changes in isopycnal displacements on the western boundary, within the top 1000 m and below 2000 m. Substantial trends are observed in isopycnal displacements in the deep ocean, underscoring the importance of deep boundary measurements to capture the variability of the Atlantic MOC.
1812-0822
2705-2741
Frajka-Williams, E.
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Meinen, C.S.
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Johns, W.E.
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Smeed, D.A.
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Duchez, A.
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Lawrence, A.J.
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Cuthbertson, D.A.
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McCarthy, G.D.
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Bryden, H.L.
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Moat, B.I.
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Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Meinen, C.S.
e1d8f782-ccdf-4f81-98c4-cc1c7701165c
Johns, W.E.
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Smeed, D.A.
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Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Lawrence, A.J.
039e4bf7-a3bf-4650-b125-ab4fedbeec46
Cuthbertson, D.A.
efbdd055-d89f-47b4-90c6-76e72565b9e2
McCarthy, G.D.
99241bcb-5667-469d-b7ae-4d308d516bd6
Bryden, H.L.
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Moat, B.I.
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Rayner, D.
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Frajka-Williams, E., Meinen, C.S., Johns, W.E., Smeed, D.A., Duchez, A., Lawrence, A.J., Cuthbertson, D.A., McCarthy, G.D., Bryden, H.L., Moat, B.I. and Rayner, D. (2015) Compensation between meridional flow components of the AMOC at 26°N. Ocean Science Discussions, 12 (6), 2705-2741. (doi:10.5194/osd-12-2705-2015).

Record type: Article

Abstract

From ten years of observations of the Atlantic meridional overturning circulation at 26° N (MOC, 2004–2014), we revisit the question of flow compensation between components of the circulation. Contrasting with early results from the observations, transport variations of the Florida Current (FC) and upper mid-ocean transports (UMO, top 1000 m east of the Bahamas) are now found to compensate on sub-annual timescales. A deep baroclinic response to wind-forcing (Ekman transport) is also found in the lower North Atlantic Deep Water (LNADW, 3000–5000 m) transport. The observed compensation between the FC and UMO transports is associated with horizontal circulation and means that their individual variability does not project onto the MOC. In contrast, covariability between Ekman and the LNADW transports does contribute to overturning. On longer timescales, the southward UMO transport has continued to strengthen, resulting in a continued decline of the MOC. Most of this interannual variability of the MOC can be traced to changes in isopycnal displacements on the western boundary, within the top 1000 m and below 2000 m. Substantial trends are observed in isopycnal displacements in the deep ocean, underscoring the importance of deep boundary measurements to capture the variability of the Atlantic MOC.

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Published date: 13 November 2015
Organisations: Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 384036
URI: http://eprints.soton.ac.uk/id/eprint/384036
ISSN: 1812-0822
PURE UUID: 85664cc9-e4de-4afc-ac03-59143bc634bd
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838
ORCID for H.L. Bryden: ORCID iD orcid.org/0000-0002-8216-6359

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Date deposited: 16 Nov 2015 10:12
Last modified: 15 Mar 2024 03:35

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Contributors

Author: E. Frajka-Williams ORCID iD
Author: C.S. Meinen
Author: W.E. Johns
Author: D.A. Smeed
Author: A. Duchez
Author: A.J. Lawrence
Author: D.A. Cuthbertson
Author: G.D. McCarthy
Author: H.L. Bryden ORCID iD
Author: B.I. Moat
Author: D. Rayner

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