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Compensation between meridional flow components of the Atlantic MOC at 26°N

Compensation between meridional flow components of the Atlantic MOC at 26°N
Compensation between meridional flow components of the Atlantic MOC at 26°N
From ten years of observations of the Atlantic meridional overturning circulation (MOC) at 26°?N (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 (UMO) transports (top 1000?m east of the Bahamas) are now found to compensate on sub-annual timescales. The observed compensation between the FC and UMO transports is associated with horizontal circulation and means that this part of the correlated variability does not project onto the MOC. A deep baroclinic response to wind-forcing (Ekman transport) is also found in the lower North Atlantic Deep Water (LNADW; 3000–5000?m) transport. In contrast, co-variability 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.
1812-0792
481-493
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
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.
99241bcb-5667-469d-b7ae-4d308d516bd6
Bryden, H.L.
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Baringer, M.O.
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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.
e69b0088-c832-4ed8-94f6-9c5e9e6f62af
Smeed, D.A.
79eece5a-c870-47f9-bba0-0a4ef0369490
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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Baringer, M.O.
b8dab4b9-918b-4bc9-a033-dcbeb03f5730
Moat, B.I.
497dbb18-a98f-466b-b459-aa2c872ad2dc
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122

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., Baringer, M.O., Moat, B.I. and Rayner, D. (2016) Compensation between meridional flow components of the Atlantic MOC at 26°N. Ocean Science, 12 (2), 481-493. (doi:10.5194/os-12-481-2016).

Record type: Article

Abstract

From ten years of observations of the Atlantic meridional overturning circulation (MOC) at 26°?N (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 (UMO) transports (top 1000?m east of the Bahamas) are now found to compensate on sub-annual timescales. The observed compensation between the FC and UMO transports is associated with horizontal circulation and means that this part of the correlated variability does not project onto the MOC. A deep baroclinic response to wind-forcing (Ekman transport) is also found in the lower North Atlantic Deep Water (LNADW; 3000–5000?m) transport. In contrast, co-variability 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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Accepted/In Press date: 17 March 2016
e-pub ahead of print date: 1 April 2016
Published date: 2016
Organisations: Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 390694
URI: http://eprints.soton.ac.uk/id/eprint/390694
ISSN: 1812-0792
PURE UUID: 52f3aa1d-824e-43dd-89eb-a4b1eed17da1
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: 04 Apr 2016 10:25
Last modified: 17 Dec 2019 01:58

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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: M.O. Baringer
Author: B.I. Moat
Author: D. Rayner

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