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Atmosphere drives recent interannual variability of the Atlantic meridional overturning circulation at 26.5°N

Atmosphere drives recent interannual variability of the Atlantic meridional overturning circulation at 26.5°N
Atmosphere drives recent interannual variability of the Atlantic meridional overturning circulation at 26.5°N
The Atlantic meridional overturning circulation (AMOC) has been observed at 26.5°N since 2004. During 2009/2010, there was a transient 30% weakening of the AMOC driven by anomalies in geostrophic and Ekman transports. Here, we use simulations based on the Met Office Forecast Ocean Assimilation Model (FOAM) to diagnose the relative importance of atmospheric forcings and internal ocean dynamics in driving the anomalous geostrophic circulation of 2009/2010. Data-assimilating experiments with FOAM accurately reproduce the mean strength and depth of the AMOC at 26.5°N. In addition, agreement between simulated and observed stream functions in the deep ocean is improved when we calculate the AMOC using a method that approximates the observing array at 26.5°N. The main features of the geostrophic circulation anomaly are captured by an ensemble of simulations without data assimilation. These model results suggest that the atmosphere played a dominant role in driving recent interannual variability of the AMOC.
AMOC, variability, ocean model, data assimilation, ocean circulation, atlantic meridional overturning circulation
0094-8276
5164-5170
Roberts, C.D.
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Waters, J.
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Peterson, K.A.
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Palmer, M.D.
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McCarthy, G.D.
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Frajka-Williams, E.
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Haines, K.
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Lea, D.J.
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Martin, M.J.
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Storkey, D.
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Blockley, E.W.
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Zuo, H.
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Roberts, C.D.
ff9336a0-6672-4d47-9d2c-014a77daeca8
Waters, J.
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Peterson, K.A.
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Palmer, M.D.
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McCarthy, G.D.
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Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Haines, K.
1a53bed0-564d-4c7e-9257-9f2200b96723
Lea, D.J.
ef5ca848-7163-4aad-b99e-e932d4680315
Martin, M.J.
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Storkey, D.
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Blockley, E.W.
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Zuo, H.
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Roberts, C.D., Waters, J., Peterson, K.A., Palmer, M.D., McCarthy, G.D., Frajka-Williams, E., Haines, K., Lea, D.J., Martin, M.J., Storkey, D., Blockley, E.W. and Zuo, H. (2013) Atmosphere drives recent interannual variability of the Atlantic meridional overturning circulation at 26.5°N. Geophysical Research Letters, 40 (19), 5164-5170. (doi:10.1002/grl.50930).

Record type: Article

Abstract

The Atlantic meridional overturning circulation (AMOC) has been observed at 26.5°N since 2004. During 2009/2010, there was a transient 30% weakening of the AMOC driven by anomalies in geostrophic and Ekman transports. Here, we use simulations based on the Met Office Forecast Ocean Assimilation Model (FOAM) to diagnose the relative importance of atmospheric forcings and internal ocean dynamics in driving the anomalous geostrophic circulation of 2009/2010. Data-assimilating experiments with FOAM accurately reproduce the mean strength and depth of the AMOC at 26.5°N. In addition, agreement between simulated and observed stream functions in the deep ocean is improved when we calculate the AMOC using a method that approximates the observing array at 26.5°N. The main features of the geostrophic circulation anomaly are captured by an ensemble of simulations without data assimilation. These model results suggest that the atmosphere played a dominant role in driving recent interannual variability of the AMOC.

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Published date: 16 October 2013
Keywords: AMOC, variability, ocean model, data assimilation, ocean circulation, atlantic meridional overturning circulation
Organisations: Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 360004
URI: http://eprints.soton.ac.uk/id/eprint/360004
ISSN: 0094-8276
PURE UUID: 99ba4f25-07ac-4215-955f-33cd764a3712
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838

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Date deposited: 20 Nov 2013 16:58
Last modified: 15 Mar 2024 03:35

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Contributors

Author: C.D. Roberts
Author: J. Waters
Author: K.A. Peterson
Author: M.D. Palmer
Author: G.D. McCarthy
Author: E. Frajka-Williams ORCID iD
Author: K. Haines
Author: D.J. Lea
Author: M.J. Martin
Author: D. Storkey
Author: E.W. Blockley
Author: H. Zuo

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