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Observed interannual variability of the Atlantic meridional overturning circulation at 26.5N

McCarthy, G., Frajka-Williams, E., Johns, W.E., Baringer, M.O., Meinen, C.S., Bryden, H.L., Rayner, D., Duchez, A., Roberts, C.D. and Cunningham, S.A. (2012) Observed interannual variability of the Atlantic meridional overturning circulation at 26.5N Geophysical Research Letters, 39, (19), pp. 1-15. (doi:10.1029/2012GL052933).

Record type: Article


The Atlantic meridional overturning circulation (MOC) plays a critical role in the climate system and is responsible for much of the heat transported by the ocean. A mooring array, nomianally at 26^\circN between the Bahamas and the Canary Islands, deployed in Apr 2004 provides continuous measurements of the strength and variability of this circulation. With seven full years of measurements, we now examine the interannual variability of the MOC. While earlier results highlighted substantial seasonal and shorter timescale variability, there had not been significant interannual variability. The mean MOC from 1 Apr 2004 to the 31 March 2009 was 18.5 Sv with the annual means having a standard deviation of only 1.0 Sv. From 1 April 2009 to 31 March 2010, the annually averaged MOC strength was just 12.8 Sv, representing a 30\% decline. This downturn persisted from early 2009 to mid-2010. We show that the cause of the decline was not only an anomalous wind-driven event from Dec 2009--Mar 2010 but also a strengthening of the geostrophic flow. In particular, the southward flow in the top 1100~m intensified, while the deep southward return transport---particularly in the deepest layer from 3000--5000~m---weakened. This rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the Atlantic.

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e-pub ahead of print date: 12 October 2012
Published date: October 2012
Keywords: atlantic meridional overturning circulation, heat transport, thermohaline circulation
Organisations: Physical Oceanography, Marine Physics and Ocean Climate


Local EPrints ID: 342371
ISSN: 0094-8276
PURE UUID: 2bc327a2-35b3-40ab-921e-226fd9739542
ORCID for E. Frajka-Williams: ORCID iD
ORCID for H.L. Bryden: ORCID iD

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Date deposited: 24 Aug 2012 08:30
Last modified: 18 Jul 2017 05:29

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Author: G. McCarthy
Author: W.E. Johns
Author: M.O. Baringer
Author: C.S. Meinen
Author: H.L. Bryden ORCID iD
Author: D. Rayner
Author: A. Duchez
Author: C.D. Roberts
Author: S.A. Cunningham

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