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), 1-15. (doi:10.1029/2012GL052933).

Download

[img]
Preview
PDF - Publishers print
Download (523Kb) | Preview
[img] PDF - Pre print
Restricted to System admin

Download (685Kb)

Description/Abstract

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.

Item Type: Article
ISSNs: 0094-8276 (print)
Keywords: atlantic meridional overturning circulation, heat transport, thermohaline circulation
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Divisions: Faculty of Natural and Environmental Sciences > Ocean and Earth Science > Physical Oceanography
National Oceanography Centre (NERC) > Marine Physics and Ocean Climate
ePrint ID: 342371
Date Deposited: 24 Aug 2012 08:30
Last Modified: 09 Oct 2014 09:19
URI: http://eprints.soton.ac.uk/id/eprint/342371

Actions (login required)

View Item View Item

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics