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Variability of the Atlantic thermohaline circulation described by three-dimensional empirical orthogonal functions

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Hawkins, E. and Sutton, R. (2007) Variability of the Atlantic thermohaline circulation described by three-dimensional empirical orthogonal functions. Climate Dynamics, 29 (7-8). pp. 745-762. ISSN 0930-7575

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To link to this article DOI: 10.1007/s00382-007-0263-8

Abstract/Summary

We describe the use of bivariate 3d empirical orthogonal functions (EOFs) in characterising low frequency variability of the Atlantic thermohaline circulation (THC) in the Hadley Centre global climate model, HadCM3. We find that the leading two modes are well correlated with an index of the meridional overturning circulation (MOC) on decadal timescales, with the leading mode alone accounting for 54% of the decadal variance. Episodes of coherent oscillations in the sub-space of the leading EOFs are identified; these episodes are of great interest for the predictability of the THC, and could indicate the existence of different regimes of natural variability. The mechanism identified for the multi-decadal variability is an internal ocean mode, dominated by changes in convection in the Nordic Seas, which lead the changes in the MOC by a few years. Variations in salinity transports from the Arctic and from the North Atlantic are the main feedbacks which control the oscillation. This mode has a weak feedback onto the atmosphere and hence a surface climatic influence. Interestingly, some of these climate impacts lead the changes in the overturning. There are also similarities to observed multi-decadal climate variability.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical and Physical Sciences > Department of Meteorology
ID Code:794
Additional Information:publisher's erratum to this article is available at http://dx.doi.org/10.1007/s00382-007-0354-6 (see Related URLs for a live link)
Publisher:Springer
Publisher Statement:The original publication is available at www.springerlink.com

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