Meridional coherence of the North Atlantic meridional overturning circulation

Rory J. Bingham*, Chris W. Hughes, Vassil Roussenov, Richard G. Williams

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

98 Citations (Scopus)

Abstract

The North Atlantic Meridional Overturning Circulation (MOC) is associated with deep water formation at high latitudes, and climatically-important ocean-atmosphere heat fluxes, hence the current substantial effort to monitor the MOC. While it is expected that, on sufficiently long time scales, variations in the MOC would be coherent across latitudes south of the deep water formation region, it is not clear whether coherence should be expected at shorter timescales. In this paper, we investigate the coherence of MOC variations in a range of ocean models. We find that, across a range of model physics, resolution, and forcing scenarios, there is a change in the character of the overturning north and south of about 40°N. To the north the variability has a strong decadal component, while to the south higher frequencies dominate. This acts to significantly reduce the meridional coherence of the MOC, even on interannual timescales. A physical interpretation in terms of an underlying meridionally coherent mode, strongest at high latitudes, but swamped by higher frequency, more localised processes south of 40°N is provided.

Original languageEnglish
Article numberL23606
JournalGeophysical Research Letters
Volume34
Issue number23
DOIs
Publication statusPublished - 16 Dec 2007

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