Latitudinal Structure of the Meridional Overturning Circulation Variability on Interannual to Decadal Time Scales in the North Atlantic Ocean
The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (538N) to 258N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (408-508N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.
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- Meteorology & Atmospheric Sciences
- 3708 Oceanography
- 3702 Climate change science
- 3701 Atmospheric sciences
- 0909 Geomatic Engineering
- 0405 Oceanography
- 0401 Atmospheric Sciences
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Related Subject Headings
- Meteorology & Atmospheric Sciences
- 3708 Oceanography
- 3702 Climate change science
- 3701 Atmospheric sciences
- 0909 Geomatic Engineering
- 0405 Oceanography
- 0401 Atmospheric Sciences