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| Titel |
The contribution of eastern-boundary density variations to the Atlantic meridional overturning circulation at 26.5° N |
| VerfasserIn |
M. P. Chidichimo, T. Kanzow, S. A. Cunningham, W. E. Johns, J. Marotzke |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 6, no. 2 ; Nr. 6, no. 2 (2010-04-26), S.475-490 |
| Datensatznummer |
250003464
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| Publikation (Nr.) |
 copernicus.org/os-6-475-2010.pdf |
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| Zusammenfassung |
| We study the contribution of eastern-boundary density variations to
sub-seasonal and seasonal anomalies of the strength and vertical structure
of the Atlantic Meridional Overturning Circulation (AMOC) at 26.5° N, by
means of the RAPID/MOCHA mooring array between April 2004 and October 2007.
The major density anomalies are found in the upper 500 m, and they are often
coherent down to 1400 m. The densities have 13-day fluctuations that are
apparent down to 3500 m. The two strategies for measuring eastern-boundary
density – a tall offshore mooring (EB1) and an array of moorings on the
continental slope (EBH) – show little correspondence in terms of amplitude,
vertical structure, and frequency distribution of the resulting basin-wide
integrated transport fluctuations, implying that there are significant
transport contributions between EB1 and EBH. Contrary to the original
planning, measurements from EB1 cannot serve as backup or replacement for
EBH: density needs to be measured directly at the continental slope to
compute the full-basin density gradient. Fluctuations in density at EBH
generate transport variability of 2 Sv rms in the AMOC, while the overall
AMOC variability is 4.8 Sv rms. There is a pronounced deep-reaching seasonal
cycle in density at the eastern boundary, which is apparent between 100 m
and 1400 m, with maximum positive anomalies in spring and maximum negative
anomalies in autumn. These changes drive anomalous southward upper mid-ocean
flow in spring, implying maximum reduction of the AMOC, and vice-versa in
autumn. The amplitude of the seasonal cycle of the AMOC arising from the
eastern-boundary densities is 5.2 Sv peak-to-peak, dominating the 6.7 Sv
peak-to-peak seasonal cycle of the total AMOC. Our analysis suggests that
the seasonal cycle in density may be forced by the strong near-coastal
seasonal cycle in wind stress curl. |
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