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| Titel |
Adjustment of the basin-scale circulation at 26° N to variations in Gulf Stream, deep western boundary current and Ekman transports as observed by the Rapid array |
| VerfasserIn |
H. L. Bryden, A. Mujahid, S. A. Cunningham, T. Kanzow |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2009-10-19), S.421-433 |
| Datensatznummer |
250002721
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| Publikation (Nr.) |
 copernicus.org/os-5-421-2009.pdf |
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| Zusammenfassung |
| The Rapid instrument array across the Atlantic Ocean along 26° N
provides unprecedented monitoring of the basin-scale circulation. A unique
feature of the Rapid array is the combination of full-depth moorings with
instruments measuring temperature, salinity, pressure time series at many
depths with co-located bottom pressure measurements so that dynamic pressure
can be measured from surface to bottom. Bottom pressure measurements show a
zonally uniform rise (and fall) of bottom pressure of 0.015 dbar on a 5 to
10 day time scale, suggesting that the Atlantic basin is filling and
draining on a short time scale. After removing the zonally uniform bottom
pressure fluctuations, bottom pressure variations at 4000 m depth against
the western boundary compensate instantaneously for baroclinic fluctuations
in the strength and structure of the deep western boundary current so there
is no basin-scale mass imbalance resulting from variations in the deep
western boundary current. After removing the mass compensating bottom
pressure, residual bottom pressure fluctuations at the western boundary just
east of the Bahamas balance variations in Gulf Stream transport. Again the
compensation appears to be especially confined close to the western boundary.
Thus, fluctuations in either Gulf Stream or deep western boundary current
transports are compensated in a depth independent (barotropic) manner very
close to the continental slope off the Bahamas. In contrast, compensation for
variations in wind-driven surface Ekman transport appears to involve
fluctuations in both western basin and eastern basin bottom pressures, though
the bottom pressure difference fluctuations appear to be a factor of 3 too
large, perhaps due to an inability to resolve small bottom pressure
fluctuations after removal of larger zonal average, baroclinic, and Gulf
Stream pressure components. For 4 tall moorings where time series dynamic
height (geostrophic pressure) profiles can be estimated from sea surface to
ocean bottom and bottom pressure can be added, there is no general
correlation between surface dynamic height and bottom pressure. Dynamic
height on each mooring is strongly correlated with sea surface height from
satellite observations and the variability in both dynamic height and
satellite sea surface height decrease sharply as the western boundary is
approached. |
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