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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 : Volume 6, Issue 1 (30/04/2009)

By Bryden, H. L.

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Book Id: WPLBN0003988655
Format Type: PDF Article :
File Size: Pages 38
Reproduction Date: 2015

Title: 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 : Volume 6, Issue 1 (30/04/2009)  
Author: Bryden, H. L.
Volume: Vol. 6, Issue 1
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Cunningham, S. A., Mujahid, A., Kanzow, T., & Bryden, H. L. (2009). 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 : Volume 6, Issue 1 (30/04/2009). Retrieved from

Description: National Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK. 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.

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

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