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Vivaldi 1991 - A study of the formation, circulation and ventilation of Eastern North Atlantic Central Water

A synoptic, hydrographic data set comprising 32 full depth CTD casts and 2500 CTD/SeaSoar profiles to 500 m is used to describe the theta /S properties and circulation of Central Water East of the Mid-Atlantic Ridge and between 39 degree N and 54 degree N. Eastward transport of 20 x 10 super(6) m su...

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Bibliographic Details
Published in:Progress in oceanography 1996, Vol.37 (2), p.167-192
Main Authors: POLLARD, R. T, GRIFFITHS, M. J, CUNNINGHAM, S. A, READ, J. F, PEREZ, F. F, RIOS, A. F
Format: Article
Language:English
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Summary:A synoptic, hydrographic data set comprising 32 full depth CTD casts and 2500 CTD/SeaSoar profiles to 500 m is used to describe the theta /S properties and circulation of Central Water East of the Mid-Atlantic Ridge and between 39 degree N and 54 degree N. Eastward transport of 20 x 10 super(6) m super(3) s super(-1) in the North Atlantic Current turns entirely northwards to the west of 54 degree N, 20 degree W. This transport consists in the upper layers of western North Atlantic Water freshened at temperatures below 10 degree C by mixing with SubArctic Intermediate Water. Northern and Southern branches of the North Atlantic Current are well defined and both turn northwards west of 20 degree W. A further 10 x 10 super(6) m super(3) s super(-1) of Eastern North Atlantic Water forms and recirculates anticyclonically to the west of Spain south of the North Atlantic Current and north of 40 degree N. Eastern North Atlantic Water is most weakly stratified east of 20 degree W and there is clear correlation between weakly stratified pycnostads and positive salinity anomalies relative to Western North Atlantic Water. Thus Eastern North Atlantic Water is a winter Mode Water in which strong winter cooling has increased the density and hence also the salinity anomaly at a given temperature. Near the southern entrance to the Rockall Trough there is evidence that salinities are also increased by Mediterranean Water influence. Circulation south of the North Atlantic Current is complex. There is no evidence for direct ventilation southwards across 40 degree N where water properties ( theta /S, potential vorticity and CFC-113) and historical data all indicate westward ventilation east of 24 degree W, with weak southward ventilation occurring further west, in the vicinity of the Azores. The circulation pattern suggested is remarkably similar to that proposed by Helland-Hansen and Nansen in 1926 (The eastern North Atlantic, Geophysiske Publicajoner, 4, 1-76), with anticyclonic circulation of colder Eastern North Atlantic Water north of 40 degree N meeting warmer water from south of 40 degree N circulating cyclonically north of the Azores Current. The distribution of pycnostads and theta /S properties between 20 degree W and 35 degree W north of the Azores indicates alternate bands of Western and Eastern North Atlantic Water moving eastward and westward respectively, including evidence for westward motion immediately south of the Southern branch of the North Atlantic Current
ISSN:0079-6611
1873-4472
DOI:10.1016/S0079-6611(96)00008-0