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Titel |
Overturning cells in the Southern Ocean and subtropical gyres |
VerfasserIn |
J. A. Polton, D. P. Marshall |
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 ; 3, no. 1 ; Nr. 3, no. 1 (2007-01-26), S.17-30 |
Datensatznummer |
250000763
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Publikation (Nr.) |
copernicus.org/os-3-17-2007.pdf |
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Zusammenfassung |
The circulation of the subtropical gyres can be decomposed
into a horizontal recirculation along contours of constant Bernoulli
potential and an overturning circulation across these contours. While
the geometry and topology of Bernoulli contours is more complicated in the
subtropical gyres than in the Southern Ocean, these subtropical overturning
circulations are very much analogous to the overturning cell found in the
Southern Ocean. This analogy is formalised through an exact integral
constraint, including the rectified effects of transient eddies. The
constraint can be interpreted either in terms of vertical fluxes of
potential vorticity, or equivalently as an integral buoyancy budget
for an imaginary fluid parcel recirculating around a closed Bernoulli
contour. Under conditions of vanishing buoyancy and mechanical
forcing, the constraint reduces to a generalised non-acceleration
condition, under which the Eulerian-mean and eddy-induced overturning
circulations exactly compensate. The terms in the integral constraint
are diagnosed in an eddy-permitting ocean
model in both the North Pacific subtropical gyre and the Southern Ocean.
The extent to which the Eulerian-mean
and eddy-induced overturning circulations compensate is discussed in each case. |
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