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| Titel |
A simple and self-consistent geostrophic-force-balance model of the thermohaline circulation with boundary mixing |
| VerfasserIn |
J. Callies, 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 ; 8, no. 1 ; Nr. 8, no. 1 (2012-01-27), S.49-63 |
| Datensatznummer |
250005396
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| Publikation (Nr.) |
 copernicus.org/os-8-49-2012.pdf |
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| Zusammenfassung |
A simple model of the thermohaline circulation (THC) is formulated,
with the objective to represent explicitly the geostrophic force
balance of the basinwide THC. The model comprises advective-diffusive
density balances in two meridional-vertical planes located at the
eastern and the western walls of a hemispheric sector basin. Boundary
mixing constrains vertical motion to lateral boundary layers along
these walls. Interior, along-boundary, and zonally integrated
meridional flows are in thermal-wind balance. Rossby waves and the
absence of interior mixing render isopycnals zonally flat except near
the western boundary, constraining meridional flow to the western
boundary layer. The model is forced by a prescribed meridional surface
density profile.
This two-plane model reproduces both steady-state density and
steady-state THC structures of a primitive-equation model. The
solution shows narrow deep sinking at the eastern high latitudes,
distributed upwelling at both boundaries, and a western boundary
current with poleward surface and equatorward deep flow. The
overturning strength has a 2/3-power-law dependence on
vertical diffusivity and a 1/3-power-law dependence on the
imposed meridional surface density difference. Convective mixing plays
an essential role in the two-plane model, ensuring that deep sinking
is located at high latitudes. This role of convective mixing is
consistent with that in three-dimensional models and marks a sharp
contrast with previous two-dimensional models.
Overall, the two-plane model reproduces crucial features of the THC as
simulated in simple-geometry three-dimensional models. At the same
time, the model self-consistently makes quantitative a conceptual
picture of the three-dimensional THC that hitherto has been expressed
either purely qualitatively or not self-consistently. |
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