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Titel |
Water masses as a unifying framework for understanding the Southern Ocean Carbon Cycle |
VerfasserIn |
D. Iudicone, K. B. Rodgers, I. Stendardo, O. Aumont, G. Madec, L. Bopp, O. Mangoni, M. Ribera d'Alcala' |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1726-4170
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Digitales Dokument |
URL |
Erschienen |
In: Biogeosciences ; 8, no. 5 ; Nr. 8, no. 5 (2011-05-04), S.1031-1052 |
Datensatznummer |
250005805
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Publikation (Nr.) |
copernicus.org/bg-8-1031-2011.pdf |
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Zusammenfassung |
The scientific motivation for this study is to understand the
processes in the
ocean interior controlling carbon transfer across 30° S.
To address this, we have developed a unified framework for
understanding the interplay between physical drivers such as buoyancy fluxes
and ocean mixing, and
carbon-specific processes such as biology, gas exchange and carbon mixing.
Given the importance of density in determining the ocean interior structure and
circulation, the framework is one that is organized by density and water masses,
and it makes combined use of Eulerian and Lagrangian diagnostics.
This is achieved through application to a
global ice-ocean circulation model
and an ocean biogeochemistry model, with both components being part of the
widely-used IPSL coupled ocean/atmosphere/carbon cycle model.
Our main new result is the dominance of the overturning circulation
(identified by water masses) in setting the vertical distribution of carbon transport from the Southern Ocean
towards the global ocean. A net contrast emerges between the
role of Subantarctic Mode Water (SAMW), associated with large northward transport and ingassing, and Antarctic Intermediate Water (AAIW),
associated with a much smaller export and outgassing.
The differences in their export rate reflects differences in their water mass formation processes.
For SAMW, two-thirds of the surface waters are provided as a result of the densification of
thermocline water (TW),
and upon densification this water carries with it a substantial
diapycnal flux of dissolved inorganic carbon (DIC).
For AAIW, principal formatin processes include buoyancy forcing and mixing, with these
serving to lighten CDW.
An additional important formation pathway of AAIW is through the effect of interior
processing (mixing, including cabelling) that serve to densify SAMW.
A quantitative evaluation of the contribution of mixing, biology and gas exchange to the DIC evolution per
water mass reveals that mixing and, secondarily, gas exchange, effectively nearly balance biology
on annual scales (while the latter process
can be dominant at seasonal scale).
The distribution of DIC in the northward flowing water
at 30° S is thus primarily set by the DIC
values of the water masses that are involved
in the formation processes. |
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