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| Titel |
Effects of mesoscale eddies on global ocean distributions of CFC-11, CO2, and δ¹⁴C |
| VerfasserIn |
Z. Lachkar, J. C. Orr, J.-C. Dutay, P. Delecluse |
| 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. 4 ; Nr. 3, no. 4 (2007-10-12), S.461-482 |
| Datensatznummer |
250001196
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| Publikation (Nr.) |
 copernicus.org/os-3-461-2007.pdf |
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| Zusammenfassung |
| Global-scale tracer simulations are typically made at coarse
resolution without explicitly modelling eddies. Here we ask what role
do eddies play in ocean uptake, storage, and meridional transport of
transient tracers. We made global anthropogenic transient-tracer
simulations in coarse-resolution (2°cosφ×2°, ORCA2) and eddy-permitting (½°cosφ×½°, ORCA05) versions of the
ocean general circulation model OPA9. Our focus is on
surface-to-intermediate waters of the southern extratropics where
air-sea tracer fluxes, tracer storage, and meridional tracer transport are
largest. Eddies have little effect on global and regional bomb
Δ14C uptake and storage. Yet for anthropogenic
CO2 and CFC-11, refining the horizontal resolution reduced
southern extratropical uptake by 25% and 28%, respectively. There is
a similar decrease in corresponding inventories, which yields better
agreement with observations. With higher resolution, eddies
strengthen upper ocean vertical stratification and reduce excessive
ventilation of intermediate waters by 20% between 60° S and
40° S. By weakening the residual circulation, i.e., the sum of
Eulerian mean flow and the opposed eddy-induced flow, eddies reduce
the supply of tracer-impoverished deep waters to the surface near the
Antarctic divergence, thus reducing the air-sea tracer flux. Thus in
the eddy permitting model, surface waters in that region have more
time to equilibrate with the atmosphere before they are transported
northward and subducted. As a result, the eddy permitting model's
inventories of CFC-11 and anthropogenic CO2 are lower in that
region because mixed-layer concentrations of both tracers equilibrate
with the atmosphere on relatively short time scales (15 days and 6
months, respectively); conversely, bomb Δ14C's
air-sea equilibration time of 6 years is so slow that, even in the
eddy permitting model, there is little time for surface concentrations
to equilibrate with the atmosphere, i.e., before surface waters are
subducted. |
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