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| Titel |
Seasonal and mesoscale variability of oceanic transport of anthropogenic CO2 |
| VerfasserIn |
Z. Lachkar, J. C. Orr, J.-C. Dutay |
| 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 ; 6, no. 11 ; Nr. 6, no. 11 (2009-11-09), S.2509-2523 |
| Datensatznummer |
250004088
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| Publikation (Nr.) |
 copernicus.org/bg-6-2509-2009.pdf |
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| Zusammenfassung |
| Estimates of the ocean's large-scale transport of anthropogenic
CO2 are based on one-time hydrographic sections, but the temporal
variability of this transport has not been investigated. The aim of
this study is to evaluate how the seasonal and mesoscale variability
affect data-based estimates of anthropogenic CO2 transport. To
diagnose this variability, we made a global anthropogenic CO2
simulation using an eddy-permitting version of the coupled ocean
sea-ice model ORCA-LIM. As for heat transport, the seasonally varying
transport of anthropogenic CO2 is largest within 20° of
the equator and shows secondary maxima in the subtropics. Ekman
transport generally drives most of the seasonal variability, but the
contribution of the vertical shear becomes important near the equator
and in the Southern Ocean. Mesoscale variabilty contributes to the
annual-mean transport of both heat and anthropogenic CO2 with
strong poleward transport in the Southern Ocean and equatorward
transport in the tropics. This "rectified" eddy transport is
largely baroclinic in the tropics and barotropic in the Southern Ocean
due to a larger contribution from standing eddies. Our analysis
revealed that most previous hydrographic estimates of meridional
transport of anthropogenic CO2 are severely biased because they
neglect temporal fluctuations due to non-Ekman velocity variations.
In each of the three major ocean basins, this bias is largest near the
equator and in the high southern latitudes. In the subtropical North
Atlantic, where most of the hydrographic-based estimates have been
focused, this uncertainty represents up to 20% and 30% of total
meridional transport of heat and CO2. Generally though, outside
the tropics and Southern Ocean, there are only small variations in
meridional transport due to seasonal variations in tracer fields and
time variations in eddy transport. For the North Atlantic, eddy
variability accounts for up to 10% and 15% of the total transport of
heat and CO2. This component is not accounted for in
coarse-resolution hydrographic surveys. |
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