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| Titel |
Variability of the transport of anthropogenic CO2 at the Greenland–Portugal OVIDE section: controlling mechanisms |
| VerfasserIn |
P. Zunino, M. I. Garcia-Ibañez, P. Lherminier, H. Mercier, A. F. Ríos, F. F. Pérez |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2014-04-29), S.2375-2389 |
| Datensatznummer |
250117381
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| Publikation (Nr.) |
 copernicus.org/bg-11-2375-2014.pdf |
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| Zusammenfassung |
| The interannual to decadal
variability in the transport of anthropogenic CO2 (Cant) across the
subpolar North
Atlantic (SPNA) is investigated, using summer data of the FOUREX and OVIDE
high-resolution transoceanic sections, from Greenland to Portugal, occupied
six times from 1997 to 2010. The transport of Cant across this section,
Tcant hereafter, is northward, with a mean value of
254 ± 29 kmol s−1 over the 1997–2010 period. We find that
Tcant undergoes interannual variability, masking any trend
different from 0 for this period. In order to understand the mechanisms
controlling the variability of Tcant across the SPNA, we propose
a new method that quantifies the transport of Cant caused by the diapycnal
and isopycnal circulation. The diapycnal component yields a large northward
transport of Cant (400 ± 29 kmol s−1) that is partially
compensated by a southward transport of Cant caused by the isopycnal
component (−171 ± 11 kmol s−1), mainly localized in the
Irminger Sea. Most importantly, the diapycnal component is found to be the
main driver of the variability of Tcant across the SPNA. Both the
Meridional Overturning Circulation (computed in density coordinates,
MOCσ) and the Cant increase in the water column have an important
effect on the variability of the diapycnal component and of Tcant
itself. Based on this analysis, we propose a simplified estimator for the
variability of Tcant based on the intensity of the MOCσ and on the difference of Cant between the upper and lower limb of the
MOCσ (ΔCant). This estimator shows a good consistency with
the diapycnal component of Tcant, and help to disentangle the
effect of the variability of both the circulation and the Cant increase on
the Tcant variability. We find that ΔCant keeps
increasing over the past decade, and it is very likely that the continuous
Cant increase in the water masses will cause an increase in Tcant
across the SPNA at long timescale. Nevertheless, at the timescale analyzed
here (1997–2010), the MOCσ controls the Tcant
variability, blurring any Tcant trend. Extrapolating the observed
ΔCant increase rate and considering the predicted slow-down of
25% of the MOCσ, Tcant across the SPNA is expected
to increase by 430 kmol s−1 during the 21st century. Consequently, an
increase in the storage rate of Cant in the SPNA could be envisaged. |
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