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| Titel |
Biological production in the Bellingshausen Sea from oxygen-to-argon ratios and oxygen triple isotopes |
| VerfasserIn |
K. Castro-Morales, N. Cassar, D. R. Shoosmith, J. Kaiser |
| 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 ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-05), S.2273-2291 |
| Datensatznummer |
250018184
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| Publikation (Nr.) |
 copernicus.org/bg-10-2273-2013.pdf |
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| Zusammenfassung |
| We present estimates of mixed-layer net community oxygen production (N) and
gross oxygen production (G) of the Bellingshausen Sea in March and April
2007. N was derived from oxygen-to-argon (O2/Ar) ratios; G was derived
using the dual-delta method from triple oxygen isotope measurements. In
addition, O2 profiles were collected at 253 CTD stations. N is often
approximated by the biological oxygen air–sea exchange flux (Fbio based
on the O2/Ar supersaturation, assuming that significant horizontal or
vertical fluxes are absent. Here we show that the effect of vertical fluxes
alone can account for Fbio values < 0 in large parts of the
Bellingshausen Sea towards the end of the productive season, which could
otherwise be mistaken to represent net heterotrophy. Thus, improved estimates
of mixed-layer N can be derived from the sum of Fbio, Fe (entrainment
from the upper thermocline during mixed-layer deepening) and Fv
(diapycnal eddy diffusion across the base of the mixed layer). In the winter
sea ice zone (WSIZ), the corresponding correction results in a small change
of Fbio = (30 ± 17) mmol m−2 d−1 to N = (34 ± 17) mmol m−2 d−1. However, in the permanent open ocean zone
(POOZ), the original Fbio value of (−17 ± 10) mmol m−2 d−1 gives
a corrected value for N of (−2 ± 18) mmol m−2 d−1. We hypothesize that in the WSIZ, enhanced water column stability
due to the release of freshwater and nutrients from sea ice melt may account
for the higher N value. These results stress the importance of accounting for
physical biases when estimating mixed-layer marine productivity from in situ
O2/Ar ratios. |
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