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| Titel |
Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone |
| VerfasserIn |
T. Fischer, D. Banyte, P. Brandt, M. Dengler, G. Krahmann, T. Tanhua, M. Visbeck |
| 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. 7 ; Nr. 10, no. 7 (2013-07-26), S.5079-5093 |
| Datensatznummer |
250018363
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| Publikation (Nr.) |
 copernicus.org/bg-10-5079-2013.pdf |
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| Zusammenfassung |
| The replenishment of consumed oxygen in the open ocean oxygen minimum zone
(OMZ) off northwest Africa is accomplished by oxygen transport across and
along density surfaces, i.e. diapycnal and isopycnal oxygen supply. Here the
diapycnal oxygen supply is investigated using a large observational set of
oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal
mixing is inferred from different sources: (i) a large-scale tracer release
experiment, (ii) microstructure profiles, and (iii) shipboard acoustic
current measurements plus density profiles. From these measurements, the
average diapycnal diffusivity in the studied depth interval from 150 to
500 m is estimated to be 1 × 10−5 m2 s−1, with lower and
upper 95% confidence limits of 0.8 × 10−5 m2 s−1 and
1.4 × 10−5 m2 s−1. Diapycnal diffusivity in this depth
range is predominantly caused by turbulence, and shows no significant vertical
gradient. Diapycnal mixing is found to contribute substantially to the oxygen
supply of the OMZ. Within the OMZ core, 1.5 μmol kg−1 yr−1 of oxygen is supplied via diapycnal mixing,
contributing about one-third of the total demand. This oxygen which is supplied
via diapycnal mixing originates from oxygen that has been laterally supplied
within the upper Central Water layer above the OMZ, and within the Antarctic
Intermediate Water layer below the OMZ. Due to the existence of a separate
shallow oxygen minimum at about 100 m depth throughout most of the study
area, there is no net vertical oxygen flux from the surface layer into the
Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways. |
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