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| Titel |
Spatiotemporal variations of nitrogen isotopic records in the Arabian Sea |
| VerfasserIn |
S.-J. Kao, B.-Y. Wang, L.-W. Zheng, K. Selvaraj, S.-C. Hsu, X. H. Sean Wan, M. Xu, C.-T. Arthur Chen |
| 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 ; 12, no. 1 ; Nr. 12, no. 1 (2015-01-05), S.1-14 |
| Datensatznummer |
250117755
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| Publikation (Nr.) |
 copernicus.org/bg-12-1-2015.pdf |
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| Zusammenfassung |
| Available reports of dissolved oxygen, δ15N of nitrate (δ
15NNO3) and δ15N of total nitrogen (δ15Nbulk) for trap material and surface/downcore sediments
from the Arabian Sea (AS) were synthesized to explore the AS' past nitrogen
dynamics. Based on 25 μmol kg−1 dissolved oxygen isopleth at
a depth of 150 m, we classified all reported data into northern and southern
groups. By using δ15Nbulk of the sediments, we obtained
geographically distinctive bottom-depth effects for the northern and southern
AS at different climate stages. After eliminating the bias caused by bottom
depth, the modern-day sedimentary δ15Nbulk values
largely reflect the δ15NNO3 supply from the bottom of
the euphotic zone. Additionally to the data set, nitrogen and carbon
contents vs. their isotopic compositions of a sediment core (SK177/11)
collected from the most southeastern part of the AS were measured for
comparison. We found a one-step increase in δ15Nbulk
starting at the deglaciation with a corresponding decrease in
δ13CTOC similar to reports elsewhere revealing a global
coherence. By synthesizing and reanalyzing all reported down core
δ15Nbulk, we derived bottom-depth correction factors at
different climate stages, respectively, for the northern and southern AS. The
diffusive sedimentary δ15Nbulk values in compiled
cores became confined after bias correction revealing a more consistent
pattern except recent 6 ka. Such high similarity to the global temporal
pattern indicates that the nitrogen cycle in the entire AS had responded to
open-ocean changes until 6 ka BP. Since 6 ka BP, further enhanced
denitrification (i.e., increase in δ15Nbulk) in the
northern AS had occurred and was likely driven by monsoon, while, in the
southern AS, we observed a synchronous reduction in
δ15Nbulk, implying that nitrogen fixation was promoted correspondingly as the
intensification of local denitrification at the northern AS basin. |
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