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| Titel |
Seasonal and interannual variations in the nitrogen cycle in the Arabian Sea |
| VerfasserIn |
T. Rixen, A. Baum, B. Gaye, B. Nagel |
| 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. 20 ; Nr. 11, no. 20 (2014-10-16), S.5733-5747 |
| Datensatznummer |
250117645
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| Publikation (Nr.) |
 copernicus.org/bg-11-5733-2014.pdf |
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| Zusammenfassung |
| The Arabian Sea plays an important role in the marine nitrogen cycle because
of its pronounced mid-water oxygen minimum zone (OMZ) in which bio-available
nitrate (NO3−) is reduced to dinitrogen gas (N2). As the
nitrogen cycle can respond fast to climate-induced changes in productivity
and circulation, the Arabian Sea sediments are an important palaeoclimatic
archive. In order to understand seasonal and interannual variations in the
nitrogen cycle, nutrient data were obtained from the literature published prior to
1993, evaluated, and compared with data measured during five expeditions
carried out in the framework of the Joint Global Ocean Flux Study (JGOFS) in
the Arabian Sea in 1995 and during a research cruise of RV
Meteor in 2007. The data comparison showed that the area
characterized by a pronounced secondary nitrite maximum (SNM) was by 63%
larger in 1995 than a similarly determined estimate based on pre-JGOFS data.
This area, referred to as the core of the denitrifying zone, showed strong
seasonal and interannual variations driven by the monsoon. During the SW
monsoon, the SNM retreated eastward due to the inflow of oxygen-enriched
Indian Ocean Central Water (ICW). During the NE monsoon, the SNM expanded
westward because of the reversal of the current regime. On an interannual
timescale, a weaker SW monsoon decreased the inflow of ICW from the
equatorial Indian Ocean and increased the accumulation of denitrification
tracers by extending the residence time of water in the SNM. This is
supported by palaeoclimatic studies showing an enhanced preservation of
accumulative denitrification tracers in marine sediments in conjunction with
a weakening of the SW monsoon during the late Holocene. |
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