Rixen, Tim, Baum, Antje, Gaye, B. and Nagel, B. (2013) Seasonal and interannual variations of the nitrogen cycle in the Arabian Sea. Biogeosciences Discussions, 11 . pp. 5733-5747. DOI https://doi.org/10.5194/bgd-10-19541-2013.

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Abstract

The Arabian Sea plays an important role in themarine nitrogen cycle because of its pronounced mid-wateroxygen minimum zone (OMZ) in which bio-available nitrate(NO−3) is reduced to dinitrogen gas (N2). As the nitrogencycle can respond fast to climate-induced changes in pro-ductivity and circulation, the Arabian Sea sediments are animportant palaeoclimatic archive. In order to understand sea-sonal and interannual variations in the nitrogen cycle, nutri-ent data were obtained from the literature published prior to1993, evaluated, and compared with data measured duringfive expeditions carried out in the framework of the JointGlobal Ocean Flux Study (JGOFS) in the Arabian Sea in1995 and during a research cruise of RVMeteorin 2007.The data comparison showed that the area characterized by apronounced secondary nitrite maximum (SNM) was by 63 %larger in 1995 than a similarly determined estimate based onpre-JGOFS data. This area, referred to as the core of thedenitrifying zone, showed strong seasonal and interannualvariations 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 NEmonsoon, the SNM expanded westward because of the re-versal of the current regime. On an interannual timescale,a weaker SW monsoon decreased the inflow of ICW fromthe equatorial Indian Ocean and increased the accumulationof denitrification tracers by extending the residence time ofwater in the SNM. This is supported by palaeoclimatic stud-ies showing an enhanced preservation of accumulative de-nitrification tracers in marine sediments in conjunction witha weakening of the SW monsoon during the late Holocene.

Document Type:	Article
Programme Area:	UNSPECIFIED
Research affiliation:	Biogeochemistry and Geology > Carbon and Nutrient Cycling
Refereed:	Yes
Open Access Journal?:	Yes
DOI:	https://doi.org/10.5194/bgd-10-19541-2013
ISSN:	1810-6285
Date Deposited:	16 Aug 2019 15:57
Last Modified:	01 Oct 2020 12:59
URI:	http://cris.leibniz-zmt.de/id/eprint/2679

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