What prevents nitrogen depletion in the oxygen minimum zone of the eastern tropical South Pacific?.

Su, Bei, Pahlow, Markus, Wagner, Hannes and Oschlies, Andreas (2015) What prevents nitrogen depletion in the oxygen minimum zone of the eastern tropical South Pacific?. Open Access Biogeosciences (BG), 12 . pp. 1113-1130. DOI 10.5194/bg-12-1113-2015.

[img]
Preview
Text
bgd-11-11095-2014.pdf - Submitted Version
Available under License Creative Commons Attribution.

Download (2894Kb) | Preview
[img]
Preview
Text
bg-12-1113-2015.pdf - Published Version
Available under License Creative Commons Attribution.

Download (524Kb) | Preview

Supplementary data:

Abstract

Local coupling between nitrogen fixation and denitrification in current biogeochemical models could result in runaway feedback in open-ocean oxygen minimum zones (OMZs), eventually stripping OMZ waters of all fixed nitrogen. This feedback does not seem to operate at full strength in the ocean, as nitrate does not generally become depleted in open-ocean OMZs. To explore in detail the possible mechanisms that prevent nitrogen depletion in the OMZ of the eastern tropical South Pacific (ETSP), we develop a box model with fully prognostic cycles of carbon, nutrients and oxygen in the upwelling region and its adjacent open ocean. Ocean circulation is calibrated with Δ14C data of the ETSP. The sensitivity of the simulated nitrogen cycle to nutrient and oxygen exchange and ventilation from outside the model domain and to remineralization scales inside an OMZ is analysed. For the entire range of model configurations explored, we find that the fixed-N inventory can be stabilized at non-zero levels in the ETSP OMZ only if the remineralization rate via denitrification is slower than that via aerobic respiration. In our optimum model configuration, lateral oxygen supply into the model domain is required at rates sufficient to oxidize at least about one fifth of the export production in the model domain to prevent anoxia in the deep ocean. Under these conditions, our model is in line with the view of phosphate as the ultimate limiting nutrient for phytoplankton, and implies that for the current notion of nitrogen fixation being favoured in N-deficit waters, the water column of the ETSP could even be a small net source of nitrate.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/264879
Additional Information: WOS:000349794900013
Research affiliation: OceanRep > SFB 754
OceanRep > SFB 754 > B1
OceanRep > The Future Ocean - Cluster of Excellence > FO-R11
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-12-1113-2015
ISSN: 1726-4170
Projects: SFB754, CARBOCHANGE, Future Ocean
Date Deposited: 11 Aug 2014 12:44
Last Modified: 19 Dec 2017 12:51
URI: http://oceanrep.geomar.de/id/eprint/25433

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...