Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database.

Zamora, Lauren, Oschlies, Andreas , Bange, Hermann W. , Craig, J. D., Huebert, K. B., Kock, Annette and Löscher, C. R. (2012) Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database. Open Access Biogeosciences (BG), 9 . pp. 5007-5022. DOI 10.5194/bg-9-5007-2012.

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Abstract

The Eastern Tropical Pacific (ETP) is believed to be one of the largest marine sources of the greenhouse gas nitrous oxide N2O). Future N2Oemissions from the ETP are highly uncertain because oxygen minimum zones are expected to expand, affecting both regional production and consumption of N2O. Here we assess three primary uncertainties in how N2O may respond to changing O2 levels: (1) the relationship between N2O production and O2 (is it linear or exponential at low O2 concentrations?), (2) the cutoff point at which net N2O production switches to net N2O consumption (uncertainties in this parameterization can lead to differences in model ETP N2O concentrations of more than 20%), and (3) the rate of net N2O consumption at low O2. Based on the MEMENTO database, which is the largest N2O dataset currently available, we find that N2O production in the ETP increases linearly rather than exponentially with decreasing O2. Additionally, net N2O consumption switches to net N2O production at ~ 10 μM O2, a value in line with recent studies that suggest consumption occurs on a larger scale than previously thought. N2O consumption is on the order of 0.129 mmol N2O m−3 yr−1 in the Peru–Chile Undercurrent. Based on these findings, it appears that recent studies substantially overestimated N2O production in the ETP. In light of expected deoxygenation, future N2O production is still uncertain, but due to higher-than-expected consumption levels, it is possible that N2Oconcentrations may decrease rather than increase as oxygen minimum zones expand.

Document Type: Article
Keywords: Biogeochemistry: Greenhouse Gases; AMMONIA-OXIDIZING ARCHAEA; TROPICAL NORTH-PACIFIC; EASTERN SOUTH-PACIFIC; MINIMUM ZONE; CONTINUOUS CULTURE; NITRATE REDUCTION; HIGH-RESOLUTION; ARABIAN SEA; EL-NINO; OCEAN
Research affiliation: OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > SFB 754 > B1
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-9-5007-2012
ISSN: 1726-4170
Related URLs:
Projects: SOPRAN, SFB754, MEMENTO, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 26 Sep 2012 09:02
Last Modified: 24 Sep 2019 00:15
URI: http://oceanrep.geomar.de/id/eprint/15422

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