TY - JOUR
T1 - Nitrous oxide production in surface waters of the mid-latitude North Atlantic Ocean
AU - Ji, Qixing
AU - Ward, Bettie
N1 - Funding Information:
The authors thank Andrew Babbin and Aimee Babbin for providing nutrient analysis on the cruise; all the crew members on R/V Endeavor for their technical assistance; and excellent technical guidance from Sergey Oleynik during laboratory analysis. Comments and suggestions from two anonymous reviewers were very insightful and contributed significantly to the analysis and interpretation of the data. The project was funded by NSF (OCE-1136345) to B.B.W. The manuscript is prepared to comply with AGU data policy. Detailed information about the data and method reported here should be addressed to qji@princeton.edu.
Publisher Copyright:
© 2017. American Geophysical Union. All Rights Reserved.
PY - 2017/3/1
Y1 - 2017/3/1
N2 - The ocean is a major source of atmospheric nitrous oxide (N2O), an important greenhouse gas and ozone-depleting agent. The oceanic flux of N2O varies regionally, and in the midlatitude North Atlantic, the production of N2O is poorly constrained. Incubation experiments with 15N-ammonium and 15N-nitrite revealed active N2O production from ammonium oxidation and nitrite reduction in the surface ocean, suggesting the midlatitude North Atlantic could be a net source for N2O, with a flux density of 0.06 µmol-N2O m−2 d−1 in the top 120 m. The peak of N2O production was detected in the upper 100 m, shallower than the depth at which highest rates of ammonium oxidation to nitrite occurred. Oxygen was not depleted in the water column, but its concentration minimum corresponded to highest N2O oversaturation and low in situ N2O production. The apparent N2O yield, i.e., the molar ratio of N2O-N production over nitrite production was 1.7% at the peak N2O production depths in the surface layer and decreased to less than 0.1% at peak ammonium oxidation depths. The majority of N2O production was apparently through “hybrid formation,” in which ammonium and nitrite each contribute one nitrogen atom to N2O formation, a process that is proposed to be mediated by ammonia oxidizing archaea.
AB - The ocean is a major source of atmospheric nitrous oxide (N2O), an important greenhouse gas and ozone-depleting agent. The oceanic flux of N2O varies regionally, and in the midlatitude North Atlantic, the production of N2O is poorly constrained. Incubation experiments with 15N-ammonium and 15N-nitrite revealed active N2O production from ammonium oxidation and nitrite reduction in the surface ocean, suggesting the midlatitude North Atlantic could be a net source for N2O, with a flux density of 0.06 µmol-N2O m−2 d−1 in the top 120 m. The peak of N2O production was detected in the upper 100 m, shallower than the depth at which highest rates of ammonium oxidation to nitrite occurred. Oxygen was not depleted in the water column, but its concentration minimum corresponded to highest N2O oversaturation and low in situ N2O production. The apparent N2O yield, i.e., the molar ratio of N2O-N production over nitrite production was 1.7% at the peak N2O production depths in the surface layer and decreased to less than 0.1% at peak ammonium oxidation depths. The majority of N2O production was apparently through “hybrid formation,” in which ammonium and nitrite each contribute one nitrogen atom to N2O formation, a process that is proposed to be mediated by ammonia oxidizing archaea.
KW - N tracer
KW - North Atlantic
KW - hybrid formation
KW - nitrous oxide
KW - surface ocean
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U2 - 10.1002/2016JC012467
DO - 10.1002/2016JC012467
M3 - Article
AN - SCOPUS:85017332080
SN - 2169-9291
VL - 122
SP - 2612
EP - 2621
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
IS - 3
ER -