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An intercomparison of oceanic methane and nitrous oxide measurements

Lookup NU author(s): Dr Jonathan Barnes, Professor Robert Upstill-Goddard

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Large-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can be validated across different laboratory groups. This study represents the first formal international intercomparison of oceanic methane and nitrous oxide measurements whereby participating laboratories received batches of seawater samples from the subtropical Pacific Ocean and the Baltic Sea. Additionally, compressed gas standards from the same calibration scale were distributed to the majority of participating laboratories to improve the analytical accuracy of the gas measurements. The computations used by each laboratory to derive the dissolved gas concentrations were also evaluated for inconsistencies (e.g., pressure and temperature corrections, solubility constants). The results from the intercomparison and intercalibration provided invaluable insights into methane and nitrous oxide measurements. It was observed that analyses of seawater samples with the lowest concentrations of methane and nitrous oxide had the lowest precisions. In comparison, while the analytical precision for samples with the highest concentrations of trace gases was better, the variability between the different laboratories was higher: 36% for methane and 27% for nitrous oxide. In addition, the comparison of different batches of seawater samples with methane and nitrous oxide concentrations that ranged over an order of magnitude revealed the ramifications of different calibration procedures for each trace gas. Finally, this study builds upon the intercomparison results to develop recommendations for improving oceanic methane and nitrous oxide measurements, with the aim of precluding future analytical discrepancies between laboratories.


Publication metadata

Author(s): Wilson ST, Bange HW, Wilson ST, Bange HW, Arévalo-Martínez DL, Barnes J, Borges AV, Brown I, Bullister JL, Burgos M, Capelle DW, Casso M, de la Paz M, Farías L, Fenwick L, Ferrón S, Garcia G, Glockzin M, Karl DM, Kock A, Laperriere S, Law CS, Manning CC, Marriner A, Myllykangas J-P, Pohlman JW, Rees AP, Santoro AE, Torres M, Tortell PD, Upstill-Goddard RC, Wisegarver DP, Zhang GL, Rehder G

Publication type: Article

Publication status: Published

Journal: Biogeosciences

Year: 2018

Volume: 15

Issue: 19

Pages: 5891-5907

Online publication date: 05/10/2018

Acceptance date: 26/09/2018

ISSN (print): 1726-4170

ISSN (electronic): 1726-4189

Publisher: EGU

URL: https://doi.org/10.5194/bg-15-5891-2018

DOI: 10.5194/bg-15-5891-2018


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