A cautionary tale: A study of a methane enhancement over the North Sea
View / Open Files
Authors
Warwick, Nicola
Fisher, RE
Lowry, D
Lanoisellé, M
Nisbet, EG
France, J
Pitt, J
O'Shea, S
Bower, KN
Allen, G
Illingworth, S
Manning, AJ
Bauguitte, S
Pisso, I
Publication Date
2017-07-27Journal Title
Journal of Geophysical Research: Atmospheres
ISSN
0148-0227
Publisher
William Byrd Press for John Hopkins Press
Volume
122
Pages
7630-7645
Type
Article
This Version
AM
Metadata
Show full item recordCitation
Cain, M., Warwick, N., Fisher, R., Lowry, D., Lanoisellé, M., Nisbet, E., France, J., et al. (2017). A cautionary tale: A study of a methane enhancement over the North Sea. Journal of Geophysical Research: Atmospheres, 122 7630-7645. https://doi.org/10.1002/2017JD026626
Abstract
Airborne measurements of a methane (CH4) plume over the North Sea from August 2013 are analyzed. The plume was only observed downwind of circumnavigated gas fields, and three methods are used to determine its source. First, a mass balance calculation assuming a gas field source gives a CH4 emission rate between 2.5±0.8x104 and 4.6±1.5x104 kg h−1. This would be greater than the industry target of a 0.5% leak rate if it were emitting for more than half the time. Second, annual average UK CH4 emissions are combined with an atmospheric dispersion model to create pseudo-observations. Clean air from the North Atlantic passed over mainland UK, picking up anthropogenic emissions. To best explain the observed plume using pseudo-observations, an additional North Sea source from the gas rigs area is added. Third, the δ13C-CH4 from the plume is shown to be -53%0, which is lighter than fossil gas but heavier than the UK average emission. We conclude that either an additional small-area mainland source is needed, combined with temporal variability in emission or transport in small-scale meteorological features. Alternatively, a combination of additional sources that are at least 75% from the mainland (-58%0) and up to 25% from the North Sea gas rigs area (-32%0) would explain the measurements. Had the isotopic analysis not been performed, the likely conclusion would have been of a gas field source of CH4. This demonstrates the limitation of analysing mole fractions alone, as the simplest explanation is rejected based on analysis of isotopic data.
Sponsorship
The MAMM project was funded by the UK Natural Environment Research Council (Grant 678 NE/I029293/1). 679 JAP and MC also acknowledge support through the ERC ACCI project, project number 680 267760. 681 IP acknowledges support from MOCA, funded by the Research Council of Norway, 682 grant 225814.
Funder references
NERC (NE/I029161/1)
European Research Council (267760)
NERC (NE/I010750/1)
National Centre for Atmospheric Science (NERC) (via University of Leeds) (R8/H12/83/003)
National Centre for Atmospheric Science (NERC) (via University of Leeds) (R8/H12/83/003)
National Centre for Atmospheric Science (NERC) (via University of Leeds) (R8H12/83/009)
Identifiers
External DOI: https://doi.org/10.1002/2017JD026626
This record's URL: https://www.repository.cam.ac.uk/handle/1810/264998
Rights
Licence:
http://www.rioxx.net/licenses/all-rights-reserved