A cautionary tale: A study of amethane enhancement over the north sea ...

• Main Authors: Cain, M, Warwick, NJ, 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, Pyle, JA
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2017
• Subjects: 37 Earth Sciences; 3701 Atmospheric Sciences; 3705 Geology; 13 Climate Action; North Atlantic
• Online Access: https://dx.doi.org/10.17863/cam.10861; https://www.repository.cam.ac.uk/handle/1810/264998

AbstractAirborne measurements of a methane (CH 4 ) 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 CH 4 emission rate between 2.5 ± 0.8×10 4 and 4.6 ± 1.5×10 4 kg h −1 . This would be greater than the industry's reported 0.5% leak rate if it were emitting for more than half the time. Second, annual average UK CH 4 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 δ 13 C‐CH 4 from the plume is shown to be −53‰, which is lighter than fossil gas but heavier than the UK average emission. We conclude that either an additional small‐area mainland ...