Abstract

Carbon isotopic studies of atmospheric methane can provide constraints on the proportion of methane emitted to the atmosphere from different sources. At Royal Holloway δ13C in atmospheric methane is measured in samples from a network of sites in the Arctic, Atlantic and from Egham, SW of London.

The carbon isotopic signature of some major Arctic and sub-Arctic methane sources has been characterised from field studies. Methane from different sources has markedly different δ13C. Methane from northern wetlands has δ13C around -70‰; Siberian natural gas is around -50‰ and forest fire emissions are around around -28‰. Thus δ13C readily identifies specific source increments. The carbon isotopic signature of the bulk methane increment in ambient Arctic air has also been measured in air samples collected at the Zeppelin station, Spitsbergen. Results indicate a primarily biogenic source of methane to the Arctic in the summer months, most likely with a large wetland contribution.