Articles | Volume 16, issue 23
Atmos. Chem. Phys., 16, 14891–14908, 2016
Atmos. Chem. Phys., 16, 14891–14908, 2016

Research article 01 Dec 2016

Research article | 01 Dec 2016

Using δ13C-CH4 and δD-CH4 to constrain Arctic methane emissions

Nicola J. Warwick1,2, Michelle L. Cain1, Rebecca Fisher3, James L. France4, David Lowry3, Sylvia E. Michel5, Euan G. Nisbet3, Bruce H. Vaughn5, James W. C. White5, and John A. Pyle1,2 Nicola J. Warwick et al.
  • 1National Centre for Atmospheric Science, NCAS, UK
  • 2Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
  • 3Department of Earth Sciences, Royal Holloway, University of London, Egham, TW20 0EX, UK
  • 4School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
  • 5Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO 80309, USA

Abstract. We present a global methane modelling study assessing the sensitivity of Arctic atmospheric CH4 mole fractions, δ13C-CH4 and δD-CH4 to uncertainties in Arctic methane sources. Model simulations include methane tracers tagged by source and isotopic composition and are compared with atmospheric data at four northern high-latitude measurement sites. We find the model's ability to capture the magnitude and phase of observed seasonal cycles of CH4 mixing ratios, δ13C-CH4 and δD-CH4 at northern high latitudes is much improved using a later spring kick-off and autumn decline in northern high-latitude wetland emissions than predicted by most process models. Results from our model simulations indicate that recent predictions of large methane emissions from thawing submarine permafrost in the East Siberian Arctic Shelf region could only be reconciled with global-scale atmospheric observations by making large adjustments to high-latitude anthropogenic or wetland emission inventories.

Short summary
Methane is an important greenhouse gas. Methane emissions from Arctic wetlands are poorly quantified and may increase in a warming climate. Using a global atmospheric model and atmospheric observations of methane and its isotopologues, we find that isotopologue data are useful in constraining Arctic wetland emissions. Our results suggest that the seasonal cycle of these emissions may be incorrectly simulated in land process models, with implications for our understanding of future emissions.
Final-revised paper