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