Using δ13C-CH4 and δD-CH4 to constrain Arctic methane emissions | CU Experts

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 coloured by source and isotopic composition and are compared with atmospheric data at four high northern 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 in high northern latitudes is much improved using a later spring kick-off and autumn decline in high northern 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 emission inventories.;

Warwick NJ; Cain ML; Fisher R; France JL; Lowry D; Michel SE; Nisbet EG; Vaughn BH; White JWC; Pyle JA

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