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

Nicola J. Warwick, Michelle L. Cain, Rebecca Fisher, James L. France, David Lowry, Sylvia E. Michel, Euan G. Nisbet, Bruce H. Vaughn, James W. C. White, John A. Pyle
2016 Atmospheric Chemistry and Physics  
<p><strong>Abstract.</strong> We present a global methane modelling study assessing the sensitivity of Arctic atmospheric CH<sub>4</sub> mole fractions, <i>δ</i><sup>13</sup>C-CH<sub>4</sub> and <i>δ</i>D-CH<sub>4</sub> 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
more » ... magnitude and phase of observed seasonal cycles of CH<sub>4</sub> mixing ratios, <i>δ</i><sup>13</sup>C-CH<sub>4</sub> and <i>δ</i>D-CH<sub>4</sub> 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.</p>
doi:10.5194/acp-16-14891-2016 fatcat:772yy4azbzavvbis6nphh6vmv4