The impact of spatially varying wetland source signatures on the atmospheric variability of dD-CH4

<p>We present the first spatially varying map of the &#948;D-CH₄signature of wetland methane emissions and model its impact on atmospheric &#948;D-CH₄. The &#948;D-CH₄ signature map is derived by relating the &#948;D-H₂O of precipitation to the measured &#948;D-CH₄ of methane wetland emissions at a variety of wetland types and locations. Since the &#948;D-H₂O of precipitation is highly latitude-dependent, including this spatial variation has the potential to have a large impact on the distribution of &#948;D-CH₄ observed in the atmosphere. This latitude-dependence means that wetland emissions at different latitudes can have very different impacts on atmospheric &#948;D-CH₄, which could provide a useful way to constrain the location of wetland methane emissions in future inverse modelling studies. Here, we assess the implications for model studies on the differences that arise by treating &#948;D-CH₄ wetland source signatures as globally uniform rather than accounting for the large spatial variation. We also assess the potential for &#948;D-CH₄ to provide an independent constraint on wetland emissions over the more abundant and widely measured &#948;¹³C-CH₄.</p>