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@ARTICLE{Thomas:892382,
      author       = {Thomas, Max and Laube, Johannes C. and Kaiser, Jan and
                      Allin, Samuel and Martinerie, Patricia and Mulvaney, Robert
                      and Ridley, Anna and Röckmann, Thomas and Sturges, William
                      T. and Witrant, Emmanuel},
      title        = {{S}tratospheric carbon isotope fractionation and
                      tropospheric histories of {CFC}-11, {CFC}-12 and {CFC}-113
                      isotopologues},
      journal      = {Atmospheric chemistry and physics / Discussions},
      volume       = {2020},
      issn         = {1680-7367},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-02043},
      pages        = {843},
      year         = {2020},
      abstract     = {We present novel measurements of the carbon isotope
                      composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113
                      (CF2ClCFCl2), three atmospheric trace gases that are
                      important for both stratospheric ozone depletion and global
                      warming. These measurements were carried out on air samples
                      collected in the stratosphere – the main sink region for
                      these gases – and on air extracted from deep polar firn
                      snow. We quantify, for the first time, the apparent isotopic
                      fractionation, εapp(13C), for these gases as they are
                      destroyed in the high- and mid-latitude stratosphere:
                      εapp(CFC-12, high-lat) = (−20.2 ± 4.4) ‰ and
                      εapp(CFC-113, high-lat) = (−9.4 ± 4.4) ‰,
                      εapp(CFC-12, mid-lat) = (−30.3 ± 10.7) ‰, and
                      εapp(CFC-113, mid-lat) = (−34.4 ± 9.8) ‰. Our CFC-11
                      measurements were not sufficient to calculate εapp(CFC-11)
                      so we instead used previously reported photolytic
                      fractionation for CFC-11 and CFC-12 to scale our
                      εapp(CFC-12), resulting in εapp(CFC-11, high-lat) =
                      (−7.8 ± 1.7) ‰ and εapp(CFC-11, mid-lat) = (−11.7 ±
                      4.2) ‰. Measurements of firn air were used to construct
                      histories of the tropospheric isotopic composition,
                      δT(13C), for CFC-11 (1950s to 2009), CFC-12 (1950s to
                      2009), and CFC-113 (1970s to 2009) – with δT(13C)
                      increasing for each gas. We used εapp(high-lat), which were
                      derived from more data, and a constant isotopic composition
                      of emissions, δE(13C), to model δT(13C, CFC-11), δT(13C,
                      CFC-12), and δT(13C, CFC-113). For CFC-11 and CFC-12,
                      modelled δT(13C) was consistent with measured δT(13C) for
                      the entire period covered by the measurements, suggesting no
                      dramatic change in δE(13C, CFC-11) or δE(13C, CFC-12) has
                      occurred since the 1950s. For CFC-113, our modelled δT(13C,
                      CFC-113) did not agree with our measurements earlier than
                      1980. While this discrepancy may be indicative of a change
                      in δE(13C, CFC-113), it is premature to assign one. Our
                      modelling predicts increasing δT(13C, CFC-11), δT(13C,
                      CFC-12), and δT(13C, CFC-113) into the future. We
                      investigated the effect of recently reported new CFC-11
                      emissions on background δT(13C, CFC-11) by fixing model
                      emissions after 2012, and comparing δT(13C, CFC-11) in this
                      scenario to the model base case. The difference in δT(13C,
                      CFC-11) between these scenarios was 1.4 ‰ in 2050. This
                      difference is smaller than our model uncertainty envelope
                      and would therefore require improved modelling and
                      measurement precision, as well as better quantified isotopic
                      source compositions, to detect.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {244 - Composition and dynamics of the upper troposphere and
                      middle atmosphere (POF3-244) / EXC3ITE - EXploring
                      Chemistry, Composition and Circulation in the stratosphere
                      with InnovativeTEchnologies (678904)},
      pid          = {G:(DE-HGF)POF3-244 / G:(EU-Grant)678904},
      typ          = {PUB:(DE-HGF)16},
      doi          = {https://doi.org/10.5194/acp-2020-843},
      url          = {https://juser.fz-juelich.de/record/892382},
}