Preprints
https://doi.org/10.5194/egusphere-2023-2924
https://doi.org/10.5194/egusphere-2023-2924
12 Jan 2024
 | 12 Jan 2024

Interannual variations in the Δ(17O) signature of atmospheric CO2 at two mid-latitude sites suggest a close link to stratosphere-troposphere exchange

Pharahilda M. Steur, Hubertus A. Scheeren, Gerbrand Koren, Getachew A. Adnew, Wouter Peters, and Harro A. J. Meijer

Abstract. Δ(17O )measurements of atmospheric CO2 have the potential to be a tracer for gross primary production and stratosphere-troposphere mixing. A positive Δ(17O) originates from intrusions of stratospheric CO2, whereas values close to zero result from equilibration of CO2 and water, predominantly happening inside plants. The stratospheric source of CO2 carrying high Δ(17O) is, however, not well defined in the current models. More and long-time atmospheric measurements are needed to improve this. We present records of the Δ(17O) of atmospheric CO2 conducted with laser absorption spectroscopy, from Lutjewad in the Netherlands (53° 24’N, 6° 21’E) and Mace Head in Ireland (53° 20’ N, 9° 54’ W), covering the period 2017–2022. The records are compared with a 3-D model simulation, and we study potential model improvements. Both records show significant interannual variability, of up to 0.3 ‰. The total range covered by smoothed monthly averages from the Lutjewad record is -0.065 to 0.046 ‰, which is significantly higher than the range of -0.009 and 0.036 ‰ of the model simulation. The 100 hPa 60–90° North monthly mean temperature anomaly was used as a proxy to scale stratospheric downwelling in the model. This strongly improves the correlation coefficient of the simulated and observed year-to-year Δ(17O) variations over the period 2019–2021, from 0.37 to 0.81. As the Δ(17O) of atmospheric CO2 seems to be dominated by stratospheric influx, its use a as a tracer for stratosphere-troposphere exchange should be further investigated.

Pharahilda M. Steur, Hubertus A. Scheeren, Gerbrand Koren, Getachew A. Adnew, Wouter Peters, and Harro A. J. Meijer

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  • RC1: 'Comment on egusphere-2023-2924', Anonymous Referee #1, 17 Jan 2024
  • RC2: 'Comment on egusphere-2023-2924', Anonymous Referee #2, 26 Feb 2024
Pharahilda M. Steur, Hubertus A. Scheeren, Gerbrand Koren, Getachew A. Adnew, Wouter Peters, and Harro A. J. Meijer

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Interannual variations in the Δ17O signature of atmospheric CO2 at two mid-latitude sites suggest a close link to stratosphere-troposphere exchange P. Steur et al. https://doi.org/10.34894/1XJG1F

Pharahilda M. Steur, Hubertus A. Scheeren, Gerbrand Koren, Getachew A. Adnew, Wouter Peters, and Harro A. J. Meijer

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Short summary
We present records of the triple oxygen isotope signature (Δ(17O)) of atmospheric CO2 conducted with laser absorption spectroscopy from two mid-latitude stations. Significant interannual variability is observed in both records. A model sensitivity study suggests that stratosphere-troposphere exchange, carrying high Δ(17O) CO2 from the stratosphere into the troposphere, causes most of the variability. This makes Δ(17O) a potential tracer for stratospheric intrusions in the troposphere.