EGU24-6354, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Interannual variations in Δ(17O) of atmospheric CO2 suggest a strong link with stratospheric input

Pharahilda Steur1, Hubertus A. Scheeren1, Gerbrand Koren2, Getachew A. Adnew3, Wouter Peters1,4, and Harro A. J. Meijer1
Pharahilda Steur et al.
  • 1Energy and Sustainability Research Institute, Centre for Isotope Research (CIO), University of Groningen, Groningen, Netherlands (
  • 2Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, the Netherlands
  • 3Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, Utrecht, the Netherlands
  • 4Environmental Sciences Group, Dept of Meteorology and Air Quality, Wageningen University and Research, Wageningen, the Netherlands

We present multiple year records of the triple oxygen isotope signature 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). Measurements were done on flask samples covering the period 2017-2022. The average uncertainty of 0.07 is about 3 times smaller than the total observed variability. 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 due to enhanced dissolution in the presence of carbonic anhydrase. A biosphere driven seasonal signal is, however, not observed in the records. 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 to 0.036 that was simulated with a 3-D transport model. One of the major model uncertainties is the representation of the stratospheric influx of Δ(17O). We modified the model using the 100 hPa 60-90° North monthly mean temperature anomaly as a proxy to scale stratospheric downwelling. This results in a strong improvement of the correlation coefficient of the simulated and the observed year-to-year Δ(17O) variations at Lutjewad over 2019 and 2022 from 0.37 to 0.81 (N=22). To infer terrestrial carbon fluxes, the contribution of the stratosphere to the observed signal should therefore be considered. In fact, as the Δ(17O) of atmospheric CO2  seems to be dominated by stratospheric influx, it might be used as a tracer for stratosphere-troposphere exchange. To further study the potential of Δ(17O) of atmospheric CO2 as a tracer for stratosphere-troposphere exchange at Lutjewad, we installed a laser absorption spectrometer at the measurement station for in-situ measurements. At Lutjewad numerous other atmospheric species are monitored, such as N2O, Rn and 14C. This will enable us to deepen our knowledge on the mechanisms that drive the interannual variability of Δ(17O) of atmospheric CO2  that we observe at Lutjewad.


How to cite: Steur, P., Scheeren, H. A., Koren, G., Adnew, G. A., Peters, W., and Meijer, H. A. J.: Interannual variations in Δ(17O) of atmospheric CO2 suggest a strong link with stratospheric input, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6354,, 2024.