EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Speleothem organic carbon isotopes as a novel tracer for terrestrial ecosystem change – new method developments

Franziska A Lechleitner1, Sarah Rowan1, Jan Strähl1, Martin Rauber1, Susan Q Lang2, and Sönke Szidat1
Franziska A Lechleitner et al.
  • 1Department of Chemistry, Biochemistry and Pharmaceutical Sciences & Oeschger Centre for Climate Change Research, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
  • 2School of the Earth, Ocean, and Environment, University of South Carolina, Columbia, SC 29208, USA

The response of terrestrial ecosystems to anthropogenic climate change remains poorly understood and constitutes a major source of uncertainty in future climate projections. Stalagmites are a well-established terrestrial climate archive (Wong and Breecker, 2015), and may also serve as a sensitive recorder of surface ecosystem processes, as they are fed by dripping water that percolates through the soil zone. Coupled climate-ecosystem paleorecords from stalagmites could prove invaluable sources of information on the response of terrestrial ecosystems to past climatic shifts and their sensitivity to climate variability exceeding the instrumental range.

Here we present results from a method development study carried out at the Laboratory for the Analysis of Radiocarbon with AMS (LARA) at the University of Bern. Our results are based on a previous protocol by Lechleitner et al. (2019), which describes a rapid, low contamination method for carbon isotope analysis (δ13C and 14C) of the speleothem non-purgeable organic carbon (NPOC) fraction for small samples (<150 mg CaCO3). Decarbonation of acid digested carbonate samples is followed by wet chemical oxidation of the NPOC and analysis of the resulting headspace CO2 via mass spectrometry to determine its isotopic composition.

We have made significant progress in resolving the main issues that precluded the routine application of the method as presented in Lechleitner et al. (2019), namely incomplete removal of inorganic carbon from the sample solutions, and contamination from extraneous carbon at different method stages. Apart from an updated pre-cleaning protocol for stalagmite samples and extensive blank assessment, a new needle setup was installed, allowing reduction of the sample amount needed, and the CO2 flow is now being monitored during decarbonation to ensure complete removal of inorganic carbon prior to the oxidation step.

These results reiterate the great promise of this method to provide accurate, ecosystem-level information on past terrestrial environments at comparatively high temporal resolution.



Lechleitner, F.A., Lang, S.Q., Haghipour, N., McIntyre, C., Baldini, J.U.L., Prufer, K.M., Eglinton, T.I., 2019. Towards organic carbon isotope records from stalagmites: coupled d13C and 14C analysis using wet chemical oxidation. Radiocarbon 61, 749–764. doi:10.1017/RDC.2019.35

Wong, C.I., Breecker, D.O., 2015. Advancements in the use of speleothems as climate archives. Quat. Sci. Rev. 127, 1–18. doi:10.1016/j.quascirev.2015.07.019

How to cite: Lechleitner, F. A., Rowan, S., Strähl, J., Rauber, M., Lang, S. Q., and Szidat, S.: Speleothem organic carbon isotopes as a novel tracer for terrestrial ecosystem change – new method developments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2967,, 2022.