PhD project offered by the IMPRS-gBGC in July 2025

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Constraining Terrestrial Biosphere Models Using Atmospheric CO2, Stable Carbon Isotope (13C), and Radiocarbon (14C) Observations

Sönke Zaehle, Christian Rödenbeck, Ana Bastos

Project description

Quantifying land-atmosphere carbon fluxes is a central challenge in Earth system science, with direct implications for climate prediction and mitigation policy (Canadell et al. 2021). Terrestrial biosphere models (TBMs) as part of comprehensive Earth System Models simulate key processes of land carbon fluxes and storage, yet their predictions often diverge significantly (Bastos et al 2020).

This PhD project will combine biosphere modelling with in-situ and atmospheric observations of carbon isotopes to reduce uncertainties in terrestrial carbon uptake and turnover. As a starting point, the PhD thesis will utilize the global version of the QUINCY model (Thum et al. 2019), coupled to the ICON-Land modelling framework as used in the CAP7 project, which delivers the German contribution to CMIP7. QUINCY, designed to simulate the coupled terrestrial carbon-nitrogen and phosphorus cycles, is one of the few models globally that includes tracers as 13C and 14C, which provide unique, complementary constraints on biospheric and anthropogenic processes. Simulated trends in atmospheric tracers—CO2 concentration, 13C, and radiocarbon (14C) — will be used to evaluate regional and global trends in carbon uptake and turnover and to evaluate their constraint on future trends on the land carbon balance.

Depending on the profile of the successful applicant, further steps of the thesis can include the further refinement of the isotope-enabled QUINCY model, further analysis of atmospheric trends using atmospheric transport models to simulate the large-scale distribution of these tracers of atmospheric trends, or the development and application of ensemble methods including machine learning to develop constraints for simulations of future developments. The outcome will be a better-constrained terrestrial carbon cycle and improved confidence in Earth system model projections under future climate scenarios.

Working group & collaborations

The candidate will be part of the Biogeochemical Signals department and will have the opportunity to collaborate with researchers from multiple institutions in Germany (within the CAP7 project) and beyond.

Requirements for the PhD project are

Applications to the IMPRS-gBGC are open to well-motivated and highly-qualified students from all countries. Prerequisites for this PhD project are:
  • Master's degree in bio(geo)chemistry, environmental science, geosciences, physics, atmospheric science, engineering, remote sensing or other disciplines related to environmental sciences.
  • Background in terrestrial carbon cycle, and experience in ecosystem or atmosphere modelling
  • Computational skills
    • Experience with programming languages like R or python
    • Knowledge of higher programming languages such as C or FORTRAN are an asset
    • Experience with gridded datasets like ERA5 or similar
  • Excellent oral and written communication skills in English
The Max Planck Society (MPS) strives for gender equality and diversity. The MPS seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply. The MPS is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.

References

Bastos et al. (2020),  Sources of uncertainty in regional and global terrestrial CO  exchange estimates. Global Biogeochemical Cycles,  34, e2019GB006393. https://doi.org/10.1029/2019GB006393

Canadell et al. (2021): Global Carbon and other Biogeochemical Cycles and Feedbacks. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., et al. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, doi: 10.1017/9781009157896.007.

CAP7 Project: https://www.dwd.de/EN/research/projects/cap7/cap7_node.html

Thum, T., et al. (2019) A new model of the coupled carbon, nitrogen, and phosphorus cycles in the terrestrial biosphere (QUINCY v1.0; revision 1996), Geosci. Model Dev., 12, 4781–4802, https://doi.org/10.5194/gmd-12-4781-2019.


>> more information about the IMPRS-gBGC + application