Constraining Terrestrial Biosphere Models Using Atmospheric CO2, Stable Carbon Isotope (13C), and Radiocarbon (14C) Observations |
Sönke Zaehle,
Christian Rödenbeck,
Ana Bastos
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Project descriptionQuantifying 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 & collaborationsThe 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 areApplications to the IMPRS-gBGC are open to well-motivated and highly-qualified students from all countries. Prerequisites for this PhD project are:
ReferencesBastos et al. (2020), Sources of uncertainty in regional and global terrestrial CO exchange estimates. Global Biogeochemical Cycles, 34, e2019GB006393. https://doi.org/10.1029/2019GB006393Canadell 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. |