Exploring the atmospheric record of δ13C in CO2 at the Amazon Tall Tower Observatory to disentangle fire signals and ecosystem processes
MSc Thesis
Contact: Santiago Botía (
sbotia@bgc-jena.mpg.de)
The are multiple ecosystem processes that can be studied using the carbon isotope composition (δ13C) of atmospheric CO2. For example, δ13C has been used to quantify ecosystem respiration (Bowling et al., 2001) or to partitioning the contribution of C3 and C4 plants to the total Net Ecosystem Exchange (NEE) (Torn et al., 2011). Along the same lines, the type of vegetation (C3/C4) that is combusted in forest or savana fires, although a challenging task, could potentially be identified using δ13C (Vernooij et al., 2022). Furthermore, seasonal or inter-annual changes in δ13C have been linked to water use efficiency by plants at global and continental scales (Randerson et al., 2005, Peters et al., 2018, Joos et al., 2024). However, a limiting factor to perform these analysis is the precision of the measurements, as changes in δ13C signatures of interest can be on the order of only a few per mil. At the Amazon Tall Tower Observatory (ATTO), the concentration and δ13C of atmospheric CO2 were measured from May 2022 until December 2024 using a cavity ring down spectrometer (G2201-i, Picarro Inc.) at several heights within and above the canopy. In this project, we aim to investigate whether this record and its precision allows to disentangle seasonal fire signals, changes in water use efficiency and/or quantify ecosystem respiration. For this we will use the Keeling plot approach and/or the Miller-Tans method to determine if the diurnal, seasonal and inter-annual changes in δ13C are detectable. Additionally, we will use an atmospheric transport model to track fire plumes and by coupling it to a vegetation model we can simulate expected changes in δ13C.
Usefull skills
Programming skills in Python or R
Knowledge on environmental physics and atmospheric dynamics
Experience or willingness to learn atmospheric transport modeling
Basic knowledge on isotope biogeochemistry
References
Bowling, D. R., Tans, P. P., & Monson, R. K. (2001). Partitioning net ecosystem carbon exchange with isotopic fluxes of CO2. Global Change Biology, 7(2), 127-145.
Joos, F., Lienert, S., and Zaehle, S. (2025): No increase is detected and modeled for the seasonal cycle amplitude of δ13C of atmospheric carbon dioxide, Biogeosciences, 22, 19–39, https://doi.org/10.5194/bg-22-19-2025.
Peters, W., van der Velde, I. R., Van Schaik, E., Miller, J. B., Ciais, P., Duarte, H. F., ... & White, J. W. (2018). Increased water-use efficiency and reduced CO2 uptake by plants during droughts at a continental scale. Nature geoscience, 11(10), 744-748
Randerson, J. T., Van der Werf, G. R., Collatz, G. J., Giglio, L., Still, C. J., Kasibhatla, P., ... & Kasischke, E. S. (2005). Fire emissions from C3 and C4 vegetation and their influence on interannual variability of atmospheric CO2 and δ13CO2. Global Biogeochemical Cycles, 19(2).
Torn, M. S., Biraud, S. C., Still, C. J., Riley, W. J., & Berry, J. A. (2011). Seasonal and interannual variability in 13C composition of ecosystem carbon fluxes in the US Southern Great Plains. Tellus B: Chemical and Physical Meteorology, 63(2), 181-195.
Vernooij, R., Dusek, U., Popa, M. E., Yao, P., Shaikat, A., Qiu, C., ... & van der Werf, G. (2021). Stable carbon isotopic composition of biomass burning emissions–implications for estimating the contribution of C3 and C4 plants. Atmospheric Chemistry and Physics Discussions, 2021, 1-35.