1,2,3,4,1,5,1,2,6- 1Heidelberg University, Institute of Environmental Physics, Physics, Heidelberg, Germany (sanam.vardag@uni-heidelberg.de)
- 2Heidelberg University, Heidelberg Center for the Environment, Heidelberg, Germany
- 3Goddard Space Flight Center, NASA, Greenbelt, Maryland, USA
- 4Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, USA
- 5now at: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- 6Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
The GOSAT satellite is in orbit since 2009 and now allows a robust evaluation of interannual variability (IAV) in land–atmosphere exchange with global coverage over a period of 15 years. We use monthly net land CO2 fluxes for 2009–2024 inferred from assimilation of GOSAT XCO2 together with in-situ CO2 data in the global inversion system TM5-4DVAR to provide a global overview of IAV of different regions and an in-depth understanding of the long-term carbon cycle over Australia.
At the global scale, we compare the net ecosystem exchange (NEE) based on TM5-4DVAR to the ensemble mean of dynamic global vegetation model (DGVM) estimates from TRENDY v13. We find that DGVMs typically exhibit weaker IAV than XCO2 inversion-based fluxes suggesting that the modelled sensitivity of NEE to hydroclimatic variability remains underestimated in DGVMs.
Following the data fusion approach of our previous studies on semiarid ecosystems (Metz et al., 2023, Metz et al., 2025, Vardag et al., 2025), we then analyse the carbon cycle over Australia, where precipitation dynamics strongly control biogenic fluxes. For Australia, the inversion indicates a pronounced sink during La Niña conditions, but also reveals an exceptionally strong sink anomaly in 2022 to 2024. We investigate the origin of these anomalies using sun-induced fluorescence (SIF) and the gross fluxes of selected DGVMs. We find that GPP has increased strongly in 2022 to 2024 and discuss the role of climate and environmental disturbances for this increase.
Overall, the extended satellite record provides a novel opportunity for improving ecosystem parameterizations and finally reducing uncertainty in the global carbon budget.
References:
Metz, E.-M., Vardag, S.N., Basu, S., Jung, M., ... , Butz, A. Soil respiration–driven CO2 pulses dominate Australia’s flux variability. Science, 379, 1332-1335, https://doi.org/10.1126/science.add7833, 2023.
Metz, E.-M., Vardag, S. N., Basu, S., Jung, M., Butz, A.: Seasonal and in terannual variability in CO2 fluxes in southern Africa seen by GOSAT. Biogeosciences, 22, 555–584, https://doi.org/10.5194/bg-22-555-2025, 2025.
Vardag, S. N., Metz, E.‐M., Artelt, L., Basu, S., Butz, A. (2025). CO2 release during soil rewetting shapes the seasonal carbon dynamics in South American Temperate region. Geophysical Research Letters, 52, https://doi.org/10.1029/2024GL111725, 2025.
How to cite: Vardag, S. N., Basu, S., Mandel, E., Grauer, R., Metz, E.-M., and Butz, A.: A 15-year XCO2-based assessment of the terrestrial carbon-cycle , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10652, https://doi.org/10.5194/egusphere-egu26-10652, 2026.
