- 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
- 5Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany
- 6Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
The annual increase of atmospheric CO2 exhibits significant inter-annual variability, primarily driven by fluctuations in the terrestrial carbon cycle. These inter-annual changes in CO2 concentrations provide a unique opportunity to study the biosphere's carbon uptake and release in response to shifting precipitation patterns and temperature extremes. Semi-arid ecosystems have been identified as significantly contributing to the inter-annual global carbon sink dynamics. However, the sparse coverage of in-situ CO2 measurements on the southern hemisphere leads to uncertainties in measurement-based carbon flux estimates for the extensive semi-arid regions located there. Also, dynamic global vegetation models (DGVMs) show a large spread in their carbon flux estimates pointing to an incomplete representation of semi-arid carbon cycle processes in most of the models. We demonstrate the potential of satellite data to improve sub-continental scale carbon flux estimates on the southern hemisphere and analyse the underlying biogenic processes.
We here discuss monthly net CO2 fluxes from 2009 to 2018 derived by assimilating Greenhouse Gases Observing Satellite (GOSAT) XCO2 measurements in the global atmospheric inversion TM5-4DVar. For the three semi-arid regions in the southern hemisphere, i.e. Australia (Metz et al., 2023), South American Temperate region and South Africa (Metz et al., 2024), we find that the DGVMs are not consistent, but single models agree well with the satellite inversion fluxes and Solar Induced Fluorescence (SIF) measurements. While the satellite inversion can only provide net land-atmosphere fluxes, those selected DGVMs model the vegetation gross fluxes and allow further analyses of the carbon exchange processes. We find a net release of CO2 caused by enhanced soil respiration following soil rewetting at the beginning of the rainy season. These CO2 emissions strongly shape the seasonal cycle of carbon fluxes in all three semi-arid regions, and in Australia, dominate the interannual flux variability. Our findings suggest that rain pulses and soil rewetting events in semi-arid regions can be analysed using satellite observations. These processes play an important role in constraining the global carbon budget and should be represented more accurately in global carbon cycle models to improve the estimation of the global carbon budget.
Metz, E.-M., et al., (2023). Soil respiration–driven CO2 pulses dominate Australia’s flux variability. Science, 379(6639), 1332-1335., https://doi.org/10.1126/science.add7833
Metz, Eva-Marie, et al. "Seasonal and inter-annual variability of carbon fluxes in southern Africa seen by GOSAT." EGUsphere 2024 (2024): 1-35. https://doi.org/10.5194/egusphere-2024-1955
How to cite: Vardag, S. N., Metz, E.-M., Basu, S., Jung, M., Artelt, L., and Butz, A.: Rewetting Driven Soil Respiration Shapes the Variability of Terrestrial CO2 Fluxes in Semi-arid Regions of the Southern Hemisphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9944, https://doi.org/10.5194/egusphere-egu25-9944, 2025.
