Evaluating Alternative Ebullition Models for Predicting Peatland Methane Emission and Its Pathways via Data–Model Fusion

Authors

Shuang Ma, Northern Arizona University
Lifen Jiang, Northern Arizona University
Rachel M. Wilson, Florida State University
Jeff P. Chanton, Florida State University
Scott Bridgham, University of Oregon
Shuli Niu, Chinese Academy of Sciences
Colleen M. Iversen, Oak Ridge National Laboratory
Avni Malhotra, Oak Ridge National Laboratory
Jiang Jiang, Nanjing Forestry University
Xingjie Lu, Sun Yat-sen University
Jason Keller, Chapman UniversityFollow
Xiaofeng Xu, San Diego State University
Daniel M. Ricciuto, Oak Ridge National Laboratory
Paul J. Hanson, Oak Ridge National Laboratory
Yiqi Luo, Northern Arizona University

Document Type

Article

Publication Date

4-27-2022

Abstract

Understanding the dynamics of peatland methane (CH₄) emissions and quantifying sources of uncertainty in estimating peatland CH₄ emissions are critical for mitigating climate change. The relative contributions of CH₄ emission pathways through ebullition, plant-mediated transport, and diffusion, together with their different transport rates and vulnerability to oxidation, determine the quantity of CH₄ to be oxidized before leaving the soil. Notwithstanding their importance, the relative contributions of the emission pathways are highly uncertain. In particular, the ebullition process is more uncertain and can lead to large uncertainties in modeled CH₄ emissions. To improve model simulations of CH₄ emission and its pathways, we evaluated two model structures: (1) the ebullition bubble growth volume threshold approach (EBG) and (2) the modified ebullition concentration threshold approach (ECT) using CH₄ flux and concentration data collected in a peatland in northern Minnesota, USA. When model parameters were constrained using observed CH₄ fluxes, the CH₄ emissions simulated by the EBG approach (RMSE = 0.53) had a better agreement with observations than the ECT approach (RMSE = 0.61). Further, the EBG approach simulated a smaller contribution from ebullition but more frequent ebullition events than the ECT approach. The EBG approach yielded greatly improved simulations of pore water CH₄ concentrations, especially in the deep soil layers, compared to the ECT approach. When constraining the EBG model with both CH₄ flux and concentration data in model–data fusion, uncertainty of the modeled CH₄ concentration profiles was reduced by 78 % to 86 % in comparison to constraints based on CH₄ flux data alone. The improved model capability was attributed to the well-constrained parameters regulating the CH₄ production and emission pathways. Our results suggest that the EBG modeling approach better characterizes CH₄ emission and underlying mechanisms. Moreover, to achieve the best model results both CH₄ flux and concentration data are required to constrain model parameterization.

Comments

This article was originally published in Biogeosciences, volume 19, in 2022. https://doi.org/10.5194/bg-19-2245-2022

Recommended Citation

Ma, S., Jiang, L., Wilson, R. M., Chanton, J. P., Bridgham, S., Niu, S., Iversen, C. M., Malhotra, A., Jiang, J., Lu, X., Huang, Y., Keller, J., Xu, X., Ricciuto, D. M., Hanson, P. J., and Luo, Y.: Evaluating alternative ebullition models for predicting peatland methane emission and its pathways via data–model fusion, Biogeosciences, 19, 2245–2262, https://doi.org/10.5194/bg-19-2245-2022, 2022.

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.