Constraining methane emission pathways via model structure selection and parameter estimation with flux and concentration data in a northern peatland

Wetland methane (CH₄) emissions constitute roughly one third of the global CH₄ budget. The relative ratio of the emission pathways (ebullition, plant-mediated transport and diffusion) determines how much CH₄ is oxidized before leaving the soil, due to their different transport rate and the differences in oxidation rates. Decades of modeling research on methane has evolved to a stage that the emission pathways are explicitly calculated with various complexities, but determining the accuracy and uncertainty of individual pathways requires more research. By taking advantage of the fact that pore water CH₄ concentration is the driving force for each emission pathway, we tested the ability of two ebullition modeling approaches to reproduce observed methane emission and the pore water concentration profile. Using data-model fusion techniques, we reduced the uncertainties of modeled methane emission from the emission pathways. We concluded that the direct effect of warming on methane emission include increased production as well as decreased consumption. The CH₄ flux data is often the only data stream for CH₄ model validation. We encourage that more attention be given to the pore water CH₄ profile for parameter optimization and a more robust estimate of CH₄ emission under future climate change.