Understanding how snow cover controls methane emissions in high-latitude peatlands through ecosystem modeling

Seasonal snow cover plays a critical role in regulating soil freeze-thaw dynamics by forming an insulating layer on top of the soil and modifying the soil thermal regime in high latitude regions. In natural wetlands, which have a significant contribution to global methane (CH₄) emissions and are sensitive to rising surface temperatures, snow cover influences the seasonality and magnitude of these emissions. Despite its importance, snow-soil-atmosphere interactions remain a major source of uncertainty in current land surface models, particularly with respect to methane dynamics during the cold season. The net methane flux is regulated by the processes of CH₄ production, oxidation, and transport, with methane transported from the soil to the atmosphere via diffusion, ebullition and plant-mediated transport. Snowpack slows down the diffusion of methane and high emissions can occur during spring snow melt and soil thaw.

In this study, we utilize the JSBACH ecosystem model and run it coupled with the HIMMELI peatland process model with a novel snow resistance implementation to assess how snowpack modifies the methane microbe and transport processes in high-latitude peatlands. The model framework is forced, calibrated and evaluated using observational data from an established pristine mire eddy covariance (EC) measurement site located in northern Finland within the Arctic-boreal region. Simulated methane fluxes and snow dynamics are compared against EC, chamber, and snowpack CH₄ diffusion gradient observations in addition to manual and automated observations of snow properties. Our preliminary results indicate that the snowpack impacts the soil freeze/thaw, anoxic conditions, methane concentrations and plant-mediated transport, therefore demonstrating the complex and non-linear relationship between seasonal snow cover and methane production, transport and oxidation processes.