Upscaling methane fluxes from closed chambers to eddy covariance based on a permafrost biogeochemistry integrated model

Northern peatlands are a major natural source of methane ( CH 4 ) to the atmosphere. Permafrost conditions and spatial heterogeneity are two of the major challenges for estimating CH 4 fluxes from the northern high latitudes. This study reports the development of a new model to upscale CH 4 fluxes from plant communities to ecosystem scale in permafrost peatlands by integrating an existing biogeochemical model DeNitrification‐DeComposition ( DNDC ) with a permafrost model Northern Ecosystem Soil Temperature ( NEST ). A new ebullition module was developed to track the changes of bubble volumes in the soil profile based on the ideal gas law and H enry's law. The integrated model was tested against observations of CH 4 fluxes measured by closed chambers and eddy covariance ( EC ) method in a polygonal permafrost area in the L ena R iver D elta, R ussia. Results from the tests showed that the simulated soil temperature, summer thaw depths and CH 4 fluxes were in agreement with the measurements at the five chamber observation sites; and the modeled area‐weighted average CH 4 fluxes were similar to the EC observations in seasonal patterns and annual totals although discrepancy existed in shorter time scales. This study indicates that the integrated model, NEST – DNDC , is capable of upscaling CH 4 fluxes from plant communities to larger spatial scales.