Keywords:methane, atmospheric inverse model, northen boreal region, peatland
Boreal and arctic terrestrial land is covered by a large areas of peatlands, where about one fifth of global terrestrial carbon is stored. The region is very sensitive to the changes in temperature and water balance; the annual average temperate increase is nearly twice the global mean change, plus it is expected to release soil carbon into the atmosphere due to the warming. The largest sources of methane (CH4) emissions from the boreal and arctic regions are natural biospheric sources, such as peatlands, wetlands and permafrost. However, their magnitude and spatial distribution still vary greatly in the process model estimates, mainly due to the heterogeneity of CH4 fluxes, and the uncertainty in wetland extent. In this study, we estimate CH4 fluxes in northern Fennoscandia, north west Russia and west Canada for 2004-2015 using the CTDAS-CH4 data assimilation system. Continuous and discrete atmospheric CH4 observations from in situ stations are assimilated, and CH4 fluxes are optimized at 1ox1o horizontal resolution in those regions. In addition, atmospheric CH4 observations from the global in situ stations are assimilated to constrain the global budget. The estimated fluxes will be compared with the process model estimates and flux observations, such as those based on the eddy covariance method, to better identify the spatial distribution and magnitude of CH4 emissions in boreal and arctic regions.