Impact of Fraserdale CO 2 observations on annual flux inversion of the North American boreal region

International audience; In TransCom-3 (Level 1), atmospheric CO 2 measurements from 76 monitoring stations for the period 1992-1996 and 16 atmospheric transport models were used to constrain annual mean CO 2 fluxes over 11 land and 11 ocean regions. The tower measurements of atmospheric CO 2 from Fraserdale, a continental site in northern Ontario, Canada are now available and processed for use in the TransCom-3 inverse modelling framework. In this short study, we show that by including this set of continental CO 2 data, the estimated flux for the North American boreal region becomes nearly zero, a reduction of about 0.26 Pg C yr −1 from the previous estimate. The uncertainty of the estimated flux for this region is also reduced by ∼30%. All transport models show negative changes for boreal North America, with the strongest responses (∼ −0.5 Pg C yr −1) shown by NIRE, NIES, CSU and SKYHI. Furthermore, models showing a strong response in boreal North America tend to show strong sensitivity in middle-and high-latitude Asian regions.