The study presents an estimate of net carbon dioxide (CO₂) exchange between the terrestrial biosphere and the atmosphere across North America for each week from 2000 to 2005. This estimate is derived from 28,000 CO₂ mole fraction observations fed into the CarbonTracker data assimilation system. The system produces surface fluxes consistent with recent atmospheric CO₂ history and provides independent constraints on net carbon fluxes. The North American terrestrial biosphere absorbed -0.65 PgC/yr on average, partly offsetting the estimated 1.85 PgC/yr release from fossil fuel burning and cement manufacturing. The uncertainty range is between -0.4 and -1.0 PgC/yr. The sink is mainly in deciduous forests along the East Coast (32%) and boreal coniferous forests (22%). During the 2002 drought, terrestrial uptake fell to -0.32 PgC/yr, indicating sensitivity to climate extremes. CarbonTracker results align well with carbon inventories used in the first North American State of the Carbon Cycle Report (SOCCR). CarbonTracker is a data assimilation system that integrates atmospheric transport models and ensemble Kalman filters to estimate surface CO₂ exchange. It uses observations from tall towers and aircraft to improve accuracy. The system has been evaluated against independent observations, showing good agreement with flask samples and column average CO₂ measurements. CarbonTracker's results are used to assess satellite-derived CO₂ columns and support climate change mitigation policies. The study highlights the importance of monitoring carbon fluxes and the role of CarbonTracker in providing detailed insights into the carbon cycle. The system is expected to be expanded to include more data and improve accuracy for future applications.The study presents an estimate of net carbon dioxide (CO₂) exchange between the terrestrial biosphere and the atmosphere across North America for each week from 2000 to 2005. This estimate is derived from 28,000 CO₂ mole fraction observations fed into the CarbonTracker data assimilation system. The system produces surface fluxes consistent with recent atmospheric CO₂ history and provides independent constraints on net carbon fluxes. The North American terrestrial biosphere absorbed -0.65 PgC/yr on average, partly offsetting the estimated 1.85 PgC/yr release from fossil fuel burning and cement manufacturing. The uncertainty range is between -0.4 and -1.0 PgC/yr. The sink is mainly in deciduous forests along the East Coast (32%) and boreal coniferous forests (22%). During the 2002 drought, terrestrial uptake fell to -0.32 PgC/yr, indicating sensitivity to climate extremes. CarbonTracker results align well with carbon inventories used in the first North American State of the Carbon Cycle Report (SOCCR). CarbonTracker is a data assimilation system that integrates atmospheric transport models and ensemble Kalman filters to estimate surface CO₂ exchange. It uses observations from tall towers and aircraft to improve accuracy. The system has been evaluated against independent observations, showing good agreement with flask samples and column average CO₂ measurements. CarbonTracker's results are used to assess satellite-derived CO₂ columns and support climate change mitigation policies. The study highlights the importance of monitoring carbon fluxes and the role of CarbonTracker in providing detailed insights into the carbon cycle. The system is expected to be expanded to include more data and improve accuracy for future applications.