Toward an Annual Carbon Dioxide Budget for the Arctic Tundra

Tundra ecosystems are important stores of carbon but as the Arctic climate warms, their carbon sink status is uncertain. Advances in low power eddy covariance sensors have permitted the measurement of trace gas fluxes in remote locations such as these where there is limited infrastructure and physical access. However, logistical challenges continue to result in incomplete datasets and often there are few observations during winter. To address this challenge, forced diffusion chambers, the process-based ecosystem model CLASSIC (the Canadian Land Surface Scheme including biogeochemical Cycles, formerly CLASS-CTEM), and a 15-year eddy covariance dataset are combined to estimate the annual net ecosystem exchange of CO₂ (NEE) for tundra ecosystems in Canada’s Southern Arctic. Key modifications to CLASSIC include the introduction of shrub and sedge plant functional types and changes to soil moisture-soil evaporation parameterizations. Our results highlight the importance of non-zero winter and shoulder season CO₂ emissions as well as the tundra and weather characteristics which influence annual NEE.