Eddy covariance mapping and quantification of surface CO₂ leakage fluxes

We present eddy covariance measurements of net CO 2 flux ( F c ) made during a controlled release of CO 2 (0.3 t d −1 from 9 July to 7 August 2008) from a horizontal well ∼100 m in length and ∼2.5 m in depth located in an agricultural field in Bozeman, MT. We isolated fluxes arising from the release ( F cr ) by subtracting fluxes corresponding to a model for net ecosystem exchange from F c . A least‐squares inversion of 611 F cr and corresponding modeled footprint functions recovered the location, length, and magnitude of the surface CO 2 flux leakage signal, although high wavenumber details of the signal were poorly resolved. The estimated total surface CO 2 leakage rate (0.32 t d −1 ) was within 7% of the release rate.