Fig. 9. Gas phase mass fraction of CO₂ and gas velocity in the coupled subsurface–surface-layer model domain 6 mo after CO₂ seepage begins for reference velocity of (a) u = 1 m s^–1, and (b) u = 5 m s^–1. (c) Liquid saturation and (d) mass fraction of CO₂ in the liquid with water velocity for infiltration of 10 cm yr^–1 (largest water velocity vector 2 x 10^–8 m s^–1).