Radius evolution of each synthetic planets (for both the 1D and 2D models). We note the locations of the midplane location of H₂O, CO₂, O₂, and CO ice lines as horizontal dashed lines for comparison. Note that the O₂ and CH₄ ice lines occur at similar positions, however in our chemical model O₂ is more abundant and hence its ice line is more relevant. Planets that begin within ~15 AU migrate inward of the water ice line by 4 Myr and hence could accrete “pristine” gas. Inward of the water ice line, all volatiles are in the gas phase.