  We reanalyzed the measurements made by Asakawa et al. [1] of the growth
velocities of single-molecule-high steps on basal ice surfaces, as we believe
the authors made a number of incorrect assumptions regarding ice growth
parameters and bulk diffusion in their experiments. Applying what we believe
are more accurate assumptions, we used the data in [1] to derive a surface
diffusion length of approximately 10 nm for water molecules on basal ice
surfaces at -8.4 C, about 500 times lower than what was reported in [1].
Moreover, in our analysis we found that no information about the height of the
Ehrlich-Schwoebel barrier could be obtained from these measurements.
