Sensitivity to various parameters of the maximum optical depth of the six main ice features. The vertical black line is the fiducial model. The dotted lines in the large panel indicate the uncertainty of the peak optical depth (horizontal) and corresponding abundance (vertical) when taking the uncertainty of all parameters into account. The varied parameters are the ice abundance, the inclination, the A_v limit, the mass fraction of small grains expressed as 1-f_ℓ, the minimum grain size, the existence of a cavity, the disk mass, and the characteristic disk radius. A typical deep observation of the JWST has a contrast ratio of 300 on the continuum (i.e., S/N = 300), which translates into a 3σ peak optical depth of ~10⁻².