  We present Herschel Space Observatory PACS spectra of T Tauri stars, in which
we detect amorphous and crystalline water ice features. Using irradiated
accretion disk models, we determine the disk structure and ice abundance in
each of the systems. Combining a model-independent comparison of the ice
feature strength and disk size with a detailed analysis of the model ice
location, we estimate that the ice emitting region is at disk radii >30AU,
consistent with a proto-Kuiper belt. Vertically, the ice emits most below the
photodesorption zone, consistent with Herschel observations of cold water
vapor. The presence of crystallized water ice at a disk location a) colder than
its crystallization temperature and b) where it should have been re-amorphized
in ~1 Myr suggests that localized generation is occurring; the most likely
cause appears to be micrometeorite impact or planetesimal collisions. Based on
simple tests with UV models and different ice distributions, we suggest that
the SED shape from 20 to 50 micron may probe the location of the water ice snow
line in the disk upper layers. This project represents one of the first
extra-solar probes of the spatial structure of the cometary ice reservoir
thought to deliver water to terrestrial planets.
