  We use X-ray Photon Correlation Spectroscopy (XPCS) to probe the dynamics of
colloidal particles in polycrystalline ice. During freezing, the dendritic ice
morphology and rejection of particles from the ice created regions of
high-particle-density, where some of the colloids were forced into contact and
formed disordered aggregates. We find that the particles in these high density
regions underwent ballistic motion coupled with both stretched and compressed
exponential decays of the intensity autocorrelation function, and that the
particles' characteristic velocity increased with temperature. We explain this
behavior in terms of ice grain boundary migration.
