  Ice plasticity has been thoroughly studied, owing to its importance in
glaciers and ice sheets dynamics. In particular, its anisotropy (easy basal
slip) has been suspected for a long time, then fully characterized 40 years
ago. More recently emerged the interest of ice as a model material to study
some fundamental aspects of crystalline plasticity. An example is the nature of
plastic fluctuations and collective dislocation dynamics. 20 years ago,
acoustic emission measurements performed during the deformation of ice single
crystals revealed that plastic flow proceeds through intermittent dislocation
avalanches, power law distributed in size and energy. This means that most of
ice plasticity takes place through few, very large avalanches, thus qualifying
associated plastic fluctuations as wild. This launched an intense research
activity on plastic intermittency in the Material Science community. The
interest of ice in this debate is reviewed, from a comparison with other
crystalline materials. In this context, ice appears as an extreme case of
plastic intermittency, characterized by scale-free fluctuations, complex space
and time correlations as well as avalanche triggering. In other words, ice can
be considered as the paradigm of wild plasticity.
