  The extent and the morphology of ice forming in a differentially heated
cavity filled with water is studied by means of experiments and numerical
simulations. We show that the main mechanism responsible for the ice shaping is
the existence of a cold upward convective current in the system. Such a current
is ascribed to the peculiar equation of state of water, i.e., the
non-monotonous dependence of density with temperature. The precise form of the
ice front depends on several factors, first the temperature difference across
the cell which drives the convection, second the wall inclination with respect
to the vertical, both of which are here explored. We propose a boundary-layer
model and a buoyancy-intensity model which account for the main features of the
ice morphology.
