  Observational data suggest that the ice shell on Enceladus is thicker at the
equator than at the pole, indicating an equator-to-pole ice flow. If the ice
shell is in an equilibrium state, the mass transport of the ice flow must be
balanced by the freezing and melting of the ice shell, which in turn is
modulated by the ocean heat transport. Here we use a numerical ocean model to
study the ice-ocean interaction and ocean circulation on Enceladus with
different salinities. We find that salinity fundamentally determines the ocean
stratification. A stratified layer forms in the low salinity ocean, affecting
the ocean circulation and heat transport. However, in the absence of tidal
heating in the ice shell, the ocean heat transport is found to always be
towards lower latitudes, resulting in freezing at the poles, which cannot
maintain the ice shell geometry against the equator-to-pole ice flow. The
simulation results suggest that either the ice shell on Enceladus is not in an
equilibrium state, or tidal dissipation in the ice shell is important in
maintaining the ice shell geometry. The simulations also suggest that a
positive feedback between cross-equatorial ocean heat transport and ice melting
results in spontaneous symmetry breaking between the two hemispheres. This
feedback may play a role in the observed interhemispheric asymmetry in the ice
shell.
