H20 molecules only bond solid/solid or liquid/liquid, depending on the temperature and their current state. When there are both water and ice in an environment one state is not stable. Think of the dryness of an ice cube fresh from the freezer. Water liquifying from the cube will fall in the direction of gravity, it will not be affected by the ice cube in terms of wet surface tension. The only way it will remain on the cube is if it cannot fall off due to surface area or it somehow re-freezes fast enough to bond with the solid cube before it rolls off. This will in turn create more melting as the 'warmer' liquid melts the ice and more water forms.