Snow ice forms by refreezing flooded snow, creating an ice layer that bonds firmly to the top surface of a floe. Ice formed by this process and makes a significant contribution to the total mass of Antarctic sea ice. The snow cover of sea ice can become flooded by sea water via a number of mechanisms, in particular when the mass of snow becomes great enough to depress the ice/snow interface below sea level. The snow cover is porous and sea water can easily infiltrate from the sides of floes to form a slush layer at the ice/snow boundary. The snow may also become flooded by water rising up brine channels within the sea ice. With sufficiently cold temperatures this slush layer freezes to form snow ice.