Superimposed ice

Superimposed ice is freshwater ice that forms from re-freezing of snow meltwater on the sea ice or slush surface as this interface is always colder than the fresh water freezing point (0.0°C). Its formation, thickness, and lifetime strongly depend on the surface energy balance. For strong melting, superimposed ice formation results from percolation and re-freezing. In contrast, for low snow wetness, compaction and subsidence of snow dominate the superimposed ice formation. The superimposed ice thickens due to grain growth in saturated snow on top of older ice. The texture of superimposed ice consists of polygonal granular crystals. Their size depends on the temperature gradient during the formation process.