NMDC Water environmental medium value set part of surrounded by surrounded by ocean water sea ice congelation sea ice 2019-01-14T18:56:29Z Sea ice which 1) has formed on the submerged surface (i.e. the base) of an existing mass of sea ice and 2) is composed of columnar crystals due to the downward growth of the crystals into the water. Congelation ice usually forms through the fusion/coalescence of platelets into solid ice. black ice