Fast Ice

Fast ice is sea ice that stays fixed in place, held fast along the coast, between grounded ridges, or over shoals, and does not drift with wind or current. It forms in situ from seawater or by freezing drift ice to the shore, and can extend a few meters or several hundred kilometers from the coast. Fast ice gives a stable platform for ice camps, over-ice roads, and freight, but its seaward edge calves and breaks out under storms and spring melt. The WMO Sea-Ice Nomenclature (WMO No. 259) defines it and separates it from drift ice; charts mark its extent because the fast-ice edge is where a vessel transitions to mobile pack.