Sea ice of no more than one winter’s growth, developing from young ice; thickness from 0.3 to 2 meters (1 to 6.6 feet). May be subdivided into thin first-year ice (white ice), medium first-year ice, and thick first-year ice. First-year ice is distinguished from older ice primarily by having a higher salinity. Undeformed first-year ice differs from older ice in that it is smoother and lacks refrozen melt ponds. Characteristically level where undisturbed by pressure, but where ridges occur, they distinguished by being larger, more angular, and more porous than multiyear ridges.
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