first-year ice
Technical term in glaciology and oceanography for sea ice that has not survived a summer melt season; typically 30 cm to 2 m thick.
In the Arctic Ocean, first-year ice covers a wide area.
Compound of 一年 (ichinen, 'one year') and 氷 (kōri, 'ice'), with rendaku voicing of こおり to ごおり.