Stages of Development

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New Ice

Frazil Ice: Fine spicules or plates of ice suspended in water.
Grease Ice: A later stage of freezing than frazil ice where the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the water a matte appearance.
Slush: Snow which is saturated and mixed with water on land or ice surfaces or as a viscous floating mass in water after a heavy snowfall.
Shuga: An accumulation of spongy white ice lumps having a diameter of a few centimetres across; they are formed from grease ice or slush and sometimes from anchor ice rising to the surface.

Nilas

Dark Nilas: Nilas up to 5 cm in thickness and which is very dark in colour.
Light Nilas: Nilas which is more than 5 cm in thickness and lighter in colour than dark nilas.
Ice Rind: A brittle, shiny crust of ice formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity. It has a thickness of about 5 cm. Easily broken by wind or swell, commonly breaking into rectangular pieces.

Young Ice

Grey Ice: Young ice 10-15 cm thick, less elastic than nilas and breaks on swell. It usually rafts under pressure.
Grey-White Ice: Young ice 15-30 cm thick. Under pressure it is more likely to ridge than to raft.

First-year Ice

Thin First-year Ice/White Ice - First Stage:	30-50 cm thick.
Thin First-year Ice/White Ice - Second Stage:	50-70 cm thick.
Medium First-year Ice:	70-120 cm thick.
Thick First-year Ice:	Greater than 120 cm thick.

Old Ice

Second-year Ice: Old ice which has survived only one summer's melt. Thicker than first-year ice, it stands higher out of the water. In contrast to multi-year ice, summer melting produces a regular pattern of numerous small puddles. Bare patches and puddles are usually greenish-blue.
Multi-year Ice: Old ice which has survived at least two summers' melt. Hummocks are smoother than on second-year ice and the ice is almost salt-free. Where bare, this ice is usually blue in colour. The melt pattern consists of large interconnecting, irregular puddles and a well-developed drainage system.