sea ice

pancake ice

pieces of new ice approximately circular, up to 10 centimeters (4 inches) thick and 0.03 to 3 meters (0.1 to 9.8 feet) in diameter, with raised edges that form from rubbing against each other; formed from the freezing together of grease ice, slush or shuga, or the reaking up of ice rind or nilas.
(Photo courtesy of the National Oceanic and Atmospheric Administration/Department of Commerce.)

pack ice

ice that is not attached to the shoreline and drifts in response to winds, currents, and other forces; some prefer the generic term drift ice, and reserve pack ice to mean drift ice that is closely packed.

open water

a large area of freely navigable water in which floes may be present in concentration under 1/10th; if there is no sea ice present, the area may be termed open water, even though icebergs are present.

open pack ice

composed of floes seldom in contact and with many leads; ice cover 4/10ths to 6/10ths.

open lead

a lead that connects two open bodies of water; ships can traverse between them through this lead; it also refers to a lead where open water is found, or a lead that has not completely frozen.

old ice

sea ice more than 2-years-old, up to 3 meters (10 feet) or more thick; hummocks on old ice are even smoother than in second-year ice, and the ice is almost salt-free; when old ice is bare of snow, it is blue and lacks the greenish tint of second-year ice.


ice is said to nip when it forcibly presses against a ship which is beset; a vessel so caught, though undamaged, is said to have been nipped.


a thin sheet of smooth, level ice less than 10 centimeters (4 inches) thick; appear darkest when thin.
Nilas are the dark sheets of ice near the bottom of the photo. (Photo courtesy of Ted Maksym, United States Naval Academy.)

new ice

a general category of ice that consists of frazil, grease ice, slush, and shuga.

multiyear ice

ice that has survived at least one melt season; it is typically 2 to 4 meters (6.6 to 13.1 feet) thick and thickens as more ice grows on its underside.
Multiyear ice. (Photo courtesy of Ted Maksym, United States Naval Academy.)


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