sea ice

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.)

melt ponds

pools of melted snow and ice on the sea ice surface created during the summer melt.
Scientist taking measurements in a melt pond. (Photo courtesy of Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory.)

marginal ice zone

a part of the seasonal ice zone that varies in width (100 to 200 kilometers, 62 to 124 miles) that extends from the ice edge into the ice pack, where waves and swells affect the ice; often characterized by highly variable ice conditions; in general, it is wider in the Antarctic than the Arctic.
A scenic view within the marginal ice zone.

level ice

floating ice with a flat surface which has never been hummocked.


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