sea ice

Broken ice floes in the Weddell Sea
6 December 2016

November 2016 brought record-low sea ice extents in both the Arctic and Antarctic.

young ice

a general category of ice that represents the transition between nilas and first-year ice; usually 10 to 30 centimeters (4 to 12 inches) thick.

very open pack ice

pack ice composed of loose, widely spaced floes; ice cover 1/10th to 3/10th.

very close pack ice

pack ice in which the floes are tightly packed but not frozen together, with very little, if any, sea water visible; ice cover practically 10/10th.

thermodynamic equilibrium thickness

the thickness at which ice no longer grows because it is so thick that heat from the ocean can no longer be conducted through the ice; it may take several years of growth and melt for ice to reach an equilibrium thickness.

thaw hole

vertical hole in floating ice formed when a puddle melts through to the underlying water.

telescoped ice

deformed sea ice in which one piece has overridden another; also called rafted ice.

summer minimum extent

the permanent ice zone that remains in summer after all melting has occurred.


a long narrow area of pack ice, about 1 kilometer (0.6 mile) or less in width, usually composed of small fragments detatched from the main mass of ice, and run together under the influence of wind or current.


thick ridges that become grounded during the winter and become part of the fast ice zone; while the rest of the fast ice melts during the summer, a stamukhi remains throughout the summer attached to the ocean bottom.


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