sea ice

ice jam

an accumulation of broken river or sea ice caught in a narrow channel.

ice floe

a cohesive sheet of ice floating in the water; the sea ice cover is made up of conglomerates of floes; ice floes are not unique to sea ice, as they also occur in rivers and lakes.
Aerial view of ice floes.

ice extent

the total area covered by some amount of ice, including open water between ice floes; ice extent is typically reported in square kilometers.

ice edge

the boundary at any given time between open water and sea, river or lake ice of any kind, whether drifting or fast; may be termed compacted when it is clear-cut, or open when it forms the indefinite edge of an area of dispersed ice.
Aerial view of the sea ice edge. (Photo courtesy of Todd Arbetter, National Snow and Ice Data Center.)

ice concentration

the fraction of an area that is covered by sea ice.

ice cluster

a concentration of sea ice, covering 100's of square kilometers, which is found in the same region every summer.

ice canopy

pack ice from the point of view of the submariner.

ice cake

a floe smaller than 20 meters (66 feet) across.


[sea ice] pressure process by which floating ice becomes broken up into hummocks.


(1) [sea ice] a smooth hill of ice that forms on the sea ice surface from eroding ridges, particularly during the summer melt; the formation of hummocks is similar to young mountain peaks with steep slopes that erode into smooth, rolling hills. (2) [frozen ground] Small lumps of soil pushed up by frost action, often found in uniformly spaced in large groups. Hummocks can form in areas of permafrost or seasonally frozen ground, and are one of the most common surface features of the Arctic.
Hummocks make the sea ice surface appear as rolling hills. (Photo courtesy of Ted Maksym, United States Naval Academy.)


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