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ice skylight

from the point of view of the submariner, thin places in the ice canopy, usually less than 1 meter (3.3 feet) thick and appearing from below as relatively light, translucent patches in dark surroundings; the under-surface of an ice skylight is normally flat; ice skylights are called large if big enough for a submarine to attempt to surface through them (120 meters, 131 yards), or small if not.

ice stream

(1) a current of ice in an ice sheet or ice cap that flows faster than the surrounding ice (2) sometimes refers to the confluent sections of a branched-valley glacier (3) obsolete synonym of valley glaciers.

ice vein

an ice-filled crack or fissure in the ground.

ice wall

an ice cliff forming the seaward margin of an inland ice sheet, ice piedmont or ice rise; the rock basement may be at or below sea level.

ice wedge

narrow ice mass that is 3 to 4 meters (10 to 13 feet) wide at the ground surface, and extends as much as 10 meters (33 feet) down; a decrease in temperature during the winter leads to ice wedge cracks in the ground around ice wedges; during the summer, these cracks accumulate melt-water and sediment, forming pseudomorphs.

ice worm

an oligochaete worm that lives on temperate glaciers or perennial snow; there are several species that range in color from yellowish-brown to reddish-brown or black; they are usually less than 1 millimeter (0.04 inch) in diameter and average about 3 millimeters (0.1 inch) long; some eat red algae.

ice-bearing permafrost

permafrost that contains ice.

ice-bonded permafrost

ice-bearing permafrost in which the soil particles are cemented together by ice.

ice-cemented glacier

a rock glacier that has interstitial ice a meter or so below the surface.

ice-cored glacier

a rock glacier that has a buried core of ice.

ice-cored topography

topography that is due almost solely to differences in the amount of excess ice underlying its surface.

ice-nucleation temperature

the temperature at which ice first forms during freezing of a soil/water system that does not initially contain ice.

ice-rich permafrost

permafrost containing excess ice.

ice-wedge cast

a filling of sediment in the space formerly occupied by an ice wedge.

ice-wedge polygon

a polygon outlined by ice wedges underlying its boundaries.


a piece of ice that has broken off from the end of a glacier that terminates in water.
Lamplugh Glacier, in Glacier Bay Alaska, shows the terminus of a typical tidewater glacier. The terminus of the glacier is heavily crevassed and jagged, and is calving small icebergs. For scale, note the man standing on the rocks in the foreground (near the center of the photograph). This photograph was taken in 1941. (Photo courtesy of W. O. Field, archived at the World Data Center for Glaciology, Boulder, CO.)

iceberg tongue

a major accumulation of icebergs projecting from the coast, held in place by grounding and joined together by fast ice.


a harbour, inlet, etc, is said to be icebound when navigation by ships is prevented due to ice, except possibly with the assistance of an icebreaker.


part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepenes or narrows.
Icefalls on three parallel glaciers. (Photo courtesy of Tom Lowell, University of Cincinnati.)


a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain.
Kalstenius Icefield, located on Ellesmere Island, Canada, shows vast stretches of ice. The icefield produces multiple outlet glaciers that flow into a larger valley glacier. The glacier in this photograph is three miles wide. (Photo courtesy of the Royal Canadian Air Force, archived at the World Data Center for Glaciology, Boulder, CO.)


a narrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has broken free.

Icelandic low

the low pressure center near Iceland (mainly between Iceland and southern Greenland); on mean charts of sea-level pressure, it is a principal center of action in the atmosphere circulation of the northern hemisphere.


an embayment in an ice front, often of temporary nature, where ships can moor alongside and unload directly into the ice shelf.


hanging spike of clear ice formed by the freezing of dripping water.


a qualitative term describing the quantity of ice in frozen ground.


a sheetlike mass of layered ice formed on the ground surface, or on river or lake ice, by freezing of successive flows of water that may seep from the ground, flow from a spring or emerge from below river or lake ice through fractures.

icing blister

a seasonal frost mound consisting only of ice and formed at least in part through lifting of one or more layers of an icing by injected water.

icing glade

an area kept clear of trees and shrubs by the annual occurrence of icings.

icing mound

a seasonal frost mound consisting exclusively of thinly layered ice, formed by freezing of successive flows of water issuing from the ground or from below river ice.

inactive ice wedge

an ice wedge that is no longer growing.

inactive rock glacier

a mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of past, but not present, movement.

infrared radiation

electromagnetic radiation of wavelengths between approximately 0.75 and 1000 millimeters; see also atmospheric radiation, terrestrial radiation, longwave radiation.

inland ice sheet

an ice sheet of considerable thickness and an area of more than about 50,000 square kilometers (12.4 million acres), resting on rock; inland ice sheets near sea level may merge into ice shelves.


(1) exposure of an object to the sun (2) intensity of incoming solar radiation incident on a unit horizontal surface at a specific level.

instrument shelter

structure to protect certain instruments from insolation and weather while at the same time ensuring sufficient ventilation.

interfacial water

water that forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground.