National Snow and Ice Data Center

hummocking

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

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hydration shattering

a form of weathering that affects all rocks; water freezes in pores and cracks, which leads to an increase in specific volume (vol/unit mass) of the water, producing stress that is greater than the tensile strength of all common rocks; ultimately leads to shattering and fracturing of the rocks.

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hydraulic conductivity

the volume of fluid passing through a unit cross section in unit time under the action of a unit hydraulic potential gradient.

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hydraulic diffusivity

the ratio of the hydraulic conductivity and the storage capacity of a groundwater aquifer.

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hydraulic thawing

artificial thawing (and removal) of frozen ground by the use of a stream or jet of water under high pressure.

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hydrochemical talik

a layer or body of cryotic (but unfrozen) ground in a permafrost area, maintained by moving mineralized groundwater.

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hydrometeor

any product of condensation or sublimation of atmospheric vapor, whether formed in free atmosphere or at the earth's surface; also any water particles blown by the wind from the earth's surface.

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hydrothermal talik

a layer or body of noncryotic unfrozen ground in a permafrost area, maintained by moving groundwater.

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hygrometer

an instrument which measures the water vapor content in the atmosphere; there are several different means of transduction used in measuring this quantity and hence various types of hygrometers; these are: a) the psychrometer, which utilizes the thermodynamic method; b) the class of instruments which depends upon a change of physical dimension due to absorption of moisture (hair hygrometer, for example); c) those which depend upon condensation of moisture (dew point hygrometer); d) the class of instruments which depend upon the change of chemical or electrical properties due to absorption of moisture, and some others.

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ice

the solid crystalline form of water.

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ice apron

a mass of ice adhering to a mountainside.

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ice blink

white glare on the underside of low clouds indicating presence of ice which may be beyond the range of vision.

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ice cake

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

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ice canopy

pack ice from the point of view of the submariner.

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ice cap

a dome-shaped mass of glacier ice that spreads out in all directions; an ice cap is usually larger than an icefield but less than 50,000 square-kilometers (12 million acres).

Ellesmere Island, Canada

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ice cave

a natural bedrock cave that contains year-round ice.

This photograph shows a 22-meter thick ice block along with ice stalactites and stalagmites in the Great Hall of Scarisoara Ice Cave, Romania. (Photograph courtesy Aurel Persoiu)

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ice cluster

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

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ice concentration

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

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ice content

the amount of ice contained in frozen or partially frozen soil or rock.

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ice core

a core sample drilled from the accumulation of snow and ice over many years that have recrystallized and have trapped air bubbles from previous time periods, the composition of which can be used to reconstruct past climates and climate change; typically removed from an ice sheet (Antarctica and Greenland) or from high mountain glaciers elsewhere.

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ice covered

land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour.

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ice divide

the boundary separating opposing flow directions of ice on a glacier or ice sheet.

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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.)

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freshwater ice

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.

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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.

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freshwater ice

ice fog

a suspension of numerous minute ice crystals in the air, reducing visibility at the earth's surface; the crystals often glitter in the sunshine; ice fog produces optical phenomena such as luminous pillars and small haloes.

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ice fringe

a very narrow ice piedmont, extending less than about 1 km inland from the sea.

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icebergs and ice shelves

ice front

the vertical cliff forming the seaward face of an ice shelf or other floating glacier, varying in height from 2 to 50 meters (2.2 to 55 yards) above sea level.

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icebergs and ice shelves

Ice gland

A column of ice in the granular snow at the top of a glacier.

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ice island

a form of tabular berg found in the Arctic Ocean, with a thickness of 30 - 50 meters (33 to 55 yards) and an area from a few thousand square meters to 500 square kilometers (123,550 acres); ice islands often have an undulating surface, which gives them a ribbed appearance from the air.

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icebergs and ice shelves

ice jam

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

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freshwater ice

ice keel

from the point of view of the submariner, a downward-projecting ridge on the underside of the ice canopy; the counterpart of a ridge; ice keels may extend as much as 50 meters (55 yards) below sea level.

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ice lens

a dominantly horizontal, lens-shaped body of ice of any dimension.

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ice limit

the average position of the ice edge in any given month or period based on observations over a number of years.

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ice patrol ship

a research ship which performs ice surveys in polar regions.

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