Glaciers Terms

arctic

(from Greek arktikos which means northern) northern polar region of the earth which includes almost the whole area of the Arctic Ocean and adjacent areas of Eurasian and North American continents.

Ice pinnacle separating from Perito Moreno Glacier. (Photo courtesy of Martyn Clark.)

Ice pinnacle separating from Perito Moreno Glacier. (Photo courtesy of Martyn Clark.)

In 1941, Hole-in-the-Wall Glacier surged, also knocking over trees during its advance. (Photo courtesy of the World Data Center for Glaciology, Boulder, CO. Photo probably taken by W.O. Field.)

In 1941, Hole-in-the-Wall Glacier surged, also knocking over trees during its advance. (Photo courtesy of the World Data Center for Glaciology, Boulder, CO. Photo probably taken by W.O. Field.)

Buys Ballots Law

Meterological law which states that if you are standing with your back to the wind in the Northern Hemisphere, low pressure will be on your left, and high pressure will be on your right. Ballot was a 19th century Dutch climatalogist.

Mt. Kefton, Antarctica

Mt. Kefton, Antarctica

north pole

90° N latitude; one of the two points where the Earth's axis of rotation meets the Earth's surface (the other being the south pole, diametrically opposite).

south pole

90° S latitude; one of the two points where the Earth's axis of rotation meets the Earth's surface (the other being the north pole, diametrically opposite).

Ice gland

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

sea ice development stage

A phrase used to classify sea ice for operational purposes using the age of the ice as a proxy for its thickness. Specific terms such as new ice, nilas, young ice, and multiyear ice are used for each stage of sea ice development.

carbon sink

A reservoir of carbon dioxide that is increasing in size.

A scenic view within the marginal ice zone.

A scenic view within the marginal ice zone.

yedoma

A type of Pleistocene-age (formed 1.8 million to 10,000 years before present) permafrost that contains a significant amount of organic material with ice content of 50-90% by volume. Thawing yedoma is a significant source of atmospheric methane.

mires

Also known as tundra mires, generally described as an area of wet, soggy, muddy ground., and often feature a layer of peat over permafrost.

dipole anomaly

An Arctic atmospheric pressure pattern characterized by high pressure centered over the northern Beaufort Sea and unusually low pressure centered over the Kara Sea. This pattern contributes to ice loss in summer, causing winds to blow ice away from the coast.

An avalanche in motion. (Photograph courtesy of © Richard Armstrong, National Snow and Ice Data Center.)

An avalanche in motion. (Photograph courtesy of © Richard Armstrong, National Snow and Ice Data Center.)

Drumlin field. Manitoba, Canada.

Drumlin field. Manitoba, Canada.

Ellesmere Island, Canada

Ellesmere Island, Canada

Explorer on Skillet Glacier in 1936. Bergschrund is visible as the dark band of ice in the background.

Explorer on Skillet Glacier in 1936. Bergschrund is visible as the dark band of ice in the background.

Glacier at the head of Canon Fiord, Ellesmere Island, Canada

Glacier at the head of Canon Fiord, Ellesmere Island, Canada

Holgate Glacier, Kenai Peninsula, Alaska

Holgate Glacier, Kenai Peninsula, Alaska

hummocking

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

cryoturbate

a body of earth material moved or disturbed by frost action.

open talik

a body of unfrozen ground that penetrates the permafrost completely, connecting suprapermafrost and subpermafrost water.

isolated cryopeg

a body of unfrozen ground, that is perennially cryotic (T < 0 degrees Celsius) and entirely surrounded by perennially frozen ground.

glacial erratic

a boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist.

thaw unconformity

a boundary sometimes identified in perennially frozen ground, representing the base of a relict active layer, as well as the corresponding earlier permafrost table.

snow squall

a brief, but intense fall of snow that greatly reduces visibility and which is often accompanied by strong winds.

snowblink

a bright white glare on the underside of clouds, produced by the reflection of light from a snow-covered surface; snowblink is lighter than ice blink, and much lighter than land sky or water sky.

ice rind

a brittle, shiny crust of floating ice, formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity; thickness less than 5 centimeters (2 inches); easily broken by wind or swell, commonly breaking into rectangular pieces.

solifluction sheet

a broad deposit of nonsorted, water-saturated, locally derived materials that is moving or has moved downslope.

buoy weather station

a buoy, either fixed or floating, which carries instruments for sensing various meteorological elements and for transmitting the data by radio.

grey-white ice

a category of young ice 15 to 30 centimeters (6 to 12 inches) thick, named for its color.

glacier cave

a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.

ice cave

a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.

meltwater conduit

a channel within, underneath, on top of, or near the side of a glacier that drains meltwater out of the glacier; usually kept open by the frictional heating of flowing water that melts the ice walls of the conduit.

marine climate

a climate dominated by the ocean; because of the moderating effect of water, sites having this climate are considered relatively mild.

thaw sink

a closed thaw basin with subterranean drainage.

snowflake

a cluster of ice crystals that falls from a cloud.

glaze

a coating of ice, generally clear and smooth but usually containing some air pockets, formed on exposed objects by freezing of a film of super-cooled water deposited by rain, drizzle, fog, or possibly condensed from super-cooled water vapor; glaze is denser, harder and more transparent, than either rime or hoarfrost.

synoptic code

a code approved by the World Meteorological Organization, by which meteorological elements observed at the earth's surface at synoptic times are encoded in groups of five figures and transmitted internationally through the GTS (Global Telecommunications System).

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.

bora

a cold wind blowing down an incline; a kind of katabatic wind.

fall wind

a cold wind blowing down an incline; a kind of katabatic wind.

gravity wind

a cold wind blowing down an incline; a kind of katabatic wind.

mountain wind

a cold wind blowing down an incline; a kind of katabatic wind.

pingo remnant

a collapsed pingo.

patch

a collection of pack ice, less than 10 kilometers (6.2 miles) across, whose limits can be seen from the masthead.

vein ice

a comprehensive term for ice of any origin occupying cracks in permafrost.

massive ice

a comprehensive term used to describe large masses of ground ice, including ice wedges, pingo ice, buried ice and large ice lenses.

ice cluster

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

whiteout

a condition in which daylight is diffused by multiple reflections between a snow surface and an overcast sky; contrasts vanish, and the observer is unable to distinguish the horizon or any snow surface feature.

dirt cone

a cone-shaped formation of ice that is covered by dirt; a dirt cone is caused by a differential pattern of ablation between the dirt covered surface and bare ice.

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.

marginal crevasse

a crevasse near the side of a glacier formed as the glacier moves past stationary valley walls; usually oriented about 45 degrees up-glacier from the side wall.

splay crevasse

a crevasse pattern that forms where ice slowly spreads out sideways; commonly found near a glacier terminus.

peat

a deposit consisting of decayed or partially decayed humified plant remains.

hoarfrost

a deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc.; the surfaces of these objects are sufficiently cooled, mostly by nocturnal radiation, to cause the direct sublimation of the water vapor contained in the ambient air.

degree-day (C or F)

a derived unit of measurement used to express the departure of the mean temperature for a day from a given reference (or base) temperature.

thaw consolidation ratio

a dimensionless ratio describing the relationship between the rate of thaw and the rate of consolidation of a thawing soil, which is considered to be a measure of the relative rates of generation and expulsion of excess water during thaw.

orbiculic cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form circular to ellipsoidal patterns.

conglomeric cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles form compound arrangements.

surface cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles have vertical or near-vertical orientation.

granic cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete loosely packed units.

fragmoidal cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are coalescing.

fragmic cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are densely packed.

granoidic cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form more or less discrete loosely packed units.

isoband cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers of similar thickness.

banded cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers.

ice sheet

a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets).

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).

ice lens

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

ice prisms

a fall of unbranched ice crystals, in the form of needles, columns, or plates, often so tiny that they seem to be suspended in the air; these are visible mainly when they glitter in the sunshine (diamond dust); they may then produce a luminous pillar or other halo phenomena; this hydrometeor, which is frequent in polar regions, occurs at very low temperatures and in stable air masses.

solifluction apron

a fan-like deposit at the base of a slope, produced by solifluction.

ice-wedge cast

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

glacier flour

a fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams and causes water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance; also called rock flour.

rock flour

a fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams, causing water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance.

grid

a finite collection of points to which the meteorological variables used in a numerical model, or interpolated from observations, apply; a field of such regular values (points) is termed gridded field.

strand crack

a fissure at the junction between an inland ice sheet, ice piedmont or ice rise and an ice shelf, the latter being subject to the rise and fall of the tide.

randkluft

a fissure that separates a moving glacier from its headwall rock; like a bergschrund.

tabular berg

a flat-topped iceberg that shows horizontal banding; typically form by breaking from an ice shelf.

ice cake

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

shuga

a form of new ice, composed of spongy, white lumps a few cm across, that tend to form in rough seas; they resemble slushy snow balls.

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.

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.

active air-cooled thermal pile

a foundation pile on which a cold air refrigeration system has been installed to remove heat from the ground.

active liquid refrigerant pile

a foundation pile on which a liquid coolant refrigeration system has been installed to remove heat from the ground.

thermal pile

a foundation pile on which natural convection or forced circulation cooling systems or devices have been installed to remove heat from the ground.

new ice

a general category of ice that consists of frazil, grease ice, slush, and shuga.

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.

thermal regime of the ground

a general term encompassing the temperature distribution and heat flows in the ground and their time-dependence.

kurum

a general term for all types of coarse clastic formations on slopes of 2-3 to 40 degrees, moving downslope mainly due to creep.

patterned ground

a general term for any ground surface exhibiting a discernibly ordered, more or less symmetrical, morphological pattern of ground and, where present, vegetation.

pressure ice

a general term for floating ice which has been squeezed together and in places forced upwards; includes rafted ice, telescoped ice, hummocked ice and ridge ice.

ground ice

a general term referring to all types of ice contained in freezing and frozen ground.

active-layer failure

a general term referring to several forms of slope failures or failure mechanisms commonly occurring in the active layer overlying permafrost.

peat plateau

a generally flat-topped expanse of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil.

negative mill

a geyser; a fountain that develops when water from a conduit is forced up to the surface of a glacier.

polar glacier

a glacier entirely below freezing, except possibly for a thin layer of melt near the surface during summer or near the bed; polar glaciers are found only in polar regions of the globe or at high altitudes.

surging glacier

a glacier that experiences a dramatic increase in flow rate, 10 to 100 times faster than its normal rate; usually surge events last less than one year and occur periodically, between 15 and 100 years.

alpine glacier

a glacier that is confined by surrounding mountain terrain; also called a mountain glacier.

mountain glacier

a glacier that is confined by surrounding mountain terrain; also called an alpine glacier.

reconstructed glacier

a glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstituted glacier, regenerated glacier, or glacier remainie.

regenerated glacier

a glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstituted or reconstructed glacier, or glacier remainie.

reconstituted glacier

a glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstructed glacier, regenerated glacier, or glacier remainie.

glacier remainie

a glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier, then re-adhering; also called reconstituted, reconstructed or regenerated glacier.

hanging glacier

a glacier that terminates at or near the top of a cliff.

subpolar glacier

a glacier whose temperature regime is between polar and temperate; usually predominantly below freezing, but could experience extensive summer melt.

retreating glacier

a glacier whose terminus is increasingly retreating upvalley compared to its previous position due to a higher level of ablation compared to accumulation.

icebound

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.

crust

a hard snow surface lying upon a softer layer; crust may be formed by sun, rain or wind, and is described as breakable crust or unbreakable crust, depending upon whether it wil break under the weight of a turning skier.

polar ice cap

a high-latitude region covered in ice; not a true ice cap, which are less than 50,000 square kilometers (12.4 million acres) and are always over land; more like an ice sheet; also called polar ice sheet.

ram

a horizontal underwater projection of ice from an ice front, ice wall, iceberg or floe.

peat hummock

a hummock consisting of peat.

turf hummock

a hummock consisting of vegetation and organic matter with or without a core of mineral soil or stones.

earth hummock

a hummock having a core of silty and clayey mineral soil which may show evidence of cryoturbation.

thermokarst mound

a hummock remaining after melting of the ice wedges surrounding an ice-wedge polygon.

cloud

a hydrometeor consisting of a visible aggregate of minute particles of liquid water or ice, or both, suspended in the free air and usually not touching the earth's surface; it may also include larger particles of liquid water or ice (precipitation particles) and non-aqueous liquid or solid particles such as those present in fumes, smoke and dust (aerosols); cloudiness is the same as cloud cover; but usually it is used in a very general sense.

fog

a hydrometeor consisting of a visible aggregate of minute water droplets (or ice crystals), suspended in the atmosphere near the earth's surface; according to international definition, fog reduces visibility below one kilometer, fog differs from cloud only in that the base of fog is at the earth's surface while clouds are above the surface; when composed of ice crystals, it is termed ice fog.

crevasse hoar

a kind of hoarfrost; ice crystals that develop by sublimation in glacial crevasses and in other cavities with cooled space and calm, still conditions under which water vapor can accumulate; physical origin is similar to depth hoar.

depth hoar

a kind of hoarfrost; ice crystals that develop by sublimation within a layer of dry snow; characterized by rapid recrystallization, usually caused by large temperature gradients; similar in physical origin to crevasse hoar; crystals are faceted, rather than rounded.

thermokarst lake

a lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice.

open water

a large area of freely navigable water in which floes may be present in concentration under 1/10th; if there is no sea ice present, the area may be termed open water, even though icebergs are present.

alas/alass

a large depression of the ground surface produced by thawing of a large area of very thick and exceedingly ice-rich permafrost.

thomson crystal

a large ice crystal found in deep, stagnant water-filled cavities of a glacier.

glacial trough

a large u-shaped valley formed from a v-shaped valley by glacial erosion.

pereletok

a layer of frozen ground which forms as part of the seasonally frozen ground (in areas free of permafrost or with a lowered permafrost table); remains frozen throughout one or several summers, and then thaws.

cryogenic aquiclude

a layer of ground which, because of its frozen state, has a low enough permeability to act as a confining bed for an aquifer.

relict active layer

a layer of ground, now perennially frozen, lying immediately below the modern active layer; its thickness indicates the greater annual depth of thaw that occurred during a previous period.

snow layer

a layer of ice crystals with similar size and shape.

residual thaw layer

a layer of thawed ground between the seasonally frozen ground and the permafrost table.

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.

active 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 present movement.

viscosity

a measure of a fluid's resistance to flow; can be thought of as a measure of fluid friction.

freezing degree-days

a measure of how cold it has been and how long it has been cold; the cumulative fdd is usually calculated as a sum of average daily degrees below freezing for a specified time period (10 days, month, season, etc.).

internal ice stress

a measure of the compactness, or strength of the ice; plays an important role in the deformation of the ice and formation of features such as ridges and leads.

mercury barometer

a mercury-filled glass tube in which the height of the mercury column is a measure of air pressure.

surface observation

a meteorological observation made on the earth's surface, in contrast with an upper-air observation.

uniaxial compression test

a method to determine the short-term strength of rocks; conducted by employing a constant loading rate until failure; the failure load is used to calculate the failure stress; can also be used to determine the elastic constants of rocks (i.e. Young's modulus, Poisson's ratio).

static cryosol

a mineral soil showing little or no evidence of cryoturbation, with permafrost within 1 meter (3.3 feet) below the surface.

turbic cryosol

a mineral soil showing marked evidence of cryoturbation, as indicated by broken horizons and displaced material.

arctic mist

a mist of ice crystals; a very light ice fog.

slush

a mixture of snow and grease ice.

frost bulb

a more or less symmetrical zone of frozen ground formed around a buried chilled pipeline or beneath or around a structure maintained at temperatures below 0 degrees Celsius.

dump moraine

a mound or layer of moraine formed along the edge of a glacier by rock that falls off the ice; sometimes called a ground moraine.

moraine

a mound, ridge, or other distinct accumulation of glacial till.

valley glacier

a mountain glacier whose flow is confined by valley walls.

icefoot

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

permafrost degradation

a naturally or artificially caused decrease in the thickness and/or areal extent of permafrost.

permafrost aggradation

a naturally or artificially caused increase in the thickness and/or areal extent of permafrost.

flaw lead

a navigable passage between pack ice and fast ice.

iceberg

a piece of ice that has broken off from the end of a glacier that terminates in water.

closed-system pingo

a pingo formed by doming of frozen ground due to freezing of injected water supplied by expulsion of pore water during permafrost aggradation in the closed talik under a former water body.

open-system pingo

a pingo formed by doming of frozen ground; caused by groundwater that moves downslope through taliks and onto the pingo surface, where it freezes.

pingo scar

a pingo remnant in a contemporary non-permafrost environment.

ice-wedge polygon

a polygon outlined by ice wedges underlying its boundaries.

sand-wedge polygon

a polygon outlined by sand wedges underlying its boundaries.

latent heat polynya

a polynya that forms from strong winds in a persistent direction that push the ice away from a barrier (the coast, fast ice, a grounded iceberg, or an ice shelf).

sensible heat polynya

a polynya that forms from the upwelling of warm (above-freezing) ocean water from lower depths; these can form in mid-ocean areas, far from coasts or other barriers.

palsa bog

a poorly-drained lowland underlain by organic-rich sediments, which contains perennially frozen peat bodies (peat plateaux) and, occasionally, palsas.

ice patrol ship

a research ship which performs ice surveys in polar regions.

lateral moraine

a ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier.

medial moraine

a ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams.

ice-cored glacier

a rock glacier that has a buried core of ice.

ice-cemented glacier

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

glacier table

a rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice.

nunatak

a rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet.

snow core

a sample of snow, either just the freshly fallen snow or the combined old and new snow on the ground, obtained by pushing a cylinder down through the snow layer and extracting it.

shield

a screen to shield a rain-gauge from the influence of the wind, or to shield a thermometer against insolation.

Fram Strait

a sea channel connecting the Arctic Ocean and the Nordic Seas, running between Greenland and Spitsbergen. Fram Strait is the passageway where most drifting sea ice exits the Arctic.

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.

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.

frost blister

a seasonal frost mound produced through doming of seasonally frozen ground by a subsurface accumulation of water under elevated hydraulic potential during progressive freezing of the active layer.

snowdrift glacier

a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a drift glacier.

drift glacier

a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a snowdrift glacier.

catchment glacier

a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a snowdrift glacier or a drift glacier.

ice quake

a shaking of ice caused by crevasse formation or jerky motion.

icing

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.

esker

a sinuous ridge of sedimentary material (typically gravel or sand) deposited by streams that cut channels under or through the glacier ice.

detachment failure

a slope failure in which the thawed or thawing portion of the active layer detaches from the underlying frozen material.

thaw slumping

a slope failure mechanism characterized by the melting of ground ice, and downslope sliding and flowing of the resulting debris.

retrogressive thaw slump

a slope failure resulting from thawing of ice-rich permafrost.

tributary glacier

a small glacier that flows into a larger glacier.

frost boil

a small mound of soil material, presumed to have been formed by frost action.

tarn

a small mountain lake or pool.

flow finger

a small percolation channel that is a beginning path for surface meltwater through snow or firn.

polycrystal

a snowflake composed of many individual ice crystals.

stone-banked (solifluction) lobe

a solifluction lobe with a stony front.

turf-banked (solifluction) lobe

a solifluction lobe with its front covered by a vegetation mat.

stone-banked (solifluction) terrace

a solifluction terrace with a stony front.

turf-banked (solifluction) terrace

a solifluction terrace with its front covered by a vegetation mat.

gas hydrate

a special form of solid clathrate compound in which crystal lattice cages or chambers, consisting of host molecules, enclose guest molecules.

snow board

a specially constructed board used to identify the surface of snow that has been recently covered by snowfall.

headwall

a steep cliff, usually the uppermost part of a cirque.

cryoplanation terrace

a step-like or table-like bench cut in bedrock in cold climate regions.

beaded stream

a stream characterized by narrow reaches linking pools or small lakes.

shore lead

a stretch of navigable water between pack ice and the shore.

climate change

a study dealing with variations in climate on many different time scales from decades to millions of years, and the possible causes of such variations; (1) in the most general sense, the term climate change encompasses all forms of climatic inconstancy (that is, any differences between long-term statistics of the meteorological elements calculated for different periods but relating to the same area) regardless of their statistical nature or physical causes; climate change may result from such factors as changes in solar activity, long-period changes in the earth's orbital elements (eccentricity, obliquity of the ecliptic, precession of equinoxes), natural internal processes of the climate system, or anthropogenic forcing (for example, increasing atmospheric concentrations of carbon dioxide and other greenhouse gases) (2) the term climate change is often used in a more restricted sense, to denote a significant change (such as a change having important economic, environmental and social effects) in the mean values of a meteorological element (in particular temperature or amount of precipitation) in the course of a certain period of time, where the means are taken over periods of the order of a decade or longer.

suspensoid

a substance dispersed throughout another substance; also called suspended phase.

cryosuction

a suction developed in freezing or partially frozen fine-grained materials as a result of temperature-dependent differences in unfrozen water content.

debris flow

a sudden and destructive variety of landslide, in which loose material on a slope, with more than 50% of particles larger than sand size, is mobilized by saturation and flows down a channel or canyon.

glacier flood

a sudden outburst of water released by a glacier.

block field

a surficial layer of angular shattered rocks formed in either modern or pleistocene periglacial environments.

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.

dilation crack

a tensile fracture in a frozen material due to surface extension caused by doming.

thermal-contraction crack

a tensile fracture resulting from thermal stresses in frozen ground.

firnspiegel

a thin sheet of ice formed on the glacier surface by rapid refreezing of solar-heated snow or firn, usually at high elevations during spring.

nilas

a thin sheet of smooth, level ice less than 10 centimeters (4 inches) thick; appear darkest when thin.

powder snow

a thin, dry snow surface which is composed of loose, fresh ice crystals.

multiple retrogressive slide

a type of mass movement associated with shear failure in unfrozen sediments underlying permafrost, leading to detachment of blocks of frozen ground that move downslope.

mud circle

a type of nonsorted circle developed in fine-grained materials.

stone earth circle

a type of nonsorted circle developed in gravelly materials.

sorted net

a type of patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, with a sorted appearance commonly due to borders of stones surrounding central areas of finer material.

diamond dust

a type of precipitation composed of slowly falling, very small, unbranched crystals of ice which often seem to float in the air; it may fall from a high cloud or from a cloudless sky, it usually occurs under frosty weather conditions (under very low air temperatures).

pressure

a type of stress characterized by uniformity in all directions; in dynamics, it is that part of the stress tensor that is independent of viscosity and depends only upon the molecular motion appropriate to the local temperature and density; it is the negative of the mean of the three normal stresses, and is, therefore, a scalar quantity expressed in units of force per unit area; in meteorology, commonly used for atmospheric pressure.

hanging valley

a valley formed by a small glacier that has a valley bottom relatively higher than nearby valleys formed by larger glaciers.

outlet glacier

a valley glacier which drains an inland ice sheet or ice cap and flows through a gap in peripheral mountains.

ice fringe

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

glacieret

a very small glacier.

grease ice

a very thin, soupy layer of frazil crystals clumped together, which makes the ocean surface resemble an oil slick.

chinook

a warm wind blowing down an incline; a kind of katabatic wind.

foehn

a warm wind blowing down an incline; a kind of katabatic wind.

waterbody encircling a palsa

a water-filled depression surrounding a palsa.

gravity wave

a wave disturbance in which buoyancy (or reduced gravity) acts as a restoring force on parcels displaced from hydrostatic equilibrium; there is a direct oscillatory conversion between potential and kinetic energy in the wave motion.

creep

a way that snow or ice can move by deforming its internal structure.

arctic high

a weak high which appears over the arctic basin during late spring, summer and early autumn; one of the centers of action in the atmosphere.

synoptic chart

a weather chart reflecting the state of the atmosphere over a large area at a given moment.

composite wedge

a wedge showing evidence of both primary and secondary filling.

sand wedge

a wedge-shaped body of sand produced by filling of a thermal contraction crack with sand either blown in from above or washed down the walls of the crack.

soil wedge

a wedge-shaped body of soil that is different in structure and texture from the surrounding soil.

rime

a white or milky and opaque granular deposit of ice formed by the rapid freezing of super-cooled water drops as they impinge upon an exposed object; it is denser and harder than hoarfrost, but lighter, softer, and less transparent than glaze.

thaw bulb

a zone of thawed ground below or surrounding a man-made structure placed on or in permafrost and maintained at temperatures above 0 degrees Celsius.

unstable air

air in which static instability prevails; this condition is determined by the vertical gradients of air temperature and humidity.

stable air mass

air mass having static stability in its lower layers; it is free from convection, has a low degree of turbulence and may have stratiform clouds or fog, or no clouds.

Siberian high

an area of high pressure which forms over Siberia in winter, and which is particularly apparent on mean charts of sea-level pressure.

seasonal ice zone

an area of ocean that extends from the permanent ice zone to the boundary where winter sea ice extent is at a maximum; here, sea ice is present only part of the year; this zone primarily consists of first-year ice.

permacrete

an artificial mixture of frozen soil materials cemented by pore ice, which forms a concrete-like construction material used in cold regions.

meridional circulation

an atmospheric circulation in a vertical plane oriented along a meridian; it consists of the vertical and the meridional (north or south) components of motion only.

subsetting

Provides the ability to narrow your search by providing specific temporal ranges and or spatial coordinates.

data analysis

Provides the user the ability to calculate or compare data parameters.

reformatting

Provides the user the ability to convert the data from its native format to a different format.

reprojection

Provides the user the ability to convert the data from its native reference projection to a different reference projection.

radar

RAdio Detection And Ranging was an original active microwave sensor that became widely operational with the onset of World War II.

standard deviation

Statistical measurement of the variation in a distribution: In science, standard deviation serves as measure of the spread of the data, or how likely a data point will fall close to the mean.

relative error

The ratio of the absolute error in a measurement to the size of the measurement.

visualization

Tools that provide visual images of data on-the-fly.

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.

hard frozen ground

frozen ground (soil or rock) which is firmly cemented by ice.

dry frozen ground

frozen ground with a very low total water content consisting almost completely of interfacial water, and not cemented by ice.

lithometer

general term for dry atmospheric suspensoids, including dust, haze, smoke and sand.

continuous permafrost

geographic area in which permafrost occurs everywhere beneath the exposed land surface with the exception of widely scattered sites, such as newly deposited unconsolidated sediments that have just been exposed to the freezing climate; mean annual soil surface temperatures are typically below -5 degrees Celsius (23 degrees Fahrenheit).

solifluction features

geomorphological features of varying scale produced by the process of solifluction.

fjord

glacial troughs that fill with sea water.

weathered ice

glacier ice that has been exposed to sun or warm wind so that the boundaries between ice crystals are partly disintegrated.

cold glacier

glacier in which most of the ice is below the pressure melting point; nonetheless, the glacier's surface may be susceptible to melt due to incoming solar radiation, and the ice at the rock/ice interface may be warmed as a result of the natural (geothermal) heat from the earth's surface.

branched-valley glacier

glacier that has one or more tributary glaciers that flow into it; distinguished from a simple valley glacier that has only a single tributary glacier.

calving glacier

glacier that loses material by calving, usually a glacier that terminates in sea, lake, or river water.

cirque glacier

glacier that resides in basins or amphitheaters near ridge crests; most cirque glaciers have a characteristic circular shape, with their width as wide or wider than their length.

global observing system

global network of observational stations which is the coordinated system of methods, techniques and facilities for making observations on a world-wide scale in the framework of the World Weather Watch, a World Meteorological Organization program.

glacial striations

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves.

glacial grooves

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.

frost-stable ground

ground (soil or rock) in which little or no segregated ice forms during seasonal freezing.

frost-susceptible ground

ground (soil or rock) in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature.

syngenetic ice

ground ice developed during the formation of syngenetic permafrost.

epigenetic ice

ground ice developed in epigenetic permafrost, or in previously formed syngenetic permafrost.

lens ice

ground ice occurring as ice lenses.

two-layer permafrost

ground in which two layers of permafrost are separated by a layer of unfrozen ground.

seasonally frozen ground

ground that freezes and thaws annually.

seasonally thawed ground

ground that thaws and refreezes annually.

halo

group of optical phenomena, in the form of rings, arcs, pillars or bright spots around the sun or moon, produced by the refraction or reflection of light by ice crystals suspended in the atmosphere (cirrus clouds, diamond dust, etc.).

accretion

growth of a cloud or precipitation particle by the collision and union of a frozen particle (ice crystal or snowflake) with a super-cooled liquid droplet which freezes on impact.

icicle

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

bedrock

hard-packed rock lying below the Earth's surface; lies in beds or layers; can be variable across geographic space; above bedrock is a layer of broken, weathered rock.

arctic haze

haze in arctic regions which reduces horizontal and slant visibility and which may extend to a height of about 10 km; it appears blue-grey when viewed away from the sun, and reddish-brown toward it.

longwave radiation

heat radiation with wavelengths greater than 4 millimeters.

dendrite

hexagonal ice crystals with complex and often fernlike branches.

semipermanent anticyclone

high pressure area largely predominate during a major portion of the year where an anticyclone appears on the mean monthly pressure charts.

snow barchan

horseshoe-shaped snowdrift, with the ends pointing down-wind.

synoptic hour

hour (UTC - Coordinated Universal Time) determined by international agreement at which meteorological observations are made simultaneously throughout the world; the primary synoptic hours are every six hours, commencing at 00:00 UTC.

ice piedmont

ice covering a costal strip of low-lying land backed by mountains; the surface of an ice piedmont slopes gently seawards and may be anything from 1 to 50 kilometers (0.6 to 31 miles) wide, fringing long stretches of coastline with ice cliffs; ice piedmonts frequently merge into ice shelves; a very narrow ice piedmont may be called an ice fringe.

sublimation ice

ice formed by reverse sublimation of water vapour on cold surfaces.

intrusive ice

ice formed from water injected into soils or rocks.

cave ice

ice formed in a closed or open cave.

close cavity ice

ice formed in a closed space, cavity or cave in permafrost.

open-cavity ice

ice formed in an open cavity or crack in the ground by reverse sublimation of water vapour.

interstitial ice

ice formed in narrow spaces between small rocks and sediment in soil.

thermal-contraction-crack ice

ice formed in thermal contraction cracks in the ground.

relict ice

ice formed in, and remaining from, the geologically recent past.

buried ice

ice formed or deposited on the ground surface and later covered by sediments.

segregated ice

ice in discrete layers or ice lenses, formed by ice segregation.

nip

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.

wedge ice

ice occurring in an ice wedge.

pore ice

ice occurring in the pores of soils and rocks.

dirty ice

ice that contains sediments stirred up and tangled in the ice as it grows.

dilation crack ice

ice that forms in dilation cracks.

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.

fast ice

ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents.

pack ice

ice that is not attached to the shoreline and drifts in response to winds, currents, and other forces; some prefer the generic term drift ice, and reserve pack ice to mean drift ice that is closely packed.

flooded sea ice

ice that is pushed into the underlying ocean water by the weight of thick snow cover on its surface; the salty ocean water floods the snow cover and creates a salty, slushy layer; flooded sea ice is more common in the antarctic because of more snowfall and thinner sea ice than in the arctic.

drift ice

ice that moves from winds, currents, or other forces.

well-bonded permafrost

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

poorly-bonded permafrost

ice-bearing permafrost in which few of the soil particles are held together by ice.

partially-bonded permafrost

ice-bearing permafrost in which some of the soil particles are not held together by ice.

ice-bonded permafrost

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

bottom bergs

icebergs that originate from near the bottom of a glacier; the color is usually black from trapped rock material or dark blue because of old, coarse, bubble-free ice; they sit low in the water due to the weight of the embedded rocks.

North Atlantic Oscillation

an oscillation in the strength of the Icelandic Low and Azores High, the two dominant surface pressure features in the North Atlantic. When both are unusually strong, the North Atlantic Oscillation (NAO) is in its positive phase; when both are unusually weak, it is in its negative phase. The NAO has climate impacts not just in the Arctic, but in North America and Europe. The NAO, identified by Sir Gilbert Walker in the 1920s, is similar to the Arctic Oscillation.

electromagnetic wave

an oscillation of the electric or magnetic field associated with the propagation of energy; characterized by their wavelengths and amplitude; propagate at the speed of light.

cornice

an overhanging accumulation of ice and wind-blown snow, characteristically found on the edge of a ridge or cliff face.

alpine layers

annual accumulations of snow and dust on a glacier.

outburst flood

any catastrophic flooding from a glacier; may originate from trapped water in cavities inside a glacier or at the margins of glaciers or from lakes that are dammed by flowing glaciers.

sea ice

any form of ice found at sea which has originated from the freezing of sea water.

floating ice

any form of ice found floating in water.

crack

any fracture or rift in floating ice not sufficiently wide to be described as a lead.

frost mound

any mound-shaped landform produced by ground freezing combined with accumulation of ground ice due to groundwater movement or the migration of soil moisture.

cold front

any non-occluded front that moves in such a way so that colder air replaces warmer air; the leading edge of a relatively cold air mass.

dead ice

any part of a glacier which has ceased to flow; dead ice is usually covered with moraine.

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.

World Meteorological Organization Program

any scientific project (field experiment, inter-comparison, etc.) internationally performed under the aegis of the World Meteorological Organization.

katabatic wind

any wind blowing down an incline; if the wind is warm, it is called a foehn or chinook; if cold, it may be a fall wind (bora), or a gravity wind (mountain wind); the opposite of anabatic wind.

anabatic wind

any wind blowing up a steep incline or mountain; the opposite of katabatic wind.

coriolis force

apparent force, due to the rotation of the earth, which acts normal to, and to the right of the velocity of a moving particle in the northern hemisphere, the movement of the particle being considered relative to that of the earth.

cyclone

area in the atmosphere in which the pressures are lower than those of the surrounding region at the same level; it is represented on a synoptic chart by a system of isobars at a specified altitude level (or a system of contours at a specified pressure level) which enclose relatively low values of pressure (or altitude); a cyclone begins when a wave (young) cyclone forms and moves along a front; a mature cyclone has well-developed warm sectors and both cold and warm fronts; an occluded cyclone is that within which there has developed an occluded front.

accumulation area

area of a glacier where more mass is gained than lost.

accumulation zone

area of a glacier where more mass is gained than lost.

high

area of high pressure in the atmosphere; used interchangeably with anticyclone.

anticyclone

area of increased atmospheric pressure relative to surrounding pressure field in the atmosphere; it is outlined by closed isobars on a synoptic surface chart, and by closed contours on a constant-pressure chart; this term is used interchangeably with high.

anticyclone

area of increased atmospheric pressure relative to surrounding pressure field in the atmosphere; outlined by closed isobars on a synoptic surface chart, and by closed contours on a constant-pressure chart; used interchangeably with high..

low

area of low pressure in the atmosphere.

ablation zone

area or zone of a glacier where snow and ice ablation exceed accumulation.

barrens

areas of discontinuous vegetation cover in the polar semi-desert of the high arctic.

average value

arithmetic mean (m) of a number (n) of values (x1, x2, ... xn), defined by the equation: m = sxi/n; annual average value is calculated from 12 monthly means; daily average (or mean) value is calculated from 24 hourly readings of a meteorological element, or often from the average of the daily maximum and minimum values (for example, of temperature); monthly average is usually calculated as the average of the daily average values.

hydraulic thawing

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

atmospheric phenomenon

as commonly used in weather observing practice, an observable occurrence of particular physical significance within the atmosphere; from the viewpoint of weather observations, the atmospheric phenomena include all hydrometeors (precipitation types and fogs), blowing snow, thunderstorms, tornadoes, waterspouts, and others.

cold low

at a given level in the atmosphere, any low that is generally characterized by colder air near its center than around its periphery; the opposite of a warm low.

warm low

at a given level in the atmosphere, any low that is generally characterized by warmer air near its center than around its periphery; the opposite of a cold low.

climatological atlas

atlas composed mainly of climatological charts; it represents especially the monthly and annual distributions of the principal climatic elements of a specific region for a relatively long period.

cyclone ciruculation

atmospheric circulation associated with a cyclone (depression, low pressure area); it is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

station pressure

atmospheric pressure observed at a station.

cirque

bowl shape or amphitheater usually sculpted out of the mountain terrain by a cirque glacier.

calve

break off from a larger ice shelf or ice sheet into the water.

metamorphism

changes in the structure and texture of snow grains which result from variations in temperature, migration of liquid water and water vapor, and pressure within the snow cover.

desiccation polygon

closed, multi-sided, patterned ground feature formed by desiccation cracks in fine-grained soil material, usually less than 2 meters (6.6 feet) in diameter.

macro-scale polygons

closed, multi-sided, roughly equidimensional, patterned ground features, typically 15 to 30 meters (16 to 33 yards) across; commonly resulting from thermal contraction cracking of the ground.

low-level clouds

clouds in the lower region of the atmosphere, from ground level to 6500 feet (2000 meters); includes stratus, stratocumulus, the bases of cumulus and cumulonimbus, and sometimes nimbostratus clouds.

slush zone

common near the snow line on a relatively flat portion of a glacier where melting snow forms slush.

sastrugi

complex, fragile shapes of snow on top of sea ice that resemble sand dunes; they form parallel to the prevailing wind direction; sastrugi can also form on snow cover over land.

close pack ice

composed of close ice that is mostly in contact; ice cover 7/10ths to 9/10ths.

open pack ice

composed of floes seldom in contact and with many leads; ice cover 4/10ths to 6/10ths.

thaw settlement

compression of the ground due to thaw consolidation.

ground moraine

continuous layer of till near the edge or underneath a steadily retreating glacier.

supercooling

cooling of a liquid to a temperature below its freezing point, without causing solidification.

ripple marks

corrugation on a snow surface caused by wind (as on sand).

desiccation crack

crack or fissure developed in fine-grained soil material as a result of shrinkage during drying.

World Meteorological Organization

created by the World Meteorological Convention and recognized as a special agency of the United Nations in 1951; the WMO consists of more than 185 member countries; and facilitates international cooperation in all aspects of meteorology.

bergschrund

crevasse that separates flowing ice from stagnant ice at the head of a glacier.

frost flowers

crystals of ice that form when water vapor becomes a solid (bypassing the liquid phase) and deposits itself on the sea ice surface; frost flowers roughen the surface and dramatically affect its electromagnetic signal.

frost jacking

cumulative upward displacement of objects embedded in the ground, caused by frost action.

convection cloud

cumuliform cloud which forms in the atmosphere as a result of convection; such clouds are also called clouds of vertical development, a cloud that has its base in the low height range but extends upward into the middle or high altitudes.

smog

currently used as a synonym for general air pollution; it was originally created by combining the words smoke and fog.

sunspot

dark spot on the sun, with cooler-than-average temperatures and strong magnetic activity

coefficient of compressibility

decrease in volume per unit volume of a substance resulting from a unit increase in pressure, under isothermic conditions.

telescoped ice

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

rafted ice

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

old snow

deposited snow whose transformation into firn is so far advanced that the original form of the ice crystals can no longer be recognized.

ablation hollows

depressions in the snow surface caused by the sun or warm, gusty wind.

anomaly

deviation of a meteorological quantity value in a given region from the normal (mean) value for the same period.

net terrestrial radiation

difference between the downward and upward terrestrial radiation fluxes; net flux of terrestrial radiation.

drift of ice

displacement of a sea ice field from its place of origin under the effect of ocean currents and winds.

mass wasting

downslope movement of soil or rock on, or near, the earth's surface under the influence of gravity.

freezing drizzle

drizzle, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight.

frost phenomena

effects of frost action on earth materials and on structures placed in or on the ground.

equinox

either of the two points of intersection of the sun's apparent annual path and the plane of the earth's equator; in the northern hemisphere the spring (vernal) equinox falls on or about 21 March, and the autumnal equinox on or about 22 September.

spring equinox

either of the two points of intersection of the sun's apparent annual path and the plane of the earth's equator; in the northern hemisphere, the spring (vernal) equinox falls on or about 21 March, and the autumnal equinox on or about 22 September.

magnetic pole

either of the two points on the earth's surface at which magnetic meridians converge; the horizontal component of the magnetic field of the earth becomes zero at this point; also called the dip pole.

dip pole

either of the two points on the earth's surface at which magnetic meridians converge; the horizontal component of the magnetic field of the earth becomes zero at this point; also called the magnetic pole.

ultraviolet radiation

electromagnetic radiation of shorter wavelength than visible radiation but longer than x-rays; roughly, radiation in the wavelength interval from 10 to 4000 angstroms.

infrared radiation

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

heat balance

equilibrium between the gain and loss of heat at a specific place or for a specific system.

arctic sea smoke

evaporation (steam) fog produced above a surface of open water within arctic ice when the air is stable and relatively cold.

steam fog

evaporation fog formed when water vapor is added to air which is much colder than the vapor's source; most commonly, when very cold air drifts across relatively warm water; also called sea smoke.

sea smoke

evaporation fog formed when water vapor is added to air which is much colder than the vapor's source; most commonly, when very cold air drifts across relatively warm water; also called steam fog.

haze

fine dust or salt particles dispersed through a portion of the atmosphere; the particles are so small that they cannot be felt or individually seen with the naked eye, but they diminish horizontal visibility and give the atmosphere a characteristic opalescent appearance that subdues all colors; a type of lithometeor.

frazil ice

fine spicules or plates of ice in suspension in water.

plastic frozen ground

fine-grained soil in which only a portion of the pore water has turned into ice.

drifting buoy

floating (or drifting on ice) ocean buoy equipped with meteorological and/or oceanographic sensing instruments linked to transmitting equipment for sending the observed data to collecting centers.

lake ice

floating ice formed in lakes.

river ice

floating ice formed in rivers.

first-year ice

floating ice of no more than one year's growth developing from young ice; thickness from 0.3 to 2 meters (1 to 6.6 feet); characteristically level where undisturbed by pressure, but where ridges occur, they are rough and sharply angular.

rotten ice

floating ice which has become honeycombed in the course of melting, and which is in an advanced state of disintegration.

level ice

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

compression flow

flow that occurs when glacier motion is decelerating down-slope.

evaporation fog

fog formed as a result of evaporation of water that is warmer than the air.

advection fog

fog which forms in the lower part of a warm moist air mass moving over a colder surface (land or water).

frost smoke

fog-like clouds, due to the contact of cold air with relatively warm water, which appear over newly-formed leads, or leeward of the ice edge, and which may persist while new ice is forming.

nonsorted stripe

form patterned ground with a striped and nonsorted appearance, due to parallel strips of vegetation-covered ground and intervening strips of relatively bare ground, oriented down the steepest available slope.

geyser

fountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.

free water

free water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity.

freeze-thaw cycle

freezing of a material followed by thawing.

open-system freezing

freezing that occurs under conditions that allow gain or loss of water by the system.

closed-system freezing

freezing that occurs under conditions that preclude the gain or loss of any water by the system.

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.

hostile ice

from the point of view of the submariner, an ice canopy containing no large ice skylights or other features which permit a submarine to surface.

friendly ice

from the point of view of the submariner, an icey canopy containing many large ice skylights or other features which permit a submarine to surface; there must be more than ten such features per 37 kilometers (30 nautical miles) along the submarine's track.

emissivity

the amount of electromagnetic energy (primarily at wavelengths longer than 1.0 micrometer) that an object emits; for example, the earth emits longwave radiation primarily in the infrared part of the electromagnetic spectrum, but also in longer microwave wavelengths; the emissivity of an object varies as the fourth power of its absolute temperature.

geothermal heat flux

the amount of heat moving steadily outward from the interior of the earth through a unit area in unit time.

crust-like cryostructure

the cryostructure of a frozen deposit of angular blocks that are coated with ice, whereas large spaces between the blocks are not filled with ice.

basal cryostructure

the cryostructure of a frozen deposit of boulders that is saturated with ice.

basal-layered cryostructure

the cryostructure of a frozen layered deposit of gravel and boulders that is saturated with ice.

massive-porous cryostructure

the cryostructure of frozen sand and gravel in which all mineral particles are bonded together with ice, but larger pore spaces are not completely filled with ice.

massive cryostructure

the cryostructure of frozen sand in which all mineral particles are bonded together with ice.

lens-type cryostructure

the cryostructure of frozen silt or loam containing numerous ice lenses.

layered cryostructure

the cryostructure of frozen silt or loam in which ice layers alternate with mineral layers that have a massive cryostructure.

massive-agglomerate cryostructure

the cryostructure of frozen silt or loam in which ice veins form an irregular three-dimensional network.

approximate thawing index

the cumulative number of degree-days above 0 degrees Celsius for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for negative degree-days in spring and fall.

thawing index

the cumulative number of degree-days above 0 degrees Celsius for a given time period.

seasonal thawing index

the cumulative number of degree-days above 0 degrees Celsius, calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (degrees Celsius) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve.

design thawing index

the cumulative number of degree-days above 0 degrees Celsius, calculated by taking the average of the seasonal thawing indices for the three warmest summers in the most recent 30 years of record.

air thawing index

the cumulative number of degree-days above 0°C for the air temperature during a given period.

approximate freezing index

the cumulative number of degree-days below 0 degrees Celsius for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for positive degree-days in spring and fall.

freezing index

the cumulative number of degree-days below 0 degrees Celsius for a given time period.

surface freezing index

the cumulative number of degree-days below 0 degrees Celsius for the surface temperature (of the ground, pavement, etc.) during a given time period.

seasonal freezing index

the cumulative number of degree-days below 0 degrees Celsius, calculated as the arithmetic sum of all the negative and positive mean daily air temperatures (degrees Celsius) for a specific station during the time period between the highest point in the fall and the lowest point the next spring on the cumulative degree-day time curve.

design freezing index

the cumulative number of degree-days below 0 degrees Celsius, calculated by taking the average of the seasonal freezing indices for the three coldest winters in the most recent 30 years of record.

air freezing index

the cumulative number of degree-days below 0° C for the air temperature during a given time period.

total annual freezing index

the cumulative number of degree-days, calculated by adding all the negative mean daily air temperatures (degrees Celsius) for a specific station during a calendar year.

total annual thawing index

the cumulative number of degree-days, calculated by adding all the positive mean daily air temperatures (degrees Celsius) for a specific station during a calendar year.

water sky

the dark appearance of the underside of a cloud layer when it is over a surface of open water; it is darker than land sky, and much darker than ice blink or snow blink.

precision

the degree of agreement between independent measurements of a single quantity obtained by applying a specific measurement procedure several times under prescribed conditions.

surface hoar

the deposition (sublimation) of ice crystals on a surface which occurs when the temperature of the surface is colder than the air above and colder than the frost point of that air.

snowfall

the depth of new snow that has accumulated since the previous day or since the previous observation.

electrical properties of frozen ground

the dielectric constant (or relative permitivity), electrical conductivity and electrical resistivity are the major electrical properties governing the flow of electric current through frozen ground.

error

the difference between a measured value of a quantity and its true value; different types of errors are inherent to observations.

mass balance

the difference between accumulation and ablation on a glacier; usually calculated on an annual basis.

net budget

the difference between accumulation and ablation; usually expressed in terms of volumes of water equivalent per unit area.

frost heave extent

the difference between the elevations of the ground surface before and after the occurrence of frost heave.

absolute error

the difference between the measured or inferred value of a quantity and its actual value.

effective terrestrial radiation

the difference between the outgoing infrared (longwave) terrestrial radiation of the earth's surface and the downward infrared counter-radiation from the atmosphere.

absolute difference

the difference, taken without regard to sign, between the values of two variables

frost sorting

the differential movement of soil particles of different sizes as a result of frost action.

frost weathering

the disintegration and break-up of soil or rock by the combined action of frost shattering, frost wedging and hydration shattering.

depth of zero annual amplitude

the distance from the ground surface downward to the level beneath which there is practically no annual fluctuation in ground temperature.

cryogenic fabric

the distinct soil micromorphology resulting from the effects of freezing and thawing processes.

westerlies

the dominant west-to-east motion of the atmosphere, centered over the middle latitudes (35 to 65 degrees latitude) of both hemispheres.

stone garland

the downslope border of stones along a sorted step, embanking an area of relatively fine-grained bare ground upslope.

snow load

the downward force on an object or structure caused by the weight of accumulated snow.

thaw penetration

the downward movement of the thawing front during thawing of frozen ground.

leeward/lee side

the downwind side.

residual stress

the effective stress generated in a thawing soil if no volume change is permitted during thaw.

atmosphere

the envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction; the system whose chemical properties, dynamic motions, and physical processes constitute the subject matter of meteorology.

heat balance of the earth-atmosphere system

the equilibrium that exists between the radiation received by the earth and atmosphere from the sun and that emitted by the earth and atmosphere.

thermal erosion

the erosion of ice-bearing permafrost by the combined thermal and mechanical action of moving water.

accuracy

the extent to which the readings of an instrument approach the true value of the calculated or measured quantities, supposing that all possible corrections are applied.

penitents

the extreme relief of ablation hollows found most often at high altitudes in the tropics; the resulting spikes of snow resemble repentant souls.

long-term strength

the failure strength of a material after a long period of creep deformation.

creep strength

the failure strength of a material at a given strain rate or after a given period under deviatoric stress.

delayed strength

the failure strength of a material at a given strain rate or after a given period under deviatoric stress.

short-term strength

the failure strength of a material under a short-term loading (e.g. up to about 10 minutes in a uniaxial compression test).

mechanical strength

the failure strength of a material under given loading conditions.

tide crack

the fissure at the line of junction between an immovable icefoot or ice wall and fast ice, the latter being subject to the rise and fall of the tide.

boreal forest

the forested region that adjoins the tundra along the arctic tree line, which has two main divisions: its northern portion is a belt of taiga or boreal woodland, while its southern portion is a belt of true forest, mainly conifers but with some hardwoods; on its southern boundary the boreal forest passes into "mixed forest" or "parkland," prairie, or steppe, depending on the rainfall.

ice segregation

the formation of discrete layers or lenses of segregated ice in freezing mineral or organic soils, as a result of the migration (and subsequent freezing) of pore water.

warm front

the forward edge of an advancing warm air mass that is displacing cooler air in its path.

ice concentration

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

upper atmosphere

the general term applied to the atmosphere above the mesopause.

temperature profile

the graphic or analytical expression of the variation in ground temperature with depth.

visibility

the greatest distance that prominent objects can be seen and identified by unaided, normal eyes.

firn water table

the height of meltwater within saturated firn that is trapped over ice in a glacier.

frost point

the highest temperature at which atmospheric moisture will sublimate in the form of hoarfrost on a cooled surface; it is analogous to the dew point.

advection

the horizontal transfer of air mass properties by the velocity field of the atmosphere.

electrical conductivity

the inverse of electrical resistivity.

circumpolar vortex

the large-scale cyclonic circulation in the middle and upper troposphere centered generally in the polar region; also called polar vortex.

atmospheric circulation

the large-scale movement of air, and the means by which heat is distributed on the surface of the Earth; may vary from year to year.

maximum ice extent

the largest sea ice extent during a given year; maximum ice extent marks the end of the growth period for sea ice, and the start of the melt season

active layer

the layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost; also known as seasonal frost.

equator

the line of latitude 0°, which is equidistant from the poles, and which separates the Northern Hemisphere from the Southern Hemisphere.

arctic circle

the line of latitude 66 degrees 34 minutes N (often taken as 66.5 degrees N); along this line, the sun does not set on the day of the summer solstice, and does not rise on the day of the winter solstice.

antarctic circle

the line of latitude 66° 34′ S (often taken as 66.5° S); along this line the sun does not set on the day of the summer solstice, and does not rise on the day of the winter solstice.

cold pole

the location that has the lowest annual mean temperature in its hemisphere.

Aleution low

the low pressure center located near the Aleutian Islands on mean charts of sea level pressure during the winter; it represents one of the main centers of action in the atmospheric circulation of the northern hemisphere.

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.

permafrost base

the lower boundary surface of permafrost, above which temperatures are perennially below 0 degrees Celsius (cryotic) and below which temperatures are perennially above 0 degrees Celsius (noncryotic).

altitudinal limit of permafrost

the lowest altitude at which mountain permafrost occurs in a given highland area outside the general permafrost region.

terminus

the lowest end of a glacier, also called the glacier toe or glacier snout.

glacier toe

the lowest end of a glacier; also called glacier snout or terminus.

glacier terminus

the lowest end of a glacier; also called glacier snout or toe.

glacier snout

the lowest end of a glacier; also called glacier terminus or toe.

continuous permafrost zone

the major subdivision of a permafrost region in which permafrost occurs everywhere beneath the exposed land surface with the exception of widely scattered sites.

discontinuous permafrost zone

the major subdivision of a permafrost region in which permafrost occurs in some areas beneath the exposed land surface, whereas other areas are free of permafrost.

dry density

the mass of a unit volume of dried material (e.g. soil).

density of frozen ground

the mass of a unit volume of frozen soil or rock.

snow density

the mass of snow per unit volume which is equal to the water content of snow divided by its depth.

specific humidity

the mass of water vapor per unit mass of air, including the water vapor (usually expressed as grams of water vapor per kilogram of air).

depth of seasonal frost penetration

the maximum thickness of the seasonally frozen layer.

frost shattering

the mechanical disintegration of rock by the pressure of water freezing in pores and along grain boundaries.

frost wedging

the mechanical disintegration, splitting or break-up of rock by the pressure of water freezing in cracks, crevices, pores, joints or bedding planes.

depth of thaw

the minimum distance between the ground surface and frozen ground at any time during the thawing season in an area subject to seasonal freezing and thawing.

firn line

the minimum elevation of firn lying on a glacier surface; each year's firn line marks a glacier's annual equilibrium line; also called firn limit.

firn limit

the minimum elevation of firn lying on a glacier surface; each year's firn line marks a glacier's annual equilibrium line; also called firn line.

snow line

the minimum elevation of snow lying on the ground or glacier surface; the snow line at the end of an ablation season marks a glacier's current equilibrium line.

frost penetration

the movement of the freezing front into the ground during freezing.

polygon trough

the narrow depression surrounding a high-centre polygon.

frost creep

the net downslope displacement that occurs when a soil, during a freeze-thaw cycle, expands normal (perpendicular) to the ground surface and settles in a nearly vertical direction.

arctic tree line

the northern limit of tree growth; the sinuous boundary between tundra and boreal forest; taken by many to delineate the actual southern boundary of the arctic zone.

Tropic of Cancer

the northern parallel of maximum solar declination, approximately 23° 27′ N latitude; the farthest northern latitude at which the sun can appear directly overhead, which occurs on the day of the summer solstice.

freezing-point depression

the number of degrees by which the freezing point of an earth material is depressed below 0 degrees Celsius.

seasonal frost

the occurrence of ground temperatures below 0 degrees Celsius for only part of the year; see also active layer.

thermokarst terrain

the often irregular topography resulting from the melting of excess ground ice and subsequent thaw settlement.

taiga

the open northern part of the boreal forest; consists of open woodland of coniferous trees growing in a rich floor of lichen (mainly reindeer moss or caribou moss), and is generally cold and swampy; lies immediately south of the tundra; in spring, it is often flooded by water from northward flowing rivers, the lower reaches of which are still frozen.

partial pressure

in a mixture of gases, each gas has a partial pressure, which is the pressure the gas would have if it occupied that volume alone.

shear strength

in geology, describes the compressive strength (ability to withstand pushing forces) of soils; results from two internal mechanisms: cohesion between soil particles, and friction caused by contact between particles; variable among different soils.

cryogenic temperature

in international materials science, this term refers to temperatures generally below -50 degrees Celsius, but usually to temperatures within a few degrees of absolute zero (-273 degrees Celsius).

steering flow

in meteorology, a basic fluid flow which exerts a strong influence upon the direction of movement of disturbances embedded in it; in the atmosphere, it is usually an air flow in the middle or upper troposphere which govern directions of the disturbances at low levels.

inversion

in meteorology, a departure from the usual (normal) decrease or increase with altitude of the value of an atmospheric property; also, the layer through which this departure occurs (the inversion layer); this term almost always refers to a temperature inversion.

shortwave radiation

in meteorology, a term used loosely to distinguish radiation in the visible and near-visible portions of the electromagnetic spectrum (roughly 0.4 to 4.0 microns in wavelength) from longwave (terrestrial) radiation.

depression

in meteorology, an area of low pressure (i.e. a low); usually applies to a particular stage in the development of a cyclone.

ridge

in meteorology, an elongated area of relatively high atmospheric pressure, almost always associated with and most clearly identified as an area of maximum anticyclonic curvature of wind flow.

trough

in meteorology, an elongated area of relatively low atmospheric pressure; the opposite of a ridge.

gauge

in meteorology, general term for any device that measures strength of wind, pressure, and other parameters; the most widespread gauges on meteorology are balance snow gauge, barometer gauge, density-of-snow gauge, dew gauge, distance gauge, rain-and snow gauge, rain-intensity gauge, standard gauge, wind gauge, etc..

front

in meteorology, generally, the interface or transition zone between two air masses of different density; since the temperature distribution is the most important regulator of the atmosphere density, a front almost invariably separates air masses of different temperature; when warmer air replaces the colder, it is a warm front, and vice-versa.

polar night

in polar regions, the portion of the year when the sun does not rise above the horizon; its length changes from twenty hours at the arctic/antarctic circle (latitude 66 degrees, 33 minutes N or S) to 179 days at the North and South Poles.

polar day

in polar regions, the portion of the year when the sun is continuously in the sky; its length changes from twenty hours at the arctic/antarctic circle (latitude 66 degrees, 33 minutes N or S) to 186 days at the north and south poles.

analysis

in synoptic meteorology, a detailed study of the state of the atmosphere over a particular region based on the actual observations.

pole of inaccessibility

in the northern hemisphere, the point in the Arctic Ocean farthest from land; in the southern hemisphere, the point on the Antarctic continent farthest from the Southern Ocean.

radiosonde

instrument intended to be carried by a balloon up through the atmosphere, equipped with sensors to measure one or several meteorological variables (pressure, temperature, humidity, etc.), and provided with a radio transmitter for sending this information to the observing station.

vane

instrument used to measure wind direction; also called wind vane.

polynya

irregularly shaped areas of persistent open water that are sustained by winds or ocean heat; they often occur near coasts, fast ice, or ice shelves.

recurring polynya

irregularly shaped areas of persistent open water that are sustained by winds or ocean heat; they often occur near coasts, fast ice, or ice shelves.

sail

the part of a ridge above sea level; like a sail on a sailboat, it catches wind and moves the ice.

keel

the part of a ridge below the ocean surface; wind, ocean currents, and other forces can push sea ice into piles that rise and form small mountains below the level sea ice surface.

summer minimum extent

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

zero curtain

the persistence of a nearly constant temperature, very close to the freezing point, during annual freezing (and occasionally during thawing) of the active layer.

fusion

the phase transition of a substance passing from the solid to the liquid state, melting; in meteorology, fusion is understood to refer to the melting of ice, which, if the ice is pure and subjected to one standard atmosphere of pressure, takes place at the ice point of 0 degrees Celsius (32 degrees Fahrenheit).

evaporation

the physical process by which a liquid or solid substance is transformed to the gaseous state; the opposite of condensation; in meteorology, evaporation usually is restricted in use to the change of water from liquid to gas, while sublimation is used to the change from solid to gas as well as from gas to solid.

condensation

the physical process by which a vapor becomes a liquid or solid; the opposite of evaporation; in meteorological usage, this term is applied only to transformation from vapor to liquid; any process in which a solid forms directly from its vapor is termed sublimation, as is the reverse process.

solstice

the point in time when the vertical rays of the sun are striking either the Tropic of Cancer (23 degrees, 30 minutes N, the summer solstice in the northern hemisphere) or the Tropic of Capricorn (23 degrees, 30 minutes S, the winter solstice in the northern hemisphere); represents the longest or shortest day of the year; in the northern hemisphere, the summer solstice falls on or about 21 June, and the winter solstice on or about 22 December.

glaciated

land covered in the past by any form of glacier is said to be glaciated.

glacierized

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

ice covered

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

periglacial phenomena

landforms and soil characteristics produced by periglacial processes.

bergy bit

large chunk of glacier ice (a very small iceberg) floating in the sea; bergy bits are usually less than 5 meters (15 feet) in size and are generally spawned from disintegrating icebergs.

piedmont glacier

large ice lobe spread out over surrounding terrain, associated with the terminus of a large mountain valley glacier.

polar vortex

large-scale cyclonic circulation in the middle and upper troposphere centered generally in the polar regions; it is often called circumpolar vortex.

permafrost

layer of soil or rock, at some depth beneath the surface, in which the temperature has been continuously below 0°C for at least several years; it exists where summer heating fails to reach the base of the layer of frozen ground.

foliation

layering in glacier ice that has distinctive crystal sizes and/or bubbles; foliation is usually caused by stress and deformation that a glacier experiences as it flows over complex terrain, but can also originate as a sedimentary feature.

cumuliform

like cumulus; generally descriptive of all clouds; vertical development in the form of rising mounds, domes or towers; driven by thermal convection and have vertical velocities greater than 1 meter (3.3 feet) per second.

polygon

literally means many angled; polygons are closed, multi-sided, roughly equidimensional shapes, bounded by more or less straight sides; some of the sides may be irregular; in cryospheric science, it refers to patterned ground formations.

lead

long, linear areas of open water that range from a few meters to over a kilometer in width, and tens of kilometers long; they develop as ice diverges, or pulls apart.

atmospheric radiation

longwave (infrared) radiation emitted by or being propagated through the atmosphere.

rock glacier

looks like a mountain glacier and has active flow; usually includes a poorly sorted mess of rocks and fine material; may include: (1) interstitial ice a meter or so below the surface ("ice-cemented"), (2) a buried core of ice ("ice-cored"), and/or (3) rock debris from avalanching snow and rock.

troposphere

lower part of the atmosphere, extending from the surface up to a height varying from about 7 to 9 kilometers (4.3 to 5.6 miles) at polar regions to approximately 17 kilometers (10.6 miles) in tropics; characterized by decreasing temperature with height, appreciable vertical wind motion, appreciable water vapor content, and weather.

pressure-melting

lowering the melting point of ice by applying pressure.

aurora

luminous phenomena, in the form of arcs, bands, draperies, or curtains in the high atmosphere over high latitudes; auroras are related to magnetic storms and the influx of charged particles from the sun, the phenomena are called aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere.

slope failure

mass movement of earth material down a slope; includes landslides, mudslides, debris flows, avalanches, etc; speed of movement can be sudden and catastrophic or slow.

avalanche

mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh addition as it descends.

arctic air mass

mass of very cold air in the arctic regions which invades lower latitudes at irregular intervals.

pingo ice

massive ice forming the core of a pingo.

mean annual ground temperature (MAGT)

mean annual temperature of the ground at a particular depth.

mean annual ground-surface temperature (MAGST)

mean annual temperature of the surface of the ground.

dielectric constant

measure of the ability of the soil to store electrical energy in the presence of an electrostatic field.

thawing (of frozen ground)

melting of the ice in frozen ground, usually as a result of a rise in temperature.

snowmelt

melting of the snowcover, and also the period during which melting of the snow cover occurs at the end of the winter.

pressure melting

melting that occurs in ice at temperatures colder than normal melting temperature because of added pressure.

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.

aerosol

non-gaseous substances, divided into solid particles or liquid droplets, held in suspension in the atmosphere.

general circulation model

numerical representation of the atmosphere and its phenomena over the entire earth, using the equations of motion and including radiation, photochemistry, and the transfer of heat, water vapor, and momentum.

general circulation

of the atmosphere; complete statistical description of atmospheric motions over the earth.

maritime

of, relating to, or adjacent to the sea.

wave ogives

ogives that show some vertical relief on a glacier; usually the dark bands are in the hollows and the light bands are in the ridges; form at the base of steep, narrow ice falls.

oriented lake

one of a group of lakes possessing a common, preferred, long-axis orientation.

cryosphere

one of the earth's spheres of irregular form existing in the zone of interaction of the atmosphere, hydrosphere and lithosphere, distinguished by negative or zero temperature and the presence of water in the solid or super-cooled state; the term refers collectively to the portions of the earth where water is in solid form, including snow cover, floating ice, glaciers, ice caps, ice sheets, seasonally frozen ground and perennially frozen ground (permafrost).

crevasse

open fissure in the glacier surface.

blow hole

opening through a snow bridge into a crevasse or system of crevasses which are otherwise sealed by snow bridges; a snowdrift usuallly forms on the lee side.

permafrost limit

outermost (latitudinal) or lowest (altitudinal) limit of the occurrence of permafrost.

very open pack ice

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

ice canopy

pack ice from the point of view of the submariner.

consolidated pack ice

pack ice in which the floes are frozen together; ice cover 10/10ths.

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.

icefall

part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepenes or narrows.

Pleistocene

part of the geologic timescale, corresponding to the time period from 1.81 million to 11,550 years before the present.

sorted stripe

patterned ground with a striped and sorted appearance, due to parallel strips of stones and intervening strips of finer material, oriented down the steepest available slope.

peatland

peat-covered terrain.

thufur

perennial hummocks formed in either the active layer in permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground.

thaw-sensitive permafrost

perennially frozen ground which, upon thawing, will experience significant thaw settlement and suffer loss of strength to a value significantly lower than that for similar material in an unfrozen condition.

thaw-stable permafrost

perennially frozen ground which, upon thawing, will not experience either significant thaw settlement or loss of strength.

accumulation season

period during which a glacier gains more mass than it loses; usually coincides with winter.

ablation season

period during which glaciers lose more mass than they gain; usually coincides with summer.

subglacial permafrost

permafrost beneath a glacier.

ice-rich permafrost

permafrost containing excess ice.

dry permafrost

permafrost containing neither free water nor ice.

mountain permafrost

permafrost existing at high altitudes in high, middle, and low latitudes.

relict permafrost

permafrost existing in areas where permafrost can not form under present climatic conditions; reflects past climatic conditions that were colder.

saline permafrost

permafrost in which part or all of the total water content is unfrozen because of freezing-point depression due to a high dissolved-solids content of the pore water.

friable permafrost

permafrost in which the soil particles are not held together by ice.

onshore permafrost

permafrost occurring beneath exposed land surfaces.

subsea permafrost

permafrost occurring beneath the sea bottom.

discontinuous permafrost

permafrost occurring in some areas beneath the exposed land surface throughout a geographic region where other areas are free of permafrost.

planetary permafrost

permafrost occurring on other planetary bodies (planets, moons, asteroids).

ice-bearing permafrost

permafrost that contains ice.

syngenetic permafrost

permafrost that formed through a rise of the permafrost table during the deposition of additional sediment or other earth material on the ground surface.

epigenetic permafrost

permafrost that formed through lowering of the permafrost base in previously deposited sediment or other earth material.

equilibrium permafrost

permafrost that is in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and with the geothermal heat flux.

disequilibrium permafrost

permafrost that is not in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and the geothermal heat flux.

isolated patches of permafrost

permafrost underlying less than 10% of the exposed land surface.

pancake ice

pieces of new ice approximately circular, up to 10 centimeters (4 inches) thick and 0.03 to 3 meters (0.1 to 9.8 feet) in diameter, with raised edges that form from rubbing against each other; formed from the freezing together of grease ice, slush or shuga, or the reaking up of ice rind or nilas.

ridge ice

piled ice formed by ridging.

melt ponds

pools of melted snow and ice on the sea ice surface created during the summer melt.

ice shelf

portion of an ice sheet that spreads out over water.

glacier pothole

potholes formed at the bottom of glaciers through erosion caused by sand and gravel in melt-water; melt-water seeps through crevasses in the glaciers, sometimes forming whirpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks.

pH

power of hydrogen; a measure of the activity of hydrogen ions in solution, and therefore, its acidity or alkalinity.

mixed precipitation

precipitation consisting of a mixture of rain and wet snow; it usually occurs when the temperature of the air layer near the ground is slightly above freezing; the British term for this mixture is sleet (which has a different meaning in the United States).

snow pellets

precipitation in the form of small, white opaque ice particles; resemble ice grains, but are round (sometimes conical) and about 2-5 mm in diameter.

snow grains

precipitation in the form of very small, white opaque ice particles; they resemble snow pellets but are more flattened and elongated, with a diameter less than 1 mm; the solid equivalent of drizzle.

hail

precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 millimeters (0.2 to 2.0 inches), or sometimes bigger, falling either separately or agglomerated into irregular lumps; when the diameter is less than about 5 millimeters (0.2 inch), the balls are called ice pellets.

ice pellet

precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 millimeters (0.2 to 2.0 inches), or sometimes more, falling either separately or agglomerated into irregular lumps; when the diameter is less that about 5 millimeters (0.2 inch), the balls are called ice pellets.

virga

precipitation that evaporates before reaching the ground.

past weather

predominant characteristic of the weather which had existed at an observing station during a given period of time (during the preceding hour or six hours), specified in the international synop code.

drain channel

preferred path for meltwater to flow from the surface through a snow cover.

atmospheric pressure

pressure (force per unit area) exerted by the atmosphere on any surface by virtue of its weight; it is equivalent to the weight of a vertical column of air extending above a surface of unit area to the outer limit of the atmosphere.

thawed ground

previously frozen ground in which all ice has melted.

calving

process by which ice breaks off a glacier's terminus; usually the term is reserved for tidewater glaciers or glaciers that end in lakes, but it can refer to ice that falls from hanging glaciers.

edge wasting

process by which warm water erodes iceberg above the waterline

cyclogenesis

process of initiation or intensification of a cyclonic circulation in the atmosphere; the opposite to cyclolysis.

cyclolysis

process of weakening or terminating of a cyclonic circulation in the atmosphere; the opposite of cyclogenesis.

pressure ridge

process that occurs when wind, ocean currents, and other forces push sea ice around into piles that rise and form small mountains above the level sea ice surface; ridges are initially thin and transparent with very sharp edges from blocks of ice piling up; also see keels.

ridging

process that occurs when wind, ocean currents, and other forces push sea ice around into piles that rise and form small mountains above the level sea ice surface; ridges are initially thin and transparent with very sharp edges from blocks of ice piling up; also see keels.

heat source

process, or region, in which energy is added to the atmosphere in the form of heat.

heat sink

process, or region, in which energy is removed from the atmosphere in the form of heat.

periglacial processes

processes associated with frost action in cold, nonglacial environments.

rawinsonde

radiosonde which is tracked by radar or radio-theodolite to measure the wind aloft.

acid precipitation

rain or snow containing acidic substances, resulting from the atmospheric pollution mainly with sulfur and nitrogen; acid precipitation has a lower pH than unpolluted rain.

freezing rain

rain, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight.

alpine

refers to high mountain areas above the timber line (where trees cease to inhabit extremely cold environments).

freezeback

refreezing of thawed materials.

polar region

regions around the North and South Poles, north of the Arctic, or south of the Antarctic Circles, respectively; characterized by polar climate, very cold temperatures, heavy glaciation, and dramatic variations in daylight hours (24 hrs darkness in winter, 24 hrs daylight in summer).

heat budget

relation between fluxes of heat into and out of a given region or body and the heat stored by the system; in general, this budget includes advective, evaporative, and other terms as well as a radiation term.

snow patch

relatively small area of snow cover remaining after the main snowmelt period.

jet stream

relatively strong winds concentrated within a narrow stream in the atmosphere; generally refers to a quasi-horizontal jet stream of maximum winds embedded in the midlatitude westerlies, and concentrated in the high troposphere.

drumlin

remnant elongated hills formed by historical glacial action; it is not clear exactly how they are formed and why they form only in some glaciated regions.

climate model

representation of the climate system based on the mathematical equations governing the behavior of the various components of the system and including treatment of key physical processes and interactions, cast in a form suitable for numerical approximation with computers.

drifting stations

research stations on the floes of the arctic ocean.

snow roller

roll-like snow formation, caused by a unique combination of snow, wind, temperature and moisture

firn

rounded, well-bonded snow that is older than one year; firn has a density greater than 550 kilograms per cubic-meter (35 pounds per cubic-foot); called névé during the first year.

sensible heat

same as enthalpy; the heat absorbed or transmitted by a substance during a change of temperature which is not accompanied by a change of state; used in meteorology in contrast to latent heat.

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.

second-year ice

sea ice which has not melted in the first summer of its existence; by the end of the second winter, it attains a thickness of 2 meters (6.6 feet) or more; it stands higher out of the water than first-year ice; summer melting has somewhat smoothed and rounded the hummocks, which accentuation of minor relief by differential melting may have caused others to develop; bare patches and puddles are usually greenish-blue.

floe

separate patch of floating ice or flat sheet of unbroken pack ice, greater than 20 meters (22 yards) across.

forel stripes

shallow, parallel grooves on the face of a large melting ice crystal.

arete

sharp, narrow ridge formed as a result of glacial erosion from both sides.

beset

situation of a vessel surrounded by ice and unable to move.

solifluction

slow downslope flow of saturated unfrozen earth materials.

semipermanent depression

slowly moving or motionless cyclone.

brine

small droplets of highly saline water that form in pockets between ice crystals, as sea ice forms and expels salt into the underlying ocean water.

frazil

small needle-like ice crystals, typically 3 to 4 millimeters in diameter, suspended in water, that represent the first stages of sea ice growth; they merge under calm conditions to form thin sheets of ice on the surface, frazil crystals consist of nearly pure fresh water.

polar low

small, shallow depression which forms mainly in winter over some high-latitude seas within a polar or arctic air mass; its motion is approximately the same as the air stream in which it is embedded.

bummocks

smooth hills of ice that form on the bottom of sea ice from eroding keels, particularly during the summer melt.

constructive metamorphism

snow metamorphism that adds molecules to sharpen the comers and edges of an ice crystal.

kinetic-growth metamorphism

snow metamorphism that builds angular facets on crystals and makes cup and scroll shaped crystals.

equi-temperature metamorphism

snow metamorphism that occurs under relatively consistent temperature conditions.

equilibrium metamorphism

snow metamorphism that occurs when there are large differences in convex and concave portions of a crystal.

radius-dependent metamorphism

snow metamorphism that occurs when there are large differences in convex and concave portions of a crystal.

temperature-gradient metamorphism

snow metamorphism that occurs when there are strong differences in temperature between the bottom and top of a snow layer.

destructive metamorphism

snow metamorphism that rounds the comers and edges of an ice crystal.

drifting snow

snow raised from the surface of the earth by the wind to a height of less than 1.5 to 2.0 meters (5 to 6.6 feet) above the surface; it dose not restrict horizontal visibility at 2 meters (6.6 feet) or more above the surface.

snow flurry

snow that falls for short durations and which often changes in intensity; flurries usually produce little accumulation.

perennial snow

snow that persists on the ground year after year.

watermelon snow

snow with red algae growing on it.

graupel

snowflakes that become rounded pellets due to riming; typical sizes are 2 to 5 millimeters in diameter (0.1 to 0.2 inch); graupel is sometimes mistaken for hail.

cryosol

soil formed in either mineral or organic materials having permafrost either within 1 meter (3.3 feet) below the surface or, if the soil is strongly cryoturbated, within 2 meters (6.6 feet) below the surface, and having a mean annual ground temperature below 0 degrees Celsius.

frost-stable soil

soil in which little or no segregated ice forms during seasonal freezing.

frost-susceptible soil

soil in which segregated ice will form (causing frost heave) under the required conditions of moisture supply and temperature.

fabric

soil micromorphology.

noncryotic ground

soil or rock at temperatures above 0 degrees Celsius.

cryotic ground

soil or rock at temperatures of 0 degrees Celsius or lower.

frozen ground

soil or rock in which part or all of the pore water has turned into ice.

unfrozen ground

soil or rock that does not contain any ice.

active construction methods in permafrost

special design and construction methods used for engineering works in permafrost areas where permafrost degradation cannot be prevented.

passive construction methods in permafrost

special design and construction methods used for engineering works in permafrost areas where preservation of the frozen condition is feasible.

construction methods in permafrost

special design and construction procedures required when engineering works are undertaken in permafrost areas.

ozone shield

stratospheric ozone layer, giving protection to the earth's surface due to intense absorption of harmful solar ultraviolet radiation by the gas.

ozonosphere

stratospheric ozone layer, giving protection to the earth's surface due to intense absorption of harmful solar ultraviolet radiation by the gas.

chattermarks

striations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice.

snowstorm

strong wind with snow.

instrument shelter

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

foundation pile

structure used when the soil near the ground surface is not strong and the weight of the building must be carried by deeper soil layers.

thermodynamics

study of the links between heat and energy. First law of thermodynamics states that heat is energy and the amount of energy within a system cannot change.

anchor ice

submerged ice which is attached to the bottom.

climate

synthesis of weather conditions in a given area, characterized by long-term statistics (mean values, variances, probabilities of extreme values, etc.) of the meteorological elements in that area; polar climate (arctic climate) is generally the climate of a geographical polar region, most commonly taken to be a climate which is too cold to support the growth of trees.

anticyclonic circulation

system of air movements (atmospheric circulation) associated with an anticyclone, which is clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere.

bottom temperature of snow cover

temperature measured at the base of the snow cover during mid- to late-winter (February/March).

sea surface temperature

temperature of the water film at the sea surface.

collapse scar

that portion of a peatland where the whole or part of a palsa or peat plateau has thawed and collapsed to the level of the surrounding peatland.

cloud amount

that portion of the sky cover which is attributed to clouds; the unit of measurement is the okta or tenths (meaning one-eighth or one-tenth) of the sky dome as seen by the observer.

zone of gas-hydrate stability

that portion of the subsurface where the conditions of temperature and pressure are suitable for the formation and preservation of gas hydrates.

relative humidity

the (dimensionless) ratio of the actual vapor pressure of the air to the saturation vapor pressure; usually expressed as a percent, and can be computed from psychrometric data.

deformability

the ability of a material to change its shape or size under the influence of an external or internal agency, such as stress, temperature, or pore pressure.

Poisson's ratio

the absolute value of the ratio between linear strain changes, perpendicular to and in the direction of a given uniaxial stress change.

dynamic Poisson's ratio

the absolute value of the ratio between the linear strain changes, perpendicular to and in the direction of a given uniaxial stress change, respectively, under dynamic loading conditions.

seasonally frozen layer (SFL)

the active layer in areas without permafrost.

seasonally thawed layer (STL)

the active layer in permafrost areas.

aggradational ice

the additional ground ice formed as a direct result of permafrost aggradation.

upward freezing

the advance of a freezing front upwards from the permafrost table during annual freezing of the active layer.

freezing front

the advancing boundary between frozen (or partially frozen) ground and unfrozen ground.

thawing front

the advancing boundary between thawed ground and frozen ground.

surface temperature

the ambient temperature indicated by a thermometer exposed to the air but sheltered from direct solar radiation, or placed in an instrument shelter 1.5 - 2.0 meters (5.0 - 6.6 feet) above ground; also called air temperature.

air temperature

the ambient temperature indicated by a thermometer exposed to the air but sheltered from direct solar radiation, or placed in an instrument shelter 1.5 to two meters above ground; also called surface temperature.

geomagnetic pole

the point of intersection of the Earth's surface with the axis of a simple magnetic dipole that best approximates the Earth's actual, more complex magnetic field; if the Earth's magnetic field were a perfect dipole then the field lines would be vertical at the geomagnetic poles, and they would therefore coincide with the magnetic poles: however, the dipole approximation is in fact far from perfect, so in reality the magnetic and geomagnetic poles lie some distance apart.

freezing pressure

the positive pressure developed at ice-water interfaces in soil as it freezes.

vapor pressure

the pressure exerted by water vapor molecules in a given volume of air.

anti-icing

the prevention of ice accumulation of aircraft, ships and other objects; the most common measures are heating or applying a dressing by brush or spray to weaken adhesion and facilitate removal.

active thermokarst

the process by which characteristic landforms are currently developing as a result of thawing of ice-rich permafrost or melting of massive ice.

thermokarst

the process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ice.

adfreeze/adfreezing

the process by which two objects are bonded together by ice formed between them.

frost action

the process of alternate freezing and thawing of moisture in soil, rock and other materials, and the resulting effects on materials and on structures placed on, or in, the ground.

artificial ground freeezing

the process of inducing or maintaining a frozen condition in earth materials by artificial means.

cryoplanation

the process through which cryoplanation terraces form.

weathering

the processes of ablation and accumulation which gradually eliminate irregularities in an ice surface.

mechanical properties of frozen ground

the properties of frozen ground governing its deformability and strength.

thermal properties of frozen ground

the properties of the ground governing the flow of heat through it, and its freezing and thawing conditions.

electricity resistivity

the property of a material that determines the electrical current flowing through a centimetre cube of the material when an electrical potential is applied to opposite faces of the cube.

thermal conductivity

the quantity of heat that will flow through a unit area of a substance in unit time under a unit temperature gradient.

lapse rate

the rate of change of any meteorological element with height.

geothermal gradient

the rate of temperature increase with depth in the subsurface.

Young's Modulus

the ratio of increase in stress acting on a test specimen, to the resulting increase in strain, under constant transverse stress.

dynamic modulus of elasticity

the ratio of stress to strain for a material under dynamic loading conditions.

hydraulic diffusivity

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

gravimetric (total) water content

the ratio of the mass of the water and ice in a sample to the dry mass of the sample, commonly expressed as a percentage.

segregation potential

the ratio of the rate of moisture migration to the temperature gradient in a frozen soil near the 0 degrees Celsius isotherm.

n-factor

the ratio of the surface freezing or thawing index to the air freezing or thawing index.

thermal diffusivity

the ratio of the thermal conductivity to the volumetric heat capacity.

volumetric (total) water content

the ratio of the volume of the water and ice in a sample to the volume of the whole sample, expressed as a fraction (or, less commonly, as a percentage).

thaw weakening

the reduction in shear strength due to the decrease in effective stresses resulting from the generation and slow dissipation of excess pore pressures when frozen soils containing ice are thawing.

antarctic zone

the region between the antarctic circle (66° 34′ S) and the South Pole; climatically, the limit of the zone may be set at about 60° S, poleward of which the prevailing westerly winds give place to easterly or variable winds; over most of this region the average temperature does not rise above 0°C (32°F) even in summer.

relative permittivity

the relative permitivity of a soil is the ratio of the permitivity of the soil to the permitivity of a vacuum.

land sky

the relatively dark appearance of the underside of a cloud layer when it is over land that is not snow covered; this term is used largely in polar regions with reference to the sky map; land sky is brighter than water sky, but is much darker than ice blink or snow blink.

North American high

the relatively weak general area of high pressure which, as shown on mean charts of sea-level pressure, covers most of North America during winter; this pressure system is not nearly as well-defined as the analogous Siberian high.

de-icing

the removal of ice accumulation on aircraft, ships and other objects by mechanical, thermal or chemical devices.

gradient wind

the same as geostrophic wind, but blowing parallel to curved isobars or contours; the curved airflow pattern around a pressure center results from a balance among pressure-gradient force, coriolis force, and centrifugal force.

synoptic-scale

the scale of the high- and low-pressure systems of the lower atmosphere; dimensions typically range from 1000 to 2500 kilometers (620 to 1550 miles; synoptic-scale circulation).

cryolithology

the study of the genesis, structure and lithology of frozen earth materials.

synoptic analysis

the study of the synoptic observation data plotted on synoptic charts aimed at analysis of the atmospheric disturbances (for example, fronts, cyclones, and anticyclones).

latitudinal zonation of permafrost

the subdivision of a permafrost region into permafrost zones, based on the percentage of the area that is underlain by permafrost.

ice-nucleation temperature

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

dew point

the temperature to which a given parcel of air must be cooled at constant pressure and constant water-vapor content in order for saturation to occur; when this temperature is below 0 degrees Celsius, it is called the frost point.

adfreeze strength

the tensile or shear strength which has to be overcome to separate two objects that are bonded together by ice.

cryotexture

the textural characteristics of frozen, fine-grained organic and mineral earth materials cemented together with ice.

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.

active-layer thickness

the thickness of the layer of the ground that is subject to annual thawing and freeing in areas underlain by permafrost.

total water content (of frozen ground)

the total amount of water (unfrozen water plus ice) contained in soil or rock.

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.

solar radiation

the total electromagnetic radiation emitted by the sun.

permafrost extent

the total geographic area containing some amount of permafrost; typically reported in square kilometers.

earth radiation

the total infrared radiation emitted from the earth's surface; to be carefully distinguished from effective terrestrial radiation, atmospheric radiation, and insolation.

snow extent

the total land area covered by some amount of snow; typically reported in square kilometers.

snowpack

the total snow and ice on the ground, including both new snow and the previous snow and ice which have not melted.

sublimation

the transition of a substance from the solid phase directly to the vapor phase, or vice versa, without passing through an intermediate liquid phase.

conduction

the transport of energy entirely resulting from the random motions of individual molecules, and not from any concerted group movement; occurs in response to temperature gradients; contrasts with convection, in which energy is transported by molecules moving together in coherent groups.

convection

the transport of energy resulting from the concerted movement of molecules in coherent groups; contrasts with conduction in which energy is transported by the random motions of molecules; atmospheric convection is nearly always turbulent and results in the vertical transport and mixing of atmospheric properties.

permafrost table

the upper boundary surface of permafrost.

seasonally-active permafrost

the uppermost layer of the permafrost which undergoes seasonal phase changes due to the lowered thawing temperature and freezing-point depression of its pore water.

frost heave

the upward or outward movement of the ground surface (or objects on, or in, the ground) caused by the formation of ice in the soil.

thermo-erosional cirque

the usually steep, horseshoe-shaped headwall of a retrogressive thaw slump.

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.

permafrost thickness

the vertical distance between the permafrost table and the permafrost base.

altitudinal zonation of permafrost

the vertical subdivision of an area of mountain permafrost into permafrost zones, based on the proportion of the ground that is perennially cryotic.

thermal expansion (or contraction) coefficient

the volume change per unit volume of a substance due to a one degree change in its temperature.

hydraulic conductivity

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

excess ice

the volume of ice in the ground which exceeds the total pore volume that the ground would have under natural unfrozen conditions.

snow water equivalent

the water content obtained from melting.

World Weather Watch

the world-wide, coordinated system of meteorological facilities and services provided by World Meteorological Organization members for the purpose of ensuring that all members obtain the meteorological information required both for operational work and for research; the essential elements of the WWW are: the global observing system, the global data-processing system, and the global telecommunication system.

frozen fringe

the zone in a freezing, frost-susceptible soil between the warmest isotherm at which ice exists in pores and the isotherm at which the warmest ice lens is growing.

geostrophic wind

theoretical wind which results from the equilibrium between horizontal components of the pressure gradient force and the coriolis force (deviating force) above the friction layer; only these two forces (no frictional force) are supposed to act on the moving air; it blows parallel to straight isobars or contours.

stamukhi

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.

lamina

thin plate, sheet or layer; laminae (plural).

needle ice

thin, elongated ice crystals that form perpendicular to the ground surface.

thaw consolidation

time-dependent compression resulting from thawing of frozen ground and subsequent draining of excess water.

ice-cored topography

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

tundra

treeless terrain, with a continuous cover of vegetation, found at both high latitudes and high altitudes.

drunken forest

trees leaning in random directions caused by melting permafrost.

high-level clouds

typically thin, white clouds above 6,000 meters (20,000 feet); at these altitudes, temperatures are so cold that clouds are composed primarily of ice crystals; includes cirrus, cirrocumulus and cirrostratus clouds.

glacier trough

u-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers.

megadunes

unlike snow dunes that are piles of drifted snow, antarctic megadunes are long, undulating waves in the surface of the ice sheet that are 2 to 4 meters (6.5 to 13 feet) high and 2 to 5 kilometers (1 to 3 miles) apart; they are slightly rounded at their crests and are so subtle that a person on the ground cannot see the pattern.

heaving pressure

upward pressure developed during freezing of the ground.

thaw hole

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

depth of snow

vertical interval between the top surface of a snow layer and the ground beneath; the layer is assumed to be evenly spread over the ground which it covers.

snowbursts

very intense showers of snow, often of short duration, that greatly restrict visibility and produce periods of rapid snow accumulation.

sikussak

very old, thick sea ice that forms in fjords; it often resembles glacial ice, because snow can pile up on the ice over many years.

niche glacier

very small glacier that occupies gullies and hollows on north-facing slopes (northern hemisphere); may develop into cirque glacier if conditions are favorable.

drizzle

very small, uniformly distributed water drops that appear to float while following air currents; unlike fog droplets, drizzle falls to the ground.

subpermafrost water

water occurring in the noncryotic ground below the permafrost.

suprapermafrost water

water occurring in unfrozen ground above perennially frozen ground.

intrapermafrost water

water occurring in unfrozen zones (taliks and cryopegs) within permafrost.

water vapor

water substance in vapor (gaseous) form; one of the most important of all constituents of the atmosphere.

interfacial water

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

glacier ice

well-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic-meter (55 pounds per cubic-foot).

retreat

when a mountain glacier's terminus doesn't extend as far downvalley as it previously did; occurs when ablation surpasses accumulation.

advance

when a mountain glacier's terminus extends farther downvalley than before; glacial advance occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.

glacial advance

when a mountain glacier's terminus extends farther downvalley than before; occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.

extending flow

when glacier motion is accelerating down-slope.

glacial retreat

when the position of a mountain glacier's terminus is farther upvalley than before; occurs when a glacier ablates more material at its terminus than it transports into that region.

luminous pillars

white or sometimes reddish vertical streaks of light extending from above and below the sun; they are caused by light reflected off the mirror-like surfaces of ice; most commonly seen at sunrise and sunset.

surface wind

wind blowing near the earth's surface; it is measured, by convention, at a height of 10 meters (33 feet) above ground in an area where the distance between the anemometer and any obstruction is at least 10 times the height of the obstruction.

blizzard

winds of at least 35 miles per hour along with considerable falling and/or blowing snow reducing visibility to less than one-quarter mile for a period of at least three hours (extremely cold temperatures are often associated with dangerous blizzard conditions, but are not a formal part of the modern definition).

equilibrium zone

zone of a glacier in which the amount of precipitation that falls is equal to the amount that melts the following summer.

icing glade

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

sporadic discontinuous permafrost

(1) (North American usage) permafrost underlying 10 - 50% of the exposed land surface

intermediate discontinuous permafrost

(1) (North American usage) permafrost underlying 35 - 65% of the area of exposed land surface

extensive discontinuous permafrost

(1) (North American usage) permafrost underlying 65 - 90% of the area of exposed land surface

design depth of frost penetration

(1) (North American usage) the mean of the three largest depths of seasonal frost penetration measured during the past thirty years, or the largest depth of seasonal frost penetration beneath a snow-free soil surface measured during the past ten years

sleet

(1) (United States) frozen raindrops that bind on impact with the ground (2) (elsewhere) a mix of rain and snow, a mix of rain and hail, or melting snow.

cryoturbation

(1) (singular) a collective term used to describe all soil movements due to frost action (2) (plural) irregular structures formed in earth materials by deep frost penetration and frost action processes, and characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits, included organic horizons and even bedrock.

(Photo courtesy of Terry Whitledge, National Oceanic and Atmospheric Administration/Department of Commerce.)

(Photo courtesy of Terry Whitledge, National Oceanic and Atmospheric Administration/Department of Commerce.)

hummock

(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.

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.

salinity

(1) a general property of aqueous solutions caused by the alkali, alkaline earth, and metal salts of strong acids (Cl, SO4 and NO3) that are not hydrolyzed (2) in soil science, the ratio of the weight of salt in a soil sample to the total weight of the sample.

jokulhlaup

(1) a large outburst flood that usually occurs when a glacially dammed lake drains catastrophically (2) any catastrophic release of water from a glacier.

scale

(1) a series of marks at regular intervals for the purpose of measuring (scale of an instrument, for example, a thermometer) (2) system of units for measuring ( 3) proportion between the size of something and the map, diagram, etc. which represents it (4) order of magnitude of a phenomenon or of a meteorological parameter.

parameter

(1) a term used loosely by many meteorologists for almost any meteorological quantity or element (2) an arbitrary constant or variable appearing in a mathematical expression; changing it can give various outcomes for the phenomena represented.

snow

(1) an ice particle formed by sublimation of vapor in the atmosphere (2) a collection of loosely bonded ice crystals deposited from the atmosphere; high density snow (greater than 550 kilograms per cubic meter; 34 pounds per cubic foot) is called firn if it is older than one year.

ablation

(1) combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes (2) reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches.

radiation

(1) emission or transfer of energy in the form of electromagnetic waves (2) the process by which electromagnetic radiation is propagated through free space by virtue of joint undulatory variations in the electric and magnetic fields in space; this concept is to be distinguished from conduction and convection.

insolation

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

arctic zone

(1) geographically, the area north of the arctic circle (66° 34′ N) (2) (same as tundra) biogeographically, the area extending northward from the arctic tree line; also used for the level above the timber line in mountains.

snow cover

(1) in general, the accumulation of snow on the ground surface (2) the areal extent of snow-covered ground, usually expressed as percent of total area in a given region.

timber line

(1) in mountainous regions, the line above which climatic conditions do not allow the upright growth of trees (2) the poleward limit of tree growth, also known as the tree line.

seasonal snow

(1) snow that accumulates during one season (2) snow that lasts for only one season.

permafrost boundary

(1) the geographical boundary between the continuous and discontinuous permafrost zones (2) the margin of a discrete body of permafrost.

absolute humidity

(1) the ratio of the mass of water vapor to the volume occupied by a mixture of water vapor and dry air (2) mass of water contained in a unit volume of moist air.

arctic front

(1) the semi-permanent, semi-continuous front between the deep, cold arctic air and the shallower, basically less cold polar air of northern latitudes (2) south boundary of the arctic air mass.

freezing point

(1) the temperature at which a pure liquid solidifies under atmospheric pressure (2) the temperature at which a ground material starts to freeze.

degree of saturation

(1) the total degree of saturation of frozen soil is the ratio of the volume of ice and unfrozen water in the soil pores to the volume of the pores (2) the degree of saturation of frozen soil by ice is the ratio of the volume of ice in the soil pores to the volume of the pores.

humidity

(1) water vapor content of the air. (2) some measure of the water-content of air; see also absolute humidity, relative humidity, specific humidity, dew point.

névé

(1) young, granular snow that has been partially melted, refrozen and compacted; névé that survives a full season is called firn; firn becomes glacial ice; (2) also refers to the accumulation zone of a glacier.

search

Allows you to search a specific database. These data search tools only query the respective database and do not search our Web site. For a Web site content search, use the Google Site Search located at the top of our Web pages.

stratosphere

a layer of the Earth's atmosphere, between the troposphere and mesosphere, that is stratified in temperature such that cooler layers are closer to the Earth's surface, and warmer layers are higher up (opposite the pattern of the troposphere near the Earth's surface); situated between about 10 to 50 kilometers (6 to 31 miles) in altitude above the surface of the moderate latitudes; at the poles, it starts at about 8 km in altitude; composition is basically the same as that of the lower atmosphere, with the addition of ozone.

cryopeg

a layer of unfrozen ground that is perennially cryotic (forming part of the permafrost), in which freezing is prevented by freezing-point depression due to the dissolved-solids content of the pore water.

basal cryopeg

a layer of unfrozen ground that is perennially cryotic (t < 0 degrees Celsius), forming the basal portion of the permafrost.

hydrochemical talik

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

hydrothermal talik

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

thermal talik

a layer or body of unfrozen ground (in a permafrost area) in which the temperature is above 0 degrees Celsius due to the local thermal regime of the ground.

transient talik

a layer or body of unfrozen ground (in a permafrost area) that is gradually being eliminated by freezing.

subglacial talik

a layer or body of unfrozen ground beneath a glacier in an area with permafrost.

subsea talik

a layer or body of unfrozen ground beneath the seabottom, and forming part of the subsea permafrost.

isolated talik

a layer or body of unfrozen ground entirely surrounded by perennially frozen ground.

closed talik

a layer or body of unfrozen ground occupying a depression in the permafrost table below a lake or river.

lake talik

a layer or body of unfrozen ground occupying a depression in the permafrost table beneath a lake.

river talik

a layer or body of unfrozen ground occupying a depression in the permafrost table beneath a river.

talik

a layer or body of unfrozen ground occurring in a permafrost area due to a local anomaly in thermal, hydrological, hydrogeological, or hydrochemical conditions.

lateral talik

a layer or body of unfrozen ground, overlain and underlain by perennially frozen ground.

marine cryopeg

a layer or body of unfrozen ground, that is perennially cryotic (T < 0 degrees Celsius), forming part of the coastal or subsea permafrost.

blind lead

a lead closed off on all sides within the ice pack.

lead shore

a lead that forms between drift ice and the coast.

isohyet

a line drawn through geographical points recording equal amounts of precipitation during a specific period.

isobar

a line of equal or constant pressure; it most often refers to a line drawn through all points of equal atmospheric pressure.

isotherm

a line of equal or constant temperature.

glacier wind

a localized current of air occuring as a result of a glacier's melting processes; when the surface of glacial ice melts, the air above the glacier cools and becomes heavier than the surrounding air and flows down the glacial valley; glacier wind can also be wind that flows out of ice caves; a kind of katabatic wind.

belt

a long area of pack ice from a few km to more than 100 kilometers in width.

strip

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.

Alberta low

a low centered on the eastern slope of the Canadian Rockies in the province of Alberta, Canada.

solifluction terrace

a low step, or bench, with a straight or lobate front, the latter reflecting local differences in the rate of solifluction movement.

iceberg tongue

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

permafrost zone

a major subdivision of a permafrost region.

icefield

a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain.

ice apron

a mass of ice adhering to a mountainside.

ice rise

a mass of ice resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by sea; no rock is exposed and there may be none above sea level; ice rises often have a dome-shaped surface; the largest known is about 100 kilometers (62 miles) across.

glacier

a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.

ozone

a nearly colorless (but faintly blue) gaseous form of oxygen, with a characteristic odor like chlorine; has a formula of O3 and a molecular weight of 48; found in trace quantities in the earth's atmosphere at all times, primarily in the stratosphere between heights of about 10 to 50 kilometers (6 to 31 miles; the ozonosphere or ozone shield) where its production results from photochemical processes involving ultraviolet radiation; its maximum concentration occurs between 20 to 25 kilometers (12 to 16 miles); in the lower atmosphere, ozone is commonly formed as a product of electrical discharges through the air.

glacier mill

a nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses.

pothole

a nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a moulin.

moulin

a nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a pothole.

reticulate ice

a network of horizontal and vertical ice veins forming a three-dimensional, often rectangular or square lattice.

albedo

a non-dimensional, unitless quantity that measures how well a surface reflects solar energy; ranges from 0 - 1; a value of 0 means the surface is a "perfect absorber," where all incoming energy is absorbed, a value of 1 means the surface is a "perfect reflector," where all incoming energy is reflected and none is absorbed.

minerogenic palsa

a palsa in which the frozen core extends below the peat into underlying mineral material.

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.

thermosyphon

a passive heat transfer device installed to remove heat from the ground.

two-phase thermosyphon

a passive heat transfer device, filled with a temperature-dependent liquid/vapour combination, installed to remove heat from the ground.

single-phase thermosyphon

a passive heat transfer device, filled with either a liquid or a gas, installed to remove heat from the ground.

polygonal pattern

a pattern consisting of numerous multi-sided, roughly equidimensional figures bounded by more or less straight sides.

sorted step

a patterned ground feature with a step-like form and a downslope border of stones embanking an area of relatively fine-grained bare ground upslope.

nonsorted step

a patterned ground feature with a step-like form and a downslope border of vegetation embanking an area of relatively bare ground upslope.

nonsorted circle

a patterned ground form that is equidimensional in several directions, with a dominantly circular outline which lacks a border of stones.

sorted circle

a patterned ground form that is equidimensional in several directions, with a dominantly circular outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material.

nonsorted polygon

a patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline which lacks a border of stones.

sorted polygon

a patterned ground form that is equidimensional in several directions, with a dominantly polygonal outline, and a sorted appearance commonly due to a border of stones surrounding a central area of finer material.

nonsorted net

a patterned ground with cells that are equidimensional in several directions, neither dominantly circular nor polygonal, and lacking borders of stones.

horn

a peak or pinnacle thinned and eroded by three or more glacial cirques.

polygonal peat plateau

a peat plateau with ice-wedge polygons.

string fen

a peatland with roughly parallel narrow ridges of peat dominated by fenland vegetation interspersed with slight depressions, many of which contain shallow pools.

palsa

a peaty permafrost mound possessing a core of alternating layers of segregated ice and peat or mineral soil material.

little ice age

a period of cooling that occurred from the 16th through the early 19th century, and was marked by expanding glaciers in Europe, North America, and Asia

glacier fire

a phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire.

temperature

a physical quantity characterizing the mean random motion of molecules in a physical body; in other words, it is a measure of the degree of hotness or coldness of a substance.

cumulonimbus

a principal cloud type (cloud genus) of vertical development, exceptionally dense and vertically developed clouds, occurring either as isolated clouds or as a line or wall of clouds with separated upper portions; these clouds appear as mountains or huge towers, at least a part of the upper portions of which are usually smooth, fibrous, or striated, and almost flattened; this part often spreads out in the form of an anvil (incus) or vast plume; under the base of cumulonimbus, which is very dark, there frequently exist virga, precipitation, and low, ragged clouds, either merged with it or not; its precipitation is often heavy and always of a showery nature.

nimbostratus

a principal cloud type (cloud genus); gray and often dark; rendered diffuse by more or less continuously falling rain, snow, sleet, etc. of the ordinary varieties and not accompanied by lightning, thunder, or hail; precipitation in most cases reaches the ground; may or may not merge with low, ragged clouds that frequently occur below.

cirrocumulus

a principal high-level cloud type (cloud genus), appearing as a thin, white patch or layer of cloud without shading, composed of very small elements in the form of grains, ripples, etc., merged or separated, and more or less regularly arranged; most of the elements have an apparent width of less than 1 degree.

cirrostratus

a principal high-level cloud type (cloud genus), appearing as a transparent, whitish cloud veil of fibrous (hair-like) or smooth appearance, totally or partially covering the sky, and often producing halo phenomena, either partial or complete.

stratus

a principal low-level cloud type (cloud genus) in the form of a low-altitude, light to dark gray cloud layer with a rather uniform base; generally diffuse and dull; this cloud formation has little structure and looks like fog, except that it is above the ground, stratus does not usually produce precipitation, but when it does occur, it is in the form of minute particles, such as drizzle, ice crystals, or fine snow grains.

cumulus

a principal low-level cloud type (cloud genus) in the form of individual, detached elements which are generally dense and possess sharp non-fibrous outlines; these elements develop vertically, appearing as rising mounds, domes, or towers, the upper parts of which often resembles a cauliflower; the sunlit parts of these clouds are mostly brilliant white; their bases are relatively dark and nearly horizontal; near the horizon the vertical development of cumulus often causes the individual clouds to appear merged; if precipitation occurs, it is usually of a showery nature.

stratocumulus

a principal low-level cloud type (cloud genus), predominantly stratiform, in the form of relatively low gray and/or whitish layer, sheet or patch; its elements are often arranged in bands or rolls that lie across the wind; light rain, snow, or sleet may fall from stratocumulus.

altostratus

a principal middle level cloud type (cloud genus) in the form of a grayish (gray) or bluish cloud sheet or layer of striated, fibrous, or uniform appearance, totally or partly covering the sky; the layer has parts thin enough to reveal the position of the sun; halo phenomena do not usually occur.

altocumulus

a principal middle level cloud type (cloud genus), white or gray, or both white and gray, which occurs as a layer or patch with a wave aspect, the elements of which appear as laminae, rounded masses, rolls, etc; these elements usually are sharply outlined, but they may become partly fibrous or diffuse; they may or may not be merged, and they generally have shadowed parts; most of the regularly arranged altocumulus elements have an apparent width of 1 - 5 degrees.

finger rafting

a process by which currents or winds push around thin ice so they slide over each other.

rafting

a process by which currents or winds push around thin ice so they slide over each other; also called finger rafting.

tongue

a projection of the ice edge up to several km in length caused by wind and current; usually forms when a valley glacier moves very quickly into a lake or ocean.

iciness

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

new snow

a recent snow deposit in which the original form of the ice crystals can be recognized.

thermo-erosional niche

a recess at the base of a river bank or coastal bluff, produced by thermal erosion of ice-bonded permafrost.

permafrost region

a region in which the temperature of some or all of the ground below the seasonally freezing and thawing layer remains continuously at or below 0 degrees Celsius for at least two consecutive years.

field

a region of space at each point of which a given physical or mathematical quantity has some definite value; for example, a gravitational field, magnetic field, or electric field; and, in meteorology, a pressure field, temperature field, etc; if the quantity specified at each point is a vector quantity, the field is said to be a vector field.

permanent ice zone

a region that is covered with sea ice year-round; most of the sea ice in the permanent ice zone is multiyear ice, but younger ice and open water may still be present; the permanent ice zone is what remains in summer after all melting has occurred (often called the summer minimum extent).

sun cups

ablation hollows that develop during intense sunshine.

brash ice

accumulation of floating ice made up of fragments not more than 2 meters (6.6 feet) across, the wreckage of other forms of ice.

glacial till

accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine.

red algae

algae common on temperate glaciers and perennial snow; its red color sometimes prompts people to call it watermelon snow.

accumulation

all processes by which snow or ice are added to a glacier, this is typically the accumulation of snow, which is slowly transformed into ice; other accumulation processes can include avalanches, wind-deposited snow, and the freezing of rain within the snow pack.

antarctic polar front

also known as the antarctic convergence; the southern front of the antarctic circumpolar current that separates the antarctic zone in the south from the polar frontal zone in the north; taken by many to delineate the actual northern boundary of the antarctic zone; characterized by sea surface temperatures near 5°-6° C and a salinity minimum of 33.8-34.0 psu produced by high rainfall.

ogives

alternate bands of light and dark ice seen on a glacier surface.

band ogives

alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.

forbes bands

alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.

sedimentary ogives

alternating bands of light and dark at the firn limit of a glacier; the light bands are usually young and lightest at the highest level up-glacier, becoming increasingly older and darker as they progress down-glacier.

ice jam

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

puddle

an accumulation of melt water on an ice surface, mainly due to melting snow, but in later stages also to the melting of ice; the initial stage consists of patches of slush.

snowdrift

an accumulation or bank of snow formed when wind blows snow against an obstruction; often considerably thicker than the surrounding snowcover.

congelation ice

an advanced form of new ice that forms as a stable sheet with a smooth bottom surface.

snow bridge

an arch formed by snow which has drifted aross a crevasse, forming first a cornice, and ultimately a covering which may completely obscure the opening.

end moraine

an arch-shaped ridge of moraine found near the end of a glacier.

arctic oscillation

an atmospheric circulation pattern in which the atmospheric pressure over the polar regions varies in opposition with that over middle latitudes (about 45 degrees N) on time scales ranging from weeks to decades; the oscillation extends through the depth of the troposphere, and from January to March, it extends upward into the stratosphere where it modulates in the strength of the westerly vortex that encircles the arctic polar cap region; the north atlantic oscillation and arctic oscillation are different ways of describing the same phenomenon.

iceport

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

blowing snow

an ensemble of snow particles raised by the wind to moderate or great heights above the ground; the horizontal visibility at eye level is generally very poor.

pingo

an eskimo term for a perennial frost mound consisting of a core of massive ice with soil and vegetation cover; the size can range from a few meters to tens of meters, in both diameter and height; can be found in continuous and discontinuous permafrost zones.

glacier tongue

an extension of a glacier or ice stream projecting seaward, usually afloat.

air mass

an extensive body of the atmosphere in which physical properties, particularly temperature and humidity, exhibit only small and continuous differences in the horizontal plane; it may extend over an area of several million square kilometers and over a height of several kilometers.

bight

an extensive crescent-shaped indentation in the ice edge, formed either by wind or current.

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.

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.

syngenetic ice wedge

an ice wedge developed during the formation of syngenetic permafrost.

epigenetic ice wedge

an ice wedge developed in epigenetic permafrost, or in previously formed syngenetic permafrost.

anti-syngenetic ice wedge

an ice wedge that grows progressively downwards into a receding slope, in a direction normal (perpendicular) to the surface.

active ice wedge

an ice wedge that is growing as a result of repeated (but not necessarily annual) winter cracking.

inactive ice wedge

an ice wedge that is no longer growing.

ice vein

an ice-filled crack or fissure in the ground.

high-center polygon

an ice-wedge polygon in which melting of the surrounding ice wedges has left the central area in a relatively elevated position.

low-center polygon

an ice-wedge polygon in which thawing of ice-rich permafrost has left the central area in a relatively depressed position.

growler

an iceberg less than 2 meters (6.6 feet) across that floats with less than 1 meter (3.3 feet) showing above water; smaller than a bergy bit.

fluted berg

an iceberg that is grooved into a curtain-like pattern; thought to be carved by small meltwater streams.

thermograph

an instrument continuously recording temperature.

equilibrium line

boundary between the accumulation area and ablation area where the mass balance is zero.

aneroid barometer

an instrument for measuring atmospheric pressure; it is constructed on the following principles: an aneroid capsule (vidie capsule, which is a thin, disk-shaped box or capsule, usually metallic) is partially evacuated of gas, and is restrained from collapsing by an external or internal spring; the deflection of the spring will be nearly proportional to the difference between the internal and external pressures; magnification of the spring deflection is obtained both by connecting capsules in series and by mechanical linkages.

thermometer

an instrument for measuring temperature; in meteorology, generally used to measure the temperature of the air or the soil.

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.

anemometer

an instrument which measures wind speed or wind speed and direction; a cup anemometer measures the wind speed from the speed of rotation of a windmill which consist of 3 or 4 hemispherical or conical cups, each fixed to the ends of horizontal arms attached to a vertical axis; a byram anemometer is a variety of the cup anemometer; a counting anemometer has cups or a fan whose rotation is transmitted to a technical counter which integrates directly the air movement speed; a hand anemometer is small portable anemometer held at arm's length by an observer making a wind speed measurement; a pressure tube anemometer (dines anemometer) is an instrument which derives wind speed from measurements of the dynamic wind pressures - wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static, this pressure difference is proportional to the square of the wind speed.

serac

an isolated block of ice that is formed where the glacier surface is fractured.

solifluction lobe

an isolated, tongue-shaped solifluction feature, up to 25 meters (27 yards) wide and 150 meters (164 yards) or more long; formed by more rapid solifluction on certain sections of a slope showing variations in gradient.

synoptic weather observation

an observation made at periodic times (usually at 3-hour and 6-hour intervals specified by the World Meteorological Organization) of sky cover, state of the sky, cloud height, atmospheric pressure at sea level, temperature, dew point, wind speed and direction, amount of precipitation, hydrometeors and lithometeors, and special phenomena that prevail at the time of the observation or observed since the previous specified observation.

upper air observation

an observation made in the free atmosphere either directly or indirectly.

Beaufort Gyre

an ocean and ice circulation pattern in the Beaufort Sea, north of Alaska. This gyre moves in a clockwise direction, fed by an average high-pressure system that fosters anti-cyclonic winds. Ice that forms in or drifts into the Beaufort Gyre has historically remained in the Arctic ice system for years, accumulating snow and thickening each winter. Beginning in the late 1990s, the ice began melting away while in the southern parts of the gyre, before completing the circulation.

snow 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) in length; some feed off red algae.

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.

theodolite

an optical instrument used to visually track a radiosonde balloon and determine its bearing and elevation while in flight.

organic cryosol

an organic soil having a surface layer containing more than 17% organic carbon by weight, with permafrost within 1 meter (3.3 feet) below the surface.

large-scale atmospheric processes

atmospheric processes with a representative scale (large-scale) of 10,000 kilometers (6,200 miles); in meteorology, it is a scale in which the curve of the earth is not negligible; the large-scale atmospheric flows are essentially nearly hydrostatic, nearly geostrophic and wave-like in appearance; they exist mainly in response to the latitudinal differences in radiative heating, to the particular value of the coriolis force and to the spatial distribution of the oceans and continents.

false ogives

bands of light and dark on a glacier that were formed by rock avalanching.

BTS method

method to predict the presence or absence of permafrost in a mountain area, using measurements of the bottom temperature of snow cover mid- to late-winter.

push moraine

moraine built out ahead of an advancing glacier.

regelation

motion of an object through ice by melting and freezing that is caused by pressure differences; this process allows a glacier to slide past small obstacles on its bed.

ablation moraine

mound or layer of moraine in the ablation zone of a glacier; the rock has been plucked from the mountainside by the moving glacier and is melting out on the ice surface.

tidewater glacier

mountain glacier that terminates in the ocean.

latent heat of fusion

the amount of heat required to cause a change of phase from solid to liquid, or the heat released when the phase change is from liquid to solid; in the case of melting snow, the phase change from ice to water requires a significant amount of heat—160 times that required to raise the temperature of the same amount of ice by just 1 degree Celsius; until the required amount of heat is supplied to completely melt all of the ice being considered, no further increase in temperature will occur.

volumetric latent heat of fusion

the amount of heat required to melt all the ice (or freeze all the pore water) in a unit volume of soil or rock.

heat capacity

the amount of heat required to raise the temperature of a unit mass of a substance by one degree.

specific heat capacity

the amount of heat required to raise the temperature of a unit mass of a substance by one degree.

apparent head capacity

the amount of heat required to raise the temperature of a unit mass of frozen ground by one degree.

volumetric heat capacity

the amount of heat required to raise the temperature of a unit volume of a substance by one degree.

heat flux

the amount of heat transferred across a surface of unit area in a unit time.

ice content

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

unfrozen water content

the amount of unfrozen (liquid) water contained in frozen soil or rock.

thaw strain

the amount that frozen ground compresses upon thawing.

Greenland high

the anticyclone that appears to overlie Greenland; analogous to the antarctic anticyclone.

ablation area

the area of a glacier where more glacier mass is lost than gained.

sea-level pressure

the atmospheric pressure at mean sea level, either directly measured or, most commonly, empirically determined from the observed station pressure.

ice limit

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

sintering

the bonding together of ice crystals.

glacier sole

the bottom of the ice of a glacier.

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.

cryofront

the boundary between cryotic and noncryotic ground as indicated by the position of the 0 degrees Celsius isotherm in the ground.

stratopause

the boundary layer between the stratosphere and the mesosphere at about 50 to 55 kilometers (31 to 34 miles).

reticulate cryostructure

the cryostructure in which horizontal and vertical ice veins form a three-dimensional, rectangular or square lattice.

tropopause

the boundary layer between the troposphere and stratosphere, where an abrupt change in temperature lapse rate usually occurs; it is defined as the lowest level at which the lapse rate decreases to 2 degrees Celsius per kilometer or less, provided that the average lapse rate between this level and all higher levels within 2 kilometers does not exceed 2 degrees Celsius per kilometer; occasionally, a second tropopause may be found if the lapse rate above the first tropopause exceeds 3 degrees Celsius per kilometer.

ice divide

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

freezing (of ground)

the changing of phase from water to ice in soil or rock.

pressure tendency

the character and amount of atmospheric pressure change for a three-hour or other specified period ending at the time of observation.

cryogenesis

the combination of thermophysical, physico-chemical and physico-mechanical processes occurring in freezing, frozen and thawing earth materials.

snow depth

the combined total depth of both old and new snow on the ground.

saturation

the condition in which the partial pressure of any fluid constituent (water in the atmospheric air) is equal to its maximum possible partial pressure under the existing environmental conditions, such that any increase in the amount of that constituent will initiate within it a change to a more condensed state; evaporation ceases under such conditions.

supercooled

the condition when a liquid remains in the liquid state even through its temperature is below its freezing point.

frost

the condition which exists when the temperature near the earth's surface and earth-bound objects falls below freezing (0 degrees Celsius or 32 degrees Fahrenheit).

supersaturation

the condition which occurs in the atmosphere when the relative humidity is greater than 100%.

periglacial

the conditions, processes and landforms associated with cold, nonglacial environments.

global telecommunication system

the coordinated global system of telecommunication facilities and arrangements for the rapid collection, exchange and distribution of observational data in the framework of the World Weather Watch, a World Meteorological Organization program.

reticulate-blocky cryostructure

the cryostructure in which horizontal and vertical ice veins form a three-dimensional, irregular rectangular lattice.

climatology

the scientific study of climate; the aspect of meteorology which studies processes of climate formation, distribution of climates over the globe, analysis of the causes of differences of climate (physical climatology), and the application of climatic data to the solution of specific design or operational problems (applied climatology); climatology may be further subdivided according to purpose or point of view: agricultural climatology, air-mass climatology, aviation climatology, bioclimatology, dynamic climatology, medical climatology, macroclimatology, mesoclimatology, microclimatology, paleoclimatology, synoptic climatology, etc..

Azores high

the semipermanent subtropical high over the North Atlantic Ocean, especially when it is located over the eastern part of the ocean; the same high over the western part of the Atlantic is called the Bermuda high; on mean charts of sea level pressure, this high is one of the primary centers of action in northern latitudes.

Bermuda high

the semipermanent subtropical high over the North Atlantic Ocean, especially when it is located over the western part of the ocean; the same high over the eastern part of the Atlantic is called the Azores high; on mean charts of sea level pressure, this high is one of the primary centers of action in northern latitudes.

basal sliding

the sliding of a glacier over bedrock.

creep of frozen ground

the slow deformation (or time-dependent shear strain) that results from long-term application of a stress too small to produce failure in the frozen material.

gelifluction

the slow downslope flow of unfrozen earth materials on a frozen substrate.

Tropic of Capricorn

the southern parallel of maximum solar declination, approximately 23° 27′ S latitude; the farthest southern latitude at which the sun can appear directly overhead, which occurs on the day of the summer solstice.

latitudinal limit of permafrost

the southernmost (northernmost) latitude at which permafrost occurs in a lowland region in the northern (southern) hemisphere.

cyclone movement

the spatial displacement of a center of low pressure caused by the local redistribution of mass in the atmosphere; the trajectory of the center is often altered by heating or cooling on the air column, which can result from thermal fluxes at the surface or latent heat transformations associated with cloud formation and precipitation; these processes change the temperature distribution in the air column, resulting in density changes which modify the surface pressures.

weather

the state of the atmosphere, mainly with respect to its effects upon life and human activities; distinguished from climate by focusing on short-term (minutes to about 15 days) variations of the atmosphere state.

cryostructure

the structural characteristics of frozen earth materials.

synoptic meteorology

the study and analysis of synoptic weather information (synoptic charts, synoptic weather observations); thus, it is a study of macro-scale atmospheric processes, as well as weather prediction based on results of synoptic studies.

geocryology

the study of earth materials having a temperature below 0 degrees Celsius.

cryopedology

the study of soils at temperatures below 0 degrees Celsius, with particular reference to soils subject to intensive frost action, and to soils overlying permafrost.