Education Center
The Cryosphere: Where the World is Frozen

GlossaryDefinition of "cryosphere"

 

NSIDC's Glossary contains general and scientific terms related to Earth's frozen places. You can search for particular terms in the Keyword box, or browse subsets of the glossary. Choose a topic and press Search to browse all the terms within specific subjects (glaciers, sea ice, etc.), or browse terms alphabetically by letter.

Keyword

Topic

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Search Results

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.

palsa

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

palsa bog

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

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.

(Photo courtesy of the National Oceanic and Atmospheric Administration/Department of Commerce.)
(Photo courtesy of the National Oceanic and Atmospheric Administration/Department of Commerce.)

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.

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.

partially-bonded permafrost

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

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.

passive single-phase thermal pile

a foundation pile provided with a single-phase natural convection cooling system to remove heat from the ground.

passive two-phase thermal pile

a foundation pile provided with a two-phase natural convection cooling system to remove heat from 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.

patch

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

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.

A photograph taken from the air reveals patterned ground surrounding thaw lakes in Alaska’s Arctic National Wildlife Refuge.  —Credit: U.S. Fish and Wildlife Service
A photograph taken from the air reveals patterned ground surrounding thaw lakes in Alaska’s Arctic National Wildlife Refuge. —Credit: U.S. Fish and Wildlife Service

peat

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

peat hummock

a hummock consisting of peat.

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.

peatland

peat-covered terrain.

penitents

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

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.

perennial snow

snow that persists on the ground year after year.

periglacial

the conditions, processes and landforms associated with cold, nonglacial environments.

periglacial phenomena

landforms and soil characteristics produced by periglacial processes.

periglacial processes

processes associated with frost action in cold, nonglacial environments.

permacrete

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

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.

permafrost aggradation

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

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).

permafrost boundary

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

permafrost degradation

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

permafrost extent

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

permafrost limit

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

permafrost table

the upper boundary surface of permafrost.

permafrost thickness

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

permafrost zone

a major subdivision of a permafrost region.

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).

pH

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

piedmont glacier

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

The massive lobe of Malaspina Glacier in Alaska is clearly visible in this photograph taken from a Space Shuttle flight in 1989.  Agassiz Glacier is the smaller glacier to the left.  The Malaspina Glacier is one of the most famous examples of this type of glacier, and is the largest piedmont glacier in the world.  Spilling out of the Seward Ice Field (visible near the top of the photograph), it covers over 5,000 square kilometers as it spreads across the coastal plain. (Photo courtesy of SPACE.com and NASA.)
The massive lobe of Malaspina Glacier in Alaska is clearly visible in this photograph taken from a Space Shuttle flight in 1989. Agassiz Glacier is the smaller glacier to the left. The Malaspina Glacier is one of the most famous examples of this type of glacier, and is the largest piedmont glacier in the world. Spilling out of the Seward Ice Field (visible near the top of the photograph), it covers over 5,000 square kilometers as it spreads across the coastal plain. (Photo courtesy of SPACE.com and NASA.)

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.

pingo ice

massive ice forming the core of a pingo.

pingo remnant

a collapsed pingo.

pingo scar

a pingo remnant in a contemporary non-permafrost environment.

planetary permafrost

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

plastic frozen ground

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

Pleistocene

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

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.

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.

polar explorer

a person working for a long time at one of the polar observing stations; Russian word is polyarnik.

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.

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.

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.

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 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).

polar vortex

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

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.

polyarnik

Russian word for a person working for a long time at one of the polar observing stations.

polycrystal

a snowflake composed of many individual ice crystals.

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.

polygon trough

the narrow depression surrounding a high-centre polygon.

polygonal pattern

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

polygonal peat plateau

a peat plateau with ice-wedge polygons.

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.

Satellite view of polynyas (dark areas) near Oates Coast, Antarctica (solid white area at bottom of photo). (Photo courtesy of NASA.)
Satellite view of polynyas (dark areas) near Oates Coast, Antarctica (solid white area at bottom of photo). (Photo courtesy of NASA.)

poorly-bonded permafrost

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

pore ice

ice occurring in the pores of soils and rocks.

pore water

water occurring in the pores of soils and rocks.

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.

powder snow

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

prairie

a treeless grassy plain.

precipitation

(1) any of the forms of water particles, whether liquid or solid, that fall from the atmosphere and reach the ground; includes: rain, drizzle, snow, snow grains, snow pellets, diamond dust, hail, and ice pellets; see also acid precipitation (2) accumulated depth of rain, drizzle and the melted water content of frozen forms of precipitation.

precision

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

present weather

weather at a station at the time of observation.

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.

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.

pressure melting

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

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.

pressure tendency

the character and amount of atmospheric pressure change for a three-hour or other specified period ending at the time of observation.

pressure-melting

lowering the melting point of ice by applying pressure.

prime meridian

the meridian (line of longitude) defined to be 0 degrees and passing through the Royal Greenwich Observatory in London; also known as the International Meridian or Greenwich Meridian; the Prime Meridian and the opposite 180th meridian (at 180 degrees longitude) separate the Eastern and Western Hemispheres.

pseudomorph

in geology, a mineral compound resulting from a process by which the primary mineral component is replaced by another, although the compound maintains constant appearance and dimensions.

psychrometer

an instrument used for measuring the water vapor content of the atmosphere; a type of hygrometer; it consists of two thermometers, one of which (the dry bulb) is an ordinary glass thermometer, while the other (wet bulb) has its bulb covered with a jacket of clean muslin which is saturated with distilled water prior to an observation; when the bulbs are suitably ventilated, they indicate the thermodynamic wet- and dry-bulb temperatures of the atmosphere; one variety is the assman psychrometer (a special form of aspiration psychrometer for which the ventilation is provided by a suction fan).

psychrometric tables

tables prepared from psychrometric data and used to obtain vapor pressure, relative humidity, and dew point from wet- and dry-bulb temperatures.

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.

push moraine

moraine built out ahead of an advancing glacier.

The Columbia Glacier surged (advanced rapidly) earlier this century, part of it flowing into a forest. The push moraine in this photograph from 1914 shows Columbia Glacier literally pushing up trees and dirt as it advanced. (Photo courtesy of D.K. Handy, archived at the World Data Center for Glaciology, Boulder, CO.)
The Columbia Glacier surged (advanced rapidly) earlier this century, part of it flowing into a forest. The push moraine in this photograph from 1914 shows Columbia Glacier literally pushing up trees and dirt as it advanced. (Photo courtesy of D.K. Handy, archived at the World Data Center for Glaciology, Boulder, CO.)

University of Colorado at Boulder Cooperative Institute for Research in Environmental Sciences (CIRES)

The National Snow and Ice Data Center
Supporting Cryospheric Research Since 1976
449 UCB  University of Colorado  Boulder, CO 80309-0449
NSIDC Home  | NSIDC Web Policy  |  Use/Copyright Info

Supported by:
NASA nsf.gov - National Science Foundation