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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.

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.


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

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.

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.

bottom temperature of snow cover

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

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.
In this photograph from 1969, small glaciers flow into the larger Columbia Glacier from mountain valleys on both sides. Columbia Glacier flows out of the Chugach Mountains into Columbia Bay, Alaska. (Photo courtesy of the United States Geological Survey. Archived at the World Data Center for Glaciology, Boulder, CO.)

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.


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.

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.


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

buoy weather station

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

buried ice

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

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.


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


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

calving glacier

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

carbon sink

A reservoir of carbon dioxide that is increasing in size.

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.

cave ice

ice formed in a closed or open cave.


striations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice.
Close up of chatter marks, Mt. Sirius, Antarctica. Lens cap in the photo is five centimeters across. (Photo courtesy of Tom Lowell, University of Cincinnati.)


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

circumpolar vortex

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


bowl shape or amphitheater usually sculpted out of the mountain terrain by a cirque glacier.
Cirque on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada. (Photo courtesy of Hazen Russel, Natural Resources Canada. Copyright Terrain Sciences Division, Geological Survey of Canada.)

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.


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.


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.


a principal high-level cloud type (cloud genus), appearing as detached clouds in the form of white, delicate filaments or white or mostly white patches or narrow bands; these clouds have a fibrous (hair-like) appearance, or a silky sheen, or both; because cirrus elements are too narrow, they do not produce a complete circular halo.

clear sky

sky with a total cloud cover of less than one okta (or one-tenth in the united states).


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.

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.

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.

climate variability

(1) in the most general sense, the term climate variability denotes the inherent characteristic of climate which manifests itself in changes with time; the degree of climate variability can be described by the differences between long-term statistics of meteorological elements calculated for different periods, (in this sense, the measure of climate variability is the same as the measure of climate change) (2) the term climate variability is often used to denote deviations of climate statistics over a given period of time (such as a specific month, season or year) from the long-term climate statistics relating to the corresponding calendar period; (in this sense, climate variability is measured by those deviations, which are usually termed anomalies).

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.


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..

close cavity ice

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