Cryosphere glossary
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, 34 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, 34 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.