Cryosphere glossary
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.
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.
Image
Satellite view of polynyas (dark areas) near Oates Coast, Antarctica (solid white area at bottom of photo).
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.
post-glacial rebound
Post-glacial rebound (sometimes called continental rebound, isostatic rebound or isostatic adjustment) is the rise of land masses that were depressed by the huge weight of ice sheets during the last ice age.