Weather front located typically in the mid-latitudes that separates arctic and polar air masses from tropical air masses. Along the polar front we get the development of the mid-latitude cyclone. Abov
e the polar front exists the polar jet stream.
Theory of the Bergen school (1918) which describes the formation and evolution of extratropical depressions in terms of the interaction between polar and tropical air masses and the characteristics of
the surface of discontinuity which separates them.
In Ahlmann's glacier classification, a glacier with an accumulation area covered by firn and with subsurface temperatures below freezing throughout the year. The two subtypes are the high polar glacie
r and the subpolar 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 altit
udes.
An obsolete term, due to Ahlmann (1935), originally in the form 'high-polar glacier', describing a glacier with an accumulation zone in which there is little or no melting and the temperature is below
the freezing point to depths of at least 200 m. See cold glacier, polythermal glacier for rough equivalents in modern terminology.
Surface area of atmospheric high pressure located at about 90 North and South latitude. These high pressure systems produced by vertically descending air currents from the polar vortex.
1. The thickest form of sea ice, one to several years old (perhaps paleocrystic), and sometimes more than 3 m (10 ft) thick. 2. The pack ice of the central Arctic Ocean. (Also called polar-cap ice.)
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 she
et.