AGGRADATION

Aggradation of the permafrost layers

AGGRADATION of the permafrost layers (from the Latin word "ad", which means "to" and "gradatio" steady increase * EN: aggradation of permafrost layers; DE: Zuwachs vorgange in Dauerfrostbodenmachtigkeiten; FR: aggradation des couches а permafrost; ES: agradacion de capas de congelacion perpetua; RU: агградация многолетнемёрзлых толщ) is the process of changing the permafrost conditions within the permafrost zone, expressed by the increase of the area of the extent, and of the thickness of the permafrost rocks, and by the lowering of their temperature.

The aggradation may have both regional and local dispositions. In the first case it is conditioned, as a rule, by the cooling of the climate, in the second case it is usually associated with the economic development of the territory, when, at the several places, the snow cover is removed or compacted, the surface is shaded, etc. The presence of the aggradation is indicated by the character of the geothermal regime, the new formation of the permafrost in the areas, where it not existed previously, and the intensification of the cryogenic processes (the frost cracking, the growth of the massive wedge ice, the formation of the multiyear heaving mounds). The process, which is opposite to the aggradation, is the degradation of the permafrost.