(1) The metamorphosis, without melting but not necessarily without advection in the vapour phase, of an assemblage of grains of snow and old crystals of ice to a new assemblage of crystals of ice, gen
erally resulting in changes of mean crystal size and orientation (fabric) and, of most significance for mass-balance purposes, an increase of density. See congelation, infiltration ice, glacier. (2) The formation of a new assemblage of crystals from an old assemblage. Sense 1 is the meaning of the term in studies of the densification of snow, while sense 2 is its everyday meaning.
In the Russian-language literature, where it is sometimes also referred to as the 'snow-firn zone', a term for the upper percolation zone. See zone. In this context the Russian word 'regelatsiya' refe
rs to refreezing, not to regelation.