As snow is deposited at the surface of a pack, compaction takes place
in two stages. There is an initial period of settlement where the rate
of volume decrease is dominated by thermal processes, reflecting the
rapid metamorphism as branched crystals break down. This is followed b
y further slower densification as pores collapse, which is largely cau
sed by the overburden. The conventional assumption is that of a linear
ly viscous relation between the rate of decrease of volume and the pre
ssure, with the viscosity depending on the density and temperature. In
view of the long time scales associated with the accumulation of pola
r snow, compared with observed pore collapse times, an alternative vie
w is that the densification takes place instantaneously, which can be
described simply by a pressure-density-temperature relation. This, of
course, may depend also on the particular snow structure which is dete
rmined by the deposit conditions and subsequent metamorphism. Here, we
investigate the special, and much simplified, case of a pressure-dens
ity law, ignoring temperature influence, to demonstrate that such a la
w is consistent with the same data used to infer the viscous law. The
function relating density to pressure is determined from observed dens
ity profiles with depth, assuming that the snow was deposited at a fix
ed constant density rho0, but no restriction on the accumulation varia
tion is necessary. The model is then used to predict the pressure, den
sity and velocity fields for general surface conditions of deposit den
sity and accumulation rate, to show how the density and velocity field
s are influenced by surface conditions for this alternative model. The
density profiles with depth are confirmed to be independent of time w
hen the deposit density is held constant, and independent of the accum
ulation rate variation.