Firn Densification: An Empirical Model

Impurity-controlled densification: a new model for stratified polar firn

A new densification model, which simulates the effect of impurities on the densification of polar firn, is presented. The classical densification models of Herron and Langway (1980) and Pimienta and Barnola (Barnola and others, 1991) are modified by assuming that the activation energy for deformation is reduced by the impurities. Motivated by recent observations, the impurity effect is formulat...

Firn Densification by Grain-boundary Sliding : a First Model

Densification in highly porous, isothermal firn occurs primarily by Newtonian sliding on grain boundaries, but the coordination number increases with density and restricts further sliding. At a relative density of about 0.6 the coordination number approaches 6 and sliding ceases to be a primary mechanism of densification; the resulting decrease in densification rate causes the critical point in...

Densification of layered firn in the ice sheet at Dome Fuji, Antarctica

In order to better understand the densification of polar firn, firn cores from the three sites within∼10 km of Dome Fuji, Antarctica, were investigated using surrogates of density: dielectric permittivities εv and εh at microwave frequencies with electrical fields in the vertical and horizontal planes respectively. Dielectric anisotropy Δε (=εv− εh) was then examined as a surrogate of the aniso...

On the impact of impurities on the densification of polar firn

Firn Model Intercomparison Experiment (FirnMICE)

Evolution of cold dry snow and firn plays important roles in glaciology; however, the physical formulation of a densification law is still an active research topic. We forced eight firn-densification models and one seasonal-snow model in six different experiments by imposing step changes in temperature and accumulation-rate boundary conditions; all of the boundary conditions were chosen to simu...