The Cryosphere An improved semi-empirical model for the densification of Antarctic firn

Abstract. A firn densification model is presented that sim-ulates steady-state Antarctic firn density profiles, as well as the temporal evolution of firn density and surface height. The model uses an improved firn densification expression that is tuned to fit depth-density observations. Liquid water pro-cesses (meltwater percolation, retention and refreezing) are also included. Two applications are presented. First, the steady-state model version is used to simulate the strong spa-tial variability in firn layer thickness across the Antarctic ice sheet. Second, the time-dependent model is run for 3 Antarc-tic locations with different climate conditions. Surface height changes are caused by a combination of accumulation, melt-ing and firn densification processes. On all 3 locations, an up-ward trend of the surface during autumn, winter and spring is present, while during summer there is a more rapid lowering of the surface. Accumulation and (if present) melt introduce large inter-annual variability in surface height trends, possi-bly hiding ice dynamical thickening and thinning.