Reply on RC3

Abstract

Firn simulations are essential for understanding Antarctic ice sheet mass change as they enable us to convert satellite altimetry observed volume changes to mass changes, and to quantify the meltwater buffering capacity of firn. Here, we present and evaluate a simulation of the contemporary Antarctic firn layer using the updated semi-empirical firn model IMAU-FDM for the period 1979–2020. In IMAU-FDM, we have improved the fresh snow density and firn compaction parameterizations, and used improved 5 atmospheric forcing. In addition, the model has been tuned and evaluated against 148 in situ observations across the ice sheet. The updated model captures the observed strong spatial variation in firn thickness and density. The temporal variation can be split into a rather stable seasonal cycle driven by snowfall, compaction and melt seasonal cycles, and more irregular decadal variations driven by snowfall anomalies. Comparison of simulated surface elevation change with altimetry shows that the decadal trends agree reasonably well, and that the performance of the updated model has improved, notably in Dronning Maud Land and Wilkins Land.