Separation of accumulation driven firn compaction from the mixed changes in surface elevation

In polar ice sheets, fluctuations of the accumulation rate directly cause the surface elevation change. Meanwhile these variations alter the overburden pressure, causing the changes in firn compaction rate that also changes the surface elevation. Knowing the importance of the accumulation driven firn compaction in contribution to the elevation change is of great interest of understanding the short-term variations in the observed elevation-time profiles, and then inferring the mass changes from those variations. In this study, we show that the characteristic of the densification rate equation in our model allows separating the accumulation caused firn compaction from the mixed term of accumulation and the accumulation driven compaction, as well as from the temperature driven compaction. We carry out numerical experiments under a constant temperature and time variable accumulation rates and use the average changes of the over-burden pressure (represented by the average accumulation rate) to drive compaction rate at each depth, comparing with those by using the long-term accumulation rate for the steady-state. Our results show that for the conditions similar to the summit of the Greenland ice sheet, increase of the accumulation rate at 1-2% a-1 will enhance the firn compaction rate, resulting in the rate of surface elevation change about 20-30% for 10-20 year period.