The Greenland ice sheet is covered by a layer of old, porous snow called firn. Firn on the Greenland ice sheet can form thick ice slabs or store liquid water in aquifers, affecting runoff and drainage. Our model study investigates conditions leading to their formation.
We find that snowfall, melt and rain determine where ice slabs and aquifers can form.
Average 1960–1980 combined melt and rain rates as a function of accumulation rate for all IMAU-FDM grid cells. Symbols indicate presence of ice lenses/slabs or aquifers for at least half of the 1960–1980 period. Arrows connect 1960–1980 (arrow base) with 2000–2020 (head) averages for two selected locations (Figure 1a): KAN-U (left) and FA-16 (right). Dashed lines represent melt/rain over accumulation (MoA) ratios of ∼0.7 and ∼1.7 (Text S1 in Supporting Information S1).
The results also suggest that ice slabs and aquifers are more abundant than previously observed. We show that, in between the ablation zone and the accumulation zone, there are always ice slabs and/or aquifers present.
Locations with modeled and OIB observed (a) ice slabs for 2010–2018 (Jullien et al., 2023), and (b) aquifers during 2010–2014 (Miège et al., 2016). Full black lines in (a) represent Mouginot et al. (2019) ice sheet basins. Gray lines are OIB 2010–2018 flightlines. Blue dots represent locations of the arrows in Figure 4. Dashed gray lines indicate elevation contours at 500 m intervals.
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