| Description |
The Greenland ice sheet is losing mass, which can contribute to sea level rise. Firn aquifers covering between 22,000 â€" 90,000 km2 have been discovered within the ice sheet. In summer, surface snowmelt infiltrates to depth, saturating pore space within the compacting firn. Recharge ceases when the surface temperatures cool below 0ºC in the fall. Instead of refreezing, the meltwater stays in liquid phase throughout the year because of the insulation produced by high snow accumulation rates. This liquid flows through the firn, and discharges from the aquifer, likely to crevasses at the edge of the ice sheet. Flow through the firn behaves according to Darcy’s law. The firn aquifer is a modern feature of the ice sheet, likely caused by warming of the Arctic associated with global climate change. Water in the aquifer recharged the aquifer within the past ~50 years. Instead of permanently storing meltwater, either through refreezing or simple storage in pore space, firn aquifers allow large volumes of meltwater to discharge from the ice sheet. The fate of that meltwater and its pathways to the ocean remain unknown and require further work as some scenarios (e.g., hydrofracturing crevasses leading to basal lubrication) could play important roles in accelerating ice flow and discharge to the ocean. |
