Spatial extent of Greenland firn aquifer detected by airborne radars, 2010-2014

• Main Author: Clément Miège
• Format: Dataset
• Language: unknown
• Published: Arctic Data Center 2018
• Subjects: Greenland; Ice Sheet
• Online Access: https://doi.org/10.18739/A2985M

Mass loss of the Greenland ice sheet has been accelerating since the 1990s, and in recent years (2009‐2012), about 85% of its rate of increase were due to increased surface melt and subsequent runoff. The Greenland surface melt extent and duration have increased over the last decade, in response to increased advection of warm air from the south during summers. Surface melt is not only occurring in the lower elevation margins of the ice sheet but also migrating toward the ice sheet interior, causing a reduction of the dry-snow zone and an expansion of the percolation zone. Widespread firn aquifers have been detected in high-accumulation regions of the ice-sheet percolation zone. In these regions, firn aquifers retain water for at least several years, storing a substantial amount of water responsible of heating the firn and delaying meltwater runoff. Their impacts on the ice sheet are numerous, including firn densification, alteration of the ice thermal state, and water input from the aquifer into the englacial hydrology system, which has the potential to affect ice dynamics and Greenland's contribution to sea level rise. This dataset provides the locations of firn aquifers for the high snow-accumulation regions of the Greenland ice sheet. To achieve this goal, we use NASA Operation IceBridge Accumulation Radar data from five campaigns (2010-2014) and pick the brighter reflection horizons in the firn which are due to strong dielectric contrasts created by the presence of water. For estimating a total firn-aquifer extent, we delineate polygons around flightlines showing water-saturated firn for the 2010-2014 period combined. With this method, we find a 21,900 km 2 total extent and an average depth to the water table of 22 m. In addition of providing the firn aquifer extents map by the mean of polygons, we also provide yearly files with firn-aquifer coordinates and depth to the water table. This way, the interannual variability can be investigated in places with repeat flightlines for the 2010-2014 time period.