| Summary: | Surface meltwater runoff dominates present-day mass loss from the Greenland Ice Sheet. In the interior, porous firn can buffer runoff by retaining meltwater unless perched impermeable horizons, such as ice slabs, develop and restrict percolation. Recent field observations suggest that such horizons might develop rapidly during extreme melt seasons. In particular, subsurface refreezing of surface meltwater during the 2012 extreme melt season created a spatially coherent refrozen melt layer across the Greenland Ice Sheet. We use airborne radar sounding data collected by the University of Kansas Center for the Remote Sensing of Ice Sheets (CReSIS) to map the extent of this layer and constrain its density and lateral connectivity at the radar footprint scale. These observations provide insights into the multi-year impact of extreme melt seasons on firn structure and meltwater drainage pathways. This data set contains detections of this melt layer from Accumulation Radar data collected by CReSIS in 2017. We use an electromagnetic forward model to invert the observed radar reflectivity to constrain the layer density and measure connectivity based on the number of laterally adjacent detections. File 2012IceLayerDetections.txt contains the latitude, longitude, layer prominence, the probability that layer density exceeds pore close-off, lateral layer connectivity, the minimum layer density consistent with the observed radar reflectivities, and the maximum layer density consistent with the observed radar reflectivities, all averaged to 1kilometer (km) grid cell along the flight lines. The files [Date]_[Segment]_CleanResults.txt contains the same data, but broken out into 18 individual text files, one for each radar flight transect analyzed. The date and segment match the CReSIS flight date and segment assigned to the analyzed radargrams.
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