Fig. 2. Radar-derived characterization of the 2012 melt layer.

a Horizontal connectivity of the 2012 melt layer, shown by color shading along flight transects. A score of 1 or greater indicates a perfectly connected layer, with dark colors indicating high connectivity. b Minimum layer density consistent with observed radar reflectivities, shown in color shading along flight transects. Dark green dots indicate high-density regions. c Radar-inferred layer prominence, shown in color shading along flight transects. Light yellow regions indicate high layer prominence. Dark blue polygons show firn aquifer extent⁴², light blue polygons the ice slab extent⁹, and the dashed black line the 1987–2007 average zero melt day contour derived from passive microwave data⁶⁴. Surface elevation contours (200 m interval) are shown in gray. The dashed black boxes in c show the regions referred to as northwest and southern Greenland in the climatological analysis and Fig. 3.