Controlling Factors on the Future Distribution of Supraglacial-lakes on the Greenland Ice Sheet

Supraglacial-lakes (SGL) are considered a key element of the hydrological system of the Greenland Ice Sheet (GrIS). Their presence reduces the surface albedo and facilitates hydrological connectivity between the supraglacial and subglacial drainage systems through hydrofracture, which affects ice flow speed, warms the ice and influences the magnitude and timing of freshwater delivery to the oceans. SGLs are widespread on the GrIS and expected to spread inland during the 21st century due to atmospheric warming. However, less is known about their precise future distribution and volume, while underlying controls are poorly constrained. Here, we present an ice sheet-wide survey of potential SGL locations, derived from digital elevation models. This was used in combination with SGL volume estimations derived from MODIS imagery and Modèle Atmosphérique Régional (MAR) surface mass balance outputs to estimate and analyse the distribution of SGLs during the 21st century. The transfer of bedrock undulations to the ice surface, which is assumed to control the distribution of surface depressions and thus SGLs, was tested by comparing the wavelength spectra of bedrock and ice surface undulations with ice thickness and the basal slip ratio. Our results demonstrate: (1) that the distribution of ice surface depressions is controlled by basal topography and ice dynamics; (2) the increase in SGL volume during the 21st century is predicted to be significant and spatially heterogeneous; (3) the largest increase is expected in the north-eastern sector of the GrIS whereas in west Greenland, where the most SGLs are currently observed, SGL expansion will be relatively modest.