Surface Expressions of Subsurface Water Storage in Northwest Greenland

Surface runoff is currently the dominant form of mass loss from the Greenland ice sheet. In order to understand its effect on global sea level rise, both in terms of magnitude and timing, we must account for the possibility that meltwater can be stored in the near-surface. Research conducted in Northwest Greenland has revealed a combination of ice slabs, buried lakes, and aquifers in the deep percolation and wet snow zones. Ice penetrating radar data also shows evidence of meltwater infiltration into firn space below the ice slabs, where liquid water is stored and then partially to fully refreezes into buried ice blobs. In order to understand how much and how often surface meltwater runs off to lower elevations or drains to the bed, we need a better understanding of how these subsurface features form, how long they persist, their interactions with one another, and how they may interact with the supraglacial and subglacial systems. Ice penetrating radar has been used to study these subsurface features, but the infrequent data collection and large spacing between flight lines makes it difficult to assess how common these features are and how they change with time. We compare ArcticDEM and Landsat data with ice penetrating radar observations between 2011 and 2017 to find and catalogue unique surface expressions of buried supraglacial lakes and ice blobs and their connections to supraglacial hydrology, as well as determine if their surface expressions can allow us to track their size, water volume, and/or refreezing rate. At this point, we have identified that buried lakes are associated with flattened basins with pressure ridges along their perimeters in DEMs. We have also found evidence for cyclic drainage and refilling of many multi-year buried lakes, and analyze Sentinel-1 radar data to constrain the timing of these drainages. Our results thus far suggest that in some cases surface remote sensing data can be used to track subsurface water storage and dynamics, improving our understanding of the water budget in NW Greenland.