Controls on water storage and drainage in crevasses on the Greenland Ice Sheet

Abstract

Surface crevasses on the Greenland Ice Sheet (GrIS) transfer nearly half of all the ice sheet's meltwater to the bed, yet when, where, and how this occurs is poorly understood. We use large-scale satellite analysis and uncrewed aerial vehicle (UAV) surveys to assess the spatial variability of meltwater ponding in crevasses across a fast-flowing sector of the western GrIS. Between 2017 and 2019 an average of a quarter of crevasse fields ponded, in roughly the same area every year. However, the locations of such ponding cannot be explained in the same way as supraglacial lakes, which collect in surface basins. Instead, we find that ponded crevasses exist in regions of compressive surface stress. We suggest that this is because compressive regimes close pathways that elsewhere allow crevasses to drain into the wider surface hydrological system. Using UAV surveys, we show that these ponded crevasses instead drain rapidly to the bed by hydrofracture. Differing drainage processes in regions of compressive and extensional regimes may have distinct consequences for subglacial drainage and the heating of the ice sheet due to energy release during meltwater refreezing.

Recognition of crevasses with high‐resolution digital elevation models: Application of geomorphometric modeling and texture analysis

“…Remote sensing approaches include analysis of data from airborne ground-penetrating radars (Dellaney & Arcone, 1995;Thompson et al, 2020), airborne and satellite imagery obtained in different spectral bands (Chudley et al, 2020;Colgan et al, 2016;Glasser & Scambos, 2008;Holt, Glasser, & Quincey, 2013;Thompson et al, 2020), and satellite laser altimetry (Liu et al, 2014). However, relatively low resolution of data, low promptness, dependence on weather conditions (e.g., cloudiness), and relatively high cost are the main disadvantages of this approach.…”