Mechanisms of Surface Meltwater Ponding and Drainage on the Greenland Ice Sheet Revealed Using SkySat Imagery and Deep Learning

Surface meltwater impacts Greenland Ice Sheet mass balance indirectly by reducing albedo and promoting hydrofracture. However, fully understanding both processes requires accurate mapping of small-scale features such as ponds, channels, and moulins that govern meltwater formation and drainage. Here we investigate surface water dynamics at high spatial (∼1 m) and temporal resolution by applying deep learning to high-resolution imagery from the SkySat constellation. We develop a U-Net model that robustly classifies surface meltwater with higher accuracy than a conventional thresholding approach. Our mapping reveals that small water features (<0.015 km²) account for a substantial fraction of surface water area in the western Greenland Ice Sheet ablation zone, especially during May (67%) and August (38%). However, we find that seasonal variability in surface water area is primarily driven by the filling and draining of 12 large supraglacial lakes. The high spatial resolution of the SkySat imagery reveals that much of this variability can be attributed to the development of narrow supraglacial channels that facilitate the drainage of upstream lakes into a single downstream lake. When the downstream lake rapidly drains, we observe synchronous lake drainage across our study site between 13–16 June. This cascading drainage event explains how lakes drain even when they are situated in compressive ice flow regimes and provides an alternative mechanism for synchronous lake drainages typically attributed to transmission of stress perturbations. Our study demonstrates that deep learning applied to high-resolution satellite imagery can provide valuable insights into supraglacial hydrology.

Duke Scholars

Author Sarah Cooley Earth and Climate Sciences

Author Jonathan Ryan Earth and Climate Sciences