Subtle height change reveals melt water movement around and under glacial ice, an example from northern Ellesmere Island, Canada

Abstract Using ICESat-2 and ArcticDEM strips we track height change in a glacial basin in northern Ellesmere Island Canada. The surface topography dips towards the middle of the basin and ArcticDEM differences show a 1–3 m increase in 2020 summer surface height over an area of 8–10 km 2 . ICESat-2 heights confirm that each melt season (2019–2024), the height change of melt water at the basin edge matches that over ice in the basin middle. The summer height increase happens at the same time as an upstream drop in surface elevation suggesting yearly episodic subglacial water movement from upstream to a downstream subglacial lake. Melt water drainage occurs in the fall to a particular elevation and apparently follows a path at the northern edge of the basin. These data illustrate subglacial melt water movement both spatially and temporally in rarely obtained detail and are consistent with data from two NASA IceBridge passes.