A team of researchers from Cambridge University used drones to show how meltwater expanded a lake until it came in contact with a fracture that formed the previous year.
The lake on the surface of the Greenland Ice Sheet partially drained, shedding light on a key process for delivering water to the base of the ice sheet.
The world's second-largest ice sheet, and the single largest contributor to global sea-level rise, is potentially becoming unstable because of fractures developing in response to faster ice flow and more meltwater forming on its surface.