A large stream of meltwater (about 5 to 10 meters in width) emerges from an upstream supraglacial lake in the Greenlandic ice on July, 21 2012, as seen from a helicopter by researcher Marco Tedesco. The darker shapes are minor streams covered by cryoconite (a mix of dust particles, soot, meteorite dust and organic material) which covers the ice sheet. Cracks cutting through the streams are visible. Along these cracks water can flow through, enlarging them and, eventually, generating moulins that can deliver meltwater through the ice. Photo credit: M. Tedesco/CCNY