National Geographic : 2010 Jun
of the spectrum, leaving the blue to be re ected. Depending on the tricks sunlight plays, blue ice can also appear white, as it does in many places around us. e camp stands beside a vast meltwater lake. Tedesco and Steiner study its depth, planning to compare their information with satellite read- ings of the depths of Greenland's supraglacial lakes. Each morning they launch a small cra to collect data. e vessel is a bait boat retro tted with remote control, sonar, a laptop-driven spec- trometer, GPS, a thermometer, and an under- water camera. Greenland's meltwater lakes are prone to drain- ing unexpectedly and quickly (thus Tedesco's unmanned research vessel). Balog once watched a lake drain overnight. e bottom of a moulin--- a vertical sha in the ice---opened up and sucked the entire lake into oblivion. In 2006 a team led by glaciologists from Woods Hole Oceanographic In a pothole burned into the ice by cryoconite, buried air and gas from bacteria and algae bubbled to the surface, where a midnight freeze trapped them.