Supraglacial lakes–ephemeral bodies of water that form atop glaciers–can form and empty in a matter of hours. The lakes typically empty either by overflowing their banks or by discharging through a moulin, a well-like crevasse in the ice. When this happens, the water from the lake drains into the bed beneath the glacier, acting like a lubricant between the ice and the land and thus accelerating the glacier’s movement. The team in the video studied the draining of two different lakes, one which voided within 2 hours and the other slower one which drained over 45 hours. The faster of the two accelerated the glacier’s movement to a maximum of 1600 meters/year, far higher than its baseline velocity of 90-100 meters/year. For more see Laboratory Equipment and this post on ice flow. (Video credit: City College of New York)
Lakes Upon Glaciers
