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)
Tag: glacier
Iceberg Calving
When sections of glaciers break off to create icebergs, scientists call it calving. Usually large sections of ice will break off and immediately capsize, with an energy equivalent to up to 40 kilotons of TNT. These large events are sufficient to cause measurable seismic signals. How hydrodynamic forces impact the contact and pressure forces between the calving iceberg and the glacier are still being researched, though recent laboratory experiments and numerical models suggest that hydrodynamics substantially increase these forces. The video above shows one of the largest calving events ever caught on camera, and the scale of the process is just stunning. (Video credit: Chasing Ice; additional information from J. C. Burton et al. 2012; submitted by jshoer)