Greenland and Antarctica are both glaciers that drain ice sheets that often flow into the ocean resulting in near-vertical cliffs. Calving events happen when chunks of the ice break off as the glacier flows into the sea. When the ocean melts the front of the ice, the calving occurs even more as the ice cliff above falls. According to a new study, slumping is another method of calving. Much larger chunks of ice could be broken off at a quicker rate by this process.
A helicopter ride over Helheim and Jakobshavn glaciers o the eastern coast of Greenland spurred the ice-cliff research. Helheim ends in near-vertical ice-cliffs reaching 30-stories high (100 meters) abruptly in the ocean. Scientists saw some crevasses on the flight which are large cracks on the ice’s top that marched towards the glacier’s end.
Tall ice cliffs might trigger big calving events and raise sea level
The co-author of the new paper in Geology, Richard Alley said that “geologists have spent decades — centuries — worrying about slumps.” When a mass of rock or sediment loses some of its strength, a slump occurs because it breaks away from its neighboring land and a slope slides down. Steep scarps typically mark slumps as a block of material moved downslope follows where the material broke away.
The research team noted, according to Alley that Helheim glacier typically has that kind of features and they were wondering if the same fate can be suffered by ice as well. “You’ve got a crevasse that serves as a head scarp and then you’ve got the stresses [within the ice] maximized down at the water level,” he says.
The team monitored the Helheim glacier to test if slumping occurs on ice cliffs when calving happens. To do so, they used real-aperture terrestrial radar interferometry. They observed that just before an initial slump an ice-flow acceleration happens is then followed by full ice-thickness calving of the glacier