Floating ice shelves off the western coast of Antarctica are breaking up at their margins, causing them to disengage from the bay walls where they attach to the coastline and retreat inland. This could cause the fracturing ice to be less capable of preventing grounded upstream ice from sliding into the sea. After studying Landsat satellite data taken of the Amundsen Sea Embayment taken from 1972 to 2011, researchers at the University of Texas examined found extensive changes in the ice shelves over time, including significant fracturing of the margins that bound the shelves. The Embayment is a huge hunk of ice that comprises one-third of the West Antarctic Ice Sheet.
“As a glacier goes afloat, becoming an ice shelf, its flow is resisted partly by the margins, which are the bay walls or the seams where two glaciers merge,” says Ginny Catania, a professor at the University of Texas and coauthor of the study, which was published in the Journal of Glaciology. “An accelerating glacier can tear away from its margins, creating rifts that negate the margins’ resistance to ice flow and causing additional acceleration.”
The video below shows a repeating cycle of the coastline (red line) moving seaward (to the left) and then turning around and moving inland as large ice masses break off. Simultaneously, the northern shear margin breaks up and retreats, thus creating the possibility of an increase of inland ice flow to the sea.