When a glacier has hundreds of bundles of (icy) joy

Argentina's Perito Moreno glacier calving (Sean Munson/Flickr)
Argentina’s Perito Moreno glacier calving (Sean Munson/Flickr)

On July 20, 2010, researchers from Swansea University in Wales were setting up equipment near Helheim Glacier in Greenland when they happened to witness a 4-kilometer crack in the ice forming that extended from one side to the other. Quickly, they set up a time-lapse camera to record one of the largest glacier calving events ever filmed.  They knew that they glacier advanced rapidly, achieving speeds as high as 30 meters per day, but they had not expected a sudden event.

As the split in the ice grew, it thrust the front part of the glacier into the ocean with great force. It rotated and flipped over into the ocean in the seconds before the glacier front fully broke off and floated away. Once the separation was complete, the ocean was filled so thickly with chunks of ice it was impossible to see the water.

This film and other data form the basis of a new study that was published last month in the journal Nature Geoscience, “Buoyant flexure and basal crevassing in dynamic mass loss at Helheim Glacier.” The researchers, Timothy D. James, Tavi Murray, Nick Selmes, Kilian Scharrer and Martin O’Leary, found the ocean itself is breaking up the glaciers. In plainer English, when a glacier reaches the sea, the front will float, bending the ice and creating crevasses at the bottom,  causing the front of the glacier to snap off. These crevasses are much harder to detect that the ones on the surface, so their role had not previously been understood.  The bending of the surface was a second discovery. The team used a stereo camera to record subtle elevation changes over two summers, capturing details that previous cruder calving studies had missed.

Scientists had long known that when a glacier calves, it breaks off into the ocean. They knew as well that this ice leads to sea level rise, a seemingly straightforward process. And now they have a fuller understanding of the hows and whys of glacier calving. This knowledge is important, because most of the Greenland’s glacial ice loss over the next 200 years is expected to be from such breaking off of ice into the ocean. Armed with a clearer grasp of the calving process,  researchers will be better able to  produce better models of ice dynamics and sea level rise—of importance to the billions who live in coastal areas, far from Helheim but intimately connected to it.