When a huge block of ice broke from the Aymery Ice Shelf in East Antarctica in 2019, scientists expected calving, but did not know exactly where it would happen. Now satellites will help scientists measure the depth and shape of cracks in the ice shelf to better predict when and where calving will occur.
Ice calving, also known as glacier calving or iceberg calving, is the breaking off of chunks of ice from the edge of a glacier, a form of ice ablation or ice breaking. In other words, ice calving is the sudden release and separation of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse.
Ice shelves make up almost 75% of the Antarctic coastline. They hold back the larger glaciers on land. If the ice shelves collapse and the Antarctic glaciers fall or melt into the ocean, the sea level will rise by 60 meters.
When scientists try to predict the future contribution of Antarctica to sea level rise, the most uncertain factor in modeling is the stability of the ice shelf. Today there is no easy way to map the depth of glacier cracks on a regional scale. However, scientists have found that satellite data can capture the depth and morphology of the surface of the ice shelf’s cracks and thus allow this information to be continuously monitored over a wide range.
Scientists studied high-resolution data collected by the ICESat-2 satellite over the Aymery Ice Shelf between October 2018 and November 2019. Laser pulses from a satellite are directed towards the surface of the Earth and use reflected photons to determine the height of the surface. Unlike other satellites, ICESat-2 resolution allows it to see finer fractures and their morphology.
Scientists processed the satellite data using an algorithm. It identifies surface ice depressions to locate and characterize fractures. Let us recall that the depression of the snow line is its decrease due to climatic changes favorable for maintaining the balance of the mass of glaciers. Since mass balance is a direct function of accumulation and ablation, variations in the height of the snow line reflect the cumulative effects of changes in temperature and precipitation.
The research results are published in the journal Remote Sensing of Environment.
Researchers have identified three types of cracks: U-shaped; parabolic and V-shaped, up to 40 meters deep in the ice shelf. They also realized that surface information gives an idea of what is happening hundreds of meters below the surface of the ice.
Basal fissure morphology — the shape and size of fissures at the base of an ice shelf — is proportional to depressions on the surface.