Revealing ice shelf fracture morphology using ICESat-2 measurements

Abstract:

Fractures are important structural features that affect the stress condition and stability of ice shelves. Monitoring changes in fracture morphology is critical for understanding the processes driving ice shelf retreat. The dense and high-resolution surface elevation measurements collected by the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) provide an excellent opportunity for studying the vertical structure of fractures. Here we developed a novel automated algorithm based on a hierarchical object-oriented approach to delineate and characterize the distribution of fractures and their vertical morphology using ICESat-2 along-track measurements. We successfully applied this method to the ICESat-2 L3A Land Ice Height (ATL06) data over the Amery Ice Shelf in East Antarctica, and retrieved vertical structural information of two major fracture fields (Swarm A and Swarm B) on the downstream portion of the ice shelf, providing a first-time estimate of ice shelf vertical fracture morphology on a broad scale. The detected fracture locations match well with visible fractures in Landsat-8 imagery, and the fracture edges are well captured from the ATL06 data. We analyzed the morphological characteristics of the fractures along with the magnitudes and directions of the principal strain rates to understand mechanisms of fracture formation. We found that the fracture depth appears to be an important factor determining the locations where new sub-fractures are likely to initiate. We anticipate that further application of the proposed method can produce important insights regarding ice-shelf vulnerability by allowing vertical structural information from ICESat-2 measurements to be integrated with the horizontal structure of fractures from satellite imagery.