Propagation of an active rift in the Ross Ice Shelf, Antarctica

Understanding propagation behavior of large rifts in ice shelves is important for understanding shelf adjustments to change and for parameterizing calving in models. We use satellite images and a comparison of two epochs of the MOA (MODIS Mosaic of Antarctica) to study the propagation of an active rift within a rift system near the western front of the Ross Ice Shelf. Between 1992 and 2012, the most upstream rift within the rift system propagated over 90 km. We observe large jumps in propagation, with average propagation rates exceeding 30-40 m/day over a period of measurement compared to periods of slower growth at 1-10 m/day. Two types of episodic propagation were observed, one driven by the orientation of the fracture plane relative to the stress field and the other driven by increasing fracture length. We use a numerical model to simulate recent propagation behavior of test fractures within a stress field. We investigate temporal connections between dynamic adjustments along flow of fractures and shelf-front geometry following the calving of B15 in early 2000. Our observations indicate longitudinal displacement of fractures following impact events at the shelf front. These events may have displaced the eastern tip of the active rift into a more favorable orientation relative to the stress field. Our observations and model simulations support findings on the Ross and other large ice shelves regarding the importance of lateral propagation and the roles of transverse compressive stress, fracture length, and material inhomogeneity in controlling propagation behavior.