High Basal Melt Rates and High Strain Rates Lead to More Fractured Ice

Abstract

Ice shelves limit the flux of grounded ice into the ocean by buttressing the discharge of land-based ice upstream. Ice shelf weakening and collapse can lead to decreased buttressing and observations increasingly show that some ice shelves have experienced increased melt and increased calving, with recent hypotheses suggesting that increased melt leads to increased fracturing. However, the specific processes that control this correlation are not yet understood, with mechanisms other than melt affecting fracturing. Here we use the topography of the ice shelf base from BedMachine to investigate how basal melting and ice deformation contribute to crevasse and melt channel formation and evolution on the Pine Island Ice Shelf in West Antarctica. We find that high basal melt rates and high first principal strain rates lead to substantial roughening of the ice shelf through a collection of features, including melt channels and crevasses. Critically, melt channels and crevasses are the deepest in all directions at locations where the highest rates of melting and straining occur simultaneously. This suggests that the combination of melt rates and strain rates work in tandem to excavate and seed the deepest melt channels and crevasses on ice shelves. These features then may form lines of weakness that transform into rifts and, ultimately, the detachment boundary for calving events. This implies that melt and fracture play an important role in controlling the dynamics of ice shelves.