Mélange controls on calving behavior at tidewater glaciers in a high-fidelity model of ice fracture

Abstract:

Calving is an important control on glacier mass balance and potential future sea level rise. Complex processes control the glacier stress and fracture state at the ice-ocean interface, making predictions of calving events extremely difficult without the aid of high-resolution information about critical environmental parameters. Mélange, the aggregation of sea-ice and icebergs sometimes found concentrated within fjords occupied by tidewater glaciers, is a natural product of glacier calving. At some fast-flowing tidewater glaciers, mélange has been shown to buttress glacial termini and suppress calving events. However, the influence of mélange on the frequency and size of calving events, and the corresponding influence of calving events on mélange state is not well understood. To understand these interactions, we use a three-dimensional discrete element model (HiDEM) to simulate glacier fracture at a high spatial resolution by allowing bonds between ice particles to break and deform given the fracture properties of ice. By explicitly simulating the fracture process, we can directly probe the effects of glacier geometry, local water level, and mélange buttressing on the likelihood and characteristics of calving events. In our simulations, we find that mélange regulates the production of icebergs by limiting the propagation of critical fractures and the prevention of iceberg overturning. Our results also indicate that mélange significantly alters the size and recurrence time distributions of calving catalogues. These findings provide a means of determining the influence of mélange in new high-resolution calving observations and can pave the way for future implementation of mélange evolution within large-scale ice sheet models.