Significant change in the dynamics of tidewater glaciers after a calving event are mainly tied to a sudden loss of resistive stresses. This article investigates how such a stress perturbation affects the whole glacier upstream. Simulations (using Elmer/Ice) and perturbation theory revealed that calving events and subsequent terminus readvance produce quasi-periodic, sawtooth oscillations in stress that originate at the terminus and propagate upstream with speeds significantly exceeding ice velocities. In laterally resisted glaciers, these signals decay within an upstream distance equivalent to a few ice thicknesses. Terminus fluctuations caused by individual calving events tend to be much higher frequency than climate variations. Thus, individual calving events have little direct impact on the viscous delivery of ice to the terminus. This suggests that the primary mechanism by which calving events can trigger instability is by causing fluctuations in stress that weaken the ice and lead to additional calving and sustained terminus retreat. Our results further demonstrate a stronger response to calving events in simulations that include the full stress tensor, highlighting the importance of accounting for higher order stresses when developing calving parameterizations for tidewater glaciers.

Read more: Amundson, J., M. Truffer, and T. Zwinger, 2022. Tidewater glacier response to individual calving events. Journal of Glaciology, 1-10, doi:10.1017/jog.2022.26