Numerical simulation of river ice cover formation and consolidation at freeze-up

Abstract

River ice researchers have noted the strong dependence of ice cover formation during freeze-up on the air temperature, which influences the ability of the cover to grow a surface ice crust which can quickly add significant resistance to mechanical thickening. However, this link between thermal and dynamic ice processes is often absent in numerical models. In this paper, a new formulation is implemented in a two-dimensional river ice model, which considers the growth of a surface ice crust in a forming ice cover and the associated increase in resistance to consolidation. The crust is permitted to grow based on a critical ice velocity criterion, and the compressive strength of the crust is specified by the user. The model simulates the failure and attendant consolidation of the ice cover in cases where the rate of thermal strengthening is exceeded by the rate of increase of applied forces. Simulations performed on an idealized channel demonstrate the effect of changing the air temperature and crust strength on ice cover formation. The new formulations better simulate the physical processes occurring at freeze-up, increasing the robustness of the model and its applicability to freeze-up scenarios, especially on steeper sloped channels which often exhibit secondary consolidations of the ice cover.