A simulation model of river ice cover thermodynamics

Abstract

A model of ice cover thermodynamics was used to simulate ice growth and decay along the international section of the St. Lawrence River for winter 1980-1981. This winter was chosen because of the exceptionally cold weather in December and January, and because of the abnormally warm air temperatures during the second half of February. At the air-ice interface, the model computes the surface energy transfer components and a resulting equilibrium surface temperature. At the lower boundary, an empirical algorith simulates the turbulent transfer of heat from the water. Within the ice, and implicit numerical solution to the general heat diffusion equation is used, permitting stable solutions for a variety of time intervals and node distances within the model. The model was used to simulate ice growth and decay at five sites characterized by their flow velocity, the date of ice-cover formation, and the water temperature regime. The model adequately represented growth rates at all five sites, but produced decay rates slower than those observed. Simulated breakup was 1-7 days later than observed, presumably because mechanical weakening of the ice was not taken into consideration. During the growth period, the model is far more sensitive to the values assigned to ice properties than it is to the error range in the meteorological variables. During the breakup period, the most sensitive boundary variable is water temperature.