Analysis of winter heat flow in an ice-covered Arctic stream

The growth of river ice during the winter of 1977–1978 is modelled for Caribou Creek, an Arctic stream near Inuvik, Northwest Territories. In midwinter, a period of extensive river icing activity, the stream flows over shallow sections of channel via narrow conduits beneath the ice cover. These relatively high-velocity sections are shown to be concentrations of locally generated friction and convected streambed heat. A nonuniform flow model is used to represent friction generation and heat transfer to ice in both shallow and deep sections of the channel. Bed heat flux is simulated from thermal measurements in the unfrozen ground beneath the channel. A relationship between flow width at shallow sections and recorded air temperature, inferred from streambed temperature recordings, is reproduced by simulating the effect of warm and cold spells on flow conduit dimensions. The low air-temperature threshold for increase in conduit cross section, −20 °C, is shown to result from heat transfer rates which offset the reduced heat loss from an insulating snow cover. Key words: ice formation, streamflow, Arctic regions, thermal analysis.