Water temperature decay under breakup ice jams

The water temperature decay under ice jams that form during the breakup of the river ice cover is evaluated using different data sets from several Canadian rivers. In all cases, the water temperature varies with downstream distance in negative exponential fashion, as indicated by a simplified, one-dimensional, formulation of heat conservation in a river. The corresponding heat transfer coefficients and derivative dimensionless quantities are very high relative to the values that would be expected by extrapolation of existing formulae for turbulent convection in rough pipes. It is suggested that these high heat transfer rates are due to two factors, both characteristic of breakup ice jams: the extreme roughness of the jam underside, and the flow through the voids of the accumulation of ice blocks that comprise the jam.