The deterioration of freshwater ice due to radiation decay

Abstract

This paper reports on the processes governing the transfer of solar radiation energy to river-ice covers, the effects of snow-cover properties on transmittance and reflectance and the nature of shortwave radiation absorption in ice leading to intergranular melt. The influence of this melt on ice strength is illustrated using previously obtained borehole jack indentation data and concomitant determinations of porosity. The indentation data are analyzed using a plastic yield approach to estimate the uniaxial compression strength for ice idealized as a Tresca material. The analysis reveals that the ultimate platen-indentation-pressure to uniaxial-compressive-strength ratio is approximately 5.7; agreeing closely with available borehole jack and uniaxial compression data for columnar grained ice at 0°C. Available data describing the strength reductions associated with intergranular melt are reviewed. They show good correspondence with those resulting from existing theoretical strength-porosity models. The utility of the borehole jack for field-portable mechanical testing of ice strength is illustrated with respect to sampling in highly variable decaying ice covers. Further research should address the mechanisms of intergrannular melt, in particular, the specific geometry and distribution of the melt and its effect on the capacity of the ice cover to resist downstream forcing.