The temperature dependence of the effective elastic shear modulus of snow

In order to determine the temperature dependence of the effective elastic properties of snow, dynamic torsional shear experiments at a frequency of 1 Hz were performed in a cold laboratory with a stress-controlled rheometer. Two types of natural snow samples of small rounded or faceted grains with partly decomposed and fragmented particles (mean size 0.4–0.5 mm) with densities in the range of 220–250 kg m−3 were tested. Results indicate that snow is a rheologically simple material, so that the data can be normalized for analysis. The mean effective elastic shear modulus G′ at −10 °C was found to be about 0.75 MPa for the density range and snow type tested. The modulus decreases with increasing temperature following an Arrhenius relation below −6 °C with an apparent activation energy of about 0.2 eV. Between −6 °C and the melting point, the decrease is much stronger showing that the modulus is highly temperature-sensitive in the range of interest for snow slab stability evaluation. An empirical relation is fitted to the data over the whole range of temperatures to provide a single smooth relation for engineering applications.