Linking the effective thermal conductivity of snow to its shear strength and density

The effective thermal conductivity of snow, k eff , is a crucial climatic and environmental variable. Here, we test the intuition that k eff is linked to microstructural and mechanical properties by attempting to relate k eff to density ρ snow , and to shear strength σ measured with a handheld shear vane. We performed 106 combined measurements of k eff , ρ snow and σ in the Alps, Svalbard, Arctic Alaska, and near the North Pole, covering essentially all snow types. We find a good correlation between k eff and ρ snow which is not significantly different from that of Sturm et al. (1997). The correlation between k eff and a combination of σ and ρ snow is stronger than with density alone. We propose an equation linking k eff , (W m −1 K −1 ) ρ snow (kg m −3 ) and σ (Pa): k eff = 7.114 10 −5 ρ snow σ 0.333 + 2.367 10 −2 . This equation places constraints on the calculation of k eff , ρ snow and σ in avalanche warning models where σ is a key variable. For our samples, we calculate σ from measured values of k eff and ρ snow using our equation and compare the value to that predicted by the French MEPRA avalanche warning model, which uses density and grain type as input data. MEPRA and the prediction of σ based on k eff and ρ snow agree within 8%. MEPRA agrees with observations within 11%. Calculating σ from density only yields values 55% lower than measured, showing the interest of using additional data to predict σ .