. The Canadian field-naturalist. 26 The Canadian Field-Naturalist Vol. 101 snowmobile runs was strongly correlated with its thickness. The thinner snow thickness was associated with higher snow specific gravities. Since values obtained between and were within the critical snow densities reported by Anderson and Benson (1963), maximum mechanical compaction had occurred after four runs and had therefore begun the metamorphic crystallization toward ice forma- tion. Snowmobile speed had an influence on snow density (Figure 3). After one traverse at slow speed (8 km/h) the density was 0
. The Canadian field-naturalist. 26 The Canadian Field-Naturalist Vol. 101 snowmobile runs was strongly correlated with its thickness. The thinner snow thickness was associated with higher snow specific gravities. Since values obtained between and were within the critical snow densities reported by Anderson and Benson (1963), maximum mechanical compaction had occurred after four runs and had therefore begun the metamorphic crystallization toward ice forma- tion. Snowmobile speed had an influence on snow density (Figure 3). After one traverse at slow speed (8 km/h) the density was as compared to at a higher speed (48 km/ h). This was attributed to the fact that fast packing expelled the snow away and the increase of snow density was then accentuated. Snow densities between the two treatments reached equilibrium after seven runs. From the data reported in Table I, snow compacted by one pass and by four passes transmitted heat from the soil below at a rate of times and 5 times that of undisturbed snow, respectively. For 1973-74 at Lennoxville, the average compacted snow thermal conductivity (X) within the whole profile was significantly higher than that of undisturbed snow (Table 2). There was a much larger increase in thermal conductivity for the untreated snow between 4 January and 16 March. Snow density doubled in o S 5 o z Tab^e L Effect of the number of snowmobile runs on snow density (g-cc~') at Lennoxville. (Mean of three replicates for three different thicknesses).. FAST SPEED SLOW SPEED Thicl cness Number 9 cm 18 cm 35 cm of runs (-4°C)* (-5°C)* (0°C)* Mean 0 ^ 1 ^* 2 ^ 3 '' 4 ^ 5 '' Mean'' ^ ^ 2 3 4 5 SNOWMOBILE RUNS Figure 3. Effect of the snowmobile speed (slow and fast) and number of runs on snow density. *Instantaneous air
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