Automatic monitoring of the effective thermal conductivity of snow in a low-Arctic shrub tundra

作者：Domine F^*; Barrere M; Sarrazin D; Morin S; Arnaud L

来源：Cryosphere, 2015, 9(3): 1265-1276.

DOI：10.5194/tc-9-1265-2015

The effective thermal conductivity of snow, k(eff), is a critical variable which determines the temperature gradient in the snowpack and heat exchanges between the ground and the atmosphere through the snow. Its accurate knowledge is therefore required to simulate snow metamorphism, the ground thermal regime, permafrost stability, nutrient recycling and vegetation growth. Yet, few data are available on the seasonal evolution of snow thermal conductivity in the Arctic. We have deployed heated needle probes on low-Arctic shrub tundra near Umiujaq, Quebec, (N56 degrees 34'; W76 degrees 29') and monitored automatically the evolution of k(eff) for two consecutive winters, 2012-2013 and 2013-2014, at four heights in the snowpack. Shrubs are 20 cm high dwarf birch. Here, we develop an algorithm for the automatic determination of k(eff) from the heating curves and obtain 404 k(eff) values. We evaluate possible errors and biases associated with the use of the heated needles. The time evolution of k(eff) is very different for both winters. This is explained by comparing the meteorological conditions in both winters, which induced different conditions for snow metamorphism. In particular, important melting events in the second year increased snow hardness, impeding subsequent densification and increase in thermal conductivity. We conclude that shrubs have very important impacts on snow physical evolution: (1) shrubs absorb light and facilitate snow melt under intense radiation; (2) the dense twig network of dwarf birch prevent snow compaction, and therefore k(eff) increase; ( 3) the low density depth hoar that forms within shrubs collapsed in late winter, leaving a void that was not filled by snow.

• 出版日期2015