2. Introduction
Approximately one-quarter of the unsheltered land in the northern hemisphere is permafrost. (Zhang et al.1999). As per many recent studies, these permafrost regions have experienced increase in soil temperature (Lemke et al. 2007; Osterkamp 2007; Frauenfeld and Zhang 2011). The increase in soil temperature results into increase in active layer thickness (ALT) which ultimately means degradation of permafrost. The presence of permafrost is highly critical to ensure water security in the northern parts of Canada as permafrost degradation can significantly alter the soil structure of the region and lead to drainage of water in lakes. (Hinzman et al. 2005). The permafrost thaw also has a positive feedback on global warming as most of the microbial decomposition occurs in the thawed layer and supplementary thawing of permafrost will further increase the rate of decomposition of the organic matter, resulting in the release of greenhouse gases such as carbon dioxide and methane (Zimov et al. 2006). In fact, MacDougall et al (2012) predicted that the greenhouse gas contribution by permafrost degradation could result into additional warming in the range of 0.23-0.27deg C during the twenty-first century.
Permafrost also influences soil moisture and this is evident as in most areas the presence of permafrost is coincided by saturated sub-surface conditions with a drier surface layer (Hinzmann et al. 1991). Woo and Marsh (1990) found that soil moisture at a continuous permafrost site is influenced by the water retention and transmission properties of frozen and thawed soil. Also, studies have shown that there is a strong relation between frost table depths and soil moisture distribution at subarctic locations (e.g. Carey and Woo, 2000; Hinkel and Nelson, 2003; Wright et al., 2009).
With the above literature review, it is important to understand what controls soil moisture and soil temperature in permafrost regions and to be able to simulate conditions as the climate warms. In this project, the main objective was therefore to compare soil moisture and soil temperature estimates from an Environment and Climate Change Canada operational model with observations from a location in discontinuous permafrost; with focus on freeze back and thaw periods.