Subsurface, surface and atmospheric processes in cold regions hydrology

The storage and modulated release of water from seasonal snowcover and perennial ice are major components of hydrological systems at high latitudes and in many mountainous regions throughout the world. In these regions, snow and ice control soil moisture, streamflow, lake levels and the development and stability of terrestrial and aquatic ecosystems. Vegetation influences the accumulation and melt of snow by intercepting falling snow, trapping wind-blown snow and sheltering underlying snow from wind and solar radiation but increasing the incidence of thermal radiation (Pomeroy et al., 2006; Stahli and Gustafsson, 2006). Snow, in turn, influences vegetation distributions by insulating underlying vegetation from low temperatures and releasing water and stored nutrients on melt (Jones, 1999). Infiltration and runoff of melt water are strongly controlled by frozen soils and permafrost, the distributions of which are influenced by topography, snow insulation and vegetation. Climate warming and associated precipitation changes are expected to lead to decreased winter snow accumulation and earlier snowmelt in many, although not all, regions that currently have seasonal snow cover (Adam et al., 2009). In certain Arctic environments, lakes are believed to be sensitive to changes in climate, with some lakes disappearing slowly and others in areas with icerich permafrost prone to rapid or catastrophic drainage (Marsh et al., 2009). Predicting the impacts of climate change and natural climate variability on cold regions hydrology is complicated by the low resolution of climate models compared with the high spatial variability of mountain and tundra landscapes, strong feedbacks associated with transitions between snow-covered and snow-free surface states, interactions between physical, chemical and biological processes, and the delicate balance between snow and rain in precipitation near the zero-degree isotherm.