Physical and optical properties of snow covering Arctic tundra on Svalbard

Snow thickness, duration of snow coverage and amount of ice coveringthe soil are crucial for the development of biota in the Arctic tundra environment. The snow thickness and optical properties control theamount of Photosynthetically Active Radiation (PAR) that is available for vegetation. A late snow cover may prevent birds from nesting onthe ground. Furthermore, ice at the snow/soil interface can be an obstacle for grazing of Svalbard reindeer and affect the microfauna population. Snow and ice thickness, and the physical and optical properties of snow covering Arctic tundra were measured on the Broggerhalvoya peninsula on western Svalbard in spring of 1997. Additionally, thicknesses of ground-covering ice were measured in spring of 1998. The initial maximum thickness of snow in the observed areas varied from 0.4 to 0.9 m. The snow around Ny-Alesund began to disappear by the beginning of June, with the entire snow pack disappearing within 2-3 weeks. At the bottom of the snow pack, there was a soil-covering ice layer between 0.05 and 0.1 m thick. We obtained radiation and reflectanceparameters (spectral albedo, attenuation of PAR and global radiation) as well as physical properties of snow (e.g. temperature and density) over six weeks from early May to late June. Electrolytic conductivity of melted snow samples from snow pits shows clearly different conductivity for different stratigraphic sections within the snow pack in early June. Later on, these contrasts disappeared as internal ice layers melted and the snow pack underwent percolation. The albedo maximum before melt onset exceeded 0.9, whereas in the later phase of melting snow surfaces exhibited significantly lower albedo due to metamorphosis, thinning, and blackening by soil-particle contamination. However, even an apparently clean' snow surface had about 30% lower albedo in mid-June than in mid-May. Observations from under-snow PAR measurements are verified using a physically based radiative transfer model. [ABSTRACT FROM AUTHOR]