Abstract
Abstract. In this study, we present the winter time surface energy balance at a polygonal tundra site in northern Siberia based on independent measurements of the net radiation, the sensible heat flux and the ground heat flux from two winter seasons. The latent heat flux is inferred from measurements of the atmospheric turbulence characteristics and a model approach. The long-wave radiation is found to be the dominant factor in the surface energy balance. The radiative losses are balanced to about 60 % by the ground heat flux and almost 40 % by the sensible heat fluxes, whereas the contribution of the latent heat flux is small. The main controlling factors of the surface energy budget are the snow cover, the cloudiness and the soil temperature gradient. Large spatial differences in the surface energy balance are observed between tundra soils and a small pond. The ground heat flux released at a freezing pond is by a factor of two higher compared to the freezing soil, whereas large differences in net radiation between the pond and soil are only observed at the end of the winter period. Differences in the surface energy balance between the two winter seasons are found to be related to differences in snow depth and cloud cover which strongly affect the temperature evolution and the freeze-up at the investigated pond.
Highlights
In scenarios of the future climate obtained from current stateof-the-art General Circulation Models (GCMs), the Arctic experiences a much more pronounced warming compared to the global average
The net radiation during the winter period is mainly determined by the long-wave radiation, as it mostly falls within the polar night, while the high albedo of the snow cover limits the role of the short-wave radiation at the beginning and the end of the period (Table 2)
Our observations suggest that the net radiation is attenuated during the high summer season by the presence of clouds, while the radiative losses are reduced during the entire winter period
Summary
In scenarios of the future climate obtained from current stateof-the-art General Circulation Models (GCMs), the Arctic experiences a much more pronounced warming compared to the global average. The strongest warming is expected to occur during winter which is already confirmed in current climate observations (Moritz et al, 2002; Johannessen et al., 2004). This warming trend is already reflected in widely increasing soil temperatures in arctic land areas underlain by permafrost In situ observations exist for a few locations and restricted time periods, but more such datasets are needed.” (ACIA, 2004) The latter is especially true for field datasets on the heat and moisture turnover at the land-atmosphere interface, which must be parameterized in an adequate way in climate models.
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