Spatial distribution of snow in Antarctica and other glacier studies using ground-penetrating radar

Sammanfattning: The overall aim of this thesis is to develop and exemplify the use of ground-penetrating radar (GPR) within the field of glaciology. The main focus is on the spatial distribution of snow in Dronning Maud Land, East Antarctica. GPR soundings of shallow snow stratigraphy were made along two continuous profiles, 800 and 1000 km long, extending from the ice shelves to the high altitude plateau. Large local and regional spatial variations in net snow accumulation were observed. The complex accumulation pattern can be explained by the ice sheet surface topography and the distribution of air pressure systems and cyclone tracks. On ice shelves the spatial variability is less than 10%, in grounded coastal areas it ranges between 20-40% and on the high altitude plateau it ranges up to 20%. In areas subjected to intense wind erosion it often exceeds 50%. These values may serve as estimates of the spatial representativity of point measurements, such as firn and ice cores. The generally high variability in accumulation rates demonstrates that the spatial representativity of point measurements must be taken into consideration in studies of snow accumulation. It is shown that GPR can be used to quantify the degree to which the accumulation rate obtained at individual coring sites over- or underestimates the local average. Furthermore, a comparison between the figures for snow accumulation calculated by the parameterisations used in two numerical ice sheet models and the results of the GPR measurements shows that the models clearly overestimate the accumulation rates in the coastal region (elevations below 2000 m). The model parameterisations of snow accumulation were improved and adapted to regional conditions by fitting them to GPR data, and the new, fitted model parameterisations explain ~45% of the variations observed. Complemented by firn core studies, GPR constitutes a powerful tool to determine net accumulation rates along profiles made over vast distances.In addition, this thesis contains two GPR case studies, in which glaciers in northern Sweden were investigated from two view points, the potential of finding paleoclimatic signals preserved in the ice, and the development of glacial cirques. Both ice thickness and the thermal regimes of three glaciers were studied, and the results are discussed in the context of the Quaternary climates. It is suggested that the optimal place in Scandinavia to search for glacier ice that contains paleoclimatic signals is in the eastern part of the Scandinavian mountain range, where the climate is relatively dry and the glacier mass turnover is low. It is also concluded that glacial cirques are in general not good proxy data for climatic reconstructions, since the climatic conditions required for the excavation of glacial cirques are not well understood.