Radar Surveys on Scandinavian Glaciers, in Search of Useful Climate Archives

ABSTRACT

Ice cores obtained from cold glaciers are known to contain detailed archives on past climates. So far, no such data-set has been retrieved from Scandinavia, in part because most Scandinavian glaciers are largely of a temperate type, thus having a less well preserved climatic signal. However, within the more continental parts of the Scandinavian mountain range, glaciers often have a substantial cold surface layer in the ablation area. Past climate variations may be reconstructed from studies of crystallography and stratigraphy of ice from the cold surface layer. The thicknesses of such cold layers at two closely situated sites in northern Sweden have been mapped by a ground based high resolution radar. The best results were obtained by using the frequency interval 700–900 MHz. The two investigated glaciers Storglaciären and Mårmaglaciären are situated 20 km from each other in an area with a strong east-west climatic gradient. The annual average air temperature is similar at the two sites, whilst the precipitation rate on Storglaciären is almost double that of Mårmaglaciären. The radar soundings show that Mårmaglaciären has a significantly thicker cold surface layer, 65 m on average compared with 30 m on Storglaciären. The difference is caused by less snow cover insulation from winter cold and less net ablation on Mårmaglaciären. The measured thicknesses of the cold surface layer therefore seem to correlate well with the degree of continentality at the sites. Radar sounding is a highly useful tool for locating glaciers containing a potential relatively well preserved climatic signal. Such glaciers may be found within the more continental parts of the Scandinavian mountain range.