Glacier area and length changes in Norway from repeat inventories

Abstract. In this study, we assess glacier area and length changes in mainland Norway from repeat Landsat TM/ETM+-derived inventories and digitized topographic maps. The multi-temporal glacier inventory consists of glacier outlines from three time ranges: 1947 to 1985 (GI_n50), 1988 to 1997 (GI₁₉₉₀), and 1999 to 2006 (GI₂₀₀₀). For the northernmost regions, we include an additional inventory (GI₁₉₀₀) based on historic maps surveyed between 1895 and 1907. Area and length changes are assessed per glacier unit, 36 subregions, and for three main parts of Norway: southern, central, and northern. The results show a decrease in the glacierized area from 2994 km² in GI_n50 to 2668 km² in GI₂₀₀₀ (total 2722 glacier units), corresponding to an area reduction of −326 km², or −11% of the initial GI_n50 area. The average length change for the full epoch (within GI_n50 and GI₂₀₀₀) is −240 m. Overall, the comparison reveals both area and length reductions as general patterns, even though some glaciers have advanced. The three northernmost subregions show the highest retreat rates, whereas the central part of Norway shows the lowest change rates. Glacier area and length changes indicate that glaciers in maritime areas in southern Norway have retreated more than glaciers in the interior, and glaciers in the north have retreated more than southern glaciers. These observed spatial trends in glacier change are related to a combination of several factors such as glacier geometry, elevation, and continentality, especially in southern Norway.