Norwegian mountain glaciers in the past, present and future

Documentation of glacier changes is a key element for reconstruction of past climate variability and early detection of global climate change. In this paper, records of Holocene glacier variations in different regions in Norway have been synthesised. During the period from approximately 8000 to 4000 cal. yr BP, most glaciers in Norway were completely melted away at least once due to high summer temperatures and/or reduced winter precipitation. Lichenometrically and historically dated moraines at Jostedalsbreen, in Jotunheimen, at Hardangerjøkulen, and at Folgefonna were used to extend records of glacier length variations back to their maximum position during the ‘Little Ice Age’. The timing of the maximum ‘Little Ice Age’ glacial advance in different parts of southern Norway varied considerably, ranging from the early 18th century to the late 19th century. Cumulative glacier length variations of glaciers in southern Norway show an overall retreat from ∼ AD 1750 to the 1930s–40s. Thereafter, most Norwegian glaciers retreated significantly. Short maritime outlet glaciers with a short response time (< 10–15 yr) started to advance in the mid-1950s, whereas long outlet glaciers with longer frontal time lag (> 15–20 yr) continued their retreat to the 1980s. In the 1990s, however, several of the maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s. Since 2000 most of the observed glaciers have retreated remarkably fast (annual frontal retreat > 100 m) mainly due to high summer temperatures. The last glacier inventory in Norway published in 1988 shows that there were 1627 glaciers covering a total area of 2609 km2 with an estimated volume of 164 km3. Modern climate–glacier relationships from mass balance data in Scandinavia have been used to present possible effects on the Norwegian glaciers of climate scenarios between 1961–1990 and 2070–2100 presented by the ‘RegClim’ project. This long-term weather ‘forecast’ for western Norway indicates a rise in the summer temperature of 2.3 °C and an increase in the winter precipitation of 16% by the end of the 21st century. This climate scenario may, if it occurs, cause the equilibrium-line altitude (ELA) to rise 260 ± 50 m. As a result, about 98% of the Norwegian glaciers are likely to disappear and the glacier area may be reduced ∼ 34% by AD 2100.