Recent Changes of the Glacier Østerdalsisen, Svartisen, Norway

ABSTRACT

Changes which have taken place since 1870 at Østerdalsisen, the largest glacier of northern Scandinavia, are well-documented. Retreat of the lower margins has been almost continuous, but the behaviour of the higher parts of the glacier has differed markedly from that of the lower part. The differences are illustrated by comparisons of photogrammetric maps from 1954, 1970 and 1979. In the last twenty-five years, there has been little retreat of the glacier margins above the 500 m contour and the net change of elevation of the glacier surface has been less than 10 m. At 300 m, however, surface lowering has exceeded 100 m. Between 1960 and 1966, annual rates of ablation measured directly at the glacier surface at about 400 m ranged from 5.5 to 8.4 m a^-1. The glacier's equilibrium line probably has remained below 1100 m throughout the last twenty-five years: observations between 1957 and 1964 indicated that it rose above 950 m in only two years. Since 1975, the upper part of the glacier Gåbrokbreen, which adjoins Østerdalsisen's accumulation zone, has re-advanced, and the rate of retreat of the southern margin of Østerdalsisen on Burfjell has declined. Future changes of position of the glacier's margins are likely to be influenced by calving into the lakes which now border much of the glacier tongue.