Storsteinsfjellbreen: Variations in mass balance from the 1950s to the 1990s

When the Norwegian Stare Power Board decided to plan an extensive water power development in the mountainous areas southeast of Narvik in northern Norway, a large mapping project was started. Detailed maps were constructed ata scale of 1:10 000 from aerial photographs taken in 1960. Several hydrometric stations were installed, and three glaciers were selected for mass balance observations. Storsteinsfjellbreen was the largest of these, and a special glacier map with 10 m contours was printed in four colours, to be used in the field work. Mass balance studies were carried out initially during one 5-year period(1964-68), and also later during another 5-year period (1991-95). Results from these periods are compared with similar data from the Swedish glacier Storglaciaren, about 45 km to the southeast. For all the years except one (1968), the net balance of these glaciers shows a similar pattern: positive years and negative years are synchronous. A new glacier map was made from a special aerial survey in 1993 at the same scale and of similar accuracy as the first map, so a comparison could be made to calculate the change in glacier volume from 1960 to 1993. From digital terrain models it could be shown that the glacier surface had dropped more than 60 m vertically on the tongue, while the thickness increased above the equilibrium line by up to 20 m. The overall mass loss amounted to 16.8 x 10(6) m(3) water during 33 years, which corresponds to an extra 2.6 l.s(-1).km(-2) (litres per sec. per sq. km) delivered to the river, in addition to the "normal" discharge due to annual precipitation, which is 36 l.s(-1).km(-2) in the area. A copy of the new glacier map is enclosed with this article.