MASS-BALANCE ESTIMATES ON THE GLACIER COMPLEX KONGSVEGEN AND SVEABREEN, SPITSBERGEN, SVALBARD, USING RADIOACTIVE LAYERS

Analyses of total beta and gamma radioactivity have been carried out o n ten shallow ice cores collected in 1989 and 1990 on Kongsvegen and S veabreen, Spitsbergen. No peak of total beta radioactivity, correspond ing to the Chernobyl accident (1986), can be identified. Chernobyl lay ers were identified by Cs-137 and Cs-134 activities, and a signal from the nuclear tests in Novaya Zemlya (1961-62), was detected at one loc ation by Cs-137 activity. The mean net accumulation for the periods 19 86-89 and 1962-88 was estimated for both glaciers. Using topographic d ata, the mean net ablation on Kongsvegen was estimated for the period 1964-90 and the mean net balances were calculated. The results agree w ith recent direct glaciological balance measurements. For the period 1 986-89, the net accumulation was higher on Sveabreen than on Kongsvege n, and the equilibrium-line altitudes (ELA) were around 450 and 520 m a.s.l., respectively. Kongsvegen had a positive balance of 0.11 m w.eq . and Sveabreen was in equilibrium, whereas for the last 26 years the balance of Kongsvegen was slightly negative (-0.10 m w.eq.) and the EL A was around 560 m a.s.l.