Fifty years of mass balance and glacier front observations at the Tarfala Research Station

In 1945 Storglaciaren located in the Kebnekaise massif, northern Sweden, was selected for a long term study of the climatic impact on glaciers and an annual mass balance programme was initiated. Since the mass balance year 1945-1946 the average annual winter precipitation has increased by 0.53 in water equivalent (w. eq.), the annual average ablation has decreased by 0.58 m w. eq., and the annual average net balance has increased from -0.80 in w. eq./year to +0.30 in w. eq./year. The decrease in ablation is caused by a decrease in summer temperature of about 1 degreesC. In addition, frontal retreat has decreased the low altitude area of the glacier and hence contributed to this decrease in ablation. A comparison with results from mass balance studies at three additional glaciers in the Kebnekaise area show that Storglaciaren is representative for the area. The mass balance of Storglaciaren is also positively correlated with each of four Norwegian glaciers, although accumulation and net balance are better correlated than ablation. Correlations become less positive with increasing distance between sites. Glacier front measurements provide filtered and delayed indications of climatic changes. Small glaciers are at present in balance with the climate. However, retreating fronts of large glaciers show that they are still adjusting to the major warming of the first half of the 1900s.