STUDIES ON VERTICAL TOTAL-BETA-ACTIVITY PROFILES OF FISSION PRODUCTS IN ACCUMULATION OF STUBACHER SONNBLICKKEES (HOHE TAUERN SALZBURG AUSTRIA)

In the years of 1965 and 1966 continuous vertical sets of samples were bored from pits comprising the uppermost perannual snowcover in the accumulation area of the Stubacher Sonnblickkees (Hohe Tauern, Salzburg, Austria). The total-beta-activity of the samples was measured in order to study the changes of the vertical distribution of fission products by summerly melting processes. An enrichment of fission products was found in the layer under the late, summer horizon. However, the weak activity of the layer underneath accumulated during the winter period is hardly influenced by meltwater percolation from the superimposed layer with high activity. An 11.75 m deep firn pit covers, the annual layers of net accumulation from 1960/61 to 1965/66. The most remarkable activity variation of the entire total-beta-activity profile of this pit is a maximum at the coinciding late summer horizons of 1962 and 63. This activity maximum proves that mass budget years with heavy fission product debris and high melting conditions cause a strong enrichment and high retention of the remaining layer for fission products. It can be assumed that this characteristic feature of the vertical activity distribution will be also found on neighboring glaciers in the region of the Mittlere Hohe Tauern. Because its relatively long time stability it is especially interesting for future dating purposes. Moreover, it was found that the period from 1961/62 to 1963/64 shows a high fission product activity in contrast to the low radioactive period from 1964/65 to 1965/66. This behavior of the firn activity is in agreement with the one of the air and the precipitation during these years. The characteristic changes of the total-beta-activity of the firn at the late summer horizon of 1964 can be also used for dating purposes. © 1969 Birkhäuser Verlag.