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Art/3-
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Extract of
"
Commission of Snow and Ice "
<M0- 336
General Assembly of Bern, Sept.-Oct. 1967
TRITIUM CONTENT IN THE FIRN LAYERS
OF AN ALPINE GLACIER
W. AMBACH, H. EISNER and L.L. THATCHER
Physics Department, University of Innsbruck
and
International Atomic Energy Agency, Vienna.
Pendant les mois d'6t6 de 1963 et 1964, on prdleva des 6chantillons de n6ve de la
zone d'accumulation du Kesselwandfemer (Alpes de l'Oetztal) pour determiner leur
teneur en tritium. On etudia, dans un puits profond de 20 m, l'accumulation nette par
annee, pour la peiiode comprise entre 1963 et 1951. Pour proceder ä un examen des
variations locales de la teneur en tritium, on preleva dans six autres puits et ä differents
endroits du Kesselwandfemer, des echantillons des couches annuelles de 1964 ä 1960.
La distribution verticale de la teneur en tritium des couches de nev6, montrait des
variations typiques, consdquence des experiences thermonucliaires. L'infiltration d'eau
de fönte peut produire des changements importants dans la teneur en tritium. En
moyenne une limite distincte est toutefois maintenue entre les couches contenant du
tritium et celles qui n'en contiennent pas beaucoup, au sens de la couche annuelle
d'accumulation nette pour 1961/62.
II
faut ajouter que des echantillons de glace pr61ev6s dans la zone d'ablation n'ont
montre presqu'aucune teneur en tritium. On peut utiliser la haute teneur en tritium
des couches de n6v6 accumutees au cours des dernieres annees, pour etude des crues
des eaux de fönte. Dans ce domaine, le tritium accumule dans les couches de neV6
plus rezentes peut jouer le röle de traceur pour l'dtude de l'6coulement de l'eau de
fönte.
Abstract
During the summer months of 1963 and 1964 firn samples for the determination
of the tritium content were taken from the accumulation area of the Kesselwandfemer
(Oetztal Alps). In a 20 m deep vertical firn pit the annual net accumulation from the
years of between 1963 and 1951 were investigated. Samples from the annual layers
between 1964 and 1960 were taken in sixother pits at various locations on the Kessel¬
wandferner in order to study the local variations in tritium content.
The vertical distribution of tritium in the firn layers shows characteristic variations
which can be attributed to thermonuclear bomb tests. Melt-water infiltration can cause
considerable changes in tritium content. On an average, however, an identifiable
boundary between tritium-containing and tritium-lacking layers is maintained within
the annual layer of net accumulation of 1961/62.
In addition, ice samples taken from the ablation area were investigated which show
no contamination by recent melt-water. The high tritium content of firn layers accumu-
lated in recent years can be used for run-offstudies. In this procedure the tritium deposi-
ted in younger firn layers can be used as a tracer for marking the melt-water flow.
Introduction
A 20 m deep vertical pit of 2 m diameter was dug in the accumulation area of the
Kesselwandfemer (Oetztal Alps, 3240 m a.s.l., L 58) in summer 1963 (fig. 1). The
annual deposits could be dated from the density profile (
x
). The position of the late
summer horizons was examined and confirmed by pollen investigations of the firn lay¬
ers (
2
). The deepest, still clearly dated late summer horizon was from 1951. It was
situated 18.50 m below the late summer horizon of 1963.
A continuous series of firn and ice samples was taken in the vertical direction by
means of a 50 cm
2
core drill. The firn samples were taken in such a way that a late
summer horizon was chosen for the beginning and end of each sample.
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| Tritium content in the firn layers of an alp... (1967) | ||||||||||||||||||||||