Isotope Studies of Ice Cores from a Temperate Alpine Glacier (Vernagtferner, Austria) with Respect to the Meltwater Flow

Abstract

Core drillings were carried out in 1979 and 1983 on the temperate Alpine glacier Vernagtferner, Ötztal Alps, Austria. In addition, studies on the variation of the water table of the firn were carried out in the bore holes. The 18O, 2H and 3H content of the cores, as well as the electrical conductivity, were measured. The isotope profiles and the electrical conductivity of the 1983 core display a strong damping in comparison with the profiles from the 1979 core for the depth from 17 to 20 m (10.5 to 13 m water equivalent) below the surface. In the 1983 core, the 3H contents are lower, and the 2H and 18O contents are more homogenized. This core section lies between the lower and upper limits of the water table fluctuations from 1979 to 1982, and it is also assumed that the transition from firn to ice takes place at this depth of the glacier. The most reasonable explanation for this damping is that within the range of the firn water table important isotopic and chemical exchanges between the meltwater and the porous medium (firn) take place. It is also possible that a small amount of meltwater is included in the firn while it is changing into ice.