Isotope hydrological studies on the perennial ice deposit of Saarhalle, Mammuthöhle, Dachstein Mts, Austria

Abstract

Abstract. A 5.28 m long ice core was extracted from the major cave ice block of the Mammuthöhle cave system. Tritium concentration in eight samples from the upper 1.2 m of the core was measured. Electrical conductivity measurements were achieved on molten water samples and stable oxygen and hydrogen isotopic compositions were also analysed. The upper ~1.2 m of ice has been deposited from precipitation fallen before the 1960s (based on tritium < 8.5 TU). The Saarhalle ice block is build from atmospheric precipitation and the water perfectly preserved the isotopic composition; however the mean 18O/16O ratio of the ice is less depleted compared to the long-term (1973–1983) 18O/16O ratio of precipitation at Feuerkogel the nearest (~32 km) reference station situated in the same elevation like Mammuthöhle cave. Characteristic fluctuation was observed in the conductivity along the studied cave ice profile. The conductivity oscillations seem to mirror the changing partition of karstic water and surface meltwater in the water supply of the ice accumulation. The ice layers with low conductivity seem to archive past events when more meltwater-like water have been drained and frozen onto the ice block.