Abstract2007_06 – University of Copenhagen

Continental Ice Body in Dobsina Ice Cave (Slovakia) - Part II. - Results of chemical and isotopic study

2nd International Workshop on Ice Caves - Proceedings - Demänovská Dolina Slovak Republic, May 8-12, 2006, p. 29-37, 2007

H.B. Clausen, S.B. Hansen, L.B. Larsen, M.-L. Siggaard-Andersen, J. Sjolte and S.C. Lundholm
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
K. Vrana
HYDEKO-KV, Planckova 4, 851 01 Bratislava, Slovakia.
J. Baker
SELOREEIG, Saffierstraat 101c, 1074 GP Amsterdam, The Netherlands.

This contribution continues information given in the workshop presentation K. Vrana et al. (2007) "Continental ice body in Dobsina Ice Cave (Slovakia) - Part I. - project and sampling phase of isotopic and chemical study".
The main goal of this project is to investigate climatic and environmental chanhes by detailed study of continental cave ice using isotopic methods and methods of chemical analysis. According to existing knowledge we supposed that cores of cave ice from Dob?in? Ice Cave could add new information to the Holocene climate record of continental Europe. There are very only records of continental ice of similar type. Changes of climate are closely related to changes in the environment, so project results are supposed to be interesting from an ecological point of view, as well.
The Dobsina ice body represents a dynamic system at a temperature close to the pressure melting point. The formation of the cave ice by various processes, like seeping and dripping groundwater, melting, refreezing, sublimation, condensation and evaporation, has formed the ice into a laminated block of frozen groundwater. Since the cave was discovered in 1870, comparison between old photos and drawings from the old times, and actual observations show that the distance from the ice surface at the Great Hall to the ceiling of the cave has been almost unchanged, meaning that the cave ice has been in a state of equilibrium for the last one and a half centuries.
The ice of the Dobsina Ice Cave provides a unique opportunity to study a climatic record preserved in a continental European setting. The study encompasses continuous stable isotope (2H and 18O) and chemically analyses performed on samples from vertically drilled ice cores. The stable isotope (δD, δ18O) records are obtained by mass-spectrographic measurements. The chemical analyses include the water soluble ions: Na+, K+, NH4+, Mg2+, Ca2+, F-, Cl-, NO3- and SO42-, and the concentration levels are determined by ion chromatographic measurements. For crystal size determination several thin sections have been taken along the ice cores and the crystal sizes recorded.
A prerequisite for using the stable isotope and the chemical records in palaeo-climatic studies is a time scale, a depth-age relationship for the ice core. A simple time scale for the cave ice has been established based on 14C dating of a bat buried in the ice, and transported by the internal movement of the ice, from the surface at the Great Hall to the finding place in the ceiling of the Ruffiny's Corridor, 2.9 m above the bottom of the ice.
The interpretation of the stable isotope records in the sense of climatic information is not straight forward because the isotope ratios are affected by the high temperature and isotopic fractionation processes occur due to different processes like evaporation, melting and refreezing. Also the chemical components are affected by various processes like re-crystallisation and removal of easy water soluble components from the ice.
The stable isotope ratios and the concentration levels of the chemical components in the laminated frozen ice body are compared with today's precipitation values from the region of the ice cave. The stable isotope ratios and the chemical data are compared to the crystal size and the visual stratigraphy determined by light transmission.