The Chemistry of Cave Ice: Two Examples from Slovenia

Abstract

Cave ice can contain a wealth of paleo-climatic and geochemical information that is rapidly being lost with the melting of the temperate zone cryosphere. The karst areas of Slovenia host over 260 ice caves. We collected samples for stable water isotope, major ion, and nutrient analyses from two Slovenian ice caves. Samples included two shallow ice cores in Snežna Cave, collected ∼5 m apart, and an ice face profile in Ivačičeva Cave. All ice isotopic ratios reflected modern precipitation that could be described by high-elevation meteoric water lines. An offset suggested that fractionation and mixing processes of melted ice affected the isotopic signals. Cation concentrations of ice in both caves showed Ca ≫ Mg > Na > K. The high Ca2+ and Mg2+ contents and elevated HCO3− concentrations indicate that CaCO3 dissolution within the local karst landscape is a primary control on ice chemistry. Low concentrations and inconsistent profile patterns of other major ions and nutrients suggest atmospheric deposition and vadose zone leaching were also primary sources of ions to the ice. Differences in Cl− and SO42− profile concentrations at similar depths in Snežna Cave imply that ice melting, water mixing, and re-freezing processes can affect the primary climatic signal stored in the ice. While temperate ice caves can be repositories of climatic information, secondary diagenetic processes that affect ice chemical composition alter the original signal. In addition to chemical analysis, physical processes within the caves must be studied at a small spatial scale to understand and interpret ice chemistry.