Half a million years of environmental change in the Alps: Reading the speleothem record

START project Y 122 Speleothems as Palioclimate Archives in the Alps Christoph SPÖTL 18.06.1999 This proposal calls for an interdisciplinary research initiative to unravel the paleoclimatic potential of speleothems, i.e. inorganically precipitated calcite in alpine caves. The goal of this project is to refine our current understanding of paleoenvironmental change in the Alpine realm during the last several hundreds of thousands of years, thus going far beyond the time range covered by the radiocarbon method. In distal parts of caves speleothems such as stalagmites and flowstones form under extremely constant physico- chemical conditions over thousands of years, thereby recording changes in mean annual air temperatures and the amount of annual precipitation. The stable isotopic composition of the precipitated calcite, the hydrogen isotopic composition of minute fluid inclusions therein and the growth texture of the calcite are the principal "proxies" used to identify and quantify variations in climate parameters. A novel isotopic technique, thermal ionization mass spectrometry (TIMS) 238 U- 234 U- 23O Th dating, will be utilized to precisely date speleothem calcite. Segments of continuous calcite growth within individual stalagmites and locally also within flowstones will be analyzed, representing high-resolution tree-ring-like archives of carbonate precipitation. Stable oxygen and carbon isotopic microsampling in conjunction with state-of-the-art petrographic techniques will be used to quantify paleoenvironmental changes in the recharge area as a function of time. In essence, the proposed initiative offers a fresh and innovative approach to a previously neglected geological paleoclimate archive in the Alps; an archive that has been shown to hold great potential in other parts of the world because of its high precision and locally high resolution. This work will complement paleoclimate research on other archives in the Alps, most notably on laminated lacustrine sediments, which are mostly of younger, post-Last Glacial Maximum age. Influence of the proposed work on the development of the field Research in Global Environmental Change is probably the most dynamic and fastest growing field in the Earth Sciences and there is hardly an issue of Nature or Science that does not contain new and exciting results. With deep-sea sediments and highlatitude ice cores at our disposal the scientific community is now realizing the demand for (a) data on low to mid-latitude continental settings that extend back beyond the calibrated radiocarbon time scale and (b) for defining and refining the regional histories of climate change that may deviate from the global trend quite significantly. That is exactly the goal that this research project will try to achieve. Inasmuch as the Alps are a major structural element controlling Europe`s regional and local climates, acquiring long-term, well calibrated, semicontinuous records of paleonvironmental change extending back several hundreds of thousands of years would greatly improve our understanding of environmental change in the Alpine realm and will hopefully provide important constraints for future generations of high-resolution numerical models of Quaternary climate change in Europe.