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Abstract

Glacier ice stores a unique range of past environmental signals and therefore serves as an invaluable archive of Earth’s climatic history. However, to fully exploit this archive, the knowledge of the age distribution of the ice is key. Radiometric dating methods are an important addition to traditional age dating techniques like annual layer counting, especially when these fail due to discontinuities in the record. This thesis aims to establish the 39Ar dating tracer as a well-understood tool for dating glacier ice. The advent of the atom-optical Atom Trap Trace Analysis (ATTA) technology for 39Ar measurements has been associated with a significant reduction of required sample sizes and the tracer can therefore now routinely be applied to glacier ice. As a major part of this thesis, the ATTA laboratory in Heidelberg was improved to deliver higher atom count rates for high-quality measurements with large long-term sample throughput. Furthermore, two studies on Alpine glaciers are presented in this thesis, the summit glacier of Weissseespitze, where part of a 6000 a continuous record was dated, and the Jamtalferner, which is a much younger, highly variable low-altitude glacier. In both campaigns, 39Ar ages are complemented by other tracer ages from radiocarbon or tritium, emphasizing the importance of this tracer in covering the full age range found in Alpine glaciers. The specific requirements for the application of 39Ar dating to glacier ice are investigated by comparing different ice sampling and sample preparation techniques. Additionally, the diffusion of argon in ice is quantified by 39Ar measurements on a long-stored ice core, showing the negligibility of contamination via this pathway for storage times below several decades. Finally, to make 39Ar, and also the gaseous dating tracers 81Kr and 85Kr, more conveniently applicable to ice dating, a new gas extraction system was designed, tested and applied to an Antarctic ice core. It enables the gas extraction from the otherwise unused waste line of a continuous flow analysis.