A Tibetan ice core covering the past 1,300 years radiometrically dated with Ar.

Ice cores from alpine glaciers are unique archives of past global and regional climate conditions. However, recovering climate records from these ice cores is often hindered by the lack of a reliable chronology, especially in the age range of 100 to 500 anni (a) for which radiometric dating has not been available so far. We report on radiometric Ar dating of an ice core from the Tibetan Plateau and the construction of a chronology covering the past 1,300 a using the obtained Ar ages.

Fast atom-trap analysis of Ar with isotope pre-enrichment.

We demonstrate fast analysis of Ar/Ar at the 10 level using a mass spectrometer for isotope pre-enrichment and an atom trap for counting. An argon gas sample first passes through a dipole mass separator that reduces the dominant isotope Ar by two orders of magnitude while preserving both the rare tracer isotope Ar and a minor stable isotope Ar for control purposes. Measurements of both natural and enriched samples with atom trap trace analysis demonstrate that the Ar/Ar ratios change less than 10%, while the overall count rates of Ar are increased by one order of magnitude.

An atom trap system for Ar dating with improved precision.

Cosmogenic Ar dating is an emerging technique in dating mountain glacier ice, mapping ocean circulation, and tracing groundwater flow. We have realized an atom-trap system for the analysis of the radioactive isotope Ar (half-life = 269 years) in environmental samples. The system is capable of analyzing small (1-5 kg) environmental water or ice samples and achieves a count rate of 10 atoms/h for Ar at the modern isotopic abundance level of 8 × 10.

Dual Separation of Krypton and Argon from Environmental Samples for Radioisotope Dating.

The noble gas radioisotopes Kr, Kr, and Ar are nearly ideal environmental tracers because of their chemical inertness and simple transport mechanisms. Recent advances in Atom Trap Trace Analysis have enabled measurements of Kr and Kr using 10-20 kg of water or ice, and Ar in only a few kilograms, making these tracers available to be applied in the earth sciences on a large-scale. To meet the resulting increase in demand, we have developed an automated process for the dual separation of krypton and argon from environmental samples based on titanium gettering and gas chromatography.