Extraction of air from ice core samples using trapping and detrapping on silica gel

Climate reconstructions from ice cores strongly rely on analysing the elemental and isotopic composition of fossil air occluded in the ice, as these provide valuable dating tools and serve as proxies for past temperature variations. Traditional techniques for extracting and measuring atmospheric gases from ice cores typically involve liquid helium or cryogenic heads for gas trapping, both of which are expensive and complex to operate. This study evaluates the use of silica gel as an alternative method, describing the design and optimisation of a trapping and detrapping system suitable for measuring δ 15 N of N 2 , δ 18 O of O 2 , δ ( O 2 / N 2 ) and the elemental and isotopic ratios of heavy noble gases, including Ar, Kr, and Xe. Systematic fractionation effects introduced by silica gel are quantified through long-term monitoring of atmospheric air, and correction and calibration protocols are developed to ensure measurement precision. For measurements of atmospheric δ 15 N , δ 18 O , δ ( O 2 / N 2 ) , and δ 40 / 36 Ar , the method achieves precision comparable to helium-based techniques when applied to high-quality ice. This supports the viability of silica gel trapping for future analyses of atmospheric permanent and noble gases from deep ice cores. • Silica gel is evaluated as a cost-effective alternative to helium-based trapping methods for extracting atmospheric gases from ice cores. • A new trapping and detrapping system is designed and optimised to measure elemental and isotopic ratios of atmospheric permanent and noble gases. • Measurement precision for key isotopic and elemental signals ( δ 15 N , δ 18 O , δ O 2 / N 2 , and δ 40 / 36 Ar ) are shown to be comparable to traditional cryogenic helium systems when applied to high-quality ice. • Systematic fractionation effects of silica gel trapping are characterised, particularly for Kr/Ar and Xe/Ar ratios.