Quasi-non-destructive water isotope measurements in ice cores using femtosecond laser ablation

We present a quasi-non-destructive technique for measuring water isotopes in ice cores using a femtosecond infrared laser ablation system. Our cold-ablation approach enables a direct solid-to-vapour transition with sub-millimetre resolution and negligible sample consumption. Experiments conducted on synthetic ice demonstrate reproducible crater formation. Utilising a pulse energy of 35 μJ and a total ablation time of 16 s, repeatable craters with a typical diameter of ∼120 μm are produced. The ablation is performed at atmospheric pressure and requires only compressed dry air.

We demonstrate a sequence of 530 craters along a 27 cm long standard CFA ice section (30 × 30 mm), with the capability to extend to a full 55 cm ice-core bag and to accommodate a complete 4″ round core. The crater spacing is 0.5 mm and a full ablation run takes approximately 30 min and is largely unattended. Finally, we present preliminary results on coupling a cavity ring-down spectroscopy (CRDS) instrument to the ablation system.

This development is relevant for very old and deep ice core samples, such as those targeted by the BEOIC project and other >1 Myr ice cores, where sample preservation and spatial resolution are crucial.