Laser spectroscopy based on the OF-CEAS technique for atmospheric water isotopes measurement in dry environments: application for Antarctica and the AWACA project.

Atmospheric water isotopes measurement in polar regions provides important information on the processes governing the water cycle, to improve climate reconstructions in ice cores.

This measurement is complicated in Antarctica, particularly in the interior of the continent where absolute humidity regularly falls below 10 ppm. For example, at Concordia station (at an altitude of more than 3,200 m) we are below this threshold around 30% of the year (see figure, left).

In this article, we present the instrumental performance of the OF-CEAS technique, developed in collaboration with AP2E company, and especially adapted for atmospheric measurements in very dry environments. We also propose a comparison of the advantages and disadvantages compared with the CRDS technique traditionally used for such measurements and developed by Picarro. Finally, we propose an estimate of the detection limits of the OF-CEAS spectrometers for 4 sites in Antarctica (figure, right) aligned along a 1100 km transect where these instruments were deployed as part of the ERC AWACA project, during the 2024-2025 summer season (https://www.lsce.ipsl.fr/archives-traceurs/glaccios/1-100-km-en-antarctique-pour-mieux-comprendre-l-evolution-de-la-calotte-glaciaire). We estimate a limit of 100 ppm of humidity for δ¹⁸O and 10 ppm of humidity for δD.

Authors: Lauwers, T., Fourré, E., Jossoud, O., Romanini, D., Prié, F., Nitti, G., Casado, M., Jaulin, K., Miltner, M., Farradèche, M., Masson-Delmotte, V., and Landais, A.

OF–CEAS laser spectroscopy to measure water isotopes in dry environments: example of application in Antarctica, Atmos. Meas. Tech., 18, 1135–1147, https://doi.org/10.5194/amt-18-1135-2025, 2025