Assessment of Continuous Flow Analysis (CFA) for High-Precision Profiles of Water Isotopes in Snow Cores

Abstract. An efficient measurement of stable water isotopes in snow profiles is required to improve our understanding of the climate signal preserved in polar firn and ice and to improve the signal to noise ratio in climate reconstructions from ice cores. To allow the analysis of snow cores, we modified a Continuous Flow Analysis system at AWI to analyze multiple snow-cores in a reasonable time and with high-quality. We here describe the CFA-setup and isotope measurements, including the methodology to quantify the mixing of the isotope signal induced by the system along its different steps, leading to smoothing of the final isotopic signal. With our obtained mixing lengths for the instrumental setup and the continuous analyze of snow-cores of 14 and 30 mm, respectively, we show that with such highly porous cores the main mixing occurs through percolation. Based on these findings we suggest technical improvements to match the imposed analytical challenge and fully resolve the stable water isotope variations from low-accumulation snow-cores. Finally, comparing discrete and CFA based profiles, we illustrate that diffusion within the snow-cores takes place during storage time in cold facilities, underlining the need of near-time analysis of collected snow cores using for example Snow-CFA systems.