Towards continuous ice core measurements of N2O and CO2

Measurements of greenhouse gases (GHGs) in ice cores have provided invaluable data, offering insights into the role of GHGs in the climate system over millennia. While previous research has successfully employed continuous analysis techniques to achieve high resolution records of methane (CH4) variations, analyses of nitrous oxide (N2O) and carbon dioxide (CO2) concentrations have historically been limited to discrete, dry-extraction, measurements due to the gases’ high solubility. Obtaining records of centennial-scale (or finer) variability in N2O and CO2, akin to that of CH4, necessitates a new approach. In this work, we employ a new laser spectrometer designed for low flow rates, accompanied by a novel, custom-built gas extraction unit, to re-extract dissolved N2O and CO2 from a synthetic melt-stream. We modify physical parameters at the gas extraction site, controlling temperature, downstream pressure and flow rate. Through optimisation of these parameters, we aim to achieve a high and consistent rate of extraction. Our findings demonstrate the potential of these developments in improving re-extraction of N2O and CO2 to obtain more accurate concentrations from analysis of a mock continuous ice core melt stream. This work marks a step towards refining and applying the method to an Antarctic ice core, contributing to a more comprehensive understanding of the finer scale palaeoclimatic variations of all major GHGs.