New CO2 Concentration Predictions and Spectral Estimation Applied to the Vostok Ice Core

Abstract

The Vostok ice core provides measurements of the CO2 concentration during the last $414\times 10^{3}$ years (yr). Estimations of power spectra show peaks, with the strongest one corresponding to a time period of around $100\times 10^{3}$ yr. In this paper, a new reconstruction method from irregular sampling is used, allowing more accurate estimation of spectral peaks. This method intrinsically decomposes the analyzed signal as a sum of sines, providing amplitudes but also phase measurements of periodic tendencies (due to the nature of the studied phenomena). This decomposition can be conducted with noisy and inaccurate measurements of the sampling instants and the concentrations. The widely used Vostok data were chosen as an example, but the method could also be applied to data from other places (e.g., dome C, Antarctica) or to study other phenomena as nitrogen dioxide NO2, methane CH4, oxygen isotope 18O (closely linked to temperature), deuterium 2H, or dust concentrations.