Nedelcu, Aneta Florentina; Kipfstuhl, Sepp; Faria, Sérgio H; Kuhs, Werner F: Raman signal of gaseous microinclusions in EDML ice [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.809738 (unpublished dataset)

The file presents results from calculating the individual nitrogen, N2, to oxygen, O2, ratio of about 230 gaseous microinclusions (MIs) using the raw data of their respective Raman spectra. The N2 / O2 ratios (R) are described by the ratio between the area of the nitrogen (AN2) and oxygen (AO2) Raman peaks when, as here, Gaussian fitting of the peaks is employed; R~AN2/AO2. The MIs are: plate like inclusions (PLIs) considered secondary relaxation features, air bubbles (ABs) less than 100 µm and considered secondary microbubbles, and air hydrates (AHs) which are primary microinclusions. The ice samples were cut at 14 different depths along the EDML ice core.

About 90% of the PLIs and ABs have the AN2/AO2 ratios between 0.3 and 1.5, while around 60% of the AHs have AN2/AO2 ratios between 2.8 and 3.3 and are mainly from depths below 1700m. Most frequent RPLIs are in the 0.5-0.6 (~20%) and 0.7-0.8 (~15%) value intervals without any clear depth preference.

The R values presented here are not corrected against the R of the atmospheric air (Rair) obtained from repeated and equivalent Raman spectra of the air in the lab room. It seems that a value of 2.9 for Rair can be considered representative for atmospheric air N2 / O2 ratios. Thus, the R of the MIs may be corrected with a factor of 3.7/2.9, while one of 3.73/3.24 was proposed by a dedicated calibration study.

Based on published literature the ratio between the amount of nitrogen and that of oxygen dissolved in ice has an estimate value of 0.7 and in low temperature water of ~2, while the ratio of their diffusion coefficients can be of 0.3 or 0.6 or else. Since PLIs are more or less transient features, which transform easily in other types of inclusions (either air microbubbles or gaseous nanoinclusions) function of the thermodynamic conditions at play, their life cycle should be dominated mainly by the N2 and O2 solubility in the ice matrix and then by the diffusion of those gases through the polar ice lattice.

Not to be neglected is the chemistry of other impurities existent in the ice and associated with the MIs containing (fractionated) air. For example on an AH can be observed minute PLIs with sharp outline when slow decomposition seems to be active; and often only tiny ABs when salts like sulfates or nitrates exist on the AH and might favour its structure perturbation.