Raman spectroscopic study on the spatial distribution of nitrogen and oxygen in natural ice clathrates and their decomposition to air bubbles

We present the results of Raman spectroscopic scans to determine the N-2/O-2 ratios on different planes through a clathrate in the GReenland fee Core Project (GRIP) deep ice core, in which the two axes of the scans are perpendicular to one another. The spectra of the individual focal planes do not point to fractionation effects of the N-2/O-2 concentrations within a clathrate specimen in the range of the precision of Raman spectroscopy. In a second study, the frequency shift of the N-2 and O-2 peaks due to decomposition of a clathrate to an air bubble is shown qualitatively. From their peak integrals, there is no indication of different retransformation rates to air bubbles between the oxygen and the nitrogen contents of clathrates. The N-2/O-2 ratios we observe in clathrates and on clathrate decomposition at different stages are retained in our measurements of air bubbles resulting from clathrate decomposition.