Associate Professor, Department of Industrial Chemistry, Meiji University
Diffusion of air molecules in antarctic ice-sheet
Diffusion of air molecules in ice was found from Raman spectroscopic study of natural ice from the Antarctic ice-sheet (T. Ikeda-Fukazawa et al., Geophys. Res. Lett. 26 (1999)). The results have important implications for the reconstruction of the paleo-atmosphere from polar ice cores. In order to investigate the diffusion of air molecules in Antarctic ice-sheets in periods of tens of thousands years, I have been studying the dynamics of water and air molecules in ice crystals.
I have performed molecular dynamics simulations involving the diffusion of air molecules (e.g., N2, O2, and CO2) in ice crystals and observed the diffusion hops for these molecules from a stable site to the adjacent site. The results showed that the diffusion mechanism for the air molecules significantly differs from small atoms, such as He. The air molecules diffuse by distorting the ice lattice (Fig. 2), whereas He atom hops from a stable interstitial site to the adjacent site without distorting the lattice (Fig. 1). The diffusion velocity for this mechanism is a few orders of magnitude larger than the value estimated from the interstitial mechanism. In order to reconstruct accurate records of the paleo-atmosphere from polar ice sheets, I have developed a model for the variation process of the distribution of air molecules in the ice sheets.
