Diffusivity and Solubility of H<sub>2</sub> in Ice Ih: Implications for the Behavior of H<sub>2</sub> in Polar Ice
John D. Patterson, E. S. Saltzman
Abstract
Abstract Reconstructions of paleoatmospheric H 2 using polar firn air and ice cores would lead to a better understanding of the H 2 biogeochemical cycle and how it is influenced by climate change and human activity. In this study, the permeability, diffusivity, and solubility of H 2 are determined experimentally in ice Ih at temperatures relevant to polar ice sheets (199–253 K). The experimental data are used in conjunction with simplified diffusion models to assess the implications for: (a) Diffusion of H 2 from pressurized closed bubbles to open pores in polar firn, (b) diffusive smoothing of H 2 gradients in the ice sheet, and (c) post‐coring diffusive losses of H 2 from ice core samples. The results indicate that diffusive equilibrium between open and closed pores is likely achieved in the firn lock‐in zone. Diffusive smoothing of atmospheric variations is significant and should be accounted for in atmospheric reconstructions on millennial time scales. Diffusive losses from a bubbly ice sample are sufficiently slow that samples may be meaningfully analyzed for H 2 after storage on the order of a year. These results suggest that the mobility of H 2 in ice should not preclude the reconstruction of paleoatmospheric H 2 from firn air and ice cores.