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Diffusivity and Solubility of H 2 in Ice Ih: Implications for the Behavior of H 2 in Polar Ice
Author(s) -
Patterson John D.,
Saltzman Eric S.
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033840
Subject(s) - firn , ice core , polar , thermal diffusivity , sea ice growth processes , ice sheet , diffusion , atmospheric sciences , chemistry , geology , glacier , climatology , cryosphere , sea ice , geomorphology , thermodynamics , sea ice thickness , physics , astronomy
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.