Investigation of Ice-Wedge Infilling Processes using Stable Oxygen and Hydrogen Isotopes, Crystallography and Occluded Gases (O2, N2, Ar)

The source and mechanism of infill of ice wedges of various ages (modern to Pleistocene) were examined for sites in the western Arctic. Several techniques were employed, including stable O-H isotope and crystallographic analyses of the ice, and gas composition (O-2, N-2 and Ar) analyses of air entrapped in the ice. The results indicate that climatic and site-specific conditions may influence the source of infilling during ice-wedge growth, so that wedge ice in wet and dry environments exhibits different characteristics. For example, Vault Creek tunnel (Alaska) ice wedges, dating from the Late Pleistocene, a cold and dry period, preserved stable O-H isotopes and gas compositions similar to those expected for ice formed by snow densification. In contrast, ice wedges from the Old Crow region (Yukon), dating from the Late Holocene, preserved isotopic and gas compositions more comparable with those expected for ice formed by the freezing of liquid water. In both ice-wedge types, the delta(O-2/Ar) values are much lower than both dissolved and atmospheric values, which may be due to the respiration of microorganisms living within ice bubbles or interstitial water at the grain boundaries. The elevated delta O-18(O2) (up to 16 parts per thousand) of the occluded gases supports the occurrence of microbial respiration. However, the delta(N-2/Ar) values do not appear to have been affected by biological processes, and as such are reflective of the infilling processes. Copyright (c) 2010 John Wiley & Sons, Ltd.