Nature and origin of massive ground ice bodies, Yukon Territory and Alaska

Abstract

Gas bubbles in ice hold relevant information on the origin and process of formation, distinguishing between an atmospheric and dissolved origin. Using ice crystallography, stable O-H isotopes and gas composition, this thesis provides new clues to the understanding of ice wedge formation and filling process in the Yukon Territory and Alaska. An improved extraction line and mass spectrometry technique were used 10 analyze the gas composition of ice bubbles (O2, N2 and Ar). Conclusions from this study infer that climatic conditions may influence the source of infilling during ice wedge growth. Wet and dry environments have result in two different signatures in ice wedges. The Vault Creek tunnel ice wedges in Alaska, dated to the late Pleistocene, a cold and dry period, preserve stable O-H isotope and gas compositions similar to those expected for ice formed by snow densification. On the other hand, ice wedges from the Old Crow region, dated to the late Holocene, preserved isotopic and gas compositions more similar to those expected for ice formed by the freezing of liquid water. In some cases, the results from the occluded gases (O2, N2 and Ar) showed low oxygen concentration and high delta18O values, indicating respiration prior to formation. These results are significant to palaeoclimatic interpretation of ice wedges in permafrost areas.