Isotope characterisation of ground ice in northern Canada

Abstract

AbstractThis paper reviews isotopic research on the characterisation and identification of various types of ground ice throughout the Canadian Arctic, including buried glacier ice, massive segregated ice, segregated ice lenses and offshore ice‐rich permafrost, as well as ice related to other cold‐region phenomena such as ice wedges, icings (aufeis), frost blisters and pingos. The formational age of ground ice bodies ranges from recent (seasonal ice in the active layer) to tens of thousands of years, when the region experienced widespread continental‐scale glaciation. Modern ice lenses generally have 18O/16O ratios of ‐18 to ‐22‰, while modern ice wedges usually range from ‐22 to ‐25‰. δ18O values as high as ‐14‰ are representative of the Hypsithermal period (4000 to 8000 years BP), while glacial‐age ice has been measured with 18O/16O ratios as low as ‐36‰. Buried glacier ice often preserves climatic variations from the time of snow deposition. Other massive ground ice bodies contain isotopic signatures (18O and 2H) that indicate variable fractionation of the isotopes during freezing of the source water at stationary freezing fronts in either open or closed systems. Placing the ice bodies into a time frame can be accomplished either through age dating of the enclosing sediments and encased organics, or by direct dating of the ice utilising tritium (3H) for relatively young ice and radiocarbon (14C) analysis of contained gas bubbles for older ice. Copyright © 2011 John Wiley & Sons, Ltd.