Isotope characterization of ground ice on Bylot Island

Over the past decades, observations of buried glacier ice exposed in thaw-slump affected terrain of the Arctic indicate that considerable amounts of Pleistocene glacier ice survived the deglaciation and are still preserved in permafrost. In exposures, relict glacier ice and intrasedimental ice often coexist and look alike but their genesis is strikingly different. Identifying the origin of ground ice is required to model its spatial distribution and abundance in the landscape. This paper aims to present a detailed description of the physico-chemical properties of glacier ice buried in the permafrost of Bylot Island (Nunavut) as well as the deposition processes that led to the burial and preservation of the ice. The massive ice exposure and ice core samples were described according to the cryostratigraphic approach, combining the analysis of permafrost cryofacies and cryostructures, ice crystallography, stable O-H isotopes and cation contents. The buried glacier ice consisted of clear to whitish englacial ice having large crystals (cm) and small gas inclusions (mm) at crystal intersections, similar to observations of englacial ice facies commonly found on contemporary glaciers and ice sheets. However, the isotopic composition of the buried ice differed markedly from contemporary glacier ice and was related to Pleistocene age isotopic composition. As most of the arctic landscapes are still strongly conditioned by its glacial legacy, the melting of this ice could lead to extensive slope failures and settlement of the ground surface, with significant impact on permafrost geosystem landscape dynamics, terrestrial and aquatic ecosystems, and attend damages to infrastructure.