Origin, Burial and Preservation of Late Pleistocene-age Glacier Ice in Arctic Permafrost (Bylot Island, NU, Canada).

Over the past decades, observations of buried glacier ice exposed in coastal bluffs and headwalls of retrogressive thaw slumps of the Arctic indicate that considerable amounts of Pleistocene glacier ice survived the deglaciation and are still preserved in permafrost. Identifying the origin of ground ice is required to model its spatial distribution and abundance, which is necessary to model the response of circumpolar permafrost regions to climate change. Here, we present a detailed description and report physical and geochemical properties of glacier ice buried in the permafrost of Bylot Island (Nunavut) as well as identify geomorphic processes that led to the burial and preservation of the ice. 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 indicated the late Pleistocene age of the ice, interpreted to be a remnant of the Laurentide Ice Sheet (LIS). This ice predates the aggradation of the permafrost and can be used as an archive to infer paleo-environmental conditions at the study site. The δ¹⁸O records of LIS remnants found along its northern margin can also be used to establish ice elevation in their source area during the late Wisconsinan, based on the δ¹⁸O-elevation relation, and to constrain modeled, physics-based, LIS geometry reconstructions. In the Canadian Arctic, the resiliency of icy permafrost to past warm intervals preserved relics of the LIS; these ice-marginal landscapes, now poised for thaw, should uncover more valuable clues about the conditions of the last major ice sheet on Earth.