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.

在过去的数十年间，通过对北极地区冻融滑塌地貌中暴露的埋藏冰川冰的观测，表明了相当数量的更新世冰川冰在冰川消融过程中得以幸存，并依然保存在永久冻土层中。在暴露的地层中，残留冰川冰和层内冰常常共存且外观相似，但其成因却截然不同。确定地面冰的起源对于模拟其在景观中的空间分布和丰富程度至关重要。本文旨在详细描述位于比洛特岛（努纳武特）永久冻土层中埋藏冰川冰的物理化学性质，以及导致冰层埋藏和保存的沉积过程。通过对大量冰暴露和冰芯样本的描述，采用低温地层学方法，结合永久冻土层冷相和冷结构分析、冰晶体学、稳定氧氢同位素和阳离子含量分析。埋藏的冰川冰由透明至乳白色的冰川冰组成，具有大晶体（厘米级）和小气泡（毫米级）在晶体交汇处，与当代冰川和冰盖中常见的冰川冰相类似。然而，埋藏冰的同位素组成与当代冰川冰显著不同，并与其更新世年龄的同位素组成相关。鉴于北极地区的景观仍受到其冰川遗产的强烈影响，该冰层的融化可能导致广泛的边坡失稳和地表沉降，对永久冻土层地理系统景观动力学、陆地和水生生态系统产生重大影响，并可能造成基础设施的损害。