Airborne radar-sounding investigations of the firn layer and subglacial environment of Devon Ice Cap, Nunavut, Canada

  • Author / Creator
    Rutishauser, Anja
  • Airborne radio-echo sounding (RES) is a powerful tool to derive properties of glaciers and ice caps over spatially extensive areas, and has fundamentally improved our understanding of the distribution and structure of near-surface snow and firn, the ice thickness distribution and englacial structure of ice masses, and the topography and thermal/hydrological properties of glacier beds. Although several airborne RES surveys have been conducted over Devon Ice Cap (DIC) in the Canadian Arctic prior to this work, the data had not been utilized to investigate either the properties of the near-surface firn or the subglacial hydrological conditions. The Devon Ice Cap is one of the largest ice masses in the Canadian Arctic, and is thought to have a cold-based interior where ice is frozen to the underlying bedrock. Under recent warming conditions leading to intensified summer melt, the firn of DIC has been affected by significant melting and refreezing processes that can complicate the measurement of the ice cap's surface mass balance. Here, we use airborne RES measurements over DIC to (i) investigate whether the nature of the glacier surface reflection can be used to characterize the spatial heterogeneity of the near-surface firn, and (ii) investigate the hydrological conditions beneath the ice cap.A comparison of airborne- and ground-based RES, along with analysis of shallow firn cores, led to the development of a novel technique where the spatial heterogeneity of firn is characterized via the scattering component of surface returns from airborne RES data. This method allows for the characterization of firn over spatially extensive areas and can help to identify regions where the structure and stratigraphy of the firn layer are affected significantly by melting and refreezing processes. Investigations of the RES reflection from the base of the ice column led to the identification and detailed characterization of a hypersaline subglacial lake and provide evidence for an extensive brine-network beneath DIC. Since basal ice temperatures are well below the pressure-melting point, this water system is considered to be brine-rich, to the point that the salinity significantly depresses its freezing point. Geological evidence suggests that a salt-bearing evaporite unit outcrops beneath DIC, and is presumed to be the solute source for the brine.The hypersaline subglacial lake beneath DIC and its surrounding hydrological and geological conditions are globally unique. The subglacial lake beneath DIC is not only the first to be discovered in the Canadian Arctic, but also the only spatially isolated hypersaline subglacial lake so far identified on Earth. This subglacial lake and the surrounding brine-network may host viable microbial habitats and could thus be world-class analogs for potential microbial habitats on other icy planetary bodies, such as Europa and Mars, where it has been suggested that sub-ice brine bodies may also exist. Thus, the unique subglacial water system beneath DIC, and the hypersaline subglacial lake in particular, are compelling targets for future in-situ sampling and biogeochemical investigations. The results from this study provide crucial information for the planning of future research over the subglacial lake and surrounding brine-network, including in-situ access and sampling of the water to explore its habitability for microbial life.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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