Bessette Jonathan T, Schroeder Dustin M, Jordan Thomas M, MacGregor Joseph A
Department of Mechanical and Aerospace Engineering University at Buffalo Buffalo NY USA.
Department of Geophysics Stanford University Stanford CA USA.
Geophys Res Lett. 2021 May 28;48(10):e2020GL091432. doi: 10.1029/2020GL091432. Epub 2021 May 20.
Radar-sounding surveys associated with the discovery of a large impact crater beneath Hiawatha Glacier, Greenland, revealed bright, flat subglacial reflections hypothesized to originate from a subglacial groundwater table. We test this hypothesis using radiometric and hydrologic analysis of those radar data. The dielectric loss between the reflection from the top of the basal layer and subglacial reflection and their reflectivity difference represent dual constraints upon the complex permittivity of the basal material. Either ice-cemented debris or fractured, well-drained bedrock explain the basal layer's radiometric properties. The subglacial reflector's geometry is parallel to isopotential hydraulic head contours, located 7.5-15.3 m below the interface, and 11 ± 7 dB brighter than the ice-basal layer reflection. We conclude that this subglacial reflection is a groundwater table and that its detection was enabled by the wide bandwidth of the radar system and unusual geologic setting, suggesting a path for future direct radar detection of subglacial groundwater elsewhere.
与格陵兰岛海华沙冰川下方一个大型撞击坑的发现相关的雷达测深调查显示，冰下存在明亮、平坦的反射，据推测这源于冰下潜水面。我们利用对这些雷达数据的辐射测量和水文分析来检验这一假设。基底层顶部反射与冰下反射之间的介电损耗及其反射率差异，对基底物质的复介电常数构成了双重约束。冰胶结碎屑或裂隙发育、排水良好的基岩都能解释基底层的辐射测量特性。冰下反射体的几何形状与等势水头等高线平行，位于界面以下7.5 - 15.3米处，比冰 - 基底层反射亮11 ± 7分贝。我们得出结论，这种冰下反射是一个潜水面，其被探测到得益于雷达系统的宽带以及特殊的地质环境，这为未来在其他地方直接通过雷达探测冰下地下水指明了一条道路。
