Collaborative Research: Polarimetric Characteristics of Radio-wave Scattering from Water Pathways within Glaciers Deduced by Laboratory Experiments and Computer Simulations

ABSTRACTMarshallOPP-0520541MatsuokaOPP0520465Intellectual优点：这是来自华盛顿大学和科罗拉多大学的首席研究人员共同提出的建议。冰川内的水路将融化的水从冰川表面输送到冰川床。水润滑了冰床，并在山区冰川中引入了显著的季节和每日冰速变化。目前的极地冰盖遇到了轻微的表面融化，但冰盖沿海地区持续变暖可能会改变这一点。如果水可以到达海床，冰流可能会显著加速，最近在格陵兰岛观察到了这一点。这最终可能导致北极淡水的快速排放，大大促进全球海平面的上升。绘制水路及其时间变化图对于了解地表融化和床润滑事件之间的空间和时间滞后，以及更广泛地理解冰川水文学和力学是至关重要的。利用探冰雷达进行遥感是研究冰层内部时空变化的一种可行方法。雷达研究可能揭示的不仅仅是基岩和内层的几何形状。首席调查员将进行实验室实验和计算机模拟，以调查冰川中散射体的形状、坡度、方位、尺寸和内容物(空气或水)如何随着雷达频率和偏振而改变无线电回波强度。他们将测量寒冷房间中冰块内钻孔和悬挂在开放空间内的热塑性聚合物的散射。后者给出了冰川中充满水的散布的模拟。在每个实验场地，他们将检查雷达极化平面相对于散射体的不同方位的多个包裹体的整体散射。实验室数据将根据离散偶极子近似(DDA)计算的特性进行分析。将使用DDA模拟来自多个圆柱体、椭球体和冰川内裂缝的总体散射，使我们能够检查雷达探测探测复杂冰川内部的能力。他们将从美国陆军寒区研究与工程实验室(CRREL)借用雷达设备，并使用CRREL设施进行实验。更广泛的影响：该项目将为两名本科生提供实验室和理论分析方面的研究经验。其次，这项研究将有助于NSF了解北极环境及其全球影响的总体目标。第三，该项目将启动不同机构的早期科学家之间的合作。第四，这个项目可以补充我们从未来对地球、火星和其他行星的极化雷达探测推断地下特征的能力。

ABSTRACTMarshallOPP-0520541MatsuokaOPP0520465Intellectual Merits: This is a collaborative proposal by Principal Investigators from the Universities of Washington and Colorado. Water pathways within glaciers transport melt water from the glacier surface to the glacier bed. Water lubricates the bed and introduces significant seasonal and daily variations in ice velocity in mountain glaciers. Current polar ice sheets encounter minor surface melting, but ongoing warming in coastal regions of the ice sheets may change this. If water can get to the bed, significant acceleration of ice flow may occur, which has recently been observed in Greenland. This could ultimately result in rapid fresh-water discharge in the Arctic, significantly contributing to global sea-level rise. Mapping water pathways and their temporal changes is crucial for understanding the spatial and temporal lags between surface melting and bed lubrication events and, more generally, glacier hydrology and mechanics. Remote sensing with ice-penetrating radar is a viable way to investigate temporal and spatial variations of the ice interior. Radar studies can potentially reveal much more than simply the geometry of the bedrock and internal layers. The Principal Investigators will carry out laboratory experiments and computer simulations to investigate how shape, slope, azimuth, dimensions, and contents (air or water) of scatterers within glaciers alter radio-echo intensities as a function of radar frequency and polarization. They will measure scattering from boreholes within an ice cube in a cold room and from thermoplastic polymers that are hanged within an open space. The latter gives an analog of water-filled scatter in glaciers. In each experimental venue, they will examine the bulk scattering from multiple inclusions for various azimuths of the radar-polarization plane relative to the scatterers. Laboratory data will be analyzed in the light of characteristics computed with Discrete Dipole Approximation (DDA). Bulk scattering from multiple cylinders, ellipsoids, and fractures within glaciers will be simulated using DDA, allowing us to examine the ability of radar sounding to explore complex glacier interiors. They will borrow the radar equipment from the U.S. Army Cold Region Research and Engineering Laboratory (CRREL) and use CRREL facilities for the experiments. Broader Impacts: The project will provide research experience for two undergraduate students in both laboratory and theoretical analysis. Second, this research will contribute NSF's overall goals to understand the Arctic environment and its global impact. Third, this project will initiate collaboration between early-career scientists at different institutions. Fourth, this project can complement our ability to infer subsurface characteristics from future polarimetric radar sounding of the Earth, Mars, and other planets.