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

【摘要】marshallopp - 0520541matsuokaopp0520465智力优点：这是华盛顿大学和科罗拉多大学的主要研究人员合作提出的一项建议。冰川内部的水通道将融水从冰川表面输送到冰川床上。水润滑了河床，并在山地冰川中引入了显著的季节和每日冰速变化。目前的极地冰盖遭遇了轻微的表面融化，但冰盖沿海地区的持续变暖可能会改变这种情况。如果水能到达河床，冰流就会显著加速，最近在格陵兰岛已经观察到这一点。这可能最终导致北极地区的淡水快速排放，严重加剧全球海平面上升。绘制水通道及其时间变化对于理解地表融化和床层润滑事件之间的时空滞后，以及更广泛地理解冰川水文和力学至关重要。探冰雷达遥感技术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。首席研究人员将进行实验室实验和计算机模拟，以调查冰川内散射体的形状、坡度、方位角、尺寸和内容（空气或水）如何改变无线电回波强度，作为雷达频率和极化的函数。他们将在寒冷的房间里测量冰块内的钻孔和悬挂在开放空间内的热塑性聚合物的散射。后者模拟了冰川中充满水的散射。在每个实验场地，他们将检查来自多个包裹体的体散射，相对于散射体，雷达偏振平面的不同方位角。实验室数据将根据离散偶极近似（DDA）计算的特性进行分析。使用DDA模拟冰川内多个圆柱体、椭球体和裂缝的体散射，使我们能够检查雷达探测探索复杂冰川内部的能力。他们将借用美国陆军寒冷地区研究与工程实验室（CRREL）的雷达设备，并使用CRREL设备进行实验。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职业科学家之间的合作。第四，这个项目可以补充我们从未来地球、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.