Collaborative Research: Investigation of Englacial Conduit Formation and Evolution

合作研究：Englacial 导管的形成和演化研究

• 批准号: 0097095
• 负责人: Robert Jacobel
• 金额: $ 20.68万
• 依托单位: Saint Olaf College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-15 至 2005-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0097095&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigation; Englacial; Conduit

ABSTRACTOPP-00-97137FountainOPP-OO-97095JacobelThis is a collaborative proposal from Principal Investigators at Portland State University and St. Olaf College. The movement of water through glaciers profoundly affects ice motion by influencing the stress distribution at the bed of the glacier. Therefore, a great deal of research has focused on the hydraulic nature of subglacial water transport. For temperate glaciers, the main source of water is surface-generated melt water. How this water reaches the glacier bed is of critical importance. Surface and englacial conditions may preferentially direct water flow to certain parts of the glacier bed and starve other parts of the bed. Therefore, an understanding of the controls on the spatial pattern of subglacial hydraulic conditions will depend on an understanding of the surficial and englacial conditions routing the water to the bed. Existing knowledge of englacial conduits has largely been a by-product of investigations into subglacial conditions. The goal of this project is to investigate the location, size, and hydraulic character of englacial conduits in an alpine glacier. This project will take place on the Storglaciaren in Tarfala, Sweden, where an extensive background of scientific wok exists and an active research program continues. The Principal Investigators will undertake a two-year field program that directly detects englacial conduits and uses ice radar to identify and trace the conduit paths. Low frequency radar measurements (5 MHz) will locate regions with strong englacial scattering suggestive of englacial water pockets and potentially productive areas for drilling. The radar will also be used to map the local bed depth and topography. Conventional hot-water drilling will penetrate the glacier to intersect englacial conduits. After a conduit is encountered, they will measure conduit diameter, water pressure, and water flow speed using down-hole instruments. They will attempt to determine the interconnectivity between conduits to measure their integrated hydraulic properties over the flow path. The path of the conduits will be traced using a high-resolution ground penetrating radar operated at 100 MHz, a frequency chosen both resolve individual conduits, and to monitor changes in echo characteristics corresponding to hydrologic changes over time.The results from this study will further our understanding of conduit origin and the controls on water routing to the bed. Identification of high-resolution radar signals with conduits of known sizes and locations will make significant progress towards future use of ice radar for detecting and mapping the location of englacial conduit. NSF Proposal Number: 0097137PI: FountainStatement of WorkWe will directly measure the geometry and hydraulics of englacial conduits The principle method of detecting englacial conduits will be drilling into the glacier to directly intersect the conduits. We will employ a hot-water drill capable of penetrating at rates of 1 m min-1. We will attempt to drill 20 boreholes in 3 different arrays for a total of 60 holes. During drilling we will monitor both drill depth and water levels. If openings appear on both sides of the borehole and flow is detected, either by natural particulates moving in the water or by a deflection of thread hanging from the camera, no further drilling in the hole will occur. If flow is detected careful hydraulic measurements will be made. The shape of the opening will be recorded and flow velocities will be measured. Within each borehole array and between arrays, we will test for interconnectivity by displacing the water in one borehole and measuring the response in other boreholes. The data from this project will test a model for the origin and evolution of conduits. Another test will compare the measured depth of a water-filled conduit and its hydraulic characteristics to that predicted by theory. The flow data and geometry of the conduits will be used to test Rothlisberger's (1972) theory. If we are able to monitor conduits over time we will also test Spring's (1980) non-steady state theory. From the borehole arrays and the radar imaging (Jacobel) we will infer the 3-dimensional topology of the conduit network at 6 different locations (over 2 years) in the glacier. These results will help to resolve the differences between the models of Shreve (1972) and Fountain and Walder (1998). More generally, spatial differences in the conduit networks imply differences in the flux of water to different areas of the bed and therefore impose an external condition on the development of subglacial hydraulic systems. These results will be reported in several journal articles.

这是波特兰州立大学和圣奥拉夫学院的主要研究人员的合作建议。水在冰川中的运动通过影响冰川底部的应力分布而深刻地影响冰的运动。 因此，大量的研究集中在冰下水输送的水力性质。 对于温带冰川来说，水的主要来源是表面产生的融水。 这些水如何到达冰川床至关重要。 表面和冰川条件可能会优先引导水流流向冰川床的某些部分，而使冰川床的其他部分挨饿。 因此，了解冰下水力条件的空间格局的控制因素将取决于了解将水引导至河床的表层和冰内条件。 现有的冰内水道知识主要是冰下条件调查的副产品。 本计画的目的是调查高山冰河内冰管道的位置、大小与水力特性。该项目将在瑞典塔尔法拉的Storglaciaren进行，那里有广泛的科学工作背景，并继续进行积极的研究计划。 主要调查人员将进行一项为期两年的实地项目，直接探测冰内管道，并使用冰雷达来识别和追踪管道路径。 低频雷达测量（5 MHz）将定位具有强烈冰内散射的区域，这表明冰内水囊和潜在的钻探生产区。 雷达亦会用来绘制当地海床深度和地形图。 传统的热水钻探将穿透冰川，与冰川内的管道相交。遇到管道后，他们将使用井下仪器测量管道直径、水压和水流速度。他们将试图确定管道之间的互连性，以测量其在流路上的综合水力特性。管道的路径将使用100 MHz的高分辨率探地雷达进行跟踪，所选频率既可以分辨单个管道，并监测随时间推移水文变化的回波特征变化。本研究的结果将进一步加深我们对水文变化的认识管道起源和控制水路由到床。 识别具有已知尺寸和位置的管道的高分辨率雷达信号将在未来使用冰雷达探测和绘制冰内管道位置方面取得重大进展。NSF提案编号：0097137 PI：喷泉工作说明书我们将直接测量冰内管道的几何形状和水力学 探测冰川内水道的主要方法是在冰川中钻孔，直接与水道相交。 我们将使用一个热水钻，其穿透速度为1 m min-1。 我们将尝试在3个不同的阵列中钻20个钻孔，总共60个孔。 在钻井过程中，我们将监测钻井深度和水位。 如果钻孔两侧出现开口，并且通过水中移动的天然颗粒或通过悬挂在摄像机上的螺纹的偏转检测到流动，则不会在孔中进行进一步的钻孔。 如果检测到流量，将进行仔细的液压测量。 将记录开口的形状并测量流速。 在每个钻孔阵列内和阵列之间，我们将通过置换一个钻孔中的水并测量其他钻孔中的响应来测试互连性。 该项目的数据将测试管道起源和演变的模型。另一个测试将比较测量的充水管道的深度和其水力特性与理论预测。 管道的流动数据和几何形状将用于检验Rothlisberger（1972）的理论。 如果我们能够监测管道随着时间的推移，我们也将测试春天（1980年）的非稳态理论。从钻孔阵列和雷达成像（Brackbel），我们将推断出冰川中6个不同位置（超过2年）的管道网络的三维拓扑结构。 这些结果将有助于解决Shreve（1972）和Fountain and Walder（1998）模型之间的差异。 更一般地说，在管道网络的空间差异意味着在不同地区的床的水通量的差异，因此施加冰下水力系统的发展的外部条件。这些结果将在几篇期刊文章中报道。