Hydraulic Permeability of Temperate Ice

温带冰的水力渗透率

• 批准号: 2129252
• 负责人: Neal Iverson
• 金额: $ 24.11万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2129252&HistoricalAwards=false
• 关键词: Hydraulic; Permeability; Temperate; Ice

Water regulates the fast flow of marine-terminating glaciers and ice streams that affect sea-level rise. Specifically, the flow of glacial ice at depth in the margins of fast-flowing ice, where the ice is near its pressure melting point, depends on the fraction of liquid water stored in the network of veins at ice-grain boundaries. It is therefore critical to understand the permeability of these systems. The goal of this project is to better understand controls on ice permeability through tests on laboratory ice and glacier ice. Experiments with laboratory ice will inform on how grain size and water content affect permeability, while experiments with glacier ice will examine how deformation of the ice affects permeability. Results of these experiments will provide a better understanding of permeability of ice near its pressure melting point as a function of grain size, water content, and deformation. The experiments are not intended to simulate interstitial water flow in a glacier. This project includes graduate and undergraduate participation and seeks to include a participant from the PolarTREC program to engage students in K-12 classrooms.This project will measure for the first time the permeability of temperate ice as a function of its grain size, water content, and foliation. The team will use a falling-head permeameter designed and tested for this application. A disk of ice, 140 mm in diameter and up to 70 mm thick, is kept under pressure and at the pressure-melting temperature while chilled water transiently flows through the disk under a head that is allowed to decrease with time. The rate of head decrease provides the permeability value. Different water contents will be achieved by varying the salinity of the ice and will be measured with a calorimetric method used successfully in prior ice-deformation experiments. Chilled water introduced to ice disks will contain fluorescein dye to allow flow networks to be studied in thin-sections after experiments. Experiments with glacier ice, collected from shallow cores at Athabasca Glacier, Alberta, will evaluate the effect of ice foliation style and orientation on permeability. These measurements may also point to differences between permeability of lab-made and glacier ice that are unrelated to structural anisotropy. Results of these experiments will provide the first test of permeability models based on Poiseuille flow of water though idealized vein networks. These untested models are the primary basis for estimating ice permeability in glacier flow models. New empirically-grounded permeability models resulting from this project will allow the water content of temperate portions of ice-stream shear margins to be estimated, thereby improving models of ice softening by water and associated ice-flow kinematics in shear margins.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

水调节着影响海平面上升的直达海洋的冰川和冰流的快速流动。具体来说，在快流冰边缘深处，冰接近其压力熔点的地方，冰川冰的流动取决于冰粒边界脉网中储存的液态水的比例。因此，了解这些系统的渗透率是至关重要的。该项目的目标是通过对实验室冰和冰川冰的测试，更好地了解对冰渗透性的控制。实验室冰的实验将揭示颗粒大小和含水量如何影响渗透性，而冰川冰的实验将研究冰的变形如何影响渗透性。这些实验的结果将更好地理解冰在压力熔点附近的渗透性，作为晶粒尺寸、含水量和变形的函数。这些实验并不是为了模拟冰川间的水流。该项目包括研究生和本科生的参与，并寻求包括来自PolarTREC项目的参与者，以吸引K-12教室的学生。该项目将首次测量温带冰的渗透性，作为其颗粒大小、含水量和叶理的函数。该团队将使用专为该应用设计和测试的降头渗透率仪。一个直径140毫米、厚达70毫米的冰盘，在压力和压力融化温度下保持不变，而冷却水在一个允许随时间减少的封头下短暂地流过冰盘。水头下降速率提供了渗透率值。不同的水含量将通过改变冰的盐度来实现，并将用在以前的冰变形实验中成功使用的量热法来测量。引入冰盘的冷冻水将含有荧光素染料，以便在实验后在薄片中研究流动网络。从阿尔伯塔省阿萨巴斯卡冰川浅层岩心采集的冰川冰实验将评估冰的叶理类型和方向对渗透率的影响。这些测量也可能指出实验室制造的冰和冰川冰之间的渗透率差异，这些差异与结构各向异性无关。这些实验的结果将提供基于泊泽维尔水通过理想脉网渗透模型的第一次测试。这些未经检验的模型是冰川流动模型中估算冰渗透性的主要依据。由该项目产生的新的基于经验的渗透率模型将允许估算冰流剪切边缘温带部分的含水量，从而改进水软化冰的模型和剪切边缘相关的冰流运动学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。