Hydraulic Permeability of Temperate Ice

水调节海洋终止冰川和冰流的快速流动，影响海平面上升。具体来说，在快速流动的冰的边缘深处的冰川冰的流动，在那里冰接近其压力熔点，取决于冰颗粒边界处的静脉网络中储存的液态水的比例。因此，了解这些系统的渗透性至关重要。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。实验室冰的实验将告知粒度和含水量如何影响渗透率，而冰川冰的实验将研究冰的变形如何影响渗透率。这些实验的结果将提供一个更好的了解渗透性的冰的压力熔点附近的粒度，含水量和变形的函数。这些实验并不是为了模拟冰川中的间隙水流。该项目包括研究生和本科生的参与，并寻求包括从PolarTREC计划的参与者，让学生在K-12教室。该项目将首次测量温带冰的渗透性作为其粒度，含水量和叶理的函数。该团队将使用为该应用设计和测试的降头渗透器。将直径为140 mm、厚度高达70 mm的冰盘保持在压力下并处于压力熔化温度，同时冷却水在允许随时间降低的压头下瞬时流过该盘。水头下降速率提供渗透率值。不同的含水量将通过改变冰的盐度来实现，并将用先前冰变形实验中成功使用的量热法来测量。引入冰盘的冷水将含有荧光素染料，以允许在实验后在薄切片中研究流动网络。 从阿尔伯塔阿萨巴斯卡冰川的浅岩芯中采集冰川冰，进行实验，以评估冰的叶理类型和方向对渗透性的影响。这些测量也可能指出实验室制造的和冰川冰的渗透性之间的差异，这与结构各向异性无关。这些实验的结果将提供第一次测试的渗透率模型的基础上Poietille流动的水通过理想化的静脉网络。这些未经测试的模型是在冰川流动模型中估计冰渗透性的主要基础。该项目所产生的新的接地渗透率模型将允许冰流剪切边缘的温带部分的含水量进行估计，从而改进冰软化模型和剪切边缘中的相关冰流运动学。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.