Collaborative Research: In Situ Borehole Measurements To Partition The Velocity Of The Greenland Ice Sheet Into Ice Deformation And Basal Sliding Components

在河床湿润的地方，冰块沿着其基底边界的滑动是运动的基本组成部分。基底滑动的估计通常是通过对观测到的地表运动进行逆分析得出的，使用的模型假设为Glen？各向同性冰的广义本构律。有证据表明，由于冰的热变化、首选结构和冰中的化学杂质等各种问题，这一定律并不能充分代表冰的变形。pi提出了一个创新的实验设计，以提高我们对冰的变形和滑动的理解。将在格陵兰冰盖上钻9个井，每个井约750米深，并延伸到床上，并使用超过675个传感器来观测冰的温度、冰的变形和基底滑动。对结果数据集的分析将产生420 × 106立方米冰块的完整3D速度场和完整应力和应变率张量。结果将用于评估和改进本构律，并将为测试反演方法提供数据集。如果格陵兰岛和南极冰盖因融化或冰山流入沿海海洋而显著退化，它们所含的水足以造成人口稠密的沿海地区和相关基础设施的大规模淹没。我们预测未来海平面上升的能力，由于无法准确地模拟连接这些冰盖和海洋的冰川动态而受到阻碍。该项目将提供数据集和对过程的深入了解，从而改进冰川动力学模型。

Sliding of an ice mass along its basal boundary is a fundamental component of motion where bed conditions are wet. Estimates of basal sliding generally result from an inverse analysis of observed surface motion using a model assuming Glen?s generalized constitutive law for isotropic ice. Evidence suggests that this law does not adequately represent ice deformation, due to a variety of issues including ice thermal variations, preferred fabric, and chemical impurities in the ice. The PIs propose an innovative experimental design to improve our understanding of the ice deformation and sliding. A grid of 9 boreholes, each approximately 750 m in depth and extending to the bed, will be drilled through the Greenland Ice Sheet and instrumented with more than 675 sensors to observe ice temperature, ice deformation, and basal sliding. Analysis of the resulting data set will yield the full 3D velocity field and full stress and strain rate tensors for a 420x106 m3 block of ice. The results will be used to assess and improve the constitutive law and will provide a data set for testing inversion methodologies.The Greenland and Antarctic Ice Sheets contain enough water to cause massive inundation of heavily populated coastal regions and associated infrastructure, if they were to degrade significantly through melting or delivery of icebergs to the coastal ocean. Our ability to predict future sea level rise is hampered by an inability to accurately model glacier dynamics that connect these ice sheets to the ocean. This project will provide data sets and consequent insight into processes that will lead to improved models of glacier dynamics.