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

冰块沿其底部边界的滑动是河床条件潮湿时运动的一个基本组成部分。基面滑移的估计通常是通过采用假定各向同性冰的Glen-S广义本构关系的模型对观测到的表面运动进行反分析的结果。有证据表明，由于包括冰热变化、首选组构和冰中的化学杂质在内的各种问题，这一定律并不能充分反映冰的变形。PI提出了一种创新的实验设计，以提高我们对冰变形和滑动的理解。一个由9个钻孔组成的网格，每个大约750米深，延伸到海床，将在格陵兰冰盖上钻孔，并安装超过675个传感器，以观测冰温、冰变形和底部滑动。对所得数据集的分析将得到420x106立方米冰块的完整3D速度场和完整的应力和应变率张量。结果将用于评估和改进本构定律，并将为测试反演方法提供数据集。格陵兰和南极冰盖含有足够的水，如果它们通过冰山融化或输送到沿海海洋而显著退化，就会造成人口稠密的沿海地区和相关基础设施的大规模洪水泛滥。我们预测未来海平面上升的能力受到无法准确建模连接这些冰盖和海洋的冰川动力学的阻碍。该项目将提供数据集和随后对过程的洞察，这些过程将导致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.