Ice streams: present-to-palaeo

冰流：从现在到古

• 批准号: 2323344
• 金额: --
• 依托单位: University of Aberdeen
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2323344
• 关键词: Ice; streams; present; palaeo

Ice streams are the arteries which drain large quantities of ice from the interior of ice sheets to the ice margin. From both palaeo and present they are known to display dynamical behaviour in relation to ice flow velocity. This is high during active ice streaming e.g. >1 km per year with subsequent shut-downs where velocity drops by order/s of magnitude. The high flow velocities are facilitated by a weak bed while significant resistance is provided by the lateral shear margins. Surface crevasses are found along the lateral shear margins, sometimes extending into the centre of the ice stream. The palaeo landform record preserves evidence of ice streaming (megascale glacial lineations, MSGL), lateral shear margins (shear margin moraines), and basal crevassing (crevasse squeeze ridges, CSRs). The genesis of CSRs is known from surging glaciers and importantly they can only be preserved when fast ice flow stops and is followed by passive ice retreat. This project aims to investigate the deformation characteristics of extant ice streams, existing crevassing theory and to apply this to the palaeo landform record to interpret past ice stream dynamics. Where possible, it will also generate quantitative palaeo-stress information. For example the orientations and ratios of tensile and shear stresses derived from the orientations of CSRs and the propagation angles between segments. The application of a geotechnical model to determine the potential overburden pressure, and thus a minimum value for ice thickness, related to the injection of sediment into basal crevasses will be investigated. The derivation of semi-quantitative data on palaeo-ice streams will be invaluable for numerical modelling of palaeo-ice sheets. The project will involve the processing and use of freely available satellite, sea floor and digital elevation model data. Mapping of ice stream surface crevasses and landforms on palaeo ice stream beds (CSRs and MSGL) will be undertaken in a GIS environment with subsequent quantification of the patterns analysed using the bespoke software FracPaQ. The spatial patterning of crevasses/CSRs and land forms will be investigated in the GIS to identify relationships between ice stream geometries and flow regimes. This studentship will suit a highly motivated individual interested in undertaking a quantitative project bringing together knowledge, skills and techniques from, glaciology, structural geology, fracture mechanics and geotechnics. The student will be supervised by a team with expertise in glaciology, geospatial analytics, geophysics and fracture mechanics.

冰流是将大量冰从冰盖内部排到冰缘的动脉。从古到今，它们都显示出与冰流速有关的动力学行为。这在活跃冰流期间是高的，例如，>1 km/年，随后关闭，其中速度以数量级/秒下降。弱床有利于高流速，而横向剪切边缘提供了显著的阻力。表面裂缝被发现沿着横向剪切边缘，有时延伸到冰流的中心。古地貌记录保存了冰流（巨型冰川线理，MSGL），横向剪切边缘（剪切边缘冰碛）和基底裂缝（裂缝挤压脊，CSR）的证据。CSR的起源是从涌动的冰川中得知的，重要的是，它们只能在快速的冰流停止并随后发生被动的冰退缩时才能被保存下来。该项目旨在研究现存冰流的变形特征，现有的裂缝理论，并将其应用于古地形记录，以解释过去的冰流动力学。在可能的情况下，它还将产生定量的古应力信息。例如，从CSR的取向和片段之间的传播角导出的拉伸应力和剪切应力的取向和比率。将研究岩土模型的应用，以确定潜在的上覆岩层压力，从而确定与沉积物注入基底裂缝有关的冰厚最小值。古冰流的半定量数据的推导对于古冰盖的数值模拟将是非常宝贵的。该项目将涉及处理和使用免费提供的卫星、海底和数字高程模型数据。冰流表面裂缝和古冰流床（CSR和MSGL）的地形图将在GIS环境中进行，随后使用定制软件FracPaQ分析模式的量化。将在地理信息系统中调查裂缝/CSR和地貌的空间格局，以确定冰流几何形状和流动状态之间的关系。这个奖学金将适合一个有兴趣从事定量项目的高度积极性的个人，该项目汇集了冰川学，结构地质学，断裂力学和岩土工程学的知识，技能和技术。该学生将由一个具有冰川学，地理空间分析，地球物理学和断裂力学专业知识的团队监督。