Ice streams: present-to-palaeo

冰流是将大量冰从冰盖内部排出到冰缘的动脉。从古代和现代来看，它们都显示出与冰流速度有关的动力学行为。这在活跃的冰流期间很高，例如每年1公里，然后关闭，速度按数量级下降/S。软床促进了高流速的形成，而侧向剪切边缘则提供了显著的阻力。沿着横向剪切边缘发现了表面裂缝，有时延伸到冰流的中心。古地貌记录保存了冰流(大尺度冰川线理，MSGL)、横向剪切边缘(剪切边缘冰隆)和底部裂隙(裂隙挤压脊，CSR)的证据。CSR的起源是从汹涌的冰川中得知的，重要的是，只有当快速的冰流停止并伴随着被动的冰退时，它们才能被保存下来。该项目旨在研究现存冰流的变形特征，现有的破洞理论，并将其应用于古地貌记录，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，由CSR的方向和节段之间的传播角度得出的拉应力和剪应力的方向和比率。将研究应用岩土模型来确定潜在的覆盖压力，从而确定与将沉积物注入底部裂缝有关的冰厚度的最小值。得出关于古冰流的半定量数据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可免费获得的卫星、海底和数字高程模型数据。将在地理信息系统环境中对古冰川床(CSR和MSGL)上的冰流表面裂缝和地貌进行测绘，然后使用定制软件FracPaQ对模式进行量化分析。将在地理信息系统中研究裂缝/CSR和地貌的空间模式，以确定冰流几何形状和流动状态之间的关系。该课程适合对从事量化项目感兴趣的人，该项目将冰川学、构造地质学、断裂力学和岩石学的知识、技能和技术结合在一起。这名学生将由一个在冰川学、地球空间分析、地球物理学和断裂力学方面拥有专业知识的团队进行指导。

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.