Ice streams: present-to-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.