Modelling and field data analysis of subglacial hydrological conditions in West Greenland

• Main Author: Dow, Christine Fiona
• Published: Swansea University 2013
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752302

The rapid drainage of Greenlandic supraglacial lakes injects a substantial volume of water to the bed of the ice sheet, however the impacts of this water pulse on the development of basal hydrological systems are largely unknown. In this thesis, a coupled hydrological model approach is introduced whereby two established models are linked together to better examine short- and long-term (i.e. diurnal vs. seasonal) subglacial impacts of rapid lake drainage. The primary aim of the thesis is to test whether substantial, efficient channels form during or following a lake drainage event, particularly in regions of thick ice. Modelling is constrained by field data from an inland site on Russell Glacier catchment, with the model also applied to a simple tidewater glacier and a marginal glacier geometry. Basal boundary conditions in the model are examined using reflection seismic techniques, including amplitude-vs.-angle analysis to determine properties of the subglacial substrate in Russell Glacier catchment. Modelling results indicate subglacial conduits do not generally form during lake drainage events, particularly under thick ice. Instead, lake drainage water is evacuated by a temporary turbulent sheet. Following lake drainage, a distributed drainage system continues to dominate in the inland ice case-study; variable basal topography at this site enhances the highly transient behaviour of this drainage system. Both shallower surface slopes and thicker ice at the inland site contribute to a lack of seasonal conduit growth. Nearer the ice margin, efficient channels develop during the melt-season at a similar rate as recorded at Alpine glaciers, although these channels are transient features and a distributed system continues to contribute to ice dynamics. However, despite increased efficiency, modelled channel size near the margin does not generally exceed 2 m2. Seismic analysis indicates that subglacial sediment is a feature in various regions of Russell Glacier catchment and could impact hydrological development.