New insights into subglacial meltwater drainage pathways from the ArcticDEM

• Main Author: Lewington, Emma La Marre
• Format: Thesis
• Language: English
• Published: 2020
• Subjects: Ice Sheet; Keewatin
• Online Access: https://etheses.whiterose.ac.uk/29127/; https://etheses.whiterose.ac.uk/29127/1/EL%202020%20New%20insights%20into%20subglacial%20meltwater%20drainage%20pathways%20from%20the%20ArcticDEM.pdf

Subglacial hydrology has been linked to some of the most dynamic ice sheet behaviour and is likely a key regulator of the impacts of climate change on ice sheet mass balance. Evidence of palaeo-meltwater drainage on the beds of former ice sheets enables a large-scale assessment of the distribution and nature of the subglacial hydrological system, which helps to contextualise spatio-temporally limited observations from contemporary ice masses. In this thesis I develop a new fully-automatic mapping method to detect and map meltwater tracks. I use this as a starting point for holistic meltwater feature mapping (i.e. incorporating a range of erosional to depositional signatures) to investigate the nature and evolution of the subglacial drainage system across the former Keewatin sector of the Laurentide Ice Sheet. I map a range of meltwater features (i.e. eskers and associated assemblages, tunnel valleys and meltwater tracks) and propose the grouping of tunnel valleys and meltwater tracks under the term ‘meltwater corridor’. I then propose a formation theory for meltwater corridors based on the repeated interaction between a conduit and the surrounding hydraulically-connected distributed drainage system driven by variable surface meltwater inputs. This is a process known to occur in contemporary settings and is able to account for the observations made from the holistic landform map. This provides new insight into the distribution and nature of the subglacial hydrological system over a large area. Results within also contribute to a better understanding of temporal relationships through the use of eskers beads and fans as a time-transgressive signature, provide a mechanism for sediment access and entrainment at the bed and links the presence of meltwater pathways to the formation and preservation of other subglacial bedforms (e.g. drumlins and ribbed moraines) and overlying ice sheet dynamics. This thesis has benefited enormously from the recent release of freely available, widespread high- resolution digital ...