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Title: Reconstructing the Newfoundland ice sheet through the last glacial cycle
Author: McHenry, Maureen T.
ISNI:       0000 0004 7653 0841
Awarding Body: Ulster University
Current Institution: Ulster University
Date of Award: 2017
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Despite a long history of research, dating back to the 1800s, we have only a generalised overview of the flow patterns and behaviour of the former Newfoundland Ice Sheet with much of its basic properties unknown or contested. While a substantial body of work has been carried out this has primarily used traditional field mapping approaches with geomorphic and sedimentary features recording local to regional scale ice sheet events being extrapolated up to ice sheet scale to produce ice sheet models. This evidence, from fragmented study areas often misses the larger scale behaviour of the ice sheet which has been revealed in palimpsest glacial landscapes revealing reorganisation of the ice sheet bed or bedform preservation by cold based ice. The problems associated with this approach has been alleviated by using the more contemporary "top-down" ice sheet interpretation in which remote sensing is used to map individual glacial landforms across the full ice sheet bed. Detailed landform maps allow for unravelling of complex flow patterns and geometries recorded in superimposition and cross-cutting bedform assemblages, thereby revealing ice flow pathways, ice divide positions and ice sheet configuration at snapshots in the ice sheets evolution and from which ice sheets can be reconstructed. This thesis applies this top-down eomorphological-data-driven approach to reconstruct the former Newfoundland Ice Sheet using a new database of greater than 165, 000 individually mapped subglacial and ice marginal glacial landforms derived from a systematic island-wide remote sensing mapping programme. This new subglacial landform record, comprising of > 50,000 glacial lineations and > 107,000 ribbed moraines, has identified a palimpsest landscape of superimposition, crosscutting and bedform preservation of more complexity than has been previously recognised. This has revealed a dynamic ice sheet continually modifying its bed during periods of shifting flow geometry, significant restructuring in ice sheet configuration, large-scale migration of primary ice dispersal centres in the order of 140km, with periods of active warm-based bedform development separated by periods of high bedform preservation. These subglacial patterns record spatial and temporal fluctuation in thermal dynamics with bedform distribution patterns also recording a disparate pattern of thermal dynamics with cold-based sluggish flow persisting for longer in the south and southeast while other sectors experienced warm-based active ice flow for much of the last glacial episode. The newly documented subglacial landforms of glacial lineations and ribbed moraines provide the primary units for the glacial inversion technique which follows a formalised framework of known glaciological principles to extract the information glacial landforms provide. A flowset approach was used to group the large number of these landforms into summary units. These represent discrete ice flow events with the characteristics of component landforms providing key information on the spatial, temporal and glaciodynamics of their development. These flowsets were used in conjunction with a reconstructed retreat pattern that was derived from the new mapping of ~ 5000 ice marginal landforms of eskers and moraines and alongside numerical dating constraints from the literature and published radiocarbon databases. These provided the full evidence base from which a twelve-phase model of the last Newfoundland Ice Sheet has been produced. This new model has significantly advanced the knowledge of the behaviour of the former Newfoundland Ice Sheet and importantly brings its response patterns into more apparent correlation with major climatic events which drove abrupt change in ice sheet behaviour during the last glacial episode. The reconstruction is therefore an important framework for further investigation of the role and response patterns of ice sheets in the wider climate system which ultimately may lead to better understanding as to how contemporary ice sheets may respond to future climate change.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available