2 results for Appleby, John Richard

  • Strain and structure of a temperate, maritime glacier : Te Moeka o Tuawe / Fox Glacier, South Westland, New Zealand : thesis submitted in fulfilment of the degree of Master of Science in Physical Geography, at Massey University, Palmerston North, New Zealand

    Appleby, John Richard (2008-05-12T23:33:33Z)

    Masters thesis
    Massey University

    The study of glaciers has an immense significance for understanding and predicting global environmental change. The Earth is a dynamic system, consisting of individual units such as the cryosphere, an understanding of which may provide the basis for predicting future environmental change on a global scale. The dynamics of a glacier, a major indicator of the climatic and environmental situation is often presented as supraglacial structures, which reflect glacier formation, deformation and flow. Although structural attributes such as folds, faults, crevasse traces and foliation are commonly described in glaciers, the origin and significance of many of these structures remains unclear. This research project mapped the surface structures of Fox Glacier, using remote sensing in the form of aerial photographs and field observations, to produce a structural glaciological interpretation of the glacier surface, structural field maps of individual structures, and a schematic structural evolution of Fox Glacier. In addition, cumulative strain, and strain rates were calculated for three different areas of the lower Fox Glacier. The relationship between the observed structures and the measured strain rates has also been considered. Fox Glacier is located in the South Westland region of the South Island of New Zealand. From the Main Divide of the Southern Alps up to 3000m altitude, Fox Glacier flows for 13 km, terminating at an altitude of 270 metres in temperate rainforest, 17 km from the present coastline. The steep gradient allows for relatively rapid ice flow. Despite being a very dynamic glacier, very little research has been carried out on Fox Glacier in recent years with most research in the area being concentrated on its neighbour the Franz Josef, and even more so on the glaciers of the Eastern side of the Main Divide (e.g. the Tasman and Mueller glaciers). There is a high level of spatial variability in structural types observed, and the cumulative strain and strain rates measured on the surface of the Fox Glacier, with the variations being linked to valley topography including long-profile gradient and valley width. Strain rates of 208.78 y-1 and -162.06 y-1 were recorded on Fox Glacier. A relationship can be determined between observed glaciological structural features and measured strain rates, suggesting strain rate has an influence on the type, magnitude, location and frequency of these features, however, the study is only a ‘snap-shot’ of the strain conditions experienced in the most dynamically active time, during the summer ablation season. Developing predictive models of the structural evolution of glaciers may help further understanding of how glaciers respond to a change in climatic input, especially climatic warming. This is particularly important for larger ice sheet outlet glaciers whose structure and flow appear to reflect and control dynamics of the ice sheet behind

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  • Structural glaciology, dynamics and evolution of Te Moeka o Tuawe Fox Glacier, New Zealand : thesis submitted in partial fulfilment of the degree of Doctor of Philosophy in Geography at Massey University, Palmerston North, New Zealand

    Appleby, John Richard (2012)

    Doctoral thesis
    Massey University

    The aim of this thesis is to investigate and identify relationships between glacier structure, dynamics and debris transport at Te Moeka o Tuawe Fox Glacier; a temperate, maritime glacier in South Westland, New Zealand. Structural analyses of steep, exceptionally dynamic alpine glaciers that respond rapidly to changes in mass balance are rare. In particular, an appreciable dearth of New Zealand-focussed investigations into structural glaciology and glacial dynamics is found in the literature. Structural glaciology of Fox Glacier is determined by field observations, analysis of remotely sensed images, and ground-penetrating radar (GPR). Dynamics are investigated and quantified by the measurement of ice flow velocity and surface deformation. Debris transport processes occurring at Fox Glacier are investigated using field and laboratory analysis of grain size and clast morphology. The structures identified on Fox Glacier during this study display similar patterns to structural features of temperate valley glaciers reported in other studies. Strain-rates measured on the surface of Fox Glacier are higher than those reported for both cold-based glaciers and warm-based alpine-style glaciers in the European Alps. However, strain rates are lower than values typically reported for surging glaciers during surge phases. Unequivocal relationships between measured strain-rates and structures are not evident from this research. This may be because many structures are undergoing passive transport down-glacier, and do not reflect the prevailing local stress regime. Or, some structures, such as crevasse traces, may be close to crevassing, without crevasses actually forming. Results and findings from this study are a useful addition to the accumulating body of work that has emerged over the last decade on the South Westland glaciers. The vast majority of that research has typically focused on glacier fluctuations in response to climate, or has attempted to link late-glacial moraine-forming events to glacier dynamics. In contrast, the present study has attempted for the first time in New Zealand, to characterise and explain the spatial pattern of structures within a valley glacier in its entirety from the névé to the snout.

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