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    A multi-parameter study of iceberg calving and the retreat of Haupapa/Tasman Glacier, South Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Geography at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Dykes, Robert Campbell
    Iceberg calving is an efficient ablation process which introduces mechanical instability to glacier systems and can cause a non–linear climatic response. This thesis quantifies the calving retreat of the freshwater–terminating Tasman Glacier and the coeval expansion of Tasman Lake, at a range of temporal and spatial scales. Tasman Glacier is the longest glacier (c. 23 km) in New Zealand, and lies east of the Main Divide of the Southern Alps, extending from a névé at 2400 m to an ice–contact lake at c. 727 m. Although 20th century warming caused down–wastage, it remained at its Little Ice Age terminus until the late 20th century. Since then, calving retreat has occurred, allowing a large proglacial lake to form. Remote sensing datasets, namely satellite imagery, time–lapse photography, and passive seismic recording were used to observe and characterise retreat and calving style and magnitude at inter–annual, sub–annual, and intra–event time–scales. Between 2000 and 2013 Tasman Glacier has retreated c. 6 km, corresponding to an average decrease in ice surface loss at the terminus of 0.37 km2 a-1, through a combination of melting of the lower glacier and iceberg calving. However, an order of magnitude increase in retreat occurred since 2006 with peak retreat rates in excess of 1.5 km2 a-1. This retreat has seen a continuation of accelerated ice loss since the formation of Tasman Lake in the late 1980s. A four–stage model for the transition between melt and calving regimes refined in this study has indicated that the processes and factors that contribute to the development of a proglacial lake at the termini of debris–covered glaciers worldwide are similar, although they act over different time–scales depending on glacier dynamics and climate regimes. At a sub–annual time–scale calving events between October 2011 and November 2012 were identified at a rate of 0.94 events d-1, with significant seasonal differences, in that the number of calving events increased during the ablation season. Calving events driven by thermo–erosional notching at the waterline were the most frequent of all calving events, followed by events initiated by over–steepening of the subaerial ice cliff, then sub–aqueous and buoyancy–driven calving events. Buoyancy–driven calving events were of the largest magnitude, and had the greatest effect on glacier retreat. Such events are initiated by a combination of glacier thinning, increased water–depth at the terminus, terminus geometry, subaqueous melt and calving, perturbations in lake level and near–field earthquakes.The increase in calving frequency during spring and summer 2011/12 was directly related to the increase in thermo–erosional notch events. Correlation of calving frequency, lake level and lake temperature time–series data reveals that the frequency changes are related to the stability in lake level and elevated lake temperatures. This indicates that although calving retreat rate has increased, low–magnitude calving events are the most frequent, but low frequency, high magnitude buoyancy–driven events have had the greatest influence on net glacier retreat. Calving events at Tasman Glacier emit seismic signals similar to those found at other calving margins globally. All calving events generated seismic signals that had emergent onsets with weak frequencies above 5 Hz, followed by a high amplitude phase with frequency content between 1 and 5 Hz and a protracted coda. The study highlighted relationships between calved iceberg size and seismic parameters (e.g., signal duration, peak amplitude and integrated amplitude) that can be used to remotely assess the frequency, style and magnitude of calving events. It was shown that seismic waveforms, signal duration, and energy indicate order–of–magnitude differences in calving event size and style. However, due to the continuum of spatial and temporal scales over which calving operates, seismic signals are generally too variable to completely substitute direct observational data. Signal analysis algorithms analogous to those used in volcano seismology have been developed for the automatic detection of iceberg calving and were thoroughly tested against independent observational datasets. The algorithms and thresholds can be readily deployed in future seismic studies of dynamic ice margins at freshwater–terminating glaciers.
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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
    (Massey University, 2012) Appleby, John Richard
    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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    Speckle photography and displacement analysis of large structures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Production Technology at Massey University
    (Massey University, 1997) North, Heather Claire
    This research demonstrates the feasibility of a full-field photographic method for remotely measuring the movement of large deforming objects. 'Large objects' could include civil engineering structures such as dam walls, buildings and bridges, and geological phenomena such as glaciers. Such structures must be examined in situ and preferably by a non contacting method. The objective is to measure motion from time lapsed photographs of the moving object. The method is based on speckle photography which is a well developed optical metrology technique for deformation measurement of engineering structures in laboratory conditions. Its application to large scale structures illuminated in sunlight at high imaging demagnifications has demanded some significant extensions and modifications to the technique. Imaging these large objects offers a unique set of challenges which include the establishment of rigid tripods from which to take the time lapsed photographs in rugged glacial terrain, the variation of illumination in terms of both quality and angle of incidence, imaging through several kilometres of turbulent atmosphere and recording the signature texture of the object surface onto film at high imaging demagnifications. The effects of these factors are considered both conceptually and experimentally, providing fundamental understanding of the problem. Displacement analysis is performed primarily by interrogation of time lapsed negative pairs using an unexpanded laser beam, as is generally the case in speckle photography. An automated system is developed to make practical the analysis of multiple points in the field of view. In parallel, a new digital technique is introduced where displacement results are obtained by pattern matching in digital versions of the speckle images. This analysis method is shown to be highly suitable for the application to glacier flow. Registration of the pair of time lapsed images is performed by calculating the affine transform describing the image misalignment (introduced at either the recording or analysis stage) within the non-deforming areas of the field of view. Use of this novel technique allows pairs of single exposures, rather than double exposures, to be examined, and it also increases the sensitivity of measurement. Two dimensional motion fields representing glacier flow are presented, leading to the conclusion that the technique is feasible in sunlight illumination, for a variety of glacial surface types and at high imaging demagnifications.