1.1 Introduction
This research focusses on the dynamics and structural glaciology of Fox Glacier, a temperate, maritime, valley glacier located on the west coast of the South Island of New Zealand. In essence, it is an investigation into what structures are present in and upon Fox Glacier, how Fox Glacier moves and deforms over time, and how these two components are interlinked. In addition, the research provides a test of structural glaciology methods and considers their use on glaciers such as Fox Glacier. Intricate linkages exist between the general dynamic behaviour (how the motion of glaciers varies in time and space) and the structural configuration (the visual representation of strain and deformation) of glaciers, whereby structures can influence flow dynamics, and vice versa. Forces external to the glacier system also exert a strong influence on structure and dynamics, in particular climate and valley topography. The myriad of structures occurring within and expressed upon the surface of valley glaciers are often the most striking feature of valley glacier environments, and can provide a substantial quantity of information with regard to the behaviour and dynamics of these alpine ice bodies.
A considerable amount of research into glacier dynamics and glacier structure has been conducted on polythermal (e.g. Hambrey and others, 2005), surging (e.g. Lawson, 1996, Lawson and others, 1994, Sharp and others, 1988a, Woodward and others, 2002), Arctic (e.g. Hudleston & Hooke, 1980) and alpine glaciers (e.g. Allen and others, 1960, Glasser and others, 2003, Goodsell and others, 2003, Goodsell and others, 2005c, Hambrey & Milnes, 1977, Herbst and others, 2006), however, 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 dynamics of valley glaciers is found in the literature.
Studies of New Zealand glaciers have largely focussed on the larger, debris covered glaciers east of the Main Divide of the Southern Alps, and have been concerned with
mass balance and snowline measurements (e.g. Chinn, 1995, Chinn and others, 2005b, Willsman and others, 2008). The only published work on the structural glaciology of a
New Zealand glacier prior to Appleby et al. (2010) was by Gunn (1964).
There are a number of reasons why glacier structures have been a research focus, because they:
1. can control the distribution of sediment facies within a glacier (e.g. Bennett and
others, 1996);
2. can control the delivery of sediments to glacier margins and therefore sediment-
landform associations (e.g. Roberson, 2008);
3. provide a way of determining glacier flow dynamics (reviewed in Hambrey and
Lawson 2000);
4. may provide information on the conditions leading to ice-shelf collapse (e.g.
Glasser & Scambos, 2008);
5. may provide an analogy to deformation within rocks (Hambrey & Milnes, 1977,
Herbst and others, 2006); and
6. may provide information for the prediction of future sea level and climate
change (e.g. Lemke and others, 2007, IPCC, 2007, Oerlamans, 2001, Vincent and others, 2004, Azam and others, 2012).
1.2 Aims and Objectives
The overarching aim of this thesis is to determine the structure and dynamics of Fox Glacier. To address this aim, a number of specific research objectives have been developed. These are:
1. To document the key aspects of the structure of the glacier, through identifying
and classifying different suites of surficial and englacial structures using aerial photography, satellite images, field-based observations, ground-penetrating radar, isotopic fractionation analysis and sedimentary analysis;
2. To assess the appropriateness of ground-penetrating radar as a technique for
3. To sample and classifythe characteristics and provenance of different glacial sedimentary facies including thrust planes, medial moraines and proglacial deposits, determine the structural processes involved in their transport and deposition and compare these facies and their origin with other glacial environments;
4. To analyse surface strain-rates on Fox Glacier using velocity measurements and
deformation polygons and to investigate the relationship between these measured strain-rates and the distribution of visible structures;
5. To analyse the structure and dynamics of Fox Glacier in the context of current
theories on structural glaciology including ideas behind the location and cause of specific structures within the valley glacier environment; with the aim of further enhancing knowledge in the field of structural glaciology.
Further to objective five, specific research questions have been posed, including: Which (if any) theory of ogive formation sufficiently explains their presence and location on temperate ice bodies such as Fox Glacier? Are current theories on the formation of shear planes sufficient to explain their occurrence on temperate glaciers? And, can the formation of smaller scale structures such as crevasse traces and foliation be explained by current deformation models?
1.3 Thesis Structure
This thesis is divided into nine chapters. Chapter Two introduces Fox Glacier as the
study site, describes the glacial history of New Zealand and considers previous
glaciological research undertaken in the region. Chapter Three reviews existing
literature and research relevant to structural glaciology. The chapter then describes the
research methods used as part of the structural investigations of this research. Chapter
Four describes the structural evolution of Fox Glacier over a ~110 year period, along
with the contemporary structures observable at Fox Glacier. This chapter is intended to
provide a ‘complete’ investigation into the contemporary and historical structural
literature and theories. Chapter Five details a study of the sedimentology of Fox Glacier, with the aim of identifying how sedimentary patterns relate to structure and
dynamism. Chapter Six introduces the technique of ground-penetrating radar and
reviews its use as a tool for investigating glacial structures, then describes the results of
a ground-penetrating radar survey of the structural glaciology of Fox Glacier. Chapter
Seven outlines the theories behind strain-rate investigations on glaciers, describes the
methods used for measuring strain-rate and presents results of a strain-rate study at Fox
Glacier. Chapter Eight provides interpretation and a discussion of the results presented
in Chapters Four, Five, Six and Seven. Following this, Chapter Nine provides general
conclusions and a summary of the key findings of the research and suggests areas of interest for future research, both on Fox Glacier and overseas. Each chapter is intended to provide a distinct investigation into a certain aspect of the structural glaciology or dynamic behavior of Fox Glacier; Investigations which, when combined into a general discussion will provide a great deal of additional knowledge and understanding of the Fox Glacier system.