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Glacial erosional systems exhibit a complex, highly scaledependent phenomenology. Some aspects of modelling the development of glacial erosional landforms in response to glacial erosional processes acting over a wide range of scales are considered. The physics of ice at the glacier sole is discussed. A simple ice-water mixture theory is proposed. A method for finding the solution of the equations of motion of ice at the glacier sole based on the finite element velocities-pressure formulation is shown, which includes novel formulations for the sliding boundary condition, compression of ice and flow of water between ice and bedrock. These finite element formulations are used to simulate flows at the ice-rock interface. The use of the Laplace equation in simulating uni-axial flow is also considered, and further simulations are carried out using this equation. The results from these finite element simulations are used to consider erosional processes occurring at the glacier bed. The processes of abrasion are considered, and previous models are shown to be physically inconsistent. Cavitation, transiency and heterogeneity are shown to have an effect on clast-bed contact forces, and the local viscosity of ice is identified as being a further controlling variable on abrasion. These results are used to consider the likely development of hummocks of bedrock. A mass-balance analysis of basal debris is carried out and shown to have an important effect on erosional patterns. The equations describing the movement of a surface normal to itself are considered. Various solution techniques for these equations are tested, and requirements for the persistence of form under lowering are given. The modelling strategy used in this thesis is a nested hierarchy, with the various hierarchical levels corresponding to different scales. The effect of this hierarchisation on the modelling is discussed with respect to the generic properties of the systems, explanation and testability.

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The basal ice of temperate-type glacier Nigardsbreen is described in terms of a sediment facies model-after Lawson (1979). The ice is characterised using data obtained from sedimentological, chemical and stable isotopic analyses. These indicate that ice nearest the glacier bed is distinguishable from the ice above descriptively and genetically. In particular, the measurement of paired Oxygen and Hydrogen isotope contents, in accordance with theory proposed by Jouzel and Souchez (1982), provides a means of separating the basal facies ice component, formed by subglacial/basal regelation processes, from ice formed by 'normal' non-fractionating firnification processes. In the latter case the basic isotope content is close to that of the original precipitation whilst in the former this precipitation (meteoric) relationship is modified when ice is subjected to more or less predictable levels of fractionation during regelation. Some 1-1.5m of the basal ice, both early and late in the melt season, was found to originate from regelation. Within the basal facies ice, both stratified debris-laden layers comprising fine gravel-dominated debris up to concentrations of 1kg/l (c30% by volume) and clear intercalated ice types, reflect the regelation processes involved in debris entrainment and the freezing on of water. Thick (up to 40cm) layers of clean macrocrystalline 'regelation1 ice are considered to have been recrystallised. Coisotopic analysis may be used to highlight the fact that mixing of waters of differing origins occurs at the ice-bed interface and that the prediction of the extent of refreezing proposed by Jouzel and Souchez appears untenable. Major cation chemical analysis, undertaken to obtain data for use in the Souchez and Tison (1981) model of basal ice formational processes, which purports to discriminate between ice formed from water squeezed through the basal ice and water flowing, or ponded, at the bed, proved inconclusive. It appears that considerable desorption from clay minerals occurs and that squeezing of basal waters through the stratified facies may occur. In the absence of a clear statement of mineralogical composition in the basal debris clay fraction, which was attempted at Nigardsbreen, the Souchez and Tison model is seen to require development before it will reveal new information about basal processes. Measurements of temperature, sliding velocity and strain within subglacial cavities, in conjunction with observations on changes in sedimentological and isotopic conditions throughout the basal facies zone, are used to test and vindicate a descriptive model of the character, origin and evolution of the basal ice. The model is in turn proposed for further test.

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Tidewater glaciers form a significant drainage catchment of glacierised areas, directly transporting meltwater from the terrestrial to the marine environment. Surface melt of glaciers in the Arctic is increasing in response to warmer atmospheric temperatures, whilst tidewater glaciers are also exposed to warmer ocean temperatures, stimulating submarine melt. Increased freshwater discharge not only freshens fjord waters, but also plays a key role in glacimarine sedimentary processes, transporting sediment to glacial fjords. Despite this, the temporal evolution of meltwater production, storage and release from tidewater glacier systems at seasonal and interannual time scales is poorly understood. This leaves large uncertainties in the predictions for future sea level rise, ocean circulation and the impacts on the marine ecosystem. This study focuses on Kronebreen, a tidewater glacier which flows into the head of Kongsfjorden, north west Svalbard. Surface melt produces freshwater runoff, which is discharged from the grounding line as a buoyant, sediment laden plume, which spreads laterally across the surface water. This supraglacial melt is the dominant freshwater source, contributing an order of magnitude more freshwater to Kongsfjorden, than direct submarine melting of the ice face. Calibration of MODIS band 1 satellite imagery with in situ measurements of Total Suspended Solids and spectral reflectance, provides a method to quantify meltwater and sediment discharge. Plume extent has been determined for each cloud free day, from June to September, 2002 - 2013. Analysis of plume extent with atmospheric temperature and modeled surface runoff, gives a source to sea insight to meltwater production, storage and discharge. The extent of the plume changes in response to meltwater; larger plumes form when discharge increases. These results reveal that meltwater discharge into Kongsfjorden lags atmospheric temperature, the primary driver of meltwater production, by over a week during June and July. This is reduced to only 1 - 2 days in August and September, indicating a decline in meltwater storage as the ablation season progresses, and the development of more efficient glacial drainage. Sediment plumes respond to meltwater production, making them a valuable tool for quantifying meltwater discharge from a tidewater glacier. Insights to glacier hydrology can also be obtained when surface processes are also considered. This furthers the understanding of tidewater glacier hydrology, which is valuable for improving the accuracy of sea level rise predictions.

Despite the importance of ice streaming to the evaluation of West Antarctic Ice Sheet (WAIS) stability, we know little about mid-to long term changes in grounding line migration, ice streaming and ice accumulation in the upper Institute Ice Stream (IIS) catchment. In this thesis ground penetrating radar (GPR) and airborne radio-echo sounding (RES) methods have been employed to investigate the subglacial topography, internal stratigraphy and Holocene flow regime of the upper IIS catchment, in and around Horseshoe Valley. High resolution step-andcollect mode GPR was employed to assess the continuity of a Blue Ice Area (BIA) horizontal ice core climate record at Patriot Hills, where analysis has revealed two unconformities in the otherwise conformable 30,000 year climate sequence. By combining these data with airborne RES returns and pre-existing ice sheet models it is suggested that these unconformities represent periods of erosion, occurring as the former ice surface was scoured by katabatic winds in front of Liberty and Mable Hills. Snow_Blow simulations suggest that katabatic winds have scoured the leeward slopes of these mountain ranges for over 10,000 years. This temporal stability can account for the large volume of BI moraine deposits in Horseshoe Valley, where compressive BI flows promote glacial erosion and near-surface debris entrainment through freeze-on processes at the ice/bed interface and compressive thrust faulting. By investigating thicker ice flows in the upper IIS catchment and the Evans Ice Stream, this thesis has also analysed debris entrainment mechanisms at depth, where clasts are incorporated into the ice flow by englacial stratigraphic folding and shearing at the glacial thermal boundary, governed by spatial and temporal changes in ice flow, ice temperature and sediment availability. Mid-to long term changes in ice flow in the wider IIS catchment have been investigated from airborne RES transects, revealing internal layer buckling, and therefore former enhanced ice-sheet flow in three distinct tributaries of the IIS. Buckled ice layers throughout the slow flowing ice in the Independence Trough and the fast-flowing ice in the Ellsworth Trough suggest that enhanced ice flow through these topographically confined regions was the source of ice streaming and iceflow reconfiguration during the mid-to-late Holocene. Although buckled layers also exist within the slow-flowing ice of Horseshoe Valley, a thicker sequence of surface-conformable layers in the upper ice column suggests slowdown more than 4000 years ago, indicating that enhanced flow switch off here cannot be attributed to late-Holocene ice flow reorganisation. The dynamic nature of ice flow in the IIS and its tributaries suggests that ice stream switching and mass change may have been regular during the Holocene, and that these changes may characterise the decline of the WAIS in this area. These results have important implications for our understanding of ice-sheet dynamics and the response of the ice sheet to climate change and provides explanations for fluctuations in debris entrainment and transportation processes in Antarctica.

When radio echo sounding polar ice sheets weak stratified reflections are visible deep inside the ice sheets. These reflections are often called internal layers. Previously it has been suggested as a result of glacier flow models that these reflections can be treated as surfaces of equal age. In order for a reflection to be related to a single age feature in an ice sheet a one dimensional wave model must be adequate to model the propagation of a wavelet down to the feature and back to the surface. In this thesis four different one dimensional models are constructed each including different physics. It is shown that for the frequencies of interest to radio echo sounding it is sufficient to use the non-dispersive high frequency values of permittivity and conductivity for the ice in the models. The models are used on data from two drill sites. The first site is Berkner Island where I constructed an instrument to measure the electrical conductivity of the 181 metre long ice core. The second site is the Greenland Ice Core Project (GRIP) site at Summit of length 3028 metres. For both sites permittivity and conductivity profiles inside the ice sheet are calculated and put into the models with an estimate of the transmitted wavelet to produce expected radio echo profiles at the sites. For Berkner despite altering many parameters no match between model result and radar data was obtained. For GRIP a satisfactory match was obtained between model result and radar data. It is concluded that the weak, specular (plane like), st Ratified reflections at depth can be treated as isochrones. The strong reflections at shallow depths are a result of a combination of spherical reflection surfaces and interference between many closely spaced layers and cannot necessarily be treated as isochrones.

Glaciers and ice caps (GIC) are central parts of the hydrological cycle, are key to understanding regional and global climate change, and are important contributors to global sea level rise, regional water resources and local biodiversity. Multispectral (visible and near-infrared) remote sensing has been used for studying GIC and their changing characteristics for several decades. Glacier surfaces can be classified into a range of facies, or zones, which can be used as proxies for annual mass balance and also play a significant role in understanding glacier energy balance. However, multispectral sensors were not designed explicitly for snow and ice observation, so it is not self-evident that they should be optimal for remote sensing of glaciers. There are no universal techniques for glacier surface classification which have been optimized with in situ reflectance spectra. Therefore, the roles that the various spectral, spatial, and radiometric properties of each sensor play in the success and output of resulting classifications remain largely unknown. Therefore, this study approaches the problem from an inverse perspective. Starting with in situ reflectance spectra from the full range of surfaces measured on two glaciers at the end of the melt season in order to capture the largest range of facies (Midtre Lovénbreen, Svalbard & Langjökull, Iceland), optimal wavelengths for glacier facies identification are investigated with principal component analysis. Two linear combinations are produced which capture the vast majority of variance in the data; the first highlights broadband albedo while the second emphasizes the difference in reflectance between blue and near-infrared wavelengths for glacier surface classification. The results confirm previous work which limited distinction to snow, slush, and ice facies. Based on these in situ data, a simple, and more importantly completely transferrable, classification scheme for glacier surfaces is presented for a range of satellite multispectral sensors. Again starting with in situ data, application of relative response functions, scaling factors, and calibration coefficients shows that almost all simulated multispectral sensors (at certain gain settings) are qualified to classify glacier accumulation and ablation areas but confuse classification of partly ash-covered glacier surfaces. In order to consider the spatial as well as the spectral properties of multispectral sensors, airborne data are spatially degraded to emulate satellite imagery; while medium-resolution sensors (~20-60 m) successfully reproduce high-resolution (2 m) observations, low-resolution sensors (i.e. 250 m+) are unable to do so. These results give confidence in results from current sensors such as ASTER and Landsat ETM+ as well as ESA’s upcoming Sentinel-2 and NASA’s recently launched LDCM. In addition, images from the Landsat data archive are used to classify glacier facies and calculate the albedo of glaciers on the Brøgger Peninsula, Svalbard. The time series is used to observe seasonal and interannual trends and investigate the role of melt-albedo feedback in thinning of Svalbard glaciers. The dissertation concludes with recommendations for glacier surface classification over a range of current and future multispectral sensors. Application of the classification schemes suggested should help to improve the understanding of recent and continuing change to GIC around the world.

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