Ice sheet reconstructions are concerned with an understanding of the dynamics of palaeo ice sheets through time. This involves ascertaining the configuration of ice domes and flow patterns, as well as the evolution of glaciation and deglaciation. The use of remotely sensed data (radar and visual/near infra-red imagery) has been a key development in these studies, allowing the rapid mapping of individual landforms over large areas. These data sources record electro-magnetic reflectance of an illuminated landscape which leads to the introduction of random and systematic bias’. This research explores the propagation of these bias’ and recommends that, in order to obtain optimum imagery, sensor spatial resolution is < 30m and solar elevation is <20º at acquisition. More problematic is the selective bias introduced by the solar azimuth in relation to the orientation of linear landforms. This cannot be removed and requires a good knowledge of the study area or an additional primary data source (e.g. radar or digital elevation model). DEMs are rapidly supplementing, and in many cases replacing, satellite imagery in landform mapping. However as they record surface elevation, rather than surface reflectance, they should be able to provide a bias-free data source for landform mapping. Methods by which the landscape can be visualised are explored with the purpose of providing a bias free method, although no single visualisation was found to be satisfactory. A suitable mapping strategy was developed through the application of these methods to the mapping of glacial landforms from a DEM of the Lake District. Once landform mapping has been completed it is common for mapped landform data to be generalised in order to reduce their complexity and so aid interpretation. This is usually a manual technique that involves reducing several thousand individual lineaments to summary lines. The thesis concludes with the development of a set of tools to help with this manual process, as well as provide quantitative verification. This is then applied to the landforms mapped from the Lake District in the previous chapter. A method for the automation of this procedure is also suggested.

The cryosphere impacts global climate in various ways. Snow and ice have a higher albedo than land or the open ocean and therefore affect the total reflectivity of the earth. Sea ice forms an insulating layer over the polar oceans controlling both heat and water vapour fluxes between the atmosphere and polar ocean. Ice sheets hold around 77% of Earth's freshwater reserves, and recent increases in ice loss from the Earth's ice sheets are cause for concern. This thesis develops numerical tools that can be used for the study of various ice processes such as ocean -- sea ice interaction, ice sheet and glacier dynamics. A coupled ocean - sea ice model is developed, using the open source, unstructured, adaptive ocean model Fluidity and a finite element sea ice model developed at the Alfred Wegener Institute of Polar and Marine Research, FESIM. The tightly coupled model is verified and validated through a series of tests, demonstrating its dynamical capabilities. The sea ice dynamics are a model of Elastic-Viscous-Plastic rheology, as described in Hunke and Dukowicz. The thermodynamic parameterisation is similar to the 1D simplest model of Parkinson and Washington which is based on the zero-layer approach of Semtner. Furthermore, a new computational framework for carrying out ice sheet simulations is presented. A thermo-mechanical, non-linear, full-Stokes model is used to carry out the exercises of the Ice Sheet Model Intercomparison Project for higher--order models (ISMIP--HOM). The results presented here show that Fluidity compares favourably with other ice sheet models. Further tests are performed to demonstrate the use of dynamic adaptive remeshing in lowering the computational cost of models compared to their structured, fixed-mesh counterparts, by focusing resolution only where and when required. Finally, initial simulations of the full Greenland ice sheet are performed demonstrating the potential utility of adaptive meshes for large-scale, full-Stokes modelling.

The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly understood, in terms of hydrology, water storage and biogeochemical processes. High temporal resolution biogeochemical sampling of bulk meltwaters at a typical, land-terminating outlet glacier of the GrIS was employed in order to infer processes at the ice sheet bed over three contrasting melt seasons. No high temporal resolution geochemical datasets previously existed for ice sheet environments, mainly due to inaccessibility. Bulk meltwaters comprised differing propOltions of waters originating from a widespread, distributed subglacial drainage system (these delayed flow waters being solute enriched due to prolonged residence times and high rock:water ratios in the contributing environments), and an efficient channelized system (dilute surface waters rapidly transmitted to the margin). Two-component chemical mixing models, in combination with MODIS satellite imagery, revealed that delayed flow was released continuously. However, higher volumes were released at times of subglacial outburst events when draining surface lakes interacted with the bed and expelled stored waters. Dissolution experiments and geochemical data indicated that these waters may have been stored at the bed over winter, or longer, and comprised one-third of delayed flow release in any given year (~O.02 km\ The geochemical data, in combination with 01 80 -H20 isotope data from bulk meltwaters and surface ice, were able to identify subglacial drainage system evolution and increasingly distant water sources contributing to bulk meltwaters. Enhanced silicate dissolution was observed compared to smaller valley glaciers, which may lead to enhanced CO2 sequestration compared to carbonate weathering' environments. Chemical weathering rates were lower than would be expected for a poly thermal ice mass, likely due to low reactivity bedrock. Ionic fluxes were higher in high melt years, which is a further indication of stored water release due to extensive basal flushing. Finally, isotopes of sulphate demonstrated that there are both oxic and anoxic conditions at the bed of the GrIS, with potential for highly anoxic sulphate reducing conditions in the interior.

Glaciers cover approximately 10% of land surface, but are rarely considered active components of global biogeochemical cycles. Research over the past two decades has revealed that active and widespread hydrological systems are present at the bed of the Antarctic and Greenlandic Ice Sheets. This has driven recent concern in the biogeochemistry of subglacial environments. The ocean waters surrounding the ice sheets harbour highly productive, ecologically and economically important waters. Only recently has an ice sheet influence, via the export of nutrients, been considered. A high-resolution hydrological dataset and dissolved and particulate geochemical record, from multiple ablation seasons of two contrasting Greenland Ice Sheet catchments were collected. These were used to infer subglacial biogeochemical weathering processes, and associated nutrient cycling. Estimates of glacial bioessential nutrient fluxes to downstream environments revealed the potential for significant export of iron and phosphorus to the near-coastal euphotic zone. Labile particulate nutrient species dominate total nutrient export due to the high concentrations of extremely fine-grained and highly reactive suspended sediments in meltwaters. Meltwater filterable iron and phosphorus concentrations were found to be temporally variable over an ablation season due to an evolving subglacial meltwater source coupled with evolution of subglacial drainage. More remote regions of the subglacial environment are progressively flushed over the course of an ablation season, releasing waters rich in nutrients compared to major ions. "Outburst events", driven by the drainage of supraglacial lakes into the subglacial environment, were found to be an especially important mechanism in driving pulses of stored, nutrient rich meltwaters downstream. It is demonstrated that dissolved macronutrient (nitrogen, phosphorus and silica) and solute export from the Greenland Ice Sheet are annually dynamic, with significantly higher fluxes in warmer melt years. This is likely to be driven through more exhaustive basal flushing by supraglacial meltwaters, and by progressively more efficient linking of remote regions of the subglacial environment with downstream drainage. Changes in nutrient export from the Greenland Ice Sheet with enhanced melting under future climate warming scenarios are therefore likely.

Over a tenth of the Earth is covered by microbially-dominated glacial ecosystems. The microbial activity on glaciers and ice sheets is postulated to have regional, potentially global, impacts on environmental biogeochemical nutrient cycling. Their activity is also believed to affect glacier surface albedo, potentially enhancing the effects of climate change in these environments. However, the magnitude and implications ofthe glacial microbial dynamics are still unknown. This PhD research aimed to elucidate the microbial dynamics within different glacier surface habitats on the Greenland Ice Sheet, together with their impacts on glacier organic matter production, nutrient export and albedo reduction. A variety of original laboratory and field studies were designed to address these aims. Microorganisms on glacier surfaces were found to be responsible for significant amounts of organic matter production, accumulation, recycling and export from glacier surfaces. The microbial communities were shown to be stable throughout a melt season, following a fast community turnover after initial snow melt. They could also be seeded by small amounts of aeolian microorganisms. The organic matter the m icrobes produced and transformed was substantial enough to reduce glacier surface albedo by -16%, equivalent to - 18 Gt yr-I of potential melt increase for the Greenland Ice Sheet, in the current climate. Furthermore, biogeochemical nutrient cycling by glacial microorganisms was successfully applied to fertilising nutrient-deprived sediment, for potential applications in countries struggling with barren soils and potentially for terraforming other planets. The results ofthis body of work thus have significant implications for predicting the impacts of climate change and anthropogenic pollution on glacial environments; future estimates of nutrient export from glaciers and the effects on downstream environments; and even for developing new soil fertilisation techniques for terrestrial and extraterrestrial use.

The Irish Ice Sheet has been an active area of research since the mid 19th century. Traditional approaches to reconstructing the Irish Ice Sheet have used the landform and sediment record to define its extent and formulate models of its geometry through the Pleistocene. Subglacial bedforms dominate the landform record and till is the dominant sediment. The bedforms demonstrate a complex ice flow history, however recent research has indicated that ice flow directions interpreted from subglacial bedform geomorphology could be misleading. It is therefore appropriate to consider other methods of investigating ice flow patterns that are independent of geomorphology. As the bedforms are primarily composed of till, an alternative approach to determining flow directions is to establish the provenance of the till using geochemistry. High density regional soil geochemical data sets comprising> 1 0,000 sample points are available for the north of Ireland. This thesis applies a multi variate statistical approach to the soil geochemistry to establish till provenance in the northern sector of the Irish Ice Sheet. Till provenance is determined for the entire region and also investigated in a range of palaeoglaciological contexts. Results are compared to recent models of flow history for the Irish Ice Sheet. Till provenance is also applied to determine the degree of glacial dispersal of gold mineralisation from known host regions in the north of Ireland. The thesis demonstrates that till in this sector of the Irish Ice Sheet shows a very strong geochemical link to local bedrock composition, with sharp geochemical transitions observed at lithological boundaries. However, subglacial transport and clear dispersal patterns are detected particularly at flow set scale in a range of palaeoglaciological contexts. Geochemical evidence is found for flow directions for each of the major phases of the history of the last Irish Ice Sheet and this evidence compliments existing models. No unequivocal glacial dispersal patterns are detected for gold, though the prospectivity of currently unexplored areas is highlighted. The research demonstrates that soil geochemistry makes a significant contribution to Quaternary research in Ireland which has not been previously recognised.

This thesis describes and interprets the glacial sediments mapped in the area of East Aberdeenshire that is included within the boundaries of Sheet 77 of the one inch to the mile geological map of Scotland, The dominant glacial sediment recorded is a grey brown till deposited from ice which moved in an eastward direction across the area. The composition of the clasts and matrix of this till is a reflection of the bedrock geology immediately underlying it. Near the coast, and in the northeast quadrant of the Sheet 77 area, this local till is succeeded by a red coloured till which was deposited from ice which moved northwards along the coast, The composition of this till is related to sediments found offshore and to the south of Sheet 77. Fluvioglacial sediments are found in association with both till deposits, being concentrated in the Dee and Don river valleys and in the coastal zone. Minor glaciolacustrine deposits, primarily associated with the red till also occur. It is deduced that most of the till was deposited by meltout and flow processes during deglaciation. Only one instance of a lodgement till has been recorded. This interpretation is strengthened by the common association of both tills with meltwater sediments which were deposited during deglaciation when large masses of stagnant ice disintegrated and melted in situ. By correlation with areas outside of Sheet 77, the glacial sediments are interpreted as having been deposited during the Late Weichselian stadial which began some 23,000 years b,p. with the area probably becoming ice free before 13,000 years b.p, The area has not been covered by ice since this time.

The controls on glacial movement remain one of the most poorly understood elements of the glacial system, largely due to the inaccessibility of the subglacial environment. Here a geotechnical study is presented that investigates the behaviour of till under pore pressure controlled decreases in normal effective stress. This is supplemented with field data from subglacial wireless probes, dGPS, GPR and a UAV survey of the glacial foreland to provide a broad view of subglacial deformation at Skalafellsjökull, Iceland. The geotechnical laboratory investigation was undertaken on till sampled from an ice marginal location at Skalafellsjökull, close to the probe deployment site. This showed that the till adhered to the Mohr-Coulomb model, behaving plastically. In addition, a back pressure shear box was used to model pore pressure controlled reductions in normal effective stress. Linearly reducing normal effective stress by increasing back pressure resulted in episodic increases in horizontal strain rates. Small reductions in shear stress resulted in large strain rate reductions but dilation hardening did not occur. Dilation hardening has previously been suggested as a causal factor in stick-slip glacial motion and a reason for the apparent scale dependence of till rheology, but these experiments suggest it may not be as significant as previously thought. High spatial variability was found throughout the field investigation in probe, dGPS and mapping data from the UAV survey. dGPS deployed above in situ subglacial probes recorded hourly ice movement indicative of stick-slip motion but it was not possible to link this motion to subglacial processes via probe data. Pore pressure data suggested spatially variable coupling to the subglacial hydrological system and inconsistent forcing by surface melt. Tilt data showed consistent movement patterns and lacked regular up-glacier movements previously thought to indicate ice-bed decoupling and sliding. The lack of evidence for forcing of velocity variability from the in situ data suggests a global forcing mechanism at this site, probably longitudinal or lateral coupling to higher velocity areas of the glacier. The spatial variability of the subglacial data has similarities to the metre scale spacing of flutes on the foreland mapped with the UAV imagery, suggesting flute formation has potential to result in complex probe behaviour.

This study examines how longitudinal foliation develops in glaciers and ice sheets in a wide range of topographic, climatic, and dynamic settings, at a variety of spatial scales. Study locations include four valley glaciers in Svalbard (Austre Brøggerbreen, Midtre Lovénbreen, Austre Lovénbreen, and Pedersenbreen), a valley glacier in Canada (Sermilik Glacier), and seven outlet glaciers in Antarctica (Hatherton Glacier, Taylor Glacier, Ferrar Glacier, Lambert Glacier, Recovery Glacier, Byrd Glacier, and Pine Island Glacier). Detailed structural mapping of the valley glaciers from satellite imagery and field-based measurements were used to document the formation of longitudinal foliation in small-scale ice masses. These findings were ‘up-scaled’ and applied to much larger glaciers and ice streams. Longitudinal foliation develops in concentrated bands at flow unit boundaries as a result of enhanced simple shear. However, longitudinal foliation is not directly observable from satellite imagery at the surface of larger-scale valley glaciers. The longitudinal structures visible at the surface of larger-scale glaciers form at flow unit boundaries and are composed of bands of steeply dipping longitudinal foliation; however, they appear as individual linear features on satellite imagery as a result of the comparatively low spatial resolution of the imagery. The persistence of flowlines in the Antarctic Ice Sheet through areas of crevassing and net ablation (blue-ice areas) suggests that they are the surface representation of a threedimensional structure. Flowlines are therefore inferred to be the surface expression of flow unit boundaries composed of bands of steeply dipping longitudinal foliation. The survival and deformation of flowlines in areas of ice flow stagnation indicates that flowlines form in their initiation zones and not along their entire length. Furthermore, these ice stagnation areas indicate that flowlines record past ice dynamics and switches in ice flow.

The Last Glacial Maximum (LGM) Patagonian Ice Sheet (PIS) provides the unique potential to reconstruct the former meridional position and precipitation rates of the Southern Westerly Wind Belt (SWWB) due to its considerable latitudinal distance perpendicular to this global wind system. To use this potential, a high-resolution 3D reconstruction of the LGM PIS would be crucial, but knowledge about even the exact planform of this biggest Quaternary ice sheet on the Southern Hemisphere, excluding Antarctica, is still very poor. The widely accepted limits of the ‘Finiglacial’ ice sheet extent, mapped over 80 years ago by Caldenius (1932), has been identified as the LGM extent at many locations (e.g. Kaplan et al., 2004, 2008a,b; Singer et al., 2004; Hein et al., 2009). However, apart from the broadly correct assignation of the ‘Finiglacial’ limit to the LGM, its resolution remains poor, imperfect, and outdated, despite some later adaptations (e.g. Hollin and Schilling, 1981a; Clapperton, 1993) with small improvements. All attempts to provide 3D reconstructions (Hollin and Schilling, 1981a; Hulton et al., 1994, 2002) date back almost 15 years and did not match the poorly constrained glacial geomorphological record. This study presents a novel attempt to cast all relevant absolute dating locations of glacial landforms into a refined spatio-chronological context of the LGM extent of the PIS. Based on this newly set spatio-chronological context, a geographical information system (GIS)-based high-resolution LGM extent reconstruction, both in planform and in 3D, is presented within this study. In contrast to its predecessors, the applied GIS-based modelling approach enables a grade of reconstruction resolution for an ice sheet, that is as big as Spain and that is otherwise found only in local valley-scale glacier reconstructions. The spatial resolution of the GIS-based 3D ice-sheet reconstruction surface lies at 100 metres, as does the implemented topographic data. This leads to a spatial ice-sheet surface resolution that is at least 200 times higher than any previous attempt to cover the entire LGM PIS. The 3D reconstruction of the LGM PIS using the newly defined extent is in good agreement with observations on vertical ice extents (Boex et al., 2013) and displays, for the first time, a realistic interaction with the complex Patagonian topography. The area of the LGM PIS is, with ca. 504,500 km2 (±8.5%) roughly a fourth of the area of Greenland and represents 554,500 km3 (±10%) of ice or 1.38 metres (±10%) of sea-level equivalent. The now available 3D reconstruction provides a starting point that, after minor revisions, could potentially allow gauging accumulation rates along up to 2,300 km perpendicular to the SWWB and, thus, inferring valuable palaeo-climatic insights from the LGM.