The Younger Dryas was the last period during which glaciers shaped large parts of the Scottish landscape. Reconstructing the palaeoclimate and glacial processes that operated during this time is crucial for the understanding of past atmosphere-cryosphere interactions and predicting future climate change. This thesis presents results from geomorphological and geological mapping in the NW Highlands of Scotland that have resulted in the reconstruction of a Younger Dryas ice cap. Reconstruction of equilibrium-line altitudes and palaeo-precipitation values suggest that the Scottish west coast was wetter than at present. Detailed sedimentological analyses of "hummocky moraines" allow the modes of moraine formation to be reconstructed in great detail and existing models to be tested. "Hummocky moraines" largely represent terrestrial ice-contact fans consisting of supraglacial debris flows and intercalated glaciofluvial units indicating an ice-marginal mode of formation. Different stages of deformation in these fans indicate highly dynamic glaciers that oscillated during retreat, partly or completely overriding previously formed landforms during readvances. Clast shape analyses reveal that debris was mostly subglacially derived and transported. The evidence is incompatible with a morphological model according to which the moraines could be formed by englacial thrusting. Comparison with modem glacial landsystems indicates the following similarities with Scottish Younger Dryas glaciers. Low winter temperatures are similar to those on Svalbard, the marginal response of Younger Dryas glaciers to temperate environments and the modes of deposition to less responsive debris-covered glaciers. High precipitation along the Scottish west coast probably suppressed continuous permafrost development and caused high mass turnover and very dynamic, dominantly temperate Younger Dryas glaciers. Only a narrow zone around the margins appears to have been frozen to the ground, aiding elevation of basal debris and rapid deposition near the snout. The specific climatic and glaciological conditions during the Younger Dryas appear not to have a single modem analogue.

A generalized engineering classification method for characterizing Pleistocene glacial materials on the basis of their glaciological mode of origin is presented in this thesis. In formulating the classification an interdisciplinary approach has been adopted. The geotechnical aspects have been based largely on data from extensive site investigations undertaken at the Brenig dam site in North Wales, supplemented where necessary by data obtained from the glaciological and geotechnical literature. Particular attention has been paid to the macrofabric of the deposits in view of the controlling influence that discontinuities exert on engineering behaviour. The glaciological appraisal of the materials has also relied heavily on detailed evaluation of the engineering behaviour and textural properties of the Brenig deposits. However, in order to extend the applicability of the proposed classification to other locations, the site-specific data has been correlated with results from current glaciological research on modern arctic and temperate glaciers. As a prerequisite for such an assessment, a reconstruction of the glacial history of the Brenig site has been attempted. The similar mineralogy of the various glacial deposits and the availability of extensive geotechnical data on the complete suite of materials has made the, site ideal for this purpose. In presenting the results of the studies, the thesis has been divided into four sections. By way of background, in Part I the methodology and scope of the investigations conducted at Brenig are presented. In Part II a comparison is made between the characteristics of Recent glacial deposits and the Pleistocene materials at Brenig. The stratigraphy and glacial chronology of the site are developed in Part III, while in Part IV the geotechnical evaluation of the site is presented and set within the glaciological framework as a basis for the proposed classification.

This thesis is concerned with layered reflections observed in the Antarctic and Greenland ice sheets during radio-echo sounding. It describes in detail layering seen with 60 and 300 MHz equipment _in the Antarctic ice sheet during three field seasons betwe~n 1974 and 1979, and discusses the effects of glaciological and equipment factors, particularly radio pulse length. The effects of changing pulse length and accumulation rate on layer echo separation are analysed, and the importance of closely spaced groups of reflectors assessed. Reflection coefficient vs depth profiles are presented for layering observed at nearly twenty sites in the Antarctic and Greenland, and are used to demonstrate the existence of two separate reflection mechanisms: changes in (a) ice density, and (b) loss tangent. Supporting density and conductivity data from ice cores are summarised. It is concluded that most layer echoes arise from layers of ice containing acidic impurities of volcanic origin~ Layer reflectivity variations_are observed over distances of tens of kilometres. Short-period fading is also observed, from which estimates of layer reflector roughness are made using the autocorrelation function and variance of the received power. The roughness estimates are shown to be consistent with a depositional origin for the surfaces. Relevant theory is summarised and a procedure developed for the remote estimation of elevated acidity levels in ice from radio-echo sounding. Such estimates are shown to compare well with direct ice core measurements. The method is used to present estimated elevated acidity profiles for the Antarctic (to ~100 kaBP) and Greenland (to ~30 kaBP), which are interpreted in terms of variations in the input of volcanogenic acid impurities to the ice sheets. The use of layering as isochronous horizons in ice flow studies is discussed in the light of new measurements, with particular emphasis on t he zone close to bedrock.

Active microwave sensors are known to provide valuable information regarding snow and ice surfaces in the polar regions, where darkness and cloud cover prevail. Here, data collected in the Arctic by a Ku-band microwave radar altimeter, designed and constructed in the UK, are analysed. The two main components of this study comprise data gathered in the East Greenland Sea marginal ice zone and over two Svalbard ice caps. A systematic treatment is made of the electromagnetic properties of snow and ice at 13.81 GHz, and the differences between various polar surface media are highlighted. Theoretical and empirical models are presented which enable calculation of the relevant dielectric and scattering properties of snow and ice layers. Parametric studies are undertaken to give insight into the range of scattering conditions likely to be encountered by a radar altimeter in the regions investigated. Examples of altimetric data and results of their analysis are presented, demonstrating the effects of different ice types and terrain upon incident altimeter pulses. Waveforms are characterised by their shape, and certain forms are linked with particular physical properties of the surface. To this a variety of supporting information is added in order to verify and validate interpretations of these results. Algorithms are proposed which enable geophysical information to be derived from altimetric data.

The growth of the Weddell Sea ice cover in 1980 is examined, using Nimbus-7 satellite Scanning Multi-channel Microwave Radiometer (SMMR) data in combination with data (positional, air temperature and atmospheric pressure) from 4 Nimbus-tracked drifting buoys. Ice concentrations are retrieved from the SMMR data by applying a cluster analysis algorithm developed by J. Comiso of NASA. Analyses of computed differential kinematic parameters (DKP)s of the buoy array offer insight into the complex mesoscale behaviour of the underlying Weddell Gyre. High frequency divergence, convergence and deformation events isolated in the DKP results, and driven largely by the regular passage of cyclones, are related to changes in ice concentration observed in the SMMR data. The profound role of the Antarctic Peninsula in influencing both atmospheric and oceanic circulation (and thus ice formation, drift and eventual decay) in the region is evaluated. Possible relationships between buoy drift in the inner pack and ice edge advance are examined, yielding information on the relative importance of ice growth in open water within the pack and that at the ice edge. After an introductory chapter, Chapter 2 describes the physical setting of the Weddell Sea. Comparisons are drawn both with other sectors of the Southern Ocean and the Arctic, emphasizing the uniqueness of the region not only in terms of its climate and oceanography but also its sea ice cover. Chapter 3 traces the evolution of passive microwave remote sensing from space as a tool for monitoring Antarctic sea ice extent and concentration; the relative merits and disadvantages of these techniques are evaluated. Chapter 4 concentrates on the use of SMMR data. Detailed comparisons are made of algorithms available for the extraction of ice concentrations from the raw brightness temperature data. The choice of algorithm used is justified. Chapter 5 is largely concerned with the analysis of the buoy data, and the kinematic behaviour of the array as a unit. These results are combined with the SMMR data in Chapter 6 to identify distinct dynamic zones and meridional advective sectors, and to compare the behaviour of the inner pack with that of the unconstrained ice edge. The evolution of a high concentration core within the unique perennial sea ice zone hugging the east coast of the Peninsula, which persists throughout the period of study is unusual enough to merit a separate sub-section. Conclusions are drawn in chapter 7.

been used to investigate the form and topography of the Antarctic ice sheet and to relate these to the physical processes of ice flow and basal conditions. Topographic roughness typically increases towards the thin ice of coastal reg ions as surface undulation wav el eng ths decrease and amplitudes increase. Temperature and velocity variations also have significant effects. The coastal zone is punctuated by embayments of severe topography immediately inland of outlet glaciers. This topographic variability has been summarized in a statistical model for the purposes of simulating satellite radar altimeter waveforms. Consideration of the relationship between bedrock and surface profiles has shown that ice temperature is a major influence on the response of the surface to bedrock irregularities. Regional subglacial water layers may al so have an important effect on surface topography. A re-analysis of models of longitudinal stress grad i ents suggests that er ystal fabrics favouring faster flow develop with distance from ice divides and that the relative depth of the zone of maximum shear fluctuates in response to topographic and glaciological constraints. Driving stress patterns have been associated with characteristic glaciological regimes and have suggested a qualitative difference between outlet glaciers and ice streams. The transition to high velocity flow in outlet glaciers has been shown to be triggered ab ruptly in response to subglac ial fjord heads. The dependence of fast flow on subglacial topography indicates a significant stabilizing effect on discharge from ice sheets and suggests that surge behaviour is unlikely within existing ice sheet outlets. The onset of basal sliding at the head of subglac ial fjords suggests a mechanism for the production of overdeepened fjords and steep headwalls through concentrated erosion. This may help in the reconstruction of the dynamics of former ice sheets. Some West Antarctic ice streams do not exhibit this rapid transition in behaviour.

In recent decades, the downwasting of several debris-covered glaciers in the Himalaya has led to the formation of large and potentially hazardous moraine- dammed lakes. The frequency of Glacial Lake Outburst Flood (GLOF) events in the Himalaya has steadily increased since the 1970s and as global temperatures continue to rise this trend is set to continue in the future. Downwasting of the debris-covered Ngozumpa Glacier in the Khumbu Himal, Nepal, has resulted in the abandonment of the lateral and terminal moraine crests, leaving them standing several tens of metres above the glacier surface. The moraines have exerted a control on the drainage of meltwater from the glacier surface and have encouraged ponding of meltwater on the glacier surface. The present study examines the evolution of perched supraglacial ponds on the Ngozumpa Glacier and assesses how the growth of these ponds affects the rate of downwasting of the glacier surface. The expansion rates of perched ponds can be rapid, up to 21,609 m ² a⁻¹, but the growth of these ponds tends to be terminated when contact is made with the englacial drainage network. The thesis documents for the first time a complete cycle of perched supra glacial pond growth and drainage and also provides direct evidence for internal ablation during pond drainage, a process that has only been inferred in previous research. The western lateral moraine has dammed back drainage from the western tributary valleys, resulting in the formation of laterally-dammed lakes. The research presented here examines the processes and rates of paraglacial reworking of the Ngozumpa moraines in order to assess the stability and longevity of the moraine dam. Approximately 1 km from the Ngozumpa terminus a large Spillway Lake has formed. Meltwater from upglacier is channelled into the lake and exits the glacier surface through an over-spill channel cut down through the western lateral moraine. The level of the Spillway Lake is thereby controlled by the height of the spillway channel through the western lateral moraine. The rate of expansion of the Spillway Lake is lower than that of the perched ponds upglacier, but as the Spillway Lake continues to enlarge and surface downwasting of the glacier surface proceeds, the lake could enter a period of rapid and unstable growth. By analogy with other glaciers in the Khumbu Rimal, it is possible that a large and potentially hazardous lake will form on the Ngozumpa within the next two decades.

The British-Irish Ice Sheet (BIIS) is predicted to have deglaciated rapidly from ~ 18 ka, in response to rising sea level and temperature, similar forcings experienced by modern polar ice sheets. As the main conduits of ice mass loss, the reaction of ice streams to these forcings is thought to have been central in determining the mode and timing of this deglaciation. However, lack of understanding of ice stream influence on the glaciology and deglaciation of ice sheets limits confidence in ice sheet model predictions. NW Scotland is an area of the last BIIS predicted to have been dominated by ice stream onset conditions. This thesis presents results from a geomorphological and terrestrial cosmogenic nuclide (TCN) analysis study which resulted in the production of a composite ice-sheet thermal regime map and retreat chronology for the last BIIS in this region. Mapping and surface exposure dating suggest that the regional glaciology and landscape evolution was dominated by the presence of ice-stream onset zones during Greenland Stadial-2 (GS-2). Mountain top erratics were uplifted and transported to high elevation during GS-2, before 16.5 ka BP. By inference, mountain summits were covered by ice during maximal ice sheet conditions. The existence of sharp thermo-mechanical contrasts, developed in response to ice streaming, are proposed as the main controls on bedrock erosion and terrestrial sediment deposition. The interpretation of ‘trimlines’ in NW Scotland as englacial thermo-mechanical boundaries, is verified by the identification of ‘rip-offs’, a newly recognised geomorphic feature in the UK, and by quantitative demonstration of the increase in glacial erosion in the vicinity of these boundaries. Geomorphic and TCN data supports a conceptual model of thermal inversion following ice-stream cessation. The first description of ‘till tails’ in the UK provides insight into the glaciological organisation and thermal evolution of the BIIS. A dated (17.6 ka BP) terrestrial glacial limit on the north Sutherland coast indicates early ice retreat from the shelf and provides a minimum ii constraint on ice-stream cessation. This indicates rapid loss of ice extent and volume following shutdown of the Minch palaeo-ice stream. Major ice sheet reorganisation c. 15-16 ka BP is suggested by the correlation of some lateral margin ages with high elevation erratic deposition ages implying significant ice thinning and margin retreat prior to this time. Additionally, thinning of ~300 m is predicted for some areas prior to 14 ka BP.

In glacierised regions, suspended sediment fluxes are highly responsive to climate-driven environmental change and can provide important information regarding the relationships between glacier variations, climate and geomorphic change. As a result, understanding patterns of suspended sediment transport and their relationship with meltwater delivery is of critical importance. However, studies of glacial suspended sediment transport are often limited by interpreting patterns of suspended sediment transfer based on whole-season data, allowing precise patterns to become masked. This thesis aims to contribute to the understanding of suspended sediment transfer in glacierised basins through the investigation of patterns of suspended sediment delivery to the proglacial area of Storglaciären, a small polythermal valley glacier located in the Tarfala valley, Arctic Sweden. High temporal resolution discharge and suspended sediment concentration data were collected during two summer field campaigns at Storglaciären. Interpretations of suspended sediment transport data were made using diurnal hysteresis and sediment availability data, combined with suspended sediment shape and magnitude data classified by applying principal component and hierarchical cluster analyses. Analysis of the dominant discharge generating processes at Storglaciären was also conducted using principal component analysis, allowing patterns of discharge to be better understood. This was complemented by analysis of the structure and evolution of the glacier drainage system by linear reservoir modelling and flow recession analysis. The results suggest that patterns of discharge and suspended sediment transport at Storglaciären are complex, with distinct processes and magnitudes of transport evident at both proglacial outlet streams, Nordjåkk and Sydjåkk. These processes are intrinsically linked to meteorological variables, with both ablation-driven and precipitation-driven discharge exerting influence over patterns of suspended sediment transport in the proglacial area of Storglaciären.

Hourly winter weather conditions of the Last Glacial Maximum (LGM) are simulated using the Community Climate Model version 3 (CCM3) on a globally resolved T170 (~75 km) grid. This simulation has been run in-tandem with a lower temporally resolved six-year climatological run. The purpose of the study is to determine: (1) whether examination of higher-resolution simulations, on both spatial and temporal scales, can enhance paleometeorological inferences based previously on monthly statistics of model output and (2) whether certain synoptic-scale events, which may have only a modest impact on seasonal statistics, might exert a disproportionate impact on geological climate records. Analysis is focused on changes in wind flow, no analogue climate “states”, synoptic scale events including Northern Hemisphere cyclogenesis, and gust events over glacial dust source regions. Results show a decrease in North Atlantic and increase in North Pacific cyclogenesis during the LGM. Storm trajectories react to the mechanical forcing of the Laurentide Ice Sheet, with Pacific storms tracking over middle Alaska and northern Canada and terminate in the Labrador Sea. The latter result supports observations and other model runs showing a significant reduction in Greenland winter precipitation. The modified Pacific track results in increased precipitation and the delivery of warmer air along the west coast of North America. This could explain “early” glacial warming inferred in this region from proxy climate records, potentially representing instead a natural regional response to ice age boundary conditions. Results also indicate a low variability, “no analogue” region just south of the Laurentide Ice Sheet margin which has appropriate conditions to harbour temperature-sensitive trees west of the Appalachian Mountains. Combined with pollen data, this lends valuable insight into the known disagreement between modern seed dispersal experiments and calculated migration rates. Finally, hourly-scale gust events over dust source regions during the LGM are two to five times greater than the modern, providing a mechanism to help explain the increased glacial dust load seen in the ice cores. Backwards air-parcel trajectories from Antarctic ice core locations show air sources over Patagonia and the Altiplano with some inputs from South Africa agreeing with recent isotopic tracer analyses. Results demonstrate that high temporal and spatial resolution simulations can provide valuable insight to add to the cornucopia of information already available from lower-resolution runs. They can also enhance our interpretation of geological records, which have been previously assumed to record longer time-scale climatological mean-states and thus ignoring any extreme synoptic events which may actually have had a disproportionate impact on their preservation.