<p>We evaluated 3-D imaging of coarse root structure and biomass using ground-penetrating radar (GPR). GPR surveys were conducted in a white pine forest in southern Ontario, Canada. GPR profiles were obtained across two test plots (6 and 17 m² area), using 1-GHz GPR and a MEMS (micro-electro-mechanical systems) accelerometer. Test plot surveys evaluated the effects of micro-topography, soil moisture content, and root diameter and spacing. In addition, with the aid of the outcome of the control test plots two other plots (25 and 400 m²area) were surveyed with varying line sample spacing to investigate the restraints on resolution brought about by line sampling density.</p> <p>Accounting for antenna tilt is necessary to determine an accurate and more precise position of root mass. The antenna tilt was >45^o pitch, >28^o roll and up to 10^o yaw due to surface micro-topography of the forest floor. Vector 3-D imaging enhanced the diffraction amplitude (15.5% increase) and centralized the position of the root. Radial surveys provided root continuity and produced better root imaging.</p> <p>GPR largely underestimates coarse root biomass when a line spacing of 25 cm is used. However similar results are found with smaller line spacing (12.5 cm). A maximum line spacing of 10 cm provided continuous root structure and differentiation of roots spaced 10 cm apart and greater. A sampling line spacing of 5 cm and an inline sampling interval of 0.5 cm in low soil moisture conditions provided the detection of roots that were a minimum of 1.4 cm in diameter.</p> / Master of Science (MSc)

This thesis investigates the application of In-Situ Recycling and provides guidelines for localities to aid in the selection of recycling methods, as well as documents a local government's experience with Cold In-Place Recycling. The recycling methods discussed in this study include Cold In-Place Recycling (CIR), Hot In-Place Recycling (HIR), and Full Depth Reclamation (FDR). These methods are performed onsite and in-place in a continuous process of milling, mixing, and placement. The In-Situ Recycling guidelines include suggestions based on: traffic characteristics, existing road condition, distress types, road access, local climate, road geometry, and other road characteristics. The guidelines are based on information from sources including NCHRP Synthesis 421, American Recycling and Reclamation Association (ARRA), FHWA, and state agencies with recycling experience. This study also resulted in documenting obstacles that localities may face when in-situ recycling, as well as the impact of limited experience with recycling. The study also evaluated the construction of Cold In-Place Recycled pavement sections in Christiansburg, VA, using Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR). Additionally, using the FWD and GPR data, alternate recycled designs were proposed in addition to a cost comparison to a conventional design. / Master of Science

Nesta pesquisa são apresentadas as contribuições dos métodos GPR e eletromagnético indutivo (equipamento EM-38) nos estudos de sítios arqueológicos de sambaquis costeiros Jabuticabeira II, Santa Marta IV, V, VII e VIII, e Encantada III, localizados no município de Jaguaruna, litoral centro-sul de Santa Catarina. Estes sítios são caracterizados por acúmulos de conchas carbonáticas construídos por sociedades do período pré-colonial (7,5 a 1,3 mil anos AP). Os estudos foram desenvolvidos, visando o mapeamento de artefatos de interesse arqueológico e de estruturas estratigráficas que auxiliem a compreensão do processo construtivo e funcional destes sítios. A interpretação dos resultados GPR foi apoiada nas modelagens numéricas GPR 2D e nas imagens 3D e integrada com os levantamentos EM-38, e tiveram como objetivos orientar as escavações arqueológicas. Os resultados permitiram encontrar alvos e artefatos arqueológicos, reduziram os custos no processo exploratório e preservaram o patrimônio histórico. Complementando o processo de interpretação integrada, os perfis estratigráficos e as análises granulométricas dos sedimentos provenientes dos furos de sondagens foram importantes para a definição dos ambientes de deposição onde os sambaquis estão assentados, corroborando de maneira significativa com as pesquisas em desenvolvimento no litoral de Santa Catarina. Em termos metodológicos, as antenas GPR blindadas de 200 MHz propiciaram um melhor compromisso entre a profundidade de investigação e a resolução vertical das camadas geo-arqueológicas, e a implementação da técnica de aquisição radial permitiu um mapeamento detalhado do sítio Jabuticabeira II de forma rápida, cobrindo uma grande área. Por outro lado, com o método eletromagnético indutivo (EM-38), a correção do efeito topográfico dos dados melhorou os contrastes de condutividade elétrica entre as estruturas arqueológicas e o background, permitindo assim, que os alvos pontuais, antes mascarados pela influência da topografia, fossem realçados. Com relação aos resultados geofísicos em estudos geoarqueológicos, no sambaqui Jabuticabeira II, foi possível caracterizar a geometria de uma estrutura geológica, associada a um paleo-canal e a deposição dos sedimentos em barras de pontal; mapear alvos arqueológicos e metálicos contemporâneos; traçar os limites do sítio; imagear uma camada conchífera, camadas antrópicas recentes e a profundidade do nível dágua; detectar a presença de dois sistemas deposicionais, paleolaguna e paleoduna, bem como delimitar o assentamento do sítio sobre estes ambientes por meio das informações das análises granulométricas dos sedimentos coletados nos furos de sondagens. Nos sambaquis de Santa Marta IV, V, VII e VIII, a integração dos dados GPR e EM38 permitiram o mapeamento de diversos alvos de grande importância para os estudos arqueológicos, tais como, paleofogueiras, sepultamentos e concentração de materiais cerâmicos e líticos, bem como feições geológicas, tais como, estruturação de camadas e paleotômbolos. Além disso, a redução do efeito topográfico sobre os dados de condutividade elétrica (EM-38) permitiu relacionar as regiões anômalas com um paleofogueira e uma concentração de material cerâmico. No sambaqui Encantada III, duas fortes anomalias GPR, caracterizadas por reflexões hiperbólicas, estavam associadas: i) a uma estrutura escura pontual, caracterizada como um bolsão de conchas carbonáticas; e ii) a presença de uma raiz de árvore concrecionada, que embora não seja de interesse arqueológico, é significativa, pois serve como um bom exemplo de ambiguidade na interpretação de dados geofísicos. Também foi possível delimitar o assentamento do sítio sobre os sedimentos da paleo-laguna, evidenciado pelas análises granulométricas dos sedimentos. / In this study, GPR and electromagnetic induction (EM-38 instrument) methodcontributions in coastal sambaqui archaeological sites (Jabuticabeira II, Santa Marta IV, V, VII and VIII as well as Encantada III) are presented. These sites are placed in Jaguaruna, Santa Catarina center-south coast. They are characterized by accumulation of carbonate shells built by societies in pre-colonial period (7.5 to 1.3 thousand years BP). The studies were developed aimed at mapping archaeological artifacts and stratigraphic structures that help to understand constructive and functional process of these sites. The interpretation of GPR results was supported by 2D GPR numerical modeling, 3D images and integrated with EM-38 surveys. They had as objectives to guide archaeological excavations. The results allowed finding archaeological targets and artifacts, reduced costs in exploratory process, and preserved historical heritage. Complementing integrated interpretation process, stratigraphic profiles and granulometric analysis of sediment from sounding drifts were important for defining the deposition environments where sambaquis (shell mounds) are settled, significantly supporting in developing research on Santa Catarina coast. Methodologically, 200 MHz shielded GPR antennas provided a better agreement between depth of investigation and vertical resolution of geoarchaeological layers, and the implementation of radial acquisition technique allowed a quickly detailed mapping of Jabuticabeira II site, covering a large area. Furthermore, with electromagnetic inductive method (EM-38), the topographic effect correction of data has improved the contrast in electrical conductivity between archaeological structures and background. Thus, punctual targets before masked by topography influence were highlighted. Regarding geophysical results in geoarchaeological studies, in Jabuticabeira II sambaqui, it was possible to characterize the geometry of a geological structure associated with a paleochannel and sediment deposition in point bars; to map archaeological and contemporary metal targets; to trace site boundary; to image shell layer, recent anthropic layers and water level depth; to detect the presence of two deposicional systems, paleolagoon and paleodune as well as to delimit the settlement site on these environments through information of granulometric analysis of sediments collected in sounding drifts. In Santa Marta IV, V, VII and VIII sambaquis, GPR and EM-38 data integration allowed mapping several targets of great importance for archaeological studies, such as paleofires, burials and concentration of ceramic and litic material as well as geological features, such as layer structuring and paleotombolos. Moreover, the reduction of topographic effect on electrical conductivity data (EM-38) allowed relating anomalous regions with a paleofire, and a concentration of ceramic material. In Encantada III sambaqui, two strong GPR anomalies characterized by hyperbolic reflections were associated with: i) a dark punctual structure, characterized as a pocket of shell carbonate, and ii) the presence of a concretion tree root that is significant, despite not of archaeological interest, because it serves as a good example of ambiguity in geophysical data interpretation. It was also possible to delimit the settlement site on paleolagoon sediments, evidenced by granulometric analysis of sediments.

Nesta pesquisa são apresentadas as contribuições dos métodos GPR e eletromagnético indutivo (equipamento EM-38) nos estudos de sítios arqueológicos de sambaquis costeiros Jabuticabeira II, Santa Marta IV, V, VII e VIII, e Encantada III, localizados no município de Jaguaruna, litoral centro-sul de Santa Catarina. Estes sítios são caracterizados por acúmulos de conchas carbonáticas construídos por sociedades do período pré-colonial (7,5 a 1,3 mil anos AP). Os estudos foram desenvolvidos, visando o mapeamento de artefatos de interesse arqueológico e de estruturas estratigráficas que auxiliem a compreensão do processo construtivo e funcional destes sítios. A interpretação dos resultados GPR foi apoiada nas modelagens numéricas GPR 2D e nas imagens 3D e integrada com os levantamentos EM-38, e tiveram como objetivos orientar as escavações arqueológicas. Os resultados permitiram encontrar alvos e artefatos arqueológicos, reduziram os custos no processo exploratório e preservaram o patrimônio histórico. Complementando o processo de interpretação integrada, os perfis estratigráficos e as análises granulométricas dos sedimentos provenientes dos furos de sondagens foram importantes para a definição dos ambientes de deposição onde os sambaquis estão assentados, corroborando de maneira significativa com as pesquisas em desenvolvimento no litoral de Santa Catarina. Em termos metodológicos, as antenas GPR blindadas de 200 MHz propiciaram um melhor compromisso entre a profundidade de investigação e a resolução vertical das camadas geo-arqueológicas, e a implementação da técnica de aquisição radial permitiu um mapeamento detalhado do sítio Jabuticabeira II de forma rápida, cobrindo uma grande área. Por outro lado, com o método eletromagnético indutivo (EM-38), a correção do efeito topográfico dos dados melhorou os contrastes de condutividade elétrica entre as estruturas arqueológicas e o background, permitindo assim, que os alvos pontuais, antes mascarados pela influência da topografia, fossem realçados. Com relação aos resultados geofísicos em estudos geoarqueológicos, no sambaqui Jabuticabeira II, foi possível caracterizar a geometria de uma estrutura geológica, associada a um paleo-canal e a deposição dos sedimentos em barras de pontal; mapear alvos arqueológicos e metálicos contemporâneos; traçar os limites do sítio; imagear uma camada conchífera, camadas antrópicas recentes e a profundidade do nível dágua; detectar a presença de dois sistemas deposicionais, paleolaguna e paleoduna, bem como delimitar o assentamento do sítio sobre estes ambientes por meio das informações das análises granulométricas dos sedimentos coletados nos furos de sondagens. Nos sambaquis de Santa Marta IV, V, VII e VIII, a integração dos dados GPR e EM38 permitiram o mapeamento de diversos alvos de grande importância para os estudos arqueológicos, tais como, paleofogueiras, sepultamentos e concentração de materiais cerâmicos e líticos, bem como feições geológicas, tais como, estruturação de camadas e paleotômbolos. Além disso, a redução do efeito topográfico sobre os dados de condutividade elétrica (EM-38) permitiu relacionar as regiões anômalas com um paleofogueira e uma concentração de material cerâmico. No sambaqui Encantada III, duas fortes anomalias GPR, caracterizadas por reflexões hiperbólicas, estavam associadas: i) a uma estrutura escura pontual, caracterizada como um bolsão de conchas carbonáticas; e ii) a presença de uma raiz de árvore concrecionada, que embora não seja de interesse arqueológico, é significativa, pois serve como um bom exemplo de ambiguidade na interpretação de dados geofísicos. Também foi possível delimitar o assentamento do sítio sobre os sedimentos da paleo-laguna, evidenciado pelas análises granulométricas dos sedimentos. / In this study, GPR and electromagnetic induction (EM-38 instrument) methodcontributions in coastal sambaqui archaeological sites (Jabuticabeira II, Santa Marta IV, V, VII and VIII as well as Encantada III) are presented. These sites are placed in Jaguaruna, Santa Catarina center-south coast. They are characterized by accumulation of carbonate shells built by societies in pre-colonial period (7.5 to 1.3 thousand years BP). The studies were developed aimed at mapping archaeological artifacts and stratigraphic structures that help to understand constructive and functional process of these sites. The interpretation of GPR results was supported by 2D GPR numerical modeling, 3D images and integrated with EM-38 surveys. They had as objectives to guide archaeological excavations. The results allowed finding archaeological targets and artifacts, reduced costs in exploratory process, and preserved historical heritage. Complementing integrated interpretation process, stratigraphic profiles and granulometric analysis of sediment from sounding drifts were important for defining the deposition environments where sambaquis (shell mounds) are settled, significantly supporting in developing research on Santa Catarina coast. Methodologically, 200 MHz shielded GPR antennas provided a better agreement between depth of investigation and vertical resolution of geoarchaeological layers, and the implementation of radial acquisition technique allowed a quickly detailed mapping of Jabuticabeira II site, covering a large area. Furthermore, with electromagnetic inductive method (EM-38), the topographic effect correction of data has improved the contrast in electrical conductivity between archaeological structures and background. Thus, punctual targets before masked by topography influence were highlighted. Regarding geophysical results in geoarchaeological studies, in Jabuticabeira II sambaqui, it was possible to characterize the geometry of a geological structure associated with a paleochannel and sediment deposition in point bars; to map archaeological and contemporary metal targets; to trace site boundary; to image shell layer, recent anthropic layers and water level depth; to detect the presence of two deposicional systems, paleolagoon and paleodune as well as to delimit the settlement site on these environments through information of granulometric analysis of sediments collected in sounding drifts. In Santa Marta IV, V, VII and VIII sambaquis, GPR and EM-38 data integration allowed mapping several targets of great importance for archaeological studies, such as paleofires, burials and concentration of ceramic and litic material as well as geological features, such as layer structuring and paleotombolos. Moreover, the reduction of topographic effect on electrical conductivity data (EM-38) allowed relating anomalous regions with a paleofire, and a concentration of ceramic material. In Encantada III sambaqui, two strong GPR anomalies characterized by hyperbolic reflections were associated with: i) a dark punctual structure, characterized as a pocket of shell carbonate, and ii) the presence of a concretion tree root that is significant, despite not of archaeological interest, because it serves as a good example of ambiguity in geophysical data interpretation. It was also possible to delimit the settlement site on paleolagoon sediments, evidenced by granulometric analysis of sediments.

GPR data interpretation is often difficult due to complex geological environments, reflections ambiguity and time-depth conversion uncertainty. Thanks to the geophysical fields interoperability it is possible to compare results of related survey methods. Radargrams from three model sites were processed and interpreted in an usual way to uniformly amplify all recorded reflections. Results were compared with ERT and EM (DEMP) data within integrated interpretation. GPR data interpretation was extended and new geological and geomorphological interpretations were uncovered. The GPR processing sequence was modified and simplified following outcomes from the integrated interpretation to ease different methods results comparison. Adapting a velocity model to precise time- depth conversion hasn't showed improvements. Key words: ground penetrating radar, electrical resistivity tomography, dipole electromagnetic profiling, integrated interpretation, integrated inversion, GPR processing optimization, sedimentary environment, velocity model

Les travaux de cette thèse concernent l'étude d'une méthode d'évaluation des constantes diélectriques du béton d'ouvrage à risque par une approche problème inverse. Pour cela des mesures radar de type GPR et un modèle électromagnétique de ces mêmes mesures seront utilisés. Les deux premiers chapitres de la thèse présentent les concepts clés, le contexte et un historique des travaux déjà réalisés dans le domaine. Le chapitre 2 propose en outre une adaptation des travaux déjà réalisés à la recherche de gradients de propriétés diélectriques dans le béton en profondeur. Cette recherche préliminaire nous a permis de redéfinir le processus de mesures pour le rendre plus adapté à nos besoins. Ainsi le chapitre 3 présente une campagne de mesure réalisée à l'aide d'un nouveau dispositif radar sur des corps d'épreuve conditionnés de telle sorte que la répartition de la teneur en eau soit maîtrisée. Dans ce chapitre, nous détaillons également un nouveau modèle numérique 3D du dispositif qui nous permet de simuler nos mesures de façon réaliste Ces simulations sont nécessaires à l'expression du problème inverse. à partir de ces mesures, dans le quatrième chapitre, nous définissons tout d'abord le problème inverse, puis en utilisant des mesures sur les corps d'épreuves saturés, pouvant être considérés comme homogènes d'un point de vue diélectrique, nous résolvons ce problème inverse par un algorithme d'optimisation basé sur celui de Levenberg-Marquardt. Les résultats obtenus par notre processus d'inversion sont cohérents avec les valeurs physiques que l'on pouvait attendre et sont indépendants des valeurs données à nos inconnues lors de l'initialisation. Ces résultats correspondent effectivement à un minimum de la fonction coût qui mesure la distance entre mesures et simulations. Nous avons ensuite étudié des stratégies pour diminuer le temps de calcul de notre processus d'inversion. Une première approche consiste à utiliser un modèle simplifié en 2D du dispositif, qui permet d'initialiser l'inversion 3D avec un point plus proche de la solution. Une autre idée consiste à utiliser au mieux les performances d'une machine multiprocesseurs en parallélisant le code 3D. Dans le chapitre 5 nous nous intéressons à des mesures sur des corps d'épreuve en béton dont la teneur en eau est une fonction affine de la profondeur. Dans ces conditions nous avons fait l'hypothèse, en première approche, que les constantes diélectriques suivent aussi ce type de loi. Après avoir redéfini les inconnues de notre problème inverse et adapté l'algorithme, nous montrons que le processus d'inversion fourni des résultats cohérents en ce qui concerne la permittivité diélectrique, mais insatisfaisant pour la conductivité. Après analyse de ces résultats nous avons proposé diverses pistes pour améliorer et valider la méthode d'inversion. Finalement en comparant l'ensemble des résultats, il apparaît que notre méthode d'inversion permet de caractériser des gradients de permittivité, mais pas de conductivité. Cela représente néanmoins une avancée significative pour la mesure de la teneur en eau dans les bétons, facteur principal influençant la constante diélectrique de ce matériau, dans le contexte du contrôle non destructif des ouvrages du génie civil. / That thesis aims to propose an assessment method of the concrete electromagnetic properties by using radar measurements in a context of building sustainability, by inverse problem. For that purpose Ground Penetrating Radar (GPR) measurements are used as well as a numerical model of the radar device. The first two chapters of the thesis present the key concepts, the context of the study, as well as the history of the research on that topic in particular in our laboratory. Chapter 2 also expands those early works on the search of electromagnetic properties of concrete in depth. That preliminary work helped us to develop a measurement device that is more fitted to our needs. Chapter 3 presents a measurement campaign that was carried out by using a new measurement device on specially made reinforced concrete slabs whose water content is monitored. In that chapter a 3D model of the device is also described. That model allows us to simulate the measurements very precisely. Those simulations are a critical link on the inverse process. Chapter 4 details the formulation of the inverse problem for the case of concrete slabs saturated with water, which can be therefore considered to have homogeneous electromagnetic properties. The problem is solved by using an optimization algorithm based on Levenberg-Marquardt method. The values obtained by the inverse process are physically acceptable and independent of the values given to the unknowns when initializing the algorithm. Those values are the minimum of the cost function that computes the distance between measured and simulated electromagnetic fields. We then studied some strategies to reduce the computing time of the inverse process. A first approach consists in the use of a 2D simplified model of our device to initialize the 3D inversion with values closer to the searched solution. Another idea is to better take advantage of all the resources of a multiprocessor computer by implementing a parallel version of the 3D code. In chapter 5 we focus on the concrete slab with water content being an affine function of depth. We define the new parameters that represent the unknowns of our problem and we adapt the previous algorithm. Then we show that the inverse process gives satisfying results with regard to the dielectric permittivity only. We suggest some ways to improve the method. Finally we conclude that our method allows to retrieve the permittivity of the concrete, but not its conductivity. Nevertheless that result represents a significant step for the measuring of water content in reinforced concrete in particular when a gradient is present, by using radar measurements.

<p>This paper deals with archaeological prospection of an Iron Age farm site in Toland, Fresta parish, Uppland County in Sweden. The purpose of the paper has been to see whether the geophysical methods applied (GPR & EM-38) could produce useful results that could motivate its use in similar surveys in the future. Geochemistry has been used for the purpose of identifying possible activity areas on the site. The results have shown that it is possible with a GPR survey to identify postholes originating from the Migration Period longhouse at the site. The combining of several methods have been important for the identification and interpretation of several areas of interest.</p>

This paper deals with archaeological prospection of an Iron Age farm site in Toland, Fresta parish, Uppland County in Sweden. The purpose of the paper has been to see whether the geophysical methods applied (GPR &amp; EM-38) could produce useful results that could motivate its use in similar surveys in the future. Geochemistry has been used for the purpose of identifying possible activity areas on the site. The results have shown that it is possible with a GPR survey to identify postholes originating from the Migration Period longhouse at the site. The combining of several methods have been important for the identification and interpretation of several areas of interest.

This hydrogeophysical field experiment evaluated the ability of high frequency (450 & 900 MHz) ground penetrating radar (GPR) to characterize the release of gasoline over an annual cycle of in situ conditions. In August 2008, 200 liters of E10 gasoline were released into the unconfined sand aquifer at CFB Borden. The 900 MHz profiling clearly shows the development of shallow (i.e., above 10 ns) high reflectivity in the vicinity of the trench immediately after the release. Additional lateral extension of high reflectivity zone was observed over the following 20 days until the seasonal water table low stand occurred, after which no further lateral movement was observed. Throughout the remainder of the monitoring, the 900 MHz profiling observed a long-term dimming of reflectivity at the periphery of the impacted zone. While direct imaging of the shallow impacted zone by the 450 MHz antennas was significantly obscured by the superposition with the direct air-ground wave arrival; its improved depth of penetration allowed the measurement of a velocity “pull-up” of an underlying stratigraphic interface resulting from the displacement of low velocity water by high velocity gasoline. The maximum pull-up was observed during the water table low stand. The ongoing changes in the pull-up magnitude during the remainder of the observation period suggest the continued redistribution of fluids in the impacted zone. Because of the shallow depth of the gasoline impacted zone, the effects of freezing during the winter period were observed in the GPR imaging. The presence of the gasoline impacted zone appears to have affected the depth of freezing, causing a depression of the frozen soil base. The dimming of the direct air-ground wave complex indicates that the contaminant phase brought to the surface by the water table fluctuations have impacted the nature of the near-surface freezing.

The Darwin-Hatherton glacial system (DHGS) drains from the East Antarctic Ice Sheet (EAIS) and through the Transantarctic Mountains (TAM) before entering the Ross Embayment. Large ice-free areas covered in glacial sediments surround the DHGS, and at least five glacial drift sheets mark the limits of previous ice extent. The glacier belongs to a group of slow-moving EAIS outlet glaciers which are poorly understood. Despite this, an extrapolation of a glacial drift sheet boundary has been used to determine the thickness of the EAIS and the advanced West Antarctic Ice Sheet (WAIS) during the Last Glacial Maximum (LGM). In order to accurately determine the past and present contributions of the Antarctic ice sheets to sea level changes, these uncertainties should be reduced. This study aims to examine the present and LGM ice dynamics of the DHGS by combining newly acquired field measurements with a 3-D numerical ice sheet-shelf model. The fieldwork included a ground penetrating radar survey of ice thickness and surface velocity measurements by GPS. In addition, an extensive dataset of airborne radar measurements and meteorological recordings from automatic weather stations were made available. The model setup involved nesting a high-resolution (1 km) model of the DHGS within a lower resolution (20 km) all-Antarctic simulation. The nested 3-D modelling procedure enables an examination of the impact of changes of the EAIS and WAIS on the DHGS behaviour, and accounts for a complex glacier morphology and surface mass balance within the glacial system. The findings of this study illustrate the difference in ice dynamics between the Darwin and Hatherton Glaciers. The Darwin Glacier is up to 1500 m thick, partially warm-based, has high driving stresses (~150 kPa), and measured ice velocities increase from 20-30 m yr⁻¹ in the upper parts to ~180 m yr⁻¹ in the lowermost steepest regions, where modelled flow velocities peak at 330 m yr⁻¹. In comparison, the Hatherton Glacier is relatively thin (<900 m), completely cold-based, has low driving stresses (~85 kPa), and is likely to flow with velocities <10 m yr⁻¹ in most regions. It is inferred that the slow velocities with which the DHGS flows are a result of high subglacial mountains restricting ice flow from the EAIS, large regions of frozen basal conditions, low SMB and undulating bedrock topography. The model simulation of LGM ice conditions within the DHGS implies that the ice thickness of the WAIS has been significantly overestimated in previous reconstructions. Results show that the surface of the WAIS and EAIS away from the TAM would have been elevated 600-750 and 0-80 m above present-day levels, respectively, for the DHGS to reach what was inferred to represent the LGM drift sheet limit. Ultimately, this research contributes towards a better understanding of the dynamic behaviour of slow moving TAM outlet glaciers, and provides new insight into past changes of the EAIS and WAIS. This will facilitate more accurate quantifications of contributions of the WAIS and EAIS to changes in global sea level.