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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
371

An ASTER Digital Elevation Model (DEM) for the Darwin-Hatherton Glacial System, Antarctica.

Smith, Nita Jane January 2007 (has links)
The Darwin-Hatherton glacial system is an outlet glacial system in the Transantarctic Mountains, Antarctica, which drains ice from the East Antarctic Ice Sheet into the Ross Ice Shelf. This research provides remotely sensed data that can be used in modeling research for the Darwin-Hatherton glacial system, which in turn can be used in mass balance research for the West Antarctic Ice Sheet. Two improved digital elevation models (DEM) are produced to cover the lower Darwin Glacier and to cover the upper Darwin and Hatherton Glaciers. The new improved DEMs are generated from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data, with a resolution of 45 m. To produce the two final DEMs, multiple DEMs are firstly adjusted to remove systematic errors and are then stacked and averaged to increase the accuracy and produce the final two DEMs. For the lower Darwin Glacier, 5 DEMs were averaged and in the upper Darwin and Hatherton Glaciers, 6 DEMs were averaged. The accuracy is quantified by a remaining error of + 9 m for the lower Darwin Glacier DEM and + 37 m for the upper Darwin and Hatherton Glaciers DEM. This is a significant improvement from the existing 200 m resolution Radarsat Antarctic mapping project (RAMPv2) DEM which has a remaining error of + 138 m over the lower Darwin Glacier and + 152 m over the upper Darwin and Hatherton Glaciers. The accuracy is assessed by comparing the ASTER and RAMPv2 DEMs to highly accurate ice, cloud and land elevation satellite (ICESat) laser altimetry data. A 15 m resolution, true colour, orthorectified image is provided for the entire Darwin-Hatherton glacial system from ASTER satellite imagery. The DEMs used to orthorectify the ASTER satellite imagery are the two new 45 m resolution ASTER DEMs. Lastly feature tracking was explored as a method for measuring surface ice velocity. This research shows that feature tracking is unsuitable for the Darwin-Hatherton glacial system if using 15 m resolution satellite imagery over a 1 to 4 year time period.
372

On the Properties of Ice at the IceCube Neutrino Telescope

Whitehead, Samuel Robert January 2008 (has links)
The IceCube Neutrino Telescope is designed to detect high energy neutrinos with a large array of photomultiplier tubes placed deep within the Antarctic ice. The way that light propagates through the ice needs to be modelled accurately to enable the paths of charged particles to be reconstructed from the distribution of their Cerenkov radiation. Light travelling through even the purest of ice will undergo scattering and absorption processes, however the ice in which IceCube is embedded has optical properties that vary significantly with depth which need to be accurately modelled. Currently, simulation of the muon background using the current ice model is unable to fully replicate experimental data. In this thesis we investigate a potential method of improving on the current generation of ice models. We introduce thin, highly absorbing layers into the current description of the detection medium and investigate the effect on the simulation of muon tracks in IceCube. We find that better agreement between simulation and data can be seen in the occupancy of optical modules, through the introduction of such absorptive layers into the existing ice layers.
373

Exploring Antarctica analyzing the outcomes of a minority focused field research program /

Garcia, Claudia Vanessa. January 2009 (has links)
Thesis (M.A.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.
374

Summertime surface mass balance and atmospheric processes on the McMurdo Ice Shelf, Antarctica : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the Department of Geography, University of Canterbury /

Clendon, Penelope Catherine. January 2009 (has links)
Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 177-204). Also available via the World Wide Web.
375

Gravity analyses for the crustal structure and subglacial geology of West Antarctica, particularly beneath Thwaites Glacier

Diehl, Theresa Marie, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.
376

High palaeolatitude record of Late Maastrichtian-Early Danian climate change, Seymour Island, Antarctica

Frost, Peter Alan January 2017 (has links)
The Latest Cretaceous period was characterised by global cooling, superimposed on this pattern of climate change were perturbations in global climate. In high palaeolatitude settings in the Southern Hemisphere short term glacial episodes may have occurred through the latest Cretaceous. The extensive sedimentary succession within the James Ross Basin, Antarctica, provided an opportunity to test the possibility of late Cretaceous glaciation in particular through the succession exposed on Seymour Island. A high resolution oxygen and carbon stable isotope record through the Late Maastrichtian – Early Danian was generated by analysing diagenetically unaltered aragonite nacre shell material from a molluscan fauna collected from the López de Bertodano Fm., part of the Marambio Group present on Seymour Island, Antarctica. The Marambio Group forms an extensive 1100 m thick Late Maastrichtian section that crops out over ~70 km2 of the southernmost part of the island. Coverage of stable isotope data for the measured stratigraphy was good with 213 screened analyses that included data from within 1 m of the K-Pg boundary located at 1029 m above datum, determined from the first occurrence of the dinoflagellate cyst Senegalinium obscurum. Stable isotope data (‰ VPDB) for primary aragonite from bivalves, cephalopods and gastropods exhibited screened stable isotope data ranges of -0.06 to +2.05‰ for δ18O and -7.54 to +3.7‰ for δ13C. Data showed that at individual stratigraphic levels the range in measured δ18O exhibited significant variability. Benthic specimens provided the majority of the stable isotope data, bivalves exhibited the widest range of δ18O and δ13C values. Data show that individual specimens from the same genus can exhibit significant variability for δ18O and δ13C and that analysis of single samples at discrete stratigraphic levels may provide an erroneous interpretation of climate change. Higher oxygen isotope values were seen mid-section and complement previous records of periods of cooler climate identified from palynology, clumped isotopes and sea level. Palaeotemperatures were calculated for δ18O values for a seawater composition of SMOW = -1.0‰, representing an ice free ocean, 6 to 14°C for bivalves, 9 to 12°C for gastropods and 9 to 15°C for cephalopods. Temperatures indicated relatively stable benthic temperatures (~10°C) with a cooling phase that commenced at ~450 m (~69.5 Ma) with the coolest temperatures developed at ~630 m (~69 Ma). Cooling trends showed a good correlation with the position of seawater lowstands. Thereafter temperatures recovered towards the K-Pg boundary before a cooling trend developed that closely correlated with the PaDa1 lowstand. Acceptance of Deccan Traps volcanism as a causal mechanism for the limited degree of observed warming close to the K-Pg event was limited by a lack of suitable specimens.
377

Differential Movement Across Byrd Glacier, Transantarctic Mountains, Antarctica as Indicated by (U-Th)/He Thermochronology and Geomorphology

January 2011 (has links)
abstract: The Byrd Glacier region of Antarctica is important for understanding the tectonic development and landscape evolution of the Transantarctic Mountains (TAM). This outlet glacier crossing the TAM marks a major discontinuity in the Neoproterozoic-early Paleozoic Ross orogen. The region has not been geologically mapped in detail, but previous studies have inferred a fault to exist beneath and parallel to the direction of flow of Byrd Glacier. Thermochronologic analysis has never been undertaken across Byrd Glacier, and little is known of the exhumation history of the region. The objectives of this study are to assess possible differential movement across the inferred Byrd Glacier fault, to measure the timing of exhumation, and to gain a better overall understanding of the structural architecture of the TAM. Apatites and zircons separated from rock samples collected from various locations north and south of Byrd Glacier were dated using single-crystal (U- Th)/He analysis. Similar cooling histories were revealed with comparable exhumation rates of 0.03 ± 0.003 and 0.04 ± 0.03 mm/yr north and south of Byrd Glacier from apatite data and somewhat similar rates of 0.06 ± 0.008 and 0.04 ± 0.01 mm/yr north and south of Byrd Glacier from zircon data. Age vs. elevation regressions indicate a vertical offset of 1379 ± 159 m and 4000 ± 3466 m from apatite and zircon data. To assess differential movement, the Kukri Peneplain (a regional unconformity) was utilized as a datum. On-site photographs, Landsat imagery, and Aster Global DEM data were combined to map Kukri Peneplain elevation points north and south of Byrd Glacier. The difference in elevation of the peneplain as projected across Byrd Glacier shows an offset of 1122 ± 4.7 m. This study suggests a model of relatively uniform exhumation followed by fault displacement that uplifted the south side of Byrd Glacier relative to the north side. Combining apatite and zircon (U-Th)/He analysis along with remote geomorphologic analysis has provided an understanding of the differential movement and exhumation history of crustal blocks in the Byrd Glacier region. The results complement thermochronologic and geomorphologic studies elsewhere within the TAM providing more information and a new approach. / Dissertation/Thesis / M.S. Geological Sciences 2011
378

Genome Sequencing and Analysis of the Psychrophilic Anoxygenic Phototrophic Bacterium Rhodoferax antarcticus sp. ANT.BR

January 2011 (has links)
abstract: Rhodoferax antarcticus strain ANT.BR, a purple nonsulfur bacterium isolated from a microbial mat in Ross Island, Antarctica, is the first described anoxygenic phototrophic bacterium that is adapted to cold habitats and is the first beta-proteobacterium to undergo complete genome sequencing. R. antarcticus has unique absorption spectra and there are no obvious intracytoplasmic membranes in cells grown phototrophically, even under low light intensity. Analysis of the finished genome sequence reveals a single chromosome (3,809,266 bp) and a large plasmid (198,615 bp) that together harbor 4,262 putative genes. The genome contains two types of Rubiscos, Form IAq and Form II, which are known to exhibit quite different kinetic properties in other bacteria. The presence of multiple Rubisco forms could give R. antarcticus high metabolic flexibility in diverse environments. Annotation of the complete genome sequence along with previous experimental results predict the presence of structural genes for three types of light-harvesting (LH) complexes, LH I (B875), LH II (B800/850), and LH III (B800/820). There is evidence that expression of genes for the LH II complex might be inhibited when R. antarcticus is under low temperature and/or low light intensity. These interesting condition-dependent light-harvesting apparatuses and the control of their expression are very valuable for the further understanding of photosynthesis in cold environments. Finally, R. antarcticus exhibits a highly motile lifestyle. The genome content and organization of all putative polar flagella genes are characterized and discussed. / Dissertation/Thesis / M.S. Molecular and Cellular Biology 2011
379

Cooperação e conflitos nas regiões polares : um cenário para o século XXI

Santos, Leo Evandro Figueiredo dos January 2016 (has links)
A presente tese trata de analisar, a partir da situação das Regiões Ártica e Antártica, questões ambientais que se inserem no campo das relações e dos estudos de segurança internacionais. Neste sentido, através de uma abordagem comparativa, ajusta-se, metodológica e teoricamente, as relações entre questões ambientais e de segurança e sua intersecção com os estudos sobre regimes internacionais. O objetivo é a partir de uma concepção de que são o Ártico (parcialmente) e a Antártica, áreas internacionais, examinar a relação existente entre a exploração de recursos naturais e questões ambientais (mudanças climáticas) e as possibilidades de conflitos e sua superação ou adiamento, em função do exame intrínseco da competição por recursos naturais (petróleo, gás, hidratos de gás, bioprospecção, recursos marinhos, água doce, turismo e rotas polares, esse último somente para o Ártico) e das mudanças climáticas e dos regimes concebidos nas Regiões Polares. Foram examinadas, ao mesmo tempo, dificuldades econômicas, ambientais, técnicas e políticas (dificuldades intrínsecas) à exploração de recursos ambientais, os efeitos das mudanças climáticas e a força dos regimes das Regiões Polares, verificando-se as respectivas capacidades de adiar ou evitar conflitos. Sendo que a força do regime foi examinada a partir do grau de impacto dos elementos que a formam: 1) efetividade do regime, 2) a resiliência do regime, 3) resistência do regime, 4) a presença do hegemon e outros Estados protagonistas, 5) mecanismos de aquiescência, que incentivem ou obriguem o respeito as regras do regime, e 6) existência de uma organização internacional vinculada. Partiu-se do pressuposto de que quanto maiores as dificuldades para exploração, menor seria a competição e, portanto, menores as possibilidades de ocorrerem conflitos. A possibilidade de ocorrência de conflitos também foi cotejada com o grau de fortalecimento dos regimes instalados nas Regiões Polares. A tese conclui que no Ártico e na Antártica as dificuldades para a exploração dos recursos naturais se equivalem. Especificamente no campo político e econômico, quanto aos minerais (inclusive água) na Antártica a dificuldade é maior na atualidade em função da vedação da exploração até 2048 e porque as pesquisas ainda são insuficientes para comprovar a viabilidade da exploração; em compensação no Ártico a localização dos recursos em áreas sob soberania ou no espaço que compreende a ZEE não enseja dificuldades políticas e jurídicas para exploração em função da aplicação da CNUDM. Por sua vez, em especial, as externalidades dos efeitos das mudanças climáticas nas Regiões Polares podem provocar o aumento do n.m.m. e alterações dos padrões climáticos, contudo conflitos não seriam inevitáveis. Em relação aos Regimes Polares ambos foram considerados fortes, contudo o regime antártico foi considerado mais fortalecido. O exame dos elementos, principalmente, a resiliência e efetividade do STA e cotejamento com o processo de consolidação do regime complexo do Ártico justificam a conclusão. Por fim conclui esta tese que as condições para exploração dos recursos naturais, os efeitos das mudanças climáticas nas e a partir das Regiões Polares e o grau de fortalecimento dos regimes internacionais lá constituídos revelam, que os conflitos, ainda que possíveis não são prováveis. / This thesis analyzes, from Arctic and Antarctic regions, environmental issues which fall within the field of international relations and security studies. In this sense, through a comparative approach sets, intends to, methodological and theoretically, the relationship between environmental and security issues and its intersection with studies on international relations. The goal is, from a design which are the Arctic (in part) and Antarctica, international areas, examining the links between the exploitation of natural resources and environmental issues (climate change) and the potential for conflicts and overcome them or postponement, due to the intrinsic exam competition for natural resources (oil, gas, gas hydrates, bioprospecting, marine resources, freshwater, tourism and polar routes, the latter only for the Arctic) and climate change and regimes in the polar regions. Were examined at the same time, economic, environmental, technical and policy difficulties (intrinsic difficulties) the exploitation of environmental resources, the effects of climate change and the strength of the polar regions regimes, verifying their ability to delay or avoid conflicts. The strength of the system was examined from the degree of impact of the elements that form it: 1) effectiveness of the system, 2) the resilience of the system, 3) regime resistance, 4) the presence of the hegemon and other protagonists States 5) compliance mechanisms that encourage or force respect the rules of the regime, and 6) the existence of a linked international organization. It started with the assumption that the greater the difficulties for exploration, would be less competition and therefore lower the chances of occurrence of conflicts. The possibility of conflict was also checked against the degree of strengthening of systems installed in the polar regions. The thesis concludes that the Arctic and Antarctic difficulties for the exploitation of natural resources are equivalent. Specifically, in the political and economic field, as minerals (including water) in Antarctica the difficulty is greater today due to the operations are prohibited up to 2048 and because the research is still insufficient to prove the viability of the exploitation; in compensation in the Arctic location of resources in areas under the sovereignty or within the EEZ that comprises not entails political and legal difficulties to exploitation due to the implementation of UNCLOS. In turn, in particular, the externalities of the effects of climate change on the polar regions can cause an increase in sea level and changes in weather patterns, however conflicts would not inevitable. Regarding the polar regimes both were considered strong, however the Antarctic regime was considered more strong. Examination of the components, especially the resilience and effectiveness of ATS and mutual comparison with the consolidation of the complex Arctic regime justify the conclusion. Finally, this thesis concludes that the conditions for exploitation of natural resources, the effects of climate change on and from the polar regions and the degree of strengthening international regimes established their reveal that the conflicts, although possible is not probable.
380

Exploring the explorers : studying the mood, mental health, cognition and the lived experience of extreme environments in a small isolated team confined to an Arctic research station

Temp, Anna Gesine Marie January 2018 (has links)
Background: The human ability to adapt to extreme environments is fascinating. Research into this adaptation has been lacking in Arctic isolated teams because it has concentrated on Antarctic teams. The hazards of the poles often confine the researchers indoors with their colleagues, reducing their privacy. This deployment also limits their contact with loved ones at home. Subsequently, over the course of polar night, rates of anxiety, depression, irritability and sleep disturbance increase (Suedfeld & Palinkas, 2008). Often, the teams complain of cognitive impairments. The High Arctic’s distinctive feature is the polar bear. The presence of bears requires Arctic research station teams to handle fire arms for their personal safety. It also means that fire arms – which are highly restricted in the Antarctic – are ever-present and easily accessible at Arctic stations. This poses a unique psychological challenge for these teams which has not been well-researched. Methodology: This thesis is an original contribution to science in that it employs a mixed-methods approach combining phenomenological interviews, cognitive testing and mental health assessment via questionnaires with a team spending a year at the Polish Polar Station, Hornsund, Svalbard. The participants were ten of the eleven winter team members who spent the year between July 2015 and June 2016 at Hornsund (“Explorers”) and an age-/gender-/education-matched control group (“Controls”). They filled in the Symptom Checklist-90-Revised and the Profile of Mood States-Brief Version in July, September, January, April and June of that year. Cognitive testing was completed in September, January and June; it comprised the Figural Learning and Memory Test, the Sustained Attention to Response Task (SART), the elevator tasks of the Test of Everyday Attention (TEA) and the Raven Standard Progressive Matrices. The interviews took place at the same time as the cognitive testing. Results: The results showed that the most stressful time reported in the questionnaires was April 2016, just after the winter isolation had ended and the sun had risen again. The Explorers reported little subjective complaints about their cognition but they performed near-ceiling on the TEA while scoring far below their Controls on the SART. This implies a dichotomy between sustained attention and inhibition in the Explorers. Their lived experiences were shaped by a struggle to adapt to the other team members rather than by struggling to adapt to the hazardous environment. The environment was perceived as awe-inspiring. Over time, the Explorers shifted their view of the team from informal colleagues to a family which they did not choose to be a member of and then, to friends. Unanimously, other people were seen as the most difficult aspect of the mission. Conclusions: This thesis provides unique insight into a non-Anglo-Saxon Arctic wintering team: the conclusions suggest that participants should receive social training to get along better and be emotionally prepared. The findings can be implemented by my research partner, the Institute of Geophysics (Warsaw) to better select and prepare their future expeditions to Hornsund. Some of the insights such as the nature of the interpersonal stressors may be applicable to space missions.

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