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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.
31

The Population ecology of wild horses in the Australian Alps

Walter, Michelle, n/a January 2002 (has links)
In this thesis I examine the population ecology of wild horses (Equus caballus) in the Australian Alps. Wild horses were first introduced into the Alps over 150 years ago. Paradoxically, they are a feral animal impacting on the environment, but are also a cultural icon. Managing wild horse populations is contentious and needs to be founded on knowledge of their population ecology. This is the first study of its kind in the Australian Alps and therefore has a broad focus. Four general areas were addressed: distribution, estimation of abundance and density, population dynamics and the influence of brumby-running. The study was conducted between 1999 and 2002 inclusive in the Australian Alps national parks, which form a contiguous protected area in south-eastern Australia from the Australian Capital Territory (ACT) in the north, through New South Wales (NSW) and into Victoria in the south. The current distribution of wild horses in the Australian Alps national parks is patchy. There are five major discrete populations in NSW and Victoria with the northern most population in Kosciuszko National Park (NSW) bordering on the ACT. A review of published material and oral history reveals historic influences on distribution. The presence of each population is associated with introductions by people. The distribution of some populations expanded after introductions and many have fluctuated over time. Distributions have been contained or reduced through control by people, natural events such as snow and drought and by geographical barriers. Park managers eliminated a population of wild horses in the ACT in the 1980s. Distributions have expanded in areas without active management (notably northern Kosciuszko National Park) and are likely to continue expanding under a policy of no management. In February and March 2001, abundance and density of wild horses were estimated by helicopter aerial survey in areas where the mapping showed horses to occur. This was the first time that these parameters have been estimated empirically. I compared three different aerial survey techniques (strip, mark-recapture and line transect) based on relative accuracy and precision and found that line transect analysis gave the highest, most precise estimate. Given that aerial surveys usually underestimate abundance, this method was also likely to be the most accurate. Mark-recapture over a 50m wide strip gave a similar result but lacked precision. Strip and mark-recapture techniques performed poorly over 200m strips because animals were missed. Numbers observed dropped off dramatically beyond the 50m strip. Line transect analysis (for both observers combined) gave an estimate of 5010 (+/- 1408SE) horses while mark recapture over 50 metres gave an estimate of 4915 (+/-2733SE). These estimates correspond to a density of 1.8 horses km-2 over the area surveyed (2789km2). The results suggest that aerial surveys of large mammals using a wide strip width (200m) and mark recapture analysis may seriously underestimate population density. The population dynamics and demography of wild horses were estimated at three sites, Big Boggy, Cowombat and Currango, every spring and autumn over 3 years. The sites were spread widely across the Alps with the aim of obtaining a broad understanding of population dynamics. The survey used Pollock�s robust design and natural markings were used to identify individuals. There was a seasonal spring peak in population size at Big Boggy with no clear seasonal trend at the other two sites. Mean wild horse densities determined at Big Boggy (2.01km-2) and Currango (2.13km-2) were not significantly (p<0.5) different to the density calculated in the aerial survey, whereas density was significantly higher at Cowombat (6.4 km-2). Census techniques were of limited use in estimating annual population growth rate because of low precision. Demographic analysis showed that none of the populations were increasing at the maximum intrinsic rate (l = 1.2), and the Big Boggy and Cowombat populations may be stable (l = 1.0/yr). There was an apparent trend of food limitation across the sites. Body condition was positively related (p<0.01) to pasture biomass. The Currango population was increasing (l = 0.09) associated with higher recruitment, body condition and pasture biomass than in the other two populations studied. The Cowombat population had the lowest annual finite rate of increase (l = 1.03), and horses at this site were in the poorest condition and pasture biomass was lowest. The Big Boggy population was intermediate between the two. Annual adult survival was constant in all populations at 0.91. Survival in the first three years of life was more variable with the average at each site ranging from 0.63/yr to 0.76/yr. An average of 0.26 female foals was born per adult female per year. Sensitivity analysis showed that population growth rate is most sensitive to changes in adult survival, followed by fecundity and then survival in the first three years of life. The dynamics observed at each site was representative of the demography of wild horses in other parts of the world and is typical for large mammalian herbivores. Brumby-running is a form of harvesting that is currently being used to control wild horses in the Alpine National Park (Victoria) and is soon to be trialled in Kosciuszko National Park (NSW). The effectiveness of brumby-running has not been assessed prior to this study. Data collected by the Alpine Brumby Management Association and predictive modelling were used to examine the influence of brumby-running on the wild horse population in Alpine National Park. Brumby-runners remove about 200 horses per year with a preference for young animals and adult females. More horses are caught in autumn (61/yr) and least in summer (30/yr) (p<0.05). Brumby-runners do not appear (p>0.05) to target horses in poor condition. One skilled brumby-runner caught an average of 1.16 horses/day, while his companions caught an average of 0.55 horses/day. Brumby-runners show behaviour analogous to social carnivores. Predictive modelling suggests that brumby-runners could suppress the population of wild horses in Alpine National Park similar to the effects of predators, or human harvesting of other large mammals. Selecting young animals in the harvest reduces the impact of harvesting on the population compared to unselective harvesting, while selecting adult females increases the predicted impact. There are several management recommendations based on the findings of this thesis that address concerns for both environmental impact and the cultural value of wild horses. The distribution of wild horses should not be allowed to expand further, and the size of the wild horse population should be prevented from increasing further. Other management recommendations that are more complex involve reducing some populations so that the level of environmental impact they are causing is acceptable. This requires a definition of �acceptable impact.� Finally managers should consider eradicating smaller populations.
32

L'ÉVOLUTION MAGMATIQUE ET TECTONO-MÉTAMORPHIQUE DU SUBSTRATUM DU DOMAINE VALAISAN (COMPLEXE DU VERSOYEN, ALPES OCCIDENTALES) - IMPLICATIONS DANS L'HISTOIRE ALPINE

Cannic, Sebastien 10 October 1996 (has links) (PDF)
Le domaine valaisan dessine la suture majeure qui marque la limite entre les zones internes et externes des Alpes occidentales et dont l'interprétation géodynamique était controversée. Cette suture est constituée d'une série de flysch (le flysch valaisan) et d'un complexe magmatique et sédimentaire (le complexe du Versoyen). Suivant les auteurs, les roches magmatiques d'affinité tholéïtique pourraient représenter: 1) une klippe d'origine piémontaise (suture d'hyper-collision), 2) une écaille ophiolitique située au front d'un prisme d'accrétion (suture océanique), 3) un complexe magmatique lié à un amincissement crustal (inversion structurale). Le but de ce travail était de trouver des arguments qui permettaient de résoudre cette controverse. Ainsi les résultats de ce travail montrent que : - Dans la région du col du Petit-Saint-Bernard (frontière franco-italienne), certaines tholéïtes sont recoupées par des filons leucocrates qui correspondent à des liquides différenciés, cogénétiques du magmatisme. Les datations UlPb sur les zircons contenus dans l'un de ces filons indiquent un âge Carbonifère supérieur- Permien inférieur pour le magmatisme du Versoyen. - Ce magmatisme présente des caractères géochimiques et isotopiques, intermédiaires entre ceux des N-MORB et des T-MORB, dans les régions du col du Petit-Saint-Bernard et de Visp (Suisse). Ces tholéïtes dériveraient de la fusion partielle d'un manteau appauvri (de type N-MORB), avec probablement la participation d'une source enrichie (de type OIB), ce qui est en accord avec une mise en place dans un domaine en cours d'océanisation. - Le complexe du Versoyen est affecté par un métamorphisme polyphasé éclogitique, puis schiste bleu et enfin schiste vert. La paragénèse éclogitique correspond à des conditions de Haute-Pression et Basse-Température (P > 13Kb, 425 < T < 475°C) qui traduisent un enfouissement à grande profondeur, lié à une subduction. Les datations Ar/Ar réalisées sur les phengites donnent des âges de refroidissement proches de 33 Ma et permettent d'établir le chemin P-T-t de ce complexe au cours de l'exhumation des éclogites. - Le complexe du Versoyen est affecté par une déformation syn-schiste vert qui correspond à un jeu normal vers le SE. La comparaison entre les données de terrain et les données sismiques ECORS suggère que les failles normales se prolongent en profondeur et s'applatissent vers 10-15 km. Cette déformation postérieure à 38 Ma explique en partie l'exhumation des éclogites. Ce jeu normal est contemporain de chevauchements dans la zone externe et pourrait accommoder un réamincissement crustal au cours de la collision alpine. Ces données montrent que l'individualisation du substratum du domaine valaisan est liée au cycle hercynien et que ses relations complexes avec le flysch sus-jacent sont liées à une inversion structurale anté-flysch, alors que son évolution tectono-métamorphique est controlée par une extension succèdant aux phases compressives.
33

Les élements présents a l'état de traces et les Hydrocarbures Aromatiques Polycycliques dans la neige et la glace prélevées au Col Gnifetti, massif du Mont Rose (4450m): implications environnementales et climatiques

Gabrieli, Jacopo 28 November 2008 (has links) (PDF)
Nous avons conçu, construit et testé un nouveau système pour la décontamination en ligne et l'analyse en continu de carottes de neige ou de glace des Alpes. L'eau de fusion obtenue à partir de la partie centrale des carottes est directement introduite dans un spectromètre de masse à quadrupole (ICP-QMS) et un conductimètre, pour la détermination en continu de différents éléments présents à l'état de traces et de la conductivité. Des échantillons sont également prélevés en discontinu pour la détermination de divers éléments présents à l'état de traces, des isotopes du Plomb et du Plutonium par spectrométrie de masse à secteur magnétique (ICP-SFMS) et par ICP-OES. L'eau de fusion obtenue à partir de la partie externe des carottes est quant à elle utilisée pour la détermination en semi-continu des Hydrocarbures Aromatiques Polycycliques (HAPs), avec extraction en ligne à l'aide de cartouches en phase solide.<br />D'importantes variations saisonnières des concentrations sont observées pour tous les éléments, aussi bien les éléments qui proviennent de manière prédominante de la croûte terrestre (Mg, Al) que les éléments enrichis par suite d'apports anthropiques (Pb). Pour comprendre ces variations à court terme, il est important de se référer aux rétro-trajectoires des masses d'air. D'autres paramètres importants sont la dynamique des inversions de températures et les caractéristiques de la couche limite. Ils jouent en effet un rôle majeur dans le transport et la dispersion des aérosols et des gaz à partir des sources d'émissions situées à basse altitude.<br />Les émissions les plus importantes de Plomb au cours de l'histoire ont eu lieu pendant les 19e et 20e siècles, et plus particulièrement des années 1950 aux années 1970. Pour déterminer si les variations observées dans la carotte du Colle Gnifetti reflètent fidèlement les variations des émissions dans les pays européens voisins, nous avons comparé les données obtenues pour la neige et la glace avec les données d'émission disponibles. De 1800 jusqu'à la première décennie du 20e siècle, les concentrations de Plomb ont augmenté de manière très marquée, atteignant un maximum dans les années 1920. Pendant les années 1920, les concentrations de Plomb décroissent rapidement d'un facteur deux, et restent à ce niveau pendant les deux décennies suivantes. Après la fin de la 2e guerre mondiale, les flux de retombées de Plomb augmentent de manière très importante par suite de l'utilisation des additifs au Plomb dans l'essence, et atteignent un maximum au milieu des années 1970. A partir de 1975, les concentrations de Plomb mesurées dans la neige et la glace du Colle Gnifetti commencent à décroître par suite des règlementations adoptées en Europe pour limiter les émissions de polluants.<br />Avant 1875, les concentrations de HAP étaient très basses: les concentrations observées dans la glace datant d'avant les années 1750 représentent très probablement le niveau de bruit de fond de ces composés. Les concentrations cumulées des HAP au cours de la décennie 1945-1955 sont supérieures d'un facteur dix aux valeurs de bruit de fond, alors que les concentrations cumulées de HAP* sont environ 40 à 50 fois plus élevées. A partir des années 1900, les concentrations de HAP augmentent de façon très importante, atteignant un maximum vers 1920. Pendant les années 1920, après la première guerre mondiale, la récession économique en Europe conduit à une chute des activités industrielles. A partir du milieu des années 1930, les concentrations de HAP doublent rapidement, atteignant un maximum pendant les années 1940. La concentration cumulée des HAP* les plus lourds décroit ensuite d'un facteur cinq de 1950 à 1975 alors que la concentration cumulée des HAP décroit d'un facteur deux. De 1975 à 2003, la concentration totale des HAP augmente à nouveau, approchant les valeurs des années 1910. De manière globale, les variations temporelles observées pour les HAP sont fortement corrélées aux variations des émissions anthropiques. Cependant, les variations détaillées sont difficiles à interpréter et pourraient être influencées par divers paramètres.<br />Le Plutonium est présent dans l'environnement par suite des essais nucléaires atmosphériques des années 1960, de la production des armes nucléaires et des rejets par l'industrie nucléaire au cours des 50 dernières années. Le profil de variations du Plutonium dans la neige et la glace du Colle Gnifetti met en évidence les trois périodes principales d'essais nucléaires atmosphériques.<br />Le rapport isotopique 206Pb/207Pb est compris entre 1.18 et 1.20 pour la glace datant d'avant 1700, en accord avec la composition des roches locale. Bien que les retombées de Plomb au Colle Gnifetti après les années 1900 soient presque entièrement dues à des apports anthropiques, on n'observe pas de variations importantes du rapport isotopique jusqu'en 1975. Ceci est lié au fait que la composition isotopique moyenne du Plomb dans l'essence et le pétrole utilisés était très semblable à la composition isotopique des roches et des sols locaux. Après 1975, on observe une décroissance brutale et forte du rapport isotopique 206Pb/207Pb, jusqu'à des valeurs proches de 1.11 en 1979-1980. Cette décroissance brutale est liée à une expérience réalisée entre 1975 et 1980 dans la région du Piémont au Nord-Ouest de l'Italie (Isotopic Lead Experiment).
34

La reconnaissance de la courbure membranaire par ArfGAP1

Mesmin, Bruno 17 December 2007 (has links) (PDF)
La formation d'un bourgeon vésiculaire repose sur une machinerie complexe qui déforme, par une action mécanique, une membrane plane en une membrane courbée. Le manteau COPI, responsable de ce phénomène dans le Golgi, se polymérise latéralement à la surface de la membrane, sous le contrôle de la petite protéine G Arf1 activée. Suite à la formation de la vésicule, Arf1 revient à l'état inactif par hydrolyse de son GTP et se dissocie de la membrane, provoquant alors le désassemblage du manteau. Cette réaction d'hydrolyse doit être finement régulée, pour ne pas intervenir trop tôt et compromettre l'assemblage du manteau. Notre laboratoire a révélé que l'activité de la protéine ArfGAP1, responsable de la désactivation d'Arf1, est hypersensible à la courbure membranaire. Ceci permettrait à ArfGAP1 de réguler de manière spatio-temporelle l'état du manteau COPI en couplant son désassemblage à la courbure membranaire qu'il a lui-même induite.<br />Au cours de ma thèse, j'ai montré que la dépendance d'ArfGAP1 à la courbure s'explique par la présence dans cette protéine de deux motifs « ALPS », qui se replient en hélices alpha lors de leur adsorption membranaire. Ce sont des hélices amphipathiques atypiques car, si elles possèdent une face hydrophobe classique, elles ont une face polaire riche en sérine et thréonine et pauvre en résidus chargés. Puisque ces résidus hydroxylés ne peuvent interagir avec les têtes polaires des lipides, la liaison d'un motif ALPS ne repose que sur l'insertion de ses résidus hydrophobes entre les lipides, ce qui est favorisé par l'écartement lipidique induit par la courbure membranaire, mais plus difficile sur membrane plane où les lipides sont plus compactés.
35

Depositional periodicity and the hierarchy of stratigraphic forcing in the Triassic carbonates of the Dolomite Alps, N. Italy

Forkner, Robert Murchison, 1977- 04 March 2014 (has links)
The Dolomite Alps of northern Italy are a classic field locality in the development carbonate stratigraphic theory. Included in the many discoveries rooted in the geology of the Dolomites is the concept of a hierarchy of stratigraphic forcing in the Alpine Triassic. The hierarchy states that carbonate sedimentation is dominantly a record of eustasy, resulting in organized stacking patterns, and that these stacking patterns reflect the interplay between low frequency (1-10 my) eustatic cycles and their component bundled high-frequency (100 & 20 kyr) eustatic cycles. The overall aim of this study is to further investigate the validity of the hierarchical model after recent dating of Anisian and Ladinian successions called the Milankovitchian periodicity and/or allocyclicity of the cyclic series into question. The study was completed using four sub-studies, 3 based on data collected in the field and a fourth based in cycle theory and computer modeling. First, it can be shown that allocyclic forcing exists in the Anisian/Ladinian platforms of the Dolomites by comparing the stratigraphic sections measured from 2 time-equivalent, independent carbonate platforms, the Latemar and Mendola Pass. Second, computer modeling of Anisian/Ladinian carbonate platform stratigraphy using Milankovitchain solar insolation as a proxy for high-frequency eustasy shows that both pure Milankovitch forcing and mixed Milankovitch/sub-Milankovitch forcing will produce synthetic carbonate platforms with stratigraphic successions comparable to those of the Anisian/Ladinian platforms of the Dolomites. Third, it can be shown that the while the Norian Dolomia Principale (a regional carbonate shelf) was affected by differential subsidence, megacycles systematically increase in their number of component cycles from 2-3:1 in the eastern Dolomites (updip) to 5-6:1 in the western Dolomites (seaward). In conclusion, the concept that carbonate platform stratigraphy is a record of an interplay between eustasy, subsidence, and sedimentation is upheld, while the validity of Milankovitchian forcing acting on all Alpine carbonate cycles is questioned. Instead, cyclic carbonates with sub-Milankovitch periodicities were common in the early and mid-Triassic, while cycles with Milankovitchian periodicities were common in the late Triassic. / text
36

Geomorphic Hazards associated with Glacial Change, Aoraki/Mount Cook region Southern Alps, New Zealand

Allen, Simon Keith January 2009 (has links)
Glacial floods and mass movements of ice, rock or debris are a significant hazard in many populated mountainous regions, often with devastating impacts upon human settlements and infrastructure. In response to atmospheric warming, glacial retreat and permafrost thaw are expected to alter high mountain geomorphic processes, and related instabilities. In the Aoraki/Mount Cook region of New Zealand's Southern Alps, a first investigation of geomorphic hazards associated with glacial change is undertaken and is based primarily on the use of remote sensing and Geographic Information Systems (GIS) for mapping, modelling, and analysing related processes and terrain. Following a comprehensive review of available techniques, remote sensing methods involving the use Advanced Spaceborne Thermal Emission and Radiometer (ASTER) imagery were applied to map glacial ice, lakes and debris accumulations in the Aoraki/Mount Cook region. Glacial lakes were mapped from two separate classification techniques using visible near infrared wavelengths, capturing highly turbid and clearer water bodies. Large volume (10⁶– 10⁸ m³) proglacial lakes have developed rapidly over recent decades, with an overall 20 % increase in lake area recorded between 2002 and 2006, increasing the potential for large mass movement impacts and flooding from displaced water. Where significant long-term glacial recession has occurred, steep moraines have been exposed, and large talus slopes occupy formerly glaciated slopes at higher elevations. At the regional-scale, these potential source areas for debris instabilities were distinguished from surrounding bedrock slopes based on image texture variance. For debris and ice covered slopes, potentially unstable situations were classified using critical slope thresholds established from international studies. GIS-based flow routing was used to explore possible intersections between zones of human use and mass movement or flood events, assuming worst-case, probable maximum runout distances. Where glacial lakes are dammed by steep moraine or outwash gravel, primarily in cirque basins east of the Main Divide, modelled debris flows initiated by potential flood events did not reach any infrastructure. Other potential peri- and para-glacial debris flows from steep moraines or talus slopes can reach main roads and buildings. The direct hazard from ice avalanches is restricted to backcountry huts and walking tracks, but impacts into large glacial lakes are possible, and could produce a far reaching hazard, with modelled clear water flood-waves capable of reaching village infrastructure and main roads both east and west of the Main Divide. A numerical modelling approach for simulating large bedrock failures has been introduced, and offers potential with which to examine possible lake impacts and related scenarios. Over 500 bedrock slope failures were analysed within a GIS inventory, revealing distinct patterns in geological and topographic distribution. Rock avalanches have occurred most frequently from greywacke slopes about and east of the Main Divide, particularly from slopes steeper than 50°, and appear the only large-magnitude failure mechanism above 2500 m. In the schist terrain west of the Main Divide, and at lower elevations, other failure types predominate. The prehistoric distribution of all failure types suggests a preference for slopes facing west to northwest, and is likely to be strongly influenced by earthquake generated failures. Over the past 100 years, seismicity has not been a factor, and the most failures have been as rock avalanches from slopes facing east to southeast, particularly evident from the glaciated, and potentially permafrost affected hangingwall of the Main Divide Fault Zone. An initial estimate of permafrost distribution based on topo-climatic relationships and calibrated locally using mean annual air temperature suggested permafrost may extend down to elevations of 3000 m on sunny slopes, and as low as 2200 m on shaded slopes near the Main Divide. A network of 15 near-surface rock temperature sensors was installed on steep rock walls, revealing marginal permafrost conditions (approaching 0 °C) extending over a much larger elevation range, occurring even where air temperature is likely to remain positive, owing to extreme topographic shading. From 19 rock failures observed over the past 100 years, 13 detachment zones were located on slopes characterized by marginal permafrost conditions, including a sequence of 4 failures that occurred during summer 2007/08, in which modelled bedrock temperatures near the base of the detachments were in the range of 1.4 to +2.5 °C. Ongoing monitoring of glacial and permafrost conditions in the Aoraki/Mount Cook region is encouraged, with more than 45 km2 of extremely steep slopes (>50°) currently ice covered or above modelled permafrost elevation limits. Approaches towards modelling and analysing glacial hazards in this region are considered to be most applicable within other remote mountain regions, where seismicity and steep topography combine with possible destabilizing influences of glacial recession and permafrost degradation.
37

Recent glacier and climate change in the New Zealand Alps

Ruddell, Andrew Reginald Unknown Date (has links) (PDF)
The sensitivity of glaciers in the Southern Alps of New Zealand is evaluated to identify the nature of recent climate change. Past glaciological observations are compiled and to these are added 4 summer field seasons on the Tasman (including Hochstetter), Dart, Fox and Franz Josef Glaciers. The field data are an important aspect in the calibration and verification of glacier modelling. The detailed studies of these glaciers provides the basis for assessing the glacier and climatic changes over the whole glacierized region. (For complete abstract open document)
38

Studies of the germination of seven Australian alpine and subalpine shrub species

MacPhee, Elizabeth Unknown Date (has links) (PDF)
Seeds of seven alpine and subalpine Australian shrub species (Acacia alpina,A. obliquinervia, Bossiaea foliosa, Hovea montana, Oxylobium ellipticum,Grevillea australis & Pimelea ligustrina) with potential to colonise in badly disturbed alpine and subalpine sites had a range of treatments (scarification,stratification, leaching, chemical soaks, freezing & diurnally fluctuating temperatures) applied to them to enhance germination success. Seeds of the hard seeded legumes responded well to scarification and stratification treatments. Acacia obliquinervia was scarified with boiling water which resulted in enhanced germination success. The scarification treatment with the best result was nicking for the other four legumes. The use of hot-watersoaks for these other legumes, of a minute or less showed some potential as a useful scarification treatment Stratification periods between 8 to 14 weeks for Acacia alpina, 12 to 14 weeks for Bossiaea foliosa, 2 to 8 weeks for Hoveamontana and 4 to 6 weeks for Oxylobium ellipticum gave significantly enhanced germination. Grevillea australis did not respond to germinationpre-treatments, except for an isolated case of nicking and stratification for 6weeks. The same treatment of older seed did not result in significantgermination. Pimelea ligustrina did not reliably respond to germination pretreatments.Germination trial results were then applied to one of the legumespeCIes (Bossiaea foliosa) as a guide to how these seeds respond to apretreatment before sowing on a disturbed site at the Bogong High Plains.The treatment of 30s in water @ l00°C and 14 weeks stratification before sowing in autumn was found to significantly enhance the field establishment success of Bossiaea foliosa.
39

Volume Change of the Tasman Glacier Using Remote Sensing

Thomas, Joel Spencer January 2008 (has links)
Mountain glaciers are expected to be the greatest contributor to sea level rise over the next century. Glaciers provide a good indicator of global climate and how to monitor their change is an increasingly important issue for climate science and for sea level rise forecasts. However, there has been little direct measurement of glacier volume change in New Zealand. This study explores the use of remotely sensed data for measuring glacier volume change from 1965 to 2006. Digital photogrammetric methods were used to extract topographic data of the Tasman Glacier from aerial photography and ASTER imagery for the years 1965, 1986, 2002 and 2006. SRTM C band data from 2000 were also analysed. Data were compared to an existing digital elvation model produced from the New Zealand Digital Topographic Database to test for their reliability. Using regression analysis, the data were filtered and points representing rock were used to correct points on the glacier ice for vertical bias. The quality of the data extracted from the aerial photography was good on rock and debris covered ice, but poor on snow. The data extracted from ASTER was much more reliable on snow in the upper glacier than the aerial photography, but was very poor in the lower debris covered region of the glacier. While the quality of the SRTM data is very high, there is a second order distortion present in the data that is evident over elevation differences. However, the overall mean difference of the SRTM rock from TOPODATA is close to zero. An overall trend could be seen in the data between dates. However, the 2006 ASTER data proved unreliable on the debris covered section of the glacier. Total volume change is therefore calculated for the period between 1965 and 2002. The data show a loss of 3:4km³ or 0:092km³ per year, an estimated 6% of the total ice in New Zealand. This is compared to estimates using the annual end of summer snowline survey between 1977 and 2005 of 1:78 km³, or 0:064km³ per year. The spatial resolution of ASTER makes high temporal resolution monitoring of volume change unlikely for the New Zealand glaciers. The infrequency of aerial photography, the high cost and vast time involved in extracting good quality elevation data from aerial photography makes it impractical for monitoring glacier volume change remotely. However, SRTM and other radar sensors may provide a better solution, as the data do not rely heavily on user processing.
40

Geomorphic Hazards associated with Glacial Change, Aoraki/Mount Cook region Southern Alps, New Zealand

Allen, Simon Keith January 2009 (has links)
Glacial floods and mass movements of ice, rock or debris are a significant hazard in many populated mountainous regions, often with devastating impacts upon human settlements and infrastructure. In response to atmospheric warming, glacial retreat and permafrost thaw are expected to alter high mountain geomorphic processes, and related instabilities. In the Aoraki/Mount Cook region of New Zealand's Southern Alps, a first investigation of geomorphic hazards associated with glacial change is undertaken and is based primarily on the use of remote sensing and Geographic Information Systems (GIS) for mapping, modelling, and analysing related processes and terrain. Following a comprehensive review of available techniques, remote sensing methods involving the use Advanced Spaceborne Thermal Emission and Radiometer (ASTER) imagery were applied to map glacial ice, lakes and debris accumulations in the Aoraki/Mount Cook region. Glacial lakes were mapped from two separate classification techniques using visible near infrared wavelengths, capturing highly turbid and clearer water bodies. Large volume (10⁶– 10⁸ m³) proglacial lakes have developed rapidly over recent decades, with an overall 20 % increase in lake area recorded between 2002 and 2006, increasing the potential for large mass movement impacts and flooding from displaced water. Where significant long-term glacial recession has occurred, steep moraines have been exposed, and large talus slopes occupy formerly glaciated slopes at higher elevations. At the regional-scale, these potential source areas for debris instabilities were distinguished from surrounding bedrock slopes based on image texture variance. For debris and ice covered slopes, potentially unstable situations were classified using critical slope thresholds established from international studies. GIS-based flow routing was used to explore possible intersections between zones of human use and mass movement or flood events, assuming worst-case, probable maximum runout distances. Where glacial lakes are dammed by steep moraine or outwash gravel, primarily in cirque basins east of the Main Divide, modelled debris flows initiated by potential flood events did not reach any infrastructure. Other potential peri- and para-glacial debris flows from steep moraines or talus slopes can reach main roads and buildings. The direct hazard from ice avalanches is restricted to backcountry huts and walking tracks, but impacts into large glacial lakes are possible, and could produce a far reaching hazard, with modelled clear water flood-waves capable of reaching village infrastructure and main roads both east and west of the Main Divide. A numerical modelling approach for simulating large bedrock failures has been introduced, and offers potential with which to examine possible lake impacts and related scenarios. Over 500 bedrock slope failures were analysed within a GIS inventory, revealing distinct patterns in geological and topographic distribution. Rock avalanches have occurred most frequently from greywacke slopes about and east of the Main Divide, particularly from slopes steeper than 50°, and appear the only large-magnitude failure mechanism above 2500 m. In the schist terrain west of the Main Divide, and at lower elevations, other failure types predominate. The prehistoric distribution of all failure types suggests a preference for slopes facing west to northwest, and is likely to be strongly influenced by earthquake generated failures. Over the past 100 years, seismicity has not been a factor, and the most failures have been as rock avalanches from slopes facing east to southeast, particularly evident from the glaciated, and potentially permafrost affected hangingwall of the Main Divide Fault Zone. An initial estimate of permafrost distribution based on topo-climatic relationships and calibrated locally using mean annual air temperature suggested permafrost may extend down to elevations of 3000 m on sunny slopes, and as low as 2200 m on shaded slopes near the Main Divide. A network of 15 near-surface rock temperature sensors was installed on steep rock walls, revealing marginal permafrost conditions (approaching 0 °C) extending over a much larger elevation range, occurring even where air temperature is likely to remain positive, owing to extreme topographic shading. From 19 rock failures observed over the past 100 years, 13 detachment zones were located on slopes characterized by marginal permafrost conditions, including a sequence of 4 failures that occurred during summer 2007/08, in which modelled bedrock temperatures near the base of the detachments were in the range of 1.4 to +2.5 °C. Ongoing monitoring of glacial and permafrost conditions in the Aoraki/Mount Cook region is encouraged, with more than 45 km2 of extremely steep slopes (>50°) currently ice covered or above modelled permafrost elevation limits. Approaches towards modelling and analysing glacial hazards in this region are considered to be most applicable within other remote mountain regions, where seismicity and steep topography combine with possible destabilizing influences of glacial recession and permafrost degradation.

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