Дисертації з теми "Glaciers – Montana"
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Brett, Melissa Carrie. "Glacier Inventories and Change in Glacier National Park." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4348.
Повний текст джерелаUrion, Celeste Josephine. "Construction of wilderness in the formation of Glacier National Park, Montana." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40018.pdf.
Повний текст джерелаWilliams, Thomas James. "Estimating organic carbon on avalanche paths in Glacier National Park, Montana." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4795.
Повний текст джерелаLambert, Callie Brooke. "Spatio-Temporal Vegetation Change as related to terrain factors at two Glacier Forefronts, Glacier National Park, Montana." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/87411.
Повний текст джерелаMaster of Science
Glacier retreat is considered a clear sign of global climate change. Although glaciers are retreating globally, comparatively little research has assessed how vegetation changes in recently deglaciated areas. The research objectives were to: 1) quantify patterns of landcover change of five classes—ice, rock, tree, shrub, and herbaceous at two glacier forefronts in Glacier National Park, and 2) determine the environmental and terrain factors that affect vegetation change at the deglaciated areas. Landsat imagery of the study locations in 1991, 2003, and 2015 were classified and validated using ground truth points and visual interpretation for accuracy. To identify terrain and environmental factors that influence change, we modeled change from nonvegetated surfaces to vegetation (code=1) and the stable non-vegetation class (code=0). Results revealed elevation, slope, topographic moisture, geology, and aspect to be associated with increased vegetation over time at Jackson Glacier forefront. Elevation, slope, solar radiation, and geology were significant at Grinnell Glacier forefront, indicating some geographic differences in important factors. New case studies on vegetation change in recently deglaciated regions can deepen our knowledge about how glacier retreat at local scales results in recharged ecosystem dynamics. This study provides further insight on the future of alpine ecosystems as they respond to global climate change and a compelling new perspective on the future of the Park. Additionally, we demonstrate the benefits of using remote sensing applications to study land cover change as a proxy for vegetation colonization, especially in remote mountainous environments.
Dussaillant, Inés. "Contribution récente des glaciers des Andes à la ressource en eau et à la hausse du niveau marin : apport des observations satellitaires." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30161.
Повний текст джерелаAndean glaciers are amongst the fastest shrinking and the largest contributors to sea level rise in the world. They also represent crucial water resources in the vast semi-arid portions of this large Andes Cordillera (10°N-56°S), sustaining river runoff during dry periods and buffering the effects of droughts. Despite the widespread shrinkage of these glaciers, direct measurement of glacier fluctuations in the Andes are sparse, short-termed and in many cases incomplete, preventing the accurate quantification of recent ice loss for the entire mountain range. Comprehensively quantifying the magnitude of this loss at different special scales is crucial to better constrain future economical, ecological and social impacts. First, we evaluated the performance of a methodology to calculate glacier mass changes on Andean glaciers using time series of digital elevation models (DEMs) derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo images. Over our validation zone, the Northern Patagonian Icefield, we found strongly negative icefield-wide mass balance rates of -1.06 ± 0.14 m w.e. yr-1 for the period 2000-2012, in good agreement with estimates from earlier studies and with a second independent estimate (-1.02 ± 0.21 m w.e. yr-1) obtained by differencing the better resolved Shuttle Radar Topography Mission (SRTM) DEM with a Satellite pour l'Observation de la Terre 5 (SPOT5) DEM. Importantly, this work permitted us to (i) validate "ASTER monitoring Ice towards eXtinction" (ASTERIX) method over the Andes; (ii) confirm the lack of penetration of the C-band SRTM radar signal into the NPI snow and firn except for a small high altitude region (above 2900 m a.s.l.) with negligible effects on NPI-wide mass balance; and (iii) provide the basis for an analysis of NPI mass balance changes during different sub-periods between 1975 and 2016 using additional DEMs. Then, we processed more than 30000 ASTER DEMs to calculate the integrated volume of ice lost by Andean glaciers during the past two decades. Andes-wide mass loss amounts to -22.9 ± 5.9 Gt yr-1 (-0.72 ± 0.22 m w.e. yr-1) for the entire period (or -26.0 ± 6.0 Gt yr-1 including subaqueous losses). All regions show consistent glacier wastage, with the most negative mass balance rates in the Patagonian Andes (-0.78 ± 0.25 m w.e. yr-1) and Tropical Andes (-0.42 ± 0.24 m w.e. yr-1). Relatively moderate loss (-0.28 ± 0.18 m w.e. yr-1) is measured in the intermediate regions of the Dry Andes. The inter-decadal patterns of glacier mass loss is an important contribution of this work, observed for the first time at an Andes-wide scale. We observe steady thinning rates in the Tropics and south of 45°S. Conversely, glaciers from the Dry Andes were stable during the 2000s, shifting to drastic thinning rates during the 2010s, coinciding with conditions of sustained drought since 2010. The evaluation of the imbalanced glacier contribution to river discharge during these two decades revealed that glaciers partially helped to mitigate the negative impacts of this sustained drought in the Dry Andes. The results obtained in this thesis contribute to the understanding of recent Andean glacier evolution at a local, regional and Andes-wide scale. We provide a high-quality, multi-decadal dataset that will be useful to constrain the diversity of present 21st century Andes-wide mass loss estimates, in the pursuit of the good calibration of glaciological and hydrological models intended to project future glacier changes and to improve water resource management in the Andes
Karakurt, Necdet. "Estimating attenuation properties of bentonite layer in Cut Bank oil field, Glacier County, Montana." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3282.
Повний текст джерелаGonzález, Reyes Alvaro Ignacio. "Modelación de la línea de equilibrio altitudinal (ELA) desde el año A.D. 1500, y variaciones climáticas recientes en los Andes Mediterráneos de Chile (30°-37°S)." Tesis, Universidad de Chile, 2019. http://repositorio.uchile.cl/handle/2250/170189.
Повний текст джерелаLa variabilidad del clima durante el último milenio (A.D 1000 - 2000), permitió que diversos glaciares de montaña a escala global hayan experimentado su máximo crecimiento en térmi- nos de su masa, respecto a actuales condiciones. Las causas climáticas de este crecimiento glaciar se relacionan con La Pequeña Edad de Hielo (PEH; A.D 1500 - 1850). Este periodo de interés paleoclimático global ha sido bien documentado en el hemisferio Norte, contrario al hemisferio Sur.. Más aún, existe un desconocimiento profundo acerca de cómo, mecanismos climáticos que actualmente afectan el clima de regiones como los Andes Mediterráneos de Chile y Argentina (AM; 30-37 S), como El Niño Oscilación del Sur, hayan afectado el balance de masa glaciar y las variaciones temporales de la línea de equilibrio altitudinal (ELA) duran- te dicho intervalo. La PEH es un antónimo a lo que acontece actualmente con los glaciares de montaña, donde en regiones como los AM diversos estudios han identificado un severo retroceso. El balance de masa glaciar (MB) y su ELA está influenciado por los cambios en la temperatura del aire, elevación de la Isoterma de 0C y las precipitaciones. La presente tesis doctoral consta de dos capítulos y un capítulo introductorio. Un primer capítulo exhibe las tendencias de las variables climáticas que actúan directamente sobre el MB, y mencionadas anteriormente. Un segundo capítulo, presenta una modelación de la ELA durante A.D 1500 - 1848 mediante un modelo forzado por tres modelos climáticos globales (GCMs). Se estudió las relaciones entre las variaciones temporales en la Temperatura Superficial del Mar (SST) del Océano Pacífico y la variabilidad temporal de la ELA. La temperatura media se ha in- crementado significativamente durante enero, febrero, marzo, y desde agosto a noviembre, considerando 1969 - 2016. La temperatura mínima, por su parte, se ha incrementado signifi- cativamente durante enero y mayo, mientras que la temperatura máxima, excepto en mayo, julio y septiembre, se ha incrementado significativamente durante 1969 - 2015. La isoterma de 0oC (ISO0) registró un incremento significativo en enero, marzo y anual durante 1858 - 2015. Tendencias en la ISO0 (años 2000 - 2015) exhiben un incremento significativo durante enero, mayo, junio y agosto. La precipitación (pp) de abril a septiembre registró una ne- gativa y significativa tendencia desde 1876, con reducciones significativas durante los meses de mayo, junio y julio. Entre 1981 - 2015, una significativa reducción ha sido registrada en la pp de abril a agosto. La ELA anual durante la PEH registró una elevación de 3775 m. Una menor elevación de la ELA fue identificada durante A.D 1640 - 1670 y 1800 - 1948. Contrariamente, una mayor elevación de la ELA fue identificada durante A.D 1550 - 1575. Propiedades espectrales de la ELA modelada indican significativas señales de entre 2 - 7 años de periodicidad, y también señales decadales a multi decadales. Significativas señales espec- trales fueron también obtenidas con el primer modo de variabilidad de la SST región Niño 3.4. Además, correlaciones significativas fueron obtenidas entre la ELA anual y la SST en la región Pacífico. Se propone que la variabilidad de la SST del océano Pacífico fue el principal modulador de los cambios temporales de la ELA en los AM durante A.D 1500 - 1848.
Pederson, Gregory Thomas. "Long-term perspectives on Northern Rockies climatic variability from tree rings in Glacier National Park, Montana." Thesis, Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/pederson/PedersonG04.pdf.
Повний текст джерелаFlorentine, Caitlyn Elizabeth. "Regional context, internal structure, and microbiological investigation of the Lone Peak Rock Glacier, Big Sky, Montana." Thesis, Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/florentine/FlorentineC0511.pdf.
Повний текст джерелаDamm, Christian. "A phytosociological study of Glacier National Park, Montana, U.S.A., with notes on the syntaxonomy of alpine vegetation in Western North America." Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963101552.
Повний текст джерелаBerthier, Etienne. "Dynamique et bilan de masse des glaciers de montagne (Alpes, Islande, Himalaya) : contribution de l'imagerie satellitaire." Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00011256.
Повний текст джерелаLes vitesses de surface des glaciers du Mont-Blanc montrent des fluctuations à court terme que nous relions à l'intensité de la fonte et à l'hydrologie sous-glaciaire. Sur le long terme, un ralentissement important (30 à 40%) suggère une réponse dynamique des glaciers aux changements climatiques.
Pour les glaciers alpins, les pertes de glace dans les zones basses s'accélèrent lors des dix dernières années alors qu'à haute altitude l'épaisseur glaciaire ne varie presque pas. Un fort amincissement à basse altitude est aussi observé en Islande et en Himalaya entre 1998-9 et 2004. Aussi, la fonte de ces glaciers expliquerait 5% de l'élévation récente
Davaze, Lucas. "Quantification du bilan de masse des glaciers de montagne à l'échelle régionale par télédétection spatiale optique." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU022/document.
Повний текст джерелаBeyond their iconic role of climate change, mountain glaciers can be considered as Earth’ essential component and natural “climate-meter”. Despite their small spatial coverage (0.5% of emerged land), mountain glaciers contribute as high as 30% of the observed sea-level rise. In some regions, they are considered as essential issues because of their importance in terms of potable water, agriculture, hydroelectricity or natural hazards. A small share is however monitored in situ (<0.0025%) and their fluctuations at regional scale are poorly known.Thanks to the development of high spatial resolution satellite sensors (metric to decametric), new methods are today available to significantly increase the number of monitored glaciers. After a state of the art of the existing methods and an identification of the limitations, we focused our attention on the development of two methods.The first one is based on the automatic detection of the snow/ice interface altitude (i.e. snowline) at the glacier surface from optical satellite images. This altitude, when estimated at the end of summer, is a proxy of the annual glacier-wide mass change at the glacier surface (called surface mass balance, SMB). Using this approach, we estimated the annual SMBs of 239 glaciers in the European Alps and 82 glaciers in the tropical Andes for the period 2000-2016 and 2000-2018, respectively. The mean mass loss are -0.74 and -1.29 m water equivalent per year for the two regions, respectively. This approach allowed to derive the first dataset of annual SMBs for individual glaciers at regional scale from optical remote sensing. We found significant relationships between the computed SMBs and the glacier morpho-topographic features (e.g. slope, median altitude, …), with steeper and higher glaciers, experiencing less mass losses. Comparison with in situ monitored SMBs revealed an overestimation of mass losses from in situ estimates, due to a low representativeness of steep glaciers (>20°) in the in situ datasets. Our study also revealed heterogeneous inter-annual variability across the European Alps, partially explained by the climatic context of the studied sub-regions, thanks to the analysis of climate reanalysis data.We developed a second method to derive the annual and summer SMBs from albedo maps, computed from MODIS images. With an application on 30 glaciers in the French Alps, this work opened the way toward a regional application of this method, in order to estimate both annual and summer SMBs.By performing regional applications on different glacierized regions, we developed and validated methods capable of deriving the annual and summer SMBs of individual mountain glaciers at regional scale, from optical remote sensing data. These data could then be used to (1) assess the impact of peculiar climatic conditions onto mountain glaciers; (2) investigate possible meteorological conditions driving the documented glacier fluctuations; (3) calibrate and validate glacio-hydrological models used to estimate the current and future contributions of mountain glaciers to the hydrological functioning of mountain catchments and to sea level rise
Michaels, Amanda Paige. "Land Use and Land Cover Change in the Crown of the Continent Ecosystem, Montana, USA from 1992-2011." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/72842.
Повний текст джерелаMaster of Science
Bórquez, González Roxana Elizabeth. "Análisis del escenario actual de los glaciares de montaña en Chile desde la mirada de la seguridad ecológica." Tesis, Universidad de Chile, 2007. http://www.repositorio.uchile.cl/handle/2250/101863.
Повний текст джерелаEchelard, Thomas. "Contribution à l'étude de la dynamique des glaciers rocheux dans les Alpes françaises par interférométrie radar différentielle (D-InSAR)." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU007/document.
Повний текст джерелаRockglaciers are one the visual expressions of mountain permafrost and have been the focus of numerous and various studies in the last two decades. Two main topics are studied by the scientific community: i) better understanding the movements of active rockglaciers and the phenomena that generate those movements; ii) assessing impact of global atmospheric change on these periglacial shapes. Here we propose to contribute to the first topic by using remote sensing method of displacement measurements already used in other countries for rockglaciers studies: Differential Interferometric Synthetic Aperture Radar (D-InSAR). D-InSAR is a method of measurement based on the phase difference between two radar images, which represent the same area but at different time intervals. The technique generates interferograms, maps of surface deformation in two-dimensions allowing for the detection and quantification (in centimeters) of variations in distance between the target and the radar between two different data acquisitions. Recent research has shown that the InSAR technique can be used to semi-quantify rockglacier deformation (under the assumption that certain conditions are respected with regard to generating and interpreting the interferograms). In the present thesis, ERS radar images (dating from 1991 to 1995) and TerraSAR-X data (dating from summer 2012) were obtained in courtesy of ESA (European Space Agency) and DLR (Deutschen Zentrums für Luft- und Raumfahrt, German Space Agency) with the aim of generating interferograms. We are interested by the detection of rockglacier movements. The ERS archives allowed us to work at French Alps scale with moderate resolution (25m in ground geometry) whereas TerraSAR-X data have better ground resolution (10m) but our analysis are more local (Haute Maurienne/Haute Tarentaise) due to the cost of the data and the time-consuming nature of the analyzes. With ERS, we selected all archives data and chose the more relevant of them. Finally 9 interferograms were generated. To analyse this amount of data two methods were employed: i) a GIS analysis of interferograms by geomorphologists (helped by ortho-images and topographic data), ii) a comparison between interferograms and existing rockglaciers shape inventory to evaluate the quality of the radar detections. At the end of the analysis a map of the French Alps with all detected rockglacier movements was produced. With TerraSAR-X data, the method of analysis was almost the same. Analyzes focused on the Haute Maurienne/Haute Tarentaise massif. A third scale of analysis is focus on Pierre Brune rockglacier which has been detected on ERS interferograms as destabilized rockglaciers (movement > 2 m/year). Further investigations have been carried out on this site (historical movements reconstitution and GPS acquisitions). Based on these studies with different scales and resolutions, we proposed a discussion about suitability of D-InSAR measurements method for long term rockglaciers monitoring as well as drawbacks and benefits of the method
Rolin, Didier. "Etude morphodynamique d'un bassin versant de haute montagne alpine : La Grande Sassière (Tignes-Savoie)." Paris 12, 2001. http://www.theses.fr/2001PA120041.
Повний текст джерелаEspinoza, Jean Marcel de Almeida. "Modelagem do retroespalhamento SAR para análise do pacote de neve superficial da Geleira Union, Montanhas Ellsworth – Antártica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131880.
Повний текст джерелаThe present thesis proposes an analytical model for interaction between a beam of microwaves in the X band and surface snowpack. To this end, statistical analysis were performed with SAR-X backscattering data and reference data from snowpits focusing the interaction between the microwave beam and the snowpack in dry snow areas. Numerical methods were employed for solution of differential equations that make up this issue. The model was proposed for Union Glacier, located in the West Antarctic Ice Sheetregarding a study area including the Antarctic western portion, recognized as the Union Glacier. The backscattering model used was based under the assumption of the Radiative Transfer Model (RTM), considering as main variables the depth of accumulated snow, the surface roughness (air-snow interface and snow-ice interface), the size of snow crystals (grain size), the density profile of the accumulated snow and snow characteristics of the layers forming the surface snowpack (thickness, shape of the interface between layers variation between dielectric layers, among others). After that, reversal statistical modelling of backscatter was performed to estimate stratigraphic parameters of the snowpack usingdata allowing the local stratigraphy of estimated variables SAR backscatter data from COSMO-SkyMed satellite. To validate the proposed model, the same input data were considered for all experiments performed experiments. These data were made up of snow stratigraphic data and snow temperature data in a 2 m depth glaciological profiles (snowpits) 2m depth and data SAR-X COSMO-SkyMed X-band SAR data (acquisition mode Stripmap / Himage with 3x3 m spatial resolution 3x3 m) acquired atin Union Glacier snowpits and remote sensing SAR data during summer 2011-2012. The results showed average density of the snow pack surface from SAR-X backscatter data SAR-X with R² ≥ 86%. The main contribution of this work is the resulting model for SAR-X backscattering for dry snow masses, which was proved to be statistically consistent with the ground truth data. Even with limited reference data, this result indicates the soundness of the proposed approach, allowing the estimation of spatial distribution ofvariations in stratigraphic parameters of the snowpack variables in dry snow areas from SAR X-band SAR data over the X band. However, snowpack parameters estimated by the method should be used carefully, as the input data used for model development may underestimate all possible variations found at the snow surface of Union Glacier.
Litt, Maxime. "Etude de la couche de surface atmosphérique et des flux turbulents sur deux glaciers de montagne dans les Andes tropicales et les alpes Françaises." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU005/document.
Повний текст джерелаWe study turbulent fluxes of sensible and latent heat, that are a poorly-known and difficult term to measure over glaciers, with the help of two field campaigns deployed over the ablation zone of Zongo glacier (16°S, Bolivia, 4900-6000 m.a.s.l.) during the austral winter dry season and over the Saint-Sorlin glacier (French Alps, 45°N, 2600-3400 m.a.s.l.) during the boreal summer. A 6-m mast allowing for wind speed and air temperature vertical profile measurements was installed, along with 2-m masts holding eddy-covariance systems. The focus is on the temporal evolution of turbulent fluxes and the applicability of the aerodynamic profile method in the complex terrain of high mountains. The assumptions of the method are discussed by characterizing the wind regimes and the turbulence. We then compute fluxes and associated errors. Above Zongo glacier, under weak synoptic forcing, katabatic flows are observed from late afternoon to early morning, with a wind-speed maximum at around 2 m. Strong synoptic forcing roughly aligns with the glacier, leading to strong downslope flows for which no wind-speed maximum is observed. Most of the days around noon, upslope flows are observed. On Saint-Sorlin glacier in summer, flows associated with low-pressure systems coming from the west or Foehn events roughly align with the glacier, leading to strong downslope winds. Wind-speed maxima are observed night and day, ~50% of the time, when synoptic forcing is moderate. Upslope flows are observed 15% of the time, when synoptic forcing is weak. The surface layer is disturbed by outer-layer eddies in strong flows and by slow oscillations if katabatic flow prevails. These disturbances influence turbulent fluxes. Random errors on the fluxes derived from the profile method are mainly due to temperature uncertainties. Errors remain small on the mean fluxes. The surface layer is rarely deeper than 2 m on both glaciers and the profile method with measurements made above that height underestimates the surface fluxes by 20% to 70%. When a wind-speed maximum is observed, fluxes are underestimated even at 2 m. The influence on the fluxes of the surface-layer disturbances is not captured by the profile method, and fluxes are about 40% smaller than the eddy-covariance fluxes. The latter are affected by large random errors due to inadequate statistical sampling of large-scale eddies and are probably underestimated, mainly due to vertical wind speed underestimation (~15%) and to vertical flux divergence. Above Zongo glacier, due to the dry high-elevation air, sublimation (a few millimeters w. e. per day) is a large energy loss for the surface. Sensible heat flux is a large energy gain in strong nocturnal downslope flows (from 30 to 50 W m-2) and strong winds, due to a marked temperature inversion. When a wind-speed maximum is observed, low wind speeds cause small turbulent fluxes (from 5 to 20 W m-2). The sum of turbulent fluxes is small in those two cases because the fluxes are opposed in sign and the biases mostly compensate. In upslope flows, the sensible heat flux is small (<5 W m-2) due to near-neutral stratification, but latent heat losses remain large (around -25 to -35 W m-2), so that the net turbulent flux is large and the biases do not compensate. Above Saint-Sorlin glacier, the latent heat flux remains small because the air is generally humid, whereas the sensible heat flux can be large (~25 W m-2) when wind speed is high. The net flux is large when wind speed is high, and the biases on net turbulent fluxes derived from the profiles can be significant
Deline, Philip. "Etude géomorphologique des interactions entre écroulements rocheux et glaciers dans la haute montagne alpine : le versant sud-est du massif du Mont-Blanc (Vallée d'Aoste, Italie)." Chambéry, 2002. http://www.theses.fr/2002CHAMS009.
Повний текст джерелаHerrera, Ossandón Mariajosé. "Estimación de las altitudes de las líneas de equilibrio en glaciares de montaña para el último ciclo glacial-interglacial en los Andes de Santiago, Chile Central." Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/143570.
Повний текст джерелаEl presente trabajo aborda la discusión sobre los factores que controlan las Alturas de las Líneas de Equilibrio (ELA's) en el último ciclo glacial-interglacial en la cordillera de Los Andes frente a Santiago. A partir del análisis de imágenes satelitales se estudia la variación histórica de las ELA's y se discutien los factores climáticos de primer orden asociados a esa variación. A partir del análisis geomorfológico y geocronológico se determina la posición y temporalidad de los estadios glaciales durante el Pleistoceno tardío. Finalmente se realiza una estimación de la posición de las ELA's durante este mismo período a partir de distintos métodos y se compara con su posición actual. El aumento de las temperaturas mínimas estacionales y anuales favorece los procesos de ablación y en consecuencia contribuyen a la disminución continua de las coberturas de nieve. Por su parte, los eventos de precipitación estival constituyen el factor clave para el aumento de las coberturas supraglaciales y el quiebre de la tendencia negativa en las áreas englaciadas de la cuenca del río Volcán, confirmando que es este el factor de primer orden que condiciona el avance de los glaciares en Los Andes subtropicales. Las Alturas de las Líneas de Equilibrio Glaciar reportan ascensos desde 1989 a 2015 lo que indica aumento de las áreas de ablación y una disminución de las áreas de acumulación y en consecuencia incrementos de procesos de fusión. El sistema glacial de San Gabriel corresponde a un avance durante un Máximo Avance Glacial Local o LLGM entre los ~45-36 ka BP, concordante con eventos de mayor precipitación y humedad en Los Andes centrales entre los ~33°S y ~35°S. Por su parte, el sistema glacial de La Engorda, registra dos pulsos de avance glacial datados entre los ~24-18 y ~10 ka BP. Estos pulsos son consistentes con los eventos húmedos reportados en Laguna Tagua Tagua (Valero-Garcés et al., 2005). Depósitos glaciolacustres y fluvioglaciales de baja energía en la zona proglacial del sistema de La Engorda, datados a través de métodos 14C, registran temporalidad vinculada con un período frío breve denominado Younger Dryas. Las variaciones en las ELA's modernas respecto a las estimadas para los períodos del Último Máximo Glacial (LGM) y Último Máximo Glacial Local (LLGM), se realizan a través de la reconstrucción de paleoglaciares, los descensos en las Alturas de las Líneas de Equilibrio son concordantes con las variaciones del flanco este de la cordillera de Los Andes, observándose disminuciones de ~1000 - 1200 metros, entre el período actual y el LGM. Los resultados de esta tesis confirman la importancia de las precipitaciones en los avances de los glaciares de montaña de Los Andes frente a Santiago y sugieren la relevancia tanto de la elevación de las temperaturas mínimas como de la disminución de la cantidad de días con registro bajo 0°C en su retroceso. Estos resultados son consistentes con las estimaciones de ELA's a escala del Pleistoceno tardío y la variación de sólo 500 metros entre el LLGM (~45-36 ka BP) en el sistema de San Gabriel y el LGM (~24-18 ka BP) en el sistema glacial de La Engorda vinculado a condiciones paleoclimáticas de mayor precipitación; por otro lado la abrupta elevación de las ELA's entre el LGM y la actualidad son coherentes con disminuciones en las precipitaciones así como también aumentos en las temperaturas. Lo anterior muestra la sensibilidad de los glaciares subtropicales de Los Andes en relación al escenario de calentamiento regional proyectado en el marco del cambio global.
Miskane, Naïma. "Les paléoenvironnements de haute montagne pendant l'holocène récent, d'après l'étude des diatomées actuelles et fossiles de deux vallées glacières de Bolivie : implications paleoclimatiques." Paris, Muséum national d'histoire naturelle, 1997. http://www.theses.fr/1997MNHN0021.
Повний текст джерелаBodin, Xavier. "Géodynamique du pergélisol alpin : fonctionnement, distribution et évolution récente. L'exemple du massif du Combeynot (Hautes Alpes)." Phd thesis, Université Paris-Diderot - Paris VII, 2007. http://tel.archives-ouvertes.fr/tel-00203233.
Повний текст джерелаTahir, Adnan Ahmad. "Impact of climate change on the snow covers and glaciers in the Upper Indus River basin and its consequences on the water reservoirs (Tarbela reservoir) – Pakistan." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20056/document.
Повний текст джерелаAgriculture based economy of Pakistan is highly dependent on the snow and glacier melt water supplies from the Upper Indus River Basin (UIB), situated in the Himalaya, Karakoram and Hindukush ranges. It is therefore essential to understand the cryosphere (snow and ice) dynamics and hydrological regime of this area under changed climate scenarios, for water resource management. The MODIS MOD10A2 remote-sensing database of snow cover products from March 2000 to December 2009 was selected to analyse the snow cover dynamics in the UIB. A database of daily flows from 13 hydrometric stations and climate data (precipitation and temperature) from 18 gauging stations, over different time periods for different stations, was made available to investigate the hydro-climatological regime in the area. Analysis of remotely sensed cryosphere (snow and ice cover) data during the last decade (2000‒2009) suggest a rather slight expansion of cryosphere in the area in contrast to most of the regions in the world where glaciers are melting rapidly. The Snowmelt Runoff Model (SRM) integrated with MODIS remote-sensing snow cover products was successfully used to simulate the daily discharges and to study the climate change impact on these discharges in the snow and glacier fed sub-catchments of UIB. The application of the SRM under future climate change scenarios indicates a doubling of summer runoff until the middle of this century. This variation in the Upper Indus River flow, decreasing capacity of existing reservoirs (Tarbela Dam) by sedimentation and the increasing demand of water uses suggests that new reservoirs shall be planned for summer flow storage to meet with the needs of irrigation supply, increasing power generation demand, flood control and water supply
Cossart, Etienne. "Evolution géomorphologique du haut bassin durancien depuis la dernière glaciation : Contribution à la compréhension du fonctionnement du système paraglaciaire." Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00139899.
Повний текст джерелаLombard, Alix. "Les variations actuelles du niveau de la mer : Observations et causes." Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00079969.
Повний текст джерелаDiverses observations disponibles depuis peu nous ont permis de quantifier les contributions des divers facteurs climatiques à la hausse observée du niveau de la mer : expansion thermique de la mer due au réchauffement des océans, fonte des glaciers de montagne et des calottes polaires, apport d'eau des réservoirs continentaux. Le bilan de ces nouvelles observations nous permet d'expliquer en partie la hausse observée du niveau de la mer. En particulier, nous montrons que l'expansion thermique des océans n'explique que 25% de la hausse séculaire du niveau de la mer enregistrée par les marégraphes depuis 50 ans, tandis qu'elle contribue à la hauteur de 50% à la montée du niveau marin au cours de la dernière décennie. Parallèlement, des études récentes estiment que la fonte des glaciers de montagne et des calottes polaires pourraient contribuer pour environ 1 mm/an à l'élévation du niveau de la mer au cours de la dernière décennie.
De plus, la forte variabilité régionale des vitesses d'évolution du niveau de la mer révélée par les observations altimétriques de Topex/Poseidon résulte en grande partie de l'expansion thermique. Nous mettons également en lumière l'importante variabilité spatio-temporelle décennale de l'expansion thermique des océans au cours des 50 dernières années, qui semble dominée par les fluctuations naturelles du climat. De plus nous posons pour la première fois la question du lien qui existe entre les fluctuations décennales de l'expansion thermique des océans et la contribution climatique des eaux continentales au niveau de la mer. Enfin, une analyse préliminaire des observations gravimétriques de la mission spatiale GRACE sur les océans nous permet d'évaluer les variations saisonnières du niveau moyen de la mer liées aux variations du bilan de masse d'eau des océans.
Damm, Christian [Verfasser]. "A phytosociological study of Glacier National Park, Montana, U.S.A., with notes on the syntaxonomy of alpine vegetation in Western North America / vorgelegt von Christian Damm." 2001. http://d-nb.info/963101552/34.
Повний текст джерелаLopes, Ana Isabel de Jesus. "Assessing climatic changes through environmental magnetic analyses of three sedimentary columns of the North Atlantic Ocean (between 29ºN and 35ºN)." Master's thesis, 2013. http://hdl.handle.net/10451/9825.
Повний текст джерелаAo longo dos últimos milhões de anos, o clima tem oscilado entre períodos glaciares e interglaciares impulsionado por variações orbitais da Terra e modulado por mecanismos de feedback. Dados paleoclimáticos sugerem que os períodos interglaciares começaram e acabaram de forma súbita, ao passo que os períodos glaciares terão resultado de uma série de eventos de arrefecimento menores, que culminaram nos períodos glaciares. Apesar da escassez de informações para períodos anteriores a 300 mil anos, sabe-se que, ao contrário dos períodos interglaciares, que são caracterizados por condições climáticas relativamente estáveis, os períodos glaciares são marcados por mudanças climáticas abruptas. O último período interglaciar, também chamado Eemiano, ter-se-á estendido desde aproximadamente há 130-140 mil até acerca de 110 mil anos. Durante este período, o clima da Terra assemelhar-se-ia em muito ao atual, sendo no entanto ligeiramente mais quente. No final deste ciclo, originou-se um período glacial que se estendeu até aproximadamente há 10 mil anos. Este último período glaciar foi marcado acentuadamente por flutuações rápidas e de curta duração, em que o clima variou entre períodos extremamente frios e outros mais quentes, conhecidos como eventos de Dansgaard-Oeschger. Associados a estes, ocorreram também os eventos de Heinrich, que corresponderam a enormes descargas de icebergs no oceano Atlântico provenientes dos glaciares que cobriam a América do Norte (Laurentide Ice Sheet-LIS) e o Norte da Europa (Fennoscandinavian Ice Sheet). A ocorrência dos eventos de Heinrich encontra-se vastamente descrita na literatura, tendo sido atribuída a ocorrência destes eventos a cada 7-13 mil anos. Estes fenómenos extremos tiveram importantes consequências no clima, um pouco por todo o mundo e alteraram profundamente a circulação oceânica global, havendo estudos que mostram a interrupção da formação da Água Profunda do Atlântico Norte (NADW) e da corrente termohalina. Atualmente ainda não existe consenso sobre o que terá originado os eventos de Heinrich, mas o modelo mais aceite estabelece que durante o último período glaciar as camadas de gelo teriam crescido promovidas pelas baixas temperaturas, estando então assentes em solos congelados. No entanto, a partir de uma certa espessura de gelo ter-se-ia começado a gerar calor na base do glaciar, o qual teria contribuído para sua destabilização, resultando assim nos eventos de Heinrich. As camadas de sedimentos depositadas no fundo oceânico durante estes fenómenos, chamadas de “Heinrich layers”, foram inicialmente identificadas em sedimentos marinhos entre as latitudes de 45º e 50ºN, mas desde então têm sido encontradas um pouco por todo o Atlântico Norte até à latitude de 37ºN, e distribuídas em longitude desde a América do Norte até à Península Ibérica. As “Heinrich layers” são identificáveis pela sua abundância em ice-rafted debris (IRD) e carbonatos detríticos, mínimos de abundância de foraminíferos e picos de Neogloboquadrina pachyderma (sinistral). O estudo das suas propriedades magnéticas revelou aumentos da susceptibilidade magnética, denotando assim aumentos da concentração de minerais ferromagnéticos, bem como da sua granulometria. A mineralogia é essencialmente composta por (titano)magnetites, que se crê terem sido originadas em rochas vulcânicas presentes na zona de captação de sedimentos da LIS. O estudo de propriedades magnéticas de sedimentos tem-se revelado extremamente muito útil não só na identificação das “Heinrich layers”, mas principalmente aplicado ao estudo de mudanças ambientais, embora se trate ainda de uma área relativamente recente. O princípio básico da utilização dos métodos magnéticos aplicado ao estudo das mudanças ambientais (tais como o clima), baseia-se no facto destas influenciarem o tipo e modo de transporte e deposição dos sedimentos, bem como reações diagenéticas. Desta forma, a partir de medições de susceptibilidade magnética, magnetizações anhisterética e isotérmica e dos parâmetros obtidos a partir das curvas de hysteresis é possível aceder a informações como a concentração, granulometria e tipo de portadores magnéticos presentes nos sedimentos e, desta forma inferir variações ambientais. Assim, e de forma a avaliar as mudanças climáticas ocorridas no Oceano Atlântico ao longo dos últimos milhares de anos, detalhadas análises magnéticas foram conduzidas em três colunas sedimentares (C02, C05 e C07) localizadas maioritariamente em montanhas submarinas entre as latitudes de 29ºN e 35ºN. Estas análises compreenderam medições de susceptibilidade magnética, magnetização remanescente anhisterética e isotérmica e curvas de histereses. Os principais portadores magnéticos correspondem a minerais ferrimagnéticos de baixa coercividade, como magnetite e/ou maghemite. Além disso, e particularmente no core C07, uma contribuição significativa de minerais de alta coercividade são também encontrados a certas profundidades, devendo-se provavelmente a um enriquecimento em hematite e/ou goethite. A sedimentologia do core C07 mostra que este é muito heterogéneo, sendo constituído por argilas, siltes e areias. O conteúdo de argila e de areia encontra-se em oposição de fase e variam entre 6-38% e 8-66%, respectivamente. O conteúdo de areia acompanha o comportamento da granulometria média dos sedimentos. Análises espectrais de parâmetros magnéticos sensíveis à concentração e granulometria dos minerais ferromagnéticos mostram periodicidades estritamente ligadas aos ciclos orbitais de Milankovitch, quando se assumem taxas de sedimentação de 1 cm/kyr e 1.6 cm/kyr, para os cores C02 e C07, respectivamente. Em ambos os cores, valores máximos de susceptibilidade magnética e portadores magnéticos grosseiros sugerem a presença de ice-rafted debris (IRD) transportados pelos icebergs durante os eventos de Heinrich, porém mais estudos como estratigrafia isotópica e composição isotópica de Ca/Sr e Sr-Nd sejam necessários para o confirmar. O outro core, C05 apresenta valores de susceptibilidade muito baixos e bastante estáveis bem como a ausência de intervalos bem definidos e idades de 14C indicam que o core deverá corresponder a um deslizamento de terras.
This study is devoted to the evaluation of climatic changes over the past thousands of years recorded on sedimentary columns of the North Atlantic Ocean. For that were conducted detailed environmental magnetic analyses along three sedimentary columns (C02, C05 and C07) with 2.5 to 3.0 m of length. These analyses comprehended measurements of magnetic susceptibility, anhysteretic and isothermal remanent magnetizations and hysteresis loops. Low coercivity ferrimagnetic carriers, magnetite and/or maghemite, appear as the main magnetic carriers. Additionally and particularly in core C07, a significant contribution of high coercivity minerals is also retrieved at some sedimentary depths, must probably corresponding to an enrichment of hematite and/or goethite. Along the cores C02 and C07, coherent transitions between stable and rather variable intervals of magnetic susceptibility and grain size are well defined, revealing different environmental conditions. Spectral analyses of magnetic parameters sensitive to the concentration and granulometry of main ferromagnetic carriers identified periodicities that are closely related to the Milankovitch orbital cycles when assumed sedimentation rates of 1 cm/kyr and 1.6 cm/kyr, for cores C02 (mostly) and C07, respectively. According to these sedimentation rates there is no close link between the variable/stable values of χ and grain size and the glacial/interglacial periods. In both cores maxima of magnetic susceptibility and coarser magnetic carriers suggest the presence of ice-rafted debris (IRD) transported by icebergs during the Heinrich events, however complementary studies are necessary to confirm it. For the remaining core C05, low and quite stable values of magnetic susceptibility as well the absence the well defined intervals and 14C ages indicate that the core correspond to landslide.