The tropical glaciers in the Bolivian Andes Mountains are small and respond quickly to changes in their climate. They are also a major source of freshwater year-round for nearby communities. Monitoring the glacial changes taking place in these glaciers has become increasingly important as they have been retreating over the past century. These glaciers are remote and the terrain treacherous making it potentially dangerous to gather data through field work. For this reason and because of advances in remote sensing technologies the use of satellite images has become the primary means to study these tropical glaciers in detail. This research study focuses on the Cordillera Apolobamba range located on the Peruvian-Bolivian border. It is an example of the methodology applied to assess the area covered by glaciers in this and other regions around the world. Using Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) images from 1985 to 2010, as well as the Glacier Inventory of Bolivia, the glacier extents of the Apolobamba are mapped. From 1975 to 2010 the portion of the range located within Bolivia's border lost 110.76 km^2 of surface ice lowering its total area from 240.36 km^2 to 129.60 km2, a 46.08% reduction. From the 1985 to 2010 the entire Apolobamba range lost 102.72 km^2 of ice lowering its total area from 261.07 km^2 to 158.35 km^2, a 39.35% reduction. An analysis of atmospheric conditions was conducted at the 500 hPa level for various climate variables using NCEP/NCAR reanalysis data. Between time period one (1975-1986) and two (1987-1995) the climate variables exhibiting a statistically significant change are air temperature with an increase of .165 degrees C and geopotential height with an increase of 2.967 m. Between time period two and three (1996-2005) the climate variables exhibiting a statistically significant change are freezing level with a 50.017 m increase, precipitation with an 60.604 mm/month decrease and wind velocity with an increase of .373 m/sec. According to the analysis conducted using the Oceanic Nino Index, the monthly sea surface temperatures exhibit no statistically significant change from 1975-2005.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on July 15, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1987. / Vita. Bibliography: leaves [144]-152.

Speckle tracking of synthetic aperture RADAR imagery (Radarsat-1/2, ALOS PALSAR) and feature tracking of optical (Landsat-7 ETM+) imagery is used to determine the entire surface velocity structure of the major ice masses of the Canadian High Arctic in 2000, 2010-2015 and for select tidewater terminating glaciers from 1999-2010. At the termini of tidewater glaciers, surface ice velocities are combined with measured/modelled ice thicknesses to derive an estimate of mass loss via dynamic (iceberg) discharge. The total dynamic discharge for the ice masses of the southern Canadian Arctic Archipelago (SCAA: Baffin and Bylot Islands) is between ~17 and 180 Mt a-1 (0.017 to 0.180 Gt a-1) for the period 2007-2011, compared to a dynamic discharge of ~2.47  ± 0.88 Gt a-1 for the northern Canadian Arctic Archipelago (NCAA: Devon, Ellesmere, Axel Heiberg Islands) for the period 2011-2015. A comparison of these values with rates of mass loss via climatic mass balance (surface melt and runoff) indicates that dynamic discharge accounted for ~3.1% of total ablation for the NCAA in 2012 and ~0.11% of total ablation in the SCAA between 2007 and 2010. This reveals that total ablation in the Canadian Arctic is currently dominated by surface melt and runoff. The glacier velocity dataset provides the most comprehensive record of ice motion and dynamic discharge in the Canadian Arctic to date and reveals a large degree of variability in glacier motion within the region over the last ~15 years. Most of the major glaciers in the NCAA have decelerated and their resultant dynamic discharge has decreased over the observation period, which is largely attributed to cyclical phases attributed to surging and pulsing. On pulse-type glaciers, variation in ice motion is largely confined to regions where the bed is located below sea level. A notable departure from the overall trend of regional velocity slowdown is the widespread acceleration of the Trinity and Wykeham Glaciers of the Prince of Wales Icefield (the largest glacier complex in the Canadian Arctic), which cannot be explained by surge or pulse mechanisms. The increased discharge from these two glaciers nearly compensates (within error) for the decrease in iceberg discharge from other glaciers across the study region and indicates that total dynamic discharge from the Canadian Arctic can be sensitive to the variations of ice flow of just a few glaciers.

Dań Zhùr (Donjek) Glacier, located in the St. Elias Mountains, Yukon, is a surge-type glacier that undergoes cyclical periods of rapid advance over a period of ~1-2 years, followed by retreat for a period of ~10 years (Kochtitzky et al., 2019). Dań Zhùr Chù’ (Donjek River) runs perpendicular to the terminus of the glacier and past surges have, at times, caused the terminus to advance enough to block the river, leading to the formation of an ice-dammed lake (Kochtitzky et al., 2020). The glacier most recently surged between 2012 and 2014, and since then Dań Zhùr Lake has drained three times: in 2017, 2018 and 2019. When a glacier dam fails, the drainage of the lake can be catastrophic and cause flooding downstream. In the case of Dań Zhùr Lake, the most recent drainage event occurred on July 13th, 2019, when the ~2.45 km2 lake drained in less than 36 hours and created an ice canyon through the glacier terminus. Time-lapse cameras and pressure sensors were used to capture the drainage event, and air photos taken during the melt season (June and September) were used to construct digital elevation models (DEMs) of the glacier terminus, lake, and lake basin. The method of drainage for the 2019 event was determined to be flotation of the terminus, leading to rapid subglacial drainage of the lake. There were also noticeable changes in water extent downstream during the 2019 event, meaning that there is a potential risk to downstream recreational users. Because of the formation of a large ice canyon after the 2019 drainage, it is very unlikely that that the lake will reform until the next surge, which is anticipated to occur around 2024. Following that surge, the size of Dań Zhùr Lake is expected to increase during the next quiescent phase, as the continued glacier recession will expose a larger basin for the lake to form in, and flotation will continue to be a likely mechanism for drainage. However, in the long term it is unlikely that ice-dammed lakes will continue to form at Dań Zhùr Glacier, as there is a trend of the maximum terminus extent during each surge being smaller than the previous one, meaning that the glacier will no longer block the flow of Dań Zhùr Chù’.

No description available.

Glacier facies represent distinct regions of a glacier surface characterized by near surface structure and density that develop as a function of spatial variations in surface melt and accumulation. In post freeze-up (autumn) synthetic aperture radar (SAR) satellite imagery, the glacier ice zone and dry snow zone have a relatively low backscatter due to the greater penetration of the radar signal into the surface. Conversely, the saturation and percolation zones are identifiable based on their high backscatter due to the presence of ice lenses and pipes acting as efficient scatterers. In this study, EnviSat ASAR imagery is used to monitor the progression of facies zones across Devon Ice Cap (DIC) from 2004 to 2011. This data is validated against in situ surface temperatures, mass balance data, and ground penetrating radar surveys from the northwest sector of DIC. Based on calibrated (sigma nought) EnviSat ASAR backscatter values, imagery from autumn 2004 to 2011 shows the disappearance of the ‘pseudo’ dry snow zone at high elevations, the migration of the glacier and superimposed ice zones to higher elevations, and reduction in area of the saturation/percolation zone. In 2011, the glacier and superimposed ice zone were at their largest extent, occupying 92% of the ice cap, leaving the saturation/percolation zone at 8% of the total area. This is indicative of anomalously high summer melt and strongly negative mass balance conditions on DIC, which results in the infilling of pore space in the exposed firn and consequent densification of the ice cap at higher elevations.

Glacier facies represent distinct regions of a glacier surface characterized by near surface structure and density that develop as a function of spatial variations in surface melt and accumulation. In post freeze-up (autumn) synthetic aperture radar (SAR) satellite imagery, the glacier ice zone and dry snow zone have a relatively low backscatter due to the greater penetration of the radar signal into the surface. Conversely, the saturation and percolation zones are identifiable based on their high backscatter due to the presence of ice lenses and pipes acting as efficient scatterers. In this study, EnviSat ASAR imagery is used to monitor the progression of facies zones across Devon Ice Cap (DIC) from 2004 to 2011. This data is validated against in situ surface temperatures, mass balance data, and ground penetrating radar surveys from the northwest sector of DIC. Based on calibrated (sigma nought) EnviSat ASAR backscatter values, imagery from autumn 2004 to 2011 shows the disappearance of the ‘pseudo’ dry snow zone at high elevations, the migration of the glacier and superimposed ice zones to higher elevations, and reduction in area of the saturation/percolation zone. In 2011, the glacier and superimposed ice zone were at their largest extent, occupying 92% of the ice cap, leaving the saturation/percolation zone at 8% of the total area. This is indicative of anomalously high summer melt and strongly negative mass balance conditions on DIC, which results in the infilling of pore space in the exposed firn and consequent densification of the ice cap at higher elevations.

Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across the chronosequences of glacier forelands. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude cirque glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over a 170-year chronosequence, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were placed throughout the glacier foreland using a random sample stratified by terrain date. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age ranges using Kruskal-Wallis and Dunn's tests. I used two models, generalized linear models (GLMs) and Classification and Regression Trees (CARTs), to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by Kruskal-Wallis tests, Dunn's tests, and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with Penstemon ellipticus favoring older terrain and Boechera lemmonii favoring moderately aged terrain. Moderate drainage and concave plots, which were important in the GLMs, explained increased species richness and Shannon's diversity across different site conditions. The CARTs were able to predict species richness, vegetation cover, Shannon's diversity, and species evenness with surface fragment sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently. / Master of Science / Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across glacier foreland terrain that has been uncovered for different lengths of time. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over terrain uncovered between zero and 170-year, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were randomly placed within each terrain age range throughout the glacier foreland. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. Shannon's diversity is a measurement of a community's diversity and uses both species richness and evenness to calculate diversity. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age using several statistical comparison tests. I used two types of statistical models to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by comparison tests and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with the species Penstemon ellipticus (rocky ledge penstemon) favoring older terrain and Boechera lemmonii (Lemmon's rockcress) favoring moderately aged terrain. Moderate drainage and concave plots explained increased species richness and Shannon's diversity across different site conditions. Species richness, vegetation cover, Shannon's diversity, and species evenness could be predicted with surface fragments sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently.

Glacier retreat is considered a clear sign of global climate change. Although a rich body of work has documented glacial response to climate warming trends, comparatively little research has assessed vegetation change in recently deglaciated areas. In this study, we assess vegetation change at two glacier forefronts in Glacier National Park, Montana, through remote sensing analysis, fieldwork validation, and statistical modelling. The research objectives were to: 1) quantify the spatial and temporal patterns of landcover change of five classes"ice, rock, tree, shrub, and herbaceous at the two glacier forefronts in Glacier National Park, and 2) determine the role of selected biophysical terrain factors (elevation, slope, aspect, solar radiation, flow accumulation, TWI, and geology) on 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. Overall accuracies were above 75% for all classified images. To identify biophysical correlates of change, we used generalized linear mixed models with non-vegetated surfaces to vegetation (code=1) or stable non-vegetation class (code=0) as a binary response variable. Results revealed elevation, slope, TWI, geology, and aspect to be associated with increased vegetation over time at Jackson Glacier forefront, whereas elevation, slope, solar radiation, and geology were significant at Grinnell Glacier forefront. 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. / Master 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.