Thesis (doctoral)--Universität Bremen, 2004. / Includes bibliographical references (p. 121-136). Also available online in PDF format.

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Understanding how debris-covered glaciers respond to climate is necessary in order to evaluate future water resources and glacier flood hazard potential, and to make sense of the glacier chronology in mountain regions, In order achieve this, it is necessary to improve the current understanding of how surface debris affects glacier ablation rate, and to develop methods by which the ablation of debris-covered glaciers can be predicted under various climatic scenarios. This thesis develops a numerical surface energy balance model that uses simple meteorological data to calculate melt beneath a debris layer of given thickness and thermal characteristics. Field data from three contrasting sites demonstrate that the assumptions made within the model concerning the thermal properties of supraglacial debris are valid during most ablation conditions and that model performance is considerably better than previous models. Model results indicate that the effect of debris on melt rate is highly dependent on meteorological conditions. Under colder climates, thin debris can accelerate ice melt by extending the ablation period at both diurnal and seasonal scales. However, in milder mid- summer conditions, even a very thin debris cover inhibits melt rate compared to that of exposed ice. The new melt model is applied to produce the first quantified ablation gradients for debris- covered glaciers, and to model the evolution of ice surfaces under a debris layer of variable thickness. Modelled ablation gradients are qualitatively similar to hypothetical ones outlined previously, and quantitatively similar to those measured in the field. The ablation gradients are used to explore the factors affecting the response of debris-covered glaciers to climate change. Beneath a debris layer of variable thickness, the melt model produced ablation topography, as observed in the field, which underwent topographic inversion over time in response to debris redistribution. Debris thickness variability was found to cause calculated ablation rate to increase compared to that calculated using a mean debris thickness by one to two orders of magnitude, suggesting that melt calculations made on the basis of spatially averaged debris thickness may be inaccurate.

The semi-arid and arid Andes of South America are characterized by large areas with glacial and periglacial environments. This study focusses on the distribution of glacial and periglacial landforms in the Las Veguitas catchment, Cordillera Frontal, Argentina. A detailed geomorphological map of the Las Veguitas catchment is presented, based on high-resolution elevation data (ALOSPALSAR), satellite imagery (Landsat 8, World View 2, Google Earth), and field studies. First, a general topographical analysis is performed for the entire Las Veguitas catchment, including elevation, slope and aspect characteristics. Second, the altitudinal range of glacial features (glaciers, debris covered glaciers and thermokarst ponds on glaciers) and the altitudinal range and predominant aspect of periglacial features (active, inactive and fossil rock glaciers) are analyzed. Currently, glaciers are restricted to ≥ 4300m, but moraines are identified to elevations of c. 3200m. Active rock glaciers extend down to c. 3450m and have a more southern aspect then both inactive and fossil rock glaciers. Third, a temporal analysis has been performed of glacier and rock glacier flow using a time series of remote sensing images. Glacier flow traced by the displacement of thermokarst lake features (2006-2016) had a mean velocity of 6.66m/yr. The mean velocity of rock glaciers (1963-2017) was much lower at 0.63m/yr. Finally, the thesis discusses limitations and uncertainties in study methods and suggestions for further research activities.

Nesse estudo foram mapeadas e mensuradas as variações de área, elevação mínima e orientação das geleiras da Colômbia e da Venezuela (trópicos internos), entre os anos 1985-2015. Para o mapeamento das áreas das geleiras foram utilizadas como base imagens Landsat, sensores TM, ETM+ e OLI. Às imagens selecionadas foi aplicado o Normalized Difference Snow Index (NDSI), no qual são utilizadas duas bandas em que o alvo apresenta comportamento espectral oposto ou com características bem distintas: bandas 2 e 5 dos sensores TM e ETM+ e bandas 3 e 6 do sensor OLI. Os dados de elevação e orientação das massas de gelo foram obtidos a partir do Modelo Digital de Elevação SRTM (Shuttle Radar Topography Mission – v03). Em 1985, a soma das áreas das sete geleiras estudadas correspondia a 92,84 km², enquanto no último ano estudado (2015/2016) esse valor passou para 36,97 km². A redução de área ocorreu em todas as geleiras analisadas, com taxas de retração anual variando entre 2,49% a.a. e 8,46% a.a. Houve retração das áreas de gelo localizadas em todos os pontos cardeais considerados, bem como, elevação da altitude nas frentes de geleiras. Além da perda de área ocorrida nas menores altitudes, onde a taxa de ablação é mais elevada, também se observou retração em alguns topos, evidenciado pela ocorrência de altitudes menores nos anos finais do estudo, em comparação com os anos iniciais. Como parte das geleiras colombianas está localizada sobre vulcões ativos, essas áreas sofrem influência tanto de fatores externos, quanto de fatores internos, podendo ocorrer perdas de massa acentuadas causadas por erupção e/ou terremoto. / In this study, glaciers located in Colombia and Venezuela (inner tropics) were mapped between 1985-2015. The area of these glaciers was measured and the variations that occurred in each glacier were compared to identify whether the glacier was growing or shrinking. The minimum elevation of the glaciers fronts and the aspect of the glaciers were analyzed. The glaciers areas ware obtained by the use of Landsat images, TM, ETM+ and OLI sensors. The Normalized Difference Snow Index (NDSI) was applied to the selected images, in which two bands were used, where the ice mass has opposite (or very different) spectral behavior: bands 2 and 5 from sensors TM and ETM+, and bands 3 and 6 from sensors OLI. The elevation and the aspect data of the glaciers were obtained from SRTM (Shuttle Radar Topography Mission – v03) Digital Elevation Model. In 1985/1986, the sum of the areas of the seven studied glaciers corresponded to 92.84 km², while in the last year analyzed (2015/2016), this value shrank to 36.97 km². The area shrinkage occurred in all the glaciers that were mapped, with annual decline rates ranging from 2.49%/year to 8.46%/year. It is also possible to observe a decrease of the ice covered in all aspects considered, as well as an elevation in all glaciers fronts. In addition to the area loss occurred at lower altitudes, where the ablation rate is higher than in higher altitudes, shrinkage in some mountain tops was also present, which is evidenced by the occurrence of lower maximum elevations in the final years of the study, when compared with the initial years. Considering that part of the Colombian’s glaciers are located on active volcanoes, these areas are influenced by external and internal factors, and the occurrence of volcanic eruption and/or earthquake can cause sharp mass losses.

Les glaciers des Alpes françaises subissent un recul généralisé depuis la fin du Petit Âge Glaciaire (PAG). Dans le contexte actuel d'élévation de la température et du fait des nombreux enjeux auxquels ils sont associés, l'amélioration de leur suivi apparaît indispensable. Avant ce travail, il n'existait pas d'étude exhaustive récente concernant l'ensemble des glaciers des Alpes françaises, les travaux de Mougin et de Vivian datant respectivement du milieu des années 1920 et 1970. L'objectif de ce travail est de dresser un inventaire diachronique des glaciers des Alpes françaises et de leurs marges proglaciaires. Les données de cet inventaire servent ensuite de base à l'étude des modalités du retrait glaciaire depuis la fin du PAG et à l'établissement de méthodes pour détecter les secteurs susceptibles d'être affectés par des instabilités. L'inventaire diachronique des glaciers des Alpes françaises est réalisé à 3 dates : (i) 2006-2009 à partir des orthophotographies récentes de l'IGN, (ii) 1967-1971 à partir des premières éditions des cartes topographiques 1 :25 000 de l'IGN, et (iii) la fin du PAG (pour les massifs du Mont Blanc, de la Vanoise et des Ecrins), en croisant documents anciens et données géomorphologiques acquises sur le terrain et par photo-interprétation. Les données sont organisées dans un Système d'Information Géographique (SIG) qui permet d'associer cartographie et base de données. La superficie des glaciers était de 275 km² en 2006-2009, 369 km² en 1967-1971 et 544 km² à la fin du PAG pour les massifs du Mont Blanc, de la Vanoise et des Ecrins. A l'échelle régionale, les glaciers ont perdu 25 % de leur superficie depuis la fin des années 1960 et 50 % de leur superficie depuis la fin du PAG. La rétraction des glaciers est environ 2,5 fois plus rapide entre 1967-1971 et 2006-2009 qu'entre la fin du PAG et 1967-1971. A l'échelle individuelle, les glaciers ont perdu en moyenne 52 % de leur superficie entre 1967-1971 et 2006-2009, et 115 ont même disparu. A l'échelle régionale comme individuelle, le retrait glaciaire présente des tendances différentes selon les massifs, la taille des glaciers et leur exposition Des méthodes simples, basées sur les données des inventaires des glaciers et des marges proglaciaires sont établies afin d'identifier les lacs potentiellement instables, les secteurs englacés favorables à la formation de futurs lacs, au déclenchement d'avalanches de séracs ou susceptibles d'être déstabilisés en masse, et les marges proglaciaires favorables à l'occurrence de glissements ou de laves de débris. / French alpine glaciers are retreating since the end of the Little Ice Age (LIA). In the context of the increasing air temperature and because of issues that they represent, it is necessary to improve glacier monitoring. Before the present study, the only two inventories covering the entire French Alps were made by Mougin (1925) and Vivian (1975). The main goal of this study is to realise a multi-temporal glacier inventory of glaciers in the French Alps and of their proglacial margins. Data from this inventory are used to study glacial retreat since the end of the LIA and to develop methods to detect sector that could be affected by instabilities. Multi-temporal inventory of French Alpine glacier glaciers is made for 3 dates: (i) 2006-2009, based on IGN recent orthophotographs, (ii) 1967-1971, based on 1: 25 000 IGN topographic maps, and (iii) the end of the LIA (for Mont Blanc, Vanoise and Ecrins massifs), crossing old documents and geomorphologic data based on field work and interpretation of orthophotographs. Data are integrated in a Geographical Information System (GIS), combining mapping and data base. Glaciers in the French Alps covered 275 km² in 2006-2009, 369 km² in 1967-1971 and 544 km² at the end of the LIA for Mont Blanc, Vanoise and Ecrins massifs. At a regional scale, glaciers lost 25 % of their 1967-1971 area and 50 % of their LIA area. Glacier shrinkage between 1967-1971 and 2006-2009 is about 2.5 times higher than between the end of the LIA and 2006-2009. At an individual scale glaciers lost 52 % of their area between 1967-1971 and 2006-2009, and 115 disappeared. At regional or individual scale, different trends in glacier shrinkage are observed according to the massifs, size and aspect of the glaciers. Simple methods, based on glaciers inventory and proglacial margins data, are developed in order to identify potential unstable lakes, glaciated sectors prone to glacier lake formation, ice avalanche triggering or mass destabilization, and proglacial margins where sliding or debris flows could occur.

Nesse estudo foram mapeadas e mensuradas as variações de área, elevação mínima e orientação das geleiras da Colômbia e da Venezuela (trópicos internos), entre os anos 1985-2015. Para o mapeamento das áreas das geleiras foram utilizadas como base imagens Landsat, sensores TM, ETM+ e OLI. Às imagens selecionadas foi aplicado o Normalized Difference Snow Index (NDSI), no qual são utilizadas duas bandas em que o alvo apresenta comportamento espectral oposto ou com características bem distintas: bandas 2 e 5 dos sensores TM e ETM+ e bandas 3 e 6 do sensor OLI. Os dados de elevação e orientação das massas de gelo foram obtidos a partir do Modelo Digital de Elevação SRTM (Shuttle Radar Topography Mission – v03). Em 1985, a soma das áreas das sete geleiras estudadas correspondia a 92,84 km², enquanto no último ano estudado (2015/2016) esse valor passou para 36,97 km². A redução de área ocorreu em todas as geleiras analisadas, com taxas de retração anual variando entre 2,49% a.a. e 8,46% a.a. Houve retração das áreas de gelo localizadas em todos os pontos cardeais considerados, bem como, elevação da altitude nas frentes de geleiras. Além da perda de área ocorrida nas menores altitudes, onde a taxa de ablação é mais elevada, também se observou retração em alguns topos, evidenciado pela ocorrência de altitudes menores nos anos finais do estudo, em comparação com os anos iniciais. Como parte das geleiras colombianas está localizada sobre vulcões ativos, essas áreas sofrem influência tanto de fatores externos, quanto de fatores internos, podendo ocorrer perdas de massa acentuadas causadas por erupção e/ou terremoto. / In this study, glaciers located in Colombia and Venezuela (inner tropics) were mapped between 1985-2015. The area of these glaciers was measured and the variations that occurred in each glacier were compared to identify whether the glacier was growing or shrinking. The minimum elevation of the glaciers fronts and the aspect of the glaciers were analyzed. The glaciers areas ware obtained by the use of Landsat images, TM, ETM+ and OLI sensors. The Normalized Difference Snow Index (NDSI) was applied to the selected images, in which two bands were used, where the ice mass has opposite (or very different) spectral behavior: bands 2 and 5 from sensors TM and ETM+, and bands 3 and 6 from sensors OLI. The elevation and the aspect data of the glaciers were obtained from SRTM (Shuttle Radar Topography Mission – v03) Digital Elevation Model. In 1985/1986, the sum of the areas of the seven studied glaciers corresponded to 92.84 km², while in the last year analyzed (2015/2016), this value shrank to 36.97 km². The area shrinkage occurred in all the glaciers that were mapped, with annual decline rates ranging from 2.49%/year to 8.46%/year. It is also possible to observe a decrease of the ice covered in all aspects considered, as well as an elevation in all glaciers fronts. In addition to the area loss occurred at lower altitudes, where the ablation rate is higher than in higher altitudes, shrinkage in some mountain tops was also present, which is evidenced by the occurrence of lower maximum elevations in the final years of the study, when compared with the initial years. Considering that part of the Colombian’s glaciers are located on active volcanoes, these areas are influenced by external and internal factors, and the occurrence of volcanic eruption and/or earthquake can cause sharp mass losses.

Lofty Hindukush, Karakoram and Himalayan (HKH) mountain ranges centered in the Northern Pakistan are host to some of the world’s largest glaciers outside the Polar Regions and are a source of water for drinking and irrigation to the millions of people living downstream. With the increase in the global temperatures, glaciers are reported as retreating globally. However, some of the glaciers in the Karakoram mountain ranges are reported as surging with positive mass balance, especially since the 1990s. This phenomenon is described as "The Karakoram Anomaly". Various efforts have been made to explain the state and fate of the HKH glaciers in the recent past. However, they are limited to quantification of the change in temperature, precipitation and river runoff, or through their impact on future climate projections. For the HKH region, temperature fluctuations have been out of the phase with hemispheric trends for past several centuries. Therefore, climate change in this region is not solely the temperature effect on melting as compared to other glaciated regions. To identify the reasons for the establishment of the Karakoram Anomaly, monthly mean climatic variables for last five decades, reported from meteorological observatories at the valley floors in HKH region, are analyzed. In addition to the climatic variables of temperature and precipitation, monthly mean synoptic observations reported by meteorological observatories in both morning and afternoon, along with monthly mean radiosonde data are used. From these data the role of different near-surface and upper atmospheric meteorological variables in maintaining the positive mass balance of the glaciers and the development of the Karakoram Anomaly can be explained. An overall warming in the region is observed. The trends in the summer temperatures, which were reported as decreasing a decade ago, are now found as increasing in updated time series. However, the overall gradient is still negative. The winter mean and maximum temperatures are increasing with accelerated trends. Both maximum and minimum temperatures in summer are not diverging anymore and the diurnal temperature range is decreasing in the most recent decade. The afternoon cloudiness is found as increasing throughout the year except for spring, which is indicative of an increase in convective uplifting. Moreover, humidity is increasing all over the region; due to evaporation in the spring, from monsoon moisture advection in summer, and due to the recycling of monsoon moisture in autumn. Furthermore, near-surface wind speed and net radiation in the region are decreasing, explaining the decrease in the summer minimum temperature and the presence of the cloudy skies. The decrease in near-surface wind speed, and net radiation, and increase in water vapor pressure put a limit on the evapotranspiration process. In addition, winter and summer precipitation is increasing. The aridity index, which is based on the ratio of precipitation and reference evaporation, indicates that region is turning moisture surplus and energy deficient. Surface atmospheric pressure and 700 hPa geopotential height is increasing due to warming in the bottom layers of the troposphere. Nighttime inversion in the lower tropospheric layers is decreasing due to warming. Analysis of gridded observed and reanalysis datasets indicates that they are not presenting a signal of change in accordance with the instrumental record. Furthermore, it is found that meteorological conditions during the summer season are still favorable for the sustenance of glaciers whereas more melting may occur in the spring season that may increase the early season river flows and may affect lower lying portions of the debris-free glaciers.

Kongsfjordhallet is situated at 79° N on the North coast of Kongsfjorden, Spitsbergen.The landscape shows a large diversity of landforms and sediments and the aim of thisstudy has been to investigate the spatial distribution and temporal differences betweenthese landforms.The most prominent landform is interpreted as a lateral moraine dividing the area fromsoutheast to northwest. This is probably a sign of a standstill during the deglaciation ofan ice-sheet glacier tongue filling the fjord. The valley-glaciers at Kongsfjordhallet haveadvanced after this event and left end moraines on top of the lateral moraine. Largeamounts of meltwater have eroded parts of the Kongsfjordhallet, creating several fossilmeltwater channels that dissect the landscape. Erratic boulders of mainly gneiss type arescattered all over the landscape, as high up as 500 m a.s.l. In addition to the erraticboulders, a lot of allochthonous material is found incorporated in local material,especially as a diamict interpreted as till that covers large parts of Kongsfjordhallet.The till can likely be correlated to one of the diamict units in the cliff sections at theKongsfjordhallet coast. At present, two large ravines drain the area, moving water fromthe glaciers to the ocean and a beach is developing in the Southeast part of the area dueto ocean transgression. Landforms from two glacial events are found, one regional andone local. An episode of high sea-level as well as fluvial and mass-wasting activity afterthe deglaciation is also recorded. The formation of the landforms in the area is believedto be after the Last Glacial Maximum and into the Holocene, but no absolute dates areavailable. / SciencePub