This study was motivated by an interest in understanding the effects of glacier retreat on late summer stream temperatures in an above-treeline proglacial stream and lake system in the southern Coast Mountains of British Columbia, Canada. Fieldwork was carried out during August and September of 2007 and focused on thermal processes controlling water temperature in the proglacial lake and a 1 km alpine reach directly downstream of the lake outlet. The proglacial lake was small (0.07 km²), featured a single inflow and outflow channel and had a residence time of approximately 4 days. The alpine reach featured continual cascading flow (25% channel gradient), marked diurnal fluctuations in discharge and variable terrain shading. It was found that warming between the inflow and outflow of the lake (1.8°C, on average) was controlled by the total heat content of the lake and cycles of mixing and stratification. A heat budget analysis indicated that the heat content of the lake was dominantly controlled by absorbed shortwave radiation and the advective effect of the inflow and outflow streams. Application of a dynamic reservoir model (DYRESM) to model observed lake temperatures (inflow, outflow and a temperature-depth profile), and comparison to other studies, suggested that suspended sediment concentration in the inflow had a dominant control on lake mixing and stratification. Based on equations developed from low-gradient channels, a stream energy budget model failed to replicate observed downstream warming rates. A spatially distributed net radiation model, along with statistical modification of the energy budget, provided insight into the processes that control stream temperatures in alpine areas. The final hybrid model showed a good match with observed downstream warming. This model accounted for the variation of width and albedo with discharge, and the spatial variability in net radiation due to topographic shading and the slope and aspect of the channel. The model also included parameters that increased the sensible and latent heat fluxes relative to values calculated from standard equations, which is consistent with the hypothesis that these fluxes are enhanced by cascading flow.

This study was motivated by an interest in understanding the effects of glacier retreat on late summer stream temperatures in an above-treeline proglacial stream and lake system in the southern Coast Mountains of British Columbia, Canada. Fieldwork was carried out during August and September of 2007 and focused on thermal processes controlling water temperature in the proglacial lake and a 1 km alpine reach directly downstream of the lake outlet. The proglacial lake was small (0.07 km²), featured a single inflow and outflow channel and had a residence time of approximately 4 days. The alpine reach featured continual cascading flow (25% channel gradient), marked diurnal fluctuations in discharge and variable terrain shading. It was found that warming between the inflow and outflow of the lake (1.8°C, on average) was controlled by the total heat content of the lake and cycles of mixing and stratification. A heat budget analysis indicated that the heat content of the lake was dominantly controlled by absorbed shortwave radiation and the advective effect of the inflow and outflow streams. Application of a dynamic reservoir model (DYRESM) to model observed lake temperatures (inflow, outflow and a temperature-depth profile), and comparison to other studies, suggested that suspended sediment concentration in the inflow had a dominant control on lake mixing and stratification. Based on equations developed from low-gradient channels, a stream energy budget model failed to replicate observed downstream warming rates. A spatially distributed net radiation model, along with statistical modification of the energy budget, provided insight into the processes that control stream temperatures in alpine areas. The final hybrid model showed a good match with observed downstream warming. This model accounted for the variation of width and albedo with discharge, and the spatial variability in net radiation due to topographic shading and the slope and aspect of the channel. The model also included parameters that increased the sensible and latent heat fluxes relative to values calculated from standard equations, which is consistent with the hypothesis that these fluxes are enhanced by cascading flow.

This study was motivated by an interest in understanding the effects of glacier retreat on late summer stream temperatures in an above-treeline proglacial stream and lake system in the southern Coast Mountains of British Columbia, Canada. Fieldwork was carried out during August and September of 2007 and focused on thermal processes controlling water temperature in the proglacial lake and a 1 km alpine reach directly downstream of the lake outlet. The proglacial lake was small (0.07 km²), featured a single inflow and outflow channel and had a residence time of approximately 4 days. The alpine reach featured continual cascading flow (25% channel gradient), marked diurnal fluctuations in discharge and variable terrain shading. It was found that warming between the inflow and outflow of the lake (1.8°C, on average) was controlled by the total heat content of the lake and cycles of mixing and stratification. A heat budget analysis indicated that the heat content of the lake was dominantly controlled by absorbed shortwave radiation and the advective effect of the inflow and outflow streams. Application of a dynamic reservoir model (DYRESM) to model observed lake temperatures (inflow, outflow and a temperature-depth profile), and comparison to other studies, suggested that suspended sediment concentration in the inflow had a dominant control on lake mixing and stratification. Based on equations developed from low-gradient channels, a stream energy budget model failed to replicate observed downstream warming rates. A spatially distributed net radiation model, along with statistical modification of the energy budget, provided insight into the processes that control stream temperatures in alpine areas. The final hybrid model showed a good match with observed downstream warming. This model accounted for the variation of width and albedo with discharge, and the spatial variability in net radiation due to topographic shading and the slope and aspect of the channel. The model also included parameters that increased the sensible and latent heat fluxes relative to values calculated from standard equations, which is consistent with the hypothesis that these fluxes are enhanced by cascading flow. / Arts, Faculty of / Geography, Department of / Graduate

As geleiras são indicadores sensíveis às mudanças climáticas, aquelas áreas marginais à geleira e proglaciais apresentam várias mudanças decorrentes da retração das geleiras. Dessa forma, esta tese propõe um modelo de desenvolvimento hidrológico e geomorfológico da zona proglacial de uma geleira no sul da ilha Rei George, ilhas Shetland do Sul, Antártica no período desde a Pequena Idade do Gelo até 2017. A compartimentação do relevo e mapeamento geomorfológico proglacial foi feito a partir de Modelo Digital de Elevação gerado a partir de imagens TanDEM-X e de uma imagem QuickBird de 2008, além de coletas de sedimentos em campo. Já para a caracterização da fenologia de gelo da superfície de lagos proglaciais, foi feita uma correlação da área de superfície líquida, obtida em imagens TerraSAR X de 2011, com as variáveis temperatura, precipitação e vento. O cenário de evolução da geleira (chamada localmente de geleira Collins) até 2070 foi elaborado a partir de metodologia de Ruckamp et al. (2011). Os compartimentos na península onde encontra-se a geleira (península Fildes) são planaltos e depressões que possuem como principais formas associadas paleovales em U e vales em anfiteatro que foram posteriormente retrabalhados por canais de degelo e processos intempéricos. A área proglacial não é homogênea e a frente da geleira apresentou distintos ambientes que foram mapeados nessa tese em setores. Os setores do lado leste são os mais dinâmicos da geleira, pois além de apresentar vários canais de água de degelo, tem feições como flutings e morainas de recessão. No cenário do comportamento da geleira para o futuro, são justamente essas áreas que deverão ser as primeiras a apresentarem retração, até 2030 É provável que no futuro, com a retração da geleira, devido a configuração do relevo subglacial, haverá formação de lagos, alagados e canais nas suas porções mais côncavas e mais tempo de atuação dos processos paraglaciais. Os setores voltados para a passagem de Drake indicam um sistema glacial ativo com capacidade de transporte de material de diferentes tamanhos e quantidade. No futuro essa área, devido ao relevo subglacial e hidrologia, provavelmente não terá a formação de lagos e feições como flutings ou morainas de recessão, se caracterizando como mais estável. Quanto a formação atual dos lagos, 7 dos 15 lagos analisados para o verão de 2011 apresentaram correlação significativa (ρ maior que 0,4) com a temperatura, enquanto 11 lagos responderam significativamente para precipitação. Os lagos atingem a área máxima de superfície líquida no final de fevereiro e congelam completamente no início de abril. O cenário de variação espacial da frente da geleira Collins revela a continuidade do processo de retração para as próximas décadas, com perda de 35% de sua área até 2070. No primeiro momento, a retração na zona proglacial formará uma área instável com alta quantidade de sedimentos nos canais. A fixação da vegetação contribuirá nessa fase para aumento da infiltração de água de degelo no solo (formação de alagados), aumento da força e cisalhamento do solo até que a paisagem atinja uma fase estável, com indícios de atividade periglacial entre 2050 e 2070. / Glaciers are sensitive indicators of climate change, those marginal and proglacial areas show several changes due to glaciers retraction. Having this in mind, this thesis proposes a hydrological and geomorphological development model for the proglacial zone of a glacier in the south of the King George island, South Shetland Islands, Antarctica in the period between the Little Ice Age and 2017. The relief compartmentation and proglacial geomorphological mapping was done using a Digital Elevation Model generated from TanDEM-X images and a QuickBird image from 2008, in addition to field sediment samples. For the characterization of the ice phenology of the proglacial lakes surface, a correlation of the net surface area, obtained from 2011 TerraSAR X images, was made with temperature, precipitation and wind variables. The evolution of the glacier (locally called Collins Glacier) until 2070 was elaborated using the methodology by Ruckamp et al. (2011). The compartments in the peninsula where the glacier is located (Fildes Peninsula) are plateaus and depressions that have U paleovalley sand amphitheatre valleys as main forms later reworked by melting channels and intemperic processes. The proglacial area is not homogeneous and the glacier front has different environments that were mapped in this thesis in sectors. The glacier eastern sectors are the most dynamic ones, as they have several melting water channels, features like flutings and moraines of recession. In the scenario for the future behaviour of the glacier, it is possible that these areas that will be the first ones to present retraction, until 2030 It is probable that in the future, with the retraction of the glacier, due to the configuration of the subglacial relief, there will be formation of lakes, flooded areas and channels in their more concave portions and more time for operation of the paraglacial processes. The sectors orientated to the Drake Passage indicate an active glacial system with capacity to transport material of different sizes and quantity. In the future this area, due to subglacial relief and hydrology, probably will not have the formation of lakes and features like flutings or moraines of recession, characterizing itself as more stable. Regarding the current lake formation, 7 of the 15 lakes analysed for the 2011 summer presented a significant correlation (ρ greater than 0.4) with temperature, while 11 lakes responded significantly to precipitation. The lakes reached the maximum net surface area at the end of February and frozen completely at the beginning of April. The spatial variation scenario of the Collins Glacier front reveals the continuity of the retraction process for the coming decades, with a loss of 35% of its area by 2070. At the first moment, the retraction in the proglacial zone will form an unstable area with a high amount of sediments in the channels. In this phase, vegetation fixation will increase the infiltration of melting water into the soil (formation of floodwaters), increase of soil strength and shear until the landscape reaches a stable phase, with indications of periglacial activity between 2050 and 2070.

As geleiras são indicadores sensíveis às mudanças climáticas, aquelas áreas marginais à geleira e proglaciais apresentam várias mudanças decorrentes da retração das geleiras. Dessa forma, esta tese propõe um modelo de desenvolvimento hidrológico e geomorfológico da zona proglacial de uma geleira no sul da ilha Rei George, ilhas Shetland do Sul, Antártica no período desde a Pequena Idade do Gelo até 2017. A compartimentação do relevo e mapeamento geomorfológico proglacial foi feito a partir de Modelo Digital de Elevação gerado a partir de imagens TanDEM-X e de uma imagem QuickBird de 2008, além de coletas de sedimentos em campo. Já para a caracterização da fenologia de gelo da superfície de lagos proglaciais, foi feita uma correlação da área de superfície líquida, obtida em imagens TerraSAR X de 2011, com as variáveis temperatura, precipitação e vento. O cenário de evolução da geleira (chamada localmente de geleira Collins) até 2070 foi elaborado a partir de metodologia de Ruckamp et al. (2011). Os compartimentos na península onde encontra-se a geleira (península Fildes) são planaltos e depressões que possuem como principais formas associadas paleovales em U e vales em anfiteatro que foram posteriormente retrabalhados por canais de degelo e processos intempéricos. A área proglacial não é homogênea e a frente da geleira apresentou distintos ambientes que foram mapeados nessa tese em setores. Os setores do lado leste são os mais dinâmicos da geleira, pois além de apresentar vários canais de água de degelo, tem feições como flutings e morainas de recessão. No cenário do comportamento da geleira para o futuro, são justamente essas áreas que deverão ser as primeiras a apresentarem retração, até 2030 É provável que no futuro, com a retração da geleira, devido a configuração do relevo subglacial, haverá formação de lagos, alagados e canais nas suas porções mais côncavas e mais tempo de atuação dos processos paraglaciais. Os setores voltados para a passagem de Drake indicam um sistema glacial ativo com capacidade de transporte de material de diferentes tamanhos e quantidade. No futuro essa área, devido ao relevo subglacial e hidrologia, provavelmente não terá a formação de lagos e feições como flutings ou morainas de recessão, se caracterizando como mais estável. Quanto a formação atual dos lagos, 7 dos 15 lagos analisados para o verão de 2011 apresentaram correlação significativa (ρ maior que 0,4) com a temperatura, enquanto 11 lagos responderam significativamente para precipitação. Os lagos atingem a área máxima de superfície líquida no final de fevereiro e congelam completamente no início de abril. O cenário de variação espacial da frente da geleira Collins revela a continuidade do processo de retração para as próximas décadas, com perda de 35% de sua área até 2070. No primeiro momento, a retração na zona proglacial formará uma área instável com alta quantidade de sedimentos nos canais. A fixação da vegetação contribuirá nessa fase para aumento da infiltração de água de degelo no solo (formação de alagados), aumento da força e cisalhamento do solo até que a paisagem atinja uma fase estável, com indícios de atividade periglacial entre 2050 e 2070. / Glaciers are sensitive indicators of climate change, those marginal and proglacial areas show several changes due to glaciers retraction. Having this in mind, this thesis proposes a hydrological and geomorphological development model for the proglacial zone of a glacier in the south of the King George island, South Shetland Islands, Antarctica in the period between the Little Ice Age and 2017. The relief compartmentation and proglacial geomorphological mapping was done using a Digital Elevation Model generated from TanDEM-X images and a QuickBird image from 2008, in addition to field sediment samples. For the characterization of the ice phenology of the proglacial lakes surface, a correlation of the net surface area, obtained from 2011 TerraSAR X images, was made with temperature, precipitation and wind variables. The evolution of the glacier (locally called Collins Glacier) until 2070 was elaborated using the methodology by Ruckamp et al. (2011). The compartments in the peninsula where the glacier is located (Fildes Peninsula) are plateaus and depressions that have U paleovalley sand amphitheatre valleys as main forms later reworked by melting channels and intemperic processes. The proglacial area is not homogeneous and the glacier front has different environments that were mapped in this thesis in sectors. The glacier eastern sectors are the most dynamic ones, as they have several melting water channels, features like flutings and moraines of recession. In the scenario for the future behaviour of the glacier, it is possible that these areas that will be the first ones to present retraction, until 2030 It is probable that in the future, with the retraction of the glacier, due to the configuration of the subglacial relief, there will be formation of lakes, flooded areas and channels in their more concave portions and more time for operation of the paraglacial processes. The sectors orientated to the Drake Passage indicate an active glacial system with capacity to transport material of different sizes and quantity. In the future this area, due to subglacial relief and hydrology, probably will not have the formation of lakes and features like flutings or moraines of recession, characterizing itself as more stable. Regarding the current lake formation, 7 of the 15 lakes analysed for the 2011 summer presented a significant correlation (ρ greater than 0.4) with temperature, while 11 lakes responded significantly to precipitation. The lakes reached the maximum net surface area at the end of February and frozen completely at the beginning of April. The spatial variation scenario of the Collins Glacier front reveals the continuity of the retraction process for the coming decades, with a loss of 35% of its area by 2070. At the first moment, the retraction in the proglacial zone will form an unstable area with a high amount of sediments in the channels. In this phase, vegetation fixation will increase the infiltration of melting water into the soil (formation of floodwaters), increase of soil strength and shear until the landscape reaches a stable phase, with indications of periglacial activity between 2050 and 2070.

As geleiras são indicadores sensíveis às mudanças climáticas, aquelas áreas marginais à geleira e proglaciais apresentam várias mudanças decorrentes da retração das geleiras. Dessa forma, esta tese propõe um modelo de desenvolvimento hidrológico e geomorfológico da zona proglacial de uma geleira no sul da ilha Rei George, ilhas Shetland do Sul, Antártica no período desde a Pequena Idade do Gelo até 2017. A compartimentação do relevo e mapeamento geomorfológico proglacial foi feito a partir de Modelo Digital de Elevação gerado a partir de imagens TanDEM-X e de uma imagem QuickBird de 2008, além de coletas de sedimentos em campo. Já para a caracterização da fenologia de gelo da superfície de lagos proglaciais, foi feita uma correlação da área de superfície líquida, obtida em imagens TerraSAR X de 2011, com as variáveis temperatura, precipitação e vento. O cenário de evolução da geleira (chamada localmente de geleira Collins) até 2070 foi elaborado a partir de metodologia de Ruckamp et al. (2011). Os compartimentos na península onde encontra-se a geleira (península Fildes) são planaltos e depressões que possuem como principais formas associadas paleovales em U e vales em anfiteatro que foram posteriormente retrabalhados por canais de degelo e processos intempéricos. A área proglacial não é homogênea e a frente da geleira apresentou distintos ambientes que foram mapeados nessa tese em setores. Os setores do lado leste são os mais dinâmicos da geleira, pois além de apresentar vários canais de água de degelo, tem feições como flutings e morainas de recessão. No cenário do comportamento da geleira para o futuro, são justamente essas áreas que deverão ser as primeiras a apresentarem retração, até 2030 É provável que no futuro, com a retração da geleira, devido a configuração do relevo subglacial, haverá formação de lagos, alagados e canais nas suas porções mais côncavas e mais tempo de atuação dos processos paraglaciais. Os setores voltados para a passagem de Drake indicam um sistema glacial ativo com capacidade de transporte de material de diferentes tamanhos e quantidade. No futuro essa área, devido ao relevo subglacial e hidrologia, provavelmente não terá a formação de lagos e feições como flutings ou morainas de recessão, se caracterizando como mais estável. Quanto a formação atual dos lagos, 7 dos 15 lagos analisados para o verão de 2011 apresentaram correlação significativa (ρ maior que 0,4) com a temperatura, enquanto 11 lagos responderam significativamente para precipitação. Os lagos atingem a área máxima de superfície líquida no final de fevereiro e congelam completamente no início de abril. O cenário de variação espacial da frente da geleira Collins revela a continuidade do processo de retração para as próximas décadas, com perda de 35% de sua área até 2070. No primeiro momento, a retração na zona proglacial formará uma área instável com alta quantidade de sedimentos nos canais. A fixação da vegetação contribuirá nessa fase para aumento da infiltração de água de degelo no solo (formação de alagados), aumento da força e cisalhamento do solo até que a paisagem atinja uma fase estável, com indícios de atividade periglacial entre 2050 e 2070. / Glaciers are sensitive indicators of climate change, those marginal and proglacial areas show several changes due to glaciers retraction. Having this in mind, this thesis proposes a hydrological and geomorphological development model for the proglacial zone of a glacier in the south of the King George island, South Shetland Islands, Antarctica in the period between the Little Ice Age and 2017. The relief compartmentation and proglacial geomorphological mapping was done using a Digital Elevation Model generated from TanDEM-X images and a QuickBird image from 2008, in addition to field sediment samples. For the characterization of the ice phenology of the proglacial lakes surface, a correlation of the net surface area, obtained from 2011 TerraSAR X images, was made with temperature, precipitation and wind variables. The evolution of the glacier (locally called Collins Glacier) until 2070 was elaborated using the methodology by Ruckamp et al. (2011). The compartments in the peninsula where the glacier is located (Fildes Peninsula) are plateaus and depressions that have U paleovalley sand amphitheatre valleys as main forms later reworked by melting channels and intemperic processes. The proglacial area is not homogeneous and the glacier front has different environments that were mapped in this thesis in sectors. The glacier eastern sectors are the most dynamic ones, as they have several melting water channels, features like flutings and moraines of recession. In the scenario for the future behaviour of the glacier, it is possible that these areas that will be the first ones to present retraction, until 2030 It is probable that in the future, with the retraction of the glacier, due to the configuration of the subglacial relief, there will be formation of lakes, flooded areas and channels in their more concave portions and more time for operation of the paraglacial processes. The sectors orientated to the Drake Passage indicate an active glacial system with capacity to transport material of different sizes and quantity. In the future this area, due to subglacial relief and hydrology, probably will not have the formation of lakes and features like flutings or moraines of recession, characterizing itself as more stable. Regarding the current lake formation, 7 of the 15 lakes analysed for the 2011 summer presented a significant correlation (ρ greater than 0.4) with temperature, while 11 lakes responded significantly to precipitation. The lakes reached the maximum net surface area at the end of February and frozen completely at the beginning of April. The spatial variation scenario of the Collins Glacier front reveals the continuity of the retraction process for the coming decades, with a loss of 35% of its area by 2070. At the first moment, the retraction in the proglacial zone will form an unstable area with a high amount of sediments in the channels. In this phase, vegetation fixation will increase the infiltration of melting water into the soil (formation of floodwaters), increase of soil strength and shear until the landscape reaches a stable phase, with indications of periglacial activity between 2050 and 2070.

Despite their relatively small ice volume, mountain glaciers contributed nearly one third of global sea level rise since 2000, with one of the largest total mass loss rates (73 ± 17 Gt a-1) occurring in the Yukon-Alaska region. However, there is uncertainty surrounding how ice dynamics are being affected by such losses and whether glacier flow instabilities, such as surges, are changing in a warming climate. The St. Elias Mountains contain a major cluster of surge-type glaciers, yet a detailed analysis of their characteristics, including surge frequency, morphology, magnitude, and propensity over time has not been undertaken on a regional basis. This thesis presents a review of surging behaviour and an updated surge event inventory in the St. Elias Mountains, and quantifies the processes influencing both surging and non-surging glacier velocity variability using a variety of remote sensing and field measurements. An updated inventory of surge-type glaciers and observed surge events (1874-2023), compiled from existing inventories, recently published articles, and velocity analysis, is used to analyze the characteristics of surge-type glaciers and velocity patterns during surge events. The modern (1985-2023) trends in annual, winter and summer velocities of selected surge-type glaciers is then used to classify dynamic instability events into 4 categories. While 231 glaciers were classified as surge-type, only 42 were observed to have experienced rapid velocity events over the period 1985-2023, through either direct measurements or remote sensing observations. For glaciers with observed rapid velocity events, these predominantly fall into two categories: Alaskan-style surges with short active and quiescent phases, and glacier pulses, which are velocity accelerations that are limited in both magnitude and extent. An unnamed former tributary to Kluane Glacier underwent a dramatic surge from 2013-18. Using a combination of air photos, remote sensing and field observations, the characteristics and changes of ‘Little Kluane Glacier’ were reconstructed from the 1940s until 2021. While only the single full surge of 2013-18 was identified, it is likely that a partial surge of just the upper north arm occurred between 1963 and 1972. Repeat Digital Elevation Models (DEMs) and velocity profiles show that the recent surge initiated from the upper north arm accumulation area in 2013, which developed into a full surge of the main trunk from 2017-18. Terminus positions show long-term retreat from 1949-2017, followed by rapid advance of >2 km from May to September 2018, with surface velocities reaching a peak of ~3600 m a-1 in summer 2018 over the lower ablation area. This was likely enhanced by the drainage of supraglacial lakes and streams to the glacier bed through crevassing as the surge progressed. Changes in surface topography caused by initial mass movement, the resulting reorganization of the supraglacial hydrological system, and ponding of surface water, may drive a partial surge into a full surge, and therefore exert a direct control on glacier dynamics. In May 2016, Kaskawulsh Glacier underwent a dramatic proglacial hydrologic reorganization instigated by the rapid drainage of proglacial Slims Lake: as a result, water which previously drained north into Ä’äy Chú, (Slims River) toward Lhú’áán Män (Kluane Lake), was redirected south into Kaskawulsh River, eventually flowing into the Gulf of Alaska. A long-term (up to ∼120 year) record of terminus retreat, thinning and surface velocities from in-situ and remote sensing observations is used to determine the impact of this reorganization on glacier dynamics. After an initial deceleration during the late 1990s, terminus velocities increased at a rate of 3 m a-2 from 2000-12, while the area of proglacial Slims Lake increased simultaneously. The rapid drainage of the lake substantially altered the velocity profile of the adjacent glacier, decreasing annual velocities by 48% within 3 km of the terminus between 2015 and 2021, at an average rate of ∼12.5 m a-2. A key cause of the rapid drop in glacier motion was a reduction in flotation of the lower part of the terminus after lake drainage. This has important implications for glacier dynamics and provides one of the first assessments of the impacts of a rapid proglacial lake drainage event on local terminus velocities. The results of this study provide an examination of factors controlling glacier dynamics, as well as the characteristics of rapid glacier velocity events, in the St. Elias Mountains. This provides insights into the behaviour of mountain glaciers, how they are changing in a warming climate, controls on glacier surging, and the hazards they may pose for downstream communities, which are particularly vulnerable to disturbances.

Este trabalho objetiva investigar a dinâmica geomorfológica glacial das áreas livres de gelo na Península Potter, Ilha Rei George, Antártica, em resposta à recente retração da geleira Polar Club. O mapeamento geomorfológico e a interpretação da evolução dos sistemas lacustres entre 2006 e 2011 das áreas livres de gelo na Península Potter foi realizado através da interpretação visual em uma imagem Quickbird (RGB432), em imagens COSMO-SkyMed polarizações VV e HH em modo spotlight processadas com filtros espaciais e perfis topográficos. Também foram considerados os aspectos morfométricos da península, interpretados através da geração de mapas de hipsometria, declividade, curvas de nível e sombreamento. A variação frontal da geleira Polar Club entre os anos de 1981 a 2015 foi obtida pela análise temporal de imagens Landsat. O mapeamento geomorfológico da Península Potter evidenciou os processos geomorfológicos proglaciais e o padrão de disposição espacial das feições lineares marginais ao gelo, como cordões morâinicos e feições glaciofluviais (relacionadas ao aporte da fusão sazonal da neve e do gelo), bem como terraços marinhos, ravinas e afloramentos rochosos. As imagens COSMO-SkyMed e a aplicação de filtros Passa Alta e Direcionais possibilitaram a delimitação das feições de interesse com maior nitidez. O modelo de evolução da variação frontal da geleira Polar Club indica que condição de último avanço glacial registrado pela geomorfologia proglacial pode estar relacionado à Pequena Idade do Gelo e que houve um contínuo processo de retração desde então. Entre 1981-2015 evidenciou-se a redução de área de 2,95km2 para a geleira Polar Club (perda de área total de 9,4%). Este processo pode estar relacionado com a tendência de aumento das temperaturas médias do ar, a tendência de aumento de dias com precipitação líquida no verão e o número de dias em que a temperatura média ultrapassou os 0°C na região nas últimas décadas. O recuo da geleira Polar Club é pouco expressivo quando comparado a outras geleiras da Ilha Rei George, no entanto, quando se observa as áreas expostas evidenciou-se que houve um aumento significativo (36,9%) no período. Através da análise da evolução dos depósitos morâinicos da Península Potter foi possível identificar três fases principais de formação de morâinas que evidenciam antigas posições da frente da geleira durante períodos de estabilização frontal. A análise da evolução dos sistemas lacustres na área de estudo evidenciou que diversos lagos sofreram alterações de área em resposta à dinâmica de retração glacial registrada para os últimos 34 anos. / This study aimed to investigate the glacial geomorphological dynamics of the ice-free areas in the Peninsula Potter, King George Island, Antarctica, in response to the recent Polar Club Glacier retreat processes. The geomorphological mapping and lacustrine systems evolution modelling between 2006-2011 were obtained with Quickbird (RGB432) image, application of the spatial digital filters in COSMO-SkyMed (cross and co-polarization, spotlight mode) images and topographic profiles visual interpretations. Also considered were the morphometric aspects of the peninsula, interpreted by generating hypsometry, slope, contour and shaded relief maps. The Polar Club Glacier frontal variation between 1981-2015 was obtained with Landsat temporal analysis. The Potter Peninsula geomorphological mapping evidenced the proglacial and geomorphological processes and the spatial distribution pattern of linear marginal to ice features, as morainic ridges and glaciofluvial features, related to the contribution of the seasonal melting of snow and ice, marine terraces, ravines and rocky outcrops. The High Pass and directional filters in COSMO-SkyMed images provided conditions for geomorphological features. The frontal glacier fluctuations modelling indicated that last glacial advance condition recorded by proglacial geomorphologic can be related Little Ice Age and continuous retreat process. Between 1981-2015 the Polar Club glacier lost 2,95km2 of total area (9,4% of total area). The retreat process can be related to the trend of rising average temperatures in recent decades, trend of increase in days with liquid precipitation in summer and the number melting degree days. The Polar Club Glacier retreat is not very significant when compared to other glaciers of King George Island, however, when observing the exposed areas was evident that there was a significant increase (36.9%). The moraine deposits evolution analysis in Peninsula Potter provided conditions for identify three main phases of moraines deposition and that show past glacier front positions during periods of glacier marginal stabilization. The analysis of the evolution of lacustrine systems in the study area evidenced changes in various lakes during last 34 years in response of glacial retreat dynamics.

Depuis la fin du Petit Age Glaciaire, les glaciers du massif du Mont-Blanc se retirent et libèrent ainsi d’importants volumes de sédiments. La fourniture sédimentaire grossière, qui est l’un des éléments de contrôle principaux de l’activité géomorphologique des torrents proglaciaires, peut être profondément modifiée. Dans le contexte de la vallée de Chamonix, où la pression urbaine est très forte, l’accélération du retrait glaciaire soulève des questionnements de la part à la fois des gestionnaires et des scientifiques sur l’évolution des risques et de la gestion des flux solides.L’objectif de ce travail de thèse est d’étudier le couplage sédimentaire entre les espaces libérés des glaces et les torrents jusqu’en fond de vallée, avec un double niveau de réponse. Le premier niveau permet de comprendre les trajectoires géomorphologiques des systèmes glacio-torrentiels depuis la fin du Petit Age Glaciaire et à l’échelle de la vallée. Il est étayé par une analyse géomorphologique et par l’étude de l’évolution du réseau hydrographique, qui s’appuie sur une modélisation et sur de nombreux documents d’archive. Cette étape souligne la diminution du potentiel du système torrentiel à remobiliser des sources sédimentaires. En conséquence, l’activité des torrents a fortement baissée depuis 150 ans. La seconde approche concerne l’étude des dynamiques récentes basée sur la comparaison diachronique de MNT LiDAR à haute résolution. Elle se focalise sur les trois systèmes glacio-torrentiels les plus grands de la vallée (Argentière, Mer de Glace et Bossons) dont les activités morphogènes ont pu être interprétées sous le prisme de crues d’occurrence décennale survenues en août 2014. Cette partie montre l’efficacité des processus de stockage sédimentaire au sein même des espaces désenglacés, ainsi que l’importance du forçage humain sur la morphogénèse torrentielle qui prime désormais sur l’influence du retrait glaciaire. L’état de la fourniture sédimentaire résulte actuellement de l’impact des différentes infrastructures, telles que les captages sous-glaciaires ou l’autoroute d’accès au Tunnel du Mont Blanc.Nos résultats montrent donc une première phase de diminution de l’activité torrentielle, principalement causée par le retrait des glaciers de 1850 à 1950, puis les conséquences pression des activités humaines sur les évolutions hydromorphologiques. La baisse de la torrentialité est toutefois ponctuée de quelques évènements, comme la crue du septembre 1920 sur l’Arveyron de la Mer de Glace, dont nous avons reconstitué les conséquences géomorphologiques. Malgré leur intensité, les effets de ces crues restent néanmoins relativement limités à l’aval immédiat des glaciers.Contrairement donc aux hypothèses initialement soulevées, le retrait glaciaire n’implique pas une augmentation de la fourniture sédimentaire, mais au contraire une diminution des apports du fait de la déconnexion entre les espaces désenglacés et les systèmes torrentiels. / Since the end of Little Ice Age, glaciers of the Mont blanc massif are retreating and large sediment volume are releasing from the ice. Thus, sediment supply, which is a main control factor of the proglacial stream geomorphic activity, could be deeply modified. Therefore, the consequences on the sediment fluxes and the risk management need to be understanding because of the present acceleration of glacier retreat and urban sprawl in the Chamonix valley. The goal of this thesis is to study the sediment coupling between stream systems and areas released by glaciers. A first approach allows understanding the geomorphic trajectory of proglacial system at the Chamonix scale since the end of the Little Ice Age. Our results supported by modelling and archives analyses, show the decreasing capacity of the hydrographic pattern to be connected with sediment sources. The second approach is lead on the LiDAR DEM multi-temporal comparison. It focuses on the three main proglacial systems: Argentière, Mer de Glace and Bossons, whom occurred a decennal flood during the 2014 summer. This part of our study underlines the storage efficiency into deglaciated areas and the increasing role of anthropic forcing. Present sediment yield to proglacial stream is leaded by facilities such as the Mont Blanc Tunnel substructure or the subglacial harnessing. Our results show that the decreasing geomorphic activity of proglacial stream in the Chamonix valley is mainly caused by glacier retreat from the early 18th Century to the middle 20th century, then it is leaded by the increasing human pressure. Nevertheless, the fall of stream activity is punctuated by extreme events, such as the 1920 flood in the Arveyron of the Mer de Glace that we reconstructed the geomorphic consequences. Despite their intensity, effects of that king of events are limited close to the glacier downstream. Contrary to our initial hypotheses, glacier retreat in the Chamonix Valley, is not follow by a geomorphic crisis of proglacial streams because of the disconnectivity between sediment released from the ice and stream systems.

Este trabalho objetiva investigar a dinâmica geomorfológica glacial das áreas livres de gelo na Península Potter, Ilha Rei George, Antártica, em resposta à recente retração da geleira Polar Club. O mapeamento geomorfológico e a interpretação da evolução dos sistemas lacustres entre 2006 e 2011 das áreas livres de gelo na Península Potter foi realizado através da interpretação visual em uma imagem Quickbird (RGB432), em imagens COSMO-SkyMed polarizações VV e HH em modo spotlight processadas com filtros espaciais e perfis topográficos. Também foram considerados os aspectos morfométricos da península, interpretados através da geração de mapas de hipsometria, declividade, curvas de nível e sombreamento. A variação frontal da geleira Polar Club entre os anos de 1981 a 2015 foi obtida pela análise temporal de imagens Landsat. O mapeamento geomorfológico da Península Potter evidenciou os processos geomorfológicos proglaciais e o padrão de disposição espacial das feições lineares marginais ao gelo, como cordões morâinicos e feições glaciofluviais (relacionadas ao aporte da fusão sazonal da neve e do gelo), bem como terraços marinhos, ravinas e afloramentos rochosos. As imagens COSMO-SkyMed e a aplicação de filtros Passa Alta e Direcionais possibilitaram a delimitação das feições de interesse com maior nitidez. O modelo de evolução da variação frontal da geleira Polar Club indica que condição de último avanço glacial registrado pela geomorfologia proglacial pode estar relacionado à Pequena Idade do Gelo e que houve um contínuo processo de retração desde então. Entre 1981-2015 evidenciou-se a redução de área de 2,95km2 para a geleira Polar Club (perda de área total de 9,4%). Este processo pode estar relacionado com a tendência de aumento das temperaturas médias do ar, a tendência de aumento de dias com precipitação líquida no verão e o número de dias em que a temperatura média ultrapassou os 0°C na região nas últimas décadas. O recuo da geleira Polar Club é pouco expressivo quando comparado a outras geleiras da Ilha Rei George, no entanto, quando se observa as áreas expostas evidenciou-se que houve um aumento significativo (36,9%) no período. Através da análise da evolução dos depósitos morâinicos da Península Potter foi possível identificar três fases principais de formação de morâinas que evidenciam antigas posições da frente da geleira durante períodos de estabilização frontal. A análise da evolução dos sistemas lacustres na área de estudo evidenciou que diversos lagos sofreram alterações de área em resposta à dinâmica de retração glacial registrada para os últimos 34 anos. / This study aimed to investigate the glacial geomorphological dynamics of the ice-free areas in the Peninsula Potter, King George Island, Antarctica, in response to the recent Polar Club Glacier retreat processes. The geomorphological mapping and lacustrine systems evolution modelling between 2006-2011 were obtained with Quickbird (RGB432) image, application of the spatial digital filters in COSMO-SkyMed (cross and co-polarization, spotlight mode) images and topographic profiles visual interpretations. Also considered were the morphometric aspects of the peninsula, interpreted by generating hypsometry, slope, contour and shaded relief maps. The Polar Club Glacier frontal variation between 1981-2015 was obtained with Landsat temporal analysis. The Potter Peninsula geomorphological mapping evidenced the proglacial and geomorphological processes and the spatial distribution pattern of linear marginal to ice features, as morainic ridges and glaciofluvial features, related to the contribution of the seasonal melting of snow and ice, marine terraces, ravines and rocky outcrops. The High Pass and directional filters in COSMO-SkyMed images provided conditions for geomorphological features. The frontal glacier fluctuations modelling indicated that last glacial advance condition recorded by proglacial geomorphologic can be related Little Ice Age and continuous retreat process. Between 1981-2015 the Polar Club glacier lost 2,95km2 of total area (9,4% of total area). The retreat process can be related to the trend of rising average temperatures in recent decades, trend of increase in days with liquid precipitation in summer and the number melting degree days. The Polar Club Glacier retreat is not very significant when compared to other glaciers of King George Island, however, when observing the exposed areas was evident that there was a significant increase (36.9%). The moraine deposits evolution analysis in Peninsula Potter provided conditions for identify three main phases of moraines deposition and that show past glacier front positions during periods of glacier marginal stabilization. The analysis of the evolution of lacustrine systems in the study area evidenced changes in various lakes during last 34 years in response of glacial retreat dynamics.