Rozprawy doktorskie na temat „Himalayan glaciers”

The majority of the 20,000 glaciers found in the Himalaya are in a state of negative mass balance, and have been for decades. Broad spatial trends in ice mass loss have been identified by large scale geodetic mass balance studies, but regional averaging of mass loss data has masked catchment or glacier scale variability. This thesis has the broad aim of examining the catchment scale variability of ice mass loss, in order to identify factors that might promote, or inhibit, more substantial ice mass loss from the region in the future. Ice mass loss rates from Everest region glaciers were calculated using the geodetic approach, over the period 2000-2015, and compared depending on glacier terminus type. Lake-terminating glaciers were found to have lost 32% more ice mass than land-terminating glaciers, and maximum surface lowering rates of lake-terminating glaciers peaked at more than twice the rate of land-terminating counterparts. Glacier hypsometry was found to be contrasting at the catchment scale, and predicted accumulation area ratio (AARs) change in response to different RCP warming scenarios emphasises the importance of considering glacier area-altitude distribution in future ice loss estimates. A more detailed assessment of the evolving geometry, dynamics and ice loss rates of nine lake-terminating glaciers suggested two phases of glacier-lake interaction may exist. A phase of dynamic lake-terminating glacier retreat was evident where terminus proximal surface lowering rates were high (up to 3 m a-1), ice front retreat rates were steady or accelerating, and surface velocities increased (by up to 10 m a-1, between 1999 and 2015). Alternatively, a phase of retreat typified by surface lowering rates akin to land-terminating glaciers (~1 m a-1), where ice front retreat rates were steady or diminishing, and where surface velocity reduction occurred. The dynamic phase of ice loss observed on lake-terminating glaciers in the Everest region is not of the same magnitude as larger waterter-minating glaciers found in other glacierised regions, probably because of the topographic confinement of host glaciers and the dominance of resistive stresses, but the now populous nature of glacial lakes in the region means the potential for amplified future ice loss exists. The impact of long-term ice loss on the topographic characteristics of debris covered glacier surfaces was also examined. Ice cliff and supraglacial pond expansion was identified as the main driver of topographic change on slow flowing, land-terminating glaciers. A more pitted surface topography of greater relief developed on most glaciers, which has implications for the energy balance at the glacier surface, and for supraglacial hydrology. Overall, the results of this thesis emphasise the need to incorporate a range of glacier dynamics scenarios and melt processes into simulations of future ice loss in the Himalaya.

The widespread negative mass balance of debris-covered glaciers in the central Himalaya is expressed through, and influenced by, glacier surface morphology, including the spatio-temporal dynamics of supraglacial ponds and ice cliffs. These features form a relatively unknown component of the overall melt budget but are thought to be key contributors to a debris-cover anomaly, whereby the insulating effect of debris is offset by enhanced melt at supraglacial ponds and ice cliffs. In this thesis we revealed the role of ice cliff evolution and supraglacial pond dynamics at seasonal to annual timescales using extensive fieldwork and assessments of remotely sensed satellite imagery from the Everest region of Nepal. Supraglacial pond dynamics were assessed over the last decade using multitemporal fine-resolution satellite imagery (~0.5−2 m), revealing a net increase in pond area but large inter-annual and seasonal variability. Coalescing and persistent ponds on Khumbu Glacier suggested that a trajectory towards large lake development was underway. Additionally, we revealed that the size distribution of ponds on debris-covered glaciers potentially leads to large classification omissions in studies using medium-resolution (e.g. 30 m) satellite imagery, on the order of 15–88% of ponded area. Instrumentation of ponds on Khumbu Glacier revealed seasonal expansion and drainage, and water temperatures conducive to englacial ablation. We surveyed 24 ponds with an unmanned surface vessel to derive their bathymetry and an empirical area-volume relationship, which can now be used to predict glacier-scale water storage fluxes. A remote sensing assessment of ice cliffs revealed that on average 49% of cliffs were associated with a supraglacial pond, and that cliff density was positively correlated with glacier mass loss. We presented the first application of 3D point cloud differencing to multi-temporal ice cliff point clouds to quantify the magnitude and spatio-temporal variation in cliff retreat, and revealed the role of ponds and local topography on controlling cliff persistence. We observed mean retreat rates of 0.30–1.49 cm d−1 during the winter interval (November 2015–May 2016) and 0.74–5.18 cm d−1 during the summer (May 2016–October 2016). Overall, by coupling remote sensing and field-based observations we produced a holistic assessment of ice cliffs and supraglacial ponds. This assessment has improved our process-based understanding of debris-covered glacier evolution and has provided the foundations for better consideration of surface processes in studies modelling glacier evolution.

Surface ponds play a key role in transferring atmospheric energy to the ice for debris-covered glaciers, but as the spatial and temporal distribution of ponds is not well documented, their effect on glacier ablation is unknown. This thesis uses remote sensing and field methods to assess the distribution of supraglacial ponds in the Langtang Valley of Nepal, then develops and applies numerical models of pond surface energy balance to determine energy receipts at the pond, glacier, and basin scales. 172 Landsat TM/ETM+ scenes are analysed to identify thawed supraglacial ponds for the debris-covered tongues of five glaciers for the period 1999-2013. There is high variability in the incidence of ponding between glaciers, and ponds are most frequent in zones of low surface gradient and velocity. The ponds show a pronounced seasonality, appearing rapidly in the pre-monsoon as snow melts, reaching a peak area in the monsoon of about 2% of the debris-covered area, then declining in the post-monsoon as ponds drain or freeze. The satellite observations are supplemented by diverse field observations on Lirung Glacier in the Langtang Valley made in 2013 and 2014, confirming that overall pond area is markedly higher in the pre-monsoon than post-monsoon. Four ponds are observed in detail showing pond drainage, stability, and growth. The thesis then advances efforts to develop a model of mass and energy balance for supraglacial ponds, using field data from a small pond on Lirung Glacier. Sensitivity testing is performed for several key parameters and alternative melt algorithms. The pond acts as a significant recipient of energy, and participates in the glacier’s local hydrologic system during the monsoon. The majority of absorbed energy leaves the pond via englacial conduits, delivering sufficient energy to melt 2612 m3 of ice (~5.3 m ablation for the pond area). Energy receipts for all Lirung Glacier ponds for 2014 are then determined, using the full model and simpler approaches based on data availability. The partition of absorbed energy between pond-proximal and englacial melt is inconsistent between ponds, and the shortwave energy balance alone is not adequate to represent pond energy absorption. The model results suggest that ponds absorbed sufficient energy to account for ~10% of Lirung Glacier’s ablation in 2014.Finally, a simplified pond surface energy-balance model is applied to assess pond energy absorption for the entire Langtang catchment, using local meteorological data for 2013 and mean monthly pond distributions from the Landsat observations. Supraglacial ponds are found to absorb sufficient atmospheric energy to account for 5-16% (mean ~12%) of the debris-covered area’s volume loss in 2013 (equivalent to 0.11 m thinning for this area). Less absorption occurs in the pre-monsoon and post-monsoon than in the monsoon due to decreased latent heat exchange. Altitude is an additional control, but seasonal surface energy balance remains positive at the ELA of 5400 m. This research suggests that due to the efficiency of supraglacial ponds as vectors of atmospheric energy to the glaciers’ interior, they may account for a considerable portion of the debris-covered area’s ablation (~10%) in spite of their low aerial coverage (1-2%), and ponds must be accounted for in studies of debris-covered glacier ablation and evolution.

Himalayan glaciers are key components of earth's cryosphere, acting as hydrological reservoirs vital to many human and natural systems. Most Himalayan glaciers are shrinking in response to changing climate, which will potentially impact water resources, natural hazards, sea level rise, and many other aspects. However, there is much uncertainty regarding the state of these glaciers, as direct field data are difficult to obtain. Accordingly, long-timespan remote sensing techniques are needed to measure changing glaciers, which have memory and often respond to climate on decadal timescales. This study uses declassified historical imagery from the Hexagon spy satellite database to fulfill this requirement. A new highly-automated, computer-vision based solution is used to extract historical terrain models from Hexagon imagery, which are used as a baseline to compute geomorphic change for glaciers in the Kingdom of Bhutan and Tibet Autonomous Region of the eastern Himalayas. In addition to glaciers, the new method is used to quantify changes resulting from the Thistle Creek Landslide (surface elevation changes resulting from the landslide show an average elevation decrease of 14.4 ± 4.3 meters in the source area, an increase of 17.6 ± 4.7 meters in the deposition area, and a decrease of 30.2 ± 5.1 meters resulting from a new roadcut) and Mount St. Helens eruption in western North America (results show an estimated 2.48 ± 0.03 km3 of material was excavated during the eruption-triggered debris slide). These additional results illustrate the applicability of Hexagon imagery to a variety of landscape processes. Regarding the primary application in the Himalayas, all studied glaciers show significant ice loss. Futhermore, the multi-decadal timespan reveals important aspects of glacier dynamics not detectable with temporally shorter datasets. Some glaciers exhibit inverted mass-balance gradients due to variations in debris-cover, while enhanced ice losses are prominent on glacier toes terminating in moraine-dammed proglacial lakes, resulting from calving caused by thermal undercutting. Remarkably, debris-covered glaciers show significant thinning despite insulating effects of the debris, likely due to poorly-understood ice cliff and melt pond mechanisms. The mean annual geodetic mass balance of 22 studied glaciers over a 32-year period is estimated to be -0.16 ± 0.03 m yr-1 water equivalent. Thus, these glaciers are not in equilibrium with current climate, and appear to be losing significant amounts of ice regardless of debris-cover.

La région du Pamir - Karakoram - Himalaya (PKH) constitue la plus grande réserve de glace terrestre après les régions polaires. Cependant, l'évolution récente de ces glaciers, indicateurs privilégiés du changement climatique en haute altitude, reste encore mal connue, du fait notamment de difficultés d'accès et de conditions climatiques qui rendent délicate l'acquisition de mesures in situ. L'objectif de cette thèse est de contribuer à l'amélioration des connaissances sur l'évolution globale des glaces du PKH au cours de la dernière décennie, en s'appuyant sur des images satellite et des modèles numériques de terrain (MNTs). Une premièreméthodologie a été développée pour assurer le suivi automatique de la distribution spatiale et de l'évolution temporelle des lacs glaciaires à partir d'images Landsat entre 1990 et 2009 sur sept zones d'études réparties le long du PKH. Ainsi, une certaine disparité des types, tailles et évolutions des lacs entre la partie orientale et occidentale du PKH a été mise en évidence. Sur la période de temps considérée, la superficie des lacs a légèrement diminué à l'ouest (Karakoram et Hindu Kush), a été en très nette augmentation à l'est (Népal et Bouthan) et relativement stable sur la partie centrale (Inde du nord-ouest). Le bilan de masse des glaciers a ensuite été calculé, à partir des variations d'épaisseurs mesurées en comparant deuxMNTs, acquis à deux dates différentes, et issus de lamission SRTM et du satellite SPOT5. Cette méthode implique un certain nombre de corrections et d'ajustements au préalable, afin de garantir des mesures les moins biaisées possible. Ainsi, la différence de résolution spatiale initiale des MNTs peut être à l'origine d'un biais fonction de l'altitude, de même que la pénétration des ondes radar de la mission SRTM dans la neige et la glace est à prendre en compte le cas échéant, pour ne pas sous-estimer les altitudes sur les glaciers. Là encore, on observe des disparités entre les différents bilans de masse régionaux sur la période 1999-2011, avec des pertes de masse modérées sur l'Himalaya central et oriental(-0.30±0.08 m a-1 w.e.), plus accentuées sur l'Himalaya occidental (-0.43±0.09 m a-1 w.e.) et des gains de masse plus à l'ouest, pour les glaciers des massifs du Pamir (+0.14±0.11 m a-1 w.e.) et du Karakoram (+0.10±0.20 m a-1 w.e.). Ces résultats confirment donc l'anomalie des glaciers du Karakoram et suggèrent des comportements similaires au Pamir. Le bilan de masse global des glaciers du PKH est estimé à -0.13±0.06 m a-1 w.e.

Glacier melt within alpine catchments provides a vital component of runoff that constitutes an important water resource for downstream populations. With future climate changes, it is expected that glacier volume change will be considerable in the coming decades, with associated implications for runoff. Estimation of future changes in glacier volume and catchment runoff is therefore essential for understanding future water resource implications in alpine environments. This thesis focuses on glacier volume and runoff changes predicted using the statistical model GERM (Glacier Evolution and Runoff Model; Huss et al., 2008a) and has three novel aims. Firstly, to provide more robust assessments of the modelling uncertainty associated with predicted glacier and runoff changes from alpine catchments than previous studies, by challenging the model to reproduce historic changes in glacier volume and evolution over 120 year periods, and comparing predicted and measured runoff. Secondly, to use this assessment of uncertainty to contextualise and understand the precision of future (to 2100 AD) runoff projections for alpine catchments under a wide range of possible climate changes scenarios. Thirdly, to develop the model so that it can be applied to a debris-covered, downwasting glacier in the Himalaya. Two further novel aspects of this thesis are the development of a more systematic and robust calibration procedure for GERM, and the application of climate data downscaling techniques that are more sophisticated than have hitherto been applied in glacio-hydrological studies. To achieve aim 1, GERM was used to forward model glacier volume and runoff for the Griesgletscher and Rhonegletscher catchments in the European Alps from 1884-2004. As a statistical model that requires catchment-specific calibration, GERM was first calibrated to each catchment using contemporary glacier volume and catchment runoff measurements (as is standard when using the model for future projections). Digital elevation models were then used to obtain the initial glacier geometry required to begin each model run, and each completed model run was subsequently used to estimate the accumulated uncertainty associated with the predicted glacier volume/runoff changes by comparing modelled with observed glacier volume/runoff change at the end of the simulation. To achieve aim 2, future model runs (2010-2100) were conducted for the same two catchments and the glacier volume/runoff uncertainty calculated from model performance in the past (aim 1) applied to future projections. Future simulations were driven by a wide-range of climate inputs to allow quantification of the uncertainty associated with climate scenarios/models. The combination of these two sources of uncertainty (GERM and climate) provides future II projections with greater awareness and better quantification of uncertainties than previous studies. Finally, to achieve aim 3, GERM was applied to the debris-covered Khumbu Glacier by adjusting the mass redistribution process of GERM (Δh-parameterisation) to reflect the downwasting behaviour of the debris-covered glacier tongue, based on observed thinning rates at Khumbu Glacier. Additionally, to account for the insulating effect of debris on ice, the modelled melt rate was reduced in proportion to debris thickness on a spatially distributed basis (i.e. debris thickness was not uniform) using observations of reduced melt at glaciers close to Khumbu. Improvements to the calibration procedure used when applying GERM were made and applied throughout this thesis by developing an automated calibration which systematically adjusts the parameters, calculates a combined goodness-of-fit statistic that allows comparison to observations of both glacier volume and runoff, and selects the optimal parameter set. Improved downscaling methods were also used and applied to all future volume and runoff change projections made during this thesis. Specifically, state-of-the-art General Circulation Model simulations were dynamically-statistically downscaled using Regional Climate Model simulations and quantile mapping, and were used to drive future model runs at all three sites. Finally, the novel adjustments made to the mass redistribution process and the inclusion of reduced melt beneath debris indicate that GERM can now be applied to debris-covered glaciers. A recommendation for future research is that GERM is further tested on additional debris- covered glaciers and applied to additional catchments in the larger Everest region. The results of the uncertainty analyses (aim 1) show that glacio-hydrological model uncertainty amounts to annual runoff errors of ±0.04 106m3yr-1 (±0.15 % yr-1), and glacier volume errors of ±0.16 % yr-1, over time periods of 120 years at Griesgletscher. At Rhonegletscher, the uncertainty assessment resulted in annual runoff errors of ±0.16 106m3yr-1 (±0.2 % yr-1) and glacier volume errors of ±0.13 % yr-1, over time periods of 120 years. Nonetheless, the key finding is that the main sources of future uncertainty relate to emissions scenarios and GCM-RCM (General Circulation Model - Regional Climate Model), combinations which lead to variations in predicted future runoff in 2100 of ±36 % at Griesgletscher and ±20 % at Rhonegletscher. The results of the future simulations (aims 2 and 3) indicate that all three glaciers that form the focus of this thesis will lose considerable volume. Specifically, by 2100, Griesgletscher is likely to have become an ice-free catchment (87-100 % ice loss); Rhonegletscher will have lost 70-90 % of ice; and Khumbu Glacier will have lost 61-92 % of ice. The results further show that mass losses will cause an initial increase in annual river discharge followed by a decline in discharge levels, such that annual discharge by 2100 will be considerably lower than present, with peak discharge at Griesgletscher occurring in 2020, at Rhonegletscher in 2075, and at Khumbu Glacier in 2045.

L'Himalaya résultant de la collision indo-asiatique, dans laquelle l'Inde plonge sous le Tibet, initie régulièrement des tremblements de terre destructeurs dont la plupart sont mortel pour les communautés népalaises et limitrophes. Telle une muraille séparant les plaines d’Inde et le haut plateau du Tibet, l’Himalaya façonne la circulation atmosphérique, affectant tant le climat régional que global. Cette thèse vise à se pencher sur l'histoire et l'évolution peu connue du climat et de la sismicité de l'Himalaya, dans une des régions les moins peuplées et la plus reculées du Népal occidental. Dans le contexte de changements climatiques et environnementaux, l'un des aspects les moins bien élucidés de l'histoire de l'Himalaya au cours du Quaternaire supérieur est celui de l'extension des glaciers ainsi que leurs impacts sur l'évolution du paysage. En nous appuyant sur des observations de terrain, sur des datations par nucléides cosmogéniques (10Be) ainsi que des observations satellitaires, nous avons pu estimer l'étendue maximale des glaciers durant le dernier maximum glaciaire. Soutenant ainsi l'hypothèse suivant laquelle la présence de glacier fut relativement plus étendue à l'échelle du Népal occidental mais pas de l’ordre d’une calotte glaciaire. Sur le plan sismologique, l’enjeu à la fois sociale, économique et politique de l’occurrence d’un séisme de magnitude plus élevée que le récent séisme de 2015 dont l’épicentre se situe près de la ville de Gorkha constitue une préoccupation majeure et motive en grande partie cette thèse. Le dernier séisme majeur ayant rompu le Main Frontal Thrust de magnitude supérieure à 8 (Mb) s’est déroulé le 6 juin 1505 et a considérablement impacté la population népalaise et environnante. Le caractère singulier du Népal occidental s’exprimant ainsi par l’hypothèse de la présence d’un hiatus sismique s’étendant sur plus de 500 ans sur base d’archives historiques et d’études paléosismologiques. Dans cette perspective, cette thèse se penche sur deux questions majeures relatives au comportement sismique de l'Himalaya : d'une part, l'hypothèse d'une lacune sismique dans l'Himalaya central et, d'autre part, de la distribution temporelle des séismes au cours de la fin du Quaternaire. A cette fin, une nouvelle approche de recherche, indépendamment du recours aux tranchées paléosismiques, a été mise en œuvre en Himalaya. En utilisant les lacs comme paleoseismomètre, au travers de la collecte de carottes sédimentaires, nous avons pu affiner la résolution temporelle et déceler des séismes à ce jours non répertorié dans les basses de données accessible et ce sur une échelle de 700 ans. La mise en évidence de séismes important (Mw>6.5) non répertorié indique que le Népal occidental connait une activité sismique comparable au centre du Népal et remet en question l’hypothèse d’un gap sismique au centre de l’Himalaya. Sur base d'une carotte sédimentaire plus longue provenant du même lac, nous avons étudié la distribution temporelle des séismes sur une période de 6000 ans, permettant ainsi de mettre en évidence le caractère aléatoire de l’occurrence des séismes constituant un changement de paradigme là où notion de cycle sismique est encore prépondérante. La mise en évidence du caractère aléatoire de l’occurrence des séismes tant à courte échelle de temps (instrumentale) qu’à l’échelle du Quaternaire infirme l’hypothèse du gap sismique au centre de l’Himalaya et mets en évidence le risque permanent pour le million de personnes concernées. Cette thèse s’achève en se penchant sur une possible relation à l’échelle globale entre la variation de taux de séismicité et les changements climatiques au cours de l’Holocène. Nous constatons ainsi que la sismicité globale connu des périodes de séismes accrue sur 7000 ans. Ces périodes de plus fortes activités semblent être synchrone avec la somme des avancées glaciaires de l'Holocène moyen et supérieur
The Himalayan collision, in which India underthrusts below Tibet, regularly produces major destructive earthquakes in Nepal and its neighboring countries, most of which are fatal to nearby communities. As a wall dividing the Indian plains and the Tibetan plateau, the Himalaya also significantly modifies the atmospheric circulation, affecting both the local and global climate. This thesis explores the poorly known Quaternary history and evolution of Himalayan climate and seismicity, more particularly in the least populated and most remote region of Western Nepal. In terms of climate and environmental change, one of the least understood aspects of Himalayan history during the late Quaternary is the extension of glaciers and their impacts on landscape evolution. Based on field observations, cosmogenic nuclide dating (10Be) and satellite observations, we estimated the maximum extent of glaciers during the Last Glacial Maximum, which supports the hypothesis of a relatively large glacier cover, but not of an extended ice cap, at the scale of Western Nepal. In terms of seismology, the social, economic and political implications of the occurrence of an earthquake of higher magnitude than the recent earthquake of 2015, whose epicenter is located near the city of Gorkha, is a major concern and largely motivates this thesis. The last major earthquake of magnitude greater than 8 (Mb) took place on 6 June 1505 and had a profound impact on the Nepalese population and the surrounding area. In Western Nepal the 1505 event was the last earthquake that ruptured the Main Frontal Thrust according to historical archives and paleoseismological studies, which gave rise to the concept of a seismic gap in western Nepal and adjacent areas in northern India. With this in mind, this thesis addresses two major issues on the Himalayan seismic behavior: on the first hand is the hypothesis of a seismic gap in the central Himalaya and on the second the temporal distribution of earthquakes during the late Quaternary. For this purpose, a new research approach independent of paleoseismic trenches was applied in the Himalaya. By using lakes as paleoseismometers, we were able to refine the temporal resolution and identify earthquakes that had not yet been documented in the accessible databases on a 700-year scale. Our results from Lake Rara highlight significant previously-unknown earthquakes (Mw>6.5) and they reveal that Western Nepal is seismically as active as central Nepal. Furthermore, they call into question the hypothesis of a seismic gap in the central Himalaya. Based on a longer sediment core from the same lake, we studied the temporal distribution of earthquakes over a period of 6000 years, which has highlighted the random nature of the occurrence of earthquakes, constituting a paradigm shift where the notion of seismic cycle is still prevalent. The random nature of the occurrence of earthquakes both on short (instrumental) and Quaternary time scales disproves the hypothesis of the seismic gap in the central Himalaya and underlines the permanent risk for the million people of concern. The final part of this thesis addresses the possible global relationship between seismic rate fluctuations and climate change during the Holocene. Our results show that the global seismicity clustered over 7000 years and appears to be synchronous with the sum of glacial advances through the Mid and Late Holocene

Palaeoglacier margins from the Zanskar Range of the north-western Indian Himalaya are reconstructed through geomorphological mapping and sedimentology. These are dated ilsing Optically Stimulated Luminescence (OSL) techniques on quartz extracted from related fluvioglacial and lacustrine deposits. A glaciated palaeosurface with broad, gentle slopes >280m above river level and high grade metamorphic erratics represents the oldest and most extensive glaciation, the Chandra Stage. This formed an ice-cap with its ice-shed to the south over the High Himalaya. A change from broad glacial troughs to narrow V -shaped gorges along with large subdued moraine ridges and drift/erratic limits defines an extensive valley glaciation, the Batal Stage, with its maximum close to -78.0±12.3ka BP (Oxygen Isotope Stage (OIS) 4). Distinct sets of moraine ridges represent a less extensive glaciation, the Kulti Stage, which is dated to shortly after the global Last Glacial Maximum (OIS 2) and a minor advance, the Sonapani, is represented by sharp crested moraine ridges < 2km from current ice bodies. The change in glacier extent and style from the Chandra Stage to the later glaciations may be related to uplift of more southerly ranges blocking monsoon precipitation and incision of the landscape such that ice reached lower altitudes over shorter horizontal distances. Batal and Kulti Stage Glacier Elevation Indexes (GEls) calculated for this and adjacent areas increase from south-west to the north-east, but decrease again towards the Indus valley, reflecting attenuation of the south-westerly monsoon and possible channelling of westerly depressions along the broad upper Indus valley. GEl values were depressed by ~500m during the Batal Stage and -300m during the Kulti Stage. Six new OSL age estimates from the Zanskar Range greatly improve the glacial chronology of the north-west Himalaya and reinforce the emerging asynchrony between this region and the Central and Eastern Himalaya, which experienced its maximum glaciation during OIS 2 rather than OIS 4. Improved glacier mass balance data, palaeoclimatic proxy data for the summer monsoon and particularly the winter westerlies, and numerical age estimates from Himalayan glaciers are required to explain this asynchronous maximum.

Spatiotemporal variability in supraglacial debris properties have the potential to affect estimations of mass balance for debris-covered glaciers. This thesis is concerned with identifying the extent to which debris properties vary in space and time, and the role of these variabilities in estimations of specific mass balance. The research presented uses a combination of methods, including statistical analysis of field data, mapping and classification of thermal and optical remotely sensed data, and numerical modelling. Near-surface debris temperature was measured in the field to investigate short term spatial and temporal variability in debris properties and its influence on debris temperature over a monsoon season. The strongest correlation between timeseries of near-surface debris temperature and meteorological controls was with air temperature, with lesser correlations between rate of change in air temperature and incoming shortwave radiation. Subtle spatial variability was also identified, controlled by site aspect and slope, grain lithology and size, and potentially moisture content and thermal conductance of the bulk debris layer. The occurrence of spatiotemporal variability in supraglacial debris distribution was identified on Baltoro Glacier over a sub-decadal timescale, considered to be primarily due to differences in input of debris to the glacier system through mass movement events. The importance of variability in debris properties was investigated using a surface energy balance and heat transfer model, where the influence of debris thickness, albedo and aerodynamic roughness length was tested. The modelling results, although not directly comparable to mass balance estimates for Khumbu Glacier, showed a 223% increase in total specific mass balance for Khumbu Glacier’s debris-covered area over a monsoon season when a spatially variable debris layer was included. Including spatially variable albedo and aerodynamic roughness length along with debris thickness reduced estimates of specific mass balance, although were still higher than the base line model simulation. Consequently, this thesis confirms the occurrence of spatially and temporally variable supraglacial debris properties, over seasonal and sub-decadal periods, and that such variability is influential for estimates of glacier mass balance.

In den Hochgebirgen Asiens bedecken Gletscher eine Fläche von ungefähr 115,000 km² und ergeben damit, neben Grönland und der Antarktis, eine der größten Eisakkumulationen der Erde. Die Sensibilität der Gletscher gegenüber Klimaschwankungen macht sie zu wertvollen paläoklimatischen Archiven in Hochgebirgen, aber gleichzeitig auch anfällig gegenüber rezenter und zukünftiger globaler Erwärmung. Dies kann vor allem in dicht besiedelten Gebieten Süd-, Ost- und Zentralasiens zu großen Problem führen, in denen Gletscher- und Schnee-Schmelzwässer eine wichtige Ressource für Landwirtschaft und Stromerzeugung darstellen. Eine erfolgreiche Prognose des Gletscherverhaltens in Reaktion auf den Klimawandel und die Minderung der sozioökonomischen Auswirkungen erfordert fundierte Kenntnisse der klimatischen Steuerungsfaktoren und der Dynamik asiatischer Gletscher. Aufgrund ihrer Abgeschiedenheit und dem erschwerten Zugang gibt es nur wenige glaziologische Geländestudien, die zudem räumlich und zeitlich sehr begrenzt sind. Daher fehlen bisher grundlegende Informationen über die Mehrzahl asiatischer Gletscher. In dieser Arbeit benutze ich verschiedene Methoden, um die Dynamik asiatischer Gletscher auf mehreren Zeitskalen zu untersuchen. Erstens teste ich eine Methode zur präzisen satelliten-gestützten Messung von Gletscheroberflächen-Geschwindigkeiten. Darauf aufbauend habe ich eine umfassende regionale Erhebung der Fliessgeschwindigkeiten und Frontdynamik asiatischer Gletscher für die Jahre 2000 bis 2008 durchgeführt. Der gewonnene Datensatz erlaubt einmalige Einblicke in die topographischen und klimatischen Steuerungsfaktoren der Gletscherfließgeschwindigkeiten in den Gebirgsregionen Hochasiens. Insbesondere dokumentieren die Daten rezent ungleiches Verhalten der Gletscher im Karakorum und im Himalaja, welches ich auf die konkurrierenden klimatischen Einflüsse der Westwinddrift im Winter und des Indischen Monsuns im Sommer zurückführe. Zweitens untersuche ich, ob klimatisch bedingte Ost-West Unterschiede im Gletscherverhalten auch auf längeren Zeitskalen eine Rolle spielen und gegebenenfalls für dokumentierte regional asynchrone Gletschervorstöße relevant sind. Dazu habe ich mittels kosmogener Nuklide Oberflächenalter von erratischen Blöcken auf Moränen ermittelt und eine glaziale Chronologie für das obere Tons Tal, in den Quellgebieten des Ganges, erstellt. Dieses Gebiet befindet sich in der Übergangszone von monsunaler zu Westwind beeinflusster Feuchtigkeitszufuhr und ist damit ideal gelegen, um die Auswirkungen dieser beiden atmosphärischen Zirkulationssysteme auf Gletschervorstöße zu untersuchen. Die ermittelte glaziale Chronologie dokumentiert mehrere Gletscherschwankungen während des Endstadiums der letzten Pleistozänen Vereisung und während des Holzäns. Diese weisen darauf hin, dass Gletscherschwankungen im westlichen Himalaja weitestgehend synchron waren und auf graduelle glaziale-interglaziale Temperaturveränderungen, überlagert von monsunalen Niederschlagsschwankungen höherer Frequenz, zurück zu führen sind. In einem dritten Schritt kombiniere ich Satelliten-Klimadaten mit Eisfluss-Abschätzungen und topographischen Analysen, um den Einfluss der Gletscher Hochasiens auf die Reliefentwicklung im Hochgebirge zu untersuchen. Die Ergebnisse dokumentieren ausgeprägte meridionale Unterschiede im Grad und im Stil der Vergletscherung und glazialen Erosion in Abhängigkeit von topographischen und klimatischen Faktoren. Gegensätzlich zu bisherigen Annahmen deuten die Daten darauf hin, dass das monsunale Klima im zentralen Himalaja die glaziale Erosion schwächt und durch den Erhalt einer steilen orographischen Barriere das Tibet Plateau vor lateraler Zerschneidung bewahrt. Die Ergebnisse dieser Arbeit dokumentieren, wie klimatische und topographische Gradienten die Gletscherdynamik in den Hochgebirgen Asiens auf Zeitskalen von 10^0 bis 10^6 Jahren beeinflussen. Die Reaktionszeit der Gletscher auf Klimaveränderungen sind eng an Eigenschaften wie Schuttbedeckung und Neigung gekoppelt, welche ihrerseits von den topographischen Verhältnissen bedingt sind. Derartige Einflussfaktoren müssen bei paläoklimatischen Rekonstruktion und Vorhersagen über die Entwicklung asiatischer Gletscher berücksichtigt werden. Desweiteren gehen die regionalen topographischen Unterschiede der vergletscherten Gebiete Asiens teilweise auf klimatische Gradienten und den langfristigen Einfluss der Gletscher auf die topographische Entwicklung des Gebirgssystems zurück.
In the high mountains of Asia, glaciers cover an area of approximately 115,000 km² and constitute one of the largest continental ice accumulations outside Greenland and Antarctica. Their sensitivity to climate change makes them valuable palaeoclimate archives, but also vulnerable to current and predicted Global Warming. This is a pressing problem as snow and glacial melt waters are important sources for agriculture and power supply of densely populated regions in south, east, and central Asia. Successful prediction of the glacial response to climate change in Asia and mitigation of the socioeconomic impacts requires profound knowledge of the climatic controls and the dynamics of Asian glaciers. However, due to their remoteness and difficult accessibility, ground-based studies are rare, as well as temporally and spatially limited. We therefore lack basic information on the vast majority of these glaciers. In this thesis, I employ different methods to assess the dynamics of Asian glaciers on multiple time scales. First, I tested a method for precise satellite-based measurement of glacier-surface velocities and conducted a comprehensive and regional survey of glacial flow and terminus dynamics of Asian glaciers between 2000 and 2008. This novel and unprecedented dataset provides unique insights into the contrasting topographic and climatic controls of glacial flow velocities across the Asian highlands. The data document disparate recent glacial behavior between the Karakoram and the Himalaya, which I attribute to the competing influence of the mid-latitude westerlies during winter and the Indian monsoon during summer. Second, I tested whether such climate-related longitudinal differences in glacial behavior also prevail on longer time scales, and potentially account for observed regionally asynchronous glacial advances. I used cosmogenic nuclide surface exposure dating of erratic boulders on moraines to obtain a glacial chronology for the upper Tons Valley, situated in the headwaters of the Ganges River. This area is located in the transition zone from monsoonal to westerly moisture supply and therefore ideal to examine the influence of these two atmospheric circulation regimes on glacial advances. The new glacial chronology documents multiple glacial oscillations during the last glacial termination and during the Holocene, suggesting largely synchronous glacial changes in the western Himalayan region that are related to gradual glacial-interglacial temperature oscillations with superimposed monsoonal precipitation changes of higher frequency. In a third step, I combine results from short-term satellite-based climate records and surface velocity-derived ice-flux estimates, with topographic analyses to deduce the erosional impact of glaciations on long-term landscape evolution in the Himalayan-Tibetan realm. The results provide evidence for the long-term effects of pronounced east-west differences in glaciation and glacial erosion, depending on climatic and topographic factors. Contrary to common belief the data suggest that monsoonal climate in the central Himalaya weakens glacial erosion at high elevations, helping to maintain a steep southern orographic barrier that protects the Tibetan Plateau from lateral destruction. The results of this thesis highlight how climatic and topographic gradients across the high mountains of Asia affect glacier dynamics on time scales ranging from 10^0 to 10^6 years. Glacial response times to climate changes are tightly linked to properties such as debris cover and surface slope, which are controlled by the topographic setting, and which need to be taken into account when reconstructing mountainous palaeoclimate from glacial histories or assessing the future evolution of Asian glaciers. Conversely, the regional topographic differences of glacial landscapes in Asia are partly controlled by climatic gradients and the long-term influence of glaciers on the topographic evolution of the orogenic system.

The Himalayan region is one of the most highly glacierised areas on Earth. Regarded as the “water towers” of Asia, the Himalayas are the source of several of the world’s major rivers. The region is inhabited by some 140 million people and ten times as many (~1.4 billion) live in its downstream river basins. Freshwater from the mountains is vital for the region’s economy and for sustaining the livelihoods of a fast-growing population. Climatic warming and the rapid retreat of Himalayan glaciers over recent decades have raised concerns about the future reliability of mountain melt-water resources, leading to warnings of catastrophic water shortages. Several previous studies have assessed climate change impacts on specific glacier-fed rivers, usually applying meso-scale catchment models for short simulation periods during which glacier dimensions remain unchanged. Few studies have attempted to estimate the effects on a regional scale, partly because of the paucity of good quality data across the Himalaya. The aim of this study was to develop a parsimonious grid-based macro-scale hydrological model for the Indus, Ganges and Brahmaputra basins that, in order to represent transient melt-water contributions from retreating glaciers, innovatively allowed glacier dimensions to change over time. The model initially was validated over the 1961-90 standard period and then applied in each basin with a range of climate-change scenarios (sensitivity analysis- and climate-model-based) over a 100-year period, to gain insight on potential changes in mean annual and winter flows (water availability proxies) at decadal time-steps. Plausible results were obtained, showing impacts vary considerably across the region (catchments in the east appear much less susceptible to glacier retreat effects than those in the west, due to the influence of the summer monsoon), and, in central and eastern Himalayan catchments, from upstream to downstream (effects diminish rapidly downstream due to higher runoff from non-glaciated parts).

Face au déclin récent des glaciers de montagne, un suivi régulier à l'échelle globale est nécessaire mais n'est pas réalisable par des campagnes de terrain. Nous montrons dans cette thèse que l'imagerie satellitaire haute résolution est une solution pour observer l'évolution dynamique et volumétrique des glaciers.
Les 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

In the Himalaya, ablation of debris-mantled valley glaciers has resulted in the formation of large, potentially unstable moraine-dammed lakes. In recent decades several Glacier Lake Outburst Floods (GLOFs) have occurred, which have resulted in destruction of land and infrastructure for several tens of kilometres down valley. As a result, the growth of supra-glacial lakes is considered to be a potential hazard to human lives and livelihoods. Therefore, there is a need for better understanding of the factors involved in lake emergence and subsequent evolution, in order to prepare for and alleviate future GLOF events. On the basis of the above premise, a detailed study of one glacier in the region, the Ngozumpa, was undertaken. The specific objectives of the study were to: 1)  study initial lake inception;  2)  understand glacial lake development cycles;  3)  monitor lake development rates; and  4)  provide a baseline for future glaciological studies on the Ngozumpa Glacier. It was found that certain criteria are requisite for glacial lake formation, and that the evolution of lakes on the glacier is controlled by the englacial base level. Two types of lake exist on the Ngozumpa; 1) ‘Perched Lakes’, occupying closed basins above the englacial water table, and 2) lakes controlled by the altitude of outflow through the lateral moraine. A single example of the second type, Spillway Lake, currently exists on the Ngozumpa. Although ‘Perched Lakes’ contribute to overall downwasting of the glacier, they are subject to rapid drainage once connection is made to englacial conduits. Spillway Lake has the potential to expand into an unstable lake if present trends continue.

Quantifying the contribution of glaciers to water resources is particularly important in locations where glaciers may provide a large percentage of total river discharge. In some remote locations, direct field measurements of melt rates are difficult to acquire, so alternate approaches are needed. Positive degree-day modeling (PDD) of glacier melt is a valuable tool to making first order approximations of the volume of melt coming from glaciers. In this study, a PDD-melt model is applied to glaciers in the Indus River watershed located in Afghanistan, China, India, and Pakistan. Here, millions of people rely on the water from the Indus River, which previous work suggests may be heavily dependent on glacier melt from high mountain regions in the northern part of the watershed. In this region, the PDD melt model calculates the range of melt volumes from more than 45,000 km2 of glaciated area. It relies on a limited suite of input variables for glaciers in the region: elevation, temperature, temperature lapse rate, melt factor, and surface area. Three global gridded climate datasets were used to determine the bounds of temperature at each glacier: UEA CRU CL 2.0, UEA CRU TS 2.1, and NCEP/NCAR 40 year reanalysis. The PDD melt model was run using four different melt scenarios: mean, minimum, maximum, and randomized. These scenarios account for differences in melt volume not captured by temperature, and take uncertainties in all input parameters into account to bound the possible melt volume. The spread in total melt volume from the model scenarios ranges between 27 km3 and 439 km3. While the difference in these calculations is large, it is highly likely the real value falls within this range. Importantly, even the smallest model volume output is a significant melt water value. This suggests that even when forcing the absolute smallest volume of melt, the glacier contribution to the Indus watershed is significant. In addition to providing information about melt volume, this model helps to highlight glaciers with the greatest contribution to total melt. Despite differences in the individual climate models, the spatial pattern in glacier melt is similar, with glaciers contributing the majority of total melt volume occurring in similar geographic regions regardless of which temperature dataset is used. For regions where glacier areas are reasonably well-constrained, contributions from individual glaciers can be quantified. Importantly, less than 5% of glaciers contribute at least 70% of the total melt volume in the watershed. The majority of these glaciers are in Pakistan, the region with the largest percentage of known glaciers with large surface areas at lower elevations. In addition to calculating current melt volumes over large glaciated areas, this model can also be used to determine future melt rates under differing climate scenarios. By applying suggested future regional temperature change to the temperature data, the impact on average melt rate over the watershed was found to increase from 3.02 m/year to 4.69 m/year with up to 2 °C temperature increase. Assuming glacier area remains relatively constant over short time periods, this would amount to a 145 km3 increase in melt volume.

Since reaching their LIAMs, Himalayan glaciers have generally undergone a period of retreat, evident from large moraines left at former ice limits. Currently, however, detailed assessments of Himalayan glacier fluctuations over the past century are limited and fail to compare spatially or temporally to records available in Central Europe, North America and Scandinavia. Consequently, the variability and magnitude of glacial change across the Himalayas, which is a key indicator of climatic change in this region, is yet to be fully understood. Against a background of poor data availability, Corona imagery and historic GLIMS glacier outlines now offer an opportunity to assess glacier extent for regions of the Himalayas pre-1980. Corona imagery, acquired by a US space-borne reconnaissance mission operational from 1960 to 1970, represents a particularly unique dataset offering high resolution imagery (~1.8 m) with stereo-scopic capabilities. Utilising Corona imagery, there is an opportunity to produce detailed maps of Himalayan glacier extent and extract ice surface elevation estimations, in some instances, for the first time. Despite having been de-classified in 1995, the use of Corona data in the Himalayas has been neglected, mainly because of orthorectification challenges related to its unique geometric distortions. Hence, there remains a need to develop a low cost and easily replicable method of accurately orthorectifying Corona imagery enabling its use as a large-scale glacier mapping tool in the Himalayas. In response to this need, Corona images are orthorectified in this study through the use of: (1) a non-metric photogrammetry approach; and (2) horizontal and vertical reference data acquired from ortho-ASTER imagery and the freely available ASTER GDEM. By comparing glacier measurements derived from Corona imagery, GLIMS data and more contemporary ASTER data, changes in glacier area, length and in some instances volume, between the 1960/70s and early 2000s, were quantified for glaciers selected within four study areas located in Uttarakhand, India and Central Nepal. Importantly, this cross-regional glacier change dataset both complements and enhances current Himalayan records. Most notably, results indicate that glaciers selected in the Bhagirathi and Pindar/Kali basins, Uttarakhand, reduced in area by a relatively small 7.97±0.29% and 7.54±0.26%, respectively. Contrastingly, glaciers selected in the more easterly located Seti and Trisula basins reduced in area by 29.78±0.2% and 50.55±0.08%, respectively. Comparisons of Corona DEM (derived from Corona stereo-pairs) and ASTER Global DEM elevations at the terminus regions of four glaciers revealed extensive surface lowering, ranging from 87±27 m to 142±27 m. For Corona processing, the methods applied were shown to orthorectify Corona images to an accuracy that allows comparable glacier outlines to be delineated, further demonstrating the mapping potential of this dataset. However, for Corona DEM extraction, the use of ASTER spatial control data was shown to be inadequate and the presence of large vertical errors in the DEMs generated hindered the measurement of glacier volume change. For this purpose, it is therefore recommended that the methods developed are tested with the use of very high resolution spatial control data.

Les glaciers de montagne ont un impact sociétal important que ce soit à l'échelle locale où ils influencent les ressources en eau et l'attractivité touristique d'une région, ou à l'échelle mondiale en contribuant au niveau des océans. Par ailleurs, les glaciers de montagne sont extrêmement sensibles aux variations climatiques et sont donc des indicateurs pertinents des évolutions climatiques passées et présentes, en particulier du réchauffement global.Une meilleure compréhension de la réponse des glaciers à ces changements, ou dynamique, est nécessaire afin d'estimer leur contribution au système Terre et leur évolution future. Les satellites d'observation de la Terre, par leur couverture globale et des acquisitions régulières, représentent un atout formidable pour suivre l'évolution des glaciers. L'archive à disposition est considérable et celle à venir promet d'être encore plus importante. Il est donc indispensable de développer des méthodes pour traiter cette masse de données.L'objectif de cette thèse est de mieux comprendre la réponse dynamique des glaciers du Pamir-Karakoram-Himalaya (PKH) et des Alpes aux changements climatiques actuels en mettant à profit les 40 années de données satellitaires disponibles. Dans un premier temps, nous avons développé une chaine de traitement semi-automatique qui permet de mesurer les vitesses annuelles de surface d'écoulement des glaciers par corrélation d'images à partir d'une archive satellitaire. Grâce à la redondance des acquisitions, il est possible d'obtenir des champs de vitesse plus complets, plus robustes et d'estimer statistiquement l'incertitude. L’application de ce traitement à l’archive Landsat a permis d’obtenirdes champs de vitesse pour l’ensemble de la région du PKH (~92 000 km2) sur la période 1998-2014et sur les Alpes (~2 000 km2, période 1999-2014) avec une couverture de 60-80 % et une incertituded’environ 4 m/an. Des champs de vitesse ont également été obtenus de manière moins systématique sur la période 1972-1998 pour le PKH. Dans un second temps, l'analyse des variations de vitesse sur ces périodes a montré un ralentissement des glaciers sur l'ensemble des deux chaines de montagne, en lien avec un amincissement des glaciers sur la même période. Les variations de vitesse sont très contrastées spatialement et sont cohérentes avec les motifs observés pour les variations d'épaisseur. En particulier, les glaciers du Karakoram et du Kunlun qui sont stables ou gagnent de la masse sur cette période montrent également des signes d'accélération, alors que les zones d'amincissement le plus important (Himalaya occidental, Nyenchen Tangla, Alpes) sont celles ou le ralentissement observé est le plus fort. Il semble donc que les variations de vitesse observées soient conditionnées au premier ordre par un signal climatique
Mountain glaciers have a high societal impact, first at a local scale since they influence the water ressources and the touristic attractivity of a region, but also at a global scale, being major contributors to the present sea-level rise. Moreover, mountain glaciers are sensitive to climate forcing and are thus relevant indicators of past and present climate change and particularly present global warming. It is thus important to analyse the dynamic of these glaciers and quantify the changes that are affecting them so that their contribution to the Earth system and their future evolution can be better estimated. Satellite Earth Observation imagery, with its global coverage and repeated acquisition, represents a unique tool to quantify temporal changes affecting glaciers. The available archive is huge and the flux of new data will increase it even more.It is thus necessary to develop new methods to process this large archive.The objective of this thesis is to quantify the dynamic response of mountain glaciers in the Pamir-Karakoram-Himalaya (PKH) and in the Alps to a changing climate, with the use of the 40-year long satellite archive. We first developped a semi-automated processing chain to derive annual ice flow velocities from feature-tracking of satellite images. The chain takes advantage of the redundancy in the archive to obtain more spatially complete and robust velocity fields and to statistically estimate the uncertainty. Application to the Landsat archive leads to the determination of an unprecedented velocity field for the entire PKH region (~92 000 km2) for the period 1998-2014 and over the Alps (2 000 km2, period 1999-2014) with a coverage of 60-80 % and a mean uncertainty of 4 m/yr.. Flow velocities have been derived less systematically for the period 1972-1998 over the PKH. Secondly, the analysis of velocity changes show a slow-down of the glaciers for most of the 2 regions. The velocity changes are spatially contrasted and coherent with the patterns of elevation changes. In particular, glaciers in the Karakoram and West Kunlun that are stable or advancing show also a clear speed-up, whereas regions where thinning is the most important (Western Himalaya, Nyenchen Tangla, Alps) show the most important slow-down. The observed velocity changes is thus primarily determined by a climatic signal

La région de l'Hindu-Kush Karakoram Himalaya (HKH) est la plus grande région englacée de la planète, hormis les calottes polaires. Dans cette région, les mesures météorologiques et de bilans de masse sont sporadiques et les observations glaciologiques concernent essentiellement les mesures de fluctuations des fronts des glaciers. Ainsi, la réponse de ces glaciers aux changements climatiques est très mal connue. Le but de ce travail de thèse est d'améliorer la connaissance des relations entre les variables météorologiques et les bilans de masse glaciaires à partir de l'étude du glacier du Chhota Shigri situé dans l'Ouest de l'Himalaya. De nombreuses mesures in-situ de bilans de masse, de vitesses d'écoulement, d'épaisseurs et de météorologie ont été réalisées depuis 2002 et au cours de ce PhD. Ces observations permettent d'analyser le comportement du glacier au regard des fluctuations climatiques. Entre 2002 et 2013, nos observations indiquent une perte de masse cumulée équivalente à une lame d'eau de -6.45 m. Par ailleurs, l'analyse des observations des flux de glace suggèrent que le glacier a connu un état proche d'un état d'équilibre avec des bilans nuls ou légèrement positifs au cours des années 1990. Nous avons dans un premier temps reconstitué les bilans de masse annuels et saisonniers depuis 1969 en utilisant un modèle degré-jour et des variables météorologiques simples, précipitations et températures. Depuis 1969, les bilans de masse sont faiblement négatifs, équivalents à -0.30 m d'eau par an. Cette reconstitution montre que le glacier était proche de l'état d'équilibre entre 1986 et 2000, ce qui confirme les résultats obtenus à partir de l'analyse des flux de glace et des mesures géodésiques. Cette étude montre également que la perte de masse glaciaire est récente et révèle des fluctuations de bilans de masse avant l'année 2000 très différentes de ce que l'on trouve dans la littérature. L'analyse des bilans de masse à l'échelle décennale révèle que les précipitations hivernales et les températures estivales jouent un rôle sensiblement équivalent. Afin de comprendre plus en détail les variables climatiques qui contrôlent le bilan de masse, nous avons, dans un second temps, analysé les flux d'énergie en surface à l'aide de stations météorologiques situées sur le glacier et à proximité du glacier. Le rayonnement de courtes longueurs d'onde contrôlent 80 % des flux d'énergie entrant en surface alors que les flux de chaleur latente, sensible et de conduction contribuent pour 13, 5 et 2 % respectivement du flux entrant total. Par ailleurs, notre étude montre que les événements de fortes précipitations au cours de la période de mousson jouent un rôle essentiel sur l'évolution des bilans de masse. Néanmoins, à cause du manque de données de précipitation dans cette région et le fort gradient régional, la distribution des précipitations sur le glacier reste mal connue
The Hindu-Kush Karakoram Himalayan (HKH) region is the largest snow and ice reservoir on the planet outside the Polar Regions. In the HKH region the mass balance and meteorological observations are sparse and the historical knowledge is mainly concentrated on snout fluctuation records. Hitherto, the understanding of glacier-climate relationship is poor in the HKH region. Therefore, the goal of the present work is to improve the understanding of glacier-climate relationship on a representative glacier ‘Chhota Shigri' in the western Himalaya. A number of in-situ measurements concerning mass balances, surface velocity, ice thickness and meteorology have been collected during and before the present PhD work since 2002. These data sets were first analyzed to understand the glacier behaviour and then used in the models to understand the glacier relationship with climatic variables. Between 2002 and 2013, glacier showed a mass wastage/unsteady-state conditions with a cumulative mass loss of –6.45 m w.e. Further, the ice flux analysis over 2002-2010 suggested that the glacier has experienced a period of steady-state or slightly positive mass balance during the 1990s. We first reconstructed the annual and seasonal mass balances using a degree day model from simple meteorological variables, precipitation and temperature. This reconstruction allowed us to examine the mass balances between 1969 and 2012. Since 1969, Chhota Shigri showed a moderate mean mass wastage at a rate of −0.30 m w.e. a-1. A period of steady-state between 1986 and 2000, already suggested by ice flux analysis and geodetic measurements, was confirmed. The mass balance evolution of this glacier revealed that the mass wastage is recent and provide a very different pattern than that of usually found in the literature on western Himalayan glaciers. The analysis of decadal time scale mass balances with meteorological variables suggested that winter precipitation and summer temperature are almost equally important drivers controlling the mass balance pattern of this glacier. Second, in order to understand the detailed physical basis of climatic drivers, a surface energy balance study was also performed using the in-situ meteorological data from the ablation area of Chhota Shigri Glacier. Net all-wave radiation was the main heat flux towards surface with 80% contribution while sensible, latent heat and conductive heat fluxes shared 13%, 5% and 2% of total heat flux, respectively. Our study showed that the intensity of snowfall events during the summer-monsoon is among the most important drivers responsible for glacier-wide mass balance evolution of Chhota Shigri Glacier. However, due to the lack of precipitation measurements and the strong precipitation gradient in this region, the distribution of precipitation on the glacier remains unknown and needs further detailed investigations

In this PhD Thesis are reported the main results from an interdisciplinary research focused on evaluating impacts and effects of black carbon (BC) on glacier snow and ice melting. With this purpose we selected two glaciers: the Changri Nup glacier (Nepal, Himalaya) and the Forni glacier (Italian Alps). The glaciers have been chosen due to their representativity (geographical setting, size, morphology) and the availability of meteorological and energy data collected at the glacier surface through Automatic Weather Stations (AWSs). In fact on both the glaciers AWSs have been installed in the recent years and they have been running without meaningful interruptions thus permitting to analyze glacier micrometeorology and to evaluate glacier surface energy balance and its variability (data are sampled with a hourly frequency all over the year). Moreover we planned and performed field campaigns to collect snow samples for describing chemical and physical features of soot and dust present in the glacier snow. More precisely, since the Autumn 2005 and AWS has been running at the melting surface of the Forni Glacier (Italian Alps). The AWS is property of UNIMI and it attends the international network SHARE (Stations at High Altitude for Research on the Environment) promoted and managed by EVK2CNR Committee. Within the Ev-K2-CNR Project SHARE on February 2010 an AWS has been installed on the debris-free surface of the Changri Nup Glacier (Nepal, Himalayas, Sagarmatha Nationa Park) at 5,700 m asl to acquire meteorological data and energy fluxes (incoming and outgoing) at the glacier surface. The AWS is property of EvK2CNR Committee. The acquired data permit the calculation of glacier energy balance and high resolution analysis of glacier albedo. In the present study more than 85.000 meteorological parameters, related to the time window 2010-2012 and collected by The Changri Nup AWS, have been analyzed, processed and validated. Average daily parameters estimated at glacier surface have been: temperature: -4.61 °C, relative humidity: 78.47%, atmospheric pressure: 505.6 hPa, SWin: 220 W m-2, SWout:136 W m-2, LWin: 240 W m-2, LWout: 280 W m-2, wind speed: 1.48 m s-1, prevalent wind direction: 183°. Yearly albedo, deriving from SWout/SWin was 0.7, with an average of 0.75 for snow and 0.26 for glacier ice. Instead data from Forni AWS were already available thanks to another PhD research presently on line at the University of Milan. Ablation season at the Changri Nup glacier occurred in summer period, in the monsoon season, when the temperature conditions (T>0°C) and radiation and rain precipitation increase the melting process. Results have been compared with the Alpine site of Forni glacier, the largest Italian valley glacier, located in the Stelvio National Park and characterized by a “strategic” location on the Central-Eastern Alpine sector, able to be reached by southern fluxes and close to the northern Alpine Italian boundary. This part of the research was performed within the SHARE STELVIO project aiming at detecting and quantifying climate change evidences and effects on a sensible area located in the Stelvio National Park – Lombardy sector (600 km2 of area). This project will permit to evaluate composition, quality and variability of high elevation atmosphere and effects on the alpine water resource (i.e. snow, glaciers and meltwater rivers). In both sites the main component deterring melting are positive temperature and shortwave radiation, this latter higher in the Himalaya due to the difference of latitude, altitude and incident direction. Melting season in the Alps is longer than in the Himalaya and in both sites the effect of latent and sensible heat fluxes have a minor effect in driving melting processes. Both sites are characterized by a typical katabatic wind regime. At the Changri Nup glacier surface some ablation stakes have been positioned in the debris free part of the glacier and two of these stakes were located nearby the AWS. Glacier ablation was evaluated through field campaigns twice: February-May 2010 and May-November 2012. The field data allowed to compare measured glacier ablation with melting amount derived from energy balance measurements and to evaluate the reliability of our computations. It was found by previous authors that absorbing aerosols and dust play a key role in varying snow and ice albedo and in driving glacier ablation on several high elevation glaciers. In this study, by coupling energy data (from the AWS) with the atmospheric measurement of BC concentration allow the investigation of the relations among atmosphere and cryosphere and to quantify impacts of atmospheric black carbon deposition on glacial ablation rates. In Himalaya atmospheric observations are carried out at the Nepal Climate Observatory-Pyramid (NCO-P) located at 5,079 m asl near the Pyramid Laboratory Observatory, while at Forni glacier a summer campaign has been held in 2012 at Guasti Hut (c. 3200 m asl). Results at Changri Nup glacier were consistent with the typical estimation available in literature of BC deposition and % of albedo reduction in premonsoon season, where the atmospheric concentration are high. Experimental results reports that at Changri Nup the % of albedo reduction has been 4.26% for an estimated BC deposition in snow of 49 µg kg-1 consistent with the concentration range of BCC in snow of 26.0–68.2 μg kg−1 due to snow density variations between 195–512 kg m−3 as reported in literature. The same estimation has been done at Forni Glacier too, but results were different because the summer BC monitoring campaign detected BC concentrations in the atmosphere typical of free troposphere background conditions, thus in the analyzed period, their deposition didn’t have a predominant effect in driving melting process. To compare the estimated BC deposition in snow deriving from atmospheric measurements, snow samples has been done at the Changri Nup glaciers and the chemical analysis allow to determine a typical premonsoon concentration consistent with literature data and with the experimental estimation done at Changri Nup glaciers. Future step will foresee a further analysis of these results, thanks also to the availability of long term dataset, moreover, in order to improve the knowledge of the effect of dust and aerosol deposition on glacier, more samples will be collected and analyzed.

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning; and, (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 195-203).
Among the existing and projected impacts of climate change, impacts on water resources are expected to exacerbate the current and future threat of global water scarcity. Glacier-dependent societies are especially vulnerable to water scarcity due to the more pronounced effects of climate change on glacial systems that govern the water availability of these societies. In this thesis, water scarcity is examined as an impact of climate change in Dharamshala and Leh, two glacier-dependent towns of northern India, while recognizing that climate change is not the only factor causing depletion of water resources in these towns. In order to show the linkage between climate change and water scarcity, evidence is presented on changes occurring in the towns' local climate parameters such as snowfall, rainfall and temperature, as well as changes in the hydrology of the water bodies that make water available to these towns. This establishes that water scarcity in these towns has been induced not only by increasing demand, but also by decreasing supply of water. In light of the water scarcity facing these towns, an investigation of the measures taken by their local governments to address this issue is presented, which reveals that the primary adaptive response employed in both towns has been supply augmentation. The driver behind this response has been the pursuit of economic development to improve the standard of living of Dharamshala and Leh's constituents. It is argued that economic development as a driver has not been effective in inducing holistic adaptive responses to water scarcity. Additionally, climate change considerations have been largely absent in the policy/planning processes that govern water management in both towns, implying that the responses of Dharamshala and Leh to water scarcity have been influenced by the pursuit of short-term economic benefits in a local economy that fails to recognize the importance of the integrity of water resources to its sustenance. The perpetuation of unsustainable economic development and failure to account for climate change impacts in local water management points to the presence of several technological, structural, financial, and political barriers to the planning/implementation of holistic climate-centric strategies for adaptation to water scarcity in Dharamshala and Leh. Therefore, in the concluding part of this thesis, recommendations are offered to enable the local governments of Dharamshala and Leh to overcome these barriers.
by Amruta Anand Sudhalkar.
M.Eng.
M.C.P.

Mt. Everest region in the central Himalaya is one of the most heavily glacierized parts of the Himalaya that is characterized by large debris-covered glaciers and many glacial lakes. The glaciers and ice are important sources of fresh water and play vital role in modulating the climate and the hydrological process. Previous studies from different parts of the Himalaya and around the world have revealed climate change at regional and global-scale and in general, shrinking of glaciers and ice caps. Climate change is thus, expected to impact in many ways to Cryosphere, hydrological process, and human livelihood. Temperature is often suggested to be increasing and considered as the main driver of change, however, in the higher elevations where the glaciers exist, climatic data are rarely available and limiting the climate related interpretation. This study is therefore conducted with the aim of linking variation of glaciers, glacial lakes, and river flow to local climatic trends in the higher elevations of Mt. Everest region. The study uses a comprehensive multi-temporal data from different sources: satellite observations, ground hydro-meteorological stations, and regular gridded and reanalysis climate data from the regional and global products (1960s to 2013). First, using the weather data from ground stations, gridded, and reanalysis products, the climatic trends and climate variability are evaluated. From 1979 to 2013, temperature has increased by 0.052 °C a-1, while the precipitation has shown an increasing tendency in 1960s to early 1990s and significantly decreasing afterward. During 1994–2013 period, at an elevation of ~ 5000 m, minimum temperature (0.072 ± 0.011 °C a-1) has increased more than maximum temperature (0.009 ± 0.012 °C a-1), with an average temperature increase of 0.044 ± 0.008 °C a-1 in the last two decades. The increases in the temperature are observed during the pre- and post-monsoon months, favouring melting ice close to the glacier terminus. At the same elevation, precipitation has significantly decreased (-9.3 ± 1.8 mm a-1) for all months, corresponding to a loss of 47 % during the monsoon. Second, the glacier changes are studied within the Sagarmatha (Mt. Everest) National Park (SNP; glacier area: ~ 400 km2) between 1962 and 2011, using multi-temporal optical satellite imagery, assisted by topographic maps. During the period, glaciers have experienced a surface area loss of 13.0 ± 3.1 %, an average terminus retreat of 403 ± 9 m, a Snow-Line Altitude (SLA) upward shifting of 182 ± 22 m, and an increasing of debris- covered area by 17.6 ± 3.1 %. An accelerated rate of glacier shrinkage is observed after the 1990s, which is caused not only due to increased temperature, but also as a result of a significant decreasing precipitation over the last decades. Moreover, selected glaciers have indicated a significant decreasing glacier flow velocities from the 1990s to recent year and a significant loss of glacier thickness (0.73 ± 0.63 m a-1) in the last decade. Third, a complete mapping and characterization of a total of 624 glacial lakes with surface area of 7.43 km2 (±18 %) are conducted in the SNP, with particular focus on conditions related to the formation of lakes using 2008 satellite imagery. Further, evolutions of glacial lakes are examined using the satellite imagery and topographic maps between 1963 and 2013. Three types of glacial lakes (supra, pro, and unconnected) present in the SNP have their distinctive potential to explain the glaciological and climatic conditions. Results show that the slope of the glacier where lakes are located influence the supraglacial lake formation. Furthermore, the slope to glacier upstream favours the formation of the supraglacial lakes, as a boundary condition. The formation of proglacial lakes is related to the growing and coalescing of the supraglacial lakes. The unconnected lakes are evaluated as a useful indicator of precipitation trend. During the study period (1960s–2011), both number and surface area of supraglacial lakes has continuously increased (number +109.7 %; area +13.3 %) with an accelerated rate in the last decade due to increase in the glacier melting. Proglacial lakes are more or less constant in both numbers and size, except Imja Lake that have exceptionally increased, while the surface area of unconnected lakes has increased from 1960s–1990s (+4.3 %) and decreased from early 1990s afterward (-10.9 %). The thesis has shown that the accelerated rate of glacier shrinkage and the decreasing of the unconnected lakes in the last decades are associated to decreasing precipitation. Supraglacial lakes behaviour confirms the acceleration of the negative mass balance of glaciers due to the reduced ice velocities caused by decreased precipitation. Finally, the hydrological dynamics of the Dudh Koshi river examined by stochastic frequency analysis, physically-based hydrological models, and multilinear regression using river discharge data and climate data. The analysis suggests that the Dudh Koshi river discharge is mainly dependent on precipitation from 1960s to 2000s, however a non-stationarity in the river discharge is observed since the early 2000s, indicating increased discharge, not justifiable by the observed weakening monsoon. The study concludes by underlining that an accelerated glacier melting as observed through the glacier change analysis affects an increasing of the discharge.

L'économie du Pakistan, fondée sur l'agriculture, est hautement dépendante de l'approvisionnement en eau issu de la fonte de la neige et des glaciers du Haut Bassin de l'Indus (UIB) qui s'étend sur les chaînes de l'Himalaya, du Karakoram et de l'Hindukush. Il est par conséquent essentiel pour la gestion des ressources en eau d'appréhender la dynamique de la cryosphère (neige et glace), ainsi que les régimes hydrologiques de cette région dans le contexte de scénarios de changement climatique. La base de données satellitaire du produit de couverture neigeuse MODIS MOD10A2 a été utilisée de mars 2000 à décembre 2009 pour analyser la dynamique du couvert neigeux de l'UIB. Les données journalières de débits à 13 stations hydrométriques et de précipitation et température à 18 postes météorologiques ont été exploitées sur des périodes variables selon les stations pour étudier le régime hydro-climatique de la région. Les analyses satellitaires de la couverture neigeuse et glaciaire suggèrent une très légère extension de la cryosphère au cours de la dernière décade (2000‒2009) en contradiction avec la rapide fonte des glaciers observée dans la plupart des régions du monde. Le modèle « Snowmelt Runoff » (SRM), associé aux produits neige du capteur MODIS a été utilisé avec succès pour simuler les débits journaliers et étudier les impacts du changement climatique sur ces débits dans les sous-bassins à contribution nivo-glaciaire de l'UIB. L'application de SRM pour différents scénarios futurs de changement climatique indique un doublement des débits pour le milieu du siècle actuel. La variation des écoulement de l'UIB, la capacité décroissante des réservoirs existants (barrage de Tarbela) à cause de la sédimentation, ainsi que la demande croissante pour les différents usages de l'eau, laissent penser que de nouveaux réservoirs sont à envisager pour stocker les écoulements d'été et répondre aux nécessités de l'irrigation, de la production hydro-électrique, de la prévention des crues et de l'alimentation en eau domestique
Agriculture 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

L’altération chimique et l’érosion physique de la croûte continentale mobilisent de grandes quantités de matière sous formes solide et dissoute. Première productrice de sédiments sur le globe, la chaîne Himalayenne délivre ~1 Gt/a de sédiments aux océans. L'importance des différents facteurs qui contrôlent les flux érodés et celle des processus d’érosion (glaciers, glissements de terrain, sols) sont pourtant encore mal définies. Il en va ainsi des facteurs climatiques, en particulier de leur impact au cours des transitions climatiques. Afin de répondre à ces questions, ce travail s’attache à comparer la composition géochimique des produits de l’érosion à celles des sédiments actuels de rivière et des archives sédimentaires de la plaine du Gange. Un premier bilan des processus d’érosion a été établi petite échelle dans le bassin Haut-Himalayan de la Khudi. L’érosion actuelle conséquente de ce bassin de ~3mm/a se produit lors de la mousson, correspond pour l'essentiel à l’érosion des sols et surtout à l'intense activité d'une zone de glissement de terrain. Grâce au développement d'une nouvelle méthode de destruction de la matière organique, la mesure de l’hydratation des silicates a pu être utilisée comme traceur inédit des sols. Sur cette base, l’inversion des compositions des sédiments de la rivière démontre que l’érosion physique est dominée à ~80% par le glissement de terrain, l’érosion de sols étant mineure et comparable aux taux d’érosion des autres bassins alentours. L’érosion chimique qui conduit à un flux d'éléments dissous de 7.9 kt/a (soit une érosion équivalente de 0.02 mm/a) semble dériver de l’altération profonde du substrat rocheux. Néanmoins les flux d'éléments dissous dessinent également une relation marquée avec les flux particulaires durant la mousson, suggérant une altération additionnelle des sédiments au cours du transport fluvial. Une approche similaire a ensuite été menée à l’échelle plus vaste du bassin de la Narayani drainant l’ensemble du Népal central. Grâce à des mesures de courant par ADCP combinées à l’échantillonnage de sédiments en profondeur, un modèle de transport sédimentaire a été utilisé pour intégrer les flux sédimentaires en profondeur et ainsi réviser le taux d’érosion moyen sur le bassin versant à une valeur de ~1.7 mm/a, proche des taux d'érosion long-terme. Un système géochimique associant la mesure du δD des silicates associée aux concentrations en carbonate s’est révélé un traceur diagnostique de l’érosion glaciaire dans le Nord du bassin, tandis que la teneur en matière organique du sédiment a pu être utilisée comme traceur des sols. L’analyse temporelle des flux de sédiments, de leur composition et du signal granulométrique, a ainsi permis d’établir que seule une faible fraction des sédiments (<20%) provenait de l’érosion par les glaciers et les sols. À l'échelle du Népal central, l’érosion physique semble donc également dominée par les glissements déclenchés lors de la période de mousson. Le grand cône alluvial de la Narayani-Gandak, situé au débouché de cette rivière dans la plaine du Ganges, a enregistré l’histoire récente de l’érosion du Népal central. Trois forages réalisés dans ce méga-cône permettent ainsi d'étudier l'évolution de l'altération et de l'érosion en Himalaya au cours du tardi-Pléistocène. Ces dépôts sédimentaires révèlent une étonnante stabilité depuis ~45 ka de la géochimie, des provenances et du degré d’altération des sédiments. Seule l’intensité de l’érosion mesurée par isotopes cosmogéniques semble augmenter au cours de l’Holocène. Par contraste, l’évolution très récente de la distribution de l’érosion dans la chaîne est marquée par un accroissement (x3) de la proportion de matériel des régions basses et plus peuplées de l'Himalaya, montrant que les activités anthropiques, via notamment une forte croissance du réseau routier durant la dernière décennie, [...]
Chemical weathering and physical erosion of the continental crust mobilise huge amounts of both solid and dissolved material. As the first sediment generator on the Earth, the Himalayan range releases around 1 Gt/y of sediment into the ocean. The relative influence of the different factors that control the eroded fluxes and the importance of the erosion processes (such as landslides, glaciers, soils) are as yet poorly understood. The same is true of the climatic factors, especially regarding their impact during climatic transition periods. In order to address those questions, this work focuses on comparing the geochemical composition of erosion products to the composition of present river sediment and of sedimentary records in the Ganga Plain. A first budget of the erosion processes was done on a small scale in the Khudi catchment of Higher Himalaya. The total present-day erosion is considerable, at around 3 mm/y and takes place during the monsoon. It is mainly linked to the soils erosion and more importantly to the intense activity of a landsliding area. The development of a new method for the destruction of organic matter enabled the use of silicates hydration as a tracer for soils. Based on this method, a mathematical inversion of the sediment compositions was performed. It highlights that the landslide is responsible for ~80% of the overall physical erosion. The soil erosion is minor and is comparable to the erosion rates measured in the neighbouring catchments. The chemical erosion leads to a dissolved flux of 7.9 kt/y (corresponding to an erosion rate of 0.02mm/y) and seems to come from the bedrock deep weathering. Nevertheless, the dissolved fluxes also appear to be linked with the particles fluxes during the monsoon. This suggests an additional weathering of the sediment during the fluvial transport. A similar approach was used on a larger scale in the Narayani catchment that drains the whole of Central Nepal. Through ADCP-based current measurements combined with deep sediment sampling, a model for sedimentary transport was used to integrate the deep sediment fluxes. The average catchment-scale erosion rate was then corrected to a value of ~1.7 mm/y, close to the long-term erosion rates. A geochemical system that combines the measurement of the δD of silicates and the concentrations of carbonates was found to be a diagnosis tracer for glacial erosion in the northern part of the catchment. The organic matter ratio was used as a tracer for soils. The temporal analysis of sediment fluxes, as well as the sediment composition and granulometry showed that only a small fraction (< 20%) of the sediment comes from glacial and soils erosion. Over the whole Central Nepal, the physical erosion seems also to be dominated by the landslides that are triggered during the monsoon. The large Narayani-Gandak alluvial fan is located at the river mouth and can be used as a record of the recent history of Central Nepal erosion. Three drillings were done in this fan to enable the study of the evolution of Himalayan weathering and erosion during the Late Pleistocene. The sedimentary deposits display a surprising stability in their geochemistry, their sources and their weathering stage for the last ~45 ky. The erosion intensity derived from cosmogenic nuclides is the only feature that seems to have risen during Holocene. However, the very recent evolution of the erosion distribution in the range is characterised by an increase (x3) of the proportion of products coming from the lower, more densely populated areas. This shows that the anthropogenic activities have had a larger impact on the erosion than the last Pleistocene-Holocene transition, especially through the rapid growth of the road network during the last decade

京都大学
新制・課程博士
博士(工学)
甲第23429号
工博第4884号
新制||工||1763(附属図書館)
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授 田中 茂信, 准教授 田中 賢治, 准教授 佐山 敬洋
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM

La présente thèse est une étude ethnographique qui examine le savoir en tant que pratique située au Ladakh, dans l’Himalaya indien. Elle analyse les implications socioculturelles des deux moteurs de changement en jeu au Ladakh: l’un est d'origine socio-économique et lié à la production du Ladakh en tant que zone frontalière, tandis que l’autre est de nature environnementale et entrainé par les changements climatiques. Alors que le Ladakh est demeuré hors de la portée de l’État bureaucratique pendant l’administration coloniale britannique, la région s’est trouvée reconfigurée en zone frontalière stratégique après l’indépendance de l’Inde des suites des guerres successives avec le Pakistan et la Chine. L’Indépendance a mené à la partition de l’Inde et du Pakistan en 1947; cette thèse examine la portée à long terme des évènements traumatisants de la partition tels qu’ils se sont déroulés au Ladakh et comment les Ladakhis établissent des liens entre ces évènements et les changements climatiques. L’État indien s’est produit dans la région à travers une volonté de dominer les montagnes, principalement par le développement d’infrastructures et par l’intégration du savoir local des Ladakhis dans l’appareil militaire. La militarisation a restructuré l'économie du Ladakh, redéfini la structure des ménages, contribué à l’exode rural, déplacé la centralité des activités agropastorales et, tel que la dissertation le soutient, altéré de manière significative la connexion de la population locale avec l'environnement. La rationalisation croissante de la perspective sur l’environnement aujourd'hui contribue à la fragmentation des liens qui unissent les domaines naturels et humains dans la cosmologie locale de même qu’à l'abandon des pratiques rituelles connexes. Parallèlement, la région est touchée par des effets distincts des changements climatiques, en particulier la récession des glaciers. La thèse juxtapose l'expérience subjective de ces vastes changements dans la vie quotidienne des villageois de la Vallée de Sham avec les faits historiques environnementaux, démontrant ainsi que les événements historiques locaux influent sur les perceptions des changements environnementaux. L'analyse démontre qu’un phénomène objectif tel que la récession des glaciers est interprété à travers des réalités locales. Plus précisément, selon la conception du monde locale, un glacier en retrait est une figure rhétorique d’une transformation de la condition humaine. Comme le fait valoir la dissertation, l’interprétation culturelle ne constitue pas un obstacle à l'objectivité de l'histoire naturelle de la cosmologie locale. L’interprétation culturelle et l'expérience empirique s’avèrent par ailleurs essentielles à la vitalité des connaissances locales sur l'environnement et à la performance des pratiques associées.
The dissertation presents an ethnographic study that examines knowledge as a situated practice in Ladakh, in the Indian Himalayas. It analyzes the sociocultural implications of two drivers of change at play in Ladakh: one is of socioeconomic origin and linked to the production of Ladakh as a border area, while the other is environmental and driven by climate change. Ladakh, which remained outside the scope of the bureaucratic state during the British colonial administration, found itself refashioned into a strategic border area following India’s independence and successive wars with Pakistan and China. Independence led to the partition of Indian into India and Pakistan in 1947; the dissertation examines the long-term, traumatic events of the partition in Ladakh, tracing connections to current perceptions of climate change. The independent Indian state has produced itself in the region through the taming of its mountains, primarily through infrastructure development and the co-optation of Ladakhi knowledge of the environment by the military apparatus. Far-reaching militarization has restructured Ladakh’s economy, consequently redefining household structure, contributing to village depopulation, displacing the centrality of agro-pastoralist activities and, as the dissertation argues, significantly altering the local population’s engagement with the environment. The increasing rationalization of the outlook on the environment today contributes to the fragmentation of links between the natural and human realms within the local cosmology and the abandonment of related ritual practices. Concurrently, the region is impacted by distinct effects of climate change, in particular glacier recession. The dissertation juxtaposes both the subjective experience of wide-ranging environmental changes and changes in everyday village life with historical facts, showing that local historical events influence perceptions of glacier recession and the depletion of natural resources. The analysis demonstrates that objective phenomena such as glacier recession are interpreted through local realities. Specifically, in the local worldview, a vanishing glacier is a trope for changes in the human condition. Yet, as the dissertation further argues, such cultural framing does not preclude the objectivity of natural history in local cosmology. Moreover, cultural framing and empirical experience, therefore, are shown to be essential to the vitality of local knowledge about the environment and to the performance of associated landscape practices.

High-resolution regional climate simulations of the Karakoram, Himalaya have been performed for investigation into the atmospheric dynamics in this region, and their role in the Karakorams snowfall accumulation and glacial evolution. It has been seen through a combination of field measurements and satellite observations that a large number of glaciers in this region are static or advancing whilst other glaciers in the central and eastern Himalaya, as well as around the world, are nearly all retreating. By performing time slice calculations for the Karakoram region through the 21st century, it is found that, despite region wide simulated temperature changes, the highly elevated regions of the Karakoram mountain range experience positive snow mass balance through the 21st century. This result arises from a strong positive correlation between snow mass balance and simulated increases in regional precipitation, which outweighs the negative correlation between snow mass balance and simulated increases in temperature.
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