One Decade of Glacier Mass Changes on the Tibetan Plateau Derived from Multisensoral Remote Sensing Data

The Tibetan Plateau (TP) with an average altitude of 4,500 meters above sea level is characterized by many glaciers and ice caps. Glaciers are a natural indicator for climate variability in this high mountain environment where meteorological stations are rare or non-existent. In addition, the melt water released from the Tibetan glaciers is feeding the headwaters of the major Asian river systems and contributes to the rising levels of endorheic lakes on the plateau. As many people directly rely on the glacier melt water a continuous glacier monitoring program is necessary in this region. In situ measurements of glaciers are important, but are spatial limited due to large logistical efforts, physical constrains and high costs. Remote sensing techniques can overcome this gap and are suitable to complement in situ measurements on a larger scale. In the last decade several remote sensing studies dealt with areal changes of glaciers on the TP. However, glacier area changes only provide a delayed signal to a changing climate and the amount of melt water released from the glaciers cannot be quantified. Therefore it is important to measure the glacier mass balance. In order to estimate glacier mass balances and their spatial differences on the TP, several remote sensing techniques and sensors were synthesized in this thesis. In a first study data from the Ice Cloud and Elevation Satellite (ICESat) mission were employed. ICESat was in orbit between 2003 and 2009 and carried a laser altimeter which recorded highly accurate surface elevation measurements. As in mid-latitudes these measurements are rather sparse glaciers on the TP were grouped into eight climatological homogeneous sub-regions in order to perform a statistical sound analysis of glacier elevation changes. To assess surface elevation changes of a single mountain glacier from ICESat data, an adequate spatial sampling of ICESat measurements need to be present. This is the case for the Grosser Aletschgletscher, located in the Swiss Alps which served as a test site in this thesis. In another study data from the current TanDEM-X satellite mission and from the Shuttle Radar Topography Mission (SRTM) conducted in February 2000 were employed to calculate glacier elevation changes. In a co-authored study, these estimates could be compared with glacier elevation changes obtained from the current French Pléiades satellite mission. In order to calculate glacier mass balances, the derived elevation changes were combined with assumptions about glacier area and ice density in all studies. In this thesis contrasting patterns of glacier mass changes were found on the TP. With an ICESat derived estimate of -15.6±10.1 Gt/a between 2003 and 2009 the average glacier mass balance on the TP was clearly negative. However, some glaciers in the central and north-western part of the TP showed a neutral mass balance or a slightly positive anomaly which was also confirmed by data from the current TanDEM-X satellite mission. A possible explanation of this anomaly in mass balance could be a compensation of the temperature driven glacier melt due to an increase in precipitation

Characterising the evolution of Himalayan debris covered 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

Quantifying Himalayan glacier change from the 1960s to early 2000s, using corona, glims and aster geospatial Data

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

COUPLING GLACIO-HYDROLOGICAL RESPONSE TO CLIMATE VARIABILITY IN MT EVEREST REGION IN CENTRAL HIMALAYA

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 \ub0C a-1, while the precipitation has shown an increasing tendency in 1960s to early 1990s and significantly decreasing afterward. During 1994\u20132013 period, at an elevation of ~ 5000 m, minimum temperature (0.072 \ub1 0.011 \ub0C a-1) has increased more than maximum temperature (0.009 \ub1 0.012 \ub0C a-1), with an average temperature increase of 0.044 \ub1 0.008 \ub0C 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 \ub1 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 \ub1 3.1 %, an average terminus retreat of 403 \ub1 9 m, a Snow-Line Altitude (SLA) upward shifting of 182 \ub1 22 m, and an increasing of debris- covered area by 17.6 \ub1 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 \ub1 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 (\ub118 %) 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\u20132011), 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\u20131990s (+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

The Hindu Kush Himalaya Assessment

This open access volume is the first comprehensive assessment of the Hindu Kush Himalaya (HKH) region. It comprises important scientific research on the social, economic, and environmental pillars of sustainable mountain development and will serve as a basis for evidence-based decision-making to safeguard the environment and advance people’s well-being. The compiled content is based on the collective knowledge of over 300 leading researchers, experts and policymakers, brought together by the Hindu Kush Himalayan Monitoring and Assessment Programme (HIMAP) under the coordination of the International Centre for Integrated Mountain Development (ICIMOD). This assessment was conducted between 2013 and 2017 as the first of a series of monitoring and assessment reports, under the guidance of the HIMAP Steering Committee: Eklabya Sharma (ICIMOD), Atiq Raman (Bangladesh), Yuba Raj Khatiwada (Nepal), Linxiu Zhang (China), Surendra Pratap Singh (India), Tandong Yao (China) and David Molden (ICIMOD and Chair of the HIMAP SC). This First HKH Assessment Report consists of 16 chapters, which comprehensively assess the current state of knowledge of the HKH region, increase the understanding of various drivers of change and their impacts, address critical data gaps and develop a set of evidence-based and actionable policy solutions and recommendations. These are linked to nine mountain priorities for the mountains and people of the HKH consistent with the Sustainable Development Goals. This book is a must-read for policy makers, academics and students interested in this important region and an essentially important resource for contributors to global assessments such as the IPCC reports. ; Constitutes the first comprehensive assessment of the Hindu Kush Himalaya region, providing an authoritative overview of the region Assembles the collective knowledge of over 300 leading researchers, practitioners, experts, and policymakers Combines the current state of knowledge of the Hindu Kush Himalaya region in one volume Offers Open Access to a set of practically oriented policy recommendation

The Hindu Kush Himalaya Assessment

This open access volume is the first comprehensive assessment of the Hindu Kush Himalaya (HKH) region. It comprises important scientific research on the social, economic, and environmental pillars of sustainable mountain development and will serve as a basis for evidence-based decision-making to safeguard the environment and advance people’s well-being. The compiled content is based on the collective knowledge of over 300 leading researchers, experts and policymakers, brought together by the Hindu Kush Himalayan Monitoring and Assessment Programme (HIMAP) under the coordination of the International Centre for Integrated Mountain Development (ICIMOD). This assessment was conducted between 2013 and 2017 as the first of a series of monitoring and assessment reports, under the guidance of the HIMAP Steering Committee: Eklabya Sharma (ICIMOD), Atiq Raman (Bangladesh), Yuba Raj Khatiwada (Nepal), Linxiu Zhang (China), Surendra Pratap Singh (India), Tandong Yao (China) and David Molden (ICIMOD and Chair of the HIMAP SC). This First HKH Assessment Report consists of 16 chapters, which comprehensively assess the current state of knowledge of the HKH region, increase the understanding of various drivers of change and their impacts, address critical data gaps and develop a set of evidence-based and actionable policy solutions and recommendations. These are linked to nine mountain priorities for the mountains and people of the HKH consistent with the Sustainable Development Goals. This book is a must-read for policy makers, academics and students interested in this important region and an essentially important resource for contributors to global assessments such as the IPCC reports. ; Constitutes the first comprehensive assessment of the Hindu Kush Himalaya region, providing an authoritative overview of the region Assembles the collective knowledge of over 300 leading researchers, practitioners, experts, and policymakers Combines the current state of knowledge of the Hindu Kush Himalaya region in one volume Offers Open Access to a set of practically oriented policy recommendation