Integrating glacier dynamics into hydrological modelling: A climate change impact assessment of the data-scarce headwaters of the Tarim River, Central Asia

This thesis addresses the complexities of conducting hydrological climate change impact assessments in mountainous, highly glacierised catchments by developing and validating a glacier dynamics module for the hydrological model SWIM. It provides the first integrated climate change impact assessment for the five headwaters of the Tarim River, NW China/Kyrgyzstan, Central Asia, overcoming the region’s severe data-scarcity. The region’s heterogeneity and limited data availability is characterised, with a focus on the quality of precipitation datasets. After using the original SWIM model for an analysis of observed glacial lake outburst floods and highlighting the model’s insufficiencies for long-term assessments, a new glacier dynamics model of intermediate complexity is developed, bridging catchment and glacier scales. This new model implements all major glacier processes, including ice movement, avalanching, sublimation and sub-debris melting. It is validated in one of the data-scarce Tarim River headwater catchments as well as the data-abundant Upper Rhone catchment, Switzerland. The model is then implemented in all five Tarim headwaters and calibrated to discharge, glacier hypsometry and mass balance, using an automatic multi-objective approach. The model provides a correction of the high mountain precipitation, a driving variable shown to be highly uncertain. It is then used to assess three IPCC climate change scenarios for the 21st century using an ensemble of eight global and one regional climate model. Impacts on glacier area and volume as well as discharge are explored, including their climate model and calibration parameter uncertainties. Results show current catchment precipitation to be 1.4–4.3 times greater than observation datasets suggest, a finding in-line with climate model simulations and remote sensing based datasets. Under a generally warmer and wetter climate, glacier cover is expected to recede and discharge may experience large increases as a consequence, especially in the near future. Uncertainties are large, however, mainly owing to climate model variability

Inventory of Glaciers in the Shaksgam Valley of the Chinese Karakoram Mountains, 1970–2014

The Shaksgam Valley, located on the north side of the Karakoram Mountains of western China, is situated in the transition zone between the Indian monsoon system and dry arid climate zones. Previous studies have reported abnormal behaviors of the glaciers in this region compared to the global trend of glacier retreat, so the region is of special interest for glacier-climatological studies. For this purpose, long-term monitoring of glaciers in this region is necessary to obtain a better understanding of the relationships between glacier changes and local climate variations. However, accurate historical and up-to-date glacier inventory data for the region are currently unavailable. For this reason, this study conducted glacier inventories for the years 1970, 1980, 1990, 2000 and 2014 (i.e., a ~10-year interval) using multi-temporal remote sensing imagery. The remote sensing data used included Corona KH-4A/B (1965–1971), Hexagon KH-9 (1980), Landsat Thematic Mapper (TM) (1990/1993), Landsat Enhanced Thematic Mapper Plus (ETM+) (2000/2001), and Landsat Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) (2014/2015) multispectral satellite images, as well as digital elevation models (DEMs) from the Shuttle Radar Topography Mission (SRTM), DEMs generated from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images (2005–2014), and Advanced Land Observing Satellite (ALOS) World 3D 30 m mesh (AW3D30). In the year 2014, a total of 173 glaciers (including 121 debris-free glaciers) (>0.5 km2), covering an area of 1478 ± 34 km2 (area of debris-free glaciers: 295 ± 7 km2) were mapped. The multi-temporal glacier inventory results indicated that total glacier area change between 1970–2014 was not significant. However, individual glacier changes showed significant variability. Comparisons of the changes in glacier terminus position indicated that 55 (32 debris-covered) glaciers experienced significant advances (~40–1400 m) between 1970–2014, and 74 (32 debris-covered) glaciers experienced significant advances (~40–1400 m) during the most recent period (2000–2014). Notably, small glaciers showed higher sensitivity to climate changes, and the glaciers located in the western part of the study site were exhibiting glacier area expansion compared to other parts of the Shaksgam Valley. Finally, regression analyses indicated that topographic parameters were not the main driver of glacier changes. On the contrary, local climate variability could explain the complex behavior of glaciers in this region