Advancing Applications of Synthetic Aperture Radar for Cryosphere Studies in Alpine Regions

Abstract

The cryosphere is a crucial component of Earth's climate system, influencing global climate patterns, sea-level rise, and freshwater availability. Within this system, the alpine cryosphere is especially important due to its sensitivity to climatic changes and their substantial impact on regional hydrology, ecosystems, and natural hazard dynamics. The accurate monitoring and assessment of alpine cryosphere presents significant challenges, primarily due to the complexity of the terrain and the variability of the environmental conditions. This dissertation aims to address these challenges by advancing synthetic aperture radar (SAR) methodologies to enhance the understandings about cryosphere processes. Particularly, the application of SAR in three essential cryosphere research areas were investigated, including glacier dynamics monitoring, snowmelt mapping, and glacier mass balance assessments. The studies were conducted in various alpine regions, including the Swiss Alps and the Karakoram, utilizing high-resolution SAR data from multiple satellite missions. The first study developed a novel cross-correlation stacking method to improve offset tracking for measuring glacier surface displacements. By leveraging temporal redundancy in SAR image series, the method significantly reduced noise interference and improved the accuracy and coverage of dis- placement estimations. The method was successfully applied and validated on the Aletsch Glacier in the Swiss Alps, demonstrating broad applicability and enhanced performance across different SAR sensors. The second study proposed an integrated framework combining SAR data with topographic information to accurately map seasonal snow melting in mountainous regions. The adaptive integration of SAR-based wet snow detection and terrain corrections significantly improved mapping accuracy compared to conventional methods. Applied in the Karakoram region, this approach provided valuable insights into snowmelt dynamics, aiding water resource management and climate adaptation strategies. The third study developed a comprehensive framework leveraging digital elevation models (DEMs) derived from the high-resolution TanDEM-X SAR data to assess the elevation and mass changes of glaciers in the Karakoram region. The proposed framework effectively integrated InSAR DEM generation, elevation change mapping and mass balance estimation, providing a scalable and robust approach for glacier mass balance assessments. The study revealed the updated mass balance of glaciers in Karakoram and detailed the spatial distribution of glacier elevation changes, contributing to a better understanding of glacier dynamics in this region. Collectively, these studies demonstrated the substantial potential of advanced SAR techniques to address challenges in alpine cryosphere research, offering scalable and accurate tools essential for climate resilience, sustainable water management, and environmental monitoring.