The change of glacier surface elevation in Karakoram holds significant relevance to the study of global climate change and regional water resource management. In this work, we focused on understanding glacier dynamics in the Karakoram region through the analysis of Digital Elevation Models (DEMs) generated from a comprehensive 481 TanDEM-X CoSSC products spanning 2011 to 2020. An iterative approach based on the residual phase with respect to the reference DEM was employed to generate high resolution DEMs. The systematic approach offered a robust methodology for extracting precise glacier elevation changes in the Karakoram with high temporal and spatial resolution, provided valuable insights into the understanding of complex glacier dynamics.

This study investigates the potential of space-borne Synthetic Aperture Radar Interferometry for efficient detection of track anomalies using the Swiss Federal Railways (SBB) railway network as an example. The condition of the ballast substructure is crucial for track service life, and moisture accumulation is a primary cause of deterioration and can manifest itself by subsidence. Current operational methods for track condition assessment have limitations, and remote sensing techniques offer a promising alternative. Using a time-series of TerraSAR-X observations, we performed a persistent scatterer interferometry (PSI) analysis to estimate surface deformations and further analysed the deformation rates and variability along a 22km track section in Switzerland. The study explores the hypothesis that the variability of PSI-derived deformation estimates along the railway track can be related to longitudinal height measurements from track geometry vehicles. When compared with chord-based measurements from SBB, our preliminary results showed a promising correlation, suggesting that the variability in deformation measurements can indeed be linked to longitudinal height measurements obtained from track geometry vehicles. If proven effective, a satellite-based evaluation method could significantly reduce resources required for railway infrastructure maintenance.

Mapping seasonal wet snow (WS) is essential for climate research, hydrological assessments and natural hazards management. It is especially crucial in Karakoram as the the water supply in the region is dominated by snow melting. However, the complex terrain in Karakoram brings great challenge when employing synthetic aperture radar (SAR) data for WS mapping. In this work, we present an algorithm that combines SAR and topographic data for WS mapping. The result shows that the proposed algorithm can efficiently reduce the uncertainty and generate robust WS map on a large scale.

We present the results of recent observations of terrestrial snow cover with KAPRI, a Ku-band polarimetric-interferometric radar system with bistatic capabilities. The bistatic configuration allows observation of phenomena which are not observable in the monostatic regime. Observations of polarization phase differences of snow cover on top of the Great Aletsch Glacier revealed that the behaviour of these parameters markedly varies between different times of year, as well as between the monostatic and bistatic acquisition modes. The bistatic capabilities of KAPRI were also recently used to characterize the coherent backscatter opposition effect (CBOE) in seasonal snow. We discuss the potential of such bistatic observations to observe quantities which are unobservable in the monostatic regime, and which could serve as new inputs for snow parameter retrieval methods.

Among the most rapid and dramatic changes related to Arctic permafrost thaw are retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making their change visible by comparing digital elevation models over time or by identifying the induced vegetation changes in time-series of optical satellite images. In this study we use digital elevation models generated from TanDEM-X observations to detect and derive volume and area change rates for RTSs on the Taymyr Peninsula. The available data takes allows to compare two time periods: from 2010/11/12 to 2016/17 and from 2017/18 to 2020/21. From 2016 onwards optical Sentinel-2 observations are available for which we manually map thaw slumps for each year in a small sub-area and compare the results to the TanDEM-X mapped RTSs. We found a strong, non-linear increase in the second time-period of the TanDEM-X period and by using the optical mapped RTSs we could attribute this increase to the Siberian heatwave in 2020.

South Rimo Glacier, one of the largest glaciers in Karakoram, showed a glacier surge event during 2018–2020. To characterize the dynamics of the surge, we assessed surface height changes by differencing a time-series of DEMs produced from high-resolution TanDEM-X radar data. In addition, we evaluated the evolution of surface velocities with offset tracking using Sentinel-1 imagery. DEM differences show that the glacier started gaining height in the middle stream since 2013 where a bulge built-up and reached a maximum observed height of 28 m in 2017. After surge activation in 2017, the velocity increased by 2–3 order of magnitude with a peak velocity of 11 m/d in August 2019. Our work highlighted the value of high resolution DEM products and velocity maps in pre-identifying glacier surge and mitigating related hazards.

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to rapid thaw in a warming climate. When ice-rich permafrost soil thaws it becomes unstable, leading to changes in the topography. The most rapid and dramatic changes occur due to retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making them detectable by comparing digital elevation models over time. Fort his study we used digital elevation models derived from bistatic single-pass radar observation from the TanDEM-X satellite pair over the time span from 2011 to 2017. Here we present area and volumetric change rates for thaw slumps from two study areas in Northern Canada (Mackenzie River Delta uplands and Banks Island). The RTSs in the two study area show large differences in terms of RTS size and growth rates. The computation of typical terrain controls like aspect, slope and RTS location (hillslope, shoreline) did not correlate with RTS activity, suggesting that other factors especially soil properties (e.g. ground ice content) play a larger role for RTS evolution.

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to rapid thaw in a warming climate. When ice-rich permafrost soil thaws it becomes unstable, leading to changes in the topography. The most rapid and dramatic changes occur due to retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making them detectable by comparing digital elevation models over time. Here we present first results of a retrogressive thaw slump detection method using bistatic single-pass radar observation from the TanDEM-X satellite pair over the time span from 2011 to 2017. Our processing chain include the digital elevation generation process, elevation model differencing, water body mask generation and a method for the detection of significant height changes. We detected 157 active RTS validated by high- to medium-resolution optical data in our study region (3700 km2) located in the Mackenzie River Delta, Northwest Territories, Canada.