Speaker
Description
Synthetic aperture radar (SAR)-based Earth observation techniques provide an effective means of monitoring glacier changes over large spatial and extended temporal scales. The Swiss Alps offer an excellent opportunity for validating remote-sensing approaches to glacier monitoring due to the high availabilty of independent glacier observations. In particular, the Great Aletsch Glacier – the largest glacier in the Alps – provides an ideal environment for developing and validating SAR-based approaches, as it is not only a designated super-test site for the TanDEM-X mission, but is also extensively monitored through long-term field observations and in-situ measurements. The resulting dense temporal sampling provides an opportunity to investigate both the spatial distribution and temporal evolution of glacier elevation change and their implications for geodetic mass balance.
In this study, the InSAR DEM differencing framework established by Li & Hajnsek (2025) is applied to the Great Aletsch Glacier using TanDEM-X single-pass bistatic SAR data acquired between 2011 and 2026 and complemented by the SwissALTI3D digital elevation model (DEM) (swisstopo 2022). The framework consists of the generation of 164 DEMs using an iterative InSAR approach, followed by DEM differencing and void filling using Gaussian Process Regression. A non-stationary uncertainty analysis is subsequently employed to quantify uncertainties in the resulting elevation changes and mass balance. GPS measurements (Leinss & Bernhard 2021) and annual glacier mass balance observations from GLAMOS (1881-2023) are used to validate the derived height changes and mass balance estimates. The dense temporal sampling is further exploited to investigate temporal variations in glacier thinning rates.
The resulting DEM time series reveals substantial elevation losses across the glacier. The mean height change over the entire Aletsch Glacier is estimated at -1.79 m yr⁻¹, with considerably stronger thinning of -6.18 m yr⁻¹ in the glacier tongue. The corresponding geodetic mass balance is estimated at -1.35 m w.e. yr⁻¹, closely matching the long-term mean annual mass balance of -1.39 m w.e. yr⁻¹ reported by GLAMOS. A strong elevation dependence is found both for the height loss and the glacier mass balance.
These results demonstrate the potential of the InSAR DEM differencing framework applied on a dense time series to provide spatially distributed measurements of glacier elevation change and geodetic mass balance. The framework is subsequently extended to additional glaciers in the Swiss Alps to assess its transferability and potential for large-scale glacier monitoring.
REFERENCES
Bundesamt für Landestopografie swisstopo 2022: swissALTI3D: Das hoch aufgelöste Terrainmodell der Schweiz.
GLAMOS 1881-2023: The Swiss Glaciers 1880-2022/23, Glaciological Reports No 1-142, Yearbooks of the Cryospheric Commission of the Swiss Academy of Sciences (SCNAT), published since 1964 by VAW / ETH Zurich.
Leinss, S., Bernhard P. 2021: TanDEM-X:Deriving InSAR Height Changes and Velocity Dynamics of Great Aletsch Glacier, IEEE Journal of Selected Topics in Applied Earth Observation s and Remote Sensing, 14, 4798-4815.
Li, S., & Hajnsek I. 2025: Geodetic glacier mass balance in the Karakoram (2011–2019) from TanDEM-X: An InSAR DEM differencing framework, Remote Sensing of Environment, 331, 115023.