Speaker
Description
Glaciers are among the most sensitive indicators of climate change and play a key role in regional hydrology. Over the past decades, Alpine glaciers have experienced accelerated mass loss, characterized by significant spatial variability in elevation-change rates (GLAMOS, 2025). SAR interferometry provides a unique opportunity for glacier monitoring by enabling consistent elevation measurements independently of cloud cover and illumination conditions. TanDEM-X bistatic single-pass acquisitions are particularly well suited for this purpose, as the absence of temporal decorrelation enables the generation of high-quality interferometric products.
This study investigates the capability of multi-temporal TanDEM-X InSAR-based digital elevation models (DEMs) to quantify recent glacier thinning and derive geodetic mass balance over Alpine glaciers, accounting for X-band snow penetration effects. To address this objective, changes between 2011 and 2026 are investigated over the Great Aletsch Glacier and the surrounding glaciers of the Jungfrau region. A total of 207 coregistered single look slant range complex pairs (CoSSC) are processed to generate a time series of high resolution DEMs through an iterative InSAR processing pipeline (Li, 2025), while the optimal perpendicular baseline range is assessed. The derived DEMs are subsequently differenced, and systematic biases are corrected through coregistration and deramping (Nuth and Kääb, 2011). Different gap-filling approaches are also compared, including Gaussian process regression, normalized regional hypsometric interpolation and local hypsometric interpolation, to identify the best-performing method. The estimated elevation trends are then used to derive the geodetic mass balance of the investigated glaciers and quantify the associated uncertainty. The DEM generation pipeline is validated using in situ GPS measurements (Leinss & Bernhard, 2021) and LiDAR acquisitions (Swisstopo, 2024), while the derived mass-balance estimates are compared with field-based glaciological mass balance measurements (GLAMOS, 1881-2025).
The resulting elevation trends for the entire period indicate a mean surface lowering of -1.70 m/yr over the entire Aletsch Glacier. Substantial differences are observed between the Konkordiaplatz area (2600-2800 m a.s.l.; -3.07 m/yr) and the glacier tongue (2000–2200 m a.s.l.; -4.98 m/yr), reflecting the strong elevation dependence of glacier thinning. Similar patterns are observed for the surrounding glaciers based on the derived hypsometric curves, while reduced surface lowering is observed over debris-covered areas, such as the tongue of the Oberaletsch Glacier. The long time series employed reveals an increase of the elevation change rates over the years, passing from -2.78 m/yr (2011-2020) to -3.60 m/yr (2020-2026) over Konkordiaplatz. The geodetic mass balance of the Aletsch Glacier over the investigated period is estimated at -1.363 m w.e. / yr, in close agreement with the corresponding in situ measurements (-1.39 m w.e. / yr).
This study demonstrates the capability and the limitations of multi-temporal TanDEM-X bistatic single-pass observations to retrieve consistent, spatially distributed glacier elevation changes in complex Alpine environments. The study further assesses the transferability of the SAR processing framework to other regions, exploring the potential of TanDEM-X time series for large-scale and systematic glacier monitoring.
References:
- GLAMOS 2025: Swiss Glacier Mass Balance, release 2025, Glacier Monitoring Switzerland, doi:10.18750/massbalance.2025.r2025.
- 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.
- Nuth, C. & Kääb, A. 2011: Co-registration and bias corrections of satellite elevation data sets for quantifying glacier thickness change. The Cryosphere, 5(2):271–290.