Abstract ID: 3.9696 | Not reviewed | Requested as: Talk | TBA | TBA

This study is part of the Glacier Mass Balance Intercomparison Exercise (GlaMBIE). Here, we present our assessment of glacier elevation change using the geodetic method (DEM differencing) based on spaceborne optical data. We exploited the potential of the SPOT-5 satellite, operational from 2002 to 2015, which provided global coverage. Since 2021, the SPOT 1-5 image archive has been freely available as part of the SPOT World Heritage program run by CNES. However, observation periods vary across regions, limiting temporal coverage to less than five years in some areas. Iceland is selected as a pilot study due to its extensive SPOT-5 temporal coverage, further complemented by ArcticDEM data. The workflow starts with generating DEM time series at a regional scale and homogenising the data, including DEM co-registration, selection, noise filtering and void filling. To address challenges posed by sparse DEM time series, we developed a method to extrapolate elevation changes over 10-year intervals using the combined DEM time series. This method relies on the assumption that a relationship exists between elevation change and elevation; therefore, an elevation trend can be derived for elevation bands. We extract median elevations for fixed elevation bands (i.e., 100 m bins) from the DEMs time series and interpolate these values over time using linear regression. Elevation data are then extrapolated for each band and pre-defined periods, and area-weighted mean elevation changes are calculated for each glacier using RGI7.0. For comparability, we also applied our approach to derive elevation changes from time series of ASTER DEMs and compared our results with the pixel-based multi-temporal approach of Hugonnet et al. (2021) over a common observation period. Regional and individual glacier estimates from both methods are evaluated. This work discusses key challenges in using spaceborne optical data for regional glacier elevation change assessments, including limitations in the temporal coverage of SPOT-5, issues with DEM generation, co-registration, noise filtering, void filling, and methods for estimating mean elevation changes. Our findings contribute to improving regional assessments of glacier mass balance and advancing geodetic approaches using optical DEM time series.