Abstract
In this study, a methodology for glacier elevation reconstruction from Digital Elevation Model (DEM) time series (tDEM) is described for modeling the evolution of glacier elevation and estimating related volume change, with focus on medium-resolution and noisy satellite DEMs. The method is robust with respect to outliers in individual DEM products. Fox Glacier and Franz Josef Glacier in New Zealand are used as test cases based on 31 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEMs and the Shuttle Radar Topography Mission (SRTM) DEM. We obtained a mean surface elevation lowering rate of −0.51 ± 0.02 m·a−1 and −0.09 ± 0.02 m·a−1 between 2000 and 2014 for Fox and Franz Josef Glacier, respectively. The specific volume difference between 2000 and 2014 was estimated as −0.77 ± 0.13 m·a−1 and −0.33 ± 0.06 m·a−1 by our tDEM method. The comparably moderate thinning rates are mainly due to volume gains after 2013 that compensate larger thinning rates earlier in the series. Terminus thickening prevailed between 2002 and 2007.
Highlights
Differencing elevation data is a widely used method to document elevation and volume changes of glaciers (e.g., [1,2,3,4,5,6])
We present a methodology for glacier elevation reconstruction from Digital Elevation Model (DEM) time series, generating a 4-dimensional (4D) DEM which includes time as an additional dimension to the traditional 3-dimensional spatial coordinates
We found that the relative co-registration accuracies of the ASTER DEMs range from approximately ±13 m to ±27 m for off-glacier terrain and in comparison to the Shuttle Radar Topography Mission (SRTM) DEM (Table 1)
Summary
Differencing elevation data is a widely used method to document elevation and volume changes of glaciers (e.g., [1,2,3,4,5,6]). Satellite altimetry data provide good accuracy and temporal resolution, which are highly valuable to quantify glacier changes, but are usually sparsely distributed on the ground. The Ice. Cloud and land Elevation Satellite (ICESat) acquired precise elevation data between 2003 and 2009 with a repeat cycle of nominally 91 days (in practice 2–3 times a year) [7], and the data have been widely exploited for deriving change in glacier elevation and volume (e.g., [1,2]). Given the fact that, if combined, a large amount of DEM data from various space sensors (e.g., ASTER, SPOT, Pleiades, WorldView, QuickBird and IKONOS satellite stereo; SRTM and TanDEM-X radar interferometry) are available, satellite-derived DEM time series have a high potential in assessing glacier elevation evolution, which is not yet fully exploited. Time series of a large number of DEMs could be used to overcome the deficiencies of individual DEMs by statistical means
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