Mapping Surface Elevation Changes of Outlet Glaciers Using Combined Laser Altimeter and Digital Elevation Model Data
Abstract
Ice surface elevation measurements from satellite and airborne laser altimeters have a relatively low error, but are spatially limited to satellite orbits and flight paths. Photogrammetric Digital Elevation Models (DEMs) have a larger error, but provide a continuous surface. We combine the complementary capabilities of these datasets to construct high-resolution (~100 m) maps of surface elevation and elevation change over rapidly changing outlet glaciers. Such a high resolution is needed to resolve the spatial variability of change over narrow ice streams and shear margins. The basic principle of our method is to constrain the DEM surfaces to the altimeter flight lines where they overlap in space and time, both reducing the registration error in the DEM and filling the gaps between altimeter paths. We use laser altimeter data from ICESat and NASA ATM as well as DEMs from the French SPOT 5 satellite. The observation areas are the Greenland outlet glaciers Jakobshavn Isbrae and Kangerdlugssuaq, and the elevation changes are estimated during the period 2007 - 2008. We register the DEMs to the overlapping altimeter data using a least-squares approach, followed by subtraction and interpolation of the residuals to yield a corrected surface. We test two geostatistical interpolation methods: Kriging and optimal linear estimation. Both methods yield similar results. For Jakobshavn, the terminus region thinned with -35 to -30 m/yr and the flow channel with approximately -20 to -10 m/yr. The remaining surface was approximately unchanged. For Kangerdlugssuaq, the terminus thinned with -20 to -7 m/yr and the flow channel with -15 m/yr. At higher elevations, the surface rose with approximately 10 m/yr. The errors are also similar, 0.3 - 7 m/yr and 0.2 - 4 m/yr, respectively, and their magnitude is largely dependent on altimeter data coverage. This information is crucial for airborne altimeter flight planning as such error maps can be used to estimate the spatial density of flights to minimize uncertainty.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.C41E0453L
- Keywords:
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- 0720 CRYOSPHERE / Glaciers;
- 0758 CRYOSPHERE / Remote sensing;
- 0776 CRYOSPHERE / Glaciology