Abstract
Abstract. Digital elevation models (DEMs) of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 32% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.
Highlights
Surface topography is an important data set for a wide range of applications from fieldwork planning to numerical modelling studies
The data were extracted using the software provided by the National Snow and Ice Data center (NSIDC) and transformed from the Topex/Poseidon ellipsoid to the WGS84 ellipsoid for consistency with the ERS-1 data and the geoid model applied
We present a new digital elevation model of Antarctica with grid spacing of 1 km, chosen to balance the proportion of grid cells that contained an interpolated value while maximising the spatial resolution of the Digital elevation models (DEMs)
Summary
Surface topography is an important data set for a wide range of applications from fieldwork planning to numerical modelling studies It can, for example, be used to validate the ability of a model to reproduce the present-day geometry of the ice sheet or as an input boundary condition for modelling or combined with other data to estimate steady-state velocities and ice thickness (Bamber et al, 2000; Budd and Warner, 1996; Warner and Budd, 2000). Significant improvements in both spatial resolution and accuracy, around the margins, should be afforded by satellite missions such as TanDEM-X – a twin satellite interferometric synthetic aperture radar mission – and CryoSat 2, both slated for launch in late 2009 Data from these missions should be available by late 2010/early 2011. Stereo-photogrammetric and cartographic data have not been used in this study they could improve the accuracy in high-relief regions such as the Transantarctic Mountains (Liu et al, 1999, updated 2001)
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