An image-enhanced DEM of the Greenland ice sheet

Abstract

We have assembled an elevation grid for the Greenland ice sheet using a combination of the best current digital elevation model (DEM) (Bamber and others, 2000a, 2001) and 44 Advanced Very High Resolution Radiometer satellite images acquired in spring 1997. The images are used to quantitatively enhance the representation of surface undulations through photoclinometry. Gridcell spacing of the new DEM is 625 m. To validate the new DEM, we compared profiles extracted from it and the Bamber and others DEM with airborne laser altimetry profiles collected in the 1990s by the Airborne Topographic Mapper (Krabill and others, 1995). The image-enhanced DEM has a greatly improved representation of decameter-relief surface features <15 km in lateral extent, and reduces the mean elevation error in regions having these features by 20–50%. Root-mean-squared errors are typically 7–15m in the Bamber DEM, and 4–10m after image enhancement. However, the photoclinometry process adds some noise. In very smooth portions of the ice sheet where decameter undulationsare absent, the photoclinometry process caused a slight increase in the rms error, from ~1 min the Bamber and others DEM to ∼2.5 min the image-enhanced DEM. The image-enhanced DEM will be useful for inferring accumulation-rate variations over the undulation field, or for improving maps of bedrock elevation through inversion of surface elevation, for example. We briefly explore the preliminary steps of this latter application.

The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets

“…The root mean square (RMS) of the residuals between the PEB DEM and the ICESat point cloud following co-registration are given in Table 1. The total RMS error of ±21.8 m is nearly three times higher than reported by Bamber et al (2001) and Scambos and Haran (2002), likely due to the more extensive sampling by ICESat relative to the airborne altimetry used in those studies, especially over ice-free terrain, where errors are much higher. The RMS errors over the interior ice sheet are more consistent with reported errors.…”

“…The standard DEM used in glaciological studies was created from a combination of satellite radar altimeter and aerial photogrammetry (Bamber et al, 2001) with a posting of up to 1 km. This DEM was enhanced to 625 m posting through photoclinometry by Scambos and Haran (2002). While these DEMs are accurate to a few meters over the relatively flat interior of the ice sheet, they have poor resolution over the steeper margins and higher-relief periphery.…”

Freshwater flux to Sermilik Fjord, SE Greenland

“…The Greenland topographic data at 625-m resolution from Bamber et al (2001) was used with the image-derived correction published by Scambos and Haran (2002), and interpolated to a 500-m grid increment covering a 400.5 by 300.5 km simulation domain for the Sermilik Fjord catchment (Fig. 1a).…”

Runoff and mass-balance simulations from the Greenland Ice Sheet at Kangerlussuaq (Søndre Strømfjord) in a 30-year perspective, 1979–2008

“…If not corrected, the use of meteorological station data from the proglacial area alone will overestimate Table 1) was defined by correcting Helman-Nipher shielded gauge observations following Allerup et al (1998Allerup et al ( , 2000. Greenland topographic data for model simulations were provided by Bamber et al (2001), and corrections were determined by Scambos and Haran (2002). The digital elevation model was aggregated to a 500-m grid-cell increment and clipped to yield a 750-by-580-km simulation domain (435 000 km 2 ) (Fig.…”