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  • 1
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    The Cryosphere
    In:  EPIC3Earth Observation and Cryosphere Science Conference, 2012-11-13-2012-11-16The Cryosphere
    Publication Date: 2017-10-17
    Description: Within ESA’s CryoSat-2 calibration and validation program (CryoVEx) an airborne campaign was carried out in the blue ice area in the vicinity of Schirmacher oasis, Dronning Maud Land, Antarctica in 2008. POLAR 5, the Alfred-Wegener-Institute’s research aircraft, carried the ESA airborne Ku-band SAR interferometric radar altimeter (ASIRAS) and a laser scanner during the CryoVEx campaign. In the blue ice area, partly covered with snow patches, a dense grid of 30 km x 40 km with a line spacing of 1 km was measured. Here, we present results of the comparisons of the final SAR processed ASIRAS elevations with the laser scanner elevation model. We will show the influence of snow patches on and the accuracy of the ASIRAS derived surface elevations by using the laser scanner DEM as reference. Furthermore, the derived Ku-band penetration depths and the thickness of the snow patches, derived from the ASIRAS data, are compared with the radar backscatter of a TerraSAR-X scene, acquired at the same time when the campaign took place. Our results show that Ku-band radar penetrates through the snow, while the snow patches do not affect the derived ASIRAS surface elevations. In contrast the radar backscatter of TerraSAR-X shows a strong correlation of the thickness of the snow patches. The results of this study highlight the need of careful waveform processing/re-tracking and though will contribute to improved CryoSat-2 elevation products.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
    Publication Date: 2023-10-24
    Description: Surface melt, driven by atmospheric temperatures and albedo, is a strong contribution of mass loss of the Greenland Ice Sheet. In the past, black carbon, algae and other light-absorbing impurities were suggested to govern albedo in Greenland’s ablation zone. Here we combine optical (MODIS/Sentinel-2) and radar (Sentinel-1) remote sensing data with airborne radar and laser scanner data, and engage firn modelling to identify the governing factors leading to dark glacier surfaces in Northeast Greenland. After the drainage of supraglacial lakes, the former lake ground is a clean surface represented by a high reflectance in Sentinel-2 data and aerial photography. These bright spots move with the ice flow and darken by more than 20% over only two years. In contrast, sites further inland do not exhibit this effect. This finding suggests that local deposition of dust, rather than black carbon or cryoconite formation, is the governing factor of albedo of fast-moving outlet glaciers. This is in agreement with a previous field study in the area which finds the mineralogical composition and grain size of the dust comparable with that of the surrounding soils.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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