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Grounding line detection and ice flow characteristics in Dronning Maud Land, Antarctica, based on ERS SAR interferometry and airborne ice thickness sounding

Wolfgang Rack(1) and Uwe Nixdorf(2)

(1) Alfred Wegener Institute for Polar and Marine Res., Columbusstrasse, 27568, Germany
(2) AWI Bremerhaven, Columbustrasse, 27568 Bremerhaven, Germany

Abstract

The mass balance of the Antarctic ice sheet is mainly determined by snow accumulation at the surface, bottom melting at the ice shelf bases, and iceberg calving from ice shelf fronts. Although it is widely assumed that the overall mass balance of Antarctica it close to equilibrium, recent investigations indicate a high temporal and spatial variability. Even slight changes in the mass balance may have significant impact on the sea level. In the framework of mass balance investigations of drainage basins in Dronning Maud Land, we analyse the ice mass transfer near the grounding line by means of ERS SAR interferometry and airborne radio echo sounding (RES). Glaciers under investigation drain a total area of about 350,000 km2 between 20W and 0W. SAR interferometry is used to locate the grounding line and to plan RES campaigns immediately seaward and landward the grounding line. RES flights were conducted by the Alfred Wegener Institute between 1995 and 2003. ERS SAR data, obtained within the VECTRA AO, were acquired from ERS-1 during the 'ice phase' in 1994 (3 day cycle) and the ERS Tandem Mission between 1995 and 1999. Although a large quantity of SAR scenes was obtained, not everywhere differential interferometry could be applied. Where possible, an ascending and descending pass was combined to obtain 2d motion vectors. The 3d flow vectors were derived under the surface parallel flow assumption, using elevation data from external sources or SAR interferometry. In some cases only interferograms either of the descending or ascending pass are available. In such cases the flow angles, derived from optical and SAR satellite images or the digital elevation model, were used in the correction algorithm to obtain the flow vector. Both interferometrically derived velocities and ice thickness data are used to reconstruct the flow field near the grounding zones, using simple assumptions for ice rheology and basal conditions. The analysis reveals the dynamic behaviour of outlet glaciers in the investigated area, which will be used for the validation of ice dynamic models. This study yields a baseline for the further monitoring of the variability of the mass flow and grounding line position.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry