Ice Sheet Topography from ERS Radar Altimetry
BS8 1SS, Bristol,
Before the launch of ERS-1, only sparse, terrestrially-derived elevation data, with generally poor accuracy, were available for much of Antarctica and the northern half of Greenland. Elevation errors in excess of 200 m existed for these regions, severely limiting the utility of ice sheet topography for glaciological applications. ERS-1 extended the limit of useful data to 81.5° providing almost complete coverage of Greenland and ~80% of Antarctica. In addition, the geodetic phase of ERS-1, from April 1994-March 1995, provided dense across-track spacing over the ice sheets. As a result, several new digital elevation models (DEMs) of both ice sheets were produced with unprecedented accuracy and spatial resolution. Most recently, ERS-1 geodetic phase data have been combined with ICESat laser altimeter measurements to provide both unparalleled vertical accuracy with high spatial resolution. These DEMs have been used in a wide range of glaciological and geodetic applications and have revolutionised our understanding of many important processes and glaciological features.
Here, I review the development of the new generation of ice sheet DEMs and their use in a range of glaciological problems. Key applications considered include: i) determining the pattern of flow over the ice sheets by modelling ice particle paths down-slope; ii) determining drainage basin areas for mass balance calculations using interferometrically-derived surface velocities, also known as the flux divergence approach; iii) identification of important glaciological features such as subglacial lakes and previously undiscovered flow features and iv) the use of accurate surface topography in inverse modelling studies to elucidate basal processes and subglacial topography. Finally, I consider what advances CryoSat could offer in terms of our knowledge of ice sheet topography, focusing in particular on the potential improvements in the key marginal areas, where steeper relief has limited the viability of previous radar altimeter systems.