Mitigating ku-Band Penetration when Generating Digital Elevation Models and Rates of Surface Elevation Changes from Swath Processing of CryoSat-2
Abstract
Reference and repeat-observations of ice sheet margin topography is critical to identify changes in ice thickness, provide estimates of mass gain or loss and thus quantify the contribution of the cryosphere to sea level change. The ESA Altimetry mission CryoSat-2 aims at gaining better insight into the evolution of the cryosphere, in particular over the steep slopes typically found along ice sheet margins where the majority of the mass loss is taking place. CryoSat's revolutionary design features a Synthetic Interferometric Radar Altimeter (SIRAL), with two antennas for interferometry, the corresponding SAR Interferometer (SARIn) mode of operation increases spatial resolution while resolving the angular origin of off-nadir echoes occurring over sloping terrain. The SARIn mode is activated over ice sheet margins and the elevation for the Point Of Closest Approach (POCA), or level-2, is a standard product of the CryoSat-2 mission. But the CryoSat-2 SARIn mode allows also the so-called CryoSat-2 Swath SARIn (CSSARIn) approach: elevations beyond the POCA are produced, leading to between 1 and 2 orders of magnitude more measurements than level-2 product. The European Space Agency project CryoTop Evolution aims to generate and deliver to the community CSSARIn elevations, Digital Elevation Models and maps of rates of surface elevation change over the Greenland and Antarctic Ice Sheets. One of the challenge in the computation of rates of surface elevation change from the measured elevations is that changes in surface condition can modify the radar horizon, in particular changes in the penetration properties of the snow or ice. For example, melt event can suddenly decrease the penetration in the firn, leading to an erroneous mass gain measurement. If retrackers have been developed to limit the effect of penetration in the POCA retrieval, CSSARIn samples far from the POCA can be heavily subject to penetration changes. Here we will present first attempts to separate changes in penetration from the rate of elevation change by including proxies for penetration in the model linking elevations to elevation changes. These proxies are extracted from the waveforms characteristics and only derived from the CryoSat-2 measurements.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.C54A..06W
- Keywords:
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- 0758 Remote sensing;
- CRYOSPHERE;
- 0799 General or miscellaneous;
- CRYOSPHERE;
- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY;
- 1241 Satellite geodesy: technical issues;
- GEODESY AND GRAVITY