Abstract
Different approaches have been proposed in recent years to map glacier zones using Synthetic Aperture Radar (SAR). Most of them rely on empirical or statistical approaches for the interpretation of backscatter intensity measurements and their seasonal variations related to the melting regime of the different glacier zones. This study focuses on the potential of polarimetric SAR measurements to characterize the scattering in the different glacier zones in order to distinguish between them. For this, a general two component scattering model is proposed, accounting for surface and sub-surface contributions in the different glacier zones. The (anisotropic) propagation through snow, firn and ice layers is also accounted for as it plays an important role in the interpretation of the polarimetric signatures. A set of five polarimetric descriptors is proposed to describe the projection of the model on the SAR measurements. The ability of the model to characterize the scattering in the different glacier zones is validated and discussed at different frequencies (X-, C-, and L-band). For this, a multi-frequency airborne SAR dataset acquired by the DLRs F-SAR sensor in West Greenland during the ARCTIC 2015 campaign is used. The achieved results indicate that L-band polarimetric measurements allow to differentiate the different glacier zones based on the sub-surface (e.g. volume) scattering characteristics. In contrast, the increased (back-) scattering complexity and the reduced penetration capability limit the potential of X- and C-band polarimetric measurements.
Highlights
Surface mass balance represents a primary term of the total mass balance of a glacier or ice sheet
The potential of model-based interpretation of polarimetric Synthetic Aperture Radar (SAR) data for the characterization of glacier zones in west Greenland has been investigated at different frequencies
The propagation through snow, firn and ice layers is accounted as it plays an important role in the interpretation of the observed polarimetric signatures
Summary
Surface mass balance represents a primary term of the total mass balance of a glacier or ice sheet. An approach based on the thresholding of winter C-band backscattering coefficients to retrieve firn masks and map the FL retreat on the Svartisen ice caps, Norway, over a 7-year period was proposed in [15]. Only few studies have addressed the modeling of PolSAR backscatter to gain a physical interpretation of polarimetric measurements of glaciers and ice sheets. The coherent signatures (including amplitude and phase information) of multi-frequency polarimetric SAR data are interpreted by means of a two-component model that describes polarimetric scattering and propagation effects across the different glacier zones. The model formulation makes use of the new results and deeper understanding developed over the last years It allows to use a set of polarimetric descriptors to characterize the main scattering processes in the different glacier zones and, in turn, to retrieve insights about their subsurface structure.
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