Abstract
Single-pass interferometric synthetic aperture radar (InSAR) is an effective technique for sea ice topographic retrieval despite the inherent dynamics of sea ice. However, the penetration of microwaves into snow-covered thick ice and the achievable height sensitivity for tens-of-centimeters thin ice are two major issues, which limit the accuracy of InSAR-derived sea ice topography. Polarimetry provides scattering information concerning the sea ice properties and has the potential, in combination with interferometry, to achieve an accurate reconstruction of a sea ice digital elevation model (DEM). This article studies the relation between polarimetric signatures and sea ice topography, and explores the possibility to compensate the penetration bias by merging copolar coherence into InSAR processing. The newly generated topographic map has a root-mean-square error under 0.3 m. For thin ice below 1 m, a positive relation between copolar phase φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coPol</sub> and surface height is observed, suggesting that φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coPol</sub> can effectively characterize thin sea ice topography. For thick ice with ridges, the maximum polarimetric phase difference Δφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">maxPol</sub> reveals a particular shape of the coherence region, which can be interpreted as oriented volume scattering. It suggests that the model-based approach using polarimetric SAR interferometry assuming an oriented volume scattering model is promising in measuring the scattering centers in thick and deformed sea ice. The study of polarimetric behavior for the InSAR DEM is, therefore, a step forward toward accurate modeling of sea ice topography from polarimetric single-pass InSAR data.
Highlights
S EA ice is frozen ocean water floating on the ocean surface found in remote polar oceans
The data were acquired from TanDEM-X Synthetic aperture radar (SAR) and Operation IceBridge (OIB) Digital Mapping System (DMS) over the western Weddell Sea, Antarctica
The area (ROI) overlaid by the DMS digital elevation model (DEM) data is used for a quantitative comparison
Summary
S EA ice is frozen ocean water floating on the ocean surface found in remote polar oceans. The forces from wind and ocean currents combined with the blocking effects at the coast and islands act on ice, resulting in an irregular spatial change of ice features. The macroscale sea ice topography is complicated due to different ice features such as rafted ice, pressure ridges, Manuscript received July 8, 2020; revised September 29, 2020; accepted October 23, 2020. Variation of surface topography affects turbulent transfers of heat and momentum [6], acting as an important variable in the atmosphere-ice-ocean system. Characterization of sea ice topography is relevant to assess the effects of environmental impacts on animals and their habitats [7], [8]. The relations between Antarctic sea ice biological communities and sea ice morphological processes (e.g., flooded snow layer and pressure ridge) are summarized in [9]. Precise characterization of the sea ice topography for various ice types has been a topic of active research for decades
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