Conference Agenda
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Cryosphere Applications I Location: Red Hall Session Chair: Francesco Banda, aresys Session Chair: Georg Fischer, German Aerospace Center (DLR) | |
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3:30pm - 3:50pm
Investigating lake ice structure with polarimetric SAR tomography 1: German Aerospace Center – Microwaves and Radar Institute, Wessling, Germany; 2: ETH Zurich – Institute of Environmental Engineering, Zurich, Switzerland; 3: University of Hamburg – Department of Earth System Sciences, Hamburg, Germany; 4: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research – Permafrost Research Section, Potsdam, Germany; 5: Humboldt-Universität zu Berlin – Department of Geography, Berlin, Germany Lakes are common features of arctic lowland permafrost regions. Increasing temperatures and changing precipitation regimes at higher latitudes affect the ice forming seasonally at their surface. In particular, the thinning of this ice layer can lead to a shift from bedfast-ice regime, where the ice reaches the bottom of the lake, to a floating-ice regime, where there still remains liquid water below the ice layer. This in turn can lead to potential greenhouse gas release from the newly unfrozen ground at the lake bottom [1]. Monitoring the ice thickness and the ice regime is therefore crucial. To this end, Synthetic Aperture Radar (SAR) is well adapted because the radar waves penetrate into the ice volume at all bands. Though the polarimetric signature of these lakes has been well studied [2], no study yet has investigated the vertical reflectivity profile from the ice layer which can be retrieved by combining SAR acquisitions coherently, in a SAR interferometry (InSAR) or SAR tomography (TomoSAR) framework. This contribution aims at reconstructing this profile in a number of lakes by exploiting the sensitivity in the height direction of multi-baseline SAR data and at improving the understanding of scattering in the lake ice volume and at its interfaces: air/ice and ice/water interfaces in the floating-ice case; air/ice and ice/frozen-ground interfaces in the bedfast-ice case. For this analysis, we propose to use the PermASAR19 airborne TomoSAR dataset, which was collected by the German Aerospace Center (DLR) in the Canadian low Arctic in the late winter season of 2019. The acquisitions are fully polarimetric, and were performed at several bands (X-, C- and L-band) with submeter spatial resolution in both range and azimuth directions, within a two-hour time window. The SAR footprint covers several lakes which are known to be shallow (only a few meters depth), and which ice thickness is expected to reach approximately 1 meter [3] [4]. Challenges arise from the thinness of the ice layer with respect to achievable resolution in height from usual beamforming methods, suggesting that high-resolution tomographic techniques like Capon beamforming are required. First analyses with separated polarizations show that scattering occurring within the ice volume and at interfaces can be observed in the reconstructed profiles, at X-band and C-band over several lakes. Combining polarimetric channels coherently in a polarimetric tomographic SAR (Pol-TomoSAR) framework will improve the physical understanding of the retrieved profiles [5]. A Pol-TomoSAR analysis over several lakes of the testsite will be presented. The results of several bands, in particular X-band and C-band, will be compared. The obtained estimated structure information will be assessed with regards to ground measurements of lake bathymetry and ice thickness [3] [4]. [1] C. D. Arp, B. M. Jones, Z. Lu, and M. S. Whitman (2012), “Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska”, Geophysical Research Letters, vol. 39, L16503, doi: 10.1029/2012GL052518 [2] D. K. Atwood, G. E. Gunn, C. Roussi, J. Wu, C. Duguay, and K. Sarabandi (2015), “Microwave Backscatter From Arctic Lake Ice and Polarimetric Implications”, IEEE Transactions on Geoscience and Remote Sensing, vol. 53, no. 11, p. 5972-5982 [3] E. J. Wilcox (2025), "Ice thickness, snow depth and lake properties for sampled lakes in and around the Trail Valley Creek watershed, NT", https://doi.org/10.5683/SP3/VP1UMC, Borealis [4] E. J. Wilcox (2025), "Lake bathymetry measurements for sampled lakes in and around the Trail Valley Creek watershed, NT", https://doi.org/10.5683/SP3/7XADY4, Borealis [5] L. Ferro-Famil, Y. Huang, and A. Reigber (2012), “High-resolution SAR tomography using full rank polarimetric spectral estimators”, 2012 IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany, pp. 5194-5197 | |
