the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Sep 2024
Brief communication: Reduced bandwidth improves the depth limit of the radar coherence method for detecting ice crystal fabric asymmetry
Abstract. Ice crystal orientation fabric strongly affects the viscous deformation of glacier ice. A popular technique to investigate ice fabric is radar polarimetry, often analysed using the coherence method. However, in fast-flowing areas with strong anisotropy, this method provides information of shallow areas below the surface only. This study proposes reducing radar bandwidth to enhance the depth limit for fabric asymmetry detection. Using data from two ice streams, we demonstrate that reduced bandwidth significantly increases the depth limit, depending on the centre frequency. This approach aims to improve the understanding of the spatial distribution of fabric, crucial for ice dynamics in fast-flowing regions.
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RC1: 'Comment on egusphere-2024-2519', Anonymous Referee #1, 21 Oct 2024
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In this paper, the authors discuss the use of the coherence method on multi-polarization ice penetrating radar data as a tool to investigate properties of ice fabric. Specifically, they demonstrate that narrowing the radar signal's bandwidth helps provide information in deeper areas. They validate their approach from experimental data.
The manuscript is in the form of a brief communication. It is concise, well written, and easy to follow. The paper should be of interest of the EGUsphere readership. I only have the following comments:
1) On Page 3, line 80, the authors state "all applied at the respective minimum available center frequencies (Table 1)". I wonder, however, if it is better to keep the same center frequency and reduce the bandwidth of the signal. Rather than change both simultaneously. Can the authors provide a comparison of the results obtained when keeping the center frequency fixed? This would be useful to other radar systems, in which data is collected in ultra-wideband mode, and then sub-banded in post-processing.
2) Minor comments:
a) In equation (5), c_0 is defined as the speed of light in vacuum, but that variable is already defined for equation (4). Please consider eliminating redundant variable definitions
b) Page 3, ~line 64-65 "and on the radar bandwidth" consider changing to " and on the bandwidth of the radar signal"
Citation: https://doi.org/10.5194/egusphere-2024-2519-RC1
Data sets
Polarimetric phase-sensitive radar measurements at EastGRIP drill site, 2019 Ole Zeising and Angelika Humbert https://doi.org/10.1594/PANGAEA.951267
Crystal c-axes (fabric analyser G50) of ice core samples (vertical thin sections) collected from the polar ice core EGRIP, 111-1714 m depth Ilka Weikusat, Nicolas Stoll, Johanna Kerch, Jan Eichler, Daniela Jansen, and Sepp Kipfstuhl https://doi.org/10.1594/PANGAEA.949248
Radar characterization of ice crystal orientation fabric and anisotropic rheology within Rutford Ice Stream, 2017-2019 T. Jordan, C. Martín, A. Brisbourne, D. Schroeder, and A. Smith https://doi.org/10.5285/D5B7E5A1-B04D-48D8-A440-C010658EC146
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