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Abstract
Abstract. Radar sounding of the thickness of temperate glaciers is challenged by substantial volume scattering, surface scattering and high attenuation rates. Lower-frequency radar sounders are often deployed to mitigate these effects, but the lack of a global synthesis of their success limits progress in system and survey design. Here we extend a recent global compilation of glacier thickness measurements (GlaThiDa) with the center frequency for radar-sounding surveys. From a maximum reported thickness of ∼ 1500 m near 1 MHz, the maximum thickness sounded decreases by ∼ 500 m per frequency decade. Between 25–100 MHz, newer airborne radar sounders generally outperform older, ground-based ones. Based on globally modeled glacier thicknesses, we conclude that a multi-element, ≤30 MHz airborne radar sounder could survey most temperate glaciers more efficiently.
Highlights
Measuring the thickness of Earth’s mountain glaciers is essential for advancing understanding of their volume, flow and future amid ongoing anthropogenic warming, consequent mass loss and contribution to sea-level rise (e.g., Farinotti et al, 2019; Zemp et al, 2019)
For all GlaThiDa entries that reported a maximum thickness for a presumed temperate glacier at the upper end of the range reported for that frequency, we reviewed the original study to validate the reported value
Based on the above synthesis, we identify a simple envelope for the maximum temperate ice thickness sounded across the more than 2 decades of frequency spanned by deployed radar sounders (Fig. 1b)
Summary
Measuring the thickness of Earth’s mountain glaciers is essential for advancing understanding of their volume, flow and future amid ongoing anthropogenic warming, consequent mass loss and contribution to sea-level rise (e.g., Farinotti et al, 2019; Zemp et al, 2019). Watts and England (1976) described what may be the primary challenge in radar sounding of temperate ice: meterscale, water-filled englacial cavities that efficiently scatter incident radio waves where the ratio of those cavities’ radius to the radar’s englacial wavelength exceeds ∼ 0.1. Their analysis favored center frequencies ≤∼ 10 MHz to increase the signal-to-clutter ratio between the ice–bed reflection (signal) and any cavity-induced volume scattering (clutter). We evaluate past and potential radar-sounder performance by examining recent global compilations of both observed and modeled glacier thickness
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