Attenuation of Sound in Glacier Ice from 2 kHz to 35 kHz

Abstract

Abstract. The acoustic damping of sound waves in natural glaciers is a largely unexplored physical property that has relevance for various applications. We present measurements of the attenuation of sound in ice with a dedicated measurement setup in situ on the Italian glacier Langenferner. The tested frequency ranges from 2 kHz to 35 kHz and probed distances between 5 meter and 90 meter. The attenuation length has been determined by two different methods and detailed investigations of systematic uncertainties. The attenuation length decreases slowly with increasing frequencies. Observed values range between 13 meter for low frequencies and 5 meter for high frequencies.The here presented results strongly improve in accuracy with respect to previous measurements. However, quantitatively the found attenuation is remarkably similar to observations at very different locations.

The Autonomous Pinger Unit of the Acoustic Navigation Network in EnEx-RANGE: an autonomous in-ice melting probe with acoustic instrumentation

“…For this analog scenario the Langenferner glacier was chosen because of the available ice volume and existing infrastructure in proximity of an alpine hut. The ice volume instrumented for the field test scenarios was located in the ablation zone of the glacier with a volume of roughly 30 m × 40 m × 10 m. These dimensions are smaller than the expected ice volume on Enceladus reflecting the smaller attenuation lengths on the Langenferner glacier (Meyer and others, 2019) compared to the assumptions for Enceladus. However, the results of the performance determined on the Langenferner can be extrapolated to different mission scenarios as on Enceladus as well as on other terrestrial sites such as Antarctica.…”

“…The data recorded during the field test can be used to estimate the maximum range at a given signal-to-noise ratio depending on the attenuation length in ice and the number of averages taken for a single measurement. The range estimation in Figure 13 uses a signal- to - noise ratio ; = 5 : 1, the attenuation length λ = 8.7 m at f sig = 10 kHz (Meyer and others, 2019), and the data from the transfer characteristics at resonance frequency. Figure 13 shows that with attenuation lengths λ > 300 m (e.g.…”

“…The dotted red line shows the configuration used in EnEx-RANGE. The solid red lines mark the attenuation lengths measured at the Langenferner glacier (Meyer and others, 2019) and the cold ice of Antarctica (Abbasi and others, 2011). …”

“…For use on Alpine glaciers, measurements of the acoustic attenuation (Meyer and others, 2019) have indicated that a resonance frequency of the pinger of about 10 or lower is favorable. The analysis and optimization of the pinger is based on simulations using the electromechanical equivalent circuit for Tonpilz-transducers.…”

Attenuation of sound in glacier ice from 2 to 35 kHz

“…The raw data are stored in the format of ROOT trees and is preprocessed with tools from the ROOT framework (Brun and Rademakers, 1997). The processed data, i.e., resulting amplitudes and uncertainties, are accessible from the PAN-GAEA server (Meyer et al, 2019), and allow for custom analysis. The analysis has been performed by a series of custom scripts in the Python (Python Software Foundation, 2018) programming language using tools from the publicly available library NumPy (NumPy Developers, 2018).…”