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 from August 2017. The tested frequency ranges from 2 kHz to 35 kHz and probed distances between 5 m and 90 m. The attenuation length has been determined by two different methods including detailed investigations of systematic uncertainties. The attenuation length decreases with increasing frequencies. Observed values range between 13 m for low frequencies and 5 m for high frequencies. The presented results improve in accuracy with respect to previous measurements. However, the observed attenuation is found to be remarkably similar to observations at very different locations.
Highlights
The acoustic properties of ice are of interest for a large variety of applications ranging from the measurement of seismic waves (Robinson, 1968) to the detection of ultra-high-energy neutrinos (Abbasi et al, 2010)
We generally find a good signal-to-noise ratio (SNR) for all measurements and the noise subtraction is a rather small correction in most cases
In this paper we report the measurement of the acoustic attenuation length on the alpine glacier Langenferner in the frequency range from 2 kHz to 35 kHz
Summary
The acoustic properties of ice are of interest for a large variety of applications ranging from the measurement of seismic waves (Robinson, 1968) to the detection of ultra-high-energy neutrinos (Abbasi et al, 2010). Measurements of seismic explosion shocks in a temperate glacier are reported in Westphal (1965) These measurements result in an amplitude attenuation length that ranges between 70 m and 4.6 m for frequencies from 2.5 kHz to 15 kHz, respectively. The basic concept of the presented measurement addresses these issues It is based on the deployment of an acoustic emitter and a receiver a few meters deep into the glacier using holes that are produced with a melting probe. The emitted acoustic power is monitored in our setup for each measurement and differences are corrected for in the analysis by normalizing to the amplitude of the emitted signal This approach corrects for a possible long-term variation in the electronic setup in terms of gain. We perform the analysis very carefully by estimating and subtracting noise, identifying systematic uncertainties, and implementing a robust error propagation using advanced bootstrapping techniques
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