Measurement of Acoustic Attenuation in South Pole Ice

TL;DR

This study measures how acoustic signals weaken in South Pole ice, finding higher attenuation than previous estimates, which impacts neutrino detection efforts.

Contribution

First direct measurement of acoustic attenuation in South Pole ice using multiple sources and analysis methods, revealing higher attenuation than prior models.

Findings

Attenuation coefficient alpha = 3.20 ± 0.57 km^(-1)

Attenuation length lambda ≈ 1/300 m

No significant depth or frequency dependence

Abstract

Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient alpha = 3.20 \pm 0.57 km^(-1) between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for lambda = 1/alpha of ~1/300 m with 20% uncertainty. No significant depth or frequency dependence has been found.