Observation of an optical anisotropy in the deep glacial ice at the geographic South Pole using a laser dust logger

We report on a depth-dependent observation of a directional anisotropy in the recorded intensity of backscattered light as measured by an oriented laser dust logger. The measurement was performed in a drill hole at the geographic South Pole about a kilometer away from the IceCube Neutrino Observatory. The drill hole has remained open for access since the SPICEcore collaboration retrieved a 1751 m ice core. We find the anisotropy axis of inline-formula $M1inlinescrollmathml\mathrm{normal\; 126}\pm \mathrm{normal\; 3}{}^{\circ }$ 42pt11ptsvg-formulamathimgcbdeda3b0f145ddea282300b6ef44b6d tc-14-2537-2020-ie00001.svg42pt11pttc-14-2537-2020-ie00001.png as measured below 1100 m to be compatible with the local flow direction. The observation is discussed in comparison to a similar anisotropy observed in data from the IceCube Neutrino Observatory and favors a birefringence-based scenario over previously suggested Mie-scattering-based explanations. In the future, the measurement principle, when combined with a full-chain simulation, may have the potential to provide a continuous record of fabric properties along the entire depth of a drill hole.