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

• Published in: The Cryosphere
• Main Authors: M. Rongen, R. C. Bay, S. Blot
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; South Pole; ice core; South pole; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-14-2537-2020; https://doaj.org/article/fd467b352ff04183bb0f582513995c6c

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 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">126</mn><mo>±</mo><mn mathvariant="normal">3</mn><msup><mi/><mo>∘</mo></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="42pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="cbdeda3b0f145ddea282300b6ef44b6d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-14-2537-2020-ie00001.svg" width="42pt" height="11pt" src="tc-14-2537-2020-ie00001.png"/></svg:svg> 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.