Research Highlights: Glaciology
To realize the full potential of IceCube, the properties of light propagation in the Antarctic ice must be well understood. We have made the most detailed measurements ever of these properties using both light sources deployed on board the IceCube sensors and a dedicated borehole laser probe called the “dust logger.”
We observed that light propagates preferentially in the direction of the movement of the South Pole glacier. We have shown that ice layers tilt by as much as 10% across IceCube, likely following the topography of the underlying bedrock almost two miles down.
We have also studied the ice stability at the bottom of the glacier, which was an uncharted region of the Antarctic ice sheet when IceCube was built. Ice sheets can deform mechanically due to their own weight, and the lower layers may not move at the same speed as the top ones, thus potentially introducing strong strains on the cables that could reduce IceCube’s longevity. Several years of measurements with 50 inclinometers deployed in the deeper sections of the array have shown a very small shearing effect, with a tilt consistently below 0.01 degrees per year. However, we also deployed a sensor to an additional 100 meters in depth, which is indicating an increasing strain below the IceCube instrumented volume.
By comparing the laser data to ice core measurements, we were able to reconstruct a detailed climate record of the last glacial period. We found evidence for the Toba volcano eruption 74,000 years ago, which had never been observed in ice-core studies. The results have played a role in the designation of the South Pole as the site of the next major American ice coring mission.