Cross section through the ice core (IMAGE) Hokkaido University Caption A cross section through the ice core used in this study (left), with one of the air-hydrate crystals in the core examined in this work (right; Tsutomu Uchida, et al. Journal of Glaciology. November 18, 2021). Credit Tsutomu Uchida, et al. Journal of Glaciology. November 18, 2021 Usage Restrictions This image is copyrighted but may be used to report this release if credited as instructed. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.