Permalink : http://hdl.handle.net/2115/45433

KEYWORDS : ice core;storage temperature;volume relaxation;cleavage crack;air hydrate crystal

We are keeping Dome Fuji ice core samples at two storage temperatures (-50 and -20℃) after deep ice core drilling reached 2503 m at the Dome Fuji station, Antarctica. Since we aimed to develop new methods for studying physical properties of ice cores, cold storage down to -50℃ was necessary to avoid volume relaxation of ice cores during storage. To compare the volume relaxation process of an ice core under different storage temperatures, we captured images using a digital camera. Many tiny bubbles and plate-like inclusions (cleavage cracks) were observed in the ice core kept at the high storage temperature (-20℃). The clear ice seen just after ice core recovery changes to milky coloured cloudy ice because of the many tiny bubbles and cleavage cracks generated. We analyzed the volume relaxation rate of each ice core sample based on the digital images; it was clear that the generation of tiny bubbles and cleavage cracks and the decomposition of air hydrate crystals were avoided effectively at a storage temperature of -50℃. In cold storage down to -50℃, various physical properties of the ice core have been successfully investigated. In the present paper, we emphasize the importance of low-temperature storage to maintain high-quality ice cores.