Ice-sheet flow conditions deduced from mechanical tests of ice core

• Published in: Annals of Glaciology
• Main Authors: Miyamoto, Atsushi, Narita, Hideki, Hondoh, Takeo, Shoji, Hitoshi, Kawada, Kunio, Watanabe, Okitsugu, Dahl-Jensen, Dorthe, Gundestrup, Niels Steen, Clausen, Henrik Brink, Duval, Paul
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1999
• Subjects: Greenland; Annals of Glaciology; Greenland ice core; Greenland Ice core Project; GRIP; ice core; Ice Sheet
• Online Access: https://curis.ku.dk/portal/da/publications/icesheet-flow-conditions-deduced-from-mechanical-tests-of-ice-core(be45faa0-74c8-11db-bee9-02004c4f4f50).html; https://doi.org/10.3189/172756499781820950

Uniaxial compression tests were performed on samples of the Greenland Ice Core Project (GRIP) deep ice core, both in the field and later in a cold-room laboratory, in order to understand the ice-flow behavior of large ice sheets. Experiments were conducted under conditions of constant strain rate (type A) and constant load (type B). Fifty-four uniaxial-compression test specimens from 1327-2922 m were selected. Each test specimen (25 mm × 25 mm × 90 mm) was prepared with its uniaxial stress axis inclined 45° from the core axis in order to examine the flow behavior of strong single-maximum ice-core samples with basal planes parallel to the horizontal plane of the ice sheet. The ice-flow enhancement factors show a gradual increase with depth down to approximately 2000 m. These results can be interpreted in terms of an increase in the fourth-order Schmid factor. Below 2000 m depth, the flow-enhancement factor increases to about 20-30 with a relatively high variability. When the Schmid factor was > 0.46, the enhancement factor obtained was higher than expected from the c -axis concentrations measured. The higher values of flow-enhancement factor were obtained from specimens with a cloudy band structure. It was revealed that cloudy bands affect ice-deformation processes, but the details remain unclear. Udgivelsesdato: June