Flow-Law Parameters of the Dye 3, Greenland, Deep Ice Core

Uniaxial compression tests under constant crosshead speed were carried out on 22 new specimens from the 268, 1890, 1944 and 2006 m depths of the Dye 3, Greenland, ice core. The measurements were made in a laboratory cold-room, using an Instron model 1131 apparatus. Test temperatures were held constant between −17° and −13° C, the approximate sample in-situ temperature. Specimens were prepared with various test orientations in relation to the long vertical core axis. The specimens were analyzed in terms of the content of dust, Cl − , NO 3 − and SO 4 2− concentrations and various other physical parameters, such as ultrasonic wave velocities, c -axis orientation patterns and grain-size. The results of the previous uniaxial compression tests show that most of the flow occurs in the Wisconsin-age ice between 1786 m and the bottom of the ice sheet. This entire depth interval is strongly anisotropic, with a vertical c -axis fabric pattern. The enhancement factor, E, which was calculated from these tests ranges from 0.03 to 17. The Wisconsin-age ice is about ten times softer (E s = 10) than artificially made laboratory ice (E = 1). The combined results of the multi-parameter correlation analyses show that E is controlled primarily by the orientation strength of c -axes and that the impurity concentration-level variations contribute to a lesser degree.