Detailed mechanical property measurements were made on the Dye-3, Greenland (65°I2'N, 43°47'W) ice core over its entire profile (2037 m) as shown in Table I. Tests were made in uniaxial compression under constant crosshead speed (specimen size, about 2,5 x 2.5 x 9 cm) and simple shear under constant load (specimen size, about 2x2x3 cm), with test temperature held constant between -12 and -17°C. The experimental results were analyzed by using the power law creep equation with enhancement factor terms. Stress exponent values of 2.7, 3.2, 2.9 were obtained for specimens (oriented so as to have the maximum resolved sheer stress in the horizontal plane of the ice core) from depths of 235 m and 247 m; 1814 m and 1816 m; and 2021 m respectively. These values are close to those obtained earlier (Barnes and others 1971) for artificial laboratory polycrystalline ice. The enhancement factor values for horizontal shear deformation, changed with depth and correlated well with the c-axis profile of Herron S and others (1981). Above the 800 m depth, the enhancement factor value ranges between about 0.5 and 1. Below the 800 m depth, the enhancement factor increases up to about 3 near the Holocene/Wisconsin transition depth (about 1786 m).

Between the 1786 m and 2037 m depths, the enhancement factor values ranged from 6 to 20 with an average value of about 10. The c-axis orientations were obtained by ultrasonic wave velocity measurements over the 1786 to 2037 m interval. The results of 114 samples measurements showed that the ice has a single maximum fabric pattern from 1786 m through to the bottom with variations in the strength of c-axis concentrations. Chemical impurity levels of NO ₃ ^-, SO₄ ^2- and C1>^- also vary over this depth interval but on average the Wisconsin ice has 2 to 4 times more chemical impurities than does the Holocene ice (Herron and Langway 1985; Finkel and Langway 1985). Additional experiments on the Dye-3 core with different impurity levels showed that impurity enhancement factors should be less than 2 (enhancement factor = fabric enhancement factor x impurity enhancement factor). We conclude, therefore, that the fabric enhancement factor is of primary significance for the high enhancement factor value of Wisconsin and basal silty ice. The strong c-axis orientations on the same ice implies a high anisotropy of the mechanical properties which was experimentally confirmed.

Table 1.Sample Depths For Uniaxial Compression And Simple Shear Tests On The Dye-3, Greenland Ice Core