Morphology and small-scale strength of ridges in the North-western Barents Sea

Four medium to large first-year ridges have been examined with respect to geometry, porosity, morphology, and physico-mechanical properties in the Barents Sea close to the island Hopen in May 2002 to 2005. The geometry and morphology of the ridges compares well with the acknowledged literature, and ridges in the Barents Sea are expected to be similar to other Arctic ridges. The size of the pores increased with depth until about 1/3 to 1/2 of the keel depth, and decreased after about 2/3–3/4 of the keel depth. The porosity throughout the keels increased with depth. The salinity of the level ice and the consolidated layer was about 4 to 5 ppt and no systematic differences were found. Altogether 494 samples were tested in uniaxial compression for ε˙nom = 10− 3 s− 1. Salinity, density and temperature was measured for each individual sample and the porosity (η) calculated. The strength (f) for different parts of the ridge and the level ice is presented and discussed as a function of η. The mean value and the coefficient of variation of f both decreased with increasing η. The strength dropped for relative air volumes (ηa) above 10% and fmax(ηa > 10%) = 2.60 MPa. The ratio of the vertical and horizontal strength of the consolidated layer (fclV / fclH) was about 1.1, and fcl was between the vertical and horizontal strength of level ice (fliV > fcl > fliH). This strength characteristics is due to the different ice texture in level ice and consolidated layer. The strength of the sail and the consolidated layer was comparable and higher than that of the rubble blocks. Brittle samples were (except for η < 5%) stronger than the ductile ones and the porosity seemed to be important for the brittle-to-ductile transition.