Structural glaciology of the fast-moving Jakobshavn Isbrae, Greenland, compared to the surging Bering Glacier, Alaska, U.S.A.

Abstract

Crevasse patterns revealing mostly brittle deformation on glacier surfaces are analyzed based on video images collected during systematic overflights of Jakobshavn Isbrae, West Greenland, the Erath's continuously fastest moving ice stream, in 1996 and 1997. Crevasse patterns on the surface of the central ice stream are distinct. All crevasses are closed, the surface appears rather smooth. Towards the margins, typical shear patterns with conjugate shears and still-closed crevasses prevail, curved patterns indicate the bending of crevasse lines into the flow direction. Outward from this zone different patterns of open crevasses occur. This suite of patterns is compared to similar data collected over Bering Glacier, Alaska, U.S.A., during its recent surge from 1993-95. There a number of patterns of mostly open crevasses is characteristic: parallel crevasses, two-directional orthogonal open crevasses, arrays of wavy crevasses, en-echelon crevasses. These patterns of the surging glacier are completely different from those of the fast-moving ice stream indicating different underlying kinematics and dynamics.