Terminus dynamics and deformation of proglacial sediments at the advancing Taku Glacier, Alaska, U.S.A.

Abstract

Taku Glacier has advanced about 7 km since 1890. The continuing advance is the result of the tidewater-glacier cycle. In the last several decades, the glacier has bulldozed a berm of marine and fluvial sediments from the fjord bottom and produced so-called push moraines. The mobilization of these sediments, which were locally lifted more than 20 m above sea level by 2004, has happened episodically rather than steadily. The last major proglacial sediment deformation was observed in 2001. Since then, most deformation has been localized within some meters of the terminus. Between 2002 and 2004 surface velocities and displacements were measured across the terminus and in the proglacial area. The displacements were highest between March and June and decreased with distance from the terminus. The sediments were presumably deforming internally rather than moving along a basal décollement. A simple model and sensitivity analysis show that major movement along this layer will most likely happen if (1) the glacier steepens its surface topography, (2) the proglacial sediment wedge shortens and steepens its surface slope or (3) the water pressure increases in order to reduce the frictional resistance.