Rapid erosion of soft sediments by tidewater glacier advance: Taku Glacier, Alaska, USA

Taku Glacier in southeast Alaska has advanced 7.5 km over the last 115 years, overriding its own glaciomarine and outwash sediments. We have documented rapid erosion of these sediments by comparing radio echo soundings (RES) along five transects (2003–2005) to earlier RES surveys (1989 and 1994) and to early bathymetric surveys of the proglacial fjord. Erosion rates, , reached 3.9 ± 0.8 m a−1 (1989–2003) at a distance, L, of 5.4 km from the 2003 terminus, where ice thickness, H, is 610 m. averaged 2.0 ± 0.1 m a−1 (1940–2005) at L = 3 km (H = 350 m), and 1.5 ± 0.2 m a−1 (1952–2005) at L = 1.5 km (H = 250 m). Detailed mapping over a 4 km2 area of the terminus revealed a deeply incised channel in line with a major outlet stream. Glaciofluvial processes must play the dominant role in the subglacial erosion and removal of these unlithified sediments.