Waterson, N.J., 2003, Subglacial erosion and the fate of coarse material in the subglacial drainage system of the Matanuska Glacier, Alaska: East Lansing, Michigan, Michigan State University, M.S. thesis, 44 p.
Meltwater streams draining temperate glaciers are known to transport considerable sediment via suspended and bed load. However, recent studies of sediment in meltwater streams discharging from vents along the margin of the Matanuska Glacier in south-central Alaska show bed load to be <1% of the total load despite the availability of coarse material at and near the glacier bed. A possible explanation for this is that much of the coarse material is being trapped within the subglacial drainage system due to an adverse slope of the glacier bed near the terminus. An estimate of the mass of coarse material potentially being trapped was calculated by determining the grain-size distribution of the debris-rich basal ice and subglacial sediment at the Matanuska and measuring the suspended sediment flux in meltwater streams and calculating an average minimum effective erosion rate for six consecutive ablation seasons. The results show that 2.85E + 08kg to 8.61 E + 08kg of coarse material could by trapped at the glacier bed each year. If deposited within 5 km2 of the glacier terminus this would be equivalent to a layer 2.9 to 9.3 cm thick. How the coarse sediment might be distributed, however, would depend on the geometry of the adverse(s) and the type and pattern of the subglacial drainage system. The average minimum effective erosion rate for the six consecutive ablation seasons of 1997-2002 is 1.13 mm/yr.
Theses and Dissertations
