Numerical simulations of glacial-valley longitudinal profile evolution

Assessing the relative efficiency of fluvial and glacial erosion through simulation of fluvial landscapes

“…Glacial steps are clearly pronounced far below the LGM ELA and suggest deep glacial scour all the way to the LGM terminus. Considering that our DEM-derived profiles reflect surface elevation rather than the elevation of bedrock beneath the potentially deep fills of glacial scours, this is consistent with the well-known observations of overdeepenings near glacial termini in Yosemite Valley and the Hetch Hetchy in the Sierra Nevada (e.g., Gutenberg et al, 1956;MacGregor et al, 2000), and glaciated basins in the Wind River Range, Wyoming, and Glacier National Park, Montana. A component of headwall erosion, particularly in Bubbs Creek, might also need to be addressed (Brocklehurst and Whipple, 2002).…”

“…Initial efforts on constructing evolution models for the glacial landscape have focussed on the larger scale end of the spectrum (Braun et al, 1999;MacGregor et al, 2000;Merrand and Hallet, 2000;Oerlemans, 1984). Predictions of these models include large overdeepenings below the long-term ELA, in addition to overdeepenings associated with tributary junctions.…”

Glaciers show direct linkage between erosion rate and chemical weathering fluxes

“…Finally, higher erosion rates could yield higher reactive surface area through bedrock erosion and particle comminution. Models of glacial erosion scale the rate of erosion with the rate of glacier sliding (Hallet, 1979;Humphrey and Raymond, 1994;MacGregor et al, 2000) or of subglacial fluvial sediment transport (Alley et al, 2003). Both of these are likely to increase in systems with higher mean annual water flux.…”

Investigating the spatial distribution of summit flats in the Uinta Mountains of northeastern Utah, USA

“…Zielinski and McCoy (1987) concluded that late Pleistocene circulation patterns across the northern Great Basin were similar to those of today, and climate simulations suggest that the jet stream and storm tracks were displaced southward by the Laurentide Ice Sheet, reinforcing a dominantly westerly airflow through this region (COHMAP, 1988). Orographic precipitation, therefore, may have produced larger glaciers with greater ice flux in the western Uintas, leading to more intense glacier erosion, (Hallet et al, 1996;Harbor, 1992;MacGregor et al, 2000) which reduced the area of summit flats relative to parts of the range farther east.…”