HR: 0800h
AN: H51C-0390    [Abstracts]
TI: The role of wind in the evolution of glaciated mountain ranges: Field observations and insights from numerical modelling
AU: * Brocklehurst, S H
EM: shb@manchester.ac.uk
AF: School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester, M13 9PL United Kingdom
AU: MacGregor, K R
EM: macgregor@macalester.edu
AF: Department of Geology, Macalester College, St Paul, MN 55105 United States
AB: Prevailing winds appear to exert a major control on the evolution of glaciated mountain ranges, particularly those oriented perpendicular to the prevailing wind. The presumed cause of this is the redistribution of wind-blown snow, which has the opposite effect from orographic precipitation in non-glaciated ranges. While fluvially-eroded ranges tend to be exhumed more on the windward side, glacially-eroded ranges seem to experience greater erosion on the leeward side. The Sangre de Cristo Range of southern Colorado runs close to north-south, cross-cutting the prevailing winds from the west (which have formed the Great Sand Dunes of the National Monument adjacent to the west side of the range). Drainage basins on both sides of the range cover similar drainage areas, but moraines are much more substantial on the eastern side of the range, indicating greater glacial incision, which we suggest reflects snow blown over the range crest. The highest peaks of the Bitterroot Range on the Idaho-Montana border lie substantially to the east of the modern drainage divide, while the moraines are again much more substantial on the eastern side of the range. We suggest that the cause of this is greater glacial erosion of both the headwalls and valley floors on the eastern side, linked to wind-blown snow from the west side of the range. Glen Avon, incised into the Cairngorm plateau in Scotland, contains a large, elongated glacially-carved lake immediately downstream of a modest cirque. We suggest that the glacier responsible for carving the lake must have had its mass balance supplemented by substantial amounts of snow blown in from the plateau above. Numerical modelling supports these field-based inferences. A 1-D numerical model of glacial longitudinal profile evolution indicates the importance of wind-blown snow. A plateau region above the valley head from which snow can blow into the valley allows substantially larger and longer-lived glaciers compared with a valley of the same size but without the plateau. The extra snow drives greater glacial erosion, both in terms of valley floor incision and headward erosion.
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1827 Glaciology (0736, 0776, 1863)
SC: Hydrology [H]
MN: Fall Meeting 2005