HR: 0800h
AN: C41A-0049    [Abstracts]
TI: Surface Velocities of Himalayan Glaciers: Implications for Glacial Erosion Potential During Climatic Change
AU: * Scherler, D
EM: dirk@geo.uni-potsdam.de
AF: Institut fuer Geowissenschaften, Universitaet Potsdam, Karl-Liebknecht-Str. 24/25, Potsdam, 14476, Germany
AU: Bookhagen, B
EM: bodo@pangea.Stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Braun Hall 118, Stanford, CA 94305-2115, United States
AU: Strecker, M R
EM: strecker@geo.uni-potsdam.de
AF: Institut fuer Geowissenschaften, Universitaet Potsdam, Karl-Liebknecht-Str. 24/25, Potsdam, 14476, Germany
AB: Mountain glaciers in the high elevations (> 3.5 km) of the Himalaya are very efficient erosion agents. Glacier size and thus the area affected by glacial erosion are controlled by climatic conditions. Understanding the impact of climate change and variability on glacial budgets and erosion requires knowledge of the erosive potential of glaciers, which is inferred to scale with ice flux. Here, we use ASTER satellite imagery in combination with the orthorectification and correlation tool COSI-Corr to derive horizontal surface velocities of glaciers from several regions across the Himalayan-Karakoram domain. Our results show that glaciers in the Eastern and Central Himalaya, where precipitation is mainly supplied by the Indian Summer Monsoon, are relatively slow, with velocities usually below 50-60 m/a. In contrast, glaciers in the Western Himalaya and Karakoram, receive a significant amount of precipitation during the winter months and are considerably faster with velocities often exceeding 80-100 m/a. This discrepancy is visible among glaciers of different size and orientation although local slope and catchment area effects may cause velocity excursions. A relatively sharp gradient appears to exist in the catchment area of the Sutlej River in the NW Himalaya of India at approximately 79°E. To the east, glaciers in the Garhwal Himalaya – among them Gangotri glacier, the largest in the Indian Himalaya – have mean velocities of around 20-40 m/a, whereas glaciers in the much drier Lahul region to the west attain mean velocities of around 30-60 m/a. Importantly, the Sutlej River valley marks a climatic transition zone from an annual summer-rainfall maximum (more than 75% of annual rainfall during the summer) to the east to a winter-rainfall maximum (more than 60% of annual rainfall during the winter) to the west. These observations corroborate the notion of a significant climatic boundary in this part of the Himalaya, which may have shifted west- and northward during past episodes of intensified summer monsoons, such as during the early Holocene. Our findings show that glaciers dominated by summer accumulation have generally lower surface velocities, hence ice-flux, and thus only limited potential to erode underlying bedrock. However, their counterparts in the Western Himalaya and Karakoram, receive moisture during all seasons, have a higher ice- flux, are more likely to have grown during an intensified winter or summer monsoon and thereby play a more important role in sculpting landscapes. Yet, if an intensified monsoon coincides with lower temperatures, such as during MIS 3-4, even glaciers in the Eastern and Central Himalaya should have had favourable conditions to advance toward much lower elevations, with higher ice flux.
DE: 0720 Glaciers
DE: 1815 Erosion
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 1855 Remote sensing (1640)
SC: Cryosphere [C]
MN: 2007 Fall Meeting