Glaciers, Erosion, and Climate Change in the Himalaya Mountains

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Erosion plays an important role in the development of the Himalaya Mountains, and is generally controlled by the interplay among tectonics, topography and climate that govern mountain building. Little is known, however, about rates of erosion at the heavily glaciarized crest of the range, and there is no consensus on whether glaciers accelerate or impede erosion in the region. This project will determine contemporary erosion rates for the Khumbu basin, at the foot of Mt Everest, through a detailed examination of the fluxes of ice and rock debris in this drainage basin. These fluxes will be determined on three time scales: during the 2-year duration of this project, ~60 years and ~10,000 years. Contemporary fluxes of ice and debris will be determined from analyses of digital topography and satellite images, existing glaciological and geomorphologic data, and field studies. These will reveal the debris advected with the ice and accumulating in the lower reaches of the glacier, and the debris that exits Khumbu Glacier through the proglacial stream. Mass balance and runoff will be modeled through the last six decades using available global climate data. Historical data documenting the glacier surface profile, surface velocities and debris cover will also guide modeled estimates of debris and ice fluxes through this period. Estimates will be made of the volume of the massive debris edifice that formed in the lower Khumbu valley since the last major glacial advance about 10,000 years ago to determine the volume of debris derived from the upper Khumbu basin. This will be accomplished using satellite imagery, digital elevation models, and available radar and gravity surveys. The erosion rate averaged over this time span can be calculated from this debris volume by accounting for the fraction of sediment evacuated fluvially during this period on the basis of the measurements of contemporary sediment flux in the Khumbu proglacial stream.This study will advance knowledge of the interactions between snow and debris that sustain massive low-latitude glaciers and shape high mountains. Glaciers are common featues of mountain ranges around the world, and this study will document their role in erosion and mobilization of sediment. This project wiil also help evaluate two important issues: how climate change may affect glaciers in the Himalaya and the probable consequences for the vast population dependent on the major rivers that emanate from the glaciers in the Himalaya and Tibet. These consequences include 1) an initial increase in runoff due to the accelerated melting followed by diminishing supplies of fresh water from the dwindling glaciers, and 2) an increasing threat of floods from ice-dammed lakes formed by rapid glacier retreat.