Glaciers, Erosion, and Climate Change in the Himalaya Mountains

侵蚀作用在喜马拉雅山脉的发育过程中起着重要的作用，通常受构造、地形和气候三者的相互作用控制。然而，人们对该山脉冰川覆盖严重的峰顶的侵蚀速率知之甚少，而且对于冰川是加速还是阻碍该地区的侵蚀，也没有达成共识。该项目将通过对该流域的冰和岩石碎片通量的详细检查，确定珠穆朗玛峰脚下的昆布盆地的当代侵蚀速率。这些通量将在三个时间尺度上确定：在这个项目的2年期间，~60年和~10,000年。将根据对数字地形和卫星图像、现有冰川学和地貌学数据以及实地研究的分析来确定冰和碎片的当代通量。这些将揭示与冰平流并积聚在冰川下游的碎片，以及通过前冰川流离开昆布冰川的碎片。将利用现有的全球气候数据对过去60年的物质平衡和径流进行模拟。记录冰川表面轮廓、表面速度和碎屑覆盖的历史数据也将指导这一时期碎屑和冰通量的建模估计。将对自大约1万年前最后一次主要冰川推进以来在昆布河谷下游形成的巨大碎片大厦的体积进行估计，以确定来自昆布盆地上游的碎片的体积。这将通过卫星图像、数字高程模型以及可用的雷达和重力测量来完成。这段时间内的平均侵蚀速率可以根据对昆布前冰川河当代沉积物通量的测量，通过计算这段时间内河流排出的沉积物的比例，从这一碎屑体积中计算出来。这项研究将促进对雪和碎片之间相互作用的了解，这些相互作用维持了大量低纬度冰川和塑造了高山。冰川是世界各地山脉的共同特征，这项研究将记录它们在侵蚀和沉积物动员中的作用。该项目还将有助于评估两个重要问题：气候变化如何影响喜马拉雅冰川，以及对依赖喜马拉雅和西藏冰川发源于主要河流的大量人口可能产生的后果。这些后果包括：1)由于冰川加速融化，最初的径流量增加，随后，冰川萎缩带来的淡水供应减少；2)冰川迅速退缩形成的冰坝湖泊造成洪水的威胁日益增加。

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.