Journal of Geophysical Research: Earth Surface
© American Geophysical Union
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ISI Journal Citation Reports © Ranking: 2015: 27/184 (Geosciences Multidisciplinary)
Online ISSN: 2169-9011
Associated Title(s): Journal of Geophysical Research
No climate-erosion feedback system in the western Himalayas
As water-laden air climbs up and over the Garhwal Himalayas, a subregion of the Himalayas found in northern India, orographic effects cause rain to fall out in two major bands. The water, primarily stemming from the summer monsoon, falls more heavily over the lower-altitude low Himalayas, with a second, lighter rain band at the border between the low and high Himalayas. Aside from being a major source of water—and flooding—this seasonal water also contributes to the erosion of the Himalayas. Previously, researchers hypothesized that a feedback system exists between the annual rains and the erosion of the Himalayas, such that the running water will eventually alter the shape of the mountains and, in turn, tectonic deformation. In a new study, Scherler et al. use measurements of beryllium cosmogenic nuclides collected at 25 sites around the Yarmuna River watershed, which winds through the Garhwal Himalayas, to measure local erosion rates.
Produced by the interaction of cosmic rays with the atmosphere, cosmogenic nuclides build up on the Earth’s surface at a predictable rate. Measuring their concentration gives an estimate of the duration of a surface’s exposure. Using their beryllium nuclide measurements, along with measurements of rainfall, stream power, and topographic characteristics, the authors analyzed which factors correlated most strongly with measured erosion rates. They found that erosion of the Himalayas in the Yamuna River catchment is controlled most strongly by factors such as the slope of the river channel or of the catchment as a whole. Erosion rates were largely unaffected by changes in rainfall rate. The authors suggest that conflicting with previous research, there is no climate feedback system on Himalayan erosion in this region.