Using Remotely-sensed Precipitation and Glacial Velocities as Climatic Indicators in the Himalaya

The Himalaya and adjacent Tibetan Plateau are the source of several major Asian rivers supporting a large, diverse ecosystem and a population of more than 1 billion people [Ives and Messerli, 1989; Barnett et al., 2005]. Large rivers such as the Indus, Sutlej, Ganges, Arun, and Brahmaputra/Tsangpo draining the southern Tibetan Plateau and the Himalaya are essential for agriculture and energy generation and are the pathways for sediments leaving the orogen. The southern Himalayan front spans the countries of India, Nepal, and Bhutan, and hosts some of the wettest inhabited placed on Earth. Along its entire length it displays a steep, 10-fold rainfall gradient reaching from the Ganges plains in the south to the very arid parts of the Tibetan Plateau in the north [Bookhagen and Burbank, 2006; in press] (Figure 1A). Precipitation in the upstream and high-elevation parts of Himalayan river basins falls as snow, causing a natural delay in the river discharge. The snowfall nourishes snowfields, and some of the world’s largest valley glaciers (Figure 1B). Thus, the hydrologic budget of Himalayan rivers is dominated by monsoonal rainfall as well snow and glacial melt, but their relative contribution is not well established. Current knowledge of rainfall and snow-cover distribution is unreliable because this remote region lacks a dense gauge network. Field observations of glaciers are scarce, and hence satellite and aerial imagery is often used to monitor recent glacier changes [Kääb, 2005; Berthier et al., 2007; Scherler et al., in review], but so far no study has covered large regions from different climatic compartments of the Himalaya to systematically study glacial behavior with respect to their controlling factors. Here, we use calibrated, remote-sensing data for precipitation and snowmelt to constrain the climatic component and combine these with glacial flow-velocity measurements.