Glacier mass changes in Rongbuk catchment on Mt. Qomolangma from 1974 to 2006 based on topographic maps and ALOS PRISM data

Elevation changes of glacier surfaces were investigated in Rongbuk Catchment (RC) on the northern slopes of Mt. Qomolangma in the central Himalayas, by comparing a digital elevation model (DEM) generated from the 2006 ALOS/PRISM imageries with the base DEM1974 derived from the 1:50,000 topographic maps. The average elevation change rate of glacier surfaces in RC was estimated at -0.47±0.23ma ^-1 between 1974 and 2006. Such surface lowering rates varied significantly with glaciers and altitudes. One of the notable results is that the debris-covered ice thinned much more rapidly than the exposed ice at higher altitudes. Overall, glaciers in RC have lost mass of -0.06±0.04Gta ^-1 during 1974-2006. Glacier imbalance constitutes about 50% or more of the Rongbuk runoff.