COMPARISON OF LATE PLEISTOCENE AND MODERN GLACIER EXTENTS IN CENTRAL NEPAL BASED ON DIGITAL ELEVATION DATA AND SATELLITE IMAGERY

Late Pleistocene and modem ice extents in central Nepal are compared t o estimate equilibrium line altitude (ELA) depressions. New techniques are used for determining the former extent of glaciers based on quant itative, objective geomorphic analyses of a similar to 90-m resolution digital elevation model (DEM). For every link of the drainage network , valley form is classified as glacial or fluvial based on cross-valle y shape and slope statistics. Down-valley transitions from glacial to fluvial form indicate the former limits of glaciation in each valley. Landsat Multispectral Scanner imagery for the same region is used to m ap current glacier extents. For both full-glacial and modern cases, EL As are computed from the glacier limits using the DEM and a toe-to-hea dwall altitude ratio of 0.5. Computed ELA depressions range from 100-9 00 m with a modal value of similar to 650 m and a mean of similar to 5 00 m, values consistent with previously published estimates for the ce ntral Himalaya but markedly smaller than estimates for many other regi ons. We suggest that this reflects reduced precipitation, rather than a small temperature depression, consistent with other evidence for a w eaker monsoon under full-glacial conditions. (C) 1998 University of Wa shington.