Abstract
ABSTRACTTo obtain information on changes in glacier mass balance in the central Nyainqentanglha Range, a comprehensive study was carried out based on digital-elevation models derived from the 1968 topographic maps, the Shuttle Radar Topography Mission DEM (2000) and TerraSAR-X/TanDEM-X (2013). Glacier area changes between 1968 and 2016 were derived from topographic maps and Landsat OLI images. This showed the area contained 715 glaciers, with an area of 1713.42 ± 51.82 km2, in 2016. Ice cover has been shrinking by 0.68 ± 0.05% a−1 since 1968. The glacier area covered by debris accounted for 11.9% of the total and decreased in the SE–NW directions. Using digital elevation model differencing and differential synthetic aperture radar interferometry, a significant mass loss of 0.46 ± 0.10 m w.e. a−1 has been recorded since 1968; mass losses accelerated from 0.42 ± 0.20 m w.e. a−1 to 0.60 ± 0.20 m w.e. a−1 between 1968–2000 and 2000–2013, with thinning noticeably greater on the debris-covered ice than the clean ice. Surface-elevation changes can be influenced by ice cliffs, as well as debris cover and land- or lake-terminating glaciers. Changes showed spatial and temporal heterogeneity and a substantial correlation with climate warming and decreased precipitation.
Highlights
The Tibetan Plateau (TP), known as the roof of the world or Third Pole, contains the largest concentration of glaciers and icefields outside the polar regions (Yao and others, 2008)
Based on the Shuttle Radar Topography Mission (SRTM) and an interferometrically derived TanDEM-X elevation model, glaciers were determined to have experienced strong surface lowering in the central Nyainqentanglha Range (CNR), at an average rate of −0.83 ± 0.57 m a−1 from 2000 to 2014 (Neckel and others, 2017)
Acquired from the United States Geological Survey (USGS), the Landsat Operational Land Imager (OLI) images are orthorectified with the SRTM digital elevation model (DEM)
Summary
The Tibetan Plateau (TP), known as the roof of the world or Third Pole, contains the largest concentration of glaciers and icefields outside the polar regions (Yao and others, 2008). Most previous studies used satellite laser altimetry or stereo photogrammetry to calculate the glacier height changes that determined pronounced negative glacier mass balances in the region (Gardelle and others, 2013; Gardner and others, 2013; Neckel and others, 2014; Kääb and others, 2015), the results did differ slightly from each other. Based on the Shuttle Radar Topography Mission (SRTM) and an interferometrically derived TanDEM-X elevation model, glaciers were determined to have experienced strong surface lowering in the CNR, at an average rate of −0.83 ± 0.57 m a−1 from 2000 to 2014 (Neckel and others, 2017) While this pronounced surface-lowering value came from five debris-covered valley glaciers which are located in the east of the study area, it does not represent large scale glacier response to climate warming. Bistatic Differential Synthetic Aperture Radar Interferometry (DInSAR) and common DEM differencing were used to estimate the geodetic glacier mass balance in different subregions of the CNR between 1968 and 2013
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