Nengfang Chao¹, Zhengtao Wang², Cheinway Hwang^2,3,*, Taoyong Jin² and Yung-Sheng Cheng³
1 MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China; nfchao@hust.edu.cn
2 School of Geodesy and Geomatics,Wuhan University, Wuhan 430079, China; ztwang@whu.edu.cn (Z.W.); tyjin@sgg.whu.edu.cn (T.J.)
3 Department of Civil Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan; king90663@gmail.com
* Correspondence: cheinway@mail.nctu.edu.tw or cheinway@gmail.com;
Tel./Fax: +886-3-571-2121 (ext. 54937)
Academic Editors: Yuei-An Liou, Chyi-Tyi Lee, Yuriy Kuleshov, Jean-Pierre Barriot, Chung-Ru Ho, Xiaofeng Li and Prasad S. Thenkabail
Received: 3 August 2016; Accepted: 10 January 2017; Published: 14 January 2017

Abstract: Several studies have indicated that glaciers in the Qinghai-Tibet plateau are thinning, resulting in reduced water supplies to major rivers such as the Yangtze, Yellow, Lancang, Indus, Ganges, Brahmaputra in China, and south Asia. Three rivers in the upstream of Yangtze River originate from glaciers around the Geladandong snow mountain group in central Tibet. Here we used elevation observations from Ice, Cloud, and land Elevation Satellite (ICESat) and reference elevations from a 3-arc-second digital elevation model (DEM) of Shuttle Radar Terrestrial Mission (SRTM), assisted with Landsat-7 images, to detect glacier elevation changes in the western (A), central (B), and eastern (C) regions of Geladandong. Robust fitting was used to determine rates of glacier elevation changes in regions with dense ICESat data, whereas a new method called rate averaging was employed to find rates in regions of low data density. The rate of elevation change was -0.158+/-0.066 m a^-1 over 2003–2009 in the entire Geladandong and it was -0.176+/-0.102 m a^-1 over 2003–2008 in Region C (by robust fitting). The rates in Regions A, B, and C were -0.418+/-0.322 m a^-1 (2000–2009), -0.432+/-0.020 m a^-1 (2000–2003), and -0.321+/-0.139 m a^-1 (2000–2008) (by rate averaging). We used in situ hydroclimatic dataset to assess these negative rates: the glacier thinning was caused by temperature rises around Geladandong, based on the temperature records over 1979–2009, 1957–2013, and 1966–2013 at stations Tuotuohe, Wudaoliang, and Anduo. The thinning Geladandong glaciers led to increased discharges recorded at the river gauge stations Tuotuohe and Chumda over 1956–2012. An unabated Geladandong glacier melting will reduce its long-term water supply to the Yangtze River Basin, causing irreversible socioeconomic consequences and seriously degrading the ecological system of the Yangtze River Basin.

Remote Sens. 2017, 9, 75; doi:10.3390/rs9010075