Glacier and lake level change from TOPEX-series and Cryosat-2 altimeters in Tanggula: Comparison with satellite imagery

Abstract

We detect long-term elevation changes near a glacier terminus and an icefield in Tanggula Mountains from altimeter data from the TOPEX/Poseidon (T/P), Jason-1 (J1), Jason-2 (J2), and Jason-3 (J3) altimeters. An altimeter processing technique is developed for the detection, including waveform retracking, quality data selection, and elevation adjustment. The altimeter-observed glacier thinning is confirmed by the direct elevation differences between the digital elevation models from the satellite missions TanDEM-X and SRTM, and by the glacier area losses from Landsat images. At the two glacier sites, the altimeter-derived elevations show seasonal oscillations, with mean rates of -3.71 ± 0.3 and -3.08 ± 0.20 m year-1 over 1993–2002 (T/P only), and -1.88 ± 0.06 and -1.46 ± 0.07 m year-1 over 1993–2020 (T/P-Jason altimeters), with abnormal changes around the 1997–1998 El Niño. The declining rates suggest that the persistent losses of glaciers in Tanggula Mountains can no longer sustain the large thinning rates. The glacier feeds the nearby Chibuzhang Co lake, and lake level and glacier level changes from Cryosat-2 are consistent with those from the T/P-Jason altimeters. The glacier meltwater contributed to the accelerated rise of the glacier-fed Chibuzhang Co, at a rate of 0.15 ± 0.05 m year-1 over 1993–2002, increasing to 0.42 ± 0.01 m year-1 over 2003–2020. The lake levels of Chibuzhang Co experienced notable drops after the 1997–1998 and 2014–2016 El Niño. The Cryosat-2 result shows the altitude effect of glacier change: the higher the glacier, the less it melts. A repeat altimeter can provide time-lapsed elevation measurements as a virtual glacier station to monitor glacier melt caused by climate change.