Abstract
Long-term observations of lake water level are essential to our understanding of the evolution of Tibetan lake system. CryoSat-2 radar altimetry data over the Tibetan Plateau (2010–2014, P2) is used to extend lake level measurements from ICESat laser altimetry (2003–2009, P1). This study evaluates the performance of CryoSat-2 data by comparing with gauge-based water levels that are calibrated by ICESat-observed water level time series, and quantifies the uncertainty of water-level change rate estimates from satellite altimetry measurements. We completely investigate the 131 lakes that were observed by both ICESat and CryoSat-2. The mean change rate of water level for all of examined lakes in P2 (0.19 ± 0.03 m·year–1) is slightly lower than that (0.21 ± 0.02 m·year–1) observed in P1. The extended lake level time series also indicates that, in the past few years, lakes in the Northern Changtang (especially in Hol Xil) showed accelerated growth; and that the extensive lake level rises north to the Gangdise Mountains, during 2003–2009, were found dampened during the CryoSat-2 observation period. The spatio-temporal heterogeneity of precipitation observed from weather stations can be used to partly explain the observed temporal pattern of lake level changes over different sub-zones of the plateau.
Highlights
Recent research reveals dramatic changes in water level and mass budgets of Tibetan lakes in the early twenty-first century [1,2,3,4], indicating a sharp alteration existing in mass balance of Asian “water tower” [2,4,5] and an evident signal of climate dynamics [3,6,7,8,9]
The results indicate good agreement between CryoSat-2 altimetry measurements and gauge data and high consistency with ICESat altimetry data
The relatively larger bias of CrySat-2 altimetry on Yamzhog Yumco could be partly attributed to the more narrow lake water extent comparing with Namco
Summary
Recent research reveals dramatic changes in water level and mass budgets of Tibetan lakes in the early twenty-first century [1,2,3,4], indicating a sharp alteration existing in mass balance of Asian “water tower” [2,4,5] and an evident signal of climate dynamics [3,6,7,8,9]. Plenty of radar altimetry missions provide practical measurements of continental water surface elevations with a temporal coverage of more than twenty years since the 1990s, such as TOPEX/POSEIDON, ERS-1/2, Envisat, and Jason-1/2, at the accuracy ranging from centimeters to decimeters [11,12] These radar altimeters are only suitable for large water bodies and many lakes are only visited by one or two satellites due to their large-size footprints and along-track/cross-track spacing [13,14]. It is necessary to seek a solution of synthesizing multiple satellite altimetry datasets for sustainable monitoring on Tibetan lake dynamics
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