The variations in the lake water storage in the Tianshan region are an important indicator of climate change and play a key role in understanding the hydrological mass balance. Based on altimetry and satellite gravity, we investigated the spatiotemporal characteristics of the lake water storage changes during 2002–2022, and examined the contributions and proportions of all of the hydrological components to the mass balance. The results indicate that the total water storage of the lake complex showed an increasing rate (0.73±0.10 Gt/a). We found two abrupt wet periods in 2010 and 2016 (the regional total mass increased by 65.73 Gt and 67.35 Gt, respectively), which were reflected not only by the lake water storage but also by the soil moisture, snow water, and even GNSS displacement fields. Compared with their contributions to the mass (22% and 14%), the variations in lake area were remarkably slight (0.01% and 0.014%). Among the hydrological components, the soil moisture played a dominant role, and the contribution of the snow accumulation changes was also considerable. The mass anomalies were closely related to the precipitation caused by the increase of water vapor content, which was further associated with the occurrence of ENSO events (r=0.55, p<0.01). The results revealed that the long-term trend of the GNSS vertical displacements exhibited a better stability after the load correction was applied, which could reflect the long-term ground deformation more accurately. This study contributes to our understanding of the complex hydrological and tectonic processes in the Tianshan region.

Satellite radar altimeters have been used to monitor sea level changes and ice sheet elevation changes for more than 3 decades. Over mountain glaciers, radar altimetry has limited applications due to contaminated radar waveforms caused by complex glacier surfaces and steep terrains. In this study, we develop a glacier-threshold method (GTM) to determine glacier elevation changes over mountain glaciers in Alaska. The GTM can detect and remove invalid elevation observations from the TOPEX/Poseidon (T/P) and Jason-2 (J2) altimeters, creating usable elevation observations from 16–92% of the raw observations. The selected elevations are used to construct long-term time series of Alaskan glacier elevation changes over 1993–2002 (T/P) and 2008–2016 (J2) at 47 sites. A crossover analysis and a Lidar comparison confirm the result from T/P and J2. Our finding shows that most of the Alaskan glaciers studied have continued to decline in recent years. The largest declining rate is -11.06 ± 0.35 m/yr over Klutlan Glacier, followed by Chitina Glacier at -8.82 ± 0.12 m/yr. Glacier thickening occurred in some accumulation zones, such as Hubbard Glacier and Logan Glacier, and also at some glacier terminuses. The mechanisms of these elevation changes are discussed using climate datasets. It is suggested that changes in environmental factors such as precipitation, air temperature and sea water temperature influence the shifts in the trends of glacier elevation changes. A sophisticated processing system and altimeter data from repeat missions can facilitate long-term monitoring of small-scaled glaciers for a better understanding of glacier dynamics.

Glacier melt in High Mountain Asia (HMA) is an indicator of climate change, and has a major impact on the regional hydrology and freshwater supply. We determined the recent states of the HMA glaciers based on the first analysis of Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) data. We used the Gravity Recovery and Climate Experiment (GRACE) and GRACE-FO data to fill the gap of ICESat-1,2 and carry out an independent validation. The agreement between ICESat-1,2 and GRACE/GRACE-FO data at the total and regional scales demonstrates the high reliability of results. Based on ICESat-1,2, the total mass change of the HMA glaciers is -28 {plus minus} 6 Gt yr-1 from 2003-2019, which are more negative than stereo imagery based literature. The spatial variability of the glacier indicates rapid thinning in Nyaingentanglha but a slight increase in West Kunlun. ICESat-2 enable new insight into the continuous measurement of the HMA glacier.