Investigating the temporal patterns of terrestrial water storage and the climatic drivers in the Tianshan mountains and their surrounding regions

Terrestrial water storage (TWS) in the Tianshan mountains and their surrounding regions has been declining for over two decades under a changing climate, making the arid region drier. Although studies have examined TWS changes there, most have focused on trend analysis or the effects of individual hydrological factors and were constrained by a short data span. As a result, the complete picture of the temporal patterns of the TWS change there has never been revealed. To fill this gap, this study conducts a comprehensive investigation into the multi-scale temporal variations of TWS using the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) and multiple hydroclimatic data. We extracted and quantified the long-term trend, seasonal signal, and interannual signal, with the interannual signal exhibiting a dominant periodicity of 7.75 years. We found an accelerated declining trend in TWS, specifically, the declining rate after 2016 was 11.8 times that before 2016. We also found that the seasonal and interannual signals derived from GRACE had 2 months and 12 months phase delay compared to the results derived from the hydroclimatic model. Precipitation was identified as the primary hydrological factor regulating TWS interannual signals, and their variations were strongly modulated by the North Atlantic Oscillation (NAO), the El Niño-Southern Oscillation (ENSO), and the Atlantic Multidecadal Oscillation (AMO). This study provides a complete picture of the TWS’s temporal patterns and atmospheric driving mechanism, thereby advancing the understanding of TWS change in the Tianshan mountains and their surrounding regions. These findings provide a scientific basis for regional water resource assessment and prediction under evolving climate conditions.