Reinterpreting Global GRACE Trends Based on Century-Long GRACE-REC Data

Assessing changes in freshwater availability accurately is crucial for societal development. Previous studies have examined long-term variations in basin-scale terrestrial water storage (TWS) using Gravity Recovery and Climate Experiment (GRACE) mission data. However, different basins exhibit distinct spatial and temporal TWS variation patterns. To better interpret the TWS trends in each basin during the GRACE era (2003-2016), this study proposes a novel criterion based on a century-long GRACE-REC data set. This criterion assesses the trends in GRACE TWS (TrendG), precipitation-induced trends (TrendPI), and non-precipitation-induced trends (TrendNPI) over the GRACE period. By calculating upper and lower bound values for long-term climate-driven TWS trends using GRACE-REC data, an indicator is provided to evaluate the range of TWS trend variations in a basin under natural conditions. Results reveal that among the 266 global basins analyzed in this study, the trends (TrendG, TrendPI, or TrendNPI) in 115 basins exceed the maximum or minimum water storage trends associated with natural climate variability. This includes 20 large basins, 34 medium basins, and 61 small basins, indicating significant TWS changes during the GRACE period. Furthermore, we analyze the driving mechanisms of TWS trends in the 20 large basins using multi-source data. The mechanisms identified through this method align well with both our analysis and previous studies, confirming the reliability of this approach for assessing TWS trends. Understanding changes in freshwater availability is crucial for the development of human societies. This study focuses on assessing long-term changes in basin-scale terrestrial water storage (TWS) using data from the Gravity Recovery and Climate Experiment (GRACE) mission. The objective of this research was to develop a new criterion to assess TWS trends in different basins during the GRACE era. We calculated the upper and lower bound values of long-term climate-driven TWS trends for a given length of time, analyzed the trends induced by precipitation and non-precipitation factors, and examined the driving mechanisms behind TWS trends in selected basins. Among the 266 global basins analyzed, 115 basins showed TWS trends that exceeded the trend bounds under natural climate variability. This indicates significant changes in TWS during the GRACE period. Our analysis of driving mechanisms aligned well with previous studies, providing confidence in the reliability of our approach. Our study reveals significant changes in TWS in numerous basins worldwide, highlighting the importance of monitoring and managing water resources effectively. A novel criterion is proposed to interpret trends in Gravity Recovery and Climate Experiment (GRACE), precipitation-induced, and non-precipitation-induced water storageThe upper and lower bounds of long-term climate-driven terrestrial water storage (TWS) trends are estimated based on one century-long GRACE-REC dataSignificant non-precipitation effects contribute to GRACE trends below the lower bounds of climate-driven TWS trends in global basins