Global hydroclimatic drivers of terrestrial water storage changes in different climates

Abstract

The Gravity Recovery and Climate Experiment (GRACE) mission provides an unprecedented way to assess terrestrial water storage changes (TWSC) worldwide. However, hydroclimatic drivers of GRACE-derived TWSC in different climates have not been systematically examined, which hinders its applications in water resources management and hydrological model development. In this study, we derived the monthly TWSC using the GRACE dataset, and analyzed its partial correlations with precipitation (P), evapotranspiration (ET), runoff (R), and temperature (T) from 2003 to 2019 under the Köppen-Geiger world climate classification system. Relative contributions of the four hydroclimatic elements (P, ET, R, and T) to TWSC were quantified using the hierarchical partitioning method. The results indicate that P mainly controls TWSC in tropical climates, hot semi-arid climate, and temperate and continental climates with dry winter. ET is the primary driver of TWSC in mid- and high-latitude regions that feature temperate and continental climates with no dry season, subarctic climates, and polar climates. T mainly influences TWSC in cold arid climates, temperate and continental climates with dry summer or no dry season, and ice cap climate. However, TWSC in many arid climates near the Tropic of Cancer and the Tropic of Capricorn are not well explained by all four hydroclimatic variables according to their non-significant partial correlations. Large trends in annual TWSC are found in South America, western Canada, eastern contiguous United States, and Africa, which are likely due to marked changes in P based on their similar spatial pattern. In particular, decreasing TWSC are found in most continental climates, which manifests a deterioration of water resources availability in these regions. Overall, our results clarify the major hydroclimatic drivers of TWSC in different climates at a global scale, which may help improve TWSC modeling and prediction through a judicious selection of explanatory hydroclimatic variables in different climates.