Quantifying the Long-term Changes of Terrestrial Water Storage and Their Driving Factors
First Author
Xiaoying Shi
shix@ornl.gov
All Authors
Yaoping Wang, Jiafu Mao, Peter E. Thornton, Ricciuto M. Daniel, and Forrest M. Hoffman
Topic
Land - River - Human
Project
E3SM
Abstract
Global warming is expected to cause changes in terrestrial water storage (TWS) across the land surface, with widespread impacts on ecosystems and society. Although extensive research has been performed to analyze TWS changes and possible drivers during the post-2000 period, when many sources of satellite data are available, longer-term evolution of TWS and associated environmental forcings remain relatively unexplored. Here we quantified the global TWS changes for the period 1941-2012 and attributed the TWS variations to environmental factors using the latest GRACE-based TWS reconstructions and 36 factorial ensemble simulations of the Energy Exascale Earth System model (E3SM) land model (ELM) version 1. We found that the multi-year TWS increased significantly over the globe (0.71 mm year-1, P < 0.01), the northern (0.6 mm year-1, P < 0.01) and southern (1.05 mm year-1, P < 0.01) hemispheres, and for most biomes (0.44–1.43 mm year-1, P < 0.01), but decreased insignificantly for tropical forests in Africa (−0.16 mm year-1, P > 0.05) and Asia (−1.28*10-3 mm year-1, P > 0.05). Climate was the dominant external driver of the TWS trends in 85% of the global land area; anthropogenic drivers, in decreasing order of importance, were atmospheric CO2 concentration, land use and land cover change, nitrogen deposition, and aerosol deposition. Among the climate factors, the most important contributor to positive trends was climatological imbalance among precipitation, evapotranspiration, and runoff. Increasing precipitation also contributed to the increasing TWS at the global and hemispheric levels, and in most of the biomes. Together, the findings revealed an intensification of the global TWS and its natural and human driving patterns, contributing to better understanding and projection of the global water cycle.
