Global models underestimate large decadal declining and rising water storage trends relative to GRACE satellite data

Bridget R. Scanlon (1) , Zizhan Zhang (2) , Himanshu Save (3) , Alexander Sun (4) , Hannes Müller Schmied (5) , Ludovicus van Beek (6) , David N. Wiese (7) , Yoshihide I Wada (8) , Di Long (2) , Robert Reedy (2) , Laurent Longuevergne (9) , Petra Döll (5) , Marc Bierkens (6)

1 JSG - Jackson School of Geosciences
2 BEG - Bureau of Economic Geology [Austin]
3 CSR - Center for Space Research [Austin]
4 CWI - Centrum voor Wiskunde en Informatica
5 Goethe-Universität Frankfurt am Main
6 Universiteit Utrecht
7 JPL - Jet Propulsion Laboratory
8 IIASA - International Institute for Applied Systems Analysis [Laxenburg]
9 GR - Géosciences Rennes

Assessing reliability of global models is critical because of increasing reliance on these models to address past and projected future climate and human stresses on global water resources. Here, we evaluate model reliability based on a comprehensive comparison of decadal trends (2002-2014) in land water storage from seven global models (WGHM, PCR-GLOBWB, GLDAS NOAH, MOSAIC, VIC, CLM, and CLSM) to trends from three Gravity Recovery and Climate Experiment (GRACE) satellite solutions in 186 river basins (∼60% of global land area). Medians of modeled basin water storage trends greatly underestimate GRACE-derived large decreasing (≤-0.5 km3/y) and increasing (≥0.5 km3/y) trends. Decreasing trends from GRACE are mostly related to human use (irrigation) and climate variations, whereas increasing trends reflect climate variations. For example, in the Amazon, GRACE estimates a large increasing trend of ∼43 km3/y, whereas most models estimate decreasing trends (-71 to 11 km3/y). Land water storage trends, summed over all basins, are positive for GRACE (∼71-82 km3/y) but negative for models (-450 to -12 km3/y), contributing opposing trends to global mean sea level change. Impacts of climate forcing on decadal land water storage trends exceed those of modeled human intervention by about a factor of 2. The model-GRACE comparison highlights potential areas of future model development, particularly simulated water storage. The inability of models to capture large decadal water storage trends based on GRACE indicates that model projections of climate and human-induced water storage changes may be underestimated.

Mots clés: terrestrial total water storage anomalies; land surface models; global mean sea level; global hydrological models; GRACE satellites

Domaines: Hydrologie

Bridget R. Scanlon, Zizhan Zhang, Himanshu Save, Alexander Sun, Hannes Müller Schmied, et al.. Global models underestimate large decadal declining and rising water storage trends relative to GRACE satellite data. Proceedings of the National Academy of Sciences of the United States of America, 2018, 115 (6), pp.E1080-E1089. ⟨10.1073/pnas.1704665115⟩. ⟨insu-01695303⟩