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

Abstract

SignificanceWe increasingly rely on global models to project impacts of humans and climate on water resources. How reliable are these models? While past model intercomparison projects focused on water fluxes, we provide here the first comprehensive comparison of land total water storage trends from seven global models to trends from Gravity Recovery and Climate Experiment (GRACE) satellites, which have been likened to giant weighing scales in the sky. The models underestimate the large decadal (2002–2014) trends in water storage relative to GRACE satellites, both decreasing trends related to human intervention and climate and increasing trends related primarily to climate variations. The poor agreement between models and GRACE underscores the challenges remaining for global models to capture human or climate impacts on global water storage trends.

Tracking Seasonal Fluctuations in Land Water Storage Using Global Models and GRACE Satellites

“…To address these issues, we conducted a comprehensive comparison of TWSA seasonal amplitudes from seven models with three GRACE mascon solutions based on 183 river basins globally. This study builds on a previous analysis that focused on TWSA trends using mostly the same basins, GRACE solutions, and models (Scanlon et al, ). However, median trends generally represent less than ~5% of the time series variance, which is dominated by seasonal amplitudes.…”

Using Satellite‐Based Vegetation Cover as Indicator of Groundwater Storage in Natural Vegetation Areas

“…Groundwater supports the growth of natural vegetation and biota as well as being a vital natural resource (Aeschbach‐Hertig & Gleeson, ). Rapid groundwater storage (GWS) depletion and its effect on surface water storage in recent years has been well documented in some of the densest populated areas of the World (Bhanja et al, ; Bhanja et al, ; Bhanja & Mukherjee, ; Döll et al, ; Feng, ; Gleeson et al, ; Mukherjee et al, ; Rodell et al, ; Rodell et al, ; Scanlon et al, ; Voss, ; Wada et al, ), thereby accentuating the socioeconomic stress over billions of people in future. GWS depletion can have adverse consequences on phreatophytes‐groundwater‐dependent natural vegetation with roots that tap the water table.…”

Using GRACE to Explain Variations in the Earth's Oblateness

“…Also, as noted by Lavallée et al (2010) and Scanlon et al (2018), geophysical models may be particularly weak in reconstructing multiple year variations. The traditional way of interpreting J 2 variations relies on the reconstruction of the observed signal by means of combining various of geophysical models.…”