Dynamics and Couplings of Terrestrial Water Storage Extremes From GRACE and GRACE-FO Missions During 2002–2024

Abstract

Hydroclimatic extremes such as droughts and floods severely impact global livelihoods, economies, and ecosystems, yet their attribution remains challenging. This study evaluates global Terrestrial Water Storage (TWS) extremeness and climate linkages using GRACE and GRACE-FO data from 2002 to 2024. By examining upper and lower deciles of TWS anomalies representing wet and dry extremes and assessing spatial dependencies, we identify key patterns, trends, and driving factors through dimensional reduction and probabilistic modeling. Results show global TWS extremes are governed by a 2–3-year oscillatory cycle linked to El Niño–Southern Oscillation, which synchronizes drought and pluvial conditions across continents. Drought extremes show broader spatial coherence than pluvial events, indicating moisture deficits propagate more uniformly through the land–atmosphere system. A weaker quasi-decadal cycle (6–10 years) modulates these responses and underlies a shift around 2011–2012. Before 2011, wet extremes intensified, while after 2012, dry extremes became dominant, particularly in interior Asia, western United States, and southern Africa. Neither pluvial nor drought extremes show significant global trends in intensity; however, they remain phase-locked, with wet events twice as intense as dry ones, reflecting asymmetric hydrologic response to moisture surpluses versus deficits. We probabilistically reconstruct TWS extremeness during satellite data gaps using leading spatio-temporal patterns. The current record, spanning less than one multidecadal cycle, remains insufficient for robust attribution. Extending satellite gravimetry is essential to refine uncertainty in attributing global pluvial and drought extremes under climate change.