Soil Moisture Dynamics in South America: A Multi‐Dataset Analysis From 1990 to 2020

Based on ERA5, GLEAM, GLDAS, and CCI SM, South America soil moisture variability is investigated. Calculations of harmonic analysis, EOF decomposition, trend evaluation, correlations, and spectral analysis reveal strong regional contrasts in SM patterns driven by major climate systems and modes. Seasonal SM variability is dominated by the migration of the Intertropical Convergence Zone (ITCZ) and the influence of the South Atlantic Convergence Zone (SACZ), especially in the Amazon and central Brazil. EOF results highlight these areas as key centres of variability, reflecting strong coupling between precipitation and SM, with significant implications for agriculture. Trend analysis shows increasing SM in northern regions, whereas central, northeastern, and southern Brazil exhibit declines, linked to changing rainfall regimes and atmospheric circulation, including the South Atlantic Subtropical High (SASH). In the Northeast, reductions in SM amplify risks related to drought and water scarcity. Power spectral analysis reveals significant periodic components—particularly in GLEAM and GLDAS, associated with ENSO and Tropical Atlantic Variability (TAV), underscoring the role of ocean–atmosphere interactions in SM dynamics. These findings emphasise the need for multi‐source datasets and robust analyses to understand and anticipate SM changes critical to agriculture, water resources, and climate resilience in South America.