Vertical Coherence Dominates Decadal Land Water Storage Change Despite Hydroclimatic Extremes and Groundwater Pumping
Abstract
Whether surface and deeper water storage trends move in the same direction underpins assessments of freshwater availability. Theory predicts vertical coherence, yet it is untested globally and questioned under climate extremes and human management. Using depth‐sensitive satellite observations spanning surface soil moisture (SSM) (Soil Moisture Active Passive) and total terrestrial water storage (GRACE/FO) for 2015–2025, we assess the vertical organization of multi‐year land water change across ∼78 million km2 of land. We find that vertical coherence dominates, with same‐sign surface and total storage trends across >70% of the analyzed area. Satellite Normalized Difference Vegetation Index reinforces this pattern, aligning with coherent trends and tracking deeper storage where surface and total trends diverge. Divergence is spatially clustered and linked to repeated hydroclimatic extremes or intensive groundwater abstraction. These results provide the first global observational test of vertical coherence in land water storage change, showing it remains dominant but can be weakened by depth‐selective climatic and anthropogenic pressures.