Warming-driven rise in soil moisture entropy signals growing instability risk in the Asian Water Tower.

The Tibetan Plateau (TP), known as the Asian Water Tower, supplies water to billions of people but is undergoing rapid warming and wetting. Whether this increased moisture stabilizes the regional hydrological system or merely provides a transient buffer remains unclear. Here we apply an entropy-based framework to quantify the structural organization of the TP's soil moisture system. During 2000-2024, regional wetting has driven a long-term decline in entropy, reflecting an increase in system order and enhanced hydrological buffering capacity. This ordering is modulated by ENSO, which regulates regional heterogeneity via a spatial dipole. However, CMIP6 projections reveal a reversal: entropy increases under continued warming and regional contrasts intensify, with some models exhibiting transition-like behavior. Our findings suggest that while current wetting provides a stabilizing buffer, continued warming is projected to amplify spatial heterogeneity, thereby elevating instability risk in the Asian Water Tower and threatening downstream water security.