Warming-driven rise in soil moisture entropy signals destabilization of the Asian Water Tower

TL;DR

This study uses an entropy-based approach to analyze soil moisture changes on the Tibetan Plateau, revealing a shift from increased stability due to wetting to potential destabilization caused by future warming, with implications for water security.

Contribution

It introduces an entropy framework to assess soil moisture system stability and demonstrates how climate warming may reverse current stability trends on the Tibetan Plateau.

Findings

Wetting has increased system stability from 2000 to 2024.

Future warming is projected to increase soil moisture entropy, indicating destabilization.

ENSO modulates regional heterogeneity and stability of soil moisture.

Abstract

The Tibetan Plateau (TP), known as the "Asian Water Tower," is currently undergoing a rapid wetting trend. While this moisture increase is often viewed as beneficial for water availability, it remains unclear whether the hydrological system itself is becoming more resilient or drifting toward instability. Here, we apply an entropy-based framework to quantify the changing structural organization of the TP's soil moisture system. We show that from 2000 to 2024, regional wetting has driven a long-term decline in entropy, reflecting an increase in system order and stability due to enhanced hydrological buffering capacity. This stability is modulated by the El Ni\~no-Southern Oscillation (ENSO), which regulates regional heterogeneity via a distinct spatial dipole. Crucially, however, CMIP6 climate projections reveal an alarming reversal: future warming triggers a rise in entropy. This transition signals a loss of systemic resilience, characterized by intensified spatial disorder and potential abrupt regime shifts by the mid-century. Our findings suggest that while current wetting provides a stabilizing buffer, continued warming is projected to amplify spatial heterogeneity, thereby destabilizing the Asian Water Tower, with significant risks for downstream water security.