The ‘Asian water tower’ is starting to wobble, computer simulations show

“Asia’s water tower” is heading towards a more unpredictable and unstable future, according to a new study measuring the Tibetan Plateau’s stability. The study, published on August 21 in Nature Communications, examined the entropy of the region to gauge how much chaos or disorder was building up in a complex system. The results were released just days before a catastrophic flash flood struck the Nepal-China border, killing hundreds and leaving a trail of devastation along the way. Chen Xiaosong, a physicist at the school of systems science at Beijing Normal University and lead author of the study, said on Thursday that from now to the end of this century, “the increase of soil water and the intensification of glacier melting [in the Tibetan Plateau] will constantly trigger such geological disasters”. Countries along the Himalayas could also face greater risks. “India will definitely be affected, but the specific impacts still require further analysis and research,” he added. Chen’s team examined the plateau’s soil moisture system from 2000 to 2024, which is closely linked to the water and climate patterns affecting nearly two billion people across South and East Asia. The researchers found that the plateau became more stable as it became wetter. “Our analysis found that entropy declined while soil moisture increased and the plateau became wetter.” But that trend is projected to reverse. “From 2025 to 2100, entropy starts to rise and the system becomes more disordered,” said Xie Yiran, the study’s first author. The projected rise in entropy is accompanied by declining soil moisture, weaker hydrological buffering and stronger regional contrasts. Lower entropy means soil-moisture variability is concentrated in a few coherent patterns, while higher entropy means it is spread across more competing patterns and the system becomes more disordered. “Traditional methods treat entropy as a core quantity, but it is difficult to calculate the entropy of complex systems directly,” Chen said. “Our entropy method can describe the overall properties and collective behaviour of a complex system and can even serve as an early-warning signal.” Xie said the approach differed from conventional climate indicators because “it does not look at a single location or the average of the whole region, but at how different parts of the system coordinate with one another”. From 2000 to 2024, soil moisture across the plateau increased significantly, with about 57.5 per cent of the region showing significant wetting and only 8.1 per cent showing significant drying. Over the same period, soil-moisture entropy declined significantly, indicating that the system became more organised, with the decline accelerating after about 2018 as the plateau became wetter. But the model predicts that the plateau’s present wetting-driven buffer may not last under continued warming by the end of this century. The study’s implications extend beyond the plateau because changes in its soil moisture can influence the South Asian monsoon, downstream river basins and extreme precipitation, while major river systems across South and East Asia support nearly two billion people. The system is also influenced by El Nino and La Nina, with Tibetan Plateau soil-moisture entropy lagging El Nino-Southern Oscillation (ENSO) entropy by about six months. ENSO is a climate cycle with two opposite phases: El Nino, the warm phase marked by above-average sea surface temperatures in the central and eastern tropical Pacific, and La Nina, the cool phase marked by below-average temperatures in the same region. Recent strong ENSO events can therefore have delayed effects on the Tibetan Plateau and surrounding regions, with the soil-moisture response lagging the climate signal by about six months. During El Nino, shifts in the Walker circulation trigger atmospheric anomalies that alter moisture transport across the plateau, changing regional precipitation and soil-moisture differences. The Walker circulation is a large-scale atmospheric overturning cell over the equatorial Pacific. “The result is a ‘see-saw’ between the western and southwestern Tibetan Plateau, with stronger regional contrasts associated with higher entropy,” Xie added. The researchers found that precipitation is the main driver of this spatial contrast, with snowfall and spring melt particularly important in the west and monsoonal rainfall dominating the southwest. The six-month lag reflects the accumulated response of the hydrological system, as soil moisture responds to precipitation after about one month while snowmelt and seasonal freeze-thaw processes can delay the signal further. The ensemble showed a significant breakpoint around 2052, after which the dominant soil-moisture mode declined at more than twice its previous rate and the contrast between western and southwestern regions increased sharply. The authors therefore describe the result as a heightened risk of instability in a complex system rather than proof of an inevitable tipping point.

The ‘Asian water tower’ is starting to wobble, computer simulations show

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}The Tibetan Plateau is losing stability, a study suggests, as a catastrophic flash flood hit on the Nepal-China border

The Tibetan Plateau is losing stability, a study suggests, as a catastrophic flash flood hit on the Nepal-China border