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Abstract

The Tibetan Plateau (TP), known as Asia’s water tower, has experienced a pronounced wetting trend in recent decades, often attributed to moisture transport anomalies through western and eastern boundaries caused by westerly anomalies. Here we show that this explanation is incomplete. Using a complex network analysis, we find that humid air advection from the Atlantic is largely blocked by concurrent drying over the Iranian Plateau, precluding a western moisture supply. Instead, the TP wetting trend arises from intensified moisture inflow from the southern boundary. We identify a previously unrecognized mid-latitude wave train, triggered by European blocking, that enhances tropical moisture transport across the southern boundary of the TP. Over recent decades, the strengthening of this wave train, together with increased wetting over South Asia driven by asymmetric tropical Pacific warming, jointly amplifies TP hydrological changes. Our results reveal a synergistic coupling between tropical forcing and mid-latitude dynamics, providing a new framework for understanding the accelerated wetting of Asia’s water tower.