Topographic modulation of lagged dust activity in the southeastern Tibetan Plateau during the Last Glacial Period

Topography exerts a fundamental control on atmospheric circulation and dust transport on the Tibetan Plateau, yet its role in modulating dust responses to global climate forcing remains unclear. The Nyingchi loess in the southeastern Tibetan Plateau provides a key archive for investigating topography-filtered dust activity and westerlies-monsoon interactions during the Last Glacial Period. Here, we present a Last Glacial loess record named KSM section in Nyingchi to decipher dust activity. We apply K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating method to establish geochronological timescale, and magnetic susceptibility and grain-size parameters to reconstruct dust activity history. Magnetic susceptibility variations are dominated by proximal coarse-grained allochthonous input, as indicated by coherent changes with sand content, suggesting episodic intensification of dust activity. These dust events broadly coincide with Heinrich event 4 (H4, ~39 ka) but exhibit a distinct millennial-scale lag. We propose that this lagged response arose from the synergy of a southward-displaced westerly jet and enhanced winter monsoon, combined with the time-transgressive exposure of glacio-fluvial sediments following H4. The canyon-valley topography of the Yarlung Zangbo then acted as an aerodynamic trap, amplifying wind transport capacity and preserving the protracted dust sequence. On orbital timescales, Northern Hemisphere summer insolation indirectly modulated dust transport via its influence on westerlies–monsoon coupling. Our results highlight how local topography filters hemispheric climate signals, providing new insights into the spatial heterogeneity of the Asian monsoon system during the Last Glacial Period.