Enhanced moisture availability in the headwater area of the Yellow River, northeastern Qinghai-Tibet Plateau, since the Last Deglacial: Multi-proxy evidence from an alpine permafrost mire

The interaction between mid-latitude westerlies and Asian monsoon introduces key uncertainties in paleoclimatology, especially for the northeastern Qinghai-Tibet Plateau (QTP) where contradictory proxy records persist despite comparable climatic settings. To address this knowledge gap, we reconstruct a 13.7-ka (1 ka = 1000 cal a BP) moisture history from an alpine permafrost mire in the headwater area of the Yellow River, integrating sedimentology (grain size, mineralogy, soil water content), geochemistry (total organic carbon, δ¹³C_org, stable elemental concentrations including Si, Al, Fe, Ti, Y, and Rb), and AMS 14C dating. The 8.95-m cryogenic loess-like sequence exhibits syngenetic permafrost features. Four effective moisture phases are identified: (1) cold-arid instability (13.7–11.5 ka); (2) gradual moistening (11.5–8.8 ka); (3) sustained wet conditions (8.8–4.6 ka); and (4) maximum effective moisture with enhanced variability (4.6–0 ka), particularly after 2.7 ka. We attribute the post-4.6 ka effective moisture maximum to intensified westerlies and a permafrost-vegetation feedback triggered by mid-Holocene thaw. These mechanisms highlight the underappreciated role of cryospheric processes in modulating regional hydroclimate. Our findings provide a valuable reference for understanding climate-permafrost-vegetation interactions since the Last Deglacial, with implications for predicting future hydrological and ecological shifts under accelerating permafrost degradation on the northeastern QTP.