Holocene hydroclimate evolution of northwestern Tibet Plateau in response to interaction between Indian summer monsoon and mid-latitude Westerlies circulation.

The scarcity of high-resolution paleoclimate records from the northwestern Tibetan Plateau (TP) limits our understanding the magnitude, extent, timing and drivers of the Indian Summer Monsoon (ISM) variability in this climatically sentisive region. Here we present a high-resolution sedimentary multi-proxy geochemical (Sr, Rb, Ca/Zr, Ti/Al, and TOC) lacustrine record from Lake Changmu Co over the northwestern WTP to infer monsoon changes spanning from 12 to 3.6 ka BP, when the lake has experienced highstands. Our results indicate that the lake productivity was lowered at the onset of Holocene (~12-10.5 ka BP), probably owing to relative none-influenced by ISM. However, the early Holocene climate optimum (~10.5-8 ka BP) was characterized by enhanced lake productivity and relative stable hydroclimate condition, corresponding to the strongest ISM driven by higher Northern Hemisphere summer insolation. The record further documented a pronounced dry event ~8 ka, expressed by reduced precipitation and diminished vegetation, which aligns temporally with the 8.2 ka cooling event. Since the middle Holocene, a trend toward colder and drier conditions would be linked to weakening ISM. Comparison of our record and North Atlantic climate change further revealed significant coherence within a dominant ~900-1000-year periodicity during the early to middle Holocene, suggesting persistent millennial-scale pacing of the northwestern TP hydroclimate by high-latitude climate variability. These results demonstrate that the Holocene hydroclimate evolution in the northwestern TP involved a transition from ISM-dominated humid early Holocene to Westerlies-influenced aridity late-Holocene.