Stefan Doberschütz

Monsoonal forcing of Holocene paleoenvironmental change on the central Tibetan Plateau inferred using a sediment record from Lake Nam Co (Xizang, China)

This study focuses on Holocene monsoon dynamics on the central Tibetan Plateau (TP) inferred using a sediment record from Lake Nam Co. A high-resolution (decadal) multi-proxy approach, using geochemical, micropaleontological, and sedimentological methods was applied. Fifteen AMS-14C ages were used to establish the chronology, assuming a reservoir effect of 1,420xa0years. Our results point to a first strong monsoonal pulse at Lake Nam Co ~11.3xa0calxa0kaxa0BP, followed by colder and drier conditions until ~10.8xa0calxa0kaxa0BP. A warm and humid climate from ~10.8 to ~9.5xa0calxa0kaxa0BP is related to a strong summer monsoon on the central TP, triggering a lake-level highstand at ~9.5xa0calxa0kaxa0BP. Declining minerogenic input after ~9.5xa0calxa0kaxa0BP indicates less moisture availability until ~7.7xa0calxa0kaxa0BP. Following stable conditions between ~7.7 and ~6.6xa0calxa0kaxa0BP, a warm and wet climate is inferred for the time span from ~6.6 to ~4.8xa0calxa0kaxa0BP. A change towards drier conditions after ~4.8xa0calxa0kaxa0BP points to a weakening of the Indian Ocean Summer Monsoon on the central TP, further diminished after ~2.0xa0calxa0kaxa0BP. A short-term wet spell occurred from ~1.5 to ~1.3xa0calxa0kaxa0BP. By comparing the results derived from Lake Nam Co with several lacustrine records from the central, northern, and eastern TP, a similar but not synchronous pattern of monsoon-driven paleoenvironmental change is observed. Although the general trend of lake and catchment evolution on the TP during the Holocene is also reproduced in this record, pronounced spatial and temporal offsets with respect to distinct climate events were detected, suggesting periods of non-uniform moisture and temperature evolution.