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-C-14 ages were used to establish the chronology, assuming a reservoir effect of 1,420 years. Our results point to a first strong monsoonal pulse at Lake Nam Co similar to 11.3 cal ka BP, followed by colder and drier conditions until similar to 10.8 cal ka BP. A warm and humid climate from similar to 10.8 to similar to 9.5 cal ka BP is related to a strong summer monsoon on the central TP, triggering a lake-level highstand at similar to 9.5 cal ka BP. Declining minerogenic input after similar to 9.5 cal ka BP indicates less moisture availability until similar to 7.7 cal ka BP. Following stable conditions between similar to 7.7 and similar to 6.6 cal ka BP, a warm and wet climate is inferred for the time span from similar to 6.6 to similar to 4.8 cal ka BP. A change towards drier conditions after similar to 4.8 cal ka BP points to a weakening of the Indian Ocean Summer Monsoon on the central TP, further diminished after similar to 2.0 cal ka BP. A short-term wet spell occurred from similar to 1.5 to similar to 1.3 cal ka BP. 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.