Asian monsoon variability during 124-206 ka inferred from oxygen isotope records of stalagmites from Yangkou Cave, Chongqing, China
Date Issued
2012
Date
2012
Author(s)
Huang, Li-Jung
Abstract
Asian monsoon (AM) variation over past 380 kyrs has been reconstructed using stalagmite oxygen isotope records from caves in China, showing that AM intensity primarily follows Northern Hemisphere summer insolation on orbital timescales. However, those 100s-kyr records were built with stalagmites mainly from Sanbao Cave only, which could bring uncertainty in interpreting long-term AM evolution. Oxygen isotope records of stalagmites with high uranium levels of 2-16 ppm, collected from Yangkou Cave were used to reconstruct AM record from 124 to 206 kyr BP. Our results show that the Yangkou stalagmite-inferred AM variation superimposes on Sanbao record, supporting the strong AM intervals at marine isotope stage (MIS) 6.3, 6.5, and 7.1 and weak AM intervals at MIS 6.2, 6.4, and 7.0. This consistency confirms that the AM events are dominant in the entire mainland and primarily follow Northern Hemisphere summer insolation and relate to the atmospheric "δ" (_^"18" )"O" variation on orbital timescales. Combined with Pacific thermal conditions, our study suggests that AM evolution could be partially controlled by the Walker Circulation. The conflict between stalagmite-inferred and loess-inferred Asian monsoon records during MIS 6 might be caused by the migration of Asian summer monsoon boundary. Advantages of high precision absolute U/Th dates with 2-sigma error as low as only ±450 yrs allow us to precisely determine the event durations and timings and to understand the AM variability and climatic forcings during MIS 6-7.
Subjects
Asian monsoon
Stalagmite
Oxygen isotope
U-Th Dating
SDGs
Type
thesis
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