Past 1000-year High Resolution Climatic Records Of Stalagmite From Gansu, China

Climate reconstruction of the past 1000 years can help us understand the disciplinarian of the climate change, and it's important for the forecast of the climate in the future. Speleothems can be well dated by U-series dating methods, and the time resolution can reach decadal to annual scale, suitable for climatic reconstruction. In this article, we analysed theδ¹³C andδ¹⁸O records of a well dated stalagmite which was found in Wanxiang cave, north-west of the Tibet Plateau, and reconstructed the history of the past 1053-year monsoon variability and vegetation evolvement. The main conclusions we got are here below:(1) After the comparison of theδ¹³C andδ¹⁸O records, we found that theδ¹³C of the stalagmite mainly reflected the changes of the vegetation types in that area at the 50-year timescale, at a shorter timescale (shorter than 50 years), It's mainly reflected the change of the cave water dynamics, and at a shorter timescale, the variation of theδ¹³C mainly reflected the change of the intensity of the Asian Summer Monsoon.Theδ¹³C record of the WX42B stalagmite which was found in Wanxiang cave has recorded the fall of theδ¹³C of recent atmospheric CO₂, shows that theδ¹³C of the stalagmites can be used to reconstruct the history of theδ¹³C of recent atmospheric CO₂.Theδ¹³C record of the WX42B stalagmite and the stalagmite of Buddha cave, which was found in Shanxi, China, can consistent to each other, shows that theδ¹³C record of the WX42B stalagmite not only reflected the vegetation evolvement in local region, but also recorded the climate information of a large area.(2) According to theδ¹³C,δ¹⁸O records of WX42B stalagmite, the past 1053 years can be divided into 3 different climate periods: 950-1315 AD strong monsoon period, 1315-1875 AD weak monsoon period and from 1875 AD to nowadays, modern strong monsoon periods. This result shows that in the warm period of the Middle Ages and modern strong monsoon periods, the Asian monsoon is strong and the precipitation is abundance in this area, and in the Little Ice Ages, the main climate character is the retreat of the Asian Monsoon and reduced precipitation.Theδ¹³C,δ¹⁸O records of WX42B stalagmite shows that 3 events was found in the past 1000 years, mainly happened in 1050, 1350 and 1600 AD. In these events, Monsoon precipitation reduced notably and the vegetation extremely degenerated. These events not only be found in other climate records in Asian Monsoon areas, but also found in the records of Greenland ice core,Scotland's precipitation and solar activity records, shows that these events not only happened in Asian Monsoon areas, maybe have a globally reflect.(3) Theδ¹³C,δ¹⁸O records of WX42B stalagmite can well correlated with the records of Greenland ice core and solar activity, shows that the climate in this region have a close connection with the polar temperature and solar activity.