East Asian Summer Monsoon Evolution During The 26.42?12.67 Ka B. P. Recorded By Stalagmite From Xianyun Cave,Fujian Province

Global climate change and its impact on the human living environment have increasingly attracted the attention of the international community.Climate change affects the living environment and development quality of humanity.The research of paleoclimate evolution,climate abrupt events and driving mechanisms can help us to understand climate change correctly,handle the relationship between humans and nature reasonably with predict future climate evolution scientifically.The climate system changed drastically between the end of the Last Glacial Maximum(LGM)and the early Holocene,from the glacial state transition to the interglacial state,defined last deglaciation.It is an outstanding opportunity for understanding the Earth's climate system to external and internal forcing.High-resolution stalagmite research shows that significant regional differences in the transformation characteristics of the millennium-scale events during the last deglaciation.Restricted by spatial distribution,lack a comprehensive understanding of regional differences and driving mechanisms.Here,We provide a high-resolution stalagmite record from Fujian to supplement lack of research.Based on 29 ²³⁰Th dating data and 786 oxygen isotope data from two stalagmite XY11 and XY7 in Xianyun Cave,reconstructed East Asian monsoon history spanning26.42?12.67 ka B.P.This study focus on the millennial monsoon enhancement event occurred in the end of the LGM and the Termination-? occurred in the last deglaciation.Compared with other high-resolution stalagmite records and paleoclimate records in high-low latitude to explore regional differences and driving mechanisms.The main conclusions are as follows:(1)The range of ?¹⁸O record in Xianyun Cave is-7.51‰?-5.23‰and the amplitude is 2.28‰,with an average value of-6.53‰.During this period,two weak monsoon events,corresponding to the H2 and H1 events in Greenland,and two strong monsoon events,corresponding to the LGM warming and the Termination-?.(2)Our record captures this millennial-scale strong monsoon events occurred in19.0?17.6 ka B.P.,synchronous with other stalagmite records from Asian monsoon region within the dating errors.However,compared with other stalagmite records,the amplitude of our record is much smaller(0.5‰),this could be attributed to the fact that the Xianyun Cave is located in the front area affected by the typical EASM and affected by the low-latitude ocean hydrological cycle process.In addition,the seasonal variation in precipitation?¹⁸O is relatively small in Xianyun Cave.Further,the boundary conditions change in ocean-continent influence the distance from water vapor sources to cave sites,generated the changes in atmospheric circulation which also be one of the reasons for this difference in amplitude.Comparison with high and low latitudes Paleoclimatic records,suggesting that the changes of boundary conditions in the late LGM,such as the rising solar radiation,the enhancement of meridional circulation in the North Atlantic and the intensification of ENSO activity had contributed significantly to this event.(3)The timing of Termination-? recorded in Xianyun Cave coincided with other stalagmites recorded in the Asian monsoon region,are synchronized with Greenland ice core and AMOC.It is support initial enhancement of the monsoon is mainly response to the climate on the northern high latitudes.In addition,the Antarctic cold reversal and the CO₂ concentration synchronous change may also influence on the Asian monsoon changes.(4)There are significant regional differences in transformation process,although Termination-? recorded in monsoon region stalagmites started synchronously within the error range.The location of Xianyun Cave is not directly affected by the Indian summer monsoon or westerly jet stream.Therefore,the Termination-? transformation shows a slow characteristic similar to the low latitudes,which may more influence from the western Pacific or the southern hemisphere.