Reconstruction of the East Asian Summer monsoon rainfall distribution at centennial scale during the Last Glacial Maximum

摘要

The Last Glacial Maximum (LGM), defined as the period between 23 and 19 ka, is considered a key climatic period with conditions in great contrast to the present. Study of this period may reveal aspects of global ice-sheet sensitivity to regional and global climate change which is critical in understanding climate teleconnections and feedback mechanisms. A stalagmite record from Linglong cave, Central China, in combination with other high-resolution stalagmite records from Southwest China and East China existing on the same moisture transport pathway allows a reconstruction of rainfall patterns during the LGM by making use of the delta O-18 differences between stalagmite records. The rainfall around both Southwest and Central East China show a prominent change centered at similar to 24 ka corresponding to the H2 event, one of the Heinrich events related to North Atlantic ice-rafting. Also, in Central East China around the periods at 22 and 20 ka, the rainfall is lower than the average during the whole LGM, while around 23, 21 and 19 ka the rainfall is higher than the average, which is opposite to the rainfall variation in Southwest China. This apparent dipole rainfall pattern during the LGM is similar to the modern East Asian Summer Monsoon ( EASM ) rainfall distribution observed during weak monsoon periods, suggesting a much weaker EASM with its front moving less far north during the LGM than at present, which may link to North Atlantic climate and shifting of the Intertropical Convergence Zone (ITCZ). Power spectral analysis reveals that the rainfall variations in Southwest China are mainly controlled by a cycle of similar to 1000-yr, while in Central East China, it is mainly controlled by cycles of similar to 1800-yr and similar to 1300 yr, which are all possible solar activity cycles, suggesting that the EASM rainfall on long term scales is dominated by external forces.