Stalagmite oxygen isotope (δ18O) records have enhanced our understanding of the history of the East Asian monsoon. However, abrupt changes in the monsoon are not constrained well enough to address certain issues and there are still unknowns in the interpretation of cave δ18O records. Here we present a new high-resolution stalagmite record from Shima Cave, central China. Anchored with 24 230Th/U dates, our sample grew from 19.7 to 17.8 ka and from 16.3 to 13.3 ka, covering much of the early portion of the last deglaciation with a temporal resolution of 7 years. Using this record and other available Asian δ18O records, we test model predictions for shifts in δ18O in Asian caves and further investigate monsoon variations on centennial to decadal timescales during the early portion of the last termination. We conclude the following regarding the interpretation of δ18O in Chinese caves. Two mechanisms affect δ18O: changes in the fraction of monsoon rainfall in annual totals (the Wang-Cheng mechanism) and changes in the amount of rainout between tropical sources and cave sites (the Yuan mechanism). The former is caused by changes in the seasonal migration of the sub-tropical jet and likely has a smaller effect on cave δ18O than the latter. The latter involves changes in rainout from both the Pacific and the Indian Ocean sources. Precisely how that change in rainout is partitioned between sources and cave sites is not fully understood; however, it is clear that some of the change takes place in China; i.e. it is not restricted to upstream sites. Rough calculations for our site suggest that mean annual rainfall may have been two-thirds of modern values at the time of the highest δ18O values during Heinrich Stadial 1 (HS1) (16.1 ka) and one fifth again higher than modern values during the Bølling (14.3 ka). Within HS1, consistent with observations from other localities, Chinese cave records exhibit a twofold structure. Within the phases, we observe a truly remarkable relationship between the North Atlantic ice rafted debris record and the Hulu-Shima Cave record, where events ranging from multi-centennial to sub-decadal timescale can be related across Eurasia. The origin of this two-phased structure may relate to different sources and extent of ice-rafted debris in the North Atlantic as well as the extent of sea ice and the Atlantic Meridional Overturning Circulation.
Bibliographical noteFunding Information:
We thank Editor Dr. Miryam Bar-Matthews and two anonymous reviewers for their constructive comments. This work was supported by National Natural Science Foundation of China (Grants 42071105 , 41931178 , 41572151 , 41571102 , 41672164 ), the U.S. National Science Foundation (Grant 1702816 ), the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant KYCX19_0789 ), the 111 Program of China (Grant D19002 ), the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant KJQN201900536 ) and the Open Fund for the State Key Laboratory of Loess and Quaternary Geology (Grant SKLLQG 1922 ).
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- Chinese stalagmite
- East Asian summer monsoon
- Heinrich stadial 1
- Last deglaciation
- Oxygen isotope interpretation