Detection of abrupt changes in East Asian monsoon from Chinese loess and speleothem records

• Main Authors: Rousseau, Denis-Didier, Bagniewski, Witold, Sun, Youbin
• Format: Other/Unknown Material
• Language: English
• Published: Zenodo 2024
• Subjects: Dansgaard-Oeschger events
• Online Access: https://doi.org/10.5281/zenodo.11241330

There is a great interest concerning recent occurrences of tipping points in the climate system and great concern about those that could occur in the near future as a result of anthropogenic forcing. A lot of attention has been devoted to the study of past Dansgaard-Oeschger events, abrupt warmings of about 12°C on a time-scale of about 50 yrs that occurred during the last glacial period. Great effort is also dedicated to understanding the Atlantic Meridionnal overturning circulation and the Amazon forest dieback, which are already entering an unstable regime leading to tipping behavior. Instead, here we focus on the study of critical transitions in the SE Asian Monsoon that have occurred in the past 3.6 Myrs by a novel combination of advanced statistical tools (KS-test, recurrence quantification analysis). The SE Asian Monsoon is characterized by variations in the grain size with the occurrence of coarse material characterizing a strong winter monsoon mechanism with grains transported from the Chinese northern deserts by strong winds generated by the Siberian High located northward. By contrast intervals of fine grain size characterized periods during which the summer monsoon was rather reinforced. We have analyzed high-resolution grain-size datasets derived from Chinese loess sequences, i.e. the CHILOMOS and the LGS640 datasets, that we compare with the Chinese composite speleothem d 18 O records that arguably provide one the best representation of the Earth’s climate in the last 650 kyrs. Although visually observed rapid grain-size variations were previously interpreted as representing millennial-scale variations, our statistical analysis shows that both winter and summer monsoons co-varied at glacial-interglacial to millennial timescales. Analyzing a third dataset, i.e., MQSG, our statistical analysis shows that both winter and summer monsoon variations reflect a three-stage evolution of increasing intensity: (1) from 3.6 Ma to 2.6 Ma, (2) from 2.6 Ma to 1.2 Ma, and (3) from 1.2 Ma to present, with the ...