High frequency pulses of East Asian monsoon climate in the last two glaciations: link with the North Atlantic |
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Authors: | Z Guo T Liu J Guiot N Wu H Lü J Han J Liu Z Gu |
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Affiliation: | Institute of Geology, Chinese Academy of Sciences, PO Box 9825, Beijing 100?029, China, CN Laboratoire de Botanique Historique et Palynologie, UA CNRS 1152, Faculté de St-Jér?me, Marseille F-13397 Cédex 20, XX
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Abstract: | Three loess sections in the Loess Plateau of China have been studied to characterize the variations of the East Asian monsoon
climate in the Late Quaternary period. Paleo-weathering profiles based on two weathering indices reveal a series of spatially
correlative intervals of lower weathering intensity (LW), in the last glacial and late penultimate glacial loess, indicating
significantly cooler or/and drier conditions. Most of them are identified at or near the transitional boundaries between loess
and soil units, suggesting that climatic conditions favorable for LW events tended to occur at or near major climatic boundaries.
Twenty-eight radiocarbon and thermoluminescence measurements, combined with Kukla's magnetic susceptibility age model date
these events at ∼14, ∼21, ∼29, ∼38, ∼52, ∼71, ∼135, and ∼145 ka BP, with ∼5–10 ka frequency inlaid within the orbitally induced
∼20-ka periodicity. The ages of the first six events in the last glacial period are therefore close to those of the coarse-grained
Heinrich layers in the North Atlantic Ocean, which resulted from massive discharges of icebergs. The results indicate that
the climate in the area affected by the East Asian monsoon has experienced high-frequency changes more or less synchronous
with the Heinrich events. These high-frequency changes have been reported by Porter and An, based on the grain-size time series
from the Luochuan loess section. Our data also reveal that similar events also occurred during the penultimate glaciation.
The mechanisms linking the Heinrich events and the East Asian monsoon climate may be similar to that driving the Younger Dryas
event which has been identified in a large number of records in China and in the surrounding oceans.
Received: 16 October 1995 / Accepted: 10 May 1996 |
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