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Influence of the intertropical convergence zone on the East Asian monsoon

2007; Nature Portfolio; Volume: 445; Issue: 7123 Linguagem: Inglês

10.1038/nature05431

1476-4687

Gergana Yancheva, Norbert R Nowaczyk, Jens Mingram, Peter Dulski, Georg Schettler, Jörg F. W. Negendank, Jiaqi Liu, Daniel M. Sigman, Larry C. Peterson, Gerald H. Haug,

Geophysics and Gravity Measurements

A palaeoclimate record spanning the past 16,000 years with nearly annual time resolution has been obtained from Lake Huguang Maar in China. The magnetic properties and titanium content of the lake sediments are thought to reflect changes in the East Asian winter monsoon strength, thus providing a complement to palaeoclimate archives that record the strength of the rain-bearing summer monsoon. The records point to an anti-correlation between winter and summer monsoon strength, best explained by migration of the intertropical convergence zone (ITCZ), a belt of low-pressure air at the Equator. Interestingly, the decline of China's Tang dynasty and the Mayan civilization broadly coincide with drought periods recorded in Lake Huguang Maar and Cariaco basin sediments, respectively. Did major shifts in the position of the ITCZ catalyse simultaneous events in civilizations on opposite sides of the Pacific Ocean? The Asian–Australian monsoon is an important component of the Earth’s climate system that influences the societal and economic activity of roughly half the world’s population. The past strength of the rain-bearing East Asian summer monsoon can be reconstructed with archives such as cave deposits1,2,3, but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct. Here we present high-resolution records of the magnetic properties and the titanium content of the sediments of Lake Huguang Maar in coastal southeast China over the past 16,000 years, which we use as proxies for the strength of the winter monsoon winds. We find evidence for stronger winter monsoon winds before the Bølling–Allerød warming, during the Younger Dryas episode and during the middle and late Holocene, when cave stalagmites suggest weaker summer monsoons1,2,3. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. Similar migrations of the intertropical convergence zone have been observed in Central America for the period ad 700 to 900 (refs 4–6), suggesting global climatic changes at that time. From the coincidence in timing, we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the Tang dynasty in China and the Classic Maya in Central America.