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variations in high northern latitude insolation, with a 23 ka periodicity punctuated by
millennial scale events (Wang et al.,
2008
). These millennial cycles show a decrease
in duration and an increase in frequency during the last two glacial periods, suggesting
that they were influenced by changes in ice sheet size. Analysis of
18
O from two
stalagmites in Dongge Cave located 1,200 km west-south-west of Hulu Cave provide
a record of precipitation changes over the past 160 ka consistent with that from Hulu
Cave and show that the Last Interglacial Monsoon began quite abruptly at 129.3
±
0.9 ka and ended equally abruptly at 119.6
0.6 ka, in accord with changes in
temperature in the North Atlantic region recorded in Greenland ice cores (Yuan et al.,
2004
).
A recurrent question in regard to past monsoonal activity in China is whether or
not the East Asian summer monsoon (EASM) and the Indian summer monsoon (ISM)
were in or out of phase. The EASM is controlled by winds blowing from the south-east
flowing across the western Pacific and the South China Sea into eastern China and
central China. The ISM is controlled by winds blowing from the south-west across
the Indian Ocean and the Bay of Bengal into southern China. A high-resolution
±
18
O
record from a stalagmite dated between 53 and 36 ka fromXiaobailong Cave in south-
east China shows that millennial scale variations in the ISM revealed in this cave were
indeed synchronous with those from Hulu Cave in the path of the EASM (Cai et al.,
2006
). In addition, some features of the ISM recorded at Xiaobailong Cave showed
a negative correlation with the Byrd Ice Core record from Antarctica, consistent with
the 'polar seesaw' hypothesis of Blunier and Brook (
2001
).
An intriguing feature to emerge from a
18
O record spanning the last 1,810 years
comes from Wanxiang Cave in semi-arid north-west China, situated between the
Qinghai-Tibetan Plateau to the south-west and the Chinese Loess Plateau to the east,
and it concerns the correlation between monsoon variability inferred from the spe-
leothem record and dynastic cultural history as portrayed in written archives (Zhang
et al.,
2008
). The monsoon in this locality was strong during Europe's Medieval
Warm Period but weak during Europe's Little Ice Age, as well as during the final
decades of the Tang, Yuan and Ming dynasties, when popular unrest was widespread
as a result of poor harvests. In contrast, the opening decades of the Northern Song
Dynasty were times of enhanced summer monsoon activity, increased rice cultivation
and population increase. Also evident in this speleothem record was a link between
solar variability and the summer monsoon, with weaker monsoons coinciding with
times of decreased solar intensity. A comparison between the
14
C record from tree
18
O record from Hoti
Cave in northern Oman also revealed a strong correlation between solar variability
and the Indian Ocean monsoon intensity during the wet interval at 9.6-6.1 ka (Neff
et al.,
2001
).
Although careful analysis of Chinese speleothems has provided a more detailed
and precise record of past climatic fluctuations in eastern Asia than would otherwise
rings, which mainly reflects changes in solar activity, and the
