Comparison of speleothem δ18O records from eastern China with solar insolation, ice core and marine records: Similarities and discrepancies on different time scales

Four 230Th-dated δ18O records in three stalagmites: one from Dragon Spring (stalagmite L12) and two from Golden Lion Caves (stalagmites JSD-01 and JSD-02) located in Libo County, southeast Guizhou, China, are presented. These records cover age ranges of 0.75–2 ka (late Holocene), 9–9.6 ka (early Holocene), 87.9–88.2 ka and 93.8–95.2 ka (late Pleistocene). They fit well with the published Dongge Cave record from the same area, where the climate has been much influenced by the East Asian Monsoon. The agreement reinforces the role of stalagmite δ18O as a proxy for regional precipitation or monsoon strength. On millennial or longer time scales, the δ18O record of Dongge Cave resembles those of Sanbao Cave in Hubei and Hulu Cave in Jiangsu of China. The matching of these records with the northern hemisphere solar-insolation variations points to the importance of insolation in affecting the East Asian Summer Monsoon strength on 103–104-yr scales. While the monsoon variations as depicted by these Chinese speleothem δ18O records show a strong coupling to insolation’s precession component (23-kyr period), other climate records of global significance extracted from oceanic and terrestrial deposits (e.g., deep-sea sediments, polar ice cores, cave deposits from non-monsoonal regions) do not. Although the latter records were thought to be also influenced by the large changes in global ice volume, they show variations modulated chiefly by insolation due to earth’s eccentricity change (100-kyr period). It is hypothesized that precession variations control the distribution of solar insolation between the northern and southern hemispheres, the ITCZ position and the modulation of low-latitude summer monsoon variability. Increasing rainfall and/or summer/winter precipitation ratio brought about by strong summer monsoons leads to δ18O depletion in stalagmites grown in monsoonal regions. One should use caution to compare speleothem δ18O records with other paleoclimate records reflecting Pleistocene ice ages on 104–105-yr timescales.