Hydroclimatic variations in southeastern China during the 4.2 ka event reflected by stalagmite records

Abstract

Abstract. Although the collapses of several Neolithic cultures in China are considered to have been associated with abrupt climate change during the 4.2 ka BP event (4.2–3.9 ka BP), the timing and nature of this event and the spatial distribution of precipitation between northern and southern China are still controversial. The hydroclimate of this event in southeastern China is still poorly known, except for a few published records from the lower reaches of the Yangtze River. In this study, a high-resolution record of monsoon precipitation between 5.3 and 3.57 ka BP based on a stalagmite from Shennong Cave, Jiangxi Province, southeast China, is presented. Coherent variations in δ18O and δ13C reveal that the climate in this part of China was dominantly wet between 5.3 and 4.5 ka BP and mostly dry between 4.5 and 3.57 ka BP, interrupted by a wet interval (4.2–3.9 ka BP). A comparison with other records from monsoonal China suggests that summer monsoon precipitation decreased in northern China but increased in southern China during the 4.2 ka BP event. We propose that the weakened East Asian summer monsoon controlled by the reduced Atlantic Meridional Overturning Circulation resulted in this contrasting distribution of monsoon precipitation between northern and southern China. During the 4.2 ka BP event the rain belt remained longer at its southern position, giving rise to a pronounced humidity gradient between northern and southern China.

The Asian Summer Monsoon: Teleconnections and Forcing Mechanisms—A Review from Chinese Speleothem δ18O Records

“…During [122]. The Dongge and Mawmluh δ 18 O records also suggest a dry hydro-climate in SW China and the ISM region, respectively (Figure 8g,h).…”

“…The Dongge and Mawmluh δ 18 O records also suggest a dry hydro-climate in SW China and the ISM region, respectively (Figure 8g,h). Thus, it appears that during this event, the monsoonal rain belt may have stayed longer in the south, and shorter in the north [122,151]. These weakened EASM and ISM may have been triggered by the reduced AMOC as a result of the melting icebergs in the North Atlantic (Figure 8i) [122,151].…”

“…Thus, it appears that during this event, the monsoonal rain belt may have stayed longer in the south, and shorter in the north [122,151]. These weakened EASM and ISM may have been triggered by the reduced AMOC as a result of the melting icebergs in the North Atlantic (Figure 8i) [122,151]. However, a recent paleoclimate data synthesis with climate-model support for western Eurasia proposed that expansion of the Siberian High is a more plausible explanation for the geographic distribution of climate perturbations near 4.2 kyr BP [229].…”

“…The spatial distribution of rainfall in monsoonal China is primarily controlled by changes in the position of the monsoonal rainfall belt in response to changes in EASM intensity coupled with some geographic considerations. It has been suggested that a weak EASM (i.e., consistent positive δ 18 O values in the monsoonal China) leads to a southward shift of the rain belt that in turn results in either a dipole (i.e., dry northern China and a wet southern China [44,122,151]) or a tripole pattern (i.e., dry northern and southern China but wet in Central China [14]). Therefore, the speleothem δ 18 O records ultimately show the integrated monsoonal signal from the moisture source to the cave sites on orbital to millennial timescales [1], in line with modeling results (e.g., [191,194,197,198]).…”

“…Significant multi-centennial variability is also evident in the Heshang record, with notably dry periods during the 8.2 kyr BP event and at 4.8-4.1 kyr BP, 3.7-3.1 kyr BP, 1.4-1.0 kyr BP and the Little Ice Age (LIA) [15]. These weak EASM events are causally linked to North Atlantic ice-rafting debris (IRD) events or Bond events through southward displacement of westerly and ITCZ circulation, in particular, the 8.2 kyr [61,226] and 4.2 kyr [122] events. The 4.2 kyr event in the EASM region may have contributed to the collapses of the Chinese Neolithic culture [227].…”