Quantification of southwest China rainfall during the 8.2 ka BP event with response to North Atlantic cooling

Abstract

Abstract. The 8.2 ka BP event could provide important information for predicting abrupt climate change in the future. Although published records show that the East Asian monsoon area responded to the 8.2 ka BP event, there is no high-resolution quantitative reconstructed climate record in this area. In this study, a reconstructed 10-year moving average annual rainfall record in southwest China during the 8.2 ka BP event is presented by comparing two highresolution stalagmite δ 18 O records from Dongge cave and Heshang cave. This decade-scale rainfall reconstruction is based on a central-scale model and is confirmed by interannual monitoring records, which show a significant positive correlation between the regional mean annual rainfall and the drip water annual average δ 18 O difference from two caves along the same monsoon moisture transport pathway from May 2011 to April 2014. Similar trends between the reconstructed rainfall and the stalagmite Mg / Ca record, another proxy of rainfall, during the 8.2 ka BP period further increase the confidence of the quantification of the rainfall record. The reconstructed record shows that the mean annual rainfall in southwest China during the central 8.2 ka BP event is less than that of present by ∼ 200 mm and decreased by ∼ 350 mm in ∼ 70 years experiencing an extreme drying period lasting for ∼ 50 years. Comparison of the reconstructed rainfall record in southwest China with Greenland ice core δ 18 O and δ 15 N records suggests that the reduced rainfall in southwest China during the 8.2 ka BP period was coupled with Greenland cooling with a possible response rate of 110 ± 30 mm • C −1 .

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

“…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].…”

“…An antiphase pattern was observed between the EASM and the South American summer monsoon (SASM) during the 8.2 kyr event [228], highlighting the global extent of this event. The teleconnection is explained by a slowdown in AMOC (triggered by a glacial lake draining event) that led to a cooling of the North Atlantic climate and a southward migration of the ITCZ, in turn reducing EASM and increasing SASM intensities [8,61,226,228].…”

The Climate Fluctuation of the 8.2 ka BP Cooling Event and the Transition into Neolithic Lifeways in North China

“…Furthermore, a 10-year moving average annual rainfall record in southwest China during the 8.2 ka BP event was reconstructed based on a central-scale model and the comparison of two high-resolution stalagmite δ 18 O records from Dongge Cave and Heshang Cave. This reconstructed record reveals that the mean annual precipitation in southwest China during the central 8.2 ka BP event was less than that of the present (1950-1990) by~200 mm and decreased by~350 mm in~70 years [34]. The stalagmite records of Shihua Cave and Nuanhe Cave in Northeast China indicate that the summer monsoon-dominated δ 18 O record only weakly express the 8.2 ka event.…”

The timing, duration and magnitude of the 8.2 ka event in global speleothem records

“…Quantitative precipitation reconstructions from Chinese speleothem records also support a significant drying over Asia during the 8.2 ka event. A calcium isotope record from Heshang cave (China) show a ~ 1/3rd decrease in precipitation at the onset of the event 39 , whilst a rainfall reconstruction using the difference in speleothem δ 18 O between two Chinese cave sites along a moisture pathway indicate a maximum 24% decrease of rainfall at the onset (350 mm year −1 ) 40 . Drier conditions in the northern hemisphere tropics and wetter conditions in the southern hemisphere tropics are also simulated by numerous climate model simulations of the 8.2 ka event and attributed to a shift in the ITCZ 14 , 15 .…”