Reconciliation of hydroclimate sequences from the Chinese Loess Plateauand low-latitude East Asian Summer Monsoon regions over thepast 14,500 years

We discuss replicated stalagmite &delta;18O records with interannual-to-multidecadal resolution from Lianhua Cave on the Chinese Loess Plateau to illustrate the precipitation history of the East Asian Summer Monsoon (EASM) region over the last 14.5 thousand years (ka BP, before 1950 CE, hereafter), and to re-evaluate the inconsistency in the proxy-inferred palaeoclimate time series in northern China. Agreement between the stalagmite &delta;18O from Lianhua and other caves from central-southern China indicates that regional climate changes after the Last Glacial were concurrent across mainland China, indicating that insolation was the primary factor controlling the evolution of the Asian Summer Monsoon (ASM). The stalagmite 18O enrichment of 2.5&permil; in the Younger Dryas and 1.7&permil; during the 8.2-ka BP event in Lianhua were larger than those in caves from central and southern China. The evidence suggests that different meridional responses of weak precipitation conditions in the ASM realm occurred during these two abrupt events, driven by high-latitude forcing in the Northern Hemisphere. The heterogeneous hydroclimate sequences in northern China inferred from different natural archives are most likely attributable to the complexity of the formations and/or some chronological uncertainty.</p

Centennial-to decadal-scale monsoon precipitation variability in the semi-humid region, northern China during the last 1860 years: Records from stalagmites in Huangye Cave

We developed a composite oxygen isotopic record of cave calcite for the last 1860 years based on three stalagmites from the Huangye Cave in eastern Gansu Province, northern China. The delta(18)O values reflect monsoon precipitation changes, with lower d18O values representing higher precipitation and vice versa. Three intervals of high precipitation were identified at AD 138-450, AD 730-1200, and AD 1860-1960. Two intervals of low precipitation occurred at AD 1320-1410 and AD 1530-1860. The reconstructed monsoon precipitation variations correlate well with other records further east in the eastern Yellow River Basin, suggesting synchronous precipitation changes during the late Holocene in the semi-humid region of northern China on decadal to centennial scales. Peak periods of warfare in dynastic transition times, such as at AD 391-420, AD 601-630, AD 1111-1140, AD 1351-1380, and AD 1621-1650, correspond to sharp declines in precipitation or temperature in semi-humid northern China, indicating a strong connection between climatic and societal changes. Our study suggests that climatic deterioration in semi-humid northern China has played an important role in Chinese societal evolution.</p

Human activity and climate change triggered the expansion of rocky desertification in the karst areas of Southwestern China

International audienceIt is conducive to the sustainable development of human beings in karst regions to research the mechanism of karstrocky desertification (KRD) expansion. Whether the large-scale KRD in southwestern China is caused by climate change orhuman activities is still controversial. In this study, the evolution of the KRD in southwestern China over the past 2000 years wasreconstructed through the high-precision δ13C record of stalagmites from Shijiangjun (SJJ) Cave, Guizhou Province, China. Theδ13C of the stalagmites from SJJ Cave exhibited heavy values from the Medieval Warm Period (MWP) to the Little Ice Age(LIA). Furthermore, the δ13C records of other stalagmites and tufa from southwestern China also showed the same significantheavy trend. Because the stalagmite δ13C could record the change of ecological environment, it indicated that the consistentchange of the stalagmites δ13C may record the process of KRD expansion in the karst regions of southwestern China. During theMWP, the stronger Asian summer monsoon and the northward movement of the rain belt led to a dry period in southwesternChina and a wet period in northern China. In contrast, it was wet in southwestern China and dry in northern China during the LIA.In addition, after the Jing-Kang event (JK event, AD1127) occurred at the end of the Northern Song dynasty, the political andeconomic center of China migrated to southern China for the first time, which changed the population distribution pattern oflarger population in the north and smaller population in the south. Therefore, the expansion of KRD in southwestern China wasexacerbated in the MWP due to the change of climate in southwestern China, the migration of a large number of people, wars, thelarge-scale reclamation of arable land, and the cultivation of large areas of crops

Obliquity pacing of the western Pacific IntertropicalConvergence Zone over the past 282,000 years

The Intertropical Convergence Zone (ITCZ) encompasses the heaviest rain belt on the Earth. Few direct long-term records, especially in the Pacific, limit our understanding of long-term natural variability for predicting future ITCZ migration. Here we present a tropical precipitation record from the Southern Hemisphere covering the past 282,000 years, inferred from a marine sedimentary sequence collected off the eastern coast of Papua New Guinea. Unlike the precession paradigm expressed in its East Asian counterpart, our record shows that the western Pacific ITCZ migration was influenced by combined precession and obliquity changes. The obliquity forcing could be primarily delivered by a cross-hemispherical thermal/ pressure contrast, resulting from the asymmetric continental configuration between Asia and Australia in a coupled East Asian–Australian circulation system. Our finding suggests that the obliquity forcing may play a more important role in global hydroclimate cycles than previously thought