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Speleothem records have radically changed our understanding of the paleo Asian monsoon (AM), but explanations for Asian summer monsoon (ASM) variations in the Holocene period are usually based on single proxy records, such as oxygen isotope (δ18O). The application of multi-proxy records to the study of the forcing mechanism and internal structure of climate events is more comprehensive and accurate in the analysis of paleoclimates than using single proxy records. Therefore, a multi-proxy speleothem record of weak ASM events in 8.0–7.0 BP from Chongqing, which showed a dry southwestern China during weak ASM episodes, was reported. The analysis of multi-proxy records of SMY2 stalagmite indicated that the beginning of the '7.2 ka event' was at 7.29 ± 0.03 ka BP, and its culmination was at 7.1 ± 0.04 ka BP. Thus, this event lasted nearly 200 a, and the main drought period lasted 50 a. Power spectrum analysis showed a significant 61 a cycle signal during the study period in the δ18O record of SMY2, which coincided with the Atlantic multidecadal oscillation activity (AMOC) cycle. This study demonstrates that the ASM during 8.0–7.0 ka BP is strongly correlated with the changes in solar activity and also sensitive to the southward shift of Intertropical Convergence Zone (ITCZ) and AMOC cycle. [ABSTRACT FROM AUTHOR]

A 230Th/U-dated stalagmite from Hulu Cave was analyzed for δ18O, δ13C, and trace elements. A ~10-yr-resolution δ18O record, spanning 51.7–42.6 ka, revealed Dansgaard-Oeschger (DO) events 14 to 11. A similar rapid transition and synchronous timing of the onset of DO 12 is evident between the Greenland and Hulu Cave records, which suggests a common forcing mechanism of DO cycles in the North Atlantic and monsoonal region of Asia. Centennial-scale monsoonal oscillations in the cave δ18O record are indicative of hydroclimatic instability during interstadials. After removing the signals of remote moisture sources, the proportion of moisture from nearby sources is found to be higher during stadials than during interstadials. To explain this, we propose that the movement of the westerly jet is an important control on the balance of nearby and distant moisture sources in East Asia. In addition, the records of δ13C and trace element ratios, which are proxies of local environmental changes, resemble the δ18O record on the scale of DO cycles, as well as on even shorter timescales. This suggests that hydrological processes and biological activity at the cave site respond sensitively to the monsoonal changes. [ABSTRACT FROM AUTHOR]

A precisely 230 Th-dated stalagmite oxygen isotope (δ 18 O) record from Dragon Cave, Shanxi Province, northern China, is proposed to reconstruct the millennial-scale changes of the East Asian Summer monsoon (EASM) during the period 53.2–1.3 ka BP (before 1950 AD). Our record shows significant millennial-scale oscillations that match in timing, characteristic, and duration with the Dansgaard/Oeschger (DO) events 14–8 and the Heinrich events 5, 4, 2, and 1 (hereafter H5, H4, H2 and H1) in high-latitude regions of the Northern Hemisphere. Especially, the H5 event is well constrained from 48.1 to 46.9 ka BP with ten 230 Th dates. Our chronology supports the NGRIP GICC05 timescale from 50 to 38 ka BP. A comprehensive comparison of the Chinese speleothem records from different regions along a north-south transect shows a unique trend towards more negative δ 18 O values from 48.0 to 38.0 ka BP, suggesting that an intensified Asian summer monsoon (ASM) across the whole monsoonal China during the interval. We speculate that the joint effect, from both the cooling of the Southern Hemisphere and the enhanced land-sea temperature contrast due to the rising summer insolation, is capable to regulate the low-latitude large-scale atmospheric circulation patterns and exert significant influences on the long-term ASM variations during the middle of Marine Isotope Stage 3. [ABSTRACT FROM AUTHOR]

A high-resolution, annual layer-counted and 230 Th-dated multi-proxy record is constructed from a stalagmite in Hulu Cave, China. These proxies, including δ 18 O, annual layer thickness (ALT), gray level (GL) and Sr/Ca, cover a time span of ~ 3000 yr from 21 to 24 ka. The physical proxies (ALT and GL) and the geochemical index (Sr/Ca), all primarily reflecting karst hydrological processes, vary in concert and their coherence is supported by wavelet analyses. Variations in the δ 18 O data agree with fluctuations in the ALT and Sr/Ca records on multi-decadal to centennial scales, suggesting that the Hulu δ 18 O signal is strongly associated with varying local rainfall amounts on short timescales. A monsoon failure event at ~ 22.2 ka correlates with a decrease in tropical rainfall, a reduction in global CH 4 and an ice-rafted event in the North Atlantic. This correlation highlights roles of the Asian monsoon and tropical hydrological cycle in modulating global CH 4 , because the high-latitude emission was inhibited during the Last Glacial Maximum (LGM). Spectral analysis of the δ 18 O record displays peaks at periodicities of 139, 59, 53, 43, 30, 23 and 19–15 yr. The absence of typical centennial solar cycles may be related to muted changes in ocean circulation during the LGM. [ABSTRACT FROM AUTHOR]

A high-resolution oxygen-isotope record from a thorium-uranium-dated stalagmite from Shanbao Cave at Shennongjia reflects variations in the amount of monsoon precipitation for the period from 11.5 to 2.1 ka (1 ka = 1000 cal aBP). Between 11.5 and 9.3 ka, a sharp decrease in δ18O indicates a rapid increase in monsoon precipitation. An interval of generally high monsoon precipitation is observed between 9.3 and 4.4 ka. An arid period has prevailed between 4.4 and 2.1 ka. The long-term trend of Shanbao record appears to follow summer insolation at 33°N latitude. An abrupt decrease in monsoon precipitation around 4.3 ka is synchronous with the collapse of Neolithic culture in central China. This abrupt change could have resulted from the amplification of the gradually decreased summer insolation by the positive vegetation-atmosphere-aerosol feedback. The weakened Asian monsoon events were in concert with decreased Greenland temperature during the early Holocene, centered at 8.2, 8.6, 9.3, 10.2 and 11.0 ka. This correlation suggests that changes in low-latitude monsoon are connected with climate change in high-latitude polar region. [ABSTRACT FROM AUTHOR]

230Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize the East Asian Monsoon precipitation from 133 to127 ka. The decadal-scale high-resolution δ18O record reveals a detailed transitional process from the Penultimate Glaciation to the Last Interglaciation. As established with 230Th dates, the age of the Termination II is determined to be 129.5±1.0 kaBP, which supports the Northern Hemisphere insolation as the triggers for the ice-age cycles. In our δ18O record, the glacial/ interglacial fluctuation reaches about 4%o, almost the same level as in other Asian Monsoon cave stalagmite δ18O records. The transition of the glacial/interglacial period in our record can be recognized as four stepwise stages, among which, a rapid rise of monsoon precipitation follows the stage of ‘Termination II pause’. The rapid rise is synchronous with the abrupt change of global methane concentration, which reflects that an increase in both Asian Monsoon precipitation and tropical wetland plays an important role in the global climate changes. [ABSTRACT FROM AUTHOR]

Our knowledge about climatic changes at centennial-scale and their causes during the Holocene climatic optimum (HCO) remains poorly constrained. Here, we present δ18O and δ13C records from a precisely dated stalagmite (13.2 to 1.9 kyr BP) from Xiniu Cave, central China. The δ18O record shows a gradual weakening in the strength of the East Asian summer monsoon (EASM) from early to middle Holocene, corresponding with a decrease in Northern Hemisphere summer insolation (NHSI). A similar pattern is absent in our δ13C record, and is replaced by persistent centennial-scale oscillations throughout the Holocene. Variations of δ13C reflect changes in vegetation density, soil CO 2 production, CO 2 degassing, prior calcite precipitation (PCP), and cave ventilation, associated with temperature and rainfall variations at local scale. Based on the δ13C record, three dry/cold events at approximately 6.0, 8.2, and 10.5 kyr BP, can be identified during the HCO (11.1 ± 0.1 to 5.4 ± 0.1 kyr BP), coinciding with the well-known Holocene Bond events. The power spectrum analysis shows that the significant periodicity (843 yr) of the δ13C record within the HCO may be related to the North Atlantic-cycle. Therefore, we speculate that the centennial-scale climatic changes during the HCO probably resulted from cooling in the North Atlantic, and that the intensified and southward Westerly jet played a role in transmitting this signal from high latitudes to central China. • Stalagmite records from central China spanning last deglaciation to Holocene. • Variations of stalagmite δ13C are controlled by both rainfall and temperature. • The timing of the HCO can be identified more clearly by using a new tool. • Centennial-scale climatic events in the HCO resonate with North Atlantic climate. [ABSTRACT FROM AUTHOR]

Asian summer monsoon (ASM) and regional rainfall responses to external and internal forcings remain actively debated, especially at significant climate transitions. Here we present decadally-resolved stalagmite stable isotope (δ18O and δ13C) and trace element records from central China to reconstruct Asian hydroclimate variability across the Marine Isotope Stage (MIS) 7/6 transition. The results demonstrate that the maximum level of effective precipitation (or precipitation/evaporation, P/E), derived from δ13C and element records, is practically similar between MIS 7.0 and early MIS 6.5, punctuated by a series of centennial-scale moisture-deficit events, in contrast to precessional-scale ASM changes (i.e., δ18O). At millennial scale, the ASM decline is positively correlated to P/E changes, with an exponential relationship between them. It reveals that Earth's boundary conditions could differently modulate ASM and P/E changes at orbital scale, while internal forcings can generate synchronous responses. Moreover, the ASM intensity and P/E conditions exhibit enhanced instability into MIS 6, about 1.5 times in amplitude of MIS 7. These millennial-scale hydroclimate variations are in line with a rise of Northern Hemisphere summer insolation, an El Niño/La Niña transition, the increased seasonality and high-frequency tropical climate variability. Hence, low-latitude hydrological conditions could be susceptible to subtle perturbations in the climate system, providing a precondition for the arrival of MIS 6. • Decadally-resolved stalagmite isotopic and element records across the MIS 7/6 transition. • Contrasting responses of ASM intensity and effective precipitation in central China. • Enhanced Asian hydroclimate instability during early MIS 6. • A role of low-latitude hydrological processes on centennial-scale Asian hydroclimate variability. [ABSTRACT FROM AUTHOR]

Knowledge of hydroclimatic dynamics in the East Asian monsoon region during the Holocene was hindered by few absolutely-dated and decadally-resolved proxy records in northern China. Here we present replicated carbonate δ 18 O records of six stalagmites with sub-decadal to multi-decadal resolutions from the Lianhua cave to reveal a detailed evolution of the East Asian Summer Monsoon (EASM) intensity in northern China since 11.5 thousand years before present (ka BP, before 1950 CE). Our composite record shows that solar forcing dominated hydroclimatic changes regionally, including an intensified monsoon at the Holocene Optimum from the termination of Younger Dryas to 6.5 ka BP, and a subsequent multi-millennial weakening monsoon, that agrees with cave records in central and southern China. However, the EASM has retreated southwards more rapidly than the Indian summer monsoon after ∼6.5 ka BP, resulting in aridity conditions occurring at 4.0 ka BP in northern China, which is almost 2000-year earlier than that in central and southern China. This north–south asynchroneity is likely related to the different regional responses among the coupling of the EASM, Indian summer monsoon, the solar forcing, and the differences in thermal forcing due to complex geographical configurations. In addition, a relative enrichment of 1‰ in 18 O data of the Lianhua record from 9.5 to 8.1 ka BP shows that the Holocene Optimum was punctuated by a millennial-long weakening monsoon interval, which is not registered among previous cave records in central and southern China. The fresh water-induced cold climate conditions in the North Atlantic region could create stronger East Asian winter monsoon, and induce a weakened EASM and a southward shift of rain belt in northern China. Therefore, it shall not be surprised that there are strong heterogeneities among regional hydroclimatic conditions across monsoonal China, given the complex interplay between external and internal forcing mechanisms over the entire Holocene. [ABSTRACT FROM AUTHOR]

Spatial differences of rainfall in monsoonal China during the last glacial period remain contentious. Here, we present new 230Th-dated stalagmite records (δ13C and δ18O) from central China (the Yangtze River valley), spanning approximately 75–10 ka BP, to address this issue. We interpret the stalagmite δ13C variations primarily as indicators of regional rainfall changes, which show significantly decreased rainfall during MIS 4 and late MIS 3 to MIS 2. On the millennial timescale, the δ13C record indicates decreased rainfall during Heinrich (H) events and increased rainfall during Dansgaard-Oeschger interstadials. The strong correlations between our δ13C record and the westerly proxies suggest that the westerly jet played a crucial role in influencing rainfall patterns in monsoonal China throughout the last glacial period. We propose that rainfall changes in central China were consistent with northern China on both orbital and millennial timescales during the last glacial period. This observation contrasts with the modern rainfall differences between northern and central China. Our results imply that with a colder climate in high northern latitudes, the rain belt over monsoonal China influenced by the westerly jet shifted further south beyond the Yangtze River Valley during MIS 4, late MIS 3 to MIS 2 and H events, leading to a consistent decrease in rainfall over central and northern China. In contrast to the rainfall records, the stalagmite δ18O values were more negative during late MIS 3. The δ18O variations on the orbital timescale are likely related to the changes in the tropical ocean conditions controlled by insolation, which determines the δ18O values in evaporated moisture before its transport into the Asian continent. On the millennial timescale, our δ13C and δ18O records exhibit coupled variations, implying that the stalagmite δ18O variations are consistent with the rainfall changes in central and northern China. • New stalagmite δ13C and δ18O records spanning the last glacial period (75–10 ka BP) from central China. • Consistent rainfall changes in central and northern China on both orbital and millennial timescales. • Coupled variations between δ13C and δ18O records on the millennial timescale. [ABSTRACT FROM AUTHOR]

We discuss replicated stalagmite δ 18 O 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 δ 18 O 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 18 O enrichment of 2.5‰ in the Younger Dryas and 1.7‰ 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. [ABSTRACT FROM AUTHOR]

The Asian monsoon (AM) is an important atmosphere circulation system of the global climate system, acting as a bridge across high-northern latitude and tropic climates. However, dynamical origins of AM variations during the Holocene remain unclear. Here we present stable isotope records (δ 18 O and δ 13 C) of a Holocene stalagmite from Niu Cave, central China, to address the nature and causes of East Asian summer monsoon (EASM) changes. Our δ 18 O record shows a gradual weakening of the EASM intensity from the middle to the late Holocene, corresponding with a decrease in Northern Hemisphere summer insolation and an enhancement of ENSO activity. The δ 13 C profile exhibits similar variability to δ 18 O record, suggesting that regional hydrological changes were primarily controlled by the large-scale summer monsoon circulation. Power spectrum analyses of δ 18 O and δ 13 C records show that the EASM intensity varies at a dominant periodicity of ~ 830 yr, probably correlated to an ENSO-like cycle. Furthermore, millennial-scale shifts in our records exhibit a strong correlation with that in ENSO proxies over the past 3000 years. The EASM-ENSO relationship may be related to the shifts in the mean position of Walker circulation and western North Pacific subtropical high. Our finding suggests that millennial-scale monsoon changes in the late Holocene are primarily modulated by changes in tropical ocean–atmosphere circulation, rather than variations in the North Atlantic thermohaline circulation. [ABSTRACT FROM AUTHOR]

Both external forcing and internal climate variability are playing significant roles in driving the East Asian summer monsoon (EASM) changes. However, dynamic linkages between these natural forcings and EASM on decadal timescales remain uncertain, partly due to the limited instrumental climate data. Here, we present a high-resolution EASM record over the past 200 years based on 2315 δ18O measurements from two annually laminated stalagmites (YX92 and YX120) in Yongxing Cave over the middle Yangtze River Valley (mid-YRV). Our records match well with the δ18O records from the nearby Heshang Cave, showing that EASM intensity in the mid-YRV varies at a dominant periodicity of ∼80 years. The multidecadal-scale oscillations in the EASM intensity are closely related to the ENSO-like states, supporting a notion that the ENSO dominantly modulates the EASM variability. Furthermore, the decadal oscillations in EASM and ENSO are synchronous with tropical volcanic eruptions during the solar minima, probably leading to the enhanced El Niño-like response, intensified EASM and strengthened ENSO-EASM coupling. Our findings imply that external forcings potentially contribute to the anomalies in ENSO and EASM during the ongoing global warming. • EASM changes at a dominant periodicity of ∼80 years over the past 200 years. • Multidecadal-scale oscillations in EASM intensity closely related to ENSO-like states. • Decadal oscillations in EASM and ENSO evolution synchronous with tropical volcanic eruptions during the solar minima. • Tropical volcanic eruptions likely enhanced the ENSO-EASM coupling. [ABSTRACT FROM AUTHOR]

Two annually-laminated and 230 Th-dated stalagmite oxygen isotope (δ 18 O) records from Dongge Cave, China, provided a high-resolution Asian Summer Monsoon (ASM) history for the past 1200 years. A close similarity between annual band thickness and stable isotope analyses (δ 13 C and δ 18 O) suggests the calcite δ 18 O is most likely a proxy associated with ASM precipitation. The two duplicated stalagmite δ 18 O records show that the ASM varies at a periodicity of ∼220 years, concordant with a dominant cycle of solar activity. A period of strong ASM activity occurred during the Spörer Minimum (1450–1550 A.D.), followed by a striking drop circa 1580 A.D., potentially consistent with the social unrest in the final decades of China's Ming Dynasty (1368–1644 A.D.). Centennial-scale changes in ASM precipitation over the last millennium match well with changes in tropical Atlantic sea surface temperatures (SSTs) and South American summer monsoon precipitation. Our findings suggest that variations in low-latitude monsoon precipitation are probably driven by shifts in the mean position of the intertropical convergence zone (ITCZ), which is further mediated by solar activity and tropical SSTs. [ABSTRACT FROM AUTHOR]

• A composite high-resolution monsoon precipitation record over the mid-YRV. • Centennial-scale oscillations in EASM rainfall related to solar activity and ENSO. • An anti-phase relationship of monsoon rainfall between the mid-YRV and tropical WNP. • A new EAP index calculated as the difference between monsoon rainfall in the mid-YRV and WNP. • A strong correlation between the EAP and SOI index. Meteorological observations reveal an inverse relationship of summer monsoon rainfall between the tropical western North Pacific (WNP) and middle Yangtze River Valley (mid-YRV) on interannual and intraseasonal timescales. This seesaw-like pattern, named the East Asian-Pacific (EAP) pattern, is one of the major teleconnections that affect summer precipitation in the mid-YRV. However, due to the scarcity of long and continuous instrumental data, the behavior and mechanism of the EAP pattern on a long timescale are poorly understood. Here, we present a composite high-resolution summer monsoon rainfall record from 230 BC to 1810 AD, based on 1221 δ 18 O measurements and 22 230Th dates from two stalagmites (EB1 and EB5) in Shenqi Cave over the mid-YRV. Our new record shows that monsoon rainfall in the mid-YRV varies at a dominant periodicity of ∼100 years, probably linked to solar activity and ENSO variability. The multi-centennial fluctuations in the EB record, broadly consistent with the North Hemisphere temperature reconstruction, display strong similarities to two stalagmite δ 18 O records from nearby Heshang and Luoshui caves. To represent the integrated hydroclimate variations over the mid-YRV, we extracted the first principal component (PC1) of these three cave δ 18 O records by using the principal component analysis. We reveal a striking inverse relationship of wet/dry conditions between the mid-YRV and tropical WNP, suggesting that changes in the EAP pattern have an important impact on centennial-scale monsoon precipitation changes. Furthermore, we compile monsoon rainfall records from the mid-YRV and WNP to reconstruct a new EAP index. This EAP index exhibits a strong correlation with the ENSO proxy, confirming that the ENSO variability may play a key role in modulating the monsoon rainfall in the mid-YRV through the EAP teleconnection. [ABSTRACT FROM AUTHOR]

• High-resolution stable isotopic records from three stalagmites are used to reconstruct EASM and EAWM changes. • Winter temperature is important for calcite δ13C variability via soil CO 2 production. • The EASM and EAWM variations are negatively correlated at a centennial scale. • The relationship of millennial-scale EASM and EAWM changes are variable. The correlation of East Asian summer and winter monsoons (EASM and EAWM) is believed to be variable at various timescales and under different climate backgrounds. In order to address this issue, high-resolution δ18O (depleted values indicating a strong EASM) and δ13C records (depleted values representing a weak EAWM) from three stalagmites, covering Marine Isotope Stages (MIS) 4 and 3, are reconstructed from an alpine cave in central China. During MIS 4, millennial-scale changes are clear in δ18O and δ13C records, while the δ13C is only characterized by centennial-scale variability across MIS 3. Changes in these speleothem δ13C records are supported by pollen records from the same area, which suggested millennial-scale alternations between conifer and deciduous broadleaf forests during MIS 4 and a stable C3-type vegetation in MIS 3. After detrended, δ18O changes are positively correlated with the δ13C record at a centennial scale, indicating an anti-phase of EASM and EAWM. In early MIS 4, however, an in-phase relationship of EASM and EAWM can be observed at a millennial scale. Thus, an anti-phased EASM/EAWM can be expected at a centennial scale, while a complicated correlation is seen at a millennial scale. These results imply a variable EASM/EAWM phase relationship under varying climatic conditions through the geological records and at different timescales. [ABSTRACT FROM AUTHOR]