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The freshwater discharge from melting ice sheets in the deglaciation or glaciation is prone to anomalies in ocean-atmosphere transport between different latitudes, which can lead to a series of abrupt millennial-scale climate events, either obvious or not, such as the Younger Dryas (YD) events and YD-like events. Marine Isotope Stage 11c (MIS 11c) serves as one of the best references for the current Holocene, and the studies of possible YD-like events and their triggering mechanisms during Holocene are conducive to the understanding of the occurrence pattern of extreme climate events. In this paper, the results of the study on the J33 δ18O sequence records of stalagmites in Jinfo Cave, Chongqing, are shown: (1) Stalagmites in the Asian monsoon climate zone reveal a millennial-scale weak monsoon event that occurred around 410 ka BP prior to the Glacial Maximum of MIS 11 interglacial period. (2) Both the 410 ka weak monsoon event and the YD event occurred during the gradual strengthening of the monsoon and ascending branch of summer insolation in the Northern Hemisphere prior to the Glacial Maximum of interglacial period. This was also a time when Atlantic Meridional Overturning Circulation (AMOC) disturbance occurred. The duration, internal structure, and pattern of the events were similar, with differences in the change magnitude and ice volume conditions. (3) The weak monsoon event that occurred in 410 ka BP was primarily influenced by the combined effects of insolation and AMOC. This event was characterized by a sustained warming process that accelerated the melting of the Greenland ice sheet, leading to the destabilization of this ice sheet. The continuous flowing of freshwater into the North Atlantic resulted in a short-lived AMOC oscillation. The weakening of the AMOC resulted in a cold anomaly over the North Atlantic. As a result of atmospheric telecorrelation, the weaker AMOC led to a weaker Asian Summer Monsoon (ASM). [ABSTRACT FROM AUTHOR]

It is conducive to the sustainable development of human beings in karst regions to research the mechanism of karst rocky desertification (KRD) expansion. Whether the large-scale KRD in southwestern China is caused by climate change or human activities is still controversial. In this study, the evolution of the KRD in southwestern China over the past 2000 years was reconstructed through the high-precision δ13C record of stalagmites from Shijiangjun (SJJ) Cave, Guizhou Province, China. The δ13C 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 significant heavy trend. Because the stalagmite δ13C could record the change of ecological environment, it indicated that the consistent change of the stalagmites δ13C may record the process of KRD expansion in the karst regions of southwestern China. During the MWP, the stronger Asian summer monsoon and the northward movement of the rain belt led to a dry period in southwestern China 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 and economic center of China migrated to southern China for the first time, which changed the population distribution pattern of larger population in the north and smaller population in the south. Therefore, the expansion of KRD in southwestern China was exacerbated in the MWP due to the change of climate in southwestern China, the migration of a large number of people, wars, the large-scale reclamation of arable land, and the cultivation of large areas of crops. [ABSTRACT FROM AUTHOR]

Cave dripwater hydrochemistry responds to environmental changes, both within and outside of the cave, and thereby conveys this information to any stalagmite fed by the drips. As stalagmites are important archives of climate proxy information, understanding how dripwater hydrochemistry responds to environmental forcing is critical. However, despite the large number of speleothems in SW China, the response of dripwater to regional climate variability is not yet adequately understood. A 3-year study of three drip sites in Xueyu Cave, Chongqing Municipality, SW China, revealed the most important mechanisms controlling dripwater chemical variability. The principal chemical indices ( pH, specific conductivity, Ca2+, Mg2+, Sr2+ and [ABSTRACT FROM AUTHOR]

We compare well-dated Holocene stalagmite δ18O records from the East Asian Summer Monsoon (EASM) region and from the Indian Summer Monsoon (ISM) region. We found that the pattern of latitudinal change of speleothem δ18O values from the Indian monsoon region to the East Asian monsoon region is almost identical to that of modern precipitation. This suggests that the modern moisture transport route from the Indian Ocean to the East Asian monsoon region has existed since at least the early Holocene. The δ18O records from both regions exhibit a remarkably similar trend of variation in that the values are more negative during the early Holocene, rapidly become heavy from the mid-Holocene, and are heaviest during the late Holocene. The stalagmite δ18O changes in the East Asian monsoon region are statistically well correlated with those in the Indian monsoon region, both over the entire Holocene and in detail over the last 2000 years. However, in contrast to the obvious consistency of the δ18O values in all of the speleothem records, both instrumental and historical climate records indicate significant spatial variations in rainfall over eastern China. The early-Holocene strong EASM pattern referred from speleothem δ18O in the East Asian monsoon region is quite different to that of other paleoclimatic records such as Holocene paleosol development in the Chinese Loess Plateau, eolian activity in the northern Chinese sandlands, and lake sediments in EASM-dominated region in China, in which the strongest EASM was documented during the mid-Holocene. These findings suggest that the speleothem δ18O record from the East Asian monsoon region may not record EASM variability, but rather that it is controlled by variations in the isotopic composition of precipitation, which is determined mainly by rainfall variability in the ISM region. [ABSTRACT FROM AUTHOR]

The time sequence of paleoclimatic changes from 245.2 to 147.9 ka B.P. has been established by high precision U-series dating by Thermal Ionization Mass Spectrometry and the analysis of the oxygen isotopes from a stalagmite of Shuinan Cave in Guilin. The oxygen isotope pattern is divided into three main intervals. The top part of the stalagmite (interval C) displays mainly relatively heavy oxygen isotopes, mostly −7 to −5‰VPDB, but at a depth of 86.5 cm below the top, there is a sharp change to values lighter than −8 ‰. This boundary, dated at 192.6 ±3.9 ka B.P. is correlated with the boundary between marine oxygen isotope stages 6 and 7. The underlying interval B has δ18O values consistently between −7.5 and −8.5‰ until 271 cm depth when there is a sharp rise in δ18O values towards values as heavy as −5‰. The upper position of this change is dated at 242.5±6.4 ka B.P. and is correlated with the boundary between marine isotope stages 7 and 8. Carbon isotope values lie between −8.5 and −11‰ and are not uniquely high or low in the three intervals, but also show rapid changes at the boundaries between intervals in the same sense as the shifts in δ18O. The pronounced shifts in δ18O are attributed to changes in the paleo-monsoon intensity which reflect major reorganizations of the climate system, but some regional characteristics are also present. The results are also consistent with previous studies of climate proxies from loess-palaesol sequences in northern China. These characteristics show that paleo-climate evolution since the late stage of the middle Pleistocene Epoch in the Guilin area not only follows the global characteristics, but also has the strong district or regional patterns. [ABSTRACT FROM AUTHOR]

Thorium-230 ages and oxygen isotope ratios of stalagmites from Dongge Cave, China, characterize the Asian Monsoon and low-latitude precipitation over the past 160,000 years. Numerous abrupt changes in [sup18]O/[sup16]O values result from changes in tropical and subtropical precipitation driven by insolation and millennial-scale circulation shifts. The Last Interglacial Monsoon lasted 9.7 ± 1.1 thousand years, beginning with an abrupt (less than 200 years) drop in [sup18]O/[sup16]O values 129.3 ± 0.9 thousand years ago and ending with an abrupt (less than 300 years) rise in [sup18]O/[sup16]O values 119.6 ± 0.6 thousand years ago. The start coincides with insolation rise and measures of full interglacial conditions, indicating that insolation triggered the final rise to full interglacial conditions. [ABSTRACT FROM AUTHOR]

Presents a study that reviewed the progress made in chronology and paleo-environment of stalagmites from karst caves in China. Results of thermally ionized mass spectometric-U series dating of stalagmites; Advances in high-resolution dating of stalagmites; Reconstruction of paleo-environments; Data collection.

It is still debated whether the stalagmite δ18O in the East Asian monsoon region indicates the intensity of the summer monsoon or the precipitation of the summer monsoon season on an annual scale. One key reason for this debate is the lack of accurate comparison between stalagmite δ18O and instrumental records. To better decipher the stalagmite δ18O in the Asian monsoon region on an annual scale, stalagmite PL1 from Pailong Cave, southeast of Yunnan, was selected. The calcite deposited from 2004 to 2019 within stalagmite PL1 was determined by laminar counting, 210Pb dating and seasonal variations in δ13C values. Seasonal scale δ18O, δ13C and Mg/Ca ratios were found to record the severe drought over Southwest China that occurred in 2009–2010. In 2009, when the severe drought was the most intense, the stalagmite δ18O, δ13C, and Mg/Ca ratios changed significantly, reflecting the hydrological response caused by climate change (decrease in precipitation). However, distinct from the δ13C and Mg/Ca ratios, the highest δ18O value was found in 2010, which reflects the influence of the evaporation in the soil and epikarst. On the annual scale, the stalagmites/precipitation δ18O in both Yunnan and eastern China are dominated by El Niño-Southern Oscillation (ENSO) activity. During the El Niño/La Niña phase, reduced/enhanced convective activities but strong/weak water vapor flux transportation occurred in the Bay of Bengal and the South China Sea, and weaker/stronger water vapor flux transportation in the Arabian Sea induced enriched/depleted precipitation δ18O and hence stalagmite δ18O in Yunnan and eastern China. On the interannual scale, the stalagmite δ18O of Yunnan is mainly affected by the strength of the South Asian summer monsoon and water vapor flux transportation from the Arabian Sea. The stronger (weaker) South Asian summer monsoon intensity will induce more (less) water vapor flux transported from the Arabian Sea and depleted (enriched) stalagmite δ18O in Yunnan. Distinct from stalagmite δ18O in Yunnan, the precipitation/stalagmite δ18O in eastern China is significantly correlated with ENSO indices on the interannual scale. Precipitation/stalagmite δ18O in eastern China is dominated by convective activities in the source area (Bay of Bengal-South China Sea). • The first report of severe drought during 2009–2010 over southwest China recorded by stalagmite. • Stalagmite δ18O in Yunnan, southwest China is dominated by the Indian monsoon intensity. • Stalagmite δ18O in eastern China is dominated by the convective activities in source area. [ABSTRACT FROM AUTHOR]

Abstract: The rare earth elements and yttrium (REY) in a Chinese stalagmite (SJ3) have been studied to delineate their possible sources and controlling mechanisms. The following results are obtained: (1) The REY in karst groundwater at the study site have very low concentrations, e.g. ranging from 59×10−6 to 614×10−6 μmol/L for La, and are transported predominantly in particle/colloidal phases.These elements show a high linear positive correlation with Fe, Mn and Al (r 2 =0.98, 0.95 and 0.91, respectively), which are also transported largely in particle/colloidal phases, suggesting a close association of REY with Fe, Mn and Al in colloidal/particle phases; (2) REY mobilization from the sources, i.e. the limestone host rock and the overlying soil layer, may not have exerted a significant influence on the REY patterns for SJ3 including anomalies of La, Ce and Y and fractionation between light and heavy REY; (3) The REY patterns of SJ3 display significant variations which are controlled in part by change in contributions from the limestone host rock and the overlying soil layer and can be associated with stadial–interstadial changes in past climate and environment. The REY contribution from the overlying soil layer is higher under a warm–humid climate phase than a cold–dry one and the REY contribution from the limestone host rock is reversed; (4) Some of the variations of the SJ3 REY patterns could not be explained with a simple mixing of different REY sources. Removal of REY from the groundwater in association with precipitation of colloidal and particle materials, an analogue to REY scavenging from seawater, is the most important mechanism influencing the SJ3 REY patterns. Strong REY “scavenging”, which may be caused by both less dynamic hydrology, longer travel-time and increased ionic strength of karst groundwater, is suggested to be responsible for the large positive Y anomalies and negative Ce anomalies and depletion of light REE relative to heavy REE during the cold–dry climate phases (e.g. the periods corresponding to the last glacial maximum and Heinrich event 1). [Copyright &y& Elsevier]

Abstract: 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 0.75–2ka (late Holocene), 9–9.6ka (early Holocene), 87.9–88.2ka and 93.8–95.2ka (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. [Copyright &y& Elsevier]

Abstract: We present a continuous record of the Asian monsoon over the last 16 ka from δ18O measurements of stalagmite calcite. Over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230Th dates. δ18O and therefore Asian monsoon intensity generally follows changes in insolation, although changes in δ18O are generally accommodated in abrupt shifts in contrast to smoothly varying insolation, indicating that threshold effects may be important. δ18O decreased dramatically (∼3‰) at the start of the Holocene (∼11.5 ka) and remained low for ∼6 ka. Four positive δ18O events centered at 11225±97 yr BP (1.05‰), 10880±117 yr BP (1.15‰), 9165±75 yr BP (1.4‰), and a double event centered at 8260±64 yr BP (1.1‰) and 8080±74 yr BP (1.0‰) punctuated this period of high monsoon intensity. All four events correlate within error with climate changes in Greenland ice cores. Thus, the relationship between the Asian monsoon and the North Atlantic observed during the glacial period appears to continue into the early Holocene. In addition, three of the four events correlate within error with outburst events from Lake Agassiz. The decline of monsoon intensity in the mid-late Holocene is characterized by an abrupt positive shift in δ18O which occurs at 3550±59 yr BP (1.1‰ in ∼100 yr). In addition, the Holocene is punctuated by numerous centennial- and multi-decadal-scale events (amplitudes 0.5 to 1‰) up to half the amplitude of the glacial interstadial events seen in the last glacial period. Thus, Holocene centennial- and multi-decadal-scale monsoon variability is significant, although not as large as glacial millennial-scale variability. The monsoon shows a strong connection with northern South American hydrological changes related by changes in ITCZ position. Spectral analysis of the δ18O record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing. However, there are numerous other significant peaks including peaks at El Niño frequencies (observed for high-resolution portions of the record between 8110 and 8250 yr) which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling Holocene monsoon climate. In addition, for this high-resolution portion, we observe a distinctive biennial oscillation of the Asian monsoon, which has been associated with the Tropospheric Biennial Oscillation (TBO). [Copyright &y& Elsevier]