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Despite the recent recognition of 17O‐excess as a promising new tracer for hydrological processes, our knowledge of the control mechanisms underlying 17O‐excess in tropical regions remains limited. To understand how microphysical processes during tropical convection affect precipitation isotope ratios, particularly 17O‐excess, in Singapore, we collected precipitation samples at minute intervals from six rain events associated with cold surges during the Northeast Monsoon seasons and analyzed their triple oxygen isotopes. Our results show that precipitation δ18O decreases in the convective zones and then gradually increases in the stratiform zones, while d‐excess exhibits an inverse trend. This correlation between δ18O and d‐excess indicates that rain evaporation plays a crucial role in regulating precipitation isotopes. Moreover, the rain events with a higher upstream rainout amount have lower δ18O and higher 17O‐excess values, suggesting that precipitation δ18O and 17O‐excess likely reflect the integrated upstream convective activity. Microphysical processes associated with upstream convection, such as rain evaporation and vapor recycling, are potential mechanisms that increase 17O‐excess values along moisture transport pathways for a rain event, and hence, undermine the effectiveness of 17O‐excess as a tracer of moisture source humidity. Contrary to the negative correlation observed in monthly precipitation, there is generally a positive correlation between d‐excess and 17O‐excess at the event scale. However, this correlation weakens as convective rain intensifies, suggesting that stronger convection can attenuate the positive correlation between d‐excess and 17O‐excess. Therefore, it is crucial to consider how tropical convection alters 17O‐excess when utilizing this tracer to interpret atmospheric dynamics and hydrological processes. Plain Language Summary: Our study investigates the impact of tropical weather systems and cloud processes on rainwater isotopes in Singapore. Understanding the factors influencing rainwater isotopes is crucial for interpreting climate dynamics. We collected rain samples at minute intervals from six events associated with cold surges during the Northeast Monsoon season and analyzed their oxygen and hydrogen isotopes. Our findings revealed that rainwater isotopes undergo changes as they progress through different phases of these weather systems, mainly due to rain evaporation. Furthermore, we observed that the amount of upstream rain affects the isotopic composition of rainwater in Singapore, suggesting that rainwater isotopes mirror the overall activity of upstream weather systems. Additionally, we found that regionally organized, stronger convection can alter the correlation between different isotopic parameters. Our research emphasizes the importance of considering the modifying effect of tropical weather systems on rainwater isotopic composition when utilizing these tracers to interpret atmospheric and hydrological processes. This highlights the significance of high‐resolution monitoring work and emphasizes the role of microphysical processes in understanding modern climate change. Key Points: Rain evaporation plays a significant role in shaping tropical precipitation isotopesIntegrated upstream convection may increase 17O‐excess along moisture transport pathwaysRegional convection can attenuate the positive correlation between d‐excess and 17O‐excess [ABSTRACT FROM AUTHOR]

The Kuroshio intrusion (KI) is a northwestward‐flowing branch of the Kuroshio Current, which enters the South China Sea (SCS) and regulates its temperature, salinity, and water mass exchanges. However, limited direct observations hinder our understanding of KI's mechanisms and responses to climate change. Here, we present a 60‐year bi‐monthly resolved coral oxygen isotope (δ18Oc) record from Dongsha Atoll, the northern SCS. The dry‐season (December–March) δ18Oc record reveals interannual to decadal variabilities of the KI. The impact of the East Asian winter monsoon (EAWM) on Dongsha δ18Oc was more pronounced during the 1970s and 1980s and after the early 2000s, while the influence of the El Niño‐Southern Oscillation (ENSO) on Dongsha δ18Oc was higher between the 1980s and 1990s. The Pacific Decadal Oscillation (PDO) may have a relatively minor effect on KI strength or may indirectly modulate KI strength through its influence on ENSO activities. Our Dongsha δ18Oc record highlight the importance of the EAWM, ENSO, and PDO in predicting future KI changes. Plain Language Summary: The Kuroshio intrusion is a branch of the Kuroshio Current. It flows into the South China Sea and affects its temperature, salinity, and water movement. We however know very little how the Kuroshio intrusion responds to climate changes. Here we present a study on the chemical composition of a coral core from Dongsha Atoll in the northern South China Sea. Our study shows that the intrusion varies markedly over the past 60 years and is connected to changes in sea surface salinity. Stronger intrusions align with stronger East Asian winter monsoon intensity and El Niño events. Understanding how the Kuroshio intrusion reacts to climate change is important for effectively managing the potential impacts of global warming on the marine ecosystem. Key Points: A 60‐year‐long coral oxygen isotope record from Dongsha Atoll, South China Sea reveals interannual to decadal variations in the Kuroshio intrusionStrong Kuroshio intrusion, corresponding to high sea surface salinity, is identifiable over the past 60 yearsThe Kuroshio intrusion variations are primarily driven by East Asian winter monsoon changes and also influenced by El Niño‐Southern Oscillation [ABSTRACT FROM AUTHOR]

Our understanding of climate dynamics during millennial-scale events is incomplete, partially due to the lack of their precise phase analyses under various boundary conditions. Here we present nine speleothem oxygen-isotope records from mid-to-low-latitude monsoon regimes with sub-centennial age precision and multi-annual resolution, spanning the Heinrich Stadial 2 (HS2) — a millennial-scale event that occurred at the Last Glacial Maximum. Our data suggests that the Greenland and Antarctic ice-core chronologies require +320- and +400-year adjustments, respectively, supported by extant volcanic evidence and radiocarbon ages. Our chronological framework shows a synchronous HS2 onset globally. Our records precisely characterize a centennial-scale abrupt "tropical atmospheric seesaw" superimposed on the conventional "bipolar seesaw" at the beginning of HS2, implying a unique response/feedback from low-latitude hydroclimate. Together with our observation of an early South American monsoon shift at the HS2 termination, we suggest a more active role of low-latitude hydroclimate dynamics underlying millennial events than previously thought. New cave records from monsoon regions improve the Greenland ice core chronological framework around the Heinrich Stadial 2 by an order of magnitude, suggesting a more active role of low-latitude hydroclimate in millennial-scale climate oscillations. [ABSTRACT FROM AUTHOR]

The impacts of anthropogenic forcing on Indian summer monsoon (ISM) rainfall are obscure, partly due to limited availability of highly resolved hydroclimate proxy records as well as the highly regionalized nature of precipitation. Here, we report an annually‐resolved speleothem oxygen isotope record from Xianren Cave, southwestern China, which represents rainfall change over the broad ISM region. We find that the region has endured at least six decadal‐scale weak monsoon events in the past three hundred years. One of them, lasting from the early to mid 19th century, shares the similar gradual, persistent trend as the most recent decline in ISM rainfall and both have a magnitude substantially larger than the others dominated by natural variability. This early weak monsoon event occurred during a historical time of intensive deforestation in the region. We conclude that the ISM trend could have been altered by the changes in land‐use and land‐cover since the early 19th century. Plain Language Summary: It is difficult to determine when human activities started to have visible effects on precipitation change. Here, we present a well‐resolved Indian summer monsoon (ISM) rainfall record, based on stable isotope studies on speleothems collected from a cave in southwestern China. The oxygen isotope record shows that ISM rainfall has six multi‐decadal decreases in the past three hundred years. One of the corresponding monsoon weakening, lasting from the early to mid 19th century, cannot be simply explained by natural variations in the climate system. This prolonged weak monsoon event was likely caused by regional‐scale changes in land‐use and land‐cover, which can be supported by carbon isotope data in speleothems as well as increased deforestation in the region. We hereby propose that observable changes in the trend of ISM rainfall caused by human activities could have occurred as early as in the early 19th century. Key Points: A speleothem oxygen isotope record shows that the Indian summer monsoon (ISM) has endured six multi‐decadal weakening in the past 300 yearsThe monsoon weakening, from the early to mid 19th century, has a similar gradual, persistent trend as the most recent decline in monsoon rainfallRegional changes in land‐use and land‐cover may have altered the trend of the ISM since the early 19th century [ABSTRACT FROM AUTHOR]

ABSTRACT A speleothem record from south-western China characterizes in detail the millennial-scale changes in Asian Monsoon (AM) intensity from 39.3 to 28.7 ka. The calcite δ18O profile, with an average resolution of ∼8 years, shows several strong monsoon events concurrent with Greenland Interstadials (GIS) 8-4. To gain a systematic perspective of AM millennial-scale variability, the new and previously reported data from the same cave are combined, showing that AM variation exhibits a broad similarity with Greenland ice δ18O records and with Antarctica but in an opposite sense. For the interval that encompasses GIS 5 and GIS 4.1, however, our stalagmite δ18O record depicts a sustained strong monsoon with no distinctive oscillation between these interstadials. Another prominent characteristic in our record is a gradual transition into Chinese Interstadial (CIS) 8, which is well constrained by an annually laminated sequence. We find that an initial rise in monsoon intensity, lasting a few centuries, significantly precedes the abrupt onset of CIS 8 in the AM realm. This suggests that atmospheric moisture and heat transport are probably capable of inducing abrupt climate change when a rapid reorganization of ocean/atmosphere circulations passes a tipping point. [ABSTRACT FROM AUTHOR]

The regional monsoons of the world have long been viewed as seasonal atmospheric circulation reversal-analogous to a thermally-driven land-sea breeze on a continental scale. This conventional view of monsoons is now being integrated at a global scale and accordingly, a new paradigm has emerged which considers regional monsoons to be manifestations of global-scale seasonal changes in response to overturning of atmospheric circulation in the tropics and subtropics, and henceforth, interactive components of a singular Global Monsoon (GM) system. The paleoclimate community, however, tends to view 'paleomonsoon' (PM), largely in terms of regional circulation phenomena. In the past decade, many high-quality speleothem oxygen isotope (δO) records have been established from the Asian Monsoon and the South American Monsoon regions that primarily reflect changes in the integrated intensities of monsoons on orbital-to-decadal timescales. With the emergence of these high-resolution and absolute-dated records from both sides of the Equator, it is now possible to test a concept of the 'Global-Paleo-Monsoon' (GPM) on a wide-range of timescales. Here we present a comprehensive synthesis of globally-distributed speleothem δO records and highlight three aspects of the GPM that are comparable to the modern GM: (1) the GPM intensity swings on different timescales; (2) their global extent; and (3) an anti-phased inter-hemispheric relationship between the Asian and South American monsoon systems on a wide range of timescales. [ABSTRACT FROM AUTHOR]

Abstract: We have obtained a high-resolution oxygen isotopic record of cave calcite from Caverna Botuverá (27°13′S, 49°09′W), southern Brazil, which covers most of the last 36 thousand years (ka), with an average resolution of a few to several decades. The chronology was determined with 46U/Th ages from two stalagmites. Tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change. We interpret our record in terms of meteoric precipitation changes, hence the variability of South American Monsoon (SAM) intensity. The oxygen isotopic profile broadly follows local insolation changes and shows clear millennial-scale variations during the last glacial period with amplitudes as large as 3‰ but with smaller centennial-scale shifts during the Holocene. The overall record is strikingly similar to, but strongly anti-correlated with, a number of records from the Northern Hemisphere. We compared our record to other precisely dated contemporaneous records from Hulu Cave eastern China. Minima in δ 18O (wet periods, intense SAM) at our site are synchronous with maxima in δ 18O (dry periods, weak East Asian Monsoon, EAM) in eastern China (within precise dating errors) and vice versa. This anti-phased precipitation relationship between two low-latitude locations may be interhemispheric in extent, based on comparison with records from other sites. Precipitation anti-phasing may be related to north–south shifts in the mean position of the intertropical convergence zone (ITCZ) and asymmetry in Hadley circulation in two hemispheres, associated not with seasonal changes as observed today, but with millennial-scale climate shifts. The millennial-scale atmospheric see-saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor''s greenhouse properties. [Copyright &y& Elsevier]

The interhemispheric anti-phase variation of monsoonal precipitation at the millennial timescale has been attributed to the latitudinal movement of the Intertropical Convergence Zone (ITCZ). However, a debate persists regarding the lead-lag or synchronous relationship between the Asian Summer Monsoon (ASM) and South American Summer Monsoon (SASM) on the onset and termination timings of the Heinrich stadials, hindering a deeper understanding of their underlying driving mechanisms. Here, we presented a new stalagmite δ18O record from Xianyun Cave, southeastern China. This record, with ∼5-year temporal resolution and an averaged uncertainty of ∼60 years on U–Th dates, spans Heinrich Stadial 2 (HS2) and represents East Asian Summer Monsoon (EASM) intensity variations. Based on our record, we further divided the evolution of the EASM during HS2 into three phases: an onset phase (HS2-I, 24,450–24,260 yr BP) and a termination phase (HS2-III, 23,950–23,630 yr BP), sandwiching a phase with relatively intensified monsoon (HS2-II, 24,260–23,950 yr BP). During the onset and termination of HS2, synchronous transition in monsoon records from both hemispheres was observed, driven by the large-scale meridional movement of the ITCZ. In HS2-I, a "Large excursion" observed in both tropical ISM and SASM records was also evidenced in the Xianyun record, suggesting an extension of the "Tropical atmospheric seesaw" to broader regions near tropical moisture sources. In phase II, our record precisely characterizes a centennial-scale strengthening of the EASM coinciding with a weakening SASM, while the Indian Summer Monsoon (ISM) showed no significant changes. The decoupling of the ISM and EASM may be related to the distinct responses of the regional ITCZ to El Niño-Southern Oscillation variabilities. Our study highlights the significant role of the tropical ocean-atmosphere coupling systems in the synchronized or divergent evolution of global monsoons within Heinrich stadials. • Synchronous anti-phase variations of interhemispheric monsoons in the HS2 onset and termination phase. • The "tropical atmospheric seesaw" at the onset phase extended to broaden regions near the tropical moisture source. • The ISM and the EASM exhibited distinct responses to a more La Niña-like state during HS2-II. [ABSTRACT FROM AUTHOR]

The difficulty in constraining the large-scale Asian summer monsoon (ASM) variability in the Chinese monsoon region (CMR) during glacial Termination II lies in our limited knowledge of the western part, primarily due to sparse paleoclimate records. To get a better picture of the ASM during Termination II, we examined a precisely dated stalagmite δ18O record between 133.1 and 127.0 kyr B.P. from Wanxiang Cave located at the ASM's northern edge in western China. In combination with published δ18O data from this cave, we have identified the 'Weak Monsoon Interval' (WMI) in the Wanxiang δ18O record and confirmed that the Heinrich 11 cold event in the North Atlantic caused the weakened ASM over the CMR via reorganization of the large-scale ocean-atmospheric circulation. However, the post-WMI change in δ18O is gradual, in contrast with the abrupt shift shown in the other cave records from southern and northeastern China. The rapid northward migration of the westerly jet relative to the Qinghai-Tibet Plateau is probably responsible for this discrepancy. This northward-positioned westerly jet prevented the more 18O-depleted moisture from the Indian Ocean from reaching the study site. Simultaneously, it facilitated the earlier northward movement of the East Asian summer monsoon (EASM) rainband that carries positive precipitation δ18O to obscure the abrupt decrease in our δ18O record. After the onset of the last interglacial, no obvious Younger Dryas (YD)-like event was recorded in Wanxiang Cave. This result is consistent with most stalagmite δ18O records in the CMR and further suggests a minimal impact of the YD-like event on ASM variabilities. The relatively large amplitude of δ18O variations observed in Wanxiang Cave between the late penultimate glacial and the last interglacial corresponds to a dominant control of the Indian summer monsoon (ISM), whereas smaller δ18O amplitudes were recorded in cave sites mainly under the influence of both ISM and EASM. Therefore, we posit that the heterogeneity of the hydroclimate in the CMR during Termination II resulted from a combination of multiple processes, that is, the westerly jet, ISM and EASM, rather than a single one. • A precisely dated stalagmite from the ASM's northern edge in western China reveals ASM variability during Termination II. • Our δ18O records capture the WMI event, which corresponds well to the HS 11 period at northern high latitudes. • Gradually changes in δ18O at the onset of the last interglacial are due to the abrupt northward shift of the westerly jet. • The YD-like event did not have a far-reaching impact on ASM variabilities in the Chinese monsoon region. • Moisture sources cause the amplitude discrepancies in Chinese stalagmite δ18O records during the penultimate deglaciation. [ABSTRACT FROM AUTHOR]

The Marine Isotope Stage (MIS) 4/3 boundary, the so-called unfinished or failed termination, is a time period during which climate shifted from glacial to near-interglacial conditions that is akin to the Termination I. Paleoclimate records on this boundary can provide insights into the mechanisms of abrupt climate change under the circumstances when the global climate system has not reached a full threshold state. However, investigations on this specific climate period are sparse largely due to limited geological records with high temporal resolution. Here, we present a new highly resolved stalagmite record from Wanxiang Cave in western China that provides a detailed evolution of the Asian summer monsoon (ASM) from its northern fringe region. Established with 7 high-precision U Th dates and 647 pairs of isotope data (δ18O and δ13C), this record spans from 59.99 kyr B.P. to 52.94 kyr B.P., and contains the whole MIS 4/3 boundary. Its δ18O reveals three Chinese Interstadials (CISs) on millennial scales, i.e., CISs A.16–17 and 14. Sub-millennial events CIS A.17a and 16a correspond to the Greenland Interstadials 17 and 16 (GISs 16 and 17). The CIS A.17b is related to the 'precursor events' (PE 17), while the PEs 14 and 16 events are not evident in our δ18O record, probably due to the gradual change of the CIS A.14b and the lower amplitude of the CIS A.16b. Compared with other climate records, particularly those from the high latitudes, our δ18O record strengthens the notion of the close teleconnection between the ASM and high-latitude climates. Gradual change in δ18O from the CIS A.17b to 17a and the smaller amplitude of the CIS A.16b and 14b are likely coupled to the gradual Antarctic temperature variations, suggesting a dominant role of southern climate process to modulate ASM variability in western China via reorganization of atmospheric circulation. In addition, the westerly jet position relative to the Qinghai-Tibet Plateau may also have suppressed the abrupt 18O-depletion during these periods. At the onset of the MIS 4/3 boundary (at ∼59.82 kyr B.P.), an increase in the Northern Hemisphere summer insolation resulted in rapid ocean-atmospheric reorganizations between the high and low latitudes. This process led to an abrupt increase in precipitation associated with strengthening of ASM circulation, which promoted soil microbial activity and the transition of vegetation type from C4 to C3 as indicated by the δ13C decreasing in the record. After that, centennial-scale variations in δ13C are mainly related to soil humidity change throughout the MIS 4/3 boundary. Our δ18O record further confirms that the MIS 4/3 deglaciation is dominated by a northern-residing forcing, but also involves climate change process from the south. On a regional scale, the δ18O record from Wanxiang Cave may be largely influenced by the Indian summer monsoon, and thus inherits signatures from the south characterized by slightly more negative δ18O than other Chinese stalagmite records on millennial timescales. • A precisely dated stalagmite from the northern edge of the ASM captures the CIS A.14-17 during the MIS 4/3 boundary. • The δ18O records correspond well to millennial-scale climatic oscillations in northern high latitudes. • The well relationship between δ18O and Antarctic climate change confirms the impact of the SH climate process on ASM. • Rapid ocean-atmospheric reorganizations act as a vital part to abrupt recovery of ASM at the onset of the MIS 4/3. • The ISM may be the dominant factor influencing variations in δ18O in western China on regional scale. [ABSTRACT FROM AUTHOR]

Mainland Southeast Asia experiences complex and variable hydroclimatic conditions, mainly due to its location at the intersection of Asian monsoon subsystems. Predicting future changes requires an in-depth understanding of paleoclimatic conditions that is currently hindered by a paucity of records in some regions. In this paper, we present the first speleothem stable isotope records from western Thailand detailing the Bølling-Allerød interstadial, Younger Dryas termination, and early- to mid-Holocene period. We find evidence of higher precipitation during the Bølling-Allerød (14,321–12,824 years before present (1950: BP)) compared to a Younger Dryas termination that starts 11,702–11,674 BP, has a rapid shift centered on 11,660–11,641 BP, and ends 11,603–11,589 BP. In addition, our records show Holocene monsoon intensity peaking at 8250 BP or before, a multi-millennia delay from the Northern Hemisphere summer insolation peak, followed by a trend to drier conditions until at least 750 BP. Assessment of the timing of the Younger Dryas termination in paleoclimate records across Southeast Asia reveals an earlier shift of the Indian Summer Monsoon to global climate shifts when compared to East Asian Summer Monsoon records. The causes of this are currently unknown. Some potentially important aspects include: an Indian Summer Monsoon influence on East Asian Summer Monsoon strength via the Indian Ocean Dipole climate pattern, the role of the Tibetan Plateau in monsoon dynamics, and exposure of the Sundaland shoreline. More high-resolution paleoclimate records, especially on the pathway of Indian Summer Monsoon to East Asian Summer Monsoon, are required for further discussion on the mechanisms controlling the differences between climate regimes. • We present two new speleothem stable isotope records from western Thailand. • Conditions trend wetter during the Bølling-Allerød. • Early and abrupt termination of the Younger Dryas (11,675–11,600 BP, ±73 years). • Change Point Analysis of records finds earlier rapid shift in Indian Summer Monsoon. • Distinct trend of increasing δ18O and δ13C values throughout Holocene. [ABSTRACT FROM AUTHOR]

Abstract Investigating controls on past variability of South American hydroclimate is critical to assessing its response to future warming scenarios. δ18O records from South America offer insight into past variability of the South American Monsoon System (SAMS). The controls, however, on precipitation δ18O values can be decoupled from precipitation amount at a given site and, thereby, limit local moisture condition reconstructions. Here we use a principal components analysis to assess the coherence of speleothem and lake core Holocene δ18O records in tropical and subtropical South America to evaluate the extent to which δ18O variability reflects changes in SAMS intensity at different sites across the region. The main mode of variability across Holocene δ18O records (PC1) closely tracks austral summertime insolation, consistent with existing work. Sites towards the periphery of the continent are heavily weighted on PC1, whereas interior sites as not. Further δ18O variability at interior sites bear little similarity to each other and implicate controls, beyond regional monsoon intensity, on these δ18O records. Further, we develop speleothem 87Sr/86Sr records spanning the Holocene from Tamboril Cave (Brazilian Highlands), Paraíso Cave (eastern Amazon Basin), Jaraguá Cave (Mato Grosso do Sul Plateau), and Botuverá Cave (Atlantic coastal plain) to investigate coupling between reconstructed monsoon variability (reflected by PC1) and local moisture conditions (interpreted from 87Sr/86Sr records). We interpret speleothem 87Sr/86Sr variability as a proxy of local moisture conditions, reflecting the degree of water-rock interaction with the cave host rock as driven by variations in water residence time. Speleothem 87Sr/86Sr records from all the sites, except Botuverá cave, do not co-vary with PC1, suggesting that local moisture conditions do not necessarily follow variations in regional monsoon intensity at these interior sites. These speleothem 87Sr/86Sr records generally suggest dry mid-Holocene conditions relative to the early- and late-Holocene, consistent with interpretations of other paleo-moisture records in the region, but timing of wet-dry transitions varies between sites. These results highlight that controls, in addition to SAMS variability, might influence δ18O variability. Further, our results suggest spatially variable local moisture conditions at interior sites that do not uniformly respond to regional monsoon intensity, and stress the need for δ18O-independent reconstructions of moisture conditions. Highlights • The main mode of speleothem δ18O variability follows austral summertime insolation. • Speleothem 87Sr/86Sr values are a feasible proxy of local moisture conditions at our study sites. • Local moisture conditions are largely decoupled from overall monsoon intensity. • Speleothem 87Sr/86Sr values suggest a widespread mid-Holocene drying across study sites. [ABSTRACT FROM AUTHOR]

Multi-proxy analysis of abrupt climate change during Ice Age Termination III (T-III) is necessary to understand Asian summer monsoon (ASM) characteristics and mechanisms. We present 230Th dates and δ 18O, δ 13C, with equilibrium diameter, carbonate deposition amount and lithological characteristics from an annually laminated stalagmite (No. YXB) in Yongxing Cave, central China. Our multi-proxy records span 243.90 to 239.20 ka before present, falling within T-III/Marine Isotope Stage 7e. The changes in δ 18O, equilibrium diameter, carbonate deposition amount, and lithological characteristics suggest a weak ASM interval during T III. By comparing these results with records from Ice Age Termination I (T-I), we find that the weakened ASM event during T-III is similar to the Younger Dryas (YD) event in terms of duration and structure. This result suggests that the YD-like event could be an inherent feature of glacial-interglacial climate cycles in the middle and late Pleistocene. The YXB δ 13C sequence, without YD-like events, is broadly similar to the δ 18O record on orbital timescale, indicating that variations in local vegetation could be driven by rising CO 2 during ice age terminations. • Stalagmite records based on layer counting chronology from Southern China. • Stalagmite δ 18O, lithological characteristics indicate a weak Asian summer monsoon interval during Termination III. • Duration and structure of weak monsoon interval during Termination III is similar to Younger Dryas. • δ 13C indicates no YD-III but driven by greenhouse gases during ice age terminations. [ABSTRACT FROM AUTHOR]

A Holocene stalagmite from Botuverá Cave, southeastern Brazil was analyzed by LA-ICPMS for Mg/Ca, Sr/Ca, Ba/Ca. The observed variability in the record was demonstrated to be modulated by prior calcite precipitation, and, thus, is interpreted to reflect monsoon intensity. We find that the calcite δ 18 O is strongly correlated with Sr/Ca, indicating that atmospheric circulation over South America and monsoon intensity have been tightly correlated throughout most of the Holocene, both directly responding to solar precession. Comparison with other contemporaneous high-resolution hydroclimate records reveals that SAMS has shown a degree of complexity during the Holocene not previously detected, with periods where the South American Convergence Zone (SACZ) expanded to cover most of the South American sub-continent, and coincident with periods of low-SST in the north Atlantic. We also detect periods where rainfall amount in northeastern and southeastern Brazil are markedly anti-phased, suggesting a north-south migration of SACZ, which it appears to be mediated by solar irradiance. The high-resolution nature of our record allow us to examine the effect that Holocene climate anomalies had upon SAMS dynamics and hydroclimate in southeastern Brazil, in particular the 8.2 ka event and the Little Ice Age. In addition to confirm the internal structure of the events, we also detect the possible consequences of the climatic anomalies upon ocean–atmosphere interactions through its effects upon SAMS. [ABSTRACT FROM AUTHOR]

A continuous high-resolution record from a precisely-dated stalagmite spanning the last precessional cycle provides new insight into the dynamics of climate change from orbital to centennial scales. A 600-mm length stalagmite (LS46) collected from the Luoshui Cave, Hubei Province, Central China, was well-dated (a total of 24 230Th dates) and high-resolved sampled for oxygen and carbon stable isotopic measurements (2047 subsamples in total). The stalagmite LS46 δ18O is consistent with other published stalagmite δ18O time series in monsoonal China, and closely tracks changes in the Northern Hemisphere summer insolation (NHSI) on July 21st throughout the past 23.5 kyr. Besides, the stalagmite LS46 δ18O shows significant correlations with the reconstructed Dali lake-level history and tree-ring δ18O records in the marginal monsoon regions. On this basis, we interpret that the stalagmite LS46 δ18O reflects the large-scale monsoon circulation with a superimposed local climate signal that might be related to effective humidity. Furthermore, the stalagmite LS46 δ18O exhibited four long-lasting extremely weak monsoon events since 7 kyr B.P.. These four weak monsoon events corresponded well with the tree-ring record in the northwestern fringe of the East Asian summer monsoon (EASM) region. Notably, the good correspondence between the stalagmite record and the tree-ring record also provides a good chronological support for our assessment of the climate and cultural evolution during the middle-late Holocene transition, the medieval warm period (MWP) and Little Ice Age (LIA). During the early-middle Holocene, the detrended δ18O profile revealed 10 multi-centennial monsoon cycles with a duration of nearly 500 yr and the amplitude of ∼0.8‰. The wavelet analysis further discloses that the EASM has nearly 500 yr and 200 yr periodic oscillations in the early-middle Holocene, research indicated that the solar activity and the North Atlantic Oscillation (NAO)/North Atlantic Deep Water (NADW) jointly drive the dominant nearly 500 yr cycle of the Asian monsoon. • A successive stalagmite δ18O/δ13C series from Central China over the past 23.5 kyr. • Stalagmite δ18O coincides with tree ring δ18O and lake level. • LS46 δ18O records 4 weak monsoon events since 7 kyr B.P. and corresponds well to the tree ring data in NW China. • ∼500 yr periodicity of AM during the Early-Mid Holocene was forced by solar activity and the NAO. [ABSTRACT FROM AUTHOR]

Abstract: Although the initiation and continuation of orbital and millennial climate transitions were reported to be roughly similar, little is yet known about the extent to which their sequences of climate events are linked together in the same physical processes. Here we present a stalagmite isotope record from Wulu Cave, southwestern China, based on 1200 oxygen isotope data and 15 230Th ages, registering a detailed history of the Asian Monsoon (AM) from 61.3 to 50.5 ka BP with an average resolution of 12 yr. Two replicated, high-resolution calcite δ18O profiles show four millennial-scale strong summer monsoon events, analogous in timing and structure to Chinese Interstadials A.17–A.14 (CIS A.17–A.14), as recorded elsewhere in China and Greenland Interstadials 17–14 (GIS 17–14). These events exhibit two distinct phases, consistent with multi-decadal/centennial shifts in Greenland temperature and storminess. This relationship reveals a tight coupling between high- and low-latitude climates at sub-millennial scales, implying a role for westerly winds in linking Greenland temperature and the AM. Around the Marine Isotope Stage (MIS) 4/3 boundary, successive AM events resemble, but in higher frequency, structure of the Bølling–Younger Dryas (YD) surrounding Termination I. Along with evidence from similar shifts in bipolar temperature and atmospheric CH4, we suggest that the recurrence of similar climate structure worldwide is likely caused by changes in Atlantic meridional overturning circulation (AMOC) at various timescales under thresholds of global ice volume boundaries, as predicted by the bipolar seesaw model. [Copyright &y& Elsevier]

Abstract: Two stalagmites (C996-1 and C996-2) collected from the Jiuxian Cave in the Shaanxi Province in central China have been studied with U-series dating and stable isotope analysis. Thirty-eight 230Th dating results showed that the stalagmite C996-1 was continuously deposited through the last 8.5ka BP (thousand years before present, present=1950AD), and C996-2 was deposited through the last 19ka BP excluding two growth hiatuses between 8.3 and 5.7ka BP, and 15.4 and 11.9ka BP. With a relatively stable boundary condition, we interpret the δ 18O of speleothem calcite as most indicative of the amount of summer monsoon precipitation, although temperature and other factors might have some minor impact. The δ 18O records show notable changes within the last glacial maximum (LGM), resembling other East Asian monsoon records such as those from the Hulu and Sanbao Caves, suggesting that significant monsoonal climate changes occurred in eastern Asia as far north as the Qinling Mountains during the LGM interval. A comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of δ 18O during the Holocene commenced as early as ∼7.5ka BP in the low-latitude monsoonal area, i.e. the Hoti Cave, while at higher latitudes this shift occurred later, such as ∼7.0ka BP in the Dongge Cave, ∼5.3ka BP in the Heshang Cave, ∼4.7ka BP in the Sanbao Cave and ∼4.5ka BP in the Jiuxian Cave. These results imply an asynchronous change of the summer monsoon precipitation occurred in East Asia during the Holocene. The asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing, which result from the complex geographical configuration. The variation of sea surface temperature (SST) in the western tropical Pacific may also have important impacts on the summer monsoon precipitation changes in central and northern China because it affects the Northwestern Pacific Subtropical High, a monsoon-front regulator. More robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail. [Copyright &y& Elsevier]

Abstract: An annual layer-counted and 230Th-dated stalagmite oxygen isotope record from Qingtian Cave in Hubei province, central China, provides an Asian Monsoon (AM) history across the Allerød to Younger Dryas (YD) transition, with an average 2.5-year resolution. Seasonal δ 18O profiles indicate that the calcite δ 18O is a sensitive proxy for AM changes, and the close similarity between the Qingtian and other cave records from eastern China suggests a large-scale regional coherence of monsoonal precipitation δ 18O variations associated with the temperature changes in high-northern latitudes. The annually-resolved chronology with a U–Th age uncertainty of less than 100 yr defines the timing, duration and transition of the early Allerød, the intra-Allerød cold period (IACP), the late Allerød, and the start of the YD. The 160-yr-long IACP, with two brief reversals, is clearly shown in both δ 18O and lamina thickness records. The early and late Allerød, separated by the IACP, are characterized by several decadal to centennial cycles of δ 18O variations, each punctuated by sub-cycles. These decadal to centennial monsoon variations correlate with the Greenland temperature changes, supporting a model simulation that the decadal North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO) are coupled via atmospheric circulation under glacial boundary conditions, perhaps affecting tropical/subtropical monsoon changes. However, the monsoon transition between the late Allerød and YD lasted 380 yr, longer than the analogous Greenland temperature shift by at least 130 yr [Stuiver, M., Grootes, P.M., GISP2 oxygen isotope ratios. Quat. Res. 53 (2000) 277–284]. This implicates other links besides the direct link between Greenland and the AM, which is now well documented. One possibility is the influence by Southern Hemisphere climate via cross-equatorial air flow [An, Z.S., The history and variability of the East Asian paleomonsoon climate. Quat. Sci. Rev. 19 (2000) 171–187]. [Copyright &y& Elsevier]