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Qunf Cave oxygen isotope (δ18Oc) record from southern Oman is one of the most significant of few Holocene Indian summer monsoon cave records. However, the interpretation of the Qunf δ18Oc remains in dispute. Here we provide a multi-proxy record from Qunf Cave and climate model simulations to reconstruct the Holocene local and regional hydroclimate changes. The results indicate that besides the Indian summer monsoon, the North African summer monsoon also contributes water vapor to southern Oman during the early to middle Holocene. In principle, Qunf δ18Oc values reflect integrated oxygen-isotope fractionations over a broad moisture transport swath from moisture sources to the cave site, rather than local precipitation amount alone, and thus the Qunf δ18Oc record characterizes primary changes in the Afro-Asian monsoon regime across the Holocene. In contrast, local climate proxies appear to suggest an overall slightly increased or unchanged wetness over the Holocene at the cave site. Southern Oman speleothem oxygen isotope and multi-proxy data reveal diverse changes in the Afro-Indian summer monsoon circulations and local hydroclimate conditions during the Holocene, confirming climate model simulations. [ABSTRACT FROM AUTHOR]

The Marine Isotope Stage (MIS5e) is characterized by a warmer climate than that of the pre-industrial period, and serves as an analog for the Current Warm Period (CWP). However, uncertainties persist regarding its climatic stability. Here, we retrieved a stalagmite (WXB075) from Wanxiang Cave in the eastern Qinghai-Tibetan Plateau, and employed absolute 230Th dating and relative annual layer data to establish a high-precision chronological framework for reconstructing the history of the Asian summer monsoon (ASM) and environmental evolution during early MIS5e with multiple proxies. The findings indicate that the annually laminated stalagmite was formed during Cooling Event 27 (C27). The deposition of WXB075 experienced a hiatus (∼125.58 ka BP) due to a significant cooling event in the North Atlantic, which may be linked to the unstable climate in the Northern Hemisphere. Additionally, the impact of meltwater discharge in high northern latitudes results in a two-phase evolution of the ASM, i.e., an initial weaker stage followed by a gradual increase (with the exception of deposition hiatus). The climatic instability of ASM is generally characterized by a quasi-60 year cycle that affects vegetation conditions, biological productivity, and karst hydroclimate dynamics. However, the increase in meltwater and decrease in temperature in the Northern Hemisphere have led to a weakened ASM and subsequent reduction in precipitation. Consequently, vegetation degradation above the cave has occurred along with a slowdown of karst hydroclimate. The vegetation conditions, organic matter content, and wet/drought of the karst hydroclimate were affected by both the large-scale monsoon circulation and local environment during extreme weakening (strengthening) of the monsoon when high-frequency climatic events of ASM occurred. A comparison of δ18O records between early MIS5e and the past 2000 years reveals that the climate during early MIS5e differed significantly from that of CWP, Medieval Warm Period (MWP), and Dark Age Cold Period (DACP) but was similar to Little Ice Age (LIA). Comparison with other geological records from the Northern Hemisphere indicates that climate instability was a widespread phenomenon during MIS5e. The power spectrum analysis of WXB075 δ18O reveals significant quasi-60 and 35 a cycles during the early MIS5e, which is consistent with the Atlantic Multidecadal Oscillation (AMO). The comprehensive results demonstrate that the ASM in the early MIS5e was closely linked to solar activity, Intertropical Convergence Zone (ITCZ) position, and Atlantic Meridional Overturning Circulation (AMOC). [ABSTRACT FROM AUTHOR]

The 8.2 ka event has been extensively studied, whereas its structure is ambiguous in North China. Here we present a high‐resolution (∼1 year) δ18O record from annual laminated speleothem from Beijing to characterize the detailed variability across this event in North China. Our record indicates a dry 8.2 ka event spanning 8.254–8.107 ka BP with a two‐stage structure superimposed by three prominent high δ18O excursions. The identical structure of speleothem δ18O records between North and central China during the event suggests a common forcing/response in East China, whereas the progressively increased offset between their average values may reflect changes in moisture source or rainout effect. A close comparison with the Greenland ice core records suggests a strong linear response of the Asian summer monsoon to the North Atlantic climate changes across the early and middle stages of the event, but a different mechanism in the termination processes. Plain Language Summary: As the most pronounced abrupt climate event in the Holocene, the 8.2 ka event has been studied using various geological archives worldwide, but its detailed structure in North China and its link to other climate systems remain poorly understood. Since the Beijing speleothem δ18O, a proxy of the precipitation δ18O, is sensitive to the Asian summer monsoon (ASM) variations, it allows us to establish precise timing and structure of the 8.2 ka event and estimate the cause of it. Our new speleothem δ18O record from Beijing reveals a two‐stage structure superimposed by three "V‐shape" excursions during the event and almost exactly covaries with another published speleothem record from central China, suggesting coherent climate changes over the east ASM domain in response to the same forcing. The gradually increased offset between them probably results from the changed atmospheric circulations. Our results suggest a fast climatic signal propagation from the North Atlantic to the ASM domain during the early and middle 8.2 ka event, and another forcing mechanism in the termination processes. Key Points: Annual laminated speleothem δ18O record from North China manifests a two‐stage 8.2 ka event superimposed by three positive excursionsHigh consistency in speleothem records from North and central China on interdecadal to multidecadal timescales indicates a common driverThe climate forcing for the termination process is different from the early and middle stages of the 8.2 ka event [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 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]

Speleothem oxygen isotope (δ18O) constitutes one of key proxies to reconstruct the Indian and East Asian summer monsoon (ISM and EASM) hydroclimate history on a wide range of timescales. Here, we use three new well-dated speleothem δ18O records from Tianmen cave, in the south-central Tibetan Plateau (TP), together with previous records from the same cave, to reconstruct a composite Tianmen record spanning over the past 414,000 years. The Tianmen δ18O record follows Northern Hemisphere summer insolation (NHSI), broadly coherent with speleothem δ18O records from both ISM and EASM regimes. In comparison with previous model simulations and modern hydroclimate analyses, the Tianmen δ18O was interpreted primarily as a proxy indicating the ISM intensity. The Tianmen δ18O record comprises both high and low NHSI time periods, which reveals an exceptional large amplitude (∼14‰) of δ18O variations at the precession band, possibly resulted from a combination effect of precipitation amount, moisture source, transport pathway, high elevation and rainout. Besides, a broad consistency on orbital-scale variability among Tianmen δ18O, δ13C and trace element records is found, suggesting that the ISM intensity regulates the effective rainfall at the cave site as well. Notably, Tianmen speleothem growth occurred merely during warm-wet interglacial periods, even during low NHSI times near the precession maximum, and in contrast, hiatuses persistently occurred throughout cold-dry glacial periods. This pattern is similar to that found in travertine formations in the region, both suggesting that the interglacial temperature might be a prerequisite for speleothem/travertine formations in the region, while the strong ISM precipitation in turn provides a sufficient condition. Our new Tianmen record, combined with a large set of speleothem records from both Asian Westerlies and Asian monsoon domains, gives further evidence to reinforce a previous hypothesis: a consistent temporal pattern in the δ18O of precipitation on orbital and millennial scales over the vast Asian monsoon and Westerlies regimes. As such, in order to reconcile the precipitation δ18O variations between speleothem and TP ice cores, we argue that the Guliya ice-core chronology may have a basal age of ∼70 ka BP , which is supported by recent dating results from the Guliya ice cap. • Speleothem δ18O records from the south-central Tibetan Plateau primarily indicate the Indian summer monsoon (ISM) intensity. • Combined effect results in a large amplitude (∼14‰) of Tianmen cave δ18O variations at the precession band. • Interglacial temperature and high ISM precipitation are critical factors for the speleothem formations in the region. [ABSTRACT FROM AUTHOR]

High-resolution and precisely dated hydroclimate records in the southeastern Tibetan Plateau (TP) remain sparse beyond the Holocene, which hampers our ability to understand the hydroclimate variability in this important Indian summer monsoon (ISM) fringe area and its global teleconnection. Here we present 3-y resolution δ18O and δ13C records from a laminated stalagmite (RG-3) from Rige Cave in the southeastern TP, spanning the Younger Dryas (YD). The records allow us to precisely characterize the timing, structure, and particularly centennial-scale events within the YD, and probe the control factors of precipitation δ18O (δ18O p) in the ISM fringe area. On centennial–millennial timescales, the Rige δ18O record shows coherent pattern with the East Asian summer monsoon (EASM) counterpart, combined with modeled δ18O p results and spatial analysis, suggesting that δ18O p in this part of the TP is largely controlled by the large-scale atmosphere circulation (or the ISM strength), and the altitude increase in the TP may not potentially result in an opposite δ18O p pattern at least in the monsoonal TP regime. We also found significant δ13C-δ18O covariation on the centennial timescale, suggesting a coincided ISM rainfall and biomass change during the YD. In the Rige records, one weak centennial-scale ISM event (namely the intra-Allerød cold period, IACP) and three strong centennial-scale ISM events within the YD (namely A1′-A2′-A3′) were prominent and occurred between ∼12,470 and 12,310 ± 14, ∼12,210–12,090 ± 12 and ∼12,010–11,920 ± 12 y BP (before present, where present = 1950 CE), respectively. Spectral analyses of Rige records also revealed a significant ∼200-y periodicity, which is nearly in-phase with observed centennial-scale variations of the North Atlantic temperature and mid-latitude westerly-jet during that time. These observations support the hypothesis that the solar de Vries cycle (207-y) triggered the centennial-scale climate variations in high northern latitude, leading to the ISM variations via fast atmospheric processes. • Precipitation δ18O and its millennial-centennial patterns in SE Tibet Plateau are controlled by large monsoon circulations • Centennial δ13C-δ18O covariations in Younger Dryas suggest a link of the local biomass to Indian summer monsoon rainfall • Centennial Indian summer monsoon events in Younger Dryas correlate precisely to the North Atlantic climate variations • Solar de Vries cycle (207-y) triggered centennial Indian summer monsoon variations via North Atlantic climate changes [ABSTRACT FROM AUTHOR]