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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]

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]