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Ice core records from Greenland provide evidence for multiple abrupt cold–warm– cold events recurring at millennial time scales during the last glacial interval. Although climate variations resembling Dansgaard–Oeschger (DO) oscillations have been identified in climate archives across the globe, our understanding of the climate and ecosystem impacts of the Greenland warming events in lower latitudes remains incomplete. Here, we investigate the influence of DO-cold-to-warm transitions on the global atmospheric circulation pattern. We comprehensively analyze δ18O changes during DO transitions in a globally distributed dataset of speleothems and set those in context with simulations of a comprehensive high-resolution climate model featuring internal millennial-scale variations of similar magnitude. Across the globe, speleothem δ18O signals and model results indicate consistent large-scale changes in precipitation amount, moisture source, or seasonality of precipitation associated with the DO transitions, in agreement with northward shifts of the Hadley circulation. Furthermore, we identify a decreasing trend in the amplitude of DO transitions with increasing distances from the North Atlantic region. This provides quantitative observational evidence for previous suggestions of the North Atlantic region being the focal point for these archetypes of past abrupt climate changes. [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]

A multiproxy record from a stalagmite collected from Torgashinskaya Cave (Southern Siberia, Russia) and growing between ca. 6 and 3.8 ka shows evidence for regional climatic changes occurring at ca. 5 ka. Interpretation of stable isotope ratios (δ18O and δ13C) and fluorescence data (intensity and wavelength of the emitted fluorescence) suggests that the interval between ca. 5 and 4.2 ka was generally warmer and drier than the interval between ca. 6 and 5 ka. The observed bipartitioning of the climate, attributable to the so-called 'middle-late Holocene transition', has a striking similarity to changes in K+ and Na+ concentration of Greenland ice cores (taken as indicators of the strength of the Siberian High and Icelandic Low, respectively), in the abundance of hematite-stained grains in subpolar North Atlantic sediments and, to lesser extent, in the summer Asian monsoon intensity deduced by δ18O from Chinese speleothems. In particular, the δ18O record at Torgashinskaya Cave can be interpreted as mostly driven by temperature changes. Besides several episodes of drift towards higher temperatures, it also strongly suggests the presence of short cooling events centered at 4.1+0.08/ -0.07 , 4.85+0.05/ -0.06 , 5.1+0.09/ -0.09 , 5.3+0.08/ -0.07 and 5.8+0.12/ -0.13 ka. Notably, the last three such events are in very good correspondence with spikes in the K+ and Na+ concentration of Greenland ice cores. Instead, the cooling around 4.1 ka could be the local response to the 4.2 event, a cold/dry episode identified in several records in the Northern Hemisphere. This suggests that δ18O of speleothem calcite from this area could be a useful proxy for defining the evolution of the Siberian High and its effect on the wider regional climate. • The first speleothem-based middle-to-late Holocene paleoclimate reconstruction from a Siberian underexplored area. • δ13C-δ18O and fluorescence timeseries reveal temperature and rainfall variations at decadal resolution. • A cold-wet to warm-dry climate shift is related to the Siberian High dynamics during the middle-late Holocene transition. [ABSTRACT FROM AUTHOR]

Present climate conditions impede the formation of calcite speleothems in the gypsum caves of the semi-arid region of Sorbas (Southern Spain). However, U-Th dating reveals the uninterrupted deposition of a 46 mm-thick carbonate flowstone in the Sorbas caves from ∼78 to ∼71 ka, during Marine Isotope Stage (MIS) 5a. This indicates that the area was vegetated during this period, producing biogenic CO 2 in soils necessary for the underground deposition of the speleothem, which contrasts with the current unvegetated landscape. During MIS 5a, rainfall recharged the karst aquifer, leading to cave seepage. The development of soils and persistent water infiltration suggests a higher precipitation/evapotranspiration ratio with respect to the present, which was likely favored by lower regional temperatures and a different annual rainfall regime. δ18O and δ13C analyses testify that the speleothem recorded climate pulses synchronous, and structurally similar, with Greenland interstadial and stadial periods, with relatively wetter conditions recorded during interstadials 21.1, 20 and 19.2, and drier periods during stadials 21.1 and 20. This demonstrates that the climate in the desert-like environment of Sorbas is sensitive to inter- and intra- hemispherical triggers, such as the extent of Northern ice sheets and the Atlantic meridional overturning circulation. Interstadials (stadials) were also characterized by a higher (lower) Atlantic/Mediterranean moisture source ratio. For the first time, we show that carbonate speleothems formed in arid gypsum caves can record reliable palaeoenvironmental information spanning multiple millennia, procuring proxies for detailed palaeoclimate reconstructions. Such speleothems are thus excellent candidates for understanding past climate dynamics and patterns in desert-like gypsum terrains. • A rare calcite speleothem from Sorbas arid region recorded MIS5a palaeoclimate. • MIS 5a climate in Sorbas was more humid than today. • Greenland stadials/interstadials impacted MIS5a rainfall dynamics. [ABSTRACT FROM AUTHOR]