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The Asian summer monsoon (ASM) is a vast climate system, whose variability is critical to the livelihoods of billions of people across the Asian continent. During the past half-century, much progress has been made in understanding variations on a wide range of timescales, yet several significant issues remain unresolved. Of note are two long-standing problems concerning orbital-scale variations of the ASM. (1) Chinese loess magnetic susceptibility records show a persistent glacial-interglacial dominated ~100 kyr (thousand years) periodicity, while the cave oxygen-isotope (δ18O) records reveal periodicity in an almost pure precession band (~20 kyr periodicity)—the “Chinese 100 kyr problem”. (2) ASM records from the Arabian Sea and other oceans surrounding the Asian continent show a significant lag of 8–10 kyr to Northern Hemisphere summer insolation (NHSI), whereas the Asian cave δ18O records follow NHSI without a significant lag—a discrepancy termed the “sea-land precession-phase paradox”. How can we reconcile these differences? Recent and more refined model simulations now provide spatial patterns of rainfall and wind across the precession cycle, revealing distinct regional divergences in the ASM domain, which can well explain a large portion of the disparities between the loess, marine, and cave proxy records. Overall, we also find that the loess, marine, and cave records are indeed complementary rather than incompatible, with each record preferentially describing a certain aspect of ASM dynamics. Our study provides new insight into the understanding of different hydroclimatic proxies and largely reconciles the “Chinese 100 kyr problem“ and “sea-land precession-phase paradox”.

This study examines the first precisely dated and temporally highly resolved speleothem record from Iberia that reconstructs the Oldest Dryas (OD). The onset of cold conditions in the study area, contemporary with the beginning of Heinrich Stadial 1, is recorded at 18.13 ± 0.08 ka, with a pronounced drop of 6.1‰ in δ13C in 250 years. Henceforth, stadial conditions depict a period of instability in the Atlantic Meridional Overturning Circulation, peaking in freshwater input from iceberg melting during Heinrich Event 1. Anomalies in the δ18O of the stalagmite attributed to such a freshwater event are found from 16.17 to 15.89 ka. Such absolute dates given to the onset of the OD in Iberia and to the main iceberg discharges are reliable anchor points for non-absolute chronologies. Two periods are identified in the OD: OD-a (18.13–16.17 ka) is characterized by wet conditions and a faster growth rate, and OD-b (15.89–14.81 ka) exhibits relative dryness and a slower growth rate. The sudden release of fresh water is considered to be the reason for the disruption of rainfall patterns in eastern Iberia. The present study also highlights the existence of heterogeneous and complex hydrological conditions during the OD in Iberia when both Atlantic and Mediterranean realms are considered.

We provide first insights into the speleogenesis of Ejulve cave (Teruel province, Iberian Range, NE Spain) by studying cave morphologies and cave deposits, combined with regional geomorphological and hydrothermal observations. Three main hydrogeomorphic evolutionary stages can be distinguised to explain the origin and evolution of the Ejulve endokarstic system. Cave pattern and cave solutional features (calcite vein fillings, tubes with rising ceiling cupolas, pendants and cusps, spongework and micro-corrosion features) suggest that the cave generated in a phreatic environment by ascending water. Cave morphologies and regional hydrothermal springs in this region suggest, but not prove, the involvement of thermal waters and related convection and condensation-corrosion mechanisms in the origin of the cave. Subsequently, the cave underwent a change to epigenic conditions driven by denudation, as a result of regional uplift. Once the karstic system was exhumated, carbonate speleothems formed in a vadose environment. Mineralogical, petrographic, isotopic and chronological (U-series dating) analyses of carbonate speleothems (i.e. stalagmites, flowstones, botryoids, spars, acicular crystals and farmed carbonate) are provided. Calcite, high-Mg calcite and aragonite are the most common minerals, whereas columnar, dendritic, micrite, mosaics and fans are the main fabrics. Mean δO values of − 7.3‰ and δC values of − 9.1‰ indicate carbonate precipitation from meteoric waters without a hydrothermal origin. Carbonate deposits formed at least since 650 ka BP. Our study suggests that hydrothermal fluid flow may explain, although the evidences are not fully conclusive, the speleogenesis of this cave., We acknowledge the predoctoral research Grant from the Government of Aragón (B158/13) and CTM2013-48639-C2-2-R (OPERA) and CGL2016-77479-R (SPYRIT) projects for funding. Fernando Gázquez was financially supported by the “HIPATIA” research program of the University of Almeria.

This article presents for the first time a large dataset of rainfall isotopic measurements (d18Op and d2Hp) sampled every day or every two days from seven sites in a west-to-east transect across northern Spain for 2010–2017. The main aim of this study is to: (1) characterize rainfall isotopic variability in northern Spain at daily and monthly time scales, and (2) assess the principal influencing factors determining rainfall isotopic variability. This comprehensive spatio-temporal approach allows exploring the role of air mass source in determining the isotopic composition of rainfall in northern Iberia by using back-trajectories; Atlantic fronts are found to be the dominant source of northern Iberia rain events studied. The relative role of air temperature and rainfall amount in determining the stable isotope composition of precipitation changes along the west-to-east transect. Air temperature appears to be the most significant influence on d18Op at daily and monthly time scales with the highest air temperature-d18Op dependency found for the Pyrenean station while a few sites in the transect show a significant negative correlation with precipitation amount. Distance from the coast, site elevation, and moisture source region (Atlantic versus Mediterranean) also significantly modulate the d18Op values and ranges but the type of precipitation (convective vs frontal rainfall) plays a key control, with convective rainfall associated with higher d18Op values. This dataset of the rainfall isotopic composition represents another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a palaeoclimate and hydrological tracer.

The Younger Dryas (YD), arguably the most widely studied millennialscale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon- Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard- Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ~11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ~11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic-Asian Monsoon-Westerlies directionality of climatic recovery., This work was supported by grants from National Nature Science Foundation of China (NSFC 41888101 and 41731174 to H.C.) and US NSF Grant (1702816 to R.L.E. and H.C.)

New speleothem records from northeastern Iberian caves provide data to explore the climatic patterns during the Holocene. We present δ13C and Mg/Ca from three speleothems from two different caves located in the Iberian Range allowing replication of the climatic signal for several millennia. Through the integration of those stalagmites covering since the Holocene onset to 2 ka, the early Holocene (11.7–8.5 ka) appears as the wettest interval. A marked change towards aridity is observed during the middle Holocene (8.5–4.8 ka) and an increase of humidity afterwards (4.8–2 ka). This three-part pattern, contrasting with other Iberian sequences, seems to be associated with the different role that seasonality has played in the response of different proxies (or records) to changes in water availability. Interpreting our speleothem records as changes in winter-spring precipitation along the Holocene allows reconciling previous data on hydrological variability from the western Mediterranean borderlands.

In glaciated areas, the environmental evolution before MIS 2 is usually poorly constrained mainly due to the later glacial erosion during the global Last Glacial Maximum (LGM). However, in carbonate areas, karst caves can preserve records of pre-LGM paleoenvironment. We studied a cave (1350 m altitude) to establish the paleoenvironmental evolution of a glaciated karst area in Picos de Europa (SW Europe). For this objective, a glacial reconstruction, cave sedimentology analyses, and macro- and micromammal remains are com bined with ten U-Th, OSL and AMS C-14 ages. The paleo-glacial reconstruction indicates glaciers descended down to 810-1040 m of altitude covering an area of 36.18 km(2) in the surroundings of Covadonga Lakes during the glacial local maximum, with the equilibrium line altitude located at 1524 +/- 36 m. The geomorphological study of the cave and the U-Th and OSL dates reveal the presence of three allochthonous alluvial sediment sequences at 132-135, 98-60 and ca. 36 ka. These last two sequences would come from the erosion of fluvioglacial sediments including teeth fragments of Pliomys coronensis (=P. lenki), an unusual species in high areas of NW Spain during the Upper Pleistocene. In addition, remains of chamois (Rupicapra pyrenaica) dated in 37-33 cal ka BP constitutes the oldest evidence of chamois above 800 m asl in the region. All the presented data indicate the development of alpine glacier-free areas covered by fluvioglacial sediments at ca. 1450 m altitude at 98-60 and 37-33 ka, corresponding to glacial retreat stages. (C) 2020 Elsevier Ltd. All rights reserved., GRUPIN6IDI/2018/000184 project (FICIY, Gobierno del Principado de Asturias, Spain, and European Union) and FUO-300-17 project (Consorcio Interauton~omico del Parque Nacional de los Picos de Europa, Spain). In addition, LRR is grant holder (Reference ACA-17-19) of the post-doctoral Clarin-COFUND Program, financed jointly by the 7th WP of the European UnioneMarie Curie Actions and Gobierno del Principado de Asturias (Spain). We thank to the grateful assistance of the National Park staff and the speleologists from Grupo Espeleol~ogico Polifemo (Oviedo), GES Monta~neiros Celtas (Vigo), Grupo de Espeleologia Dia~nu Burl~on (Corvera de Asturias), and Esp~eleo Club Aradelas (Vigo). We appreciate the work of Jo de Waele, Rafael L~opez-Martinez and other reviewer.

Western Europe is the region with the highest density of published speleothem δ18O (δ18Ospel) records worldwide. Here, we review these records in light of the recent publication of the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. We investigate how representative the spatial and temporal distribution of the available records is for climate in Western Europe and review potential sites and strategies for future studies. We show that spatial trends in precipitation δ18O are mirrored in the speleothems, providing means to better constrain the factors influencing δ18Ospel at a specific location. Coherent regional δ18Ospel trends are found over stadial-interstadial transitions of the last glacial, especially in high altitude Alpine records, where this has been attributed to a strong temperature control of δ18Ospel. During the Holocene, regional trends are less clearly expressed, due to lower signal-to-noise ratios in δ18Ospel, but can potentially be extracted with the use of statistical methods. This first assessment highlights the potential of the European region for speleothem palaeoclimate reconstruction, while underpinning the importance of knowing local factors for a correct interpretation of δ18Ospel., F.A.L. acknowledges funding by the Swiss National Science Foundation (SNSF) grant P2EZP2_172213. S.A.-M. and L.C.-B. acknowledge funding from the Geological Survey Ireland (Short Call 2017; grant number 2017-SC-056) and from the ERC-funded project GC2.0 (Global Change 2.0: Unlocking the past for a clearer future, grant number 694481). C.P.-M. acknowledges funding by the Government of Aragón predoctoral research grant B158/13 and CGL2016-77479-R (SPYRIT) project. K.R. acknowledges financial support by the German Research Foundation (DFG) grant RE3994-1/1.

Speleothem records from NE Asia are essential to understand the spatial patterns of the Asian Summer Monsoon (ASM) variability. In this paper, we present a new high-resolution and chronologically well-resolved speleothem record from Liu-li (LL) cave, NE China, through δ18O, δ13C and Sr/Ca ratio characterizing a dynamic ASM history over the past 6680 years. The LL δ18O record shows a long-term trend to higher values, following the North Hemisphere summer insolation (NHSI), with the exception of the last 2 kyr characterized by a negative δ18O excursion. The ‘2-kyr shift’ is evident in NE Asia over the past 2 kyr, originally inferred from the speleothem δ18O negative excursion in South China, as well as in many other proxy records from East China, but it merely manifests a flat trend in most of the western East Asian Summer Monsoon (EASM) and Indian Summer Monsoon (ISM) regions, rather than a negative excursion. On multi-centennial to millennial timescales, the intensification of the Tsushima Warm Current (TWC) can amplify rainfall on both sides of the Japan Sea. A close comparison between the monsoon reconstruction and the cultural changes in NE Asia suggests contemporary climatic and cultural regime-shifts, implying an important role of the ASM weakening in the collapse of Neolithic and Early Bronze cultures in this region.

The climate during the last glacial cycle was characterized by abrupt millennial-scale changes superimposed on long-term orbital control. This study examines this climate variability for northeast Iberia for the time interval 118.9 to 36.9 kyr using a multi-proxy approach (δ18O, δ13C and Mg/Ca) applied to a stalagmite that covers this period continuously. During Marine Isotope Stage (MIS) 5 and 4, δ18O is controlled by orbital pacing, whereby more humid conditions prevailed during minima in boreal summer precession. In contrast, during MIS 3 δ18O lags precession and co-varies with δ13C (ρ = 0.53, p-value