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For the first time, this article presents a large dataset of precipitation isotopic measurements (δ18 O p and δ2 H p) sampled every day or 2 d from seven sites on a west-to-east transect across northern Spain for 2010–2017. The main aim of this study is to (1) characterize the rainfall isotopic variability in northern Spain at daily and monthly timescales and (2) assess the principal factors influencing rainfall isotopic variability. The relative role of air temperature and rainfall in determining the stable isotope composition of precipitation changes along the west-to-east transect, with air temperature being highly correlated with δ18 O p at daily and monthly timescales, while a few sites along the transect show a significant negative correlation with precipitation. The highest air temperature– δ18 O p dependency is found for a station located in the Pyrenees. Frontal systems associated with North Atlantic cyclones are the dominant mechanism inducing precipitation in this region, particularly in winter. This study allows an exploration of the role of air mass source and trajectory in determining the isotopic composition of rainfall in northern Iberia by characterizing the moisture uptake for three of the seven stations. The importance of continental versus marine moisture sources is evident, with clear seasonal and spatial variations. In addition, the type of precipitation (convective versus frontal rainfall) plays a key role, with convective rainfall associated with higher δ18 O p values. This comprehensive spatiotemporal approach to analyzing the rainfall isotopic composition represents another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a paleoclimate and hydrological tracer. [ABSTRACT FROM AUTHOR]

The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

The interpretation of stable isotopes in speleothems in terms of past temperature variability or precipitation rates requires a comprehensive understanding of the climatic factors and processes that influence the δO signal in the way through the atmosphere to the cave, where carbonate precipitates acquiring its final isotopic composition. This study presents for the first time in the Iberia Peninsula an integrated analysis of the isotopic composition of rainfall (δO) during 2010-2012 years and, through a detailed monitoring survey, the transference of the primary isotopic signal throughout the soil and epikarst into the Molinos cave (Teruel, NE Spain). Both air temperature and amount of precipitation have an important effect on δO values, clearly imprinting a seasonal variability modulated by an amount effect when rainfall events are more frequent or intense. Air mass history and atmospheric circulation influences are considered through the study of weather types, synoptic-scale climate patterns and large-scale atmospheric circulation indexes (North Atlantic Oscillation and Western Mediterranean Oscillation) revealing a dominant source effect on δO values in this region where tropical North Atlantic and Western Mediterranean are the two moisture source regions. A delay of 2-3 months occurs between the dripwater oxygen isotopic composition (δO) respect to δO values as a consequence of large residence time in the epikarst. Limited calcite precipitates are found from winter to spring when δO values are less negative and dripwater rates are constant. This study suggests that NE Iberian δO proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall and, if extending present-day situation towards the recent past, a biased signal towards winter values should be expected in Molinos speleothem records. [ABSTRACT FROM AUTHOR]

Abstract This study was conducted in Ejulve cave (Spain, southwestern Europe) over a period of four years (2013–2016) to identify the factors affecting the isotopic composition of rainfall, dripwaters, and farmed calcite. The results indicate that δ18O of rainfall in the study area was mainly controlled by the temperature effect (r 2 = 0.82, p -value < 0.001) with source effect and amount effect being secondary controls. Additionally, it exhibited a seasonal pattern with lower values indicated during winter and higher in summer. The use of effective infiltration to evaluate the recharge of the epikarst is extremely important in semi-arid karst climate conditions. This analysis revealed that while the amount effect exerted a moderate control on the annual δ18O in rainfall, it had a lower influence on the isotopic variability of the rainfall potentially infiltrating the karst aquifer. The sampling of 12 drip locations in Ejulve cave indicated that seepage and seasonal drips featured similar δ18O values in dripwaters. The homogenisation process during the infiltration in the epikarst was not complete, therefore, the δ18O seasonality seen in rainfall was also observed in dripwater δ18O, albeit attenuated and lagged. With the seasonal increase in rainfall in autumn, drip rates of seasonal and seepage groups increased within a few weeks. However, the lower δ18O of autumn–winter rain was observed in dripwaters with a lag as long as 21 weeks. The δ18O in farmed calcite showed a small variation of 0.11‰ while the δ13C varied seasonally with a variation of about 0.22‰ and indicated higher values during summer and autumn and lower values in winter and spring. Seasonal and seepage sites exhibited similar δ18O variability. However, δ13C was more positive in seepage sites and was enhanced by degassing kinetics to produce a variability of up to 0.42‰ in contrast to the 0.29‰ observed in the seasonal sites. The δ18O of calcite showed dependence on the δ18O of dripwater with a weak influence of the drip rate. However, δ13C exhibited a higher correlation with the drip rate and high δ13C was explained by enhanced degassing and low water availability while low δ13C values were in concordance with higher microbial activity, vegetation productivity, and greater water availability. The ventilation of the cave during late autumn through spring favoured the higher calcite deposition rates found during that time. [ABSTRACT FROM AUTHOR]