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Reconstructing of past hydroclimates at regional scales during the Common Era (CE) is necessary to place the current warming in the context of natural climate variability. Here we present a composite record of oxygen isotope variations during last 2500 years based on eight stalagmites from four caves in the central Pyrenees (NE Spain) dominated by temperature variations, with the amount of precipitation playing a minor role. The dataset is compared with other Iberian reconstructions that show a high degree of internal coherence with respect to variability at the centennial scale. The Roman Period (RP) (especially 0–200 CE), the Medieval Climate Anomaly (MCA), and part of the Little Ice Age (LIA) represent the warmest periods, while the coldest decades occurred during the Dark Ages (DA) and most of the LIA intervals (e.g., 520–550 CE and 1800–1850 CE). Importantly, the LIA cooling or the MCA warming were not continuous or uniform and exhibited high decadal variability. The Industrial Era (IE) shows an overall warming trend although with marked cycles and partial stabilization during the last 2 decades (1990–2010). The strong coherence between the speleothem data, European temperature reconstructions and global tree-ring data informs about the regional representativeness of this new record as Pyrenean past climate variations. Solar variability, likely through its impact on the North Atlantic Oscillation, and major volcanic eruptions appear to be the two main drivers of climate in southwestern Europe during the past 2.5 millennia. [ABSTRACT FROM AUTHOR]

Understanding how El Niño‐Southern Oscillation (ENSO) responds to natural variability is of key importance for future climate projections under a warming climate. However, there is no clear consensus on what drives ENSO's variability on centennial timescales. Here, we find that the epikarst in southeastern Alaska is effective at filtering ENSO and solar irradiance signals from the Aleutian Low regional climate, which are subsequently recorded in speleothem proxy data. By applying a correlation test, we find that ENSO was significantly influenced by solar irradiance over the past ∼3,500 years. This relationship dissolved after ∼1970 CE, with ENSO now being dominated by anthropogenic forcing. This implies a new ENSO mean state that will need to be incorporated into future climate projections. Plain Language Summary: Although El Niño‐Southern Oscillation (ENSO) is one of the most important climate phenomena globally, it is currently unknown how ENSO responds to natural variability on timescales over 100 years. Natural variability refers to periodic changes in climate due to either solar forcing, the circulation of the atmosphere and ocean, volcanic eruptions, and other factors, irrespective of human intervention. Here, we help solve this problem by studying deposits in caves (speleothems) from Alaska. The speleothems are excellent at capturing atmospheric conditions over the past 3,500 years, and show that solar forcing was significantly controlling ENSO variability. However, the speleothems also show that humans have altered this natural variability, with ENSO entering a new mean state after ∼1970 CE. Key Points: Speleothems from southeastern Alaska capture El Niño‐Southern Oscillation (ENSO) variability through a teleconnection with the Aleutian LowENSO variability was strongly influenced by solar forcing before ∼1970 CEENSO significantly changed properties at ∼1970 CE, likely due to anthropogenic forcing [ABSTRACT FROM AUTHOR]

Rapid and continuous analysis of radiocarbon (14 C) concentration in carbonate samples at spatial resolution down to 100 µm has been made possible with the new LA-AMS (laser ablation accelerator mass spectrometry) technique. This novel approach can provide radiocarbon data at a spatial resolution similar to that of stable carbon (C) isotope measurements by isotope ratio mass spectrometry of micromilled samples and, thus, can help to interpret δ13 C signatures, which otherwise are difficult to understand due to numerous processes contributing to changes in the C-isotope ratio. In this work, we analyzed δ13 C and 14 C on the Holocene stalagmite SPA 127 from the high-alpine Spannagel Cave (Austria). Both proxies respond in a complex manner to climate variability. Combined stable carbon and radiocarbon profiles allow three growth periods characterized by different δ13 C signatures to be identified: (i) the period 8.5 to 8.0 ka is characterized by relatively low δ13 C values with small variability combined with a comparably high radiocarbon reservoir effect (expressed as dead carbon fraction, dcf) of around 60 %. This points towards C contributions of host rock dissolution and/or from an "old" organic matter (OM) reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 8 and 3.8 ka there was a strong variability in δ13 C with values ranging from - 8 ‰ to + 1 ‰ and a generally lower dcf. The δ13 C variability is most likely caused by changes in C exchange between cave air CO 2 and dissolved inorganic carbon in drip water in the cave, which are induced by reduced drip rates as derived from reduced stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir contributed less to stalagmite growth in this period possibly as a result of reduced meteoric precipitation or because it was exhausted. (iii) In the youngest section between 3.8 and 2.4 ka, comparably stable and low δ13 C values, combined with an increasing dcf reaching up to 50 % again, hint towards a contribution of an aged OM reservoir in the karst. This study reveals the potential of combining high-resolution 14 C profiles in speleothems with δ13 C records in order to disentangle climate-related C dynamics in karst systems. [ABSTRACT FROM AUTHOR]

Investigating the precise timing of regional-scale climate changes during glacial terminations and the interglacial periods that follow is key to unraveling the mechanisms behind these global climate shifts. Here, we present a high-precision time series of climate changes in the Austrian Alps that coincide with the later portion of Termination III (TIII), the entire penultimate interglacial (Marine Isotope Stage (MIS) 7), Termination IIIa (TIIIa), and the penultimate glacial inception (MIS 7–6 transition). Using state-of-the-art mass spectrometry techniques, we have constructed a uranium-series chronology with relative age uncertainties averaging 1.7 ‰ (2 σ) for our study period (247 to 191 thousand years before present, ka). Results reveal the onset of warming in the Austrian Alps associated with TIII at 242.5 ± 0.2 ka and the duration of MIS 7e warming between 241.8 and 236.7 (±0.6) ka. An abrupt shift towards higher δ18O values at 216.8 ka marks the onset of regional warming associated with TIIIa. Two periods of high δ18O values (greater than - 10 ‰ Vienna Pee Dee Belemnite (VPDB)) between 215.9–213.3 and 204.3–197.5 (±0.4) ka coincide with interglacial substages MIS 7c and 7a, respectively. Multiple fluorescent inclusions suggest a partial retreat of the local Alpine glacier during peak obliquity forcings at 214.3 ± 0.4 ka. Two newly collected stalagmites from Spannagel Cave (SPA146 and 183) provide high-resolution replications of the latter portion of the MIS 7a-to-6e transition. The resulting multi-stalagmite record reveals important chronological constraints on climate shifts in the Austrian Alps associated with MIS 7 while offering new insight into the timing of millennial-scale changes in the North Atlantic realm leading up to TIII and TIIIa. [ABSTRACT FROM AUTHOR]

The sensitivity of tropical Atlantic precipitation patterns to the mean position of the Intertropical Convergence Zone (ITCZ) at different time scales is well‐known. However, recent research suggests a more complex behavior of the northern hemispheric tropical rain belt related to the ITCZ in the western tropical Atlantic. Here we present a precisely dated speleothem multi‐proxy record from a well‐monitored cave in Puerto Rico, covering the period between 46.2 and 15.3 ka. The stable isotope and trace element records document a pronounced response of regional rainfall to abrupt climatic excursions in the North Atlantic across the Last Glacial such as Heinrich stadials and Dansgaard/Oeschger events. The annual to multidecadal resolution of the proxy time series allows substructural investigations of the recorded events. Spectral analysis suggests that multidecadal to centennial variability persisted in the regional hydroclimate mainly during interstadial conditions but also during the Last Glacial Maximum. In particular, we observe a strong agreement between the speleothem proxy data and the strength of the Atlantic meridional overturning circulation, supporting a persistent link of oceanic forcing to regional precipitation. Comparison to other paleo‐precipitation records enables the reconstruction of past changes in position, strength, and extent of the ITCZ in the western tropical Atlantic in response to millennial‐ and orbital‐scale global climate change. Plain Language Summary: It is important to understand the climatic circumstances of how rainfall in the western tropical Atlantic varies under a changing climate to better manage the water supply for millions of people. However, it is not well understood how rainfall varied in the past, especially during the Last Glacial period, a time of strong climate variability and abrupt climate changes. Here, we use a stalagmite from Puerto Rico to create a new record of past changes in rainfall in this region. For this purpose, we analyzed proxy data that reveal a series of wet and dry periods during the Last Glacial corresponding to rapid global climate shifts. Our rainfall‐sensitive stalagmite record captured changes of the tropical rain belt on various timescales and shows that this variability in rainfall is closely connected to changes in the strength of the ocean circulation. This suggests that the link between the ocean and the atmosphere is more robust than previously assumed. The comparison of our record with other rainfall‐sensitive records from Central America and the northern Caribbean allows for a detailed reconstruction of the spatial and temporal changes of the western tropical Atlantic rain belt. Key Points: Puerto Rican speleothem record documents multidecadal to millennial‐scale precipitation variability between 46.2 and 15.3 kaClimate proxies show a distinct rainfall response to abrupt North Atlantic climate change including Heinrich and Dansgaard/Oeschger eventsCompilation of regional precipitation records allows to reconstruct past changes in ITCZ patterns in the western tropical Atlantic [ABSTRACT FROM AUTHOR]

The climate of the western Mediterranean was characterized by a strong precipitation gradient during the Holocene driven by atmospheric circulation patterns. The scarcity of terrestrial paleoclimate archives has precluded exploring this hydroclimate pattern during Marine Isotope Stages 5 to 3. Here we present stable carbon and oxygen isotope records from three flowstones from southeast Iberia, which show that Dansgaard/Oeschger events were associated with more humid conditions. This is in agreement with other records from the Iberian Peninsula, the Mediterranean, and western Europe, which all responded in a similar way to millennial‐scale climate variability in Greenland. This general increase in precipitation during Dansgaard/Oeschger events cannot be explained by any present‐day or Holocene winter atmospheric circulation pattern. Instead, we suggest that changes in sea surface temperature played a dominant role in determining precipitation amounts in the western Mediterranean. Plain Language Summary: Climate events characterized by a sudden temperature increase of up to 10 °C occurring in less than a few decades during the last glacial are recorded in Greenland ice cores. These abrupt warmings, the Dansgaard/Oeschger events, affected large regions of the Northern Hemisphere. The understanding of the regional response in precipitation during these climate shifts is limited for the western Mediterranean, due to the restricted number of terrestrial climate records that cover the last glacial period at sufficient resolution. Speleothems and their stable isotope compositions allow to trace changes in climate and vegetation based on an accurate chronological framework. Here we present a speleothem stable isotope record that shows that the Dansgaard/Oeschger events were associated with increased rainfall and a denser vegetation in the western Mediterranean. A similar pattern was observed for western Europe and other parts of the Mediterranean, and we propose that this was related to generally higher sea surface temperatures of the surrounding oceans rather than a reorganization of atmospheric circulation. Key Points: Western Mediterranean precipitation responded to Greenland interstadials and stadials in a coherent mannerDansgaard/Oeschger interstadials were accompanied by humid climate conditions over the western MediterraneanAtmospheric circulation patterns did not induce spatial differences in precipitation during the last glacial as they did during the Holocene [ABSTRACT FROM AUTHOR]

Gyrfalcon (Falco rusticolus) is the largest falcon in the world. It inhabits a wide range of climate zones in the Northern Hemisphere, from boreal forests in the south of its range to the arid polar deserts of the High Arctic. In Greenland, because of the harsh, remote environments in which gyrfalcons live, research related to the contemporary and pre-modern periods has been limited to the north-west, central west and central east coasts, with no specific investigations being conducted for the north-east. Here, we report the first pre-modern record of a gyrfalcon in north-east Greenland, located at 80.4°N in Kronprins Christian Land. Skin tissue from a decaying gyrfalcon’s body was radiocarbon dated to 769–944 CE (common era) using a terrestrial-only calibration curve, and 1182–1456 CE using a marine-only calibration curve. Since the gyrfalcon has a mixed terrestrial/marine diet, the actual age can be said to belong between these two groups. This limited data, therefore places the presence of the gyrfalcon in north-east Greenland during a period of prolonged elevated temperatures and climate stress associated with the Medieval Climate Anomaly. Whether the gyrfalcon was part of a larger population or a straggler, and whether the species survived the whole of the Medieval Climate Anomaly in north-east Greenland, is unknown. [ABSTRACT FROM AUTHOR]

The "4.2 ka event" is frequently described as a major global climate anomaly between 4.2 and 3.9 ka, which defines the beginning of the current Meghalayan age in the Holocene epoch. The "event" has been disproportionately reported from proxy records from the Northern Hemisphere, but its climatic manifestation remains much less clear in the Southern Hemisphere. Here, we present highly resolved and chronologically well-constrained speleothem oxygen and carbon isotopes records between ∼6 and 3 ka from Rodrigues Island in the southwestern subtropical Indian Ocean, located ∼600 km east of Mauritius. Our records show that the 4.2 ka event did not manifest itself as a period of major climate change at Rodrigues Island in the context of our record's length. Instead, we find evidence for a multi-centennial drought that occurred near-continuously between 3.9 and 3.5 ka and temporally coincided with climate change throughout the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

Aragonite is a common mineral in caves hosted in dolomitic bedrock, and in particular in those from warm climate regions. It is much less common in cold caves, such as in the Alps, where the vast majority of speleothems consist of low-Mg calcite. Here we report the occurrence of modern aragonite at very low temperatures, the first of its kind from an alpine cave. In the interior part of Obstanser Eishöhle, a high-alpine cave containing perennial ice in its near-entrance zone, aragonite forms stalactites and flowstones, which coexist with calcite and locally also hydromagnesite. Precipitation of aragonite occurs at saturation indices between 0.4 and 0.6 at 1.0 ± 0.4 °C. Modern 230 Th dates of the youngest aragonite deposits demonstrate that aragonite formation is an ongoing process. δ 13 C values are high and overlap with those of the host rock. A comparison between δ 18 O values of aragonite and drip water showed that modern aragonite formation does not occur at isotopic equilibrium. Surprisingly, no radiocarbon “bomb peak” was detected in these speleothems, despite their young age. In addition, these samples are characterized by extremely high reservoir ages between 8800 and 10,100 yr, the highest ever reported for a speleothem worldwide. These data are best reconciled with a model of karst dissolution largely decoupled from the soil zone. Oxidation of disseminated pyrite in the dark gray host rock gives rise to acidic solutions driving carbonate dissolution. The dolomitic nature of the bedrock, prior calcite precipitation and ventilation-enhanced degassing leads to high Mg/Ca ratios in the drip water favoring aragonite formation. These in-situ observations confirm previous findings that temperature is not the dominant control on calcite versus aragonite formation in caves. They also suggest that ancient aragonite speleothems should be examined carefully and ideally be compared to coeval calcite samples prior to interpreting their stable isotope data in terms of environmental/climatic changes. [ABSTRACT FROM AUTHOR]

Understanding the sequence of events that take place during glacial-interglacial climate transitions is important for improving our knowledge of abrupt climate change. Here, we present a new stacked, high-resolution, precisely-dated speleothem stable isotope record from the northern Alps, which provides an important record of temperature and moisture-source changes between 134 and 111 ka for Europe and the wider North Atlantic realm. The record encompasses the penultimate deglaciation (Termination II (TII)), which lies beyond the limit of radiocarbon dating, thus providing an important new archive for a crucial period of rapid paleoclimate change. Warmer and wetter ice-free conditions were achieved by 134.1 ± 0.7 ka (modelled ages) as indicated by the presence of liquid water at the site. Temperatures warmed further at 133.7 ± 0.5 ka and led into an interstadial, synchronous with slightly elevated monsoon strength during the week monsoon interval. The interstadial experienced an unstable climate with a trough in temperature associated with a slowdown in Atlantic Meridional Overturning Circulation (AMOC) and a reduction in North Atlantic Deep Water (NADW) formation. The interstadial ended with a more extreme cold reversal lasting 500 years in which NADW formation remained active but the subpolar gyre weakened allowing cool polar waters to penetrate southwards. The main warming associated with TII was very rapid, taking place between 130.9 ± 0.9 and 130.7 ± 0.9 ka coeval with initial monsoon strengthening. Temperatures then plateaued before being interrupted by a 600-year cold event at 129.1 ± 0.6 ka, associated once again with penetration of polar waters southwards into the North Atlantic and a slowdown in monsoon strengthening. Sub-orbital climate oscillations were thus a feature of TII in the north Atlantic realm, which broadly resemble the Bølling/Allerød-Younger Dryas-8.2 ka event pattern of change observed in Termination I despite monsoon records indicating strong differences between the last and penultimate deglaciation. [ABSTRACT FROM AUTHOR]

This short article provides detailed descriptions of custom-made and commercially available hand-held drilling gear and options for water-flushing units specifically designed to obtained good-quality core material from speleothems even in remote cave regions. We use small-diameter (6-7 mm) diamond drill-core bits to obtain aliquots of calcite (as little as a few hundred milligrams) from the interior of the basal part of in-situ stalagmites. These small cores are used to date the onset of stalagmite growth and occasionally to obtain other compositional information. Larger diameter drill-core bits produce cores 25-32 mm in diameter and up to 1.3 m in length which reveal internal structures and provide axial transects for chemical and isotope analysis and material for preparation of thin sections. This system has been successfully employed to sample flowstone and thick stalagmites. Given the growing interest in speleothem as archives of past environmental change, careful sample selection is primordial to keep the impact of sampling in these unique environments at a minimum. Low-invasive drilling is an essential technique and maximizes the amount of information gained. [ABSTRACT FROM AUTHOR]

Abstract: Cave and lake isotope records from the circum-Mediterranean realm show anomalously low O isotope values suggesting high rainfall intensity during the time of sapropel 1 deposition (9.5 to 6.5ka; all ages are given before the yearAD 2000, i.e. b2k), coincident with an interval of conspicuously low sea-surface salinities in the entire Mediterranean Sea. Speleothem data from Corchia Cave (Tuscany) currently provide the most precise terrestrial chronology and constrain the wettest interval to ca. 8.2 to 7.3ka. We have traced this isotopic signal to the north and observe a synchronous isotopic change in stalagmites from southalpine and eastalpine caves, but in opposite direction. We attribute this to a shift in the local moisture balance, i.e. to a higher proportion of moisture advected from the Mediterranean Sea relative to the otherwise dominant northwesterly air masses in the Alps. This isotopic source effect can be traced up to the northern rim of the Alps, albeit with decreasing amplitude. Forest density at the treeline in the Central Alps decreased during this time interval indicating short vegetation periods consistent with rainy summers. The glaciers in the Eastern Alps, which did not show far-reaching advances during the preceding 8.2ka event, responded strongly (positively) to this humid phase. Additionally, two of the largest alluvial fans in the Eastern Alps showed a massive accumulation peak radiocarbon dated to between ca. 8.3 to 7.4ka and thus providing one of the strongest pieces of evidence for anomalously high rainfall intensities coeval with ''pluvial’ conditions in the Mediterranean region. [Copyright &y& Elsevier]

Sundqvist, H. S., Holmgren, K., Moberg, A., Spötl, C. & Mangini, A. 2009: Stable isotopes in a stalagmite from NW Sweden document environmental changes over the past 4000 years. Boreas, 10.1111/j.1502-3885.2009.00099.x. ISSN 0300-9483. This study of a 4000-year-old stalagmite from Korallgrottan in northwestern Sweden highlights the potentials and challenges when using stable isotopes in stalagmites as climate proxies, as well as the fact that the relationship between climate and proxy may change through time. Both the oxygen and the carbon isotopes display an overall trend of enrichment together with decreasing growth rates over the time period covered by the stalagmite, which is considered a generally cooling period according to current palaeoclimate understanding. The stable isotope records show enriched isotopic values during the, for Scandinavia, comparatively cold period AD 1300–1700 and depleted values during the warmer period AD 800–1000. The indication of a negative relationship between measured δ18O and surface temperature concurs with earlier reported stalagmite records from regions with a seasonal snow cover and is further supported by the fact that the stalagmite δ18O record shows general similarities with both regional and hemispheric temperature reconstructions available for the past 500 and 2000 years, respectively. Compared with a stable isotope record of lacustrine carbonates from northern Sweden, however, shifting correlations over time between the two records indicate that a local hydrological change may have taken place at Korallgrottan, or at the lake, compared with around 1000 years ago. The earlier part of the stalagmite δ18O might thus be influenced, to some extent, by another process than the later part, which means that a negative relationship between δ18O and surface temperature might not hold for the entire 4000-year-old record. [ABSTRACT FROM AUTHOR]

Abstract: Two coeval stalagmites from Katerloch Cave show pronounced intervals of low δ 18O values around 8.2, 9.1, and 10.0kyr (all ages are reported before the year 2000 AD) and represent an inorganic U–Th dated climate archive from the southeast of the European Alps, a region where only very few well-dated climate records exist. The O isotope curves, providing near-annual resolution, allow a direct comparison to the Greenland ice core records, as temperature was the primary factor controlling the O isotopic composition of Katerloch speleothems. The 8.2kyr climate anomaly lasted about one century, from 8196 to 8100yr, with a maximum amplitude of 1.1‰ at 8175yr. The event is characterized by a rapid onset and a more gradual demise and U–Th data as well as annual lamina counting support a rapid climate change towards cooler conditions within 10–20yr. There is no strong evidence that the 8.2kyr anomaly was superimposed on a pronounced longer-term cooling episode, nor do the new data support two separate cooling events within the 8.2kyr event as reported by other studies. Our record also shows a distinct climate anomaly around 9.1kyr, which lasted 70–110yr and showed a maximum amplitude of 1.0‰, i.e. it had a similar duration and amplitude as the (central) 8.2kyr event. Compared to the 8.2kyr event, the 9.1kyr anomaly shows a more symmetrical structure, but onset and demise still occurred within a few decades only. The different progression of the 8.2 (asymmetrical) and 9.1kyr anomaly (symmetrical) suggests a fundamental difference in the trigger and/or the response of the climate system. Moreover, both stalagmites show evidence of a climate anomaly around 10.0kyr, which was of comparable magnitude to the two subsequent events. Using a well constrained modern calibration between air temperature and δ 18O of precipitation for the study area and cave monitoring data (confirming speleothem deposition in Katerloch reflecting cave air temperature), a maximum cooling by ca 3°C can be inferred at 8.2 and 9.1kyr, which is similar to other estimates, e.g., from Lake Ammersee north of the Alps. The O isotopic composition of meteoric precipitation, however, is a complex tracer of the hydrological cycle and these temperature estimates do not take into account additional effects such as changes in the source area or synoptic shifts. Apart from that, the relative thickness of the seasonally controlled lamina types in the Katerloch stalagmites remains rather constant across the intervals comprising the isotopic anomalies, i.e. the stalagmite petrography argues against major shifts in seasonality during the early Holocene climate excursions. [Copyright &y& Elsevier]

A detailed study of growth periods of a flowstone from Spannagel Cave in the Zillertal Alias (Austria) at ∼2500 m above sea level, a site highly sensitive to climate changes, offers unprecedented new insights into Pleistocene climate change in Central Europe. Flowstone sample SPA 52 has a high U content (to 116 ppm); analyses of this sample reveal that episodes of calcite deposition started at 204 ± 3 ka, 135 ± 1.2 ka, and 122 ka, suggesting that at these times, the mean air temperature at this high Alpine site was within 1.5 °C of the present-day condition. The beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 ± 23 ka, as deduced from the absolutely dated oxygen isotope curve in sediments from the Bahamas, us well as with recent coral evidence from Barbados indicating a high sea level already by 135.8 ± 0.8 ka. This set of data supports evidence against Northern Hemisphere forcing of termination II, because the insolation maximum is at 127 ka. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

The last two decades have seen a considerable increase in studies using speleothems as archives of past climate variability. Caves under study are now monitored for a wide range of environmental parameters and results placed in context with speleothem data. The present study investigates trends from a seven year long monitoring of Bunker Cave, northwestern Germany, in order to assess the hydraulic response and transfer time of meteoric water from the surface to the cave. Rain-, soil-, and dripwater were collected from August 2006 to August 2013 at a monthly to bimonthly resolution and their oxygen and hydrogen isotope composition was measured. Furthermore, drip rates were quantified. Due to different drip characteristics, annual mean values were calculated for the drip rates of each drip site. Correlations of the annual mean drip rate of each site with precipitation and infiltration demonstrate that the annual infiltration, and thus the annual precipitation control the inter-annual drip-rate variability for all except one site. The hydraulic response is not delayed on an annual basis. All drip sites display identical long-term trends, which suggests a draining of a common karst reservoir over these seven years of monitoring. Correlations of soil- and dripwater monthly δ 18 O and δD values with atmospheric temperature data reveal water transfer times of 3 months to reach a depth of 40 cm (soilwater at site BW 2) and 4 months for 70 cm depth (soilwater at site BW 1). Finally, the water reaches the cave chambers (15 to 30 m below land surface) after ca. 2.5 years. Consequently, a temporal offset of 29 to 31 months (ca. 2.5 years) between the hydraulic response time (no time lag on annual basis) and the water transfer time (time lag of 29 to 31 months) was found, which is negligible with regard to Bunker Cave speleothems because of their slow growth rates. Here, proxies recording precipitation/infiltration and temperature are registered on a decadal scale. Variations in drip rate and thus precipitation and infiltration are recorded by δ 13 C and Mg/Ca ratios in speleothem calcite. Speleothem δ 18 O values reflect both temperature and precipitation signals due to drip rate-related fractionation processes. We document that long-term patterns in temperature and precipitation are recorded in dripwater patterns of Bunker Cave and that these are linked to the North Atlantic Oscillation (NAO). [ABSTRACT FROM AUTHOR]

The European Alps and their forelands provide a range of different archives and climate proxies for developing climate records in the time interval 60–8 thousand years (ka) ago. We review quantitative and semi-quantitative approaches for reconstructing climatic variables in the Austrian and Swiss sector of the Alpine region within this time interval. Available quantitative to semi-quantitative climate records in this region are mainly based on fossil assemblages of biota such as chironomids, cladocerans, coleopterans, diatoms and pollen preserved in lake sediments and peat, the analysis of oxygen isotopes in speleothems and lake sediment records, the reconstruction of past variations in treeline altitude, the reconstruction of past equilibrium line altitude and extent of glaciers based on geomorphological evidence, and the interpretation of past soil formation processes, dust deposition and permafrost as apparent in loess-palaeosol sequences. Palaeoclimate reconstructions in the Alpine region are affected by dating uncertainties increasing with age, the fragmentary nature of most of the available records, which typically only incorporate a fraction of the time interval of interest, and the limited replication of records within and between regions. Furthermore, there have been few attempts to cross-validate different approaches across this time interval to confirm reconstructed patterns of climatic change by several independent lines of evidence. Based on our review we identify a number of developments that would provide major advances for palaeoclimate reconstruction for the period 60–8 ka in the Alps and their forelands. These include (1) the compilation of individual, fragmentary records to longer and continuous reconstructions, (2) replication of climate records and the development of regional reconstructions for different parts of the Alps, (3) the cross-validation of different proxy-types and approaches, and (4) the reconstruction of past variations in climate gradients across the Alps and their forelands. Furthermore, the development of downscaled climate model runs for the Alpine region 60–8 ka, and of forward modelling approaches for climate proxies would expand the opportunities for quantitative assessments of climatic conditions in Europe within this time-interval. [ABSTRACT FROM AUTHOR]

Abstract: Pizzo Mondello section (western Sicily, Italy) yields a very rich conodont record, ranging from Late Carnian to Rhaetian in age, shedding new light into the evolution of conodonts across the Carnian/Norian boundary. Conodont biostratigraphy around the Carnian/Norian boundary is still problematic due to an inferred provincialism that affects most of the conodont species and to the occurrence of a great number of transitional forms, linked to the fast recovery of conodonts after the Middle Carnian crisis. The lower 144 m of the succession, Tuvalian to Lacian in age, were sampled in detail for a biostratigraphic and ecological study of five Upper Triassic conodont genera: Paragondolella, Carnepigondolella, Metapolygnathus, Epigondolella, and Norigondolella. After a taxonomic revision of the genera studied, meant to define the most significant morphological features for their classification, a statistical approach was applied to the study of conodont populations. Quantitative curves of the absolute abundances for each genus show potential ecological competition between Paragondolella–Carnepigondolella and later between Metapolygnathus–Epigondolella (and partially between Epigondolella–Norigondolella). Recognition of morphoclines among species, integrated by a similar ecological behaviour, supports the phylogenetic derivation of Norigondolella and Metapolygnathus from Paragondolella and that of Epigondolella from Carnepigondolella. Furthermore, cross checks of the quantitative curves evidenced the presence of three major assemblage changes: at metre 64.76 (named event T1) Carnepigondolella is replaced by its descendant Epigondolella in an evolutionary step; at metre 80 (event T2) Epigondolella is substituted by the mass occurrence of Metapolygnathus and at metre 95 (event T3) Metapolygnathus is succeeded by advanced Epigondolellae species and by Norigondolella. In looking for environmental explanations to these biological events, the conodont assemblages are compared to coeval δ 18O and δ 13C isotopic curves, based on new data from Pizzo Mondello. From the comparison, a correspondence appears between higher 13C/12C ratios and the interval between events T2–T3, but not with event T1. This is in accordance with the interpretation of event T1 as an evolutionary turnover. In more detail, we observe the possible influence of environmental conditions on the absolute abundances of all the studied genera: while Epigondolella proliferate when seawater δ 13C ranges between 2.1‰ and 2.5‰, Carnepigondolella proliferate in the range between 1.6‰ and 2.1‰; Metapolygnathus instead appears to be limited to environmental conditions related to higher δ 13C values in the seawater. We explain this behaviour by interpreting the genus Metapolygnathus as an opportunist taxon, exactly as its forerunner, the genus Paragondolella. [Copyright &y& Elsevier]

Abstract: The palaeoclimatic significance of calcareous tufa deposits found in the presently hyperarid Tadrart Acacus massif (central Sahara, SW Libya) is discussed on the basis of U/Th datings, stable isotope analyses, and the regional hydrogeological context. These deposits formed mostly between c. 9600 and 8100yr BP. The isotopic signature (δ 18O and δ 13C) of this tufa indicates that the water forming these carbonates originated as isotopically depleted rainwater as a result of the northward expansion of the SW African Monsoon system during the early Holocene. Carbonate sedimentation in the Tadrart Acacus decreased shortly before c. 8000yr BP, attributed to a drop in precipitation in the course of the well known 8.2kyr event. A correlation between tufa development and climate change in N and E Africa and in the Mediterranean basin during the early Holocene is discussed. The effect of early Holocene climate change on both the landscape and the dwellers living in the Tadrart Acacus region is also evaluated. [Copyright &y& Elsevier]

The article presents a study that explores the collapse of the Liangzhu and other Neolithic cultures in the lower Yangtze region in response to climate change. It mentions about the hydroclimatic changes that have resulted from an increasing frequency of the El Niño–Southern Oscillation in the context of weakened Northern Hemisphere summer insolation.

The most pronounced climate anomaly of the Holocene was the 8.2 ka cooling event. We present new 230Th/U-ages as well as high-resolution stable isotope and trace element data from three stalagmites from two different cave systems in Germany, which provide important information about the structure and climate variability of the 8.2 ka event in central Europe. In all three speleothems, the 8.2 ka event is clearly recorded as a pronounced negative excursion of the δ18O values and can be divided into a 'whole event' and a 'central event'. All stalagmites show a similar structure of the event with a short negative excursion prior to the 'central event', which marks the beginning of the 'whole event'. The timing and duration of the 8.2 ka event are different for the individual records, which may, however, be related to dating uncertainties. Whereas stalagmite Bu4 from Bunker Cave also shows a negative anomaly in the δ13C values and Mg content during the event, the two speleothems from the Herbstlabyrinth cave system do not show distinct peaks in the other proxies. This may suggest that the speleothem δ18O values recorded in the three stalagmites do not primarily reflect climate change at the cave site, but rather large-scale changes in the North Atlantic. This is supported by comparison with climate modelling data, which suggest that the negative peak in the speleothem δ18O values is mainly due to lower δ18O values of precipitation above the cave and that temperature only played a minor role. Alternatively, the other proxies may not be as sensitive as δ18O values to record this centennial-scale cooling event. This may particularly be the case for speleothem δ13C values as suggested by comparison with a climate modelling study simulating vegetation changes in Europe during the 8.2 ka event. Based on our records, it is not possible to resolve which of these hypotheses is most appropriate, but our multi-proxy dataset shows that regional climate evolution during the event was probably complex, although all δ18O records show a clear negative anomaly. • Three speleothems show pronounced negative peaks in δ18O values during 8.2 ka event. • All records can be divided into a 'whole event' and a 'central event'. • Other proxies show no distinct consistent peaks during the 8.2 ka event. • Magnitude of δ18O peaks can be explained by change in δ18O values of precipitation. • Speleothem δ18O values reflect large-scale changes in the North Atlantic. [ABSTRACT FROM AUTHOR]

The last glacial period was punctuated by episodes of warm and humid climate. These rapid climate instabilities, called Dansgaard/Oeschger (D/O) events, lasted between a few hundred and a few thousand years. The triggering mechanism of these events is still not comprehensively decoded and various hypotheses are debated including oscillations of the Atlantic Meridional Overturning Circulation driven by changes in the freshwater budget, changes in the elevation of the Laurentide ice-sheet and its effect on wind stress and sea-ice cover, as well as ocean–sea ice interactions internal to the Nordic Seas. Morever, two time periods during the last glacial show a distinctive reduction or even an absence of D/Os (~70 to 60 ka and ~26 to 16 ka). Those periods concur with minimum sea-level and are important constraints to test hypotheses for the D/O triggering mechanism as not all of them can explain this absence of D/O cyclicity. Knowledge about D/O cyclicity could be improved by extending the investigations to the penultimate glacial. However, existing records cover only parts of the interval between ~200 and 130 ka or are located far from the D/O event core location and may have missed some events. Especially marine records, which would be ideally located in the North Atlantic to detect D/O events, are often limited with respect to their age control during this period. Here, we present a new, replicated and precisely dated speleothem record from the northern rim of the European Alps covering the penultimate glacial. This area has previously proven to be highly sensitive to rapid millennial-scale climate variations. Between ~202 and ~133 ka before present our new Alpine speleothem record reveals a similar number of D/O events as compared to the last glacial period. D/O events were notably absent during three ~8 ka-long intervals, which coincided with sea-level low-stands during the penultimate glacial. Hence, our results strongly support findings from the last glacial that D/O-events were precluded during intervals when the Northern Hemisphere ice sheets reached their maximum extent. [ABSTRACT FROM AUTHOR]

• Periods of wet paleoclimate were recorded in cave sediments. • Five phases of latosolization were recorded in the last 100 kyr. • Intense weathering and gibbsite were synchronous with carbonate crusts. • Global scale events (e.g., Heinrich) triggered latosolization periods. The present-day semiarid region of NE Brazil experienced multiple periods of increased precipitation during the Quaternary. They were likely linked to global-scale events (e.g., Heinrich Events) and drove changes in vegetation dynamics, leading to the expansion of rainforest vegetation. Here, we hypothesize that soil features preserved in cave sediments records paleoenvironmental changes induced by global-scale events that affected NE Brazil during the Late Pleistocene - Early Holocene. To test this hypothesis, we analyzed the elemental and isotopic geochemistry composition, bulk sediment mineralogy, soil micromorphological features, and fauna fossil type and content of a well-preserved 6 m cave sediment profile spanning 103 kyr – 8 kyr in Toca de Cima do Pilão at the Serra da Capivara National Park. Our approach provides new information on the history of soil formation, vegetation, and climate of NE Brazil during the Late Pleistocene - Early Holocene. The results demonstrated that severe weathering and dense vegetation was the dominant paleoenvironmental conditions during wet periods, when latosolization was the main soil forming process. The evidence for wet and intense weathering periods was the co-existence of speleothems layers with Ferralsol features, such as runiquartz, granular microstructure, Fe nodules and gibbsite formation. Some of these features were found in layers deposited in synchrony with Heinrich Stadial and Younger Dryas periods, suggesting that past soil processes in NE Brazil were affected by those global-scale events. We propose five phases of latosolization in our study area during the last 100 kyr. The first was identified around 80 kyr, the second occurred around 29 kyr. The third coincided with Heinrich Stadial 1 (16 kyr) and the fourth likely occur during the Younger Dryas, and the fifth phase occurred during the middle Holocene. [ABSTRACT FROM AUTHOR]

Rocky desertification is a major environmental problem in the karst regions of Southwest China and seriously impacts ecological and socioeconomic development. Human activities and climate change have been proposed as the main factors responsible for the development and expansion of rocky desertification, but more evidence is needed to support this hypothesis. In this study, the history of the Asian summer monsoon (ASM) since 6200 yr BP is reconstructed based on 230Th dating and δ18O and δ13C data of a stalagmite from Feilong Cave in Guizhou Province of Southwest China. Positive δ18O and δ13C excursions record eleven interdecadal–centennial weak summer monsoon events at 1000–870, 1660–1460, 2040–1900, 2780–2460, 3020–2860, 3250–3120, 3650–3370, 4273–3980, 4820–4480, 5370–5180, and 5840–5560 yr BP. These weak ASM events were controlled by a southward shift of the Intertropical Convergence Zone and frequent El Niño events. Changes in the δ13C values of this stalagmite were mainly driven by changes in vegetation coverage and type, soil microbial activity, and regional hydrogeological conditions. The simultaneous positive excursions of δ18O and δ13C at ∼5500, 4200, and 2800 yr BP indicate a degradation of the karst ecological environment in response to the weak summer monsoon. In addition, frequent dynasty changes in China since 3000 yr BP profoundly influenced the karst ecological environment. During the Medieval Warm Period, the Jing-Kang event (JK event) resulted in the fall of the Northern Song Dynasty and led to a large-scale migration into southern China. As a consequence, the population increase in the Yangtze River basin enhanced land use, accelerated the disappearance of forests, and finally resulted in the deterioration of the regional environment. We conclude that climate change and anthropogenic activity may have jointly triggered and/or exacerbated rocky desertification in Southwest China. • The Asian summer monsoon (ASM) since 6200 yr BP weakened with decreasing solar insolation. • Frequent dynasty changes in China since profoundly influenced the karst environment. • Climate change and anthropogenic activity jointly triggered and/or exacerbated rocky desertification in Southwest China. [ABSTRACT FROM AUTHOR]

This paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods (radiocarbon, 230 Th disequilibrium, luminescence, cosmogenic nuclides) and two incremental methods based on layer counting (ice layer, varves). For each method, concise background information about the fundamental principles and methodological approaches is provided. We concentrate on the time interval of focus for the INTIMATE (Integrating Ice core, MArine and TErrestrial records) community (60–8 ka). This dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and, therefore, have to rely on correlation with proxy records obtained from different archives from various regions. For this reason, we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration. In this respect, up-to-date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology, cosmogenic 10 Be and palaeomagnetic variations. Finally, to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series, this paper provides recommendations for minimum standards of uncertainty and age datum reporting. [ABSTRACT FROM AUTHOR]

Abstract: Carbonate deposits in aqueducts are a new high-resolution data source for environmental changes during the time of the Roman Empire, notably in the fields of palaeoclimate and spring hydrology. In order to distinguish environmental effects from those related to depositional setting, laminated carbonate deposits were compared along the entire length of an ancient aqueduct channel at Patara, Turkey. The carbonate deposits, up to 80mm in thickness, are composed of lamina couplets up to 1mm thick of alternating porous microspar and dense, columnar sparite. The former formed in the dry, warm season and the latter in the wet, cool season. The presence of biofilms seems to play a role in the development of the porous laminae. The relative importance of both lamina types depends also on the location within the aqueduct: dense, coarse-crystalline laminae dominate in steep sections of the aqueduct, while porous, fine-crystalline laminae are mostly found on gentle slopes. This is attributed to the flow velocity of the water, since fast flow on steep slopes hampers the development of biofilms. Carbonate microstructures can vary considerably down the line of a specific aqueduct; hence multiple sampling is needed along the channel in order to collect specimens suitable for detailed research. δ18O profiles show oscillations with increasing amplitude downstream reflecting rising water temperatures in the channel, while evaporation plays a minor, damping role on these oscillations. The periodicity of the δ18O values can be used to recognise annual layering in order to establish the number of years an aqueduct was operating. δ13C values are higher in open masonry channel sections than in ceramic pipes, probably due to stronger degassing of CO2 in the open channel. Carbonate deposits in Roman aqueducts hold high promises as seasonally resolved archives of hydrology and climate and, possibly, of earthquakes. [Copyright &y& Elsevier]

Abstract: Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ∼120–110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ∼70–60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ∼55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today''s alpine timberline. The Unterangerberg record ended at ∼45 ka and/or was truncated by ice during the Last Glacial Maximum. [Copyright &y& Elsevier]

Abstract: We present a speleothem stable oxygen isotope record for the last 12.5ka based on two stalagmites from western Cuba. The δ 18O signal is interpreted to represent past precipitation variability. Both stalagmites show a pronounced transition from higher δ 18O values (indicating drier conditions) to more negative δ 18O values (suggesting wetter conditions) between 10 and 6ka. This transition is also visible in a planktonic δ 18O record off Haiti. On orbital timescales, the δ 18O value of Caribbean precipitation, thus, strongly resembles the oxygen isotope composition of Caribbean surface water. On millenial timescales, the speleothem δ 18O record shows a high correlation to a North Atlantic sea surface temperature (SST) record off West Africa as well as a similarity with the Bond events. Periods of lower North Atlantic SST correspond to less precipitation in the Caribbean and vice versa. The potential teleconnection to the Caribbean may reflect the position of the Intertropical Convergence Zone because a further southward position of the ITCZ leads to reduced precipitation in the northern Caribbean. [Copyright &y& Elsevier]

Abstract: High-resolution (annual to decadal) stable isotope records of oxygen and carbon are analysed from an annually laminated stalagmite from NW Scotland. The sample, which was deposited for ~1000yrs until 1996AD, has previously provided annual resolution climate reconstructions of local rainfall and regional winter North Atlantic Oscillation (wNAO) from variations in annual growth rate. For our stalagmite, for which modern cave monitoring demonstrates that equilibrium deposition is highly likely for δ18O but not for δ13C, stalagmite δ13C originally derives from soil CO2 produced predominantly by microbial respiration, modified by degassing-related kinetic fractionation, and δ18O from the composition of infiltrating water during periods of infiltrating water. Both the presence of fluorescent laminae and modern drip-water monitoring demonstrate a drip hydrology that comprises both event and storage components. Over the instrumental period, no correlations between stalagmite or rainfall δ18O and precipitation amount or temperature are observed, but correlations are observed between rainfall δ18O and 500mb height at regional IAEA monitoring stations. However, no correlations are observed between stalagmite δ18O and instrumental and reconstructed atmospheric circulation, preventing a simple palaeoclimate interpretation of the stalagmite δ18O proxy. Stalagmite δ13C has a stronger temporal autocorrelation than δ18O, indicative of soil mixing of respired CO2 and significant variability between drips and at different times; correlations with instrumental climate data are therefore not possible. The relative timing of changes in growth rate, δ18O and δ13C are discussed, and interpretations compared with other regional climate records. We conclude that, over the last millennium at this mid-latitude cave site, neither δ18O nor δ13C cannot be interpreted as a simple paleoclimate proxy. [Copyright &y& Elsevier]

Summary: Monitoring cave environments is important to understand processes in karst systems. If stalagmites from a specific cave are used as archives of past climate variability, a quantitative understanding of the soil–karst–speleothem system is crucial. The monitoring program performed in Bunker Cave (NW Germany), which includes monthly collection of climatological data as well as air and water samples from the cave and the overlying soil since 2006, is a prerequisite for the interpretation of speleothem data from the cave in terms of climate variability. The results show that Bunker Cave is a homogeneously ventilated cave with rather low pCO2 values of 580–1200ppmv, which lacks strong seasonal variations. The δ 18O value of cave drip water reflects the mean annual composition of the rain water, and the seasonal variability is strongly attenuated indicating a well-mixed karst aquifer. Hence, stalagmites from Bunker Cave should be well suited to record interannual/decadal climate trends. Seven drip sites in two cave chambers show three different types of discharge behaviour including slow seasonal drip, fast seasonal drip, and seepage-flow. The drip-rate patterns of most drip sites are consistent with the main infiltration events, taking into account a delay of several months. An instantaneous response to precipitation (i.e., piston-flow) is not observed for any drip site indicating a specific water capacity threshold in the soil/karst aquifer. Prior Calcite Precipitation (PCP) was also identified especially during times of low discharge. Though PCP is not as pronounced at Bunker Cave as in other caves, it probably has an influence on the Mg/Ca ratios of the stalagmites. [Copyright &y& Elsevier]

Abstract: Diverse interpretations have been made of carbon isotope time series in speleothems, reflecting multiple potential controls. Here we study the dynamics of 13C and 12C cycling in a particularly well-constrained site to improve our understanding of processes affecting speleothem δ13C values. The small, tubular Grotta di Ernesto cave (NE Italy) hosts annually-laminated speleothem archives of climatic and environmental changes. Temperature, air pressure, pCO2, dissolved inorganic carbon (DIC) and their C isotopic compositions were monitored for up to five years in soil water and gas, cave dripwater and cave air. Mass-balance models were constructed for CO2 concentrations and tested against the carbon isotope data. Air advection forces winter pCO2 to drop in the cave air to ca. 500ppm from a summer peak of ca. 1500ppm, with a rate of air exchange between cave and free atmosphere of approximately 0.4days. The process of cave ventilation forces degassing of CO2 from the dripwater, prior to any calcite precipitation onto the stalagmites. This phase of degassing causes kinetic isotope fractionation, i.e. 13C-enrichment of dripwater whose δ13CDIC values are already higher (by about 1‰) than those of soil water due to dissolution of the carbonate rock. A subsequent systematic shift to even higher δ13C values, from −11.5‰ in the cave drips to about −8‰ calculated for the solution film on top of stalagmites, is related to degassing on the stalagmite top and equilibration with the cave air. Mass-balance modelling of C fluxes reveals that a very small percentage of isotopically depleted cave air CO2 evolves from the first phase of dripwater degassing, and shifts the winter cave air composition toward slightly more depleted values than those calculated for equilibrium. The systematic 13C-enrichment from the soil to the stalagmites at Grotta di Ernesto is independent of drip rate, and forced by the difference in pCO2 between cave water and cave air. This implies that speleothem δ13C values may not be simply interpreted either in terms of hydrology or soil processes. [Copyright &y& Elsevier]

Past climate archives show the Last Interglacial (LIG) period as similar to slightly warmer than current temperatures. However, there is a lack of LIG proxy evidence regarding variations of the climate across large topographic features and how this manifests at different altitudes. Here, we analysed two flowstones from Bigonda Cave, northeast Italy, to reconstruct LIG climate conditions in a region where precipitation is strongly influenced by the presence of the Alps. Stable isotope ratios, trace element concentrations and speleothem petrography from 133 ka to 105 ka allowed the detection of various hydroclimate and environmental conditions. Composite speleothem δ18O records from northeast Italy were found to closely follow the Northern Hemisphere summer insolation curve, attesting to the influence of solar isolation on Earth's hydroclimate. Our reconstructions indicate a northward shift of the Intertropical Convergence Zone during the LIG maximum, permitting Atlantic-derived moisture to travel further east across North Africa than at present, before being directed north towards the Alps. The latter part of the LIG exhibited frequent, extreme precipitation events in the SE Prealps due to orographic lifting of moisture from both the Atlantic and Mediterranean seas. Socio-economic planning must prepare for extreme autumnal flooding events and serious summer droughts, particularly important in vulnerable mountainous regions. • Last Interglacial speleothem multi-proxy records from the NE Italian Prealps. • Three infiltration sources identified permits robust hydroclimate reconstruction. • Solar insolation was the main forcing mechanism of the oxygen isotope record. • The LIG was punctuated by hot dry summers and extreme cave flooding events. [ABSTRACT FROM AUTHOR]

Abstract: Speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system. However, the climatological meaning of many speleothem records cannot be interpreted unequivocally; this is particularly so for more subtle shifts and shorter time periods, but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward. An explicit description of speleothem records as time series draws attention to the nature and importance of the signal filtering processes by which the weather, the seasons, and longer-term climatic and other environmental fluctuations become encoded in speleothems. We distinguish five sources of variation that influence speleothem geochemistry, i.e. atmospheric, vegetation/soil, karstic aquifer, primary speleothem crystal growth and secondary alteration, and give specific examples of their influence. The direct role of climate diminishes progressively through these five factors. We identify and review a number of processes identified in recent and current work that bear significantly on the conventional interpretation of speleothem records, for example: [(1)] speleothem geochemistry can vary seasonally and hence a research need is to establish the proportion of growth attributable to different seasons and whether this varies over time; [(2)] whereas there has traditionally been a focus on monthly mean δ18O data of atmospheric moisture, current work emphasizes the importance of understanding the synoptic processes that lead to characteristic isotope signals, since changing relative abundance of different weather types might control their variation on the longer-term; [(3)] the ecosystem and soil zone overlying the cave fundamentally imprint the carbon and trace element signals and can show characteristic variations with time; [(4)] new modelling on aquifer plumbing allows quantification of the effects of aquifer mixing; [(5)] recent work has emphasized the importance and seasonal variability of CO2-degassing leading to calcite precipitation upflow of a depositional site on carbon isotope and trace element composition of speleothems; [(6)] although much is known about the chemical partitioning between water and stalagmites, variability in relation to crystal growth mechanisms and kinetics is a research frontier; [(7)] aragonite is susceptible to conversion to calcite with major loss of chemical information, but the controls on the rate of this process are obscure. Analytical factors are critical in generating high-resolution speleothem records. A variety of methods of trace element analysis is available, but standardization is a common problem with the most rapid methods. New stable isotope data on Irish stalagmite CC3 compares rapid laser-ablation techniques with the conventional analysis of micromilled powders and ion microprobe methods. A high degree of comparability between techniques for δ18O is found on the millimeter to centimeter scale, but a previously described high-amplitude oxygen isotope excursion around 8.3 ka is identified as an analytical artefact related to fractionation of the laser-analysis associated with sample cracking. High-frequency variability of not less than 0.5‰ may be an inherent feature of speleothem δ18O records. [Copyright &y& Elsevier]

Climate change during the Little Ice Age (LIA) was characterized by globally widespread but spatiotemporally incoherent cooling with high regional variability. However, the onset, termination, internal structure, and underlying forcing mechanisms of the LIA remain unclear. Here we present a U-Th-dated stalagmite record with an average sampling resolution of 0.8 years and mean age uncertainty less than 4 years from Shijiangjun Cave, Southwest China (SW China). We have characterized the dynamics of the Asian summer monsoon (ASM) on interdecadal to centennial timescales during the LIA at unprecedented accuracy and precision. The onset of the LIA occurred at about 1300 (A.D.) and six weak-ASM events were identified at 1340–1380, 1445–1480, 1520–1540, 1600–1630, 1650–1670, and 1695–1730 (A.D.), respectively. The overall climate variability in Chinese monsoon regions is inconsistent with that in Northwest China (NW China). During the coldest period of the LIA (i.e. after 1500 CE), SW China exhibited a cold and dry pattern, while NW China experienced a cold and wet climate. Moreover, our records from the Asian-Australian monsoon (AAM) region showed coherent changes during the LIA, arguing against the interhemispheric "see-saw" model on interdecadal-centennial timescales. Documented solar minima, lower Northern Hemisphere temperature, and positive phases of PDO and ENSO during the LIA weakened the Asian-Australian summer monsoon, decreasing precipitation throughout the AAM regions. • The onset of Little Ice Age (LIA) occurred at 1300 CE. • Six weak Asian Summer monsoon events were identified in the LIA. • During the coldest period of the LIA, SW-China showed a cold-dry pattern. • Asian-Australian monsoon (AAM) regions experienced coherent change in the LIA. • Change in temperature and ocean-atmosphere circulation weakened the AAM in LIA. [ABSTRACT FROM AUTHOR]