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It has recently been argued that tree-ring stable isotopes (TRSI) can reveal persistent long-term hydroclimate trends that are usually not captured by more traditional dendroclimatic studies using tree-ring width or density (Büntgen 2022). Since the putative long-term discrepancy between ‘growth-dependent’ ring width and density versus ‘growth-independent’ TRSI proxies is likely unrelated to biases from age-trend removal (Büntgen et al. 2021; Yang et al. 2021), we propose a re-evaluation of the predictive power of various tree-ring parameters for reconstructing climate variability at interannual to multimillennial timescales. We analyse 7800 high-resolution δ18O, δ13C, δD measurements from about 200 high-elevation conifers of the Alpine Holocene Triple Tree Ring Isotope Record (AHTTRIR; Arosio et al. 2022) to assess ultra-long climate trends well beyond the segment length of individual tree-ring samples. Despite the spatiotemporal data heterogeneity, and associated signal complexity of AHTTRIR, we show that δ18O values contain a reasonable level of coherency with summer hydroclimate variability. In line with two independent TRSI studies from central Europe and monsoon Asia (Büntgen et al. 2021; Yang et al. 2021), our new δ18O Alpine chronology reveals a significant long-term drying trend over the past 6000 years. We interpret this multimillennial hydroclimate trajectory as a response to long-term negative orbital forcing (i.e., insolation changes due to the Earth’s axial precession). Our findings advise caution when applying corrections to TRSI data in order to preserve Holocene long trends. Considering the unique paleoclimatic values of TRSI, more such records are needed from a wide range of species and regions in both hemispheres. Arosio Tito, Malin Ziehmer, Kurt Nicolussi, Christian Schluechter, Andrea Thurner, Andreas Österreicher, Peter Nyfeler, and Markus Christian Leuenberger,. 2022. “Alpine Holocene Triple Tree Ring Isotope Record.” PANGAEA, 2022. https://doi.pangaea.de/10.1594/PANGAEA.941604.Büntgen Ulf. 2022. “Scrutinizing Tree-Ring Parameters for Holocene Climate Reconstructions.” Wiley Interdisciplinary Reviews: Climate Change, e778.Yang Bao, Chun Qin, Achim Bräuning, Timothy J. Osborn, Valerie Trouet, Fredrik Charpentier Ljungqvist, Jan Esper, Lea Schneider, Jussi Grießinger, and Ulf Büntgen. 2021. “Long-Term Decrease in Asian Monsoon Rainfall and Abrupt Climate Change Events over the Past 6,700 Years.” Proceedings of the National Academy of Sciences 118 (30): e2102007118.

Linked to major volcanic eruptions around 536 and 540 CE, the onset of the Late Antique Little Ice Age has been described as the coldest period of the past two millennia. The exact timing and spatial extent of this exceptional cold phase are, however, still under debate because of the limited resolution and geographical distribution of the available proxy archives. Here, we use 106 wood anatomical thin sections from 23 forest sites and 20 tree species in both hemispheres to search for cell-level fingerprints of ephemeral summer cooling between 530 and 550 CE. After cross-dating and double-staining, we identified 89 Blue Rings (lack of cell wall lignification), nine Frost Rings (cell deformation and collapse), and 93 Light Rings (reduced cell wall thickening) in the Northern Hemisphere. Our network reveals evidence for the strongest temperature depression between mid-July and early-August 536 CE across North America and Eurasia, whereas more localised cold spells occurred in the summers of 532, 540-43, and 548 CE. The lack of anatomical signatures in the austral trees suggests limited incursion of stratospheric volcanic aerosol into the Southern Hemisphere extra-tropics, that any forcing was mitigated by atmosphere-ocean dynamical responses and/or concentrated outside the growing season, or a combination of factors. Our findings demonstrate the advantage of wood anatomical investigations over traditional dendrochronological measurements, provide a benchmark for Earth system models, support cross-disciplinary studies into the entanglements of climate and history, and question the relevance of global climate averages.

Identifying wood species in archaeological specimens is important for the evaluation of timber structures and the conservation of historic buildings. Microscopic wood anatomy is the most commonly used technique for species identification. However, its application is problematic for the analysis of deteriorated wood. In addition, a particular challenge is the distinction of Picea from Larix due to their similar microscopic features. Recently, an analysis of stable isotopes of cellulose has shown that Larix is characterized by significantly more depleted deuterium values compared to Picea as well as other conifers from the Alpine region. To verify if this fact can be used in archaeological studies, we obtained 36 specimens, most of which were not clearly identified as larch or spruce. The cellulose could be extracted from 20 of them. We identified Larix and non-Larix species (Picea) without ambiguity from the deuterium content, except for one sample with an intermediate value. In conclusion, the evaluation of deuterium content is a valuable tool for the study of archaeologic wood.

The term 'Little Ice Age' (LIA) is classically used to define a period of repeated and extensive glacier advances during the last millennium. In the meanwhile, this term is also used to address the period of relatively low temperatures between the Medieval Climate Anomaly (MCA), or Medieval Warm Period, and present-day warming. The end of the LIA is generally set to the mid or late 1800s CE, however, the published onset dates of the LIA are more variable from the mid 1200s to the late 1500s. At Mont Mine and Morteratsch glaciers, Swiss Alps, we sampled and subsequently analysed detrital as well as in situ tree remnants from the early LIA period. At both glaciers, trees with lifespans of up to about 400 years were buried at various lateral moraine sites. The corresponding advance of both glaciers can be traced from the 1280s until the 1310s. At Morteratsch glacier, this early LIA advance phase culminated likely around 1375 CE. Evidence collected at both glaciers indicates that the ice surfaces were at least c. 12-15 m from the lateral moraine crests deposited during the maximum extent of the LIA. This suggests a similar (though very slightly weaker) magnitude than later LIA advances at our sites. The advances of Mont Mine and Morteratsch glaciers coincide with relatively cool summer temperatures from the late 1200s to the late 1300s. Taken together, the onset of the Little Ice Age in the Alps can be considered to be c. 1260 CE. The Little Ice Age was not a uniform period, but had several phases as can be derived from the records of Alpine glaciers and summer temperatures. We propose a subdivision of the LIA in the European Alps into an early (1260-1380 CE), an intermediate (1380-1575 CE) and a main (1575-1860 CE) phase., The Holocene, 32 (7), ISSN:0959-6836, ISSN:1477-0911

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events are directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C corresponding to 7176 and 5259 BCE. The ~ 2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which threaten modern infrastructure.

X-ray microdensitometry on annually resolved tree-ring samples has gained an exceptional position in last-millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X-ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light-based techniques are becoming increasingly popular, and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree-ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh "long-standing wisdom" but also provide new insights. Key outcomes include (i) a demonstration of the need for mass/volume-based recalibration to accurately estimate average ring density; (ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density data sets for climate reconstructions; and (iii) insights into the relevance of analytical measurement resolution in signals derived from tree-ring density data. Finally, we provide recommendations expected to facilitate futureinter-comparability and interpretations for global change research.

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794–2016 CE at 0.79 (p, Tree rings are a crucial archive for Common Era climate reconstructions, but the degree to which methodological decisions influence outcomes is not well known. Here, the authors show how different approaches taken by 15 different groups influence the ensemble temperature reconstruction from the same data.

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411–5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short‐term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481–5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event., Key Points Rapid 14C increase of ∼6‰ with significant level was found in tree rings from California, Switzerland, and Finland around 5410 BCEFive thousand, four hundred ten BCE event occurred during a period of high solar activity and 60 years after a grand 14C excursion of ∼20‰ from 5481 to 5471 BCEThe similarity of this 14C signature to already known solar events suggests that the origin of this new 5410 BCE event is an extreme SEP

Extratropical volcanic eruptions are commonly thought to be less effective at driving large-scale surface cooling than tropical eruptions, and only the latter are commonly thought to be able to distribute sulfate globally. Here, we test both of these assumptions using a network of ice cores from the polar regions of Antarctica and Greenland covering the past 15’000 years and climate-aerosol modeling. We employ state-of-the-art analyses of trace elements, cryptoptephra and sulphur isotopes (Burke et al., 2019) to gain new insights into the timing of past eruptions, their stratospheric sulphur mass injections and subsequent sulphate aerosol lifecycle. We use this information to estimate the climate impact potential due to negative radiative forcing caused by Earth’s largest volcanic eruptions since the last Glacial. Our analysis encompasses over 1’000 eruptions and include the caldera-forming eruptions of Okmok II (Alaska, 43 BCE, VEI=6, 53°N; McConnell et al., 2020), Aniakchak II (Alaska, 1600s BCE, VEI=6, 57°N), Crater Lake (Mazama, Oregon, 5600s BCE, VEI=7, 43°N) and Laacher See (Germany, c. 13 ka BP, VEI=6, 50°N).We use our reconstructed radiative forcing and the coupled earth system models MPI-ESM1.2 and CESM (version 1.2.2) to analyze the climatic impact caused by these eruptions and compare the simulated temperature response with temperature reconstructions based on ultra-long tree-ring chronologies. Finally, based on these comparisons, we propose a number of stratigraphic age tie-points to anchor ice-core chronologies from Greenland (GICC05) and Antarctica (WD2014) to the absolute dated tree-ring chronology. We thereby aim to improve proxy synchronization throughout the Holocene -- a prerequisite for detection and attribution studies -- and invite the paleo-climate community to update climate proxy records based on ice cores to the latest chronologies. The European Research Council Grant 820047 under the European Union’s Horizon 2020 research and innovation program funded the research project THERA - Timing of Holocene Volcanic eruptions and their radiative aerosol forcing. References:Burke, A., Moore, K. A., Sigl, M., Nita, D. C., McConnell, J. R., and Adkins, J. F.: Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores, Earth Planet Sc Lett, 521, 113-119, 2019.McConnell, J. R., Sigl, M., Plunkett, G., Burke, A., Kim, W., Raible, C. C., Wilson, A. I., Manning, J. G., Ludlow, F. M., Chellman, N. J., Innes, H. M., Yang, Z., Larsen, J. F., Schaefer, J. R., Kipfstuhl, S., Mojtabavi, S., Wilhelms, F., Opel, T., Meyer, H., and Steffensen, J. P.: Extreme climate after massive eruption of Alaska’s Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom, Proceedings of the National Academy of Sciences, 117, 15443-15449, 2020.

A recent analysis of stable isotopes of the Alpine Holocene Tree-Ring Dataset, consisting of samples from 192 larch and cembran pine trees, revealed that δD and δ18O exhibit no trends in adult trees, but evidence trends in the juvenile period of the first 100 years of cambial age. In this work we applied the Spearman statistical analysis on different cambial age classes to verify if these changes were correlated with tree-ring width values, that are known to show age trends. The results prove a significant correlation between tree-ring-width (TRW) and both hydrogen and oxygen stable isotopes before 100 year of cambial age, but not afterwards, in both larch and cembran pine. A trend in the correlation values was also found between the two water isotopes, while no trend was found in correlations involving δ13C. We hypothesized the δD and δ18O values reflect the higher xylogenesis activity of the juvenile period, that is associated with reduced atom exchanges of photosynthates with xylem water. The result indicates that the climate response of δD and δ18O may differ in the juvenile and mature period of tree life at treeline.

Stable isotopes in tree-ring cellulose are important tools for climatic reconstructions even though their interpretation could be challenging due to nonclimate signals, primarily those related to tree aging. Previous studies on the presence of tree-age-related trends during juvenile as well as adult growth phases in δD, δ18O, and δ13C time series yielded variable results that are not coherent among different plant species. We analyzed possible trends in the extracted cellulose of tree rings of 85 larch trees and 119 cembran pine trees, i.e., in samples of one deciduous and one evergreen conifer species collected at the tree line in the Alps, covering nearly the whole Holocene. The age trend analyses of all tree-ring variables were conducted on the basis of mean curves established by averaging the cambial-age-aligned tree series. For cambial ages over 100 years, our results prove the absence of any age-related effect in the δD, δ18O, and δ13C time series for both the evergreen and the deciduous conifer species, with the only exception being larch δD. However, for lower cambial ages, we found trends that differ for each isotope and species; i.e., mean δ13C values in larch do not vary with aging and can be used without detrending, whereas those in cembran pine show a juvenile effect, and the data should be detrended. Mean δ18O values present two distinct aging phases for both species, complicating detrending. Similarly, mean δD values in larch change in the first 50 years, whereas cembran pine changes between 50 and 100 years. Values for these two periods of cambial age for δD and δ18O should be used with caution for climatic reconstructions, ideally complemented by additional information regarding mechanisms for these trends.

Our Sun erratically expels large amounts of energetic particles into the interplanetary space and towards Earth, which can be observed as so-called solar proton events (SPE). A strong SPE might cause major damage to satellites and could even disrupt transformers at the ground1. This rises the questions how often strong SPEs occur. Since direct observations of SPEs are limited to the last decades, cosmogenic radionuclides can be used to detect such events further back in time. The production rate of cosmogenic nuclides, such as radiocarbon, is primarily dependent on the incoming flux of highly energetic galactic cosmic rays (GCR). Under normal conditions, the Sun’s magnetic field carried by the (low energy) solar protons shields us from (high energy) GCRs, resulting in a lower production of cosmogenic radionuclides when the Sun is active. During a SPE, however, the sudden and drastic increase of high the energy solar protons themselves may lead to an elevated production of cosmogenic radionuclides on Earth. Only recently, such sharp increases in cosmogenic nuclide production occurring within less than one year have been detected in several radionuclide records (10Be, 36Cl, 14C) from ice core and tree ring records, and have been attributed to SPEs2,3.Until now, only three SPE could confidently be detected in cosmogenic radionuclide records1,4,5. The reason for this is a general lack of accurately dated and annually resolved radionuclide records and/or the strong dampening of the production signal e.g. by the carbon cycle. To find and identify such events we measured radiocarbon in tree ring records at annual resolution with accelerator mass spectrometry (AMS). In this new, accurately dated and annually resolved 14C record spanning the past about 1000 yr we found several new candidates for SPEs. Their timing and amplitude in terms of cosmogenic nuclide production was characterized by using a global carbon cycle box model. Once unambiguously identified such spiked production increases recorded in the absolutely dated tree ring record have a great potential to be used as a global tool to synchronize other not well dated (climate) records with cosmogenic radionuclides (e.g. 10Be, 36Cl).1 Schrijver, C. J. et al. (2012) Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records. Journal of Geophysical Research: Space Physics 1172 Miyake, F., Masuda, K. & Nakamura, T. (2013) Another rapid event in the carbon-14 content of tree rings. Nature communications 4, 17483 Mekhaldi, F. et al. (2015) Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4. Nature Communications 6, 86114 Miyake, F., Nagaya, K., Masuda, K. & Nakamura, T. A (2012) signature of cosmic-ray increase in AD 774-775 from tree rings in Japan. Nature 486, 240-2425 O'Hare, P. et al. (2019) Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. ( approximately 660 BC). Proc Natl Acad Sci U S A 116, 5961-5966

Mass movements in the mountains can result in some unexpected discoveries. On September 10, 2017, strikingly white components were found in the western slope of the Val Chavagl, Swiss national Parc. The first inspection identified this as residual material of a lime kiln. Strikingly, the remains of the lime kiln were stuck in the slope, i.e., they were part of the material that built up the scarp and were not merely attached or transported from above. The rest of an old, former lime kiln is part of the terrace. Vast amounts of sediment covered this lime kiln following a storm around the Munt Chavagl - Munt la Schera.Of interest to the studies of past and most recent mass movements and catastrophic flooding is the timing of the operation and destruction. The age of the lime kiln can be estimated based on historical documents and inventory of lime kilns in the region, where the oldest known so far dates to 1560 CE (Parolini 2012). No charcoal was found in the remains of the newly discovered lime kiln; therefore, another approach was proposed i.e., dating organic remains embedded in deposits of catastrophic flooding. Larch trees, which were discovered at 1840 -1860 m asl, allowed for dendrochronology and radiocarbon analysis. The results obtained indicate that the trees died in the mid 17th century, at the latest. Moreover, our chronology sets Terminus ante quem TAQ for the construction and operation of the lime kiln. Our results are relevant for understanding natural hazards as well as reconstruction and protection of cultural heritage in the region of the Swiss National Parc. Parolini, J.D., 2012. Vom Kahlschlag zum Naturreservat: Geschichte der Waldnutzung im Gebiet des Schweizerischen Nationalparks. Haupt.

Snow avalanches are natural disturbances that can cause substantial damage to forests, and endanger people and material assets. Knowledge of past avalanches is crucial for forest management and planning technical mitigation measures. Dendrogeomorphology can provide information on previous disturbances, for example tree damages, caused by avalanches in forested terrain. By analysing the past growth of trees, both temporal and spatial reconstructions of the avalanche activity in forests are possible.We use a dendrogeomorphological approach to study the past avalanche activity on an avalanche path above the city of Innsbruck in Austria. The area is of high importance for recreation (e.g. hiking, biking and skiing) as well as avalanche mitigation. Protection forest and technical protection measures are already in place (breaking mounds, catching and deflection dams) and frequently interact with avalanches. In January 2019, an avalanche with a destructive size of 3 - 4 released above the Arzler Alm mountain hut and caused considerable damage to approx. 25 ha of forest. This event provided us with the opportunity to conduct the present study. We sampled 104 trees along three longitudinal transects at elevation bands of 1200, 1100 and 1000 m a.s.l. covering the damaged area. We furthermore applied a selective sampling scheme below the forest damage along a gully where avalanches that reached the city of Innsbruck had previously been observed. Using an increment borer at least two cores per tree were taken from damaged and undisturbed trees. A mixture of conifers and broadleaved trees (mostly Picea abies (L.) Karst, Fagus sylvatica L. and Abies alba Mill.), as well as old and young trees was selected. In addition, we recorded the exact position of each tree and measured several tree parameters (e.g. diameter at breast height, tree height, damage description). Each core was then prepared following a standard dendrochronological procedure. Tree-rings were counted and ring-width was measured using a stereo microscope and a time-series analysis program (TSAP Win). Additionally, a visual detection of growth reactions (traumatic resin ducts, reaction wood, scars, callus tissue, growth suppression or releases) was performed, and tree-ring series were cross-dated and compared with local reference chronologies. Years with tree-rings showing growth anomalies potentially caused by ecological or climatic factors were discarded as possible avalanche years.Going forward we will compare years with major avalanche events identified by the dendrogeomorphological analysis, with existing extensive archival data and orthophotos. We expect this to confirm known events, but also to provide new information on unknown events. Based on the location of sampled trees, we will furthermore reconstruct the spatial extent of past events to estimate magnitude and frequency of avalanche activity in the area. Our results will also contribute to better predicting size and periodicity of future avalanche events and revealing potential changes in the avalanche regime. This in turn is relevant to calibrating and validating avalanche simulation models as well as for the design of technical and silvicultural protection and mitigation measures, which is especially important for an Alpine city like Innsbruck.

We present an approach to calibrate a regional glacier model based on the well observed period since the mid-19th century LIA maximum.We chose 30 glaciers distributed across the entire European Alps with frequent length change observations in that period. These glaciers account for 25% of today's total glacier area in the Alps. We run simulations with the Open Global Glacier Model (OGGM, https://oggm.org) driven by HISTALP (http://www.zamg.ac.at/histalp) gridded climate data. To calibrate the glaciers individually, we vary three model parameters within a reasonable range: (i) a precipitation scaling factor governing average mass-turnover and mass-balance profiles, (ii) the ice creep parameter governing basal sheer stress and the dynamics of ice flow, and (iii) a constant mass balance perturbation applied to the yearly mass-balance. This results in 1365 unique parameter combinations which were tested for all glaciers. We chose individual parameter subsets for every glacier based on objective criteria minimizing the difference between modeled and observed length changes.We find that there is no unique parameter combination satisfying our criteria for all glaciers. It is also challenging to identify an ideal parameter combination for each individual glacier, since there is a trade-off between reproducing variability (useful for paleo-climate interpretations) and reproducing observed length change (useful for projections and planing).Furthermore, model and input data uncertainties are variable in time, leading to non-unique optimal parameter sets. Therefore, we rely on an ensemble of simulations consisting of the best runs with respect to multiple statistical measures. Together with a cross-validation procedure, the ensemble produces a probabilistic uncertainty range which can be applied to Holocene glacier reconstructions and future evolution scenarios.

Variations in building activity reflect demographic, economic and social change during history. Tens of thousands of wooden constructions in Europe have been dendrochronologically dated in recent d ...

Subfossil tree remains from 38 high-elevation sites in the eastern Alps, which were mostly located in the province of Trentino, Italy, were dendrochronologically analysed. A total of 909 samples were collected, 497 of which were dated to calendar years through dendrochronology and separated into six groups. A further tree-ring series of 20 samples were cross-dated into two groups and their ages established by means of radiocarbon dating. The new Trentino Chronology that was established on the basis of these samples covers more than 80% of the last ca. 11,500 years. The uneven distribution of wood samples through time is most likely caused by different factors, for example, climatic and anthropogenic factors. According to our observations, the trees fell at the sites where they were found. The tree-ring series show that trees often died after a period of pronounced growth decline, for example, as a consequence of variations in groundwater levels. A comparison of the Holocene sample distribution of the new Trentino Chronology with contemporaneous records of other European tree-ring chronologies suggests that, at least partly, the greater scale of climatic variability influenced the depositional frequency. The new data contribute to our understanding of past climatic variability and environmental dynamics.

Wood was an essential raw material for mining maintenance in historic and prehistoric times. During the Bronze Age, the Mitterberg mining region in the Austrian Alps was one of the most important producers of copper and, consequently, a consumer of huge amounts of wood. Since the 1960s, archaeological investigations at the Troiboden dressing site at the Mitterberg main lode have uncovered mining timber both single finds as well as box-shaped wooden constructions like wet-tyes which were used to wash and concentrate crushed copper ore. Dendrochronological analyses on a set of mining timber yield calendar dates for these mining activities: a boom phase from the 14th to the 13th century BC, including two felling phases – one in the 1370s and a second from the 1290s to 1270s BC – are verifiable so far. As a result, the wood supply from nearby forests may have been exhausted rapidly, which is confirmed by palynological records from bogs in the vicinity of the excavation site. By utilising a tree-ring growth–elevation model developed by Dittmar et al. (2012), the elevations of growing sites were estimated to detect where the mining timber might have originated. To examine the model outcomes, we used tree-ring data with known origin, i.e., series from living trees and subfossil samples from the Troiboden and its vicinity. The results for the mining timber suggest that the prehistoric miners utilised trees from the vicinity of the mining site in the 14th century but at least partly sought wood from growing sites at lower elevations to continue mining during the 13th century BC.

The Scottish pine network expansion has been an ongoing task since 2006 and funding must be acknowledged to the following projects: EU project ‘Millennium’ (017008-2), Leverhulme Trust project ‘RELiC: Reconstructing 8000 years of Environmental and Landscape change in the Cairngorms (F/00268/BG)’, the Native Oak and Pine project or ‘NOAP’ (Historic Scotland) and the NERC project ‘SCOT2K:Reconstructing 2000 years of Scottish climate from tree rings (NE/K003097/1)’. Further PhD funding for Milos Rydval is acknowledged from The Carnegie Trust. Dendroarchaeology almost exclusively uses ring-width (RW) data for dating historical structures and artefacts. Such data can be used to date tree-ring sequences when regional climate dominates RW variability. However, the signal in RW data can be obscured due to site specific ecological influences (natural and anthropogenic) that impact crossdating success. In this paper, using data from Scotland, we introduce a novel tree-ring parameter (Blue Intensity – BI) and explore its utility for facilitating dendro historical dating of conifer samples. BI is similar to latewood density as they both reflect the combined hemicellulose, cellulose and lignin content in the latewood cell walls of conifer species and the amount of these compounds is strongly controlled, at least for trees growing in temperature limited locations, by late summer temperatures. BI not only expresses a strong climate signal, but is also less impacted by site specific ecological influences. It can be concurrently produced with RW data from images of finely sanded conifer samples but at a significantly reduced cost compared to traditional latewood density. Our study shows that the probability of successfully crossdating historical samples is greatly increased using BI compared to RW. Furthermore, due to the large spatial extent of the summer temperature signal expressed by such data, a sparse multi-species conifer network of long BI chronologies across Europe could be used to date and loosely provenance imported material. Postprint

The exploitation of copper deposits in the mountainous areas of the Alps gained enormous economic importance particularly in the 2nd and 1st millennium B.C., as Alpine copper began to play a central role in the metal supply of Europe. This volume summarises the current state of research on prehistoric Alpine copper exploitation from the western and southern Alps to the gates of Vienna in the eastern Alps. The 23 papers were originally presented as contributions to a conference held in September 2016 at the University of Innsbruck, which covered topics such as mountain landscapes, mining, beneficiation, smelting and the metal trade in the Bronze and Early Iron Ages. A particular focus of the present volume is the D-A-CH-funded project on ‘Prehistoric copper production in the Eastern and Central Alps: technical, social and economic dynamics in space and time’, a research collaboration between partners in Germany, Austria and Switzerland. The various contributions provide new perspectives on the questions surrounding fahlore and the different technological processes within the framework of a broader ‘chaîne opératoire’. Even with the current stage of research, it is already possible to sketch how different Alpine regions adapted more general technological and economic trends surrounding copper exploitation in very different ways.

The prehistoric salt mine of Hallstatt together with its burial ground is one of the most prominent archaeological sites in the world, and has given its name to the “Hallstatt period”, an epoch of European prehistory (800 to 400 BCE). Due to the perfect conservation in rock salt a high number of organic materials have been found, including mostly wooden artefacts and structural timber. More than 2000 samples were taken from various archaeological sites in the mines as well as at the surface. It was possible to date 763 samples by the means of dendrochronology and by 14C wiggle matching. The dendrochronological dating was possible due to crossdating with various available chronologies (like Villingen-Magdalenenberg or Dachstein/Schwarzer See). The fir (Abies alba Mill.) chronologies span the periods: -1232 to -1063; -819 to -425 and -371 to-129. The spruce (Picea abies L. Karst.) chronologies span the periods: -1228 to -1063; -813 to -669 and -342 to -123. The larch (Larix decidua Mill.) chronologies span the periods: -1393 ± 18 to-1286 ± 18 based on wiggle matching data and -252 to -164. A beech (Fagus sylvatica L.) chronology span the time -1182 to -1062.

For dendroclimatological Blue Intensity (BI) studies based on earlywood (EW) or latewood (LW) information, a demarcation between the two is necessary, which can be difficult to establish for species where the transition is subtle. Often, a percental value k is used that calculates an EW/LW boundary value for each tree ring individually based on the difference between maximum and minimum absorption. Several laboratories and authors have used different values for k (e.g. k = 30 % or k = 50 %), while wood anatomical and visual studies suggest that k is on the order of 80 %. Here, we test how different settings of k, and thus different definitions of the EW and LW proportions of a tree ring, influence the dendroclimatic potential of derived time series. To this end, we correlate instrumental temperature measurements with tree ring chronologies that are based on EW and LW information (e.g. EW absorption (EWBI), LW absorption (LWBI)), where the EW/LW proportion is varied by setting different values for k. The tree ring samples utilized are 30 cores of spruce (Picea abies) trees from a high-elevated site (ca. 1700 m a.s.l.) in the northern Alps, Austria. Overall, we achieve high correlations between temperature data and our tree ring chronologies. Regarding the stability of the climate signal under different k values, the results show that absorption intensity based parameters (ΔBI, EWBI, LWBI) are only mildly influenced by different settings of k, while width based parameters (EW width, LW width) show a larger dependence on k. LW width, for instance, was stronger correlated with temperature, the smaller the LW was chosen (and thus the higher k was set). Based on our results and the wood anatomical definition of the EW/LW boundary, we suggest that k = 80 % may be a good choice for future studies. However, since this is only a case study from one site, careful screening of the respective data set regarding an appropriate k value must accompany each dendroclimatological study.

The original version of this Article contained an error in the Data Availability section, which incorrectly read ‘All data will be freely available via https://www.ams.ethz.ch/research.html.’ The correct version states ‘http://www.ams.ethz.ch/research/published-data.html’ in place of ‘https://www.ams.ethz.ch/research.html’. This has been corrected in both the PDF and HTML versions of the Article.

A June–August Alpine temperature proxy series is developed back to AD 951 using 1,527 ring-width measurements from living trees and relict wood. The reconstruction is composed of larch data from four Alpine valleys in Switzerland and pine data from the western Austrian Alps. These regions are situated in high elevation Alpine environments where a spatially homogenous summer temperature signal exists. In an attempt to capture the full frequency range of summer temperatures over the past millennium, from inter-annual to multi-centennial scales, the regional curve standardization technique is applied to the ring width measurements. Correlations of 0.65 and 0.86 after decadal smoothing, with high elevation meteorological stations since 1864 indicate an optimal response of the RCS chronology to June–August mean temperatures. The proxy record reveals warm conditions from before AD 1000 into the thirteenth century, followed by a prolonged cool period, reaching minimum values in the 1820s, and a warming trend into the twentieth century. This latter trend and the higher frequency variations compare well with the actual high elevation temperature record. The new central Alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium. It also reveals significant similarities at inter-decadal to multi-centennial frequencies with large-scale temperature reconstructions, however, deviating during certain periods from H.H. Lamb‘s European/North Atlantic temperature history.

The landslide of Kofels located in the Otz Valley (Eastern Alps, Austria) is the largest mass movement in crystalline rock in the Alps with a total volume of 3.3 km 3 . Previous radiocarbon dates have suggested an age of the event of 9800 ± 100 years ago. The landslide and its radiocarbon dating were used to estimate a Holocene production rate for 10 Be for surface exposure dating. Tree-ring analysis and radiocarbon dating of new samples significantly refine the timing of the Kofels landslide and even enable to constrain the season during which this event occurred. Wiggle matching analysis of six radiocarbon samples constrains the event to 9527–9498 cal BP which is slightly younger and significantly more precise than the previously established age. The landslide occurred shortly after the onset of the vegetation period, i.e. in May or June. The new dating moves the Kofels landslide strikingly close to the less well constrained age of the Flims landslide, the largest of its kind in the Alps located 130 km west of Kofels (9475–9343 cal BP). This near-synchronicity of these giant mass movements raises the question of a possible common, albeit currently unknown, trigger.

Im traditionsreichen Bergbaugebiet von Schwaz/Brixlegg im Nordtiroler Unterinntal fand während der späten Bronzezeit und frühen Eisenzeit ein umfangreicher Bergbau auf Kupfererze statt, der zahlreiche Spuren im Gelände hinterlassen hat. Montanarchäologische Forschungsprojekte der Universität Innsbruck, gefördert vom österreichischen Wissenschaftsfonds FWF und vom Tiroler Wissenschaftsfonds TWF, untersuchen seit den 1990er Jahren das prähistorische Montanwesen in diesem Raum. Zu den Forschungszielen gehören die Rekonstruktion der metallurgischen Produktionskette vom Erzabbau über die Aufbereitung bis hin zur Erzverhüttung und Gewinnung von Rohkupfer sowie der Arbeits- und Lebenswelt der prähistorischen Berg- und Hüttenleute. Die bislang prospektierten und in Ausschnitten archäologisch untersuchten Befunde belegen einen zeitlichen Schwerpunkt der Bergbauaktivitäten im 12. bis 8. Jh. v. Chr. Auf einem Verhüttungsplatz bei Radfeld (Mauk A) fanden sich 1997 bei der Freilegung einer „Waschrinne“ zur nassmechanischen Aufbereitung von Schlacken einige gut erhaltene Textilfragmente. Der archäologische Befund sowie die Textilfunde, Analysen zu Textiltechnik, Fasermaterial und Farbstoffen werden im folgenden Beitrag vorgestellt. Zudem werden die funktionelle Interpretation und kulturgeschichtliche Einordnung der Textilfunde diskutiert.--Dans la célèbre région minière de Schwaz/Brixlegg en Tyrol (vallée de l’Inn) se trouvent de nombreuses traces de travaux miniers datant de l’Âge du Bronze final à l’Âge de Fer ancien. L’exploitation de l’époque se concentrait sur le cuivre gris, matière première locale pour la production du cuivre. Depuis 1993 des projets de recherches interdisciplinaires sont effectués à l`Université de Innsbruck sous la promotion du Wissenschaftsfonds autrichien (FWF) et tyrolien (TWF). Les objectifs de ces recherches comprennent la reconstruction de la chaîne opératoire pour la production du cuivre (extraction du minerai, traitement et métallurgie) aussi bien que du monde du travail et du cadre de vie des communautés de mineurs préhistoriques. La datation de ces activités tombe dans la période du 12ème au 8ème siècle av. J.-C. Une fouille archéologique sur un site de métallurgie extractive (Radfeld, Mauk A, 1997) a mis au jour les vestiges d’une installation de lavage où des scories de cuivre finement broyées ont été lavées pour récupérer des inclusions riches en cuivre. Dans ce contexte, quelques fragments de textile bien conservé ont pu être récupérés. Le textile, le matériau en lui-même, ses colorants et la technologie de sa production sont présentés et discutés dans cette contribution ainsi que l’interprétation fonctionnelle et le contexte (pré-)historique et culturel.--In the traditional mining district Schwaz-Brixlegg in North-Tyrol a large amount of archaeological remains from an extensive Late Bronze Age and Early Iron Age copper ore mining is still visible in the landscape. In 1993 the University of Innsbruck started with mining archaeological investigations in this area in the frame of several research projects, supported by the Austrian Science Fund FWF and the Tyrolian Science Fund TWF. The aim of the research program is to identify and to date prehistoric mining activities and to reconstruct the metallurgical production chain including mining, beneficiation and smelting of copper ores. Also the working and living environment of the prehistoric miners and smelters is studied. So far evidence for mining activities from the 12th to the 8th century BC could be provided. In the frame of archaeological excavations in 1997 at the Late Bronze Age smelting site Mauk A near Radfeld a few well preserved textile fragments could be recovered in the context of a washing installation, where crushed slag had been processed in order to obtain concentrates of copper rich inclusions. In this paper the textile finds will be presented in their archaeological context together with analysis on textile techniques, seam materials and dyestuffs. Furthermore, their functional interpretation and positioning in a larger historical context will be discussed.

As glaciers in the Canadian Rockies recede, glacier forefields continue to yield subfossil wood from sites overridden by these glaciers during the Holocene. Robson Glacier in British Columbia formerly extended below tree line, and recession over the last century has progressively revealed a number of buried forest sites that are providing one of the more complete records of glacier history in the Canadian Rockies during the latter half of the Holocene. The glacier was advancing ca. 5.5 km upvalley of the Little Ice Age terminus ca. 5.26 cal ka BP, at sites ca. 2 km upvalley ca. 4.02 cal ka BP and ca. 3.55 cal ka BP, and 0.5-1 km upvalley between 1140 and 1350 A.D. There is also limited evidence based on detrital wood of an additional period of glacier advance ca. 3.24 cal ka BP. This record is more similar to glacier histories further west in British Columbia than elsewhere in the Rockies and provides the first evidence for a post-Hypsithermal glacier advance at ca. 5.26 cal ka BP in the Rockies. The utilization of the wiggle-matching approach using multiple 14C dates from sample locations determined by dendrochronological analyses enabled the recognition of 14C outliers and an increase in the precision and accuracy of the dating of glacier advances. Fil: Luckman, B.H.. University Of Western Ontario; Canadá Fil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Nicolussi, K.. University of Innsbruck; Austria

The extraction and processing of metal ores, particularly those of copper and tin, are regarded as among the principal motors of Bronze Age society. The skills and risks of mining lie behind the weapons, tools and symbols that drove political and ideological change. But we hear much less about the miners themselves and their position in society. Who were these people? Were they rich and special, or expendable members of a hard-pressed workforce? In this study the spotlight moves from the adits, slags and furnaces to the bones and seeds, providing a sketch of dedicated prehistoric labourers in their habitat. The Mauken miners were largely dependent on imported meat and cereals, and scarcely hunted or foraged the resources of the local forest. They seem to be the servants of a command economy, encouraged to keep their minds on the job.

Cellulose content (CC [%]) in tree rings is usually utilized as a tool to control the quality of the α-cellulose extraction from tree-rings in the preparation of stable isotope analysis in wooden tissues. Reported amounts of CC [%] are often limited to mean values per tree. For the first time, CC [%] series from two high Alpine species, Larix decidua Mill. (European Larch, LADE) and Pinus cembra L. (Swiss stone pine, PICE) are investigated in modern wood samples and Holocene wood remains from the Early and Mid-Holocene. Modern CC [%] series reveal a species-specific low-frequency trend independent from their sampling site over the past 150 years. Climate-cellulose relationships illustrate the ability of CC [%] to record temperature in both species, but for slightly different periods within the growing season. The Holocene CC [%] series illustrate diverging low-frequency trends in both species, independent of sampling site characteristics (latitude, longitude and elevation). Moreover, potential age trends are not apparent in the two coniferous species. The arithmetic mean of CC [%] series in the Early and Mid-Holocene indicate low CC [%] succeeding cold events. In conclusion, CC [%] in tree rings show high potential to be established as novel supplementary proxy in dendroclimatology.

During prehistory fire-setting was the most appropriate technique for exploiting ore deposits. Charcoal fragments found in the course of archaeological excavations in a small mine called Mauk E in the area of Schwaz/Brixlegg (Tyrol, Austria) are argued to be evidence for the use of this technology. Dendrochronological analyses of the charcoal samples yielded calendar dates for the mining activities showing that the exploitation of the Mauk E mine lasted approximately one decade in the late 8th century BC. Dendrological studies show that the miners utilised stem wood of spruce and fir from forests with high stand density for fire-setting and that the exploitation of the Mauk E mine had only a limited impact on the local forests., Highlights ► Charcoal fragments found in a small mine are argued to be evidence for the use of fire-setting during prehistory. ► Dendrochronological analyses of the charcoal samples yielded calendar dates in the late 8th century BC. ► Selective wood procurement – only softwood species and primarily stem wood of limited diameter was common. ► The demand for wood for fire-setting activities was limited and could be met by exploiting only local forests.

A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd–6th and 9th centuries in Norway, during the 10th–13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century (or earlier) and reaching a maximum in 17th–19th centuries is supported by our data. The pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales. The number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia, although the resolution of most glacier chronologies is not enough for robust statistical correlations. Glacier retreat in the past 100–150 years corresponds to the anthropogenic global temperature increase. Many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain.

Growing scientific evidence from modern climate science is loaded with implications for the environmental history of the Roman Empire and its successor societies. The written and archaeological evidence, although richer than commonly realized, is unevenly distributed over time and space. A first synthesis of what the written records and multiple natural archives (multi-proxy data) indicate about climate change and variability across western Eurasia from c. 100 b.c. to 800 a.d. confirms that the Roman Empire rose during a period of stable and favorable climatic conditions, which deteriorated during the Empire's third-century crisis. A second, briefer period of favorable conditions coincided with the Empire's recovery in the fourth century; regional differences in climate conditions parallel the diverging fates of the eastern and western Empires in subsequent centuries. Climate conditions beyond the Empire's boundaries also played an important role by affecting food production in the Nile valley, and by encouraging two major migrations and invasions of pastoral peoples from Central Asia.

We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps covering the period AD 1053e1996 using tree-ring and lake sediment data. The new reconstruction is based on nine different calibration approaches and errors were estimated conservatively. Summer temperatures of the last millennium are characterised by two warm (AD 1053e1171 and 1823e1996) and two cold phases (AD 1172e1379 and 1573e1822). Highest pre-industrial summer temperatures of the 12th century were 0.3 � C warmer than the 20th century mean but 0.35 � C colder than proxy derived

Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring-based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from similar to 250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.