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Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data-model comparisons. Here, we illustrate this using 456 globally distributed speleothem delta O-18 records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data-model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on delta O-18 values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices. European Geosciences Union - W2017/413; Irish Centre for Research in Applied Geosciences (iCRAG); European Association of Geochemistry (Early Career Ambassadors program 2017); Quaternary Research Association UK; Navarino Environmental Observatory, Stockholm University; University College Dublin, Savillex (UK) - SF1428; Ibn Zohr University, Morocco; University of Reading; European Research Council - 694481; Natural Environment Research Council (JPI-Belmont project "PAleao-Constraints on Monsoon Evolution and Dynamics (PACMEDY)"); Geological Survey Ireland - 2017-SC-056; Royal Irish Academy; Deutsche Forschungsgemeinschaft - RE3994/2-1; Past Global Changes (PAGES) programme; info:eu-repo/semantics/publishedVersion

The interdisciplinary approach of combining expertise in environmental, geochemical, civil engineering and material sciences realizes a new level of in-depth process understanding of the prevailing biophysicochemical reaction mechanisms occurring at mineral-fluid interfaces in various anthropogenic settings such as (geo)technical and construction surroundings. Proposed investigations may focus on the interaction of solid - liquid - gas interfaces, on proxy-based forensic reconstruction and adaptation of variable and possibly unfavorable environmental and operating conditions of different spatial and temporal scales. The advanced process understanding of mineral – environment (abiotic and/or biotic) interactions, combined with newly developed and state-of-the-art environmental monitoring tools (e.g. sensor-based high-resolution data acquisition) enables the target-oriented and customized optimization and development of sustainable material alteration prevention strategies (e.g. advanced inorganic binder systems) and durable mineral-based construction materials, as well as measures against unwanted mineral formation (e.g. plugging of geological reservoirs or drainage systems). In this scope, contributions on advanced environmental monitoring strategies and tools (e.g. sensor systems, isotope/elemental tracers), processes at critical fluid-solid interfaces and high-resolution chemical, (micro-)biological, mineralogical and micro-/nanostructural analytics (e.g. FEG-EPMA, X-ray microtomography), as well as field-based testing, laboratory experiments and modelling approaches are cordially invited.

The well-known Erzberg site represents the largest siderite (FeCO 3 ) deposit in the world. It consists of various carbonates accounting for the formation of prominent CaCO 3 (dominantly aragonite) precipitates filling vertical fractures of different width (centimetres to decimetres) and length (tens of metres). These commonly laminated precipitates are known as ‘erzbergite’. This study focuses on the growth dynamics and environmental dependencies of these vein fillings. Samples recovered on-site and from mineral collections were analyzed, and these analyses were further complemented by modern water analyses from different Erzberg sections. Isotopic signatures support meteoric water infiltration and sulphide oxidation as the principal hydrogeochemical mechanism of (Ca, Mg and Fe) carbonate host rock dissolution, mobilization and vein mineralization. Clumped isotope measurements revealed cool formation temperatures of ca 0 to 10°C for the aragonite, i.e. reflecting the elevated altitude Alpine setting, but unexpectedly low for aragonite nucleation. The 238 U– 234 U– 230 Th dating yielded ages from 285·1 ± 3·9 to 1·03 ± 0·04 kyr bp and all samples collected on-site formed after the Last Glacial Maximum. The observed CaCO 3 polymorphism is primarily controlled by the high aqueous Mg/Ca ratios resulting from dissolution of Mg-rich host rocks, with Mg/Ca further evolving during prior CaCO 3 precipitation and CO 2 outgassing in the fissured aquifer. Aragonite represents the ‘normal’ mode of erzbergite formation and most of the calcite is of diagenetic (replacing aragonite) origin. The characteristic lamination (millimetre-scale) is an original growth feature and mostly associated with the deposition of stained (Fe-rich) detrital particle layers. Broader zonations (centimetre-scale) are commonly of diagenetic origin. Petrographic observations and radiometric dating support an irregular nature for most of the layering. Open fractures resulting from fault tectonics or gravitational mass movements provide water flow routes and fresh chemical reaction surfaces of the host rock carbonates and accessory sulphides. If these prerequisites are considered, including the hydrogeochemical mechanism, modern water compositions, young U-Th ages and calculated precipitation rates, it seems unlikely that the fractures had stayed open over extended time intervals. Therefore, it is most likely that they are geologically young. Published version

Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide "out-of-sample" evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (delta O-18, delta C-13) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.

Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data. The compiled data are available at http://dx.doi.org/10.17864/1947.147 .

Additional file 1. Additional figures and tables.

The Sonne-185 "VITAL" Cruise from Darwin (Australia) to Jakarta (Indonesia) from 15th September to 6th October 2005 was divided into two main parts: A transect across the Timor Strait between the Arafura Sea and East Timor and a transect across the outflow of the Indonesian Throughflow into the Indonesian Ocean between the Sunda Islands and NW Australia. The prime objective of the VITAL cruise was to recover high resolution sediment archives to decipher the variability of the Indonesian Throughflow and the Australasian climate history on decadal to millennial timescales over the past 150 000 years. To achieve this objective 58 sediment and water stations were sampled between the edge of the Arafura Sea and the Argo Abyssal Plain in the eastern Indian Ocean. The onboard CTD with water sampler was deployed at 6 stations, combined with multinet hauls for plankton sampling of defined water depth intervals. Plankton sampling with a towed plankton net were carried out at 31 stations in addition to continuous plankton sampling with the deck water pump during the entire cruise. The multicorer was deployed at 54 stations with a result of 51 high quality sediment surface samples. The multicorer was equipped with a self-registering CTD to obtain additional CTD records of the water profile and bottom water at each multicorer station. A total of 37 long cores for sampling the sediment record of the Holocene and last glacial cycle were deployed at 35 stations (22 piston cores, 15 gravity cores and 2 Kastenlot-cores) with a total recovery of more than 420 m core length (23 m maximum core length, average core length of approx. 12 m, only two deployments without recovery). All cores were measured for magnetic susceptibility in 2 cm intervals, split, described and measured for color reflectance in 1 cm ��� intervals. An initial shipboard stratigraphy was obtained by matching the magnetic susceptibility and lightness (L*) records with the SPECMAP-stack (Martinson, 1987).