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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

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 https://doi.org/10.17864/1947.147.

Oral presentation in the XIII International Seminar on Management and Biodiversity Conservation: Landscape, vegetation and climate change

Paleoclimate events, either short or long in time, can be recorded in a variety of archives along the geologic timescale, several of which are present in Southern Portugal where the geologic history spans almost the last 400 Ma. The type of paleoclimate archives will define both the type of paleoclimate event that can be studied and the resolution of the proxy used to study it. In the Algarve Region, the most abundant paleoclimate archives correspond to metasedimentary and sedimentary rocks, representing depositional environments ranging from Devonian to Quaternary periods. Several proxies such as lithology, mineralogy and organic geochemistry and biology, have been used on these archives to describe paleo-environmental changes, as for instance oceanic anoxic events and sea-level variations linked to glacial cycles. Other proxies, such as the fossil content and isotopic signatures, have also been analyzed for documenting paleoclimate systems. Concerning the Quaternary period climate record, the Algarve has no ice or lake archives, but it has continental deposits, such as estuarine sediments, calcareous tufas and speleothems, as well as archeological and historical archives, allowing reconstructing more recent paleoclimate conditions. Studying all these possible archives and paleoclimate records is a demanding task and it is thus still a work in progress. Nevertheless, significant scientific contributions in this research area already exist and are being used as a geological heritage for the Loulé-Silves-Albufeira Aspiring UNESCO Global Geopark. Indeed, the territory encompassing the Loulé-Silves-Albufeira Aspiring UNESCO Geopark has several archives and records across the geological timescale that are worth presenting. As a first example, this territory has a unique record of Triassic rock formations, the Silves Sandstone succession (known as Grés de Silves sensu lato) in which a recently discovered amphibian species, Metoposaurus algarvensis, has recently been described for the first time, based on a large concentration of bones (Brusatte et al., 2015), and new fossil remains of Henodontidae are under determination. All the studied proxies describe a transitional continental environment, characterized by arid conditions that led to the existence of temporary ponds, and ultimately the formation of evaporites, in the transition to the Jurassic, after a short marine incursion into the basin (Fechner, 1989). The coral and echinoid fossils from Jurassic limestones formation can be presented as a second attractive example of this territory paleoclimate record, allowing documenting the tropical sea conditions existing at that period. Finally, a third example of the paleoclimate archive included in the aspiring Geopark territory, is linked to the extensive and magnificent karstic landscape near Loulé, that presents speleothems and springs, with calcareous tufas, in which preliminary isotopic and palynological studies are very promising.

Oral presentation in the XIII International Seminar on Management and Biodiversity Conservation: Landscape, vegetation and climate change

Paleoclimate events, either short or long in time, can be recorded in a variety of archives along the geologic timescale, several of which are present in Southern Portugal where the geologic history spans almost the last 400 Ma. The type of paleoclimate archives will define both the type of paleoclimate event that can be studied and the resolution of the proxy used to study it. In the Algarve Region, the most abundant paleoclimate archives correspond to metasedimentary and sedimentary rocks, representing depositional environments ranging from Devonian to Quaternary periods. Several proxies such as lithology, mineralogy and organic geochemistry and biology, have been used on these archives to describe paleo-environmental changes, as for instance oceanic anoxic events and sea-level variations linked to glacial cycles. Other proxies, such as the fossil content and isotopic signatures, have also been analyzed for documenting paleoclimate systems. Concerning the Quaternary period climate record, the Algarve has no ice or lake archives, but it has continental deposits, such as estuarine sediments, calcareous tufas and speleothems, as well as archeological and historical archives, allowing reconstructing more recent paleoclimate conditions. Studying all these possible archives and paleoclimate records is a demanding task and it is thus still a work in progress. Nevertheless, significant scientific contributions in this research area already exist and are being used as a geological heritage for the Loulé-Silves-Albufeira Aspiring UNESCO Global Geopark. Indeed, the territory encompassing the Loulé-Silves-Albufeira Aspiring UNESCO Geopark has several archives and records across the geological timescale that are worth presenting. As a first example, this territory has a unique record of Triassic rock formations, the Silves Sandstone succession (known as Grés de Silves sensu lato) in which a recently discovered amphibian species, Metoposaurus algarvensis, has recently been described for the first time, based on a large concentration of bones (Brusatte et al., 2015), and new fossil remains of Henodontidae are under determination. All the studied proxies describe a transitional continental environment, characterized by arid conditions that led to the existence of temporary ponds, and ultimately the formation of evaporites, in the transition to the Jurassic, after a short marine incursion into the basin (Fechner, 1989). The coral and echinoid fossils from Jurassic limestones formation can be presented as a second attractive example of this territory paleoclimate record, allowing documenting the tropical sea conditions existing at that period. Finally, a third example of the paleoclimate archive included in the aspiring Geopark territory, is linked to the extensive and magnificent karstic landscape near Loulé, that presents speleothems and springs, with calcareous tufas, in which preliminary isotopic and palynological studies are very promising.