CRC806-Database Publications Feed (Atom) Organic geochemical and palynological evidence for Holocene natural and anthropogenic environmental change at Lake Dojran (Macedonia/Greece) 2018-10-12T15:10:14+02:00 In this study, we present lipid biomarker and palynological data for a sediment core from Lake Dojran (Macedonia/Greece), which covers the entire Holocene period. We analyzed vascular plant-derived n-alkanes, combustion-derived polycyclic aromatic hydrocarbons (PAHs), fecal steroids, and bacterial and archaeal glycerol dialkyl glycerol tetraether (GDGT) lipids in concert with microcharcoal and pollen assemblages to reconstruct climatic, environmental, and human impact in the Dojran catchment and the greater Dojran area. Overall, our results suggest a relationship between anthropogenic activity and environmental/climatic change since increased human impact corresponds to phases of higher humidity and high lake levels at Lake Dojran. During the early Holocene, the record reveals increasing temperatures and humidity and concurrent increasing vegetation cover and runoff/soil erosion, respectively. Following a thermal maximum during the middle early Holocene, temperatures decrease gradually until present. The middle-Holocene at Lake Dojran is characterized by relatively stable environmental conditions followed by greater climatic instability and strong anthropogenic overprint during the late-Holocene. The fecal stanol record reveals phases of increased human impact during the early Bronze Age, the late Bonze/early Iron Age, and the Middle Ages. A phase of low stanol and PAH concentrations from the late Iron Age until the early Middle Ages is either related to ecosystem changes and/or changes in settlement pattern since concurrent pollen data indicate intensified land use. Human impact re-intensified during the Middle Ages with some variability probably related to climatic variations of the ‘Medieval Warm Period’ and the ‘Little Ice Age’. Stephanie Kusch Jährlich rezente Pollendepositionsraten vom See Genezareth in Bezug auf regionale Wetterdaten 2018-09-28T14:28:33+02:00 Andrea Miebach On the Probabilistic Evaluation of Decadal and Paleoclimate Model Predictions 2018-09-28T14:16:54+02:00 The development of climate prediction systems for years to decades is an area of current research, as these time scales are important e.g. for the planning horizon of decision-makers. Those prediction systems can be improved by including the knowledge of past climate states. To get a better understanding of climate variations, paleoclimate models simulate climate for certain periods in the past, often key periods such as the Last Glacial Maximum (21,000 years before present), the Mid-Holocene (6,000 years before present), etc. For both decadal and paleoclimate applications, ensembles of climate predictions (a set of predictions instead of the most likely one) are evaluated to quantify the uncertainty of the predictions. The verification of such ensemble climate predictions is an ongoing field in climate research. In this thesis, the quality of decadal and paleoclimate ensemble predictions is assessed by a probabilistic evaluation that comprises different attributes such as reliability/calibration and skill. Creating decadal climate predictions is challenging and still in an experimental stage due to little experiences (e.g. with the initialization of the model components) compared to weather forecasting. We consider three experiments (b1-LR, pr-GECCO, pr-ORA) of the MiKlip (Mittelfristige Klimaprognosen) decadal prediction system. These experiments differ in the way the atmospheric and oceanic model components are initialized, the number of ensemble members, etc. Each ensemble experiment is validated using one observational dataset, i.e. we assume no observational uncertainties. The threedimensional evaluation in the atmosphere and in the ocean shows skillful and reliable areas, especially in the subtropics and mid-latitudes. However, in all experiments, we detect deficiencies in the tropical Pacific region at higher altitudes, which may result from falsely generated dynamics in the model physics. For the ocean, we see clear differences between the experiments mostly caused by differences in the initialization data. In the Pacific and the subtropical belt around the equator, pr-GECCO outperforms b1-LR and pr-ORA also in deeper layers of the ocean whereas in the North Atlantic, b1-LR and pr-ORA are more reliable compared to pr-GECCO. Pollen and macrofossils in sediment cores provide the basis for the local reconstruction of vegetation and, thus, climate for a state in the past. We determine probabilistic information of the observed pollen by estimating botanical climate transfer functions using the generalized linear model. This probabilistic information is used to optimize a multi-model ensemble created from members of PMIP3 (Paleoclimate Modelling Intercomparison Project Phase 3). For the Mid-Holocene, summer temperatures change clearly (up to 0.4 K over land) when assimilating the PMIP3 multi-model ensemble to the observed pollen data. The added value is evidenced by the predominantly positive Brier skill scores (improvement of ca. 20% on average). Another approach to estimate climate transfer functions is the quadratic discriminant analysis as used in the Bayesian biome model. To apply the Bayesian biome model, the environmental vegetation needs to fulfill similar conditions as in the Dead Sea basin, where three vegetation zones (Mediterranean, Irano-Turanian, and Saharo-Arabian territory) are considered at the transition from arid to sub-humid climate. We apply the Bayesian biome model to a sediment core drilled at the Dead Sea, which encompasses the last ca. 220,000 years. For the Eemian warming phase (approx. 130,000 to 115,000 years before present), we find similar winter temperatures and annual precipitation as for today. For the Last Glacial, the reconstructed values show generally higher precipitation rates and lower winter temperatures compared to today's climate. Andrea Miebach Loess research and migration of early modern humans in southeastern and centraleastern Europe 2018-09-28T10:00:34+02:00 The CRC806 “Our way to Europe” archeological and geoscientific research projects focuses especially on loess sections in Europe. The detailed environmental context of Upper Paleolithic cultural evolution is still a matter of controversial debates, as most of its find horizons lack the required temporal and stratigraphic resolution (e.g. Kels et al., 2014). Well before the first Anatomically Modern Humans (AHM) dispersed into Europe around 40 ka, dry steppe environments dominated the wider Danube Basin. Here aeolian mineral dust accumulated as loess-paleosol sequences (LPS; e.g. Zeeden et al., 2016) forming the preservation matrix of Upper Paleolithic finds and structures. The reconstruction of paleoclimate variability based on grain size, geochemical and magnetic proxy parameters from LPS suggests a close match to isotopic ice core, speleothems, and sea surface temperature records resembling Greenland stadial-interstadial climatic fluctuations (Zeeden et al., in press; Obreht et al., 2017). This may provide a better chronostratigraphic framework and an environmental context for the archaeological findings. The late Quaternary archeological findings are usually found in short sections, while longer loess sections provide evidence of paleoenvironmental conditions. Establishing a catena from long lowland to short hillslope loess sections, we are aiming for a better understanding of human and climate interaction. Also, we present the late Quaternary Carpathian Basin as a specific context area of early modern human dispersal into Europe (Hauck et al., in press). The multitude of Early Upper Paleolithic sites in this region suggests that it was part of a major dispersal corridor along the Danube and within the catchment area of the Danube River some 40,000 years ago. An Aurignacian land-use model describes the interaction of early modern humans with their environment and specific eco-zones. To reconstruct the latter, paleo-environmental proxies and archaeological data are examined together in regional vector models and in a GIS-based archaeological landscape approach. Kels, H., Protze, J., Sitlivy, V., Hilgers, A., Zander, A., Anghelinu, M., Bertrams, M., Lehmkuhl, F. (2014): Genesis of loess-like sediments and soils at the foothills of the Banat Mountains, Romania – Examples from the Paleolithic sites Române ̧sti and Co ̧sava. Quaternary International, 351: 213-230. Hauck, T.C., Lehmkuhl, F., Zeeden, C., Bösken, J., Thiemann, A., Richter, J. (in press): The Aurignacian way of life: Contextualizing early modern human adaptation in the Carpathian Basin. - Quaternary International, doi: /10l1016/j.quaint.2017.10.020 Obreht, I., Hambach, U., Veres, D., Zeeden, C., Bösken, J., Stevens, T., Markovi ́ c, S.B., Klasen, N., Brill, D., Burow, C., Lehmkuhl, F. (2017): Shift of large-scale atmospheric systems over Europe during late MIS 3 and implications for Modern Human dispersal. Scientifc Reports 7: 5848 Zeeden, C., Kels, H., Hambach, U., Schulte, P., Protze, J., Eckmeier, E., Markovi ́ c, S.B., Klasen, N., Lehmkuhl, F. (2016): Three climatic cycles recorded in a loess-palaeosol sequence at Semlac (Romania) – Implications for dust accumulation in south-eastern Europe. Quaternary Science Reviews154: 130-142. Zeeden, C., Hambach, U., Veres, D., Fitzsimmons, K., Obreht, I., Bösken, J., Lehmkuhl, F., (in press): Millennial scale climate oscillations recorded in the Lower Danube loess over the last glacial period. Palaeogeogr. Palaeocli- matol. Palaeoecol., doi:/10.1016/j.palaeo.2016.12.029 Jonas Viehweger;Janina Bösken Vegetationsmodellierung in der Levante anhand rezenter Klimadaten 2018-09-28T09:51:53+02:00 Andrea Miebach