@article{RainerSeppeyHammeretal.2021, author = {Rainer, Edda M. and Seppey, Christophe Victor William and Hammer, Caroline and Svenning, Mette M. and Tveit, Alexander Tosdal}, title = {The influence of above-ground herbivory on the response of Arctic soil methanotrophs to increasing CH4 concentrations and temperatures}, series = {Microorganisms : open access journal}, volume = {9}, journal = {Microorganisms : open access journal}, number = {10}, publisher = {MDPI}, address = {Basel}, issn = {2076-2607}, doi = {10.3390/microorganisms9102080}, pages = {20}, year = {2021}, abstract = {Rising temperatures in the Arctic affect soil microorganisms, herbivores, and peatland vegetation, thus directly and indirectly influencing microbial CH4 production. It is not currently known how methanotrophs in Arctic peat respond to combined changes in temperature, CH4 concentration, and vegetation. We studied methanotroph responses to temperature and CH4 concentration in peat exposed to herbivory and protected by exclosures. The methanotroph activity was assessed by CH4 oxidation rate measurements using peat soil microcosms and a pure culture of Methylobacter tundripaludum SV96, qPCR, and sequencing of pmoA transcripts. Elevated CH4 concentrations led to higher CH4 oxidation rates both in grazed and exclosed peat soils, but the strongest response was observed in grazed peat soils. Furthermore, the relative transcriptional activities of different methanotroph community members were affected by the CH4 concentrations. While transcriptional responses to low CH4 concentrations were more prevalent in grazed peat soils, responses to high CH4 concentrations were more prevalent in exclosed peat soils. We observed no significant methanotroph responses to increasing temperatures. We conclude that methanotroph communities in these peat soils respond to changes in the CH4 concentration depending on their previous exposure to grazing. This "conditioning " influences which strains will thrive and, therefore, determines the function of the methanotroph community.}, language = {en} } @article{AldiyarovSokolovAkylbayevaetal.2020, author = {Aldiyarov, Abdurakhman and Sokolov, Dmitriy and Akylbayeva, Aigerim and Nurmukan, Assel and Tokmoldin, Nurlan}, title = {On thermal stability of cryovacuum deposited CH4+H2O films}, series = {Low temperature physics}, volume = {46}, journal = {Low temperature physics}, number = {11}, publisher = {American Institute of Physics}, address = {Melville}, issn = {1063-777X}, doi = {10.1063/10.0002156}, pages = {1121 -- 1124}, year = {2020}, abstract = {Whereas stable homogenous states of aqueous hydrocarbon solutions are typically observed at high temperatures and pressures far beyond the critical values corresponding to individual components, the stability of such system may be preserved upon transition into the region of metastable states at low temperatures and low pressures. This work is dedicated to the study of the thermal stability of a water-methane mixture formed by cryogenic vapor phase deposition. The obtained thin films were studied using vibrational spectroscopy in the temperature range of 16-180 K. During thermal annealing of the samples, characteristic vibrational C-H modes of methane were monitored alongside the chamber pressure to register both structural changes and desorption of the film material. The obtained results reveal that upon the co-deposition of methane and water, methane molecules appear both in non-bound and trapped states. The observed broadening of the characteristic C-H stretching mode at 3010 cm(-1) upon an increase in temperature of the sample from 16 to 90 K, followed by narrowing of the peak as the temperature is reduced back to 16 K, indicates localization of methane molecules within the water matrix at lower temperatures.}, language = {en} } @article{ReschkeKroenerLaepple2020, author = {Reschke, Maria and Kr{\"o}ner, Igor and Laepple, Thomas}, title = {Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records}, series = {Journal of quaternary science : JQS}, volume = {36}, journal = {Journal of quaternary science : JQS}, number = {1}, publisher = {Wiley}, address = {New York}, issn = {0267-8179}, doi = {10.1002/jqs.3245}, pages = {20 -- 28}, year = {2020}, abstract = {Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation.}, language = {en} } @article{LopezdeGuerenuKurganovaKlierHaubitzetal.2022, author = {L{\´o}pez de Guere{\~n}u Kurganova, Anna and Klier, Dennis Tobias and Haubitz, Toni and Kumke, Michael Uwe}, title = {Influence of Gd3+ doping concentration on the properties of Na(Y,Gd)F-4}, series = {Photochemical \& photobiological sciences / European Society for Photobiology}, volume = {21}, journal = {Photochemical \& photobiological sciences / European Society for Photobiology}, number = {2}, publisher = {Springer}, address = {Heidelberg}, issn = {1474-905X}, doi = {10.1007/s43630-021-00161-4}, pages = {235 -- 245}, year = {2022}, abstract = {We present a systematic study on the properties of Na(Y,Gd)F-4-based upconverting nanoparticles (UCNP) doped with 18\% Yb3+, 2\% Tm3+, and the influence of Gd3+ (10-50 mol\% Gd3+). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd3+ content was found, although the cubic phase was prevalent in most samples. The Tm3+-luminescence intensity as well as the Tm3+-luminescence decay times peaked at the Gd3+ concentration of 30 mol\%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes.}, language = {en} } @article{MardoukhiMardoukhiHokkaetal.2020, author = {Mardoukhi, Ahmad and Mardoukhi, Yousof and Hokka, Mikko and Kuokkala, Veli-Tapani}, title = {Effects of test temperature and low temperature thermal cycling on the dynamic tensile strength of granitic rocks}, series = {Rock mechanics and rock engineering}, volume = {54}, journal = {Rock mechanics and rock engineering}, number = {1}, publisher = {Springer}, address = {Wien}, issn = {0723-2632}, doi = {10.1007/s00603-020-02253-6}, pages = {443 -- 454}, year = {2020}, abstract = {This paper presents an experimental procedure for the characterization of the granitic rocks on a Mars-like environment. To gain a better understanding of the drilling conditions on Mars, the dynamic tensile behavior of the two granitic rocks was studied using the Brazilian disc test and a Split Hopkinson Pressure Bar. The room temperature tests were performed on the specimens, which had gone through thermal cycling between room temperature and - 70 degrees C for 0, 10, 15, and 20 cycles. In addition, the high strain rate Brazilian disc tests were carried out on the samples without the thermal cyclic loading at test temperatures of - 30 degrees C, - 50 degrees C, and - 70 degrees C. Microscopy results show that the rocks with different microstructures respond differently to cyclic thermal loading. However, decreasing the test temperature leads to an increasing in the tensile strength of both studied rocks, and the softening of the rocks is observed for both rocks as the temperature reaches - 70 degrees C. This paper presents a quantitative assessment of the effects of the thermal cyclic loading and temperature on the mechanical behavior of studied rocks in the Mars-like environment. The results of this work will bring new insight into the mechanical response of rock material in extreme environments.}, language = {en} } @phdthesis{Krummenauer2022, author = {Krummenauer, Linda}, title = {Global heat adaptation among urban populations and its evolution under different climate futures}, doi = {10.25932/publishup-55929}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-559294}, school = {Universit{\"a}t Potsdam}, pages = {xix, 161}, year = {2022}, abstract = {Heat and increasing ambient temperatures under climate change represent a serious threat to human health in cities. Heat exposure has been studied extensively at a global scale. Studies comparing a defined temperature threshold with the future daytime temperature during a certain period of time, had concluded an increase in threat to human health. Such findings however do not explicitly account for possible changes in future human heat adaptation and might even overestimate heat exposure. Thus, heat adaptation and its development is still unclear. Human heat adaptation refers to the local temperature to which populations are adjusted to. It can be inferred from the lowest point of the U- or V-shaped heat-mortality relationship (HMR), the Minimum Mortality Temperature (MMT). While epidemiological studies inform on the MMT at the city scale for case studies, a general model applicable at the global scale to infer on temporal change in MMTs had not yet been realised. The conventional approach depends on data availability, their robustness, and on the access to daily mortality records at the city scale. Thorough analysis however must account for future changes in the MMT as heat adaptation happens partially passively. Human heat adaptation consists of two aspects: (1) the intensity of the heat hazard that is still tolerated by human populations, meaning the heat burden they can bear and (2) the wealth-induced technological, social and behavioural measures that can be employed to avoid heat exposure. The objective of this thesis is to investigate and quantify human heat adaptation among urban populations at a global scale under the current climate and to project future adaptation under climate change until the end of the century. To date, this has not yet been accomplished. The evaluation of global heat adaptation among urban populations and its evolution under climate change comprises three levels of analysis. First, using the example of Germany, the MMT is calculated at the city level by applying the conventional method. Second, this thesis compiles a data pool of 400 urban MMTs to develop and train a new model capable of estimating MMTs on the basis of physical and socio-economic city characteristics using multivariate non-linear multivariate regression. The MMT is successfully described as a function of the current climate, the topography and the socio-economic standard, independently of daily mortality data for cities around the world. The city-specific MMT estimates represents a measure of human heat adaptation among the urban population. In a final third analysis, the model to derive human heat adaptation was adjusted to be driven by projected climate and socio-economic variables for the future. This allowed for estimation of the MMT and its change for 3 820 cities worldwide for different combinations of climate trajectories and socio-economic pathways until 2100. The knowledge on the evolution of heat adaptation in the future is a novelty as mostly heat exposure and its future development had been researched. In this work, changes in heat adaptation and exposure were analysed jointly. A wide range of possible health-related outcomes up to 2100 was the result, of which two scenarios with the highest socio-economic developments but opposing strong warming levels were highlighted for comparison. Strong economic growth based upon fossil fuel exploitation is associated with a high gain in heat adaptation, but may not be able to compensate for the associated negative health effects due to increased heat exposure in 30\% to 40\% of the cities investigated caused by severe climate change. A slightly less strong, but sustainable growth brings moderate gains in heat adaptation but a lower heat exposure and exposure reductions in 80\% to 84\% of the cities in terms of frequency (number of days exceeding the MMT) and intensity (magnitude of the MMT exceedance) due to a milder global warming. Choosing a 2 ° C compatible development by 2100 would therefore lower the risk of heat-related mortality at the end of the century. In summary, this thesis makes diverse and multidisciplinary contributions to a deeper understanding of human adaptation to heat under the current and the future climate. It is one of the first studies to carry out a systematic and statistical analysis of urban characteristics which are useful as MMT drivers to establish a generalised model of human heat adaptation, applicable at the global level. A broad range of possible heat-related health options for various future scenarios was shown for the first time. This work is of relevance for the assessment of heat-health impacts in regions where mortality data are not accessible or missing. The results are useful for health care planning at the meso- and macro-level and to urban- and climate change adaptation planning. Lastly, beyond having met the posed objective, this thesis advances research towards a global future impact assessment of heat on human health by providing an alternative method of MMT estimation, that is spatially and temporally flexible in its application.}, language = {en} } @misc{ReschkeKroenerLaepple2021, author = {Reschke, Maria and Kr{\"o}ner, Igor and Laepple, Thomas}, title = {Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-53819}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-538197}, pages = {20 -- 28}, year = {2021}, abstract = {Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation.}, language = {en} } @article{MantzoukiLurlingFastneretal.2018, author = {Mantzouki, Evanthia and Lurling, Miquel and Fastner, Jutta and Domis, Lisette Nicole de Senerpont and Wilk-Wozniak, Elzbieta and Koreiviene, Judita and Seelen, Laura and Teurlincx, Sven and Verstijnen, Yvon and Krzton, Wojciech and Walusiak, Edward and Karosiene, Jurate and Kasperoviciene, Jurate and Savadova, Ksenija and Vitonyte, Irma and Cillero-Castro, Carmen and Budzynska, Agnieszka and Goldyn, Ryszard and Kozak, Anna and Rosinska, Joanna and Szelag-Wasielewska, Elzbieta and Domek, Piotr and Jakubowska-Krepska, Natalia and Kwasizur, Kinga and Messyasz, Beata and Pelechata, Aleksandra and Pelechaty, Mariusz and Kokocinski, Mikolaj and Garcia-Murcia, Ana and Real, Monserrat and Romans, Elvira and Noguero-Ribes, Jordi and Parreno Duque, David and Fernandez-Moran, Elisabeth and Karakaya, Nusret and Haggqvist, Kerstin and Demir, Nilsun and Beklioglu, Meryem and Filiz, Nur and Levi, Eti E. and Iskin, Ugur and Bezirci, Gizem and Tavsanoglu, Ulku Nihan and Ozhan, Koray and Gkelis, Spyros and Panou, Manthos and Fakioglu, Ozden and Avagianos, Christos and Kaloudis, Triantafyllos and Celik, Kemal and Yilmaz, Mete and Marce, Rafael and Catalan, Nuria and Bravo, Andrea G. and Buck, Moritz and Colom-Montero, William and Mustonen, Kristiina and Pierson, Don and Yang, Yang and Raposeiro, Pedro M. and Goncalves, Vitor and Antoniou, Maria G. and Tsiarta, Nikoletta and McCarthy, Valerie and Perello, Victor C. and Feldmann, Tonu and Laas, Alo and Panksep, Kristel and Tuvikene, Lea and Gagala, Ilona and Mankiewicz-Boczek, Joana and Yagci, Meral Apaydin and Cinar, Sakir and Capkin, Kadir and Yagci, Abdulkadir and Cesur, Mehmet and Bilgin, Fuat and Bulut, Cafer and Uysal, Rahmi and Obertegger, Ulrike and Boscaini, Adriano and Flaim, Giovanna and Salmaso, Nico and Cerasino, Leonardo and Richardson, Jessica and Visser, Petra M. and Verspagen, Jolanda M. H. and Karan, Tunay and Soylu, Elif Neyran and Maraslioglu, Faruk and Napiorkowska-Krzebietke, Agnieszka and Ochocka, Agnieszka and Pasztaleniec, Agnieszka and Antao-Geraldes, Ana M. and Vasconcelos, Vitor and Morais, Joao and Vale, Micaela and Koker, Latife and Akcaalan, Reyhan and Albay, Meric and Maronic, Dubravka Spoljaric and Stevic, Filip and Pfeiffer, Tanja Zuna and Fonvielle, Jeremy Andre and Straile, Dietmar and Rothhaupt, Karl-Otto and Hansson, Lars-Anders and Urrutia-Cordero, Pablo and Blaha, Ludek and Geris, Rodan and Frankova, Marketa and Kocer, Mehmet Ali Turan and Alp, Mehmet Tahir and Remec-Rekar, Spela and Elersek, Tina and Triantis, Theodoros and Zervou, Sevasti-Kiriaki and Hiskia, Anastasia and Haande, Sigrid and Skjelbred, Birger and Madrecka, Beata and Nemova, Hana and Drastichova, Iveta and Chomova, Lucia and Edwards, Christine and Sevindik, Tugba Ongun and Tunca, Hatice and OEnem, Burcin and Aleksovski, Boris and Krstic, Svetislav and Vucelic, Itana Bokan and Nawrocka, Lidia and Salmi, Pauliina and Machado-Vieira, Danielle and de Oliveira, Alinne Gurjao and Delgado-Martin, Jordi and Garcia, David and Cereijo, Jose Luis and Goma, Joan and Trapote, Mari Carmen and Vegas-Vilarrubia, Teresa and Obrador, Biel and Grabowska, Magdalena and Karpowicz, Maciej and Chmura, Damian and Ubeda, Barbara and Angel Galvez, Jose and Ozen, Arda and Christoffersen, Kirsten Seestern and Warming, Trine Perlt and Kobos, Justyna and Mazur-Marzec, Hanna and Perez-Martinez, Carmen and Ramos-Rodriguez, Eloisa and Arvola, Lauri and Alcaraz-Parraga, Pablo and Toporowska, Magdalena and Pawlik-Skowronska, Barbara and Niedzwiecki, Michal and Peczula, Wojciech and Leira, Manel and Hernandez, Armand and Moreno-Ostos, Enrique and Maria Blanco, Jose and Rodriguez, Valeriano and Juan Montes-Perez, Jorge and Palomino, Roberto L. and Rodriguez-Perez, Estela and Carballeira, Rafael and Camacho, Antonio and Picazo, Antonio and Rochera, Carlos and Santamans, Anna C. and Ferriol, Carmen and Romo, Susana and Miguel Soria, Juan and Dunalska, Julita and Sienska, Justyna and Szymanski, Daniel and Kruk, Marek and Kostrzewska-Szlakowska, Iwona and Jasser, Iwona and Zutinic, Petar and Udovic, Marija Gligora and Plenkovic-Moraj, Andelka and Frak, Magdalena and Bankowska-Sobczak, Agnieszka and Wasilewicz, Michal and Ozkan, Korhan and Maliaka, Valentini and Kangro, Kersti and Grossart, Hans-Peter and Paerl, Hans W. and Carey, Cayelan C. and Ibelings, Bas W.}, title = {Temperature effects explain continental scale distribution of cyanobacterial toxins}, series = {Toxins}, volume = {10}, journal = {Toxins}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2072-6651}, doi = {10.3390/toxins10040156}, pages = {24}, year = {2018}, abstract = {Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.}, language = {en} } @article{BachmannHeimbachHassenruecketal.2018, author = {Bachmann, Jennifer and Heimbach, Tabea and Hassenr{\"u}ck, Christiane and Kopprio, German A. and Iversen, Morten Hvitfeldt and Grossart, Hans-Peter and G{\"a}rdes, Astrid}, title = {Environmental Drivers of Free-Living vs. Particle-Attached Bacterial Community Composition in the Mauritania Upwelling System}, series = {Frontiers in microbiology}, volume = {9}, journal = {Frontiers in microbiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-302X}, doi = {10.3389/fmicb.2018.02836}, pages = {13}, year = {2018}, abstract = {Saharan dust input and seasonal upwelling along North-West Africa provide a model system for studying microbial processes related to the export and recycling of nutrients. This study offers the first molecular characterization of prokaryotic particle-attached (PA; > 3.0 mu m) and free-living (FL; 0.2-3.0 mu m) players in this important ecosystem during August 2016. Environmental drivers for alpha-diversity, bacterial community composition, and differences between FL and PA fractions were identified. The ultra-oligotrophic waters off Senegal were dominated by Cyanobacteria while higher relative abundances of Alphaproteobacteria, Bacteroidetes, Verrucomicrobia, and Planctomycetes (known particle-degraders) occurred in the upwelling area. Temperature, proxy for different water masses, was the best predictor for changes in FL communities. PA community variation was best explained by temperature and ammonium. Bray Curtis dissimilarities between FL and PA were generally very high and correlated with temperature and salinity in surface waters. Greatest similarities between FL and PA occurred at the deep chlorophyll maximum, where bacterial substrate availability was likely highest. This indicates that environmental drivers do not only influence changes among FL and PA communities but also differences between them. This could provide an explanation for contradicting results obtained by different studies regarding the dissimilarity/similarity between FL and PA communities and their biogeochemical functions.}, language = {en} } @misc{PaulyHelleMiramontetal.2018, author = {Pauly, Maren and Helle, Gerhard and Miramont, C{\´e}cile and B{\"u}ntgen, Ulf and Treydte, Kerstin and Reinig, Frederick and Guibal, Fr{\´e}d{\´e}ric and Sivan, Olivier and Heinrich, Ingo and Riedel, Frank and Kromer, Bernd and Balanzategui, Daniel and Wacker, Lukas and Sookdeo, Adam Sookdeo and Brauer, Achim}, title = {Subfossil trees suggest enhanced Mediterranean hydroclimate variability at the onset of the Younger Dryas}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1135}, issn = {1866-8372}, doi = {10.25932/publishup-45916}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-459169}, pages = {10}, year = {2018}, abstract = {Nearly 13,000 years ago, the warming trend into the Holocene was sharply interrupted by a reversal to near glacial conditions. Climatic causes and ecological consequences of the Younger Dryas (YD) have been extensively studied, however proxy archives from the Mediterranean basin capturing this period are scarce and do not provide annual resolution. Here, we report a hydroclimatic reconstruction from stable isotopes (delta O-18, delta C-13) in subfossil pines from southern France. Growing before and during the transition period into the YD (12 900-12 600 cal BP), the trees provide an annually resolved, continuous sequence of atmospheric change. Isotopic signature of tree sourcewater (delta O-18(sw)) and estimates of relative air humidity were reconstructed as a proxy for variations in air mass origin and precipitation regime. We find a distinct increase in inter-annual variability of sourcewater isotopes (delta O-18(sw)), with three major downturn phases of increasing magnitude beginning at 12 740 cal BP. The observed variation most likely results from an amplified intensity of North Atlantic (low delta O-18(sw)) versus Mediterranean (high delta O-18(sw)) precipitation. This marked pattern of climate variability is not seen in records from higher latitudes and is likely a consequence of atmospheric circulation oscillations at the margin of the southward moving polar front.}, language = {en} }