@misc{BoersGoswamiGhil2017, author = {Boers, Niklas and Goswami, Bedartha and Ghil, Michael}, title = {A complete representation of uncertainties in layer-counted paleoclimatic archives}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {641}, issn = {1866-8372}, doi = {10.25932/publishup-41803}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418030}, pages = {12}, year = {2017}, abstract = {Accurate time series representation of paleoclimatic proxy records is challenging because such records involve dating errors in addition to proxy measurement errors. Rigorous attention is rarely given to age uncertainties in paleoclimatic research, although the latter can severely bias the results of proxy record analysis. Here, we introduce a Bayesian approach to represent layer-counted proxy records - such as ice cores, sediments, corals, or tree rings - as sequences of probability distributions on absolute, error-free time axes. The method accounts for both proxy measurement errors and uncertainties arising from layer-counting-based dating of the records. An application to oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record reveals that the counting errors, although seemingly small, lead to substantial uncertainties in the final representation of the oxygen isotope ratios. In particular, for the older parts of the NGRIP record, our results show that the total uncertainty originating from dating errors has been seriously underestimated. Our method is next applied to deriving the overall uncertainties of the Suigetsu radiocarbon comparison curve, which was recently obtained from varved sediment cores at Lake Suigetsu, Japan. This curve provides the only terrestrial radiocarbon comparison for the time interval 12.5-52.8 kyr BP. The uncertainties derived here can be readily employed to obtain complete error estimates for arbitrary radiometrically dated proxy records of this recent part of the last glacial interval.}, language = {en} } @article{Buerger2018, author = {B{\"u}rger, Gerd}, title = {A counterexample to decomposing climate shifts and trends by weather types}, series = {International Journal of Climatology}, volume = {38}, journal = {International Journal of Climatology}, number = {9}, publisher = {Wiley}, address = {Hoboken}, issn = {0899-8418}, doi = {10.1002/joc.5519}, pages = {3732 -- 3735}, year = {2018}, abstract = {The literature contains a sizable number of publications where weather types are used to decompose climate shifts or trends into contributions of frequency and mean of those types. They are all based on the product rule, that is, a transformation of a product of sums into a sum of products, the latter providing the decomposition. While there is nothing to argue about the transformation itself, its interpretation as a climate shift or trend decomposition is bound to fail. While the case of a climate shift may be viewed as an incomplete description of a more complex behaviour, trend decomposition indeed produces bogus trends, as demonstrated by a synthetic counterexample with well-defined trends in type frequency and mean. Consequently, decompositions based on that transformation, be it for climate shifts or trends, must not be used.}, language = {en} } @misc{MolnosMamdouhPetrietal.2017, author = {Molnos, Sonja and Mamdouh, Tarek and Petri, Stefan and Nocke, Thomas and Weinkauf, Tino and Coumou, Dim}, title = {A network-based detection scheme for the jet stream core}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {625}, issn = {1866-8372}, doi = {10.25932/publishup-41909}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-419099}, pages = {75 -- 89}, year = {2017}, abstract = {The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere midlatitudes. In particular, the polar jet is located between cold arctic air to the north and warmer subtropical air to the south. Strongly meandering states therefore often lead to extreme surface weather. Some algorithms exist which can detect the 2-D (latitude and longitude) jets' core around the hemisphere, but all of them use a minimal threshold to determine the subtropical and polar jet stream. This is particularly problematic for the polar jet stream, whose wind velocities can change rapidly from very weak to very high values and vice versa. We develop a network-based scheme using Dijkstra's shortest-path algorithm to detect the polar and subtropical jet stream core. This algorithm not only considers the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states. The parameter values of the detection scheme are optimized using simulated annealing and a skill function that accounts for the zonal-mean jet stream position (Rikus, 2015). After the successful optimization process, we apply our scheme to reanalysis data covering 1979-2015 and calculate seasonal-mean probabilistic maps and trends in wind strength and position of jet streams. We present longitudinally defined probability distributions of the positions for both jets for all on the Northern Hemisphere seasons. This shows that winter is characterized by two well-separated jets over Europe and Asia (ca. 20 degrees W to 140 degrees E). In contrast, summer normally has a single merged jet over the western hemisphere but can have both merged and separated jet states in the eastern hemisphere. With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and it is therefore very suitable to analyze jet stream patterns in observations and models, enabling more advanced model-validation.}, language = {en} } @article{HaugBerkhout2012, author = {Haug, Constanze and Berkhout, Frans}, title = {Abschied von KyotoPlus?}, series = {Klimapolitik International}, journal = {Klimapolitik International}, editor = {Kleinw{\"a}chter, Kai}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1868-6222}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-81355}, pages = {73 -- 81}, year = {2012}, abstract = {Die Ergebnisse des Klimagipfels von Kopenhagen sind eine bittere Entt{\"a}uschung f{\"u}r die EU. Ihr ist es nicht gelungen, ihren F{\"u}hrungsambitionen beim globalen Klimaschutz gerecht zu werden und die Konferenz zur Weichenstellung f{\"u}r ein rechtsverbindliches Klimaabkommen nach 2012 zu nutzen. Damit steht die Union vor grundlegenden strategischen Fragen zum Kurs ihrer Klimapolitik.}, language = {de} } @phdthesis{JimenezAlvaro2023, author = {Jim{\´e}nez {\´A}lvaro, Eliana}, title = {An{\´a}lisis neotect{\´o}nico y lito-tefroestratigr{\´a}fico de los grandes movimientos en masa asociados al fallamiento activo de la cuenca intermontana Quito-Guayllabamba, Ecuador}, doi = {10.25932/publishup-62220}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-622209}, school = {Universit{\"a}t Potsdam}, pages = {195}, year = {2023}, abstract = {Within the Quito-Guayllabamba intermontane basin of Ecuador, five unusually large colluvial deposits of ancient landslides have been identified and analyzed in this study. The voluminous rotational MM-5 Guayllabamba landslide is the largest one, with a volume of 1183 million m3. The mega debris-avalanches MM-1 Conocoto, MM-3 Oyacoto, and MM-4 San Francisco were originally triggered by an initial rupture that was associated with a rotational landslide, the corresponding deposits have volumes between 399 to 317 million m3. Finally, the deposit with the smallest volume, the MM-2 Bat{\´a}n rotational landslide and debris fall, has a volume of 8,7 million m3. In this thesis, a detailed study of these large mass movements was carried out using neotectonic and litho-tephrostratigraphic methods to understand the geological and geomorphological boundary conditions that might have been relevant for triggering such mass movements. The neotectonic part of the study was based on the qualitative and quantitative geomorphic analysis of these large mass-movement deposits through the structural characterization of anticlines located east of the Quito sub-basin and their collapsed flanks that constitute the break-off areas. This part of the analysis was furthermore supported by the application of different morphometric indices to reveal tectonically forced landscape evolution processes that may have aided mass-movement generation. The litho-tephrostratigraphic part of the study was based on the analysis of petrographic, geochemical, and geochronological characteristics of soil horizons and intercalated volcanic ashes with the aim to constrain the timing of individual mass-movement events and their potential correlation. The results were integrated into chronostratigraphic schemes using break-off surfaces, cross-cutting and superposition relationships of landslide deposits and subsequently deposited strata to understand the mass movements in the tectonic and temporal context of the intermontane basin setting, as well as to identify the triggering mechanisms for each event. The MM-5 Guayllabamba mass movement is the result of the collapse of the southwestern slope of the Mojanda volcano and was triggered by the interaction of geologic and morphologic conditions approximately 0,81 Ma. The first debris-avalanche episode of the MM-3 Oyacoto and MM-4 San Francisco mass movements could be related to both geological and morphological conditions, given the highly fractured rocks and uplift of the Bellavista-Catequilla anticline that was subsequently incised at the foot of the slope by fluvial erosion. This first episode of collapse most likely occurred around 0,8 Ma. The MM-2 Bat{\´a}n mass movement was possibly also facilitated by a combination of geological and morphological conditions, most likely associated with a reduction in the lithostatic stresses affecting the Chiche and Mach{\´a}ngara formations and an increase of shear stresses during lateral fluvial scouring processes at the flanks of the source areas. This points to a linked process between river erosion and uplift processes associated with the evolution of the El Bat{\´a}n-La Bota anticline that could have occurred between 0,5 and 0,25 Ma. The voluminous MM-1 Conocoto debris avalanche, as well as the second debris avalanche episode that generated the MM-3 Oyacoto and MM-4 San Francisco mass movements, were caused by the gravitational collapse of the Mojanda and Cangahua formations that are characterized by the intercalation of volcanic ashes. The failure of the eastern flank of the anticlines probably was associated with increased available humidity related to regional Holocene climatic variations. The results of paleosol chronology combined with regional chronostratigraphic and paleoclimate data suggests that these debris avalanches were triggered between 5 and 4 ka. Active tectonics has shaped the morphological features of the Quito-Guayllabamba intermontane basin. The triggering of mass movements in this environment is associated with failure of Pleistocene lithologies (lake sediments, alluvial and volcanic deposits) subjected to ongoing deformation processes, seismic activity, and superposed episodes of climate variability. The Metropolitan District of Quito is an integral part of this complex environment and the geological, climatic, and topographic conditions that continue to influence the urban geographic space within this intermontane basin. The city of Quito comprises the area with the largest urban consolidation including the sub-basins of Quito and San Antonio, with a population of 2,872 million inhabitants, reflecting the importance of studying the inherent geological and climatic hazards that this region is confronted with.}, language = {es} } @phdthesis{Aichner2009, author = {Aichner, Bernhard}, title = {Aquatic macrophyte-derived biomarkers as palaeolimnological proxies on the Tibetan Plateau}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42095}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {The Tibetan Plateau is the largest elevated landmass in the world and profoundly influences atmospheric circulation patterns such as the Asian monsoon system. Therefore this area has been increasingly in focus of palaeoenvironmental studies. This thesis evaluates the applicability of organic biomarkers for palaeolimnological purposes on the Tibetan Plateau with a focus on aquatic macrophyte-derived biomarkers. Submerged aquatic macrophytes have to be considered to significantly influence the sediment organic matter due to their high abundance in many Tibetan lakes. They can show highly 13C-enriched biomass because of their carbon metabolism and it is therefore crucial for the interpretation of δ13C values in sediment cores to understand to which extent aquatic macrophytes contribute to the isotopic signal of the sediments in Tibetan lakes and in which way variations can be explained in a palaeolimnological context. Additionally, the high abundance of macrophytes makes them interesting as potential recorders of lake water δD. Hydrogen isotope analysis of biomarkers is a rapidly evolving field to reconstruct past hydrological conditions and therefore of special relevance on the Tibetan Plateau due to the direct linkage between variations of monsoon intensity and changes in regional precipitation / evaporation balances. A set of surface sediment and aquatic macrophyte samples from the central and eastern Tibetan Plateau was analysed for composition as well as carbon and hydrogen isotopes of n-alkanes. It was shown how variable δ13C values of bulk organic matter and leaf lipids can be in submerged macrophytes even of a single species and how strongly these parameters are affected by them in corresponding sediments. The estimated contribution of the macrophytes by means of a binary isotopic model was calculated to be up to 60\% (mean: 40\%) to total organic carbon and up to 100\% (mean: 66\%) to mid-chain n-alkanes. Hydrogen isotopes of n-alkanes turned out to record δD of meteoric water of the summer precipitation. The apparent enrichment factor between water and n-alkanes was in range of previously reported ones (≈-130 per mille) at the most humid sites, but smaller (average: -86 per mille) at sites with a negative moisture budget. This indicates an influence of evaporation and evapotranspiration on δD of source water for aquatic and terrestrial plants. The offset between δD of mid- and long-chain n-alkanes was close to zero in most of the samples, suggesting that lake water as well as soil and leaf water are affected to a similar extent by those effects. To apply biomarkers in a palaeolimnological context, the aliphatic biomarker fraction of a sediment core from Lake Koucha (34.0° N; 97.2° E; eastern Tibetan Plateau) was analysed for concentrations, δ13C and δD values of compounds. Before ca. 8 cal ka BP, the lake was dominated by aquatic macrophyte-derived mid-chain n-alkanes, while after 6 cal ka BP high concentrations of a C20 highly branched isoprenoid compound indicate a predominance of phytoplankton. Those two principally different states of the lake were linked by a transition period with high abundances of microbial biomarkers. δ13C values were relatively constant for long-chain n-alkanes, while mid-chain n-alkanes showed variations between -23.5 to -12.6 per mille. Highest values were observed for the assumed period of maximum macrophyte growth during the late glacial and for the phytoplankton maximum during the middle and late Holocene. Therefore, the enriched values were interpreted to be caused by carbon limitation which in turn was induced by high macrophyte and primary productivity, respectively. Hydrogen isotope signatures of mid-chain n-alkanes have been shown to be able to track a previously deduced episode of reduced moisture availability between ca. 10 and 7 cal ka BP, indicated by a 20 per mille shift towards higher δD values. Indications for cooler episodes at 6.0, 3.1 and 1.8 cal ka BP were gained from drops of biomarker concentrations, especially microbial-derived hopanoids, and from coincidental shifts towards lower δ13C values. Those episodes correspond well with cool events reported from other locations on the Tibetan Plateau as well as in the Northern Hemisphere. To conclude, the study of recent sediments and plants improved the understanding of factors affecting the composition and isotopic signatures of aliphatic biomarkers in sediments. Concentrations and isotopic signatures of the biomarkers in Lake Koucha could be interpreted in a palaeolimnological context and contribute to the knowledge about the history of the lake. Aquatic macrophyte-derived mid-chain n-alkanes were especially useful, due to their high abundance in many Tibetan Lakes and their ability to record major changes of lake productivity and palaeo-hydrological conditions. Therefore, they have the potential to contribute to a fuller understanding of past climate variability in this key region for atmospheric circulation systems.}, language = {en} } @article{KraemerKleinwaechter2012, author = {Kr{\"a}mer, Raimund and Kleinw{\"a}chter, Kai}, title = {Brandenburg ist klimapolitisch gut aufgestellt!}, series = {Klimapolitik International}, journal = {Klimapolitik International}, editor = {Kleinw{\"a}chter, Kai}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1868-6222}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-81285}, pages = {11 -- 20}, year = {2012}, language = {de} } @article{Schroeder2012, author = {Schr{\"o}der, Miriam}, title = {China und Indien}, series = {Klimapolitik International}, journal = {Klimapolitik International}, editor = {Kleinw{\"a}chter, Kai}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1868-6222}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-81311}, pages = {41 -- 49}, year = {2012}, abstract = {Der Artikel analysiert die neue Rolle aufsteigender Schwellenl{\"a}nder in den internationalen Klimaverhandlungen am Beispiel Chinas und Indiens. Die Ablehnung verbindlicher Reduktionsziele f{\"u}r Treibhausgase wurde in Kopenhagen als Blockadepolitik beider L{\"a}nder gewertet. China und Indien k{\"o}nnen sich in ihrer Position behaupten, da ihr gestiegenes Gewicht in der multipolaren Weltordnung und die Unt{\"a}tigkeit f{\"u}hrender Industriel{\"a}nder ihre Verhandlungsposition st{\"a}rkt. Die Autorin diskutiert Kooperationsm{\"o}glichkeiten auf subnationaler Ebene, die die Blockadeposition nationaler Regierungen umgehen k{\"o}nnen.}, language = {de} } @article{MargirierBraunGautheronetal.2019, author = {Margirier, Audrey and Braun, Jean and Gautheron, Cecile and Carcaillet, Julien and Schwartz, Stephane and Jamme, Rosella Pinna and Stanley, Jessica}, title = {Climate control on Early Cenozoic denudation of the Namibian margin as deduced from new thermochronological constraints}, series = {Earth \& planetary science letters}, volume = {527}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2019.115779}, pages = {11}, year = {2019}, abstract = {The processes that control long term landscape evolution in continental interiors and, in particular, along passive margins such as in southern Africa, are still the subject of much debate (e.g. Braun, 2018). Although today the Namibian margin is characterized by an arid climate, it has experienced climatic fluctuations during the Cenozoic and, yet, to date no study has documented the potential role of climate on its erosion history. In western Namibia, the Brandberg Massif, an erosional remnant or inselberg, provides a good opportunity to document the Cenozoic denudation history of the margin using the relationship between rock cooling or exhumation ages and their elevation. Here we provide new apatite (UThSm)/He dates on the Brandberg Inselberg that range from 151 +/- 12 to 30 +/- 2 Ma. Combined with existing apatite fission track data, they yield new constraints on the denudation history of the margin. These data document two main cooling phases since continental break-up 130 Myr ago, a rapid one (similar to 10 degrees C/Myr) following break-up and a slower one (similar to 12 degrees C/Myr) between 65 and 35 Ma. We interpret them respectively to be related to escarpment erosion following rifting and continental break-up and as a phase of enhanced denudation during the Early Eocene Climatic Optimum. We propose that during the Early Eocene Climatic Optimum chemical weathering was important and contributed significantly to the denudation of the Namibian margin and the formation of a pediplain around the Brandberg and enhanced valley incision within the massif. Additionally, aridification of the region since 35 Ma has resulted in negligible denudation rates since that time. (C) 2019 Elsevier B.V. All rights reserved.}, language = {en} } @article{LauterbachWittPlessenetal.2014, author = {Lauterbach, Stefan and Witt, Roman and Plessen, Birgit and Dulski, Peter and Prasad, Sushma and Mingram, Jens and Gleixner, Gerd and Hettler-Riedel, Sabine and Stebich, Martina and Schnetger, Bernhard and Schwalb, Antje and Schwarz, Anja}, title = {Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years}, series = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, volume = {24}, journal = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, number = {8}, publisher = {Sage Publ.}, address = {London}, issn = {0959-6836}, doi = {10.1177/0959683614534741}, pages = {970 -- 984}, year = {2014}, abstract = {In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio) geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100-4350, 3450-2850, and 1900-1500 cal. yr BP. The distinct similar to 1500year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.}, language = {en} }