@article{GarcinDeschampsMenotetal.2018, author = {Garcin, Yannick and Deschamps, Pierre and Menot, Guillemette and de Saulieu, Geoffroy and Schefuss, Enno and Sebag, David and Dupont, Lydie M. and Oslisly, Richard and Brademann, Brian and Mbusnum, Kevin G. and Onana, Jean-Michel and Ako, Andrew A. and Epp, Laura Saskia and Tjallingii, Rik and Strecker, Manfred and Brauer, Achim and Sachse, Dirk}, title = {Early anthropogenic impact on Western Central African rainforests 2,600 y ago}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {115}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {13}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1715336115}, pages = {3261 -- 3266}, year = {2018}, abstract = {A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. delta D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.}, language = {en} } @article{RamischTjallingiiHartmannetal.2018, author = {Ramisch, Arne and Tjallingii, Rik and Hartmann, Kai and Diekmann, Bernhard and Brauer, Achim}, title = {Echo of the Younger Dryas in Holocene Lake Sediments on the Tibetan Plateau}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {20}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL080225}, pages = {154 -- 163}, year = {2018}, abstract = {Reading the sediment record in terms of past climates is challenging since linking climate change to the associated responses of sedimentary systems is not always straightforward. Here we analyze the erosional response of landscapes on the Tibetan Plateau to interglacial climate forcing. Using the theory of dynamical systems on Holocene time series of geochemical proxies, we derive a sedimentary response model that accurately simulates observed proxy variation in three lake records. The model suggests that millennial variations in sediment composition reflect a self-organization of landscapes in response to abrupt climate change between 11.6 and 11.9 ka BP. The self-organization is characterized by oscillations in sediment supply emerging from a feedback between physical and chemical erosion processes, with estimated response times between 3,000 to 18,000 years depending on catchment topography. The implications of our findings emphasize the need for landscape response models to decipher the paleoclimatic code in continental sediment records. Plain Language Summary Lake sediments are an important source of information on past climates. Reading the information is not always straightforward. Complex interactions in landscapes can affect the transmission of climatic signals to the sediment record. However, the exact nature of such complex interactions remains unknown. This study compares sediment deposits of three lakes on the Tibetan Plateau. The deposits are continuous records of landscape responses to climate change during the last 12,000 years. We identified a mathematical model that accurately simulates changes in sediment composition at all sites. The model simulations suggest that an abrupt warming at the end of the last glacial period destabilized the landscapes. This caused fluctuations in the transport of sediments, which persisted for several thousand years. Our findings present evidence for a long-lasting impact of abrupt climate change on fundamental Earth surface processes.}, language = {en} } @article{RamischTjallingiiHartmannetal.2018, author = {Ramisch, Arne and Tjallingii, Rik and Hartmann, Kai and Diekmann, Bernhard and Brauer, Achim}, title = {Echo of the Younger Dryas in Holocene Lake Sediments on the Tibetan Plateau}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {20}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL080225}, pages = {11154 -- 11163}, year = {2018}, abstract = {Reading the sediment record in terms of past climates is challenging since linking climate change to the associated responses of sedimentary systems is not always straightforward. Here we analyze the erosional response of landscapes on the Tibetan Plateau to interglacial climate forcing. Using the theory of dynamical systems on Holocene time series of geochemical proxies, we derive a sedimentary response model that accurately simulates observed proxy variation in three lake records. The model suggests that millennial variations in sediment composition reflect a self-organization of landscapes in response to abrupt climate change between 11.6 and 11.9 ka BP. The self-organization is characterized by oscillations in sediment supply emerging from a feedback between physical and chemical erosion processes, with estimated response times between 3,000 to 18,000 years depending on catchment topography. The implications of our findings emphasize the need for landscape response models to decipher the paleoclimatic code in continental sediment records. Plain Language Summary Lake sediments are an important source of information on past climates. Reading the information is not always straightforward. Complex interactions in landscapes can affect the transmission of climatic signals to the sediment record. However, the exact nature of such complex interactions remains unknown. This study compares sediment deposits of three lakes on the Tibetan Plateau. The deposits are continuous records of landscape responses to climate change during the last 12,000 years. We identified a mathematical model that accurately simulates changes in sediment composition at all sites. The model simulations suggest that an abrupt warming at the end of the last glacial period destabilized the landscapes. This caused fluctuations in the transport of sediments, which persisted for several thousand years. Our findings present evidence for a long-lasting impact of abrupt climate change on fundamental Earth surface processes.}, language = {en} } @misc{GarcinDeschampsMenotetal.2018, author = {Garcin, Yannick and Deschamps, Pierre and Menot, Guillemette and de Saulieu, Geoffroy and Schefuss, Enno and Sebag, David and Dupont, Lydie M. and Oslisly, Richard and Brademann, Brian and Mbusnum, Kevin G. and Onana, Jean-Michel and Ako, Andrew A. and Epp, Laura Saskia and Tjallingii, Rik and Strecker, Manfred and Brauer, Achim and Sachse, Dirk}, title = {Human activity is the most probable trigger of the late Holocene rainforest crisis in Western Central Africa Reply}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {115}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {21}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1805582115}, pages = {E4735 -- E4736}, year = {2018}, language = {en} } @misc{NeugebauerSchwabWaldmannetal.2016, author = {Neugebauer, Ina and Schwab, M. J. and Waldmann, Nicolas D. and Tjallingii, Rik and Frank, U. and Hadzhiivanova, E. and Naumann, R. and Taha, N. and Agnon, Amotz and Enzel, Y. and Brauer, Achim}, title = {Hydroclimatic variability in the Levant during the early last glacial (similar to 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {549}, issn = {1866-8372}, doi = {10.25932/publishup-41187}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-411879}, pages = {16}, year = {2016}, abstract = {The new sediment record from the deep Dead Sea basin (ICDP core 5017-1) provides a unique archive for hydroclimatic variability in the Levant. Here, we present high-resolution sediment facies analysis and elemental composition by micro-X-ray fluorescence (mu XRF) scanning of core 5017-1 to trace lake levels and responses of the regional hydroclimatology during the time interval from ca. 117 to 75 ka, i. e. the transition between the last interglacial and the onset of the last glaciation. We distinguished six major micro-facies types and interpreted these and their alterations in the core in terms of relative lake level changes. The two end-member facies for highest and lowest lake levels are (a) up to several metres thick, greenish sediments of alternating aragonite and detrital marl laminae (aad) and (b) thick halite facies, respectively. Intermediate lake levels are characterised by detrital marls with varying amounts of aragonite, gypsum or halite, reflecting lower-amplitude, shorter-term variability. Two intervals of pronounced lake level drops occurred at similar to 110-108 +/- 5 and similar to 93-87 +/- 7 ka. They likely coincide with stadial conditions in the central Mediterranean (Melisey I and II pollen zones in Monticchio) and low global sea levels during Marine Isotope Stage (MIS) 5d and 5b. However, our data do not support the current hypothesis of an almost complete desiccation of the Dead Sea during the earlier of these lake level low stands based on a recovered gravel layer. Based on new petrographic analyses, we propose that, although it was a low stand, this well-sorted gravel layer may be a vestige of a thick turbidite that has been washed out during drilling rather than an in situ beach deposit. Two intervals of higher lake stands at similar to 108-93 +/- 6 and similar to 87-75 +/- 7 ka correspond to interstadial conditions in the central Mediterranean, i. e. pollen zones St. Germain I and II in Monticchio, and Greenland interstadials (GI) 24+23 and 21 in Greenland, as well as to sapropels S4 and S3 in the Mediterranean Sea. These apparent correlations suggest a close link of the climate in the Levant to North Atlantic and Mediterranean climates during the time of the build-up of Northern Hemisphere ice shields in the early last glacial period.}, language = {en} } @article{NeugebauerSchwabWaldmannetal.2016, author = {Neugebauer, I. and Schwab, M. J. and Waldmann, N. D. and Tjallingii, Rik and Frank, U. and Hadzhiivanova, E. and Naumann, R. and Taha, N. and Agnon, A. and Enzel, Y. and Brauer, Achim}, title = {Hydroclimatic variability in the Levant during the early last glacial (similar to 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments}, series = {Climate of the past : an interactive open access journal of the European Geosciences Union}, volume = {12}, journal = {Climate of the past : an interactive open access journal of the European Geosciences Union}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1814-9324}, doi = {10.5194/cp-12-75-2016}, pages = {75 -- 90}, year = {2016}, abstract = {The new sediment record from the deep Dead Sea basin (ICDP core 5017-1) provides a unique archive for hydroclimatic variability in the Levant. Here, we present high-resolution sediment facies analysis and elemental composition by micro-X-ray fluorescence (mu XRF) scanning of core 5017-1 to trace lake levels and responses of the regional hydroclimatology during the time interval from ca. 117 to 75 ka, i. e. the transition between the last interglacial and the onset of the last glaciation. We distinguished six major micro-facies types and interpreted these and their alterations in the core in terms of relative lake level changes. The two end-member facies for highest and lowest lake levels are (a) up to several metres thick, greenish sediments of alternating aragonite and detrital marl laminae (aad) and (b) thick halite facies, respectively. Intermediate lake levels are characterised by detrital marls with varying amounts of aragonite, gypsum or halite, reflecting lower-amplitude, shorter-term variability. Two intervals of pronounced lake level drops occurred at similar to 110-108 +/- 5 and similar to 93-87 +/- 7 ka. They likely coincide with stadial conditions in the central Mediterranean (Melisey I and II pollen zones in Monticchio) and low global sea levels during Marine Isotope Stage (MIS) 5d and 5b. However, our data do not support the current hypothesis of an almost complete desiccation of the Dead Sea during the earlier of these lake level low stands based on a recovered gravel layer. Based on new petrographic analyses, we propose that, although it was a low stand, this well-sorted gravel layer may be a vestige of a thick turbidite that has been washed out during drilling rather than an in situ beach deposit. Two intervals of higher lake stands at similar to 108-93 +/- 6 and similar to 87-75 +/- 7 ka correspond to interstadial conditions in the central Mediterranean, i. e. pollen zones St. Germain I and II in Monticchio, and Greenland interstadials (GI) 24+23 and 21 in Greenland, as well as to sapropels S4 and S3 in the Mediterranean Sea. These apparent correlations suggest a close link of the climate in the Levant to North Atlantic and Mediterranean climates during the time of the build-up of Northern Hemisphere ice shields in the early last glacial period.}, language = {en} } @article{DraegerPlessenKieneletal.2019, author = {Dr{\"a}ger, Nadine and Plessen, Birgit and Kienel, Ulrike and Siowinski, Michat and Ramisch, Arne and Tjallingii, Rik and Pinkerneil, Sylvia and Brauer, Achim}, title = {Hypolimnetic oxygen conditions influence varve preservation and delta C-13 of sediment organic matter in Lake Tiefer See, NE Germany}, series = {Journal of paleolimnolog}, volume = {62}, journal = {Journal of paleolimnolog}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-019-00084-2}, pages = {181 -- 194}, year = {2019}, abstract = {Stable carbon isotopes of sediment organic matter (delta C-13(OM)) are widely applied in paleoenvironmental studies. Interpretations of delta C-13(OM), however, remain challenging and factors that influence delta C-13(OM) may not apply across all lakes. Common explanations for stratigraphic shifts in delta C-13(OM) include changes in lake productivity or changes in inputs of allochthonous OM. We investigated the influence of different oxygen conditions (oxic versus anoxic) on the delta C-13(OM) values in the sediments of Lake Tiefer See. We analysed (1) a long sediment core from the deepest part of the lake, (2) two short, sediment-water interface cores from shallower water depths, and (3) OM in the water column, i.e. from sediment traps. Fresh OM throughout the entire water column showed a relatively constant delta C-13(OM) value of approximately -30.5 parts per thousand. Similar values, about -31 parts per thousand, were obtained for well-varved sediments in both the long and short, sediment-water interface cores. In contrast, delta C-13(OM) values from non-varved sediments in all cores were significantly less negative (-29 parts per thousand). The delta C-13(OM) values in the sediment-water interface cores from different water depths differ for sediments of the same age, if oxygen conditions at the time of deposition were different at these sites, as suggested by the state of varve preservation. Sediments deposited from AD 1924 to 1980 at 62m water depth are varved and exhibit delta C-13(OM) values around -31 parts per thousand, whereas sediments of the same age in the core from 35m water depth are not varved and show less negative delta C-13(OM) values of about -29 parts per thousand. The relation between varve occurrence and delta C-13(OM) values suggests that delta C-13(OM) is associated with oxygen conditions because varve preservation depends on hypolimnetic anoxia. A mechanism that likely influences delta C-13(OM) is selective degradation of OM under oxic conditions, such that organic components with more negative delta C-13(OM) are preferably decomposed, leading to less negative delta C-13(OM) values in the remaining, undegraded OM pool. Greater decomposition of OM in non-varved sediments is supported by lower TOC concentrations in these deposits (similar to 5\%) compared to well-varved sediments (similar to 15\%). Even in lakes that display small variations in productivity and terrestrial OM input through time, large spatial and temporal differences in hypolimnetic oxygen concentrations may be an important factor controlling sediment delta C-13(OM).}, language = {en} } @article{MuellerTjallingiiPlocienniketal.2021, author = {M{\"u}ller, Daniela and Tjallingii, Rik and Plociennik, Mateusz and Luoto, Tomi P. and Kotrys, Bartosz and Plessen, Birgit and Ramisch, Arne and Schwab, Markus Julius and Blaszkiewicz, Miroslaw and Slowinski, Michal and Brauer, Achim}, title = {New insights into lake responses to rapid climate change}, series = {Boreas}, volume = {50}, journal = {Boreas}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0300-9483}, doi = {10.23689/fidgeo-4033}, pages = {535 -- 555}, year = {2021}, abstract = {The sediment profile from Lake Goscia(z) over dot in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Goscia(z) over dot presented here spans 1662 years from the late Allerod (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/-22 years, which confirms previous results of 1140 +/- 40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted similar to 180 years, which is about a century longer than the terminal warming that was completed in similar to 70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by similar to 90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.}, language = {en} } @misc{MuellerTjallingiiPlocienniketal.2021, author = {M{\"u}ller, Daniela and Tjallingii, Rik and Plociennik, Mateusz and Luoto, Tomi P. and Kotrys, Bartosz and Plessen, Birgit and Ramisch, Arne and Schwab, Markus Julius and Blaszkiewicz, Miroslaw and Slowinski, Michal and Brauer, Achim}, title = {New insights into lake responses to rapid climate change}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {2}, issn = {0300-9483}, doi = {10.25932/publishup-56338}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-563386}, pages = {23}, year = {2021}, abstract = {The sediment profile from Lake Goscia(z) over dot in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Goscia(z) over dot presented here spans 1662 years from the late Allerod (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/-22 years, which confirms previous results of 1140 +/- 40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted similar to 180 years, which is about a century longer than the terminal warming that was completed in similar to 70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by similar to 90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.}, language = {en} } @misc{GarcinDeschampsMenotetal.2018, author = {Garcin, Yannick and Deschamps, Pierre and Menot, Guillemette and de Saulieu, Geoffroy and Schefuss, Enno and Sebag, David and Dupont, Lydie M. and Oslisly, Richard and Brademann, Brian and Mbusnum, Kevin G. and Onana, Jean-Michel and Ako, Andrew A. and Epp, Laura Saskia and Tjallingii, Rik and Strecker, Manfred and Brauer, Achim and Sachse, Dirk}, title = {No evidence for climate variability during the late Holocene rainforest crisis in Western Central Africa REPLY}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {115}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {29}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1808481115}, pages = {E6674 -- E6675}, year = {2018}, language = {en} }