@article{BenDorNeugebauerEnzeletal.2019, author = {Ben Dor, Yoav and Neugebauer, Ina and Enzel, Yehouda and Schwab, Markus Julius and Tjallingii, Rik and Erel, Yigal and Brauer, Achim}, title = {Varves of the Dead Sea sedimentary record}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {215}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2019.04.011}, pages = {173 -- 184}, year = {2019}, abstract = {The sedimentary record of the Dead Sea provides an exceptional high-resolution archive of past climate changes in the drought-sensitive eastern Mediterranean-Levant, a key region for the development of humankind at the boundary of global climate belts. Moreover, it is the only deep hypersaline lake known to have deposited long sequences of finely laminated, annually deposited sediments (i.e. varves) of varied compositions, including aragonite, gypsum, halite and clastic sediments. Vast efforts have been made over the years to decipher the environmental information stored in these evaporitic-clastic sequences spanning from the Pleistocene Lake Amora to the Holocene Dead Sea. A general characterisation of sediment facies has been derived from exposed sediment sections, as well as from shallow- and deep-water sediment cores. During high lake stands and episodes of positive water budget, mostly during glacial times, alternating aragonite and detritus laminae ('aad' facies) were accumulated, whereas during low lake stands and droughts, prevailing during interglacials, laminated detritus ('ld' facies) and laminated halite ('lh' facies) dominate the sequence. In this paper, we (i) review the three types of laminated sediments of the Dead Sea sedimentary record ('aad', 'ld' and 'lh' facies), (ii) discuss their modes of formation, deposition and accumulation, and their interpretation as varves, and (iii) illustrate how Dead Sea varves are utilized for palaeoclimate reconstructions and for establishing floating chronologies.}, language = {en} } @article{BenDorFlaxLevitanetal.2021, author = {Ben Dor, Yoav and Flax, Tomer and Levitan, Itamar and Enzel, Yehouda and Brauer, Achim and Erel, Yigal}, title = {The paleohydrological implications of aragonite precipitation under contrasting climates in the endorheic Dead Sea and its precursors revealed by experimental investigations}, series = {Chemical geology : official journal of the European Association for Geochemistry}, volume = {576}, journal = {Chemical geology : official journal of the European Association for Geochemistry}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2541}, doi = {10.1016/j.chemgeo.2021.120261}, pages = {18}, year = {2021}, abstract = {Carbonate minerals are common in both marine and lacustrine records, and are frequently used for paleoenvironmental reconstructions. The sedimentary sequence of the endorheic Dead Sea and its precursors contain aragonite laminae that provide a detailed sedimentary archive of climatic, hydrologic, limnologic and environmental conditions since the Pleistocene. However, the interpretation of these archives requires a detailed understanding of the constraints and mechanisms affecting CaCO3 precipitation, which are still debated. The implications of aragonite precipitation in the Dead Sea and in its late Pleistocene predecessor (Lake Lisan) were investigated in this study by mixing natural and synthetic brines with a synthetic bicarbonate solution that mimics flash-floods composition, with and without the addition of extracellular polymeric substances (EPS). Aragonite precipitation was monitored, and precipitation rates and carbonate yields were calculated and are discussed with respect to modern aquatic environments. The experimental insights on aragonite precipitation are then integrated with microfacies analyses in order to reconstruct and constrain prevailing limnogeological processes and their hydroclimatic drivers under low (interglacial) and high (glacial) lake level stands. Aragonite precipitation took place within days to several weeks after the mixing of the brines with a synthetic bicarbonate solution. Incubation time was proportional to bicarbonate concentration, and precipitation rates were partially influenced by ionic strength. Additionally, extracellular polymeric substances inhibited aragonite precipitation for several months. As for the lake's water budget, our calculations suggest that the precipitation of a typical aragonite lamina (0.5 mm thick) during high lake stand requires unreasonable freshwater inflow from either surface or subsurface sources. This discrepancy can be resolved by considering one or a combination of the following scenarios; (1) discontinuous aragonite deposition over parts of the lake floor; (2) supply of additional carbonate flux (or fluxes) to the lake from aeolian dust and the remobilization and dissolution of dust deposits at the watershed; (3) carbonate production via oxidation of organic carbon by sulfate-reducing bacteria. Altogether, it is suggested that aragonite laminae thickness cannot be directly interpreted for quantitatively reconstructing the hydrological balance for the entire lake, they may still prove valuable for identifying inherent hydroclimatic periodicities at a single site.}, language = {en} } @article{AnoopPrasadBasavaiahetal.2012, author = {Anoop, A. and Prasad, S. and Basavaiah, Nathani and Brauer, Achim and Shahzad, F. and Deenadayalan, K.}, title = {Tectonic versus climate influence on landscape evolution: A case study from the upper Spiti valley, NW Himalaya}, series = {Geomorphology : an international journal on pure and applied geomorphology}, volume = {145}, journal = {Geomorphology : an international journal on pure and applied geomorphology}, number = {4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2011.10.028}, pages = {32 -- 44}, year = {2012}, abstract = {We have undertaken structural, geomorphological, and morphometric analyses to investigate the role of tectonism and climate in the landscape evolution in the upper Spiti valley, NW Himalayas. Geomorphometric analyses coupled with field investigations reveal active tectonic deformation in the Spiti region. The calculated geomorphic indices (steepness, concavity and Hack) demonstrate uplift/subsidence along the Kaurik-Chango fault, whereas transverse topographic index (T-index) reveals basin tilting associated with active faulting near Hansa and Lingti valley. Investigation of well-dated Mane palaeolake sediments also provides evidence of regional tectonic instability. Four episodes (ca. 7.8, 7.4, 6.5 and 6.1 cal ka) of neotectonic activity have been identified during the period of the lake's existence. We have also compiled data on the regional climate variability and compared it with the age of the Mane palaeo-landslide. Our results indicate that the landslide occurred towards the end of the early Holocene intensified monsoon phase and is located near an active fault. Our data on regional tectonic instability and the coincidences of modern and palaeo-landslides with zones of active deformation suggest that tectonism is an important factor governing landscape stability in the Spiti region.}, language = {en} } @article{PaulyHelleMiramontetal.2018, author = {Pauly, Maren and Helle, Gerhard and Miramont, Cecile and Buentgen, Ulf and Treydte, Kerstin and Reinig, Frederick and Guibal, Frederic and Sivan, Olivier and Heinrich, Ingo and Riedel, Frank and Kromer, Bernd and Balanzategui, Daniel and Wacker, Lukas and Sookdeo, Adam and Brauer, Achim}, title = {Subfossil trees suggest enhanced Mediterranean hydroclimate variability at the onset of the Younger Dryas}, series = {Scientific reports}, volume = {8}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-018-32251-2}, pages = {8}, 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} } @article{EngelsBrauerBuddelmeijeretal.2016, author = {Engels, Stefan and Brauer, Achim and Buddelmeijer, Nico and Martin-Puertas, Celia and Rach, Oliver and Sachse, Dirk and Van Geel, Bas}, title = {Subdecadal-scale vegetation responses to a previously unknown late-Allerod climate fluctuation and Younger Dryas cooling at Lake Meerfelder Maar (Germany)}, series = {Journal of quaternary science}, volume = {31}, journal = {Journal of quaternary science}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0267-8179}, doi = {10.1002/jqs.2900}, pages = {741 -- 752}, year = {2016}, abstract = {Lake Meerfelder Maar (MFM) is the northernmost Western European sediment record with annual laminations across the Younger Dryas (YD), and the onset of the YD in the record of MFM has previously been defined as an increase in non-arboreal pollen abundance at ca. 12 680 varve a BP. Here we present a palynological record at unprecedented subdecadal resolution for MFM, covering the Allerod-YD transition. Our results show a fluctuation in pollen accumulation rates (PARs) before the onset of the YD, with lower rates between ca. 12 725 and 12 685 varve a BP. The fluctuation in PARs occurs simultaneous with a previously undescribed short fluctuation in sediment composition and varve thickness, as well as with changes in biogeochemical proxies. The combined evidence indicates signs of climatic instability ca. 45 years before the onset of the YD. The PAR records of Betula and Pinus furthermore show earlier and more abrupt changes at the onset of the YD than the percentage-records do. Finally, heliophilous herbaceous taxa show a delayed increase following the onset of the YD of ca. 145 years. This paper illustrates the potential to identify previously unrecognized climate variability and vegetation change when using subdecadal-resolution analyses. Copyright (C) 2016 John Wiley \& Sons, Ltd.}, language = {en} } @article{KaempfPlessenLauterbachetal.2019, author = {K{\"a}mpf, Lucas and Plessen, Birgit and Lauterbach, Stefan and Nantke, Carla and Meyer, Hanno and Chapligin, Bernhard and Brauer, Achim}, title = {Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy}, series = {Geology / the Geological Society of America}, volume = {48}, journal = {Geology / the Geological Society of America}, number = {1}, publisher = {American Institute of Physics}, address = {Melville, NY}, issn = {1943-2682}, doi = {10.1130/G46593.1}, pages = {3 -- 7}, year = {2019}, abstract = {Lake sediments are increasingly explored as reliable paleoflood archives. In addition to established flood proxies including detrital layer thickness, chemical composition, and grain size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria), we integrate high-resolution sediment trapping at a proximal and a distal location and stable isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux. First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in the sediment trap record covering the period 2011-2013 CE including 22 events with daily (hourly) peak runoff ranging from 10 (24) m(3) s(-1) to 79 (110) m(3) s(-1). The three- to ten-fold lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated peaks in the stable isotope values of trapped sediments. Next, we show that all nine flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated isotope values compared with endogenic calcite. In addition, even two runoff events that did not cause the deposition of visible detrital layers are distinguished by higher isotope values. Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of floods, although in some cases flood magnitudes are overestimated because local effects can result in too-high isotope values. Hence we present a proof of concept for stable isotopes as reliable tool for reconstructing flood frequency and, although with some limitations, even for flood magnitudes.}, language = {en} } @article{NwosuRoeserYangetal.2021, author = {Nwosu, Ebuka Canisius and Roeser, Patricia Angelika and Yang, Sizhong and Pinkerneil, Sylvia and Ganzert, Lars and Dittmann, Elke and Brauer, Achim and Wagner, Dirk and Liebner, Susanne}, title = {Species-level spatio-temporal dynamics of cyanobacteria in a hard-water temperate lake in the Southern Baltics}, series = {Frontiers in microbiology}, volume = {12}, journal = {Frontiers in microbiology}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {1664-302X}, doi = {10.3389/fmicb.2021.761259}, pages = {17}, year = {2021}, abstract = {Cyanobacteria are important primary producers in temperate freshwater ecosystems. However, studies on the seasonal and spatial distribution of cyanobacteria in deep lakes based on high-throughput DNA sequencing are still rare. In this study, we combined monthly water sampling and monitoring in 2019, amplicon sequence variants analysis (ASVs; a proxy for different species) and quantitative PCR targeting overall cyanobacteria abundance to describe the seasonal and spatial dynamics of cyanobacteria in the deep hard-water oligo-mesotrophic Lake Tiefer See, NE Germany. We observed significant seasonal variation in the cyanobacterial community composition (p < 0.05) in the epi- and metalimnion layers, but not in the hypolimnion. In winter-when the water column is mixed-picocyanobacteria (Synechococcus and Cyanobium) were dominant. With the onset of stratification in late spring, we observed potential niche specialization and coexistence among the cyanobacteria taxa driven mainly by light and nutrient dynamics. Specifically, ASVs assigned to picocyanobacteria and the genus Planktothrix were the main contributors to the formation of deep chlorophyll maxima along a light gradient. While Synechococcus and different Cyanobium ASVs were abundant in the epilimnion up to the base of the euphotic zone from spring to fall, Planktothrix mainly occurred in the metalimnetic layer below the euphotic zone where also overall cyanobacteria abundance was highest in summer. Our data revealed two potentially psychrotolerant (cold-adapted) Cyanobium species that appear to cope well under conditions of lower hypolimnetic water temperature and light as well as increasing sediment-released phosphate in the deeper waters in summer. The potential cold-adapted Cyanobium species were also dominant throughout the water column in fall and winter. Furthermore, Snowella and Microcystis-related ASVs were abundant in the water column during the onset of fall turnover. Altogether, these findings suggest previously unascertained and considerable spatiotemporal changes in the community of cyanobacteria on the species level especially within the genus Cyanobium in deep hard-water temperate lakes.}, language = {en} } @article{SarkarWilkesPrasadetal.2014, author = {Sarkar, Saswati and Wilkes, Heinz and Prasad, Sushma and Brauer, Achim and Riedel, Nils and Stebich, Martina and Basavaiah, Nathani and Sachse, Dirk}, title = {Spatial heterogeneity in lipid biomarker distributions in the catchment and sediments of a crater lake in central India}, series = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, volume = {66}, journal = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, publisher = {Elsevier}, address = {Oxford}, issn = {0146-6380}, doi = {10.1016/j.orggeochem.2013.11.009}, pages = {125 -- 136}, year = {2014}, abstract = {The basin-scale spatial variability in lipid biomarker proxies in lacustrine sediments, which are established tools for studying continental environmental change, has rarely been examined. It is often implicitly assumed that a lake sediment core provides an average integral of catchment sources. Here we evaluated the distribution of lipid biomarkers in a modern ecosystem and compared it with the sedimentary record. We analyzed lipid biomarkers in terrestrial and aquatic organisms and in lake surface sediments from 17 locations within the saline-alkaline Lonar crater lake in central India. Terrestrial vegetation and lake surface sediments were characterized by relatively high average chain length (ACL) index values (29.6-32.8) of leaf wax n-alkanes, consistent with suggestions that plants in drier and warmer climates produce longer chain alkyl lipids than plants in cooler and humid areas. A heterogeneous spatial distribution of ACL values in lake surface sediments was found: at locations away from the shore, the values were highest (31 or more), possibly indicating different sources and/or transport of terrestrial biomarkers. In floating, benthic microbial mats and surface sediment, n-heptadecane, carotenoids, diploptene, phytol and tetrahymanol occurred in large amounts. Interestingly, these biomarkers of a unique bacterial community were found in substantially higher concentrations in nearshore sediment samples. We suggest that human influence and subsequent nutrient supply resulted in increased primary productivity, leading to an unusually high concentration of tetrahymanol in the nearshore sediments. In summary, the data showed that substantial heterogeneity existed within the lake, but leaf wax n-alkanes in a core from the center of the lake represented an integral of catchment conditions. However, lake level fluctuation may potentially affect aquatic lipid biomarker distributions in lacustrine sediments, in addition to source changes.}, language = {en} } @article{BenDorNeugebauerEnzeletal.2020, author = {Ben Dor, Yoav and Neugebauer, Ina and Enzel, Yehouda and Schwab, Markus J. and Tjallingii, Rik and Erel, Yigal and Brauer, Achim}, title = {Reply to comment on: Ben Dor, Yoav et al. : Varves of the Dead Sea sedimentary record. - In: Quaternary science reviews : the international multidisciplinary research and review journal. - 215 (2019), S. 173 - 184. - (ISSN: 0277-3791). - https://doi.org/10.1016/j.quascirev.2019.04.011}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {231}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Amsterdam [u.a.]}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2019.106063}, pages = {5}, year = {2020}, abstract = {In the comment on "Varves of the Dead Sea sedimentary record." Quaternary Science Reviews 215 (Ben Dor et al., 2019): 173-184. by R. Bookman, two recently published papers are suggested to prove that the interpretation of the laminated sedimentary sequence of the Dead Sea, deposited mostly during MIS2 and Holocene pluvials, as annual deposits (i.e., varves) is wrong. In the following response, we delineate several lines of evidence which coalesce to demonstrate that based on the vast majority of evidence, including some of the evidence provided in the comment itself, the interpretation of these sediments as varves is the more likely scientific conclusion. We further discuss the evidence brought up in the comment and its irrelevance and lack of robustness for addressing the question under discussion.}, language = {en} } @article{WolffHaugTimmermannetal.2011, author = {Wolff, Christian Michael and Haug, Gerald H. and Timmermann, Axel and Damste, Jaap S. Sinninghe and Brauer, Achim and Sigman, Daniel M. and Cane, Mark A. and Verschuren, Dirk}, title = {Reduced interannual rainfall variability in East Africa during the last Ice Age}, series = {Science}, volume = {333}, journal = {Science}, number = {6043}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.1203724}, pages = {743 -- 747}, year = {2011}, abstract = {Interannual rainfall variations in equatorial East Africa are tightly linked to the El Nino Southern Oscillation (ENSO), with more rain and flooding during El Nino and droughts in La Nina years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall.}, language = {en} } @article{BasavaiahWiesnerAnoopetal.2014, author = {Basavaiah, Nathani and Wiesner, M. G. and Anoop, Ambili and Menzel, P. and Nowaczyk, Norbert R. and Deenadayalan, K. and Brauer, Achim and Gaye, Birgit and Naumann, R. and Riedel, N. and Stebich, M. and Prasad, Sushma}, title = {Physicochemical analyses of surface sediments from the Lonar Lake, central India - implications for palaeoenvironmental reconstruction}, series = {Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology}, volume = {184}, journal = {Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology}, number = {1}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {1863-9135}, doi = {10.1127/1863-9135/2014/0515}, pages = {51 -- 68}, year = {2014}, abstract = {We report the results of our investigations on the catchment area, surface sediments, and hydrology of the monsoonal Lonar Lake, central India. Our results indicate that the lake is currently stratified with an anoxic bottom layer, and there is a spatial heterogeneity in the sensitivity of sediment parameters to different environmental processes. In the shallow (0-5 m) near shore oxic-suboxic environments the lithogenic and terrestrial organic content is high and spatially variable, and the organics show degradation in the oxic part. Due to aerial exposure resulting from lake level changes of at least 3m, the evaporitic carbonates are not completely preserved. In the deep water (>5 m) anoxic environment the lithogenics are uniformly distributed and the delta C-13 is an indicator not only for aquatic vs. terrestrial plants but also of lake pH and salinity. The isotopic composition of the evaporites is dependent not only on the isotopic composition of source water (monsoon rainfall and stream inflow) and evaporation, but is also influenced by proximity to the isotopically depleted stream inflow. We conclude that in the deep water environment lithogenic content, and isotopic composition of organic matter can be used for palaeoenvironmental reconstruction.}, language = {en} } @article{MuellerNeugebauerBenDoretal.2022, author = {M{\"u}ller, Daniela and Neugebauer, Ina and Ben Dor, Yoav and Enzel, Yehouda and Schwab, Markus Julius and Tjallingii, Rik and Brauer, Achim}, title = {Phases of stability during major hydroclimate change ending the Last Glacial in the Levant}, series = {Scientific reports}, volume = {12}, journal = {Scientific reports}, number = {1}, publisher = {Macmillan Publishers Limited, part of Springer Nature}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-022-10217-9}, pages = {12}, year = {2022}, abstract = {In-depth understanding of the reorganization of the hydrological cycle in response to global climate change is crucial in highly sensitive regions like the eastern Mediterranean, where water availability is a major factor for socioeconomic and political development. The sediments of Lake Lisan provide a unique record of hydroclimatic change during the last glacial to Holocene transition (ca. 24-11 ka) with its tremendous water level drop of similar to 240 m that finally led to its transition into the present hypersaline water body-the Dead Sea. Here we utilize high-resolution sedimentological analyses from the marginal terraces and deep lake to reconstruct an unprecedented seasonal record of the last millennia of Lake Lisan. Aragonite varve formation in intercalated intervals of our record demonstrates that a stepwise long-term lake level decline was interrupted by almost one millennium of rising or stable water level. Even periods of pronounced water level drops indicated by gypsum deposition were interrupted by decades of positive water budgets. Our results thus highlight that even during major climate change at the end of the last glacial, decadal to millennial periods of relatively stable or positive moisture supply occurred which could have been an important premise for human sedentism.}, language = {en} } @article{AnoopPrasadPlessenetal.2013, author = {Anoop, Ambili and Prasad, S. and Plessen, Birgit and Basavaiah, Nathani and Gaye, B. and Naumann, R. and Menzel, P. and Weise, S. and Brauer, Achim}, title = {Palaeoenvironmental implications of evaporative gaylussite crystals from Lonar Lake, central India}, series = {Journal of quaternary science}, volume = {28}, journal = {Journal of quaternary science}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0267-8179}, doi = {10.1002/jqs.2625}, pages = {349 -- 359}, year = {2013}, abstract = {We have undertaken petrographic, mineralogical, geochemical and isotopic investigations on carbonate minerals found within a 10-m-long core from Lonar Lake, central India, with the aim of evaluating their potential as palaeoenvironmental proxies. The core encompasses the entire Holocene and is the first well-dated high-resolution record from central India. While calcite and/or aragonite were found throughout the core, the mineral gaylussite was found only in two specific intervals (46303890 and 2040560 cal a BP). Hydrochemical and isotope data from inflowing streams and lake waters indicate that evaporitic processes play a dominant role in the precipitation of carbonates within this lake. Isotopic (18O and 13C) studies on the evaporative gaylussite crystals and residual bulk carbonates (calcite) from the long core show that evaporation is the major control on 18O enrichment in both the minerals. However, in case of 13C additional mechanisms, for example methanogenesis (gaylussite) and phytoplankton productivity (calcium carbonate), play an additional important role in some intervals. We also discuss the relevance of our investigation for palaeoclimate reconstruction and late Holocene monsoon variability.}, 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} } @article{DietzeSlowinskiZawiskaetal.2016, author = {Dietze, Elisabeth and Slowinski, Michal and Zawiska, Izabela and Veh, Georg and Brauer, Achim}, title = {Multiple drivers of Holocene lake level changes at a lowland lake in northeastern Germany}, series = {Boreas}, volume = {45}, journal = {Boreas}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0300-9483}, doi = {10.1111/bor.12190}, pages = {828 -- 845}, year = {2016}, abstract = {Many German lakes experienced significant water level declines in recent decades that are not fully understood due to the short observation period. At a typical northeastern German groundwater-fed lake with a complex basin morphology, an acoustic sub-bottom profile was analysed together with a transect of five sediment cores, which were correlated using multiple proxies (sediment facies, -XRF, macrofossils, subfossil Cladocera). Shifts in the boundary between sand and mud deposition were controlled by lake level changes, and hence, allowed the quantification of an absolute lake level amplitude of similar to 8m for the Holocene. This clearly exceeded observed modern fluctuations of 1.3m (AD 1973-2010). Past lake level changes were traced continuously using the calcium-record. During high lake levels, massive organic muds were deposited in the deepest lake basin, whereas lower lake levels isolated the sub-basins and allowed carbonate deposition. During the beginning of the Holocene (>9700cal. a BP), lake levels were high, probably due to final melting of permafrost and dead-ice remains. The establishment of water-use intensive Pinus forests caused generally low (3-4m below modern) but fluctuating lake levels (9700-6400cal. a BP). Afterwards, the lake showed an increasing trend and reached a short-term highstand at c.5000cal. a BP (4m above modern). At the transition towards a cooler and wetter late Holocene, forests dominated by Quercus and Fagus and initial human impact probably contributed more positively to groundwater recharge. Lake levels remained high between 3800 and 800cal. a BP, but the lake system was not sensitive enough to record short-term fluctuations during this period. Lake level changes were recorded again when humans profoundly affected the drainage system, land cover and lake trophy. Hence, local Holocene water level changes reflect feedbacks between catchment and vegetation characteristics and human impact superimposed by climate change at multiple temporal scales.}, language = {en} } @article{WolffKristenJennySchettleretal.2014, author = {Wolff, Christian Michael and Kristen-Jenny, Iris and Schettler, Georg and Plessen, Birgit and Meyer, Hanno and Dulski, Peter and Naumann, Rudolf and Brauer, Achim and Verschuren, Dirk and Haug, Gerald H.}, title = {Modern seasonality in Lake Challa (Kenya/Tanzania) and its sedimentary documentation in recent lake sediments}, series = {Limnology and oceanography}, volume = {59}, journal = {Limnology and oceanography}, number = {5}, publisher = {Wiley}, address = {Waco}, issn = {0024-3590}, doi = {10.4319/lo.2014.59.5.1621}, pages = {1621 -- 1636}, year = {2014}, abstract = {From November 2006 to January 2010, a sediment trap that was cleared monthly was deployed in Lake Challa, a deep stratified freshwater lake on the eastern slope of Mt. Kilimanjaro in southern Kenya. Geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin. During the southern hemisphere summer (November-March), when the water temperature is high and the lake is biologically productive (nondiatom algae), calcite predominated in the sediment trap samples. During the "long rain" season (March-May) a small amount of organic matter and lithogenic material caused by rainfall appeared. This was followed by the cool and windy months of the southern hemisphere winter (June-October) when diatoms were the main component, indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes. The sediment trap data support the hypothesis that the light-dark lamination couplets, which are abundant in Lake Challa cores, reflect seasonal delivery to the sediments of diatom-rich particulates during the windy months and diatom-poor material during the wet season. However, interannual and spatial variability in upwelling and productivity patterns, as well as El Nino-Southern Oscillation (ENSO)-related rainfall and drought cycles, exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of Lake Challa.}, language = {en} } @article{SwierczynskiLauterbachDulskietal.2013, author = {Swierczynski, Tina and Lauterbach, Stefan and Dulski, Peter and Delgado, Jose Miguel Martins and Merz, Bruno and Brauer, Achim}, title = {Mid- to late holocene flood frequency changes in the northeastern Alps as recorded in varved sediments of Lake Mondsee (Upper Austria)}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {80}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2013.08.018}, pages = {78 -- 90}, year = {2013}, abstract = {Annually laminated (varved) lake sediments with intercalated detrital layers resulting from sedimentary input by runoff events are ideal archives to establish precisely dated records of past extreme runoff events. In this study, the mid- to late Holocene varved sediments of Lake Mondsee (Upper Austria) were analysed by combining sedimentological, geophysical and geochemical methods. This approach allows to distinguish two types of detrital layers related to different types of extreme runoff events (floods and debris flows) and to detect changes in flood activity during the last 7100 years. In total, 271 flood and 47 debris flow layers, deposited during spring and summer, were identified, which cluster in 18 main flood episodes (FE 1-18) with durations of 30-50 years each. These main flood periods occurred during the Neolithic (7100-7050 vyr BP and 6470-4450 vyr BP), the late Bronze Age and the early Iron Age (3300-3250 and 2800-2750 vyr BP), the late Iron Age (2050-2000 vyr BP), throughout the Dark Ages Cold Period (1500-1200 vyr BP), and at the end of the Medieval Warm Period and the Little Ice Age (810-430 vyr BP). Summer flood episodes in Lake Mondsee are generally more abundant during the last 1500 years, often coinciding with major advances of Alpine glaciers. Prior to 1500 vyr BP, spring/summer floods and debris flows are generally less frequent, indicating a lower number of intense rainfall events that triggered erosion. In comparison with the increase of late Holocene flood activity in western and northwestern (NW) Europe, commencing already as early as 2800 yr BP, the hydro-meteorological shift in the Lake Mondsee region occurred much later. These time lags in the onset of increased hydrological activity might be either due to regional differences in atmospheric circulation pattern or to the sensitivity of the individual flood archives. The Lake Mondsee sediments represent the first precisely dated and several millennia long summer flood record for the northeastern (NE) Alps, a key region at the climatic boundary of Atlantic, Mediterranean and East European air masses, aiding a better understanding of regional and seasonal peculiarities of flood occurrence under changing climate conditions. (C) 2013 Elsevier Ltd. All rights reserved.}, language = {en} } @article{AichnerOttSlowinskietal.2018, author = {Aichner, Bernhard and Ott, Florian and Slowinski, Michal and Norygkiewicz, Agnieszka M. and Brauer, Achim and Sachse, Dirk}, title = {Leaf wax n-alkane distributions record ecological changes during the Younger Dryas at Trzechowskie paleolake (northern Poland) without temporal delay}, series = {Climate of the past : an interactive open access journal of the European Geosciences Union}, volume = {14}, journal = {Climate of the past : an interactive open access journal of the European Geosciences Union}, number = {11}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1814-9324}, doi = {10.5194/cp-14-1607-2018}, pages = {1607 -- 1624}, year = {2018}, abstract = {While of higher plant origin, a specific source assignment of sedimentary leaf wax n-alkanes remains difficult. In addition, it is unknown how fast a changing catchment vegetation would be reflected in sedimentary leaf wax archives. In particular, for a quantitative interpretation of n-alkane C and H isotope ratios in terms of paleohydrological and paleoecological changes, a better understanding of transfer times and dominant sedimentary sources of leaf wax n-alkanes is required. In this study we tested to what extent compositional changes in leaf wax n-alkanes can be linked to known vegetation changes by comparison with high-resolution palynological data from the same archive. We analyzed leaf wax n-alkane concentrations and distributions in decadal resolution from a sedimentary record from Trzechowskie paleolake (TRZ, northern Poland), covering the Late Glacial to early Holocene (13 360-9940 yr BP). As an additional source indicator of targeted n-alkanes, compound-specific carbon isotopic data have been generated in lower time resolution. The results indicated rapid responses of n-alkane distribution patterns coinciding with major climatic and paleoecological transitions. We found a shift towards higher average chain length (ACL) values at the Allerod-Younger Dryas (YD) transition between 12 680 and 12 600 yr BP, co-evaled with a decreasing contribution of arboreal pollen (mainly Pinus and Betula) and a subsequently higher abundance of pollen derived from herbaceous plants (Poaceae, Cyperaceae, Artemisia), shrubs, and dwarf shrubs (Juniperus and Salix). The termination of the YD was characterized by a successive increase in n-alkane concentrations coinciding with a sharp decrease in ACL values between 11 580 and 11 490 yr BP, reflecting the expansion of woodland vegetation at the YD-Holocene transition. A gradual reversal to longer chain lengths after 11 200 yr BP, together with decreasing n-alkane concentrations, most likely reflects the early Holocene vegetation succession with a decline of Betula. These results show that n-alkane distributions reflect vegetation changes and that a fast (i.e., subdecadal) signal transfer occurred. However, our data also indicate that a standard interpretation of directional changes in biomarker ratios remains difficult. Instead, responses such as changes in ACL need to be discussed in the context of other proxy data. In addition, we find that organic geochemical data integrate different ecological information compared to pollen, since some gymnosperm genera, such as Pinus, produce only a very low amount of n-alkanes and for this reason their contribution may be largely absent from biomarker records. Our results demonstrate that a combination of palynological and n-alkane data can be used to infer the major sedimentary leaf wax sources and constrain leaf wax transport times from the plant source to the sedimentary sink and thus pave the way towards quantitative interpretation of compound-specific hydrogen isotope ratios for paleohydrological reconstructions.}, language = {en} } @article{HeinrichBalanzateguiBensetal.2018, author = {Heinrich, Ingo and Balanzategui, Daniel and Bens, Oliver and Blasch, Gerald and Blume, Theresa and Boettcher, Falk and Borg, Erik and Brademann, Brian and Brauer, Achim and Conrad, Christopher and Dietze, Elisabeth and Dr{\"a}ger, Nadine and Fiener, Peter and Gerke, Horst H. and G{\"u}ntner, Andreas and Heine, Iris and Helle, Gerhard and Herbrich, Marcus and Harfenmeister, Katharina and Heussner, Karl-Uwe and Hohmann, Christian and Itzerott, Sibylle and Jurasinski, Gerald and Kaiser, Knut and Kappler, Christoph and Koebsch, Franziska and Liebner, Susanne and Lischeid, Gunnar and Merz, Bruno and Missling, Klaus Dieter and Morgner, Markus and Pinkerneil, Sylvia and Plessen, Birgit and Raab, Thomas and Ruhtz, Thomas and Sachs, Torsten and Sommer, Michael and Spengler, Daniel and Stender, Vivien and St{\"u}ve, Peter and Wilken, Florian}, title = {Interdisciplinary Geo-ecological Research across Time Scales in the Northeast German Lowland Observatory (TERENO-NE)}, series = {Vadose zone journal}, volume = {17}, journal = {Vadose zone journal}, number = {1}, publisher = {Soil Science Society of America}, address = {Madison}, issn = {1539-1663}, doi = {10.2136/vzj2018.06.0116}, pages = {25}, year = {2018}, abstract = {The Northeast German Lowland Observatory (TERENO-NE) was established to investigate the regional impact of climate and land use change. TERENO-NE focuses on the Northeast German lowlands, for which a high vulnerability has been determined due to increasing temperatures and decreasing amounts of precipitation projected for the coming decades. To facilitate in-depth evaluations of the effects of climate and land use changes and to separate the effects of natural and anthropogenic drivers in the region, six sites were chosen for comprehensive monitoring. In addition, at selected sites, geoarchives were used to substantially extend the instrumental records back in time. It is this combination of diverse disciplines working across different time scales that makes the observatory TERENO-NE a unique observation platform. We provide information about the general characteristics of the observatory and its six monitoring sites and present examples of interdisciplinary research activities at some of these sites. We also illustrate how monitoring improves process understanding, how remote sensing techniques are fine-tuned by the most comprehensive ground-truthing site DEMMIN, how soil erosion dynamics have evolved, how greenhouse gas monitoring of rewetted peatlands can reveal unexpected mechanisms, and how proxy data provides a long-term perspective of current ongoing changes.}, language = {en} } @article{MartinPuertasLauterbachAllenetal.2019, author = {Martin-Puertas, Celia and Lauterbach, Stefan and Allen, Judy R. M. and Perez, Marta and Blockley, Simon and Wulf, Sabine and Huntley, Brian and Brauer, Achim}, title = {Initial Mediterranean response to major climate reorganization during the last interglacial-glacial transition}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {215}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2019.05.019}, pages = {232 -- 241}, year = {2019}, abstract = {Millennial-scale Dansgaard Oeschger (DO) variability at northern high latitudes has influenced climatic and environmental conditions in the Mediterranean during the last glacial period. There is evidence that the hemispheric transmission of the DO variability occurred at the end of DO event 25; however, the exact timing and the trigger that activated the environmental response in the Mediterranean remains incompletely understood. Here, we provide evidence that the clear millennial-scale teleconnection between Greenland and the Mediterranean started at similar to 111.4 ka BP and was initiated by a sub-millennial scale cooling in Greenland (GI-25b). High-resolution sediment proxies and the pollen record of Lago Grande di Monticchio (MON), Italy, reflect climatic instability during the last millennium of the last interglacial, which was characterised by a first and short cooling episode (MON 1) at 111.44 +/- 0.69 ka BP, coinciding with the Greenland cold sub-event GI-25b in duration and timing (within dating uncertainties). MON and Greenland (NorthGRIP ice core) also agree in recording a subsequent warm rebound phase that abruptly culminated in the stadial MON 2/GS-25, marking the transition into the last glacial period. Our results show that the GI-25b triggered an early environmental response at MON to centennial-scale climate change in Greenland as a prelude to the millennial-scale teleconnection that was maintained during the glacial period.}, language = {en} }