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Recent publications of our group
Collecting cores in the field – the start of every publication!
Foto: Roland Zech

19 Publikationen filtern

Die Publikationen filtern

Hervorgehobene Autoren sind Angehörige der Universität Jena.

  1. Paleoclimate, paleoenvironment, and human impact over the last 400 years based on lipid biomarkers from Lake Höglwörth, Germany

    ErscheinungsjahrErschienen in:Quaternary Science Advances S. Acharya, P. Strobel, M. Prochnow, S. Taut, M. Zech, A. Schwalb, R. Zech
    Lipid biomarkers are valuable proxies for reconstructing paleoclimate and paleoenvironmental changes as well as human impact. However, little attention has been paid on evaluating how the combination of biomarkers can be used to reconstruct various aspects of local paleoenvironmental conditions. This study presents a suite of lipid biomarker records from a sediment core from Lake Höglwörth, southern Germany, covering the past 400 years. Compound-specific hydrogen isotopic compositions (δD) of terrestrial n-alkanes (n-C₂₉₋ₐlkₐnₑ) and n-alkanoic acids (n-C₃₀₋ₐcid) indicate minor changes in isotopic composition of precipitation. The δD of n-C₂₂₋ₐcid is interpreted to record the isotopic composition of the lake water and evaporative enrichment, which drops after 1700 CE, coinciding with the construction of a mill and the related rerouting of a creek into Lake Höglwörth. The δD of n-C₂₅₋ₐlkₐnₑ is also enriched but decoupled from the reconstructed isotopic composition of precipitation and lake water. Therefore, we suggest that δD of n-C₂₅₋ₐlkₐnₑ reflects the leaf water isotopic composition of Sphagnum, which is present in the catchment and undergoes transpirative enrichment. Both short-chain compounds have become more enriched over the last century, maybe related to increasing temperature associated with anthropogenic climate warming. The faecal biomarkers record the changes in human population, partly related to the history of the local Monastery, the World Wars I and II as well as the intensive farming after the mid-20th century. Polycyclic aromatic hydrocarbons (PAHs) reveal a significant change in combustion activities associated with human activities such as the industrial revolution, biomass burning, and environmental cleanup as well as the implementation of emission standards. Our study demonstrates that the combination of plant wax compounds, faecal biomarkers, and PAHs from lacustrine sediment serves as a valuable tool to reconstruct and distinguish various aspects of paleoclimate and paleoenvironmental changes including human impacts.
    Universitätsbibliographie Jena:
    fsu_mods_00016348Externer Link

  2. Late Glacial summer paleohydrology across Central Europe

    ErscheinungsjahrErschienen in:Scientific Reports M. Prochnow, J. Hepp, P. Strobel, R. Zech, S. Acharya, S. Szidat, D. Rius, L. Millet, B. Glaser, M. Zech
    It is generally accepted that a weakening of the North Atlantic thermohaline circulation caused the Younger Dryas cooling. Although the role of seasonality was emphasized previously, this aspect is rarely considered yet, and it remains elusive how this impacted hydroclimate during winters and summers across Central Europe. Here, we coupled biomarker-based δ¹⁸O and δ²H from Bergsee in southern Germany to reconstruct deuterium excess as a proxy for evaporation history from the Bølling-Allerød to the Preboreal. We compared this dataset with other biomarker isotope records in Central Europe. They are all lacking a strong isotopic depletion during the Younger Dryas, which is best explained by the summer sensitivity of the biomarker proxies: As Younger Dryas summers were relatively warm, there is an absence of the strong winter cooling signals recorded in annual water isotope records like Greenland or Lake Steißlingen. Lake evaporation at Bergsee together with other paleohydrological reconstructions draw a coherent picture of the Late Glacial hydroclimate, with strong evidence for warm and dry Younger Dryas summers. Rather than a southward shift of the Westerlies during winter, we suggest that a recently proposed feedback mechanism between North Atlantic sea ice extend, strong winter cooling and summer atmospheric blocking serves as a suitable explanation for summer dryness. Additional confidence to the robustness of these biomarker records is provided by the overall agreement of paleohydrological fluctuations during the Preboreal.
    Universitätsbibliographie Jena:
    fsu_mods_00018882Externer Link

  3. Paleohydrology and human driven paleoproductivity during the Late Holocene from Schliersee, Bavaria

    ErscheinungsjahrErschienen in:Quaternary science reviews : the international multidisciplinary research and review journal M. Prochnow, K. Dulias, P. Strobel, M. Bliedtner, G. Daut, S. Szidat, G. Salazar, F. Lechleitner, S. Acharya, R. Martínez-Abarca, A. Schwarz, A. Schwalb, R. Zech
    Understanding Holocene hydroclimatic variability in the European Alps is challenging due to spatial and temporal disparities between the northern and southern Alps. In addition, interpreting lake sediment records in terms of paleohydrology is complicated by human presence during Roman and Medieval settlements, which increased soil erosion and lake eutrophication. Here, we present a ∼4440-year long sediment record from Schliersee, Bavaria, where we applied compound-specific δ²H on leaf waxes, geochemical and diatom analyses to reconstruct hydrology and lake productivity. The terrestrial δ²Hn₋C₃₁ records the isotopic composition of precipitation and is similar to leaf wax δ²H from Lake Ghirla, southern Alps, and δ¹⁸O from Spannagel cave in Austria. This provides evidence that, on millennial time scales, changes in moisture sources associated with shifts in the position of the Westerlies are one potential explanation regarding the isotope signals across the region. However, doubts remain whether the North Atlantic Oscillation as a winter signal can explain variations in summer-sensitive biomarker δ²H records. The aquatic δ²Hn₋C₂₅ records the isotopic composition of lake water and its isotopic offset to δ²Hn₋C₃₁ (Δₐq–tₑrr) is applied as a proxy for lake evaporation. We find increased evaporation during the Medieval Climate Anomaly in line with a drought reported from tree-ring studies, whereas lower evaporation prevailed during the Little Ice Age, likely due to solar forcing. Lake productivity was higher during the Roman period and Middle Ages, concomitant with land use resulting in higher nutrient inputs into the lake. The intensified use of industrial fertilizers and the drainage of untreated wastewater after the Second World War caused eutrophication during the 1950s. Despite its paleoclimatic significance, this study emphasizes that multi-proxy approaches combining assemblages of geochemical and biological proxies allow robust reconstructions of climate–landscape interactions and human impact.
    Universitätsbibliographie Jena:
    fsu_mods_00017932Externer Link

  4. North Atlantic Oscillation polarity during the past 3000 years derived from sediments of a large lowland lake, Schweriner See, in NE Germany

    ErscheinungsjahrErschienen in:Climate of the past: CP M. Adolph, S. Czerwiński, M. Dreßler, P. Strobel, M. Bliedtner, S. Lorenz, M. Debret, T. Haberzettl
    Based on a multi-dating and multi-proxy approach, we reconstruct Late Holocene environmental changes derived from sediments of Schweriner See, a large lowland lake in NE Germany, covering the past 3070⁺¹⁷⁰/₋₂₁₀ years cal BP. We infer variations in large-scale atmospheric circulation systems by combining in-lake productivity indicators obtained from traditional and high-resolution techniques (e.g. LOI₅₅₀, TOC, inc / coh), diatom assemblages, and compound-specific hydrogen isotopes (δ²HC₂₅). Before 105⁺⁹⁵/₋₇₅ cal BP (∼1850 CE), changes in productivity and the occurrence or disappearance of the diatom species Stephanocostis chantaicus reflect winter temperature variability, while variations in the compound-specific hydrogen isotopes suggest changes in the moisture source region. We observe distinct variations between (i) milder winter temperatures with a moisture source region in the southern-central North Atlantic and (ii) colder winter temperatures with a moisture source in the northern North Atlantic and/or Arctic regions. Such distinct variations in winter temperature and moisture source region are mainly modulated by the North Atlantic Oscillation (NAO). This affects, among others, westerly wind strength and pathways and, thereby, winter temperature and moisture source region for northern central Europe. Besides these long-term shifts in atmospheric conditions, short-term variations in titanium can be linked to lake-level variability, most likely influenced by changes in precipitation and/or evaporation, and after the 12th century to anthropogenic impacts. Since 105⁺⁹⁵/₋₇₅ cal BP (∼1850 CE), productivity has been driven predominantly by nutrient availability related to anthropogenic activities masking the hydroclimatic signal.
    Universitätsbibliographie Jena:
    fsu_mods_00017336Externer Link

  5. Holocene fire dynamics and their climatic controls on the southern Cape coast of South Africa - A 7.2 ka multi-proxy record from the peatland Vankervelsvlei

    ErscheinungsjahrErschienen in:Quaternary science reviews : the international multidisciplinary research and review journal P. Strobel, T. Henning, M. Bliedtner, S. Mosher, H. Rahimova, T. Haberzettl, K. Kirsten, E. Lehndorff, M. Power, M. Zech, R. Zech
    Fire is a natural phenomenon along South Africa's southern Cape coast, but identifying its climatic drivers has been a subject of considerable debate. This study investigates the hydroclimatic and fire dynamics from a 9.6 m sediment core from Vankervelsvlei covering the past 7.2 ka. The fen is located near the southern Cape coast within the year-round rainfall zone of South Africa. A reconstruction of hydroclimatic variability through time applies oxygen isotopes from hemicellulose-derived sugars and hydrogen isotopes from leaf wax-derived n-alkanes. Coupling both isotopes enables a reconstruction of the atmospheric source and seasonality of precipitation as well as estimating local relative humidity. Past trends in fire activity are inferred from macro-charcoal and polycyclic aromatic hydrocarbon (PAH) analyses, the latter serving as fire biomarkers. Results indicate high fire activity at Vankervelsvlei accompanied by generally moist conditions and a year-round rainfall regime linked to both Westerly-derived winter precipitation and Easterly- and locally-derived summer precipitation from 7.2⁺⁰.²/−₀.₂ to 4.5⁺⁰.³/−₀.₃ cal ka BP. From 4.5⁺⁰.³/−₀.₃ to 1.5⁺⁰.⁴/−₀.₂ cal ka BP, a shift to a Westerly-derived winter rainfall regime is identified. This variation features alongside reduced fire activity and persistent drought conditions as Easterly- and locally-derived summer precipitation decreased. From 1.5⁺⁰.⁴/−₀.₂ cal ka BP until present day, macro-charcoal and PAH accumulation rates show high fire activity. Paleoclimate evidence from the last two millennia suggests a variable climate with an overall increase in total moisture availability as contributions from both Westerly-derived winter precipitation and Easterly- and locally-derived summer precipitation support the year-round rainfall regime present today. Results from Vankervelsvlei support previous evidence from regional paleo-reconstructions, refining our understanding of the interplay between hydroclimatic variability and fire activity along South Africa's southern Cape coast. Our study discusses the role of large-scale climate modes, specifically the intensity of El Niño, as a potential driver of short-term hydroclimatic variability, which in turn drives fuel availability and fire activity at Vankervelsvlei during the Holocene.
    Universitätsbibliographie Jena:
    fsu_mods_00009880Externer Link

  6. A regional assessment of the deglaciation history of the Swiss Plateau based on newly obtained and re-evaluated Be-10 cosmic-ray exposure ages

    ErscheinungsjahrErschienen in:Quaternary Science Advances F. Hofmann, A. Groos, E. Garcia Morabito, J. Struck, C. Gnägi, A. Scharf, G. Rugel, S. Merchel, R. Zech
    During marine oxygen isotope stage (MIS) 2, the Swiss Plateau temporarily hosted large piedmont lobe glaciers that retreated after their maximum advance back to the fringe of the Alps. The presence of moraines in this region indicates that overall glacier recession was punctuated by repeated phases of ice-marginal stability and re-advances. The timing of these events in the region formerly covered by the eastern lobe of the Rhône (or Valais) glacier has been controversial and remains poorly constrained due to the lack of chronological data. To fill this gap, ¹⁰Be cosmic-ray exposure (CRE) dating was applied to erratic boulders inside the assumed MIS 2 maximum extent of this piedmont lobe. An erratic boulder at an ice-marginal position upstream from the suspected MIS 2 maximum extent gave an age of about 19 ka. Erratic boulders at a presumably younger ice-marginal position (Brästenberg position) yielded an average age of ca. 20 ka. However, several erratic boulders beyond the Brästenberg position gave internally consistent, but stratigraphically too young ages of ca. 17 ka. We cannot rule out that glacier recession from the Brästenberg position began no later than 17 ka. CRE dating of a moraine of a presumably younger ice-marginal position (Solothurn position) gave unrealistically old ages and an incredibly young age (86 ka, 40 ka, and 4 ka). Carbon-14 CRE dating should be applied to provide additional information on the last deglaciation of the Swiss Plateau. Nevertheless, despite outlying ages, the presented chronological data contribute to an overall consistent and increasingly refined chronology of the last deglaciation of the Swiss Plateau when compared with 59 previously published CRE ages.
    Universitätsbibliographie Jena:
    fsu_mods_00009370Externer Link

  7. Holocene vegetation, fire, climate dynamics and human impact in the upper Orkhon Valley of the Khangai Mountains, Mongolia

    ErscheinungsjahrErschienen in:Quaternary science reviews : the international multidisciplinary research and review journal C. Barhoumi, M. Bliedtner, R. Zech, H. Behling
    The Upper Orkhon Valley, located in the Khangai Mountains of Central Mongolia, is mainly covered by a forest-steppe ecosystem. This is an interesting area to study because its vegetation dynamics might have been influenced by climatic and anthropogenic drivers. This study investigates the dynamics of vegetation (pollen), human activity (pollen and NPP) and fire activity (macro-charcoal) from a lacustrine sediment core from lake Shireet Naiman Nuur, covering the last 7400 cal yr BP. The results of the pollen analysis showed a continual and constant decline of tree species in favour of the development of grasslands. Fire activity was more intense (high peak magnitude) during the mid Holocene, while it became more frequent but less intense from 5000 cal yr BP onwards, when herbaceous taxa became more present. The NPP analysis suggest that the study site was free of human activity from 7400 to 3500 cal yr BP, whereas the traces of the development of human societies that took place in the Orkhon Valley, such as pastoralism and grazing activities, have been demonstrated by the increase in coprophilous fungi and the Poaceae Cerealia-type pollen around 3200 cal yr BP, although its impact seems to have remained low.
    Universitätsbibliographie Jena:
    fsu_mods_00012911Externer Link

  8. Multi-proxy reconstruction of the last millennium paleo-environmental conditions from Lake Höglwörth, Southern Germany

    Erscheinungsjahr S. Acharya
    Universitätsbibliographie Jena:
    fsu_mods_00013477Externer Link

  9. Rapid Climate Change, Integrated Human–Environment–Historical Records and Societal Resilience in Georgia

    ErscheinungsjahrErschienen in:Sustainability C. Loveluck, L. Tielidze, M. Elashvili, A. Kurbatov, L. Gadrani, N. Erb-Satullo, H. von Suchodoletz, A. Dan, H. Laermanns, H. Brückner, U. Schlotzhauer, N. Sulava, R. Chagelishvili
    In the midlatitudes of the planet, we are facing the imminent disappearance of one of our best high-resolution (pre)historic climate and anthropogenic pollution archives, namely the loss of glacial ice, through accelerated global warming. To capture these records and interpret these vanishing archives, it is imperative that we extract ice-cores from midlatitude regions where glaciers still survive and analyse them within frameworks of inter-disciplinary research. In this paper, we focus on Georgia, part of the Greater Caucasus. Results of ice-core analyses from the region have never, to date, been integrated with its other abundant palaeo-environmental, archaeological and historical sources. We review the results of international projects on palaeo-environmental/geoarchaeological sediment archives, the archaeology of metal economies and preliminary ice-core data in Georgia. Collectively, we show that the different strands need to be integrated to fully explore relationships between climate/landscape change and human societal transformations. We then introduce an inclusive interdisciplinary framework for ongoing research on these themes, with an ultimate future goal of using data from the past to inform societal resilience strategies in the present.
    Universitätsbibliographie Jena:
    fsu_mods_00016541Externer Link

  10. Environmental controls on the distribution of GDGT molecules in Lake Höglwörth, Southern Germany

    ErscheinungsjahrErschienen in:Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry ; the official journal of the European Association of Organic Geochemists S. Acharya, R. Zech, P. Strobel, M. Bliedtner, M. Prochnow, C. De Jonge
    Tetraether lipids, such as glycerol dialkyl glycerol tetraethers (GDGTs), are an increasingly used proxy for reconstructing paleoclimatic and paleoenvironmental dynamics. On a global scale, environmental drivers controlling the distribution of GDGTs in lake systems have been described extensively. However, the drivers that control down-core sedimentary GDGT composition within single lake systems are still poorly constrained. Here, we analysed GDGTs in a sediment core collected from Lake Höglwörth (Bavaria, Germany) covering the last ∼1100 years. The increase in ratio ΣIIIa/ΣIIa values (a ratio which captures the variation of 3 structural isomers of penta- and hexamethylated brGDGTs respectively) reflects a higher contribution of branched (br) GDGTs from aquatic sources after 1800 CE. This is synchronous with a high nutrient input as a result of increased local anthropogenic activities. The climate proxy methylation of branched tetraethers (MBT'₅ME) reveals a pattern that deviates from the anticipated temperature changes during the last millennium. Instead, high MBT'₅ME values from ∼880 to 1120 CE coincide with a period of increased soil input, resulting from lake damming and/or construction of the Höglwörth monastery. Decreased values after 1800 CE until present date correspond to a higher contribution of aquatic brGDGTs, with changes in the dependency between Ia and IIa suggesting a direct influence of bacterial community changes on the MBT'₅ME. The proxy cyclisation of branched tetraethers (CBT') shows a linear increase with time, and a stepwise increase at 1700 CE, when a creek stream inflow channel was rerouted. Over time, MBT’₅ME decreases gradually, while CBT’ and ΣIIIa/ΣIIa increase. This is hypothesized to be potentially caused by decreasing water depth over time and/or post- or syn-sedimentary production of GDGTs. The degree of cyclization (DC') shows variations on shorter timescales, possibly driven by the lake mixing regime and water column redox conditions. Our results indicate that caution must be taken when interpreting GDGTs for paleoclimate and paleoenvironmental reconstruction considering the possible influence of shifts in the provenance of brGDGTs. Further studies focusing on both sedimentary and intact polar lipids are highly recommended to constrain the source (water column, or sedimentary production) of GDGTs in lake sediments.
    Universitätsbibliographie Jena:
    fsu_mods_00008607Externer Link

  11. Mid to Late Holocene moisture evolution of semi-arid Mongolia and its anti-phase relationship with monsoonal Asia

    ErscheinungsjahrErschienen in:Quaternary science reviews : the international multidisciplinary research and review journal M. Bliedtner, P. Strobel, J. Struck, M. Prochnow, E. Bazarradnaa, R. Zech
    The spatial and temporal interaction of the Westerlies and the Asian Summer Monsoon (ASM) are often suggested to drive the Holocene moisture evolution of semi-arid Mongolia and Central Asia, but so far, it has remained a controversial topic of debate. In this context, we established a high-resolution 7.4 cal ka paleohydrological record from Shireet Naiman Nuur in the central Mongolian Khangai Mountains using compound-specific biomarker δ²H analyses. Our results suggest that drier conditions from 7.4 to 3.6 cal ka BP and wetter conditions since 3.6 cal ka BP until present are indeed related to changes in atmospheric circulation pattern. A strong anti-phasing between our record and records in monsoonal Asia shows that ASM intensification during the Mid Holocene shifted the ASM limit and adjacent subsidence dry-zones northwards, leading to increased dryness at Shireet Naiman Nuur. Overall wetter conditions during the Late Holocene are related to negative North Atlantic Oscillation phases advecting moisture into central Mongolia and Shireet Naiman Nuur by southerly-displaced Westerlies.
    Universitätsbibliographie Jena:
    fsu_mods_00005728Externer Link

  12. Summer paleohydrology during the Late Glacial and Early Holocene based on δ²H and δ¹⁸O from Bichlersee, Bavaria

    ErscheinungsjahrErschienen in:Scientific Reports M. Prochnow, P. Strobel, M. Bliedtner, J. Struck, L. Bittner, S. Szidat, G. Salazar, H. Schneider, S. Acharya, M. Zech, R. Zech
    Isotope-based records provide valuable information on past climate changes. However, it is not always trivial to disentangle past changes in the isotopic composition of precipitation from possible changes in evaporative enrichment, and seasonality may need to be considered. Here, we analyzed δ²H on n-alkanes and δ¹⁸O on hemicellulose sugars in sediments from Bichlersee, Bavaria, covering the Late Glacial and Early Holocene. Our δ²H n₋C₃₁ record documents past changes in the isotopic composition of summer precipitation and roughly shows the isotope pattern known from Greenland. Both records show lower values during the Younger Dryas, but at Bichlersee the signal is less pronounced, corroborating earlier suggestions that the Younger Dryas was mainly a winter phenomenon and less extreme during summer. δ¹⁸Ofucₒsₑ records the isotopic composition of the lake water during summer and is sensitive to evaporative enrichment. Coupling δ²H n₋C₃₁ and δ¹⁸Ofucₒsₑ allows calculating lake water deuterium-excess and thus disentangling changes in the isotopic composition of precipitation and evaporative enrichment. Our deuterium-excess record reveals that the warm Bølling–Allerød and Early Holocene were characterized by more evaporative enrichment compared to the colder Younger Dryas. Site-specific hydrological conditions, seasonality, and coupling δ²H and δ¹⁸O are thus important when interpreting isotope records.
    Universitätsbibliographie Jena:
    fsu_mods_00008609Externer Link
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