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  • 1.
    Ahmed, Engy
    et al.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Sci Life Lab, Tomtebodavagen 23A, SE-17165 Solna, Sweden..
    Parducci, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Unneberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Ågren, Rasmus
    Chalmers Univ Technol, Dept Chem & Biol Engn, Sci Life Lab, SE-41296 Gothenburg, Sweden..
    Schenk, Frederik
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Rattray, Jayne E.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Univ Calgary, Biol Sci, 2500 Univ Dr NW, Calgary, AB, Canada..
    Han, Lu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics. Jilin Univ, Coll Life Sci, Ancient DNA Lab, Changchun, Jilin, Peoples R China..
    Muschitiello, Francesco
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.;Columbia Univ, Lamont Doherty Earth Observ, 61 Route 9NW, Palisades, NY USA..
    Pedersen, Mikkel W.
    Univ Cambridge, Dept Zool, Downing St, Cambridge CB2 3EJ, England..
    Smittenberg, Rienk H.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Yamoah, Kweku Afrifa
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Slotte, Tanja
    Stockholm Univ, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden.;Sci Life Lab, Tomtebodavagen 23A, SE-17165 Solna, Sweden..
    Wohlfarth, Barbara
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden..
    Archaeal community changes in Lateglacial lake sediments: Evidence from ancient DNA2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 181, p. 19-29Article in journal (Refereed)
    Abstract [en]

    The Lateglacial/early Holocene sediments from the ancient lake at Hasseldala Port, southern Sweden provide an important archive for the environmental and climatic shifts at the end of the last ice age and the transition into the present Interglacial. The existing multi-proxy data set highlights the complex interplay of physical and ecological changes in response to climatic shifts and lake status changes. Yet, it remains unclear how microorganisms, such as Archaea, which do not leave microscopic features in the sedimentary record, were affected by these climatic shifts. Here we present the metagenomic data set of Hasseldala Port with a special focus on the abundance and biodiversity of Archaea. This allows reconstructing for the first time the temporal succession of major Archaea groups between 13.9 and 10.8 ka BP by using ancient environmental DNA metagenomics and fossil archaeal cell membrane lipids. We then evaluate to which extent these findings reflect physical changes of the lake system, due to changes in lake-water summer temperature and seasonal lake-ice cover. We show that variations in archaeal composition and diversity were related to a variety of factors (e.g., changes in lake water temperature, duration of lake ice cover, rapid sediment infilling), which influenced bottom water conditions and the sediment-water interface. Methanogenic Archaea dominated during the Allerod and Younger Dryas pollen zones, when the ancient lake was likely stratified and anoxic for large parts of the year. The increase in archaeal diversity at the Younger Dryas/Holocene transition is explained by sediment infilling and formation of a mire/peatbog. (C) 2017 Elsevier Ltd. All rights reserved.

  • 2.
    Alsos, Inger Greve
    et al.
    UiT Arctic Univ Norway, Arctic Univ Museum Norway, NO-9037 Tromso, Norway..
    Lammers, Youri
    UiT Arctic Univ Norway, Arctic Univ Museum Norway, NO-9037 Tromso, Norway..
    Kjellman, Sofia E.
    UiT Arctic Univ Norway, Dept Geosci, POB 6050, NO-9037 Tromso, Norway..
    Merkel, Marie Kristine Foreid
    UiT Arctic Univ Norway, Arctic Univ Museum Norway, NO-9037 Tromso, Norway..
    Bender, Emma M.
    UiT Arctic Univ Norway, Dept Geosci, POB 6050, NO-9037 Tromso, Norway..
    Rouillard, Alexandra
    UiT Arctic Univ Norway, Dept Geosci, POB 6050, NO-9037 Tromso, Norway.;Univ Copenhagen, GLOBE Inst, Sect GeoGenet, Oster Voldgade 5-7, DK-1350 Copenhagen K, Denmark..
    Erlendsson, Egill
    Univ Iceland, Inst Life & Environm Sci, Sturlugata 7, IS-102 Reykjavik, Iceland..
    Gudmundsdottir, Esther Ruth
    Univ Copenhagen, GLOBE Inst, Sect GeoGenet, Oster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.;Univ Iceland, Nordic Volcanol Ctr, Inst Earth Sci, Sturlugata 7, IS-102 Reykjavik, Iceland..
    Benediktsson, Ivar Orn
    Univ Iceland, Inst Earth Sci, Sturlugata 7, IS-102 Reykjavik, Iceland..
    Farnsworth, Wesley R.
    Univ Iceland, Nordic Volcanol Ctr, Inst Earth Sci, Sturlugata 7, IS-102 Reykjavik, Iceland..
    Brynjolfsson, Skafti
    Iceland Inst Nat Hist, IS-600 Borgum Vio Noroursloo, Akureyri, Iceland..
    Gisladottir, Gudrun
    Univ Iceland, Inst Life & Environm Sci, Sturlugata 7, IS-102 Reykjavik, Iceland.;Univ Iceland, Inst Earth Sci, Sturlugata 7, IS-102 Reykjavik, Iceland..
    Dögg Eddudottir, Sigrun
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Archaeology.
    Schomacker, Anders
    UiT Arctic Univ Norway, Dept Geosci, POB 6050, NO-9037 Tromso, Norway..
    Ancient sedimentary DNA shows rapid post-glacial colonisation of Iceland followed by relatively stable vegetation until the Norse settlement (Landnam) AD 8702021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 259, article id 106903Article in journal (Refereed)
    Abstract [en]

    Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal yr BP and c. 8600 cal yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was initially dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, the dominant taxa were all present in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local accumulated richness and regional species pool until 8000 cal yr BP, by which time 3/4 of all taxa identified had arrived. The period 4500-1000 cal yr BP witnessed the appearance of a a small number of bryophytes, graminoids and forbs that were not recorded in earlier samples. The last millennium, after human settlement of the island (Landnam), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of increased incidence of sea ice, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.

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  • 3. Askjær, Thomas Gravgaard
    et al.
    Zhang, Qiong
    Schenk, Frederik
    Charpentier Ljungqvist, Fredrik
    Uppsala University, Swedish Collegium for Advanced Study (SCAS). Bolin Centre for Climate Research, Stockholm University, Stockholm, 10691, Sweden; Department of History, Stockholm University, Stockholm, 10691, Sweden.
    Lu, Zhengyao
    Brierley, Chris M.
    Hopcroft, Peter O.
    Jungclaus, Johann
    Shi, Xiaoxu
    Lohmann, Gerrit
    Sun, Weiyi
    Liu, Jian
    Braconnot, Pascale
    Otto-Bliesner, Bette L.
    Wu, Zhipeng
    Yin, Qiuzhen
    Kang, Yibo
    Yang, Haijun
    Multi-centennial Holocene climate variability in proxy records and transient model simulations2022In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 296, article id 107801Article in journal (Refereed)
    Abstract [en]

    Variability on centennial to multi-centennial timescales is mentioned as a feature in reconstructions of the Holocene climate. As more long transient model simulations with complex climate models become available and efforts have been made to compile large proxy databases, there is now a unique oppor-tunity to study multi-centennial variability with greater detail and a large amount of data than earlier. This paper presents a spectral analysis of transient Holocene simulations from 9 models and 120 proxy records to find the common signals related to oscillation periods and geographic dependencies and discuss the implications for the potential driving mechanisms. Multi-centennial variability is significant in most proxy records, with the dominant oscillation periods around 120-130 years and an average of 240 years. Spectra of model-based global mean temperature (GMT) agree well with proxy evidence with significant multi-centennial variability in all simulations with the dominant oscillation periods around 120-150 years. It indicates a comparatively good agreement between model and proxy data. A lack of latitudinal dependencies in terms of oscillation period is found in both the model and proxy data. However, all model simulations have the highest spectral density distributed over the Northern hemi-sphere high latitudes, which could indicate a particular variability sensitivity or potential driving mechanisms in this region. Five models also have differentiated forcings simulations with various combinations of forcing agents. Significant multi-centennial variability with oscillation periods between 100 and 200 years is found in all forcing scenarios, including those with only orbital forcing. The different forcings induce some variability in the system. Yet, none appear to be the predominant driver based on the spectral analysis. Solar irradiance has long been hypothesized to be a primary driver of multi -centennial variability. However, all the simulations without this forcing have shown significant multi -centennial variability. The results then indicate that internal mechanisms operate on multi-centennial timescales, and the North Atlantic-Arctic is a region of interest for this aspect.

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  • 4.
    Baykal, Yunus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bateman, Mark D.
    Pfaff, Katharina
    Sechi, Daniele
    Banak, Adriano
    Šuica, Sanja
    Zhang, Haobo
    Nie, Junsheng
    Eurasian Ice Sheet derived meltwater pulses and their role in driving atmospheric dust activity: Late Quaternary loess sources in SE England2022In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 296, p. 107804-107804, article id 107804Article in journal (Refereed)
    Abstract [en]

    The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25–23.5 ka and 20–19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon U–Pb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.

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  • 5.
    Baykal, Yunus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Engström-Johansson, Alexandra
    Skurzyński, Jacek
    Zhang, Hanzhi
    He, Jing
    Lu, Huayu
    Adamiec, Grzegorz
    Költringer, Chiara
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Jary, Zdzisław
    Detrital zircon U–Pb age analysis of last glacial loess sources and proglacial sediment dynamics in the Northern European Plain2021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 274, article id 107265Article in journal (Refereed)
    Abstract [en]

    Loess deposits along the northern fringe of the European loess belt potentially record past changes in dust emission from areas proximal to former ice sheets. Recent chronologies from loess deposits across this region generally agree on greatly enhanced dust deposition rates when the Fennoscandian Ice Sheet reached its maximum extent during the late last glacial. However, uncertainties over the material's source and origin limit understanding of the causes of this enhanced dust activity. In particular, loess in southwestern Poland has been attributed to multiple origins, mainly involving glaciofluvial outwash plains along the Fennoscandian Ice Sheet margin and/or local sources in the mountainous areas of the Sudetes and Western Carpathians. Here we apply detrital zircon U–Pb age analyses for a large number of grains recovered from four loess samples taken from different stratigraphic units exposed at Biały Kościół in southwestern Poland, previously luminescence dated to MIS 4–2, to assess loess provenance as well as its temporal evolution during last glacial Fennoscandian Ice Sheet fluctuations. Furthermore, we analysed the detrital zircon U–Pb age spectra of five samples from potential source sediments to constrain the history of sediment recycling and mixing within the Northern European Plain prior to deflation and loess deposition. The broad range of zircon age components detected in the four loess samples suggests both Fennoscandian and closer Peri-Gondwanan proto-sources while a narrow, dominant Carboniferous age peak is consistent with sourcing from the local Strzelin Hills in the Sudetic foreland. However, the presence of both Fennoscandian and Peri-Gondwanan derived grains in samples from potential source sediments reveals that this mixture of sediment sources is widespread across the Northern European Plain, as a result of long-term glacial and fluvial reworking of cover sediments in the proglacial area throughout the Quaternary. Local rivers draining the Sudetic foreland transported this Fennoscandian-Peri-Gondwanan sediment mixture along with particles denuded from the Strzelin Hills, resulting in a nearby, temporally stable dust source for the Biały Kościół loess during MIS 4–2, while dust emission rates were substantially increased during the last glacial maximum. Given that our model for loess formation at Biały Kościół essentially involves sediment distribution via rivers prior to short distance aeolian transport, we infer that the proportion of northern ice sheet derived particles in European loess deposits is mainly controlled by the drainage pattern of major rivers in relation to Pleistocene ice margins where glaciofluvial sediment is abundant. Based on the presence of Fennoscandian derived zircon grains in European loess deposits, we constrain a southern limit of the influence of northern ice sheet dust sources along the central European highlands that currently divide drainage between the Northern European Plain and the Danube Basins.

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  • 6. Bird, Anna
    et al.
    Millar, Ian
    Rodenburg, Tanja
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Department of Geography, Royal Holloway University of London.
    Rittner, Martin
    Vermeesch, Pieter
    Lu, Huayu
    A constant Chinese Loess Plateau dust source since the late Miocene2020In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 227, article id 106042Article in journal (Refereed)
    Abstract [en]

    The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular the degree to which changes in the dust cycle influenced climate change, were driven by climate change, and how these processes interacted. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the last 40 Ma. Previous work on the Chinese Loess Plateau argue over whether changes in dust source occur at the Pliocene-Pleistocene boundary, or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics. We present Sr, Nd and Hf isotope data from multiple sites and show that dust source largely remains unchanged across these boundaries. Shifts in geochemistry are due to changes in grain-size and weathering. While the transport pathway (river, deserts, direct aeolian) is unclear, these tracer isotopes show that dust was dominantly sourced from the Northern Tibetan Plateau, with some input from the local bedrock. This shows that a major established and constant dust source on the Tibetan Plateau has been active and unchanged since late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are a function of climate change in Tibetan Plateau source regions rather than effects from increased aridification over the Pliocene-Pleistocene boundary.

  • 7. Blockley, Simon
    et al.
    Blaauw, Maarten
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Bronk Ramsey, Christopher
    van der Plicht, Johannes
    Building and testing age models for radiocarbon dates in Lateglacial and Early Holocene sediments2007In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 26, no 15-16, p. 1915-1926Article in journal (Refereed)
    Abstract [en]

    The growing importance of understanding past abrupt climate variability at a regional and global scale has led to the realisation that independent chronologies of past environmental change need to be compared between various archives. This has in turn led to attempts at significant improvements in the required precision at which records can be dated. Radiocarbon dating is still the most prominent method for dating organic material from terrestrial and marine archives, and as such many of the recent developments in improving precision have been aimed at this technique. These include: (1) selection of the most suitable datable fractions within a record, (2) the development of better calibration curves, and (3) more precise age modelling techniques. While much attention has been focussed on the first two items, testing the possibilities of the relatively new age modelling approaches has not received much attention. Here, we test the potential for methods designed to significantly improve precision in radiocarbon-based age models, wiggle match dating and various forms of Bayesian analyses. We demonstrate that while all of the methods can perform very well, in some scenarios, caution must be taken when applying them. It appears that an integrated approach is required in real life dating situations where more than one model is applied, with strict error calculation, and with the integration of radiocarbon data with sedimentological analyses of site formation processes.

  • 8.
    Czymzik, Markus
    et al.
    Lund Univ, Dept Geol, Quaternary Sci, S-22362 Lund, Sweden..
    Adolphi, Florian
    Lund Univ, Dept Geol, Quaternary Sci, S-22362 Lund, Sweden..
    Muscheler, Raimund
    Lund Univ, Dept Geol, Quaternary Sci, S-22362 Lund, Sweden..
    Mekhaldi, Florian
    Lund Univ, Dept Geol, Quaternary Sci, S-22362 Lund, Sweden..
    Martin-Puertas, Celia
    GEZ German Res Ctr Geosci, Sect Climate Dynam & Landscape Evolut 5 2, D-14473 Potsdam, Germany..
    Aldahan, Ala
    United Arab Emirates Univ, Dept Geol, Al Ain 15551, U Arab Emirates..
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Brauer, Achim
    GEZ German Res Ctr Geosci, Sect Climate Dynam & Landscape Evolut 5 2, D-14473 Potsdam, Germany..
    A varved lake sediment record of the Be-10 solar activity proxy for the Lateglacial-Holocene transition2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 153, p. 31-39Article in journal (Refereed)
    Abstract [en]

    Solar modulated variations in cosmogenic radionuclide production provide both information on past changes in the activity of the Sun and a global synchronization tool. However, to date the use of cosmogenic radionuclides for these applications is almost exclusively based on Be-10 records from ice cores and C-14 time-series from tree rings, all including archive-specific limitations. We present the first Be-10 record from annually laminated (varved) lake sediments for the Lateglacial-Holocene transition from Meerfelder Maar. We quantify environmental influences on the catchment and, consequently, Be-10 deposition using a new approach based on regression analyses between our Be-10 record and environmental proxy time-series from the same archive. Our analyses suggest that environmental influences contribute to up to 37% of the variability in our Be-10 record, but cannot be the main explanation for major Be-10 excursions. Corrected for these environmental influences, our Be-10 record is interpreted to dominantly reflect changes in solar modulated cosmogenic radionuclide production. The preservation of a solar production signal in Be-10 from varved lake sediments highlights the largely unexplored potential of these archives for solar activity reconstruction, as global synchronization tool and, thus, for more robust paleoclimate studies.

  • 9. de Boer, Erik J.
    et al.
    Hooghiemstra, Henry
    Florens, F. B. Vincent
    Baider, Claudia
    Engels, Stefan
    Dakos, Vasilis
    Blaauw, Maarten
    Bennett, Keith D.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Rapid succession of plant associations on the small ocean island of Mauritius at the onset of the Holocene2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 68, p. 114-125Article in journal (Refereed)
    Abstract [en]

    The island of Mauritius offers the opportunity to study the poorly understood vegetation response to climate change on a small tropical oceanic island. A high-resolution pollen record from a 10 m long peat core from Kanaka Crater (560 m elevation, Mauritius, Indian Ocean) shows that vegetation shifted from a stable open wet forest Last Glacial state to a stable closed-stratified-tall-forest Holocene state. An ecological threshold was crossed at similar to 11.5 cal ka BP, propelling the forest ecosystem into an unstable period lasting similar to 4000 years. The shift between the two steady states involves a cascade of four abrupt (<150 years) forest transitions in which different tree species dominated the vegetation for a quasi-stable period of respectively similar to 1900, similar to 1100 and similar to 900 years. We interpret the first forest transition as climate-driven, reflecting the response of a small low topography oceanic island where significant spatial biome migration is impossible. The three subsequent forest transitions are not evidently linked to climate events, and are suggested to be driven by internal forest dynamics. The cascade of four consecutive events of species turnover occurred at a remarkably fast rate compared to changes during the preceding and following periods, and might therefore be considered as a composite tipping point in the ecosystem. We hypothesize that wet gallery forest, spatially and temporally stabilized by the drainage system, served as a long lasting reservoir of biodiversity and facilitated a rapid exchange of species with the montane forests to allow for a rapid cascade of plant associations.

  • 10.
    Dögg Eddudottir, Sigrun
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Archaeology. Univ Iceland, Inst Life & Environm Sci, Sturlugata 7, IS-101 Reykjavik, Iceland..
    Erlendsson, Egill
    Univ Iceland, Inst Life & Environm Sci, Sturlugata 7, IS-101 Reykjavik, Iceland..
    Gisladottir, Gudrun
    Univ Iceland, Inst Life & Environm Sci, Sturlugata 7, IS-101 Reykjavik, Iceland.;Univ Iceland, Inst Earth Sci, Sturlugata 7, IS-101 Reykjavik, Iceland..
    Landscape change in the Icelandic highland: A long-term record of the impacts of land use, climate and volcanism2020In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 240, article id 106363Article in journal (Refereed)
    Abstract [en]

    Agriculture has been practiced in Iceland since settlement (landnam; AD 877). This has caused changes in vegetation communities, soil erosion, desertification and loss of carbon stocks. Little data exist regarding vegetation and ecosystems in the Icelandic highland before landnam and therefore the impact of land use over time is poorly understood. The objectives of the study are to examine the timing, nature and causes of land degradation in the highland of Northwest Iceland. Specifically, to determine the resilience of the pre-landnam highland environment to disturbances (i.e. climate cooling and volcanism) and whether land use pressure was of sufficient magnitude to facilitate ecosystem change. A sediment core was taken from the highland lake Galtabol. A chronology for the core was constructed using known tephra layers and radiocarbon dated plant macrofossils. Pollen analysis (vegetation), coprophilous fungal spores (proxy for grazing), and sediment properties (proxies for erosion) were used to provide a high-resolution, integrated vegetation and paleoenvironmental reconstruction. The pre-landnam environment showed resilience to climate cooling and repeated tephra fall. Soon after landnam the vegetation community changed and instability increased, indicated by changes in sediment properties. The pollen and spore record suggest introduction of grazing herbivores into the area after landnam. Following landnam, indicators of soil erosion appear in the sediment properties. Intensification of soil erosion occurred during the 17th century. The Galtabol record clearly demonstrates what can happen in landscapes without adequate management of natural resources and underestimation of landscape sensitivity. Introduction of land use resulted in changes in vegetation communities, loss of resilience and onset of increased soil erosion. Paleoenvironmental reconstructions may inform future decisions on management of the highland by providing baselines for natural variability in the pre-landmim environment.

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  • 11.
    Ehnvall, Betty
    et al.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, 90183, Umeå, Sweden.
    Ratcliffe, Joshua L.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, 90183, Umeå, Sweden.
    Bohlin, Elisabet
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, 90183, Umeå, Sweden.
    Nilsson, Mats B.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, 90183, Umeå, Sweden.
    Öquist, Mats G.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, 90183, Umeå, Sweden.
    Sponseller, Ryan A.
    Department of Ecology and Environmental Science, Umeå University, Linnaeus Väg 6, S-90736, Umeå, Sweden.
    Grabs, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Landscape constraints on mire lateral expansion2023In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 302, article id 107961Article in journal (Refereed)
    Abstract [en]

    Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape.

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  • 12. Feurdean, A
    et al.
    Perşoiu, A
    Tanţău, I
    Stevens, Thomas
    Centre for Quaternary Research, Department of Geography, Royal Holloway University of London, UK.
    Magyari, E.K.
    Onac, B.P.
    Markovic, S
    Andric, M
    Connor, S
    Fărcaş, S
    Gałka, M
    Gaudeny, T
    Hoek, W
    Kolaczek, P
    Kuneš, P
    Lamentowicz, M
    Marinova, E
    Michczyńska, D.J.
    Perşoiu, I
    Płóciennik, M
    Słowiński, M
    Stancikaite, M
    Sumegi, P
    Svensson, A
    Tămaş, T
    Timar, A
    Tonkov, S
    Tóth, M
    Veski, S
    Willis, K.J.
    Zernitskaya, V
    Climate variability and associated vegetation response throughout Central and Eastern Europe (CEE) between 60 and 8 ka2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, p. 206-224Article in journal (Refereed)
  • 13.
    Gallagher, S. J.
    et al.
    Univ Melbourne, Sch Earth Sci, Melbourne, Vic 3010, Australia.
    Reuning, L.
    Rhein Westfal TH Aachen, Geol Inst, EMR Energy & Mineral Resources Grp, Wuellnerstr 2, D-52056 Aachen, Germany.
    Himmler, T.
    Geol Survey Norway, Postal Box 6315 Torgarden, N-7491 Trondheim, Norway.
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    De Vleeschouwer, D.
    Univ Bremen, MARUM Ctr Marine & Environm Sci, D-28334 Bremen, Germany;Univ Bremen, Dept Geosci, D-28334 Bremen, Germany.
    Groeneveld, J.
    Univ Bremen, MARUM Ctr Marine & Environm Sci, D-28334 Bremen, Germany;Univ Bremen, Dept Geosci, D-28334 Bremen, Germany.
    Lari, A. Rastegar
    Univ Western Australia, Sch Earth Sci, 35 Stirling Highway, Nedlands, WA 6009, Australia.
    Fulthorpe, C. S.
    Univ Texas Austin, Inst Geophys, 10100 Burnet Rd R2200, Austin, TX 78758 USA.
    Bogus, K.
    Univ Exeter, Coll Engn Math & Phys Sci, Camborne Sch Mines, Penryn TR10 9FE, Cornwall, England.
    The enigma of rare Quaternary oolites in the Indian and Pacific Oceans: A result of global oceanographic physicochemical conditions or a sampling bias?2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 200, p. 114-122Article in journal (Refereed)
    Abstract [en]

    Marine ooids are iconic indicators of shallow seawater carbonate saturation state, and their formation has traditionally been ascribed to physicochemical processes. The Indo-Pacific stands out as a region devoid of oolites, particularly during the Quaternary: the "ooid enigma". Here we present results from recent coring by the International Ocean Discovery Program (IODP Expedition 356) off west Australia that shows that ooid horizons are common in Pleistocene strata up to 730,000 years old. Extensive "ooid factories" were created due to the presence of long-lived tidally influenced flat topped tropical platforms suitable for intermittent ooid accretion over hundreds to thousands of years during highstands and times of lower sea level. This work suggests marine ooids may actually be more common in Indo-Pacific than previously reported. Past global ocean alkalinity was elevated during Pleistocene glacial periods and continental climate was generally more arid in the Indo-Pacific region compared to interglacials and the Holocene. Therefore, increased aridity associated with higher alkalinity conditions during the glacials facilitated ooid precipitation on adjacent tropical carbonate platforms particularly offshore from arid Australia. This confluence of factors suggests that more "ooid factories" may be encountered by further coring Indo-Pacific regions with Pleistocene flat long-lived carbonate shelves. However, Indo-Pacific Quaternary ooid occurrences outside Australia are rare, suggesting that the Northwest Shelf may be a unique archive of this non-skeletal precipitate. Further investigations into the petrography and geochemistry of pre-Holocene ooid occurrences will provide insights into their origin and the relative role of biotic, physicochemical and other factors in their formation. (C) 2018 Elsevier Ltd. All rights reserved.

  • 14.
    Giesecke, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moving front or population expansion: How did Picea abies (L.) Karst. become frequent in central Sweden?2005In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 24, no 23-24, p. 2495-2509Article in journal (Refereed)
    Abstract [en]

    The Holocene increase in Picea abies around four central Swedish lakes was analysed using extended pollen counts over the sections comprising the tail of frequent, but discontinuous, occurrences and the beginning of the continuous curve. Simple landscape scenarios were simulated to test possible mechanisms of the spread and population expansion of P. abies in Scandinavia. Predicted patterns of pollen accumulation rates from the landscape scenarios were compared to patterns observed at the four sites to explore how the observed curves could have come about. Simulations of a moving front scenario indicate that pollen accumulation rates should rise faster than the exponential and logistic increase observed at the four sites. Exponential increase of pollen values at the sites is most likely due to locally increasing populations. However, the geography of expanding populations may influence the shape of the curve. Empirical and model results are discussed to gain new insights into the pattern and processes of the spread of P abies in central Sweden. Propagule pressure and self-fertilisation are considered as possible explanations of why small outpost populations that may have existed before the regional expansion of P. abies did not expand earlier.

  • 15. Giesecke, Thomas
    et al.
    Bennett, Keith D.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Birks, H. John B.
    Bjune, Anne E.
    Bozilova, Elisaveta
    Feurdean, Angelica
    Finsinger, Walter
    Froyd, Cynthia
    Pokorny, Petr
    Roesch, Manfred
    Seppa, Heikki
    Tonkov, Spasimir
    Valsecchi, Verushka
    Wolters, Steffen
    The pace of Holocene vegetation change: testing for synchronous developments2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 19-20, p. 2805-2814Article, review/survey (Refereed)
    Abstract [en]

    Mid to high latitude forest ecosystems have undergone several major compositional changes during the Holocene. The temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers. Here we test the hypothesis that the timing of vegetation change was synchronous on a sub-continental scale, which implies a common trigger or a step-like change in climate parameters. Pollen diagrams from selected European regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed. The results show that the temporal pattern of vegetation change was significantly different from random. Times of change cluster around 8.2, 4.8, 3.7, and 1.2 ka, while times of higher than average stability were found around 2.1 and 5.1 ka. Compositional changes linked to the expansion of Corylus avellana and Alnus glutinosa centre around 10.6 and 9.5 ka, respectively. A climatic trigger initiating these changes may have occurred 0.5 to 1 ka earlier, respectively. The synchronous expansion of C avellana and A. glutinosa exemplify that dispersal is not necessarily followed by population expansion. The partly synchronous, partly random expansion of A. glutinosa in adjacent European regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally.

  • 16. Haberle, Simon
    et al.
    Bennett, Keith
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Postglacial formation and dynamics of North Patagonian Rainforest in the Chonos Archipelago, Southern Chile2004In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 23, no 23-24, p. 2433-2452Article in journal (Refereed)
    Abstract [en]

    Pollen analysis of continuous sediment cores from two lakes in the northern Chonos Archipelago (44°S) in southern Chile shows a complete postglacial record of vegetation change. The fossil records indicate that deglaciation was complete in the northern Chonos by at least 13,600 14C yr BP. Ericaceous heath and grassland persisted for more than 600 years after deglaciation under the influence of dry/cold climates and frequent burning. Nothofagus-Pilgerodendron-Podocarpus forest, with modern analogues in the southern Chonos Archipelago, was established across the northern islands by 12,400 14C yr BP under increasingly warm and wet climates. There is no evidence for a return to cooler climates during the Younger Dryas chronozone. The rise of Tepualia stipularis and Weinmannia trichosperma as important forest components between 10,600 and 6000 14C yr BP may be associated with climates that were warmer than present. The collapse of Pilgerodendron communities during this time may have been triggered by a combination of factors related to disturbance frequency including tephra deposition events, fire and climate change. After 6000 14C yr BP Pilgerodendron recovers and Nothofagus-Pilgerodendron-Tepualia forest persists until the present. European logging and burning activity may have increased the susceptibility of North Patagonian Rainforest to invasion by introduced species and to future collapse of the long-lived Pilgerodendron communities.

  • 17. Håkansson, Lena
    et al.
    Briner, Jason
    Alexanderson, Helena
    Aldahan, Ala
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    10Be ages from central east Greenland constrain the extent of the Greenland ice sheet during the Last Glacial Maximum2007In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 26, no 19-21, p. 2316-2321Article in journal (Refereed)
    Abstract [en]

    Traditional ice sheet reconstructions have suggested two distinctly different ice sheet regimes along the East Greenland continental margin during the Last Glacial Maximum (LGM): ice to the shelf break south of Scoresby Sund and ice extending no further than to the inner shelf at and north of Scoresby Sund. We report new 10Be ages from erratic boulders perched at 250 m a.s.l. on the Kap Brewster peninsula at the mouth of Scoresby Sund. The average 10Be ages, calculated with an assumed maximum erosion rate of 1 cm/ka and no erosion (respectively, 17.3±2.3 ka and 15.1±1.7 ka) overlap with a period of increased sediment input to the Scoresby Sund fan (19–15 ka). The results presented here suggest that ice reached at least 250 m a.s.l. at the mouth of Scoresby Sund during the LGM and add to a growing body of evidence indicating that LGM ice extended onto the outer shelf in northeast Greenland.

  • 18.
    Izdebski, Adam
    et al.
    Jagiellonian University in Krakow, Institute of History.
    Holmgren, Karin
    Stockholm University, Department of Physical Geography.
    Weiberg, Erika
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Classical archaeology and ancient history.
    Stocker, Sharon R
    University of Cincinnati, Department of Classics.
    Büntgen, Ulf
    Florenzano, Assunta
    Gogou, Alexandra
    Leroy, Suzanne A.G.
    Luterbacher, Jürg
    Martrat, Belen
    Masi, Alessia
    Mercuri, Anna Maria
    Montagna, Paolo
    Sadori, Laura
    Schneider, Adam
    Sicre, Marie-Alexandrine
    Triantaphyllou, Maria
    Xoplaki, Elena
    Realising consilience: How better communication between archaeologists, historians and natural scientists can transform the study of past climate change in the Mediterranean2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 136, p. 5-22Article in journal (Refereed)
    Abstract [en]

    This paper reviews the methodological and practical issues relevant to the ways in which natural scientists, historians and archaeologists may collaborate in the study of past climatic changes in the Mediterranean basin. We begin by discussing the methodologies of these three disciplines in the context of the consilience debate, that is, attempts to unify different research methodologies that address similar problems. We demonstrate that there are a number of similarities in the fundamental methodology between history, archaeology, and the natural sciences that deal with the past (“palaeoenvironmental sciences”), due to their common interest in studying societal and environmental phenomena that no longer exist. The three research traditions, for instance, employ specific narrative structures as a means of communicating research results. We thus present and compare the narratives characteristic of each discipline; in order to engage in fruitful interdisciplinary exchange, we must first understand how each deals with the societal impacts of climatic change. In the second part of the paper, we focus our discussion on the four major practical issues that hinder communication between the three disciplines. These include terminological misunderstandings, problems relevant to project design, divergences in publication cultures, and differing views on the impact of research. Among other recommendations, we suggest that scholars from the three disciplines should aim to create a joint publication culture, which should also appeal to a wider public, both inside and outside of academia.

  • 19. Kirchner, Nina
    et al.
    Ahlkrona, Josefin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Gowan, Evan J.
    Lötstedt, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Lea, James M.
    Noormets, Riko
    von Sydow, Lina
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Dowdeswell, Julian A.
    Benham, Toby
    Shallow ice approximation, second order shallow ice approximation, and full Stokes models: A discussion of their roles in palaeo-ice sheet modelling and development2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 135, p. 103-114Article, review/survey (Refereed)
  • 20.
    Koriche, Sifan A.
    et al.
    Univ Reading, Dept Meteorol, Reading, Berks, England.;Univ Reading, Ctr Climate Change, Reading, Berks, England.;Baylor Univ, Dept Geosci, Waco, TX 76798 USA.;Univ Texas Austin, Jackson Sch Geosci, Austin, TX 78712 USA.;JiT Jimma Univ, Sch Civil & Environm Engn, Jimma, Ethiopia..
    Singarayer, Joy S.
    Univ Reading, Dept Meteorol, Reading, Berks, England.;Univ Reading, Ctr Climate Change, Reading, Berks, England..
    Cloke, Hannah L.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Univ Reading, Dept Meteorol, Reading, Berks, England.;Univ Reading, Ctr Climate Change, Reading, Berks, England.;Univ Reading, Dept Geog & Environm Sci, Reading, Berks, England.;Ctr Nat Hazards & Disaster Sci, CNDS, Uppsala, Sweden..
    Valdes, Paul J.
    Univ Bristol, Sch Geog Sci, Bristol, Avon, England.;Univ Bristol, Cabot Inst, Bristol, Avon, England..
    Wesselingh, Frank P.
    Nat Biodivers Ctr, Leiden, Netherlands..
    Kroonenberg, Salomon B.
    Delft Univ Technol, Dept Appl Earth Sci, Delft, Netherlands..
    Wickert, Andrew D.
    Univ Minnesota, St Anthony Falls Lab, Minneapolis, MN USA.;Univ Minnesota, Dept Earth & Environm Sci, Minneapolis, MN USA.;GFZ German Res Ctr Geosci, Potsdam, Germany..
    Yanina, Tamara A.
    Moscow MV Lomonosov State Univ, Fac Geog, Moscow, Russia..
    What are the drivers of Caspian Sea level variation during the late Quaternary?2022In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 283, article id 107457Article in journal (Refereed)
    Abstract [en]

    Quaternary Caspian Sea level variations depended on geophysical processes (affecting the opening and closing of gateways and basin size/shape) and hydro-climatological processes (affecting water balance). Disentangling the drivers of past Caspian Sea level variation, as well as the mechanisms by which they impacted the Caspian Sea level variation, is much debated. In this study we examine the relative impacts of hydroclimatic change, ice-sheet accumulation and melt, and isostatic adjustment on Caspian Sea level change. We performed model analysis of ice-sheet and hydroclimate impacts on Caspian Sea level and compared these with newly collated published palaeo-Caspian sea level data for the last glacial cycle. We used palaeoclimate model simulations from a global coupled ocean-atmosphere-vegetation climate model, HadCM3, and ice-sheet data from the ICE-6G_C glacial isostatic adjustment model. Our results show that ice-sheet meltwater during the last glacial cycle played a vital role in Caspian Sea level variations, which is in agreement with hypotheses based on palaeo-Caspian Sea level information. The effect was directly linked to the reorganization and expansion of the Caspian Sea palaeo-drainage system resulting from topographic change. The combined contributions from meltwater and runoff from the expanded basin area were primary factors in the Caspian Sea transgression during the deglaciation period between 20 and 15 kyr BP. Their impact on the evolution of Caspian Sea level lasted until around 13 kyr BP. Millennial scale events (Heinrich events and the Younger Dryas) negatively impacted the surface water budget of the Caspian Sea but their influence on Caspian Sea level variation was short-lived and was outweighed by the massive combined meltwater and runoff contribution over the expanded basin. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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  • 21.
    Kremer, A.
    et al.
    Alfred Wegener Inst, Helmholtz Ctr Polar & Marine Res, Bremerhaven, Germany..
    Stein, R.
    Alfred Wegener Inst, Helmholtz Ctr Polar & Marine Res, Bremerhaven, Germany..
    Fahl, K.
    Alfred Wegener Inst, Helmholtz Ctr Polar & Marine Res, Bremerhaven, Germany..
    Ji, Z.
    State Ocean Adm, Inst Oceanog 2, Guangzhou, Guangdong, Peoples R China..
    Yang, Z.
    State Ocean Adm, Inst Oceanog 2, Guangzhou, Guangdong, Peoples R China..
    Wiers, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Matthiessen, J.
    Alfred Wegener Inst, Helmholtz Ctr Polar & Marine Res, Bremerhaven, Germany..
    Forwick, M.
    UiT Arctic Univ Norway, Tromso, Norway..
    Lowemark, L.
    Stockholm Univ, Stockholm, Sweden..
    O'Regan, M.
    Stockholm Univ, Stockholm, Sweden..
    Chen, J.
    State Ocean Adm, Inst Oceanog 2, Guangzhou, Guangdong, Peoples R China..
    Snowball, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Changes in sea ice cover and ice sheet extent at the Yermak Plateau during the last 160 ka - Reconstructions from biomarker records2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 182, p. 93-108Article in journal (Refereed)
    Abstract [en]

    The Yermak Plateau is located north of Svalbard at the entrance to the Arctic Ocean, i.e. in an area highly sensitive to climate change. A multi proxy approach was carried out on Core PS92/039-2 to study glacial interglacial environmental changes at the northern Barents Sea margin during the last 160 ka. The main emphasis was on the reconstruction of sea ice cover, based on the sea ice proxy IP25 and the related phytoplankton - sea ice index PIP25. Sea ice was present most of the time but showed significant temporal variability decisively affected by movements of the Svalbard Barents Sea Ice Sheet. For the first time, we prove the occurrence of seasonal sea ice at the eastern Yermak Plateau during glacial intervals, probably steered by a major northward advance of the ice sheet and the formation of a coastal polynya in front of it. Maximum accumulation of terrigenous organic carbon, IP25 and the phytoplankton biomarkers (brassicasterol, dinosterol, HBI III) can be correlated to distinct deglaciation events. More severe, but variable sea ice cover prevailed at the Yermak Plateau during interglacials. The general proximity to the sea ice margin is further indicated by biomarker (GDGT) - based sea surface temperatures below 2.5 degrees C.

  • 22.
    Költringer, Chiara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bradák, Balázs
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Almqvist, Bjarne
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Banak, Adriano
    Lindner, Martin
    Kurbanov, Redzhep
    Snowball, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Palaeoenvironmental implications from Lower Volga loess - Joint magnetic fabric and multi-proxy analyses2021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 267, p. 107057-Article in journal (Refereed)
    Abstract [en]

    Magnetic fabric (MF) investigations complemented by geochemical and grain surface analyses of the understudied and controversial marine isotope stage (MIS) 5 b, 4 and 3 loess deposits in the Lower Volga region, Russia show that the material has been transported and deposited by wind and to a large extent experienced post-depositional reworking. Grain surface features suggest that the material was glacially ground and fluvially transported prior to final aeolian deposition as loess. Secondary magnetic fabrics in the loess reveal pedogenic and cryogenic processes and a generally cold environment with brief shifts to warmer climate during late MIS 5 and MIS 3. Palaeowind reconstructions derived from preserved primary aeolian MF, indicate locally influenced westerly and north-westerly flow as part of a wider scale westerly wind pattern, similar to modern day winter conditions. We suggest that the climate of the last glacial in the Northern Caspian Lowland was cold and dry, with higher windspeeds and less variability during MIS 4 compared to MIS 3.

  • 23. Large, DJ
    et al.
    Spiro, B
    Ferrat, M
    Shopland, M
    Kylander, M
    Gallagher, K
    Li, X
    Shen, C
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics. Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Zhang, G
    Darling, WG
    Weiss, D
    The influence of climate, hydrology and permafrost on Holocene peat accumulation at 3500 m on the eastern Qinghai-Tibetan plateau2009In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 28, no 27-28, p. 3303-3314Article in journal (Refereed)
    Abstract [en]

    Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 14C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ13C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ13C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ18O and δD values of the spring water emanating around the peat deposit, down to −13.8 and −102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.

  • 24.
    Ljungqvist, Fredrik Charpentier
    et al.
    Uppsala University, Swedish Collegium for Advanced Study (SCAS).
    Piermattei, Alma
    Seim, Andrea
    Krusic, Paul J.
    Buntgen, Ulf
    He, Minhui
    Kirdyanov, Alexander V.
    Luterbacher, Jürg
    Schneider, Lea
    Seftigen, Kristina
    Stahle, David W.
    Villalba, Ricardo
    Yang, Bao
    Esper, Jan
    Ranking of tree-ring based hydroclimate reconstructions of the past millennium2020In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 230Article in journal (Refereed)
    Abstract [en]

    To place recent hydroclimate changes, including drought occurrences, in a long-term historical context, tree-ring records serve as an important natural archive. Here, we evaluate 46 millennium-long tree-ring based hydroclimate reconstructions for their Data Homogeneity, Sample Replication, Growth Coherence, Chronology Development, and Climate Signal based on criteria published by Esper et al. (2016) to assess tree-ring based temperature reconstructions. The compilation of 46 individually calibrated site reconstructions includes 37 different tree species and stem from North America (n = 29), Asia (n = 10); Europe (n = 5), northern Africa (n = 1) and southern South America (n = 1). For each criterion, the individual reconstructions were ranked in four groups, and results showed that no reconstruction scores highest or lowest for all analyzed parameters. We find no geographical differences in the overall ranking, but reconstructions from arid and semi-arid environments tend to score highest. A strong and stable hydroclimate signal is found to be of greater importance than a long calibration period. The most challenging trade-off identified is between high continuous sample replications, as well as a well-mixed age class distribution over time, and a good internal growth coherence. Unlike temperature reconstructions, a high proportion of the hydroclimate reconstructions are produced using individual series detrending methods removing centennial-scale variability. By providing a quantitative and objective evaluation of all available tree-ring based hydroclimate reconstructions we hope to boost future improvements in the development of such records and provide practical guidance to secondary users of these reconstructions.

  • 25. Lougheed, Bryan C.
    et al.
    Nilsson, Andreas
    Björck, Svante
    Snowball, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Muscheler, Raimund
    A deglacial palaeomagnetic master curve for Fennoscandia Providing a dating template and supporting millennial-scale geomagnetic field patterns for the past 14 ka2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 106, p. 155-166Article in journal (Refereed)
    Abstract [en]

    Reconstructions of palaeomagnetic secular variation (PSV) in sediment cores can be compared to well-dated regional PSV master curves to infer deposition age. The existing PSV master curve for Fennoscandia, "Fennostack" (Snowball et al., 2007), is limited to the past 10 ka. In this study, we construct a deglacial (for the interval 14-11 ka) PSV master curve for Fennoscandia by including data from a number of existing studies in the region, updating geochronologies where necessary. We also produce new deglacial PSV data from Baltic Sea long-core sediments. By selecting three suitable sites, one in southern Sweden and two in northwest Russia, we produce, for the first time, a deglacial PSV master curve for Fennoscandia, which will provide a useful alternative dating tool for deglacial time intervals, especially considering that deglacial sediments are often unsuitable for C-14 dating. Additionally, we use the deglacial PSV master curve to assess current hypotheses regarding geomagnetic field changes. Time varying geomagnetic field models constrained by Holocene PSV data from around the globe have predicted the presence of latitudinal and longitudinal patterns in the position of the north geomagnetic pole (NGP). Specifically, a 1350 year cycle in NGP latitude has been noted, along with two preferred dominant mode longitudinal bands for NGP; in Europe and North America (Korte et al., 2011; Nilsson et al., 2011). Most PSV studies of sediment are, however, limited to the Holocene epoch. By combining our deglacial PSV master curve with 'Fennostack', we are able to assess general patterns in inclination for the past 14 ka, and compare these to a general prediction of regional inclination for the last 14 ka, based on an extrapolation of the latitudinal and longitudinal NGP periodicity noted by Nilsson et al. (2011). The model prediction suggests that the Fennoscandian PSV for the past 14 ka should reveal three recurring intervals of generally steeper inclination due to a dominant NGP longitudinal band in Europe. We find that the Fennoscandian PSV does indeed show these intervals of generally steeper inclination for the time periods expected, supporting the hypothesised periodic NGP variation, which may represent an inherent feature of the geodynamo. (C) 2014 Elsevier Ltd. All rights reserved.

  • 26. Ma, Zhaoying
    et al.
    Zan, Jinbo
    Heller, Friedrich
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland.
    Xiao, Xue
    Fang, Xiaomin
    Wang, Genhou
    Zhang, Weilin
    Shen, Maohua
    Zhang, Yuao
    Mineralogical and magnetic variations of periglacial loess in SE Tibet reveal mid-Pleistocene expansion of Tibetan glacial activity2024In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 330, article id 108592Article in journal (Refereed)
    Abstract [en]

    The formation and evolution of the cryosphere on the Tibetan Plateau is of great significance in understanding the Earth's carbon and climatic system. Periglacial loess deposits in southeastern Tibet offer a means to constrain this history as they contain critical information on glacial grinding and frost shattering processes in high-altitude mountain regions through time, which yield lithogenic fractions of largely loess silts and sands. Based on combined analyses of lithogenic magnetic properties and mineralogical composition, here we find that increasing high mountain production and supply of fresh detrital components since the mid-Pleistocene climate transition (MPT, 1.2–0.7 Ma) led to a substantial increase of the lithogenic susceptibility and decrease in chemical weathering intensity of periglacial loess in southeastern Tibet. The agreement of these findings with similar results from eolian loess on the northern margins of the Tibetan Plateau suggests a plateau-wide glacier expansion during the MPT. Enhanced glacial erosion and freeze-thaw activities occurred in the high-altitude mountain regions of the plateau during the MPT, thereby providing vast amounts of fresh detritus for the formation of loess deposits. High and constant values of lithogenic magnetic parameters in the loess deposits after 0.7–0.6 Ma further indicate that the Middle Pleistocene is a critical period for the establishment of modern-like glacial and periglacial landforms on the Tibetan Plateau. Our results further suggest that enhanced Quaternary glaciation in SE Tibet occurred earlier than in the north, which we attribute to climate cooling combined with regional seasonal snowline lowering. As such, a close relationship exists between global climate changes, development of pan-Tibetan glaciations, and large-scale dust emission.

  • 27. Markovic, Slobodan B.
    et al.
    Hambach, Ulrich
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Kukla, George J.
    Heller, Friedrich
    Mccoy, William D.
    Oches, Eric A.
    Buggle, Bjoern
    Zoeller, Ludwig
    The last million years recorded at the Stari Slankamen (Northern Serbia) loess-palaeosol sequence: revised chronostratigraphy and long-term environmental trends2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 9-10, p. 1142-1154Article in journal (Refereed)
  • 28.
    McMichael, C. N. H.
    et al.
    Univ Amsterdam, Inst Biodivers & Ecosyst Dynam, Dept Ecosyst & Landscape Dynam, Sci Pk 904, NL-1098 GE Amsterdam, Netherlands.
    Witteveen, N. H.
    Univ Amsterdam, Inst Biodivers & Ecosyst Dynam, Dept Ecosyst & Landscape Dynam, Sci Pk 904, NL-1098 GE Amsterdam, Netherlands.
    Scholz, S.
    Univ Amsterdam, Inst Biodivers & Ecosyst Dynam, Dept Ecosyst & Landscape Dynam, Sci Pk 904, NL-1098 GE Amsterdam, Netherlands.
    Zwier, M.
    Vrije Univ, Dept Earth Sci, De Boelelaan 1085, NL-1081 HV Amsterdam, Netherlands; Univ Bergen, Dept Biol Sci, Thormohlensgate 53A, N-5006 Bergen, Norway; Univ Bergen, Bjerknes Ctr Climate Res, Thormohlensgate 53A, N-5006 Bergen, Norway.
    Prins, M. A.
    Vrije Univ, Dept Earth Sci, De Boelelaan 1085, NL-1081 HV Amsterdam, Netherlands.
    Lougheed, Bryan C.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Mothes, P.
    Escuela Politec Nacl, Inst Geofis, Quito 17012759, Ecuador.
    Gosling, W. D.
    Univ Amsterdam, Inst Biodivers & Ecosyst Dynam, Dept Ecosyst & Landscape Dynam, Sci Pk 904, NL-1098 GE Amsterdam, Netherlands.
    30,000 years of landscape and vegetation dynamics in a mid-elevation Andean valley2021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 258, article id 106866Article in journal (Refereed)
    Abstract [en]

    The mid-elevation settings of the Andes are important biodiversity hotspots, yet little is known of their long-term ecology or environmental change. Here, we assess 30,000 years of landscape and vegetation dynamics on an alluvial terrace located in a mid-elevation valley of the Ecuadorian Andes (Campo Libre). We used loss-on-ignition and particle size analysis to reconstruct past river dynamics, charcoal analysis to reconstruct past fire regimes, and phytolith analysis to reconstruct vegetation change through time. Our results show that Campo Libre was a part of the active floodplain system of the Quijos River until 18,000 cal yr BP. The biggest vegetation change in vegetation at Campo Libre occurred ca. 13,000 cal yr BP, when the site warmed and dried, transforming the swampy alluvial terrace into a palm forest. As Ho-locene precipitation increased, the site transformed back into a swamp around 7500 cal yr BP, and it remained that way until maize agriculture began around 4600 cal yr BP. Local and regional fires were absent from the system until regional fires were detected ca. 3300 cal yr BP. By ca. 2700 cal yr BP, maize cultivation became frequent and regular. Climate, tectonic activity, and the human history have shaped the modern vegetation around Campo Libre, although during different periods of the Holocene. Our results demonstrate the ability of phytoliths to reconstruct vegetation change through time, and show that the mid-elevation Andean valley systems were highly dynamic over the last 30,000 years.

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  • 29. Norstrom, E.
    et al.
    Neumann, F. H.
    Scott, L.
    Smittenberg, R. H.
    Holmstrand, H.
    Lundqvist, S.
    Snowball, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Sundqvist, H. S.
    Risberg, J.
    Bamford, M.
    Late Quaternary vegetation dynamics and hydro-climate in the Drakensberg, South Africa2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 105, p. 48-65Article in journal (Refereed)
    Abstract [en]

    A multi-proxy study of a sediment sequence from Braamhoek wetland, covering the last c. 16,000 years, reveals a record of regional climate and vegetation dynamics in the Drakensberg region, South Africa, including signals from both the organic sediment fraction (fossil pollen, charcoal, n-alkane abundance, n-alkane delta C-13, TOC) and the inorganic fraction (mineral magnetic properties). The reconstruction, supported by a robust chronology, indicates two major periods of increased regional wetness during the late Pleistocene to early Holocene phase (c. 13,800-12,600 cal yr BP; c. 10,200-8500 cal yr BP) and one during the late Holocene (c. 2000 cal yr BP to present). Drier conditions are recorded during the Younger Dryas (c. 12,600-11,300 cal yr BP) and mid-Holocene (c. 7000-2000 cal yr BP). A major decline in fynbos vegetation during the early Holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern South Africa from c. 8500 cal yr BP. Comparison with records from interior of South Africa show relatively high inter-site variability, however, the Braamhoek moisture proxies do co-vary with the speleothem isotope records from Makapansgat, suggesting a similar hydro-climate evolution in eastern and interior parts of the summer rainfall region during the studied period. On multi-millennial time scales, an inverse hydro-climatological pattern is evident between these two South African records and reconstructions from tropical locations in southeast Africa. Such a rainfall dipole between eastern tropical and southern Africa, has previously been identified on shorter time scales, i.e. on inter-annual to millennial scales. The Braamhoek study suggests that a similar dipole pattern is acting also on a multi-millennial perspective. These long-term precipitation anomalies are tentatively coupled to teleconnections from multi-millennial changes in the dynamics of the Indian Ocean Dipole (IOD) and El Nino-Southern Oscillation (ENSO). 

  • 30. Rasmussen, Christian F.
    et al.
    Christiansen, Hanne H.
    Buylaert, Jan-Pieter
    Cunningham, Alastair
    Schneider, Ramona
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Knudsen, Mads F.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    High-resolution OSL dating of loess in Adventdalen, Svalbard: Late Holocene dust activity and permafrost development2023In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 310, article id 108137Article in journal (Refereed)
    Abstract [en]

    There is considerable uncertainty over the nature and causes of Holocene dust activity in the Arctic, and its links to climatic changes. Loess deposits act as near-source archives of dust deposition and provide a means to address these uncertainties. Here we develop a fully independent age model for a loess core taken in Adventdalen, Svalbard, based on 136 quartz luminescence ages taken at 2 cm intervals. This represents the most detailed luminescence dating analysis undertaken to date on a sedimentary archive. Extensive laboratory tests and stratigraphic consistency indicate that the quartz luminescence ages are reliable. Together with grain size and cryostratigraphic analyses, as well as stratigraphic investigation of an adjacent loess exposure, the exceptional detail of the chronology combined with Bayesian age modelling uniquely allows changes in loess accumulation rates, particle size and permafrost development to be reconstructed over the last 3000 yrs on 101–103 yr timescales. The results show that loess deposition was mostly continuous over this interval, albeit with a short period of reworking or non-aeolian sedimentation during the Little Ice Age. Permafrost development in the loess is dominantly syngenetic, with ice contents increasing with depth. There is considerable variability in loess mass accumulation rate over the late Holocene, with peaks occurring during the last 250 yrs, as well as at 750–900, 1050–1200, 1400–1600, 1900–2450 and possibly 2700–3000 a. These peaks generally coincide with increased coarse silt deposition, potentially suggesting a link with greater wind activity. However, the peaks also seem to coincide with possible warm phases on Svalbard, which would rather imply that temperature-driven sediment availability in glaciofluvial source areas is the main control on dustiness in Adventdalen. In any case, the rates of loess deposition in the Adventdalen core are exceptionally high globally (up to 0.35 cm yr−1/2900 g m−2 yr−1 sedimentation and mass accumulation rates, respectively), and if representative of wider patterns across Svalbard, may suggest that the archipelago is a more important high latitude dust source than previously realised.

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  • 31.
    Razmjooei, Mohammad J.
    et al.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden..
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Coxall, Helen K.
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden..
    Baumann, Karl-Heinz
    Univ Bremen, Dept Geosci, POB 330440, D-28334 Bremen, Germany..
    Vermassen, Flor
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden..
    Niessen, Frank
    Helmholtz Ctr Polar & Marine Res AWI, Alfred Wegener Inst, Bremerhaven, Germany..
    O'Regan, Matt
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden.;Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden..
    Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments2023In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 321, article id 108382Article in journal (Refereed)
    Abstract [en]

    Despite extensive chronological studies, the relationship between the age and sub-seafloor depth of Arctic Ocean sediments remains ambiguous. This prevents confident identification of paleoceanographic changes in the Arctic during the Quaternary. Currently, age-depth models derived from uranium-series decay in Arctic sediments diverge by hundreds of thousands of years compared to those built on known evolutionary appearances and extinctions of calcareous nannoplankton, a group of globally valuable age-markers. Here we report on highresolution biostratigraphic analysis of late Quaternary sediments in six cores from the central Arctic Ocean (CAO). We applied paired light microscope (LM) and scanning electron microscope (SEM) imaging to improve nannofossil diagnosis. We argue that low abundances and poor preservation have led to misidentification of the true stratigraphic depth of the critical Pleistocene nannofossil bio-events that have underpinned age models for many Arctic sedimentary records for decades. The revised calcareous nannofossil biochronology provides a radically different geochronological framework for CAO sediments - indicating that what had previously been identified as Marine Isotope Stage (MIS) 7 (191-243 ka) in many sedimentary records is older than MIS 12 (424-478 ka). Furthermore, it suggests that previously inferred sub-stages of MIS 5 could represent full interglacial periods rather than interstadials. The results help reconcile the different dating approaches and provide a transformative step towards resolving the disparity in Quaternary Arctic age-depth models, bringing us one step closer to accurate paleoceanographic reconstructions based on sediment cores.

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  • 32.
    Ruskeeniemi, Timo
    et al.
    Geol Survey Finland, FI-02150 Espoo, Finland.
    Engstrom, Jon
    Geol Survey Finland, FI-02150 Espoo, Finland.
    Lehtimaki, Jukka
    Geol Survey Finland, FI-02150 Espoo, Finland.
    Vanhala, Heikki
    Geol Survey Finland, FI-02150 Espoo, Finland.
    Korhonen, Kimmo
    Geol Survey Finland, FI-02150 Espoo, Finland.
    Kontula, Anne
    Posiva Oy, FI-27160 Eurajoki, Finland.
    Liljedahl, Lillemor Claesson
    Swedish Nucl Fuel & Waste Management Co, Box 3091, SE-16903 Solna, Sweden.
    Naslund, Jens-Ove
    Swedish Nucl Fuel & Waste Management Co, Box 3091, SE-16903 Solna, Sweden.
    Pettersson, Rickard
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala Univ, Dept Earth Sci, SE-75236 Uppsala, Sweden.
    Subglacial permafrost evidencing re-advance of the Greenland Ice Sheet over frozen ground2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 199, p. 174-187Article in journal (Refereed)
    Abstract [en]

    Greenland Ice Sheet (GrIS) covers an area of 1.7 million km(2). It has been an important source of climate information and the air temperature history of Greenland is well known. However, the thermal history and temperature conditions of the Greenland bedrock are poorly known. There are only few records on the temperature of the proglacial bedrock and no records on bedrock temperature underneath the ice sheet. The Greenland Analogue Project (GAP) recently investigated hydrological, hydrogeological and geochemical processes in Kangerlussuaq, West Greenland. Because permafrost has a major hydrological impact in Arctic regions, the cryogenic structure of the bedrock was an important research topic. From previous studies it was already known that Kangerlussuaq is located within the zone of continuous permafrost. Temperature profiling in a new research borehole, extending horizontally 30 m underneath the ice sheet, revealed that permafrost is 350 m deep at the ice margin. This result raised the question how far the permafrost extends under the ice sheet? In order to investigate the thermal properties, we made a series of electromagnetic (EM) soundings at the ice margin area - on proglacial area and on the ice sheet - and detected, that subglacial permafrost extends at least 2 km from the ice margin to inland. We also observed a patchy unfrozen sediment layer between the ice and the frozen bedrock. Possible existence of subglacial sediments and their role in ice dynamics has been debated in many recent papers. Our successful campaign shows that geophysics can be used for bedrock investigations through thick ice, which is known to be challenging for electromagnetic methods. Our results provide the first direct evidence supporting the proposed Holocene ice re-advance over frozen ground, and contribute to the discussion on the rapid climate changes in past, to the future of the ice sheet under warming climate and hydrogeology at the ice margin.

  • 33. Schwalb, Antje
    et al.
    Dean, Walter
    Güde, Hans
    Hanisch, Sabine
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wessels, Martin
    Benthic ostracode ∂13C as sensor for early Holocene establishment of modern circulation patterns in Central Europe2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 66, no SI, p. 112-122Article in journal (Refereed)
    Abstract [en]

    Shells from adult specimen of the benthic ostracodes Limnocytherina sanctipatricii and Leucocythere mirabilis selected from a 8.7 m long piston core provide continuous stable oxygen and carbon records for the past approximately 16 ka. Oxygen isotopes from both species show identical values and track the general North Atlantic and European temperature history since deglaciation in great detail. Values of ostracode δ18O values suggest that about 16 cal ka the average annual air temperatures were about 11 °C colder than today. Carbon isotopic values from both species of ostracodes are similar during the Lateglacial and early Holocene, and show an overall decrease from −4‰ to −7‰ that is probably related to an increase in photosynthetic productivity in the water column, as suggested by an increase in organic carbon, delivering 13C-depleted organic matter to the bottom waters (carbon pump). About 9 cal ka only L. mirabilis δ13C values decreased about −2.5‰ within 300 years. Higher δ13C variability and ecological evidence suggests that L. mirabilis represents a summer signal, whereas L. sanctipatricii displays a more subdued annual average. After about 7 cal ka another −1.5% decrease for both species, accompanied by an increase in magnetic susceptibility, a decrease in carbonate content, and more positive bulk carbonate isotope values followed, suggesting higher detrital-clastic input into the lake. In order to provide a possible mechanism explaining the negative L. mirabilis δ13C-values, sediment pore water profiles of O2 and CH4 in short cores collected from sites distal to proximal to the Alpine Rhine River delta, were inspected. Sediments in cores from more proximal sites to the Rhine delta become anoxic at shallower sediment depth due to the decay of high allochthonous organic carbon input to the sediment, which greatly increases concentrations of methane in pore waters closer to the Rhine inflow. When methane is oxidized close to the sediment–water-interface, 13C-depleted carbon is added to pore water DIC that is then available for incorporation into ostracode shells. This mechanism suggests that about 9 cal ka the oxygen supply to the bottom waters, especially in summer, decreased. This stimulated methanogenesis close to the sediment–water-interface, and provided δ13C-depleted carbon to benthic dwellers. Independent evidence for methanogenesis is provided by the increase in concentration of tetrahymanol after about 9 cal ka coincident with the decrease in δ13C of L. mirabilis. We suggest that about 9 cal ka the northward retreat of the Northern Hemisphere Ice Sheets, and consequently the polar front, left the alpine region affected by a more oceanic climate, characterized by warmer winters as they occur today especially during the positive North Atlantic Oscillation Index phase. More frequently incomplete mixing of the water column may have shifted the decay of organic matter faster to anaerobic conditions in surficial sediments especially during summer. By about 7 cal ka the North Atlantic region had probably warmed sufficiently to increase precipitation in Central Europe and consequently detrital-clastic runoff to Lake Constance.

  • 34.
    Sim, Thomas G.
    et al.
    Univ Leeds, Sch Geog, Leeds, England.;Univ Exeter, Fac Environm Sci & Econ, Geog, Exeter, Devon, England..
    Swindles, Graeme T.
    Queens Univ Belfast, Sch Nat & Built Environm, Geog, Belfast, North Ireland.;Carleton Univ, Ottawa Carleton Geosci Ctr, Dept Earth Sci, Canada, ON, Canada..
    Morris, Paul J.
    Univ Leeds, Sch Geog, Leeds, England..
    Baird, Andy J.
    Univ Leeds, Sch Geog, Leeds, England..
    V. Gallego-Sala, Angela
    Univ Exeter, Fac Environm Sci & Econ, Geog, Exeter, Devon, England..
    Wang, Yuwan
    Univ Exeter, Fac Environm Sci & Econ, Geog, Exeter, Devon, England.;Univ Queensland, Sch Earth & Environm Sci, Brisbane, Australia..
    Blaauw, Maarten
    Queens Univ Belfast, Sch Nat & Built Environm, Archaeol & Palaeoecol, Belfast, North Ireland..
    Camill, Philip
    Bowdoin Coll, Coll Stn 6800, Earth & Oceanog Sci Dept, Brunswick, ME 04011 USA..
    Garneau, Michelle
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Hardiman, Mark
    Univ Portsmouth, Sch Environm Geog & Geosci, Buckingham Bldg, L Terrace, Portsmouth PO1 3HE, Hampshire, England..
    Loisel, Julie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics. Texas A&M Univ, Dept Geog, College Stn, TX 77843 USA. Univ Helsinki, Fac Biol & Environm Sci, Environm Res Programme, Environm Change Res Unit ECRU, POB 65, Viikinkaari 1, Helsinki 00014, Finland. US Geol Survey, GEMEG SC, Menlo Pk, CA 94025 USA. Adam Mickiewicz Univ, Inst Geol, Krygowskiego 12, PL-61680 Poznan, Poland. Katholieke Univ Leuven, Dept Earth & Environm Sci, Div Geog & Tourism, Celestijnenlaan 200E, B-3001 Heverlee, Belgium. Res Fdn Flanders FWO, B-1000 Brussels, Belgium. Univ Latvia, Inst Biol, Lab Geobot, Riga, Latvia. Czech Acad Sci, Inst Bot, Zamek 1, Pruhonice 25243, Czech Republic. Univ Bayreuth, Bayreuth Ctr Ecol & Environm Res BayCEER, Soil Ecol, Dr Hans Frisch Str 1-3, D-95448 Bayreuth, Germany. Thomas More Univ Appl Sci, Zandpoortvest 60, B-2800 Mechelen, Belgium. Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, Key Lab Land Surface Pattern & Simulat, Beijing 100101, Peoples R China. Linnaeus Univ, Dept Biol & Environm Sci, Kalmar, Sweden. Univ Toronto, Dept Earth Sci, 22 Ursula Franklin St, Toronto, ON M5S 3B1, Canada. Univ Montpellier, ISEM, CNRS, IRD, Montpellier, France. Coventry Univ, Ctr Agroecol Water & Resilience, Wolston Lane, Coventry CV8 3LG, Warwickshire, England. Univ Kiel, Inst Preand Protohist Archaeol, D-24098 Kiel, Germany. Goethe Univ, Dept Phys Geog, Altenhoferallee 1, D-60438 Frankfurt, Germany. Babes Bolyai Univ, UBB Inst, STAR, Kogalniceanu 1, Cluj Napoca 400084, Romania. Univ Lodz, Fac Biol & Environm Protect, Dept Biogeog Paleoecol & Nat Protect, Banacha 1-3, PL-90237 Lodz, Poland. US Geol Survey, Florence Bascom Geosci Ctr, Reston, VA USA. Univ Tartu, Inst Ecol & Earth Sci, Tartu, Estonia. Univ Munster, Inst Landscape Ecol, Ecohydrol & Biogeochem Grp, Heisenbergstr 2, D-48149 Munster, Germany. Lomonosov Moscow State Univ, Leninskiye Gory 1, Moscow 119991, Russia. Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden. Univ Victoria, Ctr Forest Biol, Dept Biol, Victoria, BC V8W 2Y2, Canada. Adam Mickiewicz Univ, Fac Geog & Geol Sci, Climate Change Ecol Res Unit, Bogumila Krygowskiego 10, PL-61680 Poznan, Poland. Univ Laval, Ctr Etud Nord, Dept Geog, Quebec City, PQ, Canada. Polish Acad Sci, Inst Geog & Spatial Org, Twarda 51-55, PL-00818 Warsaw, Poland. Univ Latvia, Dept Geol, Jelgavas Iela 1, LV-1004 Riga, Latvia. Univ Magallanes, Ctr Invest GAIA Antartica, Punta Arenas 6210427, Chile. Baden Wurttemberg State Off Cultural Heritage, Lab Archaeobot, Fischersteig 9, D-78343 Gaienhofen Hemmenhofen, Germany. Wageningen Univ & Res, Vegetat Forest & Landscape Ecol, Wageningen Environm Res, POB 47, NL--6700 AA Wageningen, Netherlands. Univ Aberdeen, Sch Geosci, Aberdeen AB24 3UF, Scotland. Shenzhen MSU BIT Univ, Int Univ Pk Rd, Shenzhen 517182, Peoples R China. Univ Gloucestershire, Ctr Environm Change & Quaternary Res, Sch Nat & Social Sci, Gloucester, England. Ctr Invest Ecosistemas Patagonia, Coyhaique, Aysen, Chile. Royal Holloway Univ London, Dept Geog, Egham TW20 0EX, Surrey, England. Inst Paleontol Humaine, CNRS, HNHP UMR 7194, Museum Natl Hist Nat, Paris, France. Trinity Coll Dublin, Sch Nat Sci, Bot Dept, Dublin, Ireland. Russian Acad Sci, Inst Geog, Staromonetny Lane, Moscow 119017, Russia. Carleton Univ, Dept Geog & Environm Studies, 1125 Colonel Dr, Ottawa, ON K1S 5B6, Albania. Bishops Univ, Dept Environm Agr & Geog, Sherbrooke, PQ J1M 1Z7, Canada. Univ Franche Comte, Chronoenvironm UMR6249, CNRS, F-25000 Besancon, France. Univ Lorraine, Interdisciplinary Lab Continental Environm, CNRS, Campus Bridoux, F-57070 Metz, France. Stockholm Univ, Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden. Stockholm Univ, Dept Phys Geog, SE-10691 Stockholm, Sweden. Univ Cologne, Inst Geog Didakt, Gronewaldstr 2, D-50931 Cologne, Germany. Univ Modena & Reggio Emilia, Dept Life Sci, Lab Palynol & Paleobot, Modena, Italy. Univ Balear Isl, Dept Hist Sci & Theory Art, ArqueoUIB, Palma De Mallorca, Spain. Univ Alberta, Dept Renewable Resources, Edmonton, AB, Canada. Univ Latvia, Dept Geog, Jelgavas Iela 1, LV-1004 Riga, Latvia. Tallinn Univ Technol, Dept Geol, Ehitajate Tee 5, EE-19086 Tallinn, Estonia. Lake & Peatland Res Ctr, Aloja, Puikule, Latvia. Russian Acad Sci, AN Severtsov Inst Ecol & Evolut, Moscow 119071, Russia. Univ Eastern Finland, Fac Sci & Forestry, Sch Forest Sci, POB 111, Joensuu FI-80101, Finland. Northeast Normal Univ, Sch Geog Sci, Key Lab Geog Proc & Ecol Secur Changbai Mt, Minist Educ, Changchun 130024, Jilin, Peoples R China. Chinese Acad Sci, Northeast Inst Geog & Agroecol, State Key Lab Black Soils Conservat & Utilizat, Changchun 130102, Jilin, Peoples R China. Univ Verona, Dept Biotechnol, Str Grazie 15, I-37134 Verona, Italy. Inst Geol & Geophys, Chinese Acad Sci, Key Lab Cenozo Geol & Environm, Beijing 100029, Peoples R China..
    Valiranta, Minna
    Anderson, Lysanna
    Apolinarska, Karina
    Augustijns, Femke
    Aunina, Liene
    Beaulne, Joannie
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Bobek, Premysl
    Borken, Werner
    Broothaerts, Nils
    Cui, Qiao-Yu
    Davies, Marissa A.
    Ejarque, Ana
    Farrell, Michelle
    Feeser, Ingo
    Feurdean, Angelica
    Fewster, Richard E.
    Univ Leeds, Sch Geog, Leeds, England..
    Finkelstein, Sarah A.
    Gaillard, Marie-Jose
    Univ Queensland, Sch Earth & Environm Sci, Brisbane, Australia..
    Gaika, Mariusz
    Heffernan, Liam
    Hoevers, Renske
    Jones, Miriam
    Juselius-Rajamaki, Teemu
    Karofeld, Edgar
    Knorr, Klaus-Holger
    Korhola, Atte
    Kupriyanov, Dmitri
    Kylander, Malin E.
    Lacourse, Terri
    Lamentowicz, Mariusz
    Lavoie, Martin
    Lemdahl, Geoffrey
    Lucow, Dominika
    Magnan, Gabriel
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Maksims, Alekss
    Mansilla, Claudia A.
    Marcisz, Katarzyna
    Marinova, Elena
    Mathijssen, Paul J. H.
    Mauquoy, Dmitri
    Mazei, Yuri A.
    Mazei, Natalia
    McCarroll, Julia
    McCulloch, Robert D.
    Milner, Alice M.
    Miras, Yannick
    Mitchell, Fraser J. G.
    Novenko, Elena
    Pelletier, Nicolas
    Peros, Matthew C.
    Piilo, Sanna R.
    Pilote, Louis-Martin
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Primeau, Guillaume
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Rius, Damien
    Robin, Vincent
    Robitaille, Mylene
    Geotop Univ Quebec Montreal, CP 8888,Succ Ctr Ville, Montreal, PQ H3C 3P8, Canada..
    Roland, Thomas P.
    Univ Exeter, Fac Environm Sci & Econ, Geog, Exeter, Devon, England..
    Ryberg, Eleonor
    Sannel, A. Britta K.
    Schittek, Karsten
    Servera-Vives, Gabriel
    Shotyk, William
    Slowinski, Michal
    Stivrins, Normunds
    Swinnen, Ward
    Thompson, Gareth
    Univ Exeter, Fac Environm Sci & Econ, Geog, Exeter, Devon, England..
    Tiunov, Alexei
    Tsyganov, Andrey N.
    Tuittila, Eeva-Stiina
    Verstraeten, Gert
    Wallenius, Tuomo
    Webb, Julia
    Willard, Debra
    Yu, Zicheng
    Zaccone, Claudio
    Zhang, Hui
    Regional variability in peatland burning at mid-to high-latitudes during the Holocene2023In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 305, article id 108020Article in journal (Refereed)
    Abstract [en]

    Northern peatlands store globally-important amounts of carbon in the form of partly decomposed plant detritus. Drying associated with climate and land-use change may lead to increased fire frequency and severity in peatlands and the rapid loss of carbon to the atmosphere. However, our understanding of the patterns and drivers of peatland burning on an appropriate decadal to millennial timescale relies heavily on individual site-based reconstructions. For the first time, we synthesise peatland macrocharcoal re-cords from across North America, Europe, and Patagonia to reveal regional variation in peatland burning during the Holocene. We used an existing database of proximal sedimentary charcoal to represent regional burning trends in the wider landscape for each region. Long-term trends in peatland burning appear to be largely climate driven, with human activities likely having an increasing influence in the late Holocene. Warmer conditions during the Holocene Thermal Maximum (similar to 9e6 cal. ka BP) were associated with greater peatland burning in North America's Atlantic coast, southern Scandinavia and the Baltics, and Patagonia. Since the Little Ice Age, peatland burning has declined across North America and in some areas of Europe. This decline is mirrored by a decrease in wider landscape burning in some, but not all sub-regions, linked to fire-suppression policies, and landscape fragmentation caused by agricultural expansion. Peatlands demonstrate lower susceptibility to burning than the wider landscape in several instances, probably because of autogenic processes that maintain high levels of near-surface wetness even during drought. Nonetheless, widespread drying and degradation of peatlands, particularly in Europe, has likely increased their vulnerability to burning in recent centuries. Consequently, peatland restoration efforts are important to mitigate the risk of peatland fire under a changing climate. Finally, we make recommendations for future research to improve our understanding of the controls on peatland fires.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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    fulltext
  • 35. Stevens, T.
    et al.
    Carter, A.
    Watson, T. P.
    Vermeesch, P.
    Ando, S.
    Bird, A. F.
    Lu, H.
    Garzanti, E.
    Cottam, M. A.
    Sevastjanova, I.
    Genetic linkage between the Yellow River, the Mu Us desert and the Chinese Loess Plateau2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 78, p. 355-368Article in journal (Refereed)
  • 36.
    Stevens, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Adamiec, Grzegorz
    Bird, Anna F.
    Lu, Huayu
    An abrupt shift in dust source on the Chinese Loess Plateau revealed through high sampling resolution OSL dating2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 82, p. 121-132Article in journal (Refereed)
  • 37.
    Stevens, Thomas
    et al.
    Centre for Quaternary Research, Department of Geography, Royal Holloway, University of London, UK.
    Markovic, Slobodan B.
    Zech, Michael
    Hambach, Ulrich
    Suemegi, Pal
    Dust deposition and climate in the Carpathian Basin over an independently dated last glacial-interglacial cycle2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 5-6, p. 662-681Article in journal (Refereed)
  • 38.
    Stevens, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sechi, Daniele
    Univ Sassari, Dept Architecture Design & Planning, Piazza Duomo 6, I-07041 Alghero, Italy..
    Bradak, Balazs
    Univ Burgos, Dept Phys, Av Cantabria S-N, Burgos 09006, Spain..
    Orbe, Ragna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Baykal, Yunus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Cossu, Giulia
    Univ Sassari, Dept Architecture Design & Planning, Piazza Duomo 6, I-07041 Alghero, Italy..
    Tziavaras, Charilaos
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Andreucci, Stefano
    Univ Cagliari, Dipartimento Sci Chim & Geol, Cittadella Univ Blocco A, I-09127 Monserrato, CA, Italy..
    Pascucci, Vincenzo
    Univ Sassari, Dept Architecture Design & Planning, Piazza Duomo 6, I-07041 Alghero, Italy.;Kazan Fed Univ, Inst Geol & Petr Technol, Kazan, Russia..
    Abrupt last glacial dust fall over southeast England associated with dynamics of the British-Irish ice sheet2020In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 250, article id 106641Article in journal (Refereed)
    Abstract [en]

    Loess deposits in southern Britain contain a record of dust, climate and landscape dynamics over the last glacial, yet their age and accumulation rate remain poorly known. Furthermore, the environmental controls on the loess-soil stratigraphy shown in the thickest deposits in southeast England are still debated. Here we apply the first high sampling resolution quartz optically stimulated luminescence study of dust accumulation and loess formation in Britain at the Pegwell Bay site in east Kent. We couple this to mineral magnetic, particle size and geochemical analyses to understand climate, environment and post depositional modification of the loess. The luminescence ages and Bayesian age modelling results suggest two phases of greatly enhanced dust accumulation at the site. Loess began to accumulate around c. 25-23.5 ka, coinciding with Heinrich event 2, and after subsequent lower accumulation rates, a second enhanced phase of deposition occurred at around 20-19 ka. We propose a model where the dynamics of the British-Irish and Fennoscandian Ice Sheets, associated glacial lake drainage, and linked reorganisations of atmospheric circulation, all controlled loess accumulation in southern Britain. Accumulation in the first phase was triggered by increased sediment supply from initial retreat of the North Sea ice lobe, and drainage of Dogger Lake. Loess accumulation during this phase was enhanced by easterly winds from Atlantic depressions tracking to the south of Britain, caused by the maximum extent of the Irish Sea Ice Stream at c. 25-24 ka. The subsequent retreat of the western part of the British Irish Ice Sheet then allowed storm tracking further north, which reduced effectiveness of dust transporting winds across southern Britain, while sediment supply and availability was reduced in North Sea source areas. A second retreat of the maximum extent of the North Sea Lobe of ice after c. 21-20 ka would have led to another abrupt input of sediment-rich ice dammed lake and meltwater from eastern England and the North Sea into the exposed southern North Sea area. This would have again dramatically increased sediment availability for transport and deposition as loess in SE England, resulting in the second dust accumulation phase. We also propose that the abrupt stratigraphic change from calcareous to non-calcareous loess up section at Pegwell Bay was driven, not by these changes in dust input, but rather deepening of the permafrost active layer after c. 21 ka. This deepening was associated with warmer and wetter conditions driven by Atlantic storms tracking further north following the regression of the Irish Sea Ice Stream and overall ice sheet retreat. As such, last glacial dust dynamics and loess accumulation in Britain is highly influenced by the interaction of the British Irish Ice Sheet the Fennoscandian Ice sheet, Atlantic storm tracks, and the topography and drainage of the exposed North Sea.

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  • 39.
    van der Plas, Geert W.
    et al.
    Univ Ghent, Dept Biol, Limnol Unit, KL Ledeganckstr 35, B-9000 Ghent, Belgium.
    De Cort, Gijs
    Univ Ghent, Dept Biol, Limnol Unit, KL Ledeganckstr 35, B-9000 Ghent, Belgium;Royal Museum Cent Africa, Dept Earth Sci, B-3080 Tervuren, Belgium.
    Petek-Sargeant, Nik
    British Museum, Dept Africa Oceania & Amer, Great Russell St, London WC1B 3DG, England.
    Wuytack, Tabitha
    Univ Ghent, Dept Biol, Limnol Unit, KL Ledeganckstr 35, B-9000 Ghent, Belgium.
    Colombaroli, Daniele
    Univ Ghent, Dept Biol, Limnol Unit, KL Ledeganckstr 35, B-9000 Ghent, Belgium;Royal Holloway Univ London, Ctr Quaternary Res, Dept Geog, Egham TW20 0EX, Surrey, England.
    Lane, Paul J.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Archaeology. Univ Cambridge, Dept Archaeol, Downing St, Cambridge CB2 3DZ, England.
    Verschuren, Dirk
    Univ Ghent, Dept Biol, Limnol Unit, KL Ledeganckstr 35, B-9000 Ghent, Belgium.
    Distinct phases of natural landscape dynamics and intensifying human activity in the central Kenya Rift Valley during the past 1300 years2019In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 218, p. 91-106Article in journal (Refereed)
    Abstract [en]

    Socio-ecological stresses currently affecting the semi-arid regions of equatorial East Africa are driving environmental changes that need to be placed in a proper context of long-term human-climate-landscape interaction. Here we present a detailed reconstruction of past human influences on the landscape of the central Kenya Rift Valley, against the backdrop of natural climate-driven ecosystem dynamics over the past 1300 years. Proxy records of vegetation dynamics (pollen), animal husbandry (fungal spores), biomass burning (charcoal) and soil mobilization (clastic mineral influx) extracted from the continuous depositional archive of Lake Bogoria reveal six distinct phases of human activity. From ca 700 to 1430 CE, strong primary response of savanna woodland ecotonal vegetation to climatic moisture-balance variation suggests that anthropogenic influence on regional ecosystem dynamics was limited. The first unambiguous ecological signature of human activities involves a mid-15th century reduction of woodland/forest trees followed by the appearance of cereal pollen, both evidence for mixed farming. From the mid-17th century, animal husbandry became a significant ecological factor and reached near-modern levels by the mid-19th century, after severe early-19th century drought had substantially changed human-landscape interaction. A short-lived peak in biomass burning and evidence for soil mobilization in low-lying areas of the Bogoria catchment likely reflects the known 19th-century establishment of irrigation agriculture, while renewed expansion of forest and woodland trees reflect the return of a wetter climate and abandonment of other farmland. Since the mid-20th century, the principal signature of human activity within the Lake Bogoria catchment is the unprecedented increase in clastic sediment flux, reflecting widespread soil erosion associated with rapidly intensifying land use. (C) 2019 Elsevier Ltd. All rights reserved.

  • 40. Vandergoes, MJ
    et al.
    Dieffenbacher-Krall, AC
    Newnham, RM
    Denton, GH
    Blaauw, Maarten
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Cooling and changing seasonality in the Southern Alps, New Zealand during the Antarctic Cold Reversal2008In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 27, no 5-6, p. 589-601Article in journal (Refereed)
    Abstract [en]

    A comprehensively 14C AMS dated pollen and chironomid record from Boundary Stream Tarn provides the first chironomid-derived temperature reconstruction to quantify temperature change during Lateglacial times (17,500–10,000 cal yr BP) in the Southern Alps, New Zealand. The records indicate a ca 1000-year disruption to the Lateglacial warming trend and an overall cooling consistent with the Antarctic Cold Reversal (ACR). The main interval of chironomid-inferred summer temperature depression (2–3 °C) lasted about 700 years during the ACR. Following this cooling event, both proxies indicate a warming step to temperatures slightly cooler than present during the Younger Dryas chronozone (12,900–11,500 cal yr BP). These results highlight a direct linkage between Antarctica and mid-latitude terrestrial climate systems and the largely asynchronous nature of the interhemispheric climate system during the last glacial transition. The greater magnitude of temperature changes shown by the chironomid record is attributed to the response of the proxies to differences in seasonal climate with chironomids reflecting summer temperature and vegetation more strongly controlled by duration of winter or by minimum temperatures. These differences imply stronger seasonality at times during the Lateglacial, which may explain some of the variability between other paleoclimate records from New Zealand and have wider implications for understanding differences between proxy records for abrupt climate change.

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  • 41.
    Weiberg, Erika
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Classical archaeology and ancient history.
    Unkel, Ingmar
    Kouli, Katerina
    Holmgren, Karin
    Avramidis, Pavlos
    Bonnier, Anton
    Dibble, Flint
    Finné, Martin
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden; Navarino Environm Observ, Costa Navarino 24001, Messinia, Greece .
    Izdebski, Adam
    Katrantsiotis, Christos
    Stocker, Sharon R.
    Andwinge, Maria
    Baika, Kalliope
    Boyd, Meighan
    Heymann, Christian
    The socio-environmental history of the Peloponnese during the Holocene: Towards an integrated understanding of the past2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 136, p. 40-65Article in journal (Refereed)
    Abstract [en]

    Published archaeological, palaeoenvironmental, and palaeoclimatic data from the Peloponnese in Greece are compiled, discussed and evaluated in order to analyse the interactions between humans and the environment over the last 9000 years. Our study indicates that the number of human settlements found scattered over the peninsula have quadrupled from the prehistoric to historical periods and that this evolution occurred over periods of climate change and seismo–tectonic activity. We show that societal development occurs both during periods of harsh as well as favourable climatic conditions. At some times, some settlements develop while others decline. Well-known climate events such as the 4.2 ka and 3.2 ka events are recognizable in some of the palaeoclimatic records and a regional decline in the number and sizes of settlements occurs roughly at the same time, but their precise chronological fit with the archaeological record remains uncertain. Local socio-political processes were probably always the key drivers behind the diverse strategies that human societies took in times of changing climate. The study thus reveals considerable chronological parallels between societal development and palaeoenvironmental records, but also demonstrates the ambiguities in these correspondences and, in doing so, highlights some of the challenges that will face future interdisciplinary projects. We suggest that there can be no general association made between societal expansion phases and periods of advantageous climate. We also propose that the relevance of climatic and environmental regionality, as well as any potential impacts of seismo-tectonics on societal development, need to be part of the interpretative frameworks.

  • 42. Workman, Claire
    et al.
    Dalen, Love
    Vartanyan, Sergey
    Shapiro, Beth
    Kosintsev, Pavel
    Sher, Andrei
    Götherström, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Barnes, Ian
    Population-level genotyping of coat colour polymorphism in woolly mammoth (Mammuthus primigenius)2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 17-18, p. 2304-2308Article in journal (Refereed)
    Abstract [en]

    Patterns in the spatial or temporal distribution of genotypes may be indicative of natural selection. Previous work on the woolly mammoth melanocortin-1 receptor (Mc1r) gene identified three polymorphic positions that suggest Pleistocene populations may have harboured both light- and dark-haired mammoths (Rompler et al., 2006, 313: 62). Here, we extend this work and present the first population-level analysis of a functional gene in an extinct species. We genotyped the Mc1r gene in 47 woolly mammoth samples excavated from sites across the central portion of the woolly mammoths' former range to examine the extent of variation of this polymorphism through time and across space. Only one individual was found to be heterozygous, indicating that the frequency of the 'light' mutant allele was very low. We conclude that light-coloured woolly mammoths would have been very rare, and may even have been non-existent if the 'light' mutant allele was strongly selected against in its homozygotic form. With the increasing availability of large-scale sequencing technologies, population-level datasets capable of identifying local adaptation will become increasingly attainable.

  • 43.
    Yi, Peng
    et al.
    Hohai Univ, State Key Lab Hydrol Water Resources & Hydraul En, Nanjing 210098, Jiangsu, Peoples R China;Joint Int Res Lab Global Change & Water Cycle, Nanjing 210098, Jiangsu, Peoples R China;Hohai Univ, Coll Hydrol & Water Resources, Nanjing 210098, Jiangsu, Peoples R China.
    Yu, Zhongbo
    Hohai Univ, State Key Lab Hydrol Water Resources & Hydraul En, Nanjing 210098, Jiangsu, Peoples R China;Joint Int Res Lab Global Change & Water Cycle, Nanjing 210098, Jiangsu, Peoples R China;Hohai Univ, Coll Hydrol & Water Resources, Nanjing 210098, Jiangsu, Peoples R China.
    Chen, Peng
    Hohai Univ, State Key Lab Hydrol Water Resources & Hydraul En, Nanjing 210098, Jiangsu, Peoples R China;Joint Int Res Lab Global Change & Water Cycle, Nanjing 210098, Jiangsu, Peoples R China;Hohai Univ, Coll Hydrol & Water Resources, Nanjing 210098, Jiangsu, Peoples R China.
    Aldahan, Ala
    United Arab Emirates Univ, Dept Geol, Al Ain 17551, U Arab Emirates.
    Hou, Xiaolin
    Chinese Acad Sci, State Key Lab Loess & Quaternary Geol, Inst Earth Environm, Xian AMS Ctr,Shaanxi Key Lab AMS Technol & Applic, Xian 710061, Shaanxi, Peoples R China;Tech Univ Denmark, Ctr Nucl Technol, Riso Campus, DK-4000 Roskilde, Denmark.
    Fan, Yukun
    Chinese Acad Sci, State Key Lab Loess & Quaternary Geol, Inst Earth Environm, Xian AMS Ctr,Shaanxi Key Lab AMS Technol & Applic, Xian 710061, Shaanxi, Peoples R China.
    Chen, Li
    Desert Res Inst, Div Hydrol Sci, Las Vegas, NV 89119 USA.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Muscheler, Raimund
    Lund Univ, Dept Geol Quaternary Sci, S-22362 Lund, Sweden.
    Zhou, Weijian
    Chinese Acad Sci, State Key Lab Loess & Quaternary Geol, Inst Earth Environm, Xian AMS Ctr,Shaanxi Key Lab AMS Technol & Applic, Xian 710061, Shaanxi, Peoples R China.
    Sudicky, Edward
    Univ Waterloo, Dept Earth & Environm Sci, Waterloo, ON N2L 3G1, Canada.
    Schwartz, Frank
    Ohio State Univ, Sch Earth Sci, Columbus, OH 43210 USA.
    Murad, Ahmed
    United Arab Emirates Univ, Dept Geol, Al Ain 17551, U Arab Emirates.
    Late Holocene pathway of Asian Summer Monsoons imprinted in soils and societal implications2019In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 215, p. 35-44Article in journal (Refereed)
    Abstract [en]

    The Asian Summer Monsoons (ASM) represent the main source of precipitation in China and East Asia with about one third of the world population and a region of widespread civilizations. Identifying the temporal and spatial patterns (pathways) of these monsoonal events during the Late Holocene to today has been a matter of debate amongst the scientific community. Here we show that the distribution patterns of the cosmogenic isotope Be-10 and oceanic I-127 in the topsoil across China exhibit imprints of the main ASM pathways. Our results indicate the monsoon pathway pattern persisted for several millennia or more and suggest a strong bond between Be-10 and water vapor transport patterns. Our data also reveal a(127)I distribution pattern controlled by the ASM pathways, rather than proximity to the sea or bedrock weathering. The persistent pathway of the ASM during the late Holocene, together with higher than average global soil iodine concentration, may have further strengthened the development of civilizations in this region of the world through reduction of iodine deficiency related diseases. (C) 2019 Elsevier Ltd. All rights reserved.

  • 44.
    Zheng, Minjie
    et al.
    Lund Univ, Dept Geol, Lund, Sweden..
    Sturevik Storm, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nilsson, Andreas
    Lund Univ, Dept Geol, Lund, Sweden..
    Adolphi, Florian
    Lund Univ, Dept Geol, Lund, Sweden.;Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, Bremerhaven, Germany.;Univ Bremen, Dept Geosci, Bremen, Germany..
    Aldahan, Ala
    United Arab Emirates Univ, Dept Geol, Al Ain, U Arab Emirates..
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Muscheler, Raimund
    Lund Univ, Dept Geol, Lund, Sweden..
    Geomagnetic dipole moment variations for the last glacial period inferred from cosmogenic radionuclides in Greenland ice cores via disentangling the climate and production signals2021In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 258Article in journal (Refereed)
    Abstract [en]

    The geomagnetic dipole moment (GDM) modulates the production rates of cosmogenic radionuclides via the shielding of galactic cosmic rays. Therefore, it is possible to use this linkage to reconstruct past changes in the GDM based on cosmogenic radionuclide records from natural archives such as ice cores. Here we present a GDM reconstruction based on 10Be and 36Cl data from two Greenland ice cores from 11.7 ka to 108 ka b2k (before A.D. 2000). We find that the cosmogenic radionuclide records reflect a mixture of climate and production effects that require separation to evaluate the changes in the GDM. To minimize climate-related variations on isotope data, we applied a multi-linear correction method by removing common variability between 10Be and 36Cl and climate parameters (accumulation rates, d18O and ion data) from radionuclide records. The resulting & ldquo;climate corrected & rdquo; radionuclide data are con-verted to GDM using a theoretical production model. Comparison of & ldquo;climate corrected & rdquo; radionuclides based GDM reconstructions with independent paleomagnetic-derived GDM records shows a good agreement. Furthermore, the & ldquo;climate correction & rdquo; leads to an improved agreement with GDM re-constructions than simply using radionuclide fluxes, lending support to the validity of our correction method to isolate production rate changes from ice core radionuclide records. With this correction method, we can extend the GDM reconstructions based on the cosmogenic radionuclides in ice cores to a period when there is a strong climate signal in the data. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). <comment>Superscript/Subscript Available</comment

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