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  • 101
    Publication Date: 2021-07-14
    Description: The 91.15 m thick St. Thomas section belongs to the Middle Globigerina Limestone, which is the intermediate member of the Globigerina Limestone Formation, and crops out along the eastern cliff of the Delimara Peninsula (the south-eastern part ofMalta Island). The sedimentary record is composed of alternating calcareous marls and marly limestones with subordinated prominent bioturbated indurated limestones that are deposited in a pelagic environment. For the first time paleomagnetic analyses of a Burdigalian succession have provided reliable data that allow the identification of five magnetozones that have been correlated to the Astronomically Tuned Neogene Time Scale, spanning the Early Miocene C6n–C5Dn interval. Calcareous plankton quantitative analyses integrated with paleomagnetic analyses, allowed us to identify and date several bioevents that have great potential for Mediterranean and extra-Mediterranean correlations in the interval between ~19.7 and ~17.2 Ma. In particular, the complete distributional range of the calcareous nannofossil Sphenolithus belemnos has been recorded as follows: the First Occurrence (FO) at 19.12 Ma, the First Common Occurrence (FCO) at 19.05 Ma, the Last Common Occurrence (LCO) at 18.44 Ma, and the Last Occurrence (LO) at 18.02 Ma. In addition, the FO and the FCO of Sphenolithus heteromorphus have been documented at 18.29 Ma and at 17.99 Ma, respectively. A new paracme interval in the lower part of the range of this species is described between 17.56 and 17.31 Ma. Concerning the planktonic Foraminifera, the main bioevents are the Common Interval top of Paragloborotalia siakensis at 19.55 Ma, a Common Interval of Globoquadrina dehiscens between 19.34 and 18.48 Ma, the Globigerinoides subquadratus FO at 18.43 Ma, and the onset of an acme interval of Paragloborotalia acrostoma that changes its coiling from random to prevalently sinistral at the same time, at 18.40 Ma. These new biostratigraphic data allowed us to place the succession in the standard Mediterranean calcareous plankton zonal schemes and to make some amendments to these schemes. The FCO of S. belemnos was revealed a more reliable marker than its FO for the base of the MNN3a Zone.With regard to the planktonic Foraminifera, the P. acrostoma AB-r/s has been used as a subzonal marker of the G. dehiscens/Catapsydrax dissimilis Zone, which now comprises three subzones instead of two. The deep marine paleoenvironmental setting, the excellent outcrops and the recognition of a continuous succession of bio-magnetostratigraphic events suggest that the St. Thomas section should be considered as a reference section for the lower Burdigalian of theMediterranean area and for future studies in the definition of the Burdigalian GSSP.
    Description: Published
    Description: 66-89
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Mediterranean; Early Miocene; Calcareous nannofossils; Planktonic Foraminifera; Magnetostratigraphy ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 102
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    University of Lisbon and the University of Évora
    In:  EPIC34th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: The state and dynamics of tundra wetlands under climate variability in Siberian Polar Regions is the topic of a joint German-Russian research project that started in 2010. Two expeditions focusing, among other topics, on limnological and paleographic characteristics of thermokarst lakes were carried out in the Indigirka River floodplain (Kytalyk, 70°N 147°E) and in the Kolyma Delta (Pokhodsk, 68°N, 161°E) in 2011 and 2012. A major objective was to explore the ages and geneses of periglacial landscapes by studying the origin, location, and shapes of eleven different thermokarst lakes. Pursuing these objectives, scientists carried out coring of ground deposits. Collected sediment cores will be analyzed for TOC, TIC, TN, TS contents, grain size composition and stable isotope ratios (δD, δ18O, δ13C) and geochronology in order reconstruct lake dynamics and to establish sedimentation rates in the different stages of lakes evolution. To distinguish different types of thermokarst lakes, hydrochemical data (e.g. pH, oxygen concentration, acidity, alkalinity, main ions) as well as temperature and electrical conductivity were measured. Based on morphometric (lake size, lake area, shoreline shape, lake orientation) and bathymetric data, different lake types were classified with respect to their form e.g. round, triangular) and orientation. Thermokarst lakes in thermokarst depressions, on the higher plain of the Khalerchinskaya Tundra (Kolyma Lowland) and lakes of floodplain genesis were classified. In the Yedoma ice complex landscape of the Indigirka River region (Kytalyk), the border of modern thermokarst lakes seems to be parallel to the border of old dry lakes basins (alas depressions). The shape of modern lakes remains round and has an average depth of 1.3 to 1.5 m. The surrounding territory is dominated by polygonal structures, including numerous small polygonal ponds. Lakes in the Kolyma Lowland are deeper (in average 2.2 to 2.5 m) and have a triangular shape and a north-eastern orientation. The Kolyma Lowland lake density is significantly higher than in the Indigirka Lowland. Bathymetric measurements allow the construction of 3D-models of lakes useful for differentiation. Physico-chemical characteristics of the studied lakes together with climatic data obtained from weather stations (e.g. air temperature, precipitation and solar radiation) helps to elucidate the modern condition of thermokarst lake formation. The project was implemented with financial support from German Science Foundation (DFG), the Russian Foundation for Basic Research (RFBR 11-04-91332) and the German Academic Exchange Service (DAAD).
    Repository Name: EPIC Alfred Wegener Institut
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  • 103
    Publication Date: 2014-06-12
    Repository Name: EPIC Alfred Wegener Institut
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  • 104
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    In:  EPIC3Proceedings of the II PAST Gateways - International converence and workshop, Trieste, Italy, 2014-05-19-2014-05-23
    Publication Date: 2014-06-23
    Description: The Greenland-Scotland Ridge (GSR) is a crucial hydrographic barrier for the exchange of water masses between the Polar Seas and the North Atlantic Ocean. Through the Miocene (5-23 Myrs; Myrs=million years ago), the Greenland-Scotland Ridge deepened at 18 Myrs and 15.5 Myrs, and again at 12.5 Myrs by changes of the Icelandic mantle plume activity, which has direct consequences for the evolution of Northern Component Water. In a sensitivity study, we investigate the effect of GSR depth variations with a global atmosphere-ocean-vegetation General Circulation Model. Oceanic characteristics of the quasi-enclosed Nordic Seas and Arctic Ocean are analyzed, as well as the critical depth threshold for the evolution of the North Atlantic Current and the East Greenland Current is examined and linked to changes in global ocean circulation.
    Repository Name: EPIC Alfred Wegener Institut
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  • 105
    Publication Date: 2014-10-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
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  • 106
    Publication Date: 2014-10-07
    Repository Name: EPIC Alfred Wegener Institut
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  • 107
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    In:  EPIC321st Symposium on Boundary Layers and Turbulence, Leeds, United Kingdom, 2014-06-09-2014-06-13
    Publication Date: 2017-10-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 108
    Publication Date: 2017-10-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 109
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    YouMaRes 5
    In:  EPIC3YouMaRes 5, Ozeaneum, Stralsund, Germany, 2014-09-10-2014-09-12Ozeaneum, Stralsund, Germany, YouMaRes 5
    Publication Date: 2014-09-15
    Description: For marine invertebrates living at low temperatures of high latitudes Thorson’s rule suggests a comparatively reduced speed of development. Several studies conducted in different climatic zones have revealed the processes involved in the maturation of benthic assemblages. However, the duration and chronology of succession, as well as the influence of environmental impacts on arctic benthic assemblages is only scarcely analysed. Long-term studies are still rare. By analysing species abundances and substrate coverage over an exposure time of one decade the following hypotheses are tested: (i) Exposition time significantly modifies the structure of arctic benthic hard-bottom assemblages, (ii) the macroscopic structure of the substrate surface has a significant influence on the structure of benthic hard-bottom assemblages, and (iii) the succession of benthic hard-bottom assemblages in the Arctic is in general slower compared to the benthic succession in all non-polar climatic zones. In 2002 forty Polyethylene growth panels were installed on an underwater cliff in Kongsfjorden (Svalbard, Norway) in about 20 m water depth. Six of these were grooved to create structural diversity on the panel surface. Once a year the ripening epibenthic assemblages were photographed by scientific divers. Until 2007 annually about eight panels were sampled and replaced, thus creating starting points for succession in different years. Additionally a ground truthing was carried out for reference. The findings of this study indicate a resilience time exceeding a decade. A strong heterogeneity can be observed between the assemblages on different panels, signifying an influence of different starting points. The results are discussed in comparison with results of related studies from this and other cold-water regions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 110
    Publication Date: 2017-10-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 111
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    In:  EPIC3Workshop on predictability of climate in the North Atlantic Sector, Bergen, Norway, 2014-06-11-2014-06-13
    Publication Date: 2014-06-18
    Repository Name: EPIC Alfred Wegener Institut
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  • 112
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    University of Lisbon and the University of Évora
    In:  EPIC3EUCOP4 – 4 th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: During the International Polar Year (IPY) 2007- 2008 education and outreach became more and more important and many different initiatives were started to foster this aim. It got obvious that without a meaningful communication of scientific results to the broader public, including all ages, the very important research outcomes will not be understood and accepted by the public. As this is a key in order to convince stakeholders, decision makers, politicians, but also just normal individuals, that these outcomes are of high importance for everybody’s daily life it and there is a high need to be active and react, it must be the goal of every scientist to make its research as understandable as possible. Maybe even more important is this content is to raise the awareness of the next generation for sensitive issues such as global change, climate warming and the impacts of the different regions of the world. Inspired by the activities of the IPY also the permafrost community started to foster their education and outreach projects. As they recognized its importance the International Permafrost Association (IPA) even launched and Education and Outreach committee in 2010 and started the collaboration with many educational institutions such as the University of the Arctic or APECS. Financially supported by the IPA this committee started its work during the last years and already could achieve some substantial outcomes. For the upcoming International Conference on Permafrost in 2016 (ICOP 2016), that will be held in Potsdam, Germany, it is intended that education and outreach will play an even more important role. For this a special education and outreach conference team was created, that will be responsible for the activities during the conference. They are planning to involve international schools and teachers to the conference activities, which will be a very new and innovative initiative. This presentation will present the proposed actions during, but also before and after, the conference. This could include a video competition for international schools to attend the event, the involvement of one or two local schools and a workshop for international teachers. A special event could be an evening lecture held by a scientist that will be open for the public. It will be a semi-entertaining, semi-scientific presentation that will be easy understandable for non-scientists. One main goal of the planned education and outreach activities will also be the possibility for children and the public to get in touch with ‘real’ scientists, communicate with them and in that way somehow close the gap between science and the daily live. All activities and events will be organized by the education and outreach conference team but mainly supported by the IPA Education and Outreach committee as well as the German ‘coole Klassen’ (cool classes) project, an initiative of the working group ‘Polar Teachers’ of the German Association of Polar Research (DGP).
    Repository Name: EPIC Alfred Wegener Institut
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  • 113
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    University of Lisbon and the University of Évora
    In:  EPIC3EUCOP4 – 4 th European Conference on Permafrost, Évora, Portugal, 2014-06-18-2014-06-21University of Lisbon and the University of Évora
    Publication Date: 2016-10-26
    Description: Ice-wedge polygons often accommodate small and shallow periglacial surface waters. They provide suitable habitats for freshwater ostracods (Crustacea, Ostracoda) in Arctic Siberian tundra landscapes, and are well known from Pleistocene and Holocene permafrost successions. Freshwater ostracods are sensitive to environmental conditions, and have been widely used as biological indicators for past and present environmental changes in temperate regions. In Arctic environments, habitat conditions of ice-wedge polygon ponds are barely constrained, and the abundance and diversity of ostracods is currently documented in scattered records with incomplete ecological characterizations. In order to further develop the ostracods potential as biological indicators from ice-wedge polygon tundra landscapes, the taxonomic and ecological range of ostracod assemblages and habitat conditions in polygon ponds in the Indigirka Lowland (north-east Siberia, Russia) were determined. Furthermore, we focused the seasonal variability of a selected pond site, its ostracod population, and the geochemical properties of ostracod valve calcite. Well-oxygenated and dilute ponds with slightly acidic pH hosted an abundant and diverse ostracod fauna. A total of 4849 identified ostracods from 8 species and 3 taxa represent the first record of the ostracod fauna in the Indigirka Lowland. Fabaeformiscandona krochini and Fabaeformiscandona groenlandica were documented for the first time in continental Siberia. Fabaeformiscandona sp. I and Fabaeformiscandona sp. II were newly found taxa holding a strong indicative potential for hydrochemical parameters. Repeated sampling of a typical low-center polygon pond revealed detailed insights in the population dynamics of Fabaeformiscandona pedata. Substrate properties, physical and hydrochemical conditions in the polygon ponds offered the ostracods largely homogeneous habitats. However, river flooding and differences in pond morphology resulted in variations in substrate, vegetation, hydrochemical and stable water isotope composition. Air temperature and precipitation were identified as the main external drivers of water temperatures, water levels, ion concentrations, and stable water isotope composition in polygon ponds on diurnal and seasonal scales. Freshwater ostracods inhabiting polygon ponds have the potential to store environmental information on a seasonal scale in their population structure and valve geochemistry. In particular, ostracod valve calcite recorded seasonal variations in stable oxygen isotopes of the ambient waters. This information needs to be interpreted carefully with regard to species-specific ecology, the pond´s water supply, and meteorological conditions. A better understanding of seasonal dynamics of ice-wedge polygons and their freshwater ostracod assemblages supports the paleoenvironmental interpretation of fossil records in response to climate change, and allows detecting changes in modern Arctic environments.
    Repository Name: EPIC Alfred Wegener Institut
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  • 114
    Publication Date: 2014-05-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 115
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    University of Lisbon and the University of Évora
    In:  EPIC34th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: Paleontological proxy data and cryolithological information from East Siberian Arctic permafrost preserve records of late Quaternary climate and environmental conditions in West Beringia and their variability which results from interglacial-glacial and interstadial-stadial dynamics. A key site for late Pleistocene Ice Complex is situated at the southern coast of Bol’shoy Lyakhovsky Island (Dmitry Laptev Strait) where coastal outcrops expose frozen sediments, ground ice, and fossil remains. A 15 m long sequence of Ice Complex permafrost accumulated continuously between 〉49 and 29 kyr BP in an ice-wedge polygon reflecting the palaeoenvironmental history from the end of the MIS4 stadial to the end of the MIS3 interstadial (Oyogos and Molotkov horizons of the Oyogosskaya Suite). The late MIS4 stadial (〉49 kyr BP) record shows a quickly developing polygon tundra while harsh cold and dry summers are reflected by sparse grass-sedge tundra-steppe and high amounts of redeposited conifers. During the early MIS3 interstadial (〉49 to 48 kyr BP) pollen records show higher Artemisia percentages within a grass-sedge tundra-steppe vegetation that supported dry conditions. The MIS3 interstadial optimum between 48 and 38 kyr BP promoted low-centered polygon tundra with shallow water in polygon centers. Moister conditions in the landscape than during the previous late MIS4 stadial are assumed while the general summer climate conditions likely remained dry, but slightly warmer as reflected by higher Salix abundances. Warmer summer air temperatures and moister conditions on landscape scale during the MIS3 optimum are revealed mainly by Salix and green algae findings in the palynological tundra-steppe records. A late MIS3 cooling trend in summer air temperatures between 38 and 29 kyr BP can be deduced from disappearing Salix pollen. The stable water isotope composition of an ice wedge (mean values of -31‰ in δ18O and -243‰ in δD) point to stable cold winter conditions. Changes in the accumulation conditions are indicated at the end of the MIS3 in transition to the MIS2. The Last Glacial Maximum (LGM) period has been rather poorly represented in East Siberian permafrost records. However, present pollen, sediment, and ground-ice stable water isotope data obtained from coastal exposures on Bol’shoy Lyakhovsky Island mirror the coldest conditions during the MIS 2 stadial (Sartan horizon of the Yanskaya Suite) period between about 26 and 22 kyr BP. The pollen record reveals a cold tundra-steppe vegetation with characteristic predominance of grass pollen over sedge pollen while the stable isotope ice-wedge data indicate extremely cold winter temperatures with mean values of -37 ‰ in δ18O and -290 ‰ in δD. By the use of combined cryolithological, sedimentological, geochemical, geochronological, and palaeontological proxy data, stadial-interstadial environmental variability in arctic West Beringia was elucidated at millennial resolution.
    Repository Name: EPIC Alfred Wegener Institut
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  • 116
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    In:  EPIC3Treffen Bund-Länderausschuß Nord- und Ostsee (BLANO), Bundesamt für Seeschifffahrt und Hydrographie (BSH), Hamburg, Germany, 2014-06-18-2014-06-18
    Publication Date: 2014-06-23
    Repository Name: EPIC Alfred Wegener Institut
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  • 117
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    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Atmospheric Chemistry and Physics, COPERNICUS GESELLSCHAFT MBH, 14(11), pp. 5853-5869, ISSN: 1680-7316
    Publication Date: 2014-06-23
    Description: Global warming is associated with large increases in surface air temperature in Siberia. Here, we apply the isotope-enabled atmospheric general circulation model ECHAM5-wiso to explore the potential of water isotope measurements at a recently opened monitoring station in Kourovka (57.04° N, 59.55° E) in order to successfully trace climate change in western Siberia. Our model is constrained to atmospheric reanalysis fields for the period 1957–2013 to facilitate the comparison with observations of δD in total column water vapour from the GOSAT satellite, and with precipitation δ18O measurements from 15 Russian stations of the Global Network of Isotopes in Precipitation. The model captures the observed Russian climate within reasonable error margins, and displays the observed isotopic gradients associated with increasing continentality and decreasing meridional temperatures. The model also reproduces the observed seasonal cycle of δ18O, which parallels the seasonal cycle of temperature and ranges from −25 ‰ in winter to −5 ‰ in summer. Investigating West Siberian climate and precipitation δ18O variability during the last 50 years, we find long-term increasing trends in temperature and δ18O, while precipitation trends are uncertain. During the last 50 years, winter temperatures have increased by 1.7 °C. The simulated long-term increase of precipitation δ18O is at the detection limit (〈1 ‰ per 50 years) but significant. West Siberian climate is characterized by strong interannual variability, which in winter is strongly related to the North Atlantic Oscillation. In winter, regional temperature is the predominant factor controlling δ18O variations on interannual to decadal timescales with a slope of about 0.5 ‰ / °C. In summer, the interannual variability of δ18O can be attributed to short-term, regional-scale processes such as evaporation and convective precipitation. This finding suggests that precipitation δ18O has the potential to reveal hydrometeorological regime shifts in western Siberia which are otherwise difficult to identify. Focusing on Kourovka, the simulated evolution of temperature, δ18O and, to a smaller extent, precipitation during the last 50 years is synchronous with model results averaged over all of western Siberia, suggesting that this site will be representative to monitor future isotopic changes in the entire region.
    Repository Name: EPIC Alfred Wegener Institut
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  • 118
    Publication Date: 2014-06-24
    Description: Since land-based biofuel production competes with conventional food production, a water-based biomass and biofuel production from cyanobacteria offers large potential. This study investigates the application potential of cyanobacteria for fuel production and by-products by mimicking nutrient depleted environmental conditions. Three Baltic cyanobacteria strains (Aphanizomenon flos-aquae, Dolichospermum lemmermannii and Nodularia spumigena) were inoculated in full nutrient levels, as well as phosphorus and nitrogen depleted medium, before being monitored for 14 days. For screening reasons, multiple parameters such as fatty acids, photosynthetic pigments including phycobilins, biovolume, photosynthetic activity, inorganic nutrients, particulate organic carbon, nitrogen and phosphorous were investigated every seven days. We observed a strong negative relationship between lipid content, growth and nutrient availability, resulting in high lipid and pigment production in combination with a limited growth rate in nutrient depleted treatments. Our results suggest that cultivation and harvest of bloom-forming cyanobacteria for fuel and by-product production are feasible in Scandinavia, but strongly depends on the desired compounds and biomass. Each cyanobacteria species originally has a species-specific chemical fingerprint that may be modified by rearing conditions and harvesting period to meet the needs of the consumer. This leads to important conclusions regarding future culturing conditions and biomass production of the desired compounds.
    Repository Name: EPIC Alfred Wegener Institut
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  • 119
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    Royal Society Publishing
    In:  EPIC3Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society Publishing, 372(2019), pp. 20130054-20130054, ISSN: 1364-503X
    Publication Date: 2018-08-10
    Description: Fluxes of lithogenic material and fluxes of three palaeo-productivity proxies (organic carbon, biogenic opal and alkenones) over the past 100 000 years were determined using the 230Th-normalization method in three sediment cores from the Subantarctic South Atlantic Ocean. Features in the lithogenic flux record of each core correspond to similar features in the record of dust deposition in the EPICA Dome C ice core. Biogenic fluxes correlate with lithogenic fluxes in each sediment core. Our preferred interpretation is that South American dust, most probably from Patagonia, constitutes a major source of lithogenic material in Subantarctic South Atlantic sediments, and that past biological productivity in this region responded to variability in the supply of dust, probably due to biologically available iron carried by the dust. Greater nutrient supply as well as greater nutrient utilization (stimulated by dust) contributed to Subantarctic productivity during cold periods, in contrast to the region south of the Antarctic Polar Front (APF), where reduced nutrient supply during cold periods was the principal factor limiting productivity. The anti-phased patterns of productivity on opposite sides of the APF point to shifts in the physical supply of nutrients and to dust as cofactors regulating productivity in the Southern Ocean.
    Repository Name: EPIC Alfred Wegener Institut
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  • 120
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    In:  EPIC3XXXIII SCAR BIENNIAL MEETING, Open Science Conference, Auckland, New Zealand, 2014-08-23-2014-08-28
    Publication Date: 2014-06-18
    Description: The distribution and internal architecture of seismostratigraphic sequences observed on the Antarctic continental slope and rise are results of sediment transport and deposition by bottom currents and ice sheets. Analysis of seismic reflection data allows to reconstruct sediment input and sediment transport patterns and to infer past changes in climate and oceanography. We observe four seismostratigraphic units which show distinct differences in location and shape of their depocentres and which accumulated at variable sedimentation rates. We used an age-depth model based on DSDP Leg 35 Site 324 for the Plio/Pleistocene and a correlation with seismic reflection characteristics from the Ross and Bellingshausen Seas, which unfortunately has large uncertainties. For the period before 21 Ma, we interpret low energy input of detritus via a palaeo-delta originating in an area of the Amundsen Sea shelf, where a palaeo-ice stream trough (Pine Island Trough East, PITE) is located today, and deposition of this material on the continental rise under sea ice coverage. For the period 21-14.1 Ma we postulate glacial erosion for the hinterland of this part of West Antarctica, which resulted in a larger depocentre and an increase in mass transport deposits. Warming during the Mid Miocene Climatic Optimum resulted in a polythermal ice sheet and led to a higher sediment supply along a broad front but with a focus via two palaeo-ice stream troughs, PITE and Abbot Trough (AT). Most of the glaciogenic debris was transported onto the eastern Amundsen Sea rise where it was shaped into levee-drifts by a re-circulating bottom current. A reduced sediment accumulation in the deep-sea subsequent to the onset of climatic cooling after 14 Ma indicates a reduced sediment supply probably in response to a colder and drier ice sheet. A dynamic ice sheet since 4 Ma delivered material offshore mainly via AT and Pine Island Trough West (PITW). Interaction of this glaciogenic detritus with a west-setting bottom current resulted in the continued formation of levee-drifts in the eastern and central Amundsen Sea.
    Repository Name: EPIC Alfred Wegener Institut
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  • 121
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    University of Lisbon and the University of Évora
    In:  EPIC34th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: The testate amoebae (Protozoa: Testacealobosea and Testaceafilosea) are a group of free-living protozoans. In 2011, in course of the POLYGON project we investigated the population of testate amoebae in across six polygons in transects from the polygon rim towards the center. At each point, samples were taken from different soil horizons of the active layer. Furthermore, we studied testate amoebae communities in sediments of polygon ponds. In total, 126 samples were analyzed. The study aims at the analysis of environmental and spatial distribution patterns of testate amoebae in a polygonal tundra landscape. The study area was located in the floodplain and the adjacent thermokarst-affected lowland along the Berelekh River, a tributary of the Indigirka River, 28 km northwest of the settlement of Chokurdakh near the Kytalyk WWF (World Wildlife Fund) station (70° 83' 12.1'' N; 147° 48' 29.9'' E). The testate amoebae records obtained consist of 150 taxa at the species and intraspecific levels related to 25 genera. The number of taxa per sample varies from individual finds the permafrost table to 20 or more species and subspecies in the surface horizons. The following conclusions can be drawn: (1) Environmental parameters that affect testate amoeba communities in arctic polygon tundra vary within the studied polygon from the rim toward the center and/or with depth; (2) the most important controls on testacean species distribution are the moisture regime, which varied according to position within the studied polygon, and pH; (3) the number of species increases from the polygon rim toward the center where warmer and wetter conditions prevail in a seasonally deeper thawed active layer; (4) along the rim-to-center gradient soil-eurybiontics and xerophiles are replaced by sphagnophiles in surface samples, and soil-eurybiontic species are replaced by hygro-hydrophiles in lower Oi and Oe soil horizons; (5) using the ecological indication of testacean taxa, increasing soil moisture can be only observed for the Oi and Oe horizons; and (6) lowermost (and coldest) Bg horizons directly above the permafrost table lack testaceans. In comparison to the modern testate amoebae record described above, 212 taxa have been found in late Pleistocene and Holocene sediments of polygon origin at various sites of NE Siberia. Differences in the paleoclimatic setting and corresponding soil conditions are reflected by species diversity and ecological indication of testate amoebae taxa. At least temperature variations during the Quaternary past can be distinguished by the composition of fossil testate amoebae communities. The study was conducted under the auspices of the joint Russian–German project 'Polygons in tundra wetlands: State and dynamics under climate variability in polar regions' (RFBR grant no. 11-04-91332-NNIO-a, grant no. HE 3622-16-1). Financial support came also from the RFBR Project no. 11-04-01171-a 'Geography and ecology of soil-inhabiting testate amoebae'.
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  • 122
    Publication Date: 2014-06-25
    Description: Marine benthic ecosystems are difficult to monitor and assess, which is in contrast to modern ecosystem-based management requiring detailed information at all important ecological and anthropogenic impact levels. Ecosystem management needs to ensure a sustainable exploitation of marine resources as well as the protection of sensitive habitats, taking account of potential multiple-use conflicts and impacts over large spatial scales. The urgent need for large-scale spatial data on benthic species and communities resulted in an increasing application of distribution modelling (DM). The use of DM techniques enables to employ full spatial coverage data of environmental variables to predict benthic spatial distribution patterns. Especially, statistical DMs have opened new possibilities for ecosystem management applications, since they are straightforward and the outputs are easy to interpret and communicate. Mechanistic modelling techniques, targeting the fundamental niche of species, and Bayesian belief networks are the most promising to further improve DM performance in the marine realm. There are many actual and potential management applications ofDMsin the marine benthic environment, these are (i) earlywarning systems for species invasion and pest control, (ii) to assess distribution probabilities of species to be protected, (iii) uses in monitoring design and spatial management frameworks (e.g. MPA designations), and (iv) establishing long-term ecosystem management measures (accounting for future climate-driven changes in the ecosystem). It is important to acknowledge also the limitations associated with DM applications in a marine management context as well as considering new areas for futureDMdevelopments. The knowledge of explanatory variables, for example, setting the basis for DM, will continue to be further developed: this includes both the abiotic (natural and anthropogenic) and the more pressing biotic (e.g. species interactions) aspects of the ecosystem.
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  • 123
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    University of Lisbon and the University of Évora
    In:  EPIC34th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: Detailed calculations of ground-ice volumes in permafrost deposits are necessary to understand and quantify the response of permafrost landscapes to thermal disturbance and thawing. Ice wedges with their polygonal surface expression are a widespread ground-ice component of permafrost lowlands. Therefore, the wedge-ice volume (WIV) is one of the major factors to be considered, both for assessing permafrost vulnerability and for quantifying deep permafrost soil carbon inventories. Here, a straightforward tool for calculating the WIV is presented. This GIS and satellite image-based method provides an interesting approach for various research disciplines where WIV is an important input parameter, including landscape and ecosystem modeling of permafrost thaw or organic carbon assessments in deep permafrost deposits. By using basic data on subsurface ice-wedge geometry, our tool can be applied to other permafrost region where polygonal-patterned ground occurs. One is able to include individual polygon geomorphometry at a specific site and the shape and size of epigenetic and/or syngenetic ice wedges in three dimensions. Exemplarily, the WIV in late Pleistocene Yedoma deposits and Holocene thermokarst deposits is calculated at four case study areas in Siberia and Alaska. Therefor, we mapped ice-wedge polygons sizes on different landscape units by using very-high-resolution satellite data. This information was combined with literature or own field data of individual ice-wedge sizes. We demonstrate that the WIV can vary considerably, not only between different permafrost regions, but also within a certain study site. Calculated WIV maxima range from 63.2 vol% to 31.4 vol% in late Pleistocene Yedoma deposits and from 13.2 vol% to 6.6 vol% in Holocene thermokarst deposits in Siberia and Alaska. Maximum WIV can be more than twice as high as calculated minimum WIV at a site. Assuming an equivalent ground-ice thickness (EGIT) from the WIV we are further able to estimate the potential surface subsidence caused by complete thawing of ice wedges. For example, adopting a possible range in Yedoma deposits thickness of 5 to 50 m in northern permafrost regions, the EGIT related to our calculated WIV maximum would range from 3.2 m to 31.6 m, respectively. In accordance to possible thermokarst deposit thicknesses of 1 to 10 m, the maximum WIV calculated for Holocene thermokarst deposits corresponds to an EGIT of 0.1 to 2.0 m, respectively.
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  • 124
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    University of Lisbon and the University of Évora
    In:  EPIC34th European Conference on Permafrost, Evora, 2014-06-18-2014-06-21Evora, University of Lisbon and the University of Évora
    Publication Date: 2014-06-18
    Description: Environmental parameters of polygonal patterned ground were monitored near the Kytalyk Station (Indigirka-Lowland, 2011-2012) as well as near the fishing village Pokhodsk (Kolyma Delta, 2012-2013) in north-east Siberia. Both sites, located in a thermokarst depression (alas) and on a flood plain of a small river branch, respectively, are typical low-center polygons of about 20 m in diameter, enclosed by polygon walls and frost cracks. Sensors recorded ground temperature up to one meter depth and soil moisture conditions in the active layer down to the permafrost table. The air temperature was measured at 2 m height on the polygon rim. In polygon ponds, electrical conductivity, water level and water temperature were logged during field seasons from mid-July to the end of August. All data loggers measured every 30 minutes to record diurnal cycles. At both sites ground and air temperature records were collected for a complete year. Furthermore, soil moisture was recorded for a year at the Pokhodsk site, where the monitoring continues until 2015. The recorded air and water temperatures co-vary and show similar daily pattern during the monitored summer period, with a general cooling trend towards the end of the season. Both air and water temperatures seem to be related to water level changes and variations in electrical conductivity. Furthermore, a ground temperature differentiation in the active layer is present. Main peaks and dips follow air temperature patterns, even in the lowermost and coldest horizon of the active layer. Compared to the record from the enclosing polygon rim the temperature differentiation in the polygonal depression is more distinct in the lower horizon and shows a wider temperature range. Soil moisture sensors show mostly constant over time moisture contents in the active layer. Surface soil horizons were driest, interrupted by some short term events, which point to abruptly increasing surface moisture (rainfall) that were also registered as a weaker increase in moisture in the deeper sections. The lowest sensor, which was located close to the permafrost table, did not measure the highest soil water content. This was recorded by the second lowest sensor three centimeters higher and coincides with field observations. The records obtained from two sites in north-east Siberia demonstrate that environmental parameters of polygonal patterned ground are closely linked to local weather variations and climate conditions.
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  • 125
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    National Oceanography Centre
    In:  EPIC3Southampton, National Oceanography Centre
    Publication Date: 2014-06-23
    Repository Name: EPIC Alfred Wegener Institut
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  • 126
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    Wissenschaftliche Auswertungen
    In:  EPIC3Warnsignal Klima : die Polarregionen ; Gebiete höchster Empfindlichkeit mit weltweiter Wirkung, (Warnsignal Klima ; 14), Hamburg, Wissenschaftliche Auswertungen, 376 p., pp. 53-61, ISBN: 978-3-9809668-6-3
    Publication Date: 2014-06-23
    Description: Permafrost a common formation in the Arctic and Sub-arctic region: As a result of the strong negative temperature balance in the Polar region, almost 25 % of the land areas of the earth are underlain by permafrost. Permafrost dominates the landscape and ecosystems of the large tundra and boreal forest areas of Northern Eurasia and North America, where it can reach thicknesses of more than 1000 m. Formed in Siberia since the Late Pliocene, permafrost has the largest extension in lowland regions non-glaciated during the Pleistocene, where permafrost never disappeared completely during last warm phases. Due to the low global sea level in glacial periods, terrestrial permafrost has been formed on the large Arctic shelf, where now submerged subsea permafrost still exists as relict of up to 400 m depth below the sea bottom. The glacial-interglacial climate dynamics during the Quaternary are mirrored in permafrost and landscape dynamics in the Arctic and Subarctic. The relief of these regions is mainly controlled by periglacial and nival processes, where periglacial landforms are strongly connected to the formation or degradation of permafrost. Especially ice-rich permafrost is very sensitive to climate warming, which results in degradation processes, such as thermokarst, thermoerosion and coastal retreat. The observed warming of the Arctic results in an increasing of the active layer thickness, a rise in permafrost temperature, and in the disappearance of discontinuous permafrost at the southern boundary. The concurrent increase in the amounts of precipitation and melt water will further intensify thermokarst processes and thaw consolidation and will result in the formation of bogs and swamps. Permafrost degradation will result in complex changes of the geoecosystems, an increase of greenhouse gas emission due to enhanced organic matter decomposition, and a destabilization of permafrost regions, which are used by men for living and for economic use. Furthermore, anthropogenic activities lead to an additional destabilization of the thermal equilibrium of frozen ground affecting the stability of constructions and buildings.
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  • 127
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-06-20
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  • 128
    Publication Date: 2014-06-24
    Description: Different environmental nitrogen sources play selective roles in the development of cyanobacterial blooms and noxious effects are often exacerbated when toxic cyanobacteria are dominant. Cylindrospermopsis raciborskii CS-505 (heterocystous, nitrogen fixing) and Raphidiopsis brookii D9 (non-N2 fixing) produce the nitrogenous toxins cylindrospermopsin (CYN) and paralytic shellfish toxins (PSTs), respectively. These toxin groups are biosynthesized constitutively by two independent putative gene clusters, whose flanking genes are target for nitrogen (N) regulation. It is not yet known how or if toxin biosynthetic genes are regulated, particularly by N-source dependency. Here we show that binding boxes for NtcA, the master regulator of N metabolism, are located within both gene clusters as potential regulators of toxin biosynthesis. Quantification of intra- and extracellular toxin content in cultures at early stages of growth under nitrate, ammonium, urea and N-free media showed that N-sources influence neither CYN nor PST production. However, CYN and PST profiles were altered under N-free medium resulting in a decrease in the predicted precursor toxins (doCYN and STX, respectively). Reduced STX amounts were also observed under growth in ammonium. Quantification of toxin biosynthesis and transport gene transcripts revealed a constitutive transcription under all tested N-sources. Our data support the hypothesis that PSTs and CYN are constitutive metabolites whose biosynthesis is correlated to cyanobacterial growth rather than directly to specific environmental conditions. Overall, the constant biosynthesis of toxins and expression of the putative toxin-biosynthesis genes supports the usage of qPCR probes in water quality monitoring of toxic cyanobacteria.
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  • 129
    Publication Date: 2014-06-14
    Description: The standard concept for the investigation of the impacts of offshore wind turbines on the marine environment (StUK) of the German Federal Maritime and Hydrographic Agency (BSH) prescribes extensive investigations on the benthic communities of the seafloor as well as on the fouling assemblages on the underwater structures of offshore wind turbines. The construction of the test site alpha ventus allowed for the first time for testing the appropriate-ness of these investigations. In the present sub-project of the StUKplus research project, the investigations according to StUK3 (BSH, 2007) were spatially and temporally extended in order to test for effects on the benthic system which could otherwise not be revealed by the StUK procedures. In the first work package of the sub-project an additional complete sam-pling campaign according to StUK was performed in the second year of the operational phase of the wind farm. The results of this work package indicate differential temporal variations of the benthic communities and of sedimentological parameters inside the wind farm and in a reference area outside the wind farm. However, the differences were mainly temporary fluctuations while persistent effects of the construction and operation of the wind farm on the benthos were not evident. Solely the biomass and species richness of the fouling assemblage on the underwater structures increased continuously since the construction of the turbines. In the second work package the turbine-related effect monitoring of the benthic communities of the seafloor was extended to the entire distance between two neighbouring turbines. No ef-fects of the turbines on the benthos and the sediment could be detected in this work package. The spatial resolution of the turbine-related effect monitoring was inadequate for detecting processes which occur in the vicinity of the turbine foundations. In none of the two work packages did the spatial and temporal extension of the benthos monitoring provide additional findings. However, deficiencies of the benthos ecological investigations according to StUK3 became evident and improvements could be deduced.
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  • 130
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 705-711, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: Complex network theory has been successfully applied to understand the structural and functional topology of many dynamical systems from nature, society and technology. Many properties of these systems change over time, and, consequently, networks reconstructed from them will, too. However, although static and temporally changing networks have been studied extensively, methods to quantify their robustness as they evolve in time are lacking. In this paper we develop a theory to investigate how networks are changing within time based on the quantitative analysis of dissimilarities in the network structure. Our main result is the common component evolution function (CCEF) which characterizes network development over time. To test our approach we apply it to several model systems, Erdős–Rényi networks, analytically derived flow-based networks, and transient simulations from the START model for which we control the change of single parameters over time. Then we construct annual climate networks from NCEP/NCAR reanalysis data for the Asian monsoon domain for the time period of 1970–2011 CE and use the CCEF to characterize the temporal evolution in this region. While this real-world CCEF displays a high degree of network persistence over large time lags, there are distinct time periods when common links break down. This phasing of these events coincides with years of strong El Niño/Southern Oscillation phenomena, confirming previous studies. The proposed method can be applied for any type of evolving network where the link but not the node set is changing, and may be particularly useful to characterize nonstationary evolving systems using complex networks.
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  • 131
    Publication Date: 2014-06-26
    Description: Arctic permafrost coasts, especially when they are unconsolidated and ground ice rich, are extremely vulnerable to climate change. Rising temperatures of air and seawater, lengthening of the open-water season and increase in storm events are likely to prompt higher rates of coastal erosion and consequently increase the rate of land loss and material transport to the near-shore zone. Many studies have addressed this issue by compiling rates of shoreline erosion over the past fifty to sixty years to find trends, yet few investigations have attempted to look at it in three dimensions and at annual time scales, although erosion of Arctic coasts is known to be very complex and nonlinear. This study focuses on high resolution short-term (one year) erosion rates and geomorphic change. It is based on DEMs that were obtained from LIDAR surveys of the Yukon Coast and Herschel Island during the AIRMETH campaigns in 2012 and 2013. The DEMs were processed to obtain a horizontal resolution of 1 meter and serve as an elevation source from which the comparison was made. The elevations from the 2012 DEM were then deducted from elevations in 2013 to obtain erosion and accumulation values for each pixel. Preliminary results show that coastal retreat encompasses a range of processes acting at different temporal and spatial scales. They can be divided into denudation and abrasion processes. Denudation is the various types of mass wasting, such as translational slides, active layer detachments or retrogressive thaw slumps. The material delivered from these abrupt events is made available for abrasion, which is transferring the material to the shoreface at longer time scales. The accumulated material temporarily protects cliffs from incident wave energy and abrasion is reactivated when the material is removed. The erosion from gullies and thermo-erosional valleys is another form of material delivery to coast. Shoreline retreats from 2 to 5 meters were recorded on the most exposed parts of the coast, while vertical changes of cliffs account locally for more than 10 meters and extend up to 20 meters laterally. Locations where these high numbers are observed are often characterised by the adjacent accumulation of material on the beach. This study shows that the pathways for the transfer of material from the coast to the sea are very diverse and are often limited by the ability of abrasion to remove material delivered by the mass wasting of coastal bluffs.
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  • 132
    Publication Date: 2014-07-01
    Description: Current sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans.
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  • 133
    Publication Date: 2020-03-05
    Description: In this study MODerate resolution Imaging Spectroradiometer (MODIS) Aqua retrievals of aerosol optical thickness (AOT) at 555 nm are compared to sun-photometer measurements from Svalbard for a period of 9 years. For the 642 daily coincident measurements that were obtained, MODIS AOT generally varies within the predicted uncertainty of the retrieval over ocean (ΔAOT = ±0.03 ± 0.05 · AOT). The results from the remote sensing have been used to examine the accuracy in estimates of aerosol optical properties in the Arctic, generated by global climate models and from in-situ measurements at the Zeppelin station, Svalbard. AOT simulated with the Norwegian Earth System Model (NorESM1-M)/ CAM4-Oslo global climate model does not reproduce the observed seasonal variability of the Arctic aerosol. The model overestimates clear-sky AOT by nearly a factor of 2 for the background summer season, while tending to underestimate the values in the spring season. Furthermore, large differences in all-sky AOT of up to one order of magnitude are found for the Coupled Model Intercomparison Project (CMIP5) model ensemble for the spring and summer seasons. Large differences between satellite/ground-based remote sensing of AOT and AOT estimated from dry and humidified scattering coefficients are found for the subarctic marine boundary layer in summer.
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  • 134
    Publication Date: 2014-06-25
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  • 135
    Publication Date: 2014-06-27
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  • 136
    Publication Date: 2014-06-30
    Description: A methodology to classify rocky shores along the North East Atlantic (NEA) region was developed. Previously, biotypes and the variability of environmental conditions within these were recognized based on abiotic data. A biological validation was required in order to support the ecological meaning of the physical typologies obtained. A database of intertidal macroalgae species occurring in the coastal area between Norway and the South Iberian Peninsula was generated. Semi-quantitative abundance data of the most representative macroalgal taxa were collected in three levels: common, rare or absent. Ordination and classification multivariate analyses revealed a clear latitudinal gradient in the distribution of macroalgae species resulting in two distinct groups: one northern and one southern group, separated at the coast of Brittany (France). In general, the results based on biological data coincided with the results based on physical characteristics. The ecological meaning of the coastal waters classification at a broad scale shown in this work demonstrates that it can be valuable as a practical tool for conservation and management purposes.
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  • 137
    Publication Date: 2014-07-08
    Repository Name: EPIC Alfred Wegener Institut
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  • 138
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    Royal Society
    In:  EPIC3Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society, 372(2018), pp. 20130283, ISSN: 1471-2962
    Publication Date: 2014-07-04
    Description: The influence of a stochastic sea ice strength parametrization on the mean climate is investigated in a coupled atmosphere–sea ice–ocean model. The results are compared with an uncoupled simulation with a prescribed atmosphere. It is found that the stochastic sea ice parametrization causes an effective weakening of the sea ice. In the uncoupled model this leads to an Arctic sea ice volume increase of about 10–20% after an accumulation period of approximately 20–30 years. In the coupled model, no such increase is found. Rather, the stochastic perturbations lead to a spatial redistribution of the Arctic sea ice thickness field. A mechanism involving a slightly negative atmospheric feedback is proposed that can explain the different responses in the coupled and uncoupled system. Changes in integrated Antarctic sea ice quantities caused by the stochastic parametrization are generally small, as memory is lost during the melting season because of an almost complete loss of sea ice. However, stochastic sea ice perturbations affect regional sea ice characteristics in the Southern Hemisphere, both in the uncoupled and coupled model. Remote impacts of the stochastic sea ice parametrization on the mean climate of non-polar regions were found to be small.
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  • 139
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    In:  EPIC3Potsdam Summer School Arctic in the Antropocene, Potsdam, 2014-06-23-2014-07-04
    Publication Date: 2014-09-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 140
    Publication Date: 2019-07-16
    Description: Organisms in all domains, Archaea, Bacteria, and Eukarya will respond to climate change with differential vulnerabilities resulting in shifts in species distribution, coexistence, and interactions. The identification of unifying principles of organism functioning across all domains would facilitate a cause and effect understanding of such changes and their implications for ecosystem shifts. For example, the functional specialization of all organisms in limited temperature ranges leads us to ask for unifying functional reasons. Organisms also specialize in either anoxic or various oxygen ranges, with animals and plants depending on high oxygen levels. Here, we identify thermal ranges, heat limits of growth, and critically low (hypoxic) oxygen concentrations as proxies of tolerance in a meta-analysis of data available for marine organisms, with special reference to domain-specific limits. For an explanation of the patterns and differences observed, we define and quantify a proxy for organismic complexity across species from all domains. Rising complexity causes heat (and hypoxia) tolerances to decrease from Archaea to Bacteria to uni- and then multicellular Eukarya. Within and across domains, taxon-specific tolerance limits likely reflect ultimate evolutionary limits of its species to acclimatization and adaptation. We hypothesize that rising taxon-specific complexities in structure and function constrain organisms to narrower environmental ranges. Low complexity as in Archaea and some Bacteria provide life options in extreme environments. In the warmest oceans, temperature maxima reach and will surpass the permanent limits to the existence of multicellular animals, plants and unicellular phytoplankter. Smaller, less complex unicellular Eukarya, Bacteria, and Archaea will thus benefit and predominate even more in a future, warmer, and hypoxic ocean.
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  • 141
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-07-01
    Repository Name: EPIC Alfred Wegener Institut
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  • 142
    Publication Date: 2014-07-08
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. They have provided a wealth of understanding regarding changes of the water isotope signals in various archives under different past climate conditions. However, so far the number of fully coupled atmosphere-ocean GCMs with explicit water isotope diagnostics is very limited. Such coupled models are required for a more comprehensive simulation of both past climates as well as related isotope changes in the Earth’s hydrological cycle. Here, we report first results of a newly developed isotope diagnostics within the Earth system model ECHAM5-JSBACH/MPIMOM. Both H218O and HDO and their relevant fractionation processes are included in all compartments and branches of the water cycle within this model. First equilibrium simulations have been performed for both pre-industrial (PI) and Last Glacial Maximum (LGM) boundary conditions. Evaluation of the PI simulation reveals a good overall model performance in accordance with available modern isotope data from vapour measurements, precipitation samples as well as marine records. The LGM experiment results in spatially varying isotope depletion in precipitation between -20‰ and 0‰ in agreement with data from various isotope records. The simulated isotopic compoisiton of ccean surface waters shows a strong glacial enrichment in the Arctic. In further model analyses we investigate how the relation between water isotopes and key climate variables, e.g. land and surface temperatures, precipitation amounts, oceanic salinity, might has changed for different regions on a glacial-interglacial time scale. Moreover, the influence of glacial climates changes on second-order isotope signals, e.g. the Deuterium excess, is examined.
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  • 143
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-06-30
    Repository Name: EPIC Alfred Wegener Institut
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  • 144
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung = Reports on polar and marine research, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 677, 206 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 145
    Publication Date: 2018-03-06
    Description: Water stable isotopologues provide integrated tracers of the atmospheric water cycle, affected by changes in air mass origin, non-convective and convective processes and continental recycling. Novel remote sensing and in situ measuring techniques have recently offered opportunities for monitoring atmospheric water vapour isotopic composition. Recently developed infrared laser spectrometers allow for continuous in situ measurements of surface water vapour δDv and δ18Ov. So far, very few intercomparisons of measurements conducted using different techniques have been achieved at a given location, due to difficulties intrinsic to the comparison of integrated with local measurements. Nudged simulations conducted with high-resolution isotopically enabled general circulation models (GCMs) provide a consistent framework for comparison with the different types of observations. Here, we compare simulations conducted with the ECHAM5-wiso model with two types of water vapour isotopic data obtained during summer 2012 at the forest site of Kourovka, western Siberia: hourly ground-based FTIR total atmospheric columnar δDv amounts, and in situ hourly Picarro δDv measurements. There is an excellent correlation between observed and predicted δDv at surface while the comparison between water column values derived from the model compares well with FTIR estimates.
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  • 146
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    In:  EPIC3Oldenburg Model United Nation (OLMUN) 2014, 14th International Session, Oldenburg (Ol), Germany, 2014-06-24-2014-06-27
    Publication Date: 2014-06-25
    Description: An overview on the global warming problem is given and some suggested solutions based on geoengineering are discussed in a rather general sense to provide background information for the event.
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  • 147
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    In:  EPIC34th European Conference on Permafrost, Evora, Portugal, 2014-06-18-2014-06-21
    Publication Date: 2014-06-26
    Description: Remote sensing has been a tool of choice for decades for studying periglacial landscape dynamics and for scaling-up field data. Remoteness, geographic extent, and harsh climates of study areas as well as logistical challenges in visiting them make aerial or satellite imagery key components of studies focusing on mapping of landforms, vegetation and hydrologic features, or simply planning field research. For some regions, the historical aerial image record now extends back 〉80 years, allowing tremendous insights into scales and rates of land surface processes such as thermokarst lake dynamics, coastal erosion, peat plateau collapse, thaw slump development, or rock glacier movement. Such long temporal archives increasingly allow correlation of observed changes with climatic or anthropogenic disturbances. Classical remote sensing tools include panchromatic and color-infrared aerial imagery, widely available across the Arctic since the 1950s and 1970s, respectively. Stereo-photogrammetric analyses provided critical three-dimensional insights for many studies. The advent of earth surface-observing satellite sensors in the 1970s brought multi-spectral Landsat and other imagery to researchers. In the 1990s, satellite synthetic aperture radar (SAR) data became widely available. Another enormous boost in usage of remote sensing data was achieved by rendering data archives public and freely available in the 2000s, namely the full Landsat and MODIS archives. In addition, commercial, very high-resolution platforms have provided sufficient spatial resolution for detecting periglacial landscape dynamics during the last decade. The 4th International Polar Year 2007/08 also helped directing remote sensing efforts to permafrost regions, followed by international activities such as the ESA Data User Element Permafrost project, an upcoming large NASA field campaign termed the Arctic Boreal Vulnerability Experiment (ABoVE), and a recent US National Academy of Sciences workshop report on Remote Sensing of Permafrost guided by numerous international experts. New sensors, processing techniques, and analysis methods available today provide promising avenues to monitor periglacial landscapes and even permafrost directly, to support and scale field research, and to parameterize and validate modeling. Here we show some of the developments in technology and applications for periglacial environments and for observing characteristics of permafrost, including multi-temporal high-resolution imagery in the visible to infrared range for change detection studies, hemispherical-scale remote sensing datasets of the physical state of the earth surface such as freeze-thaw state, interferometric SAR for detection of seasonal or long-term surface deformation in periglacial regions, airborne geophysical sensors used to map permafrost extent and talik distribution, and high-resolution elevation data from airborne interferometric SAR, LIDAR, or stereo-optical sensors to characterize periglacial features and their deformation over time.
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  • 148
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    In:  EPIC3Potsdam Summer School "Arctic in the Anthropocene", Potsdam, Germany, 2014-06-23-2014-07-04
    Publication Date: 2014-06-26
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  • 149
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    In:  EPIC3RapidEye Science Archive - 6. RESA Workshop 2014, Deutsches Zentrum für Luft- und Raumfahrt, Bonn Oberkassel, 2014-03-05-2014-03-06
    Publication Date: 2014-07-08
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  • 150
    Publication Date: 2018-08-10
    Description: Neodymium and hafnium isotopes and elemental concentrations (Sm, Nd, Hf, Zr) have been measured in three water column profiles south of the Antarctic Circumpolar Current in, and to the east of the Ross Sea, in conjunction with five bottom water samples from the Amundsen Sea Embayment. Neodymium and hafnium both appear to be released from sediments in the Embayment. In the case of Nd, this is reflected in radiogenic isotope compositions (εNd up to −5.4) and highly elevated concentrations (up to 41 pmol/kg). Hafnium isotopes, on the other hand, are only very slightly altered relative to the open ocean sites, and boundary release is most prominently indicated by elevated concentrations (〉1 pmol/kg versus ∼0.7 pmol/kg). There is also a local input of both Hf and Nd at the Marie Byrd Seamounts, which leads to Nd isotope compositions as radiogenic as −3.1, and hafnium shifted to less radiogenic compositions in local bottom water. A compilation of the new data with literature data reveals a consistent view of the influence of Antarctica on the Nd isotope composition in Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW). Sector specific Nd addition shifts AABW formed in the Atlantic sector to less radiogenic isotope compositions (average εNd = −9) relative to LCDW (average εNd = −8.4), whereas AABW in the Pacific sector is shifted to more radiogenic values (average εNd = −7). The evolution towards more radiogenic εNd with depth in LCDW in the Pacific sector is likely to reflect admixture of AABW but, in addition, is also controlled by boundary exchange with the slope as observed at the Marie Byrd Seamounts. Hafnium isotopes are relatively homogeneous in the data set, ranging between εHf = +2 and +3.8 for most samples, excluding less radiogenic compositions in deep waters close to the Marie Byrd Seamounts. The Hf isotope composition in the Pacific sector is, however, slightly less radiogenic than in the Atlantic, corresponding to an average of +3 relative to an average of +3.8. This probably reflects unradiogenic Hf inputs from Antarctica to the Pacific sector, which are vertically homogenized by reversible scavenging. The Hf isotope heterogeneity in LCDW between both sectors is likely to indicate a shorter seawater residence time for Hf than for Nd, which is consistent with the dissolved – particulate phase partitioning of both elements
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  • 151
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    Nature Publishing Group
    In:  EPIC3Nature Geoscience, Nature Publishing Group, 7(5), pp. 376-381, ISSN: 1752-0894
    Publication Date: 2014-07-14
    Description: During the Middle Miocene climate transition about 14 million years ago, the Antarctic ice sheet expanded to near-modern volume. Surprisingly, this ice sheet growth was accompanied by a warming in the surface waters of the Southern Ocean, whereas a slight deep-water temperature increase was delayed by more than 200 thousand years. Here we use a coupled atmosphere–ocean model to assess the relative effects of changes in atmospheric CO2 concentration and ice sheet growth on regional and global temperatures. In the simulations, changes in the wind field associated with the growth of the ice sheet induce changes in ocean circulation, deep-water formation and sea-ice cover that result in sea surface warming and deep-water cooling in large swaths of the Atlantic and Indian ocean sectors of the Southern Ocean. We interpret these changes as the dominant ocean surface response to a 100-thousand-year phase of massive ice growth in Antarctica. A rise in global annual mean temperatures is also seen in response to increased Antarctic ice surface elevation. In contrast, the longer-term surface and deep-water temperature trends are dominated by changes in atmospheric CO2 concentration. We therefore conclude that the climatic and oceanographic impacts of the Miocene expansion of the Antarctic ice sheet are governed by a complex interplay between wind field, ocean circulation and the sea-ice system.
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  • 152
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    In:  EPIC3International Symposium on Contribution of Glaciers and Ice Sheets to Sea-Level Change
    Publication Date: 2014-11-10
    Description: With the warming climate, ice masses on Earth are expected to increasingly contribute to a rising sea level. As for any material, the ice bodies’ temperature is a key variable to change the material’s properties, especially the rheology. In the case of ice in natural environments on Earth, temperature is always close to the material’s melting point. Therefore ice can be regarded as a ‘hot material’ (homologous temperatures T/T_m ca. 0.7 to 0.9). This means that recrystallization plays a decisive role in governing the state and thus the behaviour of the material, as it continuously resets the mechanical properties. Recrystallization as a set of control mechanisms has been recognized and interpreted in many ice cores in the last decades, and certain recrystallization regimes have been assigned to special ice-sheet depth ranges. This assignment was based on microstructure observations (mainly grain size) and estimated boundary conditions (temperature and stress/strain amounts) which change systematically with depth. To generalize the use of recrystallization regimes we decouple their occurrence from the ice-sheet depth information and connect them directly to the activators and causes: strain rate and temperature.
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  • 153
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    BIOMED CENTRAL LTD
    In:  EPIC3BMC Bioinformatics, BIOMED CENTRAL LTD, 15, pp. 218, ISSN: 1471-2105
    Publication Date: 2014-07-02
    Description: Background Light microscopic analysis of diatom frustules is widely used both in basic and applied research, notably taxonomy, morphometrics, water quality monitoring and paleoenvironmental studies. In these applications, usually large numbers of frustules need to be identified and / or measured. Although there is a need for automation in these applications, and image processing and analysis methods supporting these tasks have previously been developed, they did not become widespread in diatom analysis. While methodological reports for a wide variety of methods for image segmentation, diatom identification and feature extraction are available, no single implementation combining a subset of these into a readily applicable workflow accessible to diatomists exists. Results The newly developed tool SHERPA offers a versatile image processing workflow focused on the identification and measurement of object outlines, handling all steps from image segmentation over object identification to feature extraction, and providing interactive functions for reviewing and revising results. Special attention was given to ease of use, applicability to a broad range of data and problems, and supporting high throughput analyses with minimal manual intervention. Conclusions Tested with several diatom datasets from different sources and of various compositions, SHERPA proved its ability to successfully analyze large amounts of diatom micrographs depicting a broad range of species. SHERPA is unique in combining the following features: application of multiple segmentation methods and selection of the one giving the best result for each individual object; identification of shapes of interest based on outline matching against a template library; quality scoring and ranking of resulting outlines supporting quick quality checking; extraction of a wide range of outline shape descriptors widely used in diatom studies and elsewhere; minimizing the need for, but enabling manual quality control and corrections. Although primarily developed for analyzing images of diatom valves originating from automated microscopy, SHERPA can also be useful for other object detection, segmentation and outline-based identification problems.
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  • 154
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 691-703, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: A critical challenge in paleoclimate data analysis is the fact that the proxy data are heterogeneously distributed in space, which affects statistical methods that rely on spatial embedding of data. In the paleoclimate network approach nodes represent paleoclimate proxy time series, and links in the network are given by statistically significant similarities between them. Their location in space, proxy and archive type is coded in the node attributes. We develop a semi-empirical model for Spatio-Temporally AutocoRrelated Time series, inspired by the interplay of different Asian Summer Monsoon (ASM) systems. We use an ensemble of transition runs of this START model to test whether and how spatio–temporal climate transitions could be detectable from (paleo)climate networks. We sample model time series both on a grid and at locations at which paleoclimate data are available to investigate the effect of the spatially heterogeneous availability of data. Node betweenness centrality, averaged over the transition region, does not respond to the transition displayed by the START model, neither in the grid-based nor in the scattered sampling arrangement. The regionally defined measures of regional node degree and cross link ratio, however, are indicative of the changes in both scenarios, although the magnitude of the changes differs according to the sampling. We find that the START model is particularly suitable for pseudo-proxy experiments to test the technical reconstruction limits of paleoclimate data based on their location, and we conclude that (paleo)climate networks are suitable for investigating spatio–temporal transitions in the dependence structure of underlying climatic fields.
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  • 155
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    In:  EPIC36th International Symposium on biological and environmental chemistry of DMS(P) and related compounds, Barcelona, Spain, 2014-05-26-2014-05-29
    Publication Date: 2014-07-15
    Description: Due to the physico-chemical conditions given, i.e. the high salinity and the icy matrix, sea ice as habitat favors production of high levels of dimethylsulfoniopropionate (DMSP) by the inhabiting microalgae. DMSP and DMS (dimethylsulfide) are frequently found in high concentrations in sea ice during spring and summer. Records from winter are yet scarce, but of importance for global budgeting. Our study presents profiles of the DMS(P) in sea ice cores collected during the AWECS (Antarctic Winter Ecosytem Climate Study) cruise on RV Polarstern (ANT29-6) in the Weddell Sea. Results show that DMS(P) production in sea ice in the Weddell Sea is also significant during winter. This stands in contrast to previous measurements in Arctic winter sea ice (CFL-IPY cruise in the Circumpolar Flaw Lead Polynya), where DMS(P) concentrations were very low. Possible explanations for the differences between DMS(P) levels in the Arctic and Antarctic might be the different snow cover and thus insulation, light regimes and also microbial community structure within the ice. The DMS profiles mirrored the permeability of the sea ice following DMSP in the impermeable areas while showing losses to the ice surface and ice-water interface in the more permeable regions. DMS(P) levels were generally correlated with chlorophyll A concentrations, although the details are complex and seem to be influenced by species composition and species specific DMSP/Chla ratios. Three mayor trends determined in situ with values of 136 (±93), 32 (±15) and 5 (±2) mmol DMSP / g ChlA resemble the published values for cultures of dinoflagellates, haptophytes and diatoms. Preliminary microscopy data confirm that dinoflagellate dominated sea ice layers display higher DMSP/ChlA ratios than diatom dominated ones.
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  • 156
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    Wiley
    In:  EPIC3Ecology and Evolution, Wiley, 4(16), pp. 3147-3161, ISSN: 2045-7758
    Publication Date: 2014-09-24
    Description: Fragilariopsis kerguelensis, a dominant diatom species throughout the Antarctic Circumpolar Current, is coined to be one of the main drivers of the biological silicate pump. Here, we study the distribution of this important species and expected consequences of climate change upon it, using correlative species distribution modeling and publicly available presence-only data. As experience with SDM is scarce for marine phytoplankton, this also serves as a pilot study for this organism group. Southern Ocean. We used the maximum entropy method to calculate distribution models for the diatom F. kerguelensis based on yearly and monthly environmental data (sea surface temperature, salinity, nitrate and silicate concentrations). Observation data were harvested from GBIF and the Global Diatom Database, and for further analyses also from the Hustedt Diatom Collection (BRM). The models were projected on current yearly and seasonal environmental data to study current distribution and its seasonality. Furthermore, we projected the seasonal model on future environmental data obtained from climate models for the year 2100. Projected on current yearly averaged environmental data, all models showed similar distribution patterns for F. kerguelensis. The monthly model showed seasonality, for example, a shift of the southern distribution boundary toward the north in the winter. Projections on future scenarios resulted in a moderately to negligibly shrinking distribution area and a change in seasonality. We found a substantial bias in the publicly available observation datasets, which could be reduced by additional observation records we obtained from the Hustedt Diatom Collection. Present day distribution patterns inferred from the models coincided well with background knowledge and previous reports about F. kerguelensis distribution, showing that maximum entropy-based distribution models are suitable to map distribution patterns for oceanic planktonic organisms. Our scenario projections indicate moderate effects of climate change upon the biogeography of F. kerguelensis.
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  • 157
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    Institute of Oceanology Polish Academy of Sciences
    In:  EPIC3Gdańsk, Institute of Oceanology Polish Academy of Sciences, 86 p., ISBN: 978-83-936609-1-9
    Publication Date: 2014-06-23
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  • 158
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    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 398, pp. 1-10, ISSN: 0012-821X
    Publication Date: 2014-06-27
    Description: The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes contradictory. Here we present a record of leaf-wax δD and δ13C taken from a marine sediment core at 23°S off the coast of Namibia to reconstruct the hydrology and C3 versus C4 vegetation of southwestern Africa over the last 140 000 years (140 ka). We find lower leaf-wax δD and higher δ13C (more C4 grasses), which we interpret to indicate wetter Southern Hemisphere (SH) summer conditions and increased seasonality, during SH insolation maxima relative to minima and during the last glacial period relative to the Holocene and the last interglacial period. Nonetheless, the dominance of C4 grasses throughout the record indicates that the wet season remained brief and that this region has remained semi-arid. Our data suggest that past precipitation increases were derived from the tropics rather than from the winter westerlies. Comparison with a record from the Congo Basin indicates that hydroclimate in southwestern Africa has evolved in antiphase with that of central Africa over the last 140 ka.
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  • 159
    Publication Date: 2016-09-28
    Description: This Thesis focuses on the evaluation of the CUBE-algorithm. This was mainly developed for the application on measured data from multibeam echosounders. The measured values are generally unevenly distributed and partly inaccurate. The aim of the algorithm is to calculate a regular grid with estimates for the water depth in fixed positions out of these values. The special thing about that is that, in addition to the actual measured values, there is extra information about the data included the calculation. These are in particular information about the precision and measuring properties of the used measuring instruments. With the help of this knowledge it is tried to determine the true water depth out of the measured values to exclude inaccurate data from the regular grid. In this thesis the algorithm was applied to deep sea multibeam echosounder data, which has been measured by research vessel polarstern and assessed regarding the reliability with which incorrect values are excluded from the grid. The polarstern is operated by the Alfred Wegener Institute and used to explore the polar seas. At the institute the programs HIPS and SIPS of the company CARIS and Fledermaus by QPS are used to clean the data manually. The programs each contain an implementation of the CUBE-algorithm. After the application of the algorithm to the measured values with both programs, the visible differences in the results were analyzed. The analysis was carried out using the program ArcMap by Esri. Using a color-coded visualization of the grid and through difference grids the optical and metric deviations of the results of the algorithm to the results of a manual data cleanup were examined and compared with each other. The analysis of the comparisons has shown, that the deviations from the grid created by the CUBE-algorithm to manually cleaned data are dropped compared to uncleaned data. That means, referred to the used deep sea multibeam echosounder data, that the algorithm succeeds in excluding a part of the inaccurate data. The reliability with which this is achieved increases with the density of accurate values. In relation to Fledermaus the resuls from HIPS and SIPS showed the lover deviations compared to the manually cleaned data.
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  • 160
    Publication Date: 2014-07-21
    Description: Eulimnogammarus verrucosus is an amphipod endemic to the unique ecosystem of Lake Baikal and serves as an emerging model in ecotoxicological studies. We report here on a survey sequencing of its genome as a first step to establish sequence resources for this species. From a single lane of paired-end sequencing data, we estimated the genome size as nearly 10 Gb and we obtained an overview of the repeat content. At least two-thirds of the genome are non-unique DNA, and a third of the genomic DNA is composed of just five families of repetitive elements, including low-complexity sequences. Attempts to use off-the-shelf assembly tools failed on the available low-coverage data both before and after removal of highly repetitive components. Using a seed-based approach we nevertheless assembled short contigs covering 33 pre-microRNAs and the homeodomain-containing exon of nine Hox genes. The absence of clear evidence for paralogs implies that a genome duplication did not contribute to the large genome size. We furthermore report the assembly of the mitochondrial genome using a new, guided “crystallization” procedure. The initial results presented here set the stage for a more complete sequencing and analysis of this large genome.
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  • 161
    Publication Date: 2014-07-19
    Description: The Columbia River is the largest North American river which discharges into the Pacific Ocean and by that exports large quantities of dissolved organic carbon (DOC). In such riverine environments, terrestrially derived organic matter is a major DOC constituent and also a part of colored dissolved organic matter (CDOM). The optical properties of CDOM have previously been utilized to quantify the total dissolved organic matter (DOM) dynamics with in situ sensors. However, the validity of CDOM as quantitative proxy depends on the quality of correlation between DOC and CDOM, which has been disputed for the Columbia River. Therefore, the aim of this study was to examine the optical properties of CDOM, to investigate the seasonal variability of DOM, and to characterize its molecular composition. Furthermore, molecular imprints of primary production were investigated. From March to August 2013, 78 samples were collected at two stations in the lower Columbia River (near Portland, OR). Both stations were equipped with in situ sensors to record physical and biogeochemical data. The samples were characterized by fluorescence and absorbance analyses. On four occasions, DOM was solid-phase extracted to analyze its molecular composition using Fourier transform ion cyclotron resonance mass spectrometry. Based on the sensor data, a spring phytoplankton bloom and the spring freshet were identified. During July and August 2013, solar radiation depleted in situ CDOM fluorescence, but not absorbance. Contrary to previous studies, absorbance was identified as a valid proxy for DOC in the Columbia River (R2 =0.9). Using in situ sensor data, the estimation of DOC concentrations during the study period was achieved within a range of 33 μM. The phytoplankton bloom coincided with a shift of the fluorescence index (R2 =0.7), while changes in the freshness index correlated with higher DOC concentration during the spring freshet (R2 =0.8). The correlation between FT-ICR mass peaks and in situ parameters allowed an distinction of allochthonous and autochthonous molecules, thus elucidating the fluorescence observations on a molecular level. The results of this study are the basis for a more accurate in situ monitoring of DOM dynamics. Spectroscopic and spectrometric analyses illustrated the seasonal variability of DOM and exposed molecular imprints of primary production on the Columbia River DOM.
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  • 162
    Publication Date: 2014-06-30
    Description: Arctic permafrost coasts make up ~34% of the world’s coastline (ca. 400,000 km) and are often made of ice-rich unconsolidated sediments. This makes them highly susceptible to coastal erosion, and it is likely that large quantities of carbon are released, because permafrost soils are considered to hold approximately 50% of the global soil organic carbon pool. Current estimates of the carbon released by coastal erosion focus solely on particulate organic carbon (POC). Dissolved organic carbon (DOC) is generally not included in these calculations, because estimations of DOC contents in ground ice, which is overwhelmingly present along Arctic coasts, do not exist. In some cases, ground ice occupies as much as 90% of coastal bluffs with 40 m in height, where the coastline erodes at rates approaching 20 m/yr at its maximum. Here, we report DOC contents within permafrost from different ground ice types throughout the Arctic (Canada, Alaska, Siberia). We put them into context of Arctic organic carbon pools and fluxes, and evaluate their contribution to the Arctic carbon budget against the background of increasing permafrost degradation and enhancing coastal erosion in the future. For example, DOC concentrations in massive ground ice bodies including ice wedges range between 〈1.0 and 28.6 mg/L, while ice wedges have the greatest potential as DOC pool due to their wide spatial distribution in late Pleistocene and Holocene polygonal ground. Siberian Ice Complex deposits (Yedoma) are thought to consist of up to 50% of ice wedges by volume and are therefore a substantial pool of DOC. Intrasedimental ice (non-massive) like ice lenses and pore ice are another important part of unconsolidated permafrost deposits. DOC concentrations within intrasedimental ice differ in orders of magnitude compared to massive ice and rise up to 1200 mg/L. Although these numbers might be still small compared to the POC stocks in peat and mineral soils, DOC is chemically labile and may directly enter local food webs of the near-shore zone. Moreover, due to its lability, DOC is quickly mineralized and returned to the atmosphere when released due to permafrost degradation. Robust estimations of how much organic carbon is potentially released from permafrost are crucial for predicting the strength and timing of carbon-cycle feedback mechanisms in the Arctic. This approach shall lead to an improved understanding of how important permafrost thaw in general and the erosion of permafrost coasts in particular are for the climate development this century and beyond. This is especially important in the Arctic before the background of expected rising air and sea surface temperatures, prolongation of the open-water season, increasing storm frequency and accelerating eustatic sea level rise.
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  • 163
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    XXXVII Antarctic Treaty Consultative Meeting
    In:  EPIC3XXXVII Antarctic Treaty Consultative Meeting, Brasilia, 2014-04-28-2014-05-07Buenos Aires, XXXVII Antarctic Treaty Consultative Meeting
    Publication Date: 2014-07-01
    Repository Name: EPIC Alfred Wegener Institut
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  • 164
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    Copernicus Publications
    In:  EPIC3Nonlinear Processes in Geophysics, Copernicus Publications, 21(3), pp. 651-657, ISSN: 1607-7946
    Publication Date: 2014-07-04
    Description: Climate networks are constructed from climate time series data using correlation measures. It is widely accepted that the geographical proximity, as well as other geographical features such as ocean and atmospheric currents, have a large impact on the observable time-series similarity. Therefore it is to be expected that the spatial sampling will influence the reconstructed network. Here we investigate this by comparing analytical flow networks, networks generated with the START model and networks from temperature data from the Asian monsoon domain. We evaluate them on a regular grid, a grid with added random jittering and two variations of clustered sampling. We find that the impact of the spatial sampling on most network measures only distorts the plots if the node distribution is significantly inhomogeneous. As a simple diagnostic measure for the detection of inhomogeneous sampling we suggest the Voronoi cell size distribution.
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  • 165
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    In:  EPIC323. Sitzung des National Komitees SCAR/ISAC, Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, 2014-06-12-2014-06-13
    Publication Date: 2014-07-01
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  • 166
    Publication Date: 2014-07-21
    Description: Bathymetric survey of expeditions by RV Polarstern and RRS James Clark Ross show glacial seafloor features on North East Greenland Continental Shelf. The features are forms of lineations, transverse ridges, winding ridges and scours. Bathymetric Position Index grid and hillshade grid of multibeam echo sounders data enhance the seafloor visualization for interpretation of the features. The interpreted features are given classifications of mega-scale lineations, moraines, eskers and iceberg scours. The farthest feature located near the shelf break indicates that the Greenland Ice Sheet in North East Greenland extends till there. This finding is an annex to previous studies mentioning Greenland Ice Sheet covered the inner-middle continental shelf of North East Greenland based on seafloor morphology and covered till the shelf edge based on sedimentological studies. Glacial seafloor features also reveal the glacial dynamics present. Bathymetric data map mega-scale lineations along Westwind Troughs and the Intra-troughs. Their presence indicate former ice streams along the troughs. The ice stream in Westwind Trough is retreating due to evidence of moraines located there. Eskers also reveal an act of ice surge in Westwind Trough. Icebergs scours are abundant in shallow banks and near the shelf break.
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  • 167
    Publication Date: 2014-07-17
    Description: Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch1, 2, 3, 4. However, the same thermokarst lakes can also sequester carbon5, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47 ± 10 grams of carbon per square metre per year; mean ± standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160 petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears7, 8, 9, potentially negating the climate stabilization provided by thermokarst lakes during the late Holocene.
    Repository Name: EPIC Alfred Wegener Institut
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  • 168
    Publication Date: 2014-07-19
    Description: The climate change in the Arctic has received more attention in the recent decades. Especially the carbon-rich permafrost has become an area of intense research. It´s ice-rich grounds are especially vulnerable to climate warming and ice-thaw. Carbon stored in permafrost can be activated and can become part of the carbon cycle. The transport of organic matter (OM) by coastal erosion of thawing permafrost is one type of permafrost degradation. In this study 23 ice complex sediment samples from a coast section of Muostakh Island (Laptev Sea, East Siberia) were analyzed. Permafrost melt water and water extractable dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured. Water extractions as simulation of natural processes extracted on average between 45 % to 54 % more DOC compared to DOC in melt water. By this, a mobile fraction of organic carbon (OC) stored in ice complex sediments (~13 mg/100 g of sediment) was estimated. With DOC and TDN values C/N ratios were calculated to assess the availability of nitrogen throughout the coastal sediment profile of the coast. In the second part the amino acid content in permafrost melt waters was determined. On average, 3.64% of DOC exists in form of hydrolysable amino acids. L and D amino acid enantiomers were discriminated and the racemization states of single amino acids were determined using High Pressure Liquid Chromatography (HPLC). Amino acid enantiomers were converted into diastereomers using pre-column derivatization with o-phthaldialdehyde and N-isobutyryl-L-cysteine. The resulting fluorescent derivates were detected after separation in a reversed-phase column. Glycine and alanine were the most abundant amino acids. Highest contributions of Dforms to the total of each amino acid were found in alanine, asparagine, glutamine and serine. Based on recent estimates of sediment discharge from Muostakh Island, an annual transport of ~ 14 t DOC and ~ 0.5 t amino acids caused by coastal erosion was roughly estimated.
    Repository Name: EPIC Alfred Wegener Institut
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  • 169
    Publication Date: 2015-03-18
    Description: A thermokarst lake sediment core from the centre of Herschel Island was analysed in order to reconstruct post-glacial palaeoenvironmental changes and landscape dynamics in this part of the Western Canadian Arctic. The ice-rich island in the Southern Beaufort Sea is of outstanding scientific interest since it archives the northernmost terrestrial lake record of the Yukon Territory. Besides previously published sedimentological and biogeochemical analyses, we applied micropaleontology and hydrochemistry on pore waters. The formation of the lake occurred during the Holocene Thermal Maximum, around 11.5 to 10.0 cal ka BP. Here, brackish shallow water ostracods (Heterocyprideis sorbyana) and foraminifers (Cribroelphidium excavatum) prevailed and electrical conductivity of pore waters of approximately 13,000 µS/cm demonstrates a marine influence. Reworking from older sediments, however, cannot be ruled out completely. The lake development until about 7.0 cal ka BP was associated with a period of intense thermokarst activity and the pollen-based temperature reconstruction shows that TJuly was greater than 8°C during the early Holocene at the initial stage of Lake Herschel. The freshwater ostracod Cytherissa lacustris was the dominant species. Pollen concentrations and influx were low prior to 6.0 cal ka BP and subsequently increased, especially in the past thousand years. The ostracod association became more diverse in the Mid-Holocene; Fabaeformiscandona levanderi is the dominant species besides C. lacustris. The reconstructed TJuly were lower from 7.0 to 5.5 cal ka BP and relatively high but variable until 1.8 cal ka BP. Pollen of Cyperaceae and Poaceae were generally the most abundant taxa. However, Poaceae pollen increased in sediments younger than 3.0 cal ka BP and Cyperaceae pollen decreased after 1.8 cal ka BP. Pollen from several shrubs were found in relatively high quantities, including Alnus, Juniperus and Betula; only the latter is found in the recent tundra environment. The ostracod associations show a persistent lake with high input of allochthonous material and possibly elevated salinity. A change in the sedimentation rate between 1.8 to 0.9 cal ka BP is explained either by a hiatus due to modified drainage conditions or slumping. Bioproductivity increased, as shown by a richer fauna (Chironomidae). Foraminifers are abundant and occur together with fresh and brackish water ostracods reflecting elevated salinity. The change of facies is also recorded in pore waters chemistry characterized by lower pH values, slightly higher electrical conductivity and increased Ca, Mg, Mn, Sr and SO4 ion content. The final late-Holocene phase, beginning by 0.9 cal ka BP, was characterized by an elevated and variable NO3 ion content in pore waters, a poorer ostracod fauna and disappearance of foraminifers, as well as pollen-based TJuly below 7°C.
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  • 170
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 171
    Publication Date: 2014-07-22
    Repository Name: EPIC Alfred Wegener Institut
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  • 172
    Publication Date: 2021-07-19
    Description: In this study latent heat flux (λE) measurements made at 65 boreal and arctic eddy-covariance (EC) sites were analyses by using the Penman–Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman–Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control λE in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman–Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated λE of different ecosystem types under meteorological conditions at one site. Values of λE varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that λE is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of λE as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need to take into account vegetation type and phenology in energy exchange modeling.
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  • 173
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    Elsevier
    In:  EPIC3Global Environmental Change, Elsevier, 28, pp. 120-128, ISSN: 0959-3780
    Publication Date: 2016-10-07
    Description: Mangrove forests are among the most threatened tropical ecosystems. Their role as providers of important ecosystem services such as coastal protection, carbon storage and nursery habitats for economically important species is increasingly acknowledged. But mangrove destruction continues, and we might have to face the prospect of a world deprived of the services offered by mangrove ecosystems. Mangrove transformation and destruction is often caused by mismatches in mangrove system management. These root in interests that focus on selected ecosystem services only, but also result from a problem of fit between the spatial scales at which ecosystem services are provided, and those at which their benefits are realized. We argue that a combination of the ecosystem services concept with a careful approach to the issue of scales will help to overcome these problems and improve the management of mangrove systems. Drawing on two case studies from Indonesia and Brazil, we illustrate the relevance of our findings for different ecosystem services.
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  • 174
    Publication Date: 2019-07-17
    Description: Im Rahmen der Arbeit werden projizierte Flugbahnen von Vögeln analysiert und dabei untersucht, inwieweit die verschiedenen Eigenschaften der Flugbahnen eine Trennung in Klassen - und damit vielleicht in Arten - ermöglichen. Die Daten dafür stammen von einer Kamera auf dem Forschungsschiff Polarstern, aus deren Infrarotbildern die Flugbahnen zunächst durch ein Tracking mittels Bildanalyse und Bewegungsmodell gewonnen werden. Dabei werden unvermeidlich neben den Vogelfugbahnen auch weitere Tracks auf beispielsweise Reflexionen des Sonnenlichts gebildet. Die weitergehende Analyse zieht Parallelen zu den Eigenschaften von Correlated Random Walks und zeigt auf, dass die Vogeldaten mittels Support Vector Machine aus den verschiedenen Tracks in den Datensätzen extrahiert werden können. Untersuchungen am Modell des Correlated Random Walks deuten an, dass eine Unterteilung der Vögel in verschiedene Klassen ebenfalls möglich ist.
    Repository Name: EPIC Alfred Wegener Institut
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  • 175
    Publication Date: 2014-08-31
    Repository Name: EPIC Alfred Wegener Institut
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  • 176
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    In:  EPIC3EGU General Assembly Conference Abstracts, Vienna, 2014-04-27-2014-03-2016, pp. 14294
    Publication Date: 2014-07-22
    Description: Continental breakup is commonly preceded or accompanied by massive volcanism and deposition of flood basalts. The large volumes of magma are thought to originate from hot upwelling mantle plumes arriving at the lithosphere. The following plume conduit often leaves a trail in form of volcanic islands or aseismic ridges on the newly created oceanic crust. Due to this correlation in space and time between plume-derived structures and continental breakup, plumes are considered to have a triggering effect or even cause continental breakups. The South Atlantic is a classical example for this model including the Parana (South America) and Etendeka (Africa) flood basalts as well as the aseismic ridges Rio Grande Rise and Walvis Ridge on both conjugate margins. The Walvis Ridge connects the Etendeka flood basalts with the active volcanic islands of Tristan da Cunha, the current hotspot position. To investigate the modification of the continent ocean transition (COT) by the arriving plume head, a large geophysical on- and offshore experiment was conducted in 2011 at the intersection of Walvis Ridge with the African continent. We present two P-wave velocity models of the deep crustal structure derived from seismic refraction data. One profile crosses the ridge ~500km away from the coastline, while the other one extends along the ridge and continues onshore. 27 ocean bottom stations (OBS, spacing 13 km) were deployed for the perpendicular profile, 28 OBS, 50 land stations and 8 dynamite shots were used for the longitudinal profile. Crustal velocities beneath Walvis Ridge range between 5.5 km/s and 7.0 km/s, which are typical velocities for oceanic crust. The thickness, however, is approximately three times than normal, 17 km in the western part and increasing to 22 km towards the continent. The COT is characterized by 30 km thick crust with a high velocity lower crustal body (HVLCB) with seismic velocities up to 7.5 km/s. The western boundary of the HVLCB is at a similar longitude as similar lower crustal bodies found more south. Towards the east the HVLCB terminates against the ~40 km thick crust of the Kaoko fold belt. Here, the variation of seismic velocities indicate that hot material intruded the continental crust during the initial rifting stage. However, beyond this relatively sharp boundary (40 km wide), the remaining continental crust seems not be affected by the hot material. The second line some 500 km west of the coast indicates that the Walvis Ridge might be broader than its topographic expression. The seismic velocities are similar to those closer to the coast, but the HVLCB is thinner.
    Repository Name: EPIC Alfred Wegener Institut
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  • 177
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    In:  EPIC3SAMPLE Colloquium 2014, Bremerhaven, 2014-06-03-2014-06-06
    Publication Date: 2014-07-22
    Description: Walvis Ridge is an aseismic oceanic ridge stretching from the African continent to the Mid Atlantic Ridge, representing the trail of the Tristan da Cunha hotspot. To estimate the influence of the plume, a large-scale geophysical experiment was conducted in 2011 and the P-wave velocity models derived from seismic refraction data are presented here. A 480 km long profile consisting of 27 ocean bottom stations crosses the ridge approximately 600 km west of the coast, while another profile is located parallel to the ridge along the crest with an extension on the continent. 28 ocean bottom stations, 50 land receiver and 8 dynamite shots are distributed along the total length of 730 km. Crustal velocities beneath Walvis Ridge range between 5.5 km/s and 7.0 km/s, which are typical velocities for oceanic crust. The thickness, however, is approximately three times larger than normal: 17 km in the western part increasing to 22 km towards the continent. The continent ocean transition is characterized by 30 km thick crust with a high velocity body (HVB) in the lower crust and seismic velocities up to 7.5 km/s. The western boundary of the HVB is at a similar longitude as HVBs found more south. But different from those, the eastern boundary lies well within the continental domain, at the ~40 km thick crust of the Kaoko fold belt. Here, the variation of seismic velocities indicates that hot material intruded the continental crust during the initial rifting stage. However, beyond this relatively sharp boundary (40 km wide), the remaining continental crust seems not to be affected. The cross-profile indicates that Walvis Ridge might be broader than its topographic expression and that the northward lying seamounts are part of the ridge. A HVB can only be found at the northern flank of the ridge, but not at its base.
    Repository Name: EPIC Alfred Wegener Institut
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  • 178
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    Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
    In:  EPIC3Communications and Media Relations, Bremerhaven, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 12 p.
    Publication Date: 2014-07-22
    Repository Name: EPIC Alfred Wegener Institut
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  • 179
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    Alfred Wegener Institute
    In:  EPIC3Bremerhaven, Alfred Wegener Institute
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Data Processing Reports , notRev
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  • 180
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    ELSEVIER SCIENCE INC
    In:  EPIC3Comparative Biochemistry and Physiology C-Toxicology & Pharmacology, ELSEVIER SCIENCE INC, 162, pp. 43-50, ISSN: 1532-0456
    Publication Date: 2014-08-25
    Description: After 96 h goldfish exposure to 10, 25 or 50 mg/L of Ni2 + no Ni accumulation was found in the brain, but lipid peroxide concentration was by 44% elevated in the brain, whereas carbonyl protein content was by 45–45% decreased in the heart. High molecular mass thiol concentration was enhanced by 30% in the heart, while in the brain low molecular mass thiol concentration increased by 28–88%. Superoxide dismutase activity was by 27% and 35% increased in the brain and heart, respectively. Glutathione peroxidase activity was lowered to 38% and 62% of control values in both tissues, whereas catalase activity was increased in the heart by 15–45%, accompanied by 18–29% decreased glutathione reductase activity. The disturbances of free radical processes in the brain and heart might result from Ni-induced injuries to other organs with more prominent changes in the heart, because of close contact of this organ with blood, whereas the blood–brain barrier seems to protect the brain.
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  • 181
    Publication Date: 2014-07-22
    Description: Walvis Ridge is a prominent aseismic ridge in the South Atlantic, stretching across the whole oceanic crust from the African continent to the Mid Atlantic Ridge, representing the trail of the Tristan da Cunha hotspot. This proposed deep mantle plume emplaced the Parana flood basalts in South America and the Etendeka flood basalts on the African continent, prior and during the breakup of Gondwana. This temporal proximity indicates a causal relationship between the arriving plume head and the continental breakup. To estimate the influence of the plume, a large-scale geophysical experiment was conducted in 2011. The P-wave velocity models derived from seismic refraction data are presented here. A 480 km long profile consisting of 27 ocean bottom stations crosses the ridge approximately 600 km west of the coast, while a second profile is located ridge-parallel along its crest with an extension on the continent. 28 ocean bottom stations, 50 land receiver and 8 dynamite shots are distributed along the total length of 730 km. Crustal velocities beneath Walvis Ridge range between 5.5 km/s and 7.0 km/s, which are typical velocities for oceanic crust. The crustal thickness, however, is approximately three times larger than of normal oceanic crust: 17 km in the western part increasing to 22 km towards the continent. The continent ocean transition is characterized by 30 km thick crust with a high velocity body (HVB) in the lower crust and seismic velocities up to 7.5 km/s. The western boundary of the HVB is at a similar longitude as HVBs observed south of Walvis Ridge. But different from those, the eastern boundary lies well within the continental domain, at the 40 km thick crust of the Kaoko fold belt. Here, the variation of seismic velocities indicates that hot material intruded the continental crust during the initial rifting stage. However, beyond this relatively sharp boundary (40 km wide), the remaining continental crust seems unaffected by intrusions. The cross-profile indicates that Walvis Ridge might be broader than its topographic expression and that the northward lying seamounts are part of the ridge. A HVB can only be found at the northern flank of the ridge, but not at its base. We conclude, that the postulated arriving plume head did not modify the continental crust on a large scale, but was a rather regional anomaly.
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  • 182
    Publication Date: 2014-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 183
    Publication Date: 2014-08-18
    Description: The jumbo squid, Dosidicus gigas, can survive extended forays into the oxygen minimum zone (OMZ) of the Eastern Pacific Ocean. Previous studies have demonstrated reduced oxygen consumption and a limited anaerobic contribution to ATP production, suggesting the capacity for substantial metabolic suppression during hypoxic exposure. Here, we provide a more complete description of energy metabolism and explore the expression of proteins indicative of transcriptional and translational arrest that may contribute to metabolic suppression. We demonstrate a suppression of total ATP demand under hypoxic conditions (1% oxygen, PO2=0.8 kPa) in both juveniles (52%) and adults (35%) of the jumbo squid. Oxygen consumption rates are reduced to 20% under hypoxia relative to air-saturated controls. Concentrations of arginine phosphate (Arg-P) and ATP declined initially, reaching a new steady state (~30% of controls) after the first hour of hypoxic exposure. Octopine began accumulating after the first hour of hypoxic exposure, once Arg-P breakdown resulted in sufficient free arginine for substrate. Octopine reached levels near 30 mmol g−1 after 3.4 h of hypoxic exposure. Succinate did increase through hypoxia but contributed minimally to total ATP production. Glycogenolysis in mantle muscle presumably serves to maintain muscle functionality and balance energetics during hypoxia. We provide evidence that post-translational modifications on histone proteins and translation factors serve as a primary means of energy conservation and that select components of the stress response are altered in hypoxic squids. Reduced ATP consumption under hypoxia serves to maintain ATP levels, prolong fuel store use and minimize the accumulation of acidic intermediates of anaerobic ATP-generating pathways during prolonged diel forays into the OMZ. Metabolic suppression likely limits active, daytime foraging at depth in the core of the OMZ, but confers an energetic advantage over competitors that must remain in warm, oxygenated surface waters. Moreover, the capacity for metabolic suppression provides habitat flexibility as OMZs expand as a result of climate change.
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  • 184
    Publication Date: 2014-07-29
    Description: Permafrost is a direct indicator of climate change and permafrost temperature and active-layer thickness have been identified as Essential Climate Variables (ECV) by the global observing community. The existing data, however, were far from being homogeneous and were not yet optimized for databases, without framework for data reporting or archival and the data documentation was incomplete. Within the EU FP7 project PAGE 21, Arctic Portal has developed a central Data Management System (DMS) for permafrost monitoring parameters of the Global Terrestrial Network for Permafrost (GTN-P) and others. Each component of the DMS, including parameters, data levels and metadata formats were developed in cooperation with the GTN-P, the International Permafrost Association (IPA) and Arctic Portal. The researcher can now edit, visualize and download standardized datasets, metadata, charts and statistics of all relevant parameters for a specific site in all partner countries. The GTN-P DMS is based on an object oriented model (OOM) following the framework Model/View/Controller (MVC) of Cakephp. It is implemented with open source technologies with the PostGIS database and Geoserver. To ensure interoperability and enable potential inter-database search, the system follows the evolution of the Semantic Web (Linking Geospatial Data); the database structure and content are mapped towards xml, xslt, rdf, and owl. Moreover, metadata comply with the ISO 19115/2 and ISO TC/211 standards for geospatial information. Datasets are then normalized based on a control vocabulary registry. Tools are further developed to provide data processing, analysis capability and quality control. The end of the distribution chain deliver highly structured datasets towards modelers in NetCDF files, format developed by UNIDATA. The elaboration of this project highlights the absence of standardized data model for scientific relational databases as well as a lack of ontology definition and mapping within and between scientific communities.
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  • 185
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung = Reports on polar and marine research, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 678, 163 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 186
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2018-08-10
    Repository Name: EPIC Alfred Wegener Institut
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  • 187
    Publication Date: 2014-08-03
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  • 188
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    In:  EPIC3Workshop ARK-XXV/3, BGR Hannover, 2014-04-23-2014-04-23
    Publication Date: 2016-01-21
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  • 189
    Publication Date: 2014-09-08
    Description: The Manihiki Plateau of the western Pacific is one of the world - wide greatest Large Igneous Province (LIP) on oceanic crust. It is assumed that the Manihiki Plateau was emplaced as the centerpiece of the “Super-LIP” Ontong Java Nui by multiple volcanic phases during the Cretaceous Magnetic Quiet Period. The subsequent break-up of Ontong Java Nui led to fragmentation of the Manihiki Plateau into three sub-plateaus, which all exhibit individual relicts of the “Super-LIP” break-up. We examine two deep crustal seismic refraction/wide-angle reflection profiles crossing the two largest sub-plateaus of the Manihiki Plateau, the Western Plateaus and the High Plateau. Modeling of P- and S-wave velocities reveals surprising differences in the crustal structure between the two sub-plateaus. Whereas the High Plateau shows a constant crustal thickness of 20 km, relicts of multiple volcanic phases and break-up features at its margins, the model of the Western Plateaus reveals a crustal thickness decreasing from 17 km to only 9 km. There is only little evidence of secondary phases of volcanic activity. The main upper crustal structure on the Western Plateaus consists of fault systems and sedimentary basins. We infer that the High Plateau experienced phases of strong secondary volcanism, and that tectonic deformation was limited to its edges. The Western Plateaus, on the contrary, were deformed by crustal stretching and underwent only little to no secondary volcanism. This indicates that the two main sub-plateaus of the Manihiki Plateau experienced a different geological history and have played their individual parts in the break-up history of Ontong Java Nui.
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  • 190
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    In:  EPIC3Colloquium of the DFG Priority Program SPP1375:South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE), Bremerhaven, 2014-06-03-2014-06-06
    Publication Date: 2014-08-03
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  • 191
    Publication Date: 2014-09-23
    Description: The SCAR expert group on the International Bathymetric Chart of the Southern Ocean (IBCSO) was inaugurated in 2004. IBCSO is a regional mapping project of the General Bathymetric Chart of the Ocean (GEBCO) under the joint auspices of the Intergovernmental Oceanographic Commission (IOC) (of UNESCO) and the International Hydrographic Organization (IHO). The project aim was to create the first seamless bathymetric compilation for the entire Southern Ocean south of 60°S. In 2013, finally the first Version of IBCSO was published in the Journal Geophysical Research Letters (Arndt et al., 2013). IBCSO Version 1.0 is a prime example for an international collaboration in Antarctic Science. Over 30 institutions from 15 countries contributed data and shared their expertise to generate the, so far, largest database of bathymetric data of the Southern Ocean. From this database a digital bathymetric model (DBM) was produced. The DBM covers the entire Antarctic Treaty area in a resolution of 500 m. It is available in several formats and projections. In addition, a new map has been created of the Southern Ocean and Antarctica and now is also available to the SCAR community. Both, the DBM and the map, can be downloaded free of charge from the IBCSO web site (www.ibcso.org). In my poster presentation I will present the map product of the IBCSO project and give information about its included data sets, its distribution and its design.
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  • 192
    Publication Date: 2014-09-23
    Description: The SCAR expert group on the International Bathymetric Chart of the Southern Ocean (IBCSO) was inaugurated in 2004. IBCSO is a regional mapping project of the General Bathymetric Chart of the Ocean (GEBCO) under the joint auspices of the Intergovernmental Oceanographic Commission (IOC) (of UNESCO) and the International Hydrographic Organization (IHO). The project aim was to create the first seamless bathymetric compilation for the entire Southern Ocean south of 60°S. In 2013, finally the first Version of IBCSO was published in the Journal Geophysical Research Letters (Arndt et al., 2013). IBCSO Version 1.0 is a prime example for an international collaboration in Antarctic Science. Over 30 institutions from 15 countries contributed data and shared their expertise to generate the, so far, largest database of bathymetric data of the Southern Ocean. From this database a digital bathymetric model (DBM) was produced. The DBM covers the entire Antarctic Treaty area in a resolution of 500 m. It is available in several formats and projections. In addition, a new map has been created of the Southern Ocean and Antarctica and now is also available to the SCAR community. Both, the DBM and the map, can be downloaded free of charge from the IBCSO web site (www.ibcso.org). In my presentation I will give an overview of the IBCSO V1.0 compilation methods and highlight the improvements of the IBCSO DBM compared to global datasets. Furthermore, some tips and hints for the usage of IBCSO including the use of the Source Identifier grid (SID) will be given.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 193
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2019-02-06
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 194
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-08-05
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 195
    Publication Date: 2014-09-03
    Description: Throughout the transition from the last Glacial to the current Interglacial, rising atmospheric CO2 levels were accompanied by declining atmospheric Δ14C values. A likely mechanism, influencing both components is the deglacial release of CO2, stored for millennia in the deep Ocean, to the atmosphere. Due to its long residence time within the oceans interior this CO2 rich water mass was considerably depleted in radiocarbon. Although a large number of studies address this topic, the extent, location and pathways of the glacial carbon pool are still subjects of an ongoing debate. As deep water masses are upwelled and new intermediate waters are formed around Antarctica, the Southern Ocean is a potential area for the deglacial release of stored CO2. Here we present radiocarbon and carbonate ion data from a transect of sediment cores off New Zealand that covers the major water masses in this area, from the AAIW down to the AABW. During the Glacial, our data locate a significantly 14C depleted pool in a water depth between 2000 and 4500 m. The combination of Δ14C and [CO32-] records provides new insights into the process of oceanic-atmospheric CO2 exchange in the Southern Ocean. In addition, our results yield new implications for contradicting Δ14C records from the Southern Ocean and lower latitudes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 196
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    In:  EPIC32014 AGU Fall Meeting, San Francisco, 2014-12-15-2014-12-19
    Publication Date: 2014-12-18
    Description: The Intermediate Mode Waters formed in the Southern Ocean are critical for the lower thermocline ventilation process in the Southern Hemisphere Gyres. They also might have served as the most relevant pathways transporting climatic signals from high to low latitudes via the “oceanic tunneling” on glacial/interglacial time scales. Despite the importance of the Southern Ocean Intermediate Waters (SOIWs), our understanding on the long–term evolution, exact advection paths, and impact on the South Pacific Gyre’s thermocline is still fragmentary. Here, we present a 200 kyr record of paired Mg/Ca ratios and stable oxygen isotope from surface dweller and deep dwelling planktonic foraminifera, from the South Pacific Gyre (SPG). On average, the Mg/Ca–derived sea Surface Temperatures (Globigerina bulloides) show similar conditions during the LGM and Marine Isotope Stage (MIS) 6 (9.4 °C versus 9.9 °C). In contrast, our Mg/Ca–derived subsurface temperatures (Globorotalia inflata and Globorotalia truncatulinoides) suggest LGM from ~3 to ~2 °C colder than MIS 6. The reconstructed subsurface ice volume corrected stable oxygen isotope ratio of seawater (δ18Osw-ivc, proxy for local salinity changes) suggests opposing glacial subsurface conditions, i.e., slightly saltier–than–Holocene during MIS 6 to fresher–than–Holocene during MIS 2. Considering that subsurface hydrography at the core site is plausibly driven by the formation and/or advection of SOIWs from the South East Pacific, our results provide further support on the relevance of subsurface processes in the Southern Ocean transferring climatic signals (temperature and salinity) to the SPG. Furthermore, the contrasting subsurface glacial scenarios at the SPG’s thermocline imply that the advection of SOIWs during glacial stages could be highly variable during different glacial stages.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 197
    Publication Date: 2014-12-18
    Description: Geomagnetic excursions are short-lived deviations of the geomagnetic field from the normal range of secular variation. Despite significant advances in geomagnetic excursion research over the past 20 years, fundamental questions remain concerning the typical duration and global morphology of excursional geomagnetic fields. To answer such questions, more high-resolution, chronologically well-constrained excursion records are required, particularly from the Southern Hemisphere. We present preliminary paleomagnetic records of the Laschamp (~41 ka) and Mono Lake (~35 ka) excursions from three marine sediment cores from the Bounty Trough, New Zealand margin, and complementary volcanic records of the Laschamp excursion from lavas of Mt Ruapehu, New Zealand. Relatively high sedimentation rates of 12 – 26 cm/kyr in the Bounty Trough during glacial periods allow identification of excursional field behavior at each of the studied core locations. Each core displays one or two excursional events, with rapid directional swings between stable normal polarity and reversed excursional directions, each associated with coincident relative paleointensity minima. These anomalous paleomagnetic directions are interpreted to represent the Laschamp and Mono Lake excursions, based on a combination of tephrochronology, radiocarbon dating, and cyclostratigraphy (defined from core-scanning X-ray fluorescence and magnetic susceptibility records). Beside these records, we present results from fourteen lava flows, on Mt Ruapehu, for which 40Ar-39Ar dating indicates ages of between 39 and 45 ka. The step heating 40Ar-39Ar experiments produced particularly flat age plateaus, with corresponding 2 s.d. errors mostly approaching 1 kyr. The youngest and oldest flows carry normal polarity magnetization, however six flows, dated between 41 and 43 ka, display transitional field characteristics. Three of these flows display a declination swing of around 180o, which coincides with a previously published result from the Auckland Basalt Field. Together, these data provide rare excursion records from the southern hemisphere, which will provide an improved view of geomagnetic field morphology during these excursions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 198
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    In:  EPIC34th European Conference on Permafrost, Evora, 18 June 2014 - 21 June 2014 .
    Publication Date: 2015-03-25
    Description: The reconstruction of past temperatures with ground ice, especially with ice wedges is possible, but reduced by the missing correlation of ice veins to the exact year of their formation. Therefore, we performed recent cryogenesis tracer experiments on Samoylov Island, Northern Siberia, to calibrate a stable isotope thermometer for ice wedges. In 2002, a low centre polygon (20 m in diameter) was selected showing clearly visible (several mm wide) frost cracks and a well-developed relief between polygon wall and centre. Here, coloured Lycopodium spores, (each year a different colour) have been applied in autumn to a polygon with recent ice-wedge growth (between 2002 and 2009) to trace ground ice formed in the considered years. The spores should to be transported with snow/snowmelt into the open frost crack in spring. In 2010, 13 permafrost cores were taken from the ice-wedge polygon. In the cold laboratory, these ground-ice cores have been processed and individual ice veins have been sampled for spore identification and stable isotope analyses. Single ice veins were melted and examined under the light microscope for spores. All spores colours could be recovered, with red spores (2002) being most abundant followed by green (2003) and violet (2004). An overall decrease in spore abundance is probably related to changing hydrological conditions and polygon degradation. Additionally, frost cracking experiments (breaking cables) were installed to the polygon, intended to break when a sudden rupture (i.e. a frost cracking event) takes place. Data loggers detected the precise moments of cracking on Samoylov Island generally occurring between November, 8 and February, 10 (N=12). The stable isotope composition of every single melted ice vein has been analysed with a Picarro L2120i water isotope analyser and, if spores were present, attributed to the respective year of formation. However, attribution to the year of formation is complicated by eventual occurrence of more than one colour in a sample, which has been assessed by statistical methods. The isotope composition of single ice veins could be measured for the first time in high resolution with a Picarro laser-optical spectrometer and showed no significant isotope fractionation during freezing. The combination with meteorological data allows correlating the local temperature with the δ18O of ice-wedge ice formed in a discrete year. The δ18O and δD values of recent ice veins correspond roughly to the LMWL in Tiksi (δD=7.57 δ18O–6.8), indicative for meteoric precipitation stored in ice wedges. However, the broad scatter of the data shows large inter-annual and seasonal variability of the frost cracking process. A first comparison with meteorological data indicates that December temperatures may best explain the variability in recent ice wedge isotope composition.
    Repository Name: EPIC Alfred Wegener Institut
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  • 199
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    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Publication Date: 2014-08-06
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 200
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    In:  EPIC3Past Gateways Conference and Workshop, Trieste, Italy. 19-23 May 2014
    Publication Date: 2014-08-26
    Description: The Arctic climate has experienced a major warming over the past decades, which is unprecedented in the past 2 kyrs. There are, however, still major uncertainties about the temperature evolution during the Holocene. Most Northern Hemisphere proxy reconstructions suggest a cooling in mid-and late Holocene (e.g. Wanner et al., 2008), whereas climate model simulations show only weak changes or even a moderate warming (e.g. Lohmann et al., 2013). In this study, we used ice wedges as most promising climate archive in permafrost that were studied by stable water isotope methods. Ice wedges may be identified by vertically oriented foliations and they form by the repeated filling of winter thermal contraction cracks by snow melt water in spring. Therefore, the isotopic composition (δ18O, δD, d excess) of wedge ice may be attributed to the cold period climate conditions (winter and spring). 42 samples of organic material enclosed in ice wedges has been directly dated by Radiocarbon methods. Here, we present the first stable-isotope winter proxy record in up to centennial-scale resolution from permafrost ice wedges (Lena River Delta; Siberian Arctic) for the Holocene. The Lena ice-wedge record shows that the recent isotopic temperatures were unprecedented in the past 8000 years. While confirming the Arctic temperature reconstructions of the last two millennia (Kaufman et al., 2009), it suggests a winter warming throughout the mid and late Holocene, thus contradicting most existing other proxy records (Wanner et al., 2008). This apparent contradiction can be explained by (1) the seasonality of the ice-wedge genesis and season-specific orbital forcing, (2) greenhouse gas forcing as well as by (3) regional peculiarities (i.e. the marine transgression). We believe that the present model-data mismatch might be an artefact of the summer bias of the existing proxy records and thus, our record provides important new information for the understanding of the seasonality aspect in the northern hemisphere Holocene temperature evolution especially for the Arctic.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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