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PANGAEA tech-keyword 'featured' (6 data sets)

Mostrando recursos 1 - 20 de 74

  1. Modelling Holocene peatland dynamics

    Chaudhary, Nitin; Miller, Paul; Smith, Benjamin
    Dynamic global vegetation models (DGVMs) are designed for the study of past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks. However, current DGVMs lack functionality for the representation of peatlands, an important store of carbon at high latitudes. We demonstrate a new implementation of peatland dynamics in a customised "Arctic" version of the dynamic vegetation model LPJ-GUESS, simulating the long-term evolution of selected northern peatland ecosystems and assessing the effect of changing climate on peatland carbon balance. Our approach employs a dynamic multi-layer soil with representation of freeze-thaw processes and litter inputs from a dynamically-varying...

  2. n-Alkane deuterium analysis of soil samples from South Africa

    Herrmann, Nicole; Boom, Arnoud; Carr, Andrew S; Chase, Brian M; West, Adam G; Zabel, Matthias; Schefuß, Enno
    The hydrogen isotope composition of plant leaf wax (dDwax) has been found to record the isotope composition of precipitation (dDp). Hence, dDwax is increasingly used for palaeohydrological reconstruction. It is, however, also affected by secondary factors, such as vegetation type, evapotranspiration and environmental conditions, complicating its direct application as a quantitative palaeohydrological proxy. Here, we present dDwax data from soils along vegetation gradients and climatic transects in southern Africa to investigate the impact of different environmental factors on dDwax. We found that dDwax correlated significantly with annual dDp (obtained from the interpolated Online Isotopes in Precipitation Calculator data set) throughout...

  3. Short-term orbital forcing: A quasi-review and a reappraisal of realistic boundary conditions for climate modeling, links to source code and model output

    Cionco, Rodolfo G; Soon, Willie Wei-Hock
    The aim of this paper is to provide geoscientists with the most accurate set of the Earth's astro-climatic parameters and daily insolation quantities, able to describe the Short-Term Orbital Forcing (STOF) as represented by the ever-changing incoming solar radiation. We provide an updated review and a pragmatic tool/database using the latest astronomical models and orbital ephemeris, for the entire Holocene and 1 kyr into the future. Our results are compared with the most important database produced for studying long-term orbital forcing showing no systematic discrepancies over the full thirteen thousand years period studied. Our detailed analysis of the periods present...

  4. R-script to: Testing the impact of stratigraphic uncertainty on spectral analyses of sedimentary serie

    Martinez, Mathieu; Kotov, Sergey; De Vleeschouwer, David; Pas, Damien; Pälike, Heiko
    Spectral analysis is a key tool for identifying periodic patterns in sedimentary sequences, including astronomically related orbital signals. While most spectral analysis methods require equally spaced samples, this condition is rarely achieved either in the field or when sampling sediment core. Here, we propose a method to assess the impact of the uncertainty or error made in the measurement of the sample stratigraphic position on the resulting power spectra. We apply a Monte Carlo procedure to randomise the sample steps of depth series using a gamma distribution. Such a distribution preserves the stratigraphic order of samples and allows controlling the...

  5. Chemical analysis from two sediment cores of lake Dauriat and lake Oksana from Schefferville, subarctic Québec

    Aebischer, Stéphane; Cloquet, Christophe; Carignan, Jean; Maurice, Pierre; Pienitz, Reinhard
    Iron mining in Schefferville (1939-1977) in subarctic Quebec has left behind large numbers and quantities of tailing deposits. The impact of past mining activity on aquatic ecosystems in the Schefferville area has been studied using geochemical and isotopic (Pb, Zn and Fe) analyses of lake sediments, ore deposits, tailings and epiphytic lichens. Analysis of two sediment cores from Lakes Dauriat and Oksana reveals that the surface geochemical cycle of the Schefferville area has been profoundly disturbed by anthropogenic activity such as mining. Disturbances were particularly abrupt at the transitions from pre-mining to mining and mining to post-mining periods. Elemental and isotopic...

  6. Decadal resolution record of sediment core M74/1b_944-6 (SL 163)

    Munz, Philipp; Steinke, Stephan; Böll, Anna; Lückge, Andreas; Groeneveld, Jeroen; Kucera, Michal; Schulz, Hartmut
    The Indian summer monsoon (ISM) is an important conveyor in the ocean-atmosphere coupled system on a transregional scale. Here we present a study of a sediment core from the northern Oman margin, revealing early- to mid Holocene ISM conditions on a near 20-year resolution. We assess multiple independent proxies indicative of sea surface temperatures (SST) during the upwelling season together with bottom water conditions. We use geochemical parameters, transfer functions of planktic foraminiferal assemblages and Mg/Ca paleothermometry and find evidence corroborating previous studies that upwelling intensity varies significantly in coherence to solar sunspot cycles. The dominant ~80-90-year Gleissberg cycle was...

  7. An inventory of active rock glaciers in the northern Tien Shan of China compiled using satellite SAR interferometry

    Wang, Xiaowen; Liu, Lin; Zhao, Lin; Wu, Tonghua; Li, Zhongqin; Liu, Guoxiang
    Rock glaciers are widespread in the Tien Shan. However, rock glaciers in the Chinese part of the Tien Shan have not been systematically investigated for more than two decades. In this study, we propose a new method that combines SAR interferometry and optical images from Google Earth to map active rock glaciers (ARGs) in the Northern Tien Shan (NTS) of China. We compiled an inventory that includes 261 ARGs and quantitative information about their locations, geomorphic parameters, and down-slope velocities. Our inventory shows that most of the ARGs are moraine-derived (69 %) and facing northeast (56 %). The altitude distribution...

  8. Results from 14 neutrally buoyant RAFOS floats in the western equatorial Pacific Ocean

    Zenk, Walter; Siedler, Gerold; Ishida, Akio; Holfort, Jürgen; Kashino, Yuji; Kuroda, Yoshifumi; Miyama, Toru; Müller, Thomas J
    In the western equatorial Pacific the low-salinity core of Antarctic Intermediate Water (AAIW) is found at about 800 m depth between potential density levels Sigma-theta = 27.2 and 27.3. The pathways of AAIW and the degradation of its core are studied, from the Bismarck Sea to the Caroline Basins and into the zonal equatorial current system. Both historical and new observational data, and results from numerical circulation model runs are used. The observations include hydrographic stations from German and Japanese research vessels, and Eulerian and Lagrangian current measurements. The model is the JAMSTEC high-resolution numerical model based on the Modular...

  9. Quantification of shoreline movements along the Yukon Territory mainland coast between 1951 and 2011

    Irrgang, Anna Maria; Lantuit, Hugues; Manson, Gavin K; Günther, Frank; Grosse, Guido; Overduin, Pier Paul
    The Arctic is warming, but the impacts on its coasts are not well documented. To better understand the reaction of Arctic coasts to increasing environmental pressure, shoreline position changes along a 210 km length of the Yukon Territory mainland coast in north-west Canada were investigated for the time period from 1951 to 2011. Shoreline positions were extracted from georeferenced aerial photographs from 1951, 1953, 1954, 1972, 1976, 1992, 1994, and 1996, and from WorldView and GeoEye satellite imagery from 2011. Shoreline change was then analyzed using the Digital Shoreline Analysis System (DSAS) extension for ESRI ArcGIS. Shoreline change rates decelerated...

  10. Geochemistry and dissolved organic matter in marine shallow hydrothermal systems

    Gomez-Saez, Gonzalo V; Niggemann, Jutta; Dittmar, Thorsten; Pohlabeln, Anika M; Lang, Susan Q; Noowong, Ann; Pichler, Thomas; Wörmer, Lars; Bühring, Solveig I
    Shallow submarine hydrothermal systems are extreme environments with strong redox gradients at the interface of hot, reduced fluids and cold, oxygenated seawater. Hydrothermal fluids are often depleted in sulfate when compared to surrounding seawater and can contain high concentrations of hydrogen sulfide (H2S). It is well known that sulfur in its various oxidation states plays an important role in processing and transformation of organic matter. However, the formation and the reactivity of dissolved organic sulfur (DOS) in the water column at hydrothermal systems are so far not well understood. We investigated DOS dynamics and its relation to the physicochemical environment...

  11. Seven new species of Platyhelminthes from sandy beaches of the island of Sylt (North Sea)

    Armonies, Werner
    Climate change and species introductions strongly changed macrobenthic community composition in the North Sea during past decades. To find out whether there was a similar change in meiofauna, I re-examined a semi-exposed sandy beach of the Island of Sylt that had been intensively studied between 1965 and 1975. These previous studies provide the baseline for temporal change. As before, the analysis of species composition focused on Platyhelminthes. Minor change in the physical properties of the beach during the past decades was compensated for by including two adjoining beaches, one slightly more sheltered and the other slightly more exposed. In due consideration...

  12. Guadeloupe annual coral seawater d18O reconstruction

    Hetzinger, Steffen; Pfeiffer, Miriam; Dullo, Wolf Christian; Garbe-Schönberg, Carl-Dieter; Halfar, Jochen
    We have generated 104-year long (1895-1999) monthly d18O and Sr/Ca time series from a fast-growing Diploria strigosa coral core drilled off Guadeloupe Island, Lesser Antilles. Coral Sr/Ca reliably records interannual to decadal surface air temperature (SAT) variations in the region and shows a pronounced warming of approximately 1.5 °C since 1950, with the strongest warming (1.2 °C) occurring since 1975. This warming is also evident in SAT measured at Guadeloupe, which ends in 1951. Thus, our Sr/Ca series extends the air temperature record by 56 years. We find that the past few decades are the warmest years over the entire...

  13. Bulk sediment mineral composition of sediment core GeoB12605-3

    Liu, Xiting; Rendle-Bühring, Rebecca; Meyer, Inka; Henrich, Rüdiger
    Equatorial East Africa experienced significant variations in paleoclimatic and paleoceanographic conditions during the Holocene. These environmental changes influenced sedimentation patterns on the continental shelf. To date, however, little is known about the sediment source, its transport to, and deposition on, the Tanzanian shelf. This paper presents a new high-resolution Holocene sedimentary record off northeast Tanzania (equatorial East Africa) and provides insights into how sedimentation patterns responded to climatic and oceanographic changes during the Holocene. Based on grain-size distribution patterns and mineral assemblages, three types of shelf sediments were identified: Type I (fine-grained terrigenous sediment) is dominated by clay minerals that...

  14. Measurement of aerobic scope during the whole embryonic development of a cephalopod

    Tremblay, Nelly; Caamal-Monsreal, Claudia; Ortega, Karen; Díaz, Fernando; Celdrán, David; Rosas, Carlos
    In the context of global warming, the present study aimed to identify at which stages the embryos of the holobenthic species Octopus maya are the most sensitive to temperature. We used temperature as a tool to induce minimum (TIMR-min: 11°C) and maximum metabolic rates (TIMR-max: 30°C) on embryos that came from three wild females caught off Sisal harbor (21°10'N, 90°02'W; Yucatán, Mexico) in March 2016. Higher metabolic rate values were recorded at stages XV and XVI, when the three hearts start beating, compared to stage X, when organogenesis begins. The factorial metabolic scope (FMS = TIMR-max - TIMR-min) was higher...

  15. Pore water chemistry and sediment temperature for cores COAST_C-2 and BK-2, central Laptev Sea shelf

    Mitzscherling, Julia; Winkel, Matthias; Winterfeld, Maria; Horn, Fabian; Yang, Sizhong; Grigoriev, Mikhail N; Wagner, Dirk; Overduin, Pier Paul; Liebner, Susanne
    Submarine permafrost is more vulnerable to thawing than permafrost on land. Besides increased heat transfer from the ocean water, the penetration of salt lowers the freezing temperature and accelerates permafrost degradation. This data set provides sediment temperatures and pore water chemistry from two submarine permafrost cores from the Laptev Sea on the East Siberian Arctic Shelf which inundated about 540 and 2500 years ago. These data are published in partnership with a paper by Magritz et al., that traces how bacterial communities develop depending on duration of the marine influence and pore water chemistry. Magritz et al. (2017) show that...

  16. High-resolution 10Be concentrations in the EDC96 ice core

    Raisbeck, Grant M; Yiou, Françoise; Jouzel, Jean; Stocker, Thomas F
    A new, decadally resolved record of the 10Be peak at 41 kyr from the EPICA Dome C ice core (Antarctica) is used to match it with the same peak in the GRIP ice core (Greenland). This permits a direct synchronisation of the climatic variations around this time period, independent of uncertainties related to the ice age-gas age difference in ice cores. Dansgaard-Oeschger event 10 is in the period of best synchronisation and is found to be coeval with an Antarctic temperature maximum. Simulations using a thermal bipolar seesaw model agree reasonably well with the observed relative climate chronology in these...

  17. Shipborne rotating shadowband radiometer data of spectral irradiance components and aerosol optical depth during POLARSTERN cruise PS83 (ANT-XXIX/10)

    Witthuhn, Jonas; Deneke, Hartwig; Macke, Andreas; Bernhard, Germar
    The 19-channel rotating shadowband radiometer GUVis-3511 built by Biospherical Instruments provides automated shipborne measurements of the direct, diffuse and global spectral irradiance components without a requirement for platform stabilization. Several direct sun products, including spectral direct beam transmittance, aerosol optical depth, Ångström exponent and precipitable water, can be derived from these observations. The individual steps of the data analysis are described, and the different sources of uncertainty are discussed. The total uncertainty of the observed direct beam transmittances is estimated to be about 4 % for most channels within a 95 % confidence interval for shipborne operation. The calibration is...

  18. Present-day sediment trap particle fluxes across the tropical North Atlanitc Ocean

    Korte, Laura F; Brummer, Geert-Jan A; van der Does, Michèlle; Guerreiro, Catarina V; Hennekam, Rick; van Hateren, Johannes A; Jong, Dirk; Munday, Chris I; Schouten, Stefan; Stuut, Jan-Berend W
    Massive amounts of Saharan dust are blown from the African coast of North Africa across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect effects on global climate including reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors....

  19. Manure nitrogen production and application in cropland and rangeland during 1860 - 2014: A 5-minute gridded global data set for Earth system modeling

    Zhang, Bowen; Tian, Hanqin; Lu, Chaoqun; Dangal, R S Shree; Yang, Jia; Pan, Shufen
    Given the important role of nitrogen input from livestock system in the terrestrial nutrient cycles and the atmospheric chemical composition, it is vital to have a robust estimation of the magnitude, spatiotemporal variation of manure nitrogen production and the application to cropland and rangeland across the globe. In this study, we used the dataset from Global Livestock Impact Mapping System (GLIMS) in conjunction with country-specific annual livestock population to reconstruct the manure nitrogen production from 1860 to 2014. The estimated manure nitrogen production increased from 21.4 Tg N/yr in 1860 to 131.0 Tg N/yr in 2014, with a significant increasing...

  20. A high-temporal multiproxy study of sediment core GL1090

    Santos, Thiago P; Lessa, Douglas O; Venancio, Igor M; Chiessi, Cristiano Mazur; Mulitza, Stefan; Kuhnert, Henning; Govin, Aline; Machado, Thiago; Costa, Karen Badaraco; Toledo, Felipe Antonio de L; Dias, Bruna Borba; Albuquerque, Ana Luiza S
    Paleoceanographic reconstructions from the Brazil Current are scarce and lack the required temporal resolution to appropriately represent its variability during key periods of the last glacial-interglacial cycles. Here, we present the first high-temporal resolution multiproxy reconstruction of the Brazil Current at 24 °S covering the last 185 ka. During the last and penultimate glacial periods, our Mg/Ca-derived sea surface temperature (SST) record shows a strong cooling at ca. 47 and ca. 156 ka, respectively, that is followed by a warming trend from late-Marine Isotope Stage (MIS) 3 to MIS 1 and from late-MIS 6 to MIS5e, respectively. Importantly, the Brazil...

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