Viser treff 517-536 av 698

    • Rapid Atlantification along the Fram Strait at the beginning of the 20th century 

      Tesi, Tommaso; Muschitiello, Francesco; Mollenhauer, Gesine; Miserocchi, Stefano; Langone, Leonardo; Ceccarelli, Chiara; Panieri, Giuliana; Chiggiato, Jacopo; Nogarotto, Alessio; Hefter, Jens; Ingrosso, Gianmarco; Giglio, Federico; Giordano, Patrizia; Capotondi, Lucilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-24)
      The recent expansion of Atlantic waters into the Arctic Ocean represents undisputable evidence of the rapid changes occurring in this region. Understanding the past variability of this “Atlantification” is thus crucial in providing a longer perspective on the modern Arctic changes. Here, we reconstruct the history of Atlantification along the eastern Fram Strait during the past 800 years using ...
    • Rapid post-glacial bedrock weathering in coastal Norway 

      Andersen, Jane Lund; Margreth, Annina; Fredin, Ola; Linge, Henriette; Goodfellow, Bradley W.; Faust, Johan Christoph; Knies, Jochen; Solbakk, Terje; Brook, Edward J.; Scheiber, Thomas; van der Lelij, Roelant; Burki, Valentin Josef; Rubensdotter, Brita Lena Eleonor Fredin; Himmler, Tobias; Yesilyurt, Serdar; Christl, Marcus; Vockenhuber, Christof; Akcar, Naki (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-26)
      Quantifying bedrock weathering rates under diverse climate conditions is essential to understanding timescales of landscape evolution. Yet, weathering rates are often difficult to constrain, and associating a weathered landform to a specific formative environment can be complicated by overprinting of successive processes and temporally varying climate. In this study, we investigate three sites ...
    • Rapid Surface Lowering of Benito Glacier, Northern Patagonian Icefield 

      Ryan, Jonathan C.; Sessions, Martin; Wilson, Ryan; Wündrich, Olaf; Hubbard, Alun L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-01)
      The Patagonian Icefields, which straddle the Andes below 46°S, are two of the most sensitive ice masses on Earth to climate change. However, recent mass loss from the icefields along with its spatial and temporal variability is not well-constrained. Here we determine surface elevation changes of Benito Glacier, a 163 km2 outlet glacier draining the western flank of the North Patagonian Icefield, ...
    • The Raunis section, central Latvia, revisited: first luminescence results and re-evaluation of a key Baltic States stratigraphic site 

      Kalińska, Edyta; Alexanderson, Helena; Krievāns, Māris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-08)
      In interstadial deposits, sand interbeds gain limited consideration in comparison with organic sediments, and therefore tend to be underrepresented in paleoenvironmental reconstructions. The Raunis site, central-eastern Latvia, is an example where organic beds have already gained some attention and been used to understand the complex interactions between advance and retreat of the Scandinavian Ice ...
    • Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region: The cryptotephra record 

      Abbott, Peter M.; Austin, William E.N.; Davies, Siwan M.; Pearce, Nicholas John Geoffrey; Rasmussen, Tine Lander; Wastegård, Stefan; Brendryen, Jo (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Recent acceleration of a rock glacier complex, Ádjet, Norway, documented by 62 years of remote sensing observations 

      Eriksen, Harald Øverli; Rouyet, Line; Lauknes, Tom Rune; Berthling, Ivar; Hindberg, Heidi; Larsen, Yngvar; Corner, Geoffrey D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-23)
      Recent acceleration of rock glaciers is well recognized in the European Alps, but similar behavior is hardly documented elsewhere. Also, the controlling factors are not fully understood. Here we provide evidence for acceleration of a rock glacier complex in northern Norway, from 62 years of remote sensing data. Average annual horizontal velocity measured by aerial feature tracking increased from ...
    • Reconstructing the retreat dynamics of the Bjørnøyrenna Ice Stream based on new 3D seismic data from the central Barents Sea 

      Piasecka, Emilia Daria; Winsborrow, Monica; Andreassen, Karin; Stokes, Chris R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-01)
      The stability of contemporary ice sheets is influenced by the discharge from ice streams - corridors of fast-flowing ice bounded by ice flowing an order of magnitude slower. Reconstructions of palaeo-ice stream dynamics contribute to our understanding of ice stream sensitivity to the ocean-climate system and can aid in the numerical modelling and prediction of future changes in contemporary ice ...
    • Reconstruction of a volcano-sedimentary environment shared by the Porongos and Várzea do Capivarita complexes at 790 Ma, Dom Feliciano Belt, southern Brazil 

      Battisti, Matheus Ariel; Bitencourt, Maria de Fatima; Schmitt, Renata da Silva; Nardi, Lauro Valentim Stoll; Martil, Mariana Maturano Dias; De Toni, Giuseppe Betino; Pimentel, Márcio Martins; Armstrong, Richard; Konopásek, Jiří (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-22)
      This work investigates the pre-collisional (before ca. 650 Ma) history of the Dom Feliciano Belt in southernmost Brazil through geochronological and zircon oxygen isotope study. U–Pb SHRIMP dating of two orthogneiss samples from the Várzea do Capivarita Complex and one metarhyolite sample from the Porongos Complex yielded crystallisation ages of 786 ± 5 Ma, 780 ± 10 Ma and 787 ± 5 Ma, respectively. ...
    • Reconstruction of Atlantic Water variability during the Holocene in the western Barents Sea 

      Groot, Diane; Sørensen, Steffen Aagaard; Husum, Katrine (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-10)
      The gravity core JM09-KA11-GC from 345m water depth on the western Barents Sea margin was investigated for down-core distribution patterns of benthic Foraminifera, stable isotopes, and sedimentological parameters in order to reconstruct the flow of Atlantic water during the Holocene. The core site is located below the Atlantic water masses flowing into the Arctic Ocean and close to the Arctic front. ...
    • Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols 

      Ezat, Mohamed; Rasmussen, Tine Lander; Groeneveld, Jeroen (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-20)
      The shallow subsurface hydrography in the southern Norwegian Sea during the past 135,000 years was investigated using parallel measurements of Mg/Ca and δ18O in shells of the planktic foraminiferal species Neogloboquadrina pachyderma. Two cleaning methods were applied prior to Mg/Ca analysis, “Mg cleaning” and “full cleaning” methods. Different results were obtained, which are most likely due to a ...
    • Reconstruction of ice sheet retreat after the Last Glacial maximum in Storfjorden, southern Svalbard 

      Nielsen, Tove; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-15)
      Storfjorden is a large north-south trending sound located in the southern part of Svalbard in the northwestern Barents Sea. Presently, several glaciers drain into the northern and western part of Storfjorden. Our study area covers the southern part of the sound, which is divided by a north-south striking basement ridge (the ‘Mid-ridge’) into a narrow western trough (‘Little-Storfjorden’) and a broader ...
    • Reconstruction of the Virtual Geomagnetic Pole (VGP) path at high latitude for the last 22 kyr: The role of radial field flux patches as VGP attractor 

      Caricchi, Chiara; Campuzano, Saioa A.; Sagnotti, Leonardo; Macri, Patrizia; Lucchi, Renata Giulia (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-24)
      Reconstruction of geomagnetic field changes has a strong potential to complement geodynamo modeling and improve the understanding of Earth's core dynamics. Recent works based on geomagnetic measurements pointed out that over the last two decades the position of the north magnetic pole has been largely determined by the influence of two competing flux lobes under Canada and Siberia. In order to ...
    • Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation 

      Kipp, Michael A.; Lepland, Aivo; Buick, Roger (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-24)
      The ~2.0 Ga Zaonega Formation (ZF) holds one of the oldest phosphorites in the geologic record, reaching >15% P<sub>2</sub>O<sub>5</sub>. Understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in Earth’s early history. Here we use an array of major and trace ...
    • Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes 

      Weber, Yuki; Sinninghe Damsté, Jaap S.; Zopfi, Jakob; De Jonge, Cindy; Gilli, Adrian; Schubert, Carsten J.; Lepori, Fabio; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-23)
      Terrestrial paleoclimate archives such as lake sediments are essential for our understanding of the continental climate system and for the modeling of future climate scenarios. However, quantitative proxies for the determination of paleotemperatures are sparse. The relative abundances of certain bacterial lipids, i.e., branched glycerol dialkyl glycerol tetraethers (brGDGTs), respond to changes in ...
    • Reduced Arctic sea ice extent during the mid-Pliocene Warm Period concurrent with increased Atlantic-climate regime 

      Rahaman, Waliur; Smik, Lukas; Köseoğlu, Denizcan; Lathika, N.; Tarique, Mohd; Thamban, Meloth; Haywood, Alan; Belt, Simon T.; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-01)
      Quantifying the contribution of poleward oceanic heat transport to the Arctic Ocean is important for making future sea ice and climate predictions. To highlight its potential importance in a warmer world, we present a new record of water-mass exchange between the Atlantic and the Arctic Oceans using the authigenic neodymium isotopic composition of marine sediments from the Fram Strait during the ...
    • Reduced methane seepage from Arctic sediments during cold bottom-water conditions 

      Ferré, Benedicte; Jansson, Pär; Moser, Manuel; Serov, Pavel; Portnov, Aleksei D; Graves, Carolyn; Panieri, Giuliana; Gründger, Friederike; Berndt, Christian; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-13)
      Large amounts of methane are trapped within gas hydrate in subseabed sediments in the Arctic Ocean, and bottom-water warming may induce the release of methane from the seafloor. Yet the effect of seasonal temperature variations on methane seepage activity remains unknown as surveys in Arctic seas are conducted mainly in summer. Here we compare the activity of cold seeps along the gas hydrate stability ...
    • Reduced Numerical Model for Methane Hydrate Formation under Conditions of Variable Salinity. Time-Stepping Variants and Sensitivity 

      Peszynska, M.; Medina, F.P.; Hong, Wei-Li; Torres, M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-24)
      In this paper, we consider a reduced computational model of methane hydrate formation in variable salinity conditions, and give details on the discretization and phase equilibria implementation. We describe three time-stepping variants: Implicit, Semi-implicit, and Sequential, and we compare the accuracy and efficiency of these variants depending on the spatial and temporal discretization parameters. ...
    • REE+Y uptake and diagenesis in Recent sedimentary apatites 

      Lumiste, Kaarel; Mänd, Kaarel; Bailey, Juke; Paiste, Päärn; Lang, Liisa; Lepland, Aivo; Kirsimäe, Kalle (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-30)
      Rare Earth Elements and Yttrium (REE+Y) distribution in authigenic phases are frequently used as proxies for reconstructing past seawater conditions. Sedimentary apatite precipitates near the sediment-water interface and is therefore capable of recording the REE+Y composition of the overlying water column. While the overprinting of primary REE+Y signal during late stage diagenesis is a widely known ...
    • A refined late-Cryogenian – Ediacaran Earth history of South China: phosphorous-rich marbles of the Dabie and Sulu orogens 

      Prave, Anthony R; Meng, F.; Lepland, Aivo; Kirsimäe, Kalle; Kreitsmann, Timmu; Jiang, C.Z. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-02)
      The late-Cryogenian – Ediacaran geological framework for South China is constructed principally from sedimentary successions preserved in the central and western regions of the Yangtze Block. New stratigraphic and carbonate-carbon isotope data allow us to extend that framework into the exhumed HP-UHP subduction complexes of the eastern Dabie and Sulu orogens that separate the South and North China ...
    • Regional Morpho-Kinematic Inventory of Slope Movements in Northern Norway 

      Rouyet, Line; Lilleøren, Karianne Staalesen; Böhme, Martina; Vick, Louise Mary; Delaloye, Reynald; Etzelmüller, Bernd; Lauknes, Tom Rune; Larsen, Yngvar; Blikra, Lars Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-25)
      Mountain slopes in periglacial environments are affected by frost- and gravity-driven processes that shape the landscape. Both rock glaciers and rockslides have been intensively inventoried worldwide. Although most inventories are traditionally based on morphologic criteria, kinematic approaches based on satellite remote sensing have more recently been used to identify moving landforms at the regional ...