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  • 1
    Online Resource
    Online Resource
    Geological Society of London ; 2010
    In:  Geological Society, London, Special Publications Vol. 344, No. 1 ( 2010-01), p. 1-3
    In: Geological Society, London, Special Publications, Geological Society of London, Vol. 344, No. 1 ( 2010-01), p. 1-3
    Type of Medium: Online Resource
    ISSN: 0305-8719 , 2041-4927
    Language: English
    Publisher: Geological Society of London
    Publication Date: 2010
    detail.hit.zdb_id: 2478172-1
    detail.hit.zdb_id: 196249-8
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  • 2
    Online Resource
    Online Resource
    Geological Society of London ; 2010
    In:  Geological Society, London, Special Publications Vol. 344, No. 1 ( 2010-01), p. 5-15
    In: Geological Society, London, Special Publications, Geological Society of London, Vol. 344, No. 1 ( 2010-01), p. 5-15
    Type of Medium: Online Resource
    ISSN: 0305-8719 , 2041-4927
    Language: English
    Publisher: Geological Society of London
    Publication Date: 2010
    detail.hit.zdb_id: 2478172-1
    detail.hit.zdb_id: 196249-8
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  • 3
    In: The Holocene, SAGE Publications, Vol. 26, No. 4 ( 2016-04), p. 627-642
    Abstract: Reconstructing past vegetation and species diversity from arctic lake sediments can be challenging because of low pollen and plant macrofossil concentrations. Information may be enhanced by metabarcoding of sedimentary ancient DNA ( sedaDNA). We developed a Holocene record from Lake Skartjørna, Svalbard, using sedaDNA, plant macrofossils and sediment properties, and compared it with published records. All but two genera of vascular plants identified as macrofossils in this or a previous study were identified with sedaDNA. Six additional vascular taxa were found, plus two algal and 12 bryophyte taxa, by sedaDNA analysis, which also detected more species per sample than macrofossil analysis. A shift from Salix polaris-dominated vegetation, with Koenigia islandica, Ranunculaceae and the relatively thermophilic species Arabis alpina and Betula, to Dryas octopetala-dominated vegetation ~6600–5500 cal. BP suggests a transition from moist conditions 1–2°C warmer than today to colder/drier conditions. This coincides with a decrease in runoff, inferred from core lithology, and an independent record of declining lacustrine productivity. This mid-Holocene change in terrestrial vegetation is broadly coincident with changes in records from marine sediments off the west coast of Svalbard. Over the Holocene sedaDNA records little floristic change, and it clearly shows species persisted near the lake during time intervals when they are not detected as macrofossils. The flora has shown resilience in the presence of a changing climate, and, if future warming is limited to 2°C or less, we might expect only minor floristic changes in this region. However, the Holocene record provides no analogues for greater warming.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    RVK:
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2016
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
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  • 4
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 6 ( 2020-06-30), p. 2115-2135
    Abstract: Abstract. The Antarctic ice sheet extent in the Weddell Sea embayment (WSE) during the Last Glacial Maximum (LGM; ca. 19–25 calibrated kiloyears before present, ka cal BP) and its subsequent retreat from the shelf are poorly constrained, with two conflicting scenarios being discussed. Today, the modern Brunt Ice Shelf, the last remaining ice shelf in the northeastern WSE, is only pinned at a single location and recent crevasse development may lead to its rapid disintegration in the near future. We investigated the seafloor morphology on the northeastern WSE shelf and discuss its implications, in combination with marine geological records, to create reconstructions of the past behaviour of this sector of the East Antarctic Ice Sheet (EAIS), including ice–seafloor interactions. Our data show that an ice stream flowed through Stancomb-Wills Trough and acted as the main conduit for EAIS drainage during the LGM in this sector. Post-LGM ice stream retreat occurred stepwise, with at least three documented grounding-line still-stands, and the trough had become free of grounded ice by ∼10.5 ka cal BP. In contrast, slow-flowing ice once covered the shelf in Brunt Basin and extended westwards toward McDonald Bank. During a later time period, only floating ice was present within Brunt Basin, but large “ice slabs” enclosed within the ice shelf occasionally ran aground at the eastern side of McDonald Bank, forming 10 unusual ramp-shaped seabed features. These ramps are the result of temporary ice shelf grounding events buttressing the ice further upstream. To the west of this area, Halley Trough very likely was free of grounded ice during the LGM, representing a potential refuge for benthic shelf fauna at this time.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 5
    Online Resource
    Online Resource
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 12 ( 2020-12-04), p. 4475-4494
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 12 ( 2020-12-04), p. 4475-4494
    Abstract: Abstract. The presence of a grounded Greenland Ice Sheet on the northeastern part of the Greenland continental shelf during the Last Glacial Maximum is supported by new swath bathymetry and high-resolution seismic data, supplemented with multi-proxy analyses of sediment gravity cores from Store Koldewey Trough. Subglacial till fills the trough, with an overlying drape of maximum 2.5 m thick glacier-proximal and glacier-distal sediment. The presence of mega-scale glacial lineations and a grounding zone wedge in the outer part of the trough, comprising subglacial till, provides evidence of the expansion of fast-flowing, grounded ice, probably originating from the area presently covered with the Storstrømmen ice stream and thereby previously flowing across Store Koldewey Island and Germania Land. Grounding zone wedges and recessional moraines provide evidence that multiple halts and/or readvances interrupted the deglaciation. The formation of the grounding zone wedges is estimated to be at least 130 years, while distances between the recessional moraines indicate that the grounding line locally retreated between 80 and 400 m yr−1 during the deglaciation, assuming that the moraines formed annually. The complex geomorphology in Store Koldewey Trough is attributed to the trough shallowing and narrowing towards the coast. At a late stage of the deglaciation, the ice stream flowed around the topography on Store Koldewey Island and Germania Land, terminating the sediment input from this sector of the Greenland Ice Sheet to Store Koldewey Trough.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 6
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2016-04-04)
    Abstract: Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth’s climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP 25 as a proxy for spring sea-ice cover and alkenone-based summer sea-surface temperatures 〉 4 °C that support a seasonal sea-ice cover with an ice-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO 2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 2553671-0
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  • 7
    In: Minerals, MDPI AG, Vol. 10, No. 2 ( 2020-02-13), p. 169-
    Abstract: Mine tailings that were produced during the exploitation of the Ulveryggen siliciclastic sediment-hosted Cu deposit in northern Norway were disposed into the inner part of Repparfjorden from 1972 to 1978/1979. This study focuses on the mineralogy and geochemistry of the submarine mine tailings and underlying natural marine sediments from the inner part of Repparfjorden, as well as on the primary Ulveryggen ore. The ore mineralization from the neighboring Nussir carbonate sediment-hosted Cu deposit was studied too, due to the forthcoming mining of both deposits. Bornite and chalcopyrite are the major Cu-sulfides, and are characterized by low concentrations of potentially toxic elements including Cd, Hg, and As. The tailing material occupies the uppermost 9 cm of Repparfjorden sediments. It is characterized by predomination of a silty component with elevated Cu (up to 747.7 ppm), Ni (up to 87 ppm), and Cr (up to 417 ppm) concentrations. The high Cu concentration is related to the deposition of mine tailings. In contrast, Ni and Cr concentrations are close to those in naturally occurring stream sediments from the feeding river, Repparfjordelva, reflecting the compatibility of these elements with hosting mafic volcanics, which are widely spread in the Repparfjord Tectonic Window. Copper in the uppermost part of the sediments is bound to the acid-soluble fraction while Ni and Cr are bound to the residual fraction. Artificial placement of large masses of fine-grained material, i.e., smothering, resulted in a diminished biological activity and/or physical distortion of mostly benthic fauna, which was reflected in total organic carbon (TOC) values as low as 0.15% in the uppermost strata. Sulfide minerals are found both in natural marine sediments and in the mine tailings. They are generally well-preserved with an exception for chalcopyrite from the uppermost part of the submarine tailing, which shows signs of incipient weathering. Thermodynamic modeling confirmed that redox potential and pH are important factors in the weathering of sulfides. Available ligands contribute to the Cu speciation. In near-neutral to slightly alkaline conditions a presence of carbonates can lead to the mobilization of Cu in form of CuCO3 complexes.
    Type of Medium: Online Resource
    ISSN: 2075-163X
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2655947-X
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  • 8
    In: Geochronology, Copernicus GmbH, Vol. 1, No. 1 ( 2019-11-18), p. 53-67
    Abstract: Abstract. Amino acid racemization (AAR) geochronology is a powerful tool for dating Quaternary marine sediments across the globe, yet its application to Arctic Ocean sediments has been limited. Anomalous rates of AAR in foraminifera from the central Arctic were reported in previously published studies, indicating that either the rate of racemization is higher in this area, or inaccurate age models were used to constrain the sediment ages. This study investigates racemization rates in foraminifera from three well-dated sediment cores taken from the Yermak Plateau during the 2015 TRANSSIZ (TRansitions in the Arctic Seasonal Sea Ice Zone) expedition on RV Polarstern. D and L isomers of the amino acids aspartic acid (Asp) and glutamic acid (Glu) were separated in samples of the planktic foraminifer Neogloboquadrina pachyderma and the benthic species Cassidulina neoteretis to quantify the extent of racemization. In total, 241 subsamples were analysed, extending back to marine oxygen isotope stage (MIS) 7. Two previously published power functions, which relate the extent of racemization of Asp and Glu in foraminifera to sample age are revisited, and a comparison is made between the ages predicted by these calibrated age equations and independent geochronological constraints available for the cores. Our analyses reveal an excellent match between ages predicted by a global compilation of racemization rates for N. pachyderma and confirm that a proposed Arctic-specific calibration curve is not applicable at the Yermak Plateau. These results generally support the rates of AAR determined for other cold bottom water sites and further highlight the anomalous nature of the purportedly high rate of racemization indicated by previous analyses of central Arctic sediments.
    Type of Medium: Online Resource
    ISSN: 2628-3719
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2966593-0
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  • 9
    In: Global and Planetary Change, Elsevier BV, Vol. 201 ( 2021-06), p. 103483-
    Type of Medium: Online Resource
    ISSN: 0921-8181
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 20361-0
    detail.hit.zdb_id: 2016967-X
    SSG: 13
    SSG: 14
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  • 10
    In: Marine Micropaleontology, Elsevier BV, Vol. 136 ( 2017-10), p. 51-65
    Type of Medium: Online Resource
    ISSN: 0377-8398
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 1482923-X
    detail.hit.zdb_id: 197739-8
    SSG: 13
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