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norskArtikler, rapporter og annet (geovitenskap): Recent submissions
Now showing items 561-580 of 804
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Repeatability of high-resolution 3D seismic data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-21)High-resolution 4D (HR4D) seismic data have the potential for improving the current state-of-the-art in detecting shallow (≤500−1000 m below seafloor) subsurface changes on a very fine scale (approximately 3–6 m). Time-lapse seismic investigations commonly use conventional broadband seismic data, considered low to moderate resolution in our context. We have developed the first comprehensive time ... -
Evolution in H2O contents during deformation of polycrystalline quartz: An experimental study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-15)Shear experiments were performed in a Griggs-type apparatus at 800 °C and 1.5 GPa, at a strain rate of 2.1 × 10<sup>−5</sup>s<sup>−1</sup> using different starting materials: (i) Powder (grain size 6–10 μm) of dry Brazil quartz with 0.15 wt% added H<sub>2</sub>O, (ii) “dry” Brazil quartz porphyroclasts (grain size ∼100–200 μm), devoid of fluid inclusions embedded in the same fine grained powder, and ... -
Cryptic frenulates are the dominant chemosymbiotrophic fauna at Arctic and high latitude Atlantic cold seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-28)We provide the first detailed identification of Barents Sea cold seep frenulate hosts and their symbionts. Mitochondrial COI sequence analysis, in combination with detailed morphological investigations through both light and electron microscopy was used for identifying frenulate hosts, and comparing them to Oligobrachia haakonmosbiensis and Oligobrachia webbi, two morphologically similar species ... -
Fault-controlled asymmetric landscapes and low-relief surfaces on Vestvågøya, Lofoten, North Norway: inherited Mesozoic rift-margin structures?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-20)The Lofoten Ridge is an integral basement horst of the hyperextended continental rift-margin off northern Norway. It is a key area for studying onshore–offshore rift-related faults, and for evaluating tectonic control on landscape development along the North Atlantic margin. This paper combines onshore geomorphological relief/aspect data and fault/fracture analysis with offshore bathymetric and ... -
Geological controls on fluid flow and gas hydrate pingo development on the Barents Sea margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)In 2014, the discovery of seafloor mounds leaking methane gas into the water column in the northwestern Barents Sea became the first to document the existence of non‐permafrost related gas hydrate pingos (GHP) on the Eurasian Arctic shelf. The discovered site is given attention because the gas hydrates occur close to the upper limit of the gas hydrate stability, thus may be vulnerable to climatic ... -
Evidences of accelerating the increase in the concentration of methane in the atmosphere after 2014: satellite data for the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017)Проанализированы результаты спутникового зондирования с помощью европейского орбитального интерферометра IASI/MetOP-A и алгоритма обработки данных, разработанного в NOAA. Спутниковые измерения для умеренных и высоких широт Северного полушария дают рост скорости концентрации метана от 4–9 ppbv/год (частей на миллиард по объему) в 2010–2013 гг. до 12–17 ppbv/год в 2015–2016 гг. Глобальные оценки на ... -
Spreading of drill cuttings and sediment recovery of three exploration wells of different ages, SW Barents Sea, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-14)Five stations (≤250 m from the well heads) from three exploration wells of different ages from the SW Barents Sea were studied to investigate the spreading of drill cuttings and sediment quality. Two of the wells were drilled before the restriction of use of oil-based drilling fluids (1993). Elevated concentrations of Ba were found in sediments near all the wells with the highest concentrations ... -
Ionospheric Response Observed by EISCAT During the 6–8 September 2017 Space Weather Event: Overview
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-03)We present ionospheric plasma conditions observed by the EISCAT radars in Tromsø and on Svalbard, covering 68°–81° geomagnetic latitude, during 6–8 September 2017. This is a period when X2.2 and X9.3 X‐ray flares occurred, two interplanetary coronal mass ejections (ICMEs) arrived at the Earth accompanied by enhancements of MeV‐range energetic particle flux in both the solar wind (SEP event) and inner ... -
Cordilleran ice-sheet growth fueled primary productivity in the Gulf of Alaska, northeast Pacific Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-15)Fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity. In particular, high-nutrient, low-chlorophyll (HNLC) areas where phytoplankton growth is critically iron-limited, such as the subarctic Pacific Ocean and the Southern Ocean, are proposed to respond to increases in bioavailable Fe supply with enhanced phytoplankton productivity and carbon ... -
Area and volume of mid-latitude glacier-like forms on Mars
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-04)Although a substantial ice cover has been identified within the mid-latitudes of Mars, there is uncertainty regarding the formation, current and former volume, and dynamic evolution of these ice masses. Here, we present the first comprehensive ice volume estimate of martian glacier-like forms (GLFs) from systematic population scale mapping and volumetric analysis. The outlines of 1243 GLFs were ... -
Holocene development of subarctic permafrost peatlands in Finnmark, northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-01)Subarctic permafrost peatlands are important soil organic carbon pools, and improved knowledge about peat properties and peatland sensitivity to past climate change is essential when predicting future response to a warmer climate and associated feedback mechanisms. In this study, Holocene peatland development and permafrost dynamics of four subarctic peat plateaus in Finnmark, northern Norway have ... -
EISCAT Observation of Wave‐Like Fluctuations in Vertical Velocity of Polar Mesospheric Summer Echoes Associated With a Geomagnetic Disturbance
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-04)By analyzing a data set from the European Incoherent SCATter (EISCAT) Very High Frequency (VHF) radar at Tromsø, we find that both radar reflectivity and upward ion velocity in a polar mesospheric summer echo (PMSE) layer simultaneously increased at the commencement of a local geomagnetic disturbance, which occurred at midnight on 9 July 2013. The onset of the upward velocity was followed by periodic ... -
Early to middle Cenozoic paleoenvironment and erosion estimates of the southwestern Barents Sea: Insights from a regional mass-balance approach
(Journal article; Tidsskriftartikkel, 2018-06-02)The Cenozoic pre-glacial development of the southwestern Barents Sea is discussed, with focus on the early to middle Cenozoic net erosion that was poorly constrained. From 2D and 3D seismic mapping, the western Barents Sea continental margin development shows a complex history of structural configuration of highs and basins related to the Greenland and Eurasian plate movement and subsequent seafloor ... -
Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-20)In this study, we report lipid biomarker patterns and phylogenetic identities of key microbial communities mediating anaerobic oxidation of methane (AOM) in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. The carbon isotopic compositions (δ13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly 13C-depleted values (−114 ‰ to −82 ‰) associated with a steep depletion ... -
From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-21)In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen, Svalbard. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle ... -
A refined late-Cryogenian – Ediacaran Earth history of South China: phosphorous-rich marbles of the Dabie and Sulu orogens
(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 ... -
Methane at Svalbard and over the European Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-05)Methane (CH<sub>4</sub>) is a powerful greenhouse gas. Its atmospheric mixing ratios have been increasing since 2005. Therefore, quantification of CH<sub>4</sub> sources is essential for effective climate change mitigation. Here we report observations of the CH<sub>4</sub> mixing ratios measured at the Zeppelin Observatory (Svalbard) in the Arctic and aboard the research vessel (RV) Helmer Hanssen ... -
Comment on“The Keisarhjelmen detachment records Silurian–Devonian extensional collapse in Northern Svalbard”
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-30)<p><i>Introduction</i>: The discussed area has been investigated since the 1960s. Scientists of the Norwegian Polar Institute, the Cambridge scholar environment, the University of Münster and others have mapped, described, interpreted and contributed to the discussion through decades. Very little of this is reflected in the paper by Braathen, Osmundsen, Maher, and Ganerød, (2018). A discussion of ... -
OBS Data Analysis to Quantify Gas Hydrate and Free Gas in the South Shetland Margin (Antarctica)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-25)The presence of a gas hydrate reservoir and free gas layer along the South Shetland margin (offshore Antarctic Peninsula) has been well documented in recent years. In order to better characterize gas hydrate reservoirs, with a particular focus on the quantification of gas hydrate and free gas and the petrophysical properties of the subsurface, we performed travel time inversion of ocean-bottom ... -
Ice‐rafting patterns on the western Svalbard slope 74–0 ka: interplay between ice‐sheet activity, climate and ocean circulation
(Journal article; Tidsskriftartikkel, 2018-11-14)The distribution of ice‐rafted detritus (IRD) is studied in three cores from the western Svalbard slope (1130–1880 m water depth, 76–78°N) covering the period 74–0 ka. The aim was to provide new insight into the dynamics of the Svalbard–Barents Sea Ice Sheet during Marine Isotope Stages (MIS) 4–1 to get a better understanding of ice‐sheet interactions with changes in ocean circulation and climate ...
