Institutt for geovitenskap: Nye registreringer
Viser treff 221-240 av 1046
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Towards an improved organic carbon budget for the western Barents Sea shelf
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-03-21)There is generally a lack of knowledge on how marine organic carbon accumulation is linked to vertical export and primary productivity patterns in the Arctic Ocean. Despite the fact that annual primary production in the Arctic has increased as a consequence of shrinking sea ice, its effect on flux, preservation, and accumulation of organic carbon is still not well understood. In this study, a ... -
Reduced Numerical Model for Methane Hydrate Formation under Conditions of Variable Salinity. Time-Stepping Variants and Sensitivity
(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. ... -
Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013-07-14)Since the Last Glacial Maximum (~19 ka), coastal inundation from sea-level rise has been thawing thick subsea permafrost across the Arctic. Although subsea permafrost has been mapped on several Arctic continental shelves, permafrost distribution in the South Kara Sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood. Here we use >1300 km ... -
Aligned glaciotectonic rafts on the central Barents Sea seafloor revealing extensive glacitectonic erosion during the last deglaciation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013-12-07)Erosion rates on glaciated continental shelves are remarkably high, especially within ice stream troughs. Although glaciotectonic erosion may have considerably contributed to enhanced glacial erosion of these landscapes, entrainment mechanisms of glaciotectonically emplaced megablocks and rafts remain little understood. Here we report a northeast-southwest trending chain of over 1300 glacial rafts, ... -
Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-22)A large-scale multidisciplinary mesocosm experiment in an Arctic fjord (Kongsfjorden, Svalbard; 78°56.2′N) was used to study Arctic marine food webs and biogeochemical elements cycling at natural and elevated future carbon dioxide (CO2) levels. At the start of the experiment, marine-derived chromophoric dissolved organic matter (CDOM) dominated the CDOM pool. Thus, this experiment constituted a ... -
Modeling the evolution of climate-sensitive Arctic subsea permafrost in regions of extensive gas expulsion at the West Yamal shelf
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-10-01)Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate-sensitive Arctic environment. Expulsions of methane from shallow Russian Arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost. Here we show modeling of the permafrost evolution from the Late Pleistocene to present time at the ... -
Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-27)Natural remanent magnetization carriers in rocks can contain mixtures of magnetic minerals that interact in complex ways and are challenging to characterize by current measurement techniques. Here a nonlinear mapping scheme is described that efficiently enhances sensitivity and the resolution power of remanent Preisach maps. Using this scheme a large dynamic range of magnetic moments and coercivities ... -
The EMSO-ERIC pan-european consortium: Data benefits and lessons learned as the legal entity forms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-01)The European Multidisciplinary Seafloor and water-column Observatory (EMSO) European Research Infrastructure Consortium (ERIC) provides power, communications, sensors, and data infrastructure for continuous, high-resolution, (near-)real-time, interactive ocean observations across a multidisciplinary and interdisciplinary range of research areas including biology, geology, chemistry, physics, ... -
Plio-Pleistocene evolution of water mass exchange and erosional input at the Atlantic-Arctic gateway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-28)Water mass exchange between the Arctic Ocean and the Norwegian-Greenland Seas has played an important role for the Atlantic thermohaline circulation and Northern Hemisphere climate. We reconstruct past water mass mixing and erosional inputs from the radiogenic isotope compositions of neodymium (Nd), lead (Pb), and strontium (Sr) at Ocean Drilling Program site 911 (leg 151) from 906 m water depth on ... -
Response time correction of slow-response sensor data by deconvolution of the growth-law equation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-11)Accurate high-resolution measurements are essential to improve our understanding of environmental processes. Several chemical sensors relying on membrane separation extraction techniques have slow response times due to a dependence on equilibrium partitioning across the membrane separating the measured medium (i.e., a measuring chamber) and the medium of interest (i.e., a solvent). We present a new ... -
Revised ΔR values for the Barents Sea and its archipelagos as a pre-requisite for accurate and robust marine-based 14C chronologies
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-11)The calibration of marine 14C dates requires the incorporation of regionally specific marine reservoir offsets known as ΔR, essential for accurate and meaningful inter-archive comparisons. Revised, regional ΔR (‘ΔRR’) values for the Barents Sea are presented for molluscs and cetaceans for the two latest iterations of the marine calibration curve, based on previously published pre-bomb live-collected ... -
Physical conditions and frictional properties in the source region of a slow-slip event
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-06)Recent geodetic studies have shown that slow-slip events can occur on subduction faults, including their shallow (<15 km depth) parts where tsunamis are also generated. Although observations of such events are now widespread, the physical conditions promoting shallow slow-slip events remain poorly understood. Here we use full waveform inversion of controlled-source seismic data from the central ... -
Reconstruction of a volcano-sedimentary environment shared by the Porongos and Várzea do Capivarita complexes at 790 Ma, Dom Feliciano Belt, southern Brazil
(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. ... -
Glacially Induced Stress Across the Arctic From the Eemian Interglacial to the Present—Implications for Faulting and Methane Seepage
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-28)Strong compressive and shear stresses generated by glacial loading and unloading have a direct impact on near-surface geological processes. Glacial stresses are constantly evolving, creating stress perturbations in the lithosphere that extend significant distances away from the ice. In the Arctic, periodic methane seepage and faulting have been recurrently associated with glacial cycles. However, ... -
Rapid post-glacial bedrock weathering in coastal Norway
(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 ... -
MIS 3 age of the Veiki moraine in N Sweden – Dating the landform record of an intermediate-sized ice sheet in Scandinavia
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-14)The Veiki moraine in northern Sweden, a geomorphologically distinct landscape of ice-walled lake plains, has been interpreted to represent the former margin of an intermediate-sized pre–Last Glacial Maximum (LGM) Fennoscandian ice sheet, but its age is debated as either marine isotope stage (MIS) 5c or MIS 3. We have applied optically stimulated luminescence (OSL) and radiocarbon dating to four sites ... -
Combined X-Ray Computed Tomography and X-Ray Fluorescence Drill Core Scanning for 3-D Rock and Ore Characterization: Implications for the Lovisa Stratiform Zn-Pb Deposit and Its Structural Setting, Bergslagen, Sweden
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-29)We present the results of a pilot study that integrates automated drill core scanning technology based on simultaneous X-ray computed tomography (XCT) and X-ray fluorescence (XRF) analyses to provide high-spatialresolution (<0.2 mm) information on 3-D rock textures and structures, chemical composition, and density. Testing of its applicability for mineral exploration and research was performed by ... -
Tectonic evolution of the Indio Hills segment of the San Andreas fault in southern California, southwestern USA
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-01)Transpressional uplift domains of inverted Pliocene–Pleistocene basin fill along the San Andreas fault zone in Coachella Valley, southern California (USA), are characterized by fault linkage and segmentation and deformation partitioning. The Indio Hills wedge-shaped uplift block is located in between two boundary fault strands, the Indio Hills fault to the northeast and the main San Andreas fault ... -
Ammonium and Sulfate Assimilation Is Widespread in Benthic Foraminifera
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-20)Nitrogen and sulfur are key elements in the biogeochemical cycles of marine ecosystems to which benthic foraminifera contribute significantly. Yet, cell-specific assimilation of ammonium, nitrate and sulfate by these protists is poorly characterized and understood across their wide range of species-specific trophic strategies. For example, detailed knowledge about ammonium and sulfate assimilation ... -
Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-05)The Karasjok–Central Lapland Greenstone Belt is one of the largest Palaeoproterozoic greenstone belts in the Fennoscandian Shield and includes multiple (ultra)mafic intrusions, some with notable ore reserves, formed during three episodes at 2.44, 2.22 and 2.05 Ga. This study presents new mineralogical, geochronological and isotopic data for the Gállojávri ultramafic intrusion, in the Karasjok ...