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  • Springer  (453,137)
  • Wiley  (159,611)
  • Hindawi  (52,862)
  • American Geophysical Union
  • 2010-2014  (697,749)
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  • 1
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    Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy) (2012)
    American Geophysical Union
    Details
    Publication Date: 2024-05-09
    Description: In this paper, fluid source(s) and processes controlling the chemical composition of VOCs (Volatile Organic Compounds) in gas discharges from Mt. Etna and Vulcano Island (Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of “magmatic” and “hydrothermal” components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic matter-bearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alkene and aromatic compounds via catalytic reactions (dehydrogenation and dehydroaromatization, respectively). Nevertheless, an abiogenic origin for the light hydrocarbons cannot be ruled out. Oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions, typical of these volcanic-hydrothermal fluids, may explain the production of alcohols, esters, aldehydes, as well as O- and S-bearing heterocycles. By comparing the concentrations of hydrochlorofluorocarbons (HCFCs) in the fumarolic discharges with respect to those of background air, it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes. Finally, CFC (chlorofluorocarbon) abundances appear to be consistent with background air, although the strong air contamination that affects the Mt. Etna fumaroles may mask a possible geogenic contribution for these compounds. On the other hand, no CFCs were detected in the Vulcano gases, which are characterized by low air contribution. Nevertheless, a geogenic source for these compounds cannot be excluded on the basis of the present data.
    Description: Published
    Description: D17305
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: open
    Keywords: etna, vulcano, VOC ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Gas seepage and seismogenic structures along the North-Anatolian Fault in the eastern Sea of Marmara (2012)
    American Geophysical Union
    Details
    Publication Date: 2024-05-09
    Description: We carried out a combined geophysical and gas-geochemical survey on an active fault strand along the North-Anatolian Fault (NAF) system in the Gulf of İzmit (eastern Sea of Marmara), providing for the first time in this area data on the distribution of methane (CH4) and other gases dissolved in the bottom seawater, as well as the CH4 isotopic composition. Based on high-resolution morphobathymetric data and chirp-sonar seismic reflection profiles we selected three areas with different tectonic features associated to the NAF system, where we performed visual and instrumental seafloor inspections, including in-situ measurements of dissolved CH4, and sampling of the bottom water. Starting from background values of 2-10 nM, methane concentration in the bottom seawater increases abruptly up to 20 nM over the main NAF trace. CH4 concentration peaks up to ~120 nM were detected above mounds related probably to gas and fluids expulsion. Methane is microbial (δ13CCH4: -67.3 and -76 ‰ vs. VPDB), and was found mainly associated with pre- Holocene deposits topped by a 10-20 m thick draping of marine mud. The correlation between tectonic structures and gas-seepages at the seafloor suggests that the NAF in the Gulf of İzmit could represent a key site for long-term combined monitoring of fluid exhalations and seismicity to assess their potential as earthquake precursors.
    Description: Published
    Description: Q10018
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: JCR Journal
    Description: restricted
    Keywords: submarine ; gas seepage ; active fault ; Marmara sea ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Bioluminescence in deep-sea isidid gorgonians from the Cape Verde archipelago (2011)
    Springer
    Details
    Publication Date: 2024-03-22
    Type: Article , PeerReviewed
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  • 4
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    Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements (2013)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-03-22
    Description: The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp- 1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is 〈0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.
    Type: Article , PeerReviewed
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  • 5
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    Effects of increased isopycnal diffusivity mimicking the unresolved equatorial intermediate current system in an earth system climate model (2013)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-01-16
    Description: Earth system climate models generally underestimate dissolved oxygen concentrations in the deep eastern equatorial Pacific. This problem is associated with the "nutrient trapping" problem, described by Najjar et al. [1992], and is, at least partially, caused by a deficient representation of the Equatorial Intermediate Current System (EICS). Here we emulate the unresolved EICS in the UVic earth system climate model by locally increasing the zonal isopycnal diffusivity. An anisotropic diffusivity of ∼50,000 m 2 s-1 yields an improved global representation of temperature, salinity and oxygen. In addition, it (1) resolves most of the local "nutrient trapping" and associated oxygen deficit in the eastern equatorial Pacific and (2) reduces spurious zonal temperature gradients on isopycnals without affecting other physical metrics such as meridional overturning or air-sea heat fluxes. Finally, climate projections of low-oxygenated waters and associated denitrification change sign and apparently become more plausible
    Type: Article , PeerReviewed
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  • 6
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    Seasonality and long-term trend of Arctic Ocean surface stress in a model (2014)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-01-07
    Description: A numerical ocean sea-ice model is used to demonstrate that Arctic sea ice retreat affects momentum transfer into the ocean. A thinner and thus weaker ice cover is more easily forced by the wind, which increases the momentum flux. In contrast, increasing open water reduces momentum transfer because the ice surface provides greater drag than the open water surface. We introduce the concept of optimal ice concentration: momentum transfer increases with increasing ice concentration up to a point, beyond which frictional losses by floe interaction damp the transfer. For a common ice internal stress formulation, a concentration of 80–90% yields optimal amplification of momentum flux into the ocean. We study the seasonality and long-term evolution of Arctic Ocean surface stress over the years 1979–2012. Spring and fall feature optimal ice conditions for momentum transfer, but only in fall is the wind forcing at its maximum, yielding a peak basin-mean ocean surface stress of ∼0.08 N/m2. Since 1979, the basin-wide annual mean ocean surface stress has been increasing by 0.004 N/m2/decade, and since 2000 by 0.006 N/m2/decade. In contrast, summertime ocean surface stress has been decreasing at −0.002 N/m2/decade. These trends are linked to the weakening of the ice cover in fall, winter and spring, and to an increase in open water fraction in summer, i.e., changes in momentum transfer rather than changes in wind forcing. In most areas, the number of days per year with optimal ice concentration is decreasing. Key Points Weaker Arctic sea ice causes increased annual mean ocean surface stress (+20%) Increasing open water area in summer yields momentum flux reduction (−7%) An optimal ice concentration of 80–90% amplifies momentum transfer threefold
    Type: Article , PeerReviewed
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  • 7
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    Clay minerals as indicators of late Quaternary sedimentation constraints in the Mendeleev Rise, Amerasian Basin, Arctic Ocean (2014)
    Springer
    Details
    Publication Date: 2024-01-01
    Description: The results of study of six cores taken from different morphostructural zones in the Mendeleev Ridge area are discussed. Average contents of minerals of the illite group, chlorite, kaolinite, and smectite are about 60, 21, 12, and 5%, respectively. It was found that fluctuations of minerals along the section correlate with variations in sedimentation constraints in the Late Quaternary. Peaks of kaolinite usually coincide with increased contents of the sand fraction, probably, due to its delivery by icebergs. In contrast, illite shows good correlation with the pelite fraction, testifying to its transport mainly by ices and currents. Minerals of the chlorite and smectite groups in the studied cores are less informative.
    Type: Article , PeerReviewed
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  • 8
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    Analysis of the effects of climate-dependent factors on the formation of zooplankton communities that inhabit arctic lakes in the Anabar River Basin (2013)
    Springer
    Details
    Publication Date: 2023-12-31
    Description: The major structural characteristics of zooplankton communities that inhabit 35 Arctic lakes in the catchment basin of the Anabar River (Yakutia) have been analyzed. The ecological state of the lakes has been evaluated. The structure-forming abiotic factors that have the greatest influence on the formation of zooplankton communities have been revealed using the indirect ordination method.
    Type: Article , PeerReviewed
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  • 9
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    In situ chemistry and microbial community compositions in five deep-sea hydrothermal fluid samples from Irina II in the Logatchev field (2013)
    Wiley
    Details
    Publication Date: 2023-11-29
    Description: We present data on the co-registered geochemistry (in situ mass spectrometry) and microbiology (pyrosequencing of 16S rRNA genes; V1, V2, V3 regions) in five fluid samples from Irina II in the Logatchev hydrothermal field. Two samples were collected over 24min from the same spot and further three samples were from spatially distinct locations (20cm, 3m and the overlaying plume). Four low-temperature hydrothermal fluids from the Irina II are composed of the same core bacterial community, namely specific Gammaproteobacteria and Epsilonproteobacteria, which, however, differs in the relative abundance. The microbial composition of the fifth sample (plume) is considerably different. Although a significant correlation between sulfide enrichment and proportions of Sulfurovum (Epsilonproteobacteria) was found, no other significant linkages between abiotic factors, i.e. temperature, hydrogen, methane, sulfide and oxygen, and bacterial lineages were evident. Intriguingly, bacterial community compositions of some time series samples from the same spot were significantly more similar to a sample collected 20cm away than to each other. Although this finding is based on three single samples only, it provides first hints that single hydrothermal fluid samples collected on a small spatial scale may also reflect unrecognized temporal variability. However, further studies are required to support this hypothesis.
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  • 10
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    Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone (2014)
    Springer
    Details
    Publication Date: 2023-11-08
    Description: The distribution of the mean oceanic oxygen concentration results from a balance between ventilation and consumption. In the eastern tropical Pacific and Atlantic, this balance creates extended oxygen minimum zones (OMZ) at intermediate depth. Here, we analyze hydrographic and velocity data from shipboard and moored observations, which were taken along the 23°W meridian cutting through the Tropical North East Atlantic (TNEA) OMZ, to study the distribution and generation of oxygen variability. By applying the extended Osborn–Cox model, the respective role of mesoscale stirring and diapycnal mixing in producing enhanced oxygen variability, found at the southern and upper boundary of the OMZ, is quantified. From the well-ventilated equatorial region toward the OMZ core a northward eddy-driven oxygen flux is observed whose divergence corresponds to an oxygen supply of about 2.4 μmol kg−1 year−1 at the OMZ core depth. Above the OMZ core, mesoscale eddies act to redistribute low- and high-oxygen waters associated with westward and eastward currents, respectively. Here, absolute values of the local oxygen supply 〉10 μmol kg−1 year−1 are found, likely balanced by mean zonal advection. Combining our results with recent studies, a refined oxygen budget for the TNEA OMZ is derived. Eddy-driven meridional oxygen supply contributes more than 50 % of the supply required to balance the estimated oxygen consumption. The oxygen tendency in the OMZ, as given by the multidecadal oxygen decline, is maximum slightly above the OMZ core and represents a substantial imbalance of the oxygen budget reaching about 20 % of the magnitude of the eddy-driven oxygen supply.
    Type: Article , PeerReviewed
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