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  • 1
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    Hydrogeochemical changes before and after a major earthquake (2004)
    In:  Geology, London, Institution of Mining and Metallurgy, vol. 32, no. 8, pp. 641-644, pp. 1869, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 2004
    Keywords: Fluids ; Earthquake ; Earthquake precursor: prediction research ; Earthquake precursor: chemical (Rn, water(-level,...) ; Moerth ; Morth
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Ice export from the Laptev and East Siberia Sea derived from δ18O values (2015)
    Wiley
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    Publication Date: 2015-08-14
    Description: Ice export from the vast Arctic Siberian shelf is calculated using δ 18 O values and salinity data for water samples collected during the International Siberian Shelf Study between August and September 2008 (ISSS-08). The samples represent a wide range of salinities and δ 18 O values due to river water inputs and sea ice removal. We estimate the fraction of water that has been removed as ice by interpreting observed δ 18 O values and salinities as a result of mixing between river water and sea water end-members as well as to fractional ice removal. This method does not assume an ice end-member of fixed composition, which is especially important when applied on samples with large differences in salinity. The results show that there is net transport of ice from both the Laptev and the Eastern Siberian Seas, and in total 3000 km³ of sea ice is exported from the shelf. The annual total export of ice from the entire region, calculated from the residence time of water on the shelf, is estimated to be 860 km 3 yr −1 . Thus, changes in ice production on the shelf may have great impact on sea ice export from the Arctic Ocean. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Methane fluxes from the sea to the atmosphere across the Siberian shelf seas (2016)
    Wiley
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    Publication Date: 2016-05-12
    Description: The Laptev and East Siberian Seas have been proposed as a substantial source of methane (CH 4 ) to the atmosphere. During summer 2014, we made unique high-resolution simultaneous measurements of CH 4 in the atmosphere above, and surface waters of, the Laptev and East Siberian Seas. Turbulence driven sea-air fluxes along the ship's track were derived from these observations; an average diffusive flux of 2.99 mg m -2 d -1 was calculated for the Laptev Sea; for the ice-free portions of the western East Siberian Sea, 3.80 mg m -2 d -1 . Although seafloor bubble plumes were observed at two locations in the study area, our calculations suggest that regionally, turbulence-driven diffusive flux alone accounts for the observed atmospheric CH 4 enhancements, with only a local, limited role for bubble fluxes, in contrast to earlier reports. CH 4 in sub-ice seawater in certain areas suggests a short-lived flux also occurs annually at ice-out.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    External total alkalinity loads vs. internal generation - the influence of non-riverine alkalinity sources in the Baltic Sea (2014)
    Wiley
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    Publication Date: 2014-11-07
    Description: In this study we first present updated riverine total alkalinity (TA) loads to the various Baltic Sea sub-basins, based on monthly measurements in 82 of the major rivers that represent 85% of the total runoff. Simulations in the coupled physical-biogeochemical BALTSEM model show that these river loads together with North Sea water inflows are not sufficient to reproduce observed TA concentrations in the system, demonstrating the large influence from internal sources. Budget calculations indicate that the required internal TA generation must be similar to river loads in magnitude. The non-riverine source in the system amounts to about 2.4 mmol m -2 d -1 on average. We argue here that the majority of this source is related to denitrification together with unresolved sediment processes such as burial of reduced sulfur and/or silicate weathering. This hypothesis is supported by studies on sediment processes on a global scale, and also by data from sediment cores in the Baltic Sea. In a model simulation with all internal TA sources and sinks switched on, the net absorption of atmospheric CO 2 increased by 0.78 mol C m -2 y -1 compared to a simulation where TA was treated as a passive tracer. Our results clearly illustrate how pelagic TA sources together with anaerobic mineralization in coastal sediments generate a significant carbon sink along the aquatic continuum, mitigating CO 2 evasions from coastal and estuarine systems.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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  • 5
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    Coupling between mineral reactions, chemical changes in groundwater and earthquakes in Iceland (2016)
    Wiley
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    Publication Date: 2016-03-26
    Description: Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northern Iceland from October 2008 to June 2015 revealed 1) a long-term decrease in concentration of Si and Na and 2) an abrupt increase in concentration of Na before each of two consecutive M 〉 5 earthquakes which occurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stable isotopes), petrological and mineralogical study of drill cuttings taken from an adjacent borehole, we are able to show that 1) the long-term decrease in concentration of Si and Na was caused by constant volume replacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fractures, and 2) the abrupt increase of Na concentration before the first earthquake records a switchover to non-stoichiometric dissolution of analcime with preferential release of Na into groundwater. We attribute decay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fractured or porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are an increase of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixing between groundwater components. Both could have been triggered by pre-seismic dilation, which was also inferred in a previous study by Skelton et al. (2014). The mechanism behind pre-seismic dilation so far from the focus of an earthquake remains unknown.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
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    A centennial record of fluvial organic matter input from the discontinuous permafrost catchment of Lake Torneträsk (2013)
    Wiley
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    Publication Date: 2013-01-03
    Description: [1]  High-latitude regions are underlain by the most organic carbon (OC)-rich soils on earth and currently subject to intense climate warming, potentially increasing remobilization and mineralization of soil OC. Sub-Arctic Scandinavia is located on the 0°C mean annual isotherm and is therefore particularly vulnerable to climate change. This study aimed to establish a baseline for soil OC release over the past century into Lake Torneträsk, the largest lake in sub-Arctic Scandinavia, through bulk geochemical and molecular radiocarbon analyses in chronologically constrained sediment cores. Our results suggest a dominance of peat-derived terrestrial OC inflow. We show that the annual terrestrial OC inflow to the lake is ∼12 times higher than the in-lake produced particulate OC, and consists for a large part (ca. 60%) of old OC from deep reservoirs in the catchment. The sedimentary record shows signs of increasing inflow of more degraded terrestrial matter since ∼1975, as indicated by increasing %TOC concentrations, a lower δ 13 C value and lower TOC:TN ratios. Based on simultaneous changes in local climate and reported signs of permafrost degradation (e.g., active layer deepening, mire/peat erosion), the observed changes in the sedimentary record of Scandinavia's largest mountain lake likely reflect a climate warming-induced change in terrestrial OC inflow.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Spatiotemporal variations of pCO2 and δ13C-DIC in subarctic streams in northern Sweden (2013)
    Wiley
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    Publication Date: 2013-01-18
    Description: [1]  Current predictions of climate-related changes in high-latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO 2 concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO 2 ( p CO 2 ) and in stable isotopic composition of dissolved inorganic carbon (δ 13 C-DIC) in sub-arctic streams in northern Sweden. The selected watersheds are characterized by large variations in high-latitude boreal forest, tundra and differences in bedrock. We found that all streams generally were supersaturated in p CO 2 with an average concentration of 850 µatm. The variability in p CO 2 across streams was poorly related to vegetation cover and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream p CO 2 or δ 13 C-DIC. Stream water p CO 2 values were highest during winter baseflow when we also observed the lowest δ 13 C-DIC values and this pattern are interpreted as a high contribution from CO 2 from soil respiration. Summer base flow δ 13 C-DIC values probably are more affected by in-situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO 2 and quantify their relative importance.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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  • 8
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    Tracing terrestrial DOC in the Baltic Sea - a 3-D model study (2015)
    Wiley
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    Publication Date: 2015-10-30
    Description: The fate of terrestrial organic matter brought to the coastal seas by rivers, and its role in the global carbon cycle, are still not very well known. Here the degradation rate of terrestrial dissolved organic carbon (DOC t e r ) is studied in the Baltic Sea, a subarctic semi-enclosed sea, by releasing it as a tracer in a 3-D circulation model and applying linear decay constants. A good agreement with available observational data is obtained by parameterizing the degradation in two rather different ways; one by applying a decay time on the order of 10 years to the whole pool of DOC t e r , and one by dividing the DOC t e r into one refractory pool and one pool subject to a decay time on the order of 1 year. The choice of parameterization has a significant effect on where in the Baltic Sea the removal takes place, which can be of importance when modeling the full carbon cycle and the CO 2 exchange with the atmosphere. In both cases the biogeochemical decay operates on time scales less than the water residence time. Therefore only a minor fraction of the DOC t e r reaches the North Sea, whereas approximately 80% is removed by internal sinks within the Baltic Sea. This further implies that DOC t e r mineralization is an important link in land-sea-atmosphere cycling of carbon in coastal- and shelf seas that are heavily influenced by riverine DOC.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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  • 9
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    Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic (2012)
    Wiley
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    Publication Date: 2012-05-04
    Description: A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (∼2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss-dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. δ 15 N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in δ 13 C values appear to reflect mainly changes in plant assemblages. Positive shifts in both δ 15 N and δ 13 C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15 N-enrichment. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 10
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    Spatial variation in concentration and sources of organic carbon in the Lena River, Siberia (2017)
    Wiley
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    Publication Date: 2017-07-29
    Description: Global warming in permafrost areas is expected to change fluxes of riverine organic carbon (OC) to the Arctic Ocean. Here OC concentrations, stable carbon isotope signatures (δ 13 C) and carbon-nitrogen ratios (C/N) are presented from 22 sampling stations in the Lena River and 40 of its tributaries. Sampling was conducted during two expeditions: the first in July 2012 in the south and southeastern region and the second in June 2013 in the northern region of the Lena basin. The data showed significant spatial differences in concentrations and major sources of OC. Mean sub-catchment slopes were correlated with OC concentrations, implying that mountainous areas in general had lower concentrations than lowland areas. δ 13 C and C/N data from tributaries originating in mountainous areas indicated that both dissolved and particulate OC (DOC and POC) were mainly derived from soil organic matter (SOM). In contrast, tributaries originating in lowland areas had larger contributions from fresh vegetation to DOC, while aquatically produced OC was the major source of POC. We suggest that these differences in dominant sources indicated differences in dominant flow pathways. Tributaries with larger influence of fresh vegetation probably had surficial flow pathways, while tributaries with more SOM influence had deeper water flow pathways. Thus, the future export of OC to the Arctic Ocean will likely be controlled by changes in spatial patterns in hydroclimatology and the depth of the active layers influencing the dominant water flow pathways in Arctic river basins.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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