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  • 2015-2019  (19)
  • 2010-2014  (28)
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  • 1
    Keywords: Hochschulschrift ; Peru ; Holozän ; Siliciumisotop ; Neodymisotop
    Type of Medium: Online Resource
    Pages: Online-Ressource
    DDC: 550
    Language: English
    Note: Kiel, Univ., Diss., 2012
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  • 2
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    PANGAEA
    In:  Supplement to: Doering, Kristin; Erdem, Zeynep; Ehlert, Claudia; Fleury, Sophie; Frank, Martin; Schneider, Ralph R (2016): Changes in diatom productivity and upwelling intensity off Peru since the Last Glacial Maximum: Response to basin-scale atmospheric and oceanic forcing. Paleoceanography, 31(10), 1453-1473, https://doi.org/10.1002/2016PA002936
    Publication Date: 2023-10-28
    Description: New records of stable silicon isotope signatures (?30Si) together with concentrations of biogenic opal and organic carbon from the central (9°S) and northern (5°S) Peruvian margin reveal changes in diatom productivity and nutrient utilization during the past 20,000 years. The findings are based on a new approach using the difference between the ?30Si signatures of small (11-32 ?m) and large (〉150 ?m) diatom fractions (?30Si ) in combination with the variance in diatom assemblages for reconstruction Coscino-bSi of past upwelling intensity. Combination of our records with two previously published records from the southern upwelling area off Peru (12-15°S) shows a general decoupling of the environmental conditions at the central and southern shelf mainly caused by a northward shift of the main upwelling cell from its modern position (12-15°S) toward 9°S during Termination 1. At this time only moderate upwelling intensity and productivity levels prevailed between 9°S and 12°S interpreted by a more northerly position of Southern Westerly Winds and the South Pacific Subtropical High. Furthermore, a marked decrease in productivity at 12-15°S during Heinrich Stadial 1 coincided with enhanced biogenic opal production in the Eastern Equatorial Pacific, which was induced by a southward shift of the Intertropical Convergence Zone and enhanced northeasterly trade winds. Modern conditions were only established at the onset of the Holocene. Past changes in preformed ?30Si signatures of subsurface waters reaching the Peruvian Upwelling System did not significantly affect the preserved ?30Si signatures
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 7 datasets
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  • 3
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    PANGAEA
    In:  Supplement to: Doering, Kristin; Ehlert, Claudia; Martinez, Philippe; Frank, Martin; Schneider, Ralph R (2018): Latitudinal variations of δ30Si and δ15N signatures along the Peruvian shelf: quantifying the effects of nutrient utilization versus denitrification over the past 600 years. Biogeosciences Discussions, 16, 1-23, https://doi.org/10.5194/bg-16-2163-2019
    Publication Date: 2023-10-28
    Description: The data includes silicon isotope signatures, biogenic opal concentrations and bulk sediment nitrogen isotope signatures of three short cores between 11 and 15 degrees South of the Peruvian Coast.
    Keywords: AGE; Biogenic silica; Climate - Biogeochemistry Interactions in the Tropical Ocean; DEPTH, sediment/rock; Event label; Latitude of event; Longitude of event; M77/2; M77/2_003-2; M77/2_005-3; M77/2_024-5; M77/2_636-1; M77/2_647-1; M77/2_677; Meteor (1986); PC; Piston corer; SFB754; Standard deviation; δ15N; δ30Si, biogenic silica
    Type: Dataset
    Format: text/tab-separated-values, 120 data points
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  • 4
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    PANGAEA
    In:  Supplement to: Ehlert, Claudia; Doering, Kristin; Wallmann, Klaus; Scholz, Florian; Sommer, Stefan; Grasse, Patricia; Geilert, Sonja; Frank, Martin (2016): Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation. Geochimica et Cosmochimica Acta, 191, 102-117, https://doi.org/10.1016/j.gca.2016.07.022
    Publication Date: 2023-10-28
    Description: Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm−2 yr−1. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 6 datasets
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  • 5
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    PANGAEA
    In:  Supplement to: Ehlert, Claudia; Reckhardt, Anja; Greskowiak, Janek; Liguori, Bianca T P; Böning, Philipp; Paffrath, Ronja; Brumsack, Hans-Jürgen; Pahnke, Katharina (2016): Transformation of silicon in a sandy beach ecosystem: Insights from stable silicon isotopes from fresh and saline groundwaters. Chemical Geology, 440, 207-218, https://doi.org/10.1016/j.chemgeo.2016.07.015
    Publication Date: 2023-12-09
    Description: Dissolved silicon isotope compositions (d30Si) have been analysed for the first time in groundwaters of beach sediments, which represent a subterranean estuary with fresh groundwater discharge from a freshwater reservoir and mixing with recirculated seawater. The fresh groundwater reservoir has high and variable dissolved silica concentrations between 136 and 736 µM, but homogeneous d30Si of +1.0 ± 0.15 per mil. By contrast, the seawater is strongly depleted in dissolved silica with concentrations of 3 µM, and consequently characterised by high d30Si of +3.0 per mil. The beach groundwaters are variably enriched in dissolved silica compared to seawater (23-192 µM), and concentrations increase with depth at all sampling sites. The corresponding d30Si values are highly variable (+0.3 per mil to +2.2 per mil) and decrease with depth at each site. All groundwater d30Si values are lower than seawater and most values are lower than dissolved d30Si of freshwater discharge indicating a significant amount of lithogenic silica dissolution in beach sediments. In contrast to open North Sea sediments, diatom dissolution or formation of authigenic silica in beach sediments is very low (ca. 5 µmol Si g). Silica discharge from the beach to the coastal ocean is estimated as approximately 210 mol Si yr per meter shoreline. Considering the extent of coastline this is, at least for the study area, a significant amount of the total Si budget and amounts to ca. 1% of river and 3.5% of backbarrier tidal flat area Si input.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 6
    Publication Date: 2023-12-09
    Keywords: Aluminium; Calcium; Chlorine; DEPTH, sediment/rock; DEPTH, water; Event label; Magnesium; pH; Potassium; PUMP; Salinity; Sample material; Sampling Well; Silicon; Sodium; Spiekeroog; Spiekeroog-25A; Spiekeroog-25B; Spiekeroog-25C; Spiekeroog-26A; Spiekeroog-26B; Spiekeroog-26C; Spiekeroog-27A; Spiekeroog-27B; Spiekeroog-27C; Spiekeroog-28A; Spiekeroog-28B; Spiekeroog-28C; Spiekeroog-29A; Spiekeroog-29B; Spiekeroog-29C; Spiekeroog-30A; Spiekeroog-30B; Spiekeroog-30C; Spiekeroog-31A; Spiekeroog-31B; Spiekeroog-31C; Spiekeroog-St0; Spiekeroog-St1; Spiekeroog-St2; Spiekeroog-St3; Spiekeroog-St4; Spiekeroog-St5; Water pump; WELL; δ29Si; δ29Si, error; δ30Si, biogenic silica; δ30Si, error
    Type: Dataset
    Format: text/tab-separated-values, 568 data points
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  • 7
    Publication Date: 2023-12-09
    Keywords: Alkanile-leach (Si-Alk); DEPTH, sediment/rock; Sample type; Si-HCl leach; Silicon; Standard deviation; Station label
    Type: Dataset
    Format: text/tab-separated-values, 115 data points
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  • 8
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    PANGAEA
    In:  Supplement to: Ferdelman, Timothy G (2016): RV SONNE SO245 Cruise Report / Fahrtbericht, Antofagasta, Chile: 17. December 2015, Wellington, New Zealand: 28. January 2016, SO245 - UltraPac: Process oriented biogeochemical, microbiological and ecological investigations of the ultraoligotrophic South Pacific Gyre. Max-Planck-Institut für marine Mikrobiologie, Bremen, 104 pp, https://doi.org/10.2312/cr_so245
    Publication Date: 2024-02-02
    Description: Sediment pore water nutrient chemistry on surface sediments from the South Pacific Gyre. Pore waters were obtained by Rhizone sampling of sub-cores from box-cores retrieved during Expedition SO245. Nutrient were determined after three-fold dilution onboard on a QuAAtro39 autoanalyser (Seal Analytical) using the method based on Strickland and Parsons, 1972.
    Keywords: BC; Box corer; DEPTH, sediment/rock; Event label; GC; GeoB20402-16; GeoB20404-17; GeoB20406-15; GeoB20408-25; GeoB20410-16; GeoB20412-15; GeoB20414-15; GeoB20415-14; Gravity corer; nitrate; Nitrate; nitrite; Nitrite; Nitrogen oxide; NOx; nutrients; Optional event label; phosphate; Phosphate; pore waters; Sample ID; sediments; silicate; Silicon; SO245; SO245_10-16; SO245_12-15; SO245_14-15; SO245_15-14; SO245_2-16; SO245_4-17; SO245_6-15; SO245_8-25; Sonne_2; South Pacific Gyre; South Pacific Ocean; UltraPac, GEOTRACES
    Type: Dataset
    Format: text/tab-separated-values, 360 data points
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  • 9
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    PANGAEA
    In:  Supplement to: Grasse, Patricia; Ehlert, Claudia; Frank, Martin (2013): The influence of water mass mixing on the dissolved Si isotope composition in the Eastern Equatorial Pacific. Earth and Planetary Science Letters, 380, 60-71, https://doi.org/10.1016/j.epsl.2013.07.033
    Publication Date: 2024-05-22
    Description: Silicon isotopes are a powerful tool to investigate the cycling of dissolved silicon (Si). In this study the distribution of the Si isotope composition of dissolved silicic acid (d30Si(OH)4) was analyzed in the water column of the Eastern Equatorial Pacific (EEP) where one of the globally largest Oxygen Minimum Zones (OMZs) is located. Samples were collected at 7 stations along two meridional transects from the equator to 14°S at 85°50'W and 82°00'W off the Ecuadorian and Peruvian coast. Surface waters show a large range in isotope compositions d30Si(OH)4 (+2.2 per mil to +4.4 per mil) with the highest values found at the southernmost station at 14°S. This station also revealed the most depleted silicic acid concentrations (0.2 µmol/kg), which is a function of the high degree of Si utilization by diatoms and admixture with waters from highly productive areas. Samples within the upper water column and the OMZ at oxygen concentrations below 10 µmol/kg are characterized by a large range in d30Si(OH)4, which mainly reflects advection and mixing of different water masses, even though the highly dynamic hydrographic system of the upwelling area off Peru does not allow the identification of clear Si isotope signals for distinct water masses. Therefore we cannot rule out that also dissolution processes have an influence on the d30Si(OH)4 signature in the subsurface water column. Deep water masses (〉2000 m) in the study area show a mean d30Si(OH)4 of +1.2±0.2 per mil, which is in agreement with previous studies from the eastern and central Pacific. Comparison of the new deep water data of this study and previously published data from the central Pacific and Southern Ocean reveal substantially higher d30Si(OH)4 values than deep water signatures from the North Pacific. As there is no clear correlation between d30Si(OH)4 and silicic acid concentrations in the entire data set the distribution of d30Si(OH)4 signatures in deep waters of the Pacific is considered to be mainly a consequence of the mixing of several end member water masses with distinct Si isotope signatures including Lower Circumpolar Deep Water (LCDW) and North Pacific Deep Water (NPDW).
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; CTD/Rosette; CTD-RO; Date/Time of event; Density, sigma-theta (0); DEPTH, water; Elevation of event; Event label; Latitude of event; Longitude of event; M77/3; M77/3-CTD23; M77/3-CTD27; M77/4; M77/4_152; M77/4-CTD18; M77/4-CTD27; M77/4-CTD44; M77/4-CTD64; M77/4-CTD82; Meteor (1986); Nitrate; Oxygen; Phosphate; Salinity; SFB754; Silicate; Temperature, water, potential; δ30Si, silicic acid
    Type: Dataset
    Format: text/tab-separated-values, 490 data points
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  • 10
    Publication Date: 2021-02-08
    Description: Silicon (Si) is the second most abundant element in the Earth’s crust and is an important nutrient in the ocean. The global Si cycle plays a critical role in regulating primary productivity and carbon cycling on the continents and in the oceans. Development of the analytical tools used to study the sources, sinks, and fluxes of the global Si cycle (e.g., elemental and stable isotope ratio data for Ge, Si, Zn, etc.) have recently led to major advances in our understanding of the mechanisms and processes that constrain the cycling of Si in the modern environment and in the past. Here, we provide background on the geochemical tools that are available for studying the Si cycle and highlight our current understanding of the marine, freshwater and terrestrial systems. We place emphasis on the geochemistry (e.g., Al/Si, Ge/Si, Zn/Si, δ13 C, δ15 N, δ18 O, δ30 Si) of dissolved and biogenic Si, present case studies, such as the Silicic Acid Leakage Hypothesis, and discuss challenges associated with the development of these environmental proxies for the global Si cycle. We also discuss how each system within the global Si cycle might change over time (i.e., sources, sinks, and processes) and the potential technical and conceptual limitations that need to be considered for future studies.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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