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  • 1
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    Calibration of sediment traps and particulate organic carbon export using 234Th in the Barents Sea (2002)
    Elsevier BV
    Associated volumes
    Details
    In: Marine Chemistry, 3664
    Description / Table of Contents: Profiles of particulate and dissolved 234Th (t1/2=24.1 days) in seawater and particulate 234Th collected in drifting traps were analyzed in the Barents Sea at five stations during the ALV3 cruise (from June 28 to July 12, 1999) along a transect from 78°15′N–34°09′E to 73°49′N–31°43′E. 234Th/238U disequilibrium was observed at all locations. 234Th data measured in suspended and trapped particles were used to calibrate the catchment efficiency of the sediment traps. Model-derived 234Th fluxes were similar to 234Th fluxes measured in sediment traps based on a steady-state 234Th model. This suggests that the sediment traps were not subject to large trapping efficiency problems (collection efficiency ranges from 70% to 100% for four traps). The export flux of particulate organic carbon (POC) can be calculated from the model-derived export flux of 234Th and the POC/234Th ratio. POC/234Th ratios measured in suspended and trapped particles were very different (52.0±9.9 and 5.3±2.2 μmol dpm−1, respectively). The agreement between calculated and measured POC fluxes when the POC/234Th ratio of trapped particles was used confirms that the POC/234Th ratio in trap particles is representative of sinking particles. Large discrepancies were observed between calculated and measured POC fluxes when the POC/234Th ratio of suspended particles was used. In the Barents Sea, vertical POC fluxes are higher than POC fluxes estimated in the central Arctic Ocean and the Beaufort Sea and lower than those calculated in the Northeast Water Polynya and the Chukchi Sea. We suggest that the latter fluxes may have been strongly overestimated, because they were based on high POC/234Th ratios measured on suspended particles. It seems that POC fluxes cannot be reliably derived from thorium budgets without measuring the POC/234Th ratio of sediment trap material or of large filtered particles.
    Type of Medium: 13
    ISSN: 0304-4203 , 1872-7581
    URL: https://doi.org/10.1016/S0304-4203(02)00071-3
    URL: https://cat.telegrafenberg.de/cgi-bin/koha/opac-image.pl?thumbnail=1&imagenumber=850
    Language: English
    Note: Outline Abstract Keywords 1. Introduction 2. Methods 2.1. Sample collection 2.2. 234Th analyses 2.3. Particulate organic carbon analyses 3. Results 3.1. Hydrography 3.2. Nutrients 3.3. 234Th activities and POC concentrations 3.4. Trapped material 4. Discussion 4.1. Origins of 234Th/238U disequilibrium 4.2. Determining 234Th fluxes 4.3. Calibration of sediment trap with 234Th 4.4. Vertical flux of particulate organic carbon and the POC/234Thp ratio 5. Conclusion Acknowledgements References
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    E-BOOK
  • 2
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    Output from a global scavenging and circulation ocean model of thorium-230 and protactinium-231 (ProThorP 0.1) (2018)
    PANGAEA
    In:  Supplement to: van Hulten, Marco M P; Dutay, Jean-Claude; Roy-Barman, Matthieu (2018): A global scavenging and circulation ocean model of thorium-230 and protactinium-231 with improved particle dynamics (NEMO–ProThorP 0.1). Geoscientific Model Development, 11(9), 3537-3556, https://doi.org/10.5194/gmd-11-3537-2018
    Details
    Publication Date: 2023-02-24
    Description: This archive contains all output from the PISCES-v2 model, containing 24 carbon, nitrate, phosphate and iron tracers. The model is extended with models of lithogenic particles and thorium-230 and protactinium-231, adding eight additional tracers, namely small and big lithogenic particles, and dissolved, small and big Th-230 and Pa-231 (referred to as ProThorP). Thus the model contains 32 different tracers (ptrc) for two different simulations, as well as diagnostic data (diad). The model is executed as part of the global ocean general cirulation model NEMO in the ORCA2 configuration (2° x 2° cos(phi) x 31 layers).
    Keywords: Comment; File content; File format; File name; File size; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 29 data points
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  • 3
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    Model output of manganese concentrations from a global ocean circulation model, link to files in NetCDF format (2017)
    PANGAEA
    In:  Supplement to: van Hulten, Marco M P; Middag, Rob; Dutay, Jean-Claude; de Baar, Hein J W; Roy-Barman, Matthieu; Gehlen, Marion; Tagliabue, Alessandro; Sterl, Andreas (2017): Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese. Biogeosciences, 14(5), 1123-1152, https://doi.org/10.5194/bg-14-1123-2017
    Details
    Publication Date: 2023-02-24
    Description: Dissolved manganese (Mn) is a biologically essential element. Moreover, its oxidised form is involved in removing itself and several other trace elements from ocean waters. Here we report the longest thus far (17500 km length) full-depth ocean section of dissolved Mn in the west Atlantic Ocean, comprising 1320 data values of high accuracy. This is the GA02 transect that is part of the GEOTRACES programme, which aims to understand trace element distributions. The goal of this study is to combine these new observations with new, state-of-the-art, modelling to give a first assessment of the main sources and redistribution of Mn throughout the ocean. To this end, we simulate the distribution of dissolved Mn using a global-scale circulation model. This first model includes simple parameterisations to account for the sources, processes and sinks of Mn in the ocean. Oxidation and (photo)reduction, aggregation and settling, as well as biological uptake and remineralisation by plankton are included in the model. Our model provides, together with the observations, the following insights: – The high surface concentrations of manganese are caused by the combination of photoreduction and sources contributing to the upper ocean. The most important sources are sediments, dust, and, more locally, rivers. – Observations and model simulations suggest that surface Mn in the Atlantic Ocean moves downwards into the southward-flowing North Atlantic Deep Water (NADW), but because of strong removal rates there is no elevated concentration of Mn visible any more in the NADW south of 40° N. – The model predicts lower dissolved Mn in surface waters of the Pacific Ocean than the observed concentrations. The intense oxygen minimum zone (OMZ) in subsurface waters is deemed to be a major source of dissolved Mn also mixing upwards into surface waters, but the OMZ is not well represented by the model. Improved high-resolution simulation of the OMZ may solve this problem. – There is a mainly homogeneous background concentration of dissolved Mn of about 0.10–0.15 nM throughout most of the deep ocean. The model reproduces this by means of a threshold on particulate manganese oxides of 25 pM, suggesting that a minimal concentration of particulate Mn is needed before aggregation and removal become efficient. – The observed distinct hydrothermal signals are produced by assuming both a strong source and a strong removal of Mn near hydrothermal vents.
    Keywords: GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes
    Type: Dataset
    Format: application/zip, 393.1 MBytes
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    DATA PANGAEA
  • 4
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    (Table 2) 230Th, 230Th xs and 232Th concentrations in dissolved, particulate and total (dissolved+small particles) for all KEOPS stations, Marion Dufresne cruise MD145 (2008)
    PANGAEA
    In:  Supplement to: Venchiarutti, Célia; Jeandel, Catherine; Roy-Barman, Matthieu (2008): Particle dynamics study in the wake of Kerguelen Island using thorium isotopes. Deep Sea Research Part I: Oceanographic Research Papers, 55(10), 1343-1363, https://doi.org/10.1016/j.dsr.2008.05.015
    Details
    Publication Date: 2023-10-28
    Description: In the context of the KErguelen Ocean and Plateau compared Study (KEOPS, 19 January-13 February 2005), particle dynamics were investigated using thorium isotope measurements over and off the Kerguelen plateau. Dissolved and particulate 230Th and 232Th samples were collected at nine stations. Dissolved excess 230Th concentrations (230Thxs) vary from 0.5 to 20.8 fg/kg and particulate 230Thxs concentrations from 0.1 to 10.0 fg/kg. Dissolved and particulate 232Th concentration ranges are 16.8-450.2 pg/kg and 3.8-502.8 pg/kg, respectively. The 230Thxs concentrations increase linearly with depth down to the bottom at most of the plateau stations and down to 1000 m at the off-plateau stations. This linear trend is observed down to the bottom (1550 m) at Kerfix, the open-ocean "upstream" station located west of the Kerguelen plateau. A simple reversible scavenging model applied to these data allowed the estimation of adsorption rate constant (k1~=0.2-0.8 per year), desorption rate constant (k-1~=1-8 per year) and partition coefficients (average K=0.16±0.07). Calculated particle settling velocities S deduced from this simple model are ca. 500 m/year at most of the plateau stations and 800 m/year at all the off-plateau stations. The plateau settling velocities are relatively low for such a productive site, compared to the surrounding HNLC areas. The difference might reflect the fact that lateral advection is neglected in this model. Taking this advection into account allows the reconstruction of the observed 230Thxs linear distributions, but only if faster settling velocities are considered. This implies that the 1D model strongly underestimates the settling velocity of the particles. In the deep layers, the occurrence of intense boundary scavenging along the escarpment due to bottom sediment re-suspension and interaction with a nepheloid layer, yielding a removal of ~50% of the Th stock along the northwestward transect, is suggested.
    Keywords: CTD/Rosette; CTD-RO; Date/Time of event; DEPTH, water; Event label; Indian Ocean; Latitude of event; Longitude of event; Marion Dufresne (1995); MD145; MD145_A11; MD145_A3-3; MD145_A3-4; MD145_B1; MD145_B11; MD145_B5; MD145_C1; MD145_C11; MD145_C5; MD145_Kerfix; OISO_12, KEOPS,35MF20050113; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SPP1158; Thorium-230; Thorium-230, dissolved; Thorium-230, dissolved, standard deviation; Thorium-230, particulate; Thorium-230, particulate, standard deviation; Thorium-230, standard deviation; Thorium-230 excess; Thorium-230 excess, dissolved; Thorium-230 excess, dissolved, standard deviation; Thorium-230 excess, particulate; Thorium-230 excess, particulate, standard deviation; Thorium-230 excess, standard deviation; Thorium-232; Thorium-232, dissolved; Thorium-232, dissolved, standard deviation; Thorium-232, particulate; Thorium-232, particulate, standard deviation; Thorium-232, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 767 data points
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    DATA PANGAEA
  • 5
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    Thorium isotopes in the water column in Amundsen Basin during POLARSTERN cruises PS70 (ARK-XXII/2) in 2007 and PS94 (ARK-XXIX/3) in 2015 (2019)
    PANGAEA
    Details
    Publication Date: 2023-11-02
    Description: In this study we present dissolved ²³⁰Th and ²³²Th results, as well as amount of particulate ²³⁴Th from total ²³⁴Th. The data, obtained as part of the GEOTRACES central Arctic Ocean sections GN04 (2015) and IPY11 (2007). Samples were analyzed following GEOTRACES methods, and compared to previous results from 1991. We observe significant decreases in ²³⁰Th concentrations in the intermediate waters of the Amundsen Basin. This removal was explained by scavenging removal of dissolved ²³⁰Th on the Barents Sea Shelf and along Atlantic water inflow pathways. This finding shows that a far-field decrease of dissolved ²³⁰Th can be caused by changes in scavenging on inflow passages and highlights the importance of repeated GEOTRACES sections.
    Keywords: 230Th; Arctic Ocean; AWI_MarGeoChem; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; Marine Geochemistry @ AWI; Time series
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 6
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    Dissolved thorium 230 and particulate thorium 232 in the water column at stations PS94/125-2 and PS94/125-5 (2019)
    PANGAEA
    Details
    Publication Date: 2023-11-02
    Keywords: 230Th; Arctic Ocean; ARK-XXIX/3; AWI_MarGeoChem; CTD/Rosette; CTD-RO; Date/Time of event; DEPTH, water; Event label; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; ICP-MS, Thermo Scientific Neptune; Latitude of event; Longitude of event; Marine Geochemistry @ AWI; Polarstern; PS94; PS94/125-2; PS94/125-5; Thorium-230, dissolved; Thorium-230, error; Thorium-232, error; Thorium-232, particulate; Time series
    Type: Dataset
    Format: text/tab-separated-values, 48 data points
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    DATA PANGAEA
  • 7
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    Fraction of particulate thorium 234 in total thorium 234 in the water column at stations PS94/081-9, PS94/117-7 and PS94/125-8 (2019)
    PANGAEA
    Details
    Publication Date: 2023-11-02
    Keywords: 230Th; Arctic Ocean; ARK-XXIX/3; AWI_MarGeoChem; Date/Time of event; DEPTH, water; Event label; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; In situ pump; ISP; Latitude of event; Longitude of event; Marine Geochemistry @ AWI; Polarstern; PS94; PS94/081-9; PS94/117-7; PS94/125-8; Thorium-234, particulate, fraction of total; Time series
    Type: Dataset
    Format: text/tab-separated-values, 33 data points
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    DATA PANGAEA
  • 8
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    Dissolved thorium 230 and particulate thorium 232 in the water column at stations PS70/309-5 and PS70/400-2 (2019)
    PANGAEA
    Details
    Publication Date: 2023-11-02
    Keywords: 230Th; Arctic Ocean; ARK-XXII/2; AWI_MarGeoChem; CTD/Rosette; CTD-RO; Date/Time of event; DEPTH, water; Event label; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; ICP-MS, Thermo Scientific Neptune; Laptev Sea; Latitude of event; Longitude of event; Marine Geochemistry @ AWI; Polarstern; PS70/309-5; PS70/400-2; PS70 SPACE DAMOCLES; Thorium-230, dissolved; Thorium-230, error; Thorium-232, error; Thorium-232, particulate; Time series
    Type: Dataset
    Format: text/tab-separated-values, 48 data points
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    DATA PANGAEA
  • 9
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    230Th global thorium database (2020)
    PANGAEA
    Details
    Publication Date: 2024-03-02
    Description: In this dataset we present a global compilation of over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0-5000 years ago, or 0-5 ka) and the Last Glacial Maximum (18.5-23.5 ka). Data have been screened for age control, errors, and lithogenic corrections. Overall quality levels were computed by summing each record's scores on the individual criteria. A record is optimal if it is based on a chronology that is constrained by δ18O or 14C and it provides both the raw nuclide concentrations and the associated errors. About one quarter of the records in the database achieved this highest quality level. The large majority of the records in the database are good, passing two of the three criteria, while the remaining quarter are of fair or poor quality.
    Keywords: Comment; DEPTH, water; Distance; Flag; Focusing factor; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; Identification; LATITUDE; LONGITUDE; Ocean; ORDINAL NUMBER; Quality level; Ratio; Reference/source; Thorium-230 excess, decay-corrected; Total sediment, flux; Uranium/Thorium ratio
    Type: Dataset
    Format: text/tab-separated-values, 15667 data points
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    DATA PANGAEA
  • 10
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    What did we learn about ocean particle dynamics in the GEOSECS–JGOFS era? (2015)
    Elsevier
    Details
    Publication Date: 2015-04-01
    Print ISSN: 0079-6611
    Electronic ISSN: 1873-4472
    Topics: Geosciences , Physics
    Published by Elsevier
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    PAPER CURRENT
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