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  • 1
    Publication Date: 2015-01-30
    Description: Particles determine the residence time of many dissolved elements in seawater. Although a substantial number of field studies were conducted in the framework of major oceanographic programs as GEOSECS and JGOFS, knowledge about particle dynamics is still scarce. Moreover, the particulate trace metal behavior remains largely unknown. The GEOSECS sampling strategy during the 1970s focused on large sections across oceanic basins, where particles were collected by membrane filtration after Niskin bottle sampling, biasing the sampling toward the small particle pool. Late in this period, the first in situ pumps allowing large volume sampling were also developed. During the 1990s, JGOFS focused on the quantifi- cation of the ‘‘exported carbon flux’’ and its seasonal variability in representative biogeochemical prov- inces of the ocean, mostly using sediment trap deployments. Although scarce and discrete in time and space, these pioneering studies allowed an understanding of the basic fate of marine particles. This understanding improved considerably, especially when the analysis of oceanic tracers such as natural radionuclides allowed the first quantification of processes such as dissolved-particle exchange and par- ticle settling velocities. Because the GEOTRACES program emphasizes the importance of collecting, char- acterizing and analyzing marine particles, this paper reflects our present understanding of the sources, fate and sinks of oceanic particles at the early stages of the program.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 2
    Publication Date: 2018-03-26
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 3
    Publication Date: 2019-02-01
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2016-02-29
    Description: Abstract The {GEOTRACES} Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international {GEOTRACES} programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The {IDP2014} covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The {TEI} data in the {IDP2014} are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including {ASCII} spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the {IDP2014} also contains data quality flags and 1-� data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the {IDP2014} data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 5
    Publication Date: 2018-08-13
    Description: The GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 25 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017. This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2017-01-04
    Description: Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 54 (2007): 601-638, doi:10.1016/j.dsr2.2007.01.013.
    Description: This paper investigates ballasting and remineralization controls of carbon sedimentation in the twilight zone (100-1000 m) of the Southern Ocean. Size-fractionated (〈1 μm, 1-51 μm, 〉51 μm) suspended particulate matter was collected by large volume in-situ filtration from the upper 1000 m in the Subantarctic (55°S, 172°W) and Antarctic (66°S, 172°W) zones of the Southern Ocean during the Southern Ocean Iron Experiment (SOFeX) in January-February 2002. Particles were analyzed for major chemical constituents (POC, P, biogenic Si, CaCO3), and digital and SEM image analyses of particles were used to aid in the interpretation of the chemical profiles. Twilight zone waters at 66°S in the Antarctic had a steeper decrease in POC with depth than at 55°S in the Subantarctic, with lower POC concentrations in all size fractions at 66°S than at 55°S, despite up to an order of magnitude higher POC in surface waters at 66°S. The decay length scale of 〉51 μm POC was significantly shorter in the upper twilight zone at 66°S (δe=26 m) compared to 55°S (δe=81 m). Particles in the carbonate-producing 55°S did not have higher excess densities than particles from the diatom-dominated 66°S, indicating that there was no direct ballast effect that accounted for deeper POC penetration at 55°S. An indirect ballast effect due to differences in particle packaging and porosities cannot be ruled out, however, as aggregate porosities were high (~97%) and variable. Image analyses point to the importance of particle loss rates from zooplankton grazing and remineralization as determining factors for the difference in twilight zone POC concentrations at 55°S and 66°S, with stronger and more focused shallow remineralization at 66°S. At 66°S, an abundance of large (several mm long) fecal pellets from the surface to 150 m, and almost total removal of large aggregates by 200 m, reflected the actions of a single or few zooplankton species capable of grazing diatoms in the euphotic zone, coupled with a more diverse particle feeding zooplankton community immediately below. Surface waters with high biomass levels and high proportion of biomass in the large size fraction were associated with low particle loading at depth, with all indications implying conditions of low export. The 66°S region exhibits this “High Biomass, Low Export” (HBLE) condition, with very high 〉51 μm POC concentrations at the surface (~2.1 μM POC), but low concentrations below 200 m (〈0.07 μM POC). The 66°S region remained HBLE after iron fertilization. Iron addition at 55°S caused a ten fold increase in 〉51 μm biomass concentrations in the euphotic zone, bringing surface POC concentrations to levels found at 66°S (~3.8 μM), and a concurrent decrease in POC concentrations below 200 m. The 55°S region, which began with moderate levels of biomass and stronger particle export, transitioned to being HBLE after iron fertilization. We propose that iron addition to already HBLE waters will not cause mass sedimentation events. The stability of an iron-induced HBLE condition is unknown. Better understanding of biological pump processes in non-HBLE Subantarctic waters is needed.
    Description: This work was supported by the DOE Office of Science, Biological and Environmental Research Program. Shiptime for SOFeX was funded by NSF.
    Keywords: Ballast ; Remineralization ; POC ; Twilight Zone ; Mesopelagic ; Southern Ocean ; MULVFS ; Opal ; Carbonate ; Phosphorus
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 20 (2006): GB1006, doi:10.1029/2005GB002557.
    Description: Heightened biological activity was observed in February 1996 in the high-nutrient low-chlorophyll (HNLC) subarctic North Pacific Ocean, a region that is thought to be iron-limited. Here we provide evidence supporting the hypothesis that Ocean Station Papa (OSP) in the subarctic Pacific received a lateral supply of particulate iron from the continental margin off the Aleutian Islands in the winter, coincident with the observed biological bloom. Synchrotron X-ray analysis was used to describe the physical form, chemistry, and depth distributions of iron in size fractionated particulate matter samples. The analysis reveals that discrete micron-sized iron-rich hot spots are ubiquitous in the upper 200 m at OSP, more than 900 km from the closest coast. The specifics of the chemistry and depth profiles of the Fe hot spots trace them to the continental margins. We thus hypothesize that iron hot spots are a marker for the delivery of iron from the continental margin. We confirm the delivery of continental margin iron to the open ocean using an ocean general circulation model with an iron-like tracer source at the continental margin. We suggest that iron from the continental margin stimulated a wintertime phytoplankton bloom, partially relieving the HNLC condition.
    Description: This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research (KP1202030) to J. K. B and by NSFATM-9987457 to I. F. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Division of Chemical Sciences, Geosciences, and Biosciences of the U.S. Department of Energy at Lawrence Berkeley National Laboratory under contract DE-AC03-76SF00098.
    Keywords: Iron ; Continental margin ; HNLC ; Subarctic Pacific
    Repository Name: Woods Hole Open Access Server
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  • 8
    Publication Date: 2017-01-05
    Description: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 23 (2009): GB4034, doi:10.1029/2009GB003500.
    Description: Climate change is projected to significantly alter the delivery (stratification, boundary currents, aridification of landmasses, glacial melt) of iron to the Southern Ocean. We report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of Australia. Distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms, with higher iron stocks and fluxes observed in surface northern subantarctic waters, where atmospheric iron fluxes were greater. Subsurface waters southeast of Tasmania were also enriched with particulate iron, manganese and aluminum, indicative of a strong advective source from shelf sediments. Subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind-blown dust deposition, resulting in a strong decoupling of iron and nutrient cycles. We discuss the broader global significance our iron budgets for other ocean regions sensitive to climate-driven changes in iron supply.
    Description: T.W. was supported by a BDI grant from CNRS and Région PACA, by CNRS PICS project 3604, and by the “Soutien à la mer” CSOA CNRS-INSU. P.W.B. was supported by the New Zealand FRST Coasts and Oceans OBI. This research was supported by the Australian Government Cooperative Research Centres Programme through the Antarctic Climate and Ecosystems CRC (ACE CRC) and Australian Antarctic Science project 2720.
    Keywords: Iron ; Southern Ocean ; Biogeochemical budget ; Subantarctic ; Polar ; Australian sector
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2017-01-04
    Description: Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 90 (2012):126–148, doi:10.1016/j.gca.2012.05.009.
    Description: The ability of paired measurements of thorium isotope activity and particle concentration to constrain rate constants of sorption reactions and particle dynamics in the ocean is examined. This study is motivated by GEOTRACES and other sampling programs where Th and particle data are gathered in various oceanic environments. Our approach relies on inversions with a model of trace metal and particle cycling in the water column. First, the model is used to simulate vertical profiles of (i) the activity of three Th isotopes (228,230,234Th) in the dissolved phase, small suspended particles, and large sinking particles, and (ii) the concentration of small and large particles. The simulated profiles are then subsampled and corrupted with noise to generate a pseudo data set. These data are combined with the model with arbitrary values of rate constants of Th adsorption, Th desorption, particle sinking, particle remineralization, and particle (dis)aggregation in an effort to recover the actual values used to generate the data. Inversions are performed using a least-squares technique with varying assumptions about data noise, data sampling, and model errors. We find that accurate and precise recovery of rate parameters is possible when all data have a relative error of less than 20%, vertical sampling is dense enough to resolve activity and concentration gradients, and model errors are negligible. Estimating cycling rates from data with larger errors and (or) at locations where model assumptions are not tenable would remain challenging. On the other hand, the paired data set would improve significantly the relative precision of rate parameters compared to that of prior estimates (⩾100%), even with current data uncertainties and significant model errors. Based on these results, we advocate the joint measurement of all three Th isotopes, 228Ra, and particles collected by in situ filtration within GEOTRACES and other sampling programs targeted at the study of particle processes in the ocean.
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2017-01-04
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Progress in Oceanography 133 (2015):6-16, doi:10.1016/j.pocean.2014.12.018.
    Description: Particles determine the residence time of many dissolved elements in seawater. Although a substantial number of field studies were conducted in the framework of major oceanographic programs as GEOSECS and JGOFS, knowledge about particle dynamics is still scarce. Moreover, the particulate trace metal behavior remains largely unknown. The GEOSECS sampling strategy during the 1970’s focused on large sections across oceanic basins, where particles were collected by membrane filtration after Niskin bottle sampling, biasing the sampling towards the small particle pool. Late in this period, the first in situ pumps allowing large volume sampling were also developed. During the 1990’s, JGOFS focused on the quantification of the “exported carbon flux” and its seasonal variability in representative biogeochemical provinces of the ocean, mostly using sediment trap deployments. Although scarce and discrete in time and space, these pioneering studies allowed an understanding of the basic fate of marine particles. This understanding improved considerably, especially when the analysis of oceanic tracers such as natural radionuclides allowed the first quantification of processes such as dissolved-particle exchange and particle settling velocities. Because the GEOTRACES program emphasizes the importance of collecting, characterizing and 39 analyzing marine particles, this paper reflects our present understanding of the sources, fate and sinks of oceanic particles at the early stages of the program.
    Description: This paper arose from a workshop that was co-sponsored by ESF COST Action ES0801, "The ocean chemistry of bioactive trace elements and paleoproxies". Additional support for that workshop came from SCOR, through support to SCOR from the U.S. National Science Foundation (Grant OCE- 0938349 and OCE-1243377). Support for PJL from U.S. NSF grant OCE-0963026.
    Keywords: Historical review ; Oceanic Particle distribution sources and sinks ; GEOSECS ; JGOFS ; GEOTRACES
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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