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Datasets with PANGAEA technical keyword @ORFOISatKERFIX

Mostrando recursos 1 - 20 de 1.452

  1. Iron and aluminium and hydrogen peroxide measured on water bottle samples during Marion Dufresne cruise ANTARES-II

    Sarthou, Géraldine; Jeandel, Catherine; Brisset, Laurence; Amouroux, David; Besson, Thierry; Donard, Olivier F X
    Total dissolvable iron (TDFe), particulate iron (PFe) and hydrogen peroxide (H2O2 measurements were performed along a N-S transect in the upper 250 m in the Southern Ocean (62°00E/66°42S - 49°00S, ANTARES II cruise, February 1994). TDFe was organically extracted (APDC/DDDC-chloroform) and analysed by Graphite Furnace Atomic Absorption Spectrometry (GFAAS), PFe was analysed by GFAAS following a strong mixed-acid leach, and H2O2 was analysed on board by fluorometry. The respective detection limits are equal to 0.13 nmol/kg, 0.02 nmol/kg, and 3.0 nmol/kg. TDFe concentrations vary from 0.4 to 6.2 nmol/kg and profiles are not completely depleted in the surface. PFe concentrations...

  2. A review of Si particle fluxes in the modern ocean

    Ragueneau, Olivier; Tréguer, Paul; Leynaert, Aude; Anderson, Robert F; Brzezinski, Mark A; DeMaster, David J; Dugdale, Richard; Dymond, Jack R; Fischer, Gerhard; Francois, Roger; Heinze, Christoph; Maier-Reimer, Ernst; Martin-Jézéquel, Véronique; Nelson, David M; Quéguiner, Bernard
    Due to the major role played by diatoms in the biological pump of CO2, and to the presence of silica-rich sediments in areas that play a major role in air-sea CO2 exchange (e.g. the Southern Ocean and the Equatorial Pacific), opal has a strong potential as a proxy for paleoproductivity reconstructions. However, because of spatial variations in the biogenic silica preservation, and in the degree of coupling between the marine Si and C biogeochemical cycles, paleoreconstructions are not straitghtforward. A better calibration of this proxy in the modern ocean is required, which needs a good understanding of the mechanisms that...

  3. Hydrocarbons, sterols and alkenones at time series station KERFIX

    Ternois, Yann; Sicre, Marie-Alexandrine; Boireau, Anne; Beaufort, Luc; Miquel, Juan-Carlos; Jeandel, Catherine
    Hydrocarbons, sterols and alkenones were analyzed in samples collected from a 10 month sediment trap time series deployed in the Indian Ocean sector of the Southern Ocean. Fluxes and within-class distributions varied seasonally. During higher mass and organic carbon (OC) flux periods, which occurred in austral summer and fall, fresh marine inputs were predominant. Vertical fluxes were most intense in January, but limited to one week in duration. They were, however, low compared with other oceanic regions. In contrast, low mass and OC flux periods were characterized by a strong unresolved complex mixture (UCM) in the hydrocarbon fraction and a...

  4. Nutrients at time series station KERFIX

    Jeandel, Catherine; Ruiz-Pino, Diana; Gjata, Elvis; Poisson, Alain; Brunet, Christian; Charriaud, Edwige; Dehairs, Frank; Delille, Daniel; Fiala, Michel; Fravalo, Charles; Miquel, Juan-Carlos; Park, Young-Hyang; Pondaven, Philippe; Quéguiner, Bernard; Razouls, Suzanne; Shauer, Bernard; Tréguer, Paul
    Between January 1990 and March 1995, the research project KERFIX undertook the first regular noncoastal multiyear acquisition of parameters related to the carbon cycle in the Southern Ocean at a time series station located at 50°40' S-68°25' E, 60 miles southwest of the Kerguelen Islands. The objectives of KERFIX are (1) to monitor the ocean/atmosphere CO2 and O2 exchanges and to understand which processes govern these exchanges (2) to observe and interpret the seasonal and interannual variability of the production, flux, decomposition and dissolution of carbon and associated elements at this location. In addition, micropaleontological studies describe the present and...

  5. Bacterial abundance in the Strait of Magellan

    Talbot, V; Giuliano, L; Bruni, V; Bianchi, Micheline
    Bacterial abundance, bacterial secondary production (BSP) and potential ectoproteolytic activity (PEA) were measured at 6 stations along the Strait of Magellan, South America, toward the end of summer 1995. Because of hydrological and climatic factors, 3 main areas could be identified in which the bacterial component displayed specific characteristics. In the Pacific Ocean side, subjected to freshwater inputs from rainfalls and melting of glaciers, the bacterial activities showed the highest values (BSP: 228.2 ng C/l h; PEA: 12.2 nmol/l h). The bacterial biomass was greater than the phytoplanktonic biomass, probably due to organic inputs from land stimulating the bacterial growth....

  6. Global compilation of benthic data sets I

    Seiter, Katherina; Hensen, Christian; Schröter, Jürgen; Zabel, Matthias
    Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in...

  7. Global data compilation of benthic data sets II

    Seiter, Katherina; Hensen, Christian; Zabel, Matthias
    In this study we present a global distribution pattern and budget of the minimum flux of particulate organic carbon to the sea floor (J POC alpha). The estimations are based on regionally specific correlations between the diffusive oxygen flux across the sediment-water interface, the total organic carbon content in surface sediments, and the oxygen concentration in bottom waters. For this, we modified the principal equation of Cai and Reimers [1995] as a basic monod reaction rate, applied within 11 regions where in situ measurements of diffusive oxygen uptake exist. By application of the resulting transfer functions to other regions with...

  8. Geochemistry of sediment cores of the Southern Ocean

    Rosenthal, Yair; Boyle, Edwards A; Labeyrie, Laurent D; Oppo, Delia W
    We examine the possibility that glacial increase in the areal extent of reducing sediments might have changed the oceanic Cd inventory, thereby decoupling Cd from PO4. We suggest that the precipitation of Cd-sulfide in suboxic sediments is the single largest sink in the oceanic Cd budget and that the accumulation of authigenic Cd and U is tightly coupled to the organic carbon flux into the seafloor. Sediments from the Subantarctic Ocean and the Cape Basin (South Atlantic), where oxic conditions currently prevail, show high accumulation rates of authigenic Cd and U during glacial intervals associated with increased accumulation of organic...

  9. Stable isotope ratios of foraminifera from various DSDP/ODP sites

    Zachos, James C; Stott, Lowell D; Lohmann, Kyger C
    The equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals: late Paleocene, early Eocene, early middle Eocene, late Eocene, and early Oligocene. Paleotemperatures are calculated using standard oxygen isotope/temperature equations with adjustments to account for (1) variations in sea water delta18O related to changes in global ice volume over time and (2) latitudinal gradients in surface water delta18O. These reconstructions indicate that sea-surface temperatures (SST) of the Southern Oceans in the early Eocene were as high as 15°C, whereas temperatures during...

  10. Stable isotope record of foraminifera from the Southern Ocean

    Lynch-Stieglitz, Jean; Fairbanks, Richard G; Charles, Christopher D
    Sediment cores from the southern continental margin of Australia are near the formation region of Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water and record the changes in these water masses from the last glacial maximum through the present. Carbon and oxygen isotopes were measured on the benthic foraminiferal species Planulina wuellerstrorfi for both the Recent and last glacial maximum sections of the cores and were then used to reconstruct temperature and carbon isotopic water column profiles. The glacial oxygen isotope profile indicates a vertical temperature structure for this region similar to that in today's Subantarctic Zone. Although intermediate water...

  11. Ge/Si record of marine biogenic opal

    Shemesh, Aldo; Mortlock, Richard A; Froelich, Philip N
    We have determined germanium/silicon ratios in purified diatoms and radiolarians from siliceous sediments in Holocene core tops, one late Pleistocene piston core, and four high-latitude Southern Ocean Deep Sea Drilling Project (DSDP) sites ranging in age from Holocene to Oligocene. High-latitude Holocene diatoms in the 10- to 38-µm size fraction ([Ge/Si]opal = 0.693 +/- 0.039 * 10**-6) faithfully record the present oceanic ratio ([Ge/Si]seawater = 0.699 +/- 0.004 * 10**-6). This confirms that diatoms from siliceous oozes are monitors of seawater Ge/Si and may record past changes in rates of delivery of weathering products to the sea from continental and...

  12. Calcium carbonate global LGM Burial rate data

    Catubig, Nina R; Archer, David E; Francois, Roger; deMenocal, Peter B; Howard, William R; Yu, Ein-Fen
    Global databases of calcium carbonate concentrations and mass accumulation rates in Holocene and last glacial maximum sediments were used to estimate the deep-sea sedimentary calcium carbonate burial rate during these two time intervals. Sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate concentrations and the assumption that accumulation of noncarbonate material is uncorrelated with calcite concentration within some geographical region. Mean noncarbonate accumulation rates were estimated within each of nine regions, determined by the distribution and nature of the accumulation rate data. For core-top sediments the regions...

  13. Primary data sets of the hydrographic atlas of the Southern Ocean

    Olbers, Dirk; Gouretski, Viktor V; Seiß, Guntram; Schröter, Jens
    The general knowledge of the hydrographic structure of the Southern Ocean is still rather incomplete since observations particularly in the ice covered regions are cumbersome to be carried out. But we know from the available information that thermohaline processes have large amplitudes and cover a wide range of scales in this part of the world ocean. The modification of water masses around Antarctica have indeed a worldwide impact, these processes ultimately determine the cold state of the present climate in the world ocean. We have converted efforts of the German and Russian polar research institutions to collect and validate the presently...

  14. Size distribution of Holocene planktic foraminifer assemblages

    Schmidt, Daniela N; Renaud, Sabrina; Bollmann, Jörg; Schiebel, Ralf; Thierstein, Hans R
    The size of any organism is influenced by the surrounding ecological conditions. In this study, we investigate the effects of such factors on the size spectra of planktic foraminiferal assemblages from Holocene surface sediments. We analyzed assemblages from 69 Holocene samples, which cover the major physical and chemical gradients of the oceans. On a global scale, the range of sizes in assemblages triples from the poles to the tropics. This general temperature-related size increase is interrupted by smaller sizes at temperatures characteristic of the polar and subtropical fronts, at 2°C and 17°C, respectively, as well as in upwelling areas. On...

  15. Vertical distribution of benthic foraminifers in the Arctic Ocean

    Wollenburg, Jutta E; Mackensen, Andreas
    The vertical distribution of living (Rose Bengal stained) benthic foraminifers was determined in the upper 15 cm of sediment cores taken along transects extending from the continental shelf of Spitsbergen through the Eurasian Basin of the Arctic Ocean. Cores taken by a multiple corer were raised from 50 stations with water depths between 94 and 4427 m, from areas with moderate primary production values to areas that are among the least productive ones in the world. We believe, that in the Arctic Ocean the vertical distribution of living foraminifers is determined by the restricted availability of food. Live foraminiferal faunas...

  16. Glacial North Atlantic: Sea surface conditions reconstructed by GLAMAP 2000

    Pflaumann, Uwe; Sarnthein, Michael; Chapman, Mark R; de Abreu, Lucia; Funnell, Brian M; Hüls, Matthias; Kiefer, Thorsten; Maslin, Mark A; Schulz, Hartmut; Swallow, John; van Kreveld, Shirley A; Vautravers, Maryline J; Vogelsang, Elke; Weinelt, Mara
    The response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology. Our new reconstruction of peak glacial sea surface temperatures (SSTs) in the Atlantic is based on census counts of planktic foraminifera, using the Maximum Similarity Technique Version 28 (SIMMAX-28) modern analog technique with 947 modern analog samples and 119 well-dated sediment cores. Our study compares two slightly different scenarios of the Last Glacial Maximum (LGM), the Environmental Processes of the Ice Age: Land, Oceans, Glaciers (EPILOG), and Glacial Atlantic Ocean Mapping (GLAMAP...

  17. Foraminiferal faunal estimates of paleotemperature: Circumventing the no-analog problem yields cool ice age tropics

    Mix, Alan C; Morey, Ann E; Pisias, Nicklas G; Hostetler, Steven W
    The sensitivity of the tropics to climate change, particularly the amplitude of glacial-to-interglacial changes in sea surface temperature (SST), is one of the great controversies in paleoclimatology. Here we reassess faunal estimates of ice age SSTs, focusing on the problem of no-analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods. A new calibration strategy developed here, which uses past variability of species to define robust faunal assemblages, solves the no-analog problem and reveals ice age cooling of 5° to 6°C in the equatorial current systems of the Atlantic and eastern Pacific...

  18. (Table A1) Stable isotope ratios of foraminifera from DSDP Hole 22-215

    Zachos, James C; Stott, Lowell D; Lohmann, Kyger C

  19. (Table A1) Stable isotope ratios of foraminifera from DSDP Hole 22-213

    Zachos, James C; Stott, Lowell D; Lohmann, Kyger C

  20. (Table A1) Stable isotope ratios of foraminifera from ODP Hole 121-758A

    Zachos, James C; Stott, Lowell D; Lohmann, Kyger C

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