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PANGAEA - Publishing Network for Geoscientific & Environmental Data (839.056 recursos)

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Datasets with PANGAEA technical keyword @ORFOISatEqPac

Mostrando recursos 1 - 20 de 8.007

  1. Primary production in the equatorial Pacific

    Le Bouteiller, Aubert; Landry, Michael R; Le Borgne, Robert; Neveux, Jacques; Rodier, Martine; Blanchot, Jean; Brown, Susan L
    Under an apparent monotony characterized by low phytoplankton biomass and production, the Pacific equatorial system may hide great latitudinal differences in plankton dynamics. On the basis of 13 experiments conducted along the 180° meridian (8°S-8°N) from upwelled to oligotrophic waters, primary production was strongly correlated to chlorophyll a (chl a), and the productivity index PI (chl a-normalized production rate) varied independently of macronutrient concentrations. Rates of total (14C uptake) and new (15N-NO3 uptake) primary production were measured in situ at 3°S in nutrient-rich advected waters and at 0° where the upwelling velocity was expected to be maximal. Primary production was...

  2. Primary production in the equatorial Pacific

    Le Bouteiller, Aubert; Landry, Michael R; Le Borgne, Robert; Neveux, Jacques; Rodier, Martine; Blanchot, Jean; Brown, Susan L
    Under an apparent monotony characterized by low phytoplankton biomass and production, the Pacific equatorial system may hide great latitudinal differences in plankton dynamics. On the basis of 13 experiments conducted along the 180° meridian (8°S-8°N) from upwelled to oligotrophic waters, primary production was strongly correlated to chlorophyll a (chl a), and the productivity index PI (chl a-normalized production rate) varied independently of macronutrient concentrations. Rates of total (14C uptake) and new (15N-NO3 uptake) primary production were measured in situ at 3°S in nutrient-rich advected waters and at 0° where the upwelling velocity was expected to be maximal. Primary production was...

  3. Carbon cycle change in the Eocene

    Tripati, Aradhna K; Backman, Jan; Elderfield, Henry; Ferretti, Patrizia
    The transition from the extreme global warmth of the early Eocene 'greenhouse' climate ~55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica ~34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We...

  4. Carbon cycle change in the Eocene

    Tripati, Aradhna K; Backman, Jan; Elderfield, Henry; Ferretti, Patrizia
    The transition from the extreme global warmth of the early Eocene 'greenhouse' climate ~55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica ~34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We...

  5. Barium concentration in sediments of the central Equatorial Pacific

    Paytan, Adina; Kaster, M
    High resolution pore-water dissolved Ba concentration-depth profiles were determined at seven sites across an Equatorial Pacific productivity gradient from 12°S to 9°N, at 140°W. These data are important for understanding the physical, chemical, and biological controls on Ba recycling in the ocean, and for evaluating the paleo-oceanographic significance of Ba content in central Equatorial Pacific sediments. Pore-water Ba concentrations at all sites are higher than in the overlying bottom water, leading to a diffusive flux of Ba into the ocean. A pronounced subsurface concentration maximum exceeding barite solubility characterizes the dissolved Ba pore-water profiles, suggesting that the Ba regenerated in the...

  6. Barium concentration in sediments of the central Equatorial Pacific

    Paytan, Adina; Kaster, M
    High resolution pore-water dissolved Ba concentration-depth profiles were determined at seven sites across an Equatorial Pacific productivity gradient from 12°S to 9°N, at 140°W. These data are important for understanding the physical, chemical, and biological controls on Ba recycling in the ocean, and for evaluating the paleo-oceanographic significance of Ba content in central Equatorial Pacific sediments. Pore-water Ba concentrations at all sites are higher than in the overlying bottom water, leading to a diffusive flux of Ba into the ocean. A pronounced subsurface concentration maximum exceeding barite solubility characterizes the dissolved Ba pore-water profiles, suggesting that the Ba regenerated in the...

  7. Nutrients of pore water in sediments of the central equatorial Pacific

    Martin, William R; Bender, Michael L; Leinen, Margaret W; Orchardo, J
    Shipboard whole-core squeezing was used to measure pore water concentration vs depth profiles of [NO3]-, O2 and SiO2 at 12 stations in the equatorial Pacific along a transect from 15°S to 11°N at 135°W. The [NO3]- and SiO2 profiles were combined with fine-scale resistivity and porosity measurements to calculate benthic fluxes. After using O2 profiles, coupled with the [NO3]- profiles, to constrain the C:N of the degrading organic matter, the [NO3]- fluxes were converted to benthic organic carbon degradation rates. The range in benthic organic carbon degradation rates is 7-30 ?mol cm**-2 y**-1, with maximum values at the equator and...

  8. Nutrients of pore water in sediments of the central equatorial Pacific

    Martin, William R; Bender, Michael L; Leinen, Margaret W; Orchardo, J
    Shipboard whole-core squeezing was used to measure pore water concentration vs depth profiles of [NO3]-, O2 and SiO2 at 12 stations in the equatorial Pacific along a transect from 15°S to 11°N at 135°W. The [NO3]- and SiO2 profiles were combined with fine-scale resistivity and porosity measurements to calculate benthic fluxes. After using O2 profiles, coupled with the [NO3]- profiles, to constrain the C:N of the degrading organic matter, the [NO3]- fluxes were converted to benthic organic carbon degradation rates. The range in benthic organic carbon degradation rates is 7-30 ?mol cm**-2 y**-1, with maximum values at the equator and...

  9. Calcium carbonate preservation in the equatorial Pacific

    Prell, Warren L; Farrell, John W
    The Pliocene-Pleistocene history of CaCO3 preservation in the central equatorial Pacific is reconstructed from a suite of deep-sea cores and is compared to fluctuations in global ice volume inferred from delta18O records. The results are highlighted by: (1) a strong covariation between CaCO3 preservation and ice volume over 104 to 106 year time scales; (2) a long-term increase in ice volume and CaCO3 preservation since 3.9 Ma demonstrated by a deepening of the lysocline and the carbonate critical depth; (3) a dramatic shift to greater CaCO3 preservation at 2.9 Ma; (4) distinctive ice-volume growth and CaCO3 preservation events at 2.4...

  10. Calcium carbonate preservation in the equatorial Pacific

    Prell, Warren L; Farrell, John W
    The Pliocene-Pleistocene history of CaCO3 preservation in the central equatorial Pacific is reconstructed from a suite of deep-sea cores and is compared to fluctuations in global ice volume inferred from delta18O records. The results are highlighted by: (1) a strong covariation between CaCO3 preservation and ice volume over 104 to 106 year time scales; (2) a long-term increase in ice volume and CaCO3 preservation since 3.9 Ma demonstrated by a deepening of the lysocline and the carbonate critical depth; (3) a dramatic shift to greater CaCO3 preservation at 2.9 Ma; (4) distinctive ice-volume growth and CaCO3 preservation events at 2.4...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. Stable isotope ratios of foraminifera and sea surface temperature estimation of sediment core W2804A-14

    Jasper, John P; Hayes, John M; Mix, Alan C; Prahl, Frederick G
    Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C (epsilon p) in a central equatorial Pacific sediment core that spans the last ~255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic compostion of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region....

  16. Stable isotope ratios of foraminifera and sea surface temperature estimation of sediment core W2804A-14

    Jasper, John P; Hayes, John M; Mix, Alan C; Prahl, Frederick G
    Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C (epsilon p) in a central equatorial Pacific sediment core that spans the last ~255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic compostion of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region....

  17. Radiochemical analyses and contents of organic carbon and CaCO3 in equatorial Pacific Ocean sediments

    Yang, Yong-Liang; Elderfield, Henry; Ivanovich, Miro
    Uranium series nuclide concentrations have been measured on sediments from five box cores from an equatorial Pacific transect. 230Thexcess activities show discontinuities at the Holocene-glacial boundary as dated by 14C. The glacial sedimentation rates determined by 230Th and 14C are 2.5-3.0 cm/kyr. The Holocene rates from 230Th are much lower than those dated by 14C (1.9-2.3 cm/kyr) because of carbonate dissolution. 230Th sedimentation fluxes exceed water column supply by factors of 1.2-1.8 in the Holocene and 1.8-3.0 in the glacial sections. A number of models have been applied to calculate carbonate dissolution rates. The results show that carbonate dissolution rates...

  18. Radiochemical analyses and contents of organic carbon and CaCO3 in equatorial Pacific Ocean sediments

    Yang, Yong-Liang; Elderfield, Henry; Ivanovich, Miro
    Uranium series nuclide concentrations have been measured on sediments from five box cores from an equatorial Pacific transect. 230Thexcess activities show discontinuities at the Holocene-glacial boundary as dated by 14C. The glacial sedimentation rates determined by 230Th and 14C are 2.5-3.0 cm/kyr. The Holocene rates from 230Th are much lower than those dated by 14C (1.9-2.3 cm/kyr) because of carbonate dissolution. 230Th sedimentation fluxes exceed water column supply by factors of 1.2-1.8 in the Holocene and 1.8-3.0 in the glacial sections. A number of models have been applied to calculate carbonate dissolution rates. The results show that carbonate dissolution rates...

  19. 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...

  20. 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...

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