WorldWideScience

Sample records for equatorial pacific sediments

  1. Authigenic Uranium in Eastern Equatorial Pacific Sediments

    Science.gov (United States)

    Marcantonio, F.; Lyle, M. W.; Loveley, M. R.; Ibrahim, R.

    2014-12-01

    Authigenic U concentrations have been used as an indicator of redox state in marine sediments. Soluble U(VI) in porewaters is reduced to insoluble U(IV) under suboxic conditions setting up a diffusion gradient through which U in bottom waters is supplied to reducing sediments. Researchers have used sedimentary redox enrichment of U as a tool to identify past redox changes, which may be caused by changes in organic carbon rain rates and/or bottom water oxygen levels. Differentiating between these two explanations is important, as the former is tied to the use of authigenic U as a paleoproductivity proxy. We examined sediments from 4 sediment cores retrieved from two different localities in the Panama Basin in the eastern equatorial Pacific. Two cores were retrieved from the northern Panama basin at the Cocos Ridge, (4JC at 5° 44.7'N 85° 45.5' W, 1730 m depth; 8JC at 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the south at the Carnegie Ridge, (11JC at 0° 41.6'S 85° 20.0' W, 2452 m depth; 17JC at 0° 10.8'S 85° 52.0' W, 2846 m depth). Using 230Th systematics and seismic profiling at each of the sites, we've identified significant sediment winnowing (4JC and 11JC) and focusing (8JC and 17JC). At all sites, we believe that changes in age-model-derived sand (i.e., >63µm) mass accumulation rates (MAR) best represent changes in rain rates. Glacial rain rates are higher than those in the Holocene by a factor of 2-3 at both sites. Peak Mn levels (>1%), the brown-to-green color transition (which likely represents the oxic/post-oxic boundary), and peak U concentrations all appear in the same order with increasing depth down core. At the Carnegie sites, where MARs are greater than those at the Cocos sites, increases in authigenic U (up to 4 ppm) occur during the mid- to late Holocene at depths of 10-15 cm. At the Cocos sites, increases in authigenic U (up to 12 ppm) occur lower in the sediment column (25-30 cm) during the late glacial. The decrease

  2. Pacific Equatorial Transect

    OpenAIRE

    Pälike, Heiko; Nishi, Hiroshi; Lyle, Mitch; Raffi, Isabella; Klaus, Adam; Gamage, Kusali

    2009-01-01

    Integrated Ocean Drilling Program Expedition 320/321, "Pacific Equatorial Age Transect" (Sites U1331–U1338), was designed to recover a continuous Cenozoic record of the paleoequatorial Pacific by coring above the paleoposition of the Equator at successive crustal ages on the Pacific plate. These sediments record the evolution of the paleoequatorial climate system throughout the Cenozoic. As we gained more information about the past movement of plates and when in Earth's history "critical" cli...

  3. Deciphering Equatorial Pacific Deep Sea Sediment Transport Regimes by Core-Log-Seismic Integration

    Science.gov (United States)

    Ortiz, E.; Tominaga, M.; Marcantonio, F.

    2017-12-01

    Investigating deep-sea sediment transportation and deposition regimes is a key to accurately understand implications from geological information recorded by pelagic sediments, e.g. climate signals. However, except for physical oceanographic particle trap experiments, geochemical analyses of in situsediments, and theoretical modeling of the relation between the bottom currents and sediment particle flux, it has remained a challenging task to document the movement of deep sea sediments, that takes place over time. We utilized high-resolution, multichannel reflection seismic data from the eastern equatorial Pacific region with drilling and logging results from two Integrated Ocean Drilling Program (IODP) sites, the Pacific Equatorial Age Transect (PEAT) 7 (Site U1337) and 8 (Site U1338), to characterize sediment transportation regimes on 18-24 Ma oceanic crust. Site U1337, constructed by a series of distinct abyssal hills and abyssal basins; Site U1338, located 570 km SE from Site U1337 site and constructed by a series of ridges, seamounts, and abyssal hills. These sites are of particular interest due to their proximity to the equatorial productivity zone, areas with high sedimentation rates and preservation of carbonate-bearing sediment that provide invaluable insights on equatorial Pacific ecosystems and carbon cycle. We integrate downhole geophysical logging data as well as geochemistry and physical properties measurements on recovered cores from IODP Sites U1337 and U1338 to comprehensively examine the mobility of deep-sea sediments and sediment diagenesis over times in a quasi-3D manner. We also examine 1100 km of high resolution underway seismic surveys from site survey lines in between PEAT 7 and 8 in order to investigate changes in sediment transportation between both sites. Integrating detailed seismic interpretations, high resolution core data, and 230Th flux measurements we aim to create a detailed chronological sedimentation and sediment diagenesis history

  4. {sup 10}Be in rhodochrosite nodules from Neogene sediments along the Galapagos Ridge, equatorial Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Aldahan, A., E-mail: ala.aldahan@geo.uu.s [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); Department of Geology, United Arab Emirates University, Al Ain (United Arab Emirates); Morad, S. [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); Department of Petroleum Geosciences, Petroleum Institute, Abu Dhabi (United Arab Emirates); Possnert, G. [Tandem Laboratory, Uppsala University, Uppsala (Sweden); Sturesson, U. [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); ElSaiy, A. [Department of Geology, United Arab Emirates University, Al Ain (United Arab Emirates)

    2010-04-15

    Microcrystalline, calcian rhodochrosite occurs as nodules around burrows in late Neogene pelagic sediments from the Galapagos Ridge in the Guatemala Basin, eastern equatorial Pacific (DSDP Leg 68; Site 503). {sup 10}Be isotope revealed that the rhodochrosite nodules have formed under growth conditions much faster than those reported for Fe-Mn nodules. The overall REE patterns of the nodules and host pelagic sediments indicate element derivation mainly from marine pore water. However, variations in the shale normalised Eu values suggest influx of hydrothermal fluids into mounds area at Galapagos, which is also evidenced by the similar minor and major element contents in the nodules and host sediments.

  5. 10Be in rhodochrosite nodules from Neogene sediments along the Galapagos Ridge, equatorial Pacific

    International Nuclear Information System (INIS)

    Aldahan, A.; Morad, S.; Possnert, G.; Sturesson, U.; ElSaiy, A.

    2010-01-01

    Microcrystalline, calcian rhodochrosite occurs as nodules around burrows in late Neogene pelagic sediments from the Galapagos Ridge in the Guatemala Basin, eastern equatorial Pacific (DSDP Leg 68; Site 503). 10 Be isotope revealed that the rhodochrosite nodules have formed under growth conditions much faster than those reported for Fe-Mn nodules. The overall REE patterns of the nodules and host pelagic sediments indicate element derivation mainly from marine pore water. However, variations in the shale normalised Eu values suggest influx of hydrothermal fluids into mounds area at Galapagos, which is also evidenced by the similar minor and major element contents in the nodules and host sediments.

  6. Redox Conditions and Related Color Change in Eastern Equatorial Pacific Sediments: IODP Site U1334

    Science.gov (United States)

    Kordesch, W. E.; Gussone, N. C.; Hathorne, E. C.; Kimoto, K.; Delaney, M. L.

    2011-12-01

    This study was prompted by a 65 m thick brown-green color change in deep-sea sediments of IODP Site U1334 (0-38 Ma, 4799 m water depth) that corresponds to its equatorial crossing (caused by the Northward movement of the pacific plate). Green sediment is a visual indicator of reducing conditions in sediment due to enhanced organic matter deposition and burial. Here we use geochemical redox indicators to characterize the effect of equatorial upwelling on bottom water. The modern redox signal is captured in porewater profiles (nitrate, manganese, iron, sulfate) while trace metal Enrichment Factors (EF) in bulk sediment (manganese, uranium, molybdenum, rhenium) normalized to the detrital component (titanium) record redox state at burial. To measure export productivity we also measure biogenic barium. Porewater profiles reveal suboxic diagenesis; profiles follow the expected sequence of nitrate, manganese oxide, and iron oxide reduction with increasing depth. Constant sulfate (~28 μM) implies anoxia has not occurred. Bulk sediment Mn EF are enriched (EF > 1) throughout the record (Mn EF = 15-200) while U and Mo enrichment corresponds to green color and equatorial proximity (U EF = 4-19; Mo EF = 0-7). Constant Mn enrichment implies continuous oxygenation. Uranium and Mo enrichment near the equator represents suboxic conditions also seen in the porewater. Low Re concentrations (below detection) provide additional evidence against anoxia. A comparison of Mn EF from total digestions to samples treated with an additional reductive cleaning step distinguishes between Mn-oxides and Mn-carbonates, indicating oxygenated and reducing conditions respectively. Mn-carbonate occurrence agrees with U and Mo EF; conditions were more reducing near the equator. Bio-Ba shows significant variability over this interval (22-99 mmol g-1). Our geochemical results indicate that bottom waters became suboxic at the equator as a result of equatorial upwelling-influenced increases in organic

  7. Provenance and supply of Fe-enriched terrigenous sediments in the western equatorial Pacific and their relation to precipitation variations during the late Quaternary

    NARCIS (Netherlands)

    Wu, J.W.; Liu, Z.; Zhou, nn.

    2013-01-01

    Iron (Fe) deposition in the equatorial Pacific has important implications for the global carbon cycle, while the provenance of Fe supply and its change remain highly debated. Here, we geochemically characterize the provenance of terrigenous sediments deposited on the pathways of the Equatorial

  8. The chemistry and mineralogy of haloed burrows in pelagic sediment at DOMES Site A: The equatorial North Pacific

    Science.gov (United States)

    Piper, D.Z.; Rude, P.D.; Monteith, S.

    1987-01-01

    The chemical and mineralogical composition of burrowed sediment, recovered in 66 box cores at latitude 9??25???N and longitude 151??15???W in the equatorial Pacific, demonstrates the important role of infauna in determining the geochemistry of pelagic sediment. Haloed burrows, approximately 3 cm across, were present in many of the cores. Within early Tertiary sediment that was covered by less than 5 cm of surface Quaternary sediment in several cores, the burrows in cross-section consist of three units: (1) a dark yellowish-brown central zone of Quaternary sediment surrounded, by (2) a pale yellowish-orange zone (the halo) of Tertiary sediment, which is surrounded by (3) a metal-oxide precipitate; the enclosing Tertiary sediment is dusky brown. Several elements - Mn, Ni, Cu, Co, Zn, Sb and Ce - have been leached from the light-colored halo, whereas Cr, Cs, Hf, Rb, Sc, Ta, Th, U, the rare earth elements exclusive of Ce, and the major oxides have not been leached. The metal-oxide zone, 1-5 mm thick, contains as much as 16% MnO2, as the mineral todorokite. The composition of the todorokite, exclusive of the admixed Tertiary sediment, resembles the composition of the metal deficit of the halo and also the composition of surface ferromanganese nodules that have been interpreted as having a predominantly diagenetic origin. Thus bioturbation contributes not only to the redistribution of metals within pelagic sediment, but also to the accretion of ferromanganese nodules on the sea floor. ?? 1987.

  9. Amino acid and hexosamine in the equatorial western Pacific: vertical fluxes and individual preservation through water column to surface sediments

    Science.gov (United States)

    Kawahata, H.; Gupta, L. P.; Ishizuka, T.

    2002-12-01

    Amino acids (AA) and hexosamines (HA) are major constituents for all living organisms, constituting important fractions of labile organic carbon and nitrogen. They usually decompose rapidly than bulk OM and must be expected to be closely linked to biogeochemical processes. In spite of such importance, our understanding of degradation processes of labile components is still limited. Therefore vertical fluxes and preservation of AA and HA from water column to surface sediments are investigated at the western equatorial Pacific. The settling particles were composed of fairly fresh AA, which could be derived from siliceous diatom with less amount of calcareous plankton. In contrast, AA were degraded in sediments and porewaters. Each AA showed highly variable preservation ratio from settling to sedimentary particles. Compared with glycine, the calculated preservation ratio was the lowest (0%) for cysteine, followed by phenylalanine (6%), tyrosine (17%), methionine (47%), leucine (60%), isoleucine (65%), proline (67%), valine (91%), serine (99%), arginine (107%), threonine (112%), alanine (115%), glutamic acid (114%), aspartic acid (150%), lysine (166%) and histidine (186%). Beta-alanine and gamma-aminobutyric acid were the least labile AA. Probably they are so difficult to degrade for bacteria to get biochemical energy that the degradation proceeds fairly slowly. In contrast, after burial, even most labile, aromatic and sulfur-containing AA, degrade at a rate similar to the other protein AA. In spite of complicated reactions, most of the AA showed first-order reaction kinetics during the degradation in the sediments. The decomposition rate constant k (kyr-1) in this study was 2-3 orders lower than those in coastal marine environments. Better preservation of HA over AA in the sediments was probably due to the general incorporation of HA into structural biopolymer matrices, such as bacterial cell-walls and chitinous material. Abundant glycine in the AA in the sediments is

  10. Central Equatorial Pacific Experiment (CEPEX)

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-01

    The Earth's climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27[degree]C, but never 31[degree]C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  11. Fine scale distributions of porosity and particulate excess 210Pb, organic carbon and CaCO3 in surface sediments of the deep equatorial Pacific

    International Nuclear Information System (INIS)

    Jahnke, R.A.; Emerson, S.R.; Cochran, J.K.; Hirschberg, D.J.

    1986-01-01

    Sediment samples were recovered from the central equatorial Pacific Ocean, sectioned at 1-mm intervals, and analyzed for porosity, organic carbon, excess 210 Pb and CaCO 3 . Steep porosity gradients were measured in the upper 1 cm of the sediment column with extremely high values observed near the sediment surface. Similarly, particulate organic carbon contents are highest at the sediment surface, decrease sharply in the upper 1 cm, and are relatively constant between 1 and 5 cm. CaCO 3 values, on the other hand, are lowest at the sediment surface and increase to a constant value below 5-10 mm depth. At the carbonate ooze sites, excess 210 Pb is present throughout the upper 5 cm of the sediments suggesting relatively rapid particle mixing rates. However, extremely high excess 210 Pb activities (> 100 dpm/g) are observed at the sediment surface with sharp gradients present in the upper 1 cm which would suggest slow rates of mixing. This apparent contradiction along with the major features of the CaCO 3 and particulate organic carbon profiles can be explained by a particle-selective feeding mechanism in which organic carbon, excess 210 Pb-enriched particles are preferentially maintained at the sediment surface via ingestion and defecation by benthic organisms. (orig.)

  12. 10Be/230Th ratios as proxy for particle flux in the equatorial Pacific ocean

    International Nuclear Information System (INIS)

    Anderson, R.F.; Fleisher, M.Q.; Kubik, P.W.; Suter, M.

    1997-01-01

    Particulate 10 Be/ 230 Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs

  13. Weight Percentage of Calcium Carbonate for 17 Equatorial Pacific Cores from Brown University

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Weight percentages of calcium carbonate in this file were compiled by J. Farrell and W. L. Prell of Brown University for 17 equatorial Pacific Ocean sediment cores....

  14. Central Equatorial Pacific Experiment (CEPEX). Design document

    Energy Technology Data Exchange (ETDEWEB)

    1993-04-01

    The Earth`s climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27{degree}C, but never 31{degree}C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  15. {sup 10}Be/{sup 230}Th ratios as proxy for particle flux in the equatorial Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Fleisher, M.Q. [LDEO of Columbia Univ. (United States); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Particulate {sup 10}Be/{sup 230}Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs.

  16. Lagrangian mixed layer modeling of the western equatorial Pacific

    Science.gov (United States)

    Shinoda, Toshiaki; Lukas, Roger

    1995-01-01

    Processes that control the upper ocean thermohaline structure in the western equatorial Pacific are examined using a Lagrangian mixed layer model. The one-dimensional bulk mixed layer model of Garwood (1977) is integrated along the trajectories derived from a nonlinear 1 1/2 layer reduced gravity model forced with actual wind fields. The Global Precipitation Climatology Project (GPCP) data are used to estimate surface freshwater fluxes for the mixed layer model. The wind stress data which forced the 1 1/2 layer model are used for the mixed layer model. The model was run for the period 1987-1988. This simple model is able to simulate the isothermal layer below the mixed layer in the western Pacific warm pool and its variation. The subduction mechanism hypothesized by Lukas and Lindstrom (1991) is evident in the model results. During periods of strong South Equatorial Current, the warm and salty mixed layer waters in the central Pacific are subducted below the fresh shallow mixed layer in the western Pacific. However, this subduction mechanism is not evident when upwelling Rossby waves reach the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific due to episodes of strong wind and light precipitation associated with the El Nino-Southern Oscillation. Comparison of the results between the Lagrangian mixed layer model and a locally forced Eulerian mixed layer model indicated that horizontal advection of salty waters from the central Pacific strongly affects the upper ocean salinity variation in the western Pacific, and that this advection is necessary to maintain the upper ocean thermohaline structure in this region.

  17. Pacific Proving Grounds radioisotope imprint in the Philippine Sea sediments

    DEFF Research Database (Denmark)

    Pittauer, Daniela; Roos, Per; Qiao, Jixin

    2018-01-01

    Radionuclide concentrations were studied in sediment cores taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial Western Pacific. High resolution deposition records of anthropogenic radionuclides were collected at this site. Excess 210Pb together with excess 2...

  18. Deglacial Western Equatorial Pacific pCO2 Reconstruction Using Boron Isotopes of Planktonic Foraminiferas

    Science.gov (United States)

    Kubota, K.; Yokoyama, Y.; Ishikawa, T.; Sagawa, T.; Ikehara, M.; Yamazaki, T.

    2017-12-01

    During the last deglaciation (ca. 19 - 11 ka), partial pressure of CO2 (pCO2) of the atmosphere increased by 80 μatm. Many paleoceanographers point out that the ocean had played an important role in atmospheric CO2 rise, since the ocean have 60 times larger capacity to store carbon compared to the atmosphere. However, evidence on where carbon was transferred from the ocean to the atmosphere is still lacking, hampering our understanding of global carbon cycles in glacial-interglacial timescales. Boron isotope of skeletons of marine calcifying organisms such as corals and foraminiferas can pin down where CO2 source/sink existed, because boron isotopes of marine calcium carbonates is dependent on seawater pH, from which pCO2 of the past seawater can be reconstructed. In previous studies using the boron isotope teqnique, Martinez-Boti et al. (2015, Nature) and Kubota et al. (2014, Scientific Reports) revealed that central and eastern parts of the equatorial Pacific acted as a CO2 source (i.e., CO2 emission) during the last deglaciation, suggesting the equatorial Pacific's contribution to atmospheric CO2 rise. However, some conflicting results have been confirmed in a marine sediment record from the western part of the equatorial Pacific (Palmer & Pearson, 2003, Science), making the conclusion elusive. In this presentation, we will show new results of Mg/Ca, oxygen isotope, and boron isotope measurements during the last 35 ka on two species of surface dwelling foraminiferas (Globigerinoides ruber and G. sacculifer) which was hand-picked separatedly from a well-dated marine sediment core recovered from the West Caroline Basin (KR05-15 PC01) (Yamazaki et al., 2008, GRL). From the new records, we will discuss how the equatorial Pacific behaved during the last deglaciation and how it related to the global carbon cycles.

  19. Dissolution of biogenic ooze over basement edifices in the equatorial Pacific with implications for hydrothermal ventilation of the oceanic crust

    Science.gov (United States)

    Bekins, B.A.; Spivack, A.J.; Davis, E.E.; Mayer, L.A.

    2007-01-01

    Recent observations indicate that curious closed depressions in carbonate sediments overlying basement edifices are widespread in the equatorial Pacific. A possible mechanism for their creation is dissolution by fluids exiting basement vents from off-axis hydrothermal flow. Quantitative analysis based on the retrograde solubility of calcium carbonate and cooling of basement fluids during ascent provides an estimate for the dissolution capacity of the venting fluids. Comparison of the dissolution capacity and fluid flux with typical equatorial Pacific carbonate mass accumulation rates shows that this mechanism is feasible. By maintaining sediment-free basement outcrops, the process may promote widespread circulation of relatively unaltered seawater in the basement in an area where average sediment thicknesses are 300-500 m. The enhanced ventilation can explain several previously puzzling observations in this region, including anomalously low heat flux, relatively unaltered seawater in the basement, and aerobic and nitrate-reducing microbial activity at the base of the sediments. ?? 2007 The Geological Society of America.

  20. Upper ocean circulation modulation by phytoplankton concentration in the Equatorial Pacific and the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Sammarco, P.; Muneyama, K.; Sato, T.; AjoyKumar, A.; Frouin, R.

    gradient in the upper ocean. This strengthens the geostrophically balanced westward currents in both side of the equatorial wave-guide (within 5 degree bands). Once these currents reach the western Pacific coast, they feed the Equatorial undercurrent (EUC...

  1. Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years

    OpenAIRE

    Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco

    2016-01-01

    Biological productivity in the equatorial Pacific is relatively high compared with other low latitude regimes especially east of the dateline where divergence driven by the trade winds brings nutrient rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high nutrient low chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited in part by the availability of iron. Throughout most of the equatorial Paci...

  2. Variability in the origins and pathways of Pacific Equatorial Undercurrent water

    NARCIS (Netherlands)

    Qin, Xuerong; Sen Gupta, Alex; Van Sebille, Erik

    2015-01-01

    The Pacific Equatorial Undercurrent (EUC) transports water originating from a number of distinct source regions, eastward across the Pacific Ocean. It is responsible for supplying nutrients to the productive eastern Equatorial Pacific Ocean. Of particular importance is the transport of iron by the

  3. Regulation of primary productivity rate in the equatorial Pacific

    International Nuclear Information System (INIS)

    Barber, R.T.; Chavez, F.P.

    1991-01-01

    Analysis of the Chl-specific rate of primary productivity (P B ) as a function of subsurface nutrient concentration at >300 equatorial stations provides an answer to the question: What processes regulate primary productivity rate in the high-nutrient, low-chlorophyll waters of the equatorial Pacific? In the western Pacific where there is a gradient in 60-m [NO 3 ] from 0 to ∼12 μM, the productivity rate is a linear function of nutrient concentration; in the eastern Pacific where the gradient is from 12 to 28 μM, the productivity rate is independent of nutrient concentration and limited to ∼36 mg C(mg Chl) -1 d -1 , or a mean euphotic zone C-specific growth rate (μ) of 0.47 d -1 . However, rates downstream of the Galapagos Islands are not limited; they are 46.4 mg C(mg Chl) -1 d -1 and μ = 0.57 d -1 , very close to the predicted nutrient-regulated rates in the absence of other limitation. This pattern of rate regulation can be accounted for by a combination of eolian Fe, subsurface nutrients, and sedimentary Fe derived from the Galapagos platform. In the low-nutrient western Pacific the eolian supply of Fe is adequate to allow productivity rate to be set by subsurface nutrient concentration. In the nutrient-rich easter equatorial region eolian Fe is inadequate to support productivity rates proportional to the higher nutrient concentrations, so in this region eolian Fe is rate limiting. Around the Galapagos Islands productivity rates reach levels consistent with nutrient concentrations; sedimentary Fe from the Galapagos platform seems adequate to support increased nutrient-regulated productivity rates in this region

  4. The Pacific Equatorial Age Transect, IODP Expeditions 320 and 321: Building a 50-Million-Year-Long Environmental Record of the Equatorial Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Kusali Gamage

    2010-04-01

    Full Text Available In March 2009, the R/V JOIDES Resolution returned to operations after its extended refit and began with a drilling program ideally suited to its drilling strengths, the Pacific Equatorial Age Transect (PEAT, IODP Exp 320/321; Fig. 1A. The PEAT drilling program was developed to understand how a major oceanic region evolved over the Cenozoic Era(65–0 Ma and how it interacted with global climate. It specifically targeted the interval between 52 Ma and 0 Ma and drilled a series of sites that originated on the paleoequator. These sites have since been moved to the northwest by plate tectonics.The equatorial Pacific is an important target for paleocean ographic study because it is a significant ‘cog’ in the Earth’s climate machine, representing roughly half of the total tropical oceans that in turn represent roughly half of the total global ocean area. Prior drilling in both the Deep Sea Drilling Project (DSDP and the Ocean Drilling Program (ODP outlined the changes that have occurred through the Cenozoic (e.g., van Andel et al., 1975; Pisias et al., 1995. Not only did the earlier work fail to cover sufficient timeintervals but also many of the sites were cored with ‘first-generation’ scientific drilling technology with incomplete and disturbed sediment recovery and thus cannot be used for detailed studies.

  5. Sediment Evaluation Framework for the Pacific Northwest

    Science.gov (United States)

    The Sediment Evaluation Framework provides a regional framework for assessment, characterization and management of sediments in the Pacific Northwest to determine suitability for unconfined in-water disposal.

  6. Millennial-scale iron fertilization of the eastern equatorial Pacific over the past 100,000 years

    Science.gov (United States)

    Loveley, Matthew R.; Marcantonio, Franco; Wisler, Marilyn M.; Hertzberg, Jennifer E.; Schmidt, Matthew W.; Lyle, Mitchell

    2017-10-01

    The eastern equatorial Pacific Ocean plays a crucial role in global climate, as it is a substantial source of CO2 to the atmosphere and accounts for a significant portion of global new export productivity. Here we present a 100,000-year sediment core from the eastern equatorial Pacific, and reconstruct dust flux, export productivity and bottom-water oxygenation using excess-230Th-derived fluxes of 232Th and barium, and authigenic uranium concentrations, respectively. We find that during the last glacial period (71,000 to 41,000 years ago), increased delivery of dust to the eastern equatorial Pacific was coeval with North Atlantic Heinrich stadial events. Millennial-scale pulses of increased dust flux coincided with episodes of heightened biological productivity, suggesting that dissolution of dust released iron that promoted ocean fertilization. We also find that periods of low atmospheric CO2 concentrations were associated with suboxic conditions and increased storage of respired carbon in the deep eastern equatorial Pacific. Increases in CO2 concentrations during the deglaciation are coincident with increases in deep Pacific and Southern Ocean water oxygenation levels. We suggest that deep-ocean ventilation was a primary control on CO2 outgassing in this region, with superimposed pulses of high productivity providing a negative feedback.

  7. Neutral carbohydrate geochemistry of particulate material in the central equatorial Pacific

    Science.gov (United States)

    Hernes, Peter J.; Hedges, John I.; Peterson, Michael L.; Wakeham, Stuart G.; Lee, Cindy

    Neutral carbohydrate compositions were determined for particulate samples from plankton net tows, shallow floating sediment traps, mid-depth and deep moored sediment traps, and sediment cores collected along a north-south transect in the central equatorial Pacific Ocean during the U.S. JGOFS EqPac program. Total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon (OC) fluxes—attenuating with depth, high near the equator and decreasing poleward. OC-normalized total aldose (TCH 2,O) yields along the transect and with depth do not show any consitent patterns. Relative to a planktonic source, neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose, and preferential preservation of structural carbohydrates rich in rhamnose, xylose, fucose, and mannose. There is also evidence for an intermediately labile component rich in galactose. It appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway. Relative to other types of organic matter, neutral carbohydrates are better preserved in calcareous oozes from 12°S to 5°N than in red clays at 9°N based on OC-normalized TCH 2O yields, due to either differing sources or sorption characteristics. Weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial Pacific region. Based on weight per cent glucose, comparisons of samples between Survey I (El Niõn) and Survey II (non-El Niño) indicate that during Survey I, organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere.

  8. Is the core top modern? Observations from the eastern equatorial Pacific

    Science.gov (United States)

    Mekik, Figen; Anderson, Robert

    2018-04-01

    A compilation of ages from 67 core tops in the eastern equatorial Pacific (EEP) does not display an easily discernible regional pattern. The ages range from 790 to over 15,000 years. The youngest core tops with the highest sediment focusing factors are located in the Panama Basin. There are weak but statistically significant inverse relationships between core top age and age-model based mass accumulation rates, bioturbation depth, linear sedimentation rate and sediment focusing factors. However, we found no statistically significant relationship between core top age and calcite dissolution in sediments or 230Th-normalized mass accumulation rates. We found evidence suggesting that greater amount of sediment focusing helps to preserve the carbonate fraction of the sediment where focusing is taking place. When focusing factors are plotted against percent calcite dissolved, we observe a strong inverse relationship, and core tops younger than 4500 years tend to occur where focusing factors are high and percent calcite dissolved values are low. Using labile organic carbon fluxes to estimate bioturbation depth in the sediments results in the observation that where bioturbation depth is shallow (<4 cm), the core top age has a strong, inverse relationship with sediment accumulation rate. We used the Globorotalia menardii Fragmentation Index (MFI) as an indicator of percent calcite dissolved in deep sea sediments. There is a distinct pattern to core top calcite dissolution in the EEP which delineates bands of high surface ocean productivity as well as the clear increase in dissolution downward on the flanks of the East Pacific Rise.

  9. Biological, physical, nutrients, sediment, and other data from sediment sampler-grab, bottle, and CTD casts in the Arabian Sea, Equatorial Pacific Ocean, Northeast Atlantic Ocean, and Southern Oceans as part of the Long Term Monitoring East-West Flower Garden Banks project from 08 January 1995 to 08 April 1998 (NODC Accession 0001155)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Biological, physical, nutrients, sediment, and other data were collected using sediment sampler-grab, bottle and CTD casts in the Arabian Sea, North/South Pacific...

  10. Biogeochemical impact of a model western iron source in the Pacific Equatorial Undercurrent

    OpenAIRE

    Slemons, L.; Gorgues, T.; Aumont, Olivier; Menkès, Christophe; Murray, J. W.

    2009-01-01

    Trace element distributions in the source waters of the Pacific Equatorial Undercurrent (EUC) show the existence of elevated total acid-soluble iron concentrations. This region has been suggested to contribute enough bioavailable iron to regulate interannual and interglacial variability in biological productivity downstream in the high-nitrate low-chlorophyll upwelling zone of the eastern equatorial Pacific. We investigated the advection and first-order biogeochemical impact of an imposed, da...

  11. A Cenozoic record of the equatorial Pacific carbonate compensation depth.

    Science.gov (United States)

    Pälike, Heiko; Lyle, Mitchell W; Nishi, Hiroshi; Raffi, Isabella; Ridgwell, Andy; Gamage, Kusali; Klaus, Adam; Acton, Gary; Anderson, Louise; Backman, Jan; Baldauf, Jack; Beltran, Catherine; Bohaty, Steven M; Bown, Paul; Busch, William; Channell, Jim E T; Chun, Cecily O J; Delaney, Margaret; Dewangan, Pawan; Dunkley Jones, Tom; Edgar, Kirsty M; Evans, Helen; Fitch, Peter; Foster, Gavin L; Gussone, Nikolaus; Hasegawa, Hitoshi; Hathorne, Ed C; Hayashi, Hiroki; Herrle, Jens O; Holbourn, Ann; Hovan, Steve; Hyeong, Kiseong; Iijima, Koichi; Ito, Takashi; Kamikuri, Shin-ichi; Kimoto, Katsunori; Kuroda, Junichiro; Leon-Rodriguez, Lizette; Malinverno, Alberto; Moore, Ted C; Murphy, Brandon H; Murphy, Daniel P; Nakamura, Hideto; Ogane, Kaoru; Ohneiser, Christian; Richter, Carl; Robinson, Rebecca; Rohling, Eelco J; Romero, Oscar; Sawada, Ken; Scher, Howie; Schneider, Leah; Sluijs, Appy; Takata, Hiroyuki; Tian, Jun; Tsujimoto, Akira; Wade, Bridget S; Westerhold, Thomas; Wilkens, Roy; Williams, Trevor; Wilson, Paul A; Yamamoto, Yuhji; Yamamoto, Shinya; Yamazaki, Toshitsugu; Zeebe, Richard E

    2012-08-30

    Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

  12. Uranium in Pacific deep-sea sediments and manganese nodules

    International Nuclear Information System (INIS)

    Kunzendorf, H.; Plueger, W.L.; Friedrich, G.H.

    1983-01-01

    A total of 1344 manganese nodules and 187 pelagic sediments from 9 areas in the North and the South Pacific were analyzed for U by the delayed-neutron counting technique. A strong positive correlation between U and Fe in nodules and sediments suggests a co-precipitative removal from sea water into the Fe-rich (ferromanganese mineral phase MnO 2 . Enrichment of U and Fe in nodules from the northwestern slopes of two submarine hills (U between 6 and 9 ppm) in the equatorial nodule belt is thought to be caused by directional bottom water flow creating elevated oxygenized conditions in areas opposed to the flow. Economically important nodule deposits from the nodule belt and the Peru Basin have generally low U contents, between 3 and 5 ppm. Insignificant resources of U of about 4 x 10 5 in the Pacific manganese nodules are estimated. (orig.)

  13. Fatty acids in sediments and phytoplankton data were collected from the Equatorial Pacific Ocean as part of the Joint Global Ocean Flux Study/Equatorial Pacific Basin Study (JGOFS/EQPAC) project., from 1992-02-03 to 1992-12-13 (NODC Accession 9700180)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fatty acids in sediments and phytoplankton data were collected using plankton tow, sediments sampler - corer, pump and CTD casts from the R/V THOMAS THOMPSON in the...

  14. Ocean Color and the Equatorial Annual Cycle in the Pacific

    Science.gov (United States)

    Hammann, A. C.; Gnanadesikan, A.

    2012-12-01

    The presence of chlorophyll, colored dissolved organic matter (CDOM) and other scatterers in ocean surface waters affect the flux divergence of solar radiation and thus the vertical distribution of radiant heating of the ocean. While this may directly alter the local mixed-layer depth and temperature (Martin 1985; Strutton & Chavez 2004), non-local changes are propagated through advection (Manizza et al. 2005; Murtugudde et al. 2002; Nakamoto et al. 2001; Sweeny et al. 2005). In and coupled feedbacks (Lengaigne et al. 2007; Marzeion & Timmermann 2005). Anderson et al. (2007), Anderson et al. (2009) and Gnanadesikan & Anderson (2009) have performed a series of experiments with a fully coupled climate model which parameterizes the e-folding depth of solar irradiance in terms of surface chlorophyll-a concentration. The results have so far been discussed with respect to the climatic mean state and ENSO variability in the tropical Pacific. We extend the discussion here to the Pacific equatorial annual cycle. The focus of the coupled experiments has been the sensitivity of the coupled system to regional differences in chlorophyll concentration. While runs have been completed with realistic SeaWiFS-derived monthly composite chlorophyll ('green') and with a globally chlorophyll-free ocean ('blue'), the concentrations in two additional runs have been selectively set to zero in specific regions: the oligotrophic subtropical gyres ('gyre') in one case and the mesotrophic gyre margins ('margin') in the other. The annual cycle of ocean temperatures exhibits distinctly reduced amplitudes in the 'blue' and 'margin' experiments, and a slight reduction in 'gyre' (while ENSO variability almost vanishes in 'blue' and 'gyre', but amplifies in 'margin' - thus the frequently quoted inverse correlation between ENSO and annual amplitudes holds only for the 'green' / 'margin' comparison). It is well-known that on annual time scales, the anomalous divergence of surface currents and vertical

  15. Sensitivity of equatorial Pacific and Indian Ocean watermasses to the position of the Indonesian Throughflow

    Science.gov (United States)

    Rodgers, Keith B.; Latif, Mojib; Legutke, Stephanie

    2000-09-01

    The sensitivity of the thermal structure of the equatorial Pacific and Indian Ocean pycnoclines to a model's representation of the Indonesian Straits connecting the two basins is investigated. Two integrations are performed using the global HOPE ocean model. The initial conditions and surface forcing for both cases are identical; the only difference between the runs is that one has an opening for the Indonesian Straits which spans the equator on the Pacific side, and the other has an opening which lies fully north of the equator. The resulting sensitivity throughout much of the upper ocean is greater than 0.5°C for both the equatorial Indian and Pacific. A realistic simulation of net Indonesian Throughflow (ITF) transport (measured in Sverdrups) is not sufficient for an adequate simulation of equatorial watermasses. The ITF must also contain a realistic admixture of northern and southern Pacific source water.

  16. No iron fertilization in the equatorial Pacific Ocean during the last ice age.

    Science.gov (United States)

    Costa, K M; McManus, J F; Anderson, R F; Ren, H; Sigman, D M; Winckler, G; Fleisher, M Q; Marcantonio, F; Ravelo, A C

    2016-01-28

    The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron. Greater atmospheric dust deposition could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain. Here we present meridional transects of dust (derived from the (232)Th proxy), phytoplankton productivity (using opal, (231)Pa/(230)Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ(15)N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region. Thus, ice-age iron fertilization in the

  17. Oligocene-Miocene magnetic stratigraphy carried by biogenic magnetite at sites U1334 and U1335 (equatorial Pacific Ocean)

    Science.gov (United States)

    Channell, J. E. T.; Ohneiser, C.; Yamamoto, Y.; Kesler, M. S.

    2013-02-01

    AbstractSediments from the equatorial Pacific Ocean, at the Integrated Ocean Drilling Program sites U1334 and U1335, record reliable magnetic polarity stratigraphies back to ~26.5 Ma (late Oligocene) at sedimentation rates usually in the 5-20 m/Myr range. Putative polarity subchrons that do not appear in current polarity timescales occur within Chrons C5ACr, C5ADn, and C5Bn.1r at Site U1335; and within Chrons C6AAr.2r, C6Br, C7Ar, and C8n.1n at Site U1334. Subchron C5Dr.1n (~17.5 Ma) is recorded at both sites, supporting its apparent recording in the South Atlantic Ocean, and has an estimated duration of ~40 kyr. The Oligocene-Miocene calcareous oozes have magnetizations carried by submicron magnetite, as indicated by thermal demagnetization of magnetic remanences, the anhysteretic remanence to susceptibility ratio, and magnetic hysteresis parameters. Transmission electron microscopy of magnetic separates indicates the presence of low-titanium iron oxide (magnetite) grains with size (50-100 nm) and shape similar to modern and fossil bacterial magnetite, supporting other evidence that biogenic submicron magnetite is the principal remanence carrier in these sediments. In the equatorial Pacific Ocean, low organic-carbon burial arrests microbial pore-water sulfate reduction, thereby aiding preservation of bacterial magnetite.

  18. The role of the Indonesian Throughflow in equatorial Pacific thermocline ventilation

    Science.gov (United States)

    Rodgers, Keith B.; Cane, Mark A.; Naik, Naomi H.; Schrag, Daniel P.

    1999-09-01

    The role of the Indonesian Throughflow (ITF) in the thermocline circulation of the low-latitude Pacific Ocean is explored using a high-resolution primitive equation ocean circulation model. Seasonally forced runs for a domain with an open Indonesian passage are compared with seasonally forced runs for a closed Pacific domain. Three cases are considered: one with no throughflow, one with 10 Sv of imposed ITF transport, and one with 20 Sv of ITF transport. Two idealized tracers, one that tags northern component subtropical water and another that tags southern component subtropical water, are used to diagnose the mixing ratio of northern and southern component waters in the equatorial thermocline. It is found that the mixing ratio of north/south component waters in the equatorial thermocline is highly sensitive to whether the model accounts for an ITF. Without an ITF, the source of equatorial undercurrent water is primarily of North Pacific origin, with the ratio of northern to southern component water being approximately 2.75 to 1. The ratio of northern to southern component water in the Equatorial Undercurrent with 10 Sv of ITF is approximately 1.4 to 1, and the ratio with 20 Sv of imposed ITF is 1 to 1.25. Estimates from data suggest a mean mixing ratio of northern to southern component water of less than 1 to 1. Assuming that the mixing ratio changes approximately linearly as the ITF transport varies between 10 and 20 Sv, an approximate balance between northern and southern component water is reached when the ITF transport is approximately 16 Sv. It is also shown that for the isopycnal surfaces within the core of the equatorial undercurrent, a 2°C temperature front exists across the equator in the western equatorial Pacific, beneath the warm pool. The implications of the model results and the temperature data for the heat budget of the equatorial Pacific are considered.

  19. Anthropogenic 236U recorded in annually banded coral skeleton at Majuro atoll, the equatorial Pacific

    International Nuclear Information System (INIS)

    Sakaguchi, Aya; Eto, Asuka; Takahashi, Yoshio; Steier, Peter; Yamazaki, Atsuko; Watanabe, Tsuyoshi; Sasaki, Keiichi; Yamano, Hiroya

    2013-01-01

    Historical 236 U/ 238 U atom ratio and concentration of 236 U were determined by Accelerator Mass Spectrometry (AMS) in skeletons of dated modern coral core sample collected from Majuro atoll, equatorial Pacific, to reconstruct anthropogenic 236 U inputs to the Equatorial Pacific. The maximum hydrogen bomb-pulses of 236 U/ 238 U and 236 U concentration, 2.83x10 -9 and 1.85x10 7 atom/g, in an annually resolved coral core were captured in 1954 (Operation Castle at Bikini and Enewetok atolls). The values were abruptly decreased in a few years, and they have been gradually decreased over time. Our results allow studies of not only the present distribution pattern, but gives access to the temporal evolution of 236 U in surface seawater of North Equatorial Current which is introduced to the Japan Sea and the North West Pacific Ocean as Kuroshio and Tsushima currents over the past decades. (author)

  20. Bacterial Diversity in Deep-Sea Sediments from Afanasy Nikitin Seamount, Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, R.; Meena, R.M.; Deobagkar, D.D.

    Deep-sea sediments can reveal much about the last 200 million years of Earth history, including the history of ocean life and climate. Microbial diversity in Afanasy Nikitin seamount located at Equatorial East Indian Ocean (EEIO) was investigated...

  1. Iron sources and pathways into the Pacific Equatorial Undercurrent

    NARCIS (Netherlands)

    Qin, Xuerong; Menviel, Laurie; Sen Gupta, Alex; van Sebille, Erik

    2016-01-01

    Using a novel observationally constrained Lagrangian iron model forced by outputs from an eddy-resolving biogeochemical ocean model, we examine the sensitivity of the Equatorial Undercurrent (EUC) iron distribution to EUC source region iron concentrations. We find that elevated iron concentrations

  2. Larger CO2 source at the equatorial Pacific during the last deglaciation

    Science.gov (United States)

    Kubota, Kaoru; Yokoyama, Yusuke; Ishikawa, Tsuyoshi; Obrochta, Stephen; Suzuki, Atsushi

    2014-01-01

    While biogeochemical and physical processes in the Southern Ocean are thought to be central to atmospheric CO2 rise during the last deglaciation, the role of the equatorial Pacific, where the largest CO2 source exists at present, remains largely unconstrained. Here we present seawater pH and pCO2 variations from fossil Porites corals in the mid equatorial Pacific offshore Tahiti based on a newly calibrated boron isotope paleo-pH proxy. Our new data, together with recalibrated existing data, indicate that a significant pCO2 increase (pH decrease), accompanied by anomalously large marine 14C reservoir ages, occurred following not only the Younger Dryas, but also Heinrich Stadial 1. These findings indicate an expanded zone of equatorial upwelling and resultant CO2 emission, which may be derived from higher subsurface dissolved inorganic carbon concentration. PMID:24918354

  3. Surface temperature of the equatorial Pacific Ocean and the Indian rainfall

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    The time variation of the monthly mean surface temperature of the equatorial Pacific Ocean during 1982-1987 has been studied in relation to summer monsoon rainfall over India The ENSO events of 1982 and 1987 were related to a significant reduction...

  4. Estimates of Eastern Equatorial Pacific Sea Surface Temperatures During the Pliocene From Carbonate 'Clumped Isotope' Thermometry

    Science.gov (United States)

    Thiagarajan, N.; Tripati, A.; Eiler, J.

    2007-12-01

    The early Pliocene (5 to 3 Ma) was an interval in Earth history that was globally warmer than the present; thus, study of the details of Pliocene climate can provide insights into the dynamics of warm climates. There are two competing models of the temperature structure of the tropical Pacific upper-ocean during the early Pliocene: the dynamical 'ocean thermostat' model [1,2] and the 'El Padre' (or permanent 'El Nino') model [3], each of which predict zonal temperature gradients and mean conditions in the Eastern Equatorial Pacific (EEP), and which differ markedly from one another in these predictions. The dynamical 'ocean thermostat' model predicts an increased temperature contrast between the Western Equatorial Pacific (WEP) and EEP, enhanced thermocline tilt and intensified upwelling under warmer conditions. In contrast, the 'El Padre' model postulates a collapse of the zonal temperature gradient, reduced thermocline tilt and a reduction in upwelling and/or warmer temperatures of upwelled waters. Existing reconstructions of tropical temperatures produce WEP sea surface temperatures which agree with each other, but yield very different results in the EEP [4,5]. We have reconstructed EEP sea surface temperatures at Ocean Drilling Program (ODP) Site 847 using a few samples spanning key intervals of the last 6 million years using carbonate clumped isotope thermometer [6,7,8]. This technique is based on the temperature dependence of the abundances of 13C-18O bonds in carbonate minerals. Initial measurements of planktonic foraminifera and coccoliths from ODP Site 847 indicate cool EEP sea surface temperatures, supporting models of Pliocene climate that have enhanced zonal temperature gradients, relative to modern. Analyses of Globigerinoides sacculifer (with sac) from sediments indicate calcification temperatures of 20.3°C ± 0.1°C and seawater δ18O values of -0.8‰ ± 0.1‰ from ~6.1 to 5.1 million years ago. Measurements of a mixed coccolith assemblage from the

  5. The Pleistocene Eastern Equatorial Pacific: Insights from a New Carnegie Platform Stratigraphic Record

    Science.gov (United States)

    Gwizd, S.; Lea, D. W.

    2016-12-01

    Renewed interest in a classic Eastern Equatorial Pacific paleoceanographic site at 3° 35.85' S, 83° 57.79' W, previous site of cores V19-29 and TR163-31, prompted a re-coring in 2009 using the recently developed CDH giant piston coring system on cruise KNR195-5. Giant piston core CDH-36 (3225 m depth, 42.61 m length) nearly triples the length of previous cores at this site. When spliced together with companion multicore MC-34A (0.36 m length), these two cores generate continuous stratigraphy throughout most of the middle Pleistocene, and include recognized stratigraphic tie points ash layer "L" (Ninkovich and Shackleton, 1975) and the extinction of pink G. ruber. A new age model utilizing Bayesian analysis of 17 N. dutertrei radiocarbon dates in MC-34A and the top 3.4 m of CDH-36, and alignment of a new CDH-36 δ18O record with the LR04 benthic stack (Lisiecki and Raymo, 2005), demonstrates that this new "Carnegie Platform" (CP) record extends from 0 to 720 ka (MIS 18), tripling the timescale of previous studies, with an average sedimentation rate of 7 cm/kyr. The CP C. wuellerstorfi δ18O and δ13C records reveal strong consistencies in timing and extent of glacial and interglacial episodes with previously studied regional records. Coarse fraction percentage (%CF) ([coarse fraction/bulk dry sample] * 100) is also evaluated throughout the CP core in order to qualitatively assess dissolution cycles. The CP %CF dataset primarily records Pleistocene dissolution cycles, yet exhibits variability representative of potential local bathymetric and hydrographic effects. The timing of %CF cyclicity is consistent with processes which affect basin-wide calcium carbonate dissolution cycles, including changes in terrestrial carbon input to the oceans and changes in water mass ventilation (Shackleton, 1977; Toggweiler et al., 2006; Sexton and Barker, 2012). Establishing the stratigraphy of the CP record provides the first step towards a more thorough and extended analysis of

  6. Mid-Pliocene equatorial Pacific sea surface temperature reconstruction: a multi-proxy perspective

    Science.gov (United States)

    Dowsett, Harry J.; Robinson, Marci M.

    2009-01-01

    The Mid-Pliocene is the most recent interval of sustained global warmth, which can be used to examine conditions predicted for the near future. An accurate spatial representation of the low-latitude Mid-Pliocene Pacific surface ocean is necessary to understand past climate change in the light of forecasts of future change. Mid-Pliocene sea surface temperature (SST) anomalies show a strong contrast between the western equatorial Pacific (WEP) and eastern equatorial Pacific (EEP) regardless of proxy (faunal, alkenone and Mg/Ca). All WEP sites show small differences from modern mean annual temperature, but all EEP sites show significant positive deviation from present-day temperatures by as much as 4.4°C. Our reconstruction reflects SSTs similar to modern in the WEP, warmer than modern in the EEP and eastward extension of the WEP warm pool. The east-west equatorial Pacific SST gradient is decreased, but the pole to equator gradient does not change appreciably. We find it improbable that increased greenhouse gases (GHG) alone would cause such a heterogeneous warming and more likely that the cause of Mid-Pliocene warmth is a combination of several forcings including both increased meridional heat transport and increased GHG.

  7. Repeated Storage of Respired Carbon in the Equatorial Pacific Ocean Over the Last Three Glacial Cycles

    Science.gov (United States)

    Jacobel, A. W.; McManus, J. F.; Anderson, R. F.; Winckler, G.

    2017-12-01

    As the largest reservoir of carbon actively exchanging with the atmosphere on glacial-interglacial timescales, the deep ocean has been implicated as the likely location of carbon dioxide sequestration during Pleistocene glaciations. Despite strong theoretical underpinnings for this expectation, it has been challenging to identify unequivocal evidence for respired carbon storage in the paleoceanographic record. Data on the rate of ocean ventilation derived from paired planktonic-benthic foraminifera radiocarbon ages conflict across the equatorial Pacific, and different proxy reconstructions contradict one another about the depth and origin of the watermass containing the respired carbon. Because any change in the storage of respiratory carbon must be accompanied by corresponding changes in dissolved oxygen concentrations, proxy data reflecting bottom water oxygenation are of value in addressing these apparent inconsistencies. We present new records of the redox sensitive metal uranium from the central equatorial Pacific to qualitatively identify intervals associated with respiratory carbon storage over the past 350 kyr. Our data reveal periods of deep ocean authigenic uranium deposition in association with each of the last three glacial maxima. Equatorial Pacific export productivity data show intervals with abundant authigenic uranium are not associated with local productivity increases, indicating episodic precipitation of authigenic uranium does not directly reflect increases in situ microbial respiration, but rather occurs in response to basin-wide decreases in deep water oxygen concentrations. We combine our new data with previously published results to propose a picture of glacial carbon storage and equatorial Pacific watermass structure that is internally consistent. We conclude that respired carbon storage in the Pacific was a persistent feature of Pleistocene glaciations.

  8. Response of the equatorial Pacific to chlorophyll pigment in a mixed layer isopycnal ocean general circulation model

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Ishizaka, J.; Muneyama, K.; Frouin, R.

    The influence of phytoplankton on the upper ocean dynamics and thermodynamics in the equatorial Pacific is investigated using an isopycnal ocean general circulation model (OPYC) coupled with a mixed layer model and remotely sensed chlorophyll...

  9. Recycled iron fuels new production in the eastern equatorial Pacific Ocean.

    Science.gov (United States)

    Rafter, Patrick A; Sigman, Daniel M; Mackey, Katherine R M

    2017-10-24

    Nitrate persists in eastern equatorial Pacific surface waters because phytoplankton growth fueled by nitrate (new production) is limited by iron. Nitrate isotope measurements provide a new constraint on the controls of surface nitrate concentration in this region and allow us to quantify the degree and temporal variability of nitrate consumption. Here we show that nitrate consumption in these waters cannot be fueled solely by the external supply of iron to these waters, which occurs by upwelling and dust deposition. Rather, a substantial fraction of nitrate consumption must be supported by the recycling of iron within surface waters. Given plausible iron recycling rates, seasonal variability in nitrate concentration on and off the equator can be explained by upwelling rate, with slower upwelling allowing for more cycles of iron regeneration and uptake. The efficiency of iron recycling in the equatorial Pacific implies the evolution of ecosystem-level mechanisms for retaining iron in surface ocean settings where it limits productivity.

  10. Large-scale shifts in phytoplankton groups in the Equatorial Pacific during ENSO cycles

    Directory of Open Access Journals (Sweden)

    I. Masotti

    2011-03-01

    Full Text Available The El Niño Southern Oscillation (ENSO drives important changes in the marine productivity of the Equatorial Pacific, in particular during major El Niño/La Niña transitions. Changes in environmental conditions associated with these climatic events also likely impact phytoplankton composition. In this work, the distribution of four major phytoplankton groups (nanoeucaryotes, Prochlorococcus, Synechococcus, and diatoms was examined between 1996 and 2007 by applying the PHYSAT algorithm to the ocean color data archive from the Ocean Color and Temperature Sensor (OCTS and Sea-viewing Wide Field-of-view Sensor (SeaWiFS. Coincident with the decrease in chlorophyll concentrations, a large-scale shift in the phytoplankton composition of the Equatorial Pacific, that was characterized by a decrease in Synechococcus and an increase in nanoeucaryote dominance, was observed during the early stages of both the strong El Niño of 1997 and the moderate El Niño of 2006. A significant increase in diatoms dominance was observed in the Equatorial Pacific during the 1998 La Niña and was associated with elevated marine productivity. An analysis of the environmental variables using a coupled physical-biogeochemical model (NEMO-PISCES suggests that the Synechococcus dominance decrease during the two El Niño events was associated with an abrupt decline in nutrient availability (−0.9 to −2.5 μM NO3 month−1. Alternatively, increased nutrient availability (3 μM NO3 month−1 during the 1998 La Niña resulted in Equatorial Pacific dominance diatom increase. Despite these phytoplankton community shifts, the mean composition is restored after a few months, which suggests resilience in community structure.

  11. ENSO-driven nutrient variability recorded by central equatorial Pacific corals

    Science.gov (United States)

    LaVigne, M.; Nurhati, I. S.; Cobb, K. M.; McGregor, H. V.; Sinclair, D. J.; Sherrell, R. M.

    2012-12-01

    Recent evidence for shifts in global ocean primary productivity suggests that surface ocean nutrient availability is a key link between global climate and ocean carbon cycling. Time-series records from satellite, in situ buoy sensors, and bottle sampling have documented the impact of the El Niño Southern Oscillation (ENSO) on equatorial Pacific hydrography and broad changes in biogeochemistry since the late 1990's, however, data are sparse prior to this. Here we use a new paleoceanographic nutrient proxy, coral P/Ca, to explore the impact of ENSO on nutrient availability in the central equatorial Pacific at higher-resolution than available from in situ nutrient data. Corals from Christmas (157°W 2°N) and Fanning (159°W 4°N) Islands recorded a well-documented decrease in equatorial upwelling as a ~40% decrease in P/Ca during the 1997-98 ENSO cycle, validating the application of this proxy to Pacific Porites corals. We compare the biogeochemical shifts observed through the 1997-98 event with two pre-TOGA-TAO ENSO cycles (1982-83 and 1986-87) reconstructed from a longer Christmas Island core. All three corals revealed ~30-40% P/Ca depletions during ENSO warming as a result of decreased regional wind stress, thermocline depth, and equatorial upwelling velocity. However, at the termination of each El Niño event, surface nutrients did not return to pre-ENSO levels for ~4-12 months after, SST as a result of increased biological draw down of surface nutrients. These records demonstrate the utility of high-resolution coral nutrient archives for understanding the impact of tropical Pacific climate on the nutrient and carbon cycling of this key region.

  12. Numerical experiments on the atmospheric response to cold Equatorial Pacific conditions ('La Nina') during northern summer

    International Nuclear Information System (INIS)

    Storch, H. von; Schriever, D.; Arpe, K.; Branstator, G.W.; Legnani, R.; Ulbrich, U.

    1993-01-01

    The effect of cold conditions in the central and eastern Equatorial Pacific during Northern Summer is examined in a series of numerical experiments with the low resolution (T21) atmospheric general circulation model ECHAM2. Anomalous sea surface temperatures (SST) as observed in June 1988 were prescribed and the effect on the global circulation is examined. In the model atmosphere, the anomalous cold water in the Equatorial Pacific excites a strong and stable response over the tropical Central and East Pacific. From here stationary Rossby waves radiate into both hemispheres. The Northern Hemisphere wave train is weak and affects only the Northeast Pacific area; the Southern Hemisphere wave train arches from the Central Pacific over the southern tip of South America to the South Atlantic. This response is not only present in the basic anomaly experiment with the T21 GCM but also in experiments with SST anomalies confined to the tropics and with an envelope-formulation of the SST anomalies, in experiments with a linear model, and in high resolution (T42) model experiments. The model output is also compared to the actually observed atmospheric state in June 1988. (orig./KW)

  13. Comparative behavior of plutonium and americium in the equatorial Pacific

    International Nuclear Information System (INIS)

    Noshkin, V.E.; Wong, K.M.; Jokela, T.A.; Brunk, J.L.; Eagle, R.J.

    1983-01-01

    Inventories of 239 + 240 Pu and 241 Am greatly in excess of global fallout levels persist in the benthic environments of Bikini and Enewetak Atolls. The amount of 239 + 240 Pu mobilized to solution at the atolls can be predicted from a distribution coefficient K/sub d/ of 2.3 x 10 5 and the mean sediment concentrations. The mobilized 239 + 240 Pu has solute-like characteristics and different valence states coexist in solution - the largest fraction of the soluble plutonium is in an oxidized form (+V,VI). The adsorption of plutonium to sediments is not completely reversible because of changes that occur in the relative amounts of the mixed oxidation states in solution with time. Characteristics of 239 + 240 Pu described at one location may not necessarily describe its behavior elsewhere. The relative amounts of 241 Am to 239 + 240 Pu may be altered in future years because of mobilization and radiological decay

  14. Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

    DEFF Research Database (Denmark)

    Palacz, A. P.; Chai, F.

    2012-01-01

    The eastern equatorial Pacific plays a great role in the global carbon budget due to its enhanced biological productivity linked to the equatorial upwelling. However, as confirmed by the Equatorial Biocomplexity cruises in 2004 and 2005, nutrient upwelling supply varies strongly, partly due...... and intraseasonal time scales. Here, high resolution Pacific ROMS-CoSiNE (Regional Ocean Modeling System-Carbon, Silicon, Nitrogen Ecosystem) model results were evaluated with in situ and remote sensing data. The results of model-data comparison revealed a good agreement in domain-average hydrographic....... In order to fully resolve the complexity of biological and physical interactions in the eastern equatorial Pacific, we recommended improving CoSiNE and other models by introducing more phytoplankton groups, variable Redfield and carbon to chlorophyll ratios, as well as resolving the Fe-Si co...

  15. Pacific Circulation and the Resilience of its Equatorial Reefs

    Science.gov (United States)

    Cohen, A. L.; Drenkard, E.

    2012-12-01

    High rates of calcification by tropical reef-building corals are paramount to the maintenance of healthy reefs. Investigations of the impact of ocean acidification in both laboratory and field studies demonstrate unequivocally the dependence of coral and coral reef calcification on the carbonate ion concentration of seawater, a dependence predicted by fundamental laws of physical chemistry. Nevertheless, results from a new generation of experiments that exploit the biology of coral calcification, suggest that effects of ocean acidification can - in some instances - be mitigated with simultaneous manipulation of multiple factors. These laboratory results imply that coral reefs in regions projected to experience changes in, for example, nutrient delivery, light and flow, in addition to pH and carbonate ion concentration, may be more resilient (or vulnerable) to the effects of ocean acidification alone. If demonstrated to be true, these observations have profound implications for the conservation and management of coral reefs in the 21st century. We quantified spatial and temporal variability in rates of calcification of a dominant Indo-Pacific reef building coral across sites where changes in ocean circulation patterns drive variability in multiple physical, chemical and biological parameters. Such changes are occurring against a background of variability and trends in carbonate system chemistry. Our field data provide support for hypotheses based on laboratory observations, and show that impacts of ocean acidification on coral calcification can be partially and in some cases, fully, offset by simultaneous changes in multiple factors. Our results imply that projected changes in oceanic and atmospheric circulation patterns, driven by global warming, must be considered when predicting coral reef resilience, or vulnerability, to 21st century ocean acidification.

  16. Neogene biostratigraphy and paleoenvironments of Enewetak Atoll, equatorial Pacific Ocean

    Science.gov (United States)

    Cronin, T. M.; Bybell, L.M.; Brouwers, E.M.; Gibson, T.G.; Margerum, R.; Poore, R.Z.

    1991-01-01

    Micropaleontologic analyses of Neogene sediments from Enewetak Atoll, Marshall Islands, provide data on the age of lagoonal deposits, stratigraphic disconformities and the paleoenvironmental and subsidence history of the atoll. Benthic foraminifers, planktic foraminifers, calcareous nannofossils and ostracodes were studied from six boreholes, the deepest penetrating 1605 feet below the lagoon floor into upper Oligocene strata. The Oligocene-Miocene boundary occurs at about 1200 ft below the lagoon floor. The early and middle Miocene is characterized by brief periods of deposition and numerous hiatuses. Ostracodes and benthic foraminifers indicate a shallow-marine reefal environment with occasional brackish water conditions. Upper Miocene and lower Pliocene deposits placed in calcareous nannofossil Zones NN9-15 and in planktic foraminifer Zones N16-19 contain species-rich benthic microfaunas which indicate alternating reefal and brackish water mangrove environments. The upper Pliocene contains at least two major depositional hiatuses that coincide with a major faunal turnover in benthic foraminiferal and ostracode assemblages. The Quaternary is characterized by benthic microfaunas similar to those of modern atoll lagoons and is punctuated by at least 11 disconformities which signify periods of low sea level. Atoll subsidence rates during the last 10 Ma averaged 30 to 40 m/m.y. ?? 1991 Elsevier Science Publishers B.V. All rights reserved.

  17. Asymmetric Response of the Equatorial Pacific SST to Climate Warming and Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fukai [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Luo, Yiyong [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Lu, Jian [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington; Garuba, Oluwayemi [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington; Wan, Xiuquan [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China

    2017-09-01

    The response of the equatorial Pacific Ocean to heat fluxes of equal amplitude but opposite sign is investigated using the Community Earth System Model (CESM). Results show a strong asymmetry in SST changes. In the eastern equatorial Pacific (EEP), the warming responding to the positive forcing exceeds the cooling to the negative forcing; while in the western equatorial Pacific (WEP), it is the other way around and the cooling surpasses the warming. This leads to a zonal dipole asymmetric structure, with positive values in the east and negative values in the west. A surface heat budget analysis suggests that the SST asymmetry is mainly resulted from the oceanic horizontal advection and vertical entrainment, with both of their linear and nonlinear components playing a role. For the linear component, its change appears to be more significant over the EEP (WEP) in the positive (negative) forcing scenario, favoring the seesaw pattern of the SST asymmetry. For the nonlinear component, its change acts to warm (cool) the EEP (WEP) in both scenarios, also favorable for the development of the SST asymmetry. Additional experiments with a slab ocean confirm the dominant role of ocean dynamical processes for this SST asymmetry. The net surface heat flux, in contrast, works to reduce the SST asymmetry through its shortwave radiation and latent heat flux components, with the former being related to the nonlinear relationship between SST and convection, and the latter being attributable to Newtonian damping and air-sea stability effects. The suppressing effect of shortwave radiation on SST asymmetry is further verified by partially coupled overriding experiments.

  18. Nitrogen uptake and regeneration pathways in the equatorial Pacific: a basin scale modeling study

    Directory of Open Access Journals (Sweden)

    R. Le Borgne

    2009-11-01

    Full Text Available It is well known that most primary production is fueled by regenerated nitrogen in the open ocean. Therefore, studying the nitrogen cycle by focusing on uptake and regeneration pathways would advance our understanding of nitrogen dynamics in the marine ecosystem. Here, we carry out a basin-scale modeling study, by assessing model simulations of nitrate and ammonium, and rates of nitrate uptake, ammonium uptake and regeneration in the equatorial Pacific. Model-data comparisons show that the model is able to reproduce many observed features of nitrate, ammonium, such as the deep ammonium maximum (DAM. The model also reproduces the observed de-coupling of ammonium uptake and regeneration, i.e., regeneration rate greater than uptake rate in the lower euphotic zone. The de-coupling largely explains the observed DAM in the equatorial Pacific Ocean. Our study indicates that zooplankton excretion and remineralization of organic nitrogen play a different role in nitrogen regeneration. Rates of zooplankton excretion vary from <0.01 mmol m−3 d−1 to 0.1 mmol m−3 d−1 in the upper euphotic zone while rates of remineralization fall within a narrow range (0.015–0.025 mmol m−3 d−1 . Zooplankton excretion contributes up to 70% of total ammonium regeneration in the euphotic zone, and is largely responsible for the spatial variability of nitrogen regeneration. However, remineralization provides a steady supply of ammonium in the upper ocean, and is a major source of inorganic nitrogen for the oligotrophic regions. Overall, ammonium generation and removal are approximately balanced over the top 150 m in the equatorial Pacific.

  19. Dust Deposition and Migration of the ITCZ through the Last Glacial Cycle in the Central Equatorial Pacific (Line Islands).

    Science.gov (United States)

    Reimi Sipala, M. A.; Marcantonio, F.

    2014-12-01

    Atmospheric dust can be used to record climate change in addition to itself playing a role in several key climate processes, such as affecting Earth's albedo, fomenting rain coalescence, encouraging biological productivity, and enhancing carbon export though particle sinks. Using deep sea sediments, it is possible to quantify and locate the sources and sinks of atmospheric dust. A key area of research is the shift in the inter-tropical converge zone (ITCZ), a thermally influenced area that shifts according to the northern and southern hemisphere temperature gradient. This ongoing project focuses on the changes of the ITCZ over the Central Equatorial Pacific (CEP) over the past ~25000 years. The research focuses on two cores taken from the Line Islands Ridge at 0° 29' N (ML1208-18GC), and 4° 41' N (ML1208-31BB). The main aim is to quantify the magnitude and provenance of windblown dust deposited in the CEP, and to address questions regarding the nature of the variations of dust through ice-age climate transitions. Radiogenic isotopes (Sr, Nd, Pb) have been successfully used to distinguish between different potential dust sources in the aluminosilicates fractions of Pacific Sediments. Our preliminary Pb isotope ratios suggest that, for modern deposition, the northern core's (31BB) detrital sediment fraction is likely sourced from Asian Loess (average ratios are 206Pb/204Pb = 18.88, 207Pb/204Pb = 15.69, 208Pb/204Pb = 39.06). The equatorial core's (18GC) detrital fraction has a less radiogenic Pb signature, which is consistent with South American dust sourcing (206Pb/204Pb = 18.62, 207Pb/204Pb = 15.63, 208Pb/204Pb = 38.62). This is indicative of a strong modern ITCZ that acts as an effective barrier for inter-hemispheric dust transport. Prior to Holocene time, the changes in Pb isotope ratios in both cores appear to be in anti-phase; the northern core becomes less radiogenic up to the LGM, while the southern core becomes more radiogenic. This is potentially due to a

  20. Thorium content in bottom sediments of Pacific and Indian oceans

    International Nuclear Information System (INIS)

    Gurvich, E.G.; Lisitsyn, A.P.

    1980-01-01

    Presented are the results of 232 Th distribution study in different substance-genetic types of bottom sediments of Pacific and Indian oceans. Th content determination has been carried out by the method of instrumental neutron activation analysis. Th distribution maps in the surface layer of bottom sediments of Pacific and Indian oceans are drawn. It is noted that Indian ocean sediments are much richer with Th moreover Th distribution in different types of sediments is very non-uniform. Non-uniformity of Th distribution in different types of Pacific ocean sediments is considerably less than that of Indian ocean and exceeds it only in red oozes

  1. Assessing and Optimizing Argo profile mapping : An example in the Equatorial Pacific

    Science.gov (United States)

    Gasparin, Florent; Roemmich, Dean; Gilson, John; Sprintall, Janet

    2014-05-01

    Estimation of subsurface temperature, salinity and velocity has been revolutionized over the last decade as a result of development and deployment of the Argo Program. Argo products have become one of the major observational tools in Oceanography, used in a wide range of basic research, operational models, and education applications. To assess the skill of Argo in estimating oceanic conditions at different scales of variability in the Equatorial Pacific, we optimize Argo profile mapping by focusing on the covariance function. Decorrelation scales are discussed as well as impacts of several different interpolation schemes. The optimization is based on three points 1) Functional representation of the Argo sampled covariance, 2) Realism/Accuracy of the mapping errors and 3) Comparison with independent data such as TAO moorings and sea surface height. The last points show that Argo can represent more than 90% of the total TAO variance and around 80% of the intraseasonal TAO variability (between 10 and 100 days) at the Equator. As an illustration of the improvement, we show how Argo profiles can reveal the vertical structure and vertical phase propagation corresponding to the steric height annual cycle. We also discuss how this unique equatorial wave phenomena is modified during El Nino/La Nina events. This work anticipates a field experiment beginning in early 2014 and can be used for assessing and adapting the equatorial observational network.

  2. The response of the equatorial Pacific Ocean to a westerly wind burst in May 1986

    Science.gov (United States)

    McPhaden, Michael J.; Freitag, H. Paul; Hayes, Stanley P.; Taft, Bruce A.; Chen, Zeshi; Wyrtki, Klaus

    1988-09-01

    Western Pacific westerly wind bursts of 1- to 3-week duration are potentially important in triggering and sustaining El Niño-Southern Oscillation events. One such burst of 10-day duration and maximum speeds of greater than 10 m s-1 occurred in May 1986 west of the date line. The response to this westerly wind burst is documented from equatorial current meter moorings, thermistor chain moorings, and sea level and hydrographic data. At 0°, 165°E in the western Pacific the thermocline was depressed by 25 m, sea surface temperature dropped by 0.3°-0.4°C, and sea level rose by 10-15 cm a few days after the maximum in westerly wind speed. Likewise, the South Equatorial Current rapidly accelerated eastward and attained speeds in excess of 100 cm s-1. Vertical shear in an approximately 100 m deep surface layer reversed within a few days of the winds, consistent with a simple model of equatorial mixed layer dynamics in which vertical eddy viscosities are inferred to be O(100 cm2 s-1). A sharp Kelvin wavelike pulse in sea level propagated out of the directly forced region into the central and eastern Pacific. The pulse took 45 days to travel from Tarawa (1°N, 173°E) to La Libertad (2°S, 81°W) on the South American coast, at an average phase speed of about 300 cm s-1. This is of the same order of magnitude as, but significantly higher than, the phase speed of a first baroclinic mode Kelvin wave and is probably the result of Doppler shifting by the Equatorial Undercurrent. A rise in sea surface temperature of about 1°C in 2 days occurred at 0°N, 110°W with the passage of the pulse. However, coincidental meridional advection of a sharp sea surface temperature front, rather than zonal advection of downwelling associated with the pulse, appears to be responsible for this warming. The relevance of this wind-forced pulse to the subsequent evolution of the 1986-1987 El Niño-Southern Oscillation event is discussed in the light of these observations.

  3. Growth rates, grazing, sinking, and iron limitation of equatorial Pacific phytoplankton

    International Nuclear Information System (INIS)

    Chavez, F.P.; Buck, K.R.; Coale, K.H.; Martin, J.H.; DiTullio, G.R.; Welschmeyer, N.A.; Barber, R.T.; Jacobson, A.C.

    1991-01-01

    Concentrations of phytoplankton and NO 3 are consistently low and high in surface waters of the oceanic eastern and central equatorial Pacific, and phytoplankton populations are dominated by small solitary phytoplankton. Growth rates of natural phytoplankton populations, needed to assess the relative importance of many of the processes considered in the equatorial Pacific, were estimated by several methods. The growth rates of natural phytoplankton populations were found to be ∼0.7 d -1 or 1 biomass doubling d -1 and were similar for all methods. To keep this system in its observed balance requires that loss rates approximate observed growth rates. Grazing rates, measured with a dilution grazing experiment, were high, accounting for a large fraction of the daily production. Additions of various forms of Fe to 5-7-d incubations utilizing ultraclean techniques resulted in significant shifts in autotrophic and heterotrophic assemblages between initial samples, controls, and Fe enrichments, which were presumably due to Fe, grazing by both protistan and metazoan components, and incubation artifacts. Estimated growth rates of small pennate diatoms showed increases in Fe enrichments with respect to controls. The growth rates of the pennate diatoms were similar to those estimated for the larger size fraction of the natural populations

  4. Reflection of equatorial Kelvin waves at eastern ocean boundaries Part II: Pacific and Atlantic Oceans

    Directory of Open Access Journals (Sweden)

    J. Soares

    1999-06-01

    Full Text Available The effect of viscosity, non linearities, incident wave period and realistic eastern coastline geometry on energy fluxes are investigated using a shallow water model with a spatial resolution of 1/4 degree in both meridional and zonal directions. Equatorial and mid-latitude responses are considered. It is found that (1 the influence of the coastline geometry and the incident wave period is more important for the westward energy flux than for the poleward flux, and (2 the effect of the inclination of the eastern ocean boundary on the poleward energy flux, for the Pacific and Atlantic Oceans, decline as the period of the incident wave increases. Furthermore, the model simulations suggest that the poleward energy fluxes from meridional boundaries give plausible results for motions of seasonal and annual periods. For comparatively shorter periods, a realistic coastline geometry has to be included for more accurate results. It is recommended that any numerical model involving the reflection of baroclinic Rossby waves (of intraseasonal, seasonal or annual periods on the eastern Pacific or Atlantic Oceans, should consider the effect of the coastline geometry in order to improve the accuracy of the results.Key words. Oceanography: general (climate and interannual variability; equatorial oceanography. Oceanography: physical (eastern boundary currents.

  5. Thermal conductivity measurements of pacific illite sediment

    Science.gov (United States)

    Hickox, C. E.; McVey, D. F.; Miller, J. B.; Olson, L. O.; Silva, A. J.

    1986-07-01

    Results are reported for effective thermal conductivity measurements performed in situ and in core samples of illite marine sediment. The measurements were obtained during a recent oceanographic expedition to a study site in the north central region of the Pacific Ocean. This study was undertaken in support of the U.S. Subseabed Disposal Project, the purpose of which is to investigate the scientific feasibility of using the fine-grained sediments of the sea floor as a repository for high-level nuclear waste. In situ measurements were made and 1.5-m-long hydrostatic piston cores were taken, under remote control, from a platform that was lowered to the sea floor, 5844 m below sea level. The in situ measurement of thermal conductivity was made at a nominal depth of 80 cm below the sediment surface using a specially developed, line-source, needle probe. Thermal conductivity measurements in three piston cores and one box core (obtained several kilometers from the study site) were made on shipboard using a miniature needle probe. The in situ thermal conductivity was approximately 0.91 W · m-1 · K-1. Values determined from the cores were within the range 0.81 to 0.89 W · m-1 · K-1.

  6. Thermal conductivity measurements of Pacific illite sediment

    International Nuclear Information System (INIS)

    Hickox, C.E.; McVey, D.F.; Miller, J.B.; Olson, L.O.; Silva, A.J.

    1986-01-01

    Results are reported for effective thermal conductivity measurements performed in situ and in core samples of illite marine sediment. The measurements were obtained during a recent oceanographic expedition to a study site in the north central region of the Pacific Ocean. This study was undertaken in support of the US Subseabed Disposal Project, the purpose of which is to investigate the scientific feasibility of using the fine grained sediments of the sea floor as a repository for high level nuclear waste. In situ measurements were made and 1.5-meter long hydrostatic piston cores were taken, under remote control, from a platform that was lowered to the sea floor, 5844 m below sea level. The in situ measurement of thermal conductivity was made at a nominal depth of 80 cm below the sediment surface using a specially developed, line source, needle probe. Thermal conductivity measurements in three piston cores and one box core (obtained several kilometers from the study site) were made on shipboard using a miniature needle probe. The in situ thermal conductivity was approximately 0.91 W/m.K. Values determined from the cores were within the range 0.81 to 0.89 W/m.K

  7. A long history of equatorial deep-water upwelling in the Pacific Ocean

    Science.gov (United States)

    Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

    2017-06-01

    Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

  8. Changes in the interannual variability of the tropical Pacific as a response to an equatorial Atlantic forcing

    Directory of Open Access Journals (Sweden)

    Marta Martín-Rey

    2012-09-01

    Full Text Available Previous studies have reported that the tropical Atlantic has had an influence on tropical Pacific interannual variability since the 1970s. This variability is studied in the present work, using simulations from a coupled model in the Indo-Pacific but with observed sea surface temperature (SST prescribed over the Atlantic. The interannual variability is compared with that from a control simulation in which climatological SSTs are prescribed over the Atlantic. Differences in the Pacific mean state and in its variability are found in the forced simulation as a response to a warming in the equatorial Atlantic, characterized by a cooler background state and an increase in the variability over the tropical Pacific. A striking result is that the principal modes of tropical Pacific SST interannual variability show significant differences before and after the 1970s, providing new evidence of the Atlantic influence on the Pacific Ocean. Significant cooling (warming in the equatorial Atlantic could have caused anomalous winds in the central-easter Pacific during the summer since 1970s. The thermocline depth also seems to be altered, triggering the dynamical processes involved in the development of El Niño (La Niña phenomenon in the following winter. An increase in frequency of Niño and Niña events favouring the Central Pacific (CP ones is observed in the last three decades. Further analyses using coupled models are still necessary to help us to understand the causes of this inter-basin connection.

  9. Mechanism of seasonal eddy kinetic energy variability in the eastern equatorial Pacific Ocean

    Science.gov (United States)

    Wang, Minyang; Du, Yan; Qiu, Bo; Cheng, Xuhua; Luo, Yiyong; Chen, Xiao; Feng, Ming

    2017-04-01

    Enhanced mesoscale eddy activities or tropical instability waves (TIWs) exist along the northern front of the cold tongue in the eastern equatorial Pacific Ocean. In this study, we investigate seasonal variability of eddy kinetic energy (EKE) over this region and its associated dynamic mechanism using a global, eddy-resolving ocean general circulation model (OGCM) simulation, the equatorial mooring data, and satellite altimeter observations. The seasonal-varying enhanced EKE signals are found to expand westward from 100°W in June to 180°W in December between 0°N and 6°N. This westward expansion in EKE is closely connected to the barotropically-baroclinically unstable zonal flows that are in thermal-wind balance with the seasonal-varying thermocline trough along 4°N. By adopting an 1½-layer reduced-gravity model, we confirm that the seasonal perturbation of the thermocline trough is dominated by the anticyclonic wind stress curl forcing, which develops due to southerly winds along 4°N from June to December.

  10. Publisher Correction: Recycled iron fuels new production in the eastern equatorial Pacific Ocean.

    Science.gov (United States)

    Rafter, Patrick A; Sigman, Daniel M; Mackey, Katherine R M

    2017-12-05

    The original version of this Article contained errors in Fig. 2b and Table 2. In Fig. 2b, the white circle labels were incorrectly positioned as they referred to scenarios that were used in an earlier version of the Article. In Table 2, the following three sentences were removed from the legend 'The last two calculations are discussed in the "Methods". The first assumes that all dissolved plus the ≈0.3 nmol kg -1 of particulate iron (measured in the eastern equatorial Pacific 30 ) is bioavailable. The last calculation assumes EUC dissolved iron concentrations from 140° W'. These errors have now been corrected in both the PDF and HTML versions of the Article.

  11. The influence of Pacific Equatorial Water on fish diversity in the southern California Current System

    Science.gov (United States)

    McClatchie, Sam; Thompson, Andrew R.; Alin, Simone R.; Siedlecki, Samantha; Watson, William; Bograd, Steven J.

    2016-08-01

    The California Undercurrent transports Pacific Equatorial Water (PEW) into the Southern California Bight from the eastern tropical Pacific Ocean. PEW is characterized by higher temperatures and salinities, with lower pH, representing a source of potentially corrosive (aragonite,Ωaragonite saturation with depth. Although there is substantial variability in PEW presence as measured by spice on the 26.25-26.75 isopycnal layer, as well as in pH and aragonite saturation, we found fish diversity to be stable over the decades 1985-1996 and 1999-2011. We detected significant difference in species structure during the 1998 La Niña period, due to reduced species evenness. Species richness due to rare species was higher during the 1997/1998 El Niño compared to the La Niña but the effect on species structure was undetectable. Lack of difference in the species abundance structure in the decade before and after the 1997/1999 ENSO event showed that the assemblage reverted to its former structure following the ENSO perturbation, indicating resilience. While the interdecadal species structure remained stable, the long tail of the distributions shows that species richness increased between the decades consistent with intrusion of warm water with more diverse assemblages into the southern California region.

  12. Temperature correlations between the eastern equatorial Pacific and Antarctica over the past 230,000 years

    Science.gov (United States)

    Koutavas, Athanasios

    2018-03-01

    Tropical sea surface temperatures (SSTs) warmed and cooled in step with the Pleistocene ice age cycles, but the mechanisms are not known. It is assumed that the answer must involve radiative forcing by CO2 but SST reconstructions have been too sparse for a conclusive test. Here I present a 230,000-yr tropical SST stack from the eastern equatorial Pacific (EEP) using two new Mg/Ca reconstructions combined with three earlier ones. The EEP stack shows persistent covariation with Antarctic temperature on orbital and millennial timescales indicating tight coupling between the two regions. This coupling however cannot be explained solely by CO2 forcing because in at least one important case, the Marine Isotope Stage (MIS) 5e-5d glacial inception, both regions cooled ∼5-6.5 thousand years before CO2 decreased. More likely, their covariation was due to advection of Antarctic climate signals to the EEP by the ocean. To explain the MIS 5e-5d event and glacial inception in general the hypothesis is advanced that the cooling signal spreads globally from the Northern Hemisphere with an active ocean circulation - first from the North Atlantic to the Southern Ocean with a colder North Atlantic Deep Water, and then to the Indian and Pacific Oceans with cooler Antarctic deep and intermediate waters.

  13. Assessment of prediction skill in equatorial Pacific Ocean in high resolution model of CFS

    Science.gov (United States)

    Arora, Anika; Rao, Suryachandra A.; Pillai, Prasanth; Dhakate, Ashish; Salunke, Kiran; Srivastava, Ankur

    2018-01-01

    The effect of increasing atmospheric resolution on prediction skill of El Niño southern oscillation phenomenon in climate forecast system model is explored in this paper. Improvement in prediction skill for sea surface temperature (SST) and winds at all leads compared to low resolution model in the tropical Indo-Pacific basin is observed. High resolution model is able to capture extreme events reasonably well. As a result, the signal to noise ratio is improved in the high resolution model. However, spring predictability barrier (SPB) for summer months in Nino 3 and Nino 3.4 region is stronger in high resolution model, in spite of improvement in overall prediction skill and dynamics everywhere else. Anomaly correlation coefficient of SST in high resolution model with observations in Nino 3.4 region targeting boreal summer months when predicted at lead times of 3-8 months in advance decreased compared its lower resolution counterpart. It is noted that higher variance of winds predicted in spring season over central equatorial Pacific compared to observed variance of winds results in stronger than normal response on subsurface ocean, hence increases SPB for boreal summer months in high resolution model.

  14. Recent global-warming hiatus tied to equatorial Pacific surface cooling.

    Science.gov (United States)

    Kosaka, Yu; Xie, Shang-Ping

    2013-09-19

    Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

  15. The Sun is the climate pacemaker I. Equatorial Pacific Ocean temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Douglass, David H., E-mail: douglass@pas.rochester.edu; Knox, Robert S.

    2015-04-17

    Equatorial Pacific Ocean temperature time series data contain segments showing both a phase-locked annual signal and a phase-locked signal of period two years or three years, both locked to the annual solar cycle. Three such segments are observed between 1990 and 2014. It is asserted that these are caused by a solar forcing at a frequency of 1.0 cycle/yr. These periodic features are also found in global climate data (following paper). The analysis makes use of a twelve-month filter that cleanly separates seasonal effects from data. This is found to be significant for understanding the El Niño/La Niña phenomenon. - Highlights: • Central Pacific region temperature dataset SST3.4 from 1990 to 2014 is studied. • SST3.4 contains a sustained signal at 1.0 cycle/yr implying solar forcing. • SST3.4 also contains a signal (<1 cycle/yr) showing El Niño/La Niña effects. • This signal contains segments of period 2 or 3 years, phase locked to the annual. • A 12-month moving average improves on a “climatology” filter in removing annual effects.

  16. Changes in opal flux and the rain ratio during the last 50,000 years in the equatorial Pacific

    Science.gov (United States)

    Richaud, Mathieu; Loubere, Paul; Pichat, Sylvain; Francois, Roger

    2007-03-01

    Changes in the orgC/CaCO 3 ratio in particles sinking from the surface to the deep ocean have the potential to alter the atmospheric pCO 2 over the span of a glacial/interglacial cycle. Recent paleoceanographic and modern observational studies suggest that silica is a key factor in the global carbon biogeochemical cycle that can influence the flux ratio, especially at low latitudes, through "silicic acid leakage" [Brzezinski, M., Pride, C., Franck, M., Sigman, D., Sarmiento, J., Matsumoto, K., Gruber, N., Rau, R., Coale, K., 2002. A switch from Si(OH) 4 to NO3- depletion in the glacial Southern Ocean. Geophysical Research Letters 29, 5]. To test this hypothesis, we reconstruct biogenic fluxes of CaCO 3, orgC and Si for three equatorial Pacific cores. We find evidence that a floral shift from a SiO 2-based community to a CaCO 3-based occurred, starting in mid-marine isotope stage (MIS) 3 (24-59 cal. ka) and declining toward MIS 2 (19-24 cal. ka). This could reflect the connection of the Peru upwelling system to the subantarctic region, and we postulate that excess silica was transported from the subantarctic via the deep Equatorial Undercurrent to the eastern equatorial Pacific. In the eastern equatorial Pacific only, we document a significant decrease in rain ratio starting mid-MIS 3 toward MIS 2. This decrease is concomitant with a significant decrease in silica accumulation rates at the seabed. This pattern is not observed in the Pacific influenced by equatorial divergence and shallow upwelling, where all reconstructed fluxes (CaCO 3, orgC, and opal) increase during MIS 2. We conclude that the overall calcium carbonate pump weakened in the EEP under Peru upwelling influence.

  17. Changes in Eastern Equatorial Pacific Thermocline Structure across the Last Deglaciation: Evidence from the Carnegie Ridge

    Science.gov (United States)

    Glaubke, R.; Schmidt, M. W.; Warner, L.; Hertzberg, J. E.; Marcantonio, F.; Bianchi, T. S.

    2017-12-01

    The eastern equatorial Pacific (EEP) is an important climatological region given its influence in the modulation of the El Niño - Southern Oscillation (ENSO). The current climatic mean state of the EEP is characterized by cool sea surface temperatures (SST) and a strong, shallow thermocline. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale climate events of the last deglaciation. Here, we will present 21 kyrs of Mg/Ca paleotemperature data from the surface-dwelling foraminifera Globigerinoides ruber and the thermocline-dwelling foraminifera Neogloboquadrina dutertrei collected from piston core MV1014-02-17JC (00° 10.83'S, 85° 52.00'W; 2846 m depth) on the Carnegie Ridge. Initial results reveal a 1.3°C warming of the surface ocean from the early-Holocene until 6 kyrs, a trend present in other EEP SST reconstructions (Pena et al., 2008; Timmerman et al., 2014; Lea et al., 2000). The surface ocean subsequently cools from 6 kyrs and reaches present-day temperatures by 3.5 kyrs. The subsurface reveals a nearly monotonic cooling of 1.8°C from 10.8 kyrs to the present day, which suggest a gradual shoaling of the thermocline across the Holocene. Furthermore, an increase in the vertical temperature gradient occurs from the late- to mid-Holocene, with the sharpest temperature difference centered at 6 kyrs, coincident with the mid-Holocene peak in SSTs. Taken together, these data suggest a gradual shoaling of the thermocline across the Holocene, with the variations in SST primarily governing the intensity of the vertical temperature gradient. Future work includes extending this record back to the last glacial maximum (LGM) to assess tropical Pacific mean state change across the abrupt climate events that characterized the last deglaciation.

  18. An initial examination of carbonate production in the western equatorial Pacific: XRF results from the Pliocene-Pleistocene of IODP Site U1490

    Science.gov (United States)

    Chapman, J.; Kulhanek, D. K.; Rosenthal, Y.; Holbourn, A. E.

    2017-12-01

    International Ocean Discovery Program (IODP) Expedition 363 sought to determine the nature of and driving forces behind climate variability in the Western Pacific Warm Pool (WPWP) region throughout the Neogene on millennial, orbital, and geologic timescales. Our research focuses on the Pliocene to recent (4-0 Ma) sediment record from IODP Site U1490 to examine changes in carbonate production and burial in the WPWP as a record of variations in the regional/global carbon cycle. This interval is of particular interest because it spans the Middle Pliocene Warm Period, the initiation of Northern Hemisphere Glaciation, and the Mid-Pleistocene Transition. Site U1490 is located on the northern edge of Eauripik Rise at 05°58.95'N, 142°39.27'E in the northern part of the WPWP. At 2341 m water depth, today the site is bathed in Upper Circumpolar Deepwater. Pliocene to recent sediment primarily consists of foraminifer-rich nannofossil ooze, with the sedimentation rate varying between 1.5 and 3 cm/kyr. Initial shipboard measurement of calcium carbonate content shows little variation at low resolution (1 sample every few meters), varying between 90 and 95 wt%. We collected X-ray fluorescence (XRF) data at 2 cm resolution along the composite stratigraphic section to obtain a qualitative measure of the bulk chemistry of the sediment. We will use the weight percent calcium carbonate of discrete samples to calibrate the XRF data to generate a high-resolution carbonate record. We observe cyclical variations in the Ca/Ba, which may reflect variations in productivity and/or dissolution through this interval, although additional work is needed to fully interpret these data. Ultimately our research will allow for comparison between records obtained from these cores located in the western equatorial Pacific to those obtained in the eastern and central Pacific, which will better elucidate the nature of the carbon system during the Plio-Pleistocene.

  19. Uranium in Pacific Deep-Sea Sediments and Manganese Nodules

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar; Pluger, W. L.; Friedrich, G. H.

    1983-01-01

    A total of 1344 manganese nodules and 187 pelagic sediments from 9 areas in the North and the South Pacific were analyzed for U by the delayed-neutron counting technique. A strong positive correlation between U and Fe in nodules and sediments suggests a co-precipitative removal from sea water int...

  20. Temperature profile and nutrients data from bottle casts in the Equatorial Pacific Ocean from 19 April 1971 to 30 March 1994 (NODC Accession 0000225)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts from the ORION and EASTWARD in the Equatorial Pacific Ocean. Data were collected from 19...

  1. Variability in the correlation between Asian dust storms and chlorophyll a concentration from the North to Equatorial Pacific.

    Directory of Open Access Journals (Sweden)

    Sai-Chun Tan

    Full Text Available A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997-2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the 50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32-0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36. These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas.

  2. Solar radiation, phytoplankton pigments and the radiant heating of the equatorial Pacific warm pool

    Science.gov (United States)

    Siegel, David A.; Ohlmann, J. Carter; Washburn, Libe; Bidigare, Robert R.; Nosse, Craig T.; Fields, Erik; Zhou, Yimei

    1995-01-01

    Recent optical, physical, and biological oceanographic observations are used to assess the magnitude and variability of the penetrating flux of solar radiation through the mixed layer of the warm water pool (WWP) of the western equatorial Pacific Ocean. Typical values for the penetrative solar flux at the climatological mean mixed layer depth for the WWP (30 m) are approx. 23 W/sq m and are a large fraction of the climatological mean net air-sea heat flux (approx. 40 W/sq m). The penetrating solar flux can vary significantly on synoptic timescales. Following a sustained westerly wind burst in situ solar fluxes were reduced in response to a near tripling of mixed layer phytoplankton pigment concentrations. This results in a reduction in the penetrative flux at depth (5.6 W/sq m at 30 m) and corresponds to a biogeochemically mediated increase in the mixed layer radiant heating rate of 0.13 C per month. These observations demonstrate a significant role of biogeochemical processes on WWP thermal climate. We speculate that this biogeochemically mediated feedback process may play an important role in enhancing the rate at which the WWP climate system returns to normal conditions following a westerly wind burst event.

  3. Mechanistic Drivers of Reemergence of Anthropogenic Carbon in the Equatorial Pacific

    Science.gov (United States)

    Zhai, Ping; Rodgers, Keith B.; Griffies, Stephen M.; Slater, Richard D.; Iudicone, Daniele; Sarmiento, Jorge L.; Resplandy, Laure

    2017-09-01

    Relatively rapid reemergence of anthropogenic carbon (Cant) in the Equatorial Pacific is of potential importance for its impact on the carbonate buffering capacity of surface seawater and thereby impeding the ocean's ability to further absorb Cant from the atmosphere. We explore the mechanisms sustaining Cant reemergence (upwelling) from the thermocline to surface layers by applying water mass transformation diagnostics to a global ocean/sea ice/biogeochemistry model. We find that the upwelling rate of Cant (0.4 PgC yr-1) from the thermocline to the surface layer is almost twice as large as air-sea Cant fluxes (0.203 PgC yr-1). The upwelling of Cant from the thermocline to the surface layer can be understood as a two-step process: The first being due to diapycnal diffusive transformation fluxes and the second due to surface buoyancy fluxes. We also find that this reemergence of Cant decreases dramatically during the 1982/1983 and 1997/1998 El Niño events.

  4. Recent metalliferous sediment in the North Pacific manganese nodule area

    Science.gov (United States)

    Bischoff, J.L.; Rosenbauer, R.J.

    1977-01-01

    Quaternary sediments cored in the northeast Pacific nodule area (DOMES site C, 14??N, 126??W) contain a significant amount of hydrothermal metalliferous mud. Water content, color, mineralogy, and chemical composition are analogous to metalliferous sediments of the subequatorial East Pacific Rise. Correction for contribution of pelagic clay indicates the metalliferous fraction to be about 40% of the sediment. SiO2 and Mg are major components in the corrected composition, as they are for other metalliferous sediments similarly corrected from a variety of East Pacific Rise and DSDP metalliferous sediments. A correlation between Mg and SiO2 for these corrected sediments could indicate a hydrothermal origin for a significant portion of the SiO2. Results from DSDP in the nodule area suggest that metalliferous globules are a ubiquitous minor component of the Clipperton Oceanic Formation, which underlies much of the Pacific ferromanganese nodule belt. This indicates that deposition of hydrothermal precipitates is not confined to spreading centers. ?? 1977.

  5. An estimate of equatorial wave energy flux at 9- to 90-day periods in the Central Pacific

    Science.gov (United States)

    Eriksen, Charles C.; Richman, James G.

    1988-01-01

    Deep fluctuations in current along the equator in the Central Pacific are dominated by coherent structures which correspond closely to narrow-band propagating equatorial waves. Currents were measured roughly at 1500 and 3000 m depths at five moorings between 144 and 148 deg W from January 1981 to March 1983, as part of the Pacific Equatorial Ocean Dynamics program. In each frequency band resolved, a single complex empirical orthogonal function accounts for half to three quarters of the observed variance in either zonal or meridional current. Dispersion for equatorial first meridional Rossby and Rossby gravity waves is consistent with the observed vertical-zonal coherence structure. The observations indicate that energy flux is westward and downward in long first meridional mode Rossby waves at periods 45 days and longer, and eastward and downward in short first meridional mode Rossby waves and Rossby-gravity waves at periods 30 days and shorter. A local minimum in energy flux occurs at periods corresponding to a maximum in upper-ocean meridional current energy contributed by tropical instability waves. Total vertical flux across the 9- to 90-day period range is 2.5 kW/m.

  6. Organic sediments of the equatorial east Atlantic: Effects of origin, transport, diagenesis, and climate

    International Nuclear Information System (INIS)

    Westerhausen, L.

    1992-01-01

    The origins and diagenesis of organic matter in recent sediments of the equatorial Eastern Atlantic are assessed on the basis of the 13 C/ 12 C composition of the organic carbon (δ 13 C TOC ), the C/N ratio, and molecular biomarkers from terrigenic and marine sources. Also investigated was the effect of global climate on the 13 C/ 12 C ratios of marine organic carbon and on the origins of organic matter on sedimentary cores. The terrigenic fraction of organic carbon is calculated using a binary δ 13 C TOC mixing model. To begin with, the δ 13 C TOC values were standardized to a uniform surface water temperature and water depth. The calculated terrigenic TOC fractions amount to more than 60% for shelf sediments off the coast of Eastern Liberia, Ivory Coast, and the continental shelf of Gabun. The higher terrigenic TOC fractions of up to 20% in recent sediments on the continental shelf along the coast of Guinea to Ivory Coast are interpreted in terms of a transport of terrigenic substances in down hill direction and parallel to the coast. The effects of the global climate on the TOC accumulation rates and on the 13 C/ 12 C ratio of organic carbon were investigated in a pelogic sedimentary core (M16772) from the tropical Eastern Atlantic. Prior to this, the δ 13 C TOC values were standardized to a uniform surface temperature and a uniform 13 C/ 12 C ratio of the dissolved inorganic carbon using the UK 37 index and the δ 13 C values of G.ruber. During the cold periods the export production increases, which - together with the low CO 2 partial pressure in the atmosphere, and thus also in the surface water -induces 13 C accumulation in the marine organic carbon. There is nothing to suggest an effect of 13 C-accumulating phytoplancton, e.g. dinoflagellats, on the 13 C/ 12 C ratio. (orig./KW). 32 figs., 8 tabs [de

  7. An initial examination of carbonate variability in the western equatorial Pacific: XRF results from the lower to middle Miocene of IODP Site U1490

    Science.gov (United States)

    Valerio, D. A.; Kulhanek, D. K.; Rosenthal, Y.; Holbourn, A. E.

    2017-12-01

    International Ocean Discovery Program (IODP) Expedition 363 sought to determine the nature of and driving forces behind climate variability in the Western Pacific Warm Pool (WPWP) region throughout the Neogene on millennial, orbital, and geologic timescales. Our research focuses on the Miocene (19-9 Ma) sediment record from IODP Site U1490 to examine changes in carbonate production and burial in the WPWP as a record of variations in the regional/global carbon cycle. This interval is of particular interest because it spans the Middle Miocene Climatic Optimum, the Middle Miocene Climate Transition, and the late Miocene carbonate crash. Site U1490 is located on the northern edge of Eauripik Rise at 05°58.95'N, 142°39.27'E in the northern part of the WPWP. At 2341 m water depth, today the site is bathed in Upper Circumpolar Deepwater. Miocene sediment at Site U1490 primarily consists of clay-bearing to clay-rich foraminifer-rich nannofossil ooze, although biogenic silica (primarily radiolaria) is a significant component in the lowermost part of the record. The sedimentation rate in the early to middle Miocene was very low (calcium carbonate content of 87 wt% throughout the site, with the most significant variations in the lower to middle Miocene, where contents range from 20 to 85 wt%. We collected X-ray fluorescence (XRF) data at 1 cm resolution along the composite stratigraphic section over the 19-9 Ma interval to obtain a qualitative measure of the bulk chemistry of the sediment. We will use the weight percent calcium carbonate of discrete samples to calibrate the XRF data to generate a high-resolution carbonate record. We observe cyclical variations in the Ca/Ba, which may reflect variations in productivity and/or dissolution through this interval, although additional work is needed to fully interpret these data. Ultimately our research will allow for comparison between records obtained from these cores located in the western equatorial Pacific to those obtained

  8. Dynamical diagnostics of the SST annual cycle in the eastern equatorial Pacific: part I a linear coupled framework

    Science.gov (United States)

    Chen, Ying-Ying; Jin, Fei-Fei

    2018-03-01

    The eastern equatorial Pacific has a pronounced westward propagating SST annual cycle resulting from ocean-atmosphere interactions with equatorial semiannual solar forcing and off-equatorial annual solar forcing conveyed to the equator. In this two-part paper, a simple linear coupled framework is proposed to quantify the internal dynamics and external forcing for a better understanding of the linear part of the dynamics annual cycle. It is shown that an essential internal dynamical factor is the SST damping rate which measures the coupled stability in a similar way as the Bjerknes instability index for the El Niño-Southern Oscillation. It comprises three major negative terms (dynamic damping due to the Ekman pumping feedback, mean circulation advection, and thermodynamic feedback) and two positive terms (thermocline feedback and zonal advection). Another dynamical factor is the westward-propagation speed that is mainly determined by the thermodynamic feedback, the Ekman pumping feedback, and the mean circulation. The external forcing is measured by the annual and semiannual forcing factors. These linear internal and external factors, which can be estimated from data, determine the amplitude of the annual cycle.

  9. Revisiting the La Nina 1998 phytoplankton blooms in the equatorial Pacific

    OpenAIRE

    Gorgues, T.; Menkès, Christophe; Slemons, L.; Aumont, Olivier; Dandonneau, Yves; Radenac, Marie-Hélène; Alvain, S.; Moulin, C.

    2010-01-01

    A biogeochemical model of the tropical Pacific has been used to assess the impact of interannual variability in a western Pacific iron source on the iron-limited ecosystem of the central and eastern Pacific during the 1997-1998 El Nino A reference simulation and two simulations with an iron source in the western Pacific have been performed The two "source" simulations differed only in the temporal variability of the iron source. In the variable source simulation, the iron concentration in the...

  10. Dynamical diagnostics of the SST annual cycle in the eastern equatorial Pacific: Part II analysis of CMIP5 simulations

    Science.gov (United States)

    Chen, Ying-Ying; Jin, Fei-Fei

    2017-12-01

    In this study, a simple coupled framework established in Part I is utilized to investigate inter-model diversity in simulating the equatorial Pacific SST annual cycle (SSTAC). It demonstrates that the simulated amplitude and phase characteristics of SSTAC in models are controlled by two internal dynamical factors (the damping rate and phase speed) and two external forcing factors (the strength of the annual and semi-annual harmonic forcing). These four diagnostic factors are further condensed into a dynamical response factor and a forcing factor to derive theoretical solutions of amplitude and phase of SSTAC. The theoretical solutions are in remarkable agreement with observations and CMIP5 simulations. The great diversity in the simulated SSTACs is related to the spreads in these dynamic and forcing factors. Most models tend to simulate a weak SSTAC, due to their weak damping rate and annual harmonic forcing. The latter is due to bias in the meridional asymmetry of the annual mean state of the tropical Pacific, represented by the weak cross-equatorial winds in the cold tongue region.

  11. Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling

    Directory of Open Access Journals (Sweden)

    J. Etourneau

    2013-08-01

    Full Text Available The largest increase in export production in the eastern Pacific of the last 5.3 Myr (million years occurred between 2.2 and 1.6 Myr, a time of major climatic and oceanographic reorganization in the region. Here, we investigate the causes of this event using reconstructions of export production, nutrient supply and oceanic conditions across the Pliocene–Pleistocene in the eastern equatorial Pacific (EEP for the last 3.2 Myr. Our results indicate that the export production peak corresponds to a cold interval marked by high nutrient supply relative to consumption, as revealed by the low bulk sedimentary 15N/14N (δ15N and alkenone-derived sea surface temperature (SST values. This ∼0.6 million year long episode of enhanced delivery of nutrients to the surface of the EEP was predominantly initiated through the upwelling of nutrient-enriched water sourced in high latitudes. In addition, this phenomenon was likely promoted by the regional intensification of upwelling in response to the development of intense Walker and Hadley atmospheric circulations. Increased nutrient consumption in the polar oceans and enhanced denitrification in the equatorial regions restrained nutrient supply and availability and terminated the high export production event.

  12. Microbial diversity and stratification of South Pacific abyssal marine sediments.

    Science.gov (United States)

    Durbin, Alan M; Teske, Andreas

    2011-12-01

    Abyssal marine sediments cover a large proportion of the ocean floor, but linkages between their microbial community structure and redox stratification have remained poorly constrained. This study compares the downcore gradients in microbial community composition to porewater oxygen and nitrate concentration profiles in an abyssal marine sediment column in the South Pacific Ocean. Archaeal 16S rRNA clone libraries showed a stratified archaeal community that changed from Marine Group I Archaea in the aerobic and nitrate-reducing upper sediment column towards deeply branching, uncultured crenarchaeotal and euryarchaeotal lineages in nitrate-depleted, anaerobic sediment horizons. Bacterial 16S rRNA clone libraries revealed a similar shift on the phylum and subphylum level within the bacteria, from a complex community of Alpha-, Gamma- and Deltaproteobacteria, Actinobacteria and Gemmatimonadetes in oxic surface sediments towards uncultured Chloroflexi and Planctomycetes in the anaerobic sediment column. The distinct stratification of largely uncultured bacterial and archaeal groups within the oxic and nitrate-reducing marine sediment column provides initial constraints for their microbial habitat preferences. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  13. Biogeochemical linkage between atmosphere and ocean in the eastern equatorial Pacific Ocean: Results from the EqPOS research cruise

    Science.gov (United States)

    Furutani, H.; Inai, Y.; Aoki, S.; Honda, H.; Omori, Y.; Tanimoto, H.; Iwata, T.; Ueda, S.; Miura, K.; Uematsu, M.

    2012-12-01

    Eastern equatorial Pacific Ocean is a unique oceanic region from several biogeochemical points of view. It is a remote open ocean with relatively high marine biological activity, which would result in limited influence of human activity but enhanced effect of marine natural processes on atmospheric composition. It is also characterized as high nutrient low chlorophyll (HNLC) ocean, in which availability of trace metals such as iron and zinc limits marine primary production and thus atmospheric deposition of these trace elements to the ocean surface is expected to play an important role in regulating marine primary production and defining unique microbial community. High sea surface temperature in the region generates strong vertical air convection which efficiently brings tropospheric atmospheric composition into stratosphere. In this unique eastern equatorial Pacific Ocean, EqPOS (Equatorial Pacific Ocean and Stratospheric/Tropospheric Atmospheric Study) research cruise was organized as a part of SOLAS Japan activity to understand biogeochemical ocean-atmospheric interaction in the region. Coordinated atmospheric, oceanic, and marine biological observations including sampling/characterization of thin air-sea interfacial layer (sea surface microlayer: SML) and launching large stratospheric air sampling balloons were carried out on-board R/V Hakuho Maru starting from 29 January for 39 days. Biogeochemically important trace/long-lived gases such as CO2, dimethyl sulfide (DMS), and some volatile organic carbons (VOCs) both in the atmosphere and seawater were continuously monitored and their air-sea fluxes were also observed using gradient and eddy-covariance techniques. Atmospheric gas measurement of CO2, CH4, N2O, SF6, CO, H2, Ar and isotopic composition of selected gases were further extended to stratospheric air by balloon-born sampling in addition to a vertical profiling of O3, CO2, and H2O with sounding sondes. Physical and chemical properties of marine

  14. Widespread Anthropogenic Nitrogen in Northwestern Pacific Ocean Sediment.

    Science.gov (United States)

    Kim, Haryun; Lee, Kitack; Lim, Dhong-Il; Nam, Seung-Il; Kim, Tae-Wook; Yang, Jin-Yu T; Ko, Young Ho; Shin, Kyung-Hoon; Lee, Eunil

    2017-06-06

    Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower δ 15 N values (expressed as δ 15 N = [ 15 N: 14 N sample / 15 N: 14 N air - 1] × 1000‰; the sediment 15 N: 14 N ratio relative to the air nitrogen 15 N: 14 N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher δ 15 N values (2-3‰ higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment δ 15 N increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (N ANTH ) resulting from fossil fuel combustion and fertilizer use. We concluded that, of several processes, the input of N ANTH appears to be emerging as a new driver of change in the sediment δ 15 N value in marginal seas adjacent to China. The present results indicate that the effect of N ANTH has extended beyond the ocean water column into the deep sedimentary environment, presumably via biological assimilation of N ANTH followed by deposition. Further, the findings indicate that N ANTH is taking over from the conventional paradigm of nitrate flux from nitrate-rich deep water as the primary driver of biological export production in this region of the Pacific Ocean.

  15. Regulation of phytoplankton carbon to chlorophyll ratio by light, nutrients and temperature in the Equatorial Pacific Ocean: a basin-scale model

    Directory of Open Access Journals (Sweden)

    X. J. Wang

    2009-03-01

    Full Text Available The complex effects of light, nutrients and temperature lead to a variable carbon to chlorophyll (C:Chl ratio in phytoplankton cells. Using field data collected in the Equatorial Pacific, we derived a new dynamic model with a non-steady C:Chl ratio as a function of irradiance, nitrate, iron, and temperature. The dynamic model is implemented into a basin-scale ocean circulation-biogeochemistry model and tested in the Equatorial Pacific Ocean. The model reproduces well the general features of phytoplankton dynamics in this region. For instance, the simulated deep chlorophyll maximum (DCM is much deeper in the western warm pool (~100 m than in the Eastern Equatorial Pacific (~50 m. The model also shows the ability to reproduce chlorophyll, including not only the zonal, meridional and vertical variations, but also the interannual variability. This modeling study demonstrates that combination of nitrate and iron regulates the spatial and temporal variations in the phytoplankton C:Chl ratio in the Equatorial Pacific. Sensitivity simulations suggest that nitrate is mainly responsible for the high C:Chl ratio in the western warm pool while iron is responsible for the frontal features in the C:Chl ratio between the warm pool and the upwelling region. In addition, iron plays a dominant role in regulating the spatial and temporal variations of the C:Chl ratio in the Central and Eastern Equatorial Pacific. While temperature has a relatively small effect on the C:Chl ratio, light is primarily responsible for the vertical decrease of phytoplankton C:Chl ratio in the euphotic zone.

  16. Neodymium isotope ratios in fish debris as a tracer for a low oxygen water mass in the equatorial Pacific across the last glacial termination.

    Science.gov (United States)

    Reimi Sipala, M. A.; Marcantonio, F.

    2017-12-01

    The deep ocean has long been suggested as a potential sink of carbon during the LGM, providing storage for the drawdown of atmospheric CO2 observed in the climate record. However, the exact location, origin and pathway of this respired carbon pool remains largely unconstrained. The equatorial Pacific is an important player in the ocean biogeochemical cycling of carbon, with many researchers focusing on the changes in iron-limited systems and potential micronutrient supply changes throughout the Pleistocene glaciation. Here we attempt to isolate the role of deep water circulation changes that may be associated with changing bottom water oxygen conditions in the Central Equatorial Pacific during the last deglaciation. We measure the variability of the Nd isotopic composition of fish debris from three sites in the Central Equatorial Pacific (CEP) along a meridional transect at approximately 160° W -- 0° 28' N (ML1208-17PC), 4° 41' N (ML1208-31BB), and 7 ° 2'N (ML1208-31BB). Nd isotopic values in fish debris reflect the Nd isotopic composition of bottom water at the time of deposition and are insensitive to moderate changes in redox conditions or pore water oxygen levels. Nd isotope ratios can, therefore, be used as an effective deep-ocean water mass tracer. This work attempts to illuminate our current understanding of changes in bottom water oxygenation conditions throughout the Equatorial Pacific over the past 25 kyr. High authigenic U concentrations during peak glacial conditions have been attributed to deep-water suboxic conditions potentially associated with increased respired carbon storage. However, it is still unclear if these changes originate in the Southern Ocean, and propagate to the equatorial Pacific through an increased in penetration of Southern Ocean Intermediate water, or if they represent a change in the efficiency of the biological pump, permitting a drawdown of oxygen in bottom water without increased nutrient availability.

  17. Marine Export Production and Remineralization During Early Eocene Hyperthermal Events at ODP Site 1263, Walvis Ridge, ODP Site 1209, Shatsky Rise and ODP Site 1215, Equatorial Pacific Ocean

    Science.gov (United States)

    Lewis, A.; Griffith, E. M.; Thomas, E.; Winguth, A. M. E.

    2017-12-01

    Understanding the impacts of global hyperthermal events on marine productivity and remineralization is important for understanding the reaction of the ocean to major climate change. Marine export production and remineralization was reconstructed using marine (pelagic) barite accumulation rates (BAR) coupled with records of benthic foraminiferal assemblages across the Paleocene - Eocene Thermal Maximum (PETM) at 55.3 Ma, Eocene Thermal Maximum 2 (ETM2) 2 Ma later, and ETM3 3.1 Ma after the PETM. Marine barite accumulates in deep sea sediment precipitating in the overlying water column during degradation of organic matter exported from the photic zone. Foraminiferal data indicate the amount of organic matter reaching the seafloor. We use the difference between these records to infer changes in rates of remineralization. We present data from ODP Site on Walvis Ridge, Southeastern Atlantic; ODP Site 1209 on Shatsky Rise, North Pacific; and ODP Site 1215, equatorial Pacific. Sites 1263 and 1215 had maximum BAR roughly centered over the maximum negative PETM CIE, whereas at Site 1209 the maximum was before the PETM. The maximum BAR across ETM2 and ETM3 (0.5 and 0.25 of that at the PETM, respectively) was centered over the maximum negative CIE at Site 1263. At Site 1209, the BAR (0.5 the maximum value before the PETM) peaked before ETM2. Barite concentration at Site 1215 was low across at the smaller hyperthermals, but the onset of ETM2 had a maximum value food arrival at the seafloor during elevated BAR, thus indicating enhanced remineralization. During the PETM, at all 3 sites, increases in barite coincided with reduced BFAR. Similar trends were observed during ETM2 at Sites 1263 and 1215, suggesting dramatic changes in remineralization over all hyperthermal events at these sites. Increased remineralization rates could partly account for differences in planktonic and benthic extinction, as observed during the PETM.

  18. Role of the meridional dipole of SSTA and associated cross-equatorial flow in the tropical eastern Pacific in terminating the 2014 El Niño development

    Science.gov (United States)

    Wu, Yi-Kai; Chen, Lin; Hong, Chi-Cherng; Li, Tim; Chen, Cheng-Ta; Wang, Lu

    2018-03-01

    In the boreal spring of 2014, the oceanic and atmospheric conditions were favorable for an El Niño's development. It was predicted that in 2014, a super El Niño or at least a regular El Niño with normal magnitude, would initiate. However, the growth rate of the sea surface temperature anomaly (SSTA) in the equatorial eastern Pacific suddenly declined in the boreal summer. The physical processes responsible for the termination of the 2014 El Niño were addressed in this study. We hypothesized that a meridional dipole of SSTA, characterized by a pronounced warm SSTA over the eastern North Pacific (ENP) and cold SSTA over the eastern South Pacific (ESP), played a crucial role in blocking the 2014 El Niño's development. The observational analysis revealed that the meridional dipole of SSTA and the relevant anomalous cross-equatorial flow in the tropical eastern Pacific, induced anomalous westward ({u^' }0) currents in the equatorial eastern Pacific, leading to negative anomalous zonal advection term (- {u^' }partial \\overline T /partial xpartial \\overline T /partial znegative SSTA tendency in the boreal summer, and thus killed off the budding 2014 El Niño. The idealized numerical experiments further confirmed that the 2014 El Niño's development could be suppressed by the meridional dipole of SSTA, and both the ENP pole and ESP pole make a contribution.

  19. Free troposphere as a major source of CCN for the equatorial pacific boundary layer: long-range transport and teleconnections

    Directory of Open Access Journals (Sweden)

    A. D. Clarke

    2013-08-01

    Full Text Available Airborne aerosol measurements in the central equatorial Pacific during PASE (Pacific Atmospheric Sulfur Experiment revealed that cloud condensation nuclei (CCN activated in marine boundary layer (MBL clouds were strongly influenced by entrainment from the free troposphere (FT. About 65% entered at sizes effective as CCN in MBL clouds, while ~25% entered the MBL too small to activate but subsequently grew via gas to particle conversion. The remaining ~10% were inferred to be sea salt aerosol. FT aerosols at low carbon monoxide (CO mixing ratios ( The observed FT transport over thousands of kilometers indicates teleconnections between MBL CCN and cloud-scavenged sources of both natural and/or residual combustion origin. Nonetheless, in spite of its importance, this source of CCN number is not well represented in most current models and is generally not detectable by satellite because of the low aerosol scattering in such layers as a result of cloud scavenging. In addition, our measurements confirm nucleation in the MBL was not evident during PASE and argue against a localized linear relation in the MBL between dimethyl sulfide (DMS and CCN suggested by the CLAW hypothesis. However, when the FT is not impacted by long-range transport, sulfate aerosol derived from DMS pumped aloft in the ITCZ (Inter-Tropical Convergence Zone can provide a source of CCN to the boundary layer via FT teleconnections involving more complex non-linear processes.

  20. New species of Hebefustis Siebenaller & Hessler 1977 (Isopoda, Asellota, Nannoniscidae) from the Clarion Clipperton Fracture Zone (equatorial NE Pacific).

    Science.gov (United States)

    Kaiser, Stefanie

    2014-03-27

    Macrofaunal collections obtained during the French-German BIONOD expedition to the Clarion Clipperton Fracture Zone (CCFZ), equatorial NE Pacific, in spring 2012 yielded two new nannoniscid species, Hebefustis juansenii sp. n. and H. vecino sp. n., which are described in the current paper. The number and position of posterolateral spines of the pleotelson distinguishes the two new species from all other species in the genus. Both species are similar to each other differ, though, in the length of maxilliped epipodite, the presence of a robust spine on pereonite 2 (in H. juansenii sp. n.) as well as the shape of pereonite 4 anterior margin. They also resemble H. primitivus Menzies, 1962 but can be differentiated from the latter by the shape of lateral margins of pereonites 1-4 and the setation and shape of male pleopod 1. A distribution map and a taxonomic key to all known species in the genus are provided, as well as a checklist of known nannoniscid species from the Pacific is presented.

  1. Ca Isotope Geochemistry in Marine Deep Sea Sediments of the Eastern Pacific

    Science.gov (United States)

    Wittke, A.; Gussone, N. C.; Derigs, D.; Schälling, M.; Teichert, B. M.

    2017-12-01

    Ca isotope ratio analysis (δ44/40Ca) is a powerful tool to investigate diagenetic reactions in marine sedimentary porewater systems, as it is sensitive to processes such as carbonate dissolution, precipitation, recrystallization, ion exchange and deep fluid sources, due to the isotopic difference between dissolved Ca and solid carbonate minerals (e.g. [1];[2]). We analyzed eight sediment cores of the (paleo-) Pacific equatorial age transect. Two sediment cores show decreasing Ca isotope profiles starting at the sediment/water interface with seawater-like values down to sediment-like values due to recrystallization and an increasing in the bottom part again to seawater-like values. The other studied cores show different degrees of flattening of this middle bulge. We interpret this pattern either as an effect of sediment composition and thickness, decreasing recrystallization rates and/or fluid flux or a combination of all of these factors at the respective sampling sites. Element concentration profiles and Sr-isotope variations on some of these sediment cores show a similar behavior, supporting our findings ([3]; [4]). Seawater influx at (inactive) seamounts is supposed to cause seawater-like values at the bottom of the sediment cores by fluids migrating through the oceanic basement (e.g. [5]). While [6] hypothesizes that two seamounts or bathymetric pits are connected, with a recharge and a discharge site [7] say that uptaken fluids could be released through the surrounding seafloor as well due to diffusive exchange with the underlying oceanic crust. Our Ca isotope results combined with a transport reaction model approach support the latter hypothesis. References: [1] Teichert B. M., Gussone N. and Torres M. E. (2009) [2] Ockert C., Gussone N., Kaufhold S. and Teichert B. (2013) [3] Pälike H., Lyle M., Nishi H., Raffi I., Gamage K. and Klaus A. (eds.) (2010) [4] Voigt J., Hathorne E. C., Frank M., Vollstaedt H. and Eisenhauer A. (2015) [5] Villinger H. W

  2. Evidence of Enhanced Respired Carbon in Eastern Equatorial Pacific Deep-Waters over the last 30,000 years

    Science.gov (United States)

    Umling, N. E.; Thunell, R.

    2016-12-01

    Rapid decreases in glacial deep water reservoir ages have been observed in the Eastern Equatorial Pacific (EEP; this study), North Pacific (Rae et al., 2014), Southwest Pacific (Sikes et al., 2016), and North Atlantic (Skinner et al., 2013). It has been hypothesized that release of a deep ocean 14C-depleted, respired-carbon reservoir to the surface ocean and atmosphere is the most likely mechanism for the observed increases in atmospheric CO2 concentrations recorded in ice cores during the last glacial-interglacial transition (Broecker and Barker, 2007). This study examines whether oxygenation, organic carbon flux, and carbonate chemistry in the EEP deep-waters reflect an increase in respired carbon associated with recorded 14C-depletions using isotopic and trace element records from three Panama Basin cores (2,650-3,200 m water-depth). An increase in glacial deep-water respired carbon storage would result in a shift of DIC speciation towards lower carbonate ion concentrations along with deoxygenation of bottom waters. Specifically, we use the boron to calcium (B/Ca) and uranium to calcium (U/Ca) ratios of the benthic foraminifera Cibicidoides wuellerstorfi to reconstruct deep-water carbonate ion concentration (Yu and Elderfield, 2007; Raizsch et al., 2011). Additionally, bottom water oxygenation is estimated from the difference in δ13C of benthic foraminifera living in pore waters at the anoxic boundary and of those living in bottom water (Δ δ13C; Hoogakker et al., 2015, 2016), while carbon flux was assessed from the U/Ca and Cd/Ca of foraminiferal authigenic coatings.

  3. The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

    Science.gov (United States)

    de la Fuente, Maria; Calvo, Eva; Skinner, Luke; Pelejero, Carles; Evans, David; Müller, Wolfgang; Povea, Patricia; Cacho, Isabel

    2017-12-01

    It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state (Δ[CO32-], and therefore [CO32-]), along with δ13C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], δ13C, and [O2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a "counteracting" mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be "sequestered" by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.

  4. Assessing the Skill of Chlorophyll Forecasts: Latest Development and Challenges Ahead Using the Case of the Equatorial Pacific

    Science.gov (United States)

    Rousseaux, Cecile S.; Gregg, Watson W.

    2018-01-01

    Using a global ocean biogeochemical model combined with a forecast of physical oceanic and atmospheric variables from the NASA Global Modeling and Assimilation Office, we assess the skill of a chlorophyll concentrations forecast in the Equatorial Pacific for the period 2012-2015 with a focus on the forecast of the onset of the 2015 El Nino event. Using a series of retrospective 9-month hindcasts, we assess the uncertainties of the forecasted chlorophyll by comparing the monthly total chlorophyll concentration from the forecast with the corresponding monthly ocean chlorophyll data from the Suomi-National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (S-NPP VIIRS) satellite. The forecast was able to reproduce the phasing of the variability in chlorophyll concentration in the Equatorial Pacific, including the beginning of the 2015-2016 El Nino. The anomaly correlation coefficient (ACC) was significant (p less than 0.05) for forecast at 1-month (R=0.33), 8-month (R=0.42) and 9-month (R=0.41) lead times. The root mean square error (RMSE) increased from 0.0399 microgram chl L(exp -1) for the 1-month lead forecast to a maximum of 0.0472 microgram chl L(exp -1) for the 9-month lead forecast indicating that the forecast of the amplitude of chlorophyll concentration variability was getting worse. Forecasts with a 3-month lead time were on average the closest to the S-NPP VIIRS data (23% or 0.033 microgram chl L(exp -1)) while the forecast with a 9-month lead time were the furthest (31% or 0.042 microgram chl L(exp -1)). These results indicate the potential for forecasting chlorophyll concentration in this region but also highlights various deficiencies and suggestions for improvements to the current biogeochemical forecasting system. This system provides an initial basis for future applications including the effects of El Nino events on fisheries and other ocean resources given improvements identified in the analysis of these results.

  5. Physical profile data collected in the Equatorial Pacific during cruises to service the TAO/TRITON array, a network of deep ocean moored buoys, February 23 - December 16, 2005 (NODC Accession 0002644)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — During 2005, CTD data were collected in the equatorial Pacific Ocean during cruises to service the TAO/TRITON array, a network of deep ocean moored buoys to support...

  6. Physical and nutrient data from bottle and CTD casts from the THOMAS THOMPSON from the equatorial Pacific Ocean from 30 January 1992 to 09 March 1992 (NODC Accession 9600091)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical and nutrient data were collected from bottle and CTD casts from the THOMAS THOMPSON from the equatorial Pacific Ocean. Data were collected by the Bigelow...

  7. Physical profile and meteorological data from CTD casts during cruises to service the TAO/TRITON buoys in the equatorial Pacific from 02 March 2002 to 22 November 2002 (NODC Accession 0000945)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical profile data and meteorological data were collected from CTD casts in the equatorial Pacific Ocean during cruises to to service the TAO/TRITON buoy array....

  8. Physical profile data collected by NOAA Ship Ronald H. Brown and NOAA Ship KA'IMIMOANA during the year 2006 in the equatorial Pacific Ocean, 2006-01 to 2006-11 (NODC Accession 0012641)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD data were collected in the equatorial Pacific Ocean, during 2006, to service the TAO/TRITON array, a network of deep ocean moored buoys to support research and...

  9. The Effects of Climate Variability on Phytoplankton Composition in the Equatorial Pacific Ocean using a Model and a Satellite-Derived Approach

    Science.gov (United States)

    Rousseaux, C. S.; Gregg, W. W.

    2012-01-01

    Compared the interannual variation in diatoms, cyanobacteria, coccolithophores and chlorophytes from the NASA Ocean Biogeochemical Model with those derived from satellite data (Hirata et al. 2011) between 1998 and 2006 in the Equatorial Pacific. Using NOBM, La Ni a events were characterized by an increase in diatoms (correlation with MEI, r=-0.81, Pphytoplankton community in response to climate variability. However, satellite-derived phytoplankton groups were all negatively correlated with climate variability (r ranged from -0.39 for diatoms to -0.64 for coccolithophores, Pphytoplankton groups except diatoms than NOBM. However, the different responses of phytoplankton to intense interannual events in the Equatorial Pacific raises questions about the representation of phytoplankton dynamics in models and algorithms: is a phytoplankton community shift as in the model or an across-the-board change in abundances of all phytoplankton as in the satellite-derived approach.

  10. Analysis of equatorial plasma bubble zonal drift velocities in the Pacific sector by imaging techniques

    Directory of Open Access Journals (Sweden)

    D. Yao

    2007-03-01

    Full Text Available Using 1024 nights of data from 2002–2005 taken by the Cornell Narrow Field Imager (CNFI, we examine equatorial plasma bubble (EPB zonal drift velocity characteristics. CNFI is located at the Maui Space Surveillance Site on the Haleakala Volcano (geographic: 20.71° N, 203.83° E; geomagnetic: 21.03° N, 271.84° E on the island of Maui, Hawaii. The imager is set up to view in a magnetic field-aligned geometry in order to maximize its resolution. We calculate the zonal drift velocities using two methods: a correlation routine and an EPB west-wall intensity gradient tracking routine. These two methods yield sizeable differences in the evenings, suggesting strong pre-local midnight EPB development. An analysis of the drift velocities is also performed based on the three influencing factors of season, geomagnetic activity, and solar activity. In general, our data match published trends and drift characteristics from past studies. However, we find that the drift magnitudes are much lower than results from other imagers at similar latitude sectors but at different longitude sectors, suggesting that zonal drift velocities have a longitudinal dependence.

  11. Equatorial night-time spread-F characteristics observed from stations in the Western Pacific

    International Nuclear Information System (INIS)

    Huang Tianxi

    1985-01-01

    A comparative study of the ionospheric spread-F observed at an equatorial station. Port Moresby (9 0 24.5'S, 147 0 9.9'E; magn. Dip lat. 18 0 S), Papua new Guinea, with corresponding data from the East Asian stations during a period 27 May-19 Jun 1983, as well as the same periods for 1981 and 1982, is presented. The Port Moresby spread-F condition is particularly outstanding and persistent at night and the occurrence of spread-F between 23 LT and 05 LT near June solstice is very high, reaching 100% of all observed nights. The latitudinal variation of nocturnal spread-F, its duration and connection with sunspot number are analyzed. The relationship between long-term variation of night-time spread-F occurrence and solar activity during June and December solstices from 1954 up to 1984 at a typical lower magnetic latitudinal station. Wuhan (30 0 32.7'N, 114 0 21.5'E; magn. dip lat. 26 0 N), is also investigated. (author)

  12. Late Cenozoic stable isotope stratigraphy and paleoceanography of DSDP sites from the East equatorial and central north Pacific Ocean

    International Nuclear Information System (INIS)

    Keigwin, L.D. Jr

    1979-01-01

    Stable isotopic analyses of Middle Miocene to Quaternary foraminiferal calcite from east equatorial and central north Pacific DSDP cores have provided much new information on the paleoceanography of the Pacific Neogene. The history of delta 18 O change in planktonic foraminifera reflects the changing isotopic composition and temperature of seawater at the time of test formation. Changes in the isotopic composition of benthonic foraminfera largely reflect changes in the volume of continental ice. Isotopic data from these cores indicates the following sequence of events related to continental galaciation: (1) A permanent Antarctic ice sheet developed late in the Middle Miocene (about 13 to 11.5 m.y. ago). (2) The Late Miocene (about 11.5 to 5 m.y. ago) is marked by significant variation in delta 18 O of about 0.5% throughout, indicating instability of Antarctic ice cap size or bottom-water temperature. (3) The early Pliocene (5 to about 3 m.y. ago) was a time of relative stability in ice volume and bottom-water temperature. (4) Growth of permanent Northern Hemisphere ice sheets is inferred to have begun about 3 m.y. ago. (5) The late Pliocene (3 to about 1.8 m.y. ago) is marked by one major glaciation or bottom-water cooling dated between about 2.1 to 2.3 m.y. (6) There is some evidence that the frequency of glacial-interglacial cycles increased at about 0.9 m.y. (Auth.)

  13. Eastern equatorial Pacific sea surface temperature annual cycle in the Kiel climate model: simulation benefits from enhancing atmospheric resolution

    Science.gov (United States)

    Wengel, C.; Latif, M.; Park, W.; Harlaß, J.; Bayr, T.

    2018-05-01

    A long-standing difficulty of climate models is to capture the annual cycle (AC) of eastern equatorial Pacific (EEP) sea surface temperature (SST). In this study, we first examine the EEP SST AC in a set of integrations of the coupled Kiel Climate Model, in which only atmosphere model resolution differs. When employing coarse horizontal and vertical atmospheric resolution, significant biases in the EEP SST AC are observed. These are reflected in an erroneous timing of the cold tongue's onset and termination as well as in an underestimation of the boreal spring warming amplitude. A large portion of these biases are linked to a wrong simulation of zonal surface winds, which can be traced back to precipitation biases on both sides of the equator and an erroneous low-level atmospheric circulation over land. Part of the SST biases also is related to shortwave radiation biases related to cloud cover biases. Both wind and cloud cover biases are inherent to the atmospheric component, as shown by companion uncoupled atmosphere model integrations forced by observed SSTs. Enhancing atmosphere model resolution, horizontal and vertical, markedly reduces zonal wind and cloud cover biases in coupled as well as uncoupled mode and generally improves simulation of the EEP SST AC. Enhanced atmospheric resolution reduces convection biases and improves simulation of surface winds over land. Analysis of a subset of models from the Coupled Model Intercomparison Project phase 5 (CMIP5) reveals that in these models, very similar mechanisms are at work in driving EEP SST AC biases.

  14. Constraints on the magnitude of the deglacial migration of the ITCZ in the Central Equatorial Pacific Ocean

    Science.gov (United States)

    Reimi, Maria A.; Marcantonio, Franco

    2016-11-01

    Accurate paleo-latitudinal reconstructions of the Intertropical Convergence Zone (ITCZ) are necessary for understanding tropical hydroclimate and atmospheric circulation. Paleoclimate models and records suggest that as global temperatures increase, the ITCZ should migrate towards the warmer hemisphere. Many uncertainties remain regarding the magnitude of this migration, and few studies have focused on the Central Equatorial Pacific (CEP). Here, we use eolian dust records recovered from three locations in the CEP to address changes in dust provenance across the paleo ITCZ since the last glacial maximum (LGM). Radiogenic isotope compositions of Nd and Pb show that dust delivered to the CEP was sourced mainly from two regions: East Asia and South America. From these data we deduced that since Marine Oxygen Isotope Stage 2 (MIS2) the ITCZ has migrated north to its modern position, being displaced by as much as 7°, to as little as 2.5°. We find that the ITCZ migrated further north during the early Holocene (∼9 kyr), reaching its position furthest north during the mid-Holocene warm interval (∼7 kyr), based on an increase in South American dust at the northernmost sites.

  15. A simple estimation of equatorial Pacific response from windstress to untangle Indian Ocean dipole and basin influences on El Nino

    Digital Repository Service at National Institute of Oceanography (India)

    Izumo, T.; Vialard, J.; Dayan, H.; Lengaigne, M.; Suresh, I.

    ). To summarize, the LCS combined with a simple linear SST equation allows us  to simulate the interannual variations of U, H and SST along the equatorial Pacific reasonably  well, making it a suitable tool for our study.   2.4) AGCM experiments  We only  provide  a  brief  summary  of  the AGCM experiments used  in  this  paper... pressure gradient, with the ocean in a quasi‐stationnary state (the so‐called “fast wave”  limit,  e.g.  Neelin  et  al.  1991).  The  ocean  hence  acts  as  a  bandpass  filter  of  the  atmospheric  forcing. While  the basin modes approach (e.g. Cane and Sarachik 1979, McCreary and Moore  1981)  is  a  good  tool  to  understand  the...

  16. Detrital zircon typology and U/Pb geochronology for the Miocene Ladrilleros-Juanchaco sedimentary sequence, Equatorial Pacific (Colombia): New constraints on provenance and paleogeography in northwestern South America

    Energy Technology Data Exchange (ETDEWEB)

    Osorio-Granada, E.; RESTREPO-MORENO, S.A.; MUÑOZ-VALENCIA, J.A.; TREJOS-TAMAYO, R.A.; PARDO-TRUJILLO, A.; BARBOSA-ESPITIA, A.A.

    2017-11-01

    Typology and internal texture analyses were performed on detrital zircons obtained from the Miocene sandstones of the Ladrilleros-Juanchaco sedimentary sequence (Colombia, Equatorial Pacific). This analysis was complemented with zircon U/Pb dating to identify typology-age associations as indicators of sediment provenance. Our results show that zircons with S and P dominant typologies have internal structures/zoning indicative of igneous, and potentially also metamorphic, origins. Morphometric results suggest limited transport from source areas. Both typology and U/Pb data point to the western Cordillera as the principal source of detrital materials for this sedimentary sequence. A paleogeographic reconstruction shows that, during the Late Miocene, significant portions of the western Cordillera were uplifted and actively eroding, thereby forming a fluvio-topographic barrier that prevented sediments from the central Cordillera reaching the Pacific basins. Exhumed Miocene plutons located along the axis of the western Cordillera may also have played a role as geomorphologically active massifs. This study demonstrates that typologic analysis on detrital zircon grains is a useful tool for establishing provenance and paleogeography in complex litho-tectonic areas where overlapping U/Pb signatures can lead to contradictory results.

  17. Magnetic Hysteresis of Deep-Sea Sediments in Korea Deep Ocean Study(KODOS) Area, NE Pacific

    Science.gov (United States)

    Kim, K.; Park, C.; Yoo, C.

    2001-12-01

    The KODOS area within the Clarion-Clipperton fracture zone (C-C zone) is surrounded by the Hawaiian and Line Island Ridges to the west and the central American continent to the east. Topography of the seafloor consists of flat-topped abyssal hills and adjacent abyssal troughs, both of which run parallel in N-S direction. Sediments from the study area consist mainly of biogenic sediments. Latitudinal zonation of sedimentary facies was caused by the accumulation of biogenic materials associated with the equatorial current system and movement of the Pacific plate toward the north or northwest. The KODOS area belongs to the latitudinal transition zone having depositional characteristics between non-fossiliferous pelagic clay-dominated zone and calcareous sediment-dominated zone. The box core sediments of the KODOS area are analyzed in an attempt to obtain magnetic hysteresis information and to elucidate the relationship between hysteresis property and lithological facies. Variations in magnetic hysteresis parameters with unit layers reflect the magnetic grain-size and concentrations within the sediments. The ratios of remanant coercivity/coercive force (Hcr/Hc) and saturation remnance/saturation magnetization (Mrs/Ms) indicate that coarse magnetic grains are mainly distributed in dark brown sediments (lower part of the sediment core samples) reflecting high Hcr/Hc and low Mrs/Ms ratios. These results are mainly caused by dissolution differences with core depth. From the plotting of the ratios of hyteresis parameters, it is indicated that magnetic minerals in cubic samples are in pseudo-single domain (PSD) state.

  18. Two major Cenozoic episodes of phosphogenesis recorded in equatorial Pacific seamount deposits

    Science.gov (United States)

    Hein, J.R.; Hsueh-Wen, Yeh; Gunn, S.H.; Sliter, W.V.; Benninger, L.M.; Chung-Ho, Wang

    1993-01-01

    The phosphorites occur in a wide variety of forms, but most commonly carbonate fluorapatite (CFA) replaced middle Eocene and older carbonate sediment in a deep water environment (>1000 m). Element ratios distinguish seamount phosphorites from continental margin, plateau, and insular phosphorites. Uranium and thorium contents are low and total rare earch element (REE) contents are generally high. The paleoceanographic conditions initiated and sustained development of phosphorite by accumulation of dissolved phosphorus in the deep sea during relatively stable climatic conditions when oceanic circulation was sluggish. Fluctuations in climate, sealevel, and upwelling that accompanied the climate transitions may have driven cycles of enrichment and depletion of the deep-sea phosphorus reservoir. -from Authors

  19. New Magnetic and 10Be/9Be results from ODP site 851 (East Equatorial Pacific)

    Science.gov (United States)

    Valet, J. P.; Savranskaia, T.; Anojh, T.; Meynadier, L.; Thouveny, N.; Gacem, L.; L2NC, A. T.; Bassinot, F. C.; Simon, Q.

    2017-12-01

    The paleomagnetic record from ODP site 851 was the first long data of relative paleointensity that attempted to describe 4 Ma of geomagnetic variations. Among other features, it was characterized by an asymmetrical saw-tooth pattern of the intensity changes across reversals. The upper part of the record (0 to 1.1 Ma) was documented by stepwise alternating field (af) demagnetization of U-channels, while the deeper part could not be sampled by U-channels and instead combined shipboard measurements and stepwise demagnetized single samples within specific intervals. Thermal demagnetization was also conducted within specific intervals to assess the absence of viscous component. We performed a new detailed study using U-channels and single samples that were taken along a continuous splice section that covers the upper 80 meters of sediment. Stepwise demagnetization of the natural magnetization and of the anhysteretic magnetization were carried out for all samples and U-channels in order to improve the resolution and the reliability of relative paleointensity for the older part of the record. The new results improve the detailed magnetostratigraphy that was formerly established and provide additional details to the paleointensity results. In parallel, 10Be/9Be measurements were carried out at the same levels as the magnetic measurements to test further the controversial asymmetrical pattern of relative paleointensity. Unfortunately, the 10Be/9Be results did not provide any consistent signal. This failure most likely results from high carbonate concentration (about 85%) that yields poor adsorption of beryllium by the sediment particles and therefore generates large fluctuations. The reliability of the paleointensity record is linked to downcore homogeneity of the sediment that is characterized by little variability of carbonate content and therefore little changes in the magnetization response to the field. Summarizing poor clay content appears to be a favorable situation

  20. Caribbean Sea rainfall variability during the rainy season and relationship to the equatorial Pacific and tropical Atlantic SST

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Renguang [Institute of Global Environment and Society, Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); Kirtman, Ben P. [University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL (United States)

    2011-10-15

    The present study investigates the Caribbean Sea rainfall variability during the early and late rainy seasons and its association with sea surface temperature (SST) and air-sea interaction based on observational estimates, the NCEP Climate Forecast System (CFS) and Global Forecast System (GFS) simulations, and the CFS retrospective forecasts. Analysis of the observational estimates indicates that air-sea interaction is important over the Caribbean Sea, whereas the atmospheric forcing of SST dominates over the Gulf of Mexico. The CFS simulation captures the basic elements of this observed air-sea relationship. The GFS simulation produces spurious SST forcing of the atmosphere over the Gulf of Mexico largely due to prescribing SST. The CFS forecasts capture the air-sea relationship in the late rainy season (August-October), but cannot reproduce the SST forcing of atmosphere over the Caribbean Sea in the early rainy season (May-July). An empirical orthogonal function (EOF) analysis indicates that the leading modes of percent anomalies of the rainy season precipitation have the largest loading in the southern Caribbean Sea in observations. The model simulations and forecasts skillfully reproduce the spatial pattern, but not the temporal evolution. The Caribbean Sea rainfall variability in the early rainy season is mainly due to the tropical North Atlantic (TNA) SST anomalies in observations, is contributed by both the TNA and eastern equatorial Pacific (EEP) SST anomalies in the CFS simulation, and has an overly large impact from the EEP SST anomalies in the GFS simulation and the CFS forecasts. The observed Caribbean Sea rainfall variability in the late rainy season has a leading impact from the EEP SST anomalies, with a secondary contribution from the TNA SST anomalies. In comparison, the model simulations and forecasts overestimate the impacts of the EEP SST anomalies due to an earlier development and longer duration of the El Nino-Southern Oscillation in the CFS

  1. Mid-depth respired carbon storage and oxygenation of the eastern equatorial Pacific over the last 25,000 years

    Science.gov (United States)

    Umling, Natalie E.; Thunell, Robert C.

    2018-06-01

    A growing body of evidence suggests that respired carbon was stored in mid-depth waters (∼1-3 km) during the last glacial maximum (LGM) and released to the atmosphere from upwelling regions during deglaciation. Decreased ventilation, enhanced productivity, and enhanced carbonate dissolution are among the mechanisms that have been cited as possible drivers of glacial CO2 drawdown. However, the relative importance of each of these mechanisms is poorly understood. New approaches to quantitatively constrain bottom water carbonate chemistry and oxygenation provide methods for estimating historic changes in respired carbon storage. While increased CO2 drawdown during the LGM should have resulted in decreased oxygenation and a shift in dissolved inorganic carbon (DIC) speciation towards lower carbonate ion concentrations, this is complicated by the interplay of carbonate compensation, export productivity, and circulation. To disentangle these processes, we use a multiproxy approach that includes boron to calcium (B/Ca) ratios of the benthic foraminifera Cibicidoides wuellerstorfi to reconstruct deep-water carbonate ion concentrations ([CO32-]) and the uranium to calcium (U/Ca) ratio of foraminiferal coatings in combination with benthic foraminiferal carbon isotopes to reconstruct changes in bottom water oxygen concentrations ([O2]) and organic carbon export. Our records indicate that LGM [CO32-] and [O2] was reduced at mid water depths of the eastern equatorial Pacific (EEP), consistent with increased respired carbon storage. Furthermore, our results suggest enhanced mixing of lower Circumpolar Deep Water (LCDW) to EEP mid water depths and provide evidence for the importance of circulation for oceanic-atmospheric CO2 exchange.

  2. {sup 239}Pu and {sup 240}Pu inventories and {sup 240}Pu/{sup 239}Pu atom ratios in the equatorial Pacific Ocean water column

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Masatoshi, E-mail: myamada@cc.hirosaki-u.ac.jp [Department of Radiation Chemistry, Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564 (Japan); Zheng, Jian [Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan)

    2012-07-15

    The {sup 239+240}Pu concentrations and {sup 240}Pu/{sup 239}Pu atom ratios were determined by alpha spectrometry and inductively coupled plasma mass spectrometry for seawater samples from two stations, one at the equator and the other in the equatorial South Pacific. To better understand the fate of Pu isotopes, this study dealt with the contribution of the close-in fallout Pu from the Pacific Proving Grounds (PPG) in water columns of the Pacific Ocean. The {sup 239}Pu, {sup 240}Pu and {sup 239+240}Pu inventories over the depth interval 0-3000 m at the equator station were 10.4, 8.9 and 19.3 Bq m{sup -2}, respectively. Further, no noticeable difference was observed in {sup 239}Pu, {sup 240}Pu and {sup 239+240}Pu inventories over the depth interval 0-3000 m between the two stations. The total {sup 239+240}Pu inventories were significantly higher than the expected cumulative deposition density of global fallout. Water column {sup 239+240}Pu inventories measured in this study were lower than those reported for comparable stations in the Geochemical Ocean Sections Study, indicating that these inventories have been decreasing at average rates of 0.89 {+-} 0.07 and 0.16 {+-} 0.07 Bq m{sup -2} yr{sup -1} at the equator and equatorial South Pacific stations, respectively, from 1973 to 1990. The obtained {sup 240}Pu/{sup 239}Pu atom ratios were higher than the mean global fallout ratio of 0.18. These high atom ratios proved the existence of close-in tropospheric fallout Pu from the PPG in the Marshall Islands. The {sup 239+240}Pu inventories originating from the close-in fallout in the entire water column were estimated to be 11.1 Bq m{sup -2} at the equator station and 7.1 Bq m{sup -2} at the equatorial South Pacific Ocean station, and the relative percentages of close-in fallout Pu were 40% at the former and 34% at the latter. A significant amount of close-in fallout Pu originating from the PPG has been transported to deep layers below the 1000 m depth in the equatorial

  3. Late Neogene Orbitally-Forced Sea Surface Temperature Variability in the Eastern Equatorial Pacific as Measured by Uk'37 and TEX86

    Science.gov (United States)

    Lawrence, K. T.; Pearson, A.; Castañeda, I. S.; Peterson, L.

    2017-12-01

    Key features of late Neogene climate remain uncertain due to conflicting records derived from different sea surface temperature (SST) proxies. To resolve these disputes, it is necessary to explore both the consistencies and differences between paleotemperature estimates from critical oceanographic regimes. Here, we report orbital-scale climate variability at ODP Site 846 in the Eastern Equatorial Pacific (EEP) in the interval from 5-6 Ma using alkenone and TEX86 temperature estimates. Results from both proxies are very similar in their secular trends and magnitude of long-term temperature change; and spectral analysis demonstrates that the records are coherent and in-phase or nearly in-phase in both the obliquity and precession bands. However, we find that the temperatures reconstructed by TEX86 are consistently offset towards colder values by 2ºC with orbital-scale variations approximately twice the amplitude of the Uk'37 derived estimates. Both temperature records are antiphased - i.e. "colder" - at higher sediment alkenone concentrations, a qualitative indicator of increased glacial productivity. Temperature differences between the proxies are accentuated during glacial intervals in contrasts to modern observations of EEP surface and subsurface temperatures, which show that thermocline temperatures are fairly stable, and thus by analogy, glacial cooling and/or enhanced upwelling should have reduced rather than accentuated temperature gradients in the upper water column. Therefore, arguments that Uk'37 corresponds to temperature variability in the surface, while TEX86 responds to the subsurface, may be too simplistic. Instead, it appears generally true that high-productivity environments, including the EEP, tend to have negative TEX86 anomalies. This may reflect a dual dependence of TEX86 records on both water column temperature and local productivity. Overall, our data suggest that in the EEP and likely in other upwelling zones, paleotemperature data derived

  4. Source Evaluation and Trace Metal Contamination in Benthic Sediments from Equatorial Ecosystems Using Multivariate Statistical Techniques.

    Directory of Open Access Journals (Sweden)

    Nsikak U Benson

    Full Text Available Trace metals (Cd, Cr, Cu, Ni and Pb concentrations in benthic sediments were analyzed through multi-step fractionation scheme to assess the levels and sources of contamination in estuarine, riverine and freshwater ecosystems in Niger Delta (Nigeria. The degree of contamination was assessed using the individual contamination factors (ICF and global contamination factor (GCF. Multivariate statistical approaches including principal component analysis (PCA, cluster analysis and correlation test were employed to evaluate the interrelationships and associated sources of contamination. The spatial distribution of metal concentrations followed the pattern Pb>Cu>Cr>Cd>Ni. Ecological risk index by ICF showed significant potential mobility and bioavailability for Cu, Cu and Ni. The ICF contamination trend in the benthic sediments at all studied sites was Cu>Cr>Ni>Cd>Pb. The principal component and agglomerative clustering analyses indicate that trace metals contamination in the ecosystems was influenced by multiple pollution sources.

  5. Role of hydrology in the formation of Co-rich Mn crusts from the equatorial N Pacific, equatorial S Indian Ocean and the NE Atlantic Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Glasby, G.P.; Mountain, B.; Vineesh, T.C.; Banakar, V.K.; Rajani, R.; Ren, X.

    , the distribution of oxygen in seawater is taken from Profile PO3 which is an E-W Profile in the Equa- torial Pacific Ocean at 25°N (http://www.ewoce.org/ gallery/P3_OXYGEN.gif; Fig. 4). This profile is 4–6 degrees of latitude north of the transect from Horizon... in the Indian Ocean at 80°E (http://www. ewoce.org/gallery/18_OXYGEN.gif; Fig. 5). From this profile, it can be seen that the OMZ at ANS occurs at a water depth of ~900 m and has an oxygen content of ~45 mmol kg -1 . The Co-rich Mn crust was taken at water depth...

  6. A database of paleoceanographic sediment cores from the North Pacific, 1951-2016

    Science.gov (United States)

    Borreggine, Marisa; Myhre, Sarah E.; Mislan, K. Allison S.; Deutsch, Curtis; Davis, Catherine V.

    2017-09-01

    We assessed sediment coring, data acquisition, and publications from the North Pacific (north of 30° N) from 1951 to 2016. There are 2134 sediment cores collected by American, French, Japanese, Russian, and international research vessels across the North Pacific (including the Pacific subarctic gyre, Alaskan gyre, Japan margin, and California margin; 1391 cores), the Sea of Okhotsk (271 cores), the Bering Sea (123 cores), and the Sea of Japan (349 cores) reported here. All existing metadata associated with these sediment cores are documented here, including coring date, location, core number, cruise number, water depth, vessel metadata, and coring technology. North Pacific sediment core age models are built with isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithological proxies. Here, we evaluate the iterative generation of each published age model and provide comprehensive documentation of the dating techniques used, along with sedimentation rates and age ranges. We categorized cores according to the availability of a variety of proxy evidence, including biological (e.g., benthic and planktonic foraminifera assemblages), geochemical (e.g., major trace element concentrations), isotopic (e.g., bulk sediment nitrogen, oxygen, and carbon isotopes), and stratigraphic (e.g., preserved laminations) proxies. This database is a unique resource to the paleoceanographic and paleoclimate communities and provides cohesive accessibility to sedimentary sequences, age model development, and proxies. The data set is publicly available through PANGAEA at PANGAEA.875998" target="_blank">https://doi.org/10.1594/PANGAEA.875998.

  7. A database of paleoceanographic sediment cores from the North Pacific, 1951–2016

    Directory of Open Access Journals (Sweden)

    M. Borreggine

    2017-09-01

    Full Text Available We assessed sediment coring, data acquisition, and publications from the North Pacific (north of 30° N from 1951 to 2016. There are 2134 sediment cores collected by American, French, Japanese, Russian, and international research vessels across the North Pacific (including the Pacific subarctic gyre, Alaskan gyre, Japan margin, and California margin; 1391 cores, the Sea of Okhotsk (271 cores, the Bering Sea (123 cores, and the Sea of Japan (349 cores reported here. All existing metadata associated with these sediment cores are documented here, including coring date, location, core number, cruise number, water depth, vessel metadata, and coring technology. North Pacific sediment core age models are built with isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithological proxies. Here, we evaluate the iterative generation of each published age model and provide comprehensive documentation of the dating techniques used, along with sedimentation rates and age ranges. We categorized cores according to the availability of a variety of proxy evidence, including biological (e.g., benthic and planktonic foraminifera assemblages, geochemical (e.g., major trace element concentrations, isotopic (e.g., bulk sediment nitrogen, oxygen, and carbon isotopes, and stratigraphic (e.g., preserved laminations proxies. This database is a unique resource to the paleoceanographic and paleoclimate communities and provides cohesive accessibility to sedimentary sequences, age model development, and proxies. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.875998.

  8. Cloud cover over the equatorial eastern Pacific derived from July 1983 International Satellite Cloud Climatology Project data using a hybrid bispectral threshold method

    Science.gov (United States)

    Minnis, Patrick; Harrison, Edwin F.; Gibson, Gary G.

    1987-01-01

    A set of visible and IR data obtained with GOES from July 17-31, 1983 is analyzed using a modified version of the hybrid bispectral threshold method developed by Minnis and Harrison (1984). This methodology can be divided into a set of procedures or optional techniques to determine the proper contaminate clear-sky temperature or IR threshold. The various optional techniques are described; the options are: standard, low-temperature limit, high-reflectance limit, low-reflectance limit, coldest pixel and thermal adjustment limit, IR-only low-cloud temperature limit, IR clear-sky limit, and IR overcast limit. Variations in the cloud parameters and the characteristics and diurnal cycles of trade cumulus and stratocumulus clouds over the eastern equatorial Pacific are examined. It is noted that the new method produces substantial changes in about one third of the cloud amount retrieval; and low cloud retrievals are affected most by the new constraints.

  9. The Açu Reef morphology, distribution, and inter reef sedimentation on the outer shelf of the NE Brazil equatorial margin

    Science.gov (United States)

    do Nascimento Silva, Luzia Liniane; Gomes, Moab Praxedes; Vital, Helenice

    2018-05-01

    Submerged reefs, referred to as the Açu Reefs, have been newly observed on both sides of the Açu Incised Valley on the northeastern equatorial Brazilian outer shelf. This study aims to understand the roles of shelf physiography, its antecedent morphologies, and its inter reef sedimentation on the different development stages of the biogenic reef during last deglacial sea-level rise. The data sets consist of side-scan sonar imagery, one sparker seismic profile, 76 sediment samples, and underwater photography. Seven backscatter patterns (P1 to P7) were identified and associated with eleven sedimentary carbonate and siliciclastic facies. The inherited relief, the mouth of the paleo incised valley, and the interreef sediment distribution play major controls on the deglacial reef evolution. The reefs occur in a depth-limited 25-55 m water depth range and in a 6 km wide narrow zone of the outer shelf. The reefs crop out in a surface area over 100 km2 and occur as a series of NW-SE preferentially orientated ridges composed of three parallel ridge sets at 45, 35, and 25 m of water depth. The reefs form a series of individual, roughly linear ridges, tens of km in length, acting as barriers in addition to scattered reef mounds or knolls, averaging 4 m in height and grouped in small patches and aggregates. The reefs, currently limited at the transition between the photic and mesophotic zones, are thinly covered by red algae and scattered coral heads and sponges. Taking into account the established sea-level curves from the equatorial Brazilian northeastern shelf / Rochas Atoll and Barbados, the shelf physiography, and the shallow bedrock, the optimal conditions for reef development had to occur during a time interval (11-9 kyr BP) characterized by a slowdown of the outer shelf flooding, immediately following Meltwater Pulse-1B. This 2 kyr short interval provided unique conditions for remarkable reef backstepping into distinct parallel ridge sets. Furthermore, the Açu Reefs

  10. Core top confirmation of the carbonate ion effect in multiple species of planktic foraminifera and a reassessment of the upper water column equatorial Pacific δ13CFORAM records.

    Science.gov (United States)

    Fehrenbacher, J. S.; Spero, H. J.

    2017-12-01

    Planktic foraminifera carbon (δ13CFORAM) and oxygen (δ18OFORAM) isotope records play a vital role in paleoceanographic reconstructions. The δ18OFORAM values are typically minimally offset from equilibrium δ18O-calcite and are widely applied in oceanographic reconstructions of upper water column hydrography. In contrast, δ13CFORAM are underutilized in paleoceanographic reconstructions. δ13CFORAM are more difficult to interpret due to species-specific δ13CFORAM offsets from the δ13C of the dissolved inorganic carbon of seawater (δ13CDIC). In this study, we analyzed the δ18OFORAM and δ13CFORAM of individual foraminifera shells from a suite of planktic foraminifer species obtained from core top (Holocene) intervals from Eastern Equatorial Pacific (TR163-19), Western Caribbean (ODP 999A), and Equatorial Indian Ocean (ODP 714A) cores. We also include published records from the Western Equatorial Pacific (MW91-9 15GGC). We find the δ13CFORAM offsets from the local water column δ13CDIC are large, variable, region specific, and are correlated to the ambient carbonate ion concentration ([CO32-]) of seawater. We show that the regional offsets from δ13CDIC are due to the carbonate ion effect (CIE) on δ13CFORAM (Spero et al., 1997; Bijma et al., 1999) and variations in water column [CO32-]. More importantly, our results demonstrate that regional and/or culture based δ13CFORAM offsets from δ13CDIC are not applicable globally. Rather, owing to regional differences in water column [CO32-] and species-specific relationships between [CO32-] and δ13CFORAM, δ13CFORAM must be corrected for the regional CIE in order to infer vertical δ13CDIC gradients or to compare δ13CFORAM records from one region to another. Laboratory culture suggests the carbonate ion effect on δ18OFORAM is 1/3 that of δ13CFORAM (Spero et al., 1997). Thus, in order to obtain correct δ18OFORAM temperatures or δ18OSW (when used in conjunction with Mg/Ca) the δ18OFORAM offsets from δ18

  11. The detection of magnetotactic bacteria in deep sea sediments from the east Pacific Manganese Nodule Province.

    Science.gov (United States)

    Dong, Yi; Li, Jinhua; Zhang, Wuchang; Zhang, Wenyan; Zhao, Yuan; Xiao, Tian; Wu, Long-Fei; Pan, Hongmiao

    2016-04-01

    Magnetotactic bacteria (MTB) are distributed ubiquitously in sediments from coastal environments to the deep sea. The Pacific Manganese Nodule Province contains numerous polymetallic nodules mainly composed of manganese, iron, cobalt, copper and nickel. In the present study we used Illumina MiSeq sequencing technology to assess the communities of putative MTB in deep sea surface sediments at nine stations in the east Pacific Manganese Nodule Province. A total of 402 sequence reads from MTB were classified into six operational taxonomic units (OTUs). Among these, OTU113 and OTU759 were affiliated with the genus Magnetospira, OTU2224 and OTU2794 were affiliated with the genus Magnetococcus and Magnetovibrio, respectively, OTU3017 had no known genus affiliation, and OTU2556 was most similar to Candidatus Magnetananas. Interestingly, OTU759 was widely distributed, occurring at all study sites. Magnetism measurements revealed that all sediments were dominated by low coercivity, non-interacting single domain magnetic minerals. Transmission electron microscopy confirmed that the magnetic minerals were magnetosomes. Our data suggest that diverse putative MTB are widely distributed in deep sea surface sediments from the east Pacific Manganese Nodule Province. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  12. Interannual rainfall variability in the Amazon basin and sea-surface temperatures in the equatorial Pacific and the tropical Atlantic Oceans

    Science.gov (United States)

    Ronchail, Josyane; Cochonneau, Gérard; Molinier, Michel; Guyot, Jean-Loup; Chaves, Adriana Goretti De Miranda; Guimarães, Valdemar; de Oliveira, Eurides

    2002-11-01

    Rainfall variability in the Amazon basin is studied in relation to sea-surface temperatures (SSTs) in the equatorial Pacific and the northern and southern tropical Atlantic during the 1977-99 period, using the HiBAm original rainfall data set and complementary cluster and composite analyses.The northeastern part of the basin, north of 5 °S and east of 60 °W, is significantly related with tropical SSTs: a rainier wet season is observed when the equatorial Pacific and the northern (southern) tropical Atlantic are anomalously cold (warm). A shorter and drier wet season is observed during El Niño events and negative rainfall anomalies are also significantly associated with a warm northern Atlantic in the austral autumn and a cold southern Atlantic in the spring. The northeastern Amazon rainfall anomalies are closely related with El Niño-southern oscillation during the whole year, whereas the relationships with the tropical Atlantic SST anomalies are mainly observed during the autumn. A time-space continuity is observed between El Niño-related rainfall anomalies in the northeastern Amazon, those in the northern Amazon and south-eastern Amazon, and those in northern South America and in the Nordeste of Brazil.A reinforcement of certain rainfall anomalies is observed when specific oceanic events combine. For instance, when El Niño and cold SSTs in the southern Atlantic are associated, very strong negative anomalies are observed in the whole northern Amazon basin. Nonetheless, the comparison of the cluster and the composite analyses results shows that the rainfall anomalies in the northeastern Amazon are not always associated with tropical SST anomalies.In the southern and western Amazon, significant tropical SST-related rainfall anomalies are very few and spatially variable. The precipitation origins differ from those of the northeastern Amazon: land temperature variability, extratropical perturbations and moisture advection are important rainfall factors, as well

  13. Molecular Phylogeny Of Microbes In The Deep-Sea Sediments From Tropical West Pacific Warm Pool

    Science.gov (United States)

    Wang, F.; Xiao, X.; Wang, P.

    2005-12-01

    The presence and phylogeny of bacteria and archaea in five deep-sea sediment samples collected from west Pacific Warm Pool area (WP-0, WP-1, WP-2, WP-3, WP-4), and in five sediment layers (1cm-, 3cm-, 6cm-, 10cm-, 12cm- layer) of the 12-cm sediment core of WP-0 were checked and compared. The microbial diversity in the five deep-sea sediments were similar as revealed by denaturing gradient gel electrophoresis, and all of them contained members of non-thermophilic marine group I crenarchaeota as the predominant archaeal group. The composition of methylotrophs including methanotrophs, sulfate reducing bacteria in the WP-0 sediment core were further investigated by molecular marker based analysis of mxaF, pmoA, dsrAB, specific anoxic methane oxidation archaeal and sulfate reducing bacterial 16S rRNA genes. From MxaF amino acid sequence analysis, it was demonstrated that microbes belonging to α - Proteobacteria most related to Hyphomicrobium and Methylobacterium were dominant aerobic methylotrophs in this deep-sea sediment; and small percentage of type II methanotrophs affiliating closest to Methylocystis and Methylosinus were also detected in this environment. mxaF quantitative PCR results showed that in the west Pacific WP sediment there existed around 3× 10 4-5 methylotrophs per gram sediment, 10-100 times more than that in samples collected from several other deep-sea Pacific sediment sample, but about 10 times less than that present in samples collected from rice and flower garden soil. Diverse groups of novel archaea (named as WPA), not belonging to any known archaeal lineages were checked out. They could be placed in the euryarchaeota kingdom, separated into two distinct groups, the main group was peripherally related with methanogens, the other group related with Thermoplasma. Possible sulfate reducing bacterial related with Desulfotomaculum, Desulfacinum, Desulfomonile and Desulfanuticus were also detected in our study. The vertical distributions of WPA

  14. Towards an Accurate Orbital Calibration of Late Miocene Climate Events: Insights From a High-Resolution Chemo- and Magnetostratigraphy (8-6 Ma) from Equatorial Pacific IODP Sites U1337 and U1338

    Science.gov (United States)

    Drury, A. J.; Westerhold, T.; Frederichs, T.; Wilkens, R.; Channell, J. E. T.; Evans, H. F.; Hodell, D. A.; John, C. M.; Lyle, M. W.; Roehl, U.; Tian, J.

    2015-12-01

    In the 8-6 Ma interval, the late Miocene is characterised by a long-term -0.3 ‰ reduction in benthic foraminiferal δ18O and distinctive short-term δ18O cycles, possibly related to dynamic Antarctic ice sheet variability. In addition, the late Miocene carbon isotope shift (LMCIS) marks a permanent long-term -1 ‰ shift in oceanic δ13CDIC, which is the largest, long-term perturbation in the global marine carbon cycle since the mid Miocene Monterey excursion. Accurate age control is crucial to investigate the origin of the δ18O cyclicity and determine the precise onset of the LMCIS. The current Geological Time Scale in the 8-6 Ma interval is constructed using astronomical tuning of sedimentary cycles in Mediterranean outcrops. However, outside of the Mediterranean, a comparable high-resolution chemo-, magneto-, and cyclostratigraphy at a single DSDP/ODP/IODP site does not exist. Generating an accurate astronomically-calibrated chemo- and magneto-stratigraphy in the 8-6 Ma interval became possible with retrieval of equatorial Pacific IODP Sites U1337 and U1338, as both sites have sedimentation rates ~2 cm/kyr, high biogenic carbonate content, and magnetic polarity stratigraphies. Here we present high-resolution correlation of Sites U1337 and U1338 using Milankovitch-related cycles in core images and X-ray fluorescence core scanning data. By combining inclination and declination data from ~400 new discrete samples with shipboard measurements, we are able to identify 14 polarity reversals at Site U1337 from the young end of Chron C3An.1n (~6.03 Ma) to the onset of Chron C4n.2n (~8.11 Ma). New high-resolution (<1.5 kyr) stable isotope records from Site U1337 correlate highly with Site U1338 records, enabling construction of a high-resolution stack. Initial orbital tuning of the U1337-U1338 records show that the δ18O cyclicity is obliquity driven, indicating high-latitude climate forcing. The LMCIS starts ~7.55 Ma and is anchored in Chron C4n.1n, which is

  15. A critical evaluation of the upper ocean heat budget in the Climate Forecast System Reanalysis data for the south central equatorial Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hailong; Liu Xiangcui [State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing (China); Zhang Minghua [Institute for Terrestrial and Planetary Atmospheres, Stony Brook University, State University of New York, Stony Brook, NY (United States); Lin Wuyin, E-mail: lhl@lasg.iap.ac.cn [Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, NY (United States)

    2011-07-15

    Coupled ocean-atmospheric models suffer from the common bias of a spurious rain belt south of the central equatorial Pacific throughout the year. Observational constraints on key processes responsible for this bias are scarce. The recently available reanalysis from a coupled model system for the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) data is a potential benchmark for climate models in this region. Its suitability for model evaluation and validation, however, needs to be established. This paper examines the mixed layer heat budget and the ocean surface currents-key factors for the sea surface temperature control in the double Inter-Tropical Convergence Zone in the central Pacific-from 5 deg. S to 10 deg. S and 170 deg. E to 150 deg. W. Two independent approaches are used. The first approach is through comparison of CFSR data with collocated station observations from field experiments; the second is through the residual analysis of the heat budget of the mixed layer. We show that the CFSR overestimates the net surface flux in this region by 23 W m{sup -2}. The overestimated net surface flux is mainly due to an even larger overestimation of shortwave radiation by 44 W m{sup -2}, which is compensated by a surface latent heat flux overestimated by 14 W m{sup -2}. However, the quality of surface currents and the associated oceanic heat transport in CFSR are not compromised by the surface flux biases, and they agree with the best available estimates. The uncertainties of the observational data from field experiments are also briefly discussed in the present study.

  16. Age determination of marine sediments in the western North Pacific by aspartic acid chronology

    International Nuclear Information System (INIS)

    Harada, Naomi; Kusakabe, Masashi; Handa, Nobuhiko; Oba, Tadamichi; Matsuoka, Hiromi; Kimoto, Katsunori.

    1997-01-01

    The ages of fossil planktonic foraminifera, Pulleniatina obliquiloculata, in sediments (core 3bPC) from the western North Pacific were determined by aspartic acid chronology, which uses the racemization reaction rate constant of aspartic acid (k Asp ). Aspartic acid racemization-based ages (Asp ages) ranged from 7,600 yrBP at the surface, to 307,000 yrBP at a depth of 352.9 cm in the sediments. This sediment core was also dated by the glacial-interglacial fluctuation of σ 18 O chronology, and the ages determined by both chronologies were compared. The ages derived from aspartic acid chronology and σ 18 O stratigraphy were more or less consistent, but there appeared to be some differences in age estimates between these two dating methods at some depths within the core. In the core top sediments, the likely cause for the age discrepancy could be the loss of the surface sediment during sampling of the core. At depths of 66.3 and 139 cm within the core, Asp ages indicated reduced sedimentation rates during ca. 60,000-80,000 yrBP and ca. 140,000-190,000 yrBP. The maximum age differences in both chronologies are 33,000 yr and 46,600 yr during each of these periods. These anomalous reductions in sedimentation rates occurring during these periods could possibly be related to some geological events, such as an increased dissolution effect of the calcium carbonate in the western North Pacific. Another possible reason for these age differences could be the unreliability in σ 18 O ages of core 3bPC as they were estimated by σ 18 O ages of another core, 3aPC. (author)

  17. Comparative CO{sub 2} flux measurements by eddy covariance technique using open- and closed-path gas analysers over the equatorial Pacific Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, Fumiyoshi (Graduate School of Natural Science and Technology, Okayama Univ., Okayama (Japan); Atmosphere and Ocean Research Inst., Univ. of Tokyo, Tokyo (Japan)), Email: fkondo@aori.u-tokyo.ac.jp; Tsukamoto, Osamu (Graduate School of Natural Science and Technology, Okayama Univ., Okayama (Japan))

    2012-04-15

    Direct comparison of airsea CO{sub 2} fluxes by open-path eddy covariance (OPEC) and closed-path eddy covariance (CPEC) techniques was carried out over the equatorial Pacific Ocean. Previous studies over oceans have shown that the CO{sub 2} flux by OPEC was larger than the bulk CO{sub 2} flux using the gas transfer velocity estimated by the mass balance technique, while the CO{sub 2} flux by CPEC agreed with the bulk CO{sub 2} flux. We investigated a traditional conflict between the CO{sub 2} flux by the eddy covariance technique and the bulk CO{sub 2} flux, and whether the CO{sub 2} fluctuation attenuated using the closed-path analyser can be measured with sufficient time responses to resolve small CO{sub 2} flux over oceans. Our results showed that the closed-path analyser using a short sampling tube and a high volume air pump can be used to measure the small CO{sub 2} fluctuation over the ocean. Further, the underestimated CO{sub 2} flux by CPEC due to the attenuated fluctuation can be corrected by the bandpass covariance method; its contribution was almost identical to that of H{sub 2}O flux. The CO{sub 2} flux by CPEC agreed with the total CO{sub 2} flux by OPEC with density correction; however, both of them are one order of magnitude larger than the bulk CO{sub 2} flux

  18. Distribution of dissolved and particulate 226Ra, 210Pb and 210Po in the Bismarck Sea and western equatorial Pacific Ocean

    International Nuclear Information System (INIS)

    Peck, G.A.; Smith, J.D

    2000-01-01

    The distribution of the radionuclides 226 Ra, 210 Pb and 210 Po in the dissolved ( 210 Pb and 210 Po in the particulate (>0.45 μm) phases was measured in the upper 300 m of the Bismarck Sea off the Sepik River and along the equator from 143 deg E to 152 deg E in the western equatorial Pacific Ocean. 210 Pb and 210 Po occurred principally in the dissolved phase with a 210 Po/ 210 Pb ratio 210 Po/ 210 Pb ratios greater than 1.0. Box model calculations yielded an average atmospheric flux of 210 Pb of 4.5 mBq cm -2 year -1 to the ocean surface. The average residence times for dissolved 210 Po and dissolved 210 Pb were 0.27 years and 8.0 years respectively (in the mixed layer) and 1.45 years and 170 years (in the deeper layer). With an average residence time of 0.08 ± 0.03 years, particulate 210 Po varied little between the layers. The difference in 210 Po and 210 Pb residence times reflects the greater particle reactivity of 210 Po. The flux of particulate organic carbon was calculated to be 104 ± 21 mg m -2 day -1 from the upper 100 m and 180 ± 22 mg m -2 day -1 from 100-300 m. Copyright (2000) CSIRO Publishing

  19. Comparative CO2 flux measurements by eddy covariance technique using open- and closed-path gas analysers over the equatorial Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Fumiyoshi Kondo

    2012-04-01

    Full Text Available Direct comparison of air–sea CO2 fluxes by open-path eddy covariance (OPEC and closed-path eddy covariance (CPEC techniques was carried out over the equatorial Pacific Ocean. Previous studies over oceans have shown that the CO2 flux by OPEC was larger than the bulk CO2 flux using the gas transfer velocity estimated by the mass balance technique, while the CO2 flux by CPEC agreed with the bulk CO2 flux. We investigated a traditional conflict between the CO2 flux by the eddy covariance technique and the bulk CO2 flux, and whether the CO2 fluctuation attenuated using the closed-path analyser can be measured with sufficient time responses to resolve small CO2 flux over oceans. Our results showed that the closed-path analyser using a short sampling tube and a high volume air pump can be used to measure the small CO2 fluctuation over the ocean. Further, the underestimated CO2 flux by CPEC due to the attenuated fluctuation can be corrected by the bandpass covariance method; its contribution was almost identical to that of H2O flux. The CO2 flux by CPEC agreed with the total CO2 flux by OPEC with density correction; however, both of them are one order of magnitude larger than the bulk CO2 flux.

  20. ²³⁹Pu and ²⁴⁰Pu inventories and ²⁴⁰Pu/²³⁹Pu atom ratios in the equatorial Pacific Ocean water column.

    Science.gov (United States)

    Yamada, Masatoshi; Zheng, Jian

    2012-07-15

    The (239+240)Pu concentrations and (240)Pu/(239)Pu atom ratios were determined by alpha spectrometry and inductively coupled plasma mass spectrometry for seawater samples from two stations, one at the equator and the other in the equatorial South Pacific. To better understand the fate of Pu isotopes, this study dealt with the contribution of the close-in fallout Pu from the Pacific Proving Grounds (PPG) in water columns of the Pacific Ocean. The (239)Pu, (240)Pu and (239+240)Pu inventories over the depth interval 0-3000 m at the equator station were 10.4, 8.9 and 19.3 Bq m(-2), respectively. Further, no noticeable difference was observed in (239)Pu, (240)Pu and (239+240)Pu inventories over the depth interval 0-3000 m between the two stations. The total (239+240)Pu inventories were significantly higher than the expected cumulative deposition density of global fallout. Water column (239+240)Pu inventories measured in this study were lower than those reported for comparable stations in the Geochemical Ocean Sections Study, indicating that these inventories have been decreasing at average rates of 0.89 ± 0.07 and 0.16 ± 0.07 Bq m(-2)yr(-1) at the equator and equatorial South Pacific stations, respectively, from 1973 to 1990. The obtained (240)Pu/(239)Pu atom ratios were higher than the mean global fallout ratio of 0.18. These high atom ratios proved the existence of close-in tropospheric fallout Pu from the PPG in the Marshall Islands. The (239+240)Pu inventories originating from the close-in fallout in the entire water column were estimated to be 11.1 Bq m(-2) at the equator station and 7.1 Bq m(-2) at the equatorial South Pacific Ocean station, and the relative percentages of close-in fallout Pu were 40% at the former and 34% at the latter. A significant amount of close-in fallout Pu originating from the PPG has been transported to deep layers below the 1000 m depth in the equatorial Pacific Ocean. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    International Nuclear Information System (INIS)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1986-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10 -14 m 2 s -1 for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10 -10 m 2 s - include the anionic species pertechnetate, TcO 4 - , iodide, I - , and selenite, SO 3 -2 . Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10 -12 m 2 s -1 . The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere

  2. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    Energy Technology Data Exchange (ETDEWEB)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1985-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid-plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10/sup -14/ m/sup 2/s/sup -1/ for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10/sup -10/ m/sup 2/s/sup -1/ include the anionic species pertechnetate, TcO/sub 4//sup -/, iodide, I/sup -/, and selenite, SeO/sub 3//sup -2/. Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10/sup -12/ m/sup 2/s/sup -1/. The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere. 13 refs., 5 figs., 1 tab.

  3. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    International Nuclear Information System (INIS)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1985-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid-plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10 -14 m 2 s -1 for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10 -10 m 2 s -1 include the anionic species pertechnetate, TcO 4 - , iodide, I - , and selenite, SeO 3 -2 . Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10 -12 m 2 s -1 . The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere. 13 refs., 5 figs., 1 tab

  4. Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

    Science.gov (United States)

    Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

    2017-12-01

    Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

  5. Biogenic CaCO3 and Opal Depositions and Their Latitudinal Comparison During the Past 600 ka in the Central Equatorial Pacific

    Directory of Open Access Journals (Sweden)

    Boo-Keun Khim

    2015-01-01

    Full Text Available The orbital-scale variations in biogenic CaCO3 and opal abundance in two piston cores collected in the central equatorial Pacific (core PC5101 from a southern site at _ and core PC5103 from a northern site at _ were compared to assess latitudinal differences. The correlation between the oxygen isotope stratigraphy of planktonic foraminifera (Globigerinoides sacculifer of PC5103 with the LR04 stacks provides the age of PC5103 to be approximately 950 ka. The age of PC5103 was further refined by correlating the CaCO3 content with the well-dated core RC11-210. The age of PC5101 was also constrained by the same CaCO3 chronostratigraphic correlation with RC11-210, resulting in an age of approximately 650 ka. Distinct orbital-scale series of CaCO3 and opal variations appear to be parallel between the two cores during the past 600 ka, which are controlled mainly by eccentricity with an approximate periodicity of 100 ka. It is worth noting that the biogenic CaCO3 and opal deposition patterns in the two cores differ between interglacial and glacial periods. During interglacial periods the biogenic opal content is higher in the southern core than in the northern core, which corresponds with the present-day condition. In contrast the CaCO3 content is higher in the northern core, which is contradictory to the present-day northward decreasing CaCO3 deposition pattern from the Equator. The collection site of PC5101 is approximately 350 m deeper than that of PC5103, which significantly promotes CaCO3 dissolution and causes unexpectedly high CaCO3 content at the northern site in contrast to the biogenic opal content.

  6. Glacial magnetite dissolution in abyssal NW Pacific sediments - evidence for carbon trapping?

    Science.gov (United States)

    Korff, Lucia; von Dobeneck, Tilo; Frederichs, Thomas; Kasten, Sabine; Kuhn, Gerhard; Gersonde, Rainer; Diekmann, Bernhard

    2016-04-01

    The abyssal North Pacific Ocean's large volume, depth, and terminal position on the deep oceanic conveyor make it a candidate site for deep carbon trapping as postulated by climate theory to explain the massive glacial drawdown of atmospheric CO2. As the major basins of the North Pacific have depths of 5500-6500m, far below the modern and glacial Calcite Compensation Depths (CCD), these abyssal sediments are carbonate-free and therefore not suitable for carbonate-based paleoceanographic proxy reconstructions. Instead, paleo-, rock and environmental magnetic methods are generally well applicable to hololytic abyssal muds and clays. In 2009, the international paleoceanographic research cruise SO 202 INOPEX ('Innovative North Pacific Experiment') of the German RV SONNE collected two ocean-spanning EW sediment core transects of the North Pacific and Bering Sea recovering a total of 50 piston and gravity cores from 45 sites. Out of seven here considered abyssal Northwest Pacific piston cores collected at water depths of 5100 to 5700m with mostly coherent shipboard susceptibility logs, the 20.23m long SO202-39-3, retrieved from 5102 m water depth east of northern Shatsky Rise (38°00.70'N, 164°26.78'E), was rated as the stratigraphically most promising record of the entire core transect and selected for detailed paleo- and environmental magnetic, geochemical and sedimentological investigations. This core was dated by correlating its RPI and Ba/Ti records to well-dated reference records and obviously provides a continuous sequence of the past 940 kyrs. The most striking orck magnetic features are coherent magnetite-depleted zones corresponding to glacial periods. In the interglacial sections, detrital, volcanic and even submicron bacterial magnetite fractions are excellently preserved. These alternating magnetite preservation states seem to reflect dramatic oxygenation changes in the deep North Pacific Ocean and hint at large-scale benthic glacial carbon trapping

  7. Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412)

    DEFF Research Database (Denmark)

    Pham, M. K.; van Beek, P.; Carvalho, F. P.

    2016-01-01

    The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified...... radionuclides include: 40K, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 234U, 238U, 239Pu, 239+240Pu and 241Am for IAEA-410 and 40K, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 235U, 238U, 239Pu, 240Pu and 239+240Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes...

  8. Nannofossils in upper quaternary bottom sediments of back-arc basins in the southwestern Pacific

    Science.gov (United States)

    Dmitrenko, O. B.

    2015-05-01

    The analysis of calcareous nannoplankton assemblages in bottom sediments sampled during Cruise 21 of the R/V Akademik Mstislav Keldysh in three areas located in back-arc basins of the southwestern Pacific (western Woodlark in the Solomon Sea, Manus in the Bismarck Sea, Central Lau) reveal that they belong to the Emiliania huxleyi Acme Zone, the most detailed one in the Gartner's scale of 1977. The content of coccoliths and their taxonomic composition indicate warm subtropical-tropical conditions. Long cores demonstrate a decrease in species diversity reflecting the transition from the cold late Pleistocene to the Holocene. The changes in species diversity and presence/absence of thermophilic representatives indicate transformation of depositional environments with unstable conditions in the water column and bottom layer, seismic activity, and widely developed processes of sediment redistribution and reworking.

  9. Geotechnical properties of sediments from North Pacific and Northern Bermuda Rise

    International Nuclear Information System (INIS)

    Silva, A.J.; Laine, E.P.; Lipkin, J.; Heath, G.R.; Akers, S.A.

    1980-01-01

    Studies of geotechnical properties for the Sub-seabed Disposal Program have been oriented toward sediment characterization related to effectiveness as a containment media and determination of detailed engineering behavior. Consolidation tests of the deeper samples in the North Pacific clays indicate that the sediment column is normally consolidated. The in-situ coefficient of permeability (k) within the cored depth of 25 meters is relatively constant at 10 -7 cm/sec. Consolidated undrained (CIU) triaxial tests indicate stress-strain properties characteristic of saturated clays with effective angles of friction of 35 0 for smectite and 31 0 for illite. These results are being used in computer modeling efforts. Some general geotechnical property data from the Bermuda Rise are also discussed

  10. Equatorial Guinea.

    Science.gov (United States)

    1989-03-01

    Equatorial Guinea is situated on the Gulf of Guinea along the west African coast between Cameroon and Gabon. The people are predominantly of Bantu origin. The country's ties with Spain are significant; in 1959, it became the Spanish Equatorial region ruled by Spain's commissioner general. Recent political developments in Equatorial Guinea include the formation of the Democratic Party for Equatorial Guinea in July of 1987 and the formation of a 60-member unicameral Chamber of Representatives of the People in 1983. Concerning the population, 83% of the people are Catholic and the official language is Spanish. Poverty and serious health, education and sanitary problems exist. There is no adequate hospital and few trained physicians, no dentists, and no opticians. Malaria is endemic and immunization for yellow fever is required for entrance into the country. The water is not potable and many visitors to the country bring bottled water. The tropical climate of Equatorial Guinea provides the climate for the country's largest exports and source of economy; cacao, wood and coffee. Although the country, as a whole, has progressed towards developing a participatory political system, there are still problems of governmental corruption in the face of grave health and welfare conditions. In recent years, the country has received assistance from the World Bank and the United States to aid in its development.

  11. Environmental Drivers of Benthic Flux Variation and Ecosystem Functioning in Salish Sea and Northeast Pacific Sediments.

    Directory of Open Access Journals (Sweden)

    Rénald Belley

    Full Text Available The upwelling of deep waters from the oxygen minimum zone in the Northeast Pacific from the continental slope to the shelf and into the Salish Sea during spring and summer offers a unique opportunity to study ecosystem functioning in the form of benthic fluxes along natural gradients. Using the ROV ROPOS we collected sediment cores from 10 sites in May and July 2011, and September 2013 to perform shipboard incubations and flux measurements. Specifically, we measured benthic fluxes of oxygen and nutrients to evaluate potential environmental drivers of benthic flux variation and ecosystem functioning along natural gradients of temperature and bottom water dissolved oxygen concentrations. The range of temperature and dissolved oxygen encountered across our study sites allowed us to apply a suite of multivariate analyses rarely used in flux studies to identify bottom water temperature as the primary environmental driver of benthic flux variation and organic matter remineralization. Redundancy analysis revealed that bottom water characteristics (temperature and dissolved oxygen, quality of organic matter (chl a:phaeo and C:N ratios and sediment characteristics (mean grain size and porosity explained 51.5% of benthic flux variation. Multivariate analyses identified significant spatial and temporal variation in benthic fluxes, demonstrating key differences between the Northeast Pacific and Salish Sea. Moreover, Northeast Pacific slope fluxes were generally lower than shelf fluxes. Spatial and temporal variation in benthic fluxes in the Salish Sea were driven primarily by differences in temperature and quality of organic matter on the seafloor following phytoplankton blooms. These results demonstrate the utility of multivariate approaches in differentiating among potential drivers of seafloor ecosystem functioning, and indicate that current and future predictive models of organic matter remineralization and ecosystem functioning of soft-muddy shelf and

  12. Uranium and plutonium in anoxic marine sediments of the Santiago River mouth (Eastern Pacific, Mexico).

    Science.gov (United States)

    Almazán-Torres, María Guadalupe; Ordóñez-Regil, Eduardo; Ruiz-Fernández, Ana Carolina

    2016-11-01

    The uranium (U) and plutonium (Pu) content with depth in a sediment core collected in the continental shelf off the mouth of the Santiago River in the Mexican Pacific was studied to evaluate the contamination effects of the effluent of the Santiago-Lerma River as it moves into the sea. The large mass of terrestrial detritus delivered by the river influences the physicochemical and geochemical processes in the seafloor. Abnormal concentrations of U and Pu in sediments were examined as indicative of the effects of anoxic conditions. One of the indicators of pollution of seawater is the bacterial activity of the shallow seabed layer; and among the prevailing bacteria, the magnetotactic ones induce the formation of euhedral and framboidal shapes (pyrite). These pyrite entities are by-products of anoxic environments loaded with decomposing detrital material and are very abundant in the surface layers of the sediment core analyzed. The pyrite formation is the result of a biochemical reaction between iron and organic sulphur reduced by bacteria, and the pyrite entities precipitate to the seafloor. In the same upper zone of the profile, 238 U is readily immobilized, while 234 U is oxidized and dissolved in seawater by the effect of hot atom chemistry. This may cause the activity ratio (AR) 234 U/ 238 U disequilibrium (near 0.41). Furthermore, in the shallow layer of the sediment core, an abnormally high concentration of 239+240 Pu was detected. In this upper layer, the activity concentrations found were 3.19 Bq kg -1 for 238 U, 1.32 kg -1 for 234 U and 2.78 Bq kg -1 for 239+240 Pu. In the lower fractions of the sediment core, normal values of AR 234 U/ 238 U (≈1) were found, with traces of 239+240 Pu. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Chemical composition of marine sediments in the Pacific Ocean from Sinaloa to Jalisco, Mexico

    International Nuclear Information System (INIS)

    Martinez, T.; Lartigue, J.; Ramos, A.; Navarrete, M.; Mulller, G.

    2014-01-01

    Marine sediments from Mexico's West coast in the Pacific Ocean from Sinaloa to Jalisco were analyzed by energy-dispersive X-ray fluorescence technique. Ten sediment samples were collected in May, 2010 between 55.5 and 1264 m water depth with a Reinneck type box nucleate sampler. Sediments were dried and fractioned by granulometry. Their physical and chemical properties were determined in laboratory by standard methods, pH, and conductivity. Concentration and distribution of K, Ca, Ti Mn, Fe, Cu, Zn, Ga, Pb, Br and Sr were analyzed. In order to determine the status of the elements, enrichment factors were calculated. Total, organic carbon and CaCO 3 were also determined. Scanning electron microscopy and X-ray diffraction show predominant groups of compounds. As quality-control method, Certified Reference Material was both processed and analyzed at even conditions. Enrichment factors for K, Ca, Ti, Mn Fe, Cu, Zn, Ga, Ni, and Sr show they are conservative elements having concentrations in the range of unpolluted sites giving a base data line for the sampling zone In spite of moderately enrichment factors -1 ) and enrichment factor show the influence of anthropogenic sources with values between lowest effect level and a third part of 250 μg g -1 value, which is considered to have severe effect levels for aquatic life. (author)

  14. Fluvial fingerprints in northeast Pacific sediments: Unravelling terrestrial-ocean climate linkages

    Science.gov (United States)

    Vanlaningham, S. J.; Duncan, R.; Pisias, N.

    2004-12-01

    As the earth's climate history becomes better understood, it becomes clear that the terrestrial and oceanic systems interact in complex ways. This is seen in core sites offshore the Pacific Northwest (PNW) of North America. A correlation can be seen in oceanic biostratigraphic assemblages and down-core changes in terrestrial pollen types. However, it is difficult to determine whether this relationship is the result of a coupled migration of terrestrial vegetation and oceanic fauna on millennial timescales or the result of changes in ocean circulation patterns that create more complex pollen pathways to the core sites. This research begins to unravel the answers to this problem by examining down-core changes in sediment provenance on millennial timescales. Preliminary data characterize sediment of 24 rivers from ten geologic provinces between latitudes 36° N - 47° N. Through clay mineralogy, major and trace element geochemistry and Ar-Ar "province" ages, ten of the 24 rivers can be uniquely identified, while six of the ten geologic provinces can be uniquely constrained geochemically. With further Nd, Sr and Pb isotopic analyses, we hope to constrain the non-unique sediment sources. We will also be presenting initial down-core geochemical results from cores EW 9504-17PC and EW9504-13PC, offshore southern Oregon and central California, respectively.

  15. Phylogenetic Diversity of aprA Genes in Subseafloor Sediments on the Northwestern Pacific Margin off Japan.

    Science.gov (United States)

    Aoki, Masataka; Kakiuchi, Ryota; Yamaguchi, Takashi; Takai, Ken; Inagaki, Fumio; Imachi, Hiroyuki

    2015-01-01

    Markedly diverse sequences of the adenosine-5'-phosphosulfate reductase alpha subunit gene (aprA), which encodes a key enzyme in microbial sulfate reduction and sulfur oxidation, were detected in subseafloor sediments on the northwestern Pacific off Japan. The aprA gene sequences were grouped into 135 operational taxonomic units (90% sequence identity), including genes related to putative sulfur-oxidizing bacteria predominantly detected in sulfate-depleted deep sediments. Our results suggest that microbial ecosystems in the subseafloor biosphere have phylogenetically diverse genetic potentials to mediate cryptic sulfur cycles in sediments, even where sulfate is rarely present.

  16. Phylogenetic diversity and ecological pattern of ammonia-oxidizing archaea in the surface sediments of the western Pacific.

    Science.gov (United States)

    Cao, Huiluo; Hong, Yiguo; Li, Meng; Gu, Ji-Dong

    2011-11-01

    The phylogenetic diversity of ammonia-oxidizing archaea (AOA) was surveyed in the surface sediments from the northern part of the South China Sea (SCS). The distribution pattern of AOA in the western Pacific was discussed through comparing the SCS with other areas in the western Pacific including Changjiang Estuary and the adjacent East China Sea where high input of anthropogenic nitrogen was evident, the tropical West Pacific Continental Margins close to the Philippines, the deep-sea methane seep sediments in the Okhotsk Sea, the cold deep sea of Northeastern Japan Sea, and the hydrothermal field in the Southern Okinawa Trough. These various environments provide a wide spectrum of physical and chemical conditions for a better understanding of the distribution pattern and diversities of AOA in the western Pacific. Under these different conditions, the distinct community composition between shallow and deep-sea sediments was clearly delineated based on the UniFrac PCoA and Jackknife Environmental Cluster analyses. Phylogenetic analyses showed that a few ammonia-oxidizing archaeal subclades in the marine water column/sediment clade and endemic lineages were indicative phylotypes for some environments. Higher phylogenetic diversity was observed in the Philippines while lower diversity in the hydrothermal vent habitat. Water depth and possibly with other environmental factors could be the main driving forces to shape the phylogenetic diversity of AOA observed, not only in the SCS but also in the whole western Pacific. The multivariate regression tree analysis also supported this observation consistently. Moreover, the functions of current and other climate factors were also discussed in comparison of phylogenetic diversity. The information collectively provides important insights into the ecophysiological requirements of uncultured ammonia-oxidizing archaeal lineages in the western Pacific Ocean.

  17. Anomalous South Pacific lithosphere dynamics derived from new total sediment thickness estimates off the West Antarctic margin

    Science.gov (United States)

    Wobbe, Florian; Lindeque, Ansa; Gohl, Karsten

    2014-12-01

    Paleotopographic models of the West Antarctic margin, which are essential for robust simulations of paleoclimate scenarios, lack information on sediment thickness and geodynamic conditions, resulting in large uncertainties. A new total sediment thickness grid spanning the Ross Sea-Amundsen Sea-Bellingshausen Sea basins is presented and is based on all the available seismic reflection, borehole, and gravity modeling data offshore West Antarctica. This grid was combined with NGDC's global 5 arc minute grid of ocean sediment thickness (Whittaker et al., 2013) and extends the NGDC grid further to the south. Sediment thickness along the West Antarctic margin tends to be 3-4 km larger than previously assumed. The sediment volume in the Bellingshausen, Amundsen, and Ross Sea basins amounts to 3.61, 3.58, and 2.78 million km3, respectively. The residual basement topography of the South Pacific has been revised and the new data show an asymmetric trend over the Pacific-Antarctic Ridge. Values are anomalously high south of the spreading ridge and in the Ross Sea area, where the topography seems to be affected by persistent mantle processes. In contrast, the basement topography offshore Marie Byrd Land cannot be attributed to dynamic topography, but rather to crustal thickening due to intraplate volcanism. Present-day dynamic topography models disagree with the presented revised basement topography of the South Pacific, rendering paleotopographic reconstructions with such a limited dataset still fairly uncertain.

  18. Abundance of color bands in Neogene carbonate sediments on Ontong Java Plateau:

    DEFF Research Database (Denmark)

    Berger, W.H.; Lind, Ida

    1997-01-01

    When comparing color-band abundances within one sediment section with those of others of the same age but deposited at different depths along a transect on the northeastern flank of Ontong Java Plateau in the western equatorial Pacific (ODP Leg 130), one notes that the sections with the highest s...

  19. Nematode communities in sediments of the Kermadec Trench, Southwest Pacific Ocean

    Science.gov (United States)

    Leduc, Daniel; Rowden, Ashley A.

    2018-04-01

    Hadal trenches are characterized by environmental conditions not found in any other deep-sea environment, such as steep topography and periodic disturbance by turbidity flows, which are likely responsible for the distinct nature of benthic communities of hadal trenches relative to those of the abyssal plain. Nematodes are the most abundant metazoans in the deep-sea benthos, but it is not yet clear if different trenches host distinct nematode communities, and no data are yet available on the communities of most trenches, including the Kermadec Trench in the Southwest Pacific. Quantitative core samples from the seafloor of the Kermadec Trench were recently obtained from four sites at 6000-9000 m depth which allowed for analyses of meiofauna, and nematodes in particular, for the first time. Nematode community and trophic structure was also compared with other trenches using published data. There was a bathymetric gradient in meiofauna abundance, biomass, and community structure within the Kermadec Trench, but patterns for species richness were ambiguous depending on which metric was used. There was a change in community structure from shallow to deep sites, as well as a consistent change in community structure from the upper sediment layers to the deeper sediment layers across the four sites. These patterns are most likely explained by variation in food availability within the trench, and related to trench topography. Together, deposit and microbial feeders represented 48-92% of total nematode abundance in the samples, which suggests that fine organic detritus and bacteria are major food sources. The relatively high abundance of epigrowth feeders at the 6000 and 9000 m sites (38% and 31%, respectively) indicates that relatively freshly settled microalgal cells represent another important food source at these sites. We found a significant difference in species community structure between the Kermadec and Tonga trenches, which was due to both the presence/absence of

  20. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-26 (NODC Accession 8500007)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 26, 1984. Data were submitted by Pacific...

  1. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1986-05-28 to 1987-05-11 (NODC Accession 8900168)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from 28 May 1986 to 01 May 1983. Data were submitted by Pacific Marine...

  2. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-01 (NODC Accession 8700077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 1, 1984. Data were submitted by Pacific Marine...

  3. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1990-04-30 to 1991-05-15 (NODC Accession 9400005)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from April 30, 1990 to May 15, 1991. Data were submitted by Pacific Marine...

  4. Assessment of 210Po in agricultural soils and marine sediments of the Atlantic and Pacific oceans of Guatemala

    International Nuclear Information System (INIS)

    Garcia Vela, A.G.

    1999-01-01

    A radiochemical method consisting of 210 Polonium extraction was made to measure radioactivity in samples of soil and marine sediments of Atlantic and Pacific Ocean. The solution of polonium it was treated to obtain the deposition of the metal over a zinc disc and was measured by alpha espectrometry system based on Planar Ion Planted Silice (PIPS) system. The concern about cultivated soils its consuption products from sea and soil come from these sources. The results shows that activity of 210 Polonium in agricultural soils and marine sediments are below of ALI recommended by international standards

  5. Low level spectrometry of Fe-Mn concretions from the Pacific Ocean bed and of Pierre St. Martin cave sediments

    International Nuclear Information System (INIS)

    Dimchev, T.; Prodanov, Ya.

    1977-01-01

    Results of the nondestructive gamma-spectrometric analysis of the Fe-Mn nodules from the Pacific Ocean in the neighbourhood of the Raratonga Isles and Fiji Isles are reported. The cave sediments from the San Martin Cave in the Pyrenees and from other caves were also analyzed. The nondestructive method was used for analyzing samples using a low background scintillation gamma spectrometer. Results obtained for geological samples, soils, sediments, etc. are given for comparison. Statistical methods were applied for the quantitative analysis of the gamma spectra obtained. (author)

  6. Crystal-chemical characteristics of nontronites from bottom sediments of Pacific ocean

    International Nuclear Information System (INIS)

    Palchik, N. A.; Moroz, T. N.; Grigorieva, T. N.; Nikandrova, N. K.; Miroshnichenko, L. V.

    2017-01-01

    A crystal-chemical analysis of the nontronite samples formed in deep-water sediments of the underwater Juan-de-Fuca ridge in the Pacific ocean has been performed using powder X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy. A comparison with the previously investigated nontronites from different regions of the Sea of Okhotsk showed that the structural features of these formations are due to the difference in the physicochemical parameters of their crystallization. The values of the basal interplanar spacing d_0_0_1 (within 11–13 Å) in the samples analyzed are determined by the degree of hydration and cation filling of the interlayer space, while the differences in the IR spectra are due to isomorphic substitutions in the structure. The character of cation distribution and the nature and concentration of stacking faults in nontronite structures are determined. The differences in the composition, structure, and properties of nontronites of different origin are confirmed by theoretical calculations of their structural parameters.

  7. Crystal-chemical characteristics of nontronites from bottom sediments of Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Palchik, N. A., E-mail: nadezhda@igm.nsc.ru; Moroz, T. N.; Grigorieva, T. N. [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation); Nikandrova, N. K. [Russian Academy of Sciences, Institute of Mineralogy, Ural Branch (Russian Federation); Miroshnichenko, L. V. [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

    2017-01-15

    A crystal-chemical analysis of the nontronite samples formed in deep-water sediments of the underwater Juan-de-Fuca ridge in the Pacific ocean has been performed using powder X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy. A comparison with the previously investigated nontronites from different regions of the Sea of Okhotsk showed that the structural features of these formations are due to the difference in the physicochemical parameters of their crystallization. The values of the basal interplanar spacing d{sub 001} (within 11–13 Å) in the samples analyzed are determined by the degree of hydration and cation filling of the interlayer space, while the differences in the IR spectra are due to isomorphic substitutions in the structure. The character of cation distribution and the nature and concentration of stacking faults in nontronite structures are determined. The differences in the composition, structure, and properties of nontronites of different origin are confirmed by theoretical calculations of their structural parameters.

  8. Physical and meteorological delayed-mode full-resolution data from the Tropical Atmosphere Ocean (TAO) array in the Equatorial Pacific

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Tropical Atmosphere Ocean (TAO) array of moored buoys spans the tropical Pacific. Moorings within the array measure surface meteorological and upper-ocean...

  9. Delta Oxygen-18 and SEA SURFACE TEMPERATURE collected from KNORR in Equatorial Pacific Ocean from 0862-01-01 to 2009-01-01 (NCEI Accession 0142201)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Tropical Pacific Ocean dynamics during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) are poorly characterized due to lack of evidence from the eastern...

  10. Assessment of 238Pu and 239+240Pu, in marine sediments of the oceans Atlantic and Pacific of Guatemala

    International Nuclear Information System (INIS)

    Mendez Ochaita, L.

    2000-01-01

    In this investigation samples of marine sediments were taken from 14 places representatives of the oceans coast of Guatemala. For the assesment of 238 Pu and 239+240 Pu in sediments a radiochemical method was used to mineralize sediments and by ionic interchange it was separated from other elements, after that an electrodeposition of plutonium was made in metallic discs. The radioactivity of plutonium was measured by alpha spectrometry system and the alpha spectrums were obtained. The levels of plutonium are not higher than other countries that shown contamination. The contamination of isotope of 239+240 Pu is higher than 238 Pu and the contamination by two isotopes of plutonium is higher in the Atlantic than the Pacific ocean

  11. A comparison of microbial communities in deep-sea polymetallic nodules and the surrounding sediments in the Pacific Ocean

    Science.gov (United States)

    Wu, Yue-Hong; Liao, Li; Wang, Chun-Sheng; Ma, Wei-Lin; Meng, Fan-Xu; Wu, Min; Xu, Xue-Wei

    2013-09-01

    Deep-sea polymetallic nodules, rich in metals such as Fe, Mn, and Ni, are potential resources for future exploitation. Early culturing and microscopy studies suggest that polymetallic nodules are at least partially biogenic. To understand the microbial communities in this environment, we compared microbial community composition and diversity inside nodules and in the surrounding sediments. Three sampling sites in the Pacific Ocean containing polymetallic nodules were used for culture-independent investigations of microbial diversity. A total of 1013 near full-length bacterial 16S rRNA gene sequences and 640 archaeal 16S rRNA gene sequences with ~650 bp from nodules and the surrounding sediments were analyzed. Bacteria showed higher diversity than archaea. Interestingly, sediments contained more diverse bacterial communities than nodules, while the opposite was detected for archaea. Bacterial communities tend to be mostly unique to sediments or nodules, with only 13.3% of sequences shared. The most abundant bacterial groups detected only in nodules were Pseudoalteromonas and Alteromonas, which were predicted to play a role in building matrix outside cells to induce or control mineralization. However, archaeal communities were mostly shared between sediments and nodules, including the most abundant OTU containing 290 sequences from marine group I Thaumarchaeota. PcoA analysis indicated that microhabitat (i.e., nodule or sediment) seemed to be a major factor influencing microbial community composition, rather than sampling locations or distances between locations.

  12. Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

    Science.gov (United States)

    Münnich, M.; Neelin, J. D.

    2005-11-01

    In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

  13. Abrupt sea surface pH change at the end of the Younger Dryas in the central sub-equatorial Pacific inferred from boron isotope abundance in corals (Porites

    Directory of Open Access Journals (Sweden)

    A. Juillet-Leclerc

    2010-08-01

    Full Text Available The "δ11B-pH" technique was applied to modern and ancient corals Porites from the sub-equatorial Pacific areas (Tahiti and Marquesas spanning a time interval from 0 to 20.720 calendar years to determine the amplitude of pH changes between the Last Glacial Period and the Holocene. Boron isotopes were measured by Multi-Collector – Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS with an external reproducibility of 0.25‰, allowing a precision of about ±0.03 pH-units for pH values between 8 and 8.3. The boron concentration [B] and isotopic composition of modern samples indicate that the temperature strongly controls the partition coefficient KD for different aragonite species. Modern coral δ11B values and the reconstructed sea surface pH values for different Pacific areas match the measured pH expressed on the seawater scale and confirm the calculation parameters that were previously determined by laboratory calibration exercises. Most ancient sea surface pH reconstructions near Marquesas are higher than modern values. These values range between 8.19 and 8.27 for the Holocene and reached 8.30 at the end of the last glacial period (20.7 kyr BP. At the end of the Younger Dryas (11.50±0.1 kyr BP, the central sub-equatorial Pacific experienced a dramatic drop of up to 0.2 pH-units from the average pH of 8.2 before and after this short event. Using the marine carbonate algorithms, we recalculated the aqueous pCO2 to be 440±25 ppmV at around 11.5 kyr BP for corals at Marquesas and ~500 ppmV near Tahiti where it was assumed that pCO2 in the atmosphere was 250 ppmV. Throughout the Holocene, the difference in pCO2 between the ocean and the atmosphere at Marquesas (ΔpCO2 indicates that the surface waters behave as a moderate CO2 sink or source (−53 to 20 ppmV during El Niño-like conditions. By contrast, during the last glacial/interglacial transition, this area was a marked source of CO2 (21 to 92 ppmV for the atmosphere, highlighting

  14. Quantifying dust input to the Subarctic North Pacific - Results from surface sediments and sea water thorium isotope measurements

    Science.gov (United States)

    Winckler, G.; Serno, S.; Hayes, C.; Anderson, R. F.; Gersonde, R.; Haug, G. H.

    2012-12-01

    The Subarctic North Pacific is one of the three primary high-nutrient-low chlorophyll regions of the modern ocean, where the biological pump is relatively inefficient at transferring carbon from the atmosphere to the deep sea. The system is thought to be iron-limited. Aeolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high-nutrient-low chlorophyll status of the Subarctic North Pacific. However, constraining the size of the dust flux to the surface ocean remains difficult. Here we apply two different approaches, based on surface sediment and water column samples, respectively, obtained during the SO202/INOPEX research cruise to the Subarctic North Pacific in 2009. We map the spatial patterns of Th/U isotopes, helium isotopes and rare earth elements across surface sediments from 37 multi-core core-top sediments across the Subarctic North Pacific. In order to deconvolve the detrital endmembers in regions of the North Pacific affected by volcanic material, IRD and hemipelagic input, we use a combination of trace elements with distinct characteristics in the different endmembers. This approach allows us to calculate the relative aeolian fraction, and in combination with Thorium230-normalized mass flux data, to quantify the dust supply. Secondly, we present an innovative approach to use paired Thorium-232 and Thorium-230 concentrations of upper-ocean seawater at 7 stations along the INOPEX track. Thorium-232 in the upper water column is dominantly derived from dissolution of aeolian dust, whereas Thorium-230 data provide a measure of the thorium removal from the surface waters and, thus, allow us to derive Thorium-232 fluxes. Combined with a mean Thorium-232 concentration in dust and estimate of the thorium solubility, the Thorium-232 flux can be translated in a dust flux to the surface ocean. Dust flux estimates for the Subarctic North Pacific will be

  15. Equatorial ionospheric electric fields during the November 2004 magnetic storm

    OpenAIRE

    Fejer, Bela G.; Jensen, J. W.; Kikuchi, T.; Abdu, M. A.; Chau, J. L.

    2007-01-01

    [1] We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the November...

  16. SEDIMENTATION IN PACIFIC NORTHWEST COASTAL STREAMS -- EVIDENCE FROM REGIONAL SURVEY OF BED SUBSTRATE SIZE AND STABILITY

    Science.gov (United States)

    Excessive erosion, transport and deposition of sediment are major problems in streams and rivers throughout the United States. We examined evidence of anthropogenic sedimentation in Oregon and Washington coastal streams using relatively rapid measurements taken from surveys duri...

  17. Boundary scavenging in the Pacific Ocean

    International Nuclear Information System (INIS)

    Anderson, R.F.; Lao, Y.; Broecker, W.S.; Trumbore, S.E.; Hofmann, H.J.; Wolfli, W.

    1990-01-01

    Concentrations of U, Th, 231 Pa and 10 Be were measured in Holocene sediments from two cores collected off the west coast of South America, two cores from the East Pacific Rise, two from the equatorial Pacific and one from the south Pacific central gyre. Our results, together with data from 5 cores reported in the literature, show that boundary scavenging plays a major role in the removal of 10 Be from the Pacific Ocean. Deposition rates of 10 Be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central Pacific. Deposition of 231 Pa is 4 to 5-fold greater at the margin sites. The residence time of 10 Be with respect to chemical scavenging, defined as its inventory in the water column divided by its rate of removal to the sediments, varies regionally from >1000 years at the red-clay sites in the deep central Pacific to ∝100 years at the margin sites. Different factors control boundary scavenging of Pa and Be. For example, scavenging of 231 Pa is enhanced by metal-oxide coatings of particles, whereas this seems to have little influence on the scavenging of 10 Be. (orig.)

  18. Temperature, salinity and other measurements found in dataset CTD taken from the SOUTHERN SURVEYOR (VLHJ) in the Coastal S Pacific, Equatorial Pacific and other locations from 2003 to 2006 (NODC Accession 0043461)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, salinity, chemical, and other data were collected using CTD casts from the SOUTHERN SURVEYOR in the Iceland Sea and North / South Pacific Ocean. Data...

  19. Current meter data from moored current meter casts in the South Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1981-11-21 to 1983-11-20 (NODC Accession 8500258)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the South Pacific Ocean from November 21, 1981 to November 20, 1983. Data were submitted by...

  20. Wind and temperature data from current meter in the TOGA - Pacific Ocean (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS), 28 May 1994 to 21 March 1995 (NODC Accession 9800041)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind and temperature data were collected using current meter in the TOGA Area - Pacific Ocean (30 N to 30 S) from May 28, 1994 to March 21, 1995. Data were submitted...

  1. Bacterial Production and Enzymatic Activities in Deep-Sea Sediments of the Pacific Ocean: Biogeochemical Implications of Different Temperature Constraints

    Science.gov (United States)

    Danovaro, R.; Corinaldesi, C.; dell'Anno, A.

    2002-12-01

    The deep-sea bed, acting as the ultimate sink for organic material derived from the upper oceans primary production, is now assumed to play a key role in biogeochemical cycling of organic matter on global scale. Early diagenesis of organic matter in marine sediments is dependent upon biological processes (largely mediated by bacterial activity) and by molecular diffusion. Organic matter reaching the sea floor by sedimentation is subjected to complex biogeochemical transformations that make organic matter largely unsuitable for direct utilization by benthic heterotrophs. Extracellular enzymatic activities in the sediment is generally recognized as the key step in the degradation and utilization of organic polymers by bacteria and a key role in biopolymeric carbon mobilization is played by aminopeptidase, alkaline phosphatase and glucosidase activities. In the present study we investigated bacterial density, bacterial C production and exo-enzymatic activities (aminopeptidase, glucosidase and phosphatase activity) in deep-sea sediments of the Pacific Ocean in relation with the biochemical composition of sediment organic matter (proteins, carbohydrates and lipids), in order to gather information on organic matter cycling and diagenesis. Benthic viral abundance was also measured to investigate the potential role of viruses on microbial loop functioning. Sediment samples were collected at eight stations (depth ranging from 2070-3100 m) along two transects located at the opposite side (north and south) of ocean seismic ridge Juan Fernandez (along latitudes 33° 20' - 33° 40'), constituted by the submerged vulcanoes, which connects the Chilean coasts to Rapa Nui Island. Since the northern and southern sides of this ridge apparently displayed small but significant differences in deep-sea temperature (related to the general ocean circulation), this sampling strategy allowed also investigating the role of different temperature constraints on bacterial activity and

  2. Composition, oxygen isotope geochemistry, and origin of smectite in the metalliferous sediments of the Bauer Deep, southeast Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Cole, T G [Imperial Coll. of Science and Technology, London (UK). Geology Dept.

    1985-01-01

    The sediments of the Bauer Deep, an open ocean basin situated on the northwest Nazca Plate in the southeast Pacific, constitute a regional metalliferous deposit dominated by authigenic smectite. Two 2-metre long cores from the Bauer Deep were examined to investigate the nature and origin of the smectite. Infra-red and Mossbauer spectroscopy, and wet chemical analysis (LiBO/sub 2/ fusion) of isolated smectite, indicate the mineral is a Mg-rich, Al-rich nontronite. Oxygen isotopic compositions for isolated smectite are uniform and translate to a non-hydrothermal temperature of formation of about 3 deg C. SEM observations show an abundance of well-preserved biogenic opal in surface and near surface sediment but postburial dissolution and transformation of this phase to smectite is evident at depth. Smectite formation is the result of interaction between iron oxyhydroxide, ponded in the Bauer Deep following a hydrothermal origin at the adjacent East Pacific Rise, and biogenic opal. A reaction mechanism is proposed. Regional factors control smectite formation. In particular, formation is inhibited in areas of CaCO/sub 3/ accumulation (topographic elevations) but favoured in areas of oxyhydroxide and opal ponding (topographic depressions.)

  3. Composition, oxygen isotope geochemistry, and origin of smectite in the metalliferous sediments of the Bauer Deep, southeast Pacific

    International Nuclear Information System (INIS)

    Cole, T.G.

    1985-01-01

    The sediments of the Bauer Deep, an open ocean basin situated on the northwest Nazca Plate in the southeast Pacific, constitute a regional metalliferous deposit dominated by authigenic smectite. Two 2-metre long cores from the Bauer Deep were examined to investigate the nature and origin of the smectite. Infra-red and Mossbauer spectroscopy, and wet chemical analysis (LiBO 2 fusion) of isolated smectite, indicate the mineral is a Mg-rich, Al-rich nontronite. Oxygen isotopic compositions for isolated smectite are uniform and translate to a non-hydrothermal temperature of formation of about 3 deg C. SEM observations show an abundance of well-preserved biogenic opal in surface and near surface sediment but postburial dissolution and transformation of this phase to smectite is evident at depth. Smectite formation is the result of interaction between iron oxyhydroxide, ponded in the Bauer Deep following a hydrothermal origin at the adjacent East Pacific Rise, and biogenic opal. A reaction mechanism is proposed. Regional factors control smectite formation. In particular, formation is inhibited in areas of CaCO 3 accumulation (topographic elevations) but favoured in areas of oxyhydroxide and opal ponding (topographic depressions.) (author)

  4. Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

    Science.gov (United States)

    Zuffa, G.G.; De Rosa, R.; Normark, W.R.

    1997-01-01

    Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

  5. OGCM Simulations of Equatorial Pacific Current and Temperature to ERS-1, FSU and NMC Surface Winds and to Assimilation of Subsurface Temperature Data

    Science.gov (United States)

    Halpern, David

    1995-01-01

    The relative accuracies of three surface wind data products for the tropical Pacific Ocean during April 1992 to March 1994 were examined by analyzing temperature and current fields along the equator, which were simulated with an ocean general circulation model. Simulations were made with and without assimilation of surface and subsurface temperature data. Simulated currents were compared with observations at three sites (170oW, 140oW, 110oW) at the equator. Model-generated currents and temperatures indicated that the ERS-1 westward wind speeds were low compared to the FSU and NMC winds. With data assimilation, the agreement between simulated and observed currents was highest at 170oW and lowest at 110oW.

  6. Reconstruction of Holocene environmental changes in Southern Kurils (North-Western Pacific) based on palaeolake sediment proxies from Shikotan Island

    Science.gov (United States)

    Nazarova, Larisa; Grebennikova, Tatiana A.; Razjigaeva, Nadezhda G.; Ganzey, Larisa A.; Belyanina, Nina I.; Arslanov, Khikmat A.; Kaistrenko, Victor M.; Gorbunov, Aleksey O.; Kharlamov, Andrey A.; Rudaya, Natalia; Palagushkina, Olga; Biskaborn, Boris K.; Diekmann, Bernhard

    2017-12-01

    We investigated a well-dated sediment section of a palaeolake situated in the coastal zone of Shikotan Island (Lesser Kurils) for organic sediment-geochemistry and biotic components (diatoms, chironomids, pollen) in order to provide a reconstruction of the palaeoenvironmental changes and palaeo-events (tsunamis, sea-level fluctuations and landslides) in Holocene. During the ca 8000 years of sedimentation the changes in organic sediment-geochemistry and in composition of the diatoms and chironomids as well as the shifts in composition of terrestrial vegetation suggest that the period until ca 5800 cal yr BP was characterized by a warm and humid climate (corresponds to middle Holocene optimum) with climate cooling thereafter. A warm period reconstructed from ca 900 to at least ca 580 cal yr BP corresponds to a transition to a Nara-Heian-Kamakura warm stage and can be correlated to a Medieval Warm Period. After 580 cal yr PB, the lake gradually dried out and climatic signals could not be obtained from the declining lacustrine biological communities, but the increasing role of spruce and disappearance of the oak from the vegetation give evidences of the climate cooling that can be correlated with the LIA. The marine regression stages at the investigated site are identified for ca 6200-5900 (at the end of the middle Holocene transgression), ca 5500-5100 (Middle Jomon regression or Kemigawa regression), and ca 1070-360 cal yr BP (at the end of Heian transgression). The lithological structure of sediments and the diatom compositions give evidences for the multiple tsunami events of different strengths in the Island. Most remarkable of them can be dated at around ca 7000, 6460, 5750, 4800, 950 cal yr BP. The new results help to understand the Holocene environmental history of the Southern Kurils as a part of the Kuril-Kamchatka and Aleutian Marginal Sea-Island Arc Systems in the North-Western Pacific region.

  7. Pacific southwest United States Holocene summer paleoclimate inferred from sediment calcite oxygen isotopes (Lake Elsinore, CA)

    Science.gov (United States)

    Kirby, M.; Patterson, W. P.; Lachniet, M. S.; Anderson, M.; Noblet, J. A.

    2017-12-01

    Records of past climate inform on the natural range and mechanisms of climate change. In the arid Pacific southwest United States (pswUS), there exist a variety of Holocene records that infer past winter conditions (moisture and/or temperature). Holocene records of summer climate, however, are rare excepting short-lived (zone (Kirby et al. 2004) shows similar changes providing confidence in our longer record. Various forcing mechanisms are examined to explain the Elsinore summer record including insolation, Pacific SSTs, and trace gas radiative forcing.

  8. Sediment and PM10 flux from no-tillage cropping systems in the Pacific Northwest

    Science.gov (United States)

    Wind erosion is a concern in the Inland Pacific Northwest (PNW) United States where the emission of fine particulates from winter wheat – summer fallow (WW/SF) dryland cropping systems during high winds degrade air quality. Although no-tillage cropping systems are not yet economically viable, these ...

  9. Efficacy of 230Th normalization in sediments from the Juan de Fuca Ridge, northeast Pacific Ocean

    Science.gov (United States)

    Costa, Kassandra; McManus, Jerry

    2017-01-01

    230Th normalization is an indispensable method for reconstructing sedimentation rates and mass fluxes over time, but the validity of this approach has generated considerable debate in the paleoceanographic community. 230Th systematics have been challenged with regards to grain size bias, sediment composition (CaCO3), water column advection, and other processes. In this study, we investigate the consequences of these effects on 230Th normalization from a suite of six cores on the Juan de Fuca Ridge. The proximity of these cores (carbonate preservation, both of which may limit the usage of 230Th in this region. Despite anticipated complications, 230Th normalization effectively reconstructs nearly identical particle rain rates from all six cores, which are summarily unrelated to the total sedimentation rates as calculated from the age models. Instead the total sedimentation rates are controlled almost entirely by sediment focusing and winnowing, which are highly variable even over the short spatial scales investigated in this study. Furthermore, no feedbacks on 230Th systematics were detected as a consequence of sediment focusing, coarse fraction variability, or calcium carbonate content, supporting the robustness of the 230Th normalization technique.

  10. Organophosphate Ester Flame Retardants and Plasticizers in Ocean Sediments from the North Pacific to the Arctic Ocean.

    Science.gov (United States)

    Ma, Yuxin; Xie, Zhiyong; Lohmann, Rainer; Mi, Wenying; Gao, Guoping

    2017-04-04

    The presence of organophosphate ester (OPE) flame retardants and plasticizers in surface sediment from the North Pacific to Arctic Ocean was observed for the first time during the fourth National Arctic Research Expedition of China in the summer of 2010. The samples were analyzed for three halogenated OPEs [tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(dichloroisopropyl) phosphate], three alkylated OPEs [triisobutyl phosphate (TiBP), tri-n-butyl phosphate, and tripentyl phosphate], and triphenyl phosphate. Σ 7 OPEs (total concentration of the observed OPEs) was in the range of 159-4658 pg/g of dry weight. Halogenated OPEs were generally more abundant than the nonhalogenated OPEs; TCEP and TiBP dominated the overall concentrations. Except for that of the Bering Sea, Σ 7 OPEs values increased with increasing latitudes from Bering Strait to the Central Arctic Ocean, while the contributions of halogenated OPEs (typically TCEP and TCPP) to the total OPE profile also increased from the Bering Strait to the Central Arctic Ocean, indicating they are more likely to be transported to the remote Arctic. The median budget of 52 (range of 17-292) tons for Σ 7 OPEs in sediment from the Central Arctic Ocean represents only a very small amount of their total production volume, yet the amount of OPEs in Arctic Ocean sediment was significantly larger than the sum of polybrominated diphenyl ethers (PBDEs) in the sediment, indicating they are equally prone to long-range transport away from source regions. Given the increasing level of production and usage of OPEs as substitutes of PBDEs, OPEs will continue to accumulate in the remote Arctic.

  11. Evaluating climatic response to external radiative forcing during the late Miocene to early Pliocene: New perspectives from eastern equatorial Pacific (IODP U1338) and North Atlantic (ODP 982) locations

    Science.gov (United States)

    Drury, Anna Joy; John, Cédric M.; Shevenell, Amelia E.

    2016-01-01

    Orbital-scale climate variability during the latest Miocene-early Pliocene is poorly understood due to a lack of high-resolution records spanning 8.0-3.5 Ma, which resolve all orbital cycles. Assessing this variability improves understanding of how Earth's system sensitivity to insolation evolves and provides insight into the factors driving the Messinian Salinity Crisis (MSC) and the Late Miocene Carbon Isotope Shift (LMCIS). New high-resolution benthic foraminiferal Cibicidoides mundulus δ18O and δ13C records from equatorial Pacific International Ocean Drilling Program Site U1338 are correlated to North Atlantic Ocean Drilling Program Site 982 to obtain a global perspective. Four long-term benthic δ18O variations are identified: the Tortonian-Messinian, Miocene-Pliocene, and Early-Pliocene Oxygen Isotope Lows (8-7, 5.9-4.9, and 4.8-3.5 Ma) and the Messinian Oxygen Isotope High (MOH; 7-5.9 Ma). Obliquity-paced variability dominates throughout, except during the MOH. Eleven new orbital-scale isotopic stages are identified between 7.4 and 7.1 Ma. Cryosphere and carbon cycle sensitivities, estimated from δ18O and δ13C variability, suggest a weak cryosphere-carbon cycle coupling. The MSC termination coincided with moderate cryosphere sensitivity and reduced global ice sheets. The LMCIS coincided with reduced carbon cycle sensitivity, suggesting a driving force independent of insolation changes. The response of the cryosphere and carbon cycle to obliquity forcing is established, defined as Earth System Response (ESR). Observations reveal that two late Miocene-early Pliocene climate states existed. The first is a prevailing dynamic state with moderate ESR and obliquity-driven Antarctic ice variations, associated with reduced global ice volumes. The second is a stable state, which occurred during the MOH, with reduced ESR and lower obliquity-driven variability, associated with expanded global ice volumes.

  12. A Two Million Year Equatorial Paleogeomagnetic and Relative Paleointensity Record from IODP Site U1489 in the West Pacific Warm Pool: Towards an Improved Tuning Target.

    Science.gov (United States)

    Hatfield, R. G.; Stoner, J. S.; Kumagai, Y.

    2017-12-01

    International Ocean Discovery Program (IODP) Expedition 363 drilled nine sites in the West Pacific Warm Pool in October-December 2016. IODP Site U1489 (02°07.19'N, 141°01.67'E, 3421 meters water depth) located on the Eauripik Rise was drilled to a depth of 270 meters below sea floor using the advanced piston corer. Shipboard data revealed the upper 112 meters composite depth (mcd) consist of clay-rich nanno fossil ooze and contain all twenty-two geomagnetic reversals over the last 5 million years (Myrs). Shipboard generated rock magnetic data and post-cruise hysteresis data suggest the paleomagnetic record is carried by fine-grained pseudo-single domain magnetite. A shipboard estimate of relative paleointensity (RPI) was generated by normalizing the natural remanent magnetization (NRM) intensity after 15mT peak alternating field (AF) demagnetization of the shipboard half core measurement by whole round magnetic susceptibility (MS). Coherence of the NRM15mT/MS record with existing RPI stacks over the last 2 Myrs highlighted the potential for development of a RPI record back to the earliest Pliocene. Here we present the first u-channel measurements of the upper 40 mcd from Site U1489 spanning the last 2 Myrs. The NRM was measured at 1 cm intervals after stepwise AF demagnetization in peak fields of 15-100mT. Component inclination plots around that predicted by a geocentric axial dipole field and maximum angular deviation values are so far generally < 3° implying the paleomagnetic record is well resolved at Site U1489. Measurements of MS and anhysteretic remanent magnetization (ARM) characterize the environmental variability and provide a normalizer for the NRM to generate an estimate of RPI. The chronology is iteratively developed, initially based on polarity reversals boundaries, then by tuning MS to astronomical precession. We compare our RPI estimates to PISO-1500 and NARPI-2200 whose chronologies are based upon δ18O of benthic foraminifera to assess the

  13. Distribution and provenance of wind-blown SE Pacific surface sediments

    OpenAIRE

    Saukel, C.; Lamy, F.; Stuut, J.B.W.; Tiedemann, R.; Vogt, C.

    2011-01-01

    The reconstruction of low-latitude ocean-atmosphere interactions is one of the major issues of (paleo-) environmental studies. The trade winds, extending over 20 degrees to 30 degrees of latitude in both hemispheres, between the subtropical highs and the intertropical convergence zone, are major components of the atmospheric circulation and little is known about their long-term variability on geological time-scales, in particular in the Pacific sector. We present the modern spatial pattern of...

  14. Literature Review of Unconsolidated Sediment in San Francisco Bay and Nearby Pacific Ocean Coast

    Directory of Open Access Journals (Sweden)

    Barry R. Keller

    2009-09-01

    Full Text Available A review of the geologic literature regarding sedimentation in the San Francisco Bay estuarine system shows that the main part of the bay occupies a structural tectonic depression that developed in Pleistocene time. Eastern parts, including San Pablo Bay and Suisun Bay, have had sedimentation throughout late Mesozoic and Tertiary. Carquinez Strait and the Golden Gate may represent antecedent stream erosion. Sedimentation has included estuarine, alluvial, and eolian deposition. The ages of estuarine deposition includes the modern high sea level stand and earlier Pleistocene interglacial periods. Sediment sources can be generally divided into the Coast Ranges, particularly the Franciscan Complex, and “Sierran.” Much of the estuarine system is floored by very fine sediment, with local areas of sand floor. Near the Golden Gate, sediment size decreases in both directions away from the deep channel. Bedforms include sand waves (submarine dunes, flat beds, and rock and boulders. These are interpreted in terms of dominant transport directions. Near the Golden Gate is an ebb-tidal delta on the outside (including San Francisco bar and a flood-tidal delta on the inside (parts of Central Bay. The large tidal prism causes strong tidal currents, which in the upper part of the estuary are normally much stronger than river currents, except during large floods. Cultural influences have altered conditions, including hydraulic mining debris, blasting of rocks, dredging of navigation channels, filling of the bay, and commercial sand mining. Many of these have served to decrease the tidal prism, correspondingly decreasing the strength of tidal currents.

  15. Assessment of gamma radionuclides in sediments from the Atlantic and Pacific Oceans of Guatemala

    International Nuclear Information System (INIS)

    Orozco Chilel, R.M.

    1997-01-01

    The study consisted in the assesment of radioactivity levels in marine sediments of Guatemala due to gamma radionuclides. The samples were taken from 5 selected places, the activity of each sediment was measured by gamma spectrometry using an GE High-Purity detector. The methodology used consisted in to measure the efficiency of the Ge detector, then the calibration for Pb-210 was made. The radioactivity ranges from 1.69 Bq/Kg to 8.68 Bq/Kg for Cs-137, 356.99 Bq/Kg to 431.18 Bq/Kg for K-40, 48.71 Bq/Kg to 59.94 Bq/Kg for Ra-226 and 151.283 Bq/Kg to 224.47 Bq/Kg for Pb-210

  16. Biodiversity of nematode assemblages from deep-sea sediments of the Atacama Slope and Trench (South Pacific Ocean)

    Science.gov (United States)

    Gambi, C.; Vanreusel, A.; Danovaro, R.

    2003-01-01

    Nematode assemblages were investigated (in terms of size spectra, sex ratio, Shannon diversity, trophic structure and diversity, rarefaction statistics, maturity index, taxonomic diversity and taxonomic distinctness) at bathyal and hadal depths (from 1050 to 7800 m) in the deepest trench of the South Pacific Ocean: the Trench of Atacama. This area, characterised by very high concentrations of nutritionally-rich organic matter also at 7800-m depth, displayed characteristics typical of eutrophic systems and revealed high nematode densities (>6000 ind. 10 cm -2). Nematode assemblages from the Atacama Trench displayed a different composition than at bathyal depths. At bathyal depths 95 genera and 119 species were found (Comesomatidae, Cyatholaimidae, Microlaimidae, Desmodoridae and Xyalidae being dominant), whereas in the Atacama Trench only 29 genera and 37 species were encountered (dominated by Monhysteridae, Chromadoridae, Microlaimidae, Oxystominidae and Xyalidae). The genus Monhystera (24.4%) strongly dominated at hadal depths and Neochromadora, and Trileptium were observed only in the Atacama Trench, but not at bathyal depths. A reduction of the mean nematode size (by ca. 67%) was observed between bathyal and hadal depths. Since food availability was not a limiting factor in the Atacama Trench sediments, other causes are likely to be responsible for the reduction of nematode species richness and body size. The presence of a restricted number of families and genera in the Atacama Trench might indicate that hadal sediments limited nematode colonisation. Most of the genera reaching very high densities in Trench sediments (e.g., Monhystera) are opportunistic and were responsible for the significant decrease of the maturity index. The dominance of opportunists, which are known to be characterised by small sizes, might have contributed to the reduced nematode size at hadal depths. Shannon diversity and species richness decreased in hadal water depth and this pattern

  17. PCB concentrations in sediments from the Gulf of Nicoya estuary, Pacific coast of Costa Rica

    Directory of Open Access Journals (Sweden)

    Alison L Spongberg

    2004-12-01

    Full Text Available Thirty-one sediment samples collected from 1996-2003 from the Gulf of Nicoya estuary on the north- western coast of Costa Rica, have been obtained for PCB analyses. This is part of the first study to evaluate the PCB contamination in coastal Costa Rica.Overall, the concentrations are low, especially when compared to sediments from more temperate climates and/or sediments from more heavily industrialized areas. Values average less than 3 ng/g dw sediment, however, a few samples contained up to 7 ng/g dw sediment. Sediments with the highest concentrations were located in the Punta Morales area, where muds were sampled from among mangrove roots. The Puntarenas samples had surprisingly low PCB concentrations, likely due to their sandy lithology. The congener distribution within the majority of the samples showed signs of either recent sources or lack of degradation. However, a few sites, specifically some of the inter-gulf islands and more remote samples had congener distributions indicative of airborne contaminants and/or degradation. Considering the presence of air-borne PCBs in the Gulf of Papagayo to the north, the lack of airborne PCBs and more varied congener distribution in the Gulf of Nicoya estuary was surprisingSe analizó los bifenilos policlorados (PCB en 31 muestras de sedimentos colectadas entre 1996 -2003 en el estuario del Golfo de Nicoya, costa noroeste de Costa Rica. Esto es parte de un primer estudio para evaluar la contaminación por PCB en aguas costeras de Costa Rica. En general, las concentraciones fueron bajas especialmente cuando se les compara con sedimentos de climas templados y / o sedimentos de areas altamente industrializadas. Los valores promedio son inferiores a 3 ng / dw (peso seco de sedimento. Sin embargo, unas pocas muestras contienen hasta 7 ng/ g dw de sedimento. Los sedimentos con las concentraciones más altas están localizados en el area de Punta Morales, en cienos de entre raíces de mangle. Las

  18. Dispersed Volcanic Ash in Sediment Entering NW Pacific Ocean Subduction Zones: Towards a Regional Perspective

    Science.gov (United States)

    Scudder, R. P.; Murray, R. W.; Underwood, M.; Kutterolf, S.; Plank, T.; Dyonisius, M.; Arshad, M. A.

    2011-12-01

    Volcanic ash has long been recognized to be an important component of the global sedimentary system. Ash figures prominently in a number of sedimentary and petrophysical investigations, including how the fluid budget of subducting sediment will be affected by hydration/dehydration reactions. Additionally, many studies focus on discrete ash layers, and how to link their presence with volcanism, climate, arc evolution, biological productivity, and other processes. Less widely recognized is the ash that is mixed into the bulk sediment, or "dispersed" ash. Dispersed ash is quantitatively significant and is an under-utilized source of critical geochemical and tectonic information. Based on geochemical studies of ODP Site 1149, a composite of DSDP Sites 579 & 581, as well as IODP Sites C0011 & C0012 drilled during Expedition 322, we will show the importance of dispersed ash to the Izu-Bonin-Marianas, Kurile-Kamchatka and Nankai subduction zones. Initial geochemical analyses of the bulk sediment, as related to dispersed ash entering these subduction systems are presented here. Geochemical analysis shows that the characteristics of the three sites exhibit some variability consistent with observed lithological variations. For example, the average SiO2/Al2O3 ratios at Site 1149, Site C0011 and Site C0012 average 3.7. The composite of Sites 579 & 581 exhibits a higher average of 4.6. There are contrasts between other key major elemental indicators as well (e.g., Fe2O3). Ternary diagrams such as K2O-Na2O-CaO show that there are at least two distinct geochemical fields with Sites 1149, C0011 and C0012 clustering in one and Sites 579 & 581 in the other. Q-mode Factor Analysis was performed on the bulk sediment chemical data in order to determine the composition of potential end members of these sites. The multivariate statistics indicate that Site 1149 has 3-4 end members, consistent with the results of Scudder et al. (2009, EPSL, v. 284, pp 639), while each of the other sites

  19. Intermonsoonal equatorial jets

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.

    , respectively. Hydrographic features and transport computations favour a well developed equatorial jet during both seasons. The net surface eastward and subsurface westward flows are well balanced during the premonsoon transition period and appear...

  20. Comparisons between POC and zooplankton swimmer flux from sediment traps in the subarctic and subtropical North Pacific

    Science.gov (United States)

    Yokoi, Naoya; Abe, Yoshiyuki; Kitamura, Minoru; Honda, Makio C.; Yamaguchi, Atsushi

    2018-03-01

    Seasonal changes in zooplankton swimmer (ZS) abundance, biomass and community structure were evaluated based on samples collected by moored sediment traps at a depth of 200 m in the subarctic (SA) and subtropical (ST) western North Pacific. Based on these samples, we made comparisons on two topics: 1) latitudinal (subarctic vs. subtropical) changes in ZS abundance, biomass and community and 2) quantitative differences between the ZS and particle organic carbon (POC) fluxes based on data from moored or drifting sediment traps. The results showed that the ZS flux was greater in the SA (annual mean: 311 ind. m-2 day-1 or 258 mg C m-2 day-1) than in the ST (135 ind. m-2 day-1 or 38 mg C m-2 day-1). The peak ZS flux was observed from July-August in the SA and from April-May in the ST. The dominant taxa were Copepoda and Chaetognatha in the SA and Ostracoda and Mollusca in the ST. These latitudinal differences are likely related to the dominance of large-sized Copepoda in the SA, regional differences in the timing of the spring phytoplankton bloom, and the magnitude and size structure of primary producers. The percent composition of ZS to the total C flux (= ZS+POC flux) varied by region: 85-95% in the SA and 47-75% in the ST. These differences between the ZS composition and the total C flux are most likely caused by the dominance of large-sized Copepoda (Neocalanus spp. and Eucalanus bungii) in the SA.

  1. Biogenic silica and organic carbon in sediments from the Pacific sector of the Southern Ocean

    International Nuclear Information System (INIS)

    Giglio, F.; Langone, L.; Morigi, C.; Frignani, M.; Ravaioli, M.

    2002-01-01

    Four cores, collected during the 1995/96 Italian Antarctic cruise and located north and south of the Polar Front, provided both qualitative and quantitative information about changes of the sediment settings driven by climate changes. Biogenic silica and organic carbon flux variations and sedimentological analyses allow us to make inferences about the fluctuation of the Polar Front during the last climate cycles: the records of our cores Anta96-1 and Anta96-16 account for fluctuations of the Polar Front of at least 5 degrees with respect to the present position, with a concomitant movement of the Marginal Ice Zone. The very low accumulation rates at the study sites are probably due to the scarce availability of micronutrients. In the area south of the Polar Front, sediment accumulation, after a decrease, appears constant during the last 250,000 yr. A subdivision in glacial/interglacial stages has been proposed, which permits the identification of the warm stage 11, which is particularly important in the Southern Ocean. (author). 13 refs., 5 figs

  2. Sedimentation

    Science.gov (United States)

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  3. Interelement relationship in abyssal Pacific ferromanganese nodules and associated pelagic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y H

    1982-01-01

    By R-mode factor analysis and enrichment factor calculations, most of the elements in abyssal ferromanganese nodules and associated pelagic sediments (excluding common authigenic minerals like apatite, barite, opal and carbonates) are found to be preferentially concentrated in one of the following three major phases: aluminosilicates (e.g., Al, Si, Sc, Ga, Cr, Be, Na, K, Rb and Cs), Fe-oxides (e.g., Fe, P, S, V, Se, Te, As, B, Sn, U, Hg, Pb, Ti, Ge, Y, Zr, Nb, Pd, In, rare-earths, Hf, Th, Pa, Pu, Am, Ru and Bi), and Mn-oxides (e.g., Mn, Tl, Ag, Cd, Mg, Ca, Ba, Ra, Co, Ni, Cu, Zn, Mo, Sb and probably W). The specific association of elements with these three phases can be explained by the difference in chemical forms of elements in seawater and by fundamental differences in physicochemical properties (e.g., the pH of zero point of charge and dielectric constant) of these three phases.

  4. Interelement relationship in abyssal Pacific ferromanganese nodules and associated pelagic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y -H

    1982-06-01

    By R-mode factor analysis and enrichment factor calculations, most of the elements in abyssal ferromanganese nodules and associated pelagic sediments (excluding common authigenic minerals like apatite, barite, opal and carbonates) are found to be preferentially concentrated in one of the following three major phases: aluminosilicates (e.g., Al, Si, Sc, Ga, Cr, Be, Na, K, Rb and Cs), Fe-oxides (e.g., Fe, P, S, V, Se, Te, As, B, Sn, U, Hg, Pb, Ti, Ge, Y, Zr, Nb, Pd, In, rare-earths, Hf, Th, Pa, Pu, Am, Ru and Bi), and Mn-oxides (e.g., Mn, Tl, Ag, Cd, Mg, Ca, Ba, Ra, Co, Ni, Cu, Zn, Mo, Sb and probably W). The specific association of elements with these three phases can be explained by the difference in chemical forms of elements in seawater and by fundamental differences in physiocochemical properties (e.g., the pH of zero point of charge and dieletric constant) of these three phases.

  5. Metalliferous sediment and a silica-hematite deposit within the Blanco fracture zone, Northeast Pacific

    Science.gov (United States)

    Hein, J.R.; Clague, D.A.; Koski, R.A.; Embley, R.W.; Dunham, R.E.

    2008-01-01

    A Tiburon ROV dive within the East Blanco Depression (EBD) increased the mapped extent of a known hydrothermal field by an order of magnitude. In addition, a unique opal-CT (cristobalite-tridymite)-hematite mound was discovered, and mineralized sediments and rock were collected and analyzed. Silica-hematite mounds have not previously been found on the deep ocean floor. The light-weight rock of the porous mound consists predominantly of opal-CT and hematite filaments, rods, and strands, and averages 77.8% SiO2 and 11.8% Fe2O3. The hematite and opal-CT precipitated from a low-temperature (???115?? C), strongly oxidized, silica- and iron-rich, sulfur-poor hydrothermal fluid; a bacterial mat provided the framework for precipitation. Samples collected from a volcaniclastic rock outcrop consist primarily of quartz with lesser plagioclase, smectite, pyroxene, and sulfides; SiO2 content averages 72.5%. Formation of these quartz-rich samples is best explained by cooling in an up-flow zone of silica-rich hydrothermal fluids within a low permeability system. Opal-A, opal-CT, and quartz mineralization found in different places within the EBD hydrothermal field likely reflects decreasing silica saturation and increasing temperature of the mineralizing fluid with increasing silica crystallinity. Six push cores recovered gravel, coarse sand, and mud mineralized variously by Fe or Mn oxides, silica, and sulfides. Total rare-earth element concentrations are low for both the rock and push core samples. Ce and Eu anomalies reflect high and low temperature hydrothermal components and detrital phases. A remarkable variety of types of mineralization occur within the EBD field, yet a consistent suite of elements is enriched (relative to basalt and unmineralized cores) in all samples analyzed: Ag, Au, S, Mo, Hg, As, Sb, Sr, and U; most samples are also enriched in Cu, Pb, Cd, and Zn. On the basis of these element enrichments, the EBD hydrothermal field might best be described as a base

  6. Long-term Records of Pacific Salmon Abundance From Sediment Core Analysis: Relationships to Past Climatic Change, and Implications for the Future

    Science.gov (United States)

    Finney, B.

    2002-12-01

    The response of Pacific salmon to future climatic change is uncertain, but will have large impacts on the economy, culture and ecology of the North Pacific Rim. Relationships between sockeye salmon populations and climatic change can be determined by analyzing sediment cores from lakes where sockeye return to spawn. Sockeye salmon return to their natal lake system to spawn and subsequently die following 2 - 3 years of feeding in the North Pacific Ocean. Sockeye salmon abundance can be reconstructed from stable nitrogen isotope analysis of lake sediment cores as returning sockeye transport significant quantities of N, relatively enriched in N-15, from the ocean to freshwater systems. Temporal changes in the input of salmon-derived N, and hence salmon abundance, can be quantified through downcore analysis of N isotopes. Reconstructions of sockeye salmon abundance from lakes in several regions of Alaska show similar temporal patterns, with variability occurring on decadal to millennial timescales. Over the past 2000 years, shifts in sockeye salmon abundance far exceed the historical decadal-scale variability. A decline occurred from about 100 BC - 800 AD, but salmon were consistently more abundant 1200 - 1900 AD. Declines since 1900 AD coincide with the period of extensive commercial fishing. Correspondence between these records and paleoclimatic data suggest that changes in salmon abundance are related to large scale climatic changes over the North Pacific. For example, the increase in salmon abundance c.a. 1200 AD corresponds to a period of glacial advance in southern Alaska, and a shift to drier conditions in western North America. Although the regionally coherent patterns in reconstructed salmon abundance are consistent with the hypothesis that climate is an important driver, the relationships do not always follow patterns observed in the 20th century. A main feature of recorded climate variability in this region is the alternation between multi-decade periods of

  7. Application of the positive matrix factorization approach to identify heavy metal sources in sediments. A case study on the Mexican Pacific Coast.

    Science.gov (United States)

    González-Macías, C; Sánchez-Reyna, G; Salazar-Coria, L; Schifter, I

    2014-01-01

    During the last two decades, sediments collected in different sources of water bodies of the Tehuantepec Basin, located in the southeast of the Mexican Pacific Coast, showed that concentrations of heavy metals may pose a risk to the environment and human health. The extractable organic matter, geoaccumulation index, and enrichment factors were quantified for arsenic, cadmium, copper, chromium, nickel, lead, vanadium, zinc, and the fine-grained sediment fraction. The non-parametric SiZer method was applied to assess the statistical significance of the reconstructed metal variation along time. This inference method appears to be particularly natural and well suited to temperature and other environmental reconstructions. In this approach, a collection of smooth of the reconstructed metal concentrations is considered simultaneously, and inferences about the significance of the metal trends can be made with respect to time. Hence, the database represents a consolidated set of available and validated water and sediment data of an urban industrialized area, which is very useful as case study site. The positive matrix factorization approach was used in identification and source apportionment of the anthropogenic heavy metals in the sediments. Regionally, metals and organic matter are depleted relative to crustal abundance in a range of 45-55 %, while there is an inorganic enrichment from lithogenous/anthropogenic sources of around 40 %. Only extractable organic matter, Pb, As, and Cd can be related with non-crustal sources, suggesting that additional input cannot be explained by local runoff or erosion processes.

  8. Preliminary report: STOIC CGCM intercomparison - equatorial sections

    International Nuclear Information System (INIS)

    Davey, M; Huddleston, M; Sperber, K R.

    1999-01-01

    An intercomparison and assessment of the tropical behaviour of coupled general circulation models (CGCMs) is being carried out, to identify common strengths and weaknesses and thus guide future CGCM development. The work is being carried out as part of the CLIVAR climate research programme, as a WG-SIP (Working Group on Seasonal to Interannual Prediction) project called STOIC (Study of Tropical Oceans In CGCMs), organised by Michael Davey. This project complements a companion sub-project called ENSIP (El Ni no Simulation Intercomparison Project) organised by Mojib Latif (Max- Planck-Institute for Meteorology) that focusses on equatorial Pacific CGCM behaviour (Latif et al. 1999). Previous coupled model assessments (Mechoso et al. 1995, Neelin et al. 1992, and ENSIP) have focussed on tropical Pacific behaviour. The aim of STOIC is to look at model performance in all tropical ocean regions. This status report contains a sample of the STOIC assessment work, highlighting mean and inter- annual equatorial sea surface temperatures and zonal windstresses. The intention is to submit STOIC and ENSIP papers in mid-1999 for publication together in a refereed journal

  9. Chemical Composition of the Graphitic Black Carbon Fraction in Riverine and Marine Sediments at Submicron Scales using Carbon X-ray Spectromicroscopy

    International Nuclear Information System (INIS)

    Haberstroh, P.; Brandes, J.; Gelinas, Y.; Dickens, A.; Wirick, S.; Cody, G.

    2006-01-01

    The chemical composition of the graphitic black carbon (GBC) fraction of marine organic matter was explored in several marine and freshwater sedimentary environments along the west coast of North America and the Pacific Ocean. Analysis by carbon x-ray absorption near edge structure (C-XANES) spectroscopy and scanning transmission x-ray microscopy (STXM) show the GBC-fraction of Stillaguamish River surface sediments to be dominated by more highly-ordered and impure forms of graphite, together forming about 80% of the GBC, with a smaller percent of an aliphatic carbon component. Eel River Margin surface sediments had very little highly-ordered graphite, and were instead dominated by amorphous carbon and to a lesser extent, impure graphite. However, the GBC of surface sediments from the Washington State Slope and the Mexico Margin were composed almost solely of amorphous carbon. Pre-anthropogenic, highly-oxidized deep-sea sediments from the open Equatorial Pacific Ocean contained over half their GBC in different forms of graphite as well as highly-aliphatic carbon, low aromatic/highly-acidic aliphatic carbon, low aromatic/highly aliphatic carbon, and amorphous forms of carbon. Our results clearly show the impact of graphite and amorphous C phases in the BC fraction in modern riverine sediments and nearby marine shelf deposits. The pre-anthropogenic Equatorial Pacific GBC fraction is remarkable in the existence of highly-ordered graphite

  10. Centennial changes in North Pacific anoxia linked to tropical trade winds

    Science.gov (United States)

    Deutsch, Curtis; Berelson, William; Thunell, Robert; Weber, Thomas; Tems, Caitlin; McManus, James; Crusius, John; Ito, Taka; Baumgartner, Timothy; Ferreira, Vicente; Mey, Jacob; van Geen, Alexander

    2014-01-01

    Climate warming is expected to reduce oxygen (O2) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ15N) from multiple sediment cores. Increasing δ15N since ~1990 records an expansion of anoxia, consistent with observed O2 trends. However, this was preceded by a longer declining δ15N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O2 demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean’s largest anoxic zone will contract despite a global O2 decline.

  11. Oceanography. Centennial changes in North Pacific anoxia linked to tropical trade winds.

    Science.gov (United States)

    Deutsch, Curtis; Berelson, William; Thunell, Robert; Weber, Thomas; Tems, Caitlin; McManus, James; Crusius, John; Ito, Taka; Baumgartner, Timothy; Ferreira, Vicente; Mey, Jacob; van Geen, Alexander

    2014-08-08

    Climate warming is expected to reduce oxygen (O2) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ(15)N) from multiple sediment cores. Increasing δ(15)N since ~1990 records an expansion of anoxia, consistent with observed O2 trends. However, this was preceded by a longer declining δ(15)N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O2 demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean's largest anoxic zone will contract despite a global O2 decline. Copyright © 2014, American Association for the Advancement of Science.

  12. Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

    Energy Technology Data Exchange (ETDEWEB)

    Froellje, Henning

    2016-08-09

    Ocean circulation and cycling of trace elements within the oceanic water column is of great significance for modern and past climates. The global overturning circulation is responsible for the distribution of water masses, heat and particulate and dissolved compounds, while biological and chemical processes, such as primary productivity or particle scavenging, control the cycling of nutrients and trace elements in the ocean, and ultimately influence the ocean-atmosphere exchange of carbon. Rare earth elements (REE) and neodymium (Nd) isotopes are widely used as tracers for lithogenic element fluxes and modern and past ocean circulation and water mass mixing. The use of Nd isotopes in paleoceanographic investigations is based on the precise knowledge of processes involved in REE cycling and of the modern oceanic Nd isotope distribution. The Pacific is the largest of the world oceans, but it is highly underrepresented in present-day and past seawater Nd isotope and REE investigations compared to the Atlantic Ocean. In this study, Nd isotopes and REEs are analysed in North Pacific seawater (chapter 2) and sediment samples from the South Pacific (chapters 3-5) to contribute to a better understanding of sources and cycling of REEs and Nd isotopes in present-day seawater and to investigate past water mass mixing and circulation changes during the last glacial termination and throughout the last glacial-interglacial cycle. Neodymium isotopes in seawater and sedimentary archives (fossil fish teeth and debris, foraminifera, ferromanganese oxides, lithogenic particles) were analysed using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), and REE concentrations were analysed using isotope dilution ICP-MS. Results from combined analysis of REEs, and Nd and radium isotopes from North Pacific seawater (coastal seawaters of the Hawaiian Island of Oahu and seawater from the offshore Hawaii Ocean Time-series Station ALOHA) show a clear influence of the

  13. Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

    International Nuclear Information System (INIS)

    Froellje, Henning

    2016-01-01

    Ocean circulation and cycling of trace elements within the oceanic water column is of great significance for modern and past climates. The global overturning circulation is responsible for the distribution of water masses, heat and particulate and dissolved compounds, while biological and chemical processes, such as primary productivity or particle scavenging, control the cycling of nutrients and trace elements in the ocean, and ultimately influence the ocean-atmosphere exchange of carbon. Rare earth elements (REE) and neodymium (Nd) isotopes are widely used as tracers for lithogenic element fluxes and modern and past ocean circulation and water mass mixing. The use of Nd isotopes in paleoceanographic investigations is based on the precise knowledge of processes involved in REE cycling and of the modern oceanic Nd isotope distribution. The Pacific is the largest of the world oceans, but it is highly underrepresented in present-day and past seawater Nd isotope and REE investigations compared to the Atlantic Ocean. In this study, Nd isotopes and REEs are analysed in North Pacific seawater (chapter 2) and sediment samples from the South Pacific (chapters 3-5) to contribute to a better understanding of sources and cycling of REEs and Nd isotopes in present-day seawater and to investigate past water mass mixing and circulation changes during the last glacial termination and throughout the last glacial-interglacial cycle. Neodymium isotopes in seawater and sedimentary archives (fossil fish teeth and debris, foraminifera, ferromanganese oxides, lithogenic particles) were analysed using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), and REE concentrations were analysed using isotope dilution ICP-MS. Results from combined analysis of REEs, and Nd and radium isotopes from North Pacific seawater (coastal seawaters of the Hawaiian Island of Oahu and seawater from the offshore Hawaii Ocean Time-series Station ALOHA) show a clear influence of the

  14. Anthropogenic radionuclides in sediments in the NW Pacific Ocean and its marginal seas. Results of the 1994-1995 Japanese-Korean-Russian expeditions

    International Nuclear Information System (INIS)

    Pettersson, H.B.L.; Amano, H.; Berezhnov, V.I.; Nikitin, A.; Veletova, N.K.; Chaykovskaya, E.; Chumichev, V.B.; Chung, C.S.; Gastaud, J.; Hirose, K.; Hong, G.H.; Kim, C.K.; Kim, S.H.; Lee, S.H.; Morimoto, T.; Oda, K.; Povinec, P.P.; Togawa, O.; Suzuki, E.; Tkalin, A.; Volkov, Y.; Yoshida, K.

    1999-01-01

    Assessment of contamination of anthropogenic radionuclides from past dumping of radioactive waste in areas of the Okhotsk Sea, NW Pacific Ocean and the Sea of Japan/East Sea has been performed. Two joint Japanese-Korean-Russian scientific expeditions were carried out in 1994-1995, where seawater and seabed sediments were samples from 22 sites. Results of sediment analysis are reported here, where concentrations of 90Sr, 137Cs, 238Pu, 239,240Pu and 241Am in surface layer and bulk sediments showed on large spatial variations, ranging between -1 dry wt., -1 dry wt., -1 dry wt., 0.006 and 2.0 Bq kg -1 dry wt., 0.03 and 1.8 Bq kg -1 dry wt., respectively. However, the concentrations are comparable with those found in reference sites outside the dumping areas and they generally fall within ranges previously reported for non-dumping areas of the investigated seas. Estimates of sediment inventories indicated differences in radionuclide load between shelf/slope and basin type sediments as well as dependence on water depth. Except for the shallow areas, most of the inventories of 90Sr, 137Cs and Pu isotopes are still to be found in the water column. Total inventories (in water+sediment) show a surplus of 137Cs and Pu-isotopes compared to expected integrated global fall-out deposition, which is consistent with previous observations in non-dumping areas in the seas investigated. Analysis of sediment 238Pu/239,240Pu activity ratios showed values in accord with that of global fall-out. Analysis of radionuclide depth distributions in core samples from areas of the Sea of Okhotsk showed sedimentation rates of 0.2-0.4 g cm -2 year -1 and 0.03 g cm -2 year -1 for shelf and basin areas respectively, which is similar to values found in the Sea of Japan/East Sea. Depth profiles of 90Sr, 137Cs and Pu isotopes in cores of the basin area indicate a typical delay compared to the input records of global fall-out

  15. Characterization of Paleoredox Changes In Nw-pacific Deep-sea Sediments Using Environmental Magnetic In Combination With Geochemical-mineralogic Data

    Science.gov (United States)

    Urbat, M.; Pletsch, T.

    The understanding of environmental and oceanic controls on deep-sea sediments in the NW Pacific Ocean (ODP Site 1149A, Nadezhda Basin) benefits from the inte- gration of environmental magnetic methodology with geochemical-mineralogic XRD (x-ray defraction) and XRF (x-ray fluorescence) data. Crucially, the inherently grad- ual diagenetic processes related to paleo-redox changes in the sediment column may be more sensitively monitored using the integration of non-magnetic and magnetic data, because they do reflect various aspects of the entire postdepositional alteration. The studied 32 m long quaternary interval at Hole ODP 1149A provides an expanded record of eolian dust supply from the Asian continent, siliceous plankton accumulation and varying contributions of both discrete ash layers and disperse ash to a truly deep- sea environment (Plank et al. 2000). Recurrent diagenetic intervals appear to be related to changes in the Ocean water circulation (Kuriosho current) and concomitant produc- tivity variations as a function of glacial-interglacial paleoclimatic changes. Diagenetic intervals correspond to paleo-redox boundaries, where suboxic conditions promoted the destruction of the primary magnetic signal (iron oxides) and the precipitation of rhodochrosite (MnCO3). We used simple normative calculations on the basis of of Al and Cr contents to discriminate between the major groups of components (terrigenous, volcanogenic, biogenic, diagenetic) in combination with our magnetic results. These results form the grounds for the discrimation and independent interpretation of the genetically various sediment components in the paleoceanograhic context.

  16. Do regions outside the tropical Pacific influence ENSO through atmospheric teleconnections?

    Digital Repository Service at National Institute of Oceanography (India)

    Dayan, H.; Izumo, T.; Vialard, J.; Lengaigne, M.; Masson, S

    This paper aims at identifying oceanic regions outside the tropical Pacific, which may influence the El Ni�o Southern Oscillation (ENSO) through interannual modulation of equatorial Pacific winds An Atmospheric General Circulation Model (AGCM) 7...

  17. Nineteen-year time-series sediment trap study of Coccolithus pelagicus and Emiliania huxleyi (calcareous nannoplankton) fluxes in the Bering Sea and subarctic Pacific Ocean

    Science.gov (United States)

    Tsutsui, Hideto; Takahashi, Kozo; Asahi, Hirofumi; Jordan, Richard W.; Nishida, Shiro; Nishiwaki, Niichi; Yamamoto, Sumito

    2016-03-01

    Coccolithophore fluxes at two sediment trap stations, Station AB in the Bering Sea and Station SA in the subarctic Pacific Ocean, were studied over a nineteen-year (August 1990-July 2009) interval. Two major species, Coccolithus pelagicus and Emiliania huxleyi, occur at both stations, with Gephyrocapsa oceanica, Umbilicosphaera sibogae, Braarudosphaera bigelowii, and Syracosphaera spp. as minor components. The mean coccolithophore fluxes at Stations AB and SA increased from 28.9×106 m2 d-1 and 61.9×106 m2 d-1 in 1990-1999 to 54.4×106 m2 d-1 and 130.2×106 m2 d-1 in 2002-2009, respectively. Furthermore, in late 1999 to early 2000, there was a significant shift in the most dominant species from E. huxleyi to C. pelagicus. High abundances of E. huxleyi correspond to the positive mode of the Pacific Decadal Oscillation (PDO), while those of C. pelagicus respond to the PDO negative mode and are related to water temperature changes at huxleyi. At both stations the mean seawater temperature in the top 45 m from August to October increased ca. 1 °C with linear recurrence from 1990 to 2008. The coccosphere fluxes after Year 2000 at Stations AB and SA, and the shift in species dominance, may have been influenced by this warming.

  18. Tracing the anthropogenic lead sources in coastal sediments of SE-Pacific (36 deg. Lat. S) using stable lead isotopes

    International Nuclear Information System (INIS)

    Munoz, Praxedes N.V.; Garbe-Schoenberg, Carl-Dieter; Salamanca, Marco A.

    2004-01-01

    This study evaluates the main sources of antropogenic Pb in one of the most industrialized centers of the southern Chilean coast (36 deg. S). Stable lead isotopes ( 206 Pb/ 207 Pb, 208 Pb/ 207 Pb) were used to trace main Pb sources to coastal sediments, considering the suspended particulate matter (SPM) from marine (traps), continental (rivers) and industrial effluents, sediments and leaded gasoline samples. The atmospheric input was evaluated through natural collectors; i.e. Raqui-Tubul salt marsh. Results show that marine samples lie on a trend between industrial effluents (∼1.16, 2.44) and natural sources (1.20, 2.50), not related to gasoline consumption. Salt marsh sediments show comparable isotopic composition to marine samples, suggesting the importance of the atmospheric input in the coastal sediments, not related to the leaded gasoline composition either. The continental input (1.18, 2.48) is highly influenced by precipitation, being difficult to separate both sources (atmosphere and continental runoff), showing also similar isotopic ratio to marine sediments. The signal of industrial emissions is masked with the introduction of Pb with higher isotopic ratios, compared to the values observed in the material collected from traps (SPM ∼1.19, 2.48). The contribution of more radiogenic Pb by the upwelling is suggested

  19. Biogeographical distribution and diversity of microbes in methane hydrate-bearing deep marine sediments, on the Pacific Ocean Margin

    DEFF Research Database (Denmark)

    Inagaki, F.; Nunoura, T.; Nakagawa, S.

    2006-01-01

    The deep subseafloor biosphere is among the least-understood habitats on Earth, even though the huge microbial biomass therein plays an important role for potential long-term controls on global biogeochemical cycles. We report here the vertical and geographical distribution of microbes and their ......The deep subseafloor biosphere is among the least-understood habitats on Earth, even though the huge microbial biomass therein plays an important role for potential long-term controls on global biogeochemical cycles. We report here the vertical and geographical distribution of microbes...... of the uncultivated Deep-Sea Archaeal Group were consistently the dominant phylotype in sediments associated with methane hydrate. Sediment cores lacking methane hydrates displayed few or no Deep-Sea Archaeal Group phylotypes. Bacterial communities in the methane hydrate-bearing sediments were dominated by members...

  20. Equatorial electrojet in east Brazil longitudes

    Indian Academy of Sciences (India)

    dip latitude as the electrons/ions can move vertically along the inclined magnetic field lines. Equatorial electrojet has been extensively studied from ground, rocket ... Keywords. Equatorial electrojet; Brazilian anomaly in equatorial electrojet; asymmetries in equatorial electrojet. J. Earth Syst. Sci. 119, No. 4, August 2010, pp.

  1. The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

    Science.gov (United States)

    Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

    2016-02-01

    In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

  2. Coastal Circulation and Sediment Dynamics in War-in-the-Pacific National Historical Park, Guam; measurements of waves, currents, temperature, salinity, and turbidity, June 2007-January 2008

    Science.gov (United States)

    Storlazzi, Curt D.; Presto, M. Katherine; Logan, Joshua B.

    2009-01-01

    Flow in and around coral reefs affects a number of physical, chemical and biologic processes that influence the health and sustainability of coral reef ecosystems. These range from the residence time of sediment and contaminants to nutrient uptake and larval retention and dispersal. As currents approach a coast they diverge to flow around reef structures, causing high horizontal and vertical shear. This can result in either the rapid advection of material in localized jets, or the retention of material in eddies that form in the lee of bathymetric features. The high complexity and diversity both within and between reefs, in conjunction with past technical restrictions, has limited our understanding of the nature of flow and the resulting flux of physical, chemical, and biologic material in these fragile ecosystems. Sediment, nutrients, and other pollutants from a variety of land-based activities adversely impact many coral reef ecosystems in the U.S. and around the world. These pollutants are transported in surface water runoff, groundwater seepage, and atmospheric fallout into coastal waters, and there is compelling evidence that the sources have increased globally as a result of human-induced changes to watersheds. In Guam, and elsewhere on U.S. high islands in the Pacific and Caribbean, significant changes in the drainage basins due to agriculture, feral grazing, fires, and urbanization have in turn altered the character and volume of land-based pollution released to coral reefs. Terrigenous sediment run-off (and the associated nutrients and contaminants often absorbed to it) and deposition on coral reefs are recognized to potentially have significant impact on coral health by blocking light and inhibiting photosynthesis, directly smothering and abrading coral, and triggering increases in macro algae. Studies that combine information on watershed, surface water- and groundwater-flow, transport and fate of sediment and other pollutants in the reef environment

  3. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1984-04-16 to 1985-10-01 (NODC Accession 8700147)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from April 16, 1984 to October 1, 1985. Data were...

  4. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1987-05-01 to 1987-05-05 (NODC Accession 9000211)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from 01 May 1987 to 06 August 1988. Data were submitted...

  5. Current meter components and other data from fixed platforms from TOGA Area - Pacific (30 N to 30 S) and other locations in support of the Tropical Ocean Global Atmosphere (TOGA) and the Equatorial Pacific Ocean Climate Studies (EPOCS) projects from 1989-04-16 to 1990-05-14 (NODC Accession 9200266)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter components data were collected from fixed platforms from the TOGA Area - Pacific (30 N to 30 S) and other locations from 16 April 1989 to 14 May 1990....

  6. Current meter data from moored current meter casts in the SW Pacific (limit-147 E to 140 W) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1985-09-29 to 1986-04-01 (NODC Accession 8800136)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the SW Pacific (limit-147 E to 140 W) from September 29, 1985 to June 1, 1986. Data were...

  7. Habitat filtering of bacterioplankton communities above polymetallic nodule fields and sediments in the Clarion-Clipperton zone of the Pacific Ocean.

    Science.gov (United States)

    Lindh, Markus V; Maillot, Brianne M; Smith, Craig R; Church, Matthew J

    2018-04-01

    Deep-sea mining of commercially valuable polymetallic nodule fields will generate a seabed sediment plume into the water column. Yet, the response of bacterioplankton communities, critical in regulating energy and matter fluxes in marine ecosystems, to such disturbances is unknown. Metacommunity theory, traditionally used in general ecology for macroorganisms, offers mechanistic understanding on the relative role of spatial differences compared with local environmental conditions (habitat filtering) for community assembly. We examined bacterioplankton metacommunities using 16S rRNA amplicons from the Clarion-Clipperton Zone (CCZ) in the eastern Pacific Ocean and in global ocean transect samples to determine sensitivity of these assemblages to environmental perturbations. Habitat filtering was the main assembly mechanism of bacterioplankton community composition in the epi- and mesopelagic waters of the CCZ and the Tara Oceans transect. Bathy- and abyssopelagic bacterioplankton assemblages were mainly assembled by undetermined metacommunity types or neutral and dispersal-driven patch-dynamics for the CCZ and the Malaspina transect. Environmental disturbances may alter the structure of upper-ocean microbial assemblages, with potentially even more substantial, yet unknown, impact on deep-sea communities. Predicting such responses in bacterioplankton assemblage dynamics can improve our understanding of microbially-mediated regulation of ecosystem services in the abyssal seabed likely to be exploited by future deep-sea mining operations. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  8. Characterization of Archaeological Sediments Using Fourier Transform Infrared (FT-IR) and Portable X-ray Fluorescence (pXRF): An Application to Formative Period Pyro-Industrial Sites in Pacific Coastal Southern Chiapas, Mexico.

    Science.gov (United States)

    Neff, Hector; Bigney, Scott J; Sakai, Sachiko; Burger, Paul R; Garfin, Timothy; George, Richard G; Culleton, Brendan J; Kennett, Douglas J

    2016-01-01

    Archaeological sediments from mounds within the mangrove zone of far-southern Pacific coastal Chiapas, Mexico, are characterized in order to test the hypothesis that specialized pyro-technological activities of the region's prehistoric inhabitants (salt and ceramic production) created the accumulations visible today. Fourier transform infrared spectroscopy (FT-IR) is used to characterize sediment mineralogy, while portable X-ray fluorescence (pXRF) is used to determine elemental concentrations. Elemental characterization of natural sediments by both instrumental neutron activation analysis (INAA) and pXRF also contribute to understanding of processes that created the archaeological deposits. Radiocarbon dates combined with typological analysis of ceramics indicate that pyro-industrial activity in the mangrove zone peaked during the Late Formative and Terminal Formative periods, when population and monumental activity on the coastal plain and piedmont were also at their peaks. © The Author(s) 2015.

  9. Rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments

    Science.gov (United States)

    Elderfield, H.; Hawkesworth, C. J.; Greaves, M. J.; Calvert, S. E.

    1981-04-01

    Analyses have been made of REE contents of a well-characterized suite of deep-sea (> 4000 m.) principally todorokite-bearing ferromanganese nodules and associated sediments from the Pacific Ocean. REE in nodules and their sediments are closely related: nodules with the largest positive Ce anomalies are found on sediments with the smallest negative Ce anomalies; in contrast, nodules with the highest contents of other rare earths (3 + REE) are found on sediments with the lowest 3 + REE contents and vice versa. 143Nd /144Nd ratios in the nodules (˜0.51244) point to an original seawater source but an identical ratio for sediments in combination with the REE patterns suggests that diagenetic reactions may transfer elements into the nodules. Analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to REE contents of nodules and sediments is negligible. Inter-element relationships and leaching tests suggest that REE contents are controlled by a P-rich phase with a REE pattern similar to that for biogenous apatite and an Fe-rich phase with a pattern the mirror image of that for sea water. It is proposed that 3 + REE concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate. Processes which favour the enrichment of transition metals in equatorial Pacific nodules favour the depletion of 3 + REE in nodules and enrichment of 3 + REE in associated sediments. In contrast, Ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions.

  10. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1988-05-24 to 1989-05-26 (NODC Accession 9100207)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from 24 May 1988 to 26 May 1989. Data were submitted by...

  11. Oceanographic profile plankton, temperature, salinity collected using bottle from various unknown small boats in the South Pacific Ocean from 1981 to 1982 (NODC Accession 0002138)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, salinity and other measurements found in dataset OSD taken from unknown platform(s)in the Coastal S Pacific, Equatorial Pacific and other locations from...

  12. WATER TEMPERATURE and Other Data from DRIFTING BUOY From TOGA Area - Pacific (30 N to 30 S) from 19921208 to 19930719 (NODC Accession 9500059)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The drifting buoy data set in this accession was collected from TOGA Area - Pacific (30 N to 30 S) in Equatorial Pacific, North of Australia as part of Tropical...

  13. Indo-Pacific sea level variability during recent decades

    Science.gov (United States)

    Yamanaka, G.; Tsujino, H.; Nakano, H.; Urakawa, S. L.; Sakamoto, K.

    2016-12-01

    Decadal variability of sea level in the Indo-Pacific region is investigated using a historical OGCM simulation. The OGCM driven by the atmospheric forcing removing long-term trends clearly exhibits decadal sea level variability in the Pacific Ocean, which is associated with eastern tropical Pacific thermal anomalies. During the period of 1977-1987, the sea level anomalies are positive in the eastern equatorial Pacific and show deviations from a north-south symmetric distribution, with strongly negative anomalies in the western tropical South Pacific. During the period of 1996-2006, in contrast, the sea level anomalies are negative in the eastern equatorial Pacific and show a nearly north-south symmetric pattern, with positive anomalies in both hemispheres. Concurrently, sea level anomalies in the south-eastern Indian Ocean vary with those in the western tropical Pacific. These sea level variations are closely related to large-scale wind fields. Indo-Pacific sea level distributions are basically determined by wind anomalies over the equatorial region as well as wind stress curl anomalies over the off-equatorial region.

  14. Equatorial Indian Ocean productivity during the last 33 kyr and possible linkage to Westerly Jet variability

    Digital Repository Service at National Institute of Oceanography (India)

    Punyu, V.R.; Banakar, V.K.; Garg, A.

    The top 1 m radiocarbon dated section of a 5.6 m long sediment core retrieved from the Equatorial Indian Ocean is studied for productivity changes in response to climate variability that have taken place during the last ~33 kyr. The robust...

  15. Relationship of subseafloor microbial diversity to sediment age and organic carbon content

    Science.gov (United States)

    Walsh, E. A.; Kirkpatrick, J. B.; Sogin, M. L.; D'Hondt, S. L.

    2013-12-01

    Our tag pyrosequencing investigation of four globally distant sites reveals sediment age and total organic carbon content to be significant components in understanding subseafloor diversity. Our sampling locations include two sites from high-productivity regions (Indian Ocean and Bering Sea) and two from moderate-productivity (eastern and central equatorial Pacific Ocean). Sediment from the high-productivity sites has much higher TOC than sediment from the moderate-productivity equatorial sites. We applied a high-resolution 16S V4-V6 tag pyrosequencing approach to 24 bacterial and 17 archaeal samples, totaling 602,502 reads. We identified1,291 archaeal and 15,910 bacterial OTUs (97%) from these reads. We analyzed bacterial samples from all four sites in addition to archaeal samples from our high productivity sites. These high productivity, high TOC sites have a pronounced methane-rich sulfate-free zone at depth from which archaea have been previously considered to dominate (Biddle et al., 2006). At all four locations, microbial diversity is highest near the seafloor and drops rapidly to low but stable values with increasing sediment depth. The depth at which diversity stabilizes varies greatly from site to site, but the age at which it stabilizes is relatively constant. At all four sites, diversity reaches low stable values a few hundred thousand years after sediment deposition. The sites with high total organic carbon (high productivity sites) generally exhibit higher diversity at each sediment age than the sites with lower total organic carbon (moderate-productivity sites). Archaeal diversity is lower than bacterial diversity at every sampled depth. Biddle, J.F., Lipp, J.S., Lever, M.A., Lloyd, K.G., Sørensen, K.B., Anderson, R. et al. (2006) Heterotrophic Archaea dominate sedimentary subsurface ecosystems off Peru. PNAS 103: 3846-3851.

  16. South Pacific Convergence Zone Changes during the Late Holocene Identified from Hydrogen Isotope Ratios of Terrestrial and Aquatic Biomarkers from Freshwater Lake Sediments in Vanuatu

    Science.gov (United States)

    Maloney, A. E.; Ladd, N.; Nelson, D. B.; Sachs, J. P.; Dubois, N.

    2017-12-01

    The South Pacific Convergence Zone (SPCZ) is one of Earth's major precipitation features. Mean annual rainfall rates are as high as 10 mm/day in the Solomon Islands in the northwest portion of the SPCZ, and decline to 4 mm/day in portions of French Polynesia the southeastern reach of the SPCZ. Coral records suggest that the mean annual position and precipitation intensity associated with the SPCZ have most likely expanded and contracted on decadal to centennial timescales, but existing data is limited, making it difficult to constrain and characterize these changes. Thion Island (15.03 °S, 167.09 °E) is located off the east coast of Espírito Santo in Vanuatu, at an intermediate position in the modern SPCZ. As such, it should be sensitive to major contractions and expansions of the SPCZ, with wetter conditions when the SPCZ expands southeast, and drier conditions when it contracts to the northwest. In order to determine changes in precipitation over the past millennium on Thion Island, we collected sediment cores from two adjacent freshwater lakes on the island, White Lake and Red Lake, and measured compound specific hydrogen isotope ratios (2H/1H) of lipid biomarkers from terrestrial plants (long-chain n-alkanes and n­-alkanoic acids), aquatic plants (mid-chain n­-alkanes and n-alkanoic acids), and microalgae (dinosterol and botryococcenes). For all measured biomarkers, 2H/1H ratios were higher during the Little Ice Age (LIA, late 14th century to early 19th century) relative to the preceding Medieval Climate Anomaly (MCA) and to the 20th century, suggesting drier conditions at this location during the LIA. The magnitude of decrease in 2H/1H ratios was twice as large for microalgal dinosterol ( 40 ‰ decrease) as for leaf waxes associated with higher plants ( 20 ‰ decrease). The leaf wax data likely reflects changes in precipitation isotopes due to the amount effect, while the microalgal values should change with lake water 2H/1H, which is sensitive to both

  17. A Cenozoic record of the equatorial Pacific carbonate compensation depth

    NARCIS (Netherlands)

    Pälike, H.; Lyle, M.W.; Nishi, H.; Raffi, I.; Ridgwell, A.; Gamage, K.; Klaus, A.; Acton, G.; Anderson, L.; Backman, J.; Baldauf, J.; Beltran, C.; Bohaty, S.M.; Bown, P.; Busch, W.; Channell, J.E.T.; Chun, C.O.J.; Delaney, M.; Dewangan, P.; Jones, T.D.; Edgar, K.M.; Evans, H.; Fitch, P.; Foster, G.L.; Gussone, N.; Hasegawa, H.; Hathorne, E.C.; Hayashi, H.; Herrle, J.O.; Holbourn, A.; Hovan, S.; Hyeong, K.; Iijima, K.; Ito, T.; Kamikuri, S.; Kimoto, K.; Kuroda, J.; Leon-Rodriguez, L.; Malinverno, A.; Moore, T.C.; Murphy, B.H.; Murphy, D.P.; Nakamura, H.; Organe, K.; Ohneiser, C.; Richter, C.; Robinson, R.; Rohling, E.J.; Romero, O.; Sawada, K.; Scher, H.; Schneider, L.; Sluijs, A.; Takata, H.; Tian, J.; Tsujimoto, A.; Wade, B.S.; Westerhold, T.; Wilkens, R.; Williams, T.; Wilson, P.A.; Yamamoto, Y.; Yamamoto, S.; Yamazaki, T.; Zeebe, R.E.

    2012-01-01

    Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carboninput fromvolcanicandmetamorphicoutgassingandits removalbyweathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The

  18. Comparison of multifrequency equatorial scintillation - American and Pacific sectors

    Science.gov (United States)

    Livingston, R. C.

    1980-08-01

    In this paper we examine the severity of radio wave amplitude scintillation measured at two stations near the equator but far separated in longitude: Kwajelein, Marshall Islands (167 E), and Ancon, Peru (-77 E). The data used are long-term observations of the Defense Nuclear Agency (DNA) Wideband satellite signal intensity at VHF, UHF, and L band frequencies. The seasonal behavior of the scintillation at the two stations is similar; each shows a broad 8- to 9-month disturbed season centered about local summer. There is short-term variability in the scintillation occurrence statistics but no clear equinoctial maxima. Little difference is observed in the occurrence or severity of L band scintillation at the two stations, although a systematic difference in the frequency dependence of the scintillation produces significantly stronger VHF and UHF scintillation at Ancon. The VHF and UHF latitudinal distributions of scintillation are asymmetric about the geomagnetic equator at both stations.

  19. A Cenozoic record of the equatorial Pacific carbonate compensation depth

    Digital Repository Service at National Institute of Oceanography (India)

    Palike, H.; Lyle, M.W.; Nishi, H.; Raffi, I.; Ridgwell, A.; Gamage, K.; Klaus, A.; Acton, G.; Anderson, L.; Backman, J.; Baldauf, J.; Beltran, C.; Bohaty, S.M.; Bown, P.; Busch, W.; Channell, J.E.T.; Chun, C.O.J.; Delaney, M.; Dewangan, P.; et al.

    A. Wilson 1, Yuhji Yamamoto 49, Shinya Yamamoto 50, Toshitsugu Yamazaki 51 & Richard E. Zeebe 52       1 Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, SO... revision 7491). Scenarios were investigated as open system runs and with enabled climate feedback (temperature responsive to greenhouse gas forcing) until steady state conditions were achieved (~150 kyr). Ensembles were run on the Southampton high...

  20. Probability Distribution Function of the Upper Equatorial Pacific Current Speeds

    National Research Council Canada - National Science Library

    Chu, Peter C

    2005-01-01

    ...), constructed from hourly ADCP data (1990-2007) at six stations for the Tropical Atmosphere Ocean project satisfies the two-parameter Weibull distribution reasonably well with different characteristics between El Nino and La Nina events...

  1. Aerosol Transport Over Equatorial Africa

    Science.gov (United States)

    Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

    1999-01-01

    Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El

  2. Millennial Variability of Eastern Equatorial Bottom Water Oxygenation and Atmospheric CO2 over the past 100 kyr

    Science.gov (United States)

    Marcantonio, F.; Loveley, M.; Wisler, M.; Hostak, R.; Hertzberg, J. E.; Schmidt, M. W.; Lyle, M. W.

    2017-12-01

    Storage of respired carbon in the deep ocean may play a significant role in lowering atmospheric CO2 concentrations by about 80 ppm during the last glacial maximum compared to pre-industrial times. The cause of this sequestration and the subsequent release of the deep respired carbon pool at the last termination remains elusive. Within the last glacial period, on millennial timescales, the relationship between the CO2 cycle and any waxing and waning of a deep respired pool also remains unclear. To further our understanding of the millennial variability in the storage of a deep-ocean respired carbon pool during the last glacial, we measure authigenic uranium and 230Th-derived non-lithogenic barium fluxes (xsBa flux) in two high-sedimentation-rate cores from the Panama Basin of the Eastern Equatorial Pacific (EEP) (8JC, 6° 14.0' N, 86° 02.6' W; 1993 m water depth; 17JC 00° 10.8' S, 85° 52.0' W; 2846 m water depth). Sediment authigenic U concentrations are controlled by the redox state of sediments which, in turn, is a function of the rain of organic material from the surface ocean and the oxygen content of bottom waters. At both 8JC and 17JC, the mismatch between xsBa fluxes, a proxy for the reconstruction of oceanic productivity, and authigenic uranium concentrations suggests that the primary control of the latter values is changes in bottom water oxygenation. Peak authigenic uranium concentrations occur during glacial periods MIS 2, 3, and 4, respectively, and are two to three times higher than those during interglacial periods, MIS 1 and 5. EEP bottom waters were likely suboxic during times of the last glacial period when atmospheric CO2 concentrations were at their lowest concentrations. In addition, the pattern of increased deep-water oxygenation during times of higher CO2 during the last glacial is similar to that reported in a study of authigenic U in sediments from the Antarctic Zone of the Southern Ocean (Jaccard et al., 2016). We suggest that a respired

  3. An aftereffect of global warming on tropical Pacific decadal variability

    Science.gov (United States)

    Zheng, Jian; Liu, Qinyu; Wang, Chuanyang

    2018-03-01

    Studies have shown that global warming over the past six decades can weaken the tropical Pacific Walker circulation and maintain the positive phase of the Interdecadal Pacific Oscillation (IPO). Based on observations and model simulations, another aftereffect of global warming on IPO is found. After removing linear trends (global warming signals) from observations, however, the tropical Pacific climate still exhibited some obvious differences between two IPO negative phases. The boreal winter (DJF) equatorial central-eastern Pacific sea surface temperature (SST) was colder during the 1999-2014 period (P2) than that during 1961-1976 (P1). This difference may have been a result of global warming nonlinear modulation of precipitation; i.e., in the climatological rainy region, the core area of the tropical Indo-western Pacific warm pool receives more precipitation through the "wet-get-wetter" mechanism. Positive precipitation anomalies in the warm pool during P2 are much stronger than those during P1, even after subtracting the linear trend. Corresponding to the differences of precipitation, the Pacific Walker circulation is stronger in P2 than in P1. Consequent easterly winds over the equatorial Pacific led to a colder equatorial eastern-central Pacific during P2. Therefore, tropical Pacific climate differences between the two negative IPO phases are aftereffects of global warming. These aftereffects are supported by the results of coupled climate model experiments, with and without global warming.

  4. Pu isotopes in the western North Pacific Ocean before the accident at Fukushima Dai-ichi Nuclear Power Station

    Science.gov (United States)

    Yamada, M.; Zheng, J.; Aono, T.

    2011-12-01

    Anthropogenic radionuclides such as Pu-239 (half-life: 24100 yr), Pu-240 (half-life: 6560 yr) and Pu-241 (half-life: 14.325 yr) mainly have been released into the environment as the result of atmospheric nuclear weapons testing. In the North Pacific Ocean, two distinct sources of Pu isotopes can be identified; i.e., the global stratospheric fallout and close-in tropospheric fallout from nuclear weapons testing at the Pacific Proving Grounds in the Marshall Islands. The atom ratio of Pu-240/Pu-239 is a powerful fingerprint to identify the sources of Pu in the ocean. The Pu-240/Pu-239 atom ratios in seawater and marine sediment samples collected in the western North Pacific before the accident at Fukushima Dai-ichi Nuclear Power Station will provide useful background data for understanding the process controlling Pu transport and for distinguishing future Pu sources. The atom ratios of Pu-240/Pu-239 in water columns from the Yamato and Tsushima Basins in the Japan Sea were significantly higher than the mean global fallout ratio of 0.18; however, there were no temporal variation of atom ratios during the period from 1984 to 1993 in the Japan Sea. The total Pu-239+240 inventories in the whole water columns were approximately doubled during the period from 1984 to 1993 in the two basins. The atom ratio of Pu-240/Pu-239 in surface water from Sagami Bay, western North Pacific Ocean, was 0.224 and showed no notable variation from the surface to the bottom with the mean atom ratio being 0.234. The atom ratios for the Pacific coast, near the Rokkasho nuclear fuel reprocessing plant, were approximately the same as the 0.224 ratio obtained from Sagami Bay, western North Pacific margin. The atom ratios in the surficial sediments from Sagami Bay ranged from 0.229 to 0.247. The mean atom ratio in the sediment columns in the East China Sea ranged from 0.248 for the Changjiang estuary to 0.268 for the shelf edge. The observed atom ratios were significantly higher than the mean

  5. WATER TEMPERATURE and other data from AIRCRAFT, NOAA Ship DISCOVERER and NOAA Ship OCEANOGRAPHER in the TOGA Area - Pacific from 1981-07-01 to 1989-04-19 (NODC Accession 9300179)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The water depth and temperature data were collected in TOGA Area - Pacific (30 N to 30 S) as part of Equatorial Pacific Ocean Climate Studies from NOAA Ship...

  6. SEDIMENT PROPERTIES and Other Data from FIXED PLATFORM and Other Platforms From North Pacific Ocean from 19881030 to 19911024 (NODC Accession 9300040)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The accession contains data collected in North Pacific Ocean from Hawaiian Ocean Time Series (HOTS) project for years 1, 2 and 3 as part of Joint Global Ocean Flux...

  7. Quantum cloning machines for equatorial qubits

    International Nuclear Information System (INIS)

    Fan Heng; Matsumoto, Keiji; Wang Xiangbin; Wadati, Miki

    2002-01-01

    Quantum cloning machines for equatorial qubits are studied. For the case of a one to two phase-covariant quantum cloning machine, we present the networks consisting of quantum gates to realize the quantum cloning transformations. The copied equatorial qubits are shown to be separable by using Peres-Horodecki criterion. The optimal one to M phase-covariant quantum cloning transformations are given

  8. Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge

    OpenAIRE

    Chang, C.-P.; Zhang, Yongsheng; Li, Tim

    2000-01-01

    The interannual relationship between the East Asian summer monsoon and the tropical Pacific SSTs is studied using rainfall data in the Yangtze River Valley and the NCEP reanalysis for 1951–96. The datasets are also partitioned into two periods, 1951–77 and 1978–96, to study the interdecadal variations of this relationship. A wet summer monsoon is preceded by a warm equatorial eastern Pacific in the previous winter and followed by a cold equatorial eastern Pacific in the following fa...

  9. EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS

    International Nuclear Information System (INIS)

    Showman, Adam P.; Polvani, Lorenzo M.

    2011-01-01

    The increasing richness of exoplanet observations has motivated a variety of three-dimensional (3D) atmospheric circulation models of these planets. Under strongly irradiated conditions, models of tidally locked, short-period planets (both hot Jupiters and terrestrial planets) tend to exhibit a circulation dominated by a fast eastward, or 'superrotating', jet stream at the equator. When the radiative and advection timescales are comparable, this phenomenon can cause the hottest regions to be displaced eastward from the substellar point by tens of degrees longitude. Such an offset has been subsequently observed on HD 189733b, supporting the possibility of equatorial jets on short-period exoplanets. Despite its relevance, however, the dynamical mechanisms responsible for generating the equatorial superrotation in such models have not been identified. Here, we show that the equatorial jet results from the interaction of the mean flow with standing Rossby waves induced by the day-night thermal forcing. The strong longitudinal variations in radiative heating-namely intense dayside heating and nightside cooling-trigger the formation of standing, planetary-scale equatorial Rossby and Kelvin waves. The Rossby waves develop phase tilts that pump eastward momentum from high latitudes to the equator, thereby inducing equatorial superrotation. We present an analytic theory demonstrating this mechanism and explore its properties in a hierarchy of one-layer (shallow-water) calculations and fully 3D models. The wave-mean-flow interaction produces an equatorial jet whose latitudinal width is comparable to that of the Rossby waves, namely the equatorial Rossby deformation radius modified by radiative and frictional effects. For conditions typical of synchronously rotating hot Jupiters, this length is comparable to a planetary radius, explaining the broad scale of the equatorial jet obtained in most hot-Jupiter models. Our theory illuminates the dependence of the equatorial jet

  10. Reduced diversity and high sponge abundance on a sedimented Indo-Pacific reef system: implications for future changes in environmental quality.

    Directory of Open Access Journals (Sweden)

    Abigail Powell

    Full Text Available Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning.

  11. Reduced Diversity and High Sponge Abundance on a Sedimented Indo-Pacific Reef System: Implications for Future Changes in Environmental Quality

    Science.gov (United States)

    Powell, Abigail; Smith, David J.; Hepburn, Leanne J.; Jones, Timothy; Berman, Jade; Jompa, Jamaluddin; Bell, James J.

    2014-01-01

    Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded) and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning. PMID:24475041

  12. Geochemistry of sediment cores of the western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, P.S.N.; Cronan, D.S.; Rao, Ch.M.; Paropkari, A.L.; Topgi, R.S.; Guptha, M.V.S.; Colley, N.

    the Somali Basin, and that among the Somali Basin cores depth appears to influence the variable distributions of metals in them. Iron, aluminium and titanium appear to be mainly supplied from terrigenous sources, manganese from authigenic sources...

  13. Photoelectric panel with equatorial mounting of drive

    Science.gov (United States)

    Kukhta, M. S.; Krauinsh, P. Y.; Krauinsh, D. P.; Sokolov, A. P.; Mainy, S. B.

    2018-03-01

    The relevance of the work is determined by the need to create effective models for sunny energy. The article considers a photoelectric panel equipped with a system for tracking the sun. Efficiency of the system is provided by equatorial mounting, which compensates for the rotation of the Earth by rotating the sunny panel in the plane of the celestial equator. The specificity of climatic and geographical conditions of Tomsk is estimated. The dynamics of power variations of photoelectric panels with equatorial mounting during seasonal fluctuations in Tomsk is calculated. A mobile photovoltaic panel with equatorial mounting of the drive has been developed. The methods of design strategy for placing photovoltaic panels in the architectural environment of the city are presented. Key words: sunny energy, photovoltaics, equatorial mounting, mechatronic model, wave reducer, electric drive.

  14. Geochemistry of trace metals in shelf sediments affected by seasonal and permanent low oxygen conditions off central Chile, SE Pacific (˜36°S)

    Science.gov (United States)

    Muñoz, Praxedes; Dezileau, Laurent; Cardenas, Lissette; Sellanes, Javier; Lange, Carina B.; Inostroza, Jorge; Muratli, Jesse; Salamanca, Marco A.

    2012-02-01

    Trace metals (Cd, U, Co, Ni, Cu, Ba, Fe, Mn), total organic carbon (TOC) and C and N stable isotope signatures (δ 13C and δ 15N) were determined in short sediments cores from the inner and outer shelf off Concepción, Chile (˜36°S). The objectives were to establish the effect of environmental conditions on trace metal distributions at two shelf sites, one affected by seasonal oxygenation and the other by permanent low oxygen conditions due to the presence of the oxygen minimum zone (OMZ). We evaluate trace metals as proxies of past changes in primary productivity and the bottom water oxygen regime. Concentrations of pore water sulfides and NH4+ were also measured as indicators of the main diagenetic pathways at each site. Our results for the inner shelf (seasonal suboxia) suggest that the oxidative state of the sediments responds to seasonal pulses of organic matter and that seasonal oxygenation develops during high and low primary productivity in the water column. Here, positive fluxes (to the water column) estimated from pore water concentrations of several elements were observed (Ba, Co, Ni, Fe and Mn). The less reduced environment at this site produces authigenic enrichment of Cu associated with the formation of oxides in the oxic surface sediment layer, and the reduction of U within deeper sediment sections occur consistently with negative estimated pore water fluxes. In the outer shelf sediments (permanent suboxia, OMZ site), negative fluxes (to the sediment) were estimated for all elements, but these sediments showed authigenic enrichments only for Cd, Cu and U. The short oxygenation period during the winter season did not affect the accumulation of these metals on the shelf. The distribution of Cu, Cd and U have been preserved within the sediments and the authigenic accumulation rates estimated showed a decrease from the deep sections of the core to the surface sediments. This could be explained by a gradual decrease in the strength of the OMZ in the

  15. Magnitudes and sources of precipitation and dry deposition fluxes of industrial and natural leads to the North Pacific at Enewetak

    International Nuclear Information System (INIS)

    Settle, D.M.; Patterson, C.C.

    1982-01-01

    A total atmospheric PB input flux of 7 ng Pb cm - 2 yr - 1 was measured in the North Pacific Easterlies at Enewetak. Parameters used to measure this flux were ratio of dry deposition flux to precipitation flux; Pb/ 210 Pb in precipitation and seawater; 210 Pb flux; washout factor; and Pb concentrations in air, rain, and dry deposition deposits. Relations among these parameters estabilished at Enewetak were used to recompute and comfirm previous estimates of lead fluxes to the oceans (ng Pb cm - 2 yr - 1 ) at the following locations: North Altantic Westerlies, 170; North Pacific Westerlies, 50; and South Pacific Easterlies, 3. Prehistoric lead output fluxes to sediments (ng Pb cm - 2 yr - 1 ) at these locations have been previously measured and were 4 (Enewetak); 30 North Atlantic Westerlies; 3 North Pacific Westerlies; 4 South Pacific Easterlies. These data show that the rates of atmospheric imputs of lead to the oceans vary directly with variations in rates of upwind emission of industrial lead from urban complexes on land. In the North Pacific and North Atlantic, present rates of atmospheric lead inputs are 10-fold greater than prehistoric outputs. In equatorial regions, present inputs and past outputs are more nearly equal. These observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans. The average concentration of lead in marine air at Enewetak is 170n pg m - 3 and varies less than a factor of 2 from that mean. One to 15% of this lead comes from seaspray, while the remainder comes from sources on land. About 90% of the seaspray lead is industrial, while 80 to 99% of that originating from land sources is industrial. Concentrations of lead in rain at Enewetak range from 6 to 63 pg/g with a mean value of 28

  16. Tropical Pacific Climate, Carbon, and Ocean Biogeochemical Response to the Central American Seaway in a GFDL Earth System Model

    Science.gov (United States)

    Sentman, L. T.; Dunne, J. P.; Stouffer, R. J.; Krasting, J. P.; Wittenberg, A. T.; Toggweiler, J. R.; Broccoli, A. J.

    2017-12-01

    To explore the tropical Pacific climate, carbon, and ocean biogeochemical response to the shoaling and closure of the Central American Seaway during the Pliocene (5.3-2.6 Ma), we performed a suite of sensitivity experiments using the Geophysical Fluid Dynamics Laboratory Earth System Model, GFDL-ESM2G, varying only the seaway widths and sill depths. These novel ESM simulations include near-final closure of the seaway with a very narrow, 1º grid cell wide opening. Net mass transport through the seaway into the Caribbean is 20.5-23.1 Sv with a deep seaway, but only 14.1 Sv for the wide/shallow seaway because of the inter-basin bi-directional horizontal mass transport. Seaway transport originates from the Antarctic Circumpolar Current in the Pacific and rejoins it in the South Atlantic, reducing the Indonesian Throughflow and transporting heat and salt southward into the South Atlantic, in contrast to present-day and previous seaway simulations. Tropical Pacific mean climate and interannual variability is sensitive to the seaway shoaling, with the largest response to the wider/deeper seaway. In the tropical Pacific, the top 300-m warms 0.4-0.8°C, the equatorial east-west sea surface temperature gradient increases, the north-south sea surface temperature asymmetry at 110°W decreases, thermocline deepens 5-11 m, and the east-west thermocline gradient increases. In the Niño-3 region, ENSO amplitude increases, skewed toward more cold (La Niña) events, El Niño and La Niña develops earlier ( 3 months), the annual cycle weakens and the semi-annual and interannual cycles strengthen from increased symmetry of the north-south sea surface temperature gradient, and atmospheric global teleconnections strengthen with the seaway. The increase in global ocean overturning with the seaway results in a younger average ocean ideal age, reduced dissolved inorganic carbon inventory and marine net primary productivity, and altered inter-basin patterns of surface sediment carbonate

  17. Plutonium activities and 240Pu/ 239Pu atom ratios in sediment cores from the east China sea and Okinawa Trough: Sources and inventories

    Science.gov (United States)

    Wang, Zhong-liang; Yamada, Masatoshi

    2005-05-01

    Plutonium concentrations and 240Pu/ 239Pu atom ratios in the East China Sea and Okinawa Trough sediment cores were determined by isotope dilution inductively coupled plasma mass spectrometry after separation using ion-exchange chromatography. The results showed that 240Pu/ 239Pu atom ratios in the East China Sea and Okinawa Trough sediments, ranging from 0.21 to 0.33, were much higher than the reported value of global fallout (0.18). The highest 240Pu/ 239Pu ratios (0.32-0.33) were observed in the deepest Okinawa Trough sediment samples. These ratios suggested the US nuclear weapons tests in the early 1950s at the Pacific Proving Grounds in the Marshall Islands were a major source of plutonium in the East China Sea and Okinawa Trough sediments, in addition to the global fallout source. It was proposed that close-in fallout plutonium was delivered from the Pacific Proving Grounds test sites via early direct tropospheric fallout and transportation by the North Pacific Equatorial Circulation system and Kuroshio Current into the Okinawa Trough and East China Sea. The total 239 + 240 Pu inventories in the cores were about 150-200% of that expected from direct global fallout; about 46-67% of the total inventories were delivered from the Pacific Proving Grounds. Much higher 239 + 240 Pu inventories were observed in the East China Sea sediments than in sediments of the Okinawa Trough, because in the open oceans, part of the 239 + 240 Pu was still retained in the water column, and continued Pu scavenging was higher over the margin than the trough. According to the vertical distributions of 239 + 240 Pu activities and 240Pu/ 239Pu atom ratios in these cores, it was concluded that sediment mixing was the dominant process in controlling profiles of plutonium in this area. Faster mixing in the coastal samples has homogenized the entire 240Pu/ 239Pu ratio record today; slightly slower mixing and less scavenging in the Okinawa Trough have left the surface sediment ratios closer

  18. Penetration of tritium into the Tropical Pacific

    International Nuclear Information System (INIS)

    Fine, R.A.; Peterson, W.H.; Ostlund, H.G.

    1987-01-01

    The persistence of subsurface tritium maxima coincident with the Equatorial Currents is used to show that advection along isopycnals by the mean wind-driven circulation is the dominant process in the at most 14-year time scale for the penetration of high northern latitude water to the equator (above 26.2 sigma-theta). Ventilation of the equatorial Pacific thermocline from the north contrasts sharply with the equatorial Atlantic thermocline which is ventilated from the south. The most striking manifestation of the North Pacific circulation is evidenced by a tritium maximum and salinity minimum at the equator between 145 0 and 125 0 W located above 25.6 sigma-theta. It shows that regardless of time of sampling the easter/central equator has received the highest latitude water, probably as a consequence of recirculation by the Equatorial Currents. Between the same meridians there is a tritium maximum on and north of the equator at the surface, which is interpreted as an expression of upwelling. Its coincidence with the cool tongue (Wyrtki) provides direct evidence that the upwelling process plays a dominant role in its maintenance on a decadal time scale

  19. Bacterial Activity and Their Physiological Characteristics in the Sediments of O DP Holes 1202A and 1202D, Okinawa Trough, Western Pacific

    Directory of Open Access Journals (Sweden)

    Jiin-Shuh Jean

    2005-01-01

    Full Text Available Bacterial strains were isolated and identified from the down-core sediments of Site 1202 of ODP Leg 195 in the Okinawa Trough. Their phylogenetic relationships and physiological characteristics were determined. The isolates were cultured in aerobic and anaerobic sulfate-reducing and fermentative media at temperatures of _ and _ The results showed that there were gram-positive/negative rod- and/or sphere-shaped bacteria in the sediments at all depths from 3 to 358.3 meters below the seafloor (mbsf, but no bacteria were present at depths greater than 358.3 mbsf (> 64.73 ka in age of sediment were isolated (maximum core depth 406.5 mbsf. On the basis of the nucleotide similarities of 16S rDNA and reconstructed phylogeny, the bacterial isolates of the sediments of 10.1 mbsf (1202A002H and 241.2 mbsf (1202D027X were shown to share high identities with the Bacillus subtilis and Pseudomonas putida or _ MPD-98 strains. Physiological experiments showed that the optimal temperature for growth of the studied bacteria was _ but the bacteria obtained at some depths could tolerate temperatures up to _ The maximum salinity allowed for the growth of the cultured bacteria was 60 _ 650/00. The optimal pH for bacterial growth was 7.0 - 8.3. None of the bacteria extracted from the studied sediments could survive at pH _ or _ These halotolerant bacteria were capable of making consumption of Fe, Cu2+ , Na+, K+, Mg2+ , Ca2+, and F−, but no biogenic minerals could be identified in the present study.

  20. Studies on the concentrations of iron-55 in South Pacific Ocean water and marine organisms and in the Columbia River. Progress report, 1 April 1975--31 March 1976

    International Nuclear Information System (INIS)

    Jennings, C.D.

    1976-01-01

    Progress is reported on studies of the distribution of iron-55 in the marine environment. Direct measurements of iron-55 in seawater and in zooplankton showed that marine organisms concentrate iron-55 in preference to stable iron. Measurements of iron-55 in Pacific sediments gave us an indication of the amount of iron-55 getting through the water column. Measurements in organisms from different depths in the ocean and the measurements in sediments give us a clearer picture of the rate of vertical transport in the ocean. It is also quite clear that the iron-55 in sediments in the equatorial Pacific are concentrated in a very thin surface layer because samples more than a centimeter below the surface were below detectable limits, whereas most surface samples had detectable amounts of iron-55. A series of treatments of Columbia River sediments with hydrochloric acid of strengths 0.1 M, 0.25 M, 1.4 M, 6 M and boiling 6 M respectively, showed that decreasing specific activity results in each subsequent treatment, indicating that the iron-55 can be leached more easily than stable iron. This observation provides some clues to what may be happening to particles in seawater. Organisms may remove from particles the more easily removable iron-55 of higher specific activity, leaving behind particles with a lower specific activity

  1. Spatial distribution of organochlorine contaminants in soil, sediment, and fish in Bikini and Enewetak Atolls of the Marshall Islands, Pacific Ocean.

    Science.gov (United States)

    Wang, Jun; Caccamise, Sarah A L; Wu, Liejun; Woodward, Lee Ann; Li, Qing X

    2011-08-01

    Several nuclear tests were performed at Enewetak and Bikini Atolls in the Marshall Islands between 1946 and 1958. The events at Bikini Atoll involved several ships that were tested for durability during nuclear explosions, and 24 vessels now rest on the bottom of the Bikini lagoon. Nine soil samples were collected from different areas on the two islands of the atoll, and eighteen sediment, nine fish, and one lobster were collected in the vicinity of the sunken ships. Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polychlorinated terphenyls (PCTs) in these samples were analyzed using gas chromatography/ion trap mass spectrometry (GC/ITMS). The average recoveries ranged from 78% to 104% for the different PCB congeners. The limits of detection (LOD) for PCBs, PCTs, DDE, DDT, and dieldrin ranged 10-50 pg g(-1). Some fish from Enewetak contained PCBs at a concentration range of 37-137 ng g(-1), dry weight (dw), and most of the soils from Enewetak showed evidence of PCBs (22-392 ng g(-1)dw). Most of the Bikini lagoon sediment samples contained PCBs, and the highest was the one collected from around the Saratoga, an aircraft carrier (1555 ng g(-1)dw). Some of the fish samples, most of the soil samples, and only one of the sediment samples contained 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) and PCBs. In addition to PCBs, the soils from Enewetak Atoll contained PCTs. PCTs were not detected in the sediment samples from Bikini Atoll. The results suggest local pollution sources of PCBs, PCTs, and OCPs. Copyright © 2011. Published by Elsevier Ltd.

  2. Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine.

    Science.gov (United States)

    Marmolejo-Rodríguez, Ana Judith; Prego, Ricardo; Meyer-Willerer, Alejandro; Shumilin, Evgueni; Cobelo-García, Antonio

    2007-01-01

    Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Peña Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities.

  3. The oil boom in Equatorial Guinea

    International Nuclear Information System (INIS)

    Frynas, J.G.

    2004-01-01

    In less than a decade, Equatorial Guinea has transformed itself from an African backwater into one of the world's fastest growing economies and a sought-after political partner in the Gulf of Guinea. The sole reason for this transformation has been the discovery of oil and gas. This article outlines the rise of Equatorial Guinea as one of Africa's leading oil-producing countries and investigates the political, economic and social effects of becoming a petro-state. The article is based on the author's field research in Equatorial Guinea in the autumn of 2003 and interviews with senior oil company staff, government officials and staff of international organizations as well as secondary sources. This research demonstrates how reliance on oil and gas exports can lead to profound changes in a country's political economy. (author)

  4. Paleoclimate of Quaternary Costa Rica: Analysis of Sediment from ODP Site 1242 in the Eastern Tropical Pacific to Explore the Behavior of the Intertropical Convergence Zone (ITCZ) and Oceanic Circulation

    Science.gov (United States)

    Buczek, C. R.; Joseph, L. H.

    2017-12-01

    Studies of grain size, magnetic fabric, and terrigenous mass accumulation rates (MAR) on oceanic sediment can provide insights into climatic conditions present at or near the time of deposition by helping to delineate changes in rainfall and oceanic circulation intensities. The fairly homogenous hemipelagic nannofossil clays and clayey nannofossil oozes collected in the upper portion of Ocean Drilling Program (ODP) Site 1242 provide a 1.4 million year sediment record from the Cocos Ridge, in relatively shallow waters of the eastern tropical Pacific Ocean, off the coast of present day Central and South America. Information about shifts in rainfall and oceanic circulation provided by this study may be helpful in understanding changes in the location and behavior of the Intertropical Convergence Zone (ITCZ), and/or other climatic factors, in this area during the Pleistocene and Holocene Epochs. Approximately 130 paired side-by-side samples were selected at approximately evenly spaced intervals throughout the uppermost 190 mcd of the core. To obtain terrigenous grain size and MARs, one set of sediment samples was subject to a five-step chemical extraction process to dissolve any oxy-hydroxy coatings, remove the biogenic carbonate and silicate components, and sieve out grains larger than 63 µm. The pre- and post-extraction weights were compared to calculate a terrigenous weight percent (%) from which the terrigenous MAR values were then calculated, with the use of linear sediment rates and dry bulk density measurements determined from shipboard ODP 1242 analyses. Magnetic fabric, or anisotropy of magnetic susceptibility (AMS), was analyzed on a KLY4S-Kappabridge using the second set of samples taken in pmag cubes. Terrigenous MAR values range between 3.1 and 10.9 g/cm2/kyr, while P' (AMS) values range between 1.004 and 1.04 SI. A distinctive trend is noted in both factors, with both exhibiting relatively high initial values that then decrease from the beginning of the

  5. Isotopic composition and distribution of plutonium in northern South China Sea sediments revealed continuous release and transport of Pu from the Marshall Islands.

    Science.gov (United States)

    Wu, Junwen; Zheng, Jian; Dai, Minhan; Huh, Chih-An; Chen, Weifang; Tagami, Keiko; Uchida, Shigeo

    2014-03-18

    The (239+240)Pu activities and (240)Pu/(239)Pu atom ratios in sediments of the northern South China Sea and its adjacent Pearl River Estuary were determined to examine the spatial and temporal variations of Pu inputs. We clarified that Pu in the study area is sourced from a combination of global fallout and close-in fallout from the Pacific Proving Grounds in the Marshall Islands where above-ground nuclear weapons testing was carried out during the period of 1952-1958. The latter source dominated the Pu input in the 1950s, as evidenced by elevated (240)Pu/(239)Pu atom ratios (>0.30) in a dated sediment core. Even after the 1950s, the Pacific Proving Grounds was still a dominant Pu source due to continuous transport of remobilized Pu from the Marshall Islands, about 4500 km away, along the North Equatorial Current followed by the transport of the Kuroshio current and its extension into the South China Sea through the Luzon Strait. Using a simple two end-member mixing model, we have quantified the contributions of Pu from the Pacific Proving Grounds to the northern South China Sea shelf and the Pearl River Estuary are 68% ± 1% and 30% ± 5%, respectively. This study also confirmed that there were no clear signals of Pu from the Fukushima Daiichi Nuclear Power Plant accident impacting the South China Sea.

  6. Equatorial waves in the stratosphere of Uranus

    Science.gov (United States)

    Hinson, David P.; Magalhaes, Julio A.

    1991-01-01

    Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

  7. The evolution of the equatorial thermocline and the early Pliocene El Padre mean state

    Science.gov (United States)

    Ford, Heather L.; Ravelo, A. Christina; Dekens, Petra S.; LaRiviere, Jonathan P.; Wara, Michael W.

    2015-06-01

    The tropical Pacific thermocline strength, depth, and tilt are critical to tropical mean state and variability. During the early Pliocene (~3.5 to 4.5 Ma), the Eastern Equatorial Pacific (EEP) thermocline was deeper and the cold tongue was warmer than today, which resulted in a mean state with a reduced zonal sea surface temperature gradient or El Padre. However, it is unclear whether the deep thermocline was a local feature of the EEP or a basin-wide condition with global implications. Our measurements of Mg/Ca of Globorotalia tumida in a western equatorial Pacific site indicate Pliocene subsurface temperatures warmer than today; thus, El Padre included a basin-wide thermocline that was relatively warm, deep, and weakly tilted. At ~4 Ma, thermocline steepening was coupled to cooling of the cold tongue. Since ~4 Ma, the basin-wide thermocline cooled/shoaled gradually, with implications for thermocline feedbacks in tropical dynamics and the interpretation of TEX86-derived temperatures.

  8. Estimation of sediment properties during benthic impact experiments

    Digital Repository Service at National Institute of Oceanography (India)

    Yamazaki, T.; Sharma, R

    Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans...

  9. Seasonal-longitudinal variability of equatorial plasma bubbles

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2004-09-01

    Full Text Available We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons.

    We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1 in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2 unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3 While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2 and (3 indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from

  10. Assessing millennial-scale variability during the Holocene: A perspective from the western tropical Pacific

    Science.gov (United States)

    Khider, D.; Jackson, C. S.; Stott, L. D.

    2014-03-01

    We investigate the relationship between tropical Pacific and Southern Ocean variability during the Holocene using the stable oxygen isotope and magnesium/calcium records of cooccurring planktonic and benthic foraminifera from a marine sediment core collected in the western equatorial Pacific. The planktonic record exhibits millennial-scale sea surface temperature (SST) oscillations over the Holocene of 0.5°C while the benthic δ18Oc document 0.10‰ millennial-scale changes of Upper Circumpolar Deep Water (UCDW), a water mass which outcrops in the Southern Ocean. Solar forcing as an explanation for millennial-scale SST variability requires (1) a large climate sensitivity and (2) a long 400 year delayed response, suggesting that if solar forcing is the cause of the variability, it would need to be considerably amplified by processes within the climate system at least at the core location. We also explore the possibility that SST variability arose from volcanic forcing using a simple red noise model. Our best estimates of volcanic forcing falls short of reproducing the amplitude of observed SST variations although it produces power at low-frequency similar to that observed in the MD81 record. Although we cannot totally discount the volcanic and solar forcing hypotheses, we are left to consider that the most plausible source for Holocene millennial-scale variability lies within the climate system itself. In particular, UCDW variability coincided with deep North Atlantic changes, indicating a role for the deep ocean in Holocene millennial-scale variability.

  11. Cenozoic History of the Equatorial Indian Ocean Recorded by Nd Isotopes: The Closure of the Indonesian Gateway

    Science.gov (United States)

    Gourlan, A. T.; Meynadier, L.; Allegre, C. J.

    2005-12-01

    The northward tectonic motion of the Australian plate and the evolution of the Indonesian Island Arcs through the last 20 Ma, generate changes in the flow and the origin of the circulation between the Pacific and the Southern Indian Oceans. Indeed, the emergence of the Indonesian Archipelago and probably the rapid uplift of the island of Halmahera have dramatically reduced the Indonesian Gateway. However, the precise dating of this event is still a matter of debate. The Neodymium isotopic composition of marine sediments is an extremely good proxy to reconstruct the major changes in the past ocean circulation. The residence time of Nd is shorter than the circulation time of the global ocean. Therefore, the Nd isotopic composition varies between the different ocean basins and is function of changes in source provenances, paleocirculation, orogenic processes, and intensity of weathering on the continents as well as on the volcanic arcs. To reconstruct the evolution of the oceanic flow from the Pacific to the equatorial Indian Ocean since the Miocene, we have applied on high carbonates content sediments a leaching technique using acetic acid. The reliability of our technique has been assessed by comparison with the Hydroxylamine hydrochloride technique developed by Bayon et al (1). The Nd isotopic composition is determinated in the past seawater from the record in Fe-Mn oxides. The sedimentary sequences are accurately dated using bio and chimiostratigraphy. Three ODP Sites were chosen in the Indian Ocean with a water depth ranging from 1600 to 2800 m and mutually distant by about 3000 km. From West to East: Site 761 which is at the western edge of the Indonesian Gateway on the central northeastern part of the Wombat Plateau off NW Australia, Site 757 is located on the south of the Ninetyeast ridge and Site 707 is located in the western tropical Indian Ocean near the Seychelles Islands. Our data are compared with the first results from Site 807 located in the Pacific

  12. Changes in equatorial zonal circulations and precipitation in the context of the global warming and natural modes

    Science.gov (United States)

    Kim, B. H.; Ha, K. J.

    2017-12-01

    The strengthening and westward shift of Pacific Walker Circulation (PWC) is observed during the recent decades. However, the relative roles of global warming and natural variability on the change in PWC unclearly remain. By conducting numerical atmospheric general circulation model (AGCM) experiments using the spatial SST patterns in the global warming and natural modes which are obtained by the multi-variate EOF analysis from three variables including precipitation, sea surface temperature (SST), and divergent zonal wind, we indicated that the westward shift and strengthening of PWC are caused by the global warming SST pattern in the global warming mode and the negative Interdecadal Pacific Oscillation-like SST pattern in the natural mode. The SST distribution of the Pacific Ocean (PO) has more influence on the changes in equatorial zonal circulations and tropical precipitation than that of the Indian Ocean (IO) and Atlantic Ocean (AO). The change in precipitation is also related to the equatorial zonal circulations variation through the upward and downward motions of the circulations. The IO and AO SST anomalies in the global warming mode can affect on the changes in equatorial zonal circulations, but the influence of PO SST disturbs the Indian Walker circulation and Atlantic Walker circulation changes by the IO and AO. The zonal shift of PWC is found to be highly associated with a zonal gradient of SST over the PO through the idealized numerical AGCM experiments and predictions of CMIP5 models.

  13. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

    Kinkel, Hanno; Baumann, K.-H.; Cepek, M.

    2000-01-01

    with each other. In general, the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns. Cell densities reached a maximum of up to 300 x 10 coccospheres/l in the upwelling area of the equatorial Atlantic. Here, Emiliania huxleyi...

  14. Radioisotope mobility across the sediment/water interface in the deep sea

    International Nuclear Information System (INIS)

    ten Brink, M.R.B.

    1987-01-01

    The removal of radiotracers from water to sediments and their partitioning between phases were used to study the rates and mechanisms of transfer for trace elements across the sediment/water interface in the deep sea. The in situ mobility of 22 Na, 134 Cs, 133 Ba, 65 Zn, 125 Sb, 7 Be, 203 Hg, 54 Mn, 60 Co, 59 Fe, 113 Gd, and 141 Ce was measured using MANOP Lander benthic chambers in the N. equatorial Pacific and in San Clemente Basin. The contributions to mobility of diffusion, bioturbation, advection of pore waters, and transport across the diffusive boundary layer was assessed. The penetration of particle reactive tracers in the upper cm suggested a mixing rate of ≤10 -7 cm 2 /s at Sites C and S and ≤10 -5 cm 2 /s at Sites M and H. Greater penetration could be correlated with worm tubes but no evidence of irrigation was found. The presence of nodules did not prevent transport of soluble tracers to the underlying sediment or concentrate tracers. Diffusion was the predominant mode of transport for radiotracers in the short-term in situ experiments

  15. The Mesozoic-Cenozoic igneous intrusions and related sediment-dominated hydrothermal activities in the South Yellow Sea Basin, the Western Pacific continental margin

    Science.gov (United States)

    Yumao, Pang; Xunhua, Zhang; Guolin, Xiao; Luning, Shang; Xingwei, Guo; Zhenhe, Wen

    2018-04-01

    Various igneous complexes were identified in multi-channel seismic reflection profiles from the South Yellow Sea Basin. It is not rare that magmatic intrusions in sedimentary basins cause strong thermal perturbations and hydrothermal activities. Some intrusion-related hydrothermal vent complexes have been identified and they are considered to originate from the deep sedimentary contact aureole around igneous intrusions and terminate in upper vents structures, and are linked by a vertical conduit system. The upper vent complexes are usually eye-shaped, dome-shaped, fault-related, crater-shaped or pock-shaped in seismic profiles. A schematic model was proposed to illustrate the structures of different types of hydrothermal vent complexes. A conceptual conduit model composed of an upper pipe-like part and a lower branching part was also derived. Hydrothermal vent complexes mainly developed during the Middle-Late Cretaceous, which is coeval with, or shortly after the intrusion. The back-arc basin evolution of the area which is related to the subduction of the Paleo-Pacific plate during the Mesozoic-Cenozoic may be the principal factor for voluminous igneous complexes and vent complexes in this area. It is significant to study the characteristics of igneous complexes and related hydrothermal vent complexes, which will have implications for the future study of this area.

  16. The Pacific Ventilated Thermocline and its Influence on the Pacific Decadal Oscillation and Global Warming

    Science.gov (United States)

    Kuntz, L.; Schrag, D. P.

    2017-12-01

    Over the past century, global surface temperatures have warmed episodically despite relatively steady increases in radiative forcing. Coincident with these transitions, we identify changes in the structure of the ventilated thermocline in the Pacific as well as changes in the intensity of the equatorial undercurrent. We propose a new mechanism for the Pacific Decadal Oscillation that involves oscillations in the strength of the equatorial undercurrent and may explain multi-decadal variability of global temperatures. We suggest that the oscillation results in a greater or lesser volume of cold water reaching the eastern Pacific, which ultimately leads to a change in the heat flux out of this critical region. By varying the heat flux in the tropical Pacific in model simulations, we reproduce a stepwise pattern of warming that resembles the historical climate record without additional variability in forcing. In addition, the trajectory of the changes in thermocline structure that we now observe in the Pacific looks like it will arrive at the equator in the middle of the next decade, suggesting that the current period of reduced warming (aka "hiatus") will persist through the mid-2020s.

  17. Climate variability and predictability associated with the Indo-Pacific Oceanic Channel Dynamics in the CCSM4 Coupled System Model

    Science.gov (United States)

    Yuan, Dongliang; Xu, Peng; Xu, Tengfei

    2017-01-01

    An experiment using the Community Climate System Model (CCSM4), a participant of the Coupled Model Intercomparison Project phase-5 (CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole (IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.

  18. Temperature profile and other data collected using moored buoy in the Pacific Ocean (30-N to 30-S) as part of the International Decade of Ocean Exploration / North Pacific Experiment (IDOE/NORPAX) project from 06 November 1977 to 24 March 1978 (NODC Accession 8200053)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Air pressure, current, wind and temperature time series data were collected from moored buoys from TOGA Area in Pacific (30 N to 30 S). Buoy data from the equatorial...

  19. Climate Variability and Phytoplankton in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, Cecile

    2012-01-01

    The effect of climate variability on phytoplankton communities was assessed for the tropical and sub-tropical Pacific Ocean between 1998 and 2005 using an established biogeochemical assimilation model. The phytoplankton communities exhibited wide range of responses to climate variability, from radical shifts in the Equatorial Pacific, to changes of only a couple of phytoplankton groups in the North Central Pacific, to no significant changes in the South Pacific. In the Equatorial Pacific, climate variability dominated the variability of phytoplankton. Here, nitrate, chlorophyll and all but one of the 4 phytoplankton types (diatoms, cyanobacteria and coccolithophores) were strongly correlated (pphytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Nina events, diatoms increased and expanded westward along the cold tongue (correlation with MEI, r=-0.81), while cyanobacteria concentrations decreased significantly (r=0.78). El Nino produced the reverse pattern, with cyanobacteria populations increasing while diatoms plummeted. The diverse response of phytoplankton in the different major basins of the Pacific suggests the different roles climate variability can play in ocean biology.

  20. Tree rings and rainfall in the equatorial Amazon

    Science.gov (United States)

    Granato-Souza, Daniela; Stahle, David W.; Barbosa, Ana Carolina; Feng, Song; Torbenson, Max C. A.; de Assis Pereira, Gabriel; Schöngart, Jochen; Barbosa, Joao Paulo; Griffin, Daniel

    2018-05-01

    The Amazon basin is a global center of hydroclimatic variability and biodiversity, but there are only eight instrumental rainfall stations with continuous records longer than 80 years in the entire basin, an area nearly the size of the coterminous US. The first long moisture-sensitive tree-ring chronology has been developed in the eastern equatorial Amazon of Brazil based on dendrochronological analysis of Cedrela cross sections cut during sustainable logging operations near the Rio Paru. The Rio Paru chronology dates from 1786 to 2016 and is significantly correlated with instrumental precipitation observations from 1939 to 2016. The strength and spatial scale of the precipitation signal vary during the instrumental period, but the Rio Paru chronology has been used to develop a preliminary reconstruction of February to November rainfall totals from 1786 to 2016. The reconstruction is related to SSTs in the Atlantic and especially the tropical Pacific, similar to the stronger pattern of association computed for the instrumental rainfall data from the eastern Amazon. The tree-ring data estimate extended drought and wet episodes in the mid- to late-nineteenth century, providing a valuable, long-term perspective on the moisture changes expected to emerge over the Amazon in the coming century due to deforestation and anthropogenic climate change.

  1. Sediment studies at Bikini Atoll part 3. Inventories of some long-lived gamma-emitting radionuclides associated with lagoon surface sediments

    Energy Technology Data Exchange (ETDEWEB)

    Noshkin, V.E.

    1997-12-01

    Surface sediment samples were collected during 1979 from 87 locations in the lagoon at Bikini Atoll. The collections were made to better define the concentrations and distribution of long-lived radionuclides associated with the bottom material and to show what modifications occurred to the composition of the surface sediment from the nuclear testing program conducted by the United States at the Atoll between 1946 and 1958. This is the last of three reports on Bikini sediment studies. In this report, we discuss the concentrations and inventories of the residual long-lived gamma-emitting radionuclides in sediments from the lagoon. The gamma-emitting radionuclides detected most frequently in sediments collected in 1979, in addition to Americium-241 ({sup 241}Am) (discussed in the second report of this series), included Cesium-137 ({sup 137}Cs), Bismuth-207 ({sup 207}Bi), Europium-155 ({sup 155}Eu), and Cobalt-60 ({sup 60}Co). Other man-made, gamma-emitting radionuclides such as Europium-152,154 ({sup 152,154}Eu), Antimony-125 ({sup 125}Sb), and Rhodium-101,102m ({sup 101,102m}Rh) were occasionally measured above detection limits in sediments near test site locations. The mean inventories for {sup 137}Cs, {sup 207}Ei, {sup 155}Eu, and {sup 60}Co in the surface 4 cm of the lagoon sediment to be 1.7, 0.56, 7.76, and 0.74 TBq, respectively. By June 1997, radioactive decay would reduce these values to 1.1, 0.38, 0.62, and 0.07 TBq, respectively. Some additional loss results from a combination of different processes that continuously mobilize and return some amount of the radionuclides to the water column. The water and dissolved constituents are removed from the lagoon through channels and exchange with the surface waters of the north equatorial Pacific Ocean. Highest levels of these radionuclides are found in surface deposits lagoonward of the Bravo Crater. Lowest concentrations and inventories are associated with sediment lagoonward of the eastern reef. The quantities in

  2. Snowball Earth termination by destabilization of equatorial permafrost methane clathrate.

    Science.gov (United States)

    Kennedy, Martin; Mrofka, David; von der Borch, Chris

    2008-05-29

    The start of the Ediacaran period is defined by one of the most severe climate change events recorded in Earth history--the recovery from the Marinoan 'snowball' ice age, approximately 635 Myr ago (ref. 1). Marinoan glacial-marine deposits occur at equatorial palaeolatitudes, and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about -5 and +15 parts per thousand, respectively; these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise. This abrupt transition records a climate system in profound disequilibrium and contrasts sharply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating Phanerozoic deglaciation. Hypotheses accounting for the abruptness of deglaciation include ice albedo feedback, deep-ocean out-gassing during post-glacial oceanic overturn or methane hydrate destabilization. Here we report the broadest range of oxygen isotope values yet measured in marine sediments (-25 per thousand to +12 per thousand) in methane seeps in Marinoan deglacial sediments underlying the cap carbonate. This range of values is likely to be the result of mixing between ice-sheet-derived meteoric waters and clathrate-derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater. The equatorial palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day. A pool of this size could have provided a massive biogeochemical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excursions, abrupt unidirectional warming, cap carbonate deposition, and a marine oxygen crisis. Our findings suggest that methane released from low-latitude permafrost clathrates therefore acted as a trigger and/or strong positive feedback for deglaciation and warming. Methane hydrate

  3. Long wavelength irregularities in the equatorial electrojet

    OpenAIRE

    Kudeki, E.; Farley, D. T.; Fejer, Bela G.

    1982-01-01

    We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach...

  4. How Do Tropical Sea Surface Temperatures Influence the Seasonal Distribution of Precipitation in the Equatorial Amazon?.

    Science.gov (United States)

    Fu, Rong; Dickinson, Robert E.; Chen, Mingxuan; Wang, Hui

    2001-10-01

    Although the correlation between precipitation over tropical South America and sea surface temperatures (SSTs) over the Pacific and Atlantic has been documented since the early twentieth century, the impact of each ocean on the timing and intensity of the wet season over tropical South America and the underlying mechanisms have remained unclear. Numerical experiments have been conducted using the National Center for Atmospheric Research Community Climate Model Version 3 to explore these impacts. The results suggest the following.1)Seasonality of SSTs in the tropical Pacific and Atlantic has an important influence on precipitation in the eastern Amazon during the equinox seasons. The eastern side of the Amazon is influenced both by the direct thermal circulation of the Atlantic intertropical convergence zone (ITCZ) and by Rossby waves. These processes are enhanced by the seasonal cycles of SSTs in the tropical Atlantic and Pacific. SSTs affect Amazon precipitation much less during the solstice seasons and in the western Amazon.2)The seasonality of SSTs in the Atlantic more strongly affects Amazon rainfall than does that of the Pacific. Without the former, austral spring in the eastern equatorial Amazon would be a wet season, rather than the observed dry season. As a consequence of the lag at that time of the southward seasonal migration of the Atlantic SSTs behind that of the insolation, the Atlantic ITCZ centers itself near 10°N, instead of at the equator, imposing subsidence and low-level anticyclonic flow over the eastern equatorial Amazon, thus drying the air above the planetary boundary layer and reducing the low-level moisture convergence. Consequently, convection in the eastern Amazon is suppressed despite strong surface heating.3)Seasonality of the SSTs in the tropical Pacific also tends to reduce precipitation in the eastern Amazon during both spring and fall. In spring, subsidence is enhanced not only through a zonal direct circulation, but also through

  5. Eastern South Pacific water mass geometry during the last glacial-interglacial transition

    Science.gov (United States)

    De Pol-Holz, R.; Reyes, D.; Mohtadi, M.

    2012-12-01

    The eastern South Pacific is characterized today by a complex thermocline structure where large salinity and oxygen changes as a function of depth coexist. Surface waters from tropical origin float on top of subantarctic fresher water (the so-called 'shallow salinity minimum of the eastern south Pacific'), which in turn, flow above aged equatorial and deeper recently ventilated Antarctic Intermediate waters. Little is known however about the water mass geometry changes that could have occurred during the last glacial maximum boundary conditions (about 20,000 years before the present), despite this information being critical for the assessment of potential mechanisms that have been proposed as explanations for the deglacial onset of low oxygen conditions in the area and the atmospheric CO2 increase during the same time. Here we present benthic and planktonic foraminifera stable isotope and radiocarbon data from a set of sediment cores from the Chilean continental margin covering a large -yet still limited- geographical area and depth range. Sedimentations rates were relatively high (>10 cm/kyr) precluding major caveats from bioturbation in all of our archives. The distribution of δ13C of ΣCO2 shows the presence of a very depleted (δ13C < -1‰ V-PDB) water mass overlaying more recently ventilated waters at intermediate depths as indicated by thermocline foraminifer dwellers being more depleted in 13C than the benthic species. The origin of this depleted end-member is probably upwelling from the Southern Ocean as expressed by the radiocarbon content and the large reservoir effect associated with the last glacial maximum and the beginning of the deglaciation along the margin. Our data suggest that the Tropical waters that today bath the lower latitude cores was displaced by surface waters of southern origin and therefore in line with the evidence of a latitudinal shift of the frontal systems.

  6. The bomb 14C transient in the Pacific Ocean

    Science.gov (United States)

    Rodgers, Keith B.; Schrag, Daniel P.; Cane, Mark A.; Naik, Naomi H.

    2000-04-01

    A modeling study of the bomb 14C transient is presented for the Pacific Ocean. A primitive equation ocean circulation model has been configured for a high-resolution domain that accounts for the Indonesian Throughflow (ITF). Four separate runs were performed: (1) seasonal forcing with 20 Sv of ITF transport, (2) seasonal forcing with 10 Sv of ITF transport, (3) seasonal forcing with no ITF transport, and (4) interannual forcing with 15 Sv of ITF transport. This study has two main objectives. First, it is intended to describe the time evolution of the bomb 14C transient. This serves as a tool with which one can identify the physical processes controlling the evolving bomb 14C distribution in the Pacific thermocline and thus provides an interpretive framework for the database of Δ14C measurements in the Pacific. Second, transient tracers are applied to the physical oceanographic problem of intergyre exchange. This is of importance in furthering our understanding of the potential role of the upper Pacific Ocean in climate variability. We use bomb 14C as a dye tracer of intergyre exchange between the subtropical gyres and the equatorial upwelling regions of the equatorial Pacific. Observations show that while the atmospheric Δ14C signal peaked in the early to mid-1960s, the Δ14C levels in the surface water waters of the subtropical gyres peaked near 1970, and the Δ14C of surface waters in the equatorial Pacific continued to rise through the 1980s. It is shown that the model exhibits skill in representing the large-scale observed features observed for the bomb 14C transient in the Pacific Ocean. The model successfully captures the basin-scale inventories of bomb 14C in the tropics as well as in the extratropics of the North Pacific. For the equatorial Pacific this is attributed to the model's high meridional resolution. The discrepancies in the three-dimensional distribution of bomb 14C between the model and data are discussed within the context of the dynamical

  7. High altitude flights in equatorial regions

    Science.gov (United States)

    Redkar, R. T.

    A thorough analysis of balloon flights made from Hyderabad, India (Latitude 17°28'N, Longitude 78°35'E), and other equatorial sites has been made. It has been shown that limited success is expected for flights made from equatorial latitudes with balloons made out of natural colour polyethylene film, since the best known balloon film in the world today viz. Winzen Stratofilm is tested for low temperature brittleness only at -80°C., whereas the tropopause temperatures over equatorial latitudes vary between -80°C and -90°C. The success becomes even more critical when flights are made with heavy payloads and larger balloons particularly at night when in the absence of solar radiation the balloon film becomes more susceptible to low temperature brittle failure. It is recommended that in case of capped balloons longer caps should be used to fully cover the inflated protion of the balloon at the higher level equatorial tropopause. It is also advised that the conditions such as wind shears in the tropopause should be critically studied before launching and a day with the tropopause temperature nearer to -80°C should be chosen. Special care also should be taken while handling the balloon on ground and during launching phase. Properties of Winzen Stratofilm have been critically studied and fresh mandates have been recommended on the basis of limiting values of film stresses which caused balloon failures in the equatorial tropopause. It is also emphasized that the data on such flights is still meagre especially for flights with heavy payloads and larger balloons. It has been also shown that it is safest to use balloons made out of grey coloured film which retains its flexibility with the absorption of solar radiation, the success obtained with such balloons so far being 100%. The drawback, however, is that these balloons cannot be used for night flights. Stratospheric wind regimes over Hyderabad are also discussed with a view to determine the period over which long

  8. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    2002-05-01

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature.  This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  9. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. 

    This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.

    Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  10. Relationship of boreal summer 10-20-day and 30-60-day intraseasonal oscillation intensity over the tropical western North Pacific to tropical Indo-Pacific SST

    Science.gov (United States)

    Wu, Renguang; Cao, Xi

    2017-06-01

    The present study contrasts interannual variations in the intensity of boreal summer 10-20-day and 30-60-day intraseasonal oscillations (ISOs) over the tropical western North Pacific and their factors. A pronounced difference is found in the relationship of the two ISOs to El Niño-Southern Oscillation. The 10-20-day ISO intensity is enhanced during El Niño developing summer, whereas the 30-60-day ISO intensity is enhanced during La Niña decaying summer. The above different relationship is interpreted as follows. The equatorial central and eastern Pacific SST anomalies modify vertical wind shear, lower-level moisture, and vertical motion in a southeast-northwest oriented band from the equatorial western Pacific to the tropical western North Pacific where the 10-20-day ISOs originate and propagate. These background field changes modulate the amplitude of 10-20-day ISOs. Preceding equatorial central and eastern Pacific SST anomalies induce SST anomalies in the North Indian Ocean in summer, which in turn modify vertical wind shear and vertical motion over the tropical western North Pacific. The modified background fields influence the amplitude of the 30-60-day ISOs when they reach the tropical western North Pacific from the equatorial region. A feedback of ISO intensity on local SST change is identified in the tropical western North Pacific likely due to a net effect of ISOs on surface heat flux anomalies. This feedback is more prominent from the 10-20-day than the 30-60-day ISO intensity change.

  11. Equatorial westward electrojet impacting equatorial ionization anomaly development during the 6 April 2000 superstorm

    Science.gov (United States)

    Horvath, Ildiko; Lovell, Brian C.

    2013-11-01

    investigate the forward plasma fountain and the equatorial ionosphere in the topside region during the 6 April 2000 superstorm in the Australian sector at ~0900 LT. Space- and ground-based multi-instrument measurements, Coupled Thermosphere-Ionosphere-Plasmasphere Electrodynamics (CTIPe) simulations, and field-aligned observations comprise our results. These reveal an unusual storm development during which the eastward prompt penetration electric (E) field (PPEF) developed and operated under the continuous effects of the westward disturbance dynamo E-field (DDEF) while large-scale traveling ionospheric disturbances (TIDs) traveled equatorward and generated strong equatorward wind surges. We have identified the eastward PPEF by the superfountain effect causing the equatorial ionization anomaly (EIA)'s development with crests situated at ~±28°N (geomagnetic) in the topside ionosphere at ~840 km altitude. The westward DDEF's occurrence is confirmed by mapping the "anti-Sq" current system wherein the equatorial westward current created a weak long-lasting westward electrojet event. Line plots of vertical drift data tracked large-scale TIDs. Four scenarios, covering ~3.5 h in universal time, demonstrate that the westward DDEF became superimposed on the eastward PPEF. As these E-fields of different origins became mapped into the F region, they could interact. Consequently, the eastward PPEF-related equatorial upward E × B drift became locally reduced by up to 75 m/s near the dip equator by the westward DDEF-related equatorial downward E × B drift. Meanwhile, the EIA displayed a better development as equatorial wind surges, reproduced by CTIPe, increased from 501 to 629 m/s, demonstrating the crucial role of mechanical wind effects keeping plasma density high.

  12. Global Warming Attenuates the Tropical Atlantic-Pacific Teleconnection

    Science.gov (United States)

    Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju

    2016-01-01

    Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread warming intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by warming in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global warming. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like warming of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse warming continues, the trend in the tropical Pacific as well as the development of ENSO will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection. PMID:26838053

  13. Anthropogenic CO2 distribution in the North Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C [National Sun Yat-Sen University, Kaohsiung (Taiwan, Province of China)

    1993-06-01

    This paper discusses the penetration depth of anthropogenic CO2 in the North Pacific Ocean based on carbonate data in the literature. The carbonate data in the literature were used to supplement the tracer data showing oceanic mixing features for waters formed in the last 140 years. The deepest penetration over 2,000m was found in the northwest North Pacific. On the other hand, the shallowest penetration to less than 400m was found in the eastern equatorial Pacific. Consequently, it was suggested that penetration depth of anthropogenic CO2 has been controlled by such factors as deep water formation in the Northwest Pacific, upwelling in the equatorial Pacific, and vertical mixing in the western boundary areas. It was revealed that these results are in harmony well with results implied from tritium, C-14, and freons distributions. The total inventory of excess carbon in the North Pacific was 14.7[plus minus]4[times]10[sup 15]g around 1980. 48 refs., 10 figs.

  14. Global Warming Attenuates the Tropical Atlantic-Pacific Teleconnection.

    Science.gov (United States)

    Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju

    2016-02-03

    Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread warming intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by warming in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global warming. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like warming of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse warming continues, the trend in the tropical Pacific as well as the development of ENSO will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection.

  15. Variations and controlling factors of the coccolith weight in the Western Pacific Warm Pool over the last 200 ka

    Science.gov (United States)

    Liang, Dan; Liu, Chuanlian

    2016-06-01

    Using a coccolith weight analytic software (Particle Analyser), we analyze most abundant coccolith species in a sediment core from the central Western Pacific Warm Pool (WPWP) and calculate coccolith size and weight variations over the last 200 ka. These variations are compared with the trends of sea surface temperature (SST), primary productivity (PP), sea surface salinity (SSS), and insolation. Our results demonstrate that the size and weight of the coccoliths varied in response to variations of these factors, and their average total weight is primarily related to the relative abundance of the dominant species GEO ( Gephyrocapsa oceanica). The variation in weight of EMI ( Emiliania huxleyi) and GEE ( Gephyrocapsa ericsonii) are mainly influenced by nutrients, and the variation of GEM ( G. muellerae conformis) and GEO ( G. oceanica) weight are mainly influenced by SST. For all of the taxa weight, PP and SST present apparent precession or semi-precession cycles, we consider that the mono-coccolith weight of the Equatorial Western Pacific is primarily affected by precession drived thermocline and nutricline variation.

  16. WATER TEMPERATURE and other data from NOAA Ship DISCOVERER and NOAA Ship OCEANOGRAPHER in the TOGA Area - Pacific from 1979-04-23 to 1982-05-21 (NODC Accession 9000293)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The water depth and temperature data was collected as part of Equatorial Pacific Ocean Climate Studies from NOAA Ship Discoverer and NOAA Ship Oceanographer. The...

  17. A New 50 MHz Phased-Array Radar on Pohnpei: A Fresh Perspective on Equatorial Plasma Bubbles

    Science.gov (United States)

    Tsunoda, R. T.

    2014-12-01

    A new, phased-array antenna-steering capability has recently been added to an existing 50-MHz radar on Pohnpei, Federated States of Micronesia, in the central Pacific region. This radar, which we refer to as PAR-50, is capable of scanning in the vertical east-west plane, ±60° about the zenith. The alignment in the magnetic east-west direction allows detection of radar backscatter from small-scale irregularities that develop in the equatorial ionosphere, including those associated with equatorial plasma bubbles (EPBs). The coverage, about ±800 km in zonal distance, at an altitude of 500 km, is essentially identical to that provided by ALTAIR, a fully-steerable incoherent-scatter radar, which has been used in a number of studies of EPBs. Unlike ALTAIR, which has only been operated for several hours on a handful of selected nights, the PAR-50 has already been operated continuously, while performing repeated scans, since April 2014. In this presentation, we describe the PAR-50, then, compare it to ALTAIR and the Equatorial Atmospheric Radar (EAR); the latter is the only other phased-array system in use for equatorial studies. We then assess what we have learned about EPBs from backscatter radar measurements, and discuss how the PAR-50 can provide a fresh perspective to our understanding. Clearly, the ability to sort out the space-time ambiguities in EPB development from sequences of spatial maps of EPBs is crucial to our understanding of how EPBs develop.

  18. Structure and variances of equatorial zonal circulation in a multimodel ensemble

    Energy Technology Data Exchange (ETDEWEB)

    Yu, B. [Environment Canada, Climate Data and Analysis Section, Climate Research Division, Toronto, ON (Canada); Zwiers, F.W. [University of Victoria, Pacific Climate Impacts Consortium, Victoria, BC (Canada); Boer, G.J. [Environment Canada, Canadian Centre for Climate Modeling and Analysis, Climate Research Division, Victoria, BC (Canada); Ting, M.F. [Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY (United States)

    2012-11-15

    The structure and variance of the equatorial zonal circulation, as characterized by the atmospheric mass flux in the equatorial zonal plane, is examined and inter-compared in simulations from 9 CMIP3 coupled climate models with multiple ensemble members and the NCEP-NCAR and ERA-40 reanalyses. The climate model simulations analyzed here include twentieth century (20C3M) and twenty-first century (SRES A1B) simulations. We evaluate the 20C3M modeled zonal circulations by comparing them with those in the reanalyses. We then examine the variability of the circulation, its changes with global warming, and the associated thermodynamic maintenance. The tropical zonal circulation involves three major components situated over the Pacific, Indian, and Atlantic oceans. The three cells are supported by the corresponding diabatic heating extending deeply throughout the troposphere, with heating centers apparent in the mid-troposphere. Seasonal features appear in the zonal circulation, including variations in its intensity and longitudinal migration. Most models, and hence the multi-model mean, represent the annual and seasonal features of the circulation and the associated heating reasonably well. The multi-model mean reproduces the observed climatology better than any individual model, as indicated by the spatial pattern correlation and mean square difference of the mass flux and the diabatic heating compared to the reanalysis based values. Projected changes in the zonal circulation under A1B forcing are dominated by mass flux changes over the Pacific and Indian oceans. An eastward shift of the Pacific Walker circulation is clearly evident with global warming, with anomalous rising motion apparent over the equatorial central Pacific and anomalous sinking motions in the west and east, which favors an overall strengthening of the Walker circulation. The zonal circulation weakens and shifts westwards over the Indian Ocean under external forcing, whereas it strengthens and shifts

  19. Geomagnetic storms and electric fields in the equatorial ionosphere

    International Nuclear Information System (INIS)

    Rastogi, R.G.

    1977-01-01

    Using direct measurements of equatorial electric field during a geomagnetic storm it is shown that the large decrease in the field observed near the dip equator is due to the reversal of the equatorial electrojet current. This is caused by the imposition of an additional westward electric field on the equatorial ionosphere which was originated by the interaction of solar wind with the interplanetary magnetic field. (author)

  20. MACSAT - A Near Equatorial Earth Observation Mission

    Science.gov (United States)

    Kim, B. J.; Park, S.; Kim, E.-E.; Park, W.; Chang, H.; Seon, J.

    MACSAT mission was initiated by Malaysia to launch a high-resolution remote sensing satellite into Near Equatorial Orbit (NEO). Due to its geographical location, Malaysia can have large benefits from NEO satellite operation. From the baseline circular orbit of 685 km altitude with 7 degrees of inclination, the neighboring regions around Malaysian territory can be frequently monitored. The equatorial environment around the globe can also be regularly observed with unique revisit characteristics. The primary mission objective of MACSAT program is to develop and validate technologies for a near equatorial orbit remote sensing satellite system. MACSAT is optimally designed to accommodate an electro-optic Earth observation payload, Medium-sized Aperture Camera (MAC). Malaysian and Korean joint engineering teams are formed for the effective implementation of the satellite system. An integrated team approach is adopted for the joint development for MACSAT. MAC is a pushbroom type camera with 2.5 m of Ground Sampling Distance (GSD) in panchromatic band and 5 m of GSD in four multi-spectral bands. The satellite platform is a mini-class satellite. Including MAC payload, the satellite weighs under 200 kg. Spacecraft bus is designed optimally to support payload operations during 3 years of mission life. The payload has 20 km of swath width with +/- 30 o of tilting capability. 32 Gbits of solid state recorder is implemented as the mass image storage. The ground element is an integrated ground station for mission control and payload operation. It is equipped with S- band up/down link for commanding and telemetry reception as well as 30 Mbps class X-band down link for image reception and processing. The MACSAT system is capable of generating 1:25,000-scale image maps. It is also anticipated to have capability for cross-track stereo imaging for Digital elevation Model (DEM) generation.

  1. The equatorial F-layer: progress and puzzles

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    Full Text Available This work reviews some aspects of the ionospheric F-layer in the vicinity of the geomagnetic equator. Starting with a historical introduction, brief summaries are given of the physics that makes the equatorial ionosphere so interesting, concentrating on the large-scale structure rather than the smaller-scale instability phenomena. Several individual topics are then discussed, including eclipse effects, the asymmetries of the `equatorial trough', variations with longitude, the semiannual variation, the effects of the global thermospheric circulation, and finally the equatorial neutral thermosphere, including `superrotation' and possible topographic influences.

    Keyword: Ionosphere (equatorial ionosphere

  2. An equatorial coronal hole at solar minimum

    Science.gov (United States)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

  3. Bacterial diversity in the sediment from polymetallic nodule fields of the Clarion-Clipperton Fracture Zone.

    Science.gov (United States)

    Wang, Chun-Sheng; Liao, Li; Xu, Hong-Xiang; Xu, Xue-Wei; Wu, Min; Zhu, Li-Zhong

    2010-10-01

    The Clarion-Clipperton Fracture Zone (CCFZ) is located in the northeastern equatorial Pacific and contains abundant polymetallic nodules. To investigate its bacterial diversity, four libraries of 16S rRNA genes were constructed from sediments of four stations in different areas of the CCFZ. In total, 313 clones sequenced from the 4 libraries were assigned into 14 phylogenetic groups and 1 group of 28 unclassified bacteria. High bacterial diversity was predicted by the rarefaction analysis. The most dominant group overall was Proteobacteria, but there was variation in each library: Gammaproteobacteria was the most dominant group in two libraries, E2005-01 and ES0502, while Alphaproteobacteria and Deltaproteobacteria were the most dominant groups in libraries EP2005-03 and WS0505, respectively. Seven groups, including Alphaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Betaproteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes, were common to all four libraries. The remaining minor groups were distributed in libraries with different patterns. Most clones sequenced in this study were clustered with uncultured bacteria obtained from the environment, such as the ocean crust and marine sediment, but only distantly related to isolates. Bacteria involved in the cycling of metals, sulfur and nitrogen were detected, and their relationship with their habitat was discussed. This study sheds light on the bacterial communities associated with polymetallic nodules in the CCFZ and provides primary data on the bacterial diversity of this area.

  4. BAROMETRIC PRESSURE and Other Data from THOMAS G. THOMPSON and Other Platforms From TOGA Area - Pacific (30 N to 30 S) from 19921013 to 19921213 (NODC Accession 9600065)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data in this accession was collected as part of Joint Global Ocean Flux Study/Equatorial Pacific Basin Study (JGOFS/EQPAC) in TOGA Area - Pacific (30 N to 30 S)...

  5. Role of atmosphere-ocean interactions in supermodeling the tropical Pacific climate

    Science.gov (United States)

    Shen, Mao-Lin; Keenlyside, Noel; Bhatt, Bhuwan C.; Duane, Gregory S.

    2017-12-01

    The supermodel strategy interactively combines several models to outperform the individual models comprising it. A key advantage of the approach is that nonlinear improvements can be achieved, in contrast to the linear weighted combination of individual unconnected models. This property is found in a climate supermodel constructed by coupling two versions of an atmospheric model differing only in their convection scheme to a single ocean model. The ocean model receives a weighted combination of the momentum and heat fluxes. Optimal weights can produce a supermodel with a basic state similar to observations: a single Intertropical Convergence zone (ITCZ), with a western Pacific warm pool and an equatorial cold tongue. This is in stark contrast to the erroneous double ITCZ pattern simulated by both of the two stand-alone coupled models. By varying weights, we develop a conceptual scheme to explain how combining the momentum fluxes of the two different atmospheric models affects equatorial upwelling and surface wind feedback so as to give a realistic basic state in the tropical Pacific. In particular, we propose a mechanism based on the competing influences of equatorial zonal wind and off-equatorial wind stress curl in driving equatorial upwelling in the coupled models. Our results show how nonlinear ocean-atmosphere interaction is essential in combining these two effects to build different sea surface temperature structures, some of which are realistic. They also provide some insight into observed and modelled tropical Pacific climate.

  6. Nighttime ionospheric D region: Equatorial and nonequatorial

    Science.gov (United States)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H‧ and β as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H‧ ˜ 85.0 km and sharpness β ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H‧ ˜ 85.0 km and β ˜ 0.63 km-1, or any other realistic values of H‧ and β. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  7. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    1997-10-01

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  8. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  9. A Moessbauer study of deep sea sediments

    International Nuclear Information System (INIS)

    Minai, Y.; Tominaga, T.; Furuta, T.; Kobayashi, K.

    1981-01-01

    In order to determine the chemical states of iron in deep sea sediments, Moessbauer spectra of the sediments collected from various areas of the Pacific have been measured. The Moessbauer spectra were composed of paramagnetic ferric, high-spin ferrous, and magnetic components. The correlation of their relative abundance to the sampling location and the kind of sediments may afford clues to infer the origin of each iron-bearing phase. (author)

  10. The D1 parameter for the equatorial F1 region

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2002-01-01

    This work is a contribution to the effort at improving the representation of the F1 equatorial ionospheric region in the International Reference Ionosphere (IRI) model. The D1 parameter has been proposed for describing the F1 layer. We have therefore produced a maiden table of D1 parameter for an equatorial station. Diurnal and seasonal effects were considered. (author)

  11. Moisture dynamics of the northward and eastward propagating boreal summer intraseasonal oscillations: possible role of tropical Indo-west Pacific SST and circulation

    Science.gov (United States)

    Pillai, Prasanth A.; Sahai, A. K.

    2016-08-01

    Boreal summer intraseasonal oscillation (BSISO) has complex spatial structure due to the co-existence of equatorial eastward and off-equatorial northward propagation in the equatorial Indian Ocean. As a result, equatorial Indian Ocean convection has simultaneous northward and eastward (NE), northward only (N-only) and eastward only (E-only) propagations. It is well established that the convection propagates in the direction of increasing moist static energy (MSE). The moisture and MSE budget analysis reveals that the horizontal advection of anomalous MSE contributes to positive MSE tendency, which is in agreement with the horizontal advection of column integrated moisture anomaly. Northward movement of warm SST and the anomalous moisture advected by zonal wind are the major initiative for the northward propagation of convection from the equatorial Indian Ocean in both NE and N-only category. At the same time warm SST anomaly in the equatorial west Pacific along with moisture advection caused by anomalous meridional wind is important for the equatorial eastward branch of NE propagation. As these anomalies in the west Pacific moves northward, equatorial Indian Ocean convection establishes over the equatorial west Pacific. The absence of these processes confines the BSISO in northward direction for N-only category. In the case of E-only movement, warm SST anomaly and moisture advection by zonal component of wind causes the eastward propagation of convection. Boundary layer moisture convergence always remains east of convection center in E-only propagation, while it coincides with convection centre in other two categories. Thus the present study concludes that the difference in underlying SST and atmospheric circulation in tropical Indo-west Pacific oceanic regions encourage the differential propagation of BSISO convection through moisture dynamics.

  12. Equatorially/globally conditioned meteorological analysis of heaviest monsoon rains over India during 23-28 July 2005

    Science.gov (United States)

    Ranade, Ashwini; Singh, Nityanand

    2018-06-01

    The heaviest monsoon rainstorm of the period 1951-2007 over India occurred during 23-28 July 2005, mostly the peninsula received rainfall, and each day the rainwater over the country was 40.0 bcm (billion cubic meter) or more, highest 98.4 bcm fell on 25 July 2005. Present premise of monsoon genesis is that it evolves in association with spreading and intensification of equatorial atmospheric condition over Afro-Eurasian landmass and adjoining Indian and Pacific Oceans during boreal summer. Robust natural criteria have been applied to demarcate monsoon and other global weather regimes (GWRs) at standard levels (1000‒100 hPa). Global atmospheric (1000‒100 hPa) thermal condition and monsoon and general circulations during 23-28 July 2005 have been compared with normal features of respective parameters. Over tropics-subtropics (45°S-45°N), troposphere (1000‒250 hPa) was warmer-thicker and pressure lower than normal and mixed conditions of positive/negative departures in temperature, height/thickness and pressure over northern and southern mid-high latitudes. Noticeable changes in 3D monsoon structure were: horizontally spread and eastward-southward shifted over western North Pacific and stretched further southeastward across equatorial Pacific; intense warm-low lower tropospheric confluence-convergence across Asia-Pacific with vertical depth extending beyond 400 hPa; and intense warm-high upper tropospheric anticyclonic circulation zonally stretched and divided into three interconnected cells. Outflows from anticyclonic cells over Tibetan plateau and western North Pacific were mostly directed westward/southwestward/southward. Troposphere was warmer-thicker and pressure higher over eastern part of both subpolars-polars and cooler-thinner and pressure lower over western part. During the period, a deep cyclonic circulation moved from Bay of Bengal through central India while near-stationary atmospheric condition prevailed across the globe.

  13. Equatorial electrojet and its response to external electromagnetic effects

    Science.gov (United States)

    Bespalov, P. A.; Savina, O. N.

    2012-09-01

    In the quiet low-latitude Earth's ionosphere, a sufficiently developed current system that is responsible for the Sq magnetic-field variations is formed in quiet Sun days under the action of tidal streams. The density of the corresponding currents is maximum in the midday hours at the equatorial latitudes, where the so-called equatorial electrojet is formed. In this work, we discuss the nature of the equatorial electrojet. This paper studies the value of its response to external effects. First of all, it is concerned with estimating the possibility of using the equatorial electrojet for generating low-frequency electromagnetic signals during periodic heating of the ionosphere by the heating-facility radiation. The equatorial electrojet can also produce electrodynamic response to the natural atmospheric processes, e.g., an acoustic-gravity wave.

  14. Response of the tropical Pacific Ocean to El Niño versus global warming

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fukai; Luo, Yiyong; Lu, Jian; Wan, Xiuquan

    2016-04-15

    Climate models project an El Niño-like SST response in the tropical Pacific Ocean to global warming (GW). By employing the Community Earth System Model (CESM) and applying an overriding technique to its ocean component, Parallel Ocean Program version 2 (POP2), this study investigates the similarity and difference of formation mechanism for the changes in the tropical Pacific Ocean under El Niño and GW. Results show that, despite sharing some similarities between the two scenarios, there are many significant distinctions between GW and El Niño: 1) the phase locking of the seasonal cycle reduction is more notable under GW compared with El Niño, implying more extreme El Niño events in the future; 2) in contrast to the penetration of the equatorial subsurface temperature anomaly that appears to propagate in the form of an oceanic equatorial upwelling Kelvin wave during El Niño, the GW-induced subsurface temperature anomaly manifest in the form of off-equatorial upwelling Rossby waves; 3) while significant across-equator northward heat transport (NHT) is induced by the wind stress anomalies associated with El Niño, little NHT is found at the equator due to a symmetric change in the shallow meridional overturning circulation that appears to be weakened in both North and South Pacific under GW; and 4) the maintaining mechanisms for the eastern equatorial Pacific warming are also substantially different.

  15. [Limnology of high mountain tropical lake, in Ecuador: characteristics of sediments and rate of sedimentation].

    Science.gov (United States)

    Gunkel, Günter

    2003-06-01

    Equatorial high mountain lakes are a special type of lake occurring mainly in the South American Andes as well as in Central Africa and Asia. They occur at altitudes of a few thousand meters above sea level and are cold-water lakes (limnological study was therefore undertaken at Lake San Pablo, Ecuador, to analyze the basic limnological processes of the lake, which has a tendency for eutrophication. Sediment quality of San Pablo Lake is given under consideration of horizontal and vertical distribution using sediment cores. Significance of sediments for eutrophication process of lakes is demonstrated using phosphorus concentration of sediments as well as the phosphorus retention capacity of the sediments by ratio Fe/P. Dating of the sediments is done using 137Cs and 210Pb, but the activity of 137Cs in the sediment was very low nearly at the detection level. Sedimentation rate is determined to be 3.5 mm/year and the sediment cores represent about 110 years. P concentration of the sediments is high (approximately 5 g/kg dry substance), and P retention capacity by Fe is insufficient (Fe/P = 4). The sediment quality did not change significantly during the past decades, and the trophic state of San Pablo Lake was already less or more eutrophic 110 years ago. The contamination of the lake sediments by heavy metals is insignificant.

  16. Marine sediments and Beryllium-10 record of the geomagnetic moment variations during the Brunhes period.

    Science.gov (United States)

    Ménabréaz, Lucie; Thouveny, Nicolas; Bourlès, Didier; Demory, François

    2010-05-01

    , (3) the high-resolution deep sea floor magnetization record of the South East Pacific (Gee et al., 2000) and (4) other cosmogenic records obtained from different archives. A second normalization method using the 230Thxs (e.g. Frank et al., 1997) is presently applied on these samples and the results will allow establishing a cross evaluation and intercalibration. Two other marine sequences collected in the west-equatorial Pacific are also under investigation. These data and their combination to previous 10Be/9Be records will constitute the basis for the construction of a global marine 10Be-stack covering the whole Brunhes period and the numerous relevant excursions, as well as the Brunhes-Matuyama boundary. This study is funded through the "MAG-ORB" project ANR- 09-BLAN-0053-01.

  17. Long wavelength irregularities in the equatorial electrojet

    International Nuclear Information System (INIS)

    Kudeki, E.; Farley, D.T.; Fejer, B.G.

    1982-01-01

    We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach or exceed the ion-acoustic velocity even though the horizontal phase velocity of the wave is considerably smaller. A straightforward extension to the long wavelength regime of the usual linear theory of the electrojet instability explains this and several other observed features of these dominant primary waves

  18. Linear theory of equatorial spread F

    International Nuclear Information System (INIS)

    Hudson, M.K.; Kennel, C.F.

    1975-01-01

    A fluid dispersion relation for the drift and interchange (Rayleigh-Taylor) modes in a collisional plasma forms the basis for a linear theory of equatorial spread F. The collisional drift mode growth rate will exceed the growth rate of the Rayleigh-Taylor mode at short perpendicular wavelengths and density gradient scale lengths, and the drift mode can grow on top side as well as on bottom side density gradients. However, below the F peak, where spread F predominates, it is concluded that both the drift and the Rayleigh-Taylor modes contribute to the total spread F spectrum, the Rayleigh-Taylor mode dominating at long and the drift mode at short perpendicular wavelengths above the ion Larmor radius

  19. Equatorial circular motion in Kerr spacetime

    International Nuclear Information System (INIS)

    Pugliese, Daniela; Quevedo, Hernando; Ruffini, Remo

    2011-01-01

    We analyze the properties of circular orbits of test particles on the equatorial plane of a rotating central mass whose gravitational field is described by the Kerr spacetime. For rotating black holes and naked singularities we explore all the spatial regions where circular orbits can exist and analyze the behavior of the energy and the angular momentum of the corresponding test particles. In particular, we find all the radii at which a test particle can have zero angular momentum due to the repulsive gravity effects generated by naked singularities. We classify all the stability zones of circular orbits. It is shown that the geometric structure of the stability zones of black holes is completely different from that of naked singularities.

  20. Dynamical variability in Saturn Equatorial Atmosphere

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.; Hueso, R.; Rojas, J. F.; French, R. G.; Grupo Ciencias Planetarias Team

    2003-05-01

    Historical ground-based and recent HST observations show that Saturn's Equatorial Atmosphere is the region where the most intense large-scale dynamical variability took place at cloud level in the planet. Large-scale convective storms (nicknamed the ``Great White Spots") occurred in 1876, 1933 and 1990. The best studied case (the 1990 storm), produced a dramatic change in the cloud aspect in the years following the outburst of September 1990. Subsequently, a new large storm formed in 1994 and from 1996 to 2002 our HST observations showed periods of unusual cloud activity in the southern part of the Equator. This contrast with the aspect observed during the Voyager 1 and 2 encounters in 1980 and 1981 when the Equator was calm, except for some mid-scale plume-like features seen in 1981. Cloud-tracking of the features have revealed a dramatic slow down in the equatorial winds from maximum velocities of ˜ 475 m/s in 1980-1981 to ˜ 275 m/s during 1996-2002, as we have recently reported in Nature, Vol. 423, 623 (2003). We discuss the possibility that seasonal and ring-shadowing effects are involved in generating this activity and variability. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. SPH acknowledges a PhD fellowship from the Spanish MECD and RH a post-doc fellowship from Gobierno Vasco. RGF was supported in part by NASA's Planetary Geology and Geophysics Program NAG5-10197 and STSCI Grant GO-08660.01A.

  1. The Effect of ENSO on Phytoplankton Composition in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, Cecile

    2012-01-01

    The effect of climate variability on phytoplankton communities was assessed for the tropical and sub-tropical Pacific Ocean between 1998 and 2005 using an established biogeochemical assimilation model. The phytoplankton communities exhibited wide range of responses to climate variability, from radical shifts in the Equatorial Pacific, to changes of only a couple of phytoplankton groups in the North Central Pacific, to no significant changes in the South Pacific. In the Equatorial Pacific, climate variability dominated the variability of phytoplankton. Here, nitrate, chlorophyll and all but one of the 4 phytoplankton types (diatoms, cyanobacteria and coccolithophores) were strongly correlated (p less than 0.01) with the Multivariate El Nino Southern Oscillation Index (MEI). In the North Central Pacific, MEI and chlorophyll were significantly (pphytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Ni a events, diatoms increased and expanded westward along the cold tongue (correlation with MEI, r=-0.81), while cyanobacteria concentrations decreased significantly (r=0.78). El Nino produced the reverse pattern, with cyanobacteria populations increasing while diatoms plummeted. The diverse response of phytoplankton in the different major basins of the Pacific suggests the different roles climate variability can play in ocean biology.

  2. Coral settlement on a highly disturbed equatorial reef system.

    Science.gov (United States)

    Bauman, Andrew G; Guest, James R; Dunshea, Glenn; Low, Jeffery; Todd, Peter A; Steinberg, Peter D

    2015-01-01

    Processes occurring early in the life stages of corals can greatly influence the demography of coral populations, and successful settlement of coral larvae that leads to recruitment is a critical life history stage for coral reef ecosystems. Although corals in Singapore persist in one the world's most anthropogenically impacted reef systems, our understanding of the role of coral settlement in the persistence of coral communities in Singapore remains limited. Spatial and temporal patterns of coral settlement were examined at 7 sites in the southern islands of Singapore, using settlement tiles deployed and collected every 3 months from 2011 to 2013. Settlement occurred year round, but varied significantly across time and space. Annual coral settlement was low (~54.72 spat m(-2) yr(-1)) relative to other equatorial regions, but there was evidence of temporal variation in settlement rates. Peak settlement occurred between March-May and September-November, coinciding with annual coral spawning periods (March-April and October), while the lowest settlement occurred from December-February during the northeast monsoon. A period of high settlement was also observed between June and August in the first year (2011/12), possibly due to some species spawning outside predicted spawning periods, larvae settling from other locations or extended larval settlement competency periods. Settlement rates varied significantly among sites, but spatial variation was relatively consistent between years, suggesting the strong effects of local coral assemblages or environmental conditions. Pocilloporidae were the most abundant coral spat (83.6%), while Poritidae comprised only 6% of the spat, and Acroporidae coral spat. These results indicate that current settlement patterns are reinforcing the local adult assemblage structure ('others'; i.e. sediment-tolerant coral taxa) in Singapore, but that the replenishment capacity of Singapore's reefs appears relatively constrained, which could lead

  3. The Role of the Indian Ocean Sector for Prediction of the Coupled Indo-Pacific System: Impact of Atmospheric Coupling

    Science.gov (United States)

    Hackert, E. C.; Busalacchi, A. J.; Carton, J.; Murtugudde, R.; Arkin, P.; Evans, M. N.

    2017-01-01

    Indian Ocean (IO) dynamics impact ENSO predictability by influencing wind and precipitation anomalies in the Pacific. To test if the upstream influence of the IO improves ENSO validation statistics, a combination of forced ocean, atmosphere, and coupled models are utilized. In one experiment, the full tropical Indo-Pacific region atmosphere is forced by observed interannual SST anomalies. In the other, the IO is forced by climatological SST. Differences between these two forced atmospheric model experiments spotlight a much richer wind response pattern in the Pacific than previous studies that used idealized forcing and simple linear atmospheric models. Weak westerlies are found near the equator similar to earlier literature. However, at initialization strong easterlies between 30 deg. S to 10 deg. S and 0 deg. N to 25 deg. N and equatorial convergence of the meridional winds across the entire Pacific are unique findings from this paper. The large-scale equatorial divergence west of the dateline and northeasterly-to-northwesterly cross-equatorial flow converging on the equator east of the dateline in the Pacific are generated from interannual IO SST coupling. In addition, off-equatorial downwelling curl impacts large-scale oceanic waves (i.e., Rossby waves reflect as western boundary Kelvin waves). After 3 months, these downwelling equatorial Kelvin waves propagate across the Pacific and strengthen the NINO3 SST. Eventually Bjerknes feedbacks take hold in the eastern Pacific which allows this warm anomaly to grow. Coupled forecasts for NINO3 SST anomalies for 1993-2014 demonstrate that including interannual IO forcing significantly improves predictions for 3-9 month lead times.

  4. The role of the Indian Ocean sector for prediction of the coupled Indo-Pacific system: Impact of atmospheric coupling

    Science.gov (United States)

    Hackert, E. C.; Busalacchi, A. J.; Carton, J.; Murtugudde, R.; Arkin, P.; Evans, M. N.

    2017-04-01

    Indian Ocean (IO) dynamics impact ENSO predictability by influencing wind and precipitation anomalies in the Pacific. To test if the upstream influence of the IO improves ENSO validation statistics, a combination of forced ocean, atmosphere, and coupled models are utilized. In one experiment, the full tropical Indo-Pacific region atmosphere is forced by observed interannual SST anomalies. In the other, the IO is forced by climatological SST. Differences between these two forced atmospheric model experiments spotlight a much richer wind response pattern in the Pacific than previous studies that used idealized forcing and simple linear atmospheric models. Weak westerlies are found near the equator similar to earlier literature. However, at initialization strong easterlies between 30°S-10°S and 0°N-25°N and equatorial convergence of the meridional winds across the entire Pacific are unique findings from this paper. The large-scale equatorial divergence west of the dateline and northeasterly-to-northwesterly cross-equatorial flow converging on the equator east of the dateline in the Pacific are generated from interannual IO SST coupling. In addition, off-equatorial downwelling curl impacts large-scale oceanic waves (i.e., Rossby waves reflect as western boundary Kelvin waves). After 3 months, these downwelling equatorial Kelvin waves propagate across the Pacific and strengthen the NINO3 SST. Eventually Bjerknes feedbacks take hold in the eastern Pacific which allows this warm anomaly to grow. Coupled forecasts for NINO3 SST anomalies for 1993-2014 demonstrate that including interannual IO forcing significantly improves predictions for 3-9 month lead times.

  5. Initial investigations of microscale cellular convection in an equatorial marine atmospheric boundary layer revealed by lidar

    Science.gov (United States)

    Cooper, D. I.; Eichinger, W. E.; Ecke, R. E.; Kao, J. C. Y.; Reisner, J. M.; Tellier, L. L.

    During the Combined Sensor Program (CSP) in March of 1996, the Los Alamos National Laboratory (LANL) fielded an advanced scanning Raman lidar. The lidar was part of a larger suite of micrometeorological sensors to quantify processes associated with the ocean-atmosphere interface, including intermittency and coherent atmospheric features in the “warm pool” of the Tropical Western Pacific (TWP) near Manus Island (2° S. lat, 147° E. long). Initial inspection of the data has revealed excellent information on the microscale vertical and horizontal spatial and temporal structure of the equatorial Marine Atmospheric Boundary Layer (MABL). The data from this experiment have added to the increasing body of measurements on surface layer convection and intermittency including, for the first time, the observation of microscale cellular convective structures such as hexagonal patterns associated with Rayleigh-Bénard cells.

  6. Proton flux under radiation belts: near-equatorial zone

    International Nuclear Information System (INIS)

    Grigoryan, O.R.; Panasyuk, M.I.; Petrov, A.N.; Kudela, K.

    2005-01-01

    In this work the features of low-energy proton flux increases in near-equatorial region (McIlvein parameter L th the proton flux (with energy from tens keV up to several MeV) increases are registering regularly. However modern proton flux models (for example AP8 model) works at L>1.15 only and does not take into account near-equatorial protons. These fluxes are not too big, but the investigation of this phenomenon is important in scope of atmosphere-ionosphere connections and mechanisms of particles transport in magnetosphere. In according to double charge-exchange model the proton flux in near-equatorial region does not depend on geomagnetic local time (MLT) and longitude. However the Azur satellite data and Kosmos-484, MIR station and Active satellite data revealed the proton flux dependence on longitude. The other feature of near-equatorial proton flux is the dependence on geomagnetic local time revealed in the Sampex satellite experiment and other experiments listed above. In this work the dependences on MLT and longitude are investigated using the Active satellite (30-500 keV) and Sampex satellite (>800 keV). This data confirms that main sources of near-equatorial protons are radiation belts and ring current. The other result is that near-equatorial protons are quasi-trapped. The empirical proton flux dependences on L, B at near-equatorial longitudes are presented. (author)

  7. Relationships between the Tropical Pacific and the Southern California Current productivity at different timescales

    Science.gov (United States)

    Abella-Gutiérrez, J. L.; Herguera, J. C.

    2016-02-01

    The influence of Tropical Pacific in climate during the Common Era has been largely debated due to the lack of agreement between proxies. Some records suggest a La Niña-like conditions during the Medieval Climate Anomaly (MCA) and El Niño-like conditions during the Little Ice Age (LIA) (i.e. Graham et al., 2007), but other records suggest the contrary (i.e. Conroy et al., 2008). Here we present a 2.3Ky biogenic based record from San Lázaro Basin that, in its different modes of variability, contains both visions. Furthermore, these proxies share a centennial mode of variability that dominates the last millennium and connects the Indo-Pacific Warm Pool (IPWP) with the Western North America Drought Area Index (WNA-DAI) through variations in the thermocline.San Lázaro Basin (SLB) is a suboxic basin located in the southern dynamic boundary of the California Current System (CCS). During La Niña-like conditions, the intensification of the trade winds increase the Ekman transport and the invasion of subartic waters, with the result of a shoaled thermocline and enhanced ecosystem productivity. When the winds relax, El Niño-like conditions became, and the intrusion of warm stratified water from the tropical and subtropical regions plummeted the productivity and a coccolitophorid based ecosystem dominates. The opposite relation between Carbonates and Total Organic Carbon (TOC) in SLB sediments confirms this observations. A significant positive correlation between XRF measurements of Br/Si with TOC and Ca counts with Carbonates, allows us to study SCC variability from interannual to centennial resolution.The Spectral Analysis of Br/Si and Carbonates show a common 110y cycle that is also present in the IPWP and WNA-DAI with a ENSO-like pattern. This centennial mode is excited by warm Equatorial Pacific conditions as its variance is correlated with Galapagos precipitation record. Although Galapagos precipitation record has been related with ENSO intensity, the Br

  8. Equatorial wave activity during 2007 over Gadanki, a tropical station

    Indian Academy of Sciences (India)

    been used to investigate the wave activity in the troposphere and lower stratosphere. Waves in the ...... Oltmans S J 2001 Water vapor control at the tropopause by equatorial Kelvin .... observed in UARS microwave limb sounder temperature.

  9. An overview on the equatorial electrojet theoretical grounds

    International Nuclear Information System (INIS)

    Zamlutti, C.J.; Sobral, J.H.A.; Abdu, M.A.

    1988-01-01

    The grounds on which the equatorial electrojet theory is based are reexamined in a way as to suggest specific additional implementations in the existing electrodynamical modeling of this phenomena, making use of now existing improved computer processing speeds. (author) [pt

  10. ITER L 6 equatorial maintenance duct remote handling study

    International Nuclear Information System (INIS)

    Millard, J.

    1996-09-01

    The status and conclusions of a preliminary study of equatorial maintenance duct remote handling is reported. Due to issues with the original duct design a significant portion of the study had to be refocused on equatorial duct layout studies. The study gives an overview of some of the options for design of these ducts and the impact of the design on the equipment to work in the duct. To develop a remote handling concept for creating access through the ducts the following design tasks should be performed: define the operations sequences for equatorial maintenance duct opening and closing; review the remote handling requirements for equatorial maintenance duct opening and closing; design concept for door and pipe handling equipment and to propose preliminary procedures for material handling outsides the duct. 35 figs

  11. Modelling the development of mixing height in near equatorial region

    Energy Technology Data Exchange (ETDEWEB)

    Samah, A.A. [Univ. of Malaya, Air Pollution Research Unit, Kuala Lumpur (Malaysia)

    1997-10-01

    Most current air pollution models were developed for mid-latitude conditions and as such many of the empirical parameters used were based on observations taken in the mid-latitude boundary layer which is physically different from that of the equatorial boundary layer. In the equatorial boundary layer the Coriolis parameter f is small or zero and moisture plays a more important role in the control of stability and the surface energy balance. Therefore air pollution models such as the OMLMULTI or the ADMS which were basically developed for mid-latitude conditions must be applied with some caution and would need some adaptation to properly simulate the properties of equatorial boundary layer. This work elucidates some of the problems of modelling the evolution of mixing height in the equatorial region. The mixing height estimates were compared with routine observations taken during a severe air pollution episodes in Malaysia. (au)

  12. Onset conditions for equatorial spread F

    International Nuclear Information System (INIS)

    Mendillo, M.; Baumgardner, J.; Xiaoqing Pi; Sultan, P.J.; Tsunoda, R.

    1992-01-01

    The problem of day-to-day variability in the occurrence of equatorial spread F (ESF) is addressed using multidiagnostic observations and semiempirical modeling. The observational results are derived from a two-night case study of ESF onset conditions observed at Kwajalein Atoll (Marshall Islands) using the ALTAIR incoherent scatter radar and all-sky optical imaging techniques. The major difference between nights when ESF instabilities did not occur (August 14, 1988) and did occur (August 15, 1988) in the Kwajalein sector was that the northern meridional gradient of 6300-angstrom airglow was reduced on the night of limited ESF activity. Modeling results suggest that this unusual airglow pattern is due to equatorward neutral winds. Previous researchers have shown that transequatorial thermospheric winds can exert a control over ESF seasonal and longitudinal occurrence patterns by inhibiting Rayleigh-Taylor instability growth rates. They present evidence to suggest that this picture can be extended to far shorter time scales, namely, that 'surges' in transequatoral winds acting over characteristic times of a few hours to a day can result in a stabilizing influence upon irregularity growth rates. The seemingly capricious nature of ESF onset may thus be controlled, in part, by the inherent variability of low-latitude thermospheric winds

  13. An equatorial temperature and wind anomaly (ETWA)

    International Nuclear Information System (INIS)

    Raghavarao, R.; Wharton, L.E.; Mayr, H.G.; Brace, L.H.; Spencer, N.W.

    1991-01-01

    Data obtained from the WATS (Wind and Temperature Spectrometer) and LP (Langmuir Probe) experiments on board DE-2 (Dynamic Explorer) during high solar activity show evidence of anomalous latitudinal variations in the zonal winds and temperature at low latitudes. The zonal winds exhibit a broad maximum centered around the dip equator, flanked by minima on either side around 25 degrees; while the temperature exhibits a pronounced bowl-shaped minimum at the dip equator which is flanked by maxima. The two minima in the zonal winds and the corresponding maxima in the temperature are nearly collocated with the crests of the well known Equatorial Ionization Anomaly (EIA). The maximum in the zonal winds and the minimum in the gas temperature are collected with the trough of the EIA. The differences between the maxima and minima in temperature and zonal winds, on many occasions, are observed to exceed 100 K and 100 m/s, respectively. The characteristics of this new phenomenon have eluded present day empirical models of thermospheric temperature and winds. The connection among these variables can be understood from the ion-neutral drag effect on the motions of the neutrals that in turn affect their energy balance

  14. Plasma instabilities multifrequency study in equatorial electrojet

    International Nuclear Information System (INIS)

    Hanuise, C.

    1983-01-01

    In this thesis, multifrequential HF coherent radar results are presented, in the field plasma instabilities in equatorial electrojet. In a first part, characteristics of the irregularities observed either at the 3 meter wavelength by VHF radars, either at other wavelengths during pinpoint experiments, or in-situ by probe rockets are recalled. Theoretical studies progressed and are presented, at the same time with these experimental observations: instability linear theory, non linear theories, HF radar specificity, and problems associated to HF waves propagation and refraction in ionosphere. Original experimental results from Ethiopia are gathered in the second part. Plasma instability has been studied in different geophysical conditions and Doppler spectra characteristics are presented for each one of them. These characteristics are completely different according to the various cases; they are also different according to wether observations are made during the day in normal conditions (electric field pointed to the east at the equator) or in counter-electrojet conditions (electric field pointed to the west). The last part is concerned with theoretical interpretation of the previous results. A comprehensive view of the instability physical mechanisms, according to the geophysical conditions encountered, has been allowed by our results, VHF radar measurements at Jicamarca, or in situ probe measurements on the whole. Irregularities study has been limited to the E region [fr

  15. Condor equatorial electrojet campaign: Radar results

    International Nuclear Information System (INIS)

    Kudeki, E.; Fejer, B.G.; Farley, D.T.; Hanuise, C.

    1987-01-01

    A review of the experimental and theoretical background to the Condor equatorial electrojet compaign is followed by the presentation and discussion of VHF radar interferometer and HF radar backscatter data taken concurrently with two rocket in situ experiments reported in companion papers (Pfaff et al., this issue (a, b). Both experiments were conducted in strongly driven periods with the on-line radar interferometer displaying signatures of what has been interpreted in earlier radar work (Kudeki et al., 1982) as kilometer scale gradient drift waves. Low-frequency density fluctuations detected by in situ rocket sensors confirm the earlier interpretation. VHF radar/rocket data comparisons also indicate the existence of a turbulent layer in the upper portion of the daytime electrojet at about 108 km altitude driven purely by the two-stream instability. Nonlinear mode coupling of linearly growing two-stream waves to linearly damped 3-m vertical modes could account for the radar echoes scattered from this layer, which showed no indication of large-scale gradient drift waves. Nonlinear mode coupling may therefore compete with the wave-induced anomalous diffusion mechanism proposed recently by Sudan (1983) for the saturation of directly excited two-stream waves. Nighttime radar data show a bifurcated layer with the two parts having comparable echo strength but oppositely directed zonal drift velocities. The lower layer shows narrow backscatter spectra; the upper layer is characterized by kilometer scale waves and vertically propagating type 1 waves

  16. Radiation protection in hospitals of Equatorial Guinea

    International Nuclear Information System (INIS)

    Rabat Macambo, P.

    2001-01-01

    With a population of four hundred thousand (400.000) inhabitants and distributed in a territory of 28 thousand (28.000) km 2 , the use of ionizing radiations for medical practice in Equatorial Guinea is few and decreasing. It is used for diagnostic practices in the main hospitals of the country, where the work burden is not over 20 patients per day. The political, social and economical embryonic development of the country until recently had a negative influence on indicators and health organisations, so that even now the country does not have any radiological protection law, this shortness, in addition with the old architectural structure that x ray tools is lodging, as well as dosimetrical lack of employed staff, put this staff under risk of electromagnetic energy. This is to show the present survey of medical activities with ionizing radiation and to request technical support for implementing suitably the basic standards of radiation protection which will help us as basis for the elaboration outline law, on radiological protection in accordance with the new guidelines of the International Atomic Energy Agency. (author)

  17. Intraseasonal vertical velocity variation caused by the equatorial wave in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Horii, T.; Masumoto, Y.; Ueki, I.; PrasannaKumar, S.; Mizuno, K.

    to the theoretical solution of the equatorial waves [Matsuno, 1966] and the phase speed of the baroclinic mode, the wave that has meridional current on the equator with a quasi-biweekly period is the anti-symmetric mixed Rossby-gravity wave. In the wave... and conclusions are given in section 5. 2. Field Experiment, Data, and Methods 2.1. MISMO Ocean Observation [8] The goal of MISMO was to observe atmospheric conditions and variability associated with intraseasonal disturbances and resulting ocean responses...

  18. Time dependent response of equatorial ionospheric electric fieldsto magnetospheric disturbances

    OpenAIRE

    Fejer, Bela G.; Scherliess, L.

    1995-01-01

    We use extensive radar measurements of F region vertical plasma drifts and auroral electrojet indices to determine the storm time dependence of equatorial zonal electric fields. These disturbance drifts result from the prompt penetration of high latitude electric fields and from the dynamo action of storm time winds which produce largest perturbations a few hours after the onset of magnetic activity. The signatures of the equatorial disturbance electric fields change significantly depending o...

  19. Performance evaluation of GPS receiver under equatorial scintillation

    Directory of Open Access Journals (Sweden)

    Alison de Oliveira Moraes

    2009-06-01

    Full Text Available Equatorial scintillation is a phenomenon that occurs daily in the equatorial region after the sunset and affects radio signals that propagate through the ionosphere. Depending on the temporal and spatial situation, equatorial scintillation can represent a problem in the availability and precision of the Global Positioning System (GPS. This work is concerned with evaluating the impact of equatorial scintillation on the performance of GPS receivers. First, the morphology and statistical model of equatorial scintillation is briefly presented. A numerical model that generates synthetic scintillation data to simulate the effects of equatorial scintillation is presented. An overview of the main theoretical principles on GPS receivers is presented. The analytical models that describe the effects of scintillation at receiver level are presented and compared with numerical simulations using a radio software receiver and synthetic data. The results achieved by simulation agreed quite well with those predicted by the analytical models. The only exception is for links with extreme levels of scintillation and when weak signals are received.

  20. A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude regions.

    Science.gov (United States)

    Zhang, Luyuan; Hou, Xiaolin; Li, Hong-Chun; Xu, Xiaomei

    2018-02-01

    The influence of human nuclear activities on environmental radioactivity is not well known at low latitude regions that are distant from nuclear test sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for 129 I and 127 I to investigate this influence in a low-latitude terrestrial system. A baseline of 129 I/ 127 I atomic ratios was established at (2.04-5.14) × 10 -12 in the pre-nuclear era in this region. Controlled by the northeasterly equatorial trade winds, increased 129 I/ 127 I ratios of (20.1-69.3) × 10 -12 suggest that atmospheric nuclear weapons tests at the Pacific Proving Grounds in the central Pacific Ocean was the major source of 129 I in the sediment during 1956-1962. The 129 I/ 127 I ratios, up to 157.5 × 10 -12 after 1964, indicate a strong influence by European nuclear fuel reprocessing plants. The East Asian Winter Monsoon is found to be the dominant driving force in the atmospheric dispersion of radioactive iodine ( 129 I) from the European nuclear fuel reprocessing plants to Southeast Asia, which is also important for dispersion of other airborne pollutants from the middle-high to low latitude regions. A significant 129 I/ 127 I peak at 42.8 cm in the Taal Lake core appears to be the signal of the Chernobyl accident in 1986. In addition, volcanic activities are reflected in the iodine isotope profiles in the sediment core, suggesting the potential of using iodine isotopes as an indicator of volcanic eruptions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Compaction of microfossil and clay-rich chalk sediments

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    2001-01-01

    The aim of this study was to evaluate the role of microfossils and clay in the compaction of chalk facies sediments. To meet this aim, chalk sediments with varying micro texture were studied. The sediments have been tested uniaxially confined in a stainless-steel compaction cell. The sediments are......: 1) Pure carbonate chalk with mudstone texture from Stevns Klint (Denmark), 2) Relatively pure chalk sediments with varying content of microfossils from the Ontong Java Plateau (Western Pacific), 3) Clay-rich chalk and mixed sediments from the Caribbean. The tested samples were characterised...

  2. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    Science.gov (United States)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  3. Water masses in the Humboldt Current System: Properties, distribution, and the nitrate deficit as a chemical water mass tracer for Equatorial Subsurface Water off Chile

    Science.gov (United States)

    Silva, Nelson; Rojas, Nora; Fedele, Aldo

    2009-07-01

    Three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern South Pacific and their distributions. Oceanographic data were taken from the SCORPIO (May-June 1967), PIQUERO (May-June 1969), and KRILL (June 1974) cruises. Vertical sections of temperature, salinity, σ θ, dissolved oxygen, nitrate, nitrite, phosphate, and silicate were used to analyze the water column structure. Five water masses were identified in the zone through T- S diagrams: Subantarctic Water, Subtropical Water, Equatorial Subsurface Water, Antarctic Intermediate Water, and Pacific Deep Water. Their proportions in the sea water mixture are calculated using the mixing triangle method. Vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m. Several characteristic oceanographic features in the study area were analyzed: the shallow salinity minimum displacement towards the equator, the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south, and the equatorward intermediate Antarctic salinity minimum associated with a dissolved oxygen maximum. The nitrate deficit generated in the denitrification area off Peru and northern Chile is proposed as a conservative chemical tracer for the Equatorial Subsurface Waters off the coast of Chile, south of 25°S.

  4. Impact of effective ocean optical properties on the Pacific subtropical cell: a CGCM study

    Science.gov (United States)

    Yamanaka, G.; Tsujino, H.; Ishizaki, H.; Nakano, H.; Hirabara, M.

    2012-12-01

    The choice of ocean radiant scheme is important for modeling the upper ocean. According to the ocean-only simulation (Yamanaka et al., 2012), introduction of the chlorophyll-a dependent ocean radiant scheme results in the decreased mixed layer depth (MLD), the enhanced subtropical cell (STC), and the cooling of the eastern tropical Pacific sea surface temperature (SST). They also found that the enhanced STC results from the velocity profile change associated with the decreased Ekman boundary layer. However, the impact is not well understood when the air-sea feedback process is at work. This study examines the impact of the effective ocean optical properties on the Pacific mean fields, especially focusing on the STC, using a coupled general circulation model (CGCM). The CGCM we employed is the Meteorological Research Institute Earth System Model (MRI-ESM1). The atmospheric model is TL159L48, and the ocean model has a horizontal resolution of 1 x 0.5 deg. with 51 levels in vertical. Experimental design basically follows the CMIP5 protocol. Two experiments (CTL and SLR runs) are performed to investigate the impact of the effective ocean optical properties. In the CTL run, a conventional ocean radiant heating scheme (Paul and Simpson, 1977) is used, whereas a new ocean radiant heating scheme is used in the SLR run, where the satellite-derived chlorophyll-a distribution is taken into consideration based on Morel and Antoine (1994) as well as the effect of the varying solar angle (Ishizaki and Yamanaka, 2010). Each experiment is integrated during the period from 1985 to 2005. It is found that introduction of the new ocean radiant scheme (SLR run) changes the long-term mean wind pattern in the Pacific: easterly winds are strengthened in the equatorial Pacific, but weakened in the off-equatorial region. In the tropical Pacific, the enhanced equatorial upwelling cools the equatorial SST and the MLD becomes shallower. This is similar to the ocean-only simulation, but is more

  5. Nonlinear bounce resonances between magnetosonic waves and equatorially mirroring electrons

    Science.gov (United States)

    Chen, Lunjin; Maldonado, Armando; Bortnik, Jacob; Thorne, Richard M.; Li, Jinxing; Dai, Lei; Zhan, Xiaoya

    2015-08-01

    Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the flux of these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from an equatorial pitch angle of 90° down to lower values. However, this mechanism has not been uniquely identified yet. Here we investigate the mechanism of bounce resonance with equatorial noise (or fast magnetosonic waves). A test particle simulation is used to examine the effects of monochromatic magnetosonic waves on the equatorially mirroring energetic electrons, with a special interest in characterizing the effectiveness of bounce resonances. Our analysis shows that bounce resonances can occur at the first three harmonics of the bounce frequency (nωb, n = 1, 2, and 3) and can effectively reduce the equatorial pitch angle to values where resonant scattering by whistler mode waves becomes possible. We demonstrate that the nature of bounce resonance is nonlinear, and we propose a nonlinear oscillation model for characterizing bounce resonances using two key parameters, effective wave amplitude à and normalized wave number k~z. The threshold for higher harmonic resonance is more strict, favoring higher à and k~z, and the change in equatorial pitch angle is strongly controlled by k~z. We also investigate the dependence of bounce resonance effects on various physical parameters, including wave amplitude, frequency, wave normal angle and initial phase, plasma density, and electron energy. It is found that the effect of bounce resonance is sensitive to the wave normal angle. We suggest that the bounce resonant interaction might lead to an observed pitch angle distribution with a minimum at 90°.

  6. Association of whale sharks (Rhincodon typus) with thermo-biological frontal systems of the eastern tropical Pacific.

    Science.gov (United States)

    Ryan, John P; Green, Jonathan R; Espinoza, Eduardo; Hearn, Alex R

    2017-01-01

    Satellite tracking of 27 whale sharks in the eastern tropical Pacific, examined in relation to environmental data, indicates preferential occupancy of thermo-biological frontal systems. In these systems, thermal gradients are caused by wind-forced circulation and mixing, and biological gradients are caused by associated nutrient enrichment and enhanced primary productivity. Two of the frontal systems result from upwelling, driven by divergence in the current systems along the equator and the west coast of South America; the third results from wind jet dynamics off Central America. All whale sharks were tagged near Darwin Island, Galápagos, within the equatorial Pacific upwelling system. Occupancy of frontal habitat is pronounced in synoptic patterns of shark locations in relation to serpentine, temporally varying thermal fronts across a zonal expanse > 4000 km. 80% of shark positions in northern equatorial upwelling habitat and 100% of positions in eastern boundary upwelling habitat were located within the upwelling front. Analysis of equatorial shark locations relative to thermal gradients reveals occupancy of a transition point in environmental stability. Equatorial subsurface tag data show residence in shallow, warm (>22°C) water 94% of the time. Surface zonal current speeds for all equatorial tracking explain only 16% of the variance in shark zonal movement speeds, indicating that passive drifting is not a primary determinant of movement patterns. Movement from equatorial to eastern boundary frontal zones occurred during boreal winter, when equatorial upwelling weakens seasonally. Off Peru sharks tracked upwelling frontal positions within ~100-350 km from the coast. Off Central America, the largest tagged shark (12.8 m TL) occupied an oceanic front along the periphery of the Panama wind jet. Seasonal movement from waning equatorial upwelling to productive eastern boundary habitat is consistent with underlying trophic dynamics. Persistent shallow residence in

  7. Contribution of CRUST2.0 components to the tri-axiality of the Earth and equatorial flattening of the core

    Directory of Open Access Journals (Sweden)

    Sun Rong

    2013-08-01

    Full Text Available Equatorial flattening of the core were previously estimated to be 5 × 10−4 by using seismically derived density anomaly, and 1.7748280 × 10−5 by assuming that the ratio of polar flattening to equatorial flattening of the core is the same as that of the whole Earth. In this study, we attempted to explain the difference by applying a density-contrast stripping process to the crust in the second method. We use the CRUST2.0 model to estimate the inertia-moment contribution resulted from the density-contrast structure in the crust to a tri-axial Earth. The contribution of the density contrast in the crust was removed layer by layer. The layers include topography, bathymetry, ice, soft sediment, hard sediment, upper crust, middle crust, lower crust and the reference crust. For the boundaries of the topography and bathymetry layers, we used ETOPO5 values with a resolution of 5'. For boundaries of other layers, we used values from the CRUST2.0 model with a resolution of 2°. After the contribution of density contrast is stripped, the equatorial flattening of the core was found to be 6.544 × 10−5, which is still one order of magnitude smaller than the result given by the first method. This suggests that at least one of the methods is not correct. The influence of the uncertainty in the equatorial flattening of the core on the Free Core Nutation frequency is small, but its effect on the gravitational torque acting on the tri-axial inner core cannot be ignored. So an accurate determination of the equatorial flattening of the core is still necessary.

  8. The growth and decay of equatorial backscatter plumes

    Science.gov (United States)

    Tsunoda, R. T.

    1980-02-01

    During the past three years, a series of rocket experiments from the Kwajalein Atoll, Marshall Islands, were conducted to investigate the character of intense, scintillation-producing irregularities that occur in the nighttime equatorial ionosphere. Because the source mechanism of equatorial irregularities, believed to be the Rayleigh-Taylor instability, is analogous to that which generates plasma-density striations in a nuclear-induced environment, there is considerable interest in the underlying physics that controls the characteristics of these irregularities. A primary objective of ALTAIR investigations of equatorial irregularities is to seek an understanding of the underlying physics by establishing the relationship between meter-scale irregularities (detected by ALTAIR), and the large-scale plasma-density depletions (or 'bubbles') that contain the kilometer-scale, scintillation-producing irregularities. We describe the time evolution of backscatter 'plumes' produced by one meter equatorial field-aligned irregularities. Using ALTAIR, a fully steerable backscatter radar, to repeatedly map selected plumes, we characterize the dynamic behavior of plumes in terms of growth and a decay phase. Most of the observed characteristics are found to be consistent with equatorial-irregularity generation predicted by current theories of Rayleigh-Taylor and gradient-drift instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the bottomside F layer in establishing the initial conditions for plume growth.

  9. Manganese in the North Pacific

    International Nuclear Information System (INIS)

    Bruland, K.W.; Landing, W.M.

    1980-01-01

    A quantitative and precise method for determination of dissolved M (nmol)/kg level in seawater has been developed and used to study the distribution of Mn in the northeast Pacific. Mn concentrations in the surface mixed layer decrease from 1.0 to 0.6 nmol/kg between the central gyre and the western boundary of the California Current, then increase to values from 2 to 6 nmol/kg near the coastal boundary (in contrast to the distribution of 210 Pb). Particulate Mn in the surface waters accounts for only about 1% of the total. Vertical distributions of Mn are characterized by surface maxima, minima near 300 m, maxima at mid-depth coinciding with the oxygen minimum and the labile nutrient maxima, and concentrations in Pacific bottom waters of approximately 0.2 nmol/kg. The oceanic distribution of Mn appears to be dominated by external inputs superimposed upon ovberall scavenging which can lead to Mn maxima in (1) the surface waters due to riverine and atmospheric sources; (2) the deep ocean as a result of hydrothermal injection and/or sediment resuspension; and (3) the oxygen minimum region resulting from in-situ breakdown of organic matter, in-situ MnO 2 reduction, and/or advective-diffusive transport of dissolved Mn from anoxic slope sediments. (orig.)

  10. Effect of geomagnetic storm conditions on the equatorial ionization anomaly and equatorial temperature anomaly

    Science.gov (United States)

    Bharti, Gaurav; Bag, T.; Sunil Krishna, M. V.

    2018-03-01

    The effect of the geomagnetic storm on the equatorial ionization anomaly (EIA) and equatorial temperature anomaly (ETA) has been studied using the atomic oxygen dayglow emissions at 577.7 nm (OI 557.7 nm) and 732.0 nm (OII 732.0 nm). For the purpose of this study, four intense geomagnetic storms during the ascending phase of solar cycle 24 have been considered. This study is primarily based on the results obtained using photochemical models with necessary inputs from theoretical studies and experimental observations. The latest reaction rate coefficients, quantum yields and the corresponding cross-sections have also been incorporated in these models. The volume emission rate of airglow emissions has been calculated using the neutral densities from NRLMSISE-00 and charged densities from IRI-2012 model. The modeled volume emission rate (VER) for OI 557.7 nm shows a positive correlation with the Dst index at 150 km and negative correlation with Dst at 250 and 280 km altitudes. Latitudinal profile of the greenline emission rate at different altitudes show a distinct behaviour similar to what has been observed in EIA with crests on either sides of the equator. The EIA crests are found to show poleward movement in the higher altitude regions. The volume emission rate of 732.0 nm emission shows a strong enhancement during the main phase of the storm. The changes observed in the airglow emission rates are explained with the help of variations induced in neutral densities and parameters related to EIA and ETA. The latitudinal variation of 732.0 nm emission rate is correlated to the variability in EIA during the storm period.

  11. ­Orbital-scale variations in Indo-Pacific hydroclimate during the mid- to late Pleistocene from Lake Towuti, Indonesia

    Science.gov (United States)

    Russell, J. M.; Vogel, H.; Bijaksana, S.; Melles, M.

    2016-12-01

    The Indo-Pacific region plays a critical role in the Earth's climate system. Changes in local insolation, greenhouse gas concentrations, ice volume, and local sea level are all hypothesized to exert a dominant control on Indo-Pacific hydroclimate, yet existing records from the region are generally short and exhibit fundamental differences in orbital-scale patterns that limit our understanding of the regional climate responses to orbital-scale forcings. In 2015 we conducted an ICDP drilling program on Lake Towuti, located near the equator in central Indonesia, one of the only terrestrial sedimentary archives in the region that continuously spans multiple glacial-interglacial cycles. We recovered over 1,000 meters of core including cores though the entire sediment sequence to bedrock. Previously published organic geochemical reconstructions of vegetation from relatively short, 60 kyr long piston from Lake Towuti exhibit strong drying during the Last Glacial Maximum, indicating that central Indonesian hydroclimate is sensitive to forcing from high-latitude ice-sheets. New, inorganic geochemical and mineralogical reconstructions of lake level also indicate a strong half-precessional climate signal during the last 60 kyr in which lake level highstands occur during austral and boreal summer insolation maxima, suggesting that equatorial rainfall varies in response to remote (likely subtropical) insolation forcing of the Asian monsoons. However, the short length of these records limits our understanding of the regional hydroclimatic response to the full range of global climate boundary conditions experienced during the late Quaternary. This presentation will discuss results from the last 60 kyr and present new geochemical reconstructions from the upper 100 m of core from Lake Towuti, dated using magnetic paleointensity, tephrachronology, and optically-stimulated luminescence to span the last 500 kyr BP.

  12. Space Weather Research in the Equatorial Region: A Philosophical Reinforcement

    Science.gov (United States)

    Chukwuma, Victor; Odunaike, Rasaki; Laoye, John

    Investigations using radio waves reflected from the ionosphere, at high-and mid-latitudes indicate that ionospheric absorption can strongly increase following geomagnetic storms; which appears to suggest some definite relationship between ionospheric radio wave absorption and geomagnetic storms at these latitudes. However, corresponding earlier studies in the equatorial region did not appear to show any explicit relationship between ionospheric radio wave absorption and geomagnetic storm activity. This position appeared acceptable to the existing scientific paradigm, until in an act of paradigm shift, by a change of storm selection criteria, some more recent space weather investigations in the low latitudes showed that ionospheric radio wave absorption in the equatorial region clearly increases after intense storms. Given that these results in the equatorial region stood against the earlier results, this paper presently attempts to highlight their philosophical underpinning and posit that they constitute a scientific statement.

  13. Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

    Directory of Open Access Journals (Sweden)

    Chao-Song Huang

    2011-01-01

    Full Text Available An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles are generated after the interplanetary magnetic field (IMF turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMF Bz, the maximum value of the interplanetary electric field (IEF Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

  14. Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California

    Science.gov (United States)

    Hagstrum, J.T.; Murchey, B.L.; Bogar, R.S.

    1996-01-01

    Lower Jurassic radiolarian chert sampled at two localities in the San Rafael Mountains of southern California (???20 km north of Santa Barbara) contains four components of remanent magnetization. Components A, B???, and B are inferred to represent uplift, Miocene volcanism, and subduction/accretion overprint magnetizations, respectively. The fourth component (C), isolated between 580?? and 680??C, shows a magnetic polarity stratigraphy and is interpreted as a primary magnetization acquired by the chert during, or soon after, deposition. Both sequences are late Pliensbachian to middle Toarcian in age, and an average paleolatitude calculated from all tilt-corrected C components is 1?? ?? 3?? north or south. This result is consistent with deposition of the cherts beneath the equatorial zone of high biologic productivity and is similar to initial paleolatitudes determined for chert blocks in northern California and Mexico. This result supports our model in which deep-water Franciscan-type cherts were deposited on the Farallon plate as it moved eastward beneath the equatorial productivity high, were accreted to the continental margin at low paleolatitudes, and were subsequently distributed northward by strike-slip faulting associated with movements of the Kula, Farallon, and Pacific plates. Upper Cretaceous turbidites of the Cachuma Formation were sampled at Agua Caliente Canyon to determine a constraining paleolatitude for accretion of the Jurassic chert sequences. These apparently unaltered rocks, however, were found to be completely overprinted by the A component of magnetization. Similar in situ directions and demagnetization behaviors observed in samples of other Upper Cretaceous turbidite sequences in southern and Baja California imply that these rocks might also give unreliable results.

  15. The Genesis of Tropical Cyclone Bilis (2000) Associated with Cross-equatorial Surges

    Institute of Scientific and Technical Information of China (English)

    XU Yamei

    2011-01-01

    The purpose of this paper is to explore how a tropical cyclone forms from a pre-existing large-scale depression which has been observed and associated with cross-equatorial surges in the western North Pacific. Tropical cyclone Bilis (2000) was selected as the case to study. The research data used are from the results of the non-hydrostatic mesoscale model (MM5), which has successfully simulated the transformation of a pre-existing weak large-scale tropical depression into a strong tropical storm. The scale separation technique is used to separate the synoptic-scale and sub-synoptic-scale fields from the model output fields. The scale-separated fields show that the pre-existing synoptic-scale tropical depression and the subsynoptic scale tropical cyclone formed later were different scale systems from beginning to end. It is also shown that the pre-existing synoptic-scale tropical depression did not contract to become the tropical cyclone. A series of weak, sub-synoptic-scale low and high pressure systems appeared and disappeared in the synopticscale depression, with one of the low systems near the center of the synoptic-scale depression having deepened to become the tropical cyclone. The roles of the synoptic-scale flow and the sub-synoptic scale disturbances in the formation of the tropical cyclone are investigated by diagnoses of the scale-separated vertical vorticity equation. The results show that the early development of the sub-synoptic scale vortex was fundamentally dependent on the strengthening synoptic-scale environmental depression. The depression was strengthened by cross-equatorial surges, which increased the convergence of the synoptic-scale depression at low levels and triggered the formation of the tropical cyclone.

  16. Planktonic and Benthic Foraminifers as Geochemical Proxies Recording Hydrographic Changes in the Eastern Equatorial Pacific

    OpenAIRE

    Böschen, Tebke

    2013-01-01

    Oxygen Minimum Zones (OMZs) in the ocean represent key regions for the interaction between atmosphere and ocean waters and can be a sink or source for atmospheric CO2. Hence, they play a major role with respect to anthropogenic induced global warming. Biological productivity is very high in these areas and resulting degradation processes consume substantial amounts of dissolved oxygen from the water column, leaving certain water depths almost oxygen‐free. One of the largest and most distincti...

  17. Productivity and fishing pressure drive variability in fish parasite assemblages of the Line Islands, equatorial Pacific.

    Science.gov (United States)

    Wood, Chelsea L; Baum, Julia K; Reddy, Sheila M W; Trebilco, Rowan; Sandin, Stuart A; Zgliczynski, Brian J; Briggs, Amy A; Micheli, Fiorenza

    2015-05-01

    Variability in primary productivity and fishing pressure can shape the abundance, species composition, and diversity of marine life. Though parasites comprise nearly half of marine species, their responses to these important forces remain little explored. We quantified parasite assemblages at two spatial scales, across a gradient in productivity and fishing pressure that spans six coral islands of the Line Islands archipelago and within the largest Line Island, Kiritimati, which experiences a west-to-east gradient in fishing pressure and upwelling-driven productivity. In the across-islands data set, we found that increasing productivity was correlated with increased parasite abundance overall, but that the effects of productivity differed among parasite groups. Trophically transmitted parasites increased in abundance with increasing productivity, but directly transmitted parasites did not exhibit significant changes. This probably arises because productivity has stronger effects on the abundance of the planktonic crustaceans and herbivorous snails that serve as the intermediate hosts of trophically transmitted parasites than on the higher-trophic level fishes that are the sole hosts of directly transmitted parasites. We also found that specialist parasites increased in response to increasing productivity, while generalists did not, possibly because specialist parasites tend to be more strongly limited by host availability than are generalist parasites. After the effect of productivity was controlled for, fishing was correlated with decreases in the abundance of trophically transmitted parasites, while directly transmitted parasites appeared to track host density; we observed increases in the abundance of parasites using hosts that experienced fishing-driven compensatory increases in abundance. The within-island data set confirmed these patterns for the combined effects of productivity and fishing on parasite abundance, suggesting that our conclusions are robust across a span of spatial scales. Overall, these results indicate that there are strong and variable effects of anthropogenic and natural drivers on parasite abundance and taxonomic richness. These effects are likely to be mediated by parasite traits, particularly by parasite transmission strategies.

  18. The Climatological Seasonal Response of the Ocean Mixed Layer in the Equatorial and Tropical Pacific Ocean

    Science.gov (United States)

    1988-03-01

    response of the ocean and the seasonal changes in atmospheric forcing. The pattern of 20 DiSTPIBUTION/ AVAILABILIT Y OF aRS7RACT 21 ABSTRACT SECURITY...Speed with M LD .............................. 50 3.20 Time Rate of Change of Heat in the Water Column at 155 oE Contour Interval is 35W m 2...52 3.21 Dilerence of Net Surface Heating ad Heat .* the Water Column at 155 oE

  19. Particulate silica and Si recycling in the surface waters of the Eastern Equatorial Pacific

    DEFF Research Database (Denmark)

    Adjou, Mohamed; Tréguer, Paul; Dumousseaud, Cynthia

    2011-01-01

    SiO2) was generally waters. These low concentrations confirm low atmospheric inputs of particulate Si, consistent with reported low inputs of wind-borne material in the EEP. In spite of active upwelling of silicic acid......-rich waters the biogenic silica (bSiO2) concentrations were generally low, falling between 100 and 180 nmol Si l-1 in the upper 50 m and decreasing to less than 50 nmol Si l-1 below ~90 m. Estimates of net bSiO2 production rates revealed that the rate of production exceeded that of dissolution in the upper...

  20. Molecular characterization of Cryptosporidium isolates from humans in Equatorial Guinea.

    Science.gov (United States)

    Blanco, María Alejandra; Iborra, Asunción; Vargas, Antonio; Nsie, Eugenia; Mbá, Luciano; Fuentes, Isabel

    2009-12-01

    The aim of the study was to perform a molecular characterization of clinical isolates of Cryptosporidium species from Equatorial Guinea. Standard laboratory methods were used to identify 35 cryptosporidiosis cases among 185 patients. PCR-RFLP successfully identified 34 Cryptosporidium species from these 35 cases, comprising C. parvum (52.9%), C. hominis (44.1%) and C. meleagridis (2.9%); over 90% of the species were isolated from HIV-positive patients. This is the first report of the molecular characterization of Cryptosporidium species isolated from humans in Equatorial Guinea and shows that zoonotic and anthroponotic transmission is present in this country.

  1. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    Science.gov (United States)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  2. Instability of equatorial protons in Jupiter's mid-magnetosphere

    International Nuclear Information System (INIS)

    Northrop, T.G.; Schardt, A.W.

    1980-01-01

    Two different models for the distribution function are fit to the Jovian protons seen by Pioneer 10 inbound. The models reproduce the observed energy and angular distributions. These models are then used to assess the collisionless mirror instability. Because of the pancake proton angular distributions in the equatorial ring current region, the ring current particle population appears to be mirror unstable at times, with instability growth rates of approx.10 min. Such a time is consistent with observed proton flux autocorrelation times. An instability such as this (there are other candidates) may be responsible for the previously established proton flux flowing parallel to the magnetic field away from the equatorial region

  3. Enhanced Influence of the Tropical Atlantic SST on the Western North Pacific Subtropical High after late 1970s

    Science.gov (United States)

    Hong, C. C.

    2015-12-01

    The western North Pacific subtropical high (WNPSH) in boreal summer shows a remarkable enhancement after the late 1970s. Whereas the sea surface temperature (SST) in the North Indian Ocean (NIO) and the equatorial eastern Pacific (EEP) had been noted to have remarkable local or remote effects on enhancing the WNPSH, the influence of the Atlantic SST, so far, is hardly explored. This article reports a new finding: enhanced relationship between the tropical Atlantic (TA)-SST and the WNPSH after the late 1970s. Regression study suggests that the warm TA-SST produced a zonally overturning circulation anomaly, with descending over the central equatorial Pacific and ascending over the tropical Atlantic/eastern Pacific. The anomalous descending over the central equatorial Pacific likely induced low-level anticyclonic anomaly to the west and therefore enhanced the WNPSH. One implication of this new finding is for predictability. The well-known "spring predictability barrier" (i.e., the influence of El Niño and Southern Oscillation (ENSO) falls dramatically during boreal spring) does not apply to the TA-SST/WNPSH relationship. Conversely, the TA-SST shows consistently high correlation starting from boreal spring when the ENSO influence continues declining. The TA-SST pushes the predictability of the WNPSH in boreal summer approximately one season earlier to boreal spring.

  4. Decadal fluctuations in the western Pacific recorded by long precipitation records in Taiwan

    Science.gov (United States)

    Huang, Wan-Ru; Wang, S.-Y. Simon; Guan, Biing T.

    2018-03-01

    A 110-year precipitation record in Taiwan, located at the western edge of the subtropical North Pacific, depicts a pronounced quasi-decadal oscillation (QDO). The QDO in Taiwan exhibits a fluctuating relationship with the similar decadal variations of sea surface temperature (SST) anomalies in the central equatorial Pacific, known as the Pacific QDO. A regime change was observed around 1960, such that the decadal variation of Taiwan's precipitation became more synchronized with the Pacific QDO's coupled evolutions of SST and atmospheric circulation than before, while the underlying pattern of the Pacific QOD did not change. Using long-term reanalysis data and CMIP5 single-forcing experiments, the presented analysis suggests that increased SST in the subtropical western Pacific and the strengthened western extension of the North Pacific subtropical anticyclone may have collectively enhanced the relationship between the Taiwan precipitation and the Pacific QDO. This finding provides possible clues to similar regime changes in quasi-decadal variability observed around the western Pacific rim.

  5. Circulation, eddies, oxygen, and nutrient changes in the eastern tropical South Pacific Ocean

    Science.gov (United States)

    Czeschel, R.; Stramma, L.; Weller, R. A.; Fischer, T.

    2015-06-01

    A large subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off the coast of Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the equatorial undercurrent (EUC) is centered at 250 m depth, deeper than in earlier observations. In December 2012, the equatorial water is transported southeastward near the shelf in the Peru-Chile undercurrent (PCUC) with a mean transport of 1.4 Sv. In the oxygen minimum zone (OMZ), the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m-3 yr-1 extrapolated to an annual rate and 7.7 mmol C m-3 yr-1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation (IPO), by the phase of El Niño, by seasonal changes, and by eddies, and hence have to be interpreted with care. At and south of the Equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part silicate.

  6. Radiocarbon dating of sediment cores from Hachinohe, the Kamikita Plain

    International Nuclear Information System (INIS)

    Hitoki, Eri; Nakamura, Toshio; Matsumoto, Yui; Tsuji, Sei-ichiro; Fujine, Hisashi

    2013-01-01

    We investigated stratigraphy and chronology by analyses of Holocene sediments and radiocarbon dating of sediment cores from the Kamikita Plain. On the Kamikita Plain, which faces the Pacific coast of Northeast Japan, marine and fluvial terraces covered with tephras derived from Towada and Hakkoda volcanoes are well developed. We clarified that Towada Chuseri tephra and fluvial deposits consisted of volcanic sediments influenced an alluvial depositional system in the Kamikita Plain after a maximum of the Jomon Transgression. (author)

  7. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  8. Community Structure of Denitrifiers, Bacteria, and Archaea along Redox Gradients in Pacific Northwest Marine Sediments by Terminal Restriction Fragment Length Polymorphism Analysis of Amplified Nitrite Reductase (nirS) and 16S rRNA Genes

    Science.gov (United States)

    Braker, Gesche; Ayala-del-Río, Héctor L.; Devol, Allan H.; Fesefeldt, Andreas; Tiedje, James M.

    2001-01-01

    Steep vertical gradients of oxidants (O2 and NO3−) in Puget Sound and Washington continental margin sediments indicate that aerobic respiration and denitrification occur within the top few millimeters to centimeters. To systematically explore the underlying communities of denitrifiers, Bacteria, and Archaea along redox gradients at distant geographic locations, nitrite reductase (nirS) genes and bacterial and archaeal 16S rRNA genes (rDNAs) were PCR amplified and analyzed by terminal restriction fragment length polymorphism (T-RFLP) analysis. The suitablility of T-RFLP analysis for investigating communities of nirS-containing denitrifiers was established by the correspondence of dominant terminal restriction fragments (T-RFs) of nirS to computer-simulated T-RFs of nirS clones. These clones belonged to clusters II, III, and IV from the same cores and were analyzed in a previous study (G. Braker, J. Zhou, L. Wu, A. H. Devol, and J. M. Tiedje, Appl. Environ. Microbiol. 66:2096–2104, 2000). T-RFLP analysis of nirS and bacterial rDNA revealed a high level of functional and phylogenetic diversity, whereas the level of diversity of Archaea was lower. A comparison of T-RFLPs based on the presence or absence of T-RFs and correspondence analysis based on the frequencies and heights of T-RFs allowed us to group sediment samples according to the sampling location and thus clearly distinguish Puget Sound and the Washington margin populations. However, changes in community structure within sediment core sections during the transition from aerobic to anaerobic conditions were minor. Thus, within the top layers of marine sediments, redox gradients seem to result from the differential metabolic activities of populations of similar communities, probably through mixing by marine invertebrates rather than from the development of distinct communities. PMID:11282647

  9. Equatorial electrojet in the Indian region during the geomagnetic ...

    Indian Academy of Sciences (India)

    1998-11-14

    Nov 14, 1998 ... In the recovery phase of the storm, the electric field due to shielding layer penetrates to equatorial latitudes as an overshielding electric field with opposite polarity, westward during day- side and eastward during night side (Kelley et al. 1979). In addition to the prompt penetration elec- tric fields, there are ...

  10. Climate regulation of fire emissions and deforestation in equatorial Asia

    NARCIS (Netherlands)

    van der Werf, G. R.; Dempewolf, J.; Trigg, S. N.; Randerson, J. T.; Kasibhatla, P. S.; Giglio, L.; Murdiyarso, D.; Peters, W.; Morton, D. C.; Collatz, G. J.; Dolman, A. J.; Defries, R. S.

    2008-01-01

    Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire

  11. Backscatter measurements of 11-cm equatorial spread-F irregularities

    International Nuclear Information System (INIS)

    Tsunoda, R.T.

    1980-01-01

    In the equatorial F-region ionosphere, a turbulent cascade process has been found to exist that extends from irregularity spatial wavelengths longer than tens of kilometers down to wavelengths as short as 36 cm. To investigate the small-scale regime of wavelengths less than 36 cm, an equatorial radar experiment was conducted using a frequency of 1320 MHz that corresponds to an irregularity wavelength of 11 cm. The first observations of radar backscatter from 11-cm field-aligned irregularities (FAI) are described. These measurements extend the spatial wavelength regime of F-region FAI to lengths that approach both electron gyroradius and the Debye length. Agreement of these results with the theory of high-frequency drift waves suggests that these observations may be unique to the equatorial ionosphere. That is, the requirement of low electron densities for which the theroy calls may preclude the existence of 11-cm FAI elsewhere in the F-region ionosphere, except in equatorial plasma bubbles

  12. Characterisation of tectonic lineaments in the Central Equatorial ...

    African Journals Online (AJOL)

    Characterisation of tectonic lineaments in the Central Equatorial Atlantic region of Africa using Bouguer anomaly gravity data. ... Ife Journal of Science ... 3-D standard Euler deconvolution analysis was carried out on Bouguer anomaly gravity data for configuration definition and approximate depth estimate of tectonic ...

  13. Planktonic foraminifera from core tops of western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Guptha, M.V.S.

    distributional pattern showing upward trend in its abundance from 38 per cent at 21 degrees S latitude to 0.8 per cent at 6 degrees N latitude. Sub-tropical fauna is sparsely distributed in the Equatorial Indian Ocean. Based on these studies it is interpreted...

  14. equatorial electrojet strength in the african sector during high

    African Journals Online (AJOL)

    Preferred Customer

    shown to be consistent with the earlier similar work carried out for the American and ... reference to the quiet day night time level of H, ... February and July, and shifts equator ward to 27°N ... effect of the equatorial electrojet along this line is.

  15. Radar observation of the equatorial counter-electrojet

    International Nuclear Information System (INIS)

    Hanuise, C.; Crochet, M.; Gouin, P.; Ogubazghi, Ghebrebrhan

    1979-01-01

    Electron drift velocity in the equatorial electrojet has been measured for a few years by coherent radar techniques in Africa. For the first time such measurements were performed during a strong reversal of the ionospheric current dubbed 'counter-electrojet'. These observations agree with the theories of the plasma instabilities at the origin of the electron density irregularities giving the radar echoes

  16. Parallel responses of bees to Pleistocene climate change in three isolated archipelagos of the southwestern Pacific

    OpenAIRE

    Groom, Scott V. C.; Stevens, Mark I.; Schwarz, Michael P.

    2014-01-01

    The impacts of glacial cycles on the geographical distribution and size of populations have been explored for numerous terrestrial and marine taxa. However, most studies have focused on high latitudes, with only a few focused on the response of biota to the last glacial maximum (LGM) in equatorial regions. Here, we examine how population sizes of key bee fauna in the southwest Pacific archipelagos of Fiji, Vanuatu and Samoa have fluctuated over the Quaternary. We show that all three island fa...

  17. Post-midnight occurrence of equatorial plasma bubbles

    Science.gov (United States)

    Ajith, K. K.; Otsuka, Yuichi; Yamamoto, Mamoru; Yokoyama, Tatsuhiro; Tulasiram, S.

    2016-07-01

    The equatorial plasma bubbles (EPBs)/equatorial spread F (ESF) irregularities are an important topic of space weather interest because of their impact on transionospheric radio communications, satellite-based navigation and augmentation systems. This local plasma depleted structures develop at the bottom side F layer through Rayleigh-Taylor instability and rapidly grow to topside ionosphere via polarization electric fields within them. The steep vertical gradients due to quick loss of bottom side ionization and rapid uplift of equatorial F layer via prereversal enhancement (PRE) of zonal electric field makes the post-sunset hours as the most preferred local time for the formation of EPBs. However, there is a different class of irregularities that occurs during the post-midnight hours of June solstice reported by the previous studies. The occurrence of these post-midnight EPBs maximize during the low solar activity periods. The growth characteristics and the responsible mechanism for the formation of these post-midnight EPBs are not yet understood. Using the rapid beam steering ability of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. The responsible mechanism for the genesis of summer time post-midnight EPBs were discussed in light of growth rate of Rayleigh-Taylor instability using SAMI2 model.

  18. Impacts of the Tropical Pacific Cold Tongue Mode on ENSO Diversity Under Global Warming

    Science.gov (United States)

    Li, Yang; Li, Jianping; Zhang, Wenjun; Chen, Quanliang; Feng, Juan; Zheng, Fei; Wang, Wei; Zhou, Xin

    2017-11-01

    The causes of ENSO diversity, although being of great interest in recent research, do not have a consistent explanation. This study provides a possible mechanism focused on the background change of the tropical Pacific as a response to global warming. The second empirical orthogonal function mode of the sea surface temperature anomalies (SSTA) in the tropical Pacific, namely the cold tongue mode (CTM), represents the background change of the tropical Pacific under global warming. Using composite analysis with surface observations and subsurface ocean assimilation data sets, we find ENSO spatial structure diversity is closely associated with the CTM. A positive CTM tends to cool the SST in the eastern equatorial Pacific and warm the SST outside, as well as widen (narrow) zonal and meridional scales for El Niño (La Niña), and vice versa. Particularly in the positive CTM phase, the air-sea action center of El Niño moves west, resembling the spatial pattern of CP-El Niño. This westward shift of center is related to the weakened Bjerknes feedback (BF) intensity by the CTM. By suppressing the SSTA growth of El Niño in the eastern equatorial Pacific, the CTM contributes to more frequent occurrence of CP-El Niño under global warming.

  19. Understanding the El Niño-like Oceanic Response in the Tropical Pacific to Global Warming

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yiyong; Lu, Jian; Liu, Fukai; Liu, Wei

    2015-10-10

    The enhanced central and eastern Pacific SST warming and the associated ocean processes under global warming are investigated using the ocean component of the Community Earth System Model (CESM), Parallel Ocean Program version 2 (POP2). The tropical SST warming pattern in the coupled CESM can be faithfully reproduced by the POP2 forced with surface fluxes computed using the aerodynamic bulk formula. By prescribing the wind stress and/or wind speed through the bulk formula, the effects of wind stress change and/or the wind-evaporation-SST (WES) feedback are isolated and their linearity is evaluated in this ocean-alone setting. Result shows that, although the weakening of the equatorial easterlies contributes positively to the El Niño-like SST warming, 80% of which can be simulated by the POP2 without considering the effects of wind change in both mechanical and thermodynamic fluxes. This result points to the importance of the air-sea thermal interaction and the relative feebleness of the ocean dynamical process in the El Niño-like equatorial Pacific SST response to global warming. On the other hand, the wind stress change is found to play a dominant role in the oceanic response in the tropical Pacific, accounting for most of the changes in the equatorial ocean current system and thermal structures, including the weakening of the surface westward currents, the enhancement of the near-surface stratification and the shoaling of the equatorial thermocline. Interestingly, greenhouse gas warming in the absence of wind stress change and WES feedback also contributes substantially to the changes at the subsurface equatorial Pacific. Further, this warming impact can be largely replicated by an idealized ocean experiment forced by a uniform surface heat flux, whereby, arguably, a purest form of oceanic dynamical thermostat is revealed.

  20. Anthropogenic Pu distribution in Tropical East Pacific

    International Nuclear Information System (INIS)

    Kinoshita, Norikazu; Sumi, Takahiro; Takimoto, Kiyotaka; Nagaoka, Mika; Yokoyama, Akihiko; Nakanishi, Takashi

    2011-01-01

    The geographical distribution of the anthropogenic radionuclides 238 Pu and 239+240 Pu in the Tropical East Pacific in 2003 was studied from the viewpoint of material migration. We measured the contents of Pu isotopes in seawater and in sediment from the sea bottom. The distributions of Pu isotopes, together with those of coexisting nitrate and phosphate species and dissolved oxygen, are discussed in relation to the potential temperature and potential density (sigma-θ). The Pu contents in sediment samples were compared with those in the seawater. Horizontal migration across the Equator from north to south was investigated at depths down to ∼ 800 m in the eastern Pacific. The Pu distribution at 0-400 m correlated well with the distribution of potential temperature. Maximum Pu levels were observed in the subsurface layer at 600-800 m, corresponding to the depth where sigma-θ ∼ 27.0. It is suggested that the Pu distribution depends on the structure of the water mass and the particular temperature and salinity. The water column/sediment column inventory ratio and the vertical distribution of Pu may reflect the efficiency of scavenging in the relevant water areas. Research Highlights: → Geographical distributions of Pu isotopes were investigated from viewpoint of material migration. → Horizontal migration from north to south was found at depths down to ∼800 m in the eastern Pacific. → Pu distribution at 0-400 m was correlated with water temperature. → The distribution at 600-800 m correlated with water mass structure. → Pu in seawater and sediment gave information about efficiency of scavenging.

  1. The IOD-ENSO precursory teleconnection over the tropical Indo-Pacific Ocean: dynamics and long-term trends under global warming

    Science.gov (United States)

    Yuan, Dongliang; Hu, Xiaoyue; Xu, Peng; Zhao, Xia; Masumoto, Yukio; Han, Weiqing

    2018-01-01

    The dynamics of the teleconnection between the Indian Ocean Dipole (IOD) in the tropical Indian Ocean and El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%-15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.

  2. Possible influence of long-term sea surface temperature anomalies in the tropical Pacific on global zone

    Energy Technology Data Exchange (ETDEWEB)

    Komhyr, W D; Oltmans, S J; Grass, R D [Atmospheric Administration Climate Monitoring and Diagnostics Lab., Boulder, CO (USA); Leonard, R K [Colorado Univ., Boulder, CO (USA)

    1991-01-01

    A significant negative correlation exists between summer sea surface temperatures (SSTs) in the east equatorial Pacific and late-October south pole total ozone values. SSTs in the eastern equatorial Pacific were anomalously warmer during 1976-1987 compared with 1962-1975. QBO (quasi-biennial oscillation) easterly winds in the equatorial Pacific stratosphere were generally stronger after 1975. Before the early-to-mid 1970s the trend in global ozone was generally upward, but then turned downward. Total ozone at Hawaii and Samoa, which had been decreasing during 1976-1987, showed recovery to mid-1970s values in 1988-1989 following a drop in SSTs in the eastern equatorial Pacific to low values last observed there prior to 1976. During late October 1988, total south pole ozone, which had decreased from ca 280 Dobson units (DU) before 1980 to 140 DU in 1987, suddenly recovered to 250 DU, though substantial ozone depletion by heterogeneous photochemical processes involving polar stratospheric clouds was still evident in the south pole ozone vertical profiles. These observations suggest that the downward trend in ozone observed over the globe in recent years may have been at least partly meteorologically induced, possibly via modulation by the warmer tropical Pacific ocean waters of QBO easterly winds at the equator, of Hadley Cell circulation, or other factors. A cursory analysis of geostrophic wind flow around the Baffin Island low suggests a meteorological influence on the observed downward trend in ozone over North America during the past decade. Because ozone has a lifetime that varies from years to minutes, changes in atmospheric dynamics have a potential to not only redistribute ozone over the globe but also to change global ozone abundance. 47 refs., 5 figs., 1 tab.

  3. ENSO regimes and the late 1970's climate shift: The role of synoptic weather and South Pacific ocean spiciness

    International Nuclear Information System (INIS)

    O'Kane, Terence J.; Matear, Richard J.; Chamberlain, Matthew A.; Oke, Peter R.

    2014-01-01

    South Pacific subtropical density compensated temperature and salinity (spiciness) anomalies are known to be associated with decadal equatorial variability, however, the mechanisms by which such disturbances are generated, advect and the degree to which they modulate the equatorial thermocline remains controversial. During the late 1970's a climate regime transition preceded a period of strong and sustained El Nino events. Using an ocean general circulation model forced by the constituent mechanical and thermodynamic components of the reanalysed atmosphere we show that the late 1970's transition coincided with the arrival of a large-scale, subsurface cold and fresh water anomaly in the central tropical Pacific. An ocean reanalysis for the period 1990–2007 that assimilates subsurface Argo, XBT and CTD data, reveals that disturbances occur due to the subduction of negative surface salinity anomalies from near 30° S, 100° W which are advected along the σ=25–26 kgm −3 isopycnal surfaces. These anomalies take, on average, seven years to reach the central equatorial Pacific where they may substantially perturb the thermocline before the remnants ultimately ventilate in the region of the western Pacific warm pool. Positive (warm–salty) disturbances, known to occur due to late winter diapycnal mixing and isopycnal outcropping, arise due to both subduction of subtropical mode waters and subsurface injection. On reaching the equatorial band (10° S–0° S) these disturbances tend to deepen the thermocline reducing the model's ENSO. In contrast the emergence of negative (cold–fresh) disturbances at the equator are associated with a shoaling of the thermocline and El Nino events. Process studies are used to show that the generation and advection of anomalous density compensated thermocline disturbances critically depend on stochastic forcing of the intrinsic ocean by weather. We further show that in the absence of the inter-annual component of the atmosphere

  4. Global mode of Pi2 waves in the equatorial region

    International Nuclear Information System (INIS)

    Kitamura, Tai-ichi; Saka, Ousuke; Shimoizumi, Masashi

    1988-01-01

    Fluxgate magnetometers with accurate timing data logger were set up at two equatorial stations (Garous-Marous and Huancayo), and also at a middle latitude station (Kuju). The phase of Pi2 waves is compared among these stations. It is found that 1) Pi2 pulsations in low and equatorial latitudes are linearly polarized approximately along the magnetic meridian, 2) phase difference of the H component of Pi2 waves at different stations is much less than 1 - 10 of the pulsation period despite a large longitudinal separation (∼ 90 deg) of the stations, showing the so-called azimuthal wave number, m, to be much less than unity and 3) phase difference of the D component at different stations is variable. (author)

  5. Ongoing Analysis of Jupiter's Equatorial Hotspots and Plumes from Cassini

    Science.gov (United States)

    Choi, D. S.; Showmwn, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated results from our ongoing analysis of Cassini observations of Jupiter's equatorial meteorology. For two months preceding the spacecraft's closest approach of the planet, the ISS instrument onboard Cassini regularly imaged the atmosphere of Jupiter. We created time-lapse movies from this period that show the complex activity and interactions of the equatorial atmosphere. During this period, hot spots exhibited significant variations in size and shape over timescales of days and weeks. Some of these changes appear to be a result of interactions with passing vortex systems in adjacent latitudes. Strong anticyclonic gyres to the southeast of the dark areas converge with flow from the west and appear to circulate into a hot spot at its southwestern corner.

  6. Bottomside sinusoidal irregularities in the equatorial F region

    Science.gov (United States)

    Valladares, C. E.; Hanson, W. B.; Mcclure, J. P.; Cragin, B. L.

    1983-01-01

    By using the Ogo 6 satellite, McClure and Hanson (1973) have discovered sinusoidal irregularities in the equatorial F region ion number density. In the present investigation, a description is provided of the properties of a distinct category of sinusoidal irregularities found in equatorial data from the AE-C and AE-E satellites. The observed scale sizes vary from about 300 m to 3 km in the direction perpendicular to B, overlapping with and extending the range observed by using Ogo 6. Attention is given to low and high resolution data, a comparison with Huancayo ionograms, the confinement of 'bottomside sinusoidal' (BSS) irregularities essentially to the bottomside of the F layer, spectral characteristics, and BSS, scintillation, and ionosonde observations.

  7. Nonlinearly coupled dynamics of irregularities in the equatorial electrojet

    Energy Technology Data Exchange (ETDEWEB)

    Atul, J.K., E-mail: jkatulphysics@gmail.com [Department of Physics, College of Commerce under Magadh University, Patna 800020 (India); Sarkar, S. [FCIPT, Institute for Plasma Research, Gandhinagar 382428 (India); Singh, S.K. [Department of Physics, College of Commerce under Magadh University, Patna 800020 (India)

    2016-04-01

    Kinetic wave description is used to study the nonlinear influence of background Farley Buneman (FB) modes on the Gradient Drift (GD) modes in the equatorial electrojet ionosphere. The dominant nonlinearity is mediated through the electron flux term in the governing fluid equation which further invokes a turbulent current into the system. Electron dynamics reveals the modification in electron collision frequency and inhomogeneity scale length. It is seen that the propagation and growth rate of GD modes get modified by the background FB modes. Also, a new quasimode gets excited through the quadratic dispersion relation. Physical significance of coupled dynamics between the participating modes is also discussed. - Highlights: • Nonlinear influence of Farley Buneman mode on the Gradient drift mode, is investigated. • Electron collision frequency and density gradient scale length get modified. • A new quasimode gets excited due to the competition between these modes. • It seems to be important for modelling of Equatorial Electrojet current system.

  8. Equatorial enhancement of the nighttime OH mesospheric infrared airglow

    International Nuclear Information System (INIS)

    Baker, D J; Thurgood, B K; Harrison, W K; Mlynczak, M G; Russell, J M

    2007-01-01

    Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (Δv=2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H+O 3 is being reacted. At both the spring and autumn seasonal equinoxes when the equatorial solar UV irradiance mean is greatest, the peak volume emission rate (VER) of the nighttime Meinel infrared airglow typically appears to be both significantly brighter plus lower in altitude by several kilometres at low latitudes compared with midlatitude findings

  9. Nonlinearly coupled dynamics of irregularities in the equatorial electrojet

    International Nuclear Information System (INIS)

    Atul, J.K.; Sarkar, S.; Singh, S.K.

    2016-01-01

    Kinetic wave description is used to study the nonlinear influence of background Farley Buneman (FB) modes on the Gradient Drift (GD) modes in the equatorial electrojet ionosphere. The dominant nonlinearity is mediated through the electron flux term in the governing fluid equation which further invokes a turbulent current into the system. Electron dynamics reveals the modification in electron collision frequency and inhomogeneity scale length. It is seen that the propagation and growth rate of GD modes get modified by the background FB modes. Also, a new quasimode gets excited through the quadratic dispersion relation. Physical significance of coupled dynamics between the participating modes is also discussed. - Highlights: • Nonlinear influence of Farley Buneman mode on the Gradient drift mode, is investigated. • Electron collision frequency and density gradient scale length get modified. • A new quasimode gets excited due to the competition between these modes. • It seems to be important for modelling of Equatorial Electrojet current system.

  10. Saturn's equatorial jet structure from Cassini/ISS

    Science.gov (United States)

    García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

    2010-05-01

    Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  11. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    Science.gov (United States)

    Choi, David Sanghun; Showman, Adam P.; Vasavada, Ashwin R.; Simon-Miller, Amy A.

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are relatively cloud-free regions that emit strongly at 5 lm; improved knowledge of these features is crucial for fully understanding Galileo probe measurements taken during its descent through one. Hot spots are quasistable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-like 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. These clouds travel at 150-200 m/s, much faster than the 100 m/s hot spot and plume drift speed. This raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. Most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby wave controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed.

  12. Equatorial noise emissions with quasiperiodic modulation of wave intensity

    Czech Academy of Sciences Publication Activity Database

    Němec, F.; Santolík, Ondřej; Hrbáčková, Zuzana; Pickett, J. S.; Cornilleau-Wehrlin, N.

    2015-01-01

    Roč. 120, č. 4 (2015), s. 2649-2661 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH11122 Institutional support: RVO:68378289 Keywords : equatorial noise * magnetosonic waves * quasiperiodic modulation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.318, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020816/full

  13. Increases of equatorial total electron content (TEC) during magnetic storms

    International Nuclear Information System (INIS)

    Yeboah-Amankwah, D.

    1976-01-01

    This paper is a report on the analysis of equatorial electron content, TEC, during magnetic storms. Storms between 1969 and 1972 have been examined as part of an on-going study of TEC morphology during magnetically disturbed days. The published magnetic Ksup(p) indices and TEC data from the Legon abservatory have been employed. The general picture arising from the analysis is that the total electron content of the ionosphere is significantly enhanced during magnetic storms. (author)

  14. Seasonal predictions of equatorial Atlantic SST in a low-resolution CGCM with surface heat flux correction

    Science.gov (United States)

    Dippe, Tina; Greatbatch, Richard; Ding, Hui

    2016-04-01

    The dominant mode of interannual variability in tropical Atlantic sea surface temperatures (SSTs) is the Atlantic Niño or Zonal Mode. Akin to the El Niño-Southern Oscillation in the Pacific sector, it is able to impact the climate both of the adjacent equatorial African continent and remote regions. Due to heavy biases in the mean state climate of the equatorial-to-subtropical Atlantic, however, most state-of-the-art coupled global climate models (CGCMs) are unable to realistically simulate equatorial Atlantic variability. In this study, the Kiel Climate Model (KCM) is used to investigate the impact of a simple bias alleviation technique on the predictability of equatorial Atlantic SSTs. Two sets of seasonal forecasting experiments are performed: An experiment using the standard KCM (STD), and an experiment with additional surface heat flux correction (FLX) that efficiently removes the SST bias from simulations. Initial conditions for both experiments are generated by the KCM run in partially coupled mode, a simple assimilation technique that forces the KCM with observed wind stress anomalies and preserves SST as a fully prognostic variable. Seasonal predictions for both sets of experiments are run four times yearly for 1981-2012. Results: Heat flux correction substantially improves the simulated variability in the initialization runs for boreal summer and fall (June-October). In boreal spring (March-May), however, neither the initialization runs of the STD or FLX-experiments are able to capture the observed variability. FLX-predictions show no consistent enhancement of skill relative to the predictions of the STD experiment over the course of the year. The skill of persistence forecasts is hardly beat by either of the two experiments in any season, limiting the usefulness of the few forecasts that show significant skill. However, FLX-forecasts initialized in May recover skill in July and August, the peak season of the Atlantic Niño (anomaly correlation

  15. Regional Variations of REE Patterns in Sediments from Active Plate Boundaries

    DEFF Research Database (Denmark)

    Kunzendorf, H.; Stoffers, P.; Gwozdz, R.

    1988-01-01

    About 150 sediment samples from mid-ocean ridges (East Pacific Rise, Central Indian Ocean Ridge, Carlsberg Ridge and the Red Sea) and from a back-arc spreading environment (Lau Basin) were analyzed by instrumental neutron activation. A ratio method for rare-earth elements involving a plot...... of elemental ratios of Ce/La and Ce/Yb is proposed to characterize marine sediments. In the characterization plot East Pacific Rise and Lau Basin sediments occupy distinct fields in the plot suggesting hydrothermal overprint, while sediments from the Central Indian Ocean and the Carlsberg Ridge plot...

  16. Sources and processes affecting the distribution of dissolved Nd isotopes and concentrations in the West Pacific

    Science.gov (United States)

    Behrens, Melanie K.; Pahnke, Katharina; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2018-02-01

    Intermediate Water, and Lower Circumpolar Deep Water in the southern and equatorial West Pacific are marked by vertically and laterally almost invariant [Nd] indicating a dominance of conservative behavior of [Nd]. In contrast, Central and Intermediate Water in the North West Pacific are characterized by increasing [Nd] with depth reflecting Nd release from particles. Overall, our data demonstrate a dominant lateral transport control on [Nd] distributions and clear non-conservative modification of ɛNd in the West Pacific. The latter affords tracing of surface and subsurface zonal transport in the tropical Pacific, but prevents the use of ɛNd as strictly conservative tracer of the major meridionally circulating water masses in the West Pacific between 15°S and 28°N.

  17. Indo-Pacific sea level variability at multidecadal time scales

    Science.gov (United States)

    Merrifield, M. A.; Thompson, P. R.

    2016-12-01

    Long tide gauge and atmospheric pressure measurements are used to infer multidecadal fluctuations in trade wind forcing and the associated Indo-Pacific sea level response along coastal and equatorial waveguides. The trade wind variations are marked by a weakening beginning with the late 1970s climate shift and a subsequent return to mean conditions since the early 1990s. These fluctuations covary with multidecadal wind changes at mid-latitudes, as measured by the Pacific Decadal Oscillation or the North Pacific indices; however, the mid-latitude multidecadal variations prior to 1970 or noticeably absent in the inferred trade wind record. The different behavior of tropical and mid-latitude winds support the notion that multidecadal climate variations in the Pacific result from a combination of processes and not a single coherent mode spanning the basin. In particular, the two-decade long satellite altimeter record represents a period of apparent connection between the two regions that was not exhibited earlier in the century.

  18. Assessment of the tropical Indo-Pacific climate in the SINTEX CGCM

    Directory of Open Access Journals (Sweden)

    P. Delecluse

    2003-06-01

    Full Text Available A new coupled GCM (SINTEX has been developed. The model is formed by the atmosphere model ECHAM-4 and the ocean model ORCA. The atmospheric and oceanic components are coupled through OASIS. The domain is global and no flux correction is applied. In this study, we describe the ability of the coupled model to simulate the main features of the observed climate and its dominant modes of variability in the tropical Indo-Pacific. Three long experiments have been performed with different horizontal resolution of the atmospheric component in order to assess a possible impact of the atmosphere model resolution onto the simulated climate. Overall, the mean state is captured reasonably well, though the simulated SST tends to be too warm in the tropical Eastern Pacific and there is a model tendency to produce a double ITCZ. The model gives also a realistic representation of the temperature structure at the equator in the Pacific and Indian Ocean. The slope and the structure of the equatorial thermocline are well reproduced. Compared to the observations, the simulated annual cycle appears to be underestimated in the eastern equatorial Pacific, whereas a too pronounced seasonal variation is found in the Central Pacific. The main basic features of the interannual variability in the tropical Indo-Pacific region are reasonably well reproduced by the model. In the Indian Ocean, the characteristics of the simulated interannual variability are very similar to the results found from the observations. In the Pacific, the modelled ENSO variability appears to be slightly weaker and the simulated period a bit shorter than in the observations. Our results suggest that, both the simulated mean state and interannual variability are generally improved when the horizontal resolution of the atmospheric mode component is increased.

  19. The cycling of transuranic radionuclides in the Columbia River, its estuary and the northeast Pacific Ocean: Final report

    International Nuclear Information System (INIS)

    Beasley, T.M.

    1987-01-01

    This review summarizes work during 1985 to 1986 on the radioecology of plutonium, americium and cesium in the Columbia River sediments; radionuclide kinetics of technetium in fish, and radioactivity in the Pacific Ocean

  20. Rare earth element distributions in the West Pacific: Trace element sources and conservative vs. non-conservative behavior

    Science.gov (United States)

    Behrens, Melanie K.; Pahnke, Katharina; Paffrath, Ronja; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2018-03-01

    Recent studies suggest that transport and water mass mixing may play a dominant role in controlling the distribution of dissolved rare earth element concentrations ([REE]) at least in parts of the North and South Atlantic and the Pacific Southern Ocean. Here we report vertically and spatially high-resolution profiles of dissolved REE concentrations ([REE]) along a NW-SE transect in the West Pacific and examine the processes affecting the [REE] distributions in this area. Surface water REE patterns reveal sources of trace element (TE) input near South Korea and in the tropical equatorial West Pacific. Positive europium anomalies and middle REE enrichments in surface and subsurface waters are indicative of TE input from volcanic islands and fingerprint in detail small-scale equatorial zonal eastward transport of TEs to the iron-limited tropical East Pacific. The low [REE] of North and South Pacific Tropical Waters and Antarctic Intermediate Water are a long-range (i.e., preformed) laterally advected signal, whereas increasing [REE] with depth within North Pacific Intermediate Water result from release from particles. Optimum multiparameter analysis of deep to bottom waters indicates a dominant control of lateral transport and mixing on [REE] at the depth of Lower Circumpolar Deep Water (≥3000 m water depth; ∼75-100% explained by water mass mixing), allowing the northward tracing of LCDW to ∼28°N in the Northwest Pacific. In contrast, scavenging in the hydrothermal plumes of the Lau Basin and Tonga-Fiji area at 1500-2000 m water depth leads to [REE] deficits (∼40-60% removal) and marked REE fractionation in the tropical West Pacific. Overall, our data provide evidence for active trace element input both near South Korea and Papua New Guinea, and for a strong lateral transport component in the distribution of dissolved REEs in large parts of the West Pacific.

  1. Oceanic Channel of the IOD-ENSO teleconnection over the Indo-Pacific Ocean

    Science.gov (United States)

    Yuan, Dongliang; Wang, Jing; Zhao, Xia; Zhou, Hui; Xu, Tengfei; Xu, Peng

    2017-04-01

    The lag correlations of observations and model simulated data that participate the Coupled Model Intercomparison Project phase-5 (CMIP5) are used to study the precursory teleconnection between the Indian Ocean Dipole (IOD) and the Pacific ENSO one year later through the Indonesian seas. The results suggest that Indonesian Throughflow (ITF) play an important role in the IOD-ENSO teleconnection. Numerical simulations using a hierarchy of ocean models and climate coupled models have shown that the interannual sea level depressions in the southeastern Indian Ocean during IOD force enhanced ITF to transport warm water of the Pacific warm pool to the Indian Ocean, producing cold subsurface temperature anomalies, which propagate to the eastern equatorial Pacific and induce significant coupled ocean-atmosphere evolution. The teleconnection is found to have decadal variability. Similar decadal variability has also been identified in the historical simulations of the CMIP5 models. The dynamics of the inter-basin teleconnection during the positive phases of the decadal variability are diagnosed to be the interannual variations of the ITF associated with the Indian Ocean Dipole (IOD). During the negative phases, the thermocline in the eastern equatorial Pacific is anomalously deeper so that the sea surface temperature anomalies in the cold tongue are not sensitive to the thermocline depth changes. The IOD-ENSO teleconnection is found not affected significantly by the anthropogenic forcing.

  2. Asia Pacific energy derivatives

    International Nuclear Information System (INIS)

    Fusaro, P.C.

    1997-09-01

    Asia Pacific Energy Derivatives, from FT Energy, is the first report of its kind to examine the growth of energy derivatives within Asia Pacific and their increasing importance within this region. It provides a comprehensive overview of the subject, including analysis of: deregulation as a market driver; the impact of privatisation; the future for energy risk management tools; the unique characteristics of the Asia Pacific energy market; the role of futures exchanges in Asia; existing indexes and their performance; the differences between the Asia Pacific markets and their more mature counterparts in London and New York; non-oil derivatives, project finance and cross commodity arbitrage; the thriving Pacific Rim Over the Counter (OTC) markets. (author)

  3. A south equatorial African precipitation dipole and the associated atmospheric circulation

    Science.gov (United States)

    Dezfuli, A. K.; Zaitchik, B.; Gnanadesikan, A.

    2013-12-01

    South Equatorial Africa (SEA) is a climatically diverse region that includes a dramatic topographic and vegetation contrast between the lowland, humid Congo basin to the west and the East African Plateau to the east. Due to lack of conventional weather data and a tendency for researchers to treat East and western Africa as separate regions, dynamics of the atmospheric water cycle across SEA have received relatively little attention, particularly at subseasonal timescales. Both western and eastern sectors of SEA are affected by large-scale drivers of the water cycle associated with Atlantic variability (western sector), Indian Ocean variability (eastern sector) and Pacific variability (both sectors). However, a specific characteristic of SEA is strong heterogeneity in interannual rainfall variability that cannot be explained by large-scale climatic phenomena. For this reason, this study examines regional climate dynamics on daily time-scale with a focus on the role that the abrupt topographic contrast between the lowland Congo and the East African highlands plays in driving rainfall behavior on short timescales. Analysis of daily precipitation data during November-March reveals a zonally-oriented dipole mode over SEA that explains the leading pattern of weather-scale precipitation variability in the region. The separating longitude of the two poles is coincident with the zonal variation of topography. An anomalous counter-clockwise atmospheric circulation associated with the dipole mode appears over the entire SEA. The circulation is triggered by its low-level westerly component, which is in turn generated by an interhemispheric pressure gradient. These enhanced westerlies hit the East African highlands and produce topographically-driven low-level convergence and convection that further intensifies the circulation. Recent studies have shown that under climate change the position and intensity of subtropical highs in both hemispheres and the intensity of

  4. The Pacific SST response to volcanic eruptions over the past millennium based on the CESM-LME

    Science.gov (United States)

    Man, W.; Zuo, M.

    2017-12-01

    The impact of the northern hemispheric, tropical and southern hemispheric volcanic eruptions on the Pacific sea surface temperature (SST) and its mechanism are investigated using the Community Earth System Model Last Millennium Ensemble. Analysis of the simulations indicates that the Pacific SST features a significant El Niño-like pattern a few months after the northern hemispheric and tropical eruptions, and with a weaker such tendency after the southern hemispheric eruptions. Furthermore, the Niño3 index peaks lagging one and a half years after the northern hemispheric and tropical eruptions. Two years after all three types of volcanic eruptions, a La Niña-like pattern over the equatorial Pacific is observed, which seems to form an El Niño-Southern Oscillation (ENSO) cycle. In addition, the westerly anomalies at 850 hPa over the western-to-central Pacific appear ahead of the warm SST; hence, the El Niño-like warming over the eastern Pacific can be attributed to the weakening of the trade winds. We further examined the causes of westerly anomalies and find that a shift of the intertropical convergence zone (ITCZ) can explain the El Niño-like response to the northern hemispheric eruptions, which is not applicable for tropical or southern hemispheric eruptions. Instead, the reduction in the zonal equatorial SST gradient through the ocean dynamical thermostat mechanism, combined with the land-sea thermal contrast between the Maritime Continent (MC) and the surrounding ocean and the divergent wind induced by the decreased precipitation over the MC, can trigger the westerly anomalies over the equatorial Pacific, which is applicable for all three types of eruptions.

  5. The Relationships between Tropical Pacific and Atlantic SST and Northeast Brazil Monthly Precipitation.

    Science.gov (United States)

    Bertacchi Uvo, Cintia; Repelli, Carlos A.; Zebiak, Stephen E.; Kushnir, Yochanan

    1998-04-01

    The monthly patterns of northeast Brazil (NEB) precipitation are analyzed in relation to sea surface temperature (SST) in the tropical Pacific and Atlantic Oceans, using singular value decomposition. It is found that the relationships between precipitation and SST in both basins vary considerably throughout the rainy season (February-May). In January, equatorial Pacific SST is weakly correlated with precipitation in small areas of southern NEB, but Atlantic SST shows no significant correlation with regional precipitation. In February, Pacific SST is not well related to precipitation, but south equatorial Atlantic SST is positively correlated with precipitation over the northern Nordeste, the latter most likely reflecting an anomalously early (or late) southward migration of the ITCZ precipitation zone. During March, equatorial Pacific SST is negatively correlated with Nordeste precipitation, but no consistent relationship between precipitation and Atlantic SST is found. Atlantic SST-precipitation correlations for April and May are the strongest found among all months or either ocean. Precipitation in the Nordeste is positively correlated with SST in the south tropical Atlantic and negatively correlated with SST in the north tropical Atlantic. These relationships are strong enough to determine the structure of the seasonal mean SST-precipitation correlations, even though the corresponding patterns for the earlier months of the season are quite different. Pacific SST-precipitation correlations for April and May are similar to those for March. Extreme wet (dry) years for the Nordeste occur when both Pacific and Atlantic SST patterns for April and May occur simultaneously. A separate analysis reinforces previous findings in showing that SST in the tropical Pacific and the northern tropical Atlantic are positively correlated and that tropical Pacific-south Atlantic correlations are negligible.Time-lagged analyses show the potential for forecasting either seasonal mean

  6. Role of sea surface temperature anomalies in the tropical Indo-Pacific region in the northeast Asia severe drought in summer 2014: month-to-month perspective

    Science.gov (United States)

    Xu, Zhiqing; Fan, Ke; Wang, HuiJun

    2017-09-01

    The severe drought over northeast Asia in summer 2014 and the contribution to it by sea surface temperature (SST) anomalies in the tropical Indo-Pacific region were investigated from the month-to-month perspective. The severe drought was accompanied by weak lower-level summer monsoon flow and featured an obvious northward movement during summer. The mid-latitude Asian summer (MAS) pattern and East Asia/Pacific teleconnection (EAP) pattern, induced by the Indian summer monsoon (ISM) and western North Pacific summer monsoon (WNPSM) rainfall anomalies respectively, were two main bridges between the SST anomalies in the tropical Indo-Pacific region and the severe drought. Warming in the Arabian Sea induced reduced rainfall over northeast India and then triggered a negative MAS pattern favoring the severe drought in June 2014. In July 2014, warming in the tropical western North Pacific led to a strong WNPSM and increased rainfall over the Philippine Sea, triggering a positive EAP pattern. The equatorial eastern Pacific and local warming resulted in increased rainfall over the off-equatorial western Pacific and triggered an EAP-like pattern. The EAP pattern and EAP-like pattern contributed to the severe drought in July 2014. A negative Indian Ocean dipole induced an anomalous meridional circulation, and warming in the equatorial eastern Pacific induced an anomalous zonal circulation, in August 2014. The two anomalous cells led to a weak ISM and WNPSM, triggering the negative MAS and EAP patterns responsible for the severe drought. Two possible reasons for the northward movement of the drought were also proposed.

  7. Analysis of longitudinal variations in North Pacific alkalinity

    Science.gov (United States)

    Fry, C.; Tyrrell, T.; Achterberg, E. P.

    2016-02-01

    Carbon measurements in the ocean lack the coverage of physical measurements, so approximate alkalinity is predicted where data is unavailable. Surface alkalinity in the North Pacific is poorly characterised by predictive algorithms. Understanding the processes affecting alkalinity in this area can improve the equations. We investigated the causes of regional variations in alkalinity using GLODAPv2. We tested different hypotheses for the causes of three longitudinal phenomena in surface ocean values of Alk*, a tracer of calcium carbonate cycling. These phenomena are: (a) an increase in Alk* from east to west at 50°N, (b) an increase in Alk* from west to east at 30°N, and (c) a lack of a strong increase in Alk* from west to east in the equatorial upwelling area. We found that the most likely cause of higher Alk* on the western side of the subpolar North Pacific (at 50°N) is that denser isopycnals with higher Alk* lie at shallower depths on the western side than the eastern side. At 30°N, the main cause of higher Alk* on the eastern side of the basin is upwelling along the continental shelf of southwestern North America. Along the equator, our analyses suggest that the absence of a strong east-west trend is because the more intense upwelling on the eastern side of the basin does not, under normal conditions, lead to strong elevation of Alk*. However, surface Alk* is more strongly elevated in the eastern Equatorial Pacific during negative phases of the El-Nino-Southern Oscillation, probably because the upwelled water comes from greater depth at these times.

  8. NW Pacific mid-depth ventilation changes during the Holocene

    Science.gov (United States)

    Rella, S.; Uchida, M.

    2010-12-01

    During the last 50 years the oxygen content of North Pacific Intermediate Water primarily originating in the Okhotsk Sea has declined suggesting decreased mid-depth water circulation, likely leading to changes in biological productivity in the NW Pacific realm and a decrease in CO2 drawdown. It is therefore of high interest to elucidate the climate-oceanic interconnections of the present interglacial period (Holocene) in the NW Pacific, in order to predict possible future climate and surface productivity changes associated with a decrease in mid-depth ventilation in this ecologically sensitive region. However, such efforts have been hampered so far by the lack of appropriate sediment cores with fast sedimentation rates during the Holocene. Core CK05-04 that was recovered in 2005 from off Shimokita peninsula, Japan, at ~1000 m depth shows sedimentation rates of ~80 cm/kyr during the Holocene and therefore presents an ideal opportunity to reconstruct for the first time the Holocene ventilation history of the NW Pacific Ocean. We employ Accelerator Mass Spectroscopy (NIES-TERRA, Tsukuba) radiocarbon analysis of co-existing benthic and planktonic foraminifera to conclude on the ventilation age of the mid-depth water using benthic-planktonic radiocarbon age differences. At the conference we would like to present the results.

  9. Longitudinal Variation of the Lunar Tide in the Equatorial Electrojet

    Science.gov (United States)

    Yamazaki, Yosuke; Stolle, Claudia; Matzka, Jürgen; Siddiqui, Tarique A.; Lühr, Hermann; Alken, Patrick

    2017-12-01

    The atmospheric lunar tide is one known source of ionospheric variability. The subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere. There is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude. We use magnetic field measurements from the CHAMP satellite during July 2000 to September 2010 and from the two Swarm satellites during November 2013 to February 2017 to determine, for the first time, the complete seasonal-longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity. Significant longitudinal variability is found in the amplitude of the lunar tidal variation, while the longitudinal variability in the phase is small. The amplitude peaks in the Peruvian sector (˜285°E) during the Northern Hemisphere winter and equinoxes, and in the Brazilian sector (˜325°E) during the Northern Hemisphere summer. There are also local amplitude maxima at ˜55°E and ˜120°E. The longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field. Another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides. A tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wave number 2 (SW2), with secondary contributions by westward propagating modes with zonal wave numbers 3 (SW3) and 4 (SW4). Eastward propagating waves are largely absent from the tidal spectrum. Further study will be required for the relative importance of ionospheric conductivities and nonmigrating lunar tides.

  10. New Measurements Of Jupiter's Equatorial Region In Visible Wavelengths

    Science.gov (United States)

    Rojas, Jose; Arregi, J.; García-Melendo, E.; Barrado-Izagirre, N.; Hueso, R.; Gómez-Forrellad, J. M.; Pérez-Hoyos, S.; Sanz-Requena, J. F.; Sánchez-Lavega, A.

    2010-10-01

    We have studied the equatorial region of Jupiter, between 15ºS and 15ºN, on Cassini ISS images obtained during the Jupiter flyby at the end of 2000 and on HST images acquired in May and July 2008. We have found significant longitudinal variations in the intensity of the 6ºN eastward jet, up to 60 m s-1 in Cassini and HST observations. In the HST case we found that these longitudinal variations are associated to different cloud morphology. Photometric and radiative transfer analysis of the cloud features used as tracers in HST images shows that there is only a small height difference, no larger than 0.5 - 1 scale heights at most, between the slow ( 100 m s-1) and fast ( 150 m s-1) moving features. This suggests that speed variability at 6ºN is not dominated by vertical wind shears and we propose that Rossby wave activity is the responsible for the zonal variability. After removing this variability we found that Jupiter's equatorial jet is actually symmetric relative to the equator with two peaks of 140 - 150 m s-1 located at latitudes 6ºN and 6ºS and at a similar pressure level. We also studied a large, long-lived feature called the White Spot (WS) located at 6ºS that turns to form and desapear. The internal flow field in the White Spot indicates that it is a weakly rotating quasi-equatorial anticyclone relative to the ambient meridionally sheared flow. Acknowledgements: This work was supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  11. Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

    Science.gov (United States)

    Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of approx.140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a approx.7-day period. This oscillating motion has a wavelength of approx.20 deg and a speed of approx.100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  12. Propagation of EMIC triggered emissions toward the magnetic equatorial plane

    Science.gov (United States)

    Grison, B.; Santolik, O.; Pickett, J. S.; Omura, Y.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P.; Cornilleau-Wehrlin, N.

    2011-12-01

    EMIC triggered emissions are observed close to the equatorial plane of the magnetosphere at locations where EMIC waves are commonly observed: close to the plasmapause region and in the dayside magnetosphere close to the magnetopause. Their overall characteristics (frequency with time dispersion, generation mechanism) make those waves the EMIC analogue of rising frequency whistler-mode chorus emissions. In our observations the Poynting flux of these emissions is usually clearly arriving from the equatorial region direction, especially when observations take place at more than 5 degrees of magnetic latitude. Simulations have also confirmed that the conditions of generation by interaction with energetic ions are at a maximum at the magnetic equator (lowest value of the background magnetic field along the field line). However in the Cluster case study presented here the Poynting flux of EMIC triggered emissions is propagating toward the equatorial region. The large angle between the wave vector and the background magnetic field is also unusual for this kind of emission. The rising tone starts just above half of the He+ gyrofrequency (Fhe+) and it disappears close to Fhe+. At the time of detection, the spacecraft magnetic latitude is larger than 10 degrees and L shell is about 4. The propagation sense of the emissions has been established using two independent methods: 1) sense of the parallel component of the Poynting flux for a single spacecraft and 2) timing of the emission detections at each of the four Cluster spacecraft which were in a relatively close configuration. We propose here to discuss this unexpected result considering a reflection of this emission at higher latitude.

  13. Equatorial storm sudden commencements and interplanetary magnetic field

    International Nuclear Information System (INIS)

    Rastogi, R.G.

    1980-01-01

    A comparison is made of the signatures of interplanetary (IP) shocks in the B and theta plots of interplanetary magnetic field (IMF) data of satellites Explorer 33, 34 and 35 and in the H magnetograms at ground observatories within the equatorial electrojet belt, Huancayo, Addis Ababa and Trivandrum associated with major storm sudden commencements during 1967-70. The IP shocks showing sudden increase of the scalar value of IMF, i.e. B without any change of the latitude theta or with the southward turning of theta, were followed by a purely positive sudden increase of H, at any of the magnetic observatories, either on the dayside or the nightside of the earth. The IP shocks identified by a sudden increase of B and with the northward turning of the latitude theta (positive ΔBsub(z)) were associated with purely positive sudden commencement (SC) at the observatories in the nightside, but at the equatorial observatories in the dayside of the earth the signature of the shock was a SC in H with a preliminary negative impulse followed by the main positive excursion (SC-+). It is suggested that the SCs in H at low latitudes are composed of two effects, viz. (i) one due to hydromagnetic pressure on the magnetosphere by the solar plasma and (ii) the other due to the induced electric field associated with the solar wind velocity, V and the Z-component of the IP magnetic field (E = - V x Bsub(z)). The effect of magnetosphere electric field is faster than the effect due to the compression of the magnetosphere by the impinging solar plasma. The negative impulse of SC-+ at low latitude is seen at stations close to the dip equator and only during daytime due to the existence of high ionospheric conductivities in the equatorial electrojet region. (author)

  14. Multiple nutrient stresses at intersecting Pacific Ocean biomes detected by protein biomarkers.

    Science.gov (United States)

    Saito, Mak A; McIlvin, Matthew R; Moran, Dawn M; Goepfert, Tyler J; DiTullio, Giacomo R; Post, Anton F; Lamborg, Carl H

    2014-09-05

    Marine primary productivity is strongly influenced by the scarcity of required nutrients, yet our understanding of these nutrient limitations is informed by experimental observations with sparse geographical coverage and methodological limitations. We developed a quantitative proteomic method to directly assess nutrient stress in high-light ecotypes of the abundant cyanobacterium Prochlorococcus across a meridional transect in the central Pacific Ocean. Multiple peptide biomarkers detected widespread and overlapping regions of nutritional stress for nitrogen and phosphorus in the North Pacific Subtropical Gyre and iron in the equatorial Pacific. Quantitative protein analyses demonstrated simultaneous stress for these nutrients at biome interfaces. This application of proteomic biomarkers to diagnose ocean metabolism demonstrated Prochlorococcus actively and simultaneously deploying multiple biochemical strategies for low-nutrient conditions in the oceans. Copyright © 2014, American Association for the Advancement of Science.

  15. Preliminary study on the characteristics of aerosols over the western pacific ocean

    International Nuclear Information System (INIS)

    Hu Zhaohui; Liu Pingsheng; Liu Shijie; Yao Ying; Feng Guohua

    1996-01-01

    Marine aerosol from the western Pacific were collected by two types of samplers during a cruise from Nanhai of China through the west of Philippines to the equatorial and to the north-eastern of Solomon Archipelago. Collected samples were analyzed by PIXE. The data gave aerosol characteristics over the western Pacific, including concentrations, enrichments and mass size distributions of detected elements, and possible sources of these elements were specially researched. The result indicates that Al, Si and Fe were associated with soil particles; Cl, Br, K, Ca and S showed characteristics of the sea-salt origin; and Cu, Zn, and Pb were due to pollution from long-range transport of continental aerosol. We have also made comparison with data obtained in earlier studies over other regions of the Pacific. (author)

  16. The isotopic signature of fallout plutonium in the North Pacific

    International Nuclear Information System (INIS)

    Buesseler, K.O.

    1997-01-01

    Plutonium analyses of a dated coral record from the French Frigate Shoals in the central North Pacific indicate that there are two major sources of Pu in this basin: close-in (tropospheric) fallout from nuclear weapons testing at the Pacific Proving Grounds in the Marshall Islands in the 1950s and global (stratospheric) fallout which peaked in 1962. Furthermore, the 240 Pu/ 239 Pu atom ratio of fallout from the Pacific Proving Grounds is characteristically higher (0.24) than that of global fallout Pu (0.18-0.19). Seawater and sediment samples from the North Pacific exhibit a wide range of 240 Pu/ 239 Pu values (0.19-0.34), with a trend towards higher ratios in the subsurface waters and sediment. Deep water 240 Pu/ 239 Pu ratios are higher in the vicinity of the Marshall Islands relative to stations further from this close-in fallout source. These preliminary data suggest that fallout Pu from the Pacific Proving Grounds is more rapidly removed from the surface waters than is global fallout Pu. Plutonium geochemistry appears to be related to the physical/chemical form of Pu-bearing particles generated by different fallout sources. (author)

  17. The isotopic signature of fallout plutonium in the North Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Buesseler, K.O. [Woods Hole Oceanographic Institution, MA (United States)

    1997-07-01

    Plutonium analyses of a dated coral record from the French Frigate Shoals in the central North Pacific indicate that there are two major sources of Pu in this basin: close-in (tropospheric) fallout from nuclear weapons testing at the Pacific Proving Grounds in the Marshall Islands in the 1950s and global (stratospheric) fallout which peaked in 1962. Furthermore, the {sup 240}Pu/{sup 239}Pu atom ratio of fallout from the Pacific Proving Grounds is characteristically higher (0.24) than that of global fallout Pu (0.18-0.19). Seawater and sediment samples from the North Pacific exhibit a wide range of {sup 240}Pu/{sup 239}Pu values (0.19-0.34), with a trend towards higher ratios in the subsurface waters and sediment. Deep water {sup 240}Pu/{sup 239}Pu ratios are higher in the vicinity of the Marshall Islands relative to stations further from this close-in fallout source. These preliminary data suggest that fallout Pu from the Pacific Proving Grounds is more rapidly removed from the surface waters than is global fallout Pu. Plutonium geochemistry appears to be related to the physical/chemical form of Pu-bearing particles generated by different fallout sources. (author).

  18. Variability in equatorial B0 and B1

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2002-01-01

    Variability of ionospheric profile parameters B0 and B1, below the F2 peak is investigated for an equatorial station at two levels of solar activities. The whole 24 hours of the day and the four seasons of the year are covered. Absolute and relative variability indices were utilized in the study. Some evidences of correlations of variability index and profiles parameters were observed. Daytime values of relative variability in B1 at solar minimum were found to be greater than those of solar maximum. (author)

  19. Teleconnections of the tropical Atlantic to the tropical Indian and Pacific Oceans. A review of recent findings

    Energy Technology Data Exchange (ETDEWEB)

    Wang Chunzai [NOAA Atlantic Oceanographic and Meteorological Lab., Miami, FL (United States); Kucharski, Fred; Barimalala, Rondrotiana [The Abdus Salam International Centre for Theoretical Physics, Earth System Physics, Section Trieste (Italy); Bracco, Annalisa [School of Earth and Atmospheric Sciences Georgia, Inst. of Tech., Atlanta, GA (United States)

    2009-08-15

    Recent studies found that tropical Atlantic variability may affect the climate in both the tropical Pacific and Indian Ocean basins, possibly modulating the Indian summer monsoon and Pacific ENSO events. A warm tropical Atlantic Ocean forces a Gill-Matsuno-type quadrupole response with a low-level anticyclone located over India that weakens the Indian monsoon circulation, and vice versa for a cold tropical Atlantic Ocean. The tropical Atlantic Ocean can also induce changes in the Indian Ocean sea surface temperatures (SSTs). especially along the coast of Africa and in the western side of the Indian basin. Additionally, it can influence the tropical Pacific Ocean via an atmospheric teleconnection that is associated with the Atlantic Walker circulation. Although the Pacific El Nino does not contemporaneously correlate with the Atlantic Nino, anomalous warming or cooling of the two equatorial oceans can form an inter-basin SST gradient that induces surface zonal wind anomalies over equatorial South America and other regions in both ocean basins. The zonal wind anomalies act as a bridge linking the two ocean basins, and in turn reinforce the inter-basin SST gradient through the atmospheric Walker circulation and oceanic processes. Thus, a positive feedback seems to exist for climate variability of the tropical Pacific-Atlantic Oceans and atmospheric system, in which the inter-basin SST gradient is coupled to the overlying atmospheric wind. (orig.)

  20. Quaternary carbonate record from the equatorial Indian Ocean and its relationship with productivity changes

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Malmgren, B.A.

    Globigerinoides ruber. This indicates that CaCO fluctuations at this site do not show either a 3 y2 y1 .Pacific or an Atlantic pattern of CaCO fluctuations. Fluxes of CaCO 0.38 to 2.46 g cm ka in total sediment and 33 y2 y1 .BarAl ratios 0.58 to 3.93 g cm ka... show six-fold variability through the last 1370 ka, which points out that productivity changes are significant at this site. Fluxes of the fine CaCO component demonstrate a 26-fold change 0.02 to 3 y2 y1 . y2 y1 .0.52 g cm ka , whereas the coarse Ca...

  1. Lenticellaria and Hillerella, new kraussinoid genera (Kraussinoidea, Brachiopoda) from Indo-Pacific and Red Sea waters: evolution in the subfamily Megerliinae.

    Science.gov (United States)

    Simon, Eric G; Logan, Alan; Zuschin, Martin; Mainguy, Jerome; Mottequin, Bernard

    2016-07-08

    Two new kraussinid brachiopod genera, namely Lenticellaria gen. nov. and Hillerella gen. nov. are described from Pacific waters in the sub-equatorial zone in the Indonesian Archipelago, from Indian Ocean waters in Madagascar and from Red Sea waters in Egypt (Gulf of Aqaba) and Sudan. This fills the equatorial gap in the distribution of the superfamily Kraussinoidea, known from higher latitudes in both hemispheres. The micromorphic new material described is an excellent example of homeomorphy in brachiopods. It also provides new information on the distribution of the genus Megerlia sensu stricto and illustrates subtle variations in the evolutionary process of the reduced brachidium in Kraussinoidea.

  2. Vertical Rise Velocity of Equatorial Plasma Bubbles Estimated from Equatorial Atmosphere Radar Observations and High-Resolution Bubble Model Simulations

    Science.gov (United States)

    Yokoyama, T.; Ajith, K. K.; Yamamoto, M.; Niranjan, K.

    2017-12-01

    Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionospheric F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPBs from a space weather point of view. The development of EPBs is presently believed as an evolution of the generalized Rayleigh-Taylor instability. We have already developed a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 1 km and presented nonlinear growth of EPBs which shows very turbulent internal structures such as bifurcation and pinching. As EPBs have field-aligned structures, the latitude range that is affected by EPBs depends on the apex altitude of EPBs over the dip equator. However, it was not easy to observe the apex altitude and vertical rise velocity of EPBs. Equatorial Atmosphere Radar (EAR) in Indonesia is capable of steering radar beams quickly so that the growth phase of EPBs can be captured clearly. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller compared to those observed in postsunset hours. Further, the vertical growth of the EPBs around midnight hours ceases at relatively lower altitudes, whereas the majority of EPBs at postsunset hours found to have grown beyond the maximum detectable altitude of the EAR. The HIRB model with varying background conditions are employed to investigate the possible factors that control the vertical rise velocity and maximum attainable altitudes of EPBs. The estimated rise velocities from EAR observations at both postsunset and midnight hours are, in general, consistent with the nonlinear evolution of EPBs from the HIRB model.

  3. Push from the Pacific

    Science.gov (United States)

    Jaccard, Samuel L.; Galbraith, Eric D.

    2018-05-01

    Enhanced upwelling and CO2 degassing from the subpolar North Pacific during a warm event 14,000 years ago may have helped keep atmospheric CO2 levels high enough to propel the Earth out of the last ice age.

  4. Marine sedimentary environments on some parts of the tropical and equatorial Atlantic margins of Africa during the Late Quaternary

    Science.gov (United States)

    Barusseau, J. P.; Giresse, P.; Faure, H.; Lezine, A. M.; Masse, J. P.

    1988-01-01

    From 18,000 y B.P. up to the Present, major climatic changes combined with eustatic sea-level irregular rise controlled important variations in sedimentary conditions on the Atlantic African margin between 6°S and 21°N. The present shelf deposition of material is also controlled by climatic latitudinal gradients acting on the nature, volume and distribution of terrigenous and carbonate sediments. The evolution of sedimentary conditions during this period may be summarized as follows. Coastal terrigenous deposition Fluvial sands were emplaced in inner shelf paleo-valleys during the beginning of the Wiscon sinian regression, following a major erosion phase providing an important source for the siliciclastic part of the terrigenous influx. In tropical regions (Mauritania, Senegal), aeolian dune sands formed during the arid "glacial" period (the so-called Ogolian) on the emerged shelf, but were destroyed during the subsequent transgression. In the vicinity and south of the Equator (Coˆte d'Ivoire, Congo), aeolian input was reduced but litoral dunes of that period occurred whose remnants may be observed close to the present shoreline. At the lower stand of sea level, fine particles directly by-passed the shelf towards the continental rises and abyssal plains. During the Holocene transgression, the main sedimentary processes occurred only when standstill or slowing of the sea-level rise took place. Then littoral deposits (fine sands of the shore, dune sands and even lagoonal deposits with mangrove peats) accumulated still more or less visible paleo-shorelines. However, offshore from the equatorial river mouths, particularly the main ones (Congo), pelitic sediments settled in morphological and structural lows. High sedimentation rates were common at the beginning but they decreased during the final part of the transgression. In the tropical region terrigenous fluvial input is considerably reduced but, in their northernmost parts, aeolian contribution of silts and

  5. Preface: The International Reference Ionosphere (IRI) at equatorial latitudes

    Science.gov (United States)

    Reinisch, Bodo; Bilitza, Dieter

    2017-07-01

    This issue of Advances in Space Research includes papers that report and discuss improvements of the International Reference Ionosphere (IRI). IRI is the international standard for the representation of the plasma in Earth's ionosphere and recognized as such by the Committee on Space Research (COSPAR), the International Union of Radio Science (URSI), the International Telecommunication Union (ITU), and the International Standardization Organization (ISO). As requested, particularly by COSPAR and URSI, IRI is an empirical model relying on most of the available and reliable ground and space observations of the ionosphere. As new data become available and as older data sources are fully exploited the IRI model undergoes improvement cycles to stay as close to the existing data record as possible. The latest episode of this process is documented in the papers included in this issue using data from the worldwide network of ionosondes, from a few of the incoherent scatter radars, from the Alouette and ISIS topside sounders, and from the Global Navigation Satellite Systems (GNSS). The focus of this issue is on the equatorial and low latitude region that is of special importance for ionospheric physics because it includes the largest densities and steep density gradients in the double hump latitudinal structure, the Equatorial Ionization Anomaly (EIA), which is characteristic for this region.

  6. The Plasma Environment Associated With Equatorial Ionospheric Irregularities

    Science.gov (United States)

    Smith, Jonathon M.; Heelis, R. A.

    2018-02-01

    We examine the density structure of equatorial depletions referred to here as equatorial plasma bubbles (EPBs). Data recorded by the Ion Velocity Meter as part of the Coupled Ion Neutral Dynamics Investigation (CINDI) aboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite are used to study EPBs from 1600 to 0600 h local time at altitudes from 350 to 850 km. The data are taken during the 7 years from 2008 to 2014, more than one half of a magnetic solar cycle, that include solar minimum and a moderate solar maximum. Using a rolling ball algorithm, EPBs are identified by profiles in the plasma density, each having a depth measured as the percent change between the background and minimum density (ΔN/N). During solar moderate activity bubbles observed in the topside postsunset sector are more likely to have large depths compared to those observed in the topside postmidnight sector. Large bubble depths can be observed near 350 km in the bottomside F region in the postsunset period. Conversely at solar minimum the distribution of depths is similar in the postsunset and postmidnight sectors in all longitude sectors. Deep bubbles are rarely observed in the topside postsunset sector and never in the bottomside above 400 km in altitude. We suggest that these features result from the vertical drift of the plasma for these two solar activity levels. These drift conditions affect both the background density in which bubbles are embedded and the growth rate of perturbations in the bottomside where bubbles originate.

  7. Equatorial density depletions observed at 840 km during the great magnetic storm of March 1989

    International Nuclear Information System (INIS)

    Greenspan, M.E.; Rasmussen, C.E.; Burke, W.J.; Abdu, M.A.

    1991-01-01

    Early on March 14, 1989, a thermal plasma probe on the Defense Meteorological Satellite Program (DMSP) F9 spacecraft detected extensive and dramatic decreases in the ion density at 840 km, near 2130 LT, during two consecutive transequatorial passes over South America. The order of magnitude decreases in the ion density extended more than 4,000 km along the satellite track. The depletions were accompanied by upward and westward plasma drifts, both in excess of 100 m/s. Their onsets and terminations were marked by extremely sharp density gradients. A partial depletion was detected over the eastern Pacific during the following orbit. The DMSP F9 ground track passed slightly west of a Brazilian total electron content (TEC) station and two Brazilian ionosondes during the first depletion encounter. The TEC fell far below normal during the night of March 13-14. The ionosonde measurements indicate that, in the hour after sunset, before DMSP passed through the depletions, the F 2 layer rose rapidly and disappeared, but at the time of the first depletion encounter, h m F 2 was decreasing over one of the stations. The authors develop a phenomenological model reconciling DMSP F8, F9 and ground-based measurements. The calculations show that rapid upward drifts sustained for several hours can produce depletions in the equatorial ion density with sharp gradients at their high-latitude boundaries, consistent with the data. They discuss possible contributing mechanisms for generating these upward drifts. These include direct penetration of the magnetospheric electric field to low latitudes, the electric fields generated by the disturbance dynamo, and the effects of conductivity gradients near the dusk terminator and the South Atlantic anomaly

  8. Vesta: its shape and deformed equatorial belt predicted by the wave planetology

    Science.gov (United States)

    Kochemasov, G. G.

    2012-09-01

    At EPSC2011 we stated: "Expected detailed images of Vesta sent by DAWN spacecraft certainly will show a prominent tectonic (must be also compositional) dichotomy of this large asteroid. The assuredness is based on some mainly the HST photos and the wave planetology fundamental conception: Theorem 1 - " Ce lestial bodies are dichotomous""[1]. Now a convexo-concave shape of Vesta is well known but the huge deep depression of the south hemisphere is assigned to two random large impacts almost at one place [2, 3]. This supposition has a very small probability, besides the largest asteroid Ceres also has a large depression at one side (the Piazzi basin). The theorem 1 of the wave planetology explains that all celestial bodies (not only small ones) are subjected to a warping action of the fundamental wave1 uplifting one side and subsiding (pressing in) the opposite one. This is a manifestation of the orbital energy acting in any body moving in keplerian noncircular orbit with changing acceleration (a). Arising inertia-gravity force F= (a1 - a2) x m is very important because of large planetary masses (m) and large cosmic speeds. Increase and decrease of accelerations were much larger in the beginning of planetary formation when orbits were more elliptical. Thus, pressing in of the subsiding hemisphere-segment is so strong that it often squeezes out some mantle material appearing as elevation-mound (compare to the Hawaii in the Pacific basin and look at Hyperion with a large basin and a mound at its center, Fig, 1, 2). Vesta's prominent subsiding equatorial belt with graben systems [4] (Fig. 4, 5) is a manifestation of another general planetary rule : " Rotating celestial body tends to even angular momenta of tropics and extra-tropics by regulating mass distribution and distance to the rotation axis " [5-7]. Often observed a sensible difference in appearance and structure between tropical and extra-tropical zones of various heavenly bodies including rocky and gas planets

  9. Sediment tolerance mechanisms identified in sponges using advanced imaging techniques

    Directory of Open Access Journals (Sweden)

    Brian W. Strehlow

    2017-11-01

    Full Text Available Terrestrial runoff, resuspension events and dredging can affect filter-feeding sponges by elevating the concentration of suspended sediments, reducing light intensity, and smothering sponges with sediments. To investigate how sponges respond to pressures associated with increased sediment loads, the abundant and widely distributed Indo-Pacific species Ianthella basta was exposed to elevated suspended sediment concentrations, sediment deposition, and light attenuation for 48 h (acute exposure and 4 weeks (chronic exposure. In order to visualise the response mechanisms, sponge tissue was examined by 3D X-ray microscopy and scanning electron microscopy (SEM. Acute exposures resulted in sediment rapidly accumulating in the aquiferous system of I. basta, although this sediment was fully removed within three days. Sediment removal took longer (>2 weeks following chronic exposures, and I. basta also exhibited tissue regression and a smaller aquiferous system. The application of advanced imaging approaches revealed that I. basta employs a multilevel system for sediment rejection and elimination, containing both active and passive components. Sponges responded to sediment stress through (i mucus production, (ii exclusion of particles by incurrent pores, (iii closure of oscula and pumping cessation, (iv expulsion of particles from the aquiferous system, and (v tissue regression to reduce the volume of the aquiferous system, thereby entering a dormant state. These mechanisms would result in tolerance and resilience to exposure to variable and high sediment loads associated with both anthropogenic impacts like dredging programs and natural pressures like flood events.

  10. Tectonostratigraphic terranes of the frontier circum-Pacific region

    Energy Technology Data Exchange (ETDEWEB)

    Howell, D.G.; Jones, D.L.; Schermer, E.R.

    1983-03-01

    Many major exploration frontiers around the Pacific are in regions where complex geologic relations reflect plate-tectonic processes, crustal mobility, and accretion of exotic terranes. The destruction of the proto-Pacific ocean (Panthalassa) involved accretion of terranes to cratonal regions such as Gondwana and Laurasia. Terranes in southwestern New Zealand and eastern Antarctica were also probably accreted during the Paleozoic. The southern margin of Siberia, extending into China, underwent a protracted period of accretion from the late Precambrian through the early Mesozoic. Mid-Paleozoic accretion is reflected in the Innuitian foldbelt of the Arctic Ocean, the Black Clastic unit of the northern Rocky Mountains, and the Antler orogeny of the western US cordillera. The Mesozoic breakup of Pangaea and the acceleration of subduction aided in the rifting and dispersal of terranes from equatorial paleolatitudes. Fragments of these terranes now compose much of the continental margins of the Pacific basin, including New Zealand, Indochina, southern China, southeast Siberia, the North American cordillera, and South America. Some terranes are presently being further fragmented by post-accretionary dispersion processes such as strike-slip faulting in western North America and Japan. Although the character and distribution of terranes in the western US are fairly well documented, details are needed for other terranes around the Pacific basin. Interpretation of structure and stratigraphy at depth will be aided by more data on the timing of accretion and the nature of deformation associated with accretion and dispersion. Such data are needed for further define specific exploration targets in the circum-Pacific region.

  11. Control of tropical instability waves in the Pacific

    Science.gov (United States)

    Allen, M. R.; Lawrence, S. P.; Murray, M. J.; Mutlow, C. T.; Stockdale, T. N.; Llewellyn-Jones, D. T.; Anderson, D. L. T.

    Westward-propagating waves with periods of 20-30 days and wavelengths of ˜ 1,100km are a prominent feature of sea-surface temperatures (SSTs) in the equatorial Pacific and Atlantic Oceans. They have been attributed to instabilities due to current shear. We compare SST observations from the spaceborne Along Track Scanning Radiometer (ATSR) and TOGA-TAO moored buoys with SSTs from a model of the tropical Pacific forced with observed daily windstress data. The phases of the strongest “Tropical Instability Waves” (TIWs) in the model are in closer correspondence with those observed than we would expect if these waves simply developed from infinitesimal disturbances (in which case their phases would be arbitrary). If we filter out the intraseasonal component of the windstress, all phase-correspondence is lost. We conclude that the phases of these waves are not arbitrary, but partially determined by the intraseasonal winds. The subsurface evolution of the model suggests a possible control mechanism is through interaction with remotely-forced subsurface Kelvin and Rossby waves. This is supported by an experiment which shows how zonal wind bursts in the west Pacific can modify the TIW field, but other mechanisms, such as local feedbacks, are also possible.

  12. A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

    Science.gov (United States)

    Chatterjee, S.; Chakraborty, S. K.; Veenadhari, B.; Banola, S.

    2014-02-01

    Equatorial electrojet (EEJ) data, which are considered as a proxy index of equatorial electric field, are analyzed in conjunction with equatorial ionosonde, total electron content (TEC) and scintillation data near the equatorial ionization anomaly (EIA) crest for the equinoctial months of high solar activity years (2011-2012) to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern EIA crest. Only geomagnetically quiet and normal electrojet days are considered. The diurnal profiles of EEJ on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks. A series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of EEJ. Latitudinal profile of TEC exhibits resurgence in EIA structure around the postsunset period. Diurnal TEC profile near the EIA crest resembles postsunset secondary enhancement on the days with afternoon enhancement in EEJ. Occurrence of equatorial spread F and postsunset scintillation near the EIA crest seems to follow the secondary enhancement events in EEJ. Both the magnitude and duration of enhanced EEJ are found to be important for postsunset intensification of EIA structure and subsequent occurrence of equatorial irregularities. A critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the EIA crest. The results are validated using archived data for the years 1989-1990 and explained in terms of modulation effects of enhanced equatorial fountain.

  13. Influence of biomass burning emissions on precipitation chemistry in the equatorial forests of Africa

    International Nuclear Information System (INIS)

    Lacaux, J.P.; Lefeivre, B.; Delmas, R.A.; Cros, B.; Andreae, M.O.

    1991-01-01

    As part of the DESCAFE program (Dynamics and Chemistry of the Atmosphere in Equatorial Forest), measurements of precipitation chemistry were made at two sampling sites of the equatorial forest in the Republic of Congo. The measurements were made in order to identify and compare atmospheric sources of gases and particles (mainly biogenic sources and emissions from burning vegetation)

  14. Surface elevation change and susceptibility of different mangrove zones to sea-level rise on Pacific high islands o Micronesia

    Science.gov (United States)

    K.W. Krauss; D.R. Cahoon; J.A. Allen; K.C. Ewel; J.C. Lynch; N. Cormier

    2010-01-01

    Mangroves on Pacific high islands offer a number of important ecosystem services to both natural ecological communities and human societies. High islands are subjected to constant erosion over geologic time, which establishes an important source of terrigeneous sediment for nearby marinecommunities. Many of these sediments are deposited in mangrove forests and offer...

  15. Instabilities in the coupled equatorial ocean atmosphere system

    NARCIS (Netherlands)

    Dijkstra, H.A.; Vaart, P.C.F. van der

    1999-01-01

    The large-scale interaction between the ocean and atmosphere is one of the impor- tant factors of natural climate variability.The El-Niño/Southern Oscillation (ENSO) phenomenon in the Tropical Pacific is one of the most prominent examples of climate variability on interannual time scales.ENSO has

  16. Sediment transport and channel morphology of small, forested streams.

    Science.gov (United States)

    Marwan A. Hassan; Michael Church; Thomas E. Lisle; Francesco Brardinoni; Lee Benda; Gordon E. Grant

    2005-01-01

    This paper reviews sediment transport and channel morphology in small, forested streams in the Pacific Northwest region of North America to assess current knowledge of channel stability and morphology relevant to riparian management practices around small streams. Small channels are defined as ones in which morphology and hydraulics may be significantly influenced by...

  17. Spread F – an old equatorial aeronomy problem finally resolved?

    Directory of Open Access Journals (Sweden)

    R. F. Woodman

    2009-05-01

    Full Text Available One of the oldest scientific topics in Equatorial Aeronomy is related to Spread-F. It includes all our efforts to understand the physical mechanisms responsible for the existence of ionospheric F-region irregularities, the spread of the traces in a night-time equatorial ionogram – hence its name – and all other manifestations of the same. It was observed for the first time as an abnormal ionogram in Huancayo, about 70 years ago. But only recently are we coming to understand the physical mechanisms responsible for its occurrence and its capricious day to day variability. Several additional techniques have been used to reveal the spatial and temporal characteristics of the F-region irregularities responsible for the phenomenon. Among them we have, in chronological order, radio star scintillations, trans-equatorial radio propagation, satellite scintillations, radar backscatter, satellite and rocket in situ measurements, airglow, total electron content techniques using the propagation of satellite radio signals and, recently, radar imaging techniques. Theoretical efforts are as old as the observations. Nevertheless, 32 years after their discovery, Jicamarca radar observations showed that none of the theories that had been put forward could explain them completely. The observations showed that irregularities were detected at altitudes that were stable according to the mechanisms proposed. A breakthrough came a few years later, again from Jicamarca, by showing that some of the "stable" regions had become unstable by the non-linear propagation of the irregularities from the unstable to the stable region of the ionosphere in the form of bubbles of low density plasma. A problem remained, however; the primary instability mechanism proposed, an extended (generalized Rayleigh-Taylor instability, was too slow to explain the rapid development seen by the observations. Gravity waves in the neutral background have been proposed as a seeding mechanism to

  18. Role of interannual Kelvin wave propagations in the equatorial Atlantic on the Angola Benguela Current system

    Science.gov (United States)

    Imbol Koungue, Rodrigue Anicet; Illig, Serena; Rouault, Mathieu

    2017-06-01

    The link between equatorial Atlantic Ocean variability and the coastal region of Angola-Namibia is investigated at interannual time scales from 1998 to 2012. An index of equatorial Kelvin wave activity is defined based on Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). Along the equator, results show a significant correlation between interannual PIRATA monthly dynamic height anomalies, altimetric monthly Sea Surface Height Anomalies (SSHA), and SSHA calculated with an Ocean Linear Model. This allows us to interpret PIRATA records in terms of equatorial Kelvin waves. Estimated phase speed of eastward propagations from PIRATA equatorial mooring remains in agreement with the linear theory, emphasizing the dominance of the second baroclinic mode. Systematic analysis of all strong interannual equatorial SSHA shows that they precede by 1-2 months extreme interannual Sea Surface Temperature Anomalies along the African coast, which confirms the hypothesis that major warm and cold events in the Angola-Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Equatorial wave dynamics is at the origin of their developments. Wind anomalies in the Western Equatorial Atlantic force equatorial downwelling and upwelling Kelvin waves that propagate eastward along the equator and then poleward along the African coast triggering extreme warm and cold events, respectively. A proxy index based on linear ocean dynamics appears to be significantly more correlated with coastal variability than an index based on wind variability. Results show a seasonal phasing, with significantly higher correlations between our equatorial index and coastal SSTA in October-April season.

  19. Interannual Variation in Phytoplankton Concentration and Community in the Pacific Ocean

    Science.gov (United States)

    Rousseaux, C. S.; Gregg, W. W.

    2011-01-01

    Climate events such as El Nino have been shown to have an effect on the biology of our ocean. Because of the lack of data, we still have very little knowledge about the spatial and temporal effect these climate events may have on biological marine systems. In this study, we used the NASA Ocean Biogeochemical Model (NOBM) to assess the interannual variability in phytoplankton community in the Pacific Ocean between 1998 and 2005. In the North Central and Equatorial Pacific Ocean, changes in the Multivariate El Nino Index were associated with changes in phytoplankton composition. The model identified an increase in diatoms of approx.33 % in the equatorial Pacific in 1999 during a La Nina event. This increase in diatoms coincided with a decrease of approx.11 % in cyanobacteria concentration. The inverse relationship between cyanobacteria and diatoms concentration was significant (pphytoplankton groups known to lead to contrasting food chain at a spatial and temporal resolution unachievable when relying solely on in-situ observations.

  20. Interannual Variations in the Synoptic-Scale Disturbances over the western North Pacific

    Science.gov (United States)

    Zhou, Xingyan; Lu, Riyu

    2017-04-01

    The present study investigates the interannual variation of synoptic disturbance activities over the western North Pacific (WNP) and its relationship with the large-scale circulation and tropical SST during June-November for the period 1958-2014. It is shown that the interannual variability of 850-hPa eddy kinetic energy (EKE) anomalies over the WNP could be well described by its two leading modes of EOF, i.e., northeast pattern and southwest pattern. The high value zone of former is located over the WNP, while latter around the Philippines, which just overlap a broad area of the WNP. Background flows play an important role in the formation of these two patterns, it could induce the cyclonic ( anticyclonic ) anomalies over the variation centers which favors ( disfavors) synoptic eddies to get kinetic energy from the mean flows through barotropic energy conversion. The SST anomalies of the equatorial central and eastern Pacific also contribute to these two patterns. When the SST of equatorial central and eastern Pacific above (below) the normal, a cyclonic (anticyclonic) anomaly appears in the Philippine Sea while an anticyclonic (cyclonic) anomaly happens in the South China Sea, which will induce positive (negative) EKE anomalies over the WNP but negative (positive) anomalies over the South China Sea and the Philippines.

  1. Multistation digisonde observations of equatorial spread F in South America

    Directory of Open Access Journals (Sweden)

    B. W. Reinisch

    2004-09-01

    Full Text Available Directional ionogram and F-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of F-region density depletions that cause equatorial spread F (ESF. New ionosonde techniques quantitatively describe the prereversal uplifting of the F layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic E-layers at the two E-region intersections of the field line. No simple correlation was found.

  2. Observers in Kerr spacetimes. The ergoregion on the equatorial plane

    Energy Technology Data Exchange (ETDEWEB)

    Pugliese, D. [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics, Opava (Czech Republic); Quevedo, H. [Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico, DF (Mexico); Kazakh National University, Department of Theoretical and Nuclear Physics, Almaty (Kazakhstan)

    2018-01-15

    We perform a detailed analysis of the properties of stationary observers located on the equatorial plane of the ergosphere in a Kerr spacetime, including light-surfaces. This study highlights crucial differences between black hole and the super-spinner sources. In the case of Kerr naked singularities, the results allow us to distinguish between ''weak'' and ''strong'' singularities, corresponding to spin values close to or distant from the limiting case of extreme black holes, respectively. We derive important limiting angular frequencies for naked singularities. We especially study very weak singularities as resulting from the spin variation of black holes. We also explore the main properties of zero angular momentum observers for different classes of black hole and naked singularity spacetimes. (orig.)

  3. Seeding and layering of equatorial spread F by gravity waves

    International Nuclear Information System (INIS)

    Hysell, D.L.; Kelley, M.C.; Swartz, W.E.; Woodman, R.F.

    1990-01-01

    Studies dating back more than 15 years have presented evidence that atmospheric gravity waves play a role in initiating nighttime equatorial F region instabilities. This paper analyzes a spectabular spread F event that for the first time demonstrates a layering which, the authors argue, is controlled by a gravity wave effect. The 50-km vertical wavelength of a gravity wave which they have found is related theoretically to a plasma layering irregularity that originated at low altitudes and then was convected, intact, to higher altitudes. Gravity waves also seem to have determined bottomside intermediate scale undulations, although this fact is not as clear in the data. The neutral wind dynamo effect yields wave number conditions on the gravity wave's ability to modulate the Rayleigh-Taylor instaiblity process. Finally, after evaluating the gravity wave dispersion relation and spatial resonance conditions, we estimate the properties of the seeding wave

  4. Solar cycle signatures in the NCEP equatorial annual oscillation

    Science.gov (United States)

    Mayr, H. G.; Mengel, J. G.; Huang, F. T.; Nash, E. R.

    2009-08-01

    Our analysis of temperature and zonal wind data (1958 to 2006) from the National Center for Atmospheric Research (NCAR) reanalysis (Re-1), supplied by the National Centers for Environmental Prediction (NCEP), shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO) contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC). The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.

  5. Is there a hole in the topside, equatorial ionosphere?

    Directory of Open Access Journals (Sweden)

    D. Gallagher

    Full Text Available A paper in 2000 (Huba, 2000 found a depression in electron density in the topside ionosphere near the magnetic equator, based on the SAMI-2 physical ionospheric model. The model showed, for the first time, the formation of a hole in electron density in the altitude range 1500–2500 km at geomagnetic equatorial latitudes. The model produced the hole because of transhemispheric O+ flows that collisionally couple to H+, transporting it to lower altitudes, and thereby reducing the electron density at high altitudes. At that time and until now, no published observations have been reported to confirm or refute this numerical result. Recent, new analysis of Dynamics Explorer 1 Retarding Ion Mass Spectrometer measurements provides the first tentative experimental support for this model result. Keywords: Ionosphere, Topside, Magnetic equator, Plasmasphere

  6. Solar cycle signatures in the NCEP equatorial annual oscillation

    Directory of Open Access Journals (Sweden)

    H. G. Mayr

    2009-08-01

    Full Text Available Our analysis of temperature and zonal wind data (1958 to 2006 from the National Center for Atmospheric Research (NCAR reanalysis (Re-1, supplied by the National Centers for Environmental Prediction (NCEP, shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC. The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.

  7. Combined radar observations of equatorial electrojet irregularities at Jicamarca

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2007-03-01

    Full Text Available Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI mapping, Faraday rotation, radar imaging, oblique scattering, and multiple-frequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3–5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.

  8. The earth's equatorial principal axes and moments of inertia

    Science.gov (United States)

    Liu, H. S.; Chao, B. F.

    1991-01-01

    The earth's equatorial principal moments of inertia are given as A and B, where A is less than B, and the corresponding principal axes are given as a and b. Explicit formulas are derived for determining the orientation of a and b axes and the difference B - A using C(22) and S(22), the two gravitational harmonic coefficients of degree 2 and order 2. For the earth, the a axis lies along the (14.93 deg W, 165.07 deg E) diameter, and the b axis lies perpendicular to it along the (75.07 deg E, 104.93 deg W) diameter. The difference B - A is 7.260 x 10 to the -6th MR2. These quantities for other planets are contrasted, and geophysical implications are discussed.

  9. Rare earth element geochemistry characteristics of seawater and porewater from deep sea in western Pacific.

    Science.gov (United States)

    Deng, Yinan; Ren, Jiangbo; Guo, Qingjun; Cao, Jun; Wang, Haifeng; Liu, Chenhui

    2017-11-28

    Deep-sea sediments contain high concentrations of rare earth element (REE) which have been regarded as a huge potential resource. Understanding the marine REE cycle is important to reveal the mechanism of REE enrichment. In order to determine the geochemistry characteristics and migration processes of REE, seawater, porewater and sediment samples were systematically collected from the western Pacific for REE analysis. The results show a relatively flat REE pattern and the HREE (Heavy REE) enrichment in surface and deep seawater respectively. The HREE enrichment distribution patterns, low concentrations of Mn and Fe and negative Ce anomaly occur in the porewater, and high Mn/Al ratios and low U concentrations were observed in sediment, indicating oxic condition. LREE (Light REE) and MREE (Middle REE) enrichment in upper layer and depletion of MREE in deeper layer were shown in porewater profile. This study suggests that porewater flux in the western Pacific basin is a minor source of REEs to seawater, and abundant REEs are enriched in sediments, which is mainly caused by the extensive oxic condition, low sedimentation rate and strong adsorption capacity of sediments. Hence, the removal of REEs of porewater may result in widespread REE-rich sediments in the western Pacific basin.

  10. Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene.

    Science.gov (United States)

    Burls, Natalie J; Fedorov, Alexey V; Sigman, Daniel M; Jaccard, Samuel L; Tiedemann, Ralf; Haug, Gerald H

    2017-09-01

    An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, the world's largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400-ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.

  11. Chemistry of marine sediments

    International Nuclear Information System (INIS)

    Yen, T.F.

    1977-01-01

    Some topics considered are as follows: characterization of sediments in the vicinity of offshore petroleum production; thermal alteration experiments on organic matter in recent marine sediments as a model for petroleum genesis; composition of polluted bottom sediments in Great Lakes harbors; distribution of heavy metals in sediment fractions; recent deposition of lead off the coast of southern California; release of trace constituents from sediments resuspended during dredging operations; and migration of chemical constituents in sediment-seawater interfaces

  12. Interannual variability of the South Pacific Convergence Zone and implications for tropical cyclone genesis

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, Emmanuel M. [IRD/UPMC/CNRS/MNHN, Laboratoire d' Oceanographie et du Climat: Experimentation et Approches Numeriques (LOCEAN), Paris (France); UPMC, LOCEAN/IPSL, Paris Cedex 05 (France); Lengaigne, Matthieu [IRD/UPMC/CNRS/MNHN, Laboratoire d' Oceanographie et du Climat: Experimentation et Approches Numeriques (LOCEAN), Paris (France); National Institute of Oceanography, Goa (India); Menkes, Christophe E. [IRD/UPMC/CNRS/MNHN, Laboratoire d' Oceanographie et du Climat: Experimentation et Approches Numeriques (LOCEAN), Paris (France); Institut de Recherche pour le Developpement, Noumea (New Caledonia); Jourdain, Nicolas C. [Institut de Recherche pour le Developpement, Noumea (New Caledonia); Marchesiello, Patrick [Institut de Recherche pour le Developpement, Noumea (New Caledonia); CNES/CNRS/UPS/IRD, Laboratoire d' Etudes en Geophysique et Oceanographie Spatiale (LEGOS), Toulouse (France); Madec, Gurvan [IRD/UPMC/CNRS/MNHN, Laboratoire d' Oceanographie et du Climat: Experimentation et Approches Numeriques (LOCEAN), Paris (France); National Oceanographic Centre, Southampton (United Kingdom)

    2011-05-15

    The interannual variability of the South Pacific Convergence Zone (SPCZ) and its influence on tropical cyclone (TC) genesis in the South Pacific are investigated using observations and ERA40 reanalysis over the 1979-2002 period. In austral summer, the SPCZ displays four typical structures at interannual timescales. The first three are characterized by a diagonal orientation of the SPCZ and account for 85% of the summer seasons. One is close to climatology and the other two exhibit a 3 northward or southward departure from the SPCZ climatological position. In contrast, the fourth one, that only encompasses three austral summer seasons (the extreme 1982/1983 and 1997/1998 El Nino events and the moderate 1991/1992 El Nino event), displays very peculiar behaviour where the SPCZ largely departs from its climatological position and is zonally oriented. Variability of the western/central Pacific equatorial sea surface temperature (SST) is shown to modulate moisture transport south of the equator, thereby strongly constraining the location of the SPCZ. The SPCZ location is also shown to strongly modulate the atmospheric circulation variability in the South Pacific with specific patterns for each class. However, independently of its wide year-to-year excursions, the SPCZ is always collocated with the zero relative vorticity at low levels while the maximum vorticity axis lies 6 to the south of the SPCZ position. This coherent atmospheric organisation in the SPCZ region is shown to constrain tropical cyclogenesis to occur preferentially within 10 south of the SPCZ location as this region combines all the large-scale atmospheric conditions that favour the breeding of TCs. This analysis also reveals that cyclogenesis in the central Pacific (in the vicinity of French Polynesia) only occurs when the SPCZ displays a zonal orientation while this observation was previously attributed to El Nino years in general. Different characteristics of El Nino Southern Oscillation (ENSO

  13. A Generalized Equatorial Model for the Accelerating Solar Wind

    Science.gov (United States)

    Tasnim, S.; Cairns, Iver H.; Wheatland, M. S.

    2018-02-01

    A new theoretical model for the solar wind is developed that includes the wind's acceleration, conservation of angular momentum, deviations from corotation, and nonradial velocity and magnetic field components from an inner boundary (corresponding to the onset of the solar wind) to beyond 1 AU. The model uses a solution of the time-steady isothermal equation of motion to describe the acceleration and analytically predicts the Alfvénic critical radius. We fit the model to near-Earth observations of the Wind spacecraft during the solar rotation period of 1-27 August 2010. The resulting data-driven model demonstrates the existence of noncorotating, nonradial flows and fields from the inner boundary (r = rs) outward and predicts the magnetic field B = (Br,Bϕ), velocity v = (vr,vϕ), and density n(r,ϕ,t), which vary with heliocentric distance r, heliolatitude ϕ, and time t in a Sun-centered standard inertial plane. The description applies formally only in the equatorial plane. In a frame corotating with the Sun, the transformed velocity v' and a field B' are not parallel, resulting in an electric field with a component Ez' along the z axis. The resulting E'×B'=E'×B drift lies in the equatorial plane, while the ∇B and curvature drifts are out of the plane. Together these may lead to enhanced scattering/heating of sufficiently energetic particles. The model predicts that deviations δvϕ from corotation at the inner boundary are common, with δvϕ(rs,ϕs,ts) comparable to the transverse velocities due to granulation and supergranulation motions. Abrupt changes in δvϕ(rs,ϕs,ts) are interpreted in terms of converging and diverging flows at the cell boundaries and centers, respectively. Large-scale variations in the predicted angular momentum demonstrate that the solar wind can drive vorticity and turbulence from near the Sun to 1 AU and beyond.

  14. A tropospheric ozone maximum over the equatorial Southern Indian Ocean

    Directory of Open Access Journals (Sweden)

    L. Zhang

    2012-05-01

    Full Text Available We examine the distribution of tropical tropospheric ozone (O3 from the Microwave Limb Sounder (MLS and the Tropospheric Emission Spectrometer (TES by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem. MLS and TES observations of tropospheric O3 during 2005 to 2009 reveal a distinct, persistent O3 maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO. The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O3 observations from the Ozone Mapping Instrument (OMI and the Atmospheric Infrared Sounder (AIRS. Model results reproduce the observed May O3 maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O3 maximum is dominated by the O3 production driven by lightning nitrogen oxides (NOx emissions, which accounts for 62% of the tropospheric column O3 in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O3 maximum are rather small. The O3 productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O3 maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O3 maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.

  15. Observations of EMIC Triggered Emissions off the Magnetic Equatorial Plane

    Science.gov (United States)

    Grison, B.; Breuillard, H.; Santolik, O.; Cornilleau-Wehrlin, N.

    2016-12-01

    On 19/08/2005 Cluster spacecraft had their perigee close to the dayside of the Earth magnetic equatorial plane, at about 14 hours Magnetic Local Time. The spacecraft crossed the equator from the southern hemisphere toward the northern hemisphere. In the Southern hemisphere, at about -23° magnetic latitude (MLAT) and at distance of 5.25 Earth Radii from Earth, Cluster 3 observes an EMIC triggered emission between the He+ and the proton local gyrofrequencies. The magnetic waveform (STAFF instrument data) is transformed into the Fourier space for a study based on single value decomposition (SVD) analysis. The emission lasts about 30s. The emission frequency rises from 1Hz up to 1.9Hz. The emission polarization is left-hand, its coherence value is high and the propagation angle is field aligned (lower than 30º). The Poynting flux orientation could not be established. Based on previous study results, these properties are indicative of an observation in vicinity of the source region of the triggered emission. From our knowledge this is the first time that EMIC triggered emission are observed off the magnetic equator. In order to identify the source region we study two possibilities: a source region at higher latitudes than the observations (and particles orbiting in "Shabansky" orbits) and a source region close to the magnetic equatorial plane, as reported in previous studies. We propose to identify the source region from ray tracing analysis and to compare the observed propagation angle in several frequency ranges to the ray tracing results.

  16. Priority areas for large mammal conservation in Equatorial Guinea.

    Science.gov (United States)

    Murai, Mizuki; Ruffler, Heidi; Berlemont, Antoine; Campbell, Genevieve; Esono, Fidel; Agbor, Anthony; Mbomio, Domingo; Ebana, Agustín; Nze, Antonio; Kühl, Hjalmar S

    2013-01-01

    Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1) the relative importance of local vs. commercial hunting; 2) wildlife density of protected vs. non-protected areas; and 3) the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789) elephants and 11,097 (8,719-13,592) chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal and Río Campo

  17. Characteristics of Volcanic Stratospheric Aerosol Layer Observed by CALIOP and Ground Based Lidar at Equatorial Atmosphere Radar Site

    Science.gov (United States)

    Abo, Makoto; Shibata, Yasukuni; Nagasawa, Chikao

    2018-04-01

    We investigated the relation between major tropical volcanic eruptions in the equatorial region and the stratospheric aerosol data, which have been collected by the ground based lidar observations at at Equatorial Atmosphere Radar site between 2004 and 2015 and the CALIOP observations in low latitude between 2006 and 2015. We found characteristic dynamic behavior of volcanic stratospheric aerosol layers over equatorial region.

  18. Pacific Coastal Salmon Recovery Fund

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Congress established the Pacific Coastal Salmon Recovery Fund (PCSRF) to monitor the restoration and conservation of Pacific salmon and steelhead populations and...

  19. Persistence of deeply sourced iron in the Pacific Ocean.

    Science.gov (United States)

    Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

    2015-02-03

    Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

  20. Comparison of the accuracy of SST estimates by artificial neural networks (ANN) and other quantitative methods using radiolarian data from the Antarctic and Pacific Oceans

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Malmgren, B.A.

    ) regression, the maximum likelihood (ML) method, and artificial neural networks (ANNs), based on radiolarian faunal abundance data from surface sediments from the Antarctic and Pacific Oceans. Recent studies have suggested that ANNs may represent one...

  1. Researching Pacific island livelihoods:

    DEFF Research Database (Denmark)

    Egelund Christensen, Andreas; Mertz, Ole

    2010-01-01

    on contemporary theories of nissology and conceptual analytical frameworks for island research. Through a review of selected case-study-based island literature on changing livelihoods coming out of the South Pacific, we wish to illustrate and discuss advantages of finding common grounds for small island studies....... The focus is on two dimensions of island livelihood, migration and natural resource management, both of which are significant contributors in making island livelihoods and shaping Pacific seascapes. We argue that there is still a substantial lack of studies targeting small island dynamics that are empirical...

  2. 137Cs in the western South Pacific Ocean

    International Nuclear Information System (INIS)

    Yamada, Masatoshi; Wang Zhongliang

    2007-01-01

    The 137 Cs activities were determined for seawater samples from the East Caroline, Coral Sea, New Hebrides, South Fiji and Tasman Sea (two stations) Basins of the western South Pacific Ocean by γ spectrometry using a low background Ge detector. The 137 Cs activities ranged from 1.4 to 2.3 Bq m -3 over the depth interval 0-250 m and decreased exponentially from the subsurface to 1000 m depth. The distribution profiles of 137 Cs activity at these six western South Pacific Ocean stations did not differ from each other significantly. There was a remarkable difference for the vertical profiles of 137 Cs activity between the East Caroline Basin station in this study and the GEOSECS (Geochemical Ocean Sections Study) station at the same latitude in the Equatorial Pacific Ocean; the 137 Cs inventory over the depth interval 100-1000 m increased from 400 ± 30 Bq m -2 to 560 ± 30 Bq m -2 during the period from 1973 to 1992. The total 137 Cs inventories in the western South Pacific Ocean ranged from 850 ± 70 Bq m -2 in the Coral Sea Basin to 1270 ± 90 Bq m -2 in the South Fiji Basin. Higher 137 Cs inventories were observed at middle latitude stations in the subtropical gyre than at low latitude stations. The 137 Cs inventories were 1.9-4.5 times (2.9 ± 0.7 on average) and 1.7-4.3 times (3.1 ± 0.7 on average) higher than that of the expected deposition density of atmospheric global fallout at the same latitude and that of the estimated 137 Cs deposition density in 10 o latitude by 10 deg. longitude grid data obtained by Aoyama et al. [Aoyama M, Hirose K, Igarashi Y. Re-construction and updating our understanding on the global weapons tests 137 Cs fallout. J Environ Monit 2006;8:431-438], respectively. The possible processes for higher 137 Cs inventories in the western South Pacific Ocean than that of the expected deposition density of atmospheric global fallout may be attributable to the inter-hemisphere dispersion of the atmospheric nuclear weapons testing 137 Cs from

  3. V isotope composition in modern marine hydrothermal sediments

    Science.gov (United States)

    Wu, F.; Owens, J. D.; Nielsen, S.; German, C. R.; Rachel, M.

    2017-12-01

    Vanadium is multivalence transition metal with two isotopes (51V and 50V). Recent work has shown that large V isotope variations occur with oxygen variations in modern sediments (Wu et al., 2016 and 2017 Goldschmidt Abstracts), providing its potential as a promising proxy for determining low oxygen conditions. However, the development of V isotopes as a proxy to probe past redox conditions requires a comprehensive understanding of the modern oceanic isotopic mass balance. Therein, the scavenging of V from the hydrous iron oxides in hydrothermal fluid has been shown to be an important removal process from seawater (Rudnicki and Elderfield, 1993 GCA) but remains unquantified. In this study, we analyzed V isotopic compositions of metalliferous sediments around the active TAG hydrothermal mound from the mid-Atlantic Ridge (26° degrees North) and the Eastern Pacific Zonal Transect (GEOTRACES EPZT cruise GP16). The TAG sediments deposited as Fe oxyhydroxides from plume fall-out, and have δ51V values between -0.3 to 0‰. The good correlation between Fe and V for these metalliferous sediments indicate that the accumulation of V in these samples is directly related to the deposition of Fe oxyhydroxides, which also control their V isotope signature. The EPZT samples cover 8,000 km in the South Pacific Ocean with sedimentary areas that underlie the Peru upwelling region and the well-oxygenated deep South Pacific Ocean influenced by hydtorthermal plume material from southern East Pacific Rise (EPR). The sediments collected at the east of the EPR have δ51V values between -1.2 to -0.7‰, similar to previous δ51V of oxic sediments. In contrast, the sediments from the west of the EPR have δ51V values (-0.4 to 0‰) similar to hydrothermal sediments from the mid-Atlantic Ridge, indicating the long transportation (more than 4,000 km, Fitzsimmons et al., 2017 NG) of Fe and Mn from hydrothermal plume and their incorporation into sediments have a major impact on the cycle of V

  4. Transport and Thermohaline Structure in the Western Tropical North Pacific

    Science.gov (United States)

    Schonau, Martha Coakley

    Transport and thermohaline structure of water masses and their respective variability are observed and modeled in the western tropical North Pacific using autonomous underwater gliders, Argo climatology and a numerical ocean state estimate. The North Equatorial Current (NEC) advects subtropical and subpolar water masses into the region that are transported equatorward by the Mindanao Current (MC). Continuous glider observations of these two currents from June 2009 to December 2013 provide absolute geostrophic velocity, water mass structure, and transport. The observations are compared to Argo climatology (Roemmich and Gilson, 2009), wind and precipitation to assess forcing, and annual and interannual variability. Observations are assimilated into a regional ocean state estimate (1/6°) to examine regional transport variability and its relationship to the El Nino-Southern Oscillation phenomena (ENSO). The NEC, described in Chapter 1, is observed along 134.3°E, from 8.5°N to 16.5°N. NEC thermocline transport is relatively constant, with a variable subthermocline transport that is distinguished by countercurrents centered at 9.6°N and 13.1°N. Correlation between thermocline and subthermocline transport is strong. Isopycnals with subducted water masses, the North Pacific Tropical Water and North Pacific Intermediate Water, have the greatest fine-scale thermohaline variance. The NEC advects water masses into the MC, described in Chapter 2, that flows equatorward along the coast of Mindanao. Gliders observed the MC at a mean latitude of 8.5°N. The Mindanao Undercurrent (MUC) persists in the subthermocline offshore of the MC, with a net poleward transport of intermediate water typical of South Pacific origin. The variable subthermocline transport in the MC/MUC has an inverse linear relationship with the Nino 3.4 index and strongly impacts total transport variability. For each the MC and NEC, surface salinity and thermocline depth have a strong relationship with ENSO

  5. CONVECTIVE BURSTS AND THE COUPLING OF SATURN'S EQUATORIAL STORMS AND INTERIOR ROTATION

    International Nuclear Information System (INIS)

    Heimpel, Moritz; Aurnou, Jonathan M.

    2012-01-01

    Temporal variations of Saturn's equatorial jet and magnetic field hint at rich dynamics coupling the atmosphere and the deep interior. However, it has been assumed that rotation of the interior dynamo must be steady over tens of years of modern observations. Here we use a numerical convection model and scaling estimates to show how equatorial convective bursts can transfer angular momentum to the deeper interior. The numerical model allows angular momentum transfer between a fluid outer spherical shell and a rigid inner sphere. Convection drives a prograde equatorial jet exhibiting quasiperiodic bursts that fill the equatorial volume outside the tangent cylinder. For each burst strong changes in the equatorial surface velocity are associated with retrograde torque on the inner sphere. Our results suggest that Saturn's Great White Spot, a giant storm that was observed to fill the equatorial region in 1990, could mobilize a volume of fluid carrying roughly 15% of Saturn's moment of inertia. Conservation of angular momentum then implies that a 20% change in the equatorial jet angular velocity could change the average interior rotation rate by about 0.1%—roughly an order of magnitude less than the apparent rotation rate changes associated with Saturn's kilometric radio (SKR) signal. However, if the SKR signal originates outside the liquid metal core in a 'planetary tachocline' that separates the layer of fast zonal flow from the magnetically controlled and slowly convecting deep interior, then convective bursts can provide a possible mechanism for the observed ∼1% SKR changes.

  6. The streaming-trapped ion interface in the equatorial inner magnetosphere

    Science.gov (United States)

    Lin, J.; Horwitz, J. L.; Gallagher, D.; Pollock, C. J.

    1994-01-01

    Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the equatorial region of the inner magnetosphere. In this analysis, we have characterized such features as the equatorial ion flux anisotropy, the penetration of field-aligned ionospheric streams into the equatorial region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of equatorial ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher equatorial ion anisotropy. We may interpret these features in terms of Liouville mapping of equatorially trapped ions and the reflection of the incoming ionospheric ion streams from the equatorial potential peaks associated with such trapped ions.

  7. Fiji in the South Pacific.

    Science.gov (United States)

    Scott, Rosalind; Semaan, Leslie

    This text introduces Fiji and other island nations located in the Pacific, the world's largest ocean. Cut off from the world by vast expanses of water, these people developed a unique culture. Contents include: Teacher Overview, Geography of the South Pacific Islands, History of the South Pacific, Fiji, Traditional Village Life, Yaquna Ceremony,…

  8. Global Ocean Sedimentation Patterns: Plate Tectonic History Versus Climate Change

    Science.gov (United States)

    Goswami, A.; Reynolds, E.; Olson, P.; Hinnov, L. A.; Gnanadesikan, A.

    2014-12-01

    Global sediment data (Whittaker et al., 2013) and carbonate content data (Archer, 1996) allows examination of ocean sedimentation evolution with respect to age of the underlying ocean crust (Müller et al., 2008). From these data, we construct time series of ocean sediment thickness and carbonate deposition rate for the Atlantic, Pacific, and Indian ocean basins for the past 120 Ma. These time series are unique to each basin and reflect an integrated response to plate tectonics and climate change. The goal is to parameterize ocean sedimentation tied to crustal age for paleoclimate studies. For each basin, total sediment thickness and carbonate deposition rate from 0.1 x 0.1 degree cells are binned according to basement crustal age; area-corrected moments (mean, variance, etc.) are calculated for each bin. Segmented linear fits identify trends in present-day carbonate deposition rates and changes in ocean sedimentation from 0 to 120 Ma. In the North and South Atlantic and Indian oceans, mean sediment thickness versus crustal age is well represented by three linear segments, with the slope of each segment increasing with increasing crustal age. However, the transition age between linear segments varies among the three basins. In contrast, mean sediment thickness in the North and South Pacific oceans are numerically smaller and well represented by two linear segments with slopes that decrease with increasing crustal age. These opposing trends are more consistent with the plate tectonic history of each basin being the controlling factor in sedimentation rates, rather than climate change. Unlike total sediment thickness, carbonate deposition rates decrease smoothly with crustal age in all basins, with the primary controls being ocean chemistry and water column depth.References: Archer, D., 1996, Global Biogeochem. Cycles 10, 159-174.Müller, R.D., et al., 2008, Science, 319, 1357-1362.Whittaker, J., et al., 2013, Geochem., Geophys., Geosyst. DOI: 10.1002/ggge.20181

  9. Indo-Pacific echinoids in the tropical eastern Pacific

    Science.gov (United States)

    Lessios, H. A.; Kessing, B. D.; Wellington, G. M.; Graybeal, A.

    1996-06-01

    The existing literature reports that only one species of Indo-Pacific echinoid ( Echinometra oblonga), occurs in the eastern Pacific. In this study we confirm the presence of this species at Islas Revillagigedo and also report the presence of two species of Echinothrix (a genus hitherto unknown outside the Indo-Pacific) at Isla del Coco and at Clipperton Island. We also present evidence from isozymes and from mitochondrial DNA sequences indicating that at least one individual of Diadema at Clipperton may belong to a maternal lineage characteristic of the west Pacific species D. savignyi. These data are consistent with the hypothesis that the observed populations of Indo-Pacific echinoid species are recent arrivals to the eastern Pacific, as opposed to the view that they are relicts of Tethyan pan-tropical distributions. Echinothrix diadema, in particular, may have arrived at Isla del Coco during the 1982-1983 El Nifio. In addition to Indo-Pacific species, Clipperton, Isla del Coco and the Revillagigedos contain a complement of eastern Pacific echinoids. The echinoid faunas of these islands should, therefore, be regarded as mixtures of two biogeographic provinces. Though none of the Indo-Pacific species are known to have reached the coast of the American mainland, their presence at the offshore islands of the eastern Pacific suggests that, for some echinoids, the East Pacific Barrier is not as formidable an obstacle to migration as was previously thought.

  10. Spatial relationship of 1-meter equatorial spread-F irregularities and depletions in total electron content

    International Nuclear Information System (INIS)

    Tsunoda, R.T.; Towle, D.M.

    1979-01-01

    An experiment was conducted at Kwajalein Atoll, Marshall Islands to investigate the spatial relationship of 1-m equatorial spread-F irregularities to total electron content (TEC) depletions. A high-power radar was operated (1) in a backscatter scan mode to spatially map the distribution of 1-m irregularities, and (2) in a dual-frequency, satellite-track mode to obtain the longitudinal TEC variations. We show that radar backscatter ''plumes'' found in the disturbed, nighttime equatorial ionosphere are longitudinally coincident with TEC depletions. We suggest that the TEC depletions are probably due to the presence of plasma ''bubbles'' in the equatorial F layer

  11. The physical and theoretical basis of solar-terrestrial relationships 1. Equatorial locations

    International Nuclear Information System (INIS)

    Njau, E.C.

    1988-07-01

    The theory of solar-terrestrial relationships developed earlier by the author is extended to incorporate expressions that represent the non-linear responses of the earth-atmosphere system to incoming solar radiation in a more detailed manner. Application of the extended theory to equatorial locations leads to new and interesting features that are consistent with past observations. It also predicts the existence of new oscillations in the equatorial atmosphere whose causative physical processes are given and explained. Non-equatorial locations are treated along similar lines in Part 2 of the series. (author). 44 refs

  12. Pacific Island Pharmacovigilance

    DEFF Research Database (Denmark)

    McEwen, John; Vestergaard, Lasse S.; Sanburg, Amanda L C

    2016-01-01

    Many Pacific Island countries (PICs) are recipients of funding support from the Global Fund to Fight AIDS, Tuberculosis and Malaria (Global Fund). However, most of these countries cannot be expected to meet Global Fund and World Health Organization (WHO) minimum requirements for a functioning...

  13. DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena

    Science.gov (United States)

    Berthelier, J.; Malingre, M.; Pfaff, R.; Jasperse, J.; Parrot, M.

    2008-12-01

    DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time equatorial ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a

  14. Regional gradients in surface sediment nitrogen isotopes as a reflection of nutrient cycling and oxygen deficiency in upwelling areas off Peru and Namibia (Invited)

    Science.gov (United States)

    Schneider, R. R.; Mollier-Vogel, E.; Martinez, P.

    2010-12-01

    The sedimentary d15N signal is commonly considered as a reflection of the marine nutrient cycling and related biochemical processes in the overlying water masses. In the modern ocean all processes together result in a mean d15N value of about 5 to 6 per mill for dissolved nitrate. Deviations from this value are considered as a product mainly of nitrogen fixation and nitrate supply causing lower values, while nitrate utilization and denitrification, as well as organic matter degradation tend to shift the signal to higher values. As denitrification is only occurring under conditions of strong oxygen limitation in the water column outstandingly high d15N values in sediment records are commonly taken as indirect evidence for strong oxygen minimum conditions in the past. By comparing surface sediment values from coastal upwelling areas off Namibia and Peru, we test whether such an approach is applicable. Only the Peruvian system is characterized by a pronounced oxygen minimum zone (OMZ) that extends across the shelf and slope far into the Eastern Equatorial Pacific. For comparison we present new results for the Peruvian margin between 2°N and 20°S within and below the Peruvian OMZ in combination with a similar data set from the Namibian margin with an OMZ restricted to the inner shelf. The Peruvian sediment data is furthermore compared to d15N of dissolved nitrate in the overlying water column to better understand how regional oceanography effects the water column d15N and thus the sediment surface signal. Productivity and nitrate uptake is maximal at the position of local and perennial upwelling cells in both systems. However, due to continuous nutrient supply into the upwelling systems sedimentary d15N values on the outer shelves and slopes reveal an increase of only about 2 to 3 per mill over the mean ocean value. Only where extreme oxygen deficiency occurs, as off Peru between 10 and 20 S, the sedimentary d15N signal reaches very high values above 10 per mill

  15. Using constructed analogs to improve the skill of National Multi-Model Ensemble March–April–May precipitation forecasts in equatorial East Africa

    International Nuclear Information System (INIS)

    Shukla, Shraddhanand; Funk, Christopher; Hoell, Andrew

    2014-01-01

    In this study we implement and evaluate a simple ‘hybrid’ forecast approach that uses constructed analogs (CA) to improve the National Multi-Model Ensemble’s (NMME) March–April–May (MAM) precipitation forecasts over equatorial eastern Africa (hereafter referred to as EA, 2°S to 8°N and 36°E to 46°E). Due to recent declines in MAM rainfall, increases in population, land degradation, and limited technological advances, this region has become a recent epicenter of food insecurity. Timely and skillful precipitation forecasts for EA could help decision makers better manage their limited resources, mitigate socio-economic losses, and potentially save human lives. The ‘hybrid approach’ described in this study uses the CA method to translate dynamical precipitation and sea surface temperature (SST) forecasts over the Indian and Pacific Oceans (specifically 30°S to 30°N and 30°E to 270°E) into terrestrial MAM precipitation forecasts over the EA region. In doing so, this approach benefits from the post-1999 teleconnection that exists between precipitation and SSTs over the Indian and tropical Pacific Oceans (Indo-Pacific) and EA MAM rainfall. The coupled atmosphere-ocean dynamical forecasts used in this study were drawn from the NMME. We demonstrate that while the MAM precipitation forecasts (initialized in February) skill of the NMME models over the EA region itself is negligible, the ranked probability skill score of hybrid CA forecasts based on Indo-Pacific NMME precipitation and SST forecasts reach up to 0.45. (letter)

  16. An Analysis of Unseasonal Equatorial Plasma Bubbles in July 2014

    Science.gov (United States)

    Carter, B. A.; Currie, J. L.; Pradipta, R.; Groves, K. M.; Caton, R. G.; Yokoyama, T.

    2017-12-01

    In the equatorial ionosphere, the Raleigh-Taylor (RT) plasma instability in the post sunset region is known to cause plasma depletions, known as equatorial plasma bubbles (EPBs). These EPBs can have adverse effects on satellite-reliant technologies by causing scintillations in the phase and amplitude of Global Navigation Satellite System (GNSS) signals. The effect of EPBs on satellite-reliant technologies highlights a need for reliable forecasting of EPBs in the low-latitude regions, which requires a solid understanding of their climatology and daily variability. The climatology of EPB occurrence is known to correlate with the angle between the magnetic field and solar terminator. This angle controls the longitudinal E-region conductivity gradient across the day-night terminator, which influences the strength of the pre-reversal enhancement in the upward plasma drift, a dominant term in the linear RT growth rate. This relationship is well established from ground-based GNSS and satellite-based studies. However, reliable forecasts have not been developed by space weather forecasting agencies due to the lack of understanding of EPB daily variability. During July, EPB occurrence is small in the South-East Asia longitude sector due to the relatively large angle between the magnetic field and solar terminator. As a result, the pre-reversal enhancement in the upward plasma drift is typically low during this period, creating less favourable conditions for EPB growth. However, despite the typically low pre-reversal enhancement strength, this analysis reveals that July 2014 is not devoid of EPB events above South-East Asia. These unseasonal EPB events during July 2014 are studied in the context of the prevalently low solar and geomagnetic activity conditions. Given the lack of solar and geomagnetic control, the influence of the lower atmosphere on EPB generation (e.g., via atmospheric gravity wave seeding) is explored. These events provide a unique opportunity to investigate

  17. Priority areas for large mammal conservation in Equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Mizuki Murai

    Full Text Available Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1 the relative importance of local vs. commercial hunting; 2 wildlife density of protected vs. non-protected areas; and 3 the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789 elephants and 11,097 (8,719-13,592 chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal

  18. Complementary Use of Glider Data, Altimetry, and Model for Exploring Mesoscale Eddies in the Tropical Pacific Solomon Sea

    Science.gov (United States)

    Gourdeau, L.; Verron, J.; Chaigneau, A.; Cravatte, S.; Kessler, W.

    2017-11-01

    Mesoscale activity is an important component of the Solomon Sea circulation that interacts with the energetic low-latitude western boundary currents of the South Tropical Pacific Ocean carrying waters of subtropical origin before joining the equatorial Pacific. Mixing associated with mesoscale activity could explain water mass transformation observed in the Solomon Sea that likely impacts El Niño Southern Oscillation dynamics. This study makes synergetic use of glider data, altimetry, and high-resolution model for exploring mesoscale eddies, especially their vertical structures, and their role on the Solomon Sea circulation. The description of individual eddies observed by altimetry and gliders provides the first elements to characterize the 3-D structure of these tropical eddies, and confirms the usefulness of the model to access a more universal view of such eddies. Mesoscale eddies appear to have a vertical extension limited to the Surface Waters (SW) and the Upper Thermocline Water (UTW), i.e., the first 140-150 m depth. Most of the eddies are nonlinear, meaning that eddies can trap and transport water properties. But they weakly interact with the deep New Guinea Coastal Undercurrent that is a key piece of the equatorial circulation. Anticyclonic eddies are particularly efficient to advect salty and warm SW coming from the intrusion of equatorial Pacific waters at Solomon Strait, and to impact the characteristics of the New Guinea Coastal Current. Cyclonic eddies are particularly efficient to transport South Pacific Tropical Water (SPTW) anomalies from the North Vanuatu Jet and to erode by diapycnal mixing the high SPTW salinity.

  19. Impact of surface sensible heating over the Tibetan Plateau on the western Pacific subtropical high: A land-air-sea interaction perspective

    Science.gov (United States)

    Duan, Anmin; Sun, Ruizao; He, Jinhai

    2017-02-01

    The impact of surface sensible heating over the Tibetan Plateau (SHTP) on the western Pacific subtropical high (WPSH) with and without air-sea interaction was investigated in this study. Data analysis indicated that SHTP acts as a relatively independent factor in modulating the WPSH anomaly compared with ENSO events. Stronger spring SHTP is usually followed by an enhanced and westward extension of the WPSH in summer, and vice versa. Numerical experiments using both an AGCM and a CGCM confirmed that SHTP influences the large-scale circulation anomaly over the Pacific, which features a barotropic anticyclonic response over the northwestern Pacific and a cyclonic response to the south. Owing to different background circulation in spring and summer, such a response facilitates a subdued WPSH in spring but an enhanced WPSH in summer. Moreover, the CGCM results showed that the equatorial low-level westerly at the south edge of the cyclonic anomaly brings about a warm SST anomaly (SSTA) in the equatorial central Pacific via surface warm advection. Subsequently, an atmospheric Rossby wave is stimulated to the northwest of the warm SSTA, which in turn enhances the atmospheric dipole anomalies over the western Pacific. Therefore, the air-sea feedbacks involved tend to reinforce the effect of SHTP on the WPSH anomaly, and the role of SHTP on general circulation needs to be considered in a land-air-sea interaction framework.

  20. Determination of vertical velocities in the equatorial part of the western Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Varadachari, V.V.R.

    Using steady state two-dimensional turbulent diffusion equations of salt and heat some important characteristics of vertical circulation in the equatorial part of the Indian Ocean have been evaluated and discussed. Upwelling and sinking velocities...

  1. Surface currents in the equatorial Indian Ocean during spring and fall - An altimetry based analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Somayajulu, Y.K.

    This communication presents the results of a study aimed at investigating the nature and variability of surface currents in the equatorial Indian Ocean between 5 degrees N and 5 degrees S during spring and fall seasons. Geostrophic surface currents...

  2. Observational evidence of lower-frequency Yanai waves in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    David, D.T.; PrasannaKumar, S.; Byju, P.; Sarma, M.S.S.; Suryanarayana, A.; Murty, V.S.N.

    created by the northward shifting and strengthening of the westward flowing south equatorial current associated with positive IOD and the eastward flowing southwest monsoon current provides energy for the generation of lower-frequency Yanai waves. Vertical...

  3. Detection and Characterization of Equatorial Scintillation for Real-Time Operational Support

    National Research Council Canada - National Science Library

    McNeil, W

    1997-01-01

    The Phillips Laboratory Scintillation Network Decision Aid (PL-SCINDA) is a software tool which uses real-time data from remote sites to model ionospheric plasma depletions in the equatorial region...

  4. Investigations of equatorial ionosphere nighttime mode conversion at VLF

    Science.gov (United States)

    Hildebrand, Verne

    1993-05-01

    VLF Radiowave propagation provides one of the few viable tools for exploring the properties of the lower D-region ionosphere. Conversely, VLF communications coverage analysis and prediction is directly dependent on the quality of models for the D-region ionosphere. The VLF Omega navigation signals are an excellent and under-utilized resource for conducting D-region research in direct support of VLF communications. Stations are well placed for investigating polar, mid latitude, and equatorial phenomena. Much can be learned by fully utilizing the very stable signals radiated at five frequencies, available from each of the eight transmitters, and taking full advantage of modal structure. While the Omega signals, 10.2 to 13.6 kHz, are well below the VLF communications band, we contend that much of the knowledge gained on D-region characteristics can be directly applied at the higher frequencies. The opportunity offered by Omega needs to be exploited. With the Global Positioning System (GPS) coming onboard as the prime means for global navigation, pressure is mounting to phase out Omega. In this paper we describe how we are using Omega along with computer codes of full wave VLF propagation, provided to us by the U.S. Naval Ocean Systems Center (NOSC), for ionosphere research and by example illustrate the potential for other investigations.

  5. Equatorial segment of the mid-atlantic ridge

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics 380 refs.

  6. Equatorial segment of the mid-atlantic ridge

    International Nuclear Information System (INIS)

    1996-01-01

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics

  7. A mantle plume model for the Equatorial Highlands of Venus

    Science.gov (United States)

    Kiefer, Walter S.; Hager, Bradford H.

    1991-01-01

    The possibility that the Equatorial Highlands are the surface expressions of hot upwelling mantle plumes is considered via a series of mantle plume models developed using a cylindrical axisymmetric finite element code and depth-dependent Newtonian rheology. The results are scaled by