WorldWideScience

Sample records for equatorial pacific sediments

  1. 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...

  2. {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.

  3. 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

  4. 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

  5. Equatorial Pacific Productivity Events and Intervals in the Middle and late Miocene through XRF-Scanned Bulk Sediment Composition Data

    Science.gov (United States)

    Lyle, M. W.; Stepanova, A.; Wilson, J. K.; Marcantonio, F.

    2014-12-01

    The equatorial Pacific is the largest open ocean productivity center, responsible for nearly half of global marine new production and about 40% of CaCO3 burial. Understanding how the equatorial Pacific upwelling system has evolved over the Neogene is critical to understand the evolution of the global carbon cycle. We know from reconnaissance studies that productivity in equatorial Pacific surface waters as well as dissolution driven by deep waters have strongly affected the sediment record. We have used calibrated XRF scanning to capture anomalies in equatorial Pacific upwelling and productivity at Milankovitch-resolving resolution since the early Miocene. The 8 elements calibrated in the XRF scans can be used to distinguish intervals of high carbonate dissolution from those of high productivity. Carbonate dissolution intervals are recorded by a drop of CaCO3 relative to Aeolian clays, with little change in the ratio between estimated opal and clay (estimated by TiO2). In contrast, high production intervals have high opal/TiO2 and low CaCO3. Low CaCO3 contents are caused partly by dilution, since high production skews tropical particulate rain to be more opal-rich relative to carbonate, and additional C-org rain can help to increase CaCO3 dissolution within near-surface sediments. We observe long-lived high production anomalies modulated by orbitally-driven climate variability. Prominent intervals are found at the end of the Miocene climate optimum (~ 14 Ma), interspersed with dissolution intervals in the Carbonate Crash interval (~9-11 Ma), and in the Biogenic Bloom interval (8-4.5 Ma). Using relationships among biogenic fluxes in modern equatorial sediment trap studies, especially the positive correlations between biogenic Ba , C-org, and CaCO3 fluxes, we find that the highest production intervals have much higher opal/C-org in the particulate rain, implying an inefficient carbon pump to the deep ocean. If confirmed, productivity was not as strong a feedback to

  6. Phylogenetic Characterization of Marine Benthic Archaea in Organic-Poor Sediments of the Eastern Equatorial Pacific Ocean (ODP Site 1225

    Directory of Open Access Journals (Sweden)

    Antje Lauer

    2016-09-01

    Full Text Available Sequencing surveys of microbial communities in marine subsurface sediments have focused on organic-rich, continental margins; the database for organic-lean deep-sea sediments from mid-ocean regions is underdeveloped. The archaeal community in subsurface sediments of ODP Site 1225 in the eastern equatorial Pacific (3760 m water depth; 1.1 and 7.8 m sediment depth was analyzed by PCR, cloning and sequencing, and by denaturant gradient gel electrophoresis (DGGE of 16S rRNA genes. Three uncultured archaeal lineages with different depth distributions were found: Marine Group I (MG-I within the Thaumarchaeota, its sister lineage Marine Benthic Group A (MBG-A, the phylum-level archaeal lineage Marine Benthic Group B (also known as Deep-Sea Archaeal Group or Lokiarchaeota, and the Deep-Sea Euryarchaeotal Group 3. The MG-I phylotypes included representatives of sediment clusters that are distinct from the pelagic members of this phylum. On the scale from fully oxidized, extremely organic carbon-depleted sediments (for example, those the South Pacific Gyre to fully reduced, organic carbon-rich marine subsurface sediments (such as those of the Peru Margin, Ocean Drilling Program (ODP Site 1225 falls into the non-extreme organic carbon-lean category, and harbors archaeal communities from both ends of the spectrum.

  7. 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.

  8. 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.)

  9. Diffusive Transfer of Oxygen From Seamount Basaltic Crust Into Overlying Sediments: an Example From the Clarion-Clipperton Fracture Zone, Equatorial Pacific Ocean

    Science.gov (United States)

    Kasten, S.; Mewes, K.; Mogollón, J.; Picard, A.; Rühlemann, C.; Eisenhauer, A.; Kuhn, T.; Ziebis, W.

    2015-12-01

    Within the Clarion-Clipperton Fracture Zone (CCFZ) located in the equatorial Pacific Ocean numerous seamounts, with diameters ranging from 3 to 30 km and varying heights above the surrounding seafloor of up to 2500 m, occur throughout the deep-sea plain. There is evidence that these may serve as conduits for low-temperature hydrothermal circulation of seawater through the oceanic crust. During RV SONNE cruise SO205 in April/May 2010 and BIONOD cruise with RV ĹATALANTE in spring 2012 we took piston and gravity cores for geochemical analyses, as well as for high-resolution pore-water oxygen and nutrient measurements. Specifically, we took cores along a transect at three sites, located 400, 700 and 1000 m away from the foot of a 240 m high seamount, called 'Teddy Bare'. At all 3 sites oxygen penetrates the entire sediment column of the organic carbon-poor sediment. More importantly, oxygen concentrations initially decrease with sediment depth but increase again at depths of 3 m and 7 m above the basaltic basement, suggesting an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments. This is the first time this has been shown for the deep subsurface in the Pacific Ocean. Mirroring the oxygen concentrations nitrate concentrations accumulate with sediment depth but decrease towards the basement. Transport-reaction modeling revealed that (1) the diffusive flux of oxygen from the basaltic basement exceeds the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange between the sediment and the underlying basaltic crust occurs at orders-of-magnitude lower rates than between the sediment surface and the overlying bottom water. We furthermore show that the upward diffusion of oxygen from the basaltic basement affects the preservation of organic compounds within the oxic sediment column at all 3 sites. Our investigations indicate that an upward

  10. Latitudinal comparisons of equatorial Pacific zooplankton

    Science.gov (United States)

    Roman, M. R.; Dam, H. G.; Le Borgne, R.; Zhang, X.

    Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S-5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase "downstream" of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 μm) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally migrant zooplankton in the HNLC zone is a minor fraction of the gravitational flux (2% at 140°W, 4% at 180°) but increases in the more oligotrophic regions to the north and south where there is a deeper mixed layer and a greater relative proportion of diel migrant zooplankton.

  11. 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....

  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. 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.

  14. {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.

  15. 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.

    Wind patterns in the equatorial Pacific and Indian oceans are the factors that regulate the chlorophyll pigment distributions in the equatorial region of these oceans. Trade winds and coastline of the Pacific basin supports wave-guide dynamics...

  16. 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.

    Geochemical investigations including partition analysis have been carried out on nine sediment cores from the western equatorial Indian Ocean. The results show that a core from the Arabian Sea exhibits a greater terrigenous influence than cores from...

  17. Amplitude and timing of the Laschamp geomagnetic dipole low from the global atmospheric 10Be overproduction: Contribution of authigenic 10Be/9Be ratios in west equatorial Pacific sediments

    Science.gov (United States)

    MéNabréAz, L.; BourlèS, D. L.; Thouveny, N.

    2012-11-01

    Authigenic 10Be/9Be ratios were measured along a sediment core collected in the west equatorial Pacific in order to reconstruct cosmogenic 10Be production variations near the equator, where the geomagnetic modulation is maximum. From 60 to 20 ka, the single significant 10Be production impulse recorded at 41 ka results from the geomagnetic dipole low that triggered the Laschamp excursion. No significant 10Be overproduction signature is recorded at the age of the Mono Lake excursion (˜34 ka). A compilation of authigenic 10Be/9Be records obtained from sediments was averaged over a 1 kyr window and compared with the 1 kyr averaged 10Be flux record of Greenland ice cores. Their remarkable similarity demonstrates that 10Be production is globally modulated by geomagnetic dipole variations and redistributed by atmosphere dynamics. After calibration using absolute values of the virtual dipole moment drawn from paleomagnetic database, the authigenic 10Be/9Be stack allows reconstructing the geomagnetic dipole moment variations over the 20-50 ka time interval. Between 48 and 41 ka, the dipole moment collapsed at a rate of -1.5 × 1022 A m2 kyr-1, which will be an interesting criterion for the assessment of the loss rate of the historical field and the comparison of dipole moment loss prior to excursions and reversals. After a 2 kyr duration of the minimum dipole moment (˜1 × 1022 A m2), a slow increase started at 39 ka, progressively reaching 5 × 1022 A m2 at 20 ka. The absence of a significant dipole moment drop at 34 ka, the age of the Mono lake excursion, suggests that the duration and amplitude of the dipole weakening cannot be compared with that of the Laschamp. This study provides a reliable basis to model the production of radiocarbon and in situ cosmogenic nuclides and to improve the calibration of these dating methods.

  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. 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 (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.

  1. 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

  2. Regulation of primary productivity rate in the equatorial Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Barber, R.T. (Duke Univ. Marine Lab., Beaufort, NC (United States)); Chavez, F.P. (Monterey Bay Aquarium Research Inst., Pacific Grove, CA (United States))

    1991-12-01

    Analysis of the Chl-specific rate of primary productivity (P{sup 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{sub 3}) from 0 to {approximately}12 {mu}M, the productivity rate is a linear function of nutrient concentration; in the eastern Pacific where the gradient is from 12 to 28 {mu}M, the productivity rate is independent of nutrient concentration and limited to {approximately}36 mg C(mg Chl){sup {minus}1} d{sup {minus}1}, or a mean euphotic zone C-specific growth rate ({mu}) of 0.47 d{sup {minus}1}. However, rates downstream of the Galapagos Islands are not limited; they are 46.4 mg C(mg Chl){sup {minus}1} d{sup {minus}1} and {mu} = 0.57 d{sup {minus}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.

  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. 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.

  5. 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.

    pigment concentration from the Coastal Zone Color Scanner (CZCS). In the equatorial Pacific heat accumulation due to a higher abundance of chlorophyll pigments in the equatorial Pacific leads to a decrease of the mixed layer thickness. This generates...

  6. 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...

  7. Semidiurnal internal tide incoherence in the equatorial Pacific

    Science.gov (United States)

    Buijsman, Maarten C.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Wallcraft, Alan J.; Zamudio, Luis

    2017-07-01

    The jets in the equatorial Pacific Ocean of a realistically forced global circulation model with a horizontal resolution of 1/12.5° cause a strong loss of phase coherence in semidiurnal internal tides that propagate equatorward from the French Polynesian Islands and Hawaii. This loss of coherence is quantified with a baroclinic energy analysis, in which the semidiurnal-band terms are separated into coherent, incoherent, and cross terms. For time scales longer than a year, the coherent energy flux approaches zero values at the equator, while the total flux is ˜500 W/m. The time variability of the incoherent energy flux is compared with the internal-tide travel-time variability, which is based on along-beam integrated phase speeds computed with the Taylor-Goldstein equation. The variability of monthly mean Taylor-Goldstein phase speeds agrees well with the phase speed variability inferred from steric sea surface height phases extracted with a plane-wave fit technique. On monthly time scales, the loss of phase coherence in the equatorward beams from the French Polynesian Islands is attributed to the time variability in the vertically sheared background flow associated with the jets and tropical instability waves. On an annual time scale, the effect of stratification variability is of equal or greater importance than the shear variability is to the loss of coherence. In the model simulations, low-frequency equatorial jets do not noticeably enhance the dissipation of the internal tide, but merely decohere and scatter it.

  8. Central Equatorial Pacific Experiment (CEPEX) MODIS Airborne Simulator (MAS) Level-1B Data Products

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the Central Equatorial Pacific Experiment (CEPEX) campaign was to study the effects that Cirrus cloud radiative and surface evaporation properties...

  9. 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...

  10. 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.

  11. 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.)

  12. 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

  13. 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

  14. The Direct Response in the Equatorial Pacific to the 11 year Solar Cycle Forcing and its mechanisms

    Science.gov (United States)

    Huo, Wenjuan; Xiao, Ziniu

    2017-04-01

    The equatorial Pacific response to 11-year solar cycle is assessed in observation and ensemble historical-Nat simulations from the Coupled Model Intercomparison Project, Phase 5 (CMIP5). We find the central equatorial Pacific is sensitive to the solar forcing. A significant positive correlation is found between observed sea surface temperature (SST) anomaly and sunspot number (SSN) index with a lag of 2 years in the central Pacific. The 11-year solar signal particularly exits in the SST and zonal wind anomalies from spectrum analysis. Based on composite analysis, a warming response appears in the central Pacific with lagging the solar cycle by 1-2 years in observation, and 2-3 years in simulation results. Associated with the ocean temperature anomaly, an anomalous twin Walker circulation cells arise in the equatorial Pacific with their updraft branch centered over the central equatorial Pacific, which is significantly both in observation and simulation. Mixed layer heat budget analysis shows that the atmosphere radiation fluxes modulated by the amounts of cloud cover are responsible for the warming response pattern in the central Pacific. There is a significant positive correlation between the meridional gradient of cloud cover (Δα, Subtropics-Tropic) and zonal SST gradient (ΔT, east-west) in the equatorial Pacific. The warming response in the central equatorial Pacific is amplified by the coupled atmosphere and ocean processes. On the one hand, owing to the zonal SST gradient decreasing in the western and central Pacific but increasing in the eastern and central Pacific, anomalous zonal wind convergence appears in the central Pacific in the three years following the solar peak. The ocean heat transport effect is negative in the central equatorial Pacific, more warm water accumulates locally. On the other hand, anomalous ascending motion over the central Pacific increases the high cloud amount and lets more shortwave radiation come into surface, which combined

  15. 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...

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

    Science.gov (United States)

    Pittauer, Daniela; Roos, Per; Qiao, Jixin; Geibert, Walter; Elvert, Marcus; Fischer, Helmut W

    2018-06-01

    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 210 Pb together with excess 228 Th and anthropogenic radionuclides provided information about accumulation rates. Concentrations of Am and Pu isotopes were detected by gamma spectrometry, alpha spectrometry and ICP-MS. The Pu ratios indicate a high portion (minimum of 60%) of Pu from the Pacific Proving Grounds (PPG). This implies that the transport of PPG derived plutonium with the Mindanao Current southward is similarly effective as the previously known transport towards the north with the Kuroshio Current. The record is compared to other studies from northwest Pacific marginal seas and Lombok basin in the Indonesian Archipelago. The sediment core top was found to contain a 6 cm thick layer dominated by terrestrial organic matter, which was interpreted as a result of the 2012 Typhoon Pablo-related fast deposition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. 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

  18. Equatorial Pacific gravity lineaments: interpretations with basement topography along seismic reflection lines

    Science.gov (United States)

    Mitchell, Neil C.; Davies, Huw

    2018-03-01

    The central equatorial Pacific is interesting for studying clues to upper mantle processes, as the region lacks complicating effects of continental remnants or major volcanic plateaus. In particular, the most recently produced maps of the free-air gravity field from satellite altimetry show in greater detail the previously reported lineaments west of the East Pacific Rise (EPR) that are aligned with plate motion over the mantle and originally suggested to have formed from mantle convection rolls. In contrast, the gravity field 600 km or farther west of the EPR reveals lineaments with varied orientations. Some are also parallel with plate motion over the mantle but others are sub-parallel with fracture zones or have other orientations. This region is covered by pelagic sediments reaching 500-600 m thickness so bathymetry is not so useful for seeking evidence for plate deformation across the lineaments. We instead use depth to basement from three seismic reflection cruises. In some segments of these seismic data crossing the lineaments, we find that the co-variation between gravity and basement depth is roughly compatible with typical densities of basement rocks (basalt, gabbro or mantle), as expected for some explanations for the lineaments (e.g., mantle convection rolls, viscous asthenospheric inter-fingering or extensional deformation). However, some other lineaments are associated with major changes in basement depth with only subtle changes in the gravity field, suggesting topography that is locally supported by varied crustal thickness. Overall, the multiple gravity lineament orientations suggest that they have multiple origins. In particular, we propose that a further asthenospheric inter-fingering instability mechanism could occur from pressure variations in the asthenosphere arising from regional topography and such a mechanism may explain some obliquely oriented gravity lineaments that have no other obvious origin.

  19. Late Quaternary CaCO3 stratigraphy of the eastern equatorial Pacific

    Science.gov (United States)

    Snoeckx, Hilde; Rea, David K.

    1994-04-01

    Four patterns of CaCO3 abundance occur in cores retrieved from the eastern equatorial Pacific during the Venture 01 expedition. Core locations lie along a north-south transect at 110°W underneath the different currents of the equatorial current system and along an east-west transect from 110° to 90°W, at approximately 3°S, underneath the South Equatorial Current. The "classic" or central equatorial Pacific pattern of CaCO3 abundance maxima associated with glacial stages as defined by the δ18O record characterizes only a small portion of the area studied. In the area where the Peru current turns west to join the South Equatorial Current, the carbonate record is characterized by a broad low, centered on interglacial carbonate stage B-3 (approximately stage 5 in δ18O stratigraphy) overlying a broad mid-Brunhes maximum. Low-amplitude variations in CaCO3 percentages are superimposed on this pattern. This pattern extends westward in a long-wavelength pattern in which the B-3 carbonate low becomes decreasingly pronounced away from the equator. The fourth pattern, observed north of 10°N, is erratic and may be only local in extent.

  20. 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.

  1. 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.

  2. 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.

  3. 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)

  4. Central Pacific El Niño equatorial wave dynamics (1990-2012)

    Science.gov (United States)

    Mosquera-Vásquez, K.; Dewitte, B.; Illig, S.

    2013-12-01

    It is now recognized that two types of El Niño have existed over the last five decades, the so-called canonical Eastern Pacific El Niño with peak anomaly in the eastern Pacific and the Central Pacific El Niño that develops in the central equatorial Pacific. The dynamics of the latter remain unclear mostly because of the delicate balance between feedback processes in the central equatorial Pacific. Here we investigate the role of the equatorial Kelvin wave on the development of SST anomalies over 1989-2012, contrasting the extreme 1997/98 El Niño events with all the other moderate events during this period, and differenciating intraseasonal and interannual timescales. As a first step, the equatorial Kelvin wave is estimated based on an OGCM simulation thoroughly validated from in situ observations. It is showed that the seasonal evolution of the intraseasonal Kelvin wave (IEK) activity is distinct during CP events than during the 1997/98 El Niño, the variance peaking in boreal winter for CP events. CP events differ in terms of the duration of their warming and cooling phases, which motivates the use of the SST tendency as an index for compositing events. A composite normalised mixed-layer heat budget is thus derived that focuses on the wave-induced advection terms. The results indicate that there is no fundamental difference between strong and moderate events in terms of the relative balance between advection terms at interannual timescales in the central Pacific. In particular the anomalous zonal advection of climatological temperature has a comparable contribution to the rate of SST change. The results also indicate that the wave-induced advection accounts for ~50% of the explained variance of the total zonal anomalous advection in the central Pacific versus ~80% for the locally wind-driven zonal advection, and this has not changed over the record. Larger differences between events are found for the intraseasonal timescales, with in particular an increased

  5. 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...

  6. 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.

  7. Intraseasonal Kelvin wave along the equatorial Pacific in the two flavors of El Nino

    Science.gov (United States)

    Feng, J.; Wang, Q.; Hu, S.; Hu, D.

    2016-02-01

    The spatial structure and temporal evolution of the intraseasonal variability (ISV) of the subsurface ocean temperature (STA) in the equatorial Pacific associated with the two flavors of El Nino (i.e., the canonical or eastern Pacific (EP) El Nino and the central Pacific (CP) El Nino) are investigated using observations and 1.5-layer linear reduced gravity model. Results suggest that the ISV characteristics show some differences in the two types of El Nino, though both oscillate along the thermocline in the form of the intraseasonal equatorial Kelvin wave, which is excited in the western tropical Pacific by the zonal wind stress associated with the Madden-Julian oscillation (MJO). First, the period of dominant mode of the STA ISV during CP El Nino broadly distributes in 50-80 days with the spectra peaking in 60-65-day. By contrast, the spectrum of STA ISV during EP El Nino shows a peak in 75-80-day period. This indicates the wave speed is faster in the CP El Nino than in EP El Nino. Second, the ISV activity peaks in previous spring during the developing phase of EP El Nino, whereas during CP El Nino it becomes the most active during the mature phase. Third, the strongest IEKW occurs in the central Pacific around the dateline during CP El Nino and attenuates quickly east of 130°W due to strong eddy viscosity dissipation, while the IEKW during the EP El Nino propagates efficiently from the western to the eastern Pacific with a relative weak diffusion.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Robust increase of the equatorial Pacific rainfall and its variability in a warmed climate

    Science.gov (United States)

    Watanabe, Masahiro; Kamae, Youichi; Kimoto, Masahide

    2014-05-01

    Regional pattern of the mean precipitation changes in the latter half of the 21st century (ΔP>¯) has been interpreted in terms of mean precipitation in current climate and a magnitude of increase in mean sea surface temperature (SST). Here we use state-of-the-art climate model ensembles from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and present that the amplitude of the precipitation variability, relative to slowly varying mean precipitation, coherently increases with ΔP>¯, anchored over the central equatorial Pacific where a large SST swing occurs during El Niño-Southern Oscillation (ENSO) cycles. This increase owes to skewed probability distribution of precipitation as well as an asymmetrical precipitation response to positive and negative in situ SST anomalies and is robust despite uncertainty in the future ENSO amplitude change. The CMIP5 model ensembles also give a robust estimate of the projected ΔP>¯ over the central equatorial Pacific, showing a 7% increase per unit increase of global-mean surface temperature. Observational constraints applied to the above relationship suggest that the amounts of increases in both mean precipitation and variability should be even larger than the model averages.

  15. 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".

  16. 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.

  17. 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

  18. Epipelagic copepod distributions in the eastern equatorial Pacific during the weak La Niña event of 2001

    Directory of Open Access Journals (Sweden)

    Pritha Tutasi

    2011-07-01

    Full Text Available We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Niña event of 2001. In September-October 2001, negative anomalies of sea surface temperature from this event still remained in the eastern equatorial Pacific, mainly between Ecuador and the Galapagos Islands. The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes. There was evidence of mesoscale eddies in the study area and of the presence of the South Equatorial Current going westward at about 1°N. We identified 107 copepod species and analyzed the distribution of the 10 most abundant ones: Oncaea venusta, Subeucalanus pileatus, S. crassus, S. subtenuis, Paraeucalanus attenuatus, Pleuromamma borealis, Scolecithrix danae, Clausocalanus farrani, Temora discaudata and Calanus chilensis. Copepod distribution and abundance exhibited marked latitudinal differences related to the oceanographic conditions; abundance was highest to the southeast of the Galapagos Islands. Oncaea venusta, Pleuromamma borealis, Calanus chilensis, and Subeucalanus subtenuis were the species that best defined the Equatorial Front and the upwelling process.

  19. Zooplankton, temperature, salinity, and nutrients data from bottle and net casts in the South Pacific and Equatorial Pacific Oceans from the CORIOLIS from 05 April 1981 to 16 August 1981 (NODC Accession 0000527)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton, nutrients, and other data were collected from bottle and net casts in the South Pacific and Equatorial Pacific Oceans from the CORIOLIS from 05 April...

  20. Long-term acoustic measurement of temperature variations in the Pacific North Equatorial Current

    Science.gov (United States)

    Kaneko, Arata; Zheng, Hong; Nakano, Iwao; Yuan, Gang; Fujimori, Hidetoshi; Yoneyama, Kunio

    1996-07-01

    A 247-km path length sound transmission experiment using a single sound source sending to a remote receiver was performed during February-June 1992 along the latitudinal line of 10°N in the North Equatorial Current off Mindanao Island, Phillipines. The range-averaged temperature was reconstructed at three layers (65-500 m, 500-1500 m, and 1500-3300 m) through the inverse analysis of travel time data obtained between the source and receiver. The temperature remained nearly constant during February-March and increased by 0.8°C for the upper and middle layers and 0.2°C for the lower layer in the subsequent months. A 0.8°C temperature increase was in good agreement with expendable bathythermograph results obtained at the start and finish of the experiment. National Oceanic and Atmospheric Administration advanced very high resolution radiometer images also show evidence of a warming of the surface water by 2.0°C during the same period. It is concluded that this acoustic experiment observed a warm event which took place in the western equatorial Pacific with the decay of the 1991-1992 El Niño.

  1. 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.

  2. 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.

  3. 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.

  4. Interannual and interdecadal variability of ocean temperature along the equatorial Pacific in conjunction with ENSO

    Science.gov (United States)

    Kumar, Arun; Hu, Zeng-Zhen

    2014-03-01

    In this paper, the leading modes of ocean temperature anomalies (OTA) along the equatorial Pacific Ocean are analyzed and their connection with El Niño-Southern Oscillation (ENSO) and interdecadal variation is investigated. The first two leading modes of OTA are connected with the different phases of the canonical ENSO and display asymmetric features of ENSO evolution. The third leading mode depicts a tripole pattern with opposite variation of OTA above the thermocline in the central Pacific to that along the thermocline in the eastern and western Pacific. This mode is found to be associated with so-called ENSO-Modoki. Insignificant correlations of this mode with the first two leading modes suggest that ENSO-Modoki may be a mode that is independent to the canonical ENSO and also has longer time scales compared with the canonical ENSO. The fourth mode reflects a warming (cooling) tendency above (below) the thermocline since 2000. Both the first and second modes have a large contribution to the interdecadal change in thermocline during 1979-2012. Also, the analysis also documents that both ENSO and OTA shifted into higher frequency since 2000 compared with that during 1979-1999. Interestingly, the ENSO-Modoki related OTA mode does not have any trend or significant interdecadal shift during 1979-2012. In addition, it is shown that first four EOF modes seem robust before and after 1999/2000, suggesting that the interdecadal shift of the climate system in the tropical Pacific is mainly a frequency shift and the changes in spatial pattern are relatively small, although the mean states over two periods experienced some significant changes.

  5. 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.

  6. 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.

  7. 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.

  8. Correlations Between Topex Altimeter and Temperature Profile Data in the Equatorial Pacific

    Science.gov (United States)

    Adamec, David

    1999-01-01

    Observations of sea-surface heights from satellite altimeters have been a major contributor to monitoring the evolution of the recent major El Nino event. Assimilating altimeter data directly into numerical models only takes advantage of the surface signature provided by the data. However, that surface signature is usually indicative of processes occurring at depth, especially in the equatorial Pacific. In order for assimilation schemes to make maximum use of surface data, it is helpful to have knowledge of how to best extend that data in the vertical to account for that variability. Toward that end, the vertical correlation structure between satellite-observed sea-surface heights and in situ temperature measurements is examined using TOPEX altimeter and TOGA TAO profile data for the period 1993-1998. This time period includes several states of the tropical Pacific, including a perturbed state from 1993-1994, a quiescent state encompassing 1995-1996, and the major ENSO event of 1997-1998. Analyses for each of these periods, as well as the total period will be presented. In addition to analyses at specific depth levels, analyses for particular density surfaces will also be presented.

  9. 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.

  10. The seasonal march of the equatorial Pacific upper-ocean and its El Niño variability

    Science.gov (United States)

    Gasparin, Florent; Roemmich, Dean

    2017-08-01

    Based on two modern data sets, the climatological seasonal march of the upper-ocean is examined in the equatorial Pacific for the period 2004-2014, because of its large contribution to the total variance, its relationship to El Niño, and its unique equatorial wave phenomena. Argo provides a broadscale view of the equatorial Pacific upper-ocean based on subsurface temperature and salinity measurements for the period 2004-2015, and satellite altimetry provides synoptic observations of the sea surface height (SSH) for the period 1993-2015. Using either 11-year (1993-2003/2004-2014) time-series for averaging, the seasonal Rossby waves stands out clearly and eastward intraseasonal Kelvin wave propagation is strong enough in individual years to leave residuals in the 11-year averages, particularly but not exclusively, during El Niño onset years. The agreement of altimetric SSH minus Argo steric height (SH) residuals with GRACE ocean mass estimates confirms the scale-matching of in situ variability with that of satellite observations. Surface layer and subsurface thermohaline variations are both important in determining SH and SSH basin-wide patterns. The SH/SSH October-November maximum in the central-eastern Pacific is primarily due to a downward deflection of the thermocline (∼20 m), causing a warm subsurface anomaly (>1 °C), in response to the phasing of downwelling intraseasonal Kelvin and seasonal Rossby waves. Compared with the climatology, the stronger October-November maximum in the 2004-2014 El Niño composites is due to higher intraseasonal oscillations and interannual variability. Associated with these equatorial wave patterns along the thermocline, the western warm/fresh pool waters move zonally at interannual timescales through zonal wind stress and pressure gradient fluctuations, and cause substantial fresh (up to 0.6 psu) and warm (∼1 °C higher than the climatology) anomalies in the western-central Pacific surface-layer during the El Niño onset

  11. 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.

  12. Lead isotopes in the Eastern Equatorial Pacific record Quaternary migration of the South Westerlies

    Science.gov (United States)

    Pichat, Sylvain; Abouchami, Wafa; Galer, Stephen J. G.

    2014-02-01

    The influence of atmospheric dust on climate and biogeochemical cycles in the oceans is well understood but poorly quantified. Glacial atmospheric dust loads were generally greater than those during the Holocene, as shown, for example, by the covariation of dust fluxes in the Equatorial Pacific and Antarctic ice cores. Nevertheless, it remains unclear whether these increases in dust flux were associated with changes in sources of dust, which would in turn suggest variations in wind patterns, climate or paleo-environment. Such questions can be answered using radiogenic isotope tracers of dust provenance. Here, we present a 160-kyr high-precision lead isotope time-series of dust input to the Eastern Equatorial Pacific (EEP) from core ODP Leg 138, Site 849 (0°11.59‧ N, 110°31.18‧ W). The Pb isotope record, combined with Nd isotope data, rules out contributions from Northern Hemisphere dust sources, north of the Intertropical Convergence Zone, such as Asia or North Africa/Sahara; similarly, eolian sources in Australia, Central America, the Northern Andes and Patagonia appear insignificant based upon the radiogenic isotope data. Fluctuations in Pb isotope ratios throughout the last 160 kyr show, instead, that South America remained the prevailing source of dusts to the EEP. There are two distinct South American Pb isotope end-members, constrained to be located in the south Central Volcanic Zone (CVZ, 22° S - 27.5° S) and the South Volcanic Zone (SVZ, 33° S - 43° S), with the former most likely originating in the Atacama Desert. Dust availability in the SVZ appears to be related to the weathering of volcanic deposits and the development of ash-derived Andosols, and influenced by local factors that might include vegetation cover. Variations in the dust fluxes from the two sources are in phase with both the dust flux and temperature records from Antarctican ice cores. We show that the forcing of dust provenance over time in the EEP overall is influenced by high

  13. 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...

  14. 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...

  15. 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.

  16. Iron sources and dissolved-particulate interactions in the seawater of the Western Equatorial Pacific, iron isotope perspectives

    Science.gov (United States)

    Labatut, M.; Lacan, F.; Pradoux, C.; Chmeleff, J.; Radic, A.; Murray, J. W.; Poitrasson, F.; Johansen, A. M.; Thil, F.

    2014-10-01

    This work presents iron isotope data in the western equatorial Pacific. Marine aerosols and top core margin sediments display a slightly heavy Fe isotopic composition (δ56Fe) of 0.33 ± 0.11‰ (2SD) and 0.14 ± 0.07‰, respectively. Samples reflecting the influence of Papua New Guinea runoff (Sepik River and Rabaul volcano water) are characterized by crustal values. In seawater, Fe is mainly supplied in the particulate form and is found with a δ56Fe between -0.49 and 0.34 ± 0.07‰. The particulate Fe seems to be brought mainly by runoff and transported across continental shelves and slopes. Aerosols are suspected to enrich the surface Vitiaz Strait waters, while hydrothermal activity likely enriched New Ireland waters. Dissolved Fe isotopic ratios are found between -0.03 and 0.53 ± 0.07‰. They are almost systematically heavier than the corresponding particulate Fe, and the difference between the signature of both phases is similar for most samples with Δ56FeDFe - PFe = +0.27 ± 0.25‰ (2SD). This is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases. The dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved Fe. This process seems to be locally significantly more intense than Fe reductive dissolution documented along reducing margins. It may therefore constitute a very significant iron source to the ocean, thereby influencing the actual estimation of the iron residence time and sinks. The underlying processes could also apply to other elements.

  17. 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

    The distributions of biogenic and lithogenic silica concentrations and net silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic silica (l......-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...... euphotic layer (0-40 m) along 110°W with net production extending somewhat deeper (60-100 m) to the west along the equator. Net production rates in the surface layer were low, ranging between 5 and 40 nmol Si l-1 d-1, consistent with previous observations that diatoms are small contributors to autotrophic...

  18. Peaks in equatorial Pacific export production during the Middle Miocene Climate Transition

    Science.gov (United States)

    Griffith, E. M.; Carter, S. C.

    2016-02-01

    The Middle Miocene Climate Transition (MMCT) is one of three major benthic foraminiferal oxygen isotope (δ18O) events during the Cenozoic reflecting key changes in Earth's climate. The MMCT marks expansion of the Antarctic Ice Sheet (AIS) at 13.8 million years ago (Ma), and global cooling. Concurrent with this cooling step is a globally recognized long positive carbon isotope excursion seen in benthic and planktonic foraminifera with shorter carbon isotope maxima (CM) events linking hypotheses for global cooling at this time with changes in the carbon cycle. Associated with this time period is a pulse of evolutionary turnover in terrestrial and marine biota as well as other physical oceanographic changes. In order to test whether export production, a variable linked to marine ecosystem change, in the eastern equatorial Pacific is related to the largest CM event coincident with expansion of the AIS, a high resolution (Milankovitch cycling within the record of export production suggests that it is responding more to critical thresholds in the Earth system than being paced by orbital periodicity.

  19. 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.

  20. Interannual Salinity Variability in the Equatorial Pacific Analyzed Using CMIP5 Simulations

    Science.gov (United States)

    Zhi, H.

    2016-12-01

    Interannual salinity variability and its causes are analyzed using coupled general circulation model (CGCM) simulations. The GFDL-ESM2M model is examined in detail. Detailed analysis reveals that the model can accurately reproduce the spatial-temporal variations of the mixed layer salinity (MLS) compared with observations. The salinity budget analyses indicate that interannual salinity evolution is closely related to the Nino3.4 index and predominantly governed by the surface forcing, and the surface advection. The relationships show that the salinity anomaly simulated leads the positive peak of the Nino3.4 index by 1-2 years due to both advection and subsurface forcing. The ocean dynamics explain the sea surface salinity variance and the spatial and temporal differences during ENSO, which are equally important as the surface forcing. The MLS tendency simulated is sensitive to the ocean physics and suffers from a strong interannual biases due to the strong precipitation and weak ocean circulation in the equatorial Pacific. Due to the model biases, the effect of the freshwater flux on the salinity budget simulated is overestimated, and the contributions of the subsurface and surface advection are relatively weak but not negligible. These results may provide useful hints for the interpretation of future observations in the region.

  1. Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene

    Science.gov (United States)

    Fontorbe, Guillaume; Frings, Patrick J.; De La Rocha, Christina L.; Hendry, Katharine R.; Carstensen, Jacob; Conley, Daniel J.

    2017-08-01

    Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene ( 50-23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from -3.16 to +0.18‰ and from -0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in the δ30Si of source DSi to the region. The decrease in sponge δ30Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ30Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past.

  2. The relationship between thermocline depth and SST anomalies in the eastern equatorial Pacific: Seasonality and decadal variations

    Science.gov (United States)

    Zhu, Jieshun; Kumar, Arun; Huang, Bohua

    2015-06-01

    Even though the vital role of thermocline fluctuation in El Niño-Southern Oscillation (ENSO) cycle has been established previously, the direct relationship between the thermocline depth and sea surface temperature (SST) anomalies in the equatorial Pacific is yet to be fully understood, especially its seasonality. Thermocline depth anomalies have been found to lead SST anomalies in time with a longitude-dependent delay, but our study also suggests that the relationship shows considerable seasonal dependency and is strongest (weakest) during the boreal spring (summer). Over the eastern equatorial Pacific where there is least delay (compared to that in the western and central Pacific), the connection between thermocline and SST is the weakest during the boreal spring. This feature may be one of causes for ENSO spring persistence barrier. Furthermore, the thermocline-SST connections exhibit significant decadal variations, which are remarkably consistent with the decadal changes in the persistence barrier of SST anomalies over the eastern Pacific. It is also found that the decadal shift in the timing of the thermocline-SST connection barrier is caused by the changes in the seasonal cycle of tropical trade winds and thermocline depths.

  3. Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

    Science.gov (United States)

    Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

    2013-01-01

    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 China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For 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 (oceans, and the probability of dust storms reaching the seas. PMID:23460892

  4. 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

  5. Spatiotemporal characteristics of seasonal to multidecadal variability of pCO2 and air-sea CO2 fluxes in the equatorial Pacific Ocean

    Science.gov (United States)

    Valsala, Vinu K.; Roxy, Mathew Koll; Ashok, Karumuri; Murtugudde, Raghu

    2014-12-01

    Seasonal, interannual, and multidecadal variability of seawater pCO2 and air-sea CO2 fluxes in the equatorial Pacific Ocean for the past 45 years (1961-2005) are examined using a suite of experiments performed with an offline biogeochemical model driven by reanalysis ocean products. The processes we focus on are: (a) the evolution of seasonal cycle of pCO2 and air-sea CO2 fluxes during the dominant interannual mode in the equatorial Pacific, i.e., the El Niño-Southern Oscillation (ENSO), (b) its spatiotemporal characteristics, (c) the combined and individual effects of wind and ocean dynamics on pCO2 and CO2 flux variability and their relation to canonical (eastern Pacific) and central Pacific (Modoki) ENSOs and (d) the multidecadal variability of carbon dynamics in the equatorial Pacific and its association with the Pacific Decadal Oscillations (PDO). The simulated mean and seasonal cycle of pCO2 and CO2 fluxes are comparable with the observational estimates and with other model results. A new analysis methodology based on the traditional Empirical Orthogonal Functions (EOF) applied over a time-time domain is employed to elucidate the dominant mode of interannual variability of pCO2 and air-sea CO2 fluxes at each longitude in the equatorial Pacific. The results show that the dominant interannual variability of CO2 fluxes in the equatorial Pacific (averaged over 5°N-10°S) coevolves with that of ENSO. Generally a reduced CO2 source in the central-to-eastern equatorial Pacific evident during June-July of the El Niño year (Year:0) peaks through September of Year:0 to February of Year:+1 and recovers to a normal source thereafter. In the region between 160°W and 110°W, the canonical El Niño controls the dominant variability of CO2 fluxes (mean and RMS of anomaly from 1961 to 2005 is 0.43±0.12 PgC yr-1). However, in the western (160°E-160°W) and far eastern (110°W-90°W) equatorial Pacific, CO2 flux variability is dominantly influenced by the El Ni

  6. Mitigation of Coral Reef Warming Across the Central Pacific by the Equatorial Undercurrent: A Past and Future Divide.

    Science.gov (United States)

    Karnauskas, Kristopher B; Cohen, Anne L; Gove, Jamison M

    2016-02-16

    Global climate models (GCMs) predict enhanced warming and nutrient decline across the central tropical Pacific as trade winds weaken with global warming. Concurrent changes in circulation, however, have potential to mitigate these effects for equatorial islands. The implications for densely populated island nations, whose livelihoods depend on ecosystem services, are significant. A unique suite of in situ measurements coupled with state-of-the-art GCM simulations enables us to quantify the mitigation potential of the projected circulation change for three coral reef ecosystems under two future scenarios. Estimated historical trends indicate that over 100% of the large-scale warming to date has been offset locally by changes in circulation, while future simulations predict a warming mitigation effect of only 5-10% depending on the island. The pace and extent to which GCM projections overwhelm historical trends will play a key role in defining the fate of marine ecosystems and island communities across the tropical Pacific.

  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. A rapidly deposited pennate diatom ooze in Upper Miocene-Lower Pliocene sediment beneath the North Pacific polar front

    Science.gov (United States)

    Dickens, G.R.; Barron, J.A.

    1997-01-01

    Rapidly deposited Thalassionema-Thalassiothrix pennate diatom oozes previously have been described in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the eastern equatorial Pacific. Here we document a new occurrence of Thalassionema-Thalassiothrix ooze in Upper Miocene Lower Pliocene sediment beneath the frontal boundary of the subarctic North Pacific. The ooze is a 6 m interval of siliceous sediment at Ocean Drilling Program (ODP) sites 885/886 that was rapidly deposited between approximately 5.0 and 5.9 Ma. Bulk sediment in this interval may contain greater than 85% pennate diatom tests. There are also abundant laminae and pockets that are composed entirely of Thalassionema and Thalassiothrix diatoms. The presence of a rapidly deposited ooze dominated by pennate diatoms indicates unusual past conditions in the overlying surface waters. Time coincident deposition of such oozes at two distinct frontal boundary locations of the Pacific suggests that the unusual surface water conditions were causally linked to large-scale oceanographic change. This same oceanographic change most likely involved (1) addition of nutrients to the ocean, or (2) redistribution of nutrients within the ocean. The occurrence and origin of pennate diatom oozes may be a key component to an integrative understanding of late Neogene paleoceanography and biogeochemical cycling.

  9. 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.

  10. 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...

  11. Relationship of the South Asian Monsoon and Regional Drought with Distinct Equatorial Pacific SST Patterns on Interannual and Decadal Timescales

    Science.gov (United States)

    Hernandez, M.; Ummenhofer, C.; Anchukaitis, K. J.

    2014-12-01

    The Asian monsoon system influences the lives of over 60% of the planet's population, with widespread socioeconomic effects resulting from weakening or failure of monsoon rains. Spatially broad and temporally extended drought episodes have been known to dramatically influence human history, including the Strange Parallels Drought in the mid-18th century. Here, we explore the dynamics of sustained monsoon failure using the Monsoon Asia Drought Atlas - a high-resolution network of hydro-climatically sensitive tree-ring records - and a 1300-year pre-industrial control run of the Community Earth System Model (CESM). Spatial drought patterns in the instrumental and model-based Palmer Drought Severity Index (PDSI) during years with extremely weakened South Asian monsoon are similar to those reconstructed during the Strange Parallels Drought in the MADA. We further explore how the large-scale Indo-Pacific climate during weakened South Asian monsoon differs between interannual and decadal timescales. The Strange Parallels Drought pattern is observed during March-April-May primarily over Southeast Asia, with decreased precipitation and reduced moisture fluxes, while anomalies in June-July-August are confined to the Indian subcontinent during both individual and decadal events. Individual years with anomalous drying exhibit canonical El Niño conditions over the eastern equatorial Pacific and associated shifts in the Walker circulation, while decadal events appear to be related to anomalous warming around the dateline in the equatorial Pacific, typical of El Niño Modoki events. The results suggest different dynamical processes influence drought at different time scales through distinct remote ocean influences.

  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. 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.

  14. Investigating Eastern Equatorial Pacific Export Production and Carbonate Dissolution with XRF Core Scanning at ODP Site 846 Over the Last 5 Million Years

    Science.gov (United States)

    Jones, C.; Robinson, R. S.

    2015-12-01

    Coastal and equatorial upwelling in the Eastern Equatorial Pacific (EEP) are responsible for about 10% of the ocean's total production. The deep, cold, nutrient-rich waters supplied by upwelling originate in high latitudes, linking changes at high latitudes to the tropics. The Pliocene/Pleistocene transition which started around 2.7-3 million years ago (Ma) marked a period of higher variability in biological production and sea surface temperatures dominated by glacial/interglacial cycles. In addition, secular changes in the development of both Walker and Hadley cells appear to have impacted the strength of equatorial upwelling. However, the large positive production excursions, such as those found from 1.6 to 2.2 Ma, remain only moderately well characterized and both changes in high latitude nutrient supply and regional upwelling strength are implicated. ODP Site 846 is located in the heart of the EEP upwelling cold tongue and has ideal characteristics for examining these links and excursions. We present high-resolution (~0.5 ky) X-Ray Fluorescence (XRF) chemical profiles of Ca, Si, Ba, Mn, Fe, Al, and Ti, as well as a total nitrogen (TN%) record for the last 5 million years from ODP Site 846. We use these high resolution profiles in conjunction with other regional data to assess biogeochemical processes in the EEP over the last 5 million years. CaCO3 and SiO2 are the two dominant biogenic components and account for more than 95% of the sediment. BaSO4 and the discrete TN% measurements record total productivity. MnO and Fe2O3 are redox-sensitive species and are particularly suited to tracing dissolution related to excess bottom-water metabolic processes driven by high export production at the high-alkalinity Site 846. Al2O3 and TiO2 are tracers of terrigenous input. A transition between low amplitude and high amplitude carbonate cycles occurs at 2.8 Ma, coinciding with the Pliocene/Pleistocene transition to higher amplitude glacial cycles. Notable excursions from

  15. 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.

  16. 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.

  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 xchanges of the oceanic dynamic terms collectively caused negative 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. 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.

  20. 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

  1. 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.

  2. 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.

  3. ?14C of Atmospheric CO2 over the Subtropical and Equatorial Pacific and at Point Barrow, Alaska

    Science.gov (United States)

    Xu, X.; Trumbore, S.; Ajie, H.; Tyler, S.

    2007-12-01

    Δ14C is a unique tracer for studying the carbon cycle, especially for discriminating between fossil and biosphere carbon emissions. However observations of Δ14C variation in atmospheric CO2 are available for only a few locations. We have been measuring atmospheric 14CO2 in boundary layer air over the subtropical and equatorial Pacific and at stations in the US since 2002 to expand the 14CO2 database with high precision data that sample either at high temporal resolution (Point Barrow, Alaska) or high spatial resolution (cross-equatorial mid-Pacific). These data provide observational constraints for the roles of 14C isotope disequilibirum in the tropical terrestrial biosphere, the Southern ocean, and fossil fuel burning and enhance our understanding of the patterns of atmospheric 14CO2 distribution and its seasonal variation. Five transects of atmospheric 14CO2 were collected on shipboard over the Pacific Ocean between Los Angeles (34°N, 118°W) and Auckland, New Zealand (34°N, 177°W) from fall 2002 to summer 2005. Abundances of CO and CH4 in addition to CO2, and their stable isotopes were also measured for these samples. The high precision of our Δ14C analysis (~2‰ based on duplicate measurements) allows us to observe relatively small variations over the latitude span investigated. All five transects show that Δ14C in atmospheric CO2 were relatively uniform from the equatorial region to 30°S latitude. They also indicate a consistent decreasing trend in Δ14C (~7‰) northward of ~6°N to 30°N latitude, consistent with an increase in fossil fuel input in the northern hemisphere. From fall 2002 to summer 2005, Δ14C decreased by an average rate of 6‰/year, with a slightly higher rate of decrease over the southern ocean. Correlation between CO mixing ratio and Δ14C indicates short-term atmospheric circulation may significantly affect the 14CO2 distribution pattern and its latitudinal gradient. In addition, signals from seasonal variation of 14CO2 could

  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 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...

  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 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...

  8. 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....

  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. 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.)

  12. Variability in the subtropical-tropical cells and its effect on near-surface temperature of the equatorial Pacific: a model study

    Directory of Open Access Journals (Sweden)

    J. F. Lübbecke

    2008-02-01

    Full Text Available A set of experiments utilizing different implementations of the global ORCA-LIM model with horizontal resolutions of 2°, 0.5° and 0.25° is used to investigate tropical and extra-tropical influences on equatorial Pacific SST variability at interannual to decadal time scales. The model experiments use a bulk forcing methodology building on the global forcing data set for 1958 to 2000 developed by Large and Yeager (2004 that is based on a blend of atmospheric reanalysis data and satellite products. Whereas representation of the mean structure and transports of the (sub- tropical Pacific current fields is much improved with the enhanced horizontal resolution, there is only little difference in the simulation of the interannual variability in the equatorial regime between the 0.5° and 0.25° model versions, with both solutions capturing the observed SST variability in the Niño3-region. The question of remotely forced oceanic contributions to the equatorial variability, in particular, the role of low-frequency changes in the transports of the Subtropical Cells (STCs, is addressed by a sequence of perturbation experiments using different combinations of fluxes. The solutions show the near-surface temperature variability to be governed by wind-driven changes in the Equatorial Undercurrent. The relative contributions of equatorial and off-equatorial atmospheric forcing differ between interannual and longer, (multi- decadal timescales: for the latter there is a significant impact of changes in the equatorward transport of subtropical thermocline water associated with the lower branches of the STCs, related to variations in the off-equatorial trade winds. A conspicuous feature of the STC variability is that the equatorward transports in the interior and along the western boundary partially compensate each other at both decadal and interannual time scales, with the strongest transport extrema occurring during El Niño episodes. The behaviour is

  13. Tsunami hazard potential for the equatorial southwestern Pacific atolls of Tokelau from scenario-based simulations

    Science.gov (United States)

    Orpin, Alan R.; Rickard, Graham J.; Gerring, Peter K.; Lamarche, Geoffroy

    2016-05-01

    Devastating tsunami over the last decade have significantly heightened awareness of the potential consequences and vulnerability of low-lying Pacific islands and coastal regions. Our appraisal of the potential tsunami hazard for the atolls of the Tokelau Islands is based on a tsunami source-propagation-inundation model using Gerris Flow Solver, adapted from the companion study by Lamarche et al. (2015) for the islands of Wallis and Futuna. We assess whether there is potential for tsunami flooding on any of the village islets from a selection of 14 earthquake-source experiments. These earthquake sources are primarily based on the largest Pacific earthquakes of Mw ≥ 8.1 since 1950 and other large credible sources of tsunami that may impact Tokelau. Earthquake-source location and moment magnitude are related to tsunami-wave amplitudes and tsunami flood depths simulated for each of the three atolls of Tokelau. This approach yields instructive results for a community advisory but is not intended to be fully deterministic. Rather, the underlying aim is to identify credible sources that present the greatest potential to trigger an emergency response. Results from our modelling show that wave fields are channelled by the bathymetry of the Pacific basin in such a way that the swathes of the highest waves sweep immediately northeast of the Tokelau Islands. Our limited simulations suggest that trans-Pacific tsunami from distant earthquake sources to the north of Tokelau pose the most significant inundation threat. In particular, our assumed worst-case scenario for the Kuril Trench generated maximum modelled-wave amplitudes in excess of 1 m, which may last a few hours and include several wave trains. Other sources can impact specific sectors of the atolls, particularly distant earthquakes from Chile and Peru, and regional earthquake sources to the south. Flooding is dependent on the wave orientation and direct alignment to the incoming tsunami. Our "worst-case" tsunami

  14. 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

  15. Near-Equatorial Deep Circulation in the Indian and Pacific Oceans

    Science.gov (United States)

    1990-09-01

    HOE which included deep casts in the region were made by the R.V. Argo (cruise Dodo), the R.R.S. Discovery , the R.V. Meteor and the R.V. Atlantis II...previously unavailable in the Somali Basin. The R.V. Argo and R.R.S. Discovery data taken during August and September 1964 comprises 38 Nansen-bottle...Suppl.), 231-263. Johnson, D. A. and J. E. Damuth (1979) Deep thermohaline flow and current- controlled sedimentation in the Amirante Passage

  16. Organic-walled dinoflagellate cysts in western equatorial Atlantic surface sediments: distributions and their relation to environment.

    Science.gov (United States)

    Vink; Zonneveld; Willems

    2000-11-01

    In contrast to the wide range of studies carried out in temperate and high-latitude oceanic regions, only a few studies have focused on recent and Holocene organic-walled dinoflagellate cyst assemblages from the tropics. This information is, however, essential for fully understanding the ability of species to adapt to different oceanographic regimes, and ultimately their potential application to local and regional palaeoenvironmental and palaeoceanographic reconstructions. Surface sediment samples of the western equatorial Atlantic Ocean north of Brazil, an area greatly influenced by Amazon River discharge waters, were therefore analysed in detail for their organic-walled dinoflagellate cyst content. A diverse association of 43 taxa was identified, and large differences in cyst distribution were observed. The cyst thanatocoenosis in bottom sediments reflects the seasonal advection of Amazon River discharge water through the Guyana Current and the North Equatorial Countercurrent well into the North Atlantic. To establish potential links between cyst distribution and the environmental conditions of the upper water column, distribution patterns were compared with mean temperature, salinity, density and stratification gradients within the upper water column (0-100m) over different times of the year, using correspondence analysis and canonical correspondence analysis. The analyses show that differences in these parameters only play a subordinate role in determining species distribution. Instead, nutrient availability, or related factors, dominates the distribution pattern. The only possible indicators of slightly reduced salinities are Trinovantedinium applanatum and Lingulodinium machaerophorum. Four assemblage groups of cyst taxa with similar environmental affinities related to specific water masses/currents can be distinguished and have potential for palaeoenvironmental reconstruction.

  17. ARM Research in the Equatorial Western Pacific: A Decade and Counting

    Science.gov (United States)

    Long, C. N.; McFarlane, S. A.; DelGenio, A.; Minnis, P.; Ackerman, T. S.; Mather, J.; Comstock, J.; Mace, G. G.; Jensen, M.; Jakob, C.

    2013-01-01

    The tropical western Pacific (TWP) is an important climatic region. Strong solar heating, warm sea surface temperatures, and the annual progression of the intertropical convergence zone (ITCZ) across this region generate abundant convective systems, which through their effects on the heat and water budgets have a profound impact on global climate and precipitation. In order to accurately evaluate tropical cloud systems in models, measurements of tropical clouds, the environment in which they reside, and their impact on the radiation and water budgets are needed. Because of the remote location, ground-based datasets of cloud, atmosphere, and radiation properties from the TWP region have come primarily from short-term field experiments. While providing extremely useful information on physical processes, these short-term datasets are limited in statistical and climatological information. To provide longterm measurements of the surface radiation budget in the tropics and the atmospheric properties that affect it, the Atmospheric Radiation Measurement program established a measurement site on Manus Island, Papua New Guinea, in 1996 and on the island republic of Nauru in late 1998. These sites provide unique datasets now available for more than 10 years on Manus and Nauru. This article presents examples of the scientific use of these datasets including characterization of cloud properties, analysis of cloud radiative forcing, model studies of tropical clouds and processes, and validation of satellite algorithms. New instrumentation recently installed at the Manus site will provide expanded opportunities for tropical atmospheric science.

  18. Evidence of Glacial Mid-Depth Respired Carbon Storage in the Eastern Equatorial Pacific and Links to Deglacial Ventilation

    Science.gov (United States)

    Umling, N. E.; Thunell, R.

    2017-12-01

    A growing body of literature has sought to explain the CO2 increases of the last glacial-interglacial transition. However, much of the previous research has presented conflicting evidence for mechanisms of oceanic-atmospheric CO2 exchange. We investigate these inconsistencies and document the role of the eastern equatorial Pacific in the CO2 changes of the last glacial-interglacial transition. By recording changes in deep ocean chemistry and circulation, this study assesses both physical and biological mechanisms of oceanic-atmospheric CO2 exchange. Radiocarbon-based ventilation studies suggest two pulses of gradually increasing CO2 recorded synchronously in both thermocline and mid-depth water. This is a key departure from the earlier predictions of an isolated abyssal reservoir, consistent with respired carbon storage in mid-depth rather than deep waters. However, the radiocarbon content recorded in mid-depth and deep waters can be impacted by processes other than decreased ventilation. We investigate whether respired carbon storage did indeed occur in tandem with periods of decreased mid-depth radiocarbon content and attempt to uncover the role that circulation and water-mass mixing may have played in glacial-interglacial ventilation and biological pump variability. Here we utilize B/Ca estimates of carbonate saturation and Δδ13C oxygenation estimates to investigate the biological pump. We investigate past changes in circulation using coupled Cd/Ca and δ13C measurements to characterize changes in mid and deep water masses. Our results indicate synchronous shifts in ventilation and indicators of the biological pump suggesting that both decreased ventilation and a more efficient biological pump worked to sequester CO2 during the last glacial period and resulted in evasion of a respired carbon reservoir to the atmosphere during deglaciation. Additionally, we find that the boundary between northward-flowing Lower Circumpolar Deep Water (LCDW) and its southward

  19. 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.

    -Proteobacteria (66%) followed by β- Proteobacteria (34%), whereas no Firmicutes clones were retrieved. Notably, 29% clones from 150 cm and 18% of clones from 200 cm sediment showed high identity to sequences previously reported from mining sites, while 21% of clones...

  20. 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

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

    Science.gov (United States)

    Benson, Nsikak U; Asuquo, Francis E; Williams, Akan B; Essien, Joseph P; Ekong, Cyril I; Akpabio, Otobong; Olajire, Abaas A

    2016-01-01

    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.

  2. 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.

  3. Coping with commitment: Projecting future thermal stress on coral reefs worldwide and the potential importance of the Central Equatorial Pacific

    Science.gov (United States)

    Donner, S. D.

    2009-05-01

    Sea surface temperatures of only 1-2°C greater than the usual summer maximum can cause mass coral bleaching, a paling of the reef-building animals caused by a breakdown of the symbiosis with the colourful dinoflagellates Symbiodinium. A range of recent studies have concluded that anthropogenic climate change may rapidly increase the frequency of mass coral bleaching events, leading to declines in coral cover, shifts in the composition of corals and other reef-dwelling organisms, and stress on the human populations that depend on coral reef ecosystems for food, income and shoreline protection. Recent analysis with AVHRR observed sea surface temperatures and the results of two global climate models (GFDL CM2.0 and CM2.1) shows physical warming commitment from current accumulation of greenhouse gases in the atmosphere will cause over half of the world's coral reefs to experience harmfully frequent (p > 0.2 year-1) severe thermal stress events (DHM > 2°C/month) by 2080. An additional "societal" warming commitment, caused by the time required to shift from a "business-as-usual" emissions trajectory to a 550 ppm CO2 stabilization trajectory, may cause over 80 percent of the world's coral reefs to experience harmfully frequent events by 2030. Thermal adaptation or acclimation of 1.5°C - whether accomplished via biological mechanisms, coral community shifts and/or management interventions - would postpone the forecast by 50-80 years, possibly providing time for the world to shift from the business-as-usual emissions trajectory to a stabilization trajectory which could protect the majority of reefs from harmfully frequent thermal stress events. Sensitivity analysis using historical sea surface temperatures, bleaching reports and coral cover observations indicates that coral reefs in regions which experience high year-to-year SST variability, in particular the atolls of the central equatorial Pacific, may possess higher thermal stress thresholds and greater resistance to

  4. Test Geochemistry of Neogloboquadrina dutertrei Reveals a Deglacial Shoaling of the Deep Chlorophyll Maximum in the Eastern Equatorial Pacific

    Science.gov (United States)

    Mekik, F.

    2017-12-01

    Mg/Ca ratios from tests of Neogloboquadrina dutertrei in two cores in the eastern equatorial Pacific (EEP) spanning the last 25,000 years reveal a peak during the deglaciation which corresponds to a drop in sea surface temperatures as observed from alkenones in previously published work. This discrepancy may be explained in part by N. dutertrei recording summer and alkenones recording winter temperatures. Previously published 230Th normalized organic flux data suggest that the EEP was a region of increased surface ocean productivity, stronger upwelling, and shallower deep chlorophyll maxima (DCM) during the deglaciation. N. dutertrei test stable isotope geochemistry from core tops in the EEP reveals a variable habitat depth for this species between 30 and 125 m water depth, and that this species does not prefer a specific temperature, but rather varies its habitat depth based on the depth of the DCM and current patterns in the EEP. We calculated δ18Osw down core using the low light temperature- δ18O equation from Bemis et al. (1988), temperature estimates from both alkenones and Mg/Ca, and δ18Ocalcite from previously published stable isotope data from N. dutertrei. Our δ18Osw estimates reveal a drop from the deglaciation to the modern of 0.8 ‰ regardless of whether alkenone or Mg/Ca based temperatures are used in the calculations. However there is an offset of about 0.5 to 2 ‰between the δ18Osw estimates made with alkenones vs Mg/Ca-based temperatures. These findings suggest that the discrepancy between alkenone and Mg/Ca based temperatures is probably related to a different current regime in the region, the shoaling of the DCM, and the shoaling of the habitat depth of N. dutertrei in the EEP due to stronger upwelling and greater surface ocean productivity during the deglaciation. We also calculated bioturbation depths down core based on 230Th normalized organic carbon fluxes which reveal deeper mixing during the deglaciation. This suggests that the peak

  5. Equatorial Kelvin waves generated in the western tropical Pacific Ocean trigger mass and heat transport within the Middle America Trench off Costa Rica

    Science.gov (United States)

    Thomson, Richard E.; Davis, Earl E.

    2017-07-01

    Sequences of correlated seafloor temperature, current velocity, and acoustic backscatter events recorded at Ocean Drilling Program (ODP) sites at 4300 m depth in the Middle America Trench have been inferred to result from tidally induced turbidity currents generated in the vicinity of the 3300 m deep sill at the southern end of the trench. New data from the borehole observatories extend the temperature records to 11 years (November 2002 to December 2013) and confirm the highly episodic nature of the events. We present satellite altimetry data and ocean circulation model results to show that event timing is correlated with intraseasonal Kelvin wave motions in the equatorial Pacific. The observed temperature events had a mean (±1 standard deviation) occurrence interval of 61 (±24) days, which spans the periods of the first two baroclinic modes. Lag times between peak bottom water temperatures at the ODP sites and the passage of eastward-propagating Kelvin wave crests at locations in the eastern equatorial Pacific are consistent with the time for mode-1 waves to propagate to the southern end of the trench at a mean phase speed of 2.0 m s-1. Findings indicate that Kelvin wave currents augment tidal motions in the vicinity of the sill, triggering turbidity currents that travel northwestward along the trench axis at mean speeds of ˜0.1 m s-1. We conclude that mode-1 (or, possibly, mixed mode-1 and mode-2) baroclinic Kelvin waves generated by large-scale atmospheric processes in the western tropical Pacific lead to heat and mass transport deep within Middle America Trench in the eastern tropical Pacific.

  6. Late Quaternary paleomagnetic secular variation recorded in deep-sea sediments from the Demerara Rise, equatorial west Atlantic Ocean

    Science.gov (United States)

    Lund, Steve; Oppo, Delia; Curry, William

    2017-11-01

    We have carried out a paleomagnetic/rock magnetic study of two gravity cores and two multicores from the Demerara Rise (∼8°N), adjacent to NE South America. The magnetic measurements indicate that there is a stable natural remanent magnetization (NRM) carried primarily by detrital magnetite/titanomagnetite that preserves the local pattern of paleomagnetic secular variation (PSV). The two gravity cores have consistent patterns of directional variability. The rock magnetic intensities in both gravity cores vary by less than a factor of three. Relative paleointensity estimates have been derived by normalizing the NRM to Chi, ARM, and SIRM. Both gravity cores show the same pattern of relative paleointensity variability. 27 calibrated radiocarbon dates from our studied gravity cores and one additional piston core (Huang et al., 2014) have been used to build chronologies for the two gravity cores. Core 25GGC has bulk sedimentation rates varying from 18 to 22 cm/ky and contains a PSV record for the last 19 ka; core 9GGC has bulk sedimentation rates of 9-17 cm/ky and contains a PSV record for the last 28 ka. There are no other published, good-quality, well-dated full-vector PSV records within 4000 km of the sites, a region which constitutes almost 20% of the Earth's surface area. Our relative paleointensity records are consistent with other global records under the assumption of field intensity being largely a global-scale process. We have compared our directional PSV data statistically with eight other good-quality, well-dated low-latitude PSV records. Our statistical analysis shows that our Demerara Rise directional PSV records are consistent with those other studies and that the Late Quaternary Equatorial field variability is significantly lower than much longer-duration (780 ka to 5 Ma) variability.

  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 certifi...

  8. Sea-Surface Temperatures in the Eastern Equatorial Pacific and Surface Temperatures in the Eastern Cordillera of Colombia during El Niño: Implications for Pliocene Conditions

    Science.gov (United States)

    Pérez-Angel, L. C.; Molnar, P. H.

    2017-12-01

    Regressions of surface temperatures in the Eastern Cordillera of Colombia with sea-surface temperatures (SSTs) in the equatorial Pacific, and specifically with Niño1+2 and Niño3 temperature anomalies, show that the Eastern Cordillera warms or cools by half of the amplitude of the variation in the eastern Tropical Pacific. Because Pliocene SSTs in the eastern Tropical Pacific resemble those during major El Niño events, when SSTs warm by 4°C, these regressions suggest that the Pliocene Eastern Cordillera was possibly warmer by 2ºC at high elevations. Such post-Pliocene cooling is smaller than the 9-12ºC inferred from fossil pollen assemblages, but comparable to recent estimates of Anderson et al. of 3 ± 1ºC (1σ) since 8 Ma. This change in surface temperature could be explained by a change in regional climate associated with a different tropical Pacific SST distribution, and therefore would require neither an elevation change of the Eastern Cordillera since that time, nor a change between Pliocene and present-day temperatures in the tropics that is as large as estimates of the global change of 2.5-4°C.

  9. Sea Surface Temperatures in the Eastern Equatorial Pacific and Surface Temperatures in the Eastern Cordillera of Colombia During El Niño: Implications for Pliocene Conditions

    Science.gov (United States)

    Pérez-Angel, Lina C.; Molnar, Peter

    2017-11-01

    Regressions of surface temperatures in the Eastern Cordillera of Colombia with sea surface temperatures (SSTs) in the equatorial Pacific, and specifically with Niño1+2 and Niño3 temperature anomalies, show that the Eastern Cordillera warms or cools by approximately half of the amplitude of the variation of SSTs in the eastern tropical Pacific. Because Pliocene SSTs in the eastern tropical Pacific resemble those during major El Niño events, when SSTs warm by 4°C, these regressions suggest that the Pliocene Eastern Cordillera was warmer by 2°C at both high and low elevations. Such post-Pliocene cooling is smaller than the 9-12°C inferred from fossil pollen assemblages, but comparable to recent estimates of Anderson et al. of 3 ± 1°C (1σ) since 8 Ma. This change in surface temperature could be explained by a change in regional climate associated with a different tropical Pacific SST distribution and therefore would require neither an elevation change of the Eastern Cordillera since that time nor a change between Pliocene and present-day temperatures in the tropics that is as large as estimates of the global change of 2.5-4°C.

  10. 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 https://doi.org/10.1594/PANGAEA.875998.

  11. 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.

  12. Abrupt hydrographic changes in the equatorial Pacific and subtropical Atlantic from foraminiferal Mg/Ca indicate greenhouse origin for the thermal maximum at the Paleocene-Eocene Boundary

    Science.gov (United States)

    Tripati, Aradhna K.; Elderfield, Henry

    2004-02-01

    The Paleocene-Eocene Boundary (PEB) was marked by an extraordinary climatic event, hypothesized to originate from a large perturbation to the carbon cycle which fueled global warming, the rapid dissociation of oceanic methane hydrates. The pattern of surface warming interpreted from existing sea surface temperature records is not consistent with a greenhouse origin for this event, which would have fueled sea surface warming globally. Although oxygen isotope (δ18O)-based reconstructions indicate polar warming, results for the tropics and subtropics are ambiguous because of uncertainties associated with interpreting planktonic foraminiferal δ18O. To remedy this, we have constructed high-resolution temperature records based on Mg/Ca of multiple species of both surface and thermocline-dwelling planktonic foraminifera across the PEB in the equatorial Pacific and subtropical Atlantic. During the carbon isotope excursion (CIE), surface temperatures increased by 3.5°-4°C and thermocline temperatures warmed by 3°C. Estimates of surface water and thermocline salinity based on paired Mg/Ca and δ18O data indicate a pattern of hydrographic changes in the equatorial and subtropical oceans that is different from previously proposed, with a more vigorous hydrologic cycle during warming. The pattern of warming and salinity changes are consistent with this being a greenhouse-induced global warming event, and the timing of hydrographic changes relative to the CIE supports the hypothesis that gradual warming of intermediate/deep waters triggered methane hydrate dissociation.

  13. A first look at past sea surface temperatures in the equatorial Indian Ocean from Mg/Ca in foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Weldeab, S.; Mackensen, A.; Naidu, P.D.

    between the equatorial Indian Ocean SST and the equatorial Pacific SST suggests the possibility of a common mechanism controlling the SSTs in both the equatorial Indian Ocean and the Pacific Ocean. Citation: Saraswat, R., R. Nigam, S. Weldeab, A. Mackensen...

  14. Paleoceanography of the eastern equatorial Pacific over the past 4 million years and the geologic origins of modern Galápagos upwelling

    Science.gov (United States)

    Karnauskas, Kristopher B.; Mittelstaedt, Eric; Murtugudde, Raghu

    2017-02-01

    An isolated, volcanic archipelago at the confluence of several major ocean currents, the Galápagos Archipelago (GA) is among the most biologically diverse places on Earth. There remain many open questions concerning evolution and speciation in the GA, with the details of the geologic formation of the islands over the past millions of years representing a key source of uncertainty. Paleoceanographic sea surface temperature (SST) proxy records from the far eastern equatorial Pacific (EEP) indicate that the modern gradient of SST across the GA (the cross-island SST gradient, or CIΔT) emerged relatively abruptly ∼1.6 Ma. As the modern CI ΔT is the result of a blockage and subsequent upwelling of the Equatorial Undercurrent (EUC) by the GA, we infer from these paleoceanographic data that the modern period during which the GA is arranged such that the islands constitute a significant topographic barrier to the EUC began ∼1.6 Ma. An extensive suite of ocean circulation model experiments-new and previously published-confirms that the sign and magnitude of the change in CI ΔT captured in paleoceanographic records can be explained by the islands impinging upon the EUC. Implications for the geologic history of the Galápagos and related biogeographical questions are discussed. Additionally, these results suggest that investigations of the Pan-Pacific SST gradient (PPΔT) should use one of the available proxy sites in the EEP that is not influenced by regional, geologically forced oceanographic changes; such an analysis supports recent suggestions of a more gradual development of the modern PP ΔT over the Plio-Pleistocene.

  15. 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

  16. 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.

    Sea Surface Temperature (SST) anomalies that develop in spring in the central Pacific are crucial to the El Nino Southern Oscillation (ENSO) development. Here we use a linear, continuously stratified, ocean model, and its impulse response to a...

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

    DEFF Research Database (Denmark)

    Pittauer, Daniela; Roos, Per; Qiao, Jixin

    2018-01-01

    Th and anthropogenic radionuclides provided information about accumulation rates. Concentrations of Am and Pu isotopes were detected by gamma spectrometry, alpha spectrometry and ICP-MS. The Pu ratios indicate a high portion (minimum of 60%) of Pu from the Pacific Proving Grounds (PPG). This implies...

  18. 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

  19. The Role of Insolation and the Equatorial Pacific in South American Climate during the Holocene: A Paleoclimate Record from Laguna Blanca, Venezuela

    Science.gov (United States)

    Polissar, P. J.; Abbott, M.; Wolfe, A. P.; Bezada, M.; Vuille, M.

    2009-12-01

    Insolation forcing of tropical climate at precessional timescales appears to be a widespread phenomenon in South America. This could reflect the influence of local insolation changes on rainfall and evaporation, and hence migration of the marine intertropical convergence zone (ITCZ) and its terrestrial expression, the South American summer monsoon. However, modern interannual climate variability in South America is also closely linked to ocean-atmosphere interactions in the tropical Pacific expressed primarily as the El Niño-Southern Oscillation (ENSO). The timing of climate changes in the Northern and Southern Hemisphere tropics is one way to distinguish between these mechanisms. Precessional forcing of Atlantic ITCZ migration would cause changes in the northern and southern hemispheres that are opposite in sign. In contrast, ENSO variability has a similar character in the Andean regions of both hemispheres. Here we develop a new terrestrial paleoclimate record in the northern tropics of South America. Lake level fluctuations from Laguna Blanca, located in the Venezuelan Andes, exhibit arid-humid intervals during the past 10,000 years that occur at the same time as those in the neotropics of both hemispheres. This pattern suggests that millennial-scale climate trends in Andean South America may reflect changes in the mean state and variability of the equatorial Pacific Ocean.

  20. 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.

  1. Neogene paleoceanography of the eastern equatorial Pacific based on the radiolarian record of IODP drill sites off Costa Rica

    Science.gov (United States)

    Sandoval, María. I.; Boltovskoy, Demetrio; Baxter, Alan T.; Baumgartner, Peter O.

    2017-03-01

    The Integrated Ocean Drilling Program (IODP) Expedition 344 drilled cores following a transect across the convergent margin off Costa Rica. Two of the five sites (U1381 and U1414) are the subject of the present study. Major radiolarian faunal breaks and characteristic species groups were defined with the aid of cluster analysis, nodal analysis, and discriminant analysis of principal components. A middle-late Miocene to Pleistocene age (radiolarian zones RN5 to RN16) was determined for the sites, which agrees with the nannofossil zonations and 40Ar/39Ar and tephra layers. Considering the northward movement of the Cocos plate (˜7.3 cm/yr), and a paleolatitude calculator, it is assumed that during the Miocene the two sites were located ˜1000 km to the southwest of their current position, slightly south of the equator. The radiolarian faunas retrieved were thus seemingly formed under the influence of different oceanic currents and sources of nutrients. Changes in the radiolarian assemblages at Site U1414 point at dissimilar environmental settings associated with the colder South Equatorial Current and the warmer Equatorial Countercurrent, as well as to coastal upwelling. These differences are best reflected by changes in the abundance of the morphotype Spongurus spp., with noticeably higher values during the Miocene, than in the Pliocene and the Pleistocene. Because Spongurus spp. is generally associated with cooler waters, these abundance variations (as well as those of several other species) suggest that during the Miocene the area had a stronger influence of colder waters than during younger periods. During the Pliocene and the lowermost Pleistocene, biogenic remains are scarce, presumably due to the terrigenous input, which could have diluted and affected the preservation of pelagic fossils, as well as to the displacement of the site to warmer waters. A typically tropical fauna characterized the Pleistocene, yet with widespread presence of colder water species

  2. Late Paleocene to Eocene paleoceanography of the equatorial Pacific Ocean: Stable isotopes recorded at Ocean Drilling Program Site 865, Allison Guyot

    Science.gov (United States)

    Bralower, Timothy J.; Zachos, James C.; Thomas, Ellen; Parrow, Matthew; Paull, Charles K.; Kelly, D. Clay; Silva, Isabella Premoli; Sliter, William V.; Lohmann, Kyger C.

    1995-08-01

    An expanded and largely complete upper Paleocene to upper Eocene section was recovered from the pelagic cap overlying Allison Guyot, Mid-Pacific Mountains at Ocean Drilling Program (ODP) Site 865 (18°26'N, 179°33'W; paleodepth 1300-1500 m). Reconstructions show that the site was within a few degrees of the equator during the Paleogene. Because no other Paleogene sections have been recovered in the Pacific Ocean at such a low latitude, Site 865 provides a unique record of equatorial Pacific paleoceanography. Detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa (species of Acarinina, Morozovella, and Subbotina). We studied benthic foraminiferal isotopes at much lower resolution on species of Cibicidoides and Lenticulina, Nuttallides truempyi and Gavelinella beccariiformis, because of their exceptional rarity. The δ18O and δ13C stratigraphies from Site 865 are generally similar to those derived from other Paleocene and Eocene sections. The planktonic foraminiferal records at Site 865, however, include significantly less short-term, single-sample variability than those from higher-latitude sites, indicating that this tropical, oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability. Low-amplitude (0.1-0.8‰) oscillations on timescales of 250,000 to 300,000 years correlate between the δ13C records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters. Peak sea surface temperatures of 24°-25°C occurred in the earliest Eocene, followed by a rapid cooling of 3-6°C in the late early Eocene. Temperatures remained cool and stable through the middle Eocene. In the late Eocene, surface water temperatures decreased further. Vertical temperature gradients decreased dramatically in the late Paleocene and were relatively constant through much of the Eocene but increased markedly in the late Eocene. Intermediate waters

  3. 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

  4. Role of Equatorial Anomaly in Earthquake time precursive features: A few strong events over West Pacific zone

    Science.gov (United States)

    Devi, Minakshi; Patgiri, S.; Barbara, A. K.; Oyama, Koh-Ichiro; Ryu, K.; Depuev, V.; Depueva, A.

    2018-03-01

    The earthquake (EQ) time coupling processes between equator-low-mid latitude ionosphere are complex due to inherent dynamical status of each latitudinal zone and qualified geomagnetic roles working in the system. In an attempt to identify such process, the paper presents temporal and latitudinal variations of ionization density (foF2) covering 45°N to 35°S, during a number of earthquake events (M > 5.5). The approaches adopted for extraction of features by the earthquake induced preparatory processes are discussed in the paper through identification of parameters like the 'EQ time modification in density gradient' defined by δ = (foF2 max - foF2 min)/τmm, where τmm - time span (in days) between EQ modified density maximum and minimum, and the Earthquake time Equatorial Anomaly, i.e. EEA, one of the most significant phenomenon which develops even during night time irrespective of epicenter position. Based on the observations, the paper presents the seismic time coupling dynamics through anomaly like manifestations between equator, low and mid latitude ionosphere bringing in the global Total Electron Content (TEC) features as supporting indices.

  5. 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

    to the Tropical Instability Waves. The aim of this study is to examine patterns of spatial and temporal variability in the biological uptake of NO3, Si(OH)4 and carbon in this region, and to evaluate the role of biological and physical interactions controlling these processes over seasonal...... and intra-seasonal time scales. Here, high resolution Pacific ROMS-CoSiNE model results are combined with in situ and remote sensing data. The results of model-data comparison reveal an excellent agreement in domain-average hydrographic and biological rate estimates, and patterns of spatio...

  6. 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)

  7. 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

  8. 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.

  9. Late Holocene environmental history of southern Chocó region, Pacific Columbia; sediment, diatom and pollen analysis of El Caimito.

    NARCIS (Netherlands)

    Velez, M.I.; Wille, M.; Hooghiemstra, H.; Metkalf, S.; Vandenberghe, J.; van de Borg, K.

    2001-01-01

    We present a multi-proxy study of pollen, diatoms, sediment characteristics and major elements of a 610-cm sediment core from lake El Caimito, located in the humid rain forest of southern Chocó, Pacific Colombia. We propose an integrated reconstruction of the local basin development and of the

  10. Latitudinal distributions of terrestrial biomarkers in the sediments from the Central Pacific

    Science.gov (United States)

    Ohkouchi, N.; Kawamura, K.; Kawahata, H.; Taira, A.

    1997-05-01

    Twenty-three deep-sea surface sediments collected from the Central Pacific across a latitudinal transect at 175°E from 48°N to 15°S were studied for lipid class compounds including C 25C 36n-alkanes, C 24C 28 fatty alcohols, and C 23C 34 fatty acids, which are derived from terrestrial higher plants. Although all of these terrestrial biomarkers were most likely transported long distances in the atmosphere over the Central Pacific, their latitudinal distribution patterns are specific to each compound group. n-Alkanes (C 25C 36) are most abundant in the highest latitude (48N) and gradually decrease toward the lower latitude (13°N). Fatty alcohols (C 24C 28) rapidly decrease from 48°N to 30°N and stay relatively low in the lower latitudes. By contrast, abundances of fatty acids (C 23C 34) are relatively high in the lower latitudes, although they increase from mid to high latitudes of the Northern Hemisphere. In addition, distributions of n-Akanes (C 25C 36) in 48°N-19°N are characterized by CPI (carbon preference index) of 4.9-8.2 (av. 6.6), which are significantly higher than those (1.9-4.9; av. 2.8) in the low latitudes (15°N-15°S) . These latitudinal patterns of terrestrial biomarkers in the Central Pacific sediments are generally interpreted in terms of the different wind regimes between high and low latitudes; that is, distributions of organic molecules transported from Asia to the North Pacific by westeries are different from those by trade winds which transport aerosols from Central and South Americas to the tropical Pacific.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. Pacific lamprey (Entosphenus tridentatus) ammocoetes exposed to contaminated Portland Harbor sediments: Method development and effects on survival, growth, and behavior.

    Science.gov (United States)

    Unrein, Julia R; Morris, Jeffrey M; Chitwood, Rob S; Lipton, Joshua; Peers, Jennifer; van de Wetering, Stan; Schreck, Carl B

    2016-08-01

    Many anthropogenic disturbances have contributed to the decline of Pacific lampreys (Entosphenus tridentatus), but potential negative effects of contaminants on lampreys are unclear. Lamprey ammocoetes are the only detritivorous fish in the lower Willamette River, Oregon, USA, and have been observed in Portland Harbor sediments. Their long benthic larval stage places them at risk from the effects of contaminated sediment. The authors developed experimental methods to assess the effects of contaminated sediment on the growth and behavior of field-collected ammocoetes reared in a laboratory. Specifically, they developed methods to assess individual growth and burrowing behavior. Burrowing performance demonstrated high variability among contaminated sediments; however, ammocoetes presented with noncontaminated reference sediment initiated burrowing more rapidly and completed it faster. Ammocoete reemergence from contaminated sediments suggests avoidance of some chemical compounds. The authors conducted long-term exposure experiments on individually held ammocoetes using sediment collected from their native Siletz River, which included the following: contaminated sediments collected from 9 sites within Portland Harbor, 2 uncontaminated reference sediments collected upstream, 1 uncontaminated sediment with characteristics similar to Portland Harbor sediments, and clean sand. They determined that a 24-h depuration period was sufficient to evaluate weight changes and observed no mortality or growth effects in fish exposed to any of the contaminated sediments. However, the effect on burrowing behavior appeared to be a sensitive endpoint, with potentially significant implications for predator avoidance. Environ Toxicol Chem 2016;35:2092-2102. © 2016 SETAC. © 2016 SETAC.

  17. Polycyclic aromatic hydrocarbons in ocean sediments from the North Pacific to the Arctic Ocean.

    Science.gov (United States)

    Ma, Yuxin; Halsall, Crispin J; Xie, Zhiyong; Koetke, Danijela; Mi, Wenying; Ebinghaus, Ralf; Gao, Guoping

    2017-08-01

    Eighteen polycyclic aromatic hydrocarbons (PAHs) were measured in surficial sediments along a marine transect from the North Pacific into the Arctic Ocean. The highest average Σ 18 PAHs concentrations were observed along the continental slope of the Canada Basin in the Arctic (68.3 ± 8.5 ng g -1 dw), followed by sediments in the Chukchi Sea shelf (49.7 ± 21.2 ng g -1 dw) and Bering Sea (39.5 ± 11.3 ng g -1 dw), while the Bering Strait (16.8 ± 7.1 ng g -1 dw) and Central Arctic Ocean sediments (13.1 ± 9.6 ng g -1 dw) had relatively lower average concentrations. The use of principal components analysis with multiple linear regression (PCA/MLR) indicated that on average oil related or petrogenic sources contributed ∼42% of the measured PAHs in the sediments and marked by higher concentrations of two methylnaphthalenes over the non-alkylated parent PAH, naphthalene. Wood and coal combustion contributed ∼32%, and high temperature pyrogenic sources contributing ∼26%. Petrogenic sources, such as oil seeps, allochthonous coal and coastally eroded material such as terrigenous sediments particularly affected the Chukchi Sea shelf and slope of the Canada Basin, while biomass and coal combustion sources appeared to have greater influence in the central Arctic Ocean, possibly due to the effects of episodic summertime forest fires. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. 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)

  19. Geochemically tracking provenance changes in marine sediment from the South Pacific Gyre throughout the Cenozoic

    Science.gov (United States)

    Dunlea, A. G.; Murray, R. W.; Sauvage, J.; Spivack, A. J.; Harris, R. N.; D'Hondt, S. L.

    2012-12-01

    The South Pacific Gyre (SPG), characterized by extremely slow sedimentation rates, is the world's largest oceanic desert. The little eolian dust from continents in the Southern Hemisphere must traverse great distances to reach the SPG, and the ultra-oligotrophic waters minimize the biogenic flux of sediment to the seafloor. However sparse, the pelagic sediment that is ultimately found on the seafloor retains a chemical record that can be used to trace its origin. Using cores from Integrated Ocean Drilling Program Expedition 329, we trace downcore fluctuations in major, trace, and rare earth element (REE) composition and flux to yield clues to the geological, chemical, and biological evolution of the SPG throughout the Cenozoic. The shipboard scientific party generally described the completely oxic, brown pelagic clays recovered during Exp. 329 as zeolitic metalliferous clay. The homogenous, very fine-grained nature of these sediments speaks to the challenges we face in resolving eolian detrital material ("dust"), fine-grained ash (commonly altered), and authigenic aluminosilicates from one another. Based on ICP-ES and ICP-MS analyses followed by multivariate statistical treatments, we are developing chemical records from a number of sites located throughout the SPG. Building on earlier work at DSDP Site 596 (Zhou and Kyte, 1992, Paleocean., 7, 441-465), and based on backtrack paths from 100 Ma forward, we are working to construct a regionally and temporally continuous paleoclimatological history of the SPG. Preliminary La-Th-Sc concentrations from Sites U1367, U1368, and U1369 show a distinct authigenic influence, but several refractory elements retain their original provenance signature. Sediment ages are constrained using a constant-Co model, based on the geochemically similar work that Zhou and Kyte (1992) performed in the SPG. REE concentrations normalized to post-archean average shale (PAAS) reveal a negative Ce anomaly that becomes more pronounced closer to

  20. 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.

  1. Equatorial Guinea.

    Science.gov (United States)

    1984-06-01

    Attention in this discussion of Equatorial Guinea is directed to the following: the people, history, geography, government, political conditions, the economy, foreign relations, and relations between the US and Equatorial Guinea. The population was estimated at 304,000 in 1983 and the annual growth rate was estimated in the range of 1.7-2.5. The infant mortality rate is 142.9/1000 with a life expectancy of 44.4 years for males and 47.6 years for females. The majority of the Equatoguinean people are of Bantu origin. The largest tribe, the Fang, is indigenous to the mainland, although many now also live on Bioko Island. Portuguese explorers found the island of Bioko in 1471, and the Portuguese retained control until 1778, when the island, adjacent islets, and the commercial rights to the mainland between the Niger and Ogooue Rivers were ceded to Spain. Spain lacked the wealth and the interest to develop an extensive economic infrastructure in Equatorial Guinea during the 1st half of this century, but the Spanish did help Equatorial Guinea achieve 1 of the highest literacy rates in Africa. They also founded a good network of health care facilities. In March 1968, under pressure from Guinean nationalists, Spain announced that it would grant independence to Equatorial Guinea as rapidly as possible. A referendum was held on August 11, 1968, and 63% of the electorate voted in favor of the constitution, which provided for a government with a general assembly and presidentially appointed judges in the Supreme Court. After the coup in August 1979, power was placed in the hands of a Supreme Military Council. A new constitution came into effect after a popular vote in August 1982, abolishing the Supreme Military Council. Under the terms of the constitution, the president was given extensive powers. By the end of 1983, a 60-member Chamber of Representatives of the people had been formed. The government, which is credited with restoring greater personal freedom, is regarded

  2. 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.

  3. Rare-earth elements enrichment of Pacific seafloor sediments: the view from volcanic islands of Polynesia

    Science.gov (United States)

    Melleton, Jérémie; Tuduri, Johann; Pourret, Olivier; Bailly, Laurent; Gisbert, Thierry

    2014-05-01

    Rare-earth elements (REEs) are key metals for «green» technologies such as energy saving lamps or permanent magnets used in, e.g., wind turbines, hard disk drives, portable phone or electric or hybrid vehicles. Since several years, world demand for these metals is therefore drastically increasing. The quasi-monopolistic position of China, which produces around 95 % of global REEs production, generates risks for the industries that depend on a secure supply of REEs. In response, countries are developing and diversifying their supply sources, with new mining projects located outside China and efforts in the area of REEs recycling. Most of these projects focus on deposits related to carbonatites and alkaline-peralkaline magmatism, which are generally enriched in light REEs (LREEs) compared to the heavy REEs (HREEs)-enriched deposits of the ion-adsorption types, located in southern China. However, a recent study revealed new valuable resources corresponding to seafloor sediments located in the south-eastern and north-central Pacific. The deep-sea mud described by these authors show a higher HREE/LREE ratio than ion-adsorption deposits, a feature which significantly increases their economic interest. The authors suggest mid-ocean ridge hydrothermal activity as an explanation to this anomalous enrichment. However, several contributions have documented considerable REEs enrichment in basalts and peridotitic xenoliths from French Polynesia. Several arguments have been exposed in favour of a supergene origin, with a short migration, suggesting that REEs were collected from weathered basalts. The Tahaa volcanic island (Sous-le-Vent Island, Society Archipelago, French Polynesia) is the first location where such enrichment has been described. New petrographic and mineralogical investigations confirm a supergene mobilization of this abnormal occurrence. REE-bearing minerals (mainly phosphates of the rhabdophane group) are primarily located within basalt vesicles but also in

  4. 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...

  5. Equatorial zonal circulations: Historical perspectives

    Science.gov (United States)

    Hastenrath, Stefan

    2007-04-01

    The changing perceptions on zonal circulations in the equatorial belt are traced for (a) stratospheric wind regimes, and (b) vertical-zonal circulation cells in the troposphere. (a) Observations from the Krakatoa eruption 1883 and Berson's 1908 expedition to East Africa, along with later soundings over Batavia (Jakarta) led to the notion of "Krakatoa easterlies" around 30 km (10 mb) and "Berson westerlies" around 20 km (50 mb). Prompted by contrary observations since the late 1950s, this dogma was replaced by the notion of easterlies alternating with westerlies in the equatorial stratosphere at a rhythm of about 26 months. (b) Stimulated by Bjerknes' postulate of a "Walker circulation" along the Pacific Equator, a multitude of such cells have been hypothesized at other longitudes, in part from zonal contrasts of temperature and cloudiness. Essential for the diagnosis of equatorial zonal circulation cells is the continuity following the flow between the centers of ascending and subsiding motion. Evaluation of the recent NCEP-NCAR and ECMWF Reanalysis upper-air datasets reveals equatorial zonal circulation cells over the Pacific all year round, over the Atlantic only in boreal winter, and over the Indian Ocean only in autumn, all being seasons and oceanic longitudes with strong zonal flow in the lower troposphere.

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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

  11. 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

  12. 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...

  13. 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...

  14. Timber Harvest Effects on Sediment and Water Yields and Analysis of Sediment Load Calculation Methods in the Interior Pacific Northwest

    Science.gov (United States)

    Elverson, C.; Karwan, D. L.

    2015-12-01

    Timber harvest practices have a long-standing association with changes in water and sediment yields. We quantify the trends in water and sediment yields in the Mica Creek Experimental Watershed (MCEW) in relation to management practices with linear regression and analysis of covariance (ANCOVA). From 1991 to 2013, an increase in water yield resulted from both clearcutting and thinning treatments, with monthly water yield rate increases of 13-57% and annual water yield increases up to 210 mm (40%) in the clearcut watershed. Following treatment, annual sediment yields increased in the clearcut watershed by 40-131% and the thinned watershed by 33-163%, both relative to the control watershed, with statistically-significant monthly load increases in the year immediately following treatment. Water and sediment yield changes do not follow the same post-treatment patterns. Water yields increased immediately following treatment and, over time, gradually dropped towards pre-harvest levels. Annual sediment yields increased in some years after the harvest, but in some cases the increase was years after treatment. Monthly sediment yields increased in the first year following the clearcut harvest, but elevated monthly loads following the partial cut harvest came years later. Hence, we investigate the changes in sediment yield through an examination of water yield and sediment concentration and in response to events. We test the sensitivity of our results to different methods for computing sediment yields based on total suspended solids concentration and continuous discharge measurements. Flow-weighted sediment yield averaged 24% higher than sediment yield computed from linear-interpolated total suspended solids concentration values. During typical summer and fall conditions, flow-weighting was found to overweight storm measurements and produce large sediment yield estimates. Further work is suggested to test methods of calculating monthly sediment yields with irregularly

  15. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

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

    2000-01-01

    The present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial Atlantic. Data from a range of different samples, from the plankton, surface sediments as well as sediment cores are shown and compare...

  16. 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

  17. 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

  18. Degree of trace metal pyritization in sediments from the Pacific coast of Baja California, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nava Lopez, Carmen; Huerta Diaz, Miguel Angel [Instituto de Investigaciones Oceanologicas, Ensenada, Baja California (Mexico)

    2001-06-01

    We analyzed sediments from a core collected on the Pacific coast of Baja California, 45 km off the city of Tijuana and at 1257 m water depth (32 Celsius degrees 9.5N , 117 Celsius degrees 8.3W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate transference of Cu>Ni>Zn>>Hg y Ag from the HCl to the pyrite fraction. Sediments have degrees of pyritization (DOP) that average 7.2{+-} 4.9% with a maximum value of 18.5%. Average degrees of trace metal pyritization (DTMP) range from 6.2 {+-}2.1% to 83{+-} 8% for Mn and Hg, respectively, although maximum values for some metals were closed to 100%. This transference is apparently a function of the solubility products of metal sulfides and the relative abundances of metals in the HCl fraction, as suggested by the significant correlation (p<0.001) observed between these two parameters and the DTMP of a number of trace metals. A similar correlation was obtained from published data of two cores collected in the Gulf of Mexico. [Spanish] Se analizaron sedimentos de un nucleo recolectado en la costa del Pacifico de Baja California 45 km de la costa de la ciudad de Tijuana y a 1257 m de profundidad del agua (32 grados Celsius 9.5N, 117 grados Celsius 8.3W), para determinar su contenido de metales traza en dos fracciones operacionales definidas HCl y pirita. Los resultados indican una transferencia de Cu>Ni>Zn>>Hg y Ag de la fraccion de HCl a la fase piritica. Los grados de piritizacion (DOP) en los sedimentos promediaron 7.2{+-} 4.9%, con un valor maximo de 18.5%. Los valores promedio de los grados de piritizacion de metales traza (DTMP) abarcaron el intervalo de 6.2 {+-}2.1% a 83{+-}18% para Mn y Hg, respectivamente, aunque los valores maximos para algunos metales estuvieron cercanos al 100%. Esta transferencia aparentemente es funcion de los productos de solubilidad de los sulfuros metalicos y de la abundancia relativa de metales en la fraccion HCl, como sugiere la correlacion

  19. 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

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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.)

  5. 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)

  6. Pleistocene climates in the atlantic and pacific oceans: a comparison based on deep-sea sediments.

    Science.gov (United States)

    Ericson, D B; Wollin, G

    1970-03-13

    Comparison of Pleistocene climatic records defined by variations in abundance of planktonic Foraminifera in three cores from the southeastern Pacific with similar records in cores from the Atlantic suggests that times of warm surface water in this region of the Pacific were at least partly synchronous with times of cool water in the Altantic. This conclusion opposes the Milankovitch theory of the causation of ice ages, but it harmonizes with a modified form of Simpson's hypothesis.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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 ...

  12. Persistent organic pollutants in ocean sediments from the North Pacific to the Arctic Ocean

    Science.gov (United States)

    Ma, Yuxin; Halsall, Crispin J.; Crosse, John D.; Graf, Carola; Cai, Minghong; He, Jianfeng; Gao, Guoping; Jones, Kevin

    2015-04-01

    Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OC pesticides), and polybrominated diphenyl ethers (PBDEs) are reported in surficial sediments sampled along cruise transects from the Bering Sea to the central Arctic Ocean. OCs and PCBs all had significantly higher concentrations in the relatively shallow water (500 m) of the Bering Sea and Arctic Ocean (e.g., Canada Basin ΣPCB 149 ± 102 pg g-1 dw). Concentrations were similar to, or slightly lower than, studies from the 1990s, indicating a lack of a declining trend. PBDEs (excluding BDE-209) displayed very low concentrations (e.g., range of median values, 3.5-6.6 pg/g dw). In the shelf areas, the sediments comprised similar proportions of silt and clay, whereas the deep basin sediments were dominated by clay, with a lower total organic carbon (TOC) content. While significant positive correlations were observed between persistent organic pollutant (POP) concentrations and TOC (Pearson correlation, r = 0.66-0.75, p technical formulations (and/or marine surface waters), indicate substantial chemical processing during transfer to the benthic environment. Marked differences in sedimentation rates between the shallow and deeper water regions are apparent (the ˜5 cm-depth grab samples collected here representing ˜100 years of accumulation for the shelf sediments and ˜1000 years for the deeper ocean regions), which may bias any comparisons. Nonetheless, the sediments of the shallower coastal arctic seas appear to serve as significant repositories for POPs deposited from surface waters.

  13. 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.

  14. 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.

  15. Carbon fixation in sediments of Sino-Pacific seas-differential contributions of bacterial and archaeal domains

    Science.gov (United States)

    Das, Anindita; Cao, Wenrui; Zhang, Hongjie; Saren, Gaowa; Jiang, Mingyu; Yu, Xinke

    2017-11-01

    Oceanic stretches experiencing perpetual darkness and extreme limitation of utilizable organic matter often rely on chemosynthetic carbon (C)-fixation. However, C-fixation is not limited to carbon-deplete environments alone but might also occur in varying degrees in carbon-replete locales depending on the nature and concentration of utilizable carbon, electron donors and acceptors. Quantification of microbial C-fixation and relative contribution of domains bacteria and archaea are therefore crucial. The present experiment estimates the differential rates of C-fixation by archaea and bacteria along with the effects of different electron donors. Four Sino-Pacific marine sediments from Bashi strait (Western Pacific Warm Pool), East China Sea, South China Sea and Okinawa Trough were examined. Total microbial C-uptake was estimated by doping of aqueous NaH14CO3. Total bacterial C-uptake was measured by blocking archaeal metabolism using inhibitor GC7. Archaeal contribution was estimated by subtracting total bacterial from total microbial C-uptake. Effect of electron donor addition was analyzed by spiking with ammonium, sulfide, and reduced metals. Results suggested that C-fixation in marine sediments was not the function of archaea alone, which was in contrast to results from several recent publications. C-fixing bacteria are also equally active. Often in spite of great effort of one domain to fix carbon, the system does not become net C-fixing due to equal and opposite C-releasing activity of the other domain. Thus a C-releasing bacterial or archaeal community can become C-fixing with the change of nature and concentration of electron donors.

  16. Plutonium isotopes concentration in seawater and bottom sediment off the Pacific coast of Aomori sea area during 1991-2005

    Energy Technology Data Exchange (ETDEWEB)

    Oikawa, Shinji, E-mail: oikawa@kaiseiken.or.j [Marine Ecology Research Institute, Head Office, Research and Survey Group, Towa-Edogawabashi Bldg. 7F., 347 Yamabuki-cho, Shinjuku-ku, Tokyo 162-0801 (Japan); Watabe, Teruhisa [Marine Ecology Research Institute, Head Office, Research and Survey Group, Towa-Edogawabashi Bldg. 7F., 347 Yamabuki-cho, Shinjuku-ku, Tokyo 162-0801 (Japan); Inatomi, Naohiko [Marine Ecology Research Institute, Central Laboratory, 300 Iwawada, Onjuku-machi, Isumi-gun, Chiba 299-5105 (Japan); Isoyama, Naohiko; Misonoo, Jun; Suzuki, Chiyoshi; Nakahara, Motokazu; Nakamura, Ryoichi; Morizono, Shigemitsu; Fujii, Seiji [Marine Ecology Research Institute, Head Office, Research and Survey Group, Towa-Edogawabashi Bldg. 7F., 347 Yamabuki-cho, Shinjuku-ku, Tokyo 162-0801 (Japan); Hara, Takeya [Marine Ecology Research Institute, Central Laboratory, 300 Iwawada, Onjuku-machi, Isumi-gun, Chiba 299-5105 (Japan); Kido, Katsutoshi [Marine Ecology Research Institute, Head Office, Research and Survey Group, Towa-Edogawabashi Bldg. 7F., 347 Yamabuki-cho, Shinjuku-ku, Tokyo 162-0801 (Japan)

    2011-03-15

    A radioactivity survey was launched in 1991 to determine the background levels of {sup 239+240}Pu in the marine environment off a commercial spent nuclear fuel reprocessing plant before full operation of the facility. Particular attention was focused on the {sup 240}Pu/{sup 239}Pu atom ratio in seawater and bottom sediment to identify the origins of Pu isotopes. The concentration of {sup 239+240}Pu was almost uniform in surface water, decreasing slowly over time. Conversely, the {sup 239+240}Pu concentration varied markedly in the bottom water and was dependent upon the sampling point, with higher concentrations of {sup 239+240}Pu observed in the bottom water sample at sampling points having greater depth. The {sup 240}Pu/{sup 239}Pu atom ratio in the seawater and sediment samples was higher than that of global fallout Pu, and comparable with the data in the other sea area around Japan which has likely been affected by close-in fallout Pu originating from the Pacific Proving Grounds. The {sup 240}Pu/{sup 239}Pu atom ratio in bottom sediment samples decreased with sea depth. The land-originated Pu is not considered as the reason of the increasing {sup 239+240}Pu concentration and also decreasing the {sup 240}Pu/{sup 239}Pu atom ratio with sea depth, and further study is required to clarify it. - Research highlights: {yields} A radioactivity survey on Pu isotopes was carried out in the coastal sea adjacent the nuclear fuel reprocessing plant in Aomori, Japan during 1991-2005. {yields} The {sup 239+240}Pu concentrations were uniform in surface water from one sampling point to another and decreased with a half-life of 17.8 y on the average. {yields} The time dependent decrease of {sup 239+240}Pu concentration in bottom water became more gradual with the increase of the depth. {yields} The {sup 239+240}Pu concentrations were relatively low in sediments at the shallow sampling points, but higher at the deeper points, without time dependent changes. {yields} The higher

  17. Seasonal changes in zooplankton swimmer community collected by sediment trap moored in the western North Pacific Ocean

    Science.gov (United States)

    Yokoi, N.; Honda, M. C.; Matsuno, K.; Yamaguchi, A.

    2016-02-01

    For high-latitude oceanic region, life cycle of zooplankton is difficult to evaluate by ordinary ship-board observation. To overcome this problem, zooplankton monitoring on swimmer samples collected by sediment trap may be a powerful tool. In this study, we studied seasonal changes in zooplankton community based on the swimmer samples (>1 mm) collected by a sediment trap moored at 200 m depth at St. K2 (47°N, 160°E) in the western subarctic Pacific with one- to two-week intervals during July 2013 to May 2014. Zooplankton abundance and biomass showed clear seasonal pattern, and were higher during July-August. Cluster analysis (Bray-Curtis methods) separated samples into three groups. Occurrence of each group had clear seasonal pattern: i.e. group A characterized with high abundance with dominance of copepods Eucalanus bungii and Neocalanus plumchrus occurred during July to September, followed by group B with few abundance dominated by chaetognaths during October to December, then group C dominated by Neocalanus cristatus and Paraeuchaeta elongata during January to March. For dominant copepods, seasonal changes in population structure, lipid content and gonad developmental stage were observed. Thus, most males of E. bungii were C4 and C5 until February, while the composition of adults (C6M) suddenly increased and reached 80% at end of March. These drastic changes in copepod population structure are considered as a reflection of their arousal from diapause at that depth. Carnivorous P. elongata showed high abundance during March to July, and both egg-sac-carrying and spermatophore-attached adult females (C6F) were occurred during that period. These facts suggest that active reproduction of P. elongata was at that season. Results of this study suggest that seasonal monitoring on zooplankton swimmer collected by sediment trap is a powerful tool to evaluate life cycle of the oceanic zooplankton species.

  18. 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

  19. 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

  20. 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

  1. 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...

  2. Radioecological assessment and radiometric dating of sediment cores from dynamic sedimentary systems of Pra and Volta estuaries (Ghana) along the Equatorial Atlantic.

    Science.gov (United States)

    Klubi, E; Abril, J M; Nyarko, E; Laissaoui, A; Benmansour, M

    2017-11-01

    The Volta and Pra estuaries (Ghana, West Africa) are dynamical sedimentary systems whose natural equilibrium is being affected by anthropogenic activities. This paper reports depth-distributions of 210 Pb, 226 Ra, 234 Th, 40 K, 228 Ra and 137 Cs for two sediment cores from these estuaries. Bulk densities were not steady-state and well correlated with 40 K (p Pra, affected by intense gold mining activities along its course. Radiological and radioecological assessments have been conducted by applying the UNSCEAR protocols and the ERICA model, respectively. The measured radionuclide concentrations do not pose any significant risk for the environment and human health. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. 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...

  4. 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

  5. Effects of Sediment Layer and Shallow Portion of the Oceanic Crust on Waveforms of Broadband Ocean Bottom Seismometers in Northwest Pacific Ocean

    Science.gov (United States)

    Abe, Y.; Kawakatsu, H.

    2015-12-01

    Earthquake Research Institute, The University of Tokyo and Japan Agency for Marine-Earth Science and Technology have conducted seismic observation in the northwest Pacific Ocean with broadband ocean bottom seismometers (BBOBSs), for understanding the structure of the Earth's interior and the mechanism of plate motion (Normal Mantle Project). We have performed receiver function (RF) analyses using the waveform data, for detecting velocity discontinuities in the upper mantle, and have understood that it is essential to reveal shallower structure (especially structure of sediment) for elucidating the upper mantle structure using RFs (Abe et al., 2014, SSJ meeting; 2015, JpGU meeting). Therefore, we attempted to estimate the shallower structure by using power spectrum and auto correlation function (ACF) of ambient noise in addition to RFs. Power spectrum of horizontal seismogram of a BBOBS has several peaks due to resonances of S wave in the sediment. Godin & Chapman (1999, J. Acoust. Soc. Am.) introduced a method to estimate a 1-D velocity distribution in the sediment from the resonance frequencies. From the location of spectral peaks of a station (NM14), we estimated the velocity distribution to be Vs(z) = 0.519z0.473 (Vs: S wave velocity (km/s), z: depth (km)), assuming a sediment layer thickness of 0.3 km. Two way S wave travel time in this sediment corresponds to the arrival time of a prominent negative ACF peak of horizontal seismogram of the station. On the other hand, for P-wave RFs (0.4-2.0 Hz) of the station, the arrival time of the first positive peak is not explained only by the estimated sediment structure, and another discontinuity located a few hundred meters deeper than the bottom of the sediment is necessary to explain it. We attempt to constrain the structure of the sediment and shallow portion of the oceanic crust by analyzing RF waveforms in more detail that also explains power spectrum and ACF of ambient noise.

  6. Reconstruction of cyclical and abrupt changes in northeastern Pacific precipitation during the Late Holocene based on marine sediments preserved in Effingham Inlet, British Columbia

    Science.gov (United States)

    Dallimore, A.; Thomson, R.; Enkin, R. J.

    2009-12-01

    Accurate interpretation of paleoenvironmental time series requires the reliable chronological control now provided by an age-model of a 40 m long marine sediment core raised from Effingham Inlet in Barkley Sound, British Columbia in 2002 (Core MD02-2494). The Late-Pleistocene to Holocene age model provides detailed annual to decadal resolution of the timing of proxy paleoenvironmental indicators preserved in the core based on 46 radiocarbon dates and the presence of the Mazama Ash. Also determined is the timing of instantaneous depositional events related to seismic activity along the Cascadia subduction zone. A frequency-time analysis of the grey scale of sediment x-rays from the calibrated core, which represent the volume and timing of precipitation events in area over the past 6,000 years, show cyclical as well as abrupt “regime change” controls on the northeast Pacific and climate system. This time series, combined with a time series derived from the core using a geochemical reconstruction of Pacific decadal variability, now provide a quantitative means of comparing the marine paleoenvironmental record of ocean and climate conditions of the B.C. coast to other time series of Holocene northeastern Pacific paleoenvironmental indicators.

  7. Sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Guptha, M.V.S.; Ittekkot, V.

    through the water column but their trapping efficiency, and thus, their accuracy can be biased by hydrodynamic and biological effects (Lee et al., 1988; Gust et al., 1992; 1994). Scholten et al. (2001) showed that the 230 Thorium trapping efficiency... of sediment traps moored at different sites and water depths in eastern North Atlantic Ocean varies between 9 and 143%. In general, these trapping efficiencies increase with increasing water-depth (Scholten et al., 2001). By comparing data from various ocean...

  8. A new model evaluating Holocene sediment dynamics: Insights from a mixed carbonate-siliciclastic lagoon (Bora Bora, Society Islands, French Polynesia, South Pacific)

    Science.gov (United States)

    Isaack, Anja; Gischler, Eberhard; Hudson, J. Harold; Anselmetti, Flavio S.; Lohner, Andreas; Vogel, Hendrik; Garbode, Eva; Camoin, Gilbert F.

    2016-08-01

    found in the lagoon of nearby Tahaa, which are supposed to be induced by elevated cyclone activity. Correspondingly, enhanced erosion and run-off from the volcanic hinterland as well as lower lagoonal salinity would be associated with intense rainfall during repeated cyclone landfall. Increased amounts of coarse-grained sediment from marginal reef areas would be transported into the lagoon. However, Ti/Ca and Fe/Ca ratios as proxies for terrigenous sediment delivery have incessantly declined since the mid-Holocene. Also, benthic foraminiferal faunas do not validate reef-to-lagoon transport of sediment. Alternatively, the apparent onset of higher hydrodynamic energy conditions can be explained by more permanent southeast trade winds and higher-than-present sea level, which are supposed for the mid-late Holocene in the south Pacific. Sustained winds would have flushed higher amounts of open ocean water into the lagoon enhancing primary productivity and the amount of pelagic organisms within the lagoon while lowering lagoonal salinity. We propose the shift towards coarser-grained sedimentation patterns during the mid-late Holocene to reflect sediment-load shedding of sand aprons due to oversteepening of slopes at sand apron/lagoon edges during times of stronger trades and higher-than-present sea level of the Highstand Systems Tract, which led to redeposition of sediment even within the lagoon center. Modern conditions including a sea-level fall to modern level were reached ca. 1000 years BP, and lagoonal infill has been determined to a large part by fine-grained carbonate-dominated sediments produced within the lagoon and derived from the marignal reef. Infill of lagoonal accommodation space via sand aprons is estimated to be up to six times higher than infill by lagoonal background sedimentation and emphasizes the importance of the progradation of sand aprons. Contrary to the commonly supposed assumption that coarse-grained sediment layers within fine-grained lagoonal

  9. Food Web Bioaccumulation Model for Resident Killer Whales from the Northeastern Pacific Ocean as a Tool for the Derivation of PBDE-Sediment Quality Guidelines.

    Science.gov (United States)

    Alava, Juan José; Ross, Peter S; Gobas, Frank A P C

    2016-01-01

    Resident killer whale populations in the NE Pacific Ocean are at risk due to the accumulation of pollutants, including polybrominated diphenyl ethers (PBDEs). To assess the impact of PBDEs in water and sediments in killer whale critical habitat, we developed a food web bioaccumulation model. The model was designed to estimate PBDE concentrations in killer whales based on PBDE concentrations in sediments and the water column throughout a lifetime of exposure. Calculated and observed PBDE concentrations exceeded the only toxicity reference value available for PBDEs in marine mammals (1500 μg/kg lipid) in southern resident killer whales but not in northern resident killer whales. Temporal trends (1993-2006) for PBDEs observed in southern resident killer whales showed a doubling time of ≈5 years. If current sediment quality guidelines available in Canada for polychlorinated biphenyls are applied to PBDEs, it can be expected that PBDE concentrations in killer whales will exceed available toxicity reference values by a large margin. Model calculations suggest that a PBDE concentration in sediments of approximately 1.0 μg/kg dw produces PBDE concentrations in resident killer whales that are below the current toxicity reference value for 95 % of the population, with this value serving as a precautionary benchmark for a management-based approach to reducing PBDE health risks to killer whales. The food web bioaccumulation model may be a useful risk management tool in support of regulatory protection for killer whales.

  10. 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

  11. Oceanographic profile temperature measurements collected using bottle from the A.T. CAMERON, GADUS ATLANTICA, RYURIK, BLAGONAMERENNI, PREDPRIYATIE, and other platforms in the Antarctic, Equatorial Pacific, and other locations from 1772 to 1866 (NODC Accession 0000571)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile data were collected using bottle casts from the BEAGLE in the North / South Pacific Ocean, Indian Ocean, Southern Oceans, and Red Sea. Data were...

  12. 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

  13. 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

  14. 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.

  15. Equatorial MU Radar project

    Science.gov (United States)

    Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

    Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system

  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. 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

  18. Polycyclic Aromatic Hydrocarbons in Sediments and Bivalves on the Pacific Coast of Japan: Influence of Tsunami and Fire.

    Directory of Open Access Journals (Sweden)

    Mayu Onozato

    Full Text Available Surface sediments and at least one edible bivalve species (Ruditapes philippinarum, Mytilus galloprovincialis, and Crassostrea gigas were collected from each of seven intertidal sites in Japan in 2013. The sites had experienced varying levels of tsunami and fire disturbance following the major earthquake of 2011. Eight polycyclic aromatic hydrocarbons (PAHs were identified and analyzed by gas chromatography-mass spectrometry. Total sediment PAH concentration (CT, the sum of the average concentrations of the eight PAHs, was 21-1447 μg kg-1-dry. Relative to the average level of one type of PAH in sediments collected around Japan in 2002 (benzo[a]pyrene = 21 μg kg-1-dry, five of the seven sites showed concentrations significantly lower than this average in 2013. The CTs for the three bivalves (134-450 μg kg-1-dry were within the range of the previous reports (2.2-5335 μg kg-1-dry. The data suggest that the natural disaster did not increase PAH concentrations or affect the distribution within sediment or bivalves in Tohoku district. Although PAH concentrations at the sites pose no risk to human health, the findings highlight that the observed PAH levels derive from pre- rather than post-quake processes.

  19. Influence of physical and biological processes on the seasonal cycle of biogenic flux in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vidya, P.J.; PrasannaKumar, S.; Gauns, M.; Verenkar, A; Unger, D.; Ramaswamy, V.

    Seasonal cycle of biogenic fluxes obtained from sediment trap at two locations 5°24` N, 86°46` E (southern Bay of Bengal trap; SBBT) and 3°34` N, 77°46` E (equatorial Indian Ocean trap; EIOT) within the equatorial Indian Ocean (EIO) were examined...

  20. Equatorial jet - a case study

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; PrasannaKumar, S.

    and formation of a subsurface high salinity core are, apparently, manifestations of vertical advection of momentum associated with the jet. The driving force behind the equatorial undercurrent in the Indian Ocean ceases to exist in May, causing undercurrent...

  1. Coastal Sedimentation Associated with the Tohoku Tsunami of 11 March 2011 in South Kuril Islands, NW Pacific Ocean

    Science.gov (United States)

    Razjigaeva, N. G.; Ganzey, L. A.; Grebennikova, T. A.; Ivanova, E. D.; Kharlamov, A. A.; Kaistrenko, V. M.; Shishkin, A. A.

    2013-06-01

    Sediment deposited by the Tohoku tsunami of March 11, 2011 in the Southern Kurils (Kunashir, Shikotan, Zeleniy, Yuri, Tanfiliev islands) was radically different from sedimentation during local strong storms and from tsunamis with larger runup at the same location. Sediments from the 2011 Tohoku tsunami were surveyed in the field, immediately and 6 months after the event, and analyzed in the laboratory for sediment granulometry, benthos Foraminifa assemblages, and diatom algae. Run-up elevation and inundation distance were calculated from the wrackline (accumulations of driftwood, woody debris, grass, and seaweed) marking the distal edge of tsunami inundation. Run-up of the tsunami was 5 m at maximum, and 3-4 m on average. Maximum distance of inundation was recorded in river mouths (up to 630 m), but was generally in the range of 50-80 m. Although similar to the local strong storms in runup height, the tsunami generally did not erode the coast, nor leave a deposit. However, deposits uncharacteristic of tsunami, described as brown aleuropelitic (silty and clayey) mud rich in organic matter, were found in closed bays facing the South Kuril Strait. These closed bays were covered with sea ice at the time of tsunami. As the tsunami waves broke the ice, the ice floes enhanced the bottom erosion on shoals and destruction of low-lying coastal peatland even at modest ranges of runup. In the muddy tsunami deposits, silt comprised up to 64 % and clay up to 41.5 %. The Foraminifera assemblages displayed features characteristic of benthic microfauna in the near-shore zone. Deep-sea diatoms recovered from tsunami deposits in two closely situated bays, namely Krabovaya and Otradnaya bays, had different requirements for environmental temperature, suggesting these different diatoms were brought to the bays by the tsunami wave entraining various water masses when skirting the island from the north and from the south.

  2. Chemical and temperature profile data from bottle and CTD casts in the Pacific Ocean as part of the Joint Global Ocean Flux Study/Equatorial Pacific Basin Study (JGOFS/EQPAC) project, from 1992-03-19 to 1992-10-21 (NODC Accession 9700115)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Chemical and temperature profile data were collected using bottle and CTD casts from the THOMAS THOMPSON in the Pacific Ocean from March 19, 1992 to October 21,...

  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. 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

  8. 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.

  9. Last 150-year variability in Japanese anchovy ( Engraulis japonicus) abundance based on the anaerobic sediments of the Yellow Sea Basin in the western North Pacific

    Science.gov (United States)

    Huang, Jiansheng; Sun, Yao; Jia, Haibo; Tang, Qisheng

    2016-02-01

    Relatively short historical catch records show that anchovy populations have exhibited large variability over multi-decadal timescales. In order to understand the driving factors (anthropogenic and/or natural) of such variability, it is essential to develop long-term time series of the population prior to the occurrence of notable anthropogenic impact. Well-preserved fish scales in the sediments are regarded as useful indicators reflecting the fluctuations of fish populations over the last centuries. This study aims to validate the anchovy scale deposition rate as a proxy of local anchovy biomass in the Yellow Sea adjoining the western North Pacific. Our reconstructed results indicated that over the last 150 years, the population size of anchovy in the Yellow Sea has exhibited great fluctuations with periodicity of around 50 years, and the pattern of current recovery and collapse is similar to that of historical records. The pattern of large-scale population synchrony with remote ocean basins provides further evidence proving that fish population dynamics are strongly affected by global and basin-scale oceanic/climatic variability.

  10. Eastern Pacific Ocean Conference

    Science.gov (United States)

    The promotion of interaction among investigators of all oceanographic disciplines studying the eastern Pacific Ocean was the goal of the 1990 Eastern Pacific Ocean Conference (EPOC), held October 17-19 on the snow-covered slopes of Mt. Hood, Oreg. Thirty oceanographers representing all disciplines attended.Dick Barber, Duke University Marine Lab, Beaufort, N.C., chaired a session on the eastern equatorial Pacific Ocean, emphasizing issues related to biological activity. Steve Ramp of the Naval Postgraduate School in Montery, Calif., chaired a session on recent results from northern and central California experiments. On October 19, following an early morning earthquake, a business meeting and discussions regarding a collaboration in future experiments were held.

  11. 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...

  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. 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...

  14. An improved model of equatorial scintillation

    Science.gov (United States)

    Secan, J. A.; Bussey, R. M.; Fremouw, E. J.; Basu, Sa.

    1995-05-01

    One of the main limitations of the modeling work that went into the equatorial section of the Wideband ionospheric scintillation model (WBMOD) was that the data set used in the modeling was limited to two stations near the dip equator (Ancon, Peru, and Kwajalein Island, in the North Pacific Ocean) at two fixed local times (nominally 1000 and 2200). Over the past year this section of the WBMOD model has been replaced by a model developed using data from three additional stations (Ascension Island, in the South Atlantic Ocean, Huancayo, Peru, and Manila, Phillipines; data collected under the auspices of the USAF Phillips Laboratory Geophysics Directorate) which provide a greater diversity in both latitude and longitude, as well as cover the entire day. The new model includes variations with latitude, local time, longitude, season, solar epoch, and geomagnetic activity levels. The way in which the irregularity strength parameter CkL is modeled has also been changed. The new model provides the variation of the full probability distribution function (PDF) of log (CkL) rather than simply the average of log (CkL). This permits the user to specify a threshold on scintillation level, and the model will calculate the percent of the time that scintillation will exceed that level in the user-specified scenario. It will also permit calculation of scintillation levels at a user-specified percentile. A final improvement to the WBMOD model is the implementation of a new theory for calculating S4 on a two-way channel.

  15. Variability of photosynthetic pigments in the Colombian Pacific ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    University of Concepcion, Oceanography Department, Cabina 5, Concepción, Casilla 160-C, Chile. e-mail: erodrig@udec.cl. Variability of the oceanographic conditions in the Colombian Pacific Ocean, a part of the Panama. Basin, is subjected to the variability of wind conditions in the equatorial part of the Pacific Ocean.

  16. Sediment mineralogy based on visible and near-infrared reflectance spectroscopy

    Science.gov (United States)

    Jarrard, R.D.; Vanden Berg, M.D.; ,

    2006-01-01

    Visible and near-infrared spectroscopy (VNIS) can be used to measure reflectance spectra (wavelength 350-2500 nm) for sediment cores and samples. A local ground-truth calibration of spectral features to mineral percentages is calculated by measuring reflectance spectra for a suite of samples of known mineralogy. This approach has been tested on powders, core plugs and split cores, and we conclude that it works well on all three, unless pore water is present. Initial VNIS studies have concentrated on determination of relative proportions of carbonate, opal, smectite and illite in equatorial Pacific sediments. Shipboard VNIS-based determination of these four components was demonstrated on Ocean Drilling Program Leg 199. ?? The Geological Society of London 2006.

  17. Neotectonics in the northern equatorial Brazilian margin

    Science.gov (United States)

    Rossetti, Dilce F.; Souza, Lena S. B.; Prado, Renato; Elis, Vagner R.

    2012-08-01

    An increasing volume of publications has addressed the role of tectonics in inland areas of northern Brazil during the Neogene and Quaternary, despite its location in a passive margin. Hence, northern South America plate in this time interval might have not been as passive as usually regarded. This proposal needs further support, particularly including field data. In this work, we applied an integrated approach to reveal tectonic structures in Miocene and late Quaternary strata in a coastal area of the Amazonas lowland. The investigation, undertaken in Marajó Island, mouth of the Amazonas River, consisted of shallow sub-surface geophysical data including vertical electric sounding and ground penetrating radar. These methods were combined with morphostructural analysis and sedimentological/stratigraphic data from shallow cores and a few outcrops. The results revealed two stratigraphic units, a lower one with Miocene age, and an upper one of Late Pleistocene-Holocene age. An abundance of faults and folds were recorded in the Miocene deposits and, to a minor extent, in overlying Late Pleistocene-Holocene strata. In addition to characterize these structures, we discuss their origin, considering three potential mechanisms: Andean tectonics, gravity tectonics related to sediment loading in the Amazon Fan, and rifting at the continental margin. Amongst these hypotheses, the most likely is that the faults and folds recorded in Marajó Island reflect tectonics associated with the history of continental rifting that gave rise to the South Atlantic Ocean. This study supports sediment deposition influenced by transpression and transtension associated with strike-slip divergence along the northern Equatorial Brazilian margin in the Miocene and Late Pleistocene-Holocene. This work records tectonic evidence only for the uppermost few ten of meters of this sedimentary succession. However, available geological data indicate a thickness of up to 6 km, which is remarkably thick for

  18. The indicative significance of the tropical Pacific precipitation for the evolution of ITCZ over the last four glacial/interglacial cycles

    Science.gov (United States)

    Zhang, Shuai; Qi, Yiquan; Li, Tiegang; Chang, Fengming; Yu, Zhoufei

    2017-04-01

    Multiple planktonic foraminiferal calcite Mg/Ca and δ18O were studied to reconstruct the high-resolution records of sea water δ18O in the sediment core KX97322-4, which was recovered from the Ontong-Java Plateau in the western equatorial Pacific (WEP), the core region of the western Pacific warm pool (WPWP). By combining the two proxies together, we obtained the upper water temperature and salinity over the last four glacial/interglacial cycles. We also removed the influence from global ice volume change to salinity to reconstruct the local precipitation history. By comparing SST records of the WEP with the Eastern Equatorial Pacific since MIS 10, we find that the tropical Pacific was more likely in the phase of El Niño-like during Terminations and warming stage in glacial. Meanwhile, the mean position of the intertropical convergence zone (ITCZ) was moving northward and more water vapor and heat were taken to middle and high latitude regions. By comparing precipitation records of multi-position in the WPWP with the East Asian summer monsoon (EASM) records, we find that the tropical Pacific hydrological variation was associated with the ITCZ changes and even could impact EASM precipitation. When the isolation became stronger, the globe was warming and evaporation-precipitation ratio in the WEP enhanced, the ITCZ with more moisture shifted from the tropical areas to the temperate latitude, then East Asia precipitation was strengthened. While the situation would reverse when the solar radiation decreased. During the processes, the zonal thermal state would adjust the extent of the ITCZ variation. Our finding provides further evidence for the relationship between the WPWP hydrological status and the EASM precipitation, the tropical Pacific zonal thermal state and the ITCZ change during the last four glacial/interglacial cycles.

  19. Irregularities and Forecast Studies of Equatorial Spread

    Science.gov (United States)

    2016-07-13

    document in the published literature . The result implies that the aeronomy of the postsunset equatorial ionosphere is sufficiently well understood for...of equatorial spread F in the Peruvian sector, J. Geophys. Res. Space Physics, 119, 38153827, doi:10.1002/2014JA019889. ◦ Hysell, D. L., M. A. Milla...L. Condori, and J. W. Meriwether (2014), Data-driven numer- ical simulations of equatorial spread F in the Peruvian sector: 2. Autumnal equinox, J

  20. 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

  1. 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.

    Andaluz de Ciencias de la Tierra, Universidad de Granada, Campus Fuentenueva, 18002 Granada, Spain. 39 Department of Geological Sciences, University of South Carolina, 701 Sumter Street, EWS 617, Columbia SC 29208, USA. 40 Department of Geosciences...

  2. 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...

  3. Paleoceanography of the tropical eastern pacific ocean.

    Science.gov (United States)

    Grigg, R W; Hey, R

    1992-01-10

    The East Pacific Barrier (EPB) is the most effective marine barrier to dispersal of tropical shallow-water fauna in the world today. The fossil record of corals in the eastern Pacific suggests this has been true throughout the Cenozoic. In the Cretaceous, the EPB was apparently less effective in limiting dispersal. Equatorial circulation in the Pacific then appears to have been primarily east to west and the existence of oceanic atolls (now drowned guyots) in the eastern Pacific probably aided dispersal. Similarly, in the middle and early Mesozoic and late Paleozoic, terranes in the central tropical Pacific likely served as stepping stones to dispersal of tropical shelf faunas, reducing the isolating effect of an otherwise wider Pacific Ocean (Panthalassa).

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

    Science.gov (United States)

    Zheng, Jian; Liu, Qinyu; Wang, Chuanyang

    2017-05-01

    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.

  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. Radiocarbon of settling particles from the hemipelagic region of the Western Pacific Warm Pool

    International Nuclear Information System (INIS)

    Kawahata, H.; Murayama, M.

    2000-01-01

    Particle organic radiocarbon (POCΔ 14 C) of settling particles collected by time-series sediment traps deployed in the Western Pacific Warm Pool (WPWP) was analyzed by accelerator mass spectrometry (AMS). The (POCΔ 14 C) during period 2 (August to October), when mass fluxes were relatively high, was comparable to the Δ 14 C values (80-100 per thousand; per mille) in corals from Tarawa (Guilderson et al., 1998). In contrast, low Δ 14 C values of POC were observed during periods 1, 3 and 4. One of the possible processes behind decreasing Δ 14 C values is river water input. Probably during periods 1, 3 and 4 the surface water at Site 1 was under the influence of the South Equatorial Current, flowing toward the west along the coastal line of New Guinea and transporting appreciable amount of solutes and suspended matter to the hemipelagic region

  8. 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

  9. Increased Sediments, but not Nutrients, may Facilitate Dominance of Halimeda Opuntia Through Interactions with Light on Fringing Reefs in the South Pacific

    Science.gov (United States)

    Grier, S.; Gyles, S.; Marrufo, J.; Sura, S.; Barber, P. H.; Fong, P.

    2016-02-01

    Phase-shifts from coral to algal communities are occurring worldwide on tropical reef systems, making it important to understand the ecological processes that may promote and maintain algal dominance. Two anthropogenic stressors, increased sedimentation and nutrient inputs, may interact with light availability to facilitate algal dominance and may also support a diverse microbial community on the algal's thallus. We conducted paired 3 factor fully-crossed field and mesocosm experiments varying light (+/- shade), nutrients (+/- fertilizer), and sediments (+/-) to determine their effects on growth of a common calcifying green alga, Halimeda opuntia, and its microbial epiphytes. The field study was on a shallow back reef habitat comprised of dead coral heads now dominated by algae, while the mesocosm experiment was in a flow through water table. In both experiments, there was a significant interaction between light and sediment, while nutrients had no effect on growth. However, in the mesocosm experiment, sediments had a strong positive effect on growth in the light but not in the shade, suggesting sediments may have provided protective shade in this high light environment. In contrast, in the field, sediments had a negative effect in ambient light, while growth was overall lower and more variable in the shade, suggesting that shading by sediments was negative in this environment. Further, metagenomic analysis of the microbial community in the field experiment revealed an increase in the relative abundance of Cardiobacteriaceae in shaded treatments. Our results suggest that anthropogenic increases in sediments interacting with light may allow Halimeda opuntia to dominate shallow reef zones that were previously dominated by coral and may contribute to changes in the algal microbiome. Thus, our work suggests that future conservation efforts need to encompass limiting sediment fluxes to fringing reef systems.* first 3 authors contributed equally

  10. 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...

  11. 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.

  12. 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.

  13. Distribution of organic sulphur compounds in Mesozoic and Cenozoic sediments from the Atlantic and Pacific Oceans and the Gulf of California

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Haven, H.L. ten; Rullkotter, J.; Leeuw, J.W. de

    1990-01-01

    Gas chromatography-mass spectrometry data of the "aromatic hydrocarbon" fractions of nearly 100 Deep Sea Drilling Project and Ocean Drilling Program sediment samples have been re-examined for the occurrence of organic sulfur compounds. Approximately 70% of the samples contain OSC with varying

  14. IAEA/RCA regional TC project for East Asia and the Pacific: Restoration of soil fertility and sustenance of agricultural productivity (RAS/5/039). Part II. Soil erosion/sedimentation and associated pesticide contamination

    International Nuclear Information System (INIS)

    Bernard, Claud

    2004-01-01

    Increasing attention is being paid to accelerated soil erosion and associated land degradation because of their impact on sustainable development and environmental protection. Soil erosion and associated sedimentation cause not only on site degradation of a non-renewable natural resource but also offsite problems such as downstream sediment deposition in fields, floodplains and water bodies, water pollution, eutrophication and reservoir siltation. There is, therefore, an urgent need for obtaining reliable quantitative data on the extent and actual rates of soil erosion worldwide to provide a more comprehensive assessment of the magnitude of the problems, actual rates of erosion and sedimentation and to define suitable major land use types and underpin the selection of effective soil conservation measures. The use of fallout radionuclides, in particular the 137 Cs technique affords an effective and valuable means for studying erosion and deposition within the landscape. The key advantage of this approach is that it can provide retrospective information on medium-term erosion/deposition rates and spatial patterns of soil redistribution, without the need for long-term monitoring programmes. The overall objective of this project is to develop improved soil, water, nutrient, and crop management practices while counteracting predominant soil degradation processes to increase and sustain crop productivity in the East Asia and Pacific region. To achieve this two complimentary approaches are utilized. We refer here specifically to Part II, whose specific objective is to measure soil erosion/ sedimentation rates and associated pesticide contamination. For this purpose, the 137 Cs and related techniques will be utilized to measure erosion/sedimentation rates and to define soil distribution patterns in the landscape. Also radiotracer and conventional techniques will be applied to determine pesticide contamination levels in soil, water and plant. This part of the project will

  15. Change in the Nd isotopic composition of the bottom water and detrital sediments on the Bering Slope over the last 500 kyrs with implications for the formation of the North Pacific Intermediate Water

    Science.gov (United States)

    Jang, K.; Huh, Y.; Han, Y.

    2015-12-01

    The Bering Sea is a potential location for the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) and may play an important role in the global heat distribution. We reconstructed the neodymium isotopic ratio (ɛNd) of authigenic Fe-Mn oxide coatings and detrital sediments on the Bering Slope (IODP Expedition 323 site U1345; water depth 1008 m) over the last 500 kyrs. The ɛNd is a quasi-conservative water mass tracer. We compared three different leaching techniques to assure that authigenic signals are captured without contamination from terrigenous sources: (1) leaching (3 hours) with 0.02 M hydroxylamine hydrochloride (HH) in 25% buffered acetic acid after decarbonation; sediment/solution (v/v) > 10, (2) leaching (1 hour) with 0.02 M HH in 25% buffered acetic acid without decarbonation; sediment/solution ~ 1, and (3) leaching (1 hour) with 0.005 M HH in 1.5% buffered acetic acid-0.003 M Na-EDTA without decarbonation; sediment/solution > 40. The low Al concentrations and less radiogenic ɛNdvalues indicated that method (2) is the most appropriate leaching process. The average ɛNd of the authigenic fraction over the last 500 kyrs is -3.3 ± 0.9 (1σ, n=38), with large temporal fluctuations. The ɛNd of authigenic and detrital fractions are well correlated (r2 ~ 0.66), suggesting that the bottom water composition in the Bering Sea was governed by terrigenous inflow from surrounding areas. Radiogenic ɛNd peaks (up to -1.9) seem to be influenced by radiogenic water inflow from the the Kamchatka or Aluetian arcs. The high bulk density and low b* values imply higher terrigenous versus biological contribution and enhanced sea ice formation. Subsequent brine formation would have triggered sinking of radiogenic surface water, forming the NPIW. On the other hand, non-radiogenic ɛNd troughs (down to -5.3) are observed at times of low bulk density and high b* values. We presume higher biological productivity which is supported by the high opal content at

  16. Some effects of a mean zonal thermocline gradient on planetary equatorial waves

    Directory of Open Access Journals (Sweden)

    M. Pontaud

    1995-11-01

    Full Text Available Planetary equatorial waves are studied with the shallow water equations in the presence of a mean zonal thermocline gradient. The interactions between this gradient and waves are represented by three non-linear terms in the equations: one in the wind-forcing formulation in the x-momentum equation, and two for the advection of mass and divergence of the velocity field in the continuity equation. When the mean gradient is imposed but small, these three (linearized terms will perturb the behaviour of the equatorial waves. This paper gives a simple analytic treatment of this problem. The equatorial Kelvin mode is first solved with all three contributions, using a Wentzel-Kramers-Brillouin method. The Kelvin mode shows a spatial or/and temporal growth when the thermocline gradient is negative which is the usual situation in the equatorial Pacific ocean (deep thermocline in the west and shallow in the east. The more robust and efficient contribution comes from the advection term. The single effect of the advection of the mean zonal thermocline gradient is then studied for the Kelvin and planetary Rossby modes. The Kelvin mode remains unstable (damped, while the Rossby modes appear damped (unstable for a negative (positive thermocline gradient.

  17. 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.

  18. 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

  19. 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.

  20. 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)

  1. 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

  2. Modern non-pollen palynomorphs from East African Lake sediments

    NARCIS (Netherlands)

    Gelorini, V.; Verbeken, A.; van Geel, B.; Cocquyt, C.; Verschuren, D.

    2011-01-01

    This paper presents an illustrated guide to the identification of non-pollen palynomorphs (NPPs) preserved in lake-sediment archives from equatorial East Africa. Modern NPPs were recovered from recently deposited surface sediment in 20 small crater lakes in western Uganda, located along

  3. Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size-island age model in the Pacific

    Science.gov (United States)

    Perry, CT; Kench, PS; Smithers, SG; Riegl, BR; Gulliver, P.; Daniells, JJ

    2017-09-01

    Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly ( 4-5 mm yr-1) under a "bucket-fill" type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by 5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of 1500 yr before island initiation (at 3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

  4. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

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

    2000-01-01

    tenuis are strongly diminished, causing an increase in relative abundance of the lower photic zone taxa Florisphaera profunda and Gladiolithus flabellatus. During the past 140,000 years the surface water circulation of the equatorial Atlantic has changed drastically, as can be seen from changes...

  5. Equatorial electrojet in east Brazil longitudes

    Indian Academy of Sciences (India)

    and West Africa. It is felt that a systematic study of the geomagnetic/ionospheric observations at suit- able sites in Brazil is important to understand EEJ and aspects of space weather. Acknowledgements. The data from the Kyushu network of equatorial electrojet stations is acknowledged. Rastogi and. Chandra are thankful ...

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

    Science.gov (United States)

    Kim, Byeong-Hee; Ha, Kyung-Ja

    2017-07-01

    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 changes in Indian Walker Circulation and Atlantic Walker Circulation which are affected by the anomalous SST over 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.

  7. 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.

  8. Equatorial electrojet in the Indian region during the geomagnetic ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 125; Issue 3. Equatorial electrojet in the Indian region ... A strong (–50 nT) and a long duration counterelectrojet, right from 08 to 13 hr on 14 November 1998 was observed resulting in the absence of equatorialEs at Thumba. Absence of the equatorial ionization ...

  9. Particle sinking dynamics and POC fluxes in the Eastern Tropical South Pacific based on 234Th budgets and sediment trap deployments

    Science.gov (United States)

    Haskell, William Z., II; Berelson, William M.; Hammond, Douglas E.; Capone, Douglas G.

    2013-11-01

    Assuming steady-state over seasonal to annual timescales, and limited horizontal export of dissolved nutrients, the vertical fluxes of limiting nutrients into the euphotic zone should be balanced by particle export. Sediment traps and 234Th budgets have both been used extensively throughout the oceans as a means to measure this particulate flux from the upper ocean. One main goal of these efforts has been to determine the amount of CO2 fixed by primary producers in the surface ocean that is exported as particulate organic carbon (POC) and conversely, the decrease of particle flux with depth has been used to estimate remineralization rates of nutrients. Although disagreement between trap-derived and 234Th-derived fluxes has often been noted, the possible reasons for the imbalance are numerous, and thus often it is difficult to assign causes. Here, we examine many commonly implicated contributors to the disagreement, allowing us to assess data from a recent 2-year study in the ETSP that shows systematic disagreement between the two methods. Averaging results from both years, sediment traps collected 0.2-1.5 mmol C m-2 d-1 (mean: 0.74 mmol C m-2 d-1) of POC, while the thorium-based method estimated an average POC flux of 1.5-14 mmol C m- d-1 (mean: 6.2 mmol C m-2 d-1). The study area spans regions of differing ecological structure, as inferred from trap mineralogy, and the flux disagreement coincides with this ecological range. We interpret the difference as undercollection of poorly ballasted, slowly sinking particles by the sediment traps. Using both methods simultaneously offers insight into ecosystem structure and resulting particle flux dynamics. The thorium deficit-based flux is 5-10% of previously published estimates of primary productivity based on 14C incubations (Pennington et al., 2006), and 8-20% of concurrent estimates based on 14C incubations and oxygen supersaturation (Capone et al., personal communication; Prokopenko et al., personal communication).

  10. 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

  11. The Longitudinal Variation of Equatorial Electrodynamics Observations

    Science.gov (United States)

    Yizengaw, E.; Zesta, E.; Moldwin, M.; Valladares, C. E.; Damtie, B.; Mebrahtu, A.; Biouele, C. M.; Yumoto, K.; Pfaff, R. F.; Heelis, R. A.

    2010-12-01

    The uneven distribution of ground-based instruments due to the large ocean coverage in the equatorial regions hinders our ability to obtain a global understanding of the dynamics and structure of the equatorial ionosphere. In Africa, which has been mostly devoid of ground-based instruments, the ionospheric density structure has been traditionally estimated by model interpolation over vast geographic areas. Recent ground- and space-based observations have shown that geomagnetic storms can have dramatic longitudinal differences in equatorial ionospheric electrodynamics, such as enhanced generation of F-region plasma irregularities, and super fountain effect at low latitudes. For example, satellite observations have shown very unique equatorial ionospheric density structures in the African region. The African region is the longitude sector where the occurrence of large scale bubble activity (zonal width, depletion level, and spacing) peaks. No other region in the globe shows similar characteristics. One of the possible driving mechanisms that govern the equatorial electrodynamics is the vertical ExB drift, which strongly affects the structure and dynamics of the ionosphere in the low/mid-latitude region. According to the observations performed at different longitudes, using recently deployed limited ground-based instruments, the vertical ExB drift has significant longitudinal differences. This paper presents initial results of vertical ExB drifts observed at three different longitudes: East African, West African, and West American sectors. The drift is estimated using a pairs of ground-based magnetometers technique. In the African sector stations from the AMBER, INTERMAGNET, and MAGDAS, and in the American sector SAMBA and LISN magnetometer arrays have been used for this study. Finally, the comparison between the magnetometer estimated ExB drift and the vertical drift observations (VEFI and IVM) on board C/NOFS satellites have also been performed, showing promising

  12. 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.

  13. 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.

  14. Rare Central Pacific El Niño Events Caused by Interdecadal Tropical Pacific Variability

    Science.gov (United States)

    Zhong, Wenxiu; Zheng, Xiaotong; Cai, Wenju

    2017-04-01

    The frequency of Central Pacific (CP) El Niño events displays strong decadal-variability but the associated dynamics is still not clear. The Inter-decadal Pacific Oscillation (IPO) and the Tropical Pacific Decadal Variability (TPDV) are two dominant modes of the Pacific low-frequency variability that can modify high-frequency behaviors. Using a 500-year control integration of Geophysical Fluid Dynamics Laboratory Earth System Model simulation, we find that the mean state, determined by the two independent modes of tropical Pacific decadal variability, strongly affects CP El Niño frequency and the associated developing processes. A positive TPDV features a shallow thermocline and cool sea surface temperature anomalies (SSTAs) across the central-to-western tropical Pacific, and a negative IPO features cool SSTAs and strong trade winds along the equatorial Pacific. The combination of a positive TPDV and a negative IPO generates a decadal mean state, in which the climatological zonal temperature gradient is reduced, equatorward and westward current anomalies are harder to be generated over the central-to-western tropical Pacific, resulting in the lack of CP El Niño.

  15. 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.

  16. Equatorial Electrojet Observations in the African Continent

    Science.gov (United States)

    Yizengaw, E.; Moldwin, M. B.; Mebrahtu, A.; Damtie, B.; Pfaff, R.; Zesta, E.

    2008-12-01

    Although Satellite observations in the African sector show unique equatorial ionospheric structures that can severely impact navigation and communication systems, the study of ionospheric disturbances in this region is difficult due to the lack of ground-based instruments. This has created a gap in global understanding of the physics behind the evolution and formation of plasma irregularities in the equatorial region, which imposes limitations on ionospheric density modeling efforts. Therefore, in order to have a more complete global understanding of equatorial ionosphere motion, the international space science community has begun to develop an observational infrastructure in the African sector. This includes the deployment of a number of arrays of small instruments, including the AMBER magnetometer array, through the International Heliophysical Year (IHY) cooperative program with the United Nations Basic Space Science (UNBSS) program. Two AMBER magnetometers have been deployed successfully at Adigrat (~6°N magnetic) in Ethiopia and at Medea in Algeria (28°N magnetic), and became fully operational on 03 August 2008. The remaining two AMBER magnetometers will be deployed soon in Cameroon and Namibia. One of the prime scientific objectives of AMBER is to understand the processes governing electrodynamics of the equatorial ionosphere as a function of latitude, local time, magnetic activity, and season in the African region. The most credible driving mechanism of ionospheric plasma (E × B drift) can be estimated using two magnetometers, one right at the equator and the other about 6 off the equator. Therefore, using the AMBER magnetometer at Adigrat and the INTERMAGNET magnetometer located at Addis Ababa (0.9°N magnetic) in Ethiopia, the equatorial electrojet (E × B drift) activities in that longitudinal sector of the African continent is estimated. The paper also presents the comparison between the estimated vertical drift and the drift values obtained from the

  17. The field of the equatorial electrojet from CHAMP data

    Directory of Open Access Journals (Sweden)

    J.-L. Le Mouël

    2006-03-01

    Full Text Available We apply a simple linear transform, the along-track second derivative, to four years of scalar and vectorial data from the CHAMP satellite. This transform, reminiscent of techniques used in the interpretation of aeromagnetic surveys, is applied either to the geocentric spherical components of the field or to its intensity. After averaging in time and space, we first produce a map of the crustal field, then maps of the equatorial electrojet field at all local times and all universal times. The seasonal variation of the electrojet, its evolution with the solar cycle, and the effect of geomagnetic activity are discussed. The variation of the electrojet with longitude, an intriguing feature revealed by satellite data, is described in some detail, and it is shown that this longitude dependance is stable in time. The existence of a counterelectrojet in the morning, everywhere except over the Pacific Ocean, is established. The signatures of closure electric currents and of interhemispheric currents are also evidenced.

  18. What drove the Pacific and North America climate anomalies in winter 2014/15?

    Science.gov (United States)

    Peng, Peitao; Kumar, Arun; Hu, Zeng-Zhen

    2017-12-01

    In late 2014 and early 2015, the canonical atmospheric response to the El Niño and Southern Oscillation (ENSO) event was not observed in the central and eastern equatorial Pacific, although Niño3.4 index exceeded the threshold for a weak El Niño. In an effort to understand why it was so, this study deconvoluted the observed 2014/15 December-January-February (DJF) mean sea surface temperature (SST), precipitation and 200 hPa stream function anomalies into the leading patterns related to the principal components of DJF SST variability. It is noted that the anomalies of these variables were primarily determined by the patterns related to two SST modes: one is the North Pacific mode (NPM), and the other the ENSO mode. The NPM was responsible for the apparent lack of coupled air-sea relationship in the central equatorial Pacific and the east-west structure of the circulation anomalies over North America, while the ENSO mode linked to SSTs in the central and eastern equatorial Pacific as well as the circulation in the central equatorial Pacific. Further, the ENSO signal in DJF 2014/15 likely evolved from the NPM pattern in winter 2013/14. Its full development, however, was impeded by the easterly anomalies in the central equatorial Pacific that was associated with negative SST anomalies in the southeastern subtropical Pacific. In addition, the analyses also indicates that the SST anomalies in the Niño3.4 region alone were not adequate for capturing the coupling of oceanic and atmospheric anomalies in the tropical Pacific, due to the fact that this index cannot distinguish whether the SST anomaly in the Niño3.4 region is associated with the ENSO mode or NPM, or both.

  19. Equatorial ionospheric electrodynamics during solar flares

    Science.gov (United States)

    Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding

    2017-05-01

    Previous investigations on ionospheric responses to solar flares focused mainly on the photoionization caused by the increased X-rays and extreme ultraviolet irradiance. However, little attention was paid to the related electrodynamics. In this letter, we explored the equatorial electric field (EEF) and electrojet (EEJ) in the ionosphere at Jicamarca during flares from 1998 to 2008. It is verified that solar flares increase dayside eastward EEJ but decrease dayside eastward EEF, revealing a negative correlation between EEJ and EEF. The decreased EEF weakens the equatorial fountain effect and depresses the low-latitude electron density. During flares, the enhancement in the Cowling conductivity may modulate ionospheric dynamo and decrease the EEF. Besides, the decreased EEF is closely related to the enhanced ASY-H index that qualitatively reflects Region 2 field-aligned current (R2 FAC). We speculated that solar flares may also decrease EEF through enhancing R2 FAC that leads to an overshielding-like effect.

  20. 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

  1. Equatorial Kelvin waves do not vanish

    Science.gov (United States)

    O'Brien, James J.; Parham, Fred

    1992-01-01

    In the last several years many scientists have been using poorly resolved coupled models to study the ENSO. It has been very common to state that an ENSO cycle found in a model cannot have oceanic Kelvin waves as a mechanism because such waves do not exist in an ocean model with coarse grid spaing. In this note it is demonstrated that equatorial Kelvin waves can exist in models with coarse grids.

  2. Seasonal Cycle of Cross Equatorial Flow in the Central Equatorial Indian Ocean

    Science.gov (United States)

    McPhaden, Michael; Wang, Yi

    2017-04-01

    This study investigates the seasonal cycle of meridional currents in the upper layers of central equatorial Indian Ocean using acoustic Doppler current profiler (ADCP) data and other data sets along 80.5°E for the period 2004-13. The ADCP data set is the most comprehensive collection of direct velocity measurements in the central Indian Ocean to date, providing new insights into cross equatorial flow in this region. Mean meridional currents are characterized by subsurface divergence between 50-100 m depths with relatively weak convergence above, driven by the annual mean westward pressure gradient force and the surface westerly wind stress respectively. However, in response to a mean northward component of the surface wind stress, the maximum mean surface layer convergence is shifted off the equator to 0.75°N. Evidence is also presented for the existence of a shallow equatorial roll, consisting of a northward wind-driven surface drift overlaying a southward subsurface flow. Cross equatorial transports during boreal summer and winter indicate that a quasi-steady Sverdrup transport balance dominates the seasonal cycle of upper-layer meridional currents. In addition, semi-annually varying westerly monsoon transition winds force Ekman convergence in the surface layer and set up transient zonal pressure gradients that drive seasonally enhanced meridional geostrophic divergence in the thermocline. These results quantify expectations from ocean circulation theories for equatorial Indian Ocean meridional circulation patterns with a high degree of confidence given the length of the data records.

  3. 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

  4. 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

  5. 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.

  6. Strong post-midnight Equatorial Ionospheric Anomaly and Equatorial spread F Observations during magnetically quiet period

    Science.gov (United States)

    Moldwin, M. B.; Yizengaw, E.; Sahai, Y.

    2008-12-01

    Post sunset equatorial ionospheric irregularities, especially during magnetically active periods, have been a subject of many studies. The most prominent irregularities often observed right after sunset are the resurgence of the equatorial ionospheric anomaly (EIA) and equatorial spread F (ESF). It is well understood and documented that pre-reversal enhancement, due to the ionospheric conductivity gradient at the dusk, is one of the prime triggering mechanisms for the post-sunset irregularities in the equatorial region. However, less attention has been given to the equatorial irregularities (EIA and ESF) that often occur in post-midnight, especially during magnetically quiet periods. It has been suggested that the primary process responsible for the dramatic post-midnight ESF during magnetically active periods is the change in magnitude and direction of the usual equatorial electric field. Earlier studies speculated that during magnetically active post-midnight periods the change in electric field direction from westward to eastward for a short intervals cause an upward E × B drift, resulting in increased h'F and decreased electron densities at the magnetic equator. Individual scans of Jicamarca vertical drift also often observe significant upward drift during post-midnight periods. We present a case of post-midnight strong equatorial ionospheric anomaly during a magnetically quiet (Kp < 3) period using TOPEX altimeter TEC data. Simultaneously, the ionosonde station at S.J. Campos (23.2°S, 45.9°W; dip lat. 17.6°S) observed strong ESF and unusual h'F height rise during post-midnight period, where TOPEX detected strong EIA. At the same time ROCSAT-1 and DMSP satellites also clearly show existence of EIA during post-midnight period at their orbiting altitude. The former satellite also detected post-midnight in situ density irregularities (such as bubbles) at the same time as strong EIA and ESF. The questions here are what triggers these post-midnight equatorial

  7. Characteristics of Extreme Summer Convection over equatorial America and Africa

    Science.gov (United States)

    Zuluaga, M. D.; Houze, R.

    2013-12-01

    Fourteen years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) version 7 data for June-August show the temporal and spatial characteristics of extreme convection over equatorial regions of the American and African continents. We identify three types of extreme systems: storms with deep convective cores (contiguous convective 40 dBZ echoes extending ≥10 km in height), storms with wide convective cores (contiguous convective 40 dBZ echoes with areas >1,000 km2) and storms with broad stratiform regions (stratiform echo >50,000 km2). European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis is used to describe the environmental conditions around these forms of extreme convection. Storms with deep convective cores occur mainly over land: in the equatorial Americas, maximum occurrence is in western Mexico, Northern Colombia and Venezuela; in Africa, the region of maximum occurrence is a broad zone enclosing the central and west Sudanian Savanna, south of the Sahel region. Storms with wide convective radar echoes occur in these same general locations. In the American sector, storms with broad stratiform precipitation regions (typifying robust mesoscale convective systems) occur mainly over the eastern tropical Pacific Ocean and the Colombia-Panama bight. In the African sector, storms with broad stratiform precipitation areas occur primarily over the eastern tropical Atlantic Ocean near the coast of West Africa. ECMWF reanalyses show how the regions of extreme deep convection associated with both continents are located mainly in regions affected by diurnal heating and influenced by atmospheric jets in regions with strong humidity gradients. Composite analysis of the synoptic conditions leading to the three forms of extreme convection provides insights into the forcing mechanisms in which these systems occur. These analyses show how the monsoonal flow directed towards the Andes slopes is mainly what concentrates the occurrence of extreme

  8. Role of the Interannual equatorial Kelvin wave propagations in the equatorial Atlantic on the Angola Benguela current system.

    Science.gov (United States)

    Anicet Imbol Koungue, Rodrigue; Illig, Serena; Rouault, Mathieu

    2017-04-01

    The link between equatorial Atlantic Ocean variability and the coastal region of Angola and Namibia is investigated at interannual time scales from 1998 to 2012. An index of the equatorial Kelvin wave activity is defined based on equatorial PIRATA in situ data. Results show a significant correlation between monthly dynamic height anomalies derived from the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA), monthly Sea Surface Height anomalies (SSHA) derived from altimetry and SSHA calculated with an Ocean Linear Model. This allows interpreting PIRATA record into equatorial Kelvin wave signal. 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 SSH anomalies shows that they precede by one month extreme interannual SST anomalies along the African coast, suggesting that major warm and cold events in the Angola-Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Wave dynamics along the equatorial wave guide, as inferred from the Ocean Linear Model, 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 polewards along the African coast triggering extreme warm and cold events respectively. A proxy index based on linear ocean dynamics appears to be significantly more skilful in forecasting coastal variability than an index based on wind variability.

  9. 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.

  10. 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

  11. Cloud amount/frequency, NITRATE and other data from THOMAS G. THOMPSON and MOANA WAVE in the TOGA Area - Pacific from 1985-06-18 to 1988-07-28 (NODC Accession 9100061)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Conductivity, Temperature and Depth (CTD) and nutrient data were collected as part of Western Equatorial Pacific Ocean Circulation Study (WEPOCS). Three year...

  12. 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...

  13. Gravity-driven structures and rift basin evolution: Rio Muni Basin, offshore equatorial West Africa

    Energy Technology Data Exchange (ETDEWEB)

    Turner, J.P. [Univ. of Birmingham (United Kingdom)

    1995-08-01

    Offshore Equatorial Guinea, west Africa, gravity-driven nappes, more than 1 km thick and 15 km from head to toe, provide key evidence in reconstructing the late synrift: evolution of this part of the South Atlantic margin basin system. Furthermore, Aptian-Cenomanian carbonate and clastic rocks in the nappes` allochthonous hanging walls are attracting interest as a new exploration play in west Africa. The nappes exhibit a range of geometries that suggest they share many of the same deformation processes as thin-skin thrust and linked extensional fault systems. Not only are these structures significant in their own right, representing a rare example of gravity tectonics in the virtual absence of major halokinesis, but their presence may record an other-wise undetectable process active during the transition from a rift basin to a passive continental margin. A review of Equatorial Guinea in its pre-Atlantic configuration, alongside neighboring basins in Brazil (the Sergipe-Alagoas basin) and Gabon, suggests that gravity gliding was sustained by a relatively steep, westward paleoslope promoted by east-ward offset of the locus of thermal uplift from the rift basin (i.e., a simple shear model of basin formation). In contrast to gravity-driven structures in most postrift settings, the Equatorial Guinea nappes developed at the close of the Aptian-Albian synrift episode in response to a growing bathymetric deep caused by rapid subsidence outpacing restricted sedimentation.

  14. 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

  15. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    Science.gov (United States)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind

  16. A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude region

    DEFF Research Database (Denmark)

    Zhang, Luyuan; Hou, Xiaolin; Li, Hong-chun

    2017-01-01

    The influence of human nuclear activities on environmental radioactivity is not well known at low latitude region that are distant from nuclear tests sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for 129I and 127I to investigate...... this influence in a low-latitude terrestrial system. A baseline of 129I/127I 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 129I/127I 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 129I in the sediment during 1956–1962. The 129I/129I 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...

  17. 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.

  18. Recent sediment dynamics in hadal trenches

    DEFF Research Database (Denmark)

    Turnewitsch, Robert; Falahat, Saeed; Stehlikova, Jirina

    2014-01-01

    the surface ocean. It has been speculated that the shape of hadal trenches helps to 'funnel' particulate matter into the deeper parts of the trench, leading to sediment 'focussing' and improved benthic food supply. Here we investigate for five Northwest Pacific trenches the efficiency of sediment focussing...

  19. Evolution features of the surface latent heat flux anomalies over the tropical Pacific associated with two types of ENSO events

    Science.gov (United States)

    Liu, Zhiyuan; Zhou, Lian-Tong

    2017-09-01

    The present study investigates the features of the surface latent heat flux (LHF) anomalies and their related variables over the tropical Pacific during two types of El Niño-Southern Oscillation (ENSO) events and seeks a possible candidate for the main contributions to the LHF anomalies. During El Niño Modoki and canonical El Niño events, the LHFs show positive anomalies over the equatorial central Pacific and in the areas immediately south of the equatorial eastern Pacific. In addition, the largest magnitudes and widest ranges of positive LHF anomalies for both types of events occur during their mature stages rather than during their developing or decaying phases. Analyses show that the positive LHF anomalies associated with both events are largely affected by the positive sea-air humidity difference anomalies. However, the negative surface wind speed anomalies associated with the canonical El Niño events clearly contribute to the decreases in the positive LHF anomalies over the central Pacific and in the area immediately north of the equatorial eastern Pacific due to the presence of westerly and northerly anomalies, respectively. Moreover, over the equatorial central Pacific and in the area immediately south of the eastern Pacific, the LHF anomalies are mainly influenced by oceanic variables during both types of ENSO events, indicating an atmospheric response to oceanic forcing. In contrast, outside of the area spanning 10° north and south of the equator in the tropical Pacific and with the exception of the southeastern region, the LHF anomalies are greatly influenced by atmospheric variables, suggesting an oceanic response to atmospheric forcing. Distinct differences exist during the mature event phase, with oceanic forcing dominating the equatorial central Pacific during El Niño Modoki events and the area immediately south of the equatorial eastern Pacific during canonical El Niño events. In addition, both types of ENSO events suggest the increasing

  20. A Pacific Ocean general circulation model for satellite data assimilation

    Science.gov (United States)

    Chao, Y.; Halpern, D.; Mechoso, C. R.

    1991-01-01

    A tropical Pacific Ocean General Circulation Model (OGCM) to be used in satellite data assimilation studies is described. The transfer of the OGCM from a CYBER-205 at NOAA's Geophysical Fluid Dynamics Laboratory to a CRAY-2 at NASA's Ames Research Center is documented. Two 3-year model integrations from identical initial conditions but performed on those two computers are compared. The model simulations are very similar to each other, as expected, but the simulations performed with the higher-precision CRAY-2 is smoother than that with the lower-precision CYBER-205. The CYBER-205 and CRAY-2 use 32 and 64-bit mantissa arithmetic, respectively. The major features of the oceanic circulation in the tropical Pacific, namely the North Equatorial Current, the North Equatorial Countercurrent, the South Equatorial Current, and the Equatorial Undercurrent, are realistically produced and their seasonal cycles are described. The OGCM provides a powerful tool for study of tropical oceans and for the assimilation of satellite altimetry data.

  1. Fading of Jupiter's South Equatorial Belt

    Science.gov (United States)

    Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

    2011-01-01

    One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

  2. Observational features of equatorial coronal hole jets

    Directory of Open Access Journals (Sweden)

    G. Nisticò

    2010-03-01

    Full Text Available Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km s−1, while the deceleration rate appears to be about 0.11 km s−2, less than solar gravity. The average jet visibility time is about 30 min, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and equatorial coronal hole jets.

  3. 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.

  4. Deep and bottom water export from the Southern Ocean to the Pacific over the past 38 million years

    Science.gov (United States)

    van de Flierdt, T.; Frank, M.; Halliday, A.N.; Hein, J.R.; Hattendorf, B.; Gunther, D.; Kubik, P.W.

    2004-01-01

    The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137-01, "Nova," 7219 m water depth) and southwest Pacific deep water (63KD, "Tasman," 1700 m water depth). The crusts were dated using 10Be/9Be ratios combined with constant Co-flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present-day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway. Copyright 2004 by the American Geophysical Union.

  5. Central Pacific-like Warming Event Induced by Eastern Pacific Event and Possible Mechanism

    Science.gov (United States)

    Wang, Y.; Ma, Y.; Xue, Y.

    2015-12-01

    In contrast to the canonical eastern Pacific (EP) event, a new type of El Niño, named as central Pacific (CP) event with the warming center locating at the central equatorial Pacific, has been identified in recent years. In this study, we examine the relationship between these two types of ENSOs. Negative correlations between them is found to be up to more than 0.5 with statistical significance at α=0.01 level when the EP index leads the CP one about 20~22 months during the last 35 years, which are also evident in the related atmospheric and oceanic fields. We argue the possible mechanism for the appearance of this relationship lies in the mean climate change in the north extra-tropical Pacific in the last three decades, during which period the mean zonal wind became stronger due to the strengthening of the Subtropical High. Meanwhile, the NPO-like sea level pressure pattern, which forms during the decaying of the cold EP event, induces extratropical SST warm anomalies via surface heat fluxes. Because of the enhancement of the so-called wind-evaporation-SST (WES) feedback associated with the stronger mean zonal wind, these extratropical warming anomalies can be transported to the equatorial band more effectively, which eventually leads to the trigger of a CP-like event. In addition, the eastward expansion of the west Pacific warm pool since 1985 makes the central equatorial Pacific more sensitive to induce deep convection over there, providing a favorable circumstance for the CP regime. Considering the CP and CP-like events only become prevalent in recent decades and its distinct dynamics from the EP events, we speculate that this kind of relationship is a tropical reflection of extratropical climate change under the warming background in the central Pacific. How these kinds of mean state change happened and their relationship with the global climate change and changes in the sea/land thermal gradient in the last three decades need further research.

  6. Evidence of Late Palaeocene-Early Eocene equatorial rain forest ...

    Indian Academy of Sciences (India)

    2009-11-02

    Nov 2, 2009 ... Prevalence of excessive humid climate during this period has been seen as a result of equatorial positioning of Indian subcontinent, superimposed by a long term global warming phase (PETM and EECO) during the early Palaeogene. The study presents clear evidence that highly diversified equatorial rain ...

  7. 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)

  8. Equinoctial asymmetry of a low-latitude ionosphere-thermosphere system and equatorial irregularities: evidence for meridional wind control

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2009-05-01

    Full Text Available Nocturnal ionospheric height variations were analyzed along the meridian of 100° E by using ionosonde data. Two ionosondes were installed near the magnetic conjugate points at low latitudes, and the third station was situated near the magnetic equator. Ionospheric virtual heights were scaled every 15 min and vertical E×B drift velocities were inferred from the equatorial station. By incorporating the inferred equatorial vertical drift velocity, ionospheric bottom heights with the absence of wind were modeled for the two low-latitude conjugate stations, and the deviation in heights from the model outputs was used to infer the transequatorial meridional thermospheric winds. The results obtained for the September and March equinoxes of years 2004 and 2005, respectively, were compared, and a significant difference in the meridional wind was found. An oscillation with a period of approximately 7 h of the meridional wind existed in both the equinoxes, but its amplitude was larger in September as compared to that in March. When the equatorial height reached the maximum level due to the evening enhancement of the zonal electric field, the transequatorial meridional wind velocity reached approximately 10 and 40 m/s for the March and September equinoxes, respectively. This asymmetry of the ionosphere-thermosphere system was found to be associated with the previously reported equinoctial asymmetry of equatorial ionospheric irregularities; the probability for equatorial irregularities to occur is higher in March as compared to that in September at the Indian to Western Pacific longitudes. Numerical simulations of plasma bubble developments were conducted by incorporating the transequatorial neutral wind effect, and the results showed that the growth time (e-folding time of the bubble was halved when the wind velocity changed from 10 to 40 m/s.

  9. 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.

  10. 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

  11. 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.

  12. 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)

  13. 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 Pacific or an Atlantic pattern of CaCO sub(3) fluctuations. Fluxes of CaCO sub(3) (0.38 to 2.46 g cm sup(-2) ka sup(-1)) in total sediment and Ba/Al ratios (0.58 to 3.93 g cm sup(-2) ka sup(-1)) show six-fold variability through the last 1370 ka...

  14. Air-Sea Coupling Over The Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gopika, N.

    .1 Introduction 13 1.2 Equatorial Indian Ocean 13 1.3 Geographic location of the study area 17 1.4 Previous Work 18 1.5 Present Work 27 1.5.1 Motivation 27 1.5.2 Objectives 27 Chapter 2: Data and Methods 29 2... 1.5.1 Motivation Equatorial regions are special areas of the world ocean where intense air- sea interaction takes place and the ocean and atmosphere is tightly coupled. Equatorial Indian Ocean, in spite of its very special characteristics...

  15. Strong Equatorial Seasonality during Early Eocene greenhouse

    Science.gov (United States)

    Samanta, Arpita; Sarkar, Anindya

    2017-04-01

    A warm greenhouse climate, punctuated by a series of rapid warming events (known as hyperthermals), is characteristic of the Late Paleocene to Early Eocene period. Rapid addition of 13C depleted carbon to the exogenic carbon cycle, in an otherwise overall higher atmospheric CO2 level, is thought to set off the hyperthermal events. For understanding the fate of ongoing global warming and response of the climate system and biota, researchers for past few decades are paying more attention to comprehend this climatic enigma. Existing proxies from the most distinct hyperthermal event i.e., PETM indicate that the mean annual sea surface temperature (MASST) was comparatively higher (by ˜8 ˚ C) at high latitude and to a lesser extent towards the equator. Apart from the prominent hyperthermal events the rest of the Early Eocene was significantly warmer and thought to be more equable compare to present. Terrestrial proxy records from the mid-latitude regions indicated that the Mean Annual Temperature (MAT) and Minimum Winter Temperature (MWT) was high, thus reducing the seasonality or difference between MWT and Maximum Summer Temperature (MST). In absence of proxy data from the low latitude region, a ≥40 ˚ C summer temperature was predicted assuming a mild Eocene temperature gradient of ˜0.4 ˚ C/ ˚ latitude and mid-latitude temperature data. Even question was raised about the existence of the tropical rain forest in such climatic extreme. Recent pollen census data, on contrary, suggest proliferation of the tropical rain forest during this climatic extreme. Important in this context is that there is a very few direct evidence of Late Paleocene-Early Eocene MAT and seasonality data from the low latitude/equatorial regions. To resolve this issue, oxygen and carbon isotope ratios of larger benthic foraminifera (Nummulites burdigalensis) were measured in laser based carbonate device attached with the Delta V advantage continuous flow stable isotope ratio mass spectrometer

  16. Ore grade manganese nodules from the central Indian basin: an evaluation

    Digital Repository Service at National Institute of Oceanography (India)

    Sudhakar, M.

    processes. The results indicate that the nodules from siliceous sediments approximate the diagenetic end members of the series, as described in the Pacific, and are similar in composition to the north equatorial Pacific ore grade nodules. Siliceous sediments...

  17. 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

  18. 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)

  19. 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.

    A set of seven core tops from western equatorial Indian ocean were analysed for planktonic foraminifera, which has yielded 20 planktonic foraminiferal species. Among them Globorotalia menardii, Globigerinoides sacculifer and G. ruber constitute...

  20. 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

  1. Geomagnetic storm and equatorial spread-F

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2004-09-01

    Full Text Available In August 2000, a new ionospheric sounding station was established at Sao Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S, Brazil, by the University of Vale do Paraiba (UNIVAP. Another ionospheric sounding station was established at Palmas (10.2° S, 48.2° W; dip latitude 5.5° S, Brazil, in April 2002, by UNIVAP in collaboration with the Lutheran University Center of Palmas (CEULP, Lutheran University of Brazil (ULBRA. Both the stations are equipped with digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI. In order to study the effects of geomagnetic storms on equatorial spread-F, we present and discuss three case studies, two from the ionospheric sounding observations at Sao Jose dos Campos (September and November 2000 and one from the simultaneous ionospheric sounding observations at Sao Jose dos Campos and Palmas (July 2003. Salient features from these ionospheric observations are presented and discussed in this paper. It has been observed that sometimes (e.g. 4-5 November 2000 the geomagnetic storm acts as an inhibitor (high strong spread-F season, whereas at other times (e.g. 11-12 July 2003 they act as an initiator (low strong spread-F season, possibly due to corresponding changes in the quiet and disturbed drift patterns during different seasons.

  2. 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)

  3. Equatorial Magnetohydrodynamic Shallow Water Waves in the Solar Tachocline

    Science.gov (United States)

    Zaqarashvili, Teimuraz

    2018-03-01

    The influence of a toroidal magnetic field on the dynamics of shallow water waves in the solar tachocline is studied. A sub-adiabatic temperature gradient in the upper overshoot layer of the tachocline causes significant reduction of surface gravity speed, which leads to trapping of the waves near the equator and to an increase of the Rossby wave period up to the timescale of solar cycles. Dispersion relations of all equatorial magnetohydrodynamic (MHD) shallow water waves are obtained in the upper tachocline conditions and solved analytically and numerically. It is found that the toroidal magnetic field splits equatorial Rossby and Rossby-gravity waves into fast and slow modes. For a reasonable value of reduced gravity, global equatorial fast magneto-Rossby waves (with the spatial scale of equatorial extent) have a periodicity of 11 years, matching the timescale of activity cycles. The solutions are confined around the equator between latitudes ±20°–40°, coinciding with sunspot activity belts. Equatorial slow magneto-Rossby waves have a periodicity of 90–100 yr, resembling the observed long-term modulation of cycle strength, i.e., the Gleissberg cycle. Equatorial magneto-Kelvin and slow magneto-Rossby-gravity waves have the periodicity of 1–2 years and may correspond to observed annual and quasi-biennial oscillations. Equatorial fast magneto-Rossby-gravity and magneto-inertia-gravity waves have periods of hundreds of days and might be responsible for observed Rieger-type periodicity. Consequently, the equatorial MHD shallow water waves in the upper overshoot tachocline may capture all timescales of observed variations in solar activity, but detailed analytical and numerical studies are necessary to make a firm conclusion toward the connection of the waves to the solar dynamo.

  4. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    Science.gov (United States)

    Quirchmayr, Ronald

    2017-06-01

    We discuss some aspects of the velocity field and particle trajectories beneath periodic traveling equatorial surface waves over a flat bed in a flow with uniform underlying currents. The system under study consists of the governing equations for equatorial ocean waves within a non-inertial frame of reference, where Euler's equation of motion has to be suitably adjusted, in order to account for the influence of the earth's rotation.

  5. Why was Atmospheric Circulation Decoupled from Tropical Pacific SSTs in 2014/15 winter?

    Science.gov (United States)

    Peng, P.

    2015-12-01

    In late 2014 and early 2015, although Niño3.4 index exceeded the threshold for a weak-moderate El Niño, a canonical atmospheric response to ENSO event was not observed in the central and eastern equatorial Pacific. In an effort to understand why it was so, this study decomposed the DJF mean sea surface temperature (SST), precipitation rate and 200hPa stream function anomalies observed in the 2014/15 winter into the patterns related to the principal components of the DJF SST variability. It is found that the anomalies of these variables were mainly determined by the patterns related to two SST modes, one is the North Pacific Mode (NPM), and the other the El Niño and South Oscillation (ENSO) mode. The NPM was the dominant factor and was responsible for the apparent uncoupled air-sea relationship in the central equatorial Pacific and the east-west structure of the circulation anomalies over North America. The ENSO mode was important for SSTs in the central and eastern equatorial Pacific and for the circulation in the central equatorial Pacific. Further, ENSO signal likely evolved from the NPM pattern in the 2013/14 winter, however, its full development was impeded by the unusual persistence of the strong NPM throughout the year. The analysis for DJF 2014/15 winter indicates that the SST anomalies in Niño3.4 alone were not adequate for capturing the coupling of ocean and atmosphere anomalies in the tropical Pacific, due to the fact that it can't distinguish if the SST anomaly in the Niño3.4 region is associated with the ENSO mode or NPM, or both.

  6. Meridional equatorial electrojet current in the American sector

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.

    Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  7. Meridional equatorial electrojet current in the American sector

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    1999-02-01

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  8. Sensitivity of Coupled Tropical Pacific Model Biases to Convective Parameterization in CESM1

    Science.gov (United States)

    Woelfle, M. D.; Yu, S.; Bretherton, C. S.; Pritchard, M. S.

    2018-01-01

    Six month coupled hindcasts show the central equatorial Pacific cold tongue bias development in a GCM to be sensitive to the atmospheric convective parameterization employed. Simulations using the standard configuration of the Community Earth System Model version 1 (CESM1) develop a cold bias in equatorial Pacific sea surface temperatures (SSTs) within the first two months of integration due to anomalous ocean advection driven by overly strong easterly surface wind stress along the equator. Disabling the deep convection parameterization enhances the zonal pressure gradient leading to stronger zonal wind stress and a stronger equatorial SST bias, highlighting the role of pressure gradients in determining the strength of the cold bias. Superparameterized hindcasts show reduced SST bias in the cold tongue region due to a reduction in surface easterlies despite simulating an excessively strong low-level jet at 1-1.5 km elevation. This reflects inadequate vertical mixing of zonal momentum from the absence of convective momentum transport in the superparameterized model. Standard CESM1simulations modified to omit shallow convective momentum transport reproduce the superparameterized low-level wind bias and associated equatorial SST pattern. Further superparameterized simulations using a three-dimensional cloud resolving model capable of producing realistic momentum transport simulate a cold tongue similar to the default CESM1. These findings imply convective momentum fluxes may be an underappreciated mechanism for controlling the strength of the equatorial cold tongue. Despite the sensitivity of equatorial SST to these changes in convective parameterization, the east Pacific double-Intertropical Convergence Zone rainfall bias persists in all simulations presented in this study.

  9. Episodic Sediment Supply from Mountains and Downstream Emplacement within Large Tropical Basins

    Science.gov (United States)

    Aalto, Rolf; Aufdenkampe, Anthony; Maurice, Laurence

    2010-05-01

    Application of a new geochronological method for high-resolution 210-Pb dating over the past century has facilitated the identification of individual floodplain sedimentation events across disparate large river basins. Two examples include the pristine 72,000 km2 Beni River basin in northern Bolivia and the similarly natural 36,000 km2 Strickland River basin in Papua New Guinea - that are located on either side of the Equatorial Pacific warm pool that drives the ENSO phenomenon. Published research suggests that large, rapid-rise, cold-phase ENSO floods account for the preponderance of sediment accumulation within these two tropical systems. The vast scale of these temporally discrete deposits (typically 10s to 100s of millions of tonnes throughout these large river systems) begs the question: where did all this sedimentary material originate? Huge deposits require a similarly massive supply from hillslopes and transport of that material to depocentres 100s of km away, often episodically within the very short timescale of a single large flood event. We have identified the principal source of this sedimentary material to be extensive landslides throughout the high-relief headwaters - failures that deliver huge charges of pulverized rock and soil directly into canyons (in both the Bolivian Andes and the PNG Highlands), where raging floodwaters provide efficient transport to lowland depocentres. We explore this theme by presenting results from our ongoing research in these basins, including new data and techniques that we are currently using to track processes and provide better insight into the details of such enormous mass budgets. Daily discharge data from Bolivia are coupled with radionuclide concentrations, particle size distribution, and biochemistry of carbon and major elements in sediment to elucidate the considerable inter-annual variation of sediment supply from the Andes. Perturbations in the rate and quality of supply directly result from the interaction of

  10. Equatorial Kelvin waves: A UARS MLS view

    Science.gov (United States)

    Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien; Waters, Joe W.

    1994-01-01

    Data from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS) are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves. The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined. For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone. The ratios of the ozone perturbation amplitude to the temperature perturbation amplitude for the various observed Kelvin wave modes are in agreement with model estimates and LIMS (Limb Infrared Monitor of the Stratosphere) observations in the lower half of the region sampled but appear to be too large in the upper stratosphere and lower mesosphere.

  11. Distribution and activity of hydrogenase enzymes in subsurface sediments

    Science.gov (United States)

    Adhikari, R.; Nickel, J.; Glombitza, C.; Spivack, A. J.; D'Hondt, S. L.; Kallmeyer, J.

    2013-12-01

    Metabolically active microbial communities are present in a wide range of subsurface environments. Techniques like enumeration of microbial cells, activity measurements with radiotracer assays and the analysis of porewater constituents are currently being used to explore the subsurface biosphere, alongside with molecular biological analyses. However, many of these techniques reach their detection limits due to low microbial activity and abundance. Direct measurements of microbial turnover not just face issues of insufficient sensitivity, they only provide information about a single specific process rather than an overall microbial activity. Since hydrogenase enzymes are intracellular and ubiquitous in subsurface microbial communities, the enzyme activity represents a measure of total activity of the entire microbial community. A hydrogenase activity assay could quantify total metabolic activity without having to identify specific processes. This would be a major advantage in subsurface biosphere studies, where several metabolic processes can occur simultaneously. We quantified hydrogenase enzyme activity and distribution in sediment samples from different aquatic subsurface environments (Lake Van, Barents Sea, Equatorial Pacific and Gulf of Mexico) using a tritium-based assay. We found enzyme activity at all sites and depths. Volumetric hydrogenase activity did not show much variability between sites and sampling depths, whereas cell-specific activity ranged from 10-5 to 1 nmol H2 cell-1 d-1. Activity was lowest in sediment layers where nitrate was detected. Higher activity was associated with samples in which sulfate was the predominant electron acceptor. We found highest activity in samples from environments with >10 ppm methane in the pore water. The results show that cell-specific hydrogenase enzyme activity increases with decreasing energy yield of the electron acceptor used. It is not possible to convert volumetric or cell-specific hydrogenase activity into a

  12. Late Quaternary surface circulation in the east equatorial South Atlantic: Evidence from Alkenone sea surface temperatures

    Science.gov (United States)

    Schneider, Ralph R.; Müller, Peter J.; Ruhland, GöTz

    1995-04-01

    Angola Basin and Walvis Ridge records of past sea surface temperatures (SST) derived from the alkenone Uk37 index are used to reconstruct the surface circulation in the east equatorial South Atlantic for the last 200,000 years. Comparison of SST estimates from surface sediments between 5° and 20°S with modern SST data suggests that the alkenone temperatures represent annual mean values of the surface mixed layer. Alkenone-derived temperatures for the warm climatic maxima of the Holocene and the penultimate interglacial are 1 to 4°C higher than latest Holocene values. All records show glacial to interglacial differences of about 3.5°C in annual mean SST, which is about 1.5°C greater than the difference estimated by CLIMAP (1981) for the eastern Angola Basin. At the Walvis Ridge, significant SST variance is observed at all of the Earth's orbital periodicities. SST records from the Angola Basin vary predominantly at 23- and 100-kyr periodicities. For the precessional cycle, SST changes at the Walvis Ridge correspond to variations of boreal summer insolation over Africa and lead ice volume changes, suggesting that the east equatorial South Atlantic is sensitive to African monsoon intensity via trade-wind zonality. Angola Basin SST records lag those from the Walvis Ridge and the equatorial Atlantic by about 3 kyr. The comparison of Angola Basin and Walvis Ridge SST records implies that the Angola-Benguela Front (ABF) (currently at about 14-16°S) has remained fairly stationary between 12° and 20°S (the limits of our cores) during the last two glacial-interglacial cycles. The temperature contrast associated with the ABF exhibits a periodic 23-kyr variability which is coherent with changes in boreal summer insolation over Africa. These observations suggest that surface waters north of the present ABF have not directly responded to monsoon-modulated changes in the trade-wind vector, that the central field of zonally directed trades in the southern hemisphere was not

  13. Western Pacific Hydroclimate Linked to Global Climate Variability Over the Past Two Millennia

    Science.gov (United States)

    Griffiths, Michael L.; Kimbrough, Alena K.; Gagan, Michael K.; Drysdale, Russell N.; Cole, Julia E.; Johnson, Kathleen R.; Zhao, Jian-Xin; Cook, Benjamin I.; Hellstrom, John C.; Hantoro, Wahyoe S.

    2016-01-01

    Interdecadal modes of tropical Pacific ocean-atmosphere circulation have a strong influence on global temperature, yet the extent to which these phenomena influence global climate on multicentury timescales is still poorly known. Here we present a 2,000-year, multiproxy reconstruction of western Pacific hydroclimate from two speleothem records for southeastern Indonesia. The composite record shows pronounced shifts in monsoon rainfall that are antiphased with precipitation records for East Asia and the central-eastern equatorial Pacific. These meridional and zonal patterns are best explained by a poleward expansion of the Australasian Intertropical Convergence Zone and weakening of the Pacific Walker circulation (PWC) between B1000 and 1500 CE Conversely, an equatorward contraction of the Intertropical Convergence Zone and strengthened PWC occurred between B1500 and 1900 CE. Our findings, together with climate model simulations, highlight the likelihood that century-scale variations in tropical Pacific climate modes can significantly modulate radiatively forced shifts in global temperature.

  14. Western Pacific hydroclimate linked to global climate variability over the past two millennia.

    Science.gov (United States)

    Griffiths, Michael L; Kimbrough, Alena K; Gagan, Michael K; Drysdale, Russell N; Cole, Julia E; Johnson, Kathleen R; Zhao, Jian-Xin; Cook, Benjamin I; Hellstrom, John C; Hantoro, Wahyoe S

    2016-06-08

    Interdecadal modes of tropical Pacific ocean-atmosphere circulation have a strong influence on global temperature, yet the extent to which these phenomena influence global climate on multicentury timescales is still poorly known. Here we present a 2,000-year, multiproxy reconstruction of western Pacific hydroclimate from two speleothem records for southeastern Indonesia. The composite record shows pronounced shifts in monsoon rainfall that are antiphased with precipitation records for East Asia and the central-eastern equatorial Pacific. These meridional and zonal patterns are best explained by a poleward expansion of the Australasian Intertropical Convergence Zone and weakening of the Pacific Walker circulation (PWC) between ∼1000 and 1500 CE Conversely, an equatorward contraction of the Intertropical Convergence Zone and strengthened PWC occurred between ∼1500 and 1900 CE. Our findings, together with climate model simulations, highlight the likelihood that century-scale variations in tropical Pacific climate modes can significantly modulate radiatively forced shifts in global temperature.

  15. Milankovitch cycles in an equatorial delta from the Miocene of Borneo

    Science.gov (United States)

    Marshall, Nathan; Zeeden, Christian; Hilgen, Frederik; Krijgsman, Wout

    2017-08-01

    The factors controlling sedimentary cyclicity in deltaic systems are a subject of intense debate, and more research, in different deltaic environments and time periods, is needed to better understand the possible mechanisms. Offshore and Pleistocene case studies are more common than proximal and more ancient, greenhouse-climate examples. Furthermore, many studies lack a (statistical) cyclostratigraphic element. The paleo-Mahakam delta of Eastern Kalimantan, Borneo developed during the globally warm middle Miocene, in an equatorial setting, making it of interest to comprehend cyclic sedimentation in a period of warmer yet rapidly changing climate. In this study, statistical analysis of lithological changes shows that regular sandstone/shale alternations occur in a distinct pattern of cycles with thicknesses of ∼90, ∼30, and ∼17 m. Using independent dating, these thicknesses translate into periods of about 100, 40, and 20 kyr, matching the known periods of Earth's orbital eccentricity, obliquity and precession. The obliquity dominance in the middle interval is markedly similar to that observed in the global marine isotope (benthic δ18O) and other cyclic proxy records for this time interval. Despite a mismatch in the number of 40 kyr cycles compared to the global record that can be plausibly linked to the major sea-level drop at ∼13.8 Ma and facies shifts, it appears that the proximal setting of the paleo-Mahakam's sedimentation was dominantly controlled by allogenic orbital forcing, probably as a consequence of glacioeustasy. In particular, the observed obliquity dominance at paleo-equatorial latitudes, as seen in other records, highlights the dominance of orbital forcing, and potentially glacioeustatic sea level change, during this crucial period of warmer climate.

  16. 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

  17. On the collapse of the meridional SST gradient in the eastern tropical South Pacific during Heinrich stadial 1

    Science.gov (United States)

    Kienast, S. S.; Dubois, N.; Kienast, M.; Francois, R. H.; Hill, P. S.

    2011-12-01

    The equatorial Pacific plays a crucial role in the present-day climate system. The El Nino-Southern Oscillation (ENSO) Phenomenon , which originates from perturbations of the ocean atmosphere system in this region, affects climate and the carbon cycle worldwide. One of the factors controlling ENSO variability is the meridional temperature gradient across the equator. Here we present multiproxy records of several cores located strategically across the frontal system separating the tropical warm pool north of the equator from the cold tongue off Peru. Alkenone-based sea surface temperature (SST) reconstructions display a 50% reduction in the temperature gradient across this front during Heinrich stadial 1 (H1). This dramatic change in sea surface conditions is paralleled by a) perturbations of the marine nitrogen cycle as recorded by d15N of bulk sediment and b) a maximum in continental input as recorded by 232-thorium. While 232-thorium fluxes clearly indicate an increase in overall continental input during H1, grain- size analyses suggest that the proportion of dust-sized particles in the continental fraction did not vary significantly between the last glacial maximum, H1, and the Holocene. Implications for ocean atmosphere dynamics and comparisons to model predictions for this time period will be discussed.

  18. Modulation of Cenozoic climate by weathering of large igneous provinces on continents drifting through equatorial humid belt

    Science.gov (United States)

    Muttoni, G.; Kent, D. V.

    2011-12-01

    The small reservoir of CO2 in the atmosphere (pCO2) that modulates climate through the greenhouse effect is a delicate balance between large fluxes of sources and sinks. The major long-term source of CO2 is global degassing from sea-floor spreading, subduction, hotspot activity, and metamorphism; the ultimate sink is through weathering of continental silicates. Most carbon cycle models are driven by changes in the source flux, in particular, variable rates of ocean floor production (and concomitant subduction) but the area/age versus age distribution of the modern ocean is compatible with a steady rate since 180 Ma (Rowley, 2002 GSA Bulletin). We previously suggested (2008 PNAS) that evidence of high pCO2 and warm climates in the Cretaceous-early Cenozoic could be explained by the subduction of Tethyan ocean crust loaded with equatorial carbonate-rich pelagic (more readily subductable) sediments since the onset of India's northward flight at ~120 Ma up until the CO2-producing decarbonation factory slowed down with collision of India and Asia at the Early Eocene Climate Optimum at 50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO2 by efficient silicate weathering would further lower the level of pCO2. Continued weathering uptake was influenced by the southerly extrusion of SE Asia in response to the Indian indentor starting at ~40 Ma (Molnar & Tapponnier, 1975 Science) as well as the emplacement of the Ethiopian traps near the Equator at 30 Ma. The ongoing impingement of India into Asia and resultant southerly tectonic extrusion of SE Asia (Replumaz & Tapponnier, 2003 JGR) makes it the dominant new area in the equatorial humid belt. Moreover, SE Asia presently accounts for 25% of CO2 consumption of all basaltic provinces, which account for ~1/3 of the total consumption by continental silicate weathering (Dessert et al., 2003 Chemical Geology) that is within the range of

  19. Is the enrichment of metals in Mn-Fe nodules from the central Pacific correlated with glacial-interglacial stages?

    Science.gov (United States)

    Wegorzewski, A.; Kuhn, T.

    2012-12-01

    during the growth of these layers in the CCFZ. In contrast to the PB there is no suboxic front, only low organic carbon and almost no mobilizable Mn in the deeper sediments of the CCFZ (Mewes, K., unpub. data). Mobilizable Mn seems to be only present in the upper 10-20 cm of the sediment column. Therefore, we suggest periods of less ventilated or even suboxic bottom water may have mobilized the Mn from sediments and initiated diagenetic growth. Bradtmiller et al. (2010) found indications that at least during the last glacial stage the deep water of the Pacific were less ventilated. High resolution analyses of the upper 1.6 mm of a nodule revealed a correlation between high Mn/Fe ratios and glacial stages (Reichert, 2012) supporting our hypothesis. Bradtmiller L.I., Anderson R.F., Sachs J.P., Fleisher M.Q. (2010): A deeper respired carbon pool in the glacial equatorial Pacific Ocean. Earth Planet. Lett. 299: 417-425 Bodei,S., Manceau, A., Geoffroy, N., Baronnet, A. and Buatier, M. (2007): Formation of todorokite from vernadite in Ni-rich hemipelagic sediments. Geochem. Cosmochem. Acta, 71: 5698-5716 Reichert, P. (2012): Geochronology and Geochemistry of the ferromanganese nodule 56KG2 from the German license area. Dipl. Thesis, University Kiel. Halbach, P., Friedrich G., Von Stackelberg, U. (1988): The Manganese Nodule Belt of the Pacific Ocean. Enke, 254p.

  20. Should the Master Equatorial Be a Slave?

    Science.gov (United States)

    Gawronski, W.; Ahlstrom, H. G., Jr.; Bernardo, A. M.

    2000-10-01

    The article describes the existing 70-m antenna control system, the master equatorial (ME) control system, and their "master--slave" interaction through the autocollimator coupling. The analysis describes the open-loop models of the antenna and ME, obtained through field tests and system identification. Next, the performances of closed-loop systems of the antenna and ME are evaluated. The closed-loop performance indicates that a single control algorithm can replace three existing algorithms and that the mode-switching algorithm is no longer required. This new single control algorithm provides significant performance improvement at minimal cost, using primarily existing equipment. Different configurations of the antenna and ME are proposed and evaluated. In the existing configuration, the ME is a master: it follows a target, and the antenna is a slave, following the ME. This arrangement causes occasional problems. Since antenna drives were designed for rates smaller than 0.25 deg/s and for accelerations smaller than 0.2 deg/s^2, tracking at high rates (e.g., near the keyhole) may leave the antenna outside the autocollimator acquisition range. It causes the breakdown of the ME-antenna optical link and termination of the track. Here we analyze two new ME-antenna configurations. Configuration A is a modification of the existing configuration with new control algorithms and a command preprocessor added, where the antenna follows the ME. Configuration B also includes new control algorithms and a command preprocessor, but unlike Configuration A, the ME is a slave and follows the antenna. It serves, in effect, as an antenna position sensor. Analysis shows that both configurations are feasible for high-rate tracking using the existing autocollimator. Configuration B, however, is superior as it has much smaller autocollimator errors. Finally, for the existing configuration and for Configurations A, there is no provision for ME wrap direction, while Configuration B would

  1. 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.

  2. Chemistry of surface sediment along a north-south transect across the equator in the Central Indian Basin: An assessment of biogenic and detrital influences on elemental burial on the seafloor

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Parthiban, G.; Pattan, J.N.; Jauhari, P.

    is dominated by siliceous ooze deposition. The carbonate compensation depth and the carbonate lysocline are located in a narrow depth zone of around 300 m thickness. The equatorial biogenic sediment domain is inturrupted by a detrital clay zone between 0...

  3. 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.

  4. Miocene biochronology and paleoceanography of the North Pacific

    Science.gov (United States)

    Keller, G.

    1981-01-01

    Biostratigraphic correlation based on microfossil datum levels, directly or indirectly tied to the paleomagnetic time scale, provides a high resolution time control for the Miocene in the equatorial and middle latitude North Pacific. Faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen Pacific. Faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen isotope record of foraminifers, reveal the paleoclimatic and paleoceanographic history. The planktic foraminiferal assemblage change in the early Miocene, extinction of Oligocene fauna and rise of a highly diverse Neogene fauna, appears to be related to increased water mass stratification in the world oceans presumably resulting from the establishment of circum-Antarctic circulation. An increase in the siliceous productivity in the eastern equatorial Pacific region between 20 and 18 Ma suggests that the vertical and horizontal circulation was intensified at that time. Climates cooled rapidly during the middle Miocene between 14 and 13 Ma suggesting the growth of a major east Antarctic ice sheet. Paleoclimatic conditions remained generally cool, although oscillating, during the late Miocene. In the late early to middle Miocene faunal provincialism developed between low and middle latitudes, and by late Miocene time a distinct provincialism similar to the present was established. ?? 1981.

  5. Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes

    Directory of Open Access Journals (Sweden)

    P. Ricaud

    2009-06-01

    Full Text Available In this paper we use the total columns of nitrous oxide (N2O as retrieved from the radiance spectra as measured by the Infrared Atmospheric Sounding Interferometer (IASI instrument aboard the MetOp-A platform and distributed by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT during the March–May (MAM 2008 period. Since the total column of N2O reflects concentrations in the middle troposphere, cloud-free columnar N2O measurements are used to assess transport processes in the equatorial band (10° S–10° N. We compare the measured data set with the outputs produced by the 3-D chemical-transport model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008 concentrations, MOCAGE results have been scaled by a factor 1.0125 in order to represent the change in concentration of N2O since 2004. IASI N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2 and a minimum over South America (4.86×10−3 kg m−2 in reasonable agreement with the outputs from MOCAGE despite the fact that emissions of N2O are more intense over America than over Africa. The amplitude of the longitudinal variation of total column N2O along the equatorial band is twice as intense in the measurements (~1.6% than as in the model calculations (~0.8%, and much greater than the IASI mean random error (0.16–0.33%. A difference between the two data sets is observed above the Western Pacific (110° E–150° E with a marked minimum in IASI compared to MOCAGE. Recent theoretical studies (Ricaud et al., 2007 and 2009 have shown the potentially important effect of the Walker and the Hadley cells on the tropospheric distribution of N2O in producing a local maximum in N2O above Africa. Based on equatorial total columns of N2O retrieved from IASI, our results are

  6. 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...

  7. ­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.

  8. Tropical Pacific Mean State and ENSO Variability across Marine Isotope Stage 3

    Science.gov (United States)

    Hertzberg, J. E.; Schmidt, M. W.; Marcantonio, F.; Bianchi, T. S.

    2017-12-01

    The El Niño/Southern Oscillation (ENSO) phenomenon is the largest natural interannual signal in the Earth's climate system and has widespread effects on global climate that impact millions of people worldwide. A series of recent research studies predict an increase in the frequency of extreme El Niño and La Niña events as Earth's climate continues to warm. In order for climate scientists to forecast how ENSO will evolve in response to global warming, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past, especially across past abrupt warming events. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale warming events of the last ice age. This study aims to reconstruct changes in the tropical Pacific mean state and ENSO variability across Marine Isotope Stage 3 from a sediment core recovered from the Eastern Equatorial Pacific cold tongue (MV1014-02-17JC, 0°10.8' S, 85°52.0' W, 2846 m water depth). In this region, thermocline temperatures are significantly correlated to ENSO variability - thus, we analyzed Mg/Ca ratios in the thermocline dwelling foraminifera Neogloboquadrina dutertrei as a proxy for thermocline temperatures in the past. Bulk ( 50 tests/sample) foraminifera Mg/Ca temperatures are used to reconstruct long-term variability in the mean state, while single shell ( 1 test/sample, 60 samples) Mg/Ca analyses are used to assess thermocline temperature variance. Based on our refined age model, we find that thermocline temperature increases of up to 3.5°C occur in-step with interstadial warming events recorded in Greenland ice cores. Cooler thermocline temperatures prevail during stadial intervals and Heinrich Events. This suggests that interstadials were more El-Niño like, while stadials and Heinrich Events were more La-Niña like. These temperature changes are compared to new records of dust flux

  9. The influence of buried nodules on the mobility of metals in deep sea sediments

    Science.gov (United States)

    Heller, Christina; Kuhn, Thomas

    2017-04-01

    Hydrothermal fluids can extract significant amounts of heat from oceanic lithosphere by lateral fluid flow through permeable basaltic crust of an age of up to 65 Ma. Fluid recharge and discharge occur at basement outcrops in between impermeable pelagic deep sea sediments. Recharge of oxic seawater causes upward oxygen diffusion into sediments overlying the permeable basalt in areas proximal to recharge sites. It is suggested that this oxygen has a strong impact on sediments and Mn-nodules during fluid exposure time. The aim of this study is to investigate if/how fluid flow through oceanic crust influence the distribution and element budget of Mn-nodules. Nodules occur widespread at the seafloor of the Clarion-Clipperton Zone (CCZ) in the equatorial North Pacific and were analyzed in many studies worldwide. Nodules buried in the deep sea sediments could be found only rarely (von Stackelberg, 1997, Geol. Soc. Spec. Publ., 119: 153-176). High resolution side-scan sonar recordings (unpublished Data BGR Hannover) indicate that there exist a coherent layer of nodules buried in the sediments of the working area. During the expedition SO 240/FLUM nodules were found on the sediment surface in 4200 to 4300 m water depth as well as in the sediment down to 985 cm below seafloor. In general, nodules consist of different nm- to µm-thick, dense and porous layers. The geochemical composition of bulk nodules and single nodule layers were determined by XRF, ICP-MS/OES, XRD and by high resolution analyses with electron microprobe and LA-ICP-MS. Dense layers have low Mn/Fe ratios ( 10) and high Ni+Cu and Li concentrations. The different compositions depend on different formation processes of the layers. They were formed by metal precipitation from oxic (hydrogenetic) and suboxic (diagenetic) bottom-near seawater and/or pore water (Wegorzewski and Kuhn, 2014, Mar. Geol. 357, 123-138). Preliminary results show that there are significant differences between the geochemical composition

  10. On the variability of ozone in the equatorial eastern Pacific boundary layer

    Science.gov (United States)

    Gómez Martín, J. C.; Vömel, H.; Hay, T. D.; Mahajan, A. S.; Ordóñez, C.; Parrondo Sempere, M. C.; Gil-Ojeda, M.; Saiz-Lopez, A.

    2016-09-01

    Observations of surface ozone (O3) mixing ratios carried out during two ground-based field campaigns in the Galápagos Islands are reported. The first campaign, Primera Investigación sobre la Química, Evolución y Reparto de Ozono, was carried out from September 2000 to July 2002. The second study, Climate and HAlogen Reactivity tropicaL EXperiment, was conducted from September 2010 to March 2012. These measurements complement the Southern Hemisphere ADditional OZonesonde observations made with weekly to monthly frequency at Galápagos. In this work, the daily, intraseasonal, seasonal and interannual variability of O3 in the marine boundary layer are described and compared to those observed in other tropical locations. The O3 diurnal cycle shows two regimes: (i) photochemical destruction followed by nighttime recovery in the cold season (July to November) and (ii) daytime advection and photochemical loss followed by nighttime depositional loss associated to windless conditions in the warm season (February to April). Wavelet spectral analysis of the intraseasonal variability of O3 reveals components with periods characteristic of tropical instability waves. The O3 seasonal variation in Galápagos is typical of the Southern Hemisphere, with a maximum in August and a minimum in February-March. Comparison with other measurements in remote tropical ocean locations shows that the change of the surface O3 seasonal cycle across the equator is explained by the position of the Intertropical Convergence Zone and the O3 levels upwind.

  11. 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.

  12. Bayesian estimation of observation error covariance matrix in the equatorial Pacific

    Science.gov (United States)

    Ueno, G.

    2016-02-01

    We develop a Bayesian technique for estimating the parameters in the observation noise covariance matrix Rt for ensemble data assimilation. We design a posterior distribution by using the ensemble-approximated likelihood and a Wishart prior distribution and present an iterative algorithm for parameter estimation. The present algorithm is identified as the expectation-maximization (EM) algorithm for a Gaussian mixture model and can estimate a number of parameters in Rt. The algorithm is an extension of that by Ueno and Nakamura (2014) for maximum-likelihood estimation. An advantage of the proposed method is that Rt can be estimated online, and more importantly, the temporal smoothness of Rt can be controlled by adequately choosing two parameters of the prior distribution, the covariance matrix S and the number of degrees of freedom ν. The parameters S and ν may vary with the time at which Rt is estimated. The ν parameter can be objectively estimated by maximizing the marginal likelihood. The present formalism can handle cases in which the number of data points or the data positions varies with time, the former case of which is exemplified in the experiments. We present an application to a coupled atmosphere-ocean model under each of the following assumptions: Rt is a scalar multiple of a fixed matrix (Rt=αtΣ, where αt is the scalar parameter and Σ is the fixed matrix), Rt is a diagonal matrix, Rt has fixed eigenvectors, or Rt has no specific structure. We verify that the proposed algorithm works well and that only a limited number of iterations are necessary. When Rt has one of the structures mentioned above, by assuming the prior covariance matrix to be the previous estimate, namely S=\\hat{R}t-1, we obtain the Bayesian estimate of Rt that varies smoothly in time compared to the maximum-likelihood estimate at each time. When Rt has no specific structure, we need to regularize S=\\hat{R}t-1 to maintain the positive-definiteness of S. Through twin experiments, we find that the best estimate of Rt is, in general, obtained by a combination of structure-free Rt and tapered S by the decorrelation lengths of half the size of the model ocean basin. From experiments using real observations, we find that the estimates of the structured Rt (having fixed structure Σ and being diagonal), lead to overfitting of the data compared to the structure-free Rt.

  13. 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.

  14. Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California

    Science.gov (United States)

    Hagstrum, Jonathan T.; Murchey, Benita L.; Bogar, Robert 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. 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.

  16. 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.

  17. 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.

  18. Occurrence of Equatorial F Region Irregularities: Evidence for Tropospheric Seeding

    Science.gov (United States)

    McClure, J. P.; Singh, S.; Bamgboye, D. K.; Johnson, F. S.; Kil, Hyosub

    1998-01-01

    We present a new gap-free version of the seasonal and longitudinal 0 (s/l) variations of P(sub EFI), the equatorial F region irregularity (EFI) occurrence probability, based on data from the AE-E spacecraft. The agreement of this and three earlier partial P(sub EFI) patterns verifies all four. We reinterpret another earlier gap-ridden pattern, that of D(bar)(sub RSF), a topside ionogram index of average darkening by range spread F. We compare it with P(sub EFI) and, using ionosonde radio science considerations, we conclude that D(bar)(sub RSF) = P(sub EFI) times a factor depending on the average number of topside plasma bubbles visible to the ionosonde. The s/l variations of D(baar)(sub RSF) thus imply s/l variations in the average spacing of bubbles, whose seeds have an occurrence probability pattern P(sub seed). For discussion we assume P(sub EFI) = P(sub inst)P(sub seed) is the pattern of F region instability. The P(sub EFI) pattern, which is by definition independent of seed and/or bubble spacing, is far too complex to be explained by the dominant paradigm, that of changes in P(sub inst) by simple changes in the F region altitude and/or north-south asymmetry. We examine evidence behind this dominance, and find it unconvincing. Both the asymmetry and sunset-node/altitude hypotheses of 1984 and 1985, respectively, seem to be partly based on misunderstood data, and their features appear displaced in time and space from those of our repeatable P(sub EFI) pattern. In contrast, if P(sub seed) variations influence the P(sub EFI) pattern and depend on thermospheric gravity waves from tropospheric convection near the dip equator, then the seasonal maxima (minima) Of P(sub EFI) could be explained, since they all occur above relatively warm (cold) surface features, where convection is maximal (minimal). Also, the hypothesis of the dominance of the P(sub seed) term could explain an unusual December/January P(sub EFI) maximum in the deep, wide, normal Pacific minimum in the

  19. Aquatic sediments

    International Nuclear Information System (INIS)

    Bonner, J.S.; Autenrieth, R.L.; Schreiber, L.

    1990-01-01

    The authors present a literature review concerning sediment properties, interactions, and conditions. Topics of discussion include the following: biological activity and toxicity; nutrients; metals; organic compounds; dredging; radionuclides; oxygen demand and organic carbon; mathematical modeling; sediment transport and suspension; and paleolimnology

  20. A three-dimensional autonomous nonlinear dynamical system modelling equatorial ocean flows

    Science.gov (United States)

    Ionescu-Kruse, Delia

    2018-04-01

    We investigate a nonlinear three-dimensional model for equatorial flows, finding exact solutions that capture the most relevant geophysical features: depth-dependent currents, poleward or equatorial surface drift and a vertical mixture of upward and downward motions.

  1. 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)

  2. Seabed Disposal Program: geochemical and sedimentological studies of north Pacific sediments. Progress report, January 1, 1975--December 31, 1975 (including quarterly progress report, October 1, 1975--December 31, 1975)

    International Nuclear Information System (INIS)

    Heath, G.R.

    1976-01-01

    Continued work on field data and cores from study are MPG-2 (33 0 20'N, 151 0 00'W) has shown that sediments are being laid down over the entire region, but that the rate of deposition in depressions is up to 70 percent greater than the rate on ridge tops. The relative fractionation has generally been constant for more than 30 million years, leading to a high degree of confidence in the predictability of the geologic future of the region, and implying that singular events and climatic changes have little effect on patterns of deposition. Continued monitoring of manganese nodule compositions has failed to identify any deposits that can be considered potentially mineable either now or in the future. Bulk samples of the major types of the deep-sea clays recovered by 10-12 meter sediment cores have been prepared for experiments on sorption properties of heavy metals and transuranic elements

  3. Different Strokes: Spanish Policy toward Cuba and Equatorial ...

    African Journals Online (AJOL)

    Spanish policy toward Cuba and Equatorial Guinea up to the end of the 19th century differed markedly. The policy itself is difficult to define but the general principle emphasized the exploitation of the resources of the colonies for the benefit of Spain. It also provided for the spread of Spanish culture and the Christian faith.

  4. Clean advice for oily money : Consulting for Equatorial Guinea

    NARCIS (Netherlands)

    Lachotzki, F.; Karssing, E.D.

    2011-01-01

    Equatorial Guinea is one of the most extraordinary countries in the world, if also one of the most obscure. Its tremendous yearly revenue from the oil concessions it grants in its Gulf of Guinea territorial waters is little known, but so too is its abysmal record on human rights. The deep-rooted

  5. Relation between the continental TCZ and the TCZ over Equatorial ...

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Relation between the continental TCZ and the TCZ over Equatorial Indian Ocean. Competition: Air ascending in the TCZ descends in the surrounding region . So when there are two TCZs over the same longitudinal belt, each tries to suppress the other. Active spells of ...

  6. Variable influence on the equatorial troposphere associated with ...

    Indian Academy of Sciences (India)

    Sudden stratospheric warming (SSW) events are identified to investigate their influence on the equatorial tropospheric climate. Composite analysis of warming events from Era-Interim (1979–2013) record a cooling of the tropical lower stratosphere with corresponding changes in the mean meridional stratosphericcirculation.

  7. 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 ...

  8. Solar Wind Associated with Near Equatorial Coronal Hole

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Present study probes temporal changes in the area and radiative flux of near equatorial coronal hole associated with solar wind parameters such as wind speed, density, magnetic field and temperature. Using high temporal resolution data from SDO/AIA for the two wave-lengths 193 Å and 211 Å, area and ...

  9. equatorial electrojet strength in the african sector during high

    African Journals Online (AJOL)

    Preferred Customer

    electrojet current. The electric fields that drive the equatorial electrojet current have been found to consist of three components with different origins. (Reddy, 1981): a) an electric field originating in the dynamo action of the global scale wind system in the lower atmosphere, which is the driving electric field on quiet days with ...

  10. Equatorial electrojet in the south Atlantic anomaly region

    Indian Academy of Sciences (India)

    Ronchi C, Sudan R N and Similon P L 1990 Effect of short- scale turbulence on kilometer wavelength irregularities in the equatorial electrojet; J. Geophys. Res. 95 189–200. Sarabhai V and Nair K N 1971 Morphology of the geomag- netic field variations and a study of the interplanetary magnetic field fluctuations in relation ...

  11. Mesoscale model simulation of low level equatorial winds over ...

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/jess/118/04/0295-0307. Keywords. Equatorial region; low-level meteorological parameters; biomass burning; haze; southeast Asia; Sarawak. Abstract. The large-scale vegetation fires instigated by the local farmers during the dry period of the major El Ni˜no event in 1997 can be considered ...

  12. Solar Wind Associated with Near Equatorial Coronal Hole M ...

    Indian Academy of Sciences (India)

    2015-05-25

    May 25, 2015 ... Probably, during the early his- tory of solar system formation, strong solar wind might have played a dominant role. 355 .... (Atmospheric Imaging Assembly), we have considered near equatorial coronal hole data with 1 hour time ... thermal or kinetic energy of the solar wind? (iii) at what height in the solar ...

  13. A biweekly mode in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, D.; Senan, R.; Murty, V.S.N.; Fernando, V.

    propagating biweekly waves with zonal wavelength in the range 2100 to 6100 km. An ocean model forced by high-resolution scatterometer wind stress is used to show that the observed biweekly variability is due to equatorially trapped mixed Rossby-gravity waves...

  14. 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

  15. The equatorial disc of the Be star X Persei

    NARCIS (Netherlands)

    Telting, JH; Waters, LBFM; Roche, P; Boogert, ACA; Clark, JS; de Martino, D; Persi, P

    1998-01-01

    We study the long-term behaviour of the equatorial disc of the Be/X-ray binary X Persei (X Per), combining new low-resolution IUE spectra and IR photometry with UV, optical and IR observations collected from the literature. We find that the near-UV continuum level of X Per varies along with the

  16. Equatorial electrojet in the Indian region during the geomagnetic ...

    Indian Academy of Sciences (India)

    1998-11-14

    Nov 14, 1998 ... November 1998 reaching a minimum of about –120 nT around midnight of 13–14 November 1998. Features of the equatorial electrojet in the Indian region are studied during the geomagnetic storm event of 13–14 November 1998, based on the geomagnetic data from the chain of observatories in India.

  17. Observations of ULF wave related equatorial electrojet and density fluctuations

    Science.gov (United States)

    Yizengaw, E.; Zesta, E.; Biouele, C. M.; Moldwin, M. B.; Boudouridis, A.; Damtie, B.; Mebrahtu, A.; Anad, F.; Pfaff, R. F.; Hartinger, M.

    2013-10-01

    We report on Pc5 wave related electric field and vertical drift velocity oscillations at the equator as observed by ground magnetometers for an extended period on 9 August 2008. We show that the magnetometer-estimated equatorial E×B drift oscillates with the same frequency as ULF Pc5 waves, creating significant ionospheric density fluctuations. We also show ionospheric density fluctuations during the period when we observed ULF wave activity. At the same time, we detect the ULF activity on the ground using ground-based magnetometer data from the African Meridian B-field Education and Research (AMBER) and the South American Meridional B-field Array (SAMBA). From space, we use magnetic field observations from the GOES 12 and the Communication/Navigation Outage and Forecast System (C/NOFS) satellites. Upstream solar wind conditions are provided by the ACE spacecraft. We find that the wave power observed on the ground also occurs in the upstream solar wind and in the magnetosphere. All these observations demonstrate that Pc5 waves with a likely driver in the solar wind can penetrate to the equatorial ionosphere and modulate the equatorial electrodynamics. While no direct drift measurements from equatorial radars exist for the 9 August 2008 event, we used JULIA 150 km radar drift velocities observed on 2 May 2010 and found similar fluctuations with the period of 5-8 min, as a means of an independent confirmation of our magnetometer derived drift dynamics.

  18. Yanai waves in the western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Chatterjee, A; Shankar, D.; McCreary, J.P.; Vinayachandran, P.N.

    Observations and models have shown the presence of intraseasonal fluctuations in 20-30-day and 10-20-day bands in the equatorial Indian Ocean west of 60 degrees E (WEIO). Their spatial and temporal structures characterize them as Yanai waves, which...

  19. Variable influence on the equatorial troposphere associated with ...

    Indian Academy of Sciences (India)

    DOI 10.1007/s12040-017-0802-6. Variable influence on the equatorial troposphere associated with SSW using ERA-Interim. Sourabh Bal1,4,∗. , Semjon Schimanke2, Thomas Spangehl3 and Ulrich Cubasch1. 1Institute for Meteorology, Freie Universität, Berlin, Germany. 2Swedish Meteorological and Hydrological Institute, ...

  20. 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

  1. Interannual variation of the Asian-Pacific oscillation

    Science.gov (United States)

    Wang, Lu; Chen, Lin

    2017-03-01

    Previous studies have identified an Asian-Pacific Oscillation (APO) teleconnection pattern, which exhibits an out-of-phase relationship in the summer tropospheric temperature with warming over the Eurasia and cooling over the Northern Pacific and the Northern America, and vice versa. But the interannual variation of this teleconnection remains obscure. This study points out that interannual variation of the APO teleconnection is associated with the second empirical orthogonal function (EOF) mode of the northern-hemisphere upper tropospheric temperature during boreal summer, which accounts for 14% of the variance. A heat budget analysis is conducted for the Eurasian region and the North Pacific region respectively to reveal the cause of the zonal dipole mode temperature structure. For the Eurasia region, the warming is contributed by the adiabatic heating process due to downward vertical motion anomalies. For the Northern Pacific region, the temperature variation is mainly contributed by zonal advection associated with interannual zonal wind perturbation acting on the climatological temperature gradient. Composite analysis and numerical experiments with an atmospheric general circulation model (AGCM) shows the interannual zonal wind perturbation is related to the sea surface temperature anomalies over the equatorial eastern Pacific.

  2. 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.

  3. Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic

    Science.gov (United States)

    Korte, Laura F.; Brummer, Geert-Jan A.; van der Does, Michèlle; Guerreiro, Catarina V.; Hennekam, Rick; van Hateren, Johannes A.; Jong, Dirk; Munday, Chris I.; Schouten, Stefan; Stuut, Jan-Berend W.

    2017-05-01

    Massive amounts of Saharan dust are blown from the coast of northern Africa across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect effects on global climate which include reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors. The sediment traps were deployed at five ocean sites along a transatlantic transect between north-west Africa and the Caribbean along 12° N, in a downwind extension of the land-based dust collectors placed at 19° N on the Mauritanian coast in Iouîk. In this paper, we lay out the setup of the monitoring experiment and present the particle fluxes from sediment trap sampling over 24 continuous and synchronized intervals from October 2012 through to November 2013. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the downwind sediment trap sites, and with satellite observations of Saharan dust outbreaks. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the east and west, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iouîk. Downwind increasing Al, Fe and K contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic Ocean, admixture of re-suspended clay

  4. Tropical Pacific sea-surface temperatures and preceding sea level pressure anomalies in the subtropical North Pacific

    Science.gov (United States)

    Anderson, Bruce T.

    2003-12-01

    The correspondence of sea-surface temperature (SST) anomalies to changes in antecedent large-scale sea level pressure anomalies is investigated using reanalysis data. By statistically examining linearly coupled precursor sea level pressure fields and subsequent SST fields for different lag periods, it is possible to isolate a precursor mode of sea level pressure (SLP) variability in the central subtropical North Pacific that precedes variations in the January-March El Niño/Southern Oscillation (ENSO) by approximately 12-15 months. A sea level pressure index, which captures the important characteristics of this precursor mode of variability, is developed and evaluated. It is shown that both analyzed and observed versions of the index are significantly correlated with the January-March ENSO one year later. The SLP index is then used to examine the evolution of the surface circulation and temperature structures leading up to mature ENSO events. Initially, the January-March subtropical North Pacific SLP anomalies are associated with changes in the intensity of the subtropical trade wind regime over the North Pacific, as well as with SST anomalies over the eastern equatorial Pacific and subtropical central Pacific. In agreement with the correlation statistics associated with the SLP and lagged NINO3.4 indices, both the sea level pressure field and the SST field subsequently develop ENSO-like structures over the course of the following year. Significant discussion of these results and pertinent areas of future research are provided within the broader context of the ENSO system.

  5. Understanding the El Niño-like Oceanic Response in the Tropical Pacific to Global Warming

    Science.gov (United States)

    Luo, Y.; Lu, J.; Liu, F.

    2015-12-01

    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.

  6. 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.

  7. Eastern Pacific tropical cyclones intensified by El Niño delivery of subsurface ocean heat.

    Science.gov (United States)

    Jin, F-F; Boucharel, J; Lin, I-I

    2014-12-04

    The El Niño Southern Oscillation (ENSO) creates strong variations in sea surface temperature in the eastern equatorial Pacific, leading to major climatic and societal impacts. In particular, ENSO influences the yearly variations of tropical cyclone (TC) activities in both the Pacific and Atlantic basins through atmospheric dynamical factors such as vertical wind shear and stability. Until recently, however, the direct ocean thermal control of ENSO on TCs has not been taken into consideration because of an apparent mismatch in both timing and location: ENSO peaks in winter and its surface warming occurs mostly along the Equator, a region without TC activity. Here we show that El Niño--the warm phase of an ENSO cycle--effectively discharges heat into the eastern North Pacific basin two to three seasons after its wintertime peak, leading to intensified TCs. This basin is characterized by abundant TC activity and is the second most active TC region in the world. As a result of the time involved in ocean transport, El Niño's equatorial subsurface 'heat reservoir', built up in boreal winter, appears in the eastern North Pacific several months later during peak TC season (boreal summer and autumn). By means of this delayed ocean transport mechanism, ENSO provides an additional heat supply favourable for the formation of strong hurricanes. This thermal control on intense TC variability has significant implications for seasonal predictions and long-term projections of TC activity over the eastern North Pacific.

  8. 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.

  9. Operational surface currents derived from satellite altimeters and scatterometers; Pilot Study for the Tropical Pacific

    Science.gov (United States)

    Lagerloef, G.

    1 and diagnose model errors. Another immediate application of these data relates to fisheries management and ma- rine wildlife research in the region. Movements of several species of sea turtle in the tropical region are being tracked by satellite with System Argos. Results show that some turtle tracks follow meandering portions of the North Equatorial Current and North Equatorial Counter Current. The surface current data allow researchers to exam- ine the oceanography of the habitat these turtles are using, for example, and evaluate to what extent they are using the equatorial currents and regions of surface convergence. Findings indicate that different species/stocks use different habitats. Some forage at or near the surface at convergences and others forage sub-surface away from currents (Polovina et al., 2002). References: Bonjean, F. and G.S.E. Lagerloef, 2002: Diagnostic model and analysis of the surface currents in the Tropical Pacific Ocean, J. Phys. Oceanogr., In press. Lagerloef,G.S.E., G.Mitchum, R.Lukas and P.Niiler, 1999: Tropical Pacific near sur- face currents estimated from altimeter, wind and drifter data, J. Geophys. Res., 104, 23,313-23,326. Polovina, J. J., G. H. Balazs, E. A Howell, D. M. Parker, M. P. Seki, and P. H. Dutton, 2002. Forage and migration habitat of loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea) sea turtles in the central North Pacific Ocean. Fish. Oceanogr., In Review.

  10. Sediment Acoustics

    National Research Council Canada - National Science Library

    Stoll, R

    2001-01-01

    ... variables such as porosity and grain-size distribution. The model is based on the classical Biot theory extended to take into account various mechanisms of energy loss that are known to be important in marine sediments...

  11. Revisit the interannual variability of the North Equatorial Current transport with ECMWF ORA-S3

    Science.gov (United States)

    Zhai, Fangguo; Hu, Dunxin

    2013-03-01

    interannual variability of the North Equatorial Current (NEC) transport in the tropical northwestern Pacific Ocean is investigated with the output from ECMWF Ocean Analysis/Reanalysis System 3 (ORA-S3). The results show that the amplitude and root mean square (RMS) of interannual NEC transport anomalies increase from about 3.0-4.0 Sv and 2.0 Sv at 170°E to above 5.0 and 3.4 Sv at 135°E, respectively. The NEC transport variation agrees well with the variation of the sea surface height (SSH) anomaly difference between the southern and northern boundaries of the NEC region. Further analysis near the Philippine coast suggests that their good agreement mainly comes from the agreement of the NEC transport and SSH variations south of the gyre boundary. Around the bifurcation point off the Philippine coast, the southern branch of the NEC transport is highly related to El Niño-Southern Oscillation (ENSO) events. During El Niño/La Niña years, westerly/easterly wind anomalies and positive/negative wind stress curl anomalies develop in the tropical northwestern Pacific Ocean south of 20°N before the mature phase. The wind forcing center moves eastward with time and reaches the easternmost position around 170°E several months before the mature phase. This wind forcing generates upwelling/downwelling Rossby waves, which propagate westward to result in negative/positive SSH anomalies, hence inducing a cyclonic/anticyclonic gyre anomaly, which is responsible for the increase/decrease of the NEC transport. The northern branch of the NEC transport near the Philippine coast has no significant simultaneous relation with ENSO events.

  12. Ship-Borne Geochemical Investigations of Deep-Sea Manganese-Nodule Deposits in the Pacific Using a Radioisotope Energy-Dispersive X-Ray System

    DEFF Research Database (Denmark)

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

    1974-01-01

    A radioisotope energy-dispersive X-ray (EDX) system has been used on board the German research vessel “Valdivia” during an exploration expedition in the northern equatorial Pacific in 1973. The instrumentation used consisted of an X-ray detection system incorporating a 30 mm2 effective-area Si (Li...

  13. Longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics

    Science.gov (United States)

    Yizengaw, E.; Zesta, E.; Moldwin, M. B.; Damtie, B.; Mebrahtu, A.; Valladares, C. E.; Pfaff, R. F.

    2012-07-01

    Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian ˜37°E and 290°E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation, such as

  14. North Pacific Meridional Mode over the Common Era

    Science.gov (United States)

    Sanchez, S. C.; Charles, C. D.; Amaya, D. J.; Miller, A. J.

    2016-12-01

    The Pacific Meridional Mode (PMM) has been increasingly recognized as an influential mode of variability for channeling extratropical anomalies to the equatorial ocean-atmosphere system. The PMM has been identified as an important precursor for ENSO, a source of much decadal power in the tropical Pacific, and is potentially intensifying. It is still unknown why the Pacific Meridional Mode might be intensifying; most arguments center around the changing mean state associated with anthropogenic global warming. There are a number of processes by which the background state could influence the PMM: altering the location of trade winds, the characteristics of stochastic forcing, the sensitivity of latent heat flux to surface wind anomalies, the wind response to SST anomalies, or changing the Intertropical Convergence Zone (ITCZ) structure. Recent work has found that the PMM is particularly sensitive to ITCZ shifts in intensity and location (using a simple linear coupled model, [Martinez-Villalobos and Vimont 2016]). Over the last millennium the ITCZ has experienced epochs of notable latitudinal shifts to balance the cross equatorial energy transport. Here we investigate how the strength of the PMM may have varied with these shifts in the ITCZ over the Common Era using the CESM-Last Millennium Ensemble (LME). We assess the strength of the PMM pathway by the degree of air-sea coupling and the amplitude of tropical decadal variability. We expect the ITCZ location and the degree of air-sea coupling (WES feedback) to play a critical role in determining the effectiveness and intensity of the PMM pathway. We verify our inferences in the LME with coral paleoproxy records from the central tropical Pacific. Chiefly we target records from the Line Islands (spanning 1°N to 6°N) to infer variations in the location of the ITCZ and the amplitude of decadal variability. This work enables us to discuss the idea of an intensifying PMM in a more historical context.

  15. 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.

  16. 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.

  17. 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.

  18. Industrial concessions, fires and air pollution in Equatorial Asia

    Science.gov (United States)

    Spracklen, D. V.; Reddington, C. L.; Gaveau, D. L. A.

    2015-09-01

    Forest and peatland fires in Indonesia emit large quantities of smoke leading to poor air quality across Equatorial Asia. Marlier et al (2015 Environ. Res. Lett. 10 085005) explore the contribution of fires occurring on oil palm, timber (wood pulp and paper) and natural forest logging concessions to smoke emissions and exposure of human populations to the resulting air pollution. They find that one third of the population exposure to smoke across Equatorial Asia is caused by fires in oil palm and timber concessions in Sumatra and Kalimantan. Logging concessions have substantially lower fire emissions, and contribute less to air quality degradation. This represents a compelling justification to prevent reclassification of logging concessions into oil palm or timber concessions after logging. This can be achieved by including logged forests in the Indonesian moratorium on new plantations in forested areas.

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. Equatorial electrojet in the south Atlantic anomaly region

    Indian Academy of Sciences (India)

    Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of the lowest magnetic field intensity in the region of rapid changes in the declination. The daily ...

  4. 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

  5. Climatic Variation at Thumba Equatorial Rocket Launching Station, India

    OpenAIRE

    K. V. S. Namboodiri; P. K. Dileep; Koshy Mammen

    2013-01-01

    Long-term (45 years) diversified surface meteorological records from Thumba Equatorial Rocket Launching Station (TERLS), India, were collected and analysed to study the long-term changes in the overall climatology, climatology pertained to a particular observational time, mean daily climatology in temperature, inter-annual variability in temperature, interannual variability in surface pressure, and rainfall for the main Indian seasons—South West and North East monsoons and inter-annual mean m...

  6. 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

  7. 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.

  8. Modulation of precipitation over West Africa by equatorial waves

    Science.gov (United States)

    Schlüter, Andreas; van der Linden, Roderick; Vogel, Peter; Fink, Andreas H.; Knippertz, Peter

    2017-04-01

    Equatorial waves can couple with deep convection and thus modulate rainfall on the synoptic timescale throughout the tropics. Until now, however, no comparative study of the influence of all the different wave types on precipitation has been performed specifically for West Africa. To fill this gap, the following wave types were analyzed for the pre-/post- and full monsoon season (April to October): (1) the Madden-Julian Oscillation (MJO), (2) Kelvin waves, (3) equatorial Rossby waves, (4) eastward-propagating inertia gravity waves, (5) mixed Rossby-gravity waves and (6) tropical disturbances/African Easterly Waves. The different wave types were filtered in the wavenumber-frequency spectrum of outgoing longwave radiation. Eight different wave phases were defined from a phase diagram that can be calculated from the time-derivative of the filtered wave signal. Subsequently, composites of dynamical and thermodynamical fields for each wave phase of the different wave types were plotted using the ERA Interim reanalysis from the European Centre for Medium-Range Weather Forecasts. This way the propagation of the wave can be depicted. All aforementioned wave types, except the fast eastward-propagating inertia gravity wave, show consistent and significant influence on West African rainfall. The influence of the waves can be seen far into the subtropics for some wave types. The expected theoretical structure is confirmed by the analysis of upper- and lower-level divergence, wind and geopotential height. An interaction between the tropical and extratropical regime appears to occur for the MJO and equatorial Rossby waves. The mechanism involved in this interaction, however, is not fully understood. Composites of low-level wind shear, convective available potential energy and mid-level moisture are used to analyze whether waves create favorable conditions for the organization of convection. Additionally, the source regions of moisture were identified using moisture fields and

  9. 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...

  10. Mismo field experiment in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Masumoto, Y.; Kuroda, Y.; Katsumata, M.; Mizuno, K.; Takayabu, Y.N.; Yoshizaki, M.; Shareef, A.; Fujiyoshi, Y.; McPhaden, M.J.; Murty, V.S.N.; Shirooka, R.; Yasunaga, K.; Yamada, H.; Sato, N.; Ushiyama, T.; Moteki, Q.; Seiki, A.; Fujita, M.; Ando, K.; Hase, H.; Ueki, I.; Horii, T.; Yokoyama, C.; Miyakawa, T.

    Ocean in early December. All observations were collected during an El Nino and a positive Indian Ocean Dipole (IOD) event, which tended to suppress convection in the western Pacific and eastern Indian Ocean in throughout much of November 2006. However...

  11. The Pacific University Alliance

    International Nuclear Information System (INIS)

    Peddicord, K.L.; Graham, J.A.

    1996-01-01

    The Pacific University Alliance represents a partnership between universities from the Pacific Rim countries in North America and Asia with international companies in the field of nuclear technology. This partnership builds on a strong academic base to address 'world problems' and to prepare students to meet the challenges for the global nuclear industry of the 21st century. (author)

  12. PACIFIC NORTHWEST CYBER SUMMIT

    Energy Technology Data Exchange (ETDEWEB)

    Lesperance, Ann M.; Matlock, Gordon W.; Becker-Dippmann, Angela S.; Smith, Karen S.

    2013-08-07

    On March 26, 2013, the Snohomish County Public Utility District (PUD) and the U.S. Department of Energy’s (DOE’s) Pacific Northwest National Laboratory (PNNL) jointly hosted the Pacific Northwest Cyber Summit with the DOE’s Office of Electricity Delivery and Energy Reliability, the White House, Washington State congressional delegation, Washington State National Guard, and regional energy companies.

  13. Early 20th Century Arctic Warming Intensified by Pacific and Atlantic Multidecadal Variability

    Science.gov (United States)

    Tokinaga, H.; Xie, S. P.; Mukougawa, H.

    2017-12-01

    We investigate the influence of Pacific and Atlantic multidecadal variability on the Arctic temperature, with a particular focus on the early 20th century Arctic warming. Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing than at present. We find that the concurrent phase shift of Pacific and Atlantic multidecadal variability is the major driver for the early 20th century Arctic warming. Atmospheric model simulations reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early Arctic warming is associated with the cold-to-warm phase shifts of Atlantic and Pacific multidecadal variability modes, a SST pattern reminiscent of the positive phase of the Pacific decadal and Atlantic multidecadal oscillations. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. The equatorial Pacific warming deepens the Aleutian low, advecting warm air to the North American Arctic. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, cold-to-warm phase shift of the Pacific and Atlantic multidecadal variability. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  14. 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.

  15. 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)

  16. Low-frequency variability of temperature in the vicinity of the equatorial Pacific thermocline in SODA : role of equatorial wave dynamics and ENSO asymmetry

    OpenAIRE

    Dewitte, Boris; Thual, S.; Yeh, S. W.; An, S. I.; Moon, B. K.; Giese, B. S.

    2009-01-01

    ISI Document Delivery No.: 514DQ Times Cited: 8 Cited Reference Count: 42 Cited References: Adler RF, 2003, J HYDROMETEOROL, V4, P1147, DOI 10.1175/1525-7541(2003)0042.0.CO;2 An SI, 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL021699 An S.I., 2008, THEOR APPL CLIMATOL, V97, P29 An SI, 2005, J CLIMATE, V18, P2617, DOI 10.1175/JCLI3433.1 An SI, 2004, J CLIMATE, V17, P2399, DOI 10.1175/1520-0442(2004)0172.0.CO;2 BJORNSSON H, 1997, 971 CCGCR MCGILL U, P6709 Blanke B, 1997, J CLIMATE, V10, P1473...

  17. 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.

    with the Messin- ian salinity crisis and onset of northern hemisphere glaciation, respectively. At Tropic Seamount, the NW, W and SW slopes of the seamount were steep and covered with manganese crusts from the plateau at 1000 m to a water depth of 2500 m. Volcanic...

  18. Radar sounding of the Medusae Fossae Formation Mars: equatorial ice or dry, low-density deposits?

    Science.gov (United States)

    Watters, Thomas R; Campbell, Bruce; Carter, Lynn; Leuschen, Carl J; Plaut, Jeffrey J; Picardi, Giovanni; Orosei, Roberto; Safaeinili, Ali; Clifford, Stephen M; Farrell, William M; Ivanov, Anton B; Phillips, Roger J; Stofan, Ellen R

    2007-11-16

    The equatorial Medusae Fossae Formation (MFF) is enigmatic and perhaps among the youngest geologic deposits on Mars. They are thought to be composed of volcanic ash, eolian sediments, or an ice-rich material analogous to polar layered deposits. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard the Mars Express Spacecraft has detected nadir echoes offset in time-delay from the surface return in orbits over MFF material. These echoes are interpreted to be from the subsurface interface between the MFF material and the underlying terrain. The delay time between the MFF surface and subsurface echoes is consistent with massive deposits emplaced on generally planar lowlands materials with a real dielectric constant of approximately 2.9 +/- 0.4. The real dielectric constant and the estimated dielectric losses are consistent with a substantial component of water ice. However, an anomalously low-density, ice-poor material cannot be ruled out. If ice-rich, the MFF must have a higher percentage of dust and sand than polar layered deposits. The volume of water in an ice-rich MFF deposit would be comparable to that of the south polar layered deposits.

  19. Pacific tectonics: Eastern-Pacific "stationarity" of EPR and causative association with Equator

    Science.gov (United States)

    Bostrom, R. C.

    2003-04-01

    The fundamentals of present-day Pacific tectonics are observed to be: its N/S mirror-symmetry about the Equator, displayed by the major transforms; its E/W asymmetry, represented by the western motion of the world's largest plate, originating in the eastern Equatorial Pacific; and correspondingly, development of the globally most voluminous subduction, at the western Pacific margin. The configuration seen at present is maintained at a fundamental level. The maximum in convective upwelling develops as coalescing plumes in the Galapagos region in the eastern Pacific. This has been found (Lonsdale 1988; McGuire and Hilde 2002; Chen and Lin 2002) to produce steady westward propagation of the Nazca/Cocos axis. Continually renewed, it determines the orientation and locus of a quasi-stationary EPR, centered on the Equator. Magnetic dating of boundaries in satellite gravity images records the Cenozoic history of the EPR, namely re-orientation in consequence of slow counter-clockwise re-orientation of the Equator. Relative to the present, during Maastrichtian times both Equator and plate motion were aligned WNW, recorded paleomagnetically and by features in the western, older part of the Pacific crust. Material subducted at that time accumulated principally beneath the SE Asia margin. Its slow heating is believed to play a role in the deep-seated activity and back-arc spreading associated with latter-day convergence in that region. The mechanism primarily responsible for the Pacific regime may be that mantle convection is not immune, as is generally tacitly supposed, to the minute westward tilt (c. 0.36°) under which it takes place. The latter, now astronomically quantifiable without tidal identification, represents the attraction component of water and solid-Earth masses which averaged over unit day lags the direction of purely geocentric g. Under gravity minutely E/W asymmetric, convection as always promoting the most efficient dissipative configuration, favors

  20. 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.

  1. 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.

  2. High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes

    Directory of Open Access Journals (Sweden)

    D. Pallam Raju

    1998-08-01

    Full Text Available The first-ever high resolution 2-D maps of OI 630.0 nm dayglow obtained from equatorial latitudes clearly reveal the movement as a large-scale feature of the equatorial ionization anomaly (EIA. These also show the presence of wave-like features classified as gravity waves presumably originating at the crest of the EIA, similar to the equatorial electrojet acting as a source of these waves. These results are presented and discussed.Key words. Atmospheric composition and structure (Airglow and aurora · Ionosphere (Equatorial ionosphere; Instruments and techniques.

  3. High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes

    Directory of Open Access Journals (Sweden)

    D. Pallam Raju

    Full Text Available The first-ever high resolution 2-D maps of OI 630.0 nm dayglow obtained from equatorial latitudes clearly reveal the movement as a large-scale feature of the equatorial ionization anomaly (EIA. These also show the presence of wave-like features classified as gravity waves presumably originating at the crest of the EIA, similar to the equatorial electrojet acting as a source of these waves. These results are presented and discussed.

    Key words. Atmospheric composition and structure (Airglow and aurora · Ionosphere (Equatorial ionosphere; Instruments and techniques.

  4. Spatiotemporal variability and propagation of equatorial noise observed by Cluster

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej; Pickett, J. S.; Gurnett, D. A.; Maksimovic, M.; Cornilleau-Wehrlin, N.

    2002-01-01

    Roč. 107, A12, 1495 (2002), s. SMP 43-1-43-8, doi: 10.1029/2001JA009159 ISSN 0148-0227 R&D Projects: GA ČR GA205/01/1064 Grant - others:NASA(US) NAG5-9974 Institutional research plan: CEZ:AV0Z3042911; CEZ:MSM 113200004 Keywords : outer plasmasphere * proton-cyclotron frequency * electromagnetic equatorial noise Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.245, year: 2002

  5. Provisional hourly values of equatorial Dst for 1971

    Science.gov (United States)

    Sugiura, M.; Poros, D. J.

    1972-01-01

    Tables and plots of provisional hourly values of the equatorial Dst index for 1971 are given, a table of daily mean Dst values for 1971 is also provided. The base line values for the four observatories, Hermanus, Kakioka, Honolulu, and San Juan, were obtained from extrapolations using the coefficients for the secular variations determined for the previous years. Examining the Dst values for quiet days, the base lines so determined appear to be slightly low, so that the Dst index for quiet periods tends to be high.

  6. Ventilation changes in the northeast Pacific during the last deglaciation

    Science.gov (United States)

    VanGeen, A.; Fairbanks, R.G.; Dartnell, P.; McGann, M.; Gardner, J.V.; Kashgarian, Michaele

    1996-01-01

    Under present climate conditions, convection at high latitudes of the North Pacific is restricted to shallower depths than in the North Atlantic. To what extent this asymmetry between the two ocean basins was maintained over the past 20 kyr is poorly known because there are few unambiguous proxy records of ventilation from the North Pacific. We present new data for two sediment cores from the California margin at 800 and 1600 m depth to argue that the depth of ventilation shifted repeatedly in the northeast Pacific over the course of deglaciation. The evidence includes benthic foraminiferal Cd/Ca, 18O/16O, and 13C/12C data as ell as radiocarbon age differences between benthic and planktonic foraminifera. A number of features in the shallower of the two cores, including an interval of laminated sediments, are consistent with changes in ventilation over the past 20 kyr suggested by alternations between laminated and bioturbated sediments in the Santa Barbara Basin and the Gulf of California [Keigwin and Jones, 1990; Kennett and Ingram, 1995; Behl and Kennett, 1996]. Data from the deeper of the two California margin cores suggest that during times of reduced ventilation at 800 m, ventilation was enhanced at 1600 m depth, and vice versa. This pronounced depth dependence of ventilation needs to be taken into account when exploring potential teleconnections between the North Pacific and the North Atlantic.

  7. 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.

  8. 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)

  9. Linguistic Diversity in the Pacific.

    Science.gov (United States)

    Crowley, Terry

    1999-01-01

    Reviews Peter Muhlhausler's book "Linguistic Ecology: Language Change and Linguistic Imperialism in the Pacific Region." Discusses the linguistic diversity of the Pacific, the linguistic impact of colonialism in the Pacific, and the role of linguists in the evolving linguistic situation in the Pacific. (Author/VWL)

  10. Visual sedimentation.

    Science.gov (United States)

    Huron, Samuel; Vuillemot, Romain; Fekete, Jean-Daniel

    2013-12-01

    We introduce Visual Sedimentation, a novel design metaphor for visualizing data streams directly inspired by the physical process of sedimentation. Visualizing data streams (e. g., Tweets, RSS, Emails) is challenging as incoming data arrive at unpredictable rates and have to remain readable. For data streams, clearly expressing chronological order while avoiding clutter, and keeping aging data visible, are important. The metaphor is drawn from the real-world sedimentation processes: objects fall due to gravity, and aggregate into strata over time. Inspired by this metaphor, data is visually depicted as falling objects using a force model to land on a surface, aggregating into strata over time. In this paper, we discuss how this metaphor addresses the specific challenge of smoothing the transition between incoming and aging data. We describe the metaphor's design space, a toolkit developed to facilitate its implementation, and example applications to a range of case studies. We then explore the generative capabilities of the design space through our toolkit. We finally illustrate creative extensions of the metaphor when applied to real streams of data.

  11. 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.)

  12. 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.

  13. Funnel-shaped, low-frequency equatorial waves

    Science.gov (United States)

    Boardsen, S. A.; Gallagher, D. L.; Gurnett, D. A.; Peterson, W. K.; Green, J. L.

    1992-01-01

    Funnel-shaped, low-frequency radiation, as observed in frequency time spectrograms, is frequently found at the earth's magnetic equator which extends from the proton-cyclotron frequency up to the lower hybrid frequency. Ray-tracing calculations can qualitatively reproduce the observed frequency-time characteristics of these emissions if the waves are propagating in the fast magnetosonic mode starting with wave normal angles of about 88 deg at the magnetic equator. The funnel-shaped emissions are consistent with generation by protons with a ring-type velocity space distribution. A ring-shaped region of positive slope in the velocity space density distribution of protons is observed near the Alfven velocity, indicating that the ring protons strongly interact with the waves. Ray-tracing calculations show that for similar equatorial wave normal angles lower-frequency fast magnetosonic waves are more closely confined to the magnetic equator than higher-frequency fast magnetosonic waves. For waves refracted back toward the equator at similar magnetic latitudes, the lower-frequency waves experience stronger damping in the vicinity of the equator than higher-frequency waves. Also, wave growth is restricted to higher frequencies at larger magnetic latitudes. Wave damping at the equator and wave growth off the equator favors equatorial wave normal angle distributions which lead to the funnel-shaped frequency time characteristic.

  14. Neutronic analysis of the Diagnostic Equatorial Ports in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, Alejandro [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Bertalot, Luciano, E-mail: luciano.bertalot@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Maquet, Philippe; Pitcher, Charles Spencer; Portales, Mickael [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Serikov, Arkady [Karlsruhe Institute of Technology KIT, 76344 Eggenstein-Leopoldshafen (Germany); Udintsev, Victor; Walsh, Michael [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

    2015-10-15

    Highlights: • Reduction of the streaming around Equatorial Ports. • Solutions for the mitigation of narrow gap streaming. • Importance of the environment and the radiation cross talk. - Abstract: The Diagnostic Port Plugs provide an infrastructure for integrating the diagnostics necessary to operate the machine, while withstanding the nuclear and mechanical loads. They have to provide neutron shielding in order to ensure accessibility to the Port Interspace (PI) region for maintenance operations. This report is about the study to mitigate the ITER Shutdown Dose Rate in Port Interspace. This is a strong design driver for the Equatorial Port Plugs (EPPs) requiring a neutron attenuation of 7 orders of magnitude while maintaining the weight limit. To achieve this challenging task, the design has evolved to an improved double labyrinth configuration with welded shims at the back of the EPP to reduce the gap with the Vacuum Vessel Port Extension. This proved to be very successful for this task. Neutron stoppers have been placed after the gaps necessary for the insertion of the Diagnostic Shielding Modules (DSMs) housed inside the EPP. Effort was also placed in the further development of the DSMs. The latest design relies on a stainless steel structure and lightweight efficient neutron absorbing materials inside. Studies of cross talk with lower ports and the influence of the streaming through the blanket area are presented to give the status of the radiation environment in the Port Interspace region and their contribution to the Shutdown Dose Rate (SDR).

  15. Intense equatorial flux spots on the surface of Earth's core

    Science.gov (United States)

    Jackson, A.

    2003-04-01

    A vast number of vector measurements of the Earth's magnetic field have recently become available from the satellite Oersted, currently in orbit monitoring the core magnetic field. In this presentation I will present new maps of the Earth's magnetic field at the surface of the fluid core derived from these satellite data which show intense flux spots in equatorial regions; the images are derived using a maximum entropy technique which is capable of reconstructing images with high dynamic range more precisely than conventional techniques. The intensity of these features is unusually large - they are comparable to high-latitude flux patches near the poles, previously identified as the major component of the dynamo field. A comparison with sunspots is tempting, though they are probably not associated with expulsion of toroidal magnetic field as is the case for the sun. Indeed, the tendency for pairing of these spots to the north and south of the geographical equator suggests they might be associated with the tops of so-called `Taylor columns' (indicative of the dominance of the rotation of the Earth) which have previously been suggested to be associated with the four high-latitude flux patches near the poles. Equatorially-trapped waves are known to exist in theory, and a correct interpretation of these features might lead to constraints on the strength of the hidden toroidal magnetic field within the Earth, as well as constraints on other physical regimes.

  16. Longitudinal Variability of Equatorial Electrodynamics and Density Irregularities

    Science.gov (United States)

    Yizengaw, E.; Doherty, P.

    2017-12-01

    The longitudinal variability of equatorial electrodynamics or scintillations has not been thoroughly investigated due to the lack of ground-based instruments that track the temporal variation of electrodynamics at different longitudes. Thus, study of longitudinal variability of electrodynamics has been possible only using in situ observations. In this paper, for the first time, we present the longitudinal variability of the nightside equatorial electrodynamics signatures that may be responsible for the formation of bubbles and scintillation activities. It is well known that the H-component geomagnetic field at low latitudes shows clear signatures for external currents during dayside and nightside. Thus, by removing Sq and ring currents contribution, it is possible to eliminate the gradual drift of the background field. Conspicuously, the residual geomagnetic field signature shows interestingly well-defined increase in ΔH during nightside, indicating the existence of eastward electric field at night. It is also well known that the Pedersen conductivity exhibits a large gradient across the sunset terminator due to large E-region conductivity on dayside compared to conductivity on nightside. This causes the positive charges to be accumulated at the terminator followed by the formation of divergent electric field at the terminator, which is eastward and maps along the equipotential field lines to F-region. In this paper, we present the longitudinal variability of the nightside divergent eastward electric field using the longitudinal chain of AMBER magnetometer network.

  17. Uranium in phosphorites of submarine untains in the Pacific Ocean

    International Nuclear Information System (INIS)

    Baturin, G.N.; Kochenov, A.V.; Dubinchuk, V.T.

    1982-01-01

    Uranium geochemical behaviour was studied under present sharply oxidizing conditions of sedimentation within the boundaries of submarine mountains in the Pacific Ocean (pelagic zone). It has been ascertained that the uranium content in phosphorites of submarine mountains in the Pacific Ocean does not exceed 10 -4 % which is considerably lower as compared phosphorites of submarine margins of the continents and terrestrial deposits. Iron and manganese hydroxides are the most active concentrators of uranium in a sharply oxidizing environment and to a lesser degree - phosphates, silicates, carbonates. Uranium bonded to phosphate is not an isomorphic impurity in it [ru

  18. 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...... of microfossils and fine-grained silica and clay. Samples with relatively pure chalk mud supported texture compact along a common stress - matrix porosity trend. Microfossils thus have a passive role, apparently because they are supported by the chalk mud. Samples with fine-grained silica and clay can be modelled...

  19. 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

  20. 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

  1. 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.

  2. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-01-01

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean–atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region. PMID:28559341

  3. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-06-01

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  4. Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability.

    Science.gov (United States)

    Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi

    2017-06-13

    With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.

  5. Study of equatorial regions of Moon with the help of backscattering ...

    Indian Academy of Sciences (India)

    sensors are used for analyzing the equatorial region of the Moon (60. ◦. N to 60 ... In this paper we have discussed the scattering behaviour of lunar equatorial region where the value of. CPR >1. Studies .... Figure 1. Generic hybrid polarity architecture in which the transmitted field is circularly polarized (right or left), and the.

  6. A note on new indices for the equatorial Indian Ocean oscillation

    Indian Academy of Sciences (India)

    It is now well known that there is a strong association of the extremes of the Indian summer monsoon rainfall (ISMR) with the El Niño and southern oscillation (ENSO) and the Equatorial Indian Ocean Oscillation (EQUINOO), later being an east–west oscillation in convection anomaly over the equatorial Indian Ocean. So far ...

  7. The role of the Southern Hemisphere semiannual oscillation in the development of a precursor to central and eastern Pacific Southern Oscillation warm events

    Science.gov (United States)

    Meehl, Gerald A.; van Loon, Harry; Arblaster, Julie M.

    2017-07-01

    The semiannual oscillation (SAO) is a twice-yearly northward movement (in May-June-July (MJJ) and November-December-January (NDJ)) of the circumpolar trough of sea level pressure (SLP) in the Southern Hemisphere with effects throughout the troposphere. During MJJ the second harmonic of SLP, describing the SAO, has low values of SLP north of 50°S in the subtropical South Pacific, while the first harmonic, which is dominant over the Australian sector, increases to its peak. This once-a-year peak in negative SLP gradients (decreasing to the east) between Australia and the ocean to its east extends to the equatorial Pacific. Southern Oscillation warm events since 1950, with an intensification of this seasonal cycle, have larger-amplitude SST anomalies in the eastern equatorial Pacific in MJJ and during the following mature phase in NDJ. Weak amplification of the seasonal cycle in MJJ tends to be followed by larger-amplitude SST anomalies in the central equatorial Pacific during NDJ.

  8. Role of observed Pacific trade wind trends in the recent hiatus and future projections

    Science.gov (United States)

    Maher, Nicola; England, Matthew; Gupta, Alex Sen; Spence, Paul

    2017-04-01

    Over the period 2001-2013 a slowdown (or 'hiatus') in global surface temperature has been observed. Recent studies have identified Pacific decadal variability as a major driver of hiatus and accelerated warming periods. Here we use an eddy-permitting global ocean model to investigate the role of the observed 1992-2011 trade wind intensification and associated atmospheric surface changes related with a strong negative phase of the Interdecadal Pacific Oscillation (IPO) in driving ocean circulation and heat content changes. We find a strengthening of the Pacific shallow overturning cells and Equatorial Undercurrent (EUC) in response to strengthened winds, which brings cooler water to the surface of the eastern Pacific and transports additional heat into the subsurface western Pacific. The intensified winds also increase the volume and heat transport of the Indonesian Throughflow, moving some of the additional heat from the western Pacific into the Indian Ocean. The net result is a warmer subsurface western Pacific, a cooler upper eastern Pacific and a warmer subsurface Indian Ocean, with an overall increase in Indo-Pacific heat content. Extended experiments with a symmetric reversal of the atmospheric state examine how the ocean would respond if the winds (and other associated atmospheric variables) were to revert to their initial state. We find a slowdown of the EUC and Pacific shallow overturning cells, resulting in a return to climatological SST conditions in the western and eastern Pacific. The ITF also slows toward its original strength. However, the temperature, heat content and ITF responses are not entirely symmetric due to an overall increase in the surface heat flux into the ocean associated with the cooler surface of the Pacific and irreversible heat transfer from the Pacific into the Indian Ocean via the ITF. There is also irreversible heat transport across the thermocline via diapycnal mixing, further contributing to this asymmetry. Consequently, after

  9. Contrasting global teleconnection features of the eastern Pacific and central Pacific El Niño events

    Science.gov (United States)

    Alizadeh-Choobari, O.

    2017-12-01

    Being triggered by different physical processes, the eastern Pacific (EP) and central Pacific (CP) El Niño events have several different teleconnection features around the globe. Using the ERA-Interim re-analysis monthly data during the period 1980-2016, the El Niño-Southern Oscillation (ENSO) teleconnections on the global scale and their statistical significance are investigated, with an emphasis on the contrasting features of the EP and CP El Niño events. With some exceptions, the EP El Niño and La Niña have generally similar teleconnection patterns with the reversed sign, while in some parts of the globe different and occasionally contrasting teleconnections of the EP and CP El Niño events are identified. Compared to the CP El Niño, more regions of the world are influenced by the statistically significant positive surface pressure anomalies during the EP El Niño, particularly over the Indian Ocean, tropical Atlantic and Northern Africa. It is found that the mid-tropospheric geopotential height anomalies across the globe are significantly different during the EP and CP El Niño events. Associated with different surface pressure and mid-tropospheric geopotential height anomalies, precipitation anomalies in many regions of the world are found different during the EP and CP El Niño events, particularly over the tropical Pacific, central to eastern equatorial Atlantic and the eastern Sahara. While central and eastern equatorial Atlantic experience statistically significant negative (positive) rainfall anomalies during the EP El Niño (La Niña), the CP El Niño does not have a strong influence on the amount of annual rainfall over the equatorial Atlantic. For the first time, statistically significant anomalously dry conditions are found over some parts of the Middle East and Southwest Asia during La Niña, and over the eastern Sahara during the EP El Niño.

  10. 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

  11. 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...

  12. Late Cretaceous Turbidite Reservoirs Along the Equatorial West African Margin: An Industry Perspective on Source-to-Sink Relationships

    Science.gov (United States)

    Wilson, Jonathan; Kohlmann, Fabian; Nicoll, Graeme

    2017-04-01

    The source-to-sink mindset provides an important framework for the exploration geologist. It enables an integrated understanding of hinterland and basin, and can lead to subsurface risk mitigation, particularly with respect to predicting reservoir location and quality. Despite the numerous benefits associated with source-to-sink analysis, such studies are time-consuming to generate, encompassing a large array of disciplines and data, and are not routinely performed within the hydrocarbon industry. The discovery of several significant hydrocarbon fields along the equatorial West African margin has been followed by a series of expensive failures throughout the last decade associated with reservoir quality/presence. This paper discusses a case study focused on the equatorial West African margin, demonstrating how three well-known but effective approaches can be integrated to reconstruct source-to-sink relationships in an ancient sedimentary system, helping de-risk exploration efforts. The first step is to characterize the hinterland. To do this, detailed information was collected for two separate but interlinked datasets—mineral deposits and hard rock geochronology. Combined, these two datasets allow an understanding of the timing and nature of an areas tectonic evolution to be easily developed. The data can be used alongside stratigraphic data and geodynamic information from a plate tectonic model to reconstruct topography and bathymetry of the earth at different episodes of geological time. Paleo digital elevation models (PDEMs) give a first-order approximation of hinterland topography and therefore allow possible sediment source areas to be identified and potential sediment transport pathways to be visualized by means of the digital reconstruction of paleo-drainage networks and their attendant watersheds. This integrated global dataset of hinterland geochronology provides useful "source" information complemented by "sink" information contained within a detrital

  13. 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.

  14. Ocean currents shape the microbiome of Arctic marine sediments

    NARCIS (Netherlands)

    Hamdan, L.J.; Coffin, R.B.; Sikaroodi, M.; Greinert, J.; Treude, T.; Gillevet, P.M.

    2013-01-01

    Prokaryote communities were investigated on the seasonally stratified Alaska Beaufort Shelf (ABS). Water and sediment directly underlying water with origin in the Arctic, Pacific or Atlantic oceans were analyzed by pyrosequencing and length heterogeneity-PCR in conjunction with physicochemical and

  15. 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...

  16. Pelagic microplastics around an archipelago of the Equatorial Atlantic.

    Science.gov (United States)

    Ivar do Sul, Juliana A; Costa, Monica F; Barletta, Mário; Cysneiros, Francisco José A

    2013-10-15

    Plastic marine debris is presently widely recognised as an important environmental pollutant. Such debris is reported in every habitat of the oceans, from urban tourist beaches to remote islands and from the ocean surface to submarine canyons, and is found buried and deposited on sandy and cobble beaches. Plastic marine debris varies from micrometres to several metres in length and is potentially ingested by animals of every level of the marine food web. Here, we show that synthetic polymers are present in subsurface plankton samples around Saint Peter and Saint Paul Archipelago in the Equatorial Atlantic Ocean. To explain the distribution of microplastics around the Archipelago, we proposed a generalised linear model (GLM) that suggests the existence of an outward gradient of mean plastic-particle densities. Plastic items can be autochthonous or transported over large oceanic distances. One probable source is the small but persistent fishing fleet using the area. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. 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.

  18. Analytical solutions for J 2-perturbed unbounded equatorial orbits

    Science.gov (United States)

    Martinusi, Vladimir; Gurfil, Pini

    2013-01-01

    While solutions for bounded orbits about oblate spheroidal planets have been presented before, similar solutions for unbounded motion are scarce. This paper develops solutions for unbounded motion in the equatorial plane of an oblate spheroidal planet, while taking into account only the J 2 harmonic in the gravitational potential. Two cases are distinguished: A pseudo-parabolic motion, obtained for zero total specific energy, and a pseudo-hyperbolic motion, characterized by positive total specific energy. The solutions to the equations of motion are expressed using elliptic integrals. The pseudo-parabolic motion unveils a new orbit, termed herein the fish orbit, which has not been observed thus far in the perturbed two-body problem. The pseudo-hyperbolic solutions show that significant differences exist between the Keplerian flyby and the flyby performed under the the J 2 zonal harmonic. Numerical simulations are used to quantify these differences.

  19. 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.

  20. 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 (p<0.05) throughout the period of study. The use of a numerical model allows us to assess the impact climate variability has on key phytoplankton groups known to lead to contrasting food chain at a spatial and temporal resolution unachievable when relying solely on in-situ observations.

  1. 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.

  2. 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

  3. Prevalence of refractive errors in children in Equatorial Guinea.

    Science.gov (United States)

    Soler, Margarita; Anera, Rosario G; Castro, José J; Jiménez, Raimundo; Jiménez, José R

    2015-01-01

    The aim of this work is to evaluate the epidemiological aspects of the refractive errors in school-aged children in Malabo (Island of Bioko), Equatorial Guinea (western-central Africa). A total of 425 schoolchildren (209 male subjects and 216 female subjects, aged between 6 and 16 years) were examined to evaluate their refraction errors in Malabo, Equatorial Guinea (western-central Africa). The examination included autorefraction with cycloplegia, measurement of visual acuity (VA) for far vision, and the curvature radii of the main meridians of the anterior surface of the cornea. A low prevalence of myopia was found (≤-0.50 diopters [D] spherical equivalent), with unilateral and bilateral myopia being 10.4 and 5.2%, respectively. The prevalence of unilateral and bilateral hypermetropia (≥2.0 D spherical equivalent) was 3.1 and 1.6%, respectively. Astigmatism (≤-0.75 D) was found in unilateral form in 32.5% of these children, whereas bilateral astigmatism was found in 11.8%. After excluding children having any ocular pathology, the low prevalence of high refractive errors signified good VA in these children. Significant differences were found in the distribution of the refractive errors by age and type of schooling (public or private) but not by sex. In general, the radii of the anterior of the cornea did not vary significantly with age. The mean refractive errors found were low and therefore VA was high in these children. There was a low prevalence of myopia, with significantly higher values in those who attended private schools (educationally and socioeconomically more demanding). Astigmatism was the most frequent refractive error.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  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. Blunt ocean dynamical thermostat in response of tropical eastern Pacific SST to global warming

    Science.gov (United States)

    An, Soon-Il; Im, Seul-Hee

    2014-10-01

    Using an intermediate ocean-atmosphere coupled model (ICM) for the tropical Pacific, we investigated the role of the ocean dynamical thermostat (ODT) in regulating the tropical eastern Pacific sea surface temperature (SST) under global warming conditions. The external, uniformly distributed surface heating results in the cooling of the tropical eastern Pacific "cold tongue," and the amplitude of the cooling increases as more heat is added but not simply linearly. Furthermore, an upper bound for the influence of the equatorially symmetric surface heating on the cold tongue cooling exists. The additional heating beyond the upper bound does not cool the cold tongue in a systematic manner. The heat budget analysis suggests that the zonal advection is the primary factor that contributes to such nonlinear SST response. The radiative heating due to the greenhouse effect (hereafter, RHG) that is obtained from the multi-model ensemble of the Climate Model Intercomparison Project Phase III (CMIP3) was externally given to ICM. The RHG obtained from the twentieth century simulation intensified the cold tongue cooling and the subtropical warming, which were further intensified by the RHG from the doubled CO2 concentration simulation. However, the cold tongue cooling was significantly reduced and the negative SST response region was shrunken toward the equator by the RHG from the quadrupled CO2 concentration simulation, while the subtropical warming increased further. A systematic RHG forced experiment having the same spatial pattern of RHG from doubled CO2 concentration simulation with different amplitude of forcing revealed that the ocean dynamical response to global warming tended to enhance the cooling in the tropical eastern Pacific by virtue of meridional advection and upwelling; however, these cooling effects could not fully compensate a given RHG warming as the external forcing becomes larger. Moreover, the feedback by the zonal thermal advection actually exerted the

  11. 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...

  12. 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.

  13. 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.

  14. 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.

  15. A multi-model approach to the Atlantic Equatorial mode: impact on the West African monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Losada, T.; Rodriguez-Fonseca, B. [Universidad Complutense de Madrid, Madrid (Spain); Janicot, S.; Gervois, S. [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Chauvin, F. [GAME/CNRM, Meteo-France/CNRS, Toulouse (France); Ruti, P. [Progetto Speciale Clima Globale, Ente Nazionale per le NuoveTecnologie, Rome (Italy)

    2010-07-15

    This paper is focused on the West African anomalous precipitation response to an Atlantic Equatorial mode whose origin, development and damping resembles the observed one during the last decades of the XXth century. In the framework of the AMMA-EU project, this paper analyses the atmospheric response to the Equatorial mode using a multimodel approach with an ensemble of integrations from 4 AGCMs under a time varying Equatorial SST mode. The Guinean Gulf precipitation, which together with the Sahelian mode accounts for most of the summer West African rainfall variability, is highly coupled to this Equatorial Atlantic SST mode or Atlantic Nino. In a previous study, done with the same models under 1958-1997 observed prescribed SSTs, most of the models identify the Equatorial Atlantic SST mode as the one most related to the Guinean Gulf precipitation. The models response to the positive phase of equatorial Atlantic mode (warm SSTs) depicts a direct impact in the equatorial Atlantic, leading to a decrease of the local surface temperature gradient, weakening the West African Monsoon flow and the surface convergence over the Sahel. (orig.)

  16. Decisive Thaw: The Changing Pattern of Relations between Nigeria and Equatorial Guinea, 1980-2005

    Directory of Open Access Journals (Sweden)

    David Aworawo

    2010-04-01

    Full Text Available This article examines the nature and changing pattern of relations between Nigeria and Equatorial Guinea from 1980-2005. It states that relations between the countries improved tremendously in the quarter century covered in this study compared to the two decades preceding that time frame (1960-1980 due to of a number of domesticpolitical and economic changes that occurred in both countries, as well as the transformation of the international system in the late 1980s and early 1990s. The paper explores the specific changes that took place in Nigerian-Equatorial Guinean relations from1980 onwards and the factors that influenced them. The termination of the brutal and violent rule of President Macias Nguema in Equatorial Guinea opened the way for improved relations between Nigeria and Equatorial Guinea. The shift from dependence on cocoa to petroleum exports in Equatorial Guinea also helped to promote cordial relations since the ill-treatment of Nigerian workers in Equatorial Guinea’s cocoa plantations had been a thorny issue in Nigerian-Equatorial Guinean relations in previous decades. The end of the Cold War and apartheid between 1989 and 1994 were also important factors that shaped relations. All these were issues that had previously negatively affected cordial relations between the countries. Thisarticle therefore discusses relations between Nigeria and Equatorial Guinea within the context of the post-Cold War international system and intra-African relations. It also argues that although improvements were recorded in Nigerian-Equatorial Guinean relations between 1980 and 2005, there remain numerous avenues that could be explored for yet better relations.

  17. Interdecadal variability of the ENSO teleconnection to the wintertime North Pacific

    Science.gov (United States)

    O'Reilly, Christopher H.

    2018-02-01

    The El Niño/Southern Oscillation (ENSO) strongly influences the large-scale atmospheric circulation over the extratropical North Pacific during boreal winter, which has an important impact on North American winter climate. This study analyses the interdecadal variability of the ENSO teleconnection to the wintertime extratropical North Pacific, over the period 1900-2010, using a range of observationally derived datasets and an ensemble of atmospheric model simulations. The observed teleconnection strength is found to vary substantially over the 20th century. Specifically, 31-year periods in the early-century (1912-1942), mid-century (1946-1976) and the late-century (1980-2010) are identified in the observations when the ENSO teleconnection to the North Pacific circulation are found to be particularly strong, weak and strong respectively. The ENSO teleconnection to the North Pacific in the atmospheric model ensemble is weak in the mid-century period and substantially stronger in the late-century, closely following the variability in the observed ENSO-North Pacific teleconnection. In the early-century, however, the atmospheric model also exhibits a weak teleconnection to the North Pacific, unlike in observations. In a subset of the model realisations that exhibit similar ENSO-North Pacific teleconnection as in observations during the early-century period there are large differences in extratropical circulation but not in equatorial Pacific precipitation anomalies, in contrast to the late-century period. This suggests that the high correlation in the early century period is largely due to internal extratropical variability. The important implications of these results for seasonal predictability and the assessment of seasonal forecasting systems are discussed.

  18. 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,…

  19. 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

  20. Miocene stable isotope record: a detailed deep pacific ocean study and its paleoclimatic implications.

    Science.gov (United States)

    Woodruff, F; Savin, S M; Douglas, R G

    1981-05-08

    Deep Sea Drilling Project site 289 in the western equatorial Pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the Miocene deep ocean. The isotopic record reflects major changes in paleoclimate and paleoceanography, probably dominated by a major phase of Antarctic ice-cap growth. The transition from a relatively unglaciated world to one similar to today occurred between 16.5 x 10(6) and 13 x 10(6) years before the present, with the greatest change occurring between approximately 14.8 x 10(6) and 14.0 x 10(6) years before the present.

  1. 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

  2. A space system integrating earth observation and mobile communications for equatorial remote areas

    Science.gov (United States)

    Ceballos, Decio C.

    1993-10-01

    The integration of two constellations of light and low-cost satellites, the Equatorial Communications (ECO) system and a polar orbit system for World Observation and Monitoring (WOM), is proposed. The WOM involves eight satellites and portable data reception and processing equipment. Onboard data compression enables UHF transmission of earth observation data. A system for global coverage with a temporal result of two passes per day is proposed. The ECO involves eight satellites in an equatorial constellation at 2000 mm. This system can supply low-orbit communications for equatorial countries and assist in the daily monitoring of ecologically protected areas.

  3. Mid-Holocene tropical Pacific climate state, annual cycle, and ENSO in PMIP2 and PMIP3

    Science.gov (United States)

    An, Soon-Il; Choi, Jung

    2014-08-01

    Using the Paleoclimate Modeling Inter-comparison Project Phase 2 and 3 (PMIP2 and PMIP3), we investigated the tropical Pacific climate state, annual cycle, and El Niño-Southern Oscillation (ENSO) during the mid-Holocene period (6,000 years before present; 6 ka run). When the 6 ka run was compared to the control run (0 ka run), the reduced sea surface temperature (SST) and the reduced precipitation due to the basin-wide cooling, and the intensified cross-equatorial surface winds due to the hemispheric discrepancy of the surface cooling over the tropical Pacific were commonly observed in both the PMIP2 and PMIP3, but changes were more dominant in the PMIP3. The annual cycle of SST was weaker over the equatorial eastern Pacific, because of the orbital forcing change and the deepening mixed layer, while it was stronger over the equatorial western pacific in both the PMIP2 and PMIP3. The stronger annual cycle of the equatorial western Pacific SST was accompanied by the intensified annual cycle of the zonal surface wind, which dominated in the PMIP3 in particular. The ENSO activity in the 6 ka run was significantly suppressed in the PMIP2, but marginally reduced in the PMIP3. In general, the weakened air-sea coupling associated with basin-wide cooling, reduced precipitation, and a hemispheric contrast in the climate state led to the suppression of ENSO activity, and the weakening of the annual cycle over the tropical eastern Pacific might lead to the intensification of ENSO through the frequency entrainment. Therefore, the two opposite effects are slightly compensated for by each other, which results in a small reduction in the ENSO activity during the 6 ka in the PMIP3. On the whole, in PMIP2/PMIP3, the variability of canonical (or conventional) El Niño tends to be reduced during 6 ka, while that of CP/Modoki El Niño tends to be intensified.

  4. 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...

  5. Cenozoic siliciclastic sediment budget at continent-scale, Africa.

    Science.gov (United States)

    Guillocheau, François; Robin, Cécile; Calves, Gérôme; Baby, Guillaume

    2013-04-01

    Siliciclastic sediment budget measurements was performed along the margins and onshore basins of Africa for Cenozoic times. Our objective was first to quantify the ratio between onshore and offshore sediment preservation in the case of a relief with mostly no mountain belt and secondly to understand the factors forcing the sediment supply along the passive margins of Africa that can be long to very-long relief deformation (mantle dynamics, ridge push…) or climate changes (with the major aridification of Africa since Middle Miocene). This study is based on basin-scale regional sections (seismic reflection data from industry and academics, wells correlation), calibrated in age and lithology on different types of wells (industry, DSDP/ODP). Most of the effort was on the revaluation of the ages (calibration and uncertainties). The volumes of sediments and uncertainties on depth conversion velocity laws, lithology and ages were measured using software developed by J. Braun (Grenoble University, France). • The sediment preserved onshore (750 000 km3) is one of magnitude less than was is preserved offshore • The main deformations controlling the sediment supply are (1) the growth or the domes of the East African rift and (2) the marginal bulge of the central and equatorial segments of the South Atlantic Ocean (from southern Angola to Guinea). • The aridification of Africa since at least Middle Miocene is very sensitive in the south (fossilization of the relief of the South African Plateau) and in the northwest, with a sharp decrease of the sediment supply. • Some buffer effects are very important, for example for the Nile and the Zambezi, where sediments were first stored in onshore basins, Sudan or Malawi rift, and later drained because of a capture (Nile) or a regional stress change (Zambezi). Keywords: Africa, Cenozoic, Siliciclastic sediment fluxes, Deformation, Climate

  6. 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

  7. Iapetus' Geophysics: Rotation Rate, Shape, and Equatorial Ridge

    Science.gov (United States)

    Castillo-Rogez, J. C.; Matson, D. L.; Sotin, C.; Johnson, T. V.; Lunine, J. I.; Thomas, P. C.

    2007-01-01

    Iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now. The evidence is (a) its present 79.33-day rotation or spin rate, (b) its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of approximately 16 h, and (c) its high, equatorial ridge, which is unique in the Solar System. This paper reports the results of an investigation into the coupling between Iapetus' thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition, porosity, short-lived radioactive isotopes (SLRI), and temperature. The thermal model uses conductive heat transfer with temperature-dependent conductivity. Only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape. Short-lived radioactive isotopes provide the heat needed to decrease porosity in Iapetus? early history. This increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16-h rotational shape and the high vertical relief of the topography. Long-lived radioactive isotopes and SLRI raise internal temperatures high enough that significant tidal dissipation can start, and despin Iapetus to synchronous rotation. This occurred several hundred million years after Iapetus formed. The models also constrain the time when Iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by SLRI decay in this early period. The amount of heat available from short-lived radioactivity is not a free parameter but is fixed by the time when Iapetus accreted, by the canonical concentration of Al-26, and, to a lesser extent, by the concentration of Fe-60. The needed amount of heat is available only if Iapetus accreted between 2.5 and 5.0Myr after the formation of the calcium aluminum

  8. Varieties of submesoscale dynamics in the south-west Pacific.

    Science.gov (United States)

    Srinivasan, K.; Renault, L.; McWilliams, J. C.

    2016-02-01

    The large-scale circulation in the topographically complex south-west Pacific region con-sists of an equatorward western boundary current along the coast of Papua New Guinea andwestern Solomon sea, the equatorial currents to the north and east of the Solomon islands,and the multiple jet-like zonal currents generated by the numerous islands to the south in theCoral Sea. Employing a hierarchy of nested, realistic ocean modeling experiments in ROMS,with horizontal resolutions as fine as 500m, we examine the dynamics of submesoscales inthis region. We construct spatial maps of statistics of the surface divergence (δ), vortic-ity (ζ)), buoyancy gradient (∇b) and the frontogenetic tendency (Tadv ), to identify areas ofactive submesoscales and their seasonal variability. More specifically, such areas are charac-terized by high variance of δ, ζ, ∇b and Tadv and a corresponding high negative skewnessin surface divergence, since frontogenesis is a downwelling-dominant physical process. Suchareas include sites in and around the Solomon Sea, with eddy generation through separa-tion of bottom-drag generated shear layers, the Coral Sea open ocean mixed-layer submesoscale `soup'generated through baroclinic instability and frontogenesis, and lastly, Equatorial fronts thatwe believe are hitherto unobserved and thought to be largely absent on theoretical groundsrequiring the presence of background rotation in frontogenesis. While the Coral Sea subme-soscale soup peaks in the (Southern hemisphere) winter, Equatorial frontal activity showsa summer-spring maximum. The dynamics of frontogenesis is particularly complex in theSolomon Sea where topographically generated eddies interact with mixed-layer buoyancygradients, that are in turn controlled by interplay of the warm equatorial currents to thenorth, the cooler Coral sea intrusions from the south and rather significantly, the strongand highly seasonal rainfall patterns and the corresponding freshwater input. A concomi

  9. 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)

  10. 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.

  11. Direct measurement of nitrogen gas fluxes from continental shelf sediments

    Science.gov (United States)

    Devol, Allan H.

    1991-01-01

    IT has been suggested that denitrification in continental shelf and slope sediments is the most important sink in the marine nitrogen cycle1-4. This conclusion has been reached, not from direct measurements of denitrification in these areas, but rather from indirect estimates derived from pore-water models of diagenetic processes. In highly bioturbated continental shelf and slope sediments with steep pore-water gradients, such indirect estimates may not be applicable5,6.1 have now made direct, in situ measurements of denitrification in sediments of the eastern North Pacific continental margin by determining the flux of molecular nitrogen out of the sediments into the overlying water. Denitrification rates in continental shelf sedim