WorldWideScience

Sample records for boundary upwelling systems

  1. On the Past, Present, and Future of Eastern Boundary Upwelling Systems

    Science.gov (United States)

    Bograd, S. J.; Black, B.; Garcia-Reyes, M.; Rykaczewski, R. R.; Thompson, S. A.; Turley, B. D.; van der Sleen, P.; Sydeman, W. J.

    2016-12-01

    Coastal upwelling in Eastern Boundary Upwelling Systems (EBUS) drives high productivity and marine biodiversity and supports lucrative commercial fishing operations. Thus there is significant interest in understanding the mechanisms underlying variations in the upwelling process, its drivers, and potential changes relative to global warming. Here we review recent results from a combination of regional and global observations, reanalysis products, and climate model projections that describe variability in coastal upwelling in EBUS. Key findings include: (1) interannual variability in California Current upwelling occurs in two orthogonal seasonal modes: a winter/early spring mode dominated by interannual variability and a summer mode dominated by long-term increasing trend; (2) there is substantial coherence in year-to-year variability between this winter/spring upwelling mode and upper trophic level demographic processes, including fish growth rates (rockfish and salmon) and seabird phenology, breeding success and survival; (3) a meta-analysis of existing literature suggests consistency with the Bakun (1990) hypothesis that rising global greenhouse-gas concentrations would result in upwelling-favorable wind intensification; however, (4) an ensemble of coupled, global ocean-atmosphere models finds limited evidence for intensification of upwelling-favorable winds over the 21st century, although summertime winds near the poleward boundaries of climatalogical upwelling zones are projected to intensify. We will also review a new comparative research program between the California and Benguela Upwelling Systems, including efforts to understand patterns of change and variation between climate, upwelling, fish, and seabirds.

  2. Upwelling systems in eastern boundary currents have been ...

    African Journals Online (AJOL)

    spamer

    In the Benguela system north of 32°S, winds are upwelling-favourable and currents are equatorward all year, but stronger in summer. The current strengthens in summer, when water parcels with high steric heights move into the region offshore of the jet from the Agulhas Retroflection area at the same time that steric heights ...

  3. Seasonal regulation of primary production in eastern boundary upwelling systems

    Science.gov (United States)

    Messié, Monique; Chavez, Francisco P.

    2015-05-01

    The regulation of seasonal satellite-derived primary production (PP) was investigated within a 150 km coastal box in four eastern boundary upwelling systems (EBUS): California, Peru, Northwest Africa and Benguela. The following regulating factors were considered: (1) wind-driven nitrate supply; (2) iron supply inferred from proxies (shelf mud belt width, modeled atmospheric iron deposition, river discharge); (3) temperature; (4) light and (5) physical export consisting of offshore export, eddy-driven and wind-driven subduction. The ratio of potential new production (carbon-equivalent of nitrate supply) to primary production, termed the N-ratio, is shown to be an indicator of PP limitation by nitrate supply (low N-ratios) vs. inhibition by other factors (high N-ratios). The factors regulating PP were assessed by analyzing the N-ratios and computing spatial correlations between PP and each factor each month. The regulation of primary production was found to vary spatially, seasonally and from one EBUS to another. Macronutrient supply is shown to be the dominant regulating factor off Northwest Africa and during some seasons and locations in other systems. Light regulation within the mixed layer occurs in all EBUS in winter but may only inhibit PP (high N-ratios) off Peru and Benguela. Evidence for iron limitation was found in each EBUS (except Northwest Africa) at varying levels and was greatest off Peru during austral winter when iron demand by phytoplankton increases due to low light levels. Rapid offshore advection combined with wind-driven and/or eddy-driven subduction may inhibit PP off California. A simple generalization regarding the regulation of primary production in EBUS is not forthcoming.

  4. On the warm nearshore bias in Pathfinder monthly SST products over Eastern Boundary upwelling systems

    CSIR Research Space (South Africa)

    Dufois, F

    2012-01-01

    Full Text Available Using in situ sea surface temperature (SST) data and MODIS/TERRA SST, the monthly AVHRR Pathfinder (version 5.0 and 5.2) SST product was evaluated within the four main Eastern Boundary Upwelling Systems. A warm bias in the monthly Pathfinder data...

  5. The distribution and impacts of harmful algal bloom species in eastern boundary upwelling systems

    Science.gov (United States)

    Trainer, V. L.; Pitcher, G. C.; Reguera, B.; Smayda, T. J.

    2010-04-01

    Comparison of harmful algal bloom (HAB) species in eastern boundary upwelling systems, specifically species composition, bloom densities, toxin concentrations and impacts are likely to contribute to understanding these phenomena. We identify and describe HABs in the California, Canary, Benguela and Humboldt Current systems, including those that can cause the poisoning syndromes in humans called paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), and amnesic shellfish poisoning (ASP), as well as yessotoxins, ichthyotoxins, and high-biomass blooms resulting in hypoxia and anoxia. Such comparisons will allow identification of parameters, some unique to upwelling systems and others not, that contribute to the development of these harmful blooms.

  6. Under pressure: Climate change, upwelling and eastern boundary upwelling ecosystems

    Directory of Open Access Journals (Sweden)

    Marisol eGarcía-Reyes

    2015-12-01

    Full Text Available The IPCC AR5 provided an overview of the likely effects of climate change on Eastern Boundary Upwelling Systems (EBUS, stimulating increased interest in research examining the issue. We use these recent studies to develop a new synthesis describing climate change impacts on EBUS. We find that model and observational data suggest coastal upwelling-favorable winds in poleward portions of EBUS have intensified and will continue to do so in the future. Although evidence is weak in data that are presently available, future projections show that this pattern might be driven by changes in the positioning of the oceanic high-pressure systems rather than by deepening of the continental low-pressure systems, as previously proposed. There is low confidence regarding the future effects of climate change on coastal temperatures and biogeochemistry due to uncertainty in the countervailing responses to increasing upwelling and coastal warming, the latter of which could increase thermal stratification and render upwelling less effective in lifting nutrient-rich deep waters into the photic zone. Although predictions of ecosystem responses are uncertain, EBUS experience considerable natural variability and may be inherently resilient. However, multi-trophic level, end-to-end (i.e., winds to whales studies are needed to resolve the resilience of EBUS to climate change, especially their response to long-term trends or extremes that exceed pre-industrial ranges.

  7. Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

    Science.gov (United States)

    Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

    2018-02-01

    In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

  8. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

    Directory of Open Access Journals (Sweden)

    V. Rossi

    2009-08-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. Since they are populated by several physical oceanic structures such as filaments and eddies, which interact with the biological processes, it is a major challenge to study this sub- and mesoscale activity in connection with the chlorophyll distribution. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs, and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs, which allow us to divide each areas in two different subsystems. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. We also proposed a ranking of the four EBUS based on the averaged mixing intensity. When investigating the links with chlorophyll concentration, the previous subsystems reveal distinct biological signatures. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean. This study provides new insights for the understanding of the variable biological productivity in the ocean, which results from both dynamics of the marine ecosystem and of the 3-D turbulent medium.

  9. Projected changes in upwelling-favorable winds at the ocean's eastern boundaries systems: large scale and synoptic scale

    Science.gov (United States)

    Aguirre, Catalina; Rojas, Maisa; Garreaud, René

    2017-04-01

    The Eastern Boundary Upwelling Systems (EBUS) maintains high productive fisheries and marine ecosystems. A comprehensive understanding of coastal air-sea interaction, the biogeochemical responses, and mechanisms of climate variability and change at the EBUS has gained importance. The CMIP5 simulations under the rcp85 scenario have showed a poleward displacement of the coastal upwelling-favorable winds in the ocean's eastern boundaries, -associated with a poleward migration of the subtropical atmospheric high-pressure cells. In this work we analyze historical and future simulations (rcp85) of 17 CMIP5 models to investigate the relationship between the large-scale response of the upwelling-favorable winds (through a geostrophic adjustment), with the synoptic scale variability associated to the coastal atmospheric low-level jets during the upwelling season in the Humboldt, Beguela, California and Canarias upwelling systems. Results show that the spatial pattern of the alongshore winds trends is highly consistent with that obtained from geostrophic alongshore winds (calculated from the surface pressure field), indicating the importance of the large-scale signal related to the poleward relocation of the subtropical anticyclones. On the other hand, Kolmogorov-Smirnov tests were applied to assess the statistical significance of the differences in the empirical cumulative distributions between the present and future alongshore winds at different latitudes. At higher latitudes most of the models show a significant different cumulative distribution. In particular, the alongshore wind speed values that in the present day data are in the upper quartile, which are typically associated to mid-latitude synoptic perturbations, increases (decreases) its probability 10%-15% (0%-10%) at higher (lower) latitudes to the end of the century. These results suggest that the poleward migration of the subtropical anticyclones is related with a poleward displacement of the mid

  10. Termination of a continent-margin upwelling system at the Permian-Triassic boundary (Opal Creek, Alberta, Canada)

    Science.gov (United States)

    Schoepfer, Shane D.; Henderson, Charles M.; Garrison, Geoffrey H.; Foriel, Julien; Ward, Peter D.; Selby, David; Hower, James C.; Algeo, Thomas J.; Shen, Yanan

    2013-06-01

    Models of mass extinctions caused by greenhouse warming depend on the ability of warming to affect the oxygenation of the ocean, either through slowing circulation or changes in biological productivity and the organic carbon budget. Opal Creek, Alberta, Canada is a biostratigraphically continuous Permian-Triassic Boundary (PTB) section deposited in deep water on an outer shelf setting in the vast and understudied Panthalassic Ocean, along the western margin of Pangaea. The latest-Permian extinction is here represented as the disappearance of the previously dominant benthic fauna (siliceous sponges). On the basis of nitrogen and reduced sulfur isotopes as well as productivity-sensitive trace elements, the Middle Permian at Opal Creek is interpreted as a highly productive coastal upwelling zone where vigorous denitrification and sulfate reduction occurred in a mid-water oxygen minimum. Similar conditions appear to have continued into the latest Permian until the onset of a euxinic episode represented by a discrete pyrite bed and several trace element indicators of high productivity. This euxinic pulse is followed by the extinction of benthic fauna and a shift in nitrogen and sulfur isotopes to more normal marine values, suggesting the cessation of coastal upwelling and the consequent weakening of the mid-water oxygen minimum. The Lower Triassic appears to be a dysoxic, relatively unproductive environment with a bottom water oxygen minimum. Rhenium-osmium isotope systematics show a minimum of radiogenic Os near the main extinction event, which may be due to volcanic input, and increasingly radiogenic values approaching the PTB, possibly due to increased continental erosion. The Opal Creek system demonstrates that, while the biogeochemical crisis in the latest Permian was capable of impacting the coastal upwelling modality of ocean circulation, a transient increase in productivity likely drove the system toward euxinia and, ultimately, extinction.

  11. Modeling the dynamical sinking of biogenic particles in eastern-boundary upwelling systems

    Science.gov (United States)

    Rossi, Vincent; Monroy, Pedro; López, Cristobal; Hernández-García, Emilio; Dewitte, Boris; Paulmier, Aurélien; Garçon, Véronique

    2017-04-01

    Although most of the organic material produced by photosynthesis in the upper ocean is recycled in surface waters, a significant portion sinks into the deep ocean where it is stored for long time-scales. Knowledge of the export flux of organic carbon from the sea surface to depths is needed to estimate the efficiency of the biological carbon pump, a key process of global carbon cycling. We study how the sinking of biogenic particles produced in the euphotic layer is affected by subsurface ocean currents as derived from a regional dynamical model. In the range of sizes and densities appropriate for marine biogenic particles, the sinking trajectories are given by the equation of motion of small particles in a fluid flow (Maxey-Riley equation). We use a modelled 3-dimensional velocity field with major energetic structures in the mesoscale and we assess the influence of physical processes such as the Coriolis force and the inertia of the particles. We find that the latter forces are negligible as compared to the most important terms, which are passive motion with the velocity of the flow and a constant added vertical velocity due to gravity. Horizontal two-dimensional clustering is observed at depth, similar to the inhomogeneities observed in sinking ocean particles. Based on ensemble experiments, we explore the influence of the mean flow and the mesoscale eddy field on particles lateral advection and size fractionation. This modeling framework allows us to extend the concept of particle source funnels and helps interpreting particles fluxes estimated from sediment traps deployed in upwelling systems, informing the spatial mismatch between surface production and particle export.

  12. Western boundary upwelling dynamics off Oman

    Science.gov (United States)

    Vic, Clément; Capet, Xavier; Roullet, Guillaume; Carton, Xavier

    2017-05-01

    Despite its climatic and ecosystemic significance, the coastal upwelling that takes place off Oman is not well understood. A primitive-equation, regional model forced by climatological wind stress is used to investigate its dynamics and to compare it with the better-known Eastern Boundary Upwellings (EBUs). The solution compares favorably with existing observations, simulating well the seasonal cycles of thermal structure, surface circulation (mean and turbulent), and sea-surface temperature (SST). There is a 1.5-month lag between the maximum of the upwelling-favorable wind-stress-curl forcing and the oceanic response (minima in sea-surface height and SST), which we attribute to onshore-propagating Rossby waves. A southwestward-flowing undercurrent (opposite to the direction of the near-surface flow) is also simulated with a core depth of 1000 m, much deeper than found in EBUs (150-200 m). An EKE budget reveals that, in contrast to EBUs, the upwelling jet is more prone to barotropic than baroclinic instability and the contribution of locally-generated instabilities to EKE is higher by an order of magnitude. Advection and redistribution of EKE by standing mesoscale features also play a significant role in EKE budget.

  13. An annually-resolved palaeoenvironmental archive for the Eastern Boundary North Atlantic upwelling system: Sclerochronology of Glycymeris glycymeris (Bivalvia) shells from the Iberian shelf

    Science.gov (United States)

    Freitas, Pedro; Monteiro, Carlos; Butler, Paul; Reynolds, David; Richardson, Christopher; Gaspar, Miguel; Scourse, James

    2015-04-01

    The seasonally variable western Iberia upwelling system, albeit placed at a crucial climatic boundary position to record high frequency climate events, lacks well-dated high-resolution records of environmental variability. Bivalve shells provide robust high-resolution archives of oceanographic and climatic variability on timescales of decades to millennia. In particular, the North Atlantic Ocean region has recently seen several noteworthy sclerochronological and geochemical reconstructions based on bivalve shells (mainly Arctica islandica) of high frequency oceanographic and climatic conditions during the last millennium. However, due to the absence of Arctica islandica and similarly long-lived bivalves, sclerochronological palaeoenvironmental studies of southern European coastal shelf seas are scarce. In particular, none of these studies focus on reconstructing the variability of an eastern boundary upwelling system. The relatively long-lived bivalve (>100 years) Glycymeris glycymeris occurs in European and North West African coastal shelf seas and provides a valid annually resolved archive of environmental conditions during growth. Annual growth increment width series from living G. glycymeris shells, collected in 2014 on the western Iberian continental shelf (ca. 35 m water depth), were used to construct a statistically robust, ca. 70-year long absolutely-dated chronology. Sub-annually resolved (11 to 22 samples per year) oxygen stable isotope (δ18Oshell) data covering three years of shell growth, together with the direct evaluation of the time of growth mark deposition in shells collected during the autumn and winter months, were used to constrain the season of growth and to evaluate the seasonal bias of the sea-surface temperature signal preserved in the δ18Oshelldata. The growth increment width and δ18Oshell series, once robustly calibrated against modelled and instrumental oceanographic and climatic series, potentially provide novel insights into the

  14. Four large coastal upwelling areas are created by eastern boundary ...

    African Journals Online (AJOL)

    spamer

    1991, Christensen and Pauly 1993, Jarre-Teichmann 1998). Such trophic flow models were developed for four ecosystems in upwelling areas, namely off northern and central. Peru in the Humboldt Current (4–14°S), off California and Oregon in the California Current (28–42°N), south of Cape Blanc in the Canary Current.

  15. Relation between Upwelling Intensity and the Variability of Physical and Chemical Parameters in the Southern Benguela Upwelling System

    Directory of Open Access Journals (Sweden)

    Hassan Ebrahiem Ismail

    2015-01-01

    Full Text Available The extent to which wind-driven seasonal upwelling cycles manifest in surface ocean temperature and nutrient variability along a monitoring line in the Southern Benguela upwelling system was investigated. Monitoring conducted monthly over a six-year period shows that surface temperature and nutrient concentrations exhibit very poor seasonality and weak correlation with the upwelling index. This is, despite clear evidence for spatial inshore-offshore gradients in temperature, nutrients, and chlorophyll, consistent with an upwelling regime. The upper ocean temperature gradient shows a much better correspondence to the upwelling index but at the same time demonstrates that surface heating, and not vertical mixing related to upwelling, controls the upper ocean temperature gradient. The results suggest that remote sensing techniques would be inadequate tools to monitor upwelling events in the Southern Benguela. Also, the incidence of phytoplankton blooms is more likely triggered by stratified conditions associated with surface heating than relaxation of upwelling winds.

  16. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    The biogeochemical cycles of organic carbon, nutrients, oxygen, and sulfur in the oceans have been suggested to dominantly occur across the shelf–ocean transition over the continental margin, although this zone represents only a small percentage of the global ocean area. Coastal upwelling zones...... in eastern boundary upwelling systems is an example of the most productive ocean waters over continental margins where intense supply of nutrients occur from deeper ocean waters. Interesting questions arise related to the biogeochemical cycles in such upwelling systems; such as 1) how the recently observed...... these questions centering on shelf–ocean exchange and biogeochemical cycle in the coastal upwelling systems under oxic and anoxic conditions. Firstly, I developed a new biogeochemical model which resolves coupling between cycles of the elements nitrogen, oxygen, phosphate, and sulfur by considering several key...

  17. A Model Analysis for the Design and Deployment of an Eulerian Sediment Trap Mooring Array in a Western Boundary Upwelling System from Southeast Brazil

    Directory of Open Access Journals (Sweden)

    URSULA MENDOZA

    2014-06-01

    Full Text Available This work addresses the design and configuration of a Eulerian sediment trap mooring array, which was deployed at the shelf edge (zm ≈ 140 m 80 km off Cabo Frio, SE- Brazil (23° S. The site was subject to interplay between the Tropical Waters (TW of the Brazil Current (BC, intrusions from the South Atlantic Central Waters (SACW, which are the source of upwelling in the region, and other oceanographic processes. Detailed computations were used to optimize the total weight, buoyancy balance, and maximum acceptable tilt to avoid hydrodynamic bias in the trapping efficiency and array adaptation to the local oceanographic conditions with the assistance of Matlab and Muringa programs and Modular Ocean Model 4.0 (MOM; i.e., to assert the vertical distribution of the meridional current component. The velocity range of the current component was determined by short term measurements to be between 0.1 and 0.5 m/s. Projections led to a resulting minimum anchor weight of 456 kg. The necessary line tension was ascertained by using the appropriate distribution of a series of buoys along the array, which finally attained a high vertical load of 350 kg because of the attached oceanographic equipment. Additional flotation devices resulted in a stable mooring array as reflected by their low calculated tilt (2.6° ± 0.6°. A low drag of 16 N was computed for the maximum surface current velocity of 0.5 m/s. The Reynolds number values ranged from 4 × 104 to 2 × 105 and a cone-trap aspect ratio of 1.75 was used to assess the trap sampling efficiency upon exposure to different current velocities.

  18. Seasonal sources of carbon to the Brazilian upwelling system

    Science.gov (United States)

    Coelho-Souza, Sergio A.; Pereira, Gilberto C.; Lopez, Maria S.; Guimaraes, Jean R. D.; Coutinho, Ricardo

    2017-07-01

    Environmental heterogeneity on coastal areas is an outcome of several hydrodynamic forces. Particularly, wind-driven upwelling is usually associated with alternating periods of water mixing and stratification. In addition, the effects of near shore oceanographic conditions may vary with coastline topography and anthropogenic impacts. Herein we evaluated the seasonal differences in the hydrodynamics of the Cabo Frio upwelling system (Brazil) in function of its local bay. Surface and deep water from 5 contrasting coastal areas were sampled 13 times during the spring/summer and in the fall/winter periods to use two-way Analysis of Variance comparing the measured variables in function of season and depth. Northeastern wind was predominant during both seasons but it was more intense during the spring/summer period when water temperature was colder and concentration of nutrients peaked. Southwestern wind was more common during the fall/winter period and was associated with cold fronts that decreased water salinity inner the bay. Consequently, the concentrations of nutrients, chlorophylls, prokaryotic secondary production (PSP) as well as fluorescent and non-fluorescent particles were significantly higher during the upwelling season while the concentration of particulate organic matter (POM) was highest during the non-upwelling season. Respectively, mean nitrate concentration varied from 2.2 to 0.9 μM, ammonium from 2.7 to 1.0 μM, chlorophyll a from 2.4 to 1.4 mg m-3, PSP from 1.8 to 1.0 μgC.L-1 h-1 and POM from 2.6 to 6.4 mg L-1. Contrasting surface and deep waters, mean nitrate concentration ranged from 0.9 to 2.2 μM, POM from 4.2 to 5.2 mg L-1 and PSP from 1.9 to 0.8 μgC.L-1 h-1. Three scenarios were identified: water stratification, upwelling and water homogenization. The first two scenarios were more common outside the bay during the upwelling season. When upwelling was intense, deep water temperature in the bay dropped to less than 20 °C resulting in the

  19. Seasonal, sub-seasonal and spatial fluctuations in oxygen-depleted bottom waters in an embayment of an eastern boundary upwelling system: St Helena Bay

    Science.gov (United States)

    Pitcher, G. C.; Probyn, T. A.

    2015-08-01

    The considerable impact of oxygen deficient waters on marine resources in St Helena Bay has generated interest in exploring the vulnerability of South Africa's largest and most productive bay to further deoxygenation in response to climate change. Seasonal, sub-seasonal and spatial fluctuations in bottom dissolved oxygen (DO) are examined in St Helena Bay to facilitate better interpretation of historical data. DO measurements in relation to physical, chemical and biological variables were made between November 2013 and November 2014. Alongshore bay characteristics were assessed through comparison of variables along the 50 m depth contour. A mean coefficient of variation of 0.35 provided a measure of the relative variability of near-bottom DO concentrations along this contour. Across-shelf transects captured the seasonal development of hypoxia in relation to the distribution of phytoplankton biomass. DO was lowest in autumn in the south of the bay prior to winter ventilation of the bottom waters. Exceptional dinoflagellate blooms forming extensive subsurface thin layers preceded the autumn DO minima. The development of hypoxia at inner and central stations prior to expansion beyond the boundaries of the bay provided evidence of local drawdown. Coincident with the seasonal decline of DO within the bay was an increase in macronutrient concentrations which tended to mirror DO concentrations. Indication of denitrification in the suboxic waters in the south of the bay was provided through evidence of a nitrate deficit in autumn supported by elevated nitrite concentrations. Superimposed on the seasonal decline of DO concentrations in the bottom waters were sub-seasonal events of hypoxia and anoxia linked to episodic deposition of organic matter as indicated by increases in bottom Chl a concentrations.

  20. A biophysical model applied to the Benguela upwelling system ...

    African Journals Online (AJOL)

    A three-dimensional biophysical model for the Benguela upwelling system is described. The model (NORWECOM) has been used in previous works to study model circulation, primary production and dispersion of particles (fish larvae and pollution) in the North Sea. The primary task of this work has been to validate its ...

  1. The physical oceanography of upwelling systems and the development of harmful algal blooms

    Science.gov (United States)

    Pitcher, G.C.; Figueiras, F.G.; Hickey, B.M.; Moita, M.T.

    2011-01-01

    The upwelling systems of the eastern boundaries of the world’s oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs. PMID:22053120

  2. The physical oceanography of upwelling systems and the development of harmful algal blooms

    Science.gov (United States)

    Pitcher, G. C.; Figueiras, F. G.; Hickey, B. M.; Moita, M. T.

    2010-04-01

    The upwelling systems of the eastern boundaries of the world’s oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs.

  3. Nutrient pumping by submesoscale circulations in the mauritanian upwelling system

    Science.gov (United States)

    Hosegood, P. J.; Nightingale, P. D.; Rees, A. P.; Widdicombe, C. E.; Woodward, E. M. S.; Clark, D. R.; Torres, R. J.

    2017-12-01

    Observations made within a cold filament in the Mauritanian upwelling system demonstrate that intense submesoscale circulations at the peripheral edges of the filament are likely responsible for anomalously high levels of observed primary productivity by resupplying nutrients to the euphotic zone. Measurements made on the shelf within the recently upwelled water reveal that primary production (PP) of 8.2 gC/m-2 day-1 was supported by nitrate concentrations (NC) of 8 mmol m-3. Towards the front that defined the edge of the filament containing the upwelled water as it was transported offshore, PP dropped to 1.6 gC m-2 day-1 whilst NC dropped to 5.5 mmol m-3. Thus, whilst the observed nutrients on the shelf accounted for 90% of new production, this value dropped to ∼60% near the filament's front after accounting for vertical turbulent fluxes and Ekman pumping. We demonstrate that the N15 was likely to have been supplied at the front by submesoscale circulations that were directly measured as intense vertical velocities ⩾100 m day-1 by a drifting acoustic Doppler current profiler that crossed a submesoscale surface temperature front. At the same time, a recently released tracer was subducted out of the mixed layer within 24 h of release, providing direct evidence that the frontal circulations were capable of accessing the reservoir of nutrients beneath the pycnocline. The susceptibility of the filament edge to submesoscale instabilities was demonstrated by O(1) Rossby numbers at horizontal scales of 1-10 km. The frontal circulations are consistent with instabilities arising from a wind-driven nonlinear Ekman buoyancy flux generated by the persistent northerly wind stress that has a down-front component at the northern edge of the inshore section of the filament. The prevalence of submesoscale instabilities and their associated vertical circulations are proposed to be a key mechanism operating at sub-grid scales and sustaining new production throughout the upwelling

  4. Oxygen cycling in the northern Benguela Upwelling System: Modelling oxygen sources and sinks

    Science.gov (United States)

    Schmidt, Martin; Eggert, Anja

    2016-12-01

    This paper elucidates the oxygen dynamics in the northern Benguela Upwelling System by means of process oriented, numerical modelling. Owing to the complex physical-biological interaction in this system, a coupled hydrodynamic-biogeochemical model is required to grasp the various aspects of the oxygen dynamics. We used high-resolution atmospheric fields derived from observations to force our model, available since 1999. The model results represent a 15 years, consistent data set of realistic hydrographic and ecosystem variables, including oxygen distribution patterns. After a concise description of the main aspects of the model, we use the model data to analyse the components contributing to the oxygen dynamics, namely, the ocean circulation, the exchange between ocean and atmosphere as well as the local biogeochemical oxygen cycling in the system. We thoroughly validate the model with available field observations and remote sensing data. The strengths of coastal upwelling, which controls the nutrient supply to the euphotic zone, as well as the poleward undercurrent that carries oxygen and nutrients to the shelf in the northern Benguela Upwelling System are well reproduced in the model. Among the biological oxygen sinks, mineralisation in the sediment, respiration of zooplankton and nitrification in the water column are important. We also found that vertical migration of zooplankton in response to the oxygen conditions provides a regulating feedback, which may prevent a complete deoxygenation of suboxic waters. As long as oxygen or nitrate are available in the bottom waters, the activities of chemolithoautotrophic sulphur bacteria on the sediment surface keep the redoxcline within the sediment and prevent the release of hydrogen sulphide into the water column. By horizontal integration of the simulated ocean-atmosphere oxygen flux, it can be shown that the Kunene upwelling cell between 16 ° S and 18 ° S is a boundary between the equatorial ocean, characterise by

  5. The influence of summer upwelling at the western boundary of the Cantabrian coast

    Science.gov (United States)

    Prego, R.; Varela, M.; deCastro, M.; Ospina-Alvarez, N.; Garcia-Soto, C.; Gómez-Gesteira, M.

    2012-02-01

    Recent characterizations of atmospheric conditions favorable to upwelling events in the Western Cantabrian Sea have stressed the need to analyze the significance of the orientation of the coast on the phenomenon of upwelling. Surface-wind fields for the northwestern Galician marine area were provided by the QuikSCAT satellite and an SST map was elaborated using the NASA GHRSST satellite data. A cruise was conducted aboard the RV Lura in June 2009 during northern prevailing winds. Data of thermohaline variables, concentration of dissolved oxygen, dissolved inorganic nitrogen, chlorophyll, dissolved and particulate organic carbon and nitrogen and phytoplankton abundances were obtained. When the upwelling developed west of the Cape Ortegal was strong, the Eastern North Atlantic Central Water mixed with coastal water eastward of the Cape and the upwelled seawater reached the westernmost of the Northern Galician Rias, the Ria of Ortigueira. Incoming seawater was poor in nitrate and chlorophyll concentrations when compared to that of the upwelling events in the Western Galician Rias. The phytoplankton assemblages were typical of summer upwelling blooms in the latter Rias but phytoplankton biomass was lower in the Ria of Ortigueira and the species were indicatives of initial (inner ria under continental influence) and advanced (outer ria under upwelling inputs) stages of phytoplankton succession. The observed process arose when the upwelling edge-zone reaches a change of coastal orientation as may also occur in other upwelling regions.

  6. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-02-28

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from jets characteristic of pulse jet mixers (PJMs) has been analyzed, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell break through? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored.

  7. Iron, nutrient and phytoplankton biomass relationships in upwelled waters of the California coastal system

    Science.gov (United States)

    Fitzwater, Steve E.; Johnson, Kenneth S.; Elrod, Virginia A.; Ryan, John P.; Coletti, Luke J.; Tanner, Sara J.; Gordon, R. Michael; Chavez, Francisco P.

    2003-10-01

    We report measurements of dissolvable and particulate iron, particulate Al, nutrients and phytoplankton biomass in surface waters during the termination of one upwelling event and the initiation of a second event in August 2000. These events occurred in the area of the Año Nuevo upwelling center off the coast of central California. The first event was observed after ˜8 days of continuous upwelling favorable winds, while the second event was observed through the onset of upwelling favorable winds to wind reversals ˜3 days later. Coincident with the upwelling signatures of low temperature and high salinity were significantly elevated concentrations of nitrate and silicate with average concentrations greater than 15 and 20 μM, respectively, during both upwelling events. Dissolvable Fe concentrations (TD-Fe) were significantly higher in the second event, 6.5 versus 1.2 nM Fe found in the first event. Nitrate was reduced by ˜5 μM day -1 within this second upwelled plume as compared to a drawdown of ˜2 μM day -1 within the first plume. Silicate was reduced in a ratio of 1.2 mol Si:mol NO 3 in the high Fe waters of the second plume as compared to a ratio of 2.2 in the lower Fe waters of the first plume. The observed differences in nutrient utilization are consistent with some degree of iron limitation. The area of increased dissolvable Fe in the second upwelling event was coincident with elevated particulate Fe concentrations, indicating the particulate pool as a possible source of the observed increase in TD-Fe. The elevated particulate Fe in surface waters was a result of resuspended sediments in the bottom boundary layer (BBL) of the shallow shelf being transported to the surface during upwelling. Particulate (and dissolvable) iron concentrations were significantly reduced as upwelling continued. This was most probably due to a decoupling of the BBL from upwelled source waters as the upwelling front moved offshore and/or reduced turbulence in the BBL as

  8. Defining seascapes for marine unconsolidated shelf sediments in an eastern boundary upwelling region: The southern Benguela as a case study

    Science.gov (United States)

    Karenyi, Natasha; Sink, Kerry; Nel, Ronel

    2016-02-01

    Marine unconsolidated sediment habitats, the largest benthic ecosystem, are considered physically controlled ecosystems driven by a number of local physical processes. Depth and sediment type are recognised key drivers of these ecosystems. Seascape (i.e., marine landscape) habitat classifications are based solely on consistent geophysical features and provide an opportunity to define unconsolidated sediment habitats based on processes which may vary in distribution through space and time. This paper aimed to classify unconsolidated sediment seascapes and explore their diversity in an eastern boundary upwelling region at the macro-scale, using the South African west coast as a case study. Physical variables such as sediment grain size, depth and upwelling-related variables (i.e., maximum chlorophyll concentration, austral summer bottom oxygen concentration and sediment organic carbon content) were included in the analyses. These variables were directly measured through sampling, or collated from existing databases and the literature. These data were analysed using multivariate Cluster, Principal Components Ordination and SIMPER analyses (in PRIMER 6 + with PERMANOVA add-in package). There were four main findings; (i) eight seascapes were identified for the South African west coast based on depth, slope, sediment grain size and upwelling-related variables, (ii) three depth zones were distinguished (inner, middle and outer shelf), (iii) seascape diversity in the inner and middle shelves was greater than the outer shelf, and (iv) upwelling-related variables were responsible for the habitat diversity in both inner and middle shelves. This research demonstrates that the inclusion of productivity and its related variables, such as hypoxia and sedimentary organic carbon, in seascape classifications will enhance the ability to distinguish seascapes on continental shelves, where productivity is most variable.

  9. Nutrient supply, surface currents, and plankton dynamics predict zooplankton hotspots in coastal upwelling systems

    Science.gov (United States)

    Messié, Monique; Chavez, Francisco P.

    2017-09-01

    A simple combination of wind-driven nutrient upwelling, surface currents, and plankton growth/grazing equations generates zooplankton patchiness and hotspots in coastal upwelling regions. Starting with an initial input of nitrate from coastal upwelling, growth and grazing equations evolve phytoplankton and zooplankton over time and space following surface currents. The model simulates the transition from coastal (large phytoplankton, e.g., diatoms) to offshore (picophytoplankton and microzooplankton) communities, and in between generates a large zooplankton maximum. The method was applied to four major upwelling systems (California, Peru, Northwest Africa, and Benguela) using latitudinal estimates of wind-driven nitrate supply and satellite-based surface currents. The resulting zooplankton simulations are patchy in nature; areas of high concentrations coincide with previously documented copepod and krill hotspots. The exercise highlights the importance of the upwelling process and surface currents in shaping plankton communities.

  10. Constraining trace metal paleo-proxies for black shale deposition in upwelling systems: the Benguela upwelling system offshore Namibia

    Science.gov (United States)

    Cofrancesco, J.; Riedinger, N.; Owens, J. D.

    2016-12-01

    Geochemical trace metal paleo-proxies are powerful tools for reconstructing the depositional environment of black shales. However, not all relationships and environmental conditions have been well-studied as discrepancies remain between geochemical and sedimentological proxies. While there are numerous proxies for understanding endmember redox conditions there is still a significant gap in regards to constraining oxygen minimum zones (OMZ) in ancient settings, for instance Devonian epeiric sea black shale deposits. This study aims to explore the application of geochemical and sedimentological proxies on a modern marginal marine setting - the Benguela upwelling system, offshore Namibia. This region is a modern analogue to ancient black shale formation. In this upwelling system the lateral transport of the shelf mudbelt's organic-rich sediments, deposited under anoxic (sulfidic) bottom waters, are being re-deposited under the oxygen-rich water column of the upper slope, resulting in a secondary transported organic carbon depocenter. To assess the geochemical inventory of these two different areas of organic carbon preservation, we obtained a transect of sediment cores along the shelf and slope, via the R/V MIRABILIS as a part of the 2015 Regional Graduate Network in Oceanography (RGNO) program in Namibia. The core sites were strategically sited in areas of differing water depth and redox conditions to capture a range of trace metal enrichments and organic carbon inventory. Sediments were analyzed for major elements, iron phases, and grain-size distribution. Trace metals were analyzed in the bottom water, pore water, and surface sediments. Results showed a large enrichment variation for several redox sensitive trace metals. Overall, the trace metals follow the expected trend for redox proxies, with highest enrichment in the sediments below the anoxic bottom waters. Interestingly though, some redox sensitive metals show higher enrichment in the bioturbated, mildly

  11. Seasonality of coastal upwelling trends under future warming scenarios along the southern limit of the canary upwelling system

    Science.gov (United States)

    Sousa, Magda Catarina; Alvarez, Ines; deCastro, Maite; Gomez-Gesteira, Moncho; Dias, João Miguel

    2017-04-01

    The Canary Upwelling Ecosystem (CUE) is one of the four most important upwelling sites around the world in terms of primary production, with coastal upwelling mostly a year-round phenomenon south of 30°N. Based on annual future projections, several previous studies indicated that global warming will intensify coastal upwelling in the northern region and will induce its weakening at the southernmost latitudes. However, analysis of historical data, showed that coastal upwelling depends on the length of the time series, the season, and even the database used. Thus, despite previous efforts, an overall detailed description of seasonal upwelling trends and their effects on sea surface temperature (SST) along the Canary coast over the 21st century remains unclear. To address this issue, several regional and global wind and SST climate models from CORDEX and CMIP5 projects for the period 1976-2099 were analyzed. This research provides new insights about coastal upwelling trends under future warming scenarios for the CUE, with results showing opposite patterns for upwelling index (UI) trends depending on the season. A weakening of the UI occurs from May to August all along the coast, whereas it increases from October to April. Analysis of SST trends reveals a general warming throughout the area, although the warming rate is considerably lower near the shore than at open ocean locations due to coastal upwelling effects. In addition, SST projections show higher warming rates from May to August than from October to April in response to the future decreasing trend in the UI during the summer months.

  12. Trends in the number of extreme hot SST days along the Canary Upwelling System due to the influence of upwelling

    Directory of Open Access Journals (Sweden)

    Xurxo Costoya

    2014-07-01

    Full Text Available Trends in the number of extreme hot days (days with SST anomalies higher than the 95% percentile were analyzed along the Canary Upwelling Ecosystem (CUE over the period 1982- 2012 by means of SST data retrieved from NOAA OI1/4 Degree. The analysis will focus on the Atlantic Iberian sector and the Moroccan sub- region where upwelling is seasonal (spring and summer are permanent, respectively. Trends were analyzed both near coast and at the adjacent ocean where the increase in the number of extreme hot days is higher. Changes are clear at annual scale with an increment of 9.8±0.3 (9.7±0.1 days dec-1 near coast and 11.6±0.2 (13.5±0.1 days dec-1 at the ocean in the Atlantic Iberian sector (Moroccan sub-region. The differences between near shore and ocean trends are especially patent for the months under intense upwelling conditions. During that upwelling season the highest differences in the excess of extreme hot days between coastal and ocean locations (Δn(#days dec-1 occur at those regions where coastal upwelling increase is high. Actually, Δn and upwelling trends have shown to be significantly correlated in both areas, R=0.88 (p<0.01 at the Atlantic Iberian sector and R=0.67 (p<0.01 at the Moroccan sub-region.

  13. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from pulse jet mixers (PJMs) has been analyzed in some detail, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell breakthrough? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored. The central upwell must satisfy several criteria to be considered a free jet. First, it must travel for several diameters in a nearly constant direction. Second, its velocity must decay with the inverse of elevation. Third, it should have an approximately Gaussian profile. Fourth, the influence of surface or body forces must be negligible. A combination of historical data in a 12.75 ft test vessel, newly analyzed data from the 8 ft test vessel, and conservation of momentum arguments derived specifically for PJM operating conditions demonstrate that the central upwell satisfies these criteria where vigorous breakthrough is achieved. An essential feature of scaling from one vessel to the next is the requirement that the underlying physics does not change adversely. One may have confidence in scaling if (1) correlations and formulas capture the relevant physics; (2) the underlying physics does not change from the conditions under which it was developed to the conditions of interest; (3) all factors relevant to scaling have been incorporated, including flow, material, and geometric considerations; and (4) the uncertainty in the relationships is sufficiently narrow to meet required specifications. Although the central upwell

  14. A Lagrangian study tracing water parcel origins in the Canary Upwelling System

    Directory of Open Access Journals (Sweden)

    Evan Mason

    2012-08-01

    Full Text Available The regional ocean circulation within the Canary Upwelling System between 31°N and 35°N is studied using numerical tools. Seasonal mean and near-instantaneous velocity fields from a previously-generated climatological Regional Ocean Modelling System (ROMS solution of the Canary Basin are used to force a series of offline Lagrangian particle-tracking experiments. The primary objective is to identify the pathways through which water parcels arrive at the upwelling region north of Cape Ghir. Examining year-long pathways, the Azores Current contributes over 80% of particles annually, of which a large proportion arrive directly from offshore (from the northwest, while others travel along the shelf and slope from the Gulf of Cadiz. The remaining ~20% originate within the Gulf of Cadiz or come from the south, although the southern contribution is only significant in autumn and winter. When season-long pathways are considered, the alongshore contributions become increasingly important: northern contributions reach 40% in spring and summer, while southern values exceed 35% in winter. This study also shows that coastal upwelling changes both spatially and temporally. Upwelling becomes intensified near Cape Beddouza, with most upwelling occurring within ~40 km from shore although significant values may reach as far as 120 km offshore north of Cape Beddouza; at these locations the offshore integrated upwelling reaches as much as 4 times the offshore Ekman transport. In the Cape Beddouza area (32°N to 33°N, upwelling is negligible in February but intensifies in autumn, reaching as much as 3 times the offshore Ekman transport.

  15. High silicate:nitrate ratios in eastern boundary upwelling waters may produce greater carbon drawdown than predicted from Redfield C:N ratios

    Science.gov (United States)

    Dugdale, R. C.; Fuller, J. R.; Marchi, A.; Parker, A. E.; Wilkerson, F. P.

    2010-12-01

    The Redfield ratio defines the average ratio of changes in major nutrient concentrations during primary production as 106:16:1, C:N:P. This ratio and the phytoplankton uptake or drawdown of nitrate (new production in the ocean) are often used to estimate carbon production and export of carbon to the deep ocean. Elevated nitrate in upwelled water is rapidly drawn down by diatoms, usually within 3-5 days and the assumption is that carbon drawdown ceases at that end of that time. However, in large-volume enclosure experiments using silicate-rich San Francisco Bay water, silicate drawdown continued well after nitrate was exhausted by phytoplankton growth. Enclosure experiments made with water upwelled at Point. Reyes, northern California followed the same pattern of silicate drawdown continuing past nitrate exhaustion. Dissolved inorganic carbon (DIC) drawdown tracked silicate drawdown after nitrate exhaustion; i.e. the DIC drawdown followed more closely the drawdown of silicate than nitrate. The drawdown of DIC calculated from nitrate drawdown using Redfield resulted in an underestimate of the measured DIC disappearance. In upwelling waters with Si:N ratios of greater than l, the uptake of DIC may be substantially underestimated. The implication of these preliminary results is that coastal upwelling in basins rich in silicate, e.g. in the North Pacific, may account for substantially more drawdown of CO2 than would be calculated from upwelled nitrate concentrations. In eastern boundary upwelling areas, a modification of the Redfield ratio to incorporate C:Si is necessary since these areas are dominated by diatoms. Victor Smetacek’s designation of diatoms as the "workhorses of the sea" becomes more appropriate than ever. Their obligate requirement for Si to construct their frustules makes them responsible for this re-interpretation of estimating carbon drawdown using the Redfield ratio. In these circumstances we may better define new production in terms of silicate

  16. Microbial diversity of a Brazilian coastal region influenced by an upwelling system and anthropogenic activity.

    Directory of Open Access Journals (Sweden)

    Juliano C Cury

    Full Text Available BACKGROUND: Upwelling systems are characterised by an intense primary biomass production in the surface (warmest water after the outcrop of the bottom (coldest water, which is rich in nutrients. Although it is known that the microbial assemblage plays an important role in the food chain of marine systems and that the upwelling systems that occur in southwest Brazil drive the complex dynamics of the food chain, little is known about the microbial composition present in this region. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a molecular survey based on SSU rRNA gene from the three domains of the phylogenetic tree of life present in a tropical upwelling region (Arraial do Cabo, Rio de Janeiro, Brazil. The aim was to analyse the horizontal and vertical variations of the microbial composition in two geographically close areas influenced by anthropogenic activity (sewage disposal/port activity and upwelling phenomena, respectively. A lower estimated diversity of microorganisms of the three domains of the phylogenetic tree of life was found in the water of the area influenced by anthropogenic activity compared to the area influenced by upwelling phenomena. We observed a heterogenic distribution of the relative abundance of taxonomic groups, especially in the Archaea and Eukarya domains. The bacterial community was dominated by Proteobacteria, Cyanobacteria and Bacteroidetes phyla, whereas the microeukaryotic community was dominated by Metazoa, Fungi, Alveolata and Stramenopile. The estimated archaeal diversity was the lowest of the three domains and was dominated by uncharacterised marine Crenarchaeota that were most closely related to Marine Group I. CONCLUSIONS/SIGNIFICANCE: The variety of conditions and the presence of different microbial assemblages indicated that the area of Arraial do Cabo can be used as a model for detailed studies that contemplate the correlation between pollution-indicating parameters and the depletion of microbial

  17. The significance of nitrogen regeneration for new production within a filament of the Mauritanian upwelling system

    Science.gov (United States)

    Clark, Darren R.; Widdicombe, Claire E.; Rees, Andrew P.; Woodward, E. Malcolm S.

    2016-05-01

    The Lagrangian progression of a biological community was followed in a filament of the Mauritanian upwelling system, north-west Africa, during offshore advection. The inert dual tracers sulfur hexafluoride and helium-3 labelled a freshly upwelled patch of water that was mapped for 8 days. Changes in biological, physical, and chemical characteristics were measured, including phytoplankton productivity, nitrogen assimilation, and regeneration. Freshly upwelled water contained high nutrient concentrations but was depleted in N compared to Redfield stoichiometry. The highest rate of primary productivity was measured on the continental shelf, associated with high rates of nitrogen assimilation and a phytoplankton community dominated by diatoms and flagellates. Indicators of phytoplankton abundance and activity decreased as the labelled water mass transited the continental shelf slope into deeper water, possibly linked to the mixed layer depth exceeding the light penetration depth. By the end of the study, the primary productivity rate decreased and was associated with lower rates of nitrogen assimilation and lower nutrient concentrations. Nitrogen regeneration and assimilation took place simultaneously. Results highlighted the importance of regenerated NH4+ in sustaining phytoplankton productivity and indicate that the upwelled NO3- pool contained an increasing fraction of regenerated NO3- as it advected offshore. By calculating this fraction and incorporating it into an f ratio formulation, we estimated that of the 12.38 Tg C of annual regional production, 4.73 Tg C was exportable.

  18. Climate change in the Iberian Upwelling System: a numerical study using GCM downscaling

    Science.gov (United States)

    Cordeiro Pires, Ana; Nolasco, Rita; Rocha, Alfredo; Ramos, Alexandre M.; Dubert, Jesus

    2016-07-01

    The present work aims at evaluating the impacts of a climate change scenario on the hydrography and dynamics of the Iberian Upwelling System. Using regional ocean model configurations, the study domain is forced with three different sets of surface fields: a climatological dataset to provide the control run; a dataset obtained from averaging several global climate models (GCM) that integrate the Intergovernmental Panel for Climate Change (IPCC) models used in climate scenarios, for the same period as the climatological dataset; and this same dataset but for a future period, retrieved from the IPCC A2 climate scenario. After ascertaining that the ocean run forced with the GCM dataset for the present compared reasonably well with the climatologically forced run, the results for the future run (relative to the respective present run) show a general temperature increase (from +0.5 to +3 °C) and salinity decrease (from -0.1 to -0.3), particularly in the upper 100-200 m, although these differences depend strongly on season and distance to the coast. There is also strengthening of the SST cross-shore gradient associated to upwelling, which causes narrowing and shallowing of the upwelling jet. This effect is contrary to the meridional wind stress intensification that is also observed, which would tend to strengthen the upwelling jet.

  19. Spatial characteristics of sediment trace metals in an eastern boundary upwelling retention area (St. Helena Bay, South Africa): A hydrodynamic-biological pump hypothesis

    CSIR Research Space (South Africa)

    Monteiro, PMS

    2005-10-01

    Full Text Available St. Helena Bay, is a retention zone located in the southern Benguela upwelling system, and is an important fish nursery. However, it suffers from seasonal bottom water hypoxia causing major economic losses. Anoxic conditions are linked to sulfide...

  20. Contrasting biogeochemical responses of ENSO induced upwelling variability in the Humboldt Current System

    Science.gov (United States)

    Franco, Ana C.; Gruber, Nicolas; Münnich, Matthias

    2017-04-01

    The Humboldt Current System (HCS) is one of the most productive ecosystems in the world. This high productivity is supported by a large input of nutrients from the subsurface layers to the surface due to year-round upwelling. However, upwelling also supplies waters with low pH and low aragonite saturation state potentially affecting many organisms, especially those that calcify. The influence, extent and source of upwelled water vary substantially on interannual timescales in association with the El Niño/Southern Oscillation (ENSO) phenomenon, generating natural contrasting responses on the biogeochemistry of this system. Here we analyze these responses using an eddy resolving, basin-scale ocean model that covers the whole Pacific Ocean with high resolution (4 km) on the west coast of South America. We performed a simulation of the last 30 years (hindcast simulation) that allows us to investigate the influence of at least eight El Niño episodes and eight La Niña episodes on productivity variations and changes in oxygen concentration and aragonite saturation state. An absolute change in surface omega aragonite of almost 2 units, as well as an absolute change of the aragonite saturation depth of 200 m result from the change of an El Niño phase to a La Niña phase. This variability is on the same order of magnitude as the projected change in the aragonite saturation state in a centennial timescale. During La Niña events, a lower aragonite saturation state values and reduced oxygen concentration in the surface layer are a direct consequence of enhanced upwelling and increased net primary productivity. The opposite is true during El Niño events, where high values of omega aragonite occur in concordance with extraordinarily low net primary productivity values.

  1. Variability in the Benguela Current upwelling system over the past 70,000 years

    Science.gov (United States)

    Summerhayes, C. P.; Kroon, D.; Rosell-Melé, A.; Jordan, R. W.; Schrader, H.-J.; Hearn, R.; Villanueva, J.; Grimalt, J. O.; Eglinton, G.

    This study was designed to see if the intensity and location of upwelling in the Benguela Current Upwelling System off Namibia changed significantly during the last 70,000 years. Most of the analytical work focused on geochemical, micropalaeontological and stable isotopic analyses of a 6.5m long combined pilot and piston core, PGPC12, from 1017m on the continental slope close to Walvis Bay. The slope sediments are rich in organic matter. Most of it is thought to represent deposition beneath a productive shelf edge upwelling system, but some is supplied by downslope nearbottom flow of material probably resuspended on the outer continental shelf. Temporal changes in upwelling intensity as represented by fluctuations in the accumulation of organic matter do not show the simple ‘classical’ pattern of less upwelling and lower productivity in interglacials and more upwelling and higher productivity in glacials, but instead show a pattern of higher frequency fluctuations. The broad changes in organic carbon accumulation reach maxima at times when the earth-sun distance was greatest, indicating that this accumulation responded to changes in the precession index; at these times monsoons would have been weakest and Trade Winds strongest. Maximum accumulation of organic matter on the slope occurred in the last interstadial (isotope stage 3), and coincided with coldest sea surface temperatures as recorded by alkenone data (U k37), and by nannofossil assemblages. It is attributed largely to increased productivity in situ, rather than the lateral supply of material eroded from older organic rich deposits exposed by the lowering of sealevel at that time. The enhanced productivity is attributed to a strengthening of upwelling-favourable winds in this area in response to the minimal solar insolation typical of this period. Diatoms generally are not abundant in these sediments, so appear to be unreliable indicators of productivity over the continental slope. When sealevel was

  2. Contrasting energy allocation strategies of two sympatric Merluccius species in an upwelling system.

    Science.gov (United States)

    Rey, J; Fernandez-Peralta, L; Quintanilla, L F; Hidalgo, M; Presas, C; Salmeron, F; Puerto, M A

    2015-03-01

    This study investigated the somatic growth and energy allocation strategy of two sympatric hake species (Merluccius polli and Merluccius senegalensis), coexisting under the strong influence of the Mauritanian upwelling. The results revealed that ontogeny, bathymetry, geography and reproduction shaped the differences found between the condition dynamics of the two species. Aside from species-specific differences, individuals were observed in better condition in the northernmost area (more influenced by the permanent upwelling) and in the deepest waters, probably the most favourable habitat for Merluccius spp. Both species also displayed contrasting trade-offs in energy allocation probably due to the dissimilarity of their habitats, which favours the existence of divergent adaptive strategies in response to different ontogenic requirements. It was hypothesized that M. polli invests in mass and energy reserves while sacrificing growth, as larger sizes may not provide an ecological advantage in a deeper and more stable environment. Moreover, M. senegalensis capitalizes on a steady growth without major disruptions, enabling earlier spawning at the expense of a lower somatic mass, which is fitting to a less stable shallower environment. This study sheds new light on differences in the biological traits and life strategies of Merluccius spp., which permit their overlap in a complex upwelling system and may contribute to the long-lasting scientific-based management of these species. © 2015 The Fisheries Society of the British Isles.

  3. Development of a marsh-based upwelling injection system to treat domestic wastewater from coastal dwellings

    Energy Technology Data Exchange (ETDEWEB)

    Rusch, K.A.; Jones, S.C.

    1999-07-01

    The objective of this study was the design, construction and evaluation of a natural, marsh-based system using a sand/soil bed in a shallow upwelling field to remove fecal coliforms from coastal dwelling wastewater. Wastewater was injected at a 15 foot depth and movement of the wastewater was monitored with wells at 5, 10, and 15 foot depths. Monitoring salinity showed development of an extensive fresh water plume at the 5 foot depth, less at the 10 foot and none at the 15 foot depth; the system effectively reduced the fecal coliform concentrations to <1 colony per 100 mL as the wastewater traveled through the soil.

  4. Ocean variability over the Agulhas Bank and its dynamical connection with the southern Benguela upwelling system

    CSIR Research Space (South Africa)

    Blanke, B

    2009-12-01

    Full Text Available and interannual variability. We put the stress on wind forcing since the seasonal and interannual variability of the Benguela upwelling system depends significantly on wind variability [Blanke et al., 2002, 2005], with the appearance of subsequent SST...-resolution child model is designed to encompass the Agulhas Bank and its surroundings and has a temporal and spatial resolution three times finer than the parent grid (approximately 15 min and 8 km, respec- tively). The child model has 233 � 185 grid points...

  5. Holocene Evolution of two Upwelling Systems - Offshore Northern California and the Central Gulf of California

    Science.gov (United States)

    Barron, J. A.; Bischoff, J. L.; Bukry, D.; Heusser, L.; Herbert, T. D.; Lyle, M.

    2002-12-01

    High resolution records from offshore northern California \\(ODP 1019\\) and the central Gulf of California \\(DSDP 480 and BAM80 E17\\) reveal both similarities and differences in the Holocene evolution of these upwelling systems. Common themes include: 1\\ ) an earlier Holocene period \\(11.6-8.2 ka\\) with relatively high calcium carbonate deposition, probably reflecting a maximum in summer insolation; 2\\ ) increasing diatom deposition during the middle and late Holocene, likely signaling an intensification of seasonal northwest winds; and 3\\ ) the onset of modern oceanic conditions between 3.5 and 3.2 ka, possibly associated with the expression of increasing ENSO variability. At ODP 1019 off northern California, cooler alkenone-based SST's and the rarity of the subtropical-diatom Pseudoeunotia doliolus suggest that the California Current was rather broad during the middle part of the Holocene \\(ca. 8.2-3.2 ka\\), perhaps similar to the conditions that exist during a modern La Niña. Decreasing wt. % CaCO3 relatively low, but increasing wt. % organic C, and low to moderate estimated opal content typify this middle Holocene interval. Beginning at 5.2 ka, increasing coastal redwood pollen is evidence that coastal fog and coastal upwelling were becoming more important. Subsequently, at ca. 3.5 ka, a doubling of estimated opal coupled with increased coastal redwood pollen suggests a further enhancement of seasonal coastal upwelling. At about the same time \\(ca. 3.2 ka\\), a sustained ca. 1 deg. C increase in alkenone SST and 3-fold increase in P. doliolus imply warming of fall and winter SST's. An enhancement of the interannual variability of surface water conditions at this time is probably associated with an increasing expression of ENSO variability. In the central Gulf of California between ca. 11.0 and 8.2 ka, biosilica production was generally low compared to that of the latest Holocene, suggesting that wintertime NW winds were relatively weak. Stepwise

  6. Recognition of boundary feedback systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1989-01-01

    A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback...... stabilizability. It is shown that it is possible to use the calculus to consider more general feedback systems in a variational setup....

  7. Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

    Science.gov (United States)

    Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel

    2017-04-01

    Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg

  8. Dynamics of oxygen depletion in the nearshore of a coastal embayment of the southern Benguela upwelling system

    CSIR Research Space (South Africa)

    Pitcher, GC

    2014-04-01

    Full Text Available Acquisition of high resolution time series of water column and bottom dissolved oxygen (DO) concentrations inform the dynamics of oxygen depletion in St Helena Bay in the southern Benguela upwelling system at several scales of variability. The bay...

  9. A model-based insight into the coupling of nitrogen and sulfur cycles in a coastal upwelling system

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar; Canfield, Donald Eugene; Fennel, Katja

    2014-01-01

    The biogeochemical cycling in oxygen-minimum zones (OMZs) is dominated by the interactions of microbial nitrogen transformations and, as recently observed in the Chilean upwelling system, also through the energetically less favorable remineralization of sulfate reduction. The latter process is ma...

  10. Sources of short-lived bromocarbons in the Iberian upwelling system

    Directory of Open Access Journals (Sweden)

    S. Raimund

    2011-06-01

    Full Text Available Seawater concentrations of the four brominated trace gases, dibromomethane (CH2Br2, bromodichloromethane (CHBrCl2, dibromochloromethane (CHBr2Cl and bromoform (CHBr3 were measured at different depths of the water column in the Iberian upwelling off Portugal during summer 2007. Statistical analysis of the data set revealed three distinct clusters, caused by different sea surface temperature. Bromocarbon concentrations were elevated in recently upwelled and aged upwelled waters (mean values of 30 pmol l−1 for CHBr3, while concentrations in the open ocean were significantly lower (7.4 pmol l−1 for CHBr3. Comparison with other productive marine areas revealed that the Iberian upwelling had higher halocarbon concentrations than the Mauritanian upwelling. However, the concentrations off the Iberian Peninsula were still much lower than those of coastal macroalgal-influenced waters or those of Polar regions dominated by cold water adapted diatoms. Correlations with biological variables and marker pigments indicated that phytoplankton was a source of bromocarbon in the open ocean. By contrast, in upwelled water masses along the coast, halocarbons showed weaker correlations to marker pigments but were significantly influenced by the tidal frequency. Our results indicate a strong intertidal coastal source of bromocarbon and transport by surface currents of these enriched waters towards the upwelling region.

  11. Inorganic carbon dynamics in the upwelling system off the Oregon coast and implications for commercial shellfish hatcheries

    Science.gov (United States)

    Vance, J. M.; Hales, B. R.

    2010-12-01

    The increasing absorption of anthropogenic CO2 by the global ocean and concomitant decrease in pH will alter seawater carbonate chemistry in ways that may negatively impact calcifying organisms. In particular, the change in saturation state (Ω) of calcium carbonate minerals calcite and aragonite may be energetically unfavorable for shell formation while favoring shell dissolution. Eastern boundary upwelling systems may provide insights into how ecosystems respond to future conditions of ocean acidification when deep water with high dissolved inorganic carbon (DIC), low pH and low Ω is forced toward the surface. Mortality in commercial seed stock and reduced wild set of the oyster Crassostrea gigas in the northeast Pacific during 2005-2009 reinforced the need for understanding biological responses to acidified ocean water. In response, a long-term strategy to understand local carbonate chemistry dynamics, seasonal perturbations and the effects on development of calcifying bivalves was developed. At present, a time-series of pCO2 measurements was implemented in April 2010 in Netarts Bay, Oregon at Whiskey Creek Shellfish Hatchery (WCH). The intake sits at a depth of 0.5-8ft and water is pumped in at 100gpm. A line taken off the intake is run continuously through a thermosalinograph at approximately 1.5gpm into a showerhead style equilibrator in which the headspace is recirculated by aerating the water for enhanced gas exchange. CO2 in equilibrated air is analyzed by NDIR. Additionally two discrete samples of intake seawater were taken across tidal cycles weekly and analyzed for total CO2 (TCO2) according to the methods of Hales et al. (2004) and pCO2 for quality control. The pCO2 in the bay exhibits a diurnal cycle representative of daytime photosynthesis and nighttime respiration. However, the phasing and profiles of these cycles are dominated by tidal mixing and are affected by the introduction of high pCO2 water during upwelling events. Diurnal pCO2 during

  12. Influence of upwelling on distribution of chaetognath (zooplankton) in the oxygen deficient zone of the eastern Arabian Sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Kusum, K.K.; Vineetha, G.; Raveendran, T.V.; Muraleedharan, K.R.; Biju, A.; Achuthankutty, C.T.

    process. Our observation suggests that the temporal physical event (upwelling) plays a decisive role in the heterogeneity of the spatial abundance, community composition and diversity of chaetognaths in this least studied eastern boundary current system....

  13. Primary production and nitrogen regeneration processes in surface waters of the Peruvian upwelling system

    Science.gov (United States)

    Fernández, C.; Farías, L.; Alcaman, M. E.

    2009-12-01

    Tracer experiments ( 15N and 13C) were carried out off the Peruvian upwelling system in order to evaluate the potential role of regenerated nitrogen in sustaining biological productivity in surface waters (0-15 m depth range). Rates of daily carbon uptake in surface waters showed values ranging between 6 and 200 mg C m -3 d -1. Maximum integrated rates were obtained in northern Peru (up to 5.5 g m -2 d -1). Parallel measurements of nitrogen uptake showed a stronger utilization of ammonium compared to nitrate at all stations, with surface ammonium uptake values reaching up to 0.15 μmol N L -1 d -1. Ammonium was also actively regenerated in surface waters, at rates as high as 0.5 μmol N L -1 d -1, whereas ammonium oxidation to nitrate (nitrification) occurred at lower rates (sustain a fraction of the observed photoautotrophic carbon fixation. The contribution of nitrogen regenerating processes to primary production in terms of DIN could represent as much as 50% of NH 4 assimilated in surface waters (through ammonium regeneration) as well as a variable fraction (2-16%) of nitrate through nitrification.

  14. Optimal boundary control and boundary stabilization of hyperbolic systems

    CERN Document Server

    Gugat, Martin

    2015-01-01

    This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary.  The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization.  Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples.  To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled.  Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.

  15. Particle Fluxes and Bulk Geochemical Characterization of the Cabo Frio Upwelling System in Southeastern Brazil: Sediment Trap Experiments between Spring 2010 and Summer 2012

    Directory of Open Access Journals (Sweden)

    ANA LUIZA S. ALBUQUERQUE

    2014-06-01

    Full Text Available Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis during its trajectory to the shelf edge.

  16. Offshore expansion of the Brazilian coastal upwelling zones during Marine Isotope Stage 5

    Science.gov (United States)

    Lessa, Douglas V. O.; Santos, Thiago P.; Venancio, Igor M.; Albuquerque, Ana Luiza S.

    2017-11-01

    Paleoceanographic reconstructions in upwelling regions can provide relevant information about changes in primary productivity, ocean-atmosphere interactions and the carbon budget. Here, we assessed new data on planktonic foraminifera from a sediment core located near to coastal upwelling zones along the Brazilian coast. Our new data was combined with previous records to reveal the state of upwelling systems along the western South Atlantic margin throughout the last two deglacial and interglacial periods sensu lato. Despite the contemporary oligotrophic scenario of the Santos Basin, a remarkably high relative abundance of Globigerina bulloides and low temperatures at a depth of 100 m indicated upwelling conditions similar to current shelf upwelling zones from 130 to 90 kyr BP. Comparing these results with previous studies, we argue that Brazilian shelf upwelling zones expanded offshore between 20 and 28°S. We develop two conceptual scenarios to characterize the system: (1) during Marine Isotopic Stage (MIS 5), the system expanded along the continental margin between 20 and 28°S following the eccentricity maximum; and (2) after 20 kyr BP, the system retracted to current continental shelf zones. We propose a new mechanism whereby variation of the Earth's eccentricity, which drives seasonality, is the main factor controlling expansion or retraction of the Brazilian upwelling system. Absence of such conditions in more recent periods supports our model and indicates that current upwelling zones are the remnants of a larger upwelling system. However, more studies are required to better define the latitudinal boundaries of the Brazilian upwelling system in the past and its possible influences over the regional carbon budget.

  17. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    Directory of Open Access Journals (Sweden)

    Katherine Rose Marie Mackey

    2014-11-01

    Full Text Available Coastal California is a dynamic upwelling region where nitrogen (N and iron (Fe can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13-30 M in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts.

  18. Changes of coastal upwelling systems in the Atlantic, Indian and Pacific oceans recorded from alkenone-derived sea surface temperatures and other multiproxy information

    Science.gov (United States)

    El Ouahabi, Anuar; Martrat, Belen; Lopez, Jordi F.; Grimalt, Joan O.

    2014-05-01

    Upwelling regions have received limited attention in paleoceanography, particularly for what concerns their changes at high temporal resolution. Furthermore, they have generally been considered independently. The lack of integrated studies of the evolution of the main coastal upwelling systems has limited the present degree of understanding of the links between global ocean dynamics and intensity and geographic distribution of these highly productive sites. In the present study, an integrated assessment of sea surface temperature (SST) records based on literature available alkenone-data on the upwelling regions of North-West Africa, North-West Arabian Sea, Namibia and Peru encompassing the last 25 kyr is reported. Additionally, in order to consider the complex effects of regional processes literature-available multiproxy data (marine, ice cores and speleothems records; PIG2LIG-4FUTURE database; Geophysical Research Abstracts Vol. 14, EGU2012-13825) has also been used to constrain upwelling features. This approach has allowed the description of high resolution temporal and spatial upwelling patterns and the interdependences between ocean dynamics and upwelling shifts. The spatio-temporal SST-upwelling patterns during the deglaciation-Holocene stage have been discussed. Suitable proxies for the upwelling and advection processes, such as CaCO3, TOC and Opal, Nd and carbon isotopes, respectively have been studied. Temporal snapshots at approximately at 22 ka, 15 ka, 12 ka, 8 ka, and 5 ka BP have been identified. These transitions illustrate flips between contrasting states. Major environmental and climatic changes have been observed before and after this type of transition, e.g. the one at 5 ka BP. These observations provide interesting clues on mechanisms, location of forcings and sustainers. The high temporal resolution records examined provide good constraints on the timing and magnitude of oceanic processes related with upwelling change and therefore an assessment

  19. CO2 Fluxes: The Upwelling Systems of South America & South Africa

    Science.gov (United States)

    Karagali, Ioanna; Badger, Merete; Soresen, Lise Lotte

    2010-12-01

    In order to estimate the atmospheric concentration of car- bon dioxide knowledge of the fluxes between the ocean and atmosphere are important. Different ocean regions can act as sinks or sources of CO2 depending on temperature, salinity and biological activity. The flux of CO2 depends on the partial pressures of atmospheric and oceanic CO2 and the exchange velocity which is commonly parametrized by the wind speed. Direct in-situ measurements are expensive, operationally demanding and of low spatial resolution. It has been shown that in- direct estimation of oceanic pCO2 is possible due to its strong dependence on temperature, however primary production also influences the concentration of CO2 in the water. The present study aims at estimating the oceanic pCO2 with the use of satellite measurements for water temperature and chlorophyll-a (chl-A). Envisat MERIS Level 2 Reduced Resolution products were used for the chl-A concentration. Sea Surface Temperature data were taken from a composite optimally interpolated SST product of the Danish Meteorological Institute (DMI). In-situ measurements were retrieved during the Danish Galathea III expedition, from August 2006 until April 2007. Based on [4] and [5], empirical algorithms for the estimation of pCO2,w were created using regression analyses. The final result was an estimate of the pCO2,w along the known upwelling systems of North Chile-Peru and Namibia. Estimates of pCO2,w produced by different combinations of physical parameters are compared with measurements. Correlation coefficients show that there was a dependency of pCO2,w with SST, Salinity and chl-A.

  20. Impact of tropical cyclones on the evolution of the monsoon-driven upwelling system in the coastal waters of the northern South China Sea

    Science.gov (United States)

    Zheng, Binxin; Li, Yunhai; Li, Jiufa; Shu, Fangfang; He, Jia

    2017-12-01

    An upwelling system exists in the coastal waters of the northern South China Sea (NSCS), a region that is frequently affected by tropical cyclones in summer. This study investigates the evolution of the NSCS monsoon-driven upwelling system and the effects of the Talim and Doksuri tropical cyclones on the system using in situ observational data obtained at three mooring stations, one land-based meteorological station, and concurrent satellite remote sensing data for the NSCS coastal waters from May to July 2012. The results show that the occurrence and evolution of the upwelling system were mainly controlled by the Asian southwest monsoon, while the eastward current also made important contributions to the upwelling intensity. A decrease in the bottom water temperature and shifts in the along-shore and cross-shore currents were direct evidence of the establishment, existence, and recovery of this upwelling. Tropical cyclones have significant impacts on hydrodynamics and can thus influence the evolution of the NSCS upwelling system by changing the local wind and current fields. Variations in water level and local current systems impeded the development of upwelling during tropical cyclones Talim and Doksuri in the study area, which have low-frequency fluctuations of approximately 2-10 days. These variations were the results of the coupled interactions between local wind fields, coastal trapped waves, and other factors. The hydrodynamic environment of the marine water (including coastal upwelling system) rapidly recovered to normal sea conditions after each cyclone passed due to the relatively short duration of the impact of a tropical cyclone on the dynamic environment of the waters.

  1. Coastal upwelling ecosystems are often identified as regions ...

    African Journals Online (AJOL)

    spamer

    upwelled water from aged upwelled water, and the coastal transition zone front, which defines the boundary between the coastal upwelling region and the adjacent ocean (Smith 1992, 1995). The strong density gradient across the coastal transition zone front sets up an equatorward jet that is most intense in summer (Smith.

  2. Modeling coastal upwelling around a small-scale coastline promontory

    Science.gov (United States)

    Haas, K. A.; Cai, D.; Freismuth, T. M.; MacMahan, J.; Di Lorenzo, E.; Suanda, S. H.; Kumar, N.; Miller, A. J.; Edwards, C. A.

    2016-12-01

    On the US west coast, northerly winds drive coastal ocean upwelling, an important process which brings cold nutrient rich water to the nearshore. The coastline geometry has been shown to be a significant factor in the strength of the upwelling process. In particular, the upwelling in the lee of major headlands have been shown to be enhanced. Recent observations from the Pt. Sal region on the coast of southern California have shown the presence of cooler water south of a small (350 m) rocky promontory (Mussel Pt.) during upwelling events. The hypothesis is that the small scale promontory is creating a lee side enhancement to the upwelling. To shed some light on this process, numerical simulations of the inner shelf region centered about Pt. Sal are conducted with the ROMS module of the COAWST model system. The model system is configured with four nested grids with resolutions ranging from approximately 600 m to the outer shelf ( 200 m) to the inner shelf ( 66 m) and finally to the surf zone ( 22 m). A solution from a 1 km grid encompassing our domain provides the boundary conditions for the 600 m grid. Barotropic tidal forcing is incorporated at the 600 m grid to provide tidal variability. This model system with realistic topography and bathymetry, winds and tides, is able to isolate the forcing mechanisms that explain the emergence of the cold water mass. The simulations focus on the time period of June - July, 2015 corresponding to the pilot study in which observational experiment data was collected. The experiment data in part consists of in situ measurement, which includes mooring with conductivity, temperature, depth, and flow velocity. The model simulations are able to reproduce the important flow features including the cooler water mass south of Mussel Pt. As hypothesized, the strength of the upwelling is enhanced on the side of Mussel Pt. In addition, periods of wind relaxation where the upwelling ceases and even begins to transform towards downwelling is

  3. Boundary controllability of integrodifferential systems in Banach ...

    Indian Academy of Sciences (India)

    the regularity of optimal boundary controls for parabolic equations with quadratic cost criterion. Recently Han and Park [7] derived a set of sufficient conditions for the boundary controllability of a semilinear system with a nonlocal condition. The purpose of this paper is to study the boundary controllability of nonlinear ...

  4. Working with boundaries in systems psychodynamic consulting

    Directory of Open Access Journals (Sweden)

    Henk Struwig

    2012-01-01

    Full Text Available Orientation: The researcher described the systems psychodynamics of boundary management in organisations. The data showed how effective boundary management leads to good holding environments that, in turn, lead to containing difficult emotions.Research purpose: The purpose of the research was to produce a set of theoretical assumptions about organisational boundaries and boundary management in organisations and, from these, to develop a set of hypotheses as a thinking framework for practising consulting psychologists when they work with boundaries from a systems psychodynamic stance.Motivation for the study: The researcher used the belief that organisational boundaries reflect the essence of organisations. Consulting to boundary managers could facilitate a deep understanding of organisational dynamics.Research design, approach and method: The researcher followed a case study design. He used systems psychodynamic discourse analysis. It led to six working hypotheses.Main findings: The primary task of boundary management is to hold the polarities of integration and differentiation and not allow the system to become fragmented or overly integrated. Boundary management is a primary task and an ongoing activity of entire organisations.Practical/managerial implications: Organisations should work actively at effective boundary management and at balancing integration and differentiation. Leaders should become aware of how effective boundary management leads to good holding environments that, in turn, lead to containing difficult emotions in organisations.Contribution/value-add: The researcher provided a boundary-consulting framework in order to assist consultants to balance the conceptual with the practical when they consult.

  5. Modern sedimentation in the Cabo Frio upwelling system, Southeastern Brazilian shelf

    Directory of Open Access Journals (Sweden)

    Michel M. de Mahiques

    2005-09-01

    Full Text Available The analyses of Uk'37 paleotemperatures and sedimentological parameters in box cores from the Cabo Frio upwelling zone, southeastern Brazil, were used to understand the modern sedimentation as well as to evaluate the role played by the upwelling process in the sedimentary patterns. Three box-cores located closer to the upwelling area show a general trend of cooling waters taking place in the last 700 years. Since the present upwelling is dependent on local and remote wind regime, a phase of dominating NE winds favors a more effective upward transport of the cold thermocline level South Atlantic CentralWater towards the coast. The intensification in the upwelling regime for the last ca. 700 years can be associated with the strengthening of the NE winds off the area and a possible increase of the Brazil Current mesoscale activity. Nevertheless, the lack of significant correlation of the paleotemperatures and most of sedimentological parameters indicate that upwelling is not the only sedimentation mechanism in the area. Also, the comparison of sedimentological parameters reveals that eventual temporal changes are superimposed by the geographical variability. Sedimentation rates vary from 0.26 mm.yr-1 to 0.66 mm.yr-1.As análises de Uk'37 paleotemperaturas e de parâmetros sedimentológicos em amostras de box-core da zona de ressurgência de Cabo Frio, sudeste do Brasil, foram usadas para compreender os processos de sedimentação moderna na área, bem como avaliar o papel desempenhado pela ressurgência no estabelecimento dos padrões sedimentológicos principais. Como observado em três box-cores localizados nas proximidades da área de ressurgência, é possível verificar uma tendência geral de resfriamento das águas nos últimos 700 anos (idade calibrada. Uma vez que o processo de ressurgência é dependente do regime de ventos local e remoto, uma fase de ventos predominantes de NE favorece um deslocamento mais efetivo das águas frias da

  6. The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

    Science.gov (United States)

    Graco, Michelle I.; Purca, Sara; Dewitte, Boris; Castro, Carmen G.; Morón, Octavio; Ledesma, Jesús; Flores, Georgina; Gutiérrez, Dimitri

    2017-10-01

    Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996-2011) recorded off the coast of Callao (12° 02' S, 77° 29' W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997-1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend

  7. Influences of riverine and upwelling waters on the coastal carbonate system off Central Chile and their ocean acidification implications

    Science.gov (United States)

    Vargas, Cristian A.; Contreras, Paulina Y.; Pérez, Claudia A.; Sobarzo, Marcus; Saldías, Gonzalo S.; Salisbury, Joe

    2016-06-01

    A combined data set, combining data from field campaigns and oceanographic cruises, was used to ascertain the influence of both river discharges and upwelling processes, covering spatial and temporal variation in dissolved inorganic carbon (DIC) and aragonite saturation state. This work was conducted in one of the most productive river-influenced upwelling areas in the South Pacific coasts (36°S). Additionally, further work was also conducted to ascertain the contribution of different DIC sources, influencing the dynamics of DIC along the land-ocean range. Six sampling campaigns were conducted across seven stations at the Biobío River basin, covering approximately 200 km. Three research cruises were undertaken simultaneously, covering the adjacent continental shelf, including 12 sampling stations for hydrographic measurements. Additionally, six stations were also sampled for chemical analyses, covering summer, winter, and spring conditions over 2010 and 2011. Our results evidenced that seaward extent of the river plume was more evident during the winter field campaign, when highest riverine DIC fluxes were observed. The carbonate system along the river-ocean continuum was very heterogeneous varying over spatial and temporal scales. High DIC and pCO2 were observed in river areas with larger anthropogenic effects. CO2 supersaturation at the river plume was observed during all campaigns due to the influence of low pH river waters in winter/spring and high-pCO2 upwelling waters in summer. δ13CDIC evidenced that main DIC sources along the river and river plume corresponded to the respiration of terrestrial organic matter. We have linked this natural process to the carbonate saturation on the adjacent river-influenced coastal area, suggesting that Ωaragonite undersaturation in surface/subsurface waters is largely modulated by the influence of both river discharge and coastal upwelling events in this productive coastal area. Conditions of low Ωaragonite might impact

  8. The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

    Directory of Open Access Journals (Sweden)

    M. I. Graco

    2017-10-01

    Full Text Available Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ. It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996–2011 recorded off the coast of Callao (12° 02′ S, 77° 29′ W. The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes. The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997–1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The

  9. Palaeoceanographic Variability of the Benguela Upwelling System Depending on the Northern Hemisphere Glaciation (NHG) - Indicated by Organic-Walled Dinoflagellates

    Science.gov (United States)

    Bork, M.

    2003-12-01

    The causes and effects of the intensification of growth of the northern Hemisphere ice caps at around 3.2 and 2.74 Ma BP are still unclear. Possible causes are changes in the global ocean circulation and the global carbon cycle, which might have resulted from tectonic processes, solar insolation changes, or the interaction between both processes. The Benguela upwelling area forms a key area within the global ocean system. Here, warm and saline Indian Ocean waters enter the South Atlantic Ocean and are transported to the north. Variability of this inflow may thus result in changes in deep-water production in the North Atlantic, thereby influencing the global thermohaline circulation. Furthermore, the Benguela area is characterized by extremely high bioproductivity in surface waters as a result of year-round upwelling. Variations in the upwelling intensity might lead to changes in atmospheric ¤CO2. To study the changes in the circulation and the upwelling intensity, within this region organic-walled dinoflagellate cysts from two high-resolution cores (ODP 1084 and1082) covering the time interval from 3.3 to 2.5 Ma BP were investigated. Due to their sensitiveness to ecological parameters, organic-walled dinoflagellates reflect oceanographic characteristics keenly. The analyses discover clear distribution differences of individual species, especially of those that are sensible or resistant against aerobic decay. The sensible species, (Protoperidinium and Echinidinium), have their highest abundance from 2.76 to 2.73 Ma BP, a time interval in which the resistant species show no significant changes in their abundance. This implies that during this time interval the oxygen was reduced in the deep- and porewater suggesting that the global ocean deepwater circulation was weakened. Comparing these results with the known intensification of the NHG at around 2.74 Ma BP leads to the speculation that the increasing of ice caps in the northern hemisphere is highly associated with

  10. Impacts of coastal upwelling off east Vietnam on the regional winds system: An air-sea-land interaction

    Science.gov (United States)

    Zheng, Zhe-Wen; Zheng, Quanan; Kuo, Yi-Chun; Gopalakrishnan, Ganesh; Lee, Chia-Ying; Ho, Chung-Ru; Kuo, Nan-Jung; Huang, Shih-Jen

    2016-12-01

    In this study, we analyze the influence of coastal upwelling off southeast Vietnam (CUEV) on local wind field using numerical simulations based on atmospheric model of Weather Research and Forecasting (WRF). Several scenarios are simulated by forcing identical model configurations with different SST fields. Based on simulation results, the relationship between CUEV and reduction of wind forcing is numerically evidenced. With the influence of a typical cold patch with a temperature drop of 3-5 °C, the local wind speeds can drop to less than 70% of original level. We find that the mechanism of response of the wind reduction to CUEV is enhancement of sea-breeze induced wind modulation. Onshore sea-breeze will enhance, while the contrast between land and sea is even more striking due to the contribution of a distinct coastal upwelling. This implies that air-sea-land interaction dominates the process of local wind system modulation in response to transient CUEV. This result sheds a new light on the air-sea interaction process within the SCS basin.

  11. The effects of a winter upwelling on biogeochemical and planktonic components in an area close to the Galician Upwelling Core: The Sound of Corcubión (NW Spain)

    Science.gov (United States)

    Varela, Manuel; Álvarez-Ossorio, Ma Teresa; Bode, Antonio; Prego, Ricardo; Bernárdez, Patricia; Garcia-Soto, Carlos

    2010-10-01

    To study the biogeochemical response and the coupling plankton-benthos to an unusual winter upwelling event a cruise was carried out in February 2005 in the Sound of Corcubión, near Cape Finisterre (NW Iberian Peninsula), the Galician upwelling core. This area represents the northern boundary of the Eastern North Atlantic Upwelling System (ENAUS). The spatial distribution of plankton assemblages (phytoplankton and zooplankton), chlorophyll, physical and chemical parameters as well as diatom distribution in surface sediments, were studied in a total of 17 stations in the Sound. The upwelling processes caused an important accumulation of water in the inner Sound and near the Cape. This accumulation zone must be persistent through the upwelling events in the area, including those of summer, as indicated by the diatoms' distribution in the sediment. Unlike the summer upwelling events, the main effect of winter upwelling in the area is the increase in solar radiation due to the persistent clear skies. In this season nutrient supply is not critical due to water column mixing. The meteorological conditions were equivalent to those of early spring. As a result, both phyto- and zooplankton species assemblages were typical of spring blooms in Galician coasts. The bloom lasted for up to 6 days, as estimated from the availability and uptake of nitrogen forms. Winter blooms represented ca. 20% of total annual phytoplankton biomass, and 30% of the average biomass during summer upwelling, in the period 1997-2007, as estimated from the analysis of both, in situ and satellite derived chlorophyll.

  12. On Mario Bunge's Definition of System and System Boundary

    Science.gov (United States)

    Cavallo, Andrew M.

    2012-01-01

    In this short paper we discuss Mario Bunge's definition of system boundary. It is quickly discovered that Bunge's definition of system and system boundary are both deficient. We thus propose new definitions, which (hopefully) improve the situation. Our definition of system boundary works off the same intuition behind Bunge's.

  13. Coastal upwelling south of Madagascar: Temporal and spatial variability

    Science.gov (United States)

    Ramanantsoa, Juliano D.; Krug, M.; Penven, P.; Rouault, M.; Gula, J.

    2018-02-01

    Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds.

  14. Total and mesoscale long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

    Science.gov (United States)

    Lovecchio, Elisa; Gruber, Nicolas; Münnich, Matthias; Byrne, David; Lachkar, Zouhair

    2017-04-01

    The ocean's biological pump is often simplified to a purely vertical process. Nevertheless, the horizontal transport of organic carbon can be substantial, especially in coastal regions such as the Canary Upwelling System (CanUS), one of the four major Eastern Boundary Upwelling Systems, characterized by high shelf productivity and an intense lateral exchange of mass and tracers with the adjacent oligotrophic waters. Despite its importance, the magnitude of this lateral flux has not yet been constrained. Here, we quantify the lateral export of organic carbon from the CanUS to the open North Atlantic using the Regional Ocean Modeling System (ROMS) coupled to a biogeochemical ecosystem module. The model is run on an Atlantic telescopic grid with a strong refinement towards the north-western African shelf, to combine an eddy-resolving resolution in the region of study with a full Atlantic basin perspective. Our results reveal that over the whole CanUS more than a third of the Net Community Production (NCP) in the nearshore 100 km is transported offshore, amounting to about 19 Tg C yr-1. The offshore transport dominates the lateral fluxes up to 1500 km into the subtropical North Atlantic, along the way adding organic carbon to the upper 100 m at rates of between 8% and 34% of the alongshore average NCP. The remineralization at depth of this extra organic carbon leads to strongly negative vertically-integrated NCP throughout the whole offshore region of the CanUS, i.e. it makes the offshore region net heterotrophic. Substantial subregional variability shapes the spatial pattern of the fluxes in the CanUS. In particular, the central subregion surrounding Cape Blanc is the most efficient in terms of collecting and laterally exporting the organic carbon, resulting in a sharp peak of watercolumn heterotrophy. A decomposition of the organic carbon fluxes into a time-mean component and a time-variable, i.e., mesoscale component reveals a large contribution of the mesoscale

  15. Evidence of an intermittent deep equatorward flow in the Peru upwelling system

    Science.gov (United States)

    Pietri, Alice; Echevin, Vincent; Testor, Pierre; Chaigneau, Alexis; Mortier, Laurent; Grados, Carmen; Albert, Aurelie; Beguery, Laurent; Bhairy, Nagib

    2013-04-01

    In April-May 2010, 6 consecutive repeated cross-shore sections of ~100 km were occupied by a Slocum glider off the coast of Pisco (14°S) in the southernmost Peruvian upwelling region. The collected temperature and salinity data, acquired from the surface to 1000m depth and the depth-integrated velocity, estimated from the glider drift between two dives, are used to estimate absolute geostrophic alongshore velocities and study the spatio-temporal variability of the near-coastal circulation during a 5-week time period. Besides providing interesting information on the surface frontal jet and surfacing poleward undercurrent trapped on the continental shelf and slope, the glider data reveal the presence of a subsurface deep equatorward current. The dynamics and origin of this current, which can transport up to ˜2 Sv northward, are investigated using simulations from an eddy-resolving regional model (ROMS). This relatively strong equatorward subsurface current is associated with a poleward propagating coastal trapped wave of equatorial origin, with a strongly sheared vertical structure. A simple linear coastal wave model which successfully reproduces part of the observed vertical structure of the current, indicates that it corresponds to a third baroclinic mode of coastal wave.

  16. Boundary Controllability of Nonlinear Fractional Integrodifferential Systems

    Directory of Open Access Journals (Sweden)

    Ahmed HamdyM

    2010-01-01

    Full Text Available Sufficient conditions for boundary controllability of nonlinear fractional integrodifferential systems in Banach space are established. The results are obtained by using fixed point theorems. We also give an application for integropartial differential equations of fractional order.

  17. Oceanographical patterns during a summer upwelling-downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

    Science.gov (United States)

    Ospina-Alvarez, N.; Prego, R.; Álvarez, I.; deCastro, M.; Álvarez-Ossorio, M. T.; Pazos, Y.; Campos, M. J.; Bernárdez, P.; Garcia-Soto, C.; Gómez-Gesteira, M.; Varela, M.

    2010-07-01

    Summer upwelling and downwelling processes were characterized in the Northern Galician Rias during July and August 2008 by means of sampling carried out onboard R/V Mytilus (CSIC) and R/V Lura (IEO). Thermohaline variables, dissolved oxygen, nutrients, chlorophyll, phytoplankton, ciliates and zooplankton abundances were measured at sections located in the Rias of Viveiro, Barqueiro and Ortigueira and their adjacent shelves. Ekman transport was calculated from QuikSCAT satellite, upwelling intensity estimated with upwelling index from the average daily geostrophic winds, and SST maps obtained from NASA GHRSST satellite. Ekman transport and SST behaviour showed two different patterns: (i) offshore and upwelling favourable conditions on 13-22nd of July; (ii) onshore and downwelling favourable conditions from 23rd July to 19th August. During upwelling, TS diagram showed an intrusion of Eastern North Atlantic Central Water affecting the continental shelf but not the rias. Nutrient salt concentrations increased with depth, reaching their maximum values near the mouth of Ortigueira Ria. During downwelling, coastal water increased its temperature (18.5-19.8 °C) and was retained inside rias; nutrients were nearly depleted, except for the innermost ria (estuarine zone) due to fluvial nutrient inputs. In this inner area, the maximum of chlorophyll- a (Barqueiro Ria) was observed. Low phytoplankton abundances were measured in both cases, even though a short increase in the plankton biomass was observed inside rias during upwelling, while under downwelling a small red tide of Lingulodinium polyedrum was detected. During the upwelling period Northern Rias tend to be mesotrophic systems as revealed by nutrient concentrations, chlorophyll levels and plankton abundances. On the contrary, in similar situations, the Western Rias behaves as eutrophics. In the Northern Galician shelf, the average of upwelling (downwelling) was 1.9±0.8 (2.1±1.0) events yr -1 from May to September

  18. Dynamics of plankton populations in upwelling areas

    Science.gov (United States)

    Szekielda, K. H. (Principal Investigator)

    1975-01-01

    The author has identified the following significant results. Spectral properties of the upwelled waters off the NW coast of Africa were studied with observations derived from aircraft and Skylab. Results indicate that the two-channel, ratio approach is ineffective in determining surface chlorophyll concentrations. Ocean color boundaries and temperature gradients were found to be directly correlated with each other and also with fishing effort in the upwelling region. Photographic and scanner data derived from Skylab were effective in locating ocean boundaries and mapping temperature distributions.

  19. Export of pre-aged, labile DOM from a central California coastal upwelling system: Insights from D/L amino acids and Δ14C signatures

    Science.gov (United States)

    Walker, B. D.; Shen, Y.; Benner, R. H.; Druffel, E. R. M.

    2014-12-01

    Coastal upwelling zones are among the most productive regions in the world and play a major role in global carbon and nitrogen cycles. Recent research suggests that a substantial fraction of newly fixed organic matter is exported offshore in the form of dissolved organic matter (DOM). However, to date only a few studies have examined DOM composition in the context of production and export from upwelling systems. The ultimate fate and geochemical impact of coastal DOM exported to offshore and mesopelagic ecosystems also remains largely unknown. Between 2007-2009 we conducted a high-resolution biogeochemical time series at the Granite Canyon Marine Pollution Studies Lab in part to evaluate the seasonal production and export of DOM from the Central CA coast. Our previous work demonstrated substantial, albeit disparate, seasonal production of dissolved organic carbon and nitrogen (DOC, DON) - with high DON (and low C:N ratios) produced during upwelling and high DOC produced during summer/fall water column stratification (Walker and McCarthy, 2012). Here we present new total dissolved D/L amino acid (TDAA) and UV-oxidizable DOC radiocarbon (Δ14C) data with the goal of determining the relative sources (heterotrophic vs. autotrophic), bioavailability, microbial processing and 14C-ages of C-rich vs. N-rich DOM exported from this upwelling system. Our results suggest that C-rich DOM produced during water column stratification carries a large microbial signature (i.e. high D/L AA ratios and non-protein AA abundance), whereas N-rich DOM produced during upwelling appears to be fresh, autotrophic DOM (i.e. lowest D/L AA ratios and highest TDAA abundance). DOM Δ14C signatures also did not approximate in situ dissolved inorganic carbon (DIC), and instead were far more negative and highly correlated to water mass density. Together our results indicate a previously unrecognized source of highly labile yet pre-aged DOM potentially impacting offshore and mesopelagic ecosystems.

  20. Zooplankton associated with the oxygen minimum zone system in the northern upwelling region of Chile during March 2000

    Science.gov (United States)

    Escribano, Ruben; Hidalgo, Pamela; Krautz, Cristina

    2009-07-01

    Zooplankton in the coastal upwelling region off northern Chile may play a significant biogeochemical role by promoting carbon flux into the subsurface OMZ (oxygen minimum zone). This work identifies the dominant zooplankton species inhabiting the area influenced by the OMZ in March 2000 off Iquique (20°S, northern Chile). Abundance and vertical distribution studies revealed 17 copepod and 9 euphausiid species distributed between the surface and 600 m at four stations sampled both by day and by night. Some abundant species remained in the well-oxygenated upper layer (30 m), with no evidence of diel vertical migration, apparently restricted by a shallow (40-60 m) oxycline. Other species, however, were found closely associated with the OMZ. The large-sized copepod Eucalanus inermis was found below the oxycline and performed diel vertical migrations into the OMZ, whereas the very abundant Euphausia mucronata performed extensive diel vertical migrations between the surface waters and the core of the OMZ (200 m), even crossing it. A complete assessment of copepods and euphausiids revealed that the whole sampled water column (0-600 m) is occupied by distinct species having well-defined habitats, some of them within the OMZ. Ontogenetic migrations were evident in Eucalanidae and E. mucronata. Estimates of species biomass showed a substantial (>75% of total zooplankton biomass) daily exchange of C between the photic layer and the OMZ. Both E. inermis and E. mucronata can actively exchange about 37.8 g C m -2 d -1 between the upper well-oxygenated (0-60 m) layer and the deeper (60-600 m) OMZ layer. This migrant biomass may contribute about 7.2 g C m -2 d -1 to the OMZ system through respiration, mortality, and production of fecal pellets within the OMZ. This movement of zooplankton in and out of the OMZ, mainly as a result of the migratory behavior of E. mucronata, suggests a very efficient mechanism for introducing large amounts of freshly produced carbon into the OMZ

  1. Fractal boundaries in chaotic hamiltonian systems

    Science.gov (United States)

    Viana, R. L.; Mathias, A. C.; Marcus, F. A.; Kroetz, T.; Caldas, I. L.

    2017-10-01

    Fractal structures are typically present in the dynamics of chaotic orbits in non-integrable open Hamiltonian systems and result from the extremely complicated nature of the invariant manifolds of unstable periodic orbits. Exit basins, the set of initial conditions leading to orbits escaping through a given exit, have very frequently fractal boundaries. In this work we analyze exit basin boundaries in a dynamical system of physical interest, namely the motion of charged particles in a magnetized plasma subjected to electrostatic drift waves, and characterize in a quantitative way the fractality of these structures and their observable consequences, as the final-state uncertainty.

  2. Short-term variability during an anchor station study in the southern Benguela upwelling system: Nitrogen supply to the euphotic zone during a quiscent phase in the upwelling cycle

    Science.gov (United States)

    Waldron, H. N.; Probyn, T. A.

    An anchor station was occupied for a period of five days during the austral autumn in a semi-closed embayment adjacent to an upwelling centre in the southern Benguela. The water column was divided into a Bottom Mixed Layer (BML) and Sun-Warmed Surface Layer (SWSL) on the basis of its temperature, salinity, dissolved O 2 and NO 3 profiles. Fine-scale vertical structure of NH 4 at the base of the water column showed its release from the sediment and rapid nitrification above 1m from the sea bed, which can explain the enhanced NO 3 concentrations found in the BML. No evidence of horizontal advection of a different water mass, type or body was found during the study period but there were large vertical oscillations of the BML/SWSL interface. Vertical transport of NO 3 through mechanisms other than upwelling, was inferred from vertical eddy diffusion coefficients (K ZN). It was sufficient to support new production of between 34.23mg Cm 2h -1 and 54.18mg Cm 2h -1. NO 3 transport (and hence new production) was in approximate balance with te NH 4 release from the sediment. Regenerated production was found to dominate however, with f-ratios of between 0.35 and 0.29. The relationship between primary productivity and K ZN in the study areas was compared with other oceanic regimes. Both new and regenerated production were higher than the other systems for given values of K ZN, a situation thought to result from physical quiescence which did not preclude the vertical transport of NO 3 and the presence of large grazer and decomposer communities.

  3. Hamiltonian discretization of boundary control systems

    NARCIS (Netherlands)

    Golo, Goran; Talasila, Viswanath; Schaft, Arjan van der; Maschke, Bernhard

    2004-01-01

    A fundamental problem in the simulation and control of complex physical systems containing distributed-parameter components concerns finite-dimensional approximation. Numerical methods for partial differential equations (PDEs) usually assume the boundary conditions to be given, while more often than

  4. Hamiltonian discretization of boundary control systems

    NARCIS (Netherlands)

    Golo, G.; Talasila, V.; van der Schaft, Arjan; Maschke, B.M.

    A fundamental problem in the simulation and control of complex physical systems containing distributed-parameter components concerns finite-dimensional approximation. Numerical methods for partial differential equations (PDEs) usually assume the boundary conditions to be given, while more often than

  5. Upwelling regions, the most fertile of the seas' habitats, are also ...

    African Journals Online (AJOL)

    spamer

    THE UPWELLING FLORA. Components. A distinct upwelling diatom community has not evolved, based on species checklists for the major eastern boundary currents (Benguela, Peru, North-. West Africa and California) and regionally contiguous, minor upwelling centres (Gulf of Panama, Baja. California – De Jager 1955, ...

  6. Distribution of surface carbon dioxide and air-sea exchange in the upwelling system off the Galician coast

    Science.gov (United States)

    Borges, Alberto V.; Frankignoulle, Michel

    2002-05-01

    Data on the distribution of the partial pressure of CO2 (pCO2) were obtained during six cruises off the Galician coast, a region characterized by a seasonal upwelling. The values of pCO2 over the continental shelf are highly variable and range between 265 and 415 μatm during the upwelling season and between 315 and 345 μatm during the downwelling season. Both the continental shelf and off-shelf waters behave as significant net sinks of atmospheric CO2. The computation of the air-sea fluxes of CO2 over the continental shelf yields a net influx in the range of -2.3 (+/-0.6) to -4.7 (+/-1.0) mmol C m-2 d-1 during the upwelling season and -3.5 (+/-0.8) to -7.0 (+/-1.5) mmol C m-2 d-1 on an annual basis. During the upwelling season and on an annual basis, although the observed air-sea gradients of CO2 over the continental shelf are significantly stronger than those in off-shelf waters, the computed air-sea CO2 fluxes are not significantly different because of the important incertitude introduced in the calculations by the estimated error on wind speed measurements. The presence of upwelling filaments increases the influx of atmospheric CO2 in the off-shelf waters. During summer, important short-term variations of pCO2 are observed that are related to both upwelling and temperature variations. During winter the cooling of water causes important undersaturation of CO2 related to the effect of temperature on the dissolved inorganic carbon equilibrium constants.

  7. Role of nutrient recycling in upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1979-01-01

    The regeneration of nitrogen is an important process that increases the efficiency of the upwelling ecosystem by enlarging their spatial scales. Ammonium regeneration was considered to contribute 42 to 72 percent of phytoplankton nitrogen requirements in the northwest Africa, Peru, and Baja California upwelling systems. Zooplankton are responsible for the largest portion of regenerated nitrogen; however, fish and benthic sediments may be nearly as large. Comparisons of the importance of ammonium regeneration in upwelling areas with coastal and open ocean regions indicate that the percentage contributions are similar. Future nutrient regeneration studies are needed to assess the recycling of benthic sediments, microzooplankton, gelatinous zooplankton, demersal fish, bacterioplankton, and mollusks.

  8. A model of trophic flows in the northern Benguela upwelling system during the 1980s

    DEFF Research Database (Denmark)

    Shannon, L.J.; Jarre, Astrid

    1999-01-01

    in the northern Benguela during the 1980s was high, comparable to that of the Peruvian system in the 1960s and almost double that of the northern Benguela during the 1970s. Horse mackerel and hake catches were both high, with fishing on hake being ecologically more expensive. Biomass of benthic producers, meio...

  9. Late-glacial to holocene changes in winds, upwelling, and seasonal production of the northern California current system

    Science.gov (United States)

    Sancetta, C.; Lyle, M.; Heusser, L.; Zahn, R.; Bradbury, J.P.

    1992-01-01

    A core 120 km off the coast of southern Oregon was examined for changes in lithology, diatoms, and pollen over the past 30,000 yr. Primary production during the late Pleistocene was about half that of the Holocene. Evidence from diatoms and pollen indicates that summer upwelling was much weaker, implying an absence of strong northerly winds. Early Pliocene diatoms found throughout the late Pleistocene section were probably derived from diatomites east of the Cascades and provide evidence for strong easterly winds over a dry continental interior. The findings verify predictions of a climate model based on glacial maximum conditions. There is no compelling evidence for a climatic reversal corresponding to the European Younger Dryas chron. During the early Holocene (9000-7000 yr B.P.) there may have been years when winds were insufficiently strong to support upwelling, so that warm stratified waters lay closer to the coast. ?? 1992.

  10. On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

    Science.gov (United States)

    Lovecchio, Elisa; Gruber, Nicolas; Münnich, Matthias; Lachkar, Zouhair

    2017-07-01

    A compilation of measurements of net community production (NCP) in the upper waters of the eastern subtropical North Atlantic had suggested net heterotrophic conditions, purportedly supported by the lateral export of organic carbon from the adjacent, highly productive Canary Upwelling System (CanUS). Here, we quantify and assess this lateral export using the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. We employ a new Atlantic telescopic grid with a strong refinement towards the northwestern African shelf to combine an eddy-resolving resolution in the CanUS with a full Atlantic basin perspective. Our climatologically forced simulation reveals an intense offshore flux of organic carbon that transports about 19 Tg C yr-1 away from the nearshore 100 km over the whole CanUS, amounting to more than a third of the NCP in this region. The offshore transport extends beyond 1500 km into the subtropical North Atlantic, adding organic carbon along the way to the upper 100 m at rates of between 8 and 34 % of the alongshore average NCP as a function of offshore distance. Although the divergence of this lateral export of organic carbon enhances local respiration, the upper 100 m layer in our model remains net autotrophic in the entire eastern subtropical North Atlantic. However, the vertical export of this organic carbon and its subsequent remineralization at depth makes the vertically integrated NCP strongly negative throughout this region, with the exception of a narrow band along the northwestern African shelf. The magnitude and efficiency of the lateral export varies substantially between the different subregions. In particular, the central coast near Cape Blanc is particularly efficient in collecting organic carbon on the shelf and subsequently transporting it offshore. In this central subregion, the offshore transport adds as much organic carbon as nearly 60 % of the local NCP to the upper 100

  11. Production regimes in four eastern boundary current systems

    Science.gov (United States)

    Carr, M. E.; Kearns, E. J.

    2003-01-01

    High productivity (maxima 3 g C m(sup -2)day(sup -1)) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements ofthe wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highlycorrelated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due toavailability of iron, physical retention, or differences in planktonic community structure.

  12. Ecological features of harmful algal blooms in coastal upwelling ...

    African Journals Online (AJOL)

    The mass mortalities that accompany anoxia, common to the Benguela and Peru upwelling systems, may be a trophic control mechanism to maintain biogeochemical balance and regional homeostasis, which are vital to upwelling ecosystem dynamics. Some traditional concepts of phytoplankton ecology may not completely

  13. A system boundary identification method for life cycle assessment

    DEFF Research Database (Denmark)

    Li, Tao; Zhang, Hongchao; Liu, Zhichao

    2014-01-01

    Life cycle assessment (LCA) is a useful tool for quantifying the overall environmental impacts of a product, process, or service. The scientific scope and boundary definition are important to ensure the accuracy of LCA results. Defining the boundary in LCA is difficult and there are no commonly...... of processes considered, and the gradient of the fitting curve trends to zero gradually. According to the threshold rules, a relatively accurate system boundary could be obtained.It is found from this research that the system boundary curve describes the growth of life cycle impact assessment (LCIA) results...... accepted scientific methods yet. The objective of this research is to present a comprehensive discussion of system boundaries in LCA and to develop an appropriate boundary delimitation method.A product system is partitioned into the primary system and interrelated subsystems. The hierarchical relationship...

  14. Role of physical forcings and nutrient availability on the control of satellite-based chlorophyll a concentration in the coastal upwelling area of the Sicilian Channel

    Directory of Open Access Journals (Sweden)

    Bernardo Patti

    2010-08-01

    Full Text Available The northern sector of the Sicilian Channel is an area of favourable upwelling winds, which ought to support primary production. However, the values for primary production are low when compared with other Mediterranean areas and very low compared with the most biologically productive regions of the world’s oceans: California, the Canary Islands, Humboldt and Benguela. The aim of this study was to identify the main factors that limit phytoplankton biomass in the Sicilian Channel and modulate its monthly changes. We compared satellite-based estimates of chlorophyll a concentration in the Strait of Sicily with those observed in the four Eastern Boundary Upwelling Systems mentioned above and in other Mediterranean wind-induced coastal upwelling systems (the Alboran Sea, the Gulf of Lions and the Aegean Sea. Our results show that this low level of chlorophyll is mainly due to the low nutrient level in surface and sub-surface waters, independently of wind-induced upwelling intensity. Further, monthly changes in chlorophyll are mainly driven by the mixing of water column and wind-induced and/or circulation-related upwelling processes. Finally, primary production limitation due to the enhanced stratification processes resulting from the general warming trend of Mediterranean waters is not active over most of the coastal upwelling area off the southern Sicilian coast.

  15. Tectonics of oblique plate boundary systems

    Science.gov (United States)

    Díaz-Azpiroz, Manuel; Brune, Sascha; Leever, Karen A.; Fernández, Carlos; Czeck, Dyanna M.

    2016-12-01

    The relative displacement between lithospheric plates normally results in obliquely deforming plate boundaries. This is simply caused by the fact that, on plate tectonics basis, irregularly shaped plate boundaries are rarely perpendicular or parallel to small-circle rotation paths, which describe plate motion on a sphere (Fig. 1a). Global current relative plate motions estimated from geological data (DeMets et al., 2010; Argus et al., 2011) and GPS measurements (e.g., Kreemer et al., 2003; Argus et al., 2010) provide insight to the prevalent degrees of obliquity on Earth's surface. Based on these global data sets, Philippon and Corti (2016), statistically show that current orthogonal boundaries (obliquity angle smaller than 10°) represent around 8% of the total boundary length whereas strike-slip boundaries (obliquity angle larger than 80°) are encountered in plate boundaries present oblique relative motions. Furthermore, changes in plate kinematics leading to migration or jumps in the rotation poles necessarily cause obliquity along former pure strike-slip or convergent/divergent boundaries (Fig. 1b).

  16. Boundary control of nonlinear coupled heat systems using backstepping

    KAUST Repository

    Bendevis, Paul

    2016-10-20

    A state feedback boundary controller is designed for a 2D coupled PDE system modelling heat transfer in a membrane distillation system for water desalination. Fluid is separated into two compartments with nonlinear coupling at a membrane boundary. The controller sets the temperature on one boundary in order to track a temperature difference across the membrane boundary. The control objective is achieved by an extension of backstepping methods to these coupled equations. Stability of the target system via Lyapunov like methods, and the invertibility of the integral transformation are used to show the stability of the tracking error.

  17. Seasonal cycle of N:P:TA stoichiometry as a modulator of CO2 buffering in eastern boundary upwelling systems

    CSIR Research Space (South Africa)

    Gregor, L

    2013-10-01

    Full Text Available were classified into summer, autumn, and winter. Nitrate, phosphate, dissolved inorganic carbon, and total alkalinity ratios were used in a stoichiometric reconstruction model to determine the contribution of biogeochemical processes on a parcel...

  18. Singular boundary perturbations of distributed systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1990-01-01

    Some problems arising in real-life control applications are addressed--namely, problems concerning non-smooth control inputs on the boundary of the spatial domain. The classical variational approach is extended, and sufficient conditions are given for the solutions to continuous functions of time...

  19. Regularity of pointwise boundary control systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1992-01-01

    We will in these notes address some problems arising in "real-life" control application, namely problems concerning distributional control inputs on the boundary of the spatial domain. We extend the classical variational approach and give easily checkable sufficient conditions for the solutions...

  20. N2O production and consumption from stable isotopic and concentration data in the Peruvian coastal upwelling system

    Science.gov (United States)

    Bourbonnais, Annie; Letscher, Robert T.; Bange, Hermann W.; Échevin, Vincent; Larkum, Jennifer; Mohn, Joachim; Yoshida, Naohiro; Altabet, Mark A.

    2017-04-01

    The ocean is an important source of nitrous oxide (N2O) to the atmosphere, yet the factors controlling N2O production and consumption in oceanic environments are still not understood nor constrained. We measured N2O concentrations and isotopomer ratios, as well as O2, nutrient and biogenic N2 concentrations, and the isotopic compositions of nitrate and nitrite at several coastal stations during two cruises off the Peru coast ( 5-16°S, 75-81°W) in December 2012 and January 2013. N2O concentrations varied from below equilibrium values in the oxygen deficient zone (ODZ) to up to 190 nmol L-1 in surface waters. We used a 3-D-reaction-advection-diffusion model to evaluate the rates and modes of N2O production in oxic waters and rates of N2O consumption versus production by denitrification in the ODZ. Intramolecular site preference in N2O isotopomer was relatively low in surface waters (generally -3 to 14‰) and together with modeling results, confirmed the dominance of nitrifier-denitrification or incomplete denitrifier-denitrification, corresponding to an efflux of up to 0.6 Tg N yr-1 off the Peru coast. Other evidence, e.g., the absence of a relationship between ΔN2O and apparent O2 utilization and significant relationships between nitrate, a substrate during denitrification, and N2O isotopes, suggest that N2O production by incomplete denitrification or nitrifier-denitrification decoupled from aerobic organic matter remineralization are likely pathways for extreme N2O accumulation in newly upwelled surface waters. We observed imbalances between N2O production and consumption in the ODZ, with the modeled proportion of N2O consumption relative to production generally increasing with biogenic N2. However, N2O production appeared to occur even where there was high N loss at the shallowest stations.

  1. Slip systems, dislocation boundaries and lattice rotations in deformed metals

    DEFF Research Database (Denmark)

    Winther, Grethe

    2009-01-01

    Metals are polycrystals and consist of grains, which are subdivided on a finer scale upon plastic deformation due to formation of dislocation boundaries. The crystallographic alignment of planar dislocation boundaries in face centred cubic metals, like aluminium and copper, deformed to moderate...... slip systems. Actual prediction of the dislocation boundary alignment has become possible through establishment of general relations between slip systems and dislocation boundary planes. The practical relevance of these relations has been exemplified by applying them as a basis for further prediction...... of the mechanical anisotropy of rolled sheets. The rotation of the crystallographic lattice in each grain during deformation also exhibits grain orientation dependence, originating from the slip systems. A combined analysis of dislocation boundaries and lattice rotations concludes that the two phenomena are coupled...

  2. Electrostatic potential of phase boundary in Coulomb systems

    NARCIS (Netherlands)

    Iosilevski, [No Value; Chigvintsev, A

    Any interface boundary in an equilibrium system of Coulomb particles is accompanied by the existence of a finite difference in the average electrostatic potential through this boundary. This interface potential drop is a thermodynamic quantity. It depends on temperature only and does not depend on

  3. Slip systems, lattice rotations and dislocation boundaries

    DEFF Research Database (Denmark)

    Winther, Grethe

    2008-01-01

    Plastic deformation by slip induces rotations of the crystallographic lattice and evolution of dislocation structures. Both lattice rotations and dislocation structures exhibit a dependence on the grain orientation, which reflects underlying relations to the slip pattern. Relations between the type...... of dislocation structure formed, in particular the crystallographic alignment of dislocation boundaries, and the slip pattern are demonstrated. These relations are applied to polycrystals deformed in tension and rolling, producing good agreement with experiment for rolling but less good agreement for tension...... of these discrepancies is discussed. Finally, the implications of the relations between slip and dislocation structures for the modelling of mechanical properties are discussed....

  4. On weak solvability of boundary value problems for elliptic systems

    OpenAIRE

    Ponce, Felipe; Lebedev, Leonid,; Rendón, Leonardo,

    2013-01-01

    This paper concerns with existence and uniqueness of a weak solution for elliptic systems of partial differential equations with mixed boundary conditions. The proof is based on establishing the coerciveness of bilinear forms, related with the system of equations, which depend on first-order derivatives of vector functions in Rn. The condition of coerciveness relates to Korn's type inequalities. The result is illustrated by an example of boundary value problems for a class of elliptic equatio...

  5. Zonation of bacterioplankton communities along aging upwelled water in the northern Benguela upwelling

    Directory of Open Access Journals (Sweden)

    Benjamin eBergen

    2015-06-01

    Full Text Available Upwelling areas are shaped by enhanced primary production in surface waters, accompanied by a well-investigated planktonic succession. Although bacteria play an important role in biogeochemical cycles of upwelling systems, little is known about bacterial community composition and its development during upwelling events. The aim of this study was to investigate the succession of bacterial assemblages in aging upwelled water of the Benguela upwelling from coastal to offshore sites. Water from the upper mixed layer at 12 stations was sampled along two transects from the origin of the upwelling to a distance of 220 km. 16S rRNA gene amplicon sequencing was then used in a bacterial diversity analysis and major bacterial taxa were quantified by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH. Additionally, bacterial cell numbers and bacterial production were assessed . Community statistical analysis revealed a reproducible zonation along the two transects, with four clusters of significantly different microbial assemblages. Clustering was mainly driven by phytoplankton composition and abundance. Similar to the temporal succession that occurs during phytoplankton blooms in temperate coastal waters, operational taxonomic units (OTUs affiliated with Bacteroidetes and Gammaproteobacteria were dominant during algal blooming whereas Pelagibacterales were highly abundant in regions with low algal abundance. The most dominant heterotrophic OTU (9% of all reads was affiliated with Pelagibacterales and showed a strong negative correlation with phytoplankton. By contrast, the second most abundant heterotrophic OTU (6% of all reads was affiliated with the phylum Verrucomicrobia and correlated positively with phytoplankton. Together with the close relation of bacterial production and phytoplankton abundance, our results showed that bacterial community dynamics is strongly driven by the development and composition of the phytoplankton

  6. Stability and boundary stabilization of 1-D hyperbolic systems

    CERN Document Server

    Bastin, Georges

    2016-01-01

    This monograph explores the modeling of conservation and balance laws of one-dimensional hyperbolic systems using partial differential equations. It presents typical examples of hyperbolic systems for a wide range of physical engineering applications, allowing readers to understand the concepts in whichever setting is most familiar to them. With these examples, it also illustrates how control boundary conditions may be defined for the most commonly used control devices. The authors begin with the simple case of systems of two linear conservation laws and then consider the stability of systems under more general boundary conditions that may be differential, nonlinear, or switching. They then extend their discussion to the case of nonlinear conservation laws and demonstrate the use of Lyapunov functions in this type of analysis. Systems of balance laws are considered next, starting with the linear variety before they move on to more general cases of nonlinear ones. They go on to show how the problem of boundary...

  7. Spatio-temporal variation of microphytoplankton in the upwelling system of the south-eastern Arabian Sea during the summer monsoon of 2009

    Directory of Open Access Journals (Sweden)

    Lathika Cicily Thomas

    2013-02-01

    Full Text Available The phytoplankton standing crop was assessed in detail along the South Eastern Arabian Sea (SEAS during the different phases of coastal upwelling in 2009. During phase 1 intense upwelling was observed along the southern transects(8°N and 8.5°N. The maximum chlorophyll a concentration (22.7 mg m-3 was observedin the coastal waters off Thiruvananthapuram (8.5°N. Further north there was no signature of upwelling, with extensive Trichodesmium erythraeum blooms. Diatoms dominated in these upwelling regions with thecentric diatom Chaetoceros curvisetus being the dominant species along the 8°N transect. Along the 8.5°N transect pennate diatoms like Nitzschia seriata and Pseudo-nitzschia sp. dominated. Duringphase 2, upwelling of varying intensity was observed throughout the study area with maximum chlorophyll a concentrations along the 9°N transect (25 mg m-3 with Chaetoceros curvisetus as the dominantphytoplankton. Along the 8.5°N transect pennate diatoms during phase 1 were replaced by centric diatoms like Chaetoceros sp. The presence of solitary pennate diatoms Amphora sp. and Navicula sp.were significant in the waters off Kochi. Upwelling was waning during phase 3 and was confined to the coastal waters of the southern transects with the highest chlorophyll a concentration of 11.2 mg m-3. Along withdiatoms, dinoflagellate cell densities increased in phases 2 and 3. In the northern transects (9°N and 10°N the proportion of dinoflagellates was comparatively higher and was represented mainly by Protoperidinium spp.

  8. Boundary conditions for hyperbolic systems of partial differentials equations.

    Science.gov (United States)

    Guaily, Amr G; Epstein, Marcelo

    2013-07-01

    An easy-to-apply algorithm is proposed to determine the correct set(s) of boundary conditions for hyperbolic systems of partial differential equations. The proposed approach is based on the idea of the incoming/outgoing characteristics and is validated by considering two problems. The first one is the well-known Euler system of equations in gas dynamics and it proved to yield set(s) of boundary conditions consistent with the literature. The second test case corresponds to the system of equations governing the flow of viscoelastic liquids.

  9. Boundaries, political systems and fertility in Europe.

    Science.gov (United States)

    Decroly, J; Grasland, C

    1993-01-01

    "We propose considering cross-border discontinuities in the context of homogeneous regions, that is, focusing on the detection and explanation of significant levels of organization of space by societies [in Europe]....We attempt to isolate macro-structures, which will provide us with an intermediary or systemic explanation for the behaviour observed....Our preoccupation here is whether countries or political blocs constitute levels of spatial organization. We can pose the question this way: do different areas in a same country show behavioural patterns which are, on average, more similar than those of areas in different countries?...We shall examine the distribution of total fertility (TFRs) in 724 areas of Europe in 1980 and 1988." excerpt

  10. Inside Out: Organizations as Service Systems Equipped with Relational Boundaries

    Directory of Open Access Journals (Sweden)

    María Jimena Crespo Garrido

    2017-04-01

    Full Text Available Currently, literature on organizational boundaries is at the center of a heated debate, characterized by a shift from a transactional approach to a broader immaterial perspective centered on the concept of boundless organizations. However, the overestimation of the effects of contemporary dematerialization on business processes can lead to the progressive neglect of the existence of corporate borders. In light of this consideration, the present work aims at proposing a new type of criterion for defining organizational boundaries, halfway between the conception of the firm’s total openness and total closure. To this end, the authors envisage the use of a new interpretive logic defined as “relational”, resulting from the specification of the systemic view (and as the sum of the logic underlying the viable systems approach (VSA. This approach views the definition of boundaries. Therefore, in the large and intricate scenery of the studies dedicated to organizational boundaries, this work contributes to a better understanding of border selection as an interactive and changeable process capable of pushing organizations towards a greater awareness of their strategic dimension. This paper also offers some insights for future research, suggesting that both scholars and professionals investigate, firstly, new frontiers for the identification of organizational boundaries and, secondly, the possible positive repercussions that new organizational redesign modes could determine for a greater competitive success.

  11. Exact boundary controllability of nodal profile for quasilinear hyperbolic systems

    CERN Document Server

    Li, Tatsien; Gu, Qilong

    2016-01-01

    This book provides a comprehensive overview of the exact boundary controllability of nodal profile, a new kind of exact boundary controllability stimulated by some practical applications. This kind of controllability is useful in practice as it does not require any precisely given final state to be attained at a suitable time t=T by means of boundary controls, instead it requires the state to exactly fit any given demand (profile) on one or more nodes after a suitable time t=T by means of boundary controls. In this book we present a general discussion of this kind of controllability for general 1-D first order quasilinear hyperbolic systems and for general 1-D quasilinear wave equations on an interval as well as on a tree-like network using a modular-structure construtive method, suggested in LI Tatsien's monograph "Controllability and Observability for Quasilinear Hyperbolic Systems"(2010), and we establish a complete theory on the local exact boundary controllability of nodal profile for 1-D quasilinear hyp...

  12. The system of equations for mixed BVP with one Dirichlet boundary condition and three Neumann boundary conditions

    Science.gov (United States)

    Yusop, Nur Syaza Mohd; Mohamed, Nurul Akmal

    2017-05-01

    Boundary Element Method (BEM) is a numerical way to approximate the solutions of a Boundary Value Problem (BVP). The potential problem which involves the Laplace's equation on the square shape domain will be considered where the boundary is divided into four sets of linear boundary elements. We study the derivation system of equation for mixed BVP with one Dirichlet Boundary Condition (BC) is prescribed on one element of the boundary and Neumann BC on the other three elements. The mixed BVP will be reduced to a Boundary Integral Equation (BIE) by using a direct method which involves Green's second identity representation formula. Then, linear interpolation is used where the boundary will be discretized into some linear elements. As the result, we then obtain the system of linear equations. In conclusion, the specific element in the mixed BVP will have the specific prescribe value depends on the type of boundary condition. For Dirichlet BC, it has only one value at each node but for the Neumann BC, there will be different values at the corner nodes due to outward normal. Therefore, the assembly process for the system of equations related to the mixed BVP may not be as straight forward as Dirichlet BVP and Neumann BVP. For the future research, we will consider the different shape domains for mixed BVP with different prescribed boundary conditions.

  13. Classical system boundaries cannot be determined within quantum Darwinism

    Science.gov (United States)

    Fields, Chris

    Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.

  14. Optimal control problems for impulsive systems with integral boundary conditions

    Directory of Open Access Journals (Sweden)

    Allaberen Ashyralyev

    2013-03-01

    Full Text Available In this article, the optimal control problem is considered when the state of the system is described by the impulsive differential equations with integral boundary conditions. Applying the Banach contraction principle the existence and uniqueness of the solution is proved for the corresponding boundary problem by the fixed admissible control. The first and second variation of the functional is calculated. Various necessary conditions of optimality of the first and second order are obtained by the help of the variation of the controls.

  15. The boundary-domain integral method for elliptic systems

    CERN Document Server

    Pomp, Andreas

    1998-01-01

    This monograph gives a description of all algorithmic steps and a mathematical foundation for a special numerical method, namely the boundary-domain integral method (BDIM). This method is a generalization of the well-known boundary element method, but it is also applicable to linear elliptic systems with variable coefficients, especially to shell equations. The text should be understandable at the beginning graduate-level. It is addressed to researchers in the fields of numerical analysis and computational mechanics, and will be of interest to everyone looking at serious alternatives to the well-established finite element methods.

  16. Spatio-temporal variability of upwelling along the southwest coast of India based on satellite observations

    Science.gov (United States)

    Jayaram, Chiranjivi; Kumar, P. K. Dinesh

    2018-03-01

    Upwelling phenomenon along the eastern boundaries of global ocean has received greater attention in the recent times due to its environmental and economic significance in the global warming and the scenario of changing climate as opined by IPCC AR5. In this context, the availabile satellite data on sea surface winds, sea surface temperature (SST), sea level anomaly (SLA) and chlorophyll-a concentration (Chl-a), for the period 1981-2016 were analyzed to identify the coastal upwelling pattern in the Southeastern Arabian Sea (SEAS). Synergistic approach, using winds, SST, SLA and Chl-a revealed that strong upwelling was prevailing between 8°N and 12°N. During the study period, geographical differences existed in the peak values of upwelling favorable conditions considered for study. Analysis of the alongshore winds which are conducive for upwelling were observed to be curtailed towards the northern part of the study region between 2005 and 2010. Also, the strength of upwelling reduced during the strong ENSO years of 1997 and 2015. Linear regression based trend analysis of upwelling indices like Ekman transport, SST and chlorophyll along the coast, during the upwelling period, revealed slight increase in the strength towards the southern region while it decreased to the north during the study period.

  17. Ego boundary as process: a systemic-contextual approach.

    Science.gov (United States)

    Polster, S

    1983-08-01

    This paper examines the ego boundary construct, outlining its origin and development within psychoanalytic theory and demonstrating the ways in which its interpretation and use have been affected and circumscribed by the structural model upon which psychoanalytic theory is based. In particular, I will discuss the sequence of reasoning by which the construct boundary became synonymous with barrier at the expense of consideration of its role in maintaining contact and exchange with the world. The contributions and limitations of the mathematical model of Kurt Lewin are also discussed. An alternative systemic-contextual model is proposed, a model which describes boundary not as barrier but as dialectical processes of separation and inclusion which mediate a person's complex relationship with the world.

  18. Short-term variability of surface carbon dioxide and sea-air CO2 fluxes in the shelf waters of the Galician coastal upwelling system

    Directory of Open Access Journals (Sweden)

    Alba Marina Cobo-Viveros

    2013-01-01

    Full Text Available Using data collected during the DYBAGA and ECO cruises, remote sensing chlorophyll-a estimations and the averaged upwelling index of the previous fortnight (Iw’, we studied the variability of the sea surface CO2 fugacity (fCO2 over the Galician continental shelf during three seasonal cycles. Sea surface salinity (SSS distribution controlled fCO2 mainly in spring, while sea surface temperature (SST did so during periods of intense cooling in November and warming in June. The uptake of carbon by photosynthetic activity, which was more intense during spring and autumn, masked the surface increase in the dissolved inorganic carbon concentration during upwelling events, especially during spring. A significant low correlation between fCO2 and Iw’ was found during spring and summer when upwelling events were observed, whereas no relationship was observed during the downwelling period. High fCO2 exceeding atmospheric values was only found during the summer stratification breakdown. Although sea-air CO2 fluxes showed a marked inter-annual variability, surface waters off the Galician coast were net sinks for atmospheric CO2 in every seasonal cycle, showing a lower CO2 uptake (~65% compared to previously published values. Marked inter-annual changes in the sea-air CO2 fluxes seem to be influenced by fresh water inputs on the continental shelf under different meteorological scenarios.

  19. Free boundary problems in PDEs and particle systems

    CERN Document Server

    Carinci, Gioia; Giardinà, Cristian; Presutti, Errico

    2016-01-01

    In this volume a theory for models of transport in the presence of a free boundary is developed. Macroscopic laws of transport are described by PDE's. When the system is open, there are several mechanisms to couple the system with the external forces. Here a class of systems where the interaction with the exterior takes place in correspondence of a free boundary is considered. Both continuous and discrete models sharing the same structure are analysed. In Part I a free boundary problem related to the Stefan Problem is worked out in all details. For this model a new notion of relaxed solution is proposed for which global existence and uniqueness is proven. It is also shown that this is the hydrodynamic limit of the empirical mass density of the associated particle system. In Part II several other models are discussed. The expectation is that the results proved for the basic model extend to these other cases. All the models discussed in this volume have an interest in problems arising in several research fields...

  20. System, subsystem, hive: boundary problems in computational theories of consciousness

    Directory of Open Access Journals (Sweden)

    Tomer Fekete

    2016-07-01

    Full Text Available A computational theory of consciousness should include a quantitative measure of consciousness, or MoC, that (i would reveal to what extent a given system is conscious, (ii would make it possible to compare not only different systems, but also the same system at different times, and (iii would be graded, because so is consciousness. However, unless its design is properly constrained, such an MoC gives rise to what we call the boundary problem: an MoC that labels a system as conscious will do so for some – perhaps most – of its subsystems, as well as for irrelevantly extended systems (e.g., the original system augmented with physical appendages that contribute nothing to the properties supposedly supporting consciousness, and for aggregates of individually conscious systems (e.g., groups of people. This problem suggests that the properties that are being measured are epiphenomenal to consciousness, or else it implies a bizarre proliferation of minds. We propose that a solution to the boundary problem can be found by identifying properties that are intrinsic or systemic: properties that clearly differentiate between systems whose existence is a matter of fact, as opposed to those whose existence is a matter of interpretation (in the eye of the beholder. We argue that if a putative MoC can be shown to be systemic, this ipso facto resolves any associated boundary issues. As test cases, we analyze two recent theories of consciousness in light of our definitions: the Integrated Information Theory and the Geometric Theory of consciousness.

  1. Upwelling regions, the most fertile of the seas' habitats, are also ...

    African Journals Online (AJOL)

    spamer

    Two classical views need to be unified in assessing the dynamics of red ... The classical. (narrow) physical view is that coastal upwelling systems are generated by an onshore, wind-induced inflow of deeper, colder, nutrient-rich water, which upwells to maintain the ...... for conditioning is variable, influenced by the degree to.

  2. Characterization of the structure and cross-shore transport properties of a coastal upwelling filament using three-dimensional finite-size Lyapunov exponents

    Science.gov (United States)

    Bettencourt, João. H.; Rossi, Vincent; Hernández-García, Emilio; Marta-Almeida, Martinho; López, Cristóbal

    2017-09-01

    The three-dimensional structure, dynamics, and dispersion characteristics of a simulated upwelling filament in the Iberian upwelling system are analyzed using Lagrangian tools. We used a realistic regional simulation of the western Iberian shelf which is concomitant with an in situ oceanographic campaign that surveyed the area. We compute 3-D fields of finite-size Lyapunov exponents (FSLE) from 3-D velocity fields and extract the field's ridges to study the spatial distribution and temporal evolution of the Lagrangian Coherent Structures (LCSs) evolving around the filament. We find that the most intense curtain-like LCSs delimit the boundaries of the whole filamentary structure whose general properties match well the observations. The filament interior is characterized by small dispersion of fluid elements. Furthermore, we identify a weak LCS separating the filament into a warmer vein and a colder filament associated with the interaction of a mesoscale eddy with the upwelling front. The cold upwelled water parcels move along the filament conserving their density. The filament itself is characterized by small dispersion of fluid elements in its interior. The comparison of LCSs with potential temperature and salinity gradient fields shows that the outer limits of the filament coincide with regions of large hydrographic gradients, similar to those observed, explaining the isolation of the interior of the filament with the surrounding waters. We conclude that the Lagrangian analysis used in this work is useful in explaining the dynamics of cross-shore exchanges of materials between coastal regions and the open ocean due to mesoscale processes.

  3. What dynamics drive future wind scenarios for coastal upwelling off Peru and Chile?

    Science.gov (United States)

    Belmadani, Ali; Echevin, Vincent; Codron, Francis; Takahashi, Ken; Junquas, Clémentine

    2014-10-01

    The dynamics of the Peru-Chile upwelling system (PCUS) are primarily driven by alongshore wind stress and curl, like in other eastern boundary upwelling systems. Previous studies have suggested that upwelling-favorable winds would increase under climate change, due to an enhancement of the thermally-driven cross-shore pressure gradient. Using an atmospheric model on a stretched grid with increased horizontal resolution in the PCUS, a dynamical downscaling of climate scenarios from a global coupled general circulation model (CGCM) is performed to investigate the processes leading to sea-surface wind changes. Downscaled winds associated with present climate show reasonably good agreement with climatological observations. Downscaled winds under climate change show a strengthening off central Chile south of 35°S (at 30°S-35°S) in austral summer (winter) and a weakening elsewhere. An alongshore momentum balance shows that the wind slowdown (strengthening) off Peru and northern Chile (off central Chile) is associated with a decrease (an increase) in the alongshore pressure gradient. Whereas the strengthening off Chile is likely due to the poleward displacement and intensification of the South Pacific Anticyclone, the slowdown off Peru may be associated with increased precipitation over the tropics and associated convective anomalies, as suggested by a vorticity budget analysis. On the other hand, an increase in the land-sea temperature difference is not found to drive similar changes in the cross-shore pressure gradient. Results from another atmospheric model with distinct CGCM forcing and climate scenarios suggest that projected wind changes off Peru are sensitive to concurrent changes in sea surface temperature and rainfall.

  4. Outside the paradigm of upwelling rias in NW Iberian Peninsula: Biogeochemical and phytoplankton patterns of a non-upwelling ria

    Science.gov (United States)

    Ospina-Alvarez, Natalia; Varela, Manuel; Doval, María Dolores; Gómez-Gesteira, Moncho; Cervantes-Duarte, Rafael; Prego, Ricardo

    2014-02-01

    The Atlantic Galician rias show the effect of natural eutrophication during ENACW upwelling episodes when large amounts of nutrients are injected. However, the Cantabrian Galician rias do not appear to be disturbed by upwelling events and it can be hypothesized that eutrophy is not inherent to the Galician rias. This question was tackled regarding the biogeochemical and phytoplankton characteristic in the Ria of Barqueiro, located on the western boundary of the Cantabrian Sea, from January 2008 to January 2009. Thermohaline, PAR and fluorescence profiles, dissolved oxygen, nutrient salts, DOC, DON and chlorophyll concentrations, phytoplankton abundances and primary production were monthly determined in a monitoring station (43°45.509‧N-07°39.493‧W); moreover, the daily upwelling index information and fluvial contributions from Sor River were considered. Throughout the year only four annual oceanographic periods were observed: spring, summer stratification, autumn and winter, unlike the Atlantic rias, where a long upwelling period occurs with usually outstanding upwelling processes. Nutrient concentrations (a maximum of 6.2 μM of nitrate, 0.5 μM of nitrite, 2.8 μM of ammonium, 0.4 μM of phosphate and 5.7 μM of silicate), organic matter (98 μM of DOC, 14 μM of DON, 16.4 μM of POC and 2.0 μM of PON), Chl-a (1.1 μg L-1), primary production (280 gC m-2 yr-1) and phytoplankton abundance were clearly lower (about half) when compared to those reported for the other rias during upwelling. Diatoms dominated the phytoplankton assemblages especially during spring and autumn blooms. In summer, although the wind conditions were favorable, upwelling was not observed in the Ria and a mixing of diatoms and dinoflagellates co-dominated the phytoplankton community with a lower contribution of diatoms in comparison to the Atlantic rias. The paradigm of natural eutrophication reported for the Galician rias was not observed in the Ria of Barqueiro, which may be

  5. Dynamics of a "low-enrichment high-retention" upwelling center over the southern Senegal shelf

    Science.gov (United States)

    Ndoye, Siny; Capet, Xavier; Estrade, Philippe; Sow, Bamol; Machu, Eric; Brochier, Timothée.; Döring, Julian; Brehmer, Patrice

    2017-05-01

    Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross-shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δx≈ 2 km) are sufficient to reproduce the SSUS frontal system. Our main focus is on the 3-D upwelling circulation which turns out to be profoundly different from 2-D theory: cold water injection onto the shelf and upwelling are strongly concentrated within a few tens of kilometers south of Cape Verde and largely arise from flow divergence in the alongshore direction; a significant fraction of the upwelled waters are retained nearshore over long distances while travelling southward under the influence of northerly winds. Another source of complexity, regional-scale alongshore pressure gradients, also contributes to the overall retention of upwelled waters over the shelf. Varying the degree of realism of atmospheric and oceanic forcings does not appreciably change these conclusions. This study sheds light on the dynamics and circulation underlying the recurrent sea surface temperature pattern observed during the upwelling season and offers new perspectives on the connections between the SSUS physical environment and its ecosystems. It also casts doubt on the validity of upwelling intensity estimations based on simple Ekman upwelling indices at such local scales.

  6. Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses

    Directory of Open Access Journals (Sweden)

    José M. R. Alves

    2013-05-01

    Full Text Available The Regional Ocean Modeling System ocean model is used to simulate the decadal evolution of the regional waters in offshore Iberia in response to atmospheric fields given by ECMWF ERA-40 (1961–2001 and ERA-Interim (1989–2008 reanalyses. The simulated sea surface temperature (SST fields are verified against satellite AVHRR SST, and they are analysed to characterise the variability and trends of coastal upwelling in the region. Opposing trends in upwelling frequency are found at the northern limit, where upwelling has been decreasing in recent decades, and at its southern edge, where there is some evidence of increased upwelling. These results confirm previous observational studies and, more importantly, indicate that observed SST trends are not only due to changes in radiative or atmospheric heat fluxes alone but also due to changes in upwelling dynamics, suggesting that such a process may be relevant in climate change scenarios.

  7. On the upwelling dynamics off northwest Africa in 2009-2012

    Science.gov (United States)

    Menna, Milena; Poulain, Pierre-Marie; Faye, Saliou; Diaw, Basirou; Centurioni, Luca; Lazar, Alban; Gaye, Amadou; Sow, Bamol Ali; Dragone, Dominique

    2014-05-01

    Drifter data, satellite maps and time series of SST, upwelling index and ocean surface wind products are used to characterise the North Western Africa upwelling system in the period 2009-2012, with particular focus to the region between Cap Blanc (Mauritania) and Cap Vert (Senegal). This region corresponds to the southern part of the seasonal translation of the Trade winds along the western African coast and the relative upwelling has a marked seasonal periodicity. The upwelling season generally starts in late November and persists until early July north of 20°N, whereas it starts in late December until May in the south; in June the upwelling events south of Cap Blanc disappear and gradually the residual cold water mixes with the warm surface tropical Atlantic water. The most intense upwelling episodes are recorded between February and May and the upwelling index reaches its maximum in April-May (values larger than 1000 m3/s). These episodes usually coincide with maximum intensities of upwelling favourable winds (Trade winds) and are characterised by a mean duration of 5-10 days, SST values lower than 20.2°C and upwelling index larger than 700 m3/s. Cold and nutrient-rich coastal near-surface waters are upwelled and transported offshore (westward) by means of energetic filaments rooted at specific locations along the coasts of Mauritania and Senegal. Four recurrent upwelling filaments (SST lower than 20°C), with an offshore extension between 200 km and 400 km, are observed and characterised. These filaments persist for a few weeks, and they subsequently mix with the surrounding waters. The filament formation is generally associated with the topographic features (capes) of the region. Wind vorticity fields show positive values close to the coast between Cape Vert and Cape Blanc during the upwelling seasons; larger values correspond with the location of the main cold water filaments. Cold water upwelled in the Cap Vert region are transported both westward, toward

  8. Upwelling along the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, C.S.; Varadachari, V.V.R.

    An examination of the physical characteristics of the shelf waters off Karaikal in the premonsoon period and off Madras and Waltair in the premonsoon and monsoon periods reveals the presence of upwelling along the East Coast of India...

  9. Coastal upwelling ecosystems are often identified as regions ...

    African Journals Online (AJOL)

    spamer

    The coastal upwelling front forms soon after the onset of upwelling and is advected offshore as upwelling proceeds. During periods of sustained upwelling, the ... mixed, shallow zone where surface and bottom .... 3: Interannual mussel toxicity at a mussel farm in Saldanha Bay showing measured levels of (a) saxitoxin.

  10. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    Science.gov (United States)

    Addison, J. A.; Barron, J. A.; Finney, B.; Kusler, J. E.; Bukry, D.; Heusser, L. E.; Alexander, C. R., Jr.

    2016-12-01

    The Holocene upwelling history of the northern California continental slope is examined using a 7-m-long marine sediment core (TN062-O550; 40.9°N, 124.6°W, 550 m water depth) collected offshore from Eureka, CA, that spans the last 7,400 calibrated years before present (cal yrs BP). A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with global Holocene millennial-scale warm intervals. Results show biogenic sediment accumulation in TN062-O550 varied considerably during the Holocene, despite being located within 50 km of the mouth of the Eel River, one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at 2900 cal yr BP indicates the onset of modern upwelling in the CCS, and that this period also corresponds to the most intense period of upwelling in the last 7,400 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification as recorded in TN062-O550 corresponds closely to that seen at nearby ODP Site 1019 as well as in the Santa Barbara Basin of southern California. Other CCS records with less high-quality age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone-derived sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we tentatively suggest that regional CCS warming may be conducive to upwelling intensification in the future.

  11. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    Science.gov (United States)

    Addison, Jason A.; Barron, John A.; Finney, Bruce P.; Kusler, Jennifer E.; Bukry, David; Heusser, Linda E.; Alexander, Clark R.

    2017-01-01

    The Holocene upwelling history of the northern California continental slope is examined using the high-resolution record of TN062-O550 (40.9°N, 124.6°W, 550 m water depth). This 7-m-long marine sediment core spans the last ∼7500 years, and we use it to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with Holocene millennial-scale warm intervals. A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test this hypothesis. The record of biogenic accumulation in TN062-O550 shows considerable Holocene variability despite being located within 50 km of the mouth of the Eel River, which is one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at ∼2900 calibrated years before present (cal yr BP) indicates the onset of modern upwelling in the CCS, and this period also corresponds to the most intense period of upwelling in the last 7500 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification at TN062-O550 corresponds closely to that seen at nearby ODP Site 1019, as well as in the Santa Barbara Basin of southern California. Other CCS records with less refined age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we suggest that CCS warming may be conducive to upwelling intensification, though future changes are unclear as the mechanisms forcing SST variability may differ.

  12. System and method for free-boundary surface extraction

    KAUST Repository

    Algarni, Marei

    2017-10-26

    A method of extracting surfaces in three-dimensional data includes receiving as inputs three-dimensional data and a seed point p located on a surface to be extracted. The method further includes propagating a front outwardly from the seed point p and extracting a plurality of ridge curves based on the propagated front. A surface boundary is detected based on a comparison of distances between adjacent ridge curves and the desired surface is extracted based on the detected surface boundary.

  13. Biogeochemical cycling in the ocean. Part 1: Introduction to the effects of upwelling along the west coast of North America

    Science.gov (United States)

    Howe, John T.

    1986-01-01

    Coastal upwelling is examined as it relates to the cycling of chemical species in coastal waters along the west coast of North America. The temporal and spatial features of upwelling phenomena in the Eastern boundary regions of the North Pacific Ocean are presented and discussed in terms of upwelling episodes. Climate conditions affecting upwelling include: thermal effects, wind-induced shear stress which moves surface layers, and the curl of the wind stress vector which is thought to affect the extent and nature of upwelling and the formation of offshore convergent downwelling fronts. These effects and the interaction of sunlight and upwelled nutrients which result in a biological bloom in surface waters is modeled analytically. The roles of biological and chemical species, including the effects of predation, are discussed in that context, and relevant remote sensing and in situ observations are presented. Climatological, oceanographic, biological, physical, chemical events, and processes that pertain to biogeochemical cycling are presented and described by a set of partial differential equations. Simple preliminary results are obtained and are compared with data. Thus a fairly general framework has been laid where the many facets of biogeochemical cycling in coastal upwelled waters can be examined in their relationship to one another, and to the whole, to whatever level of detail or approximation is warranted or desired.

  14. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast

    OpenAIRE

    Sald?var-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, H?ctor; Lluch-Cota, Daniel; del Monte-Luna, Pablo

    2016-01-01

    The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series ana...

  15. Evaluation of Recharge Trench System, North Boundary Containment Treatment System, Rocky Mountain Arsenal, Commerce City, Colorado

    National Research Council Canada - National Science Library

    Corcoran, Maureen K; Patrick, David M; Gaggiani, Neville G; May, James H

    2005-01-01

    ...) at Rocky Mountain Arsenal (RMA), located in Commerce City, CO. The NBCTS is a 6,740-fT (2,054-M)-long multicomponent system that precludes off-site movement of contaminated water at the north boundary of RMA...

  16. Hydrodynamic limits for one-dimensional particle systems with moving boundaries

    OpenAIRE

    Chayes, L.; G. Swindle

    1996-01-01

    We analyze a new class of one-dimensional interacting particle systems featuring random boundaries with a random motion that is coupled to the local particle density. We show that the hydrodynamic limiting behavior in these systems corresponds to the solution of an appropriate. Stefan (free-boundary) equation and describe some applications of these results.

  17. Bayesian Statistics and Uncertainty Quantification for Safety Boundary Analysis in Complex Systems

    Science.gov (United States)

    He, Yuning; Davies, Misty Dawn

    2014-01-01

    The analysis of a safety-critical system often requires detailed knowledge of safe regions and their highdimensional non-linear boundaries. We present a statistical approach to iteratively detect and characterize the boundaries, which are provided as parameterized shape candidates. Using methods from uncertainty quantification and active learning, we incrementally construct a statistical model from only few simulation runs and obtain statistically sound estimates of the shape parameters for safety boundaries.

  18. Observed impact of upwelling events on water properties and biological activity off the southwest coast of New Caledonia.

    Science.gov (United States)

    Ganachaud, Alexandre; Vega, Andrés; Rodier, Martine; Dupouy, Cécile; Maes, Christophe; Marchesiello, Patrick; Eldin, Gerard; Ridgway, Ken; Le Borgne, Robert

    2010-01-01

    The upwelling events that follow strong trade wind episodes have been described in terms of their remarkable signature in the sea surface temperature southwest off New Caledonia. Upwelling brings deeper, and colder waters to the surface, causing 2-4 degrees C drops in temperature in a few hours, followed by a slower relaxation over several days. Upwelling may sporadically bring nutrients to the surface under certain conditions, and increase the biological productivity. Two multidisciplinary hydrographic cruises allow the impact of upwelling on the chemical and biological properties of the water to be documented. Both cruises took place in austral summer (December 2004 and December 2005), but the first cruise occurred during a strong upwelling event, while the second cruise occurred in calm conditions. The water properties and planktonic composition show important contrasts, with a strong southeastward current (the "ALIS current of New Caledonia") competing with the upwelling system. Our analysis suggests that, while observed productivities are far less than those of typical upwelling systems, some wind events in New Caledonia may contribute to biological activity. A currentmeter mooring, deployed during the second cruise, documents the ocean response to a changing wind field and the local impact of upwelling on currents and temperatures on the water column. The results are discussed, with the help of climatology, Argo float profiler data, satellite data and of a high-resolution numerical simulation. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  19. Trends of the Galician upwelling in the context of climate change

    Science.gov (United States)

    Casabella, N.; Lorenzo, M. N.; Taboada, J. J.

    2014-10-01

    Coastal upwelling is a phenomenon of great importance both for the study of ocean dynamics and for the development of fish production in some coastal regions. Our study region, the Galician coast, lies at the northern end of the Canary-Iberian Peninsula upwelling system. Knowing the changes provoked by climate change on this upwelling system is particularly relevant for the future of this area taking into account the social and economic importance of fishing activities in this region. In this paper we study the trends in the intensity and frequency of upwelling in the Galician coast and the expected changes in this phenomenon for the next decades using three regional models implemented within the European project ENSEMBLES. As a main result, we observe that the models show a positive trend in both the intensity and frequency of upwelling phenomenon for the future, particularly significant in spring and summer which are the seasons favorable for upwelling. In autumn and winter there are no significant changes.

  20. Dislocations, boundaries and slip systems in cube grains of rolled aluminium

    DEFF Research Database (Denmark)

    Wei, Yili; Godfrey, A.; Liu, W.

    2011-01-01

    The relationship between the dislocation content of boundaries and the active slip systems is explored by characterisation of Burgers vectors, dislocation lines and relative densities in 11 boundaries in near-cube grains in 10% rolled aluminium. To provide a good basis for comparison, all...

  1. Generalization of special features of boundary element method realization in Ukrainian computer-aided programming systems

    OpenAIRE

    Korobanov, Yurii M.; Lishchuk, Ohnieslav M.; Lishchuk, Ivan M.

    2014-01-01

    The generalization of theoretical bases for engineering calculations of ship structures in the Ukrainian computer-aided design systems is performed. The mathematical base of the boundary elements method is set out; the boundary integral equation is presented. The method of fictitious loads is considered as the basis of ship structures calculation realization.

  2. Boundary-fitted coordinate systems for numerical solution of partial differential equations - A review

    Science.gov (United States)

    Thompson, J. F.; Warsi, Z. U. A.; Mastin, C. W.

    1982-01-01

    A comprehensive review of methods of numerically generating curvilinear coordinate systems with coordinate lines coincident with all boundary segments is given. Some general mathematical framework and error analysis common to such coordinate systems is also included. The general categories of generating systems are those based on conformal mapping, orthogonal systems, nearly orthogonal systems, systems produced as the solution of elliptic and hyperbolic partial differential equations, and systems generated algebraically by interpolation among the boundaries. Also covered are the control of coordinate line spacing by functions embedded in the partial differential operators of the generating system and by subsequent stretching transformation. Dynamically adaptive coordinate systems, coupled with the physical solution, and time-dependent systems that follow moving boundaries are treated. References reporting experience using such coordinate systems are reviewed as well as those covering the system development.

  3. Surface circulation and upwelling patterns around Sri Lanka

    Science.gov (United States)

    de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

    2013-09-01

    Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side. The region is characterised by bi-annually reversing monsoon winds resulting from seasonal differential heating and cooling of the continental land mass and the ocean. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and the Regional Ocean Modelling System (ROMS) configured to the study region and forced with ECMWF interim data. The model was run for 2 yr to examine the seasonal and shorter term (∼10 days) variability. The results confirmed the presence of the reversing current system in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC) transporting 9.5 Sv during the Northeast (NE) monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast. During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast and is shown to be due to flow convergence and divergence associated with offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind driven flow along the east and west coasts: during the SW (NE) monsoon the flow along the

  4. Feeding Relationship between Octopus vulgaris (Cuvier, 1797 Early Life-Cycle Stages and Their Prey in the Western Iberian Upwelling System: Correlation of Reciprocal Lipid and Fatty Acid Contents

    Directory of Open Access Journals (Sweden)

    Sílvia Lourenço

    2017-07-01

    Full Text Available Under the influence of the Western Iberian upwelling system, the Iberian Atlantic coast holds important hatcheries and recruitment areas for Octopus vulgaris. Recently identified as an octopus hatchery, the Ría de Vigo harbors an important mesozooplankton community that supports O. vulgaris paralarvae during the first days of their planktonic stage. This study represents a preliminary approach to determine the nutritional link between wild O. vulgaris hatchlings, paralarvae and their zooplankton prey in the Ría de Vigo, by analyzing their lipid class content and fatty acid profiles. The results show that octopus hatchlings are richer in structural lipids as phospholipids and cholesterol, while the zooplankton is richer in reserve lipids like triacylglycerol and waxes. Zooplankton samples are also particularly rich in C18:1n9 and 22:6n3 (DHA, that seem to be successfully incorporated by O. vulgaris paralarvae thus resulting in a distinct fatty acid profile to that of the hatchlings. On the other hand, content in C20:4n6 (ARA is maintained high through development, even though the zooplankton is apparently poorer in this essential fatty acid, confirming its importance for the development of O. vulgaris paralarvae. The content in monounsaturated fatty acids, particularly C18:1n7, and the DHA: EPA ratio are suggested as trophic markers of the diet of O. vulgaris paralarvae.

  5. A question of fit: reflections on boundaries, organizations and social-ecological systems.

    Science.gov (United States)

    Sternlieb, Faith; Bixler, R Patrick; Huber-Stearns, Heidi; Huayhuaca, Ch'aska

    2013-11-30

    Although there is acknowledgment that the complexity of social-ecological systems governance demands representation from diverse perspectives, there is little agreement in the literature on how to cross both fiat (human-demarcated) and bona fide (physical) boundaries to address such complexities. As a cohort of interdisciplinary scholars, we navigate the boundary between science and practice to address the question of fit regarding the role of organizations in transcending boundaries. We found there is a need to rectify discrepancies between theories about boundaries and theories about organizations. To this end, we propose a conceptual framework to analyze transboundary organizations, an umbrella term to group the literature on boundary organizations, intermediaries and bridging organizations; we introduce this term to illustrate they are not mutually exclusive and to facilitate interdisciplinary research. We first examine social-ecological systems (SES), a framework intended to improve understandings of boundaries and governance. We then continue to unpack the complexity of boundaries and organizations, specifically through important transboundary concepts such as scale and organizational learning. This helps frame our examination of the literature on: 1) boundary organizations; 2) bridging organizations (third-party entities); and 3) intermediaries (distinguished by their position between other actors). Our review identifies a number of discrepancies that pertain to the types of boundaries discussed and the roles assigned to organizations governing SES. Important characteristics have emerged from our review of transboundary organizations including legitimacy, saliency, urgency, and credibility. In developing a conceptual framework, we argue that transboundary organizations: 1) expand upon the boundary spectrum, 2) incorporate transboundary concepts, and 3) hybridize characteristics of boundary, bridging, and intermediary organizations. We conclude with a number

  6. Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Malik, A; Fernandes, C; Gonsalves, M.J.B.D.; Subina, N.S.; Mamatha, S.S.; Krishna, K.S.; Varik, S.; RituKumari; Gauns, M.; Cejoice, R.P.; Pandey, S.S.; Jineesh, V.K.; Kamaleson, A; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.S; LokaBharathi, P.A

    Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May–September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions...

  7. Existence of positive solutions for a system of semipositone fractional boundary value problems

    Directory of Open Access Journals (Sweden)

    Johnny Henderson

    2016-05-01

    Full Text Available We investigate the existence of positive solutions for a system of nonlinear Riemann-Liouville fractional differential equations with sign-changing nonlinearities, subject to coupled integral boundary conditions.

  8. Aquifer Boundary of the Wood River Valley Aquifer System, South-Central Idaho

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This dataset contains the boundary of the Wood River Valley aquifer system as modified and expanded from that defined by Skinner and others (2007): It has been...

  9. On a system of higher-order multi-point boundary value problems

    Directory of Open Access Journals (Sweden)

    Johnny Henderson

    2012-07-01

    Full Text Available We investigate the existence and nonexistence of positive solutions for a system of nonlinear higher-order ordinary differential equations subject to some multi-point boundary conditions.

  10. Undiscovered natural gas resources Total Petroleum System unit boundaries for Bangladesh (tps8bg)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This coverage includes arcs, polygons, and polygon labels that describe the Total Petroleum System boundaries of the natural gas resources of Bangladesh. This...

  11. Biogeochemical and ecological impacts of boundary currents in the Indian Ocean

    Science.gov (United States)

    Hood, Raleigh R.; Beckley, Lynnath E.; Wiggert, Jerry D.

    2017-08-01

    Monsoon forcing and the unique geomorphology of the Indian Ocean basin result in complex boundary currents, which are unique in many respects. In the northern Indian Ocean, several boundary current systems reverse seasonally. For example, upwelling coincident with northward-flowing currents along the coast of Oman during the Southwest Monsoon gives rise to high productivity which also alters nutrient stoichiometry and therefore, the species composition of the resulting phytoplankton blooms. During the Northeast Monsoon most of the northern Indian Ocean boundary currents reverse and favor downwelling. Higher trophic level species have evolved behavioral responses to these seasonally changing conditions. Examples from the western Arabian Sea include vertical feeding migrations of a copepod (Calanoides carinatus) and the reproductive cycle of a large pelagic fish (Scomberomorus commerson). The impacts of these seasonal current reversals and changes in upwelling and downwelling circulations are also manifested in West Indian coastal waters, where they influence dissolved oxygen concentrations and have been implicated in massive fish kills. The winds and boundary currents reverse seasonally in the Bay of Bengal, though the associated changes in upwelling and productivity are less pronounced. Nonetheless, their effects are observed on the East Indian shelf as, for example, seasonal changes in copepod abundance and zooplankton community structure. In contrast, south of Sri Lanka seasonal reversals in the boundary currents are associated with dramatic changes in the intensity of coastal upwelling, chlorophyll concentration, and catch per unit effort of fishes. Off the coast of Java, monsoon-driven changes in the currents and upwelling strongly impact chlorophyll concentrations, seasonal vertical migrations of zooplankton, and sardine catch in Bali Strait. In the southern hemisphere the Leeuwin is a downwelling-favorable current that flows southward along western Australia

  12. Although most of the phytoplankton of the Benguela upwelling ...

    African Journals Online (AJOL)

    spamer

    the vicinity of the upwelling front, which is displaced from the coast during the active phase of upwelling. There, increased ... warm, near-surface water corresponds to the onshore movement of the upwelling front and will often be .... picked up from dark-red water after being found swimming with their heads above the water, ...

  13. 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

  14. Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

    Science.gov (United States)

    Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

    2017-03-01

    The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

  15. The scaling and shift of morphogen gene expression boundary in a nonlinear reaction diffusion system.

    Science.gov (United States)

    Li, Wei-Shen; Shao, Yuan-Zhi

    2014-06-01

    The scaling and shift of the gene expression boundary in a developing embryo are two key problems with regard to morphogen gradient formation in developmental biology. In this study, a bigradient model was applied to a nonlinear reaction diffusion system (NRDS) to investigate the location of morphogen gene expression boundary. In contrast to the traditional synthesis-diffusion-degradation model, the introduction of NRDS in this study contributes to the precise gene expression boundary at arbitrary location along the anterior-posterior axis other than simply midembryo even when the linear characteristic lengths of two morphogens are equal. The scaling location depends on the ratio of two morphogen influxes (w) and concentrations (r) as well as the nonlinear reaction diffusion parameters (a, n). We also formulate a direct relationship between the shift in the gene expression boundary and the influx of morphogen and find that enhancing the morphogen influx is helpful to build up a robust gene expression boundary. By analyzing the robustness of the morphogen gene expression boundary and comparing with the relevant results in linear reaction diffusion system, we determine the precise range of the ratio of the two morphogen influxes with a lower shift in the morphogen gene expression boundary and increased system robustness.

  16. Analytic Approximations to Nonlinear Boundary Value Problems Modeling Beam-Type Nano-Electromechanical Systems

    Science.gov (United States)

    Zou, Li; Liang, Songxin; Li, Yawei; Jeffrey, David J.

    2017-03-01

    Nonlinear boundary value problems arise frequently in physical and mechanical sciences. An effective analytic approach with two parameters is first proposed for solving nonlinear boundary value problems. It is demonstrated that solutions given by the two-parameter method are more accurate than solutions given by the Adomian decomposition method (ADM). It is further demonstrated that solutions given by the ADM can also be recovered from the solutions given by the two-parameter method. The effectiveness of this method is demonstrated by solving some nonlinear boundary value problems modeling beam-type nano-electromechanical systems.

  17. Analytic approximations to nonlinear boundary value problems modeling beam-type nano-electromechanical systems

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Li [Dalian Univ. of Technology, Dalian City (China). State Key Lab. of Structural Analysis for Industrial Equipment; Liang, Songxin; Li, Yawei [Dalian Univ. of Technology, Dalian City (China). School of Mathematical Sciences; Jeffrey, David J. [Univ. of Western Ontario, London (Canada). Dept. of Applied Mathematics

    2017-06-01

    Nonlinear boundary value problems arise frequently in physical and mechanical sciences. An effective analytic approach with two parameters is first proposed for solving nonlinear boundary value problems. It is demonstrated that solutions given by the two-parameter method are more accurate than solutions given by the Adomian decomposition method (ADM). It is further demonstrated that solutions given by the ADM can also be recovered from the solutions given by the two-parameter method. The effectiveness of this method is demonstrated by solving some nonlinear boundary value problems modeling beam-type nano-electromechanical systems.

  18. First-principle proof of the modified collision boundary conditions for the hard-sphere system

    Science.gov (United States)

    Tessarotto, Massimo; Cremaschini, Claudio

    2014-05-01

    A fundamental issue lying at the foundation of classical statistical mechanics is the determination of the collision boundary conditions that characterize the dynamical evolution of multi-particle probability density functions (PDF) and are applicable to systems of hard-spheres undergoing multiple elastic collisions. In this paper it is proved that, when the deterministic N-body PDF is included in the class of admissible solutions of the Liouville equation, the customary form of collision boundary conditions adopted in previous literature becomes physically inconsistent and must actually be replaced by suitably modified collision boundary conditions.

  19. Humpback whale “super-groups” – A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System

    Science.gov (United States)

    Seakamela, S. Mduduzi; Meÿer, Michael A.; Kirkman, Stephen P.; Barendse, Jaco; Cade, David E.; Hurwitz, David; Kennedy, Amy S.; Kotze, Pieter G. H.; McCue, Steven A.; Thornton, Meredith; Vargas-Fonseca, O. Alejandra; Wilke, Christopher G.

    2017-01-01

    Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent “fishy” smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding

  20. Humpback whale "super-groups" - A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System.

    Science.gov (United States)

    Findlay, Ken P; Seakamela, S Mduduzi; Meÿer, Michael A; Kirkman, Stephen P; Barendse, Jaco; Cade, David E; Hurwitz, David; Kennedy, Amy S; Kotze, Pieter G H; McCue, Steven A; Thornton, Meredith; Vargas-Fonseca, O Alejandra; Wilke, Christopher G

    2017-01-01

    Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events

  1. Humpback whale "super-groups" - A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae in the Benguela Upwelling System.

    Directory of Open Access Journals (Sweden)

    Ken P Findlay

    Full Text Available Southern Hemisphere humpback whales (Megaptera novaeangliae generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens, hyperiid amphipods (Themisto gaudichaudii, mantis shrimp (Pterygosquilla armata capensis and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015 identified large tightly-spaced groups (20 to 200 individuals of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude

  2. Framework to Define Structure and Boundaries of Complex Health Intervention Systems: The ALERT Project

    DEFF Research Database (Denmark)

    Boriani, Elena; Esposito, Roberto; Frazzoli, Chiara

    2017-01-01

    of a framework with focus on systems and system boundaries of interdisciplinary projects. As an example on how to apply our framework, we analyzed ALERT [an integrated sensors and biosensors’ system (BEST) aimed at monitoring the quality, health, and traceability of the chain of the bovine milk...

  3. Numerical solution of system of boundary value problems using B-spline with free parameter

    Science.gov (United States)

    Gupta, Yogesh

    2017-01-01

    This paper deals with method of B-spline solution for a system of boundary value problems. The differential equations are useful in various fields of science and engineering. Some interesting real life problems involve more than one unknown function. These result in system of simultaneous differential equations. Such systems have been applied to many problems in mathematics, physics, engineering etc. In present paper, B-spline and B-spline with free parameter methods for the solution of a linear system of second-order boundary value problems are presented. The methods utilize the values of cubic B-spline and its derivatives at nodal points together with the equations of the given system and boundary conditions, ensuing into the linear matrix equation.

  4. Impact of a coastal-trapped wave on the near-coastal circulation of the Peru upwelling system from glider data

    Science.gov (United States)

    Pietri, Alice; Echevin, Vincent; Testor, Pierre; Chaigneau, Alexis; Mortier, Laurent; Grados, Carmen; Albert, Aurélie

    2014-03-01

    Geostrophic alongshore velocity data from a glider repetitive section off the coast of Peru (14°S) are used to study the cross-shore structure and temporal variability of the Peru current system during a 5 week period in April-May 2010. Besides providing substantial information on the surface frontal jet associated with the Peru Coastal Current and the surfacing Peru-Chile Undercurrent that flows poleward trapped on the continental shelf and slope, the glider data reveal the presence of an intense deep equatorward current, which transports up to ˜2.5 Sv. The dynamics of this current are investigated using an eddy-resolving regional model. The variability of the vertically sheared alongshore flow is shown to be related to the passage of a poleward propagating coastal-trapped wave likely of equatorial origin. Solutions from a two-dimensional, linear, coastal wave model suggest that the alongshore current observed vertical structure is associated with the second and third baroclinic modes of the coastal-trapped wave.

  5. Surface circulation and upwelling patterns around Sri Lanka

    Science.gov (United States)

    de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

    2014-10-01

    Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (~10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over 2010-2012) and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the

  6. Drop interaction with solid boundaries in liquid/liquid systems

    Science.gov (United States)

    Bordoloi, Ankur Deep

    The present experimental work was motivated primarily by the CO 2 sequestration process. In a possible scenario during this process, gravity driven CO2 bubbles coalesce at an interface near the rock surface. In another scenario, trapped CO2 fluid may escape from a porous matrix overcoming interfacial force inside a pore. Based on these potential scenarios, the current research was divided into two broad experimental studies. In the first part, coalescence at a quiescent interface of two analogous fluids (silicone oil and water/glycerin mixture) was investigated for water/glycerin drops with Bond number (Bo) ~7 and Ohnesorge number ~ 0.01 using high-speed imaging and time-resolved tomographic PIV. Two perturbation cases with a solid particle wetted in oil and water/glycerin placed adjacent to the coalescing drop were considered. The results were compared with coalescence of a single drop and that of a drop neighBored by a second drop of equivalent size. Each perturbing object caused an initial tilting of the drop, influencing its rupture location, subsequent film retraction and eventual collapse behavior. Once tilted, drops typically ruptured near their lowest vertical position which was located either toward or away from the perturbing object depending on the case. The trends in local retraction speed of the ruptured film and the overall dynamics of the collapsing drops were discussed in detail. In the second part, the motion of gravity driven drops (B o~0.8-11) through a confining orifice d/Dglycerin, surrounded by silicone oil, fall toward and encounter the orifice plate after reaching terminal speed. The effects of surface wettability were investigated for Both round-edged and sharp-edged orifices. For the round-edged case, a thin film of surrounding oil prevented the drop fluid from contacting the orifice surface, such that the flow outcomes of the drops were independent of surface wettability. For d/D<0.8, the Boundary between drop capture and release depended

  7. Diffusive boundary layers over varying topography

    KAUST Repository

    Dell, R. W.

    2015-03-25

    Diffusive bottom boundary layers can produce upslope flows in a stratified fluid. Accumulating observations suggest that these boundary layers may drive upwelling and mixing in mid-ocean ridge flank canyons. However, most studies of diffusive bottom boundary layers to date have concentrated on constant bottom slopes. We present a study of how diffusive boundary layers interact with various idealized topography, such as changes in bottom slope, slopes with corrugations and isolated sills. We use linear theory and numerical simulations in the regional ocean modeling system (ROMS) model to show changes in bottom slope can cause convergences and divergences within the boundary layer, in turn causing fluid exchanges that reach far into the overlying fluid and alter stratification far from the bottom. We also identify several different regimes of boundary-layer behaviour for topography with oceanographically relevant size and shape, including reversing flows and overflows, and we develop a simple theory that predicts the regime boundaries, including what topographies will generate overflows. As observations also suggest there may be overflows in deep canyons where the flow passes over isolated bumps and sills, this parameter range may be particularly significant for understanding the role of boundary layers in the deep ocean.

  8. Effects of Seasonal Upwelling on Inorganic and Organic Matter Dynamics in the Water Column of Eastern Pacific Coral Reefs.

    Directory of Open Access Journals (Sweden)

    Ines Stuhldreier

    Full Text Available The Gulf of Papagayo at the northern Pacific coast of Costa Rica experiences pronounced seasonal changes in water parameters caused by wind-driven coastal upwelling. While remote sensing and open water sampling already described the physical nature of this upwelling, the spatial and temporal effects on key parameters and processes in the water column have not been investigated yet, although being highly relevant for coral reef functioning. The present study investigated a range of water parameters on two coral reefs with different exposure to upwelling (Matapalo and Bajo Rojo in a weekly to monthly resolution over one year (May 2013 to April 2014. Based on air temperature, wind speed and water temperature, three time clusters were defined: a May to November 2013 without upwelling, b December 2013 to April 2014 with moderate upwelling, punctuated by c extreme upwelling events in February, March and April 2014. During upwelling peaks, water temperatures decreased by 7°C (Matapalo and 9°C (Bajo Rojo to minima of 20.1 and 15.3°C respectively, while phosphate, ammonia and nitrate concentrations increased 3 to 15-fold to maxima of 1.3 μmol PO43- L-1, 3.0 μmol NH4+ L-1 and 9.7 μmol NO3- L-1. This increased availability of nutrients triggered several successive phytoplankton blooms as indicated by 3- (Matapalo and 6-fold (Bajo Rojo increases in chlorophyll a concentrations. Particulate organic carbon and nitrogen (POC and PON increased by 40 and 70% respectively from February to April 2014. Dissolved organic carbon (DOC increased by 70% in December and stayed elevated for at least 4 months, indicating high organic matter release by primary producers. Such strong cascading effects of upwelling on organic matter dynamics on coral reefs have not been reported previously, although likely impacting many reefs in comparable upwelling systems.

  9. Effects of Seasonal Upwelling on Inorganic and Organic Matter Dynamics in the Water Column of Eastern Pacific Coral Reefs.

    Science.gov (United States)

    Stuhldreier, Ines; Sánchez-Noguera, Celeste; Rixen, Tim; Cortés, Jorge; Morales, Alvaro; Wild, Christian

    2015-01-01

    The Gulf of Papagayo at the northern Pacific coast of Costa Rica experiences pronounced seasonal changes in water parameters caused by wind-driven coastal upwelling. While remote sensing and open water sampling already described the physical nature of this upwelling, the spatial and temporal effects on key parameters and processes in the water column have not been investigated yet, although being highly relevant for coral reef functioning. The present study investigated a range of water parameters on two coral reefs with different exposure to upwelling (Matapalo and Bajo Rojo) in a weekly to monthly resolution over one year (May 2013 to April 2014). Based on air temperature, wind speed and water temperature, three time clusters were defined: a) May to November 2013 without upwelling, b) December 2013 to April 2014 with moderate upwelling, punctuated by c) extreme upwelling events in February, March and April 2014. During upwelling peaks, water temperatures decreased by 7°C (Matapalo) and 9°C (Bajo Rojo) to minima of 20.1 and 15.3°C respectively, while phosphate, ammonia and nitrate concentrations increased 3 to 15-fold to maxima of 1.3 μmol PO43- L-1, 3.0 μmol NH4+ L-1 and 9.7 μmol NO3- L-1. This increased availability of nutrients triggered several successive phytoplankton blooms as indicated by 3- (Matapalo) and 6-fold (Bajo Rojo) increases in chlorophyll a concentrations. Particulate organic carbon and nitrogen (POC and PON) increased by 40 and 70% respectively from February to April 2014. Dissolved organic carbon (DOC) increased by 70% in December and stayed elevated for at least 4 months, indicating high organic matter release by primary producers. Such strong cascading effects of upwelling on organic matter dynamics on coral reefs have not been reported previously, although likely impacting many reefs in comparable upwelling systems.

  10. Cross shelf hydrographic and hydrochemical conditions and their short term variability at the northern Benguela during a normal upwelling season

    Science.gov (United States)

    Mohrholz, Volker; Eggert, Anja; Junker, Tim; Nausch, Günther; Ohde, Thomas; Schmidt, Martin

    2014-11-01

    Cross shelf hydrographic and hydrochemical conditions were investigated during the seasonal maximum of upwelling in the northern Benguela upwelling system. The study combines in situ observations, remotely sensed data and results of a regional 3-dimensional numerical model. In situ observations were recorded along a cross shelf transect off Namibia starting at 20°S 13°E, repeated five times during 16 August 2011 until 19 September 2011. Comparison of wind forcing and sea surface temperatures during the time of the expedition with long-term climatological data as well as the index of intensity of the Benguela upwelling indicates "normal" upwelling conditions in austral winter 2011 in the northern Benguela. Small scale temporal (days) and spatial (km) variability is high during the upwelling season, primarily caused by highly variable wind forcing and dynamics of mesoscale structures like eddies and filaments as found in remotely sensed data. This mesoscale dynamics impact the applicability of a conceptual 2-dimensional circulation model, i.e. a linear succession along the cross-shelf transect. Therefore, an age proxy for surface water was constructed based on oxygen and heat fluxes during the first aging period and on salinity and heat fluxes during the second phase. The application of an age proxy instead of distance to shore successfully validates the succession concept. Furthermore, the investigation of the upwelling strengths by analytical and circulation models verified their dependence on coastal- and curl driven upwelling processes with the onshore dominance of coastal upwelling. In the investigated time period, offshore, curl driven upwelling dominated with a maximum located on the shelf.

  11. Boundaries of the John H. Chafee Coastal Barrier Resources System

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This Coastal Barrier Resources System (CBRS) data set, produced by the U.S. Fish and Wildlife Service (Service), contains areas designated as undeveloped coastal...

  12. Performance of Numerical Boundary Condition based on Active Wave Absorption System

    DEFF Research Database (Denmark)

    Trouch, P.; Rouck, J. de; Frigaard, Peter

    2001-01-01

    The implementation and performance of a new active wave generating‐absorbing boundary condition for a numerical model based on the Volume Of Fluid (VOF) method for tracking free surfaces is presented. This numerical boundary condition AWAVOF is based on an active wave absorption system...... that was first developed in the context of physical wave flume experiments, using a wave paddle. The method applies to regular and irregular waves. Velocities are measured at one location inside the computational domain. The reflected wave train is separated from the incident wave field in front of a structure...... by means of digital filtering and subsequent superposition of the measured velocity signals. The incident wave signal is corrected, so that the reflected wave is effectively absorbed at the boundary. The effectiveness of the active wave generating‐absorbing boundary condition is proved using numerical...

  13. The use of circulation weather types to predict upwelling activity along the Western Iberian Peninsula coast

    Science.gov (United States)

    Ramos, Alexandre M.; Cordeiro Pires, Ana; Sousa, Pedro M.; Trigo, Ricardo M.

    2013-04-01

    Coastal upwelling is a phenomenon that occurs in most western oceanic coasts due to the presence of mid-latitude high-pressure systems that generate equatorward winds along the coast and consequent offshore displacement of surface waters that in turn cause deeper, colder, nutrient-rich waters to arise. In western Iberian Peninsula (IP) the high-pressure system associated to northerly winds occurs mainly during spring and summer. Upwelling systems are economically relevant, being the most productive regions of the world ocean and crucial for fisheries. In this work, we evaluate the intra- and inter-annual variability of the Upwelling Index (UI) off the western coast of the IP considering four locations at various latitudes: Rias Baixas, Aveiro, Figueira da Foz and Cabo da Roca. In addition, the relationship between the variability of the occurrence of several circulation weather types (Ramos et al., 2011) and the UI variability along this coast was assessed in detail, allowing to discriminate which types are frequently associated with strong and weak upwelling activity. It is shown that upwelling activity is mostly driven by wind flow from the northern quadrant, for which the obtained correlation coefficients (for the N and NE types) are higher than 0.5 for the four considered test locations. Taking into account these significant relationships, we then developed statistical multi-linear regression models to hindcast upwelling series (April to September) at the four referred locations, using monthly frequencies of circulation weather types as predictors. Modelled monthly series reproduce quite accurately observational data, with correlation coefficients above 0.7 for all locations, and relatively small absolute errors. Ramos AM, Ramos R, Sousa P, Trigo RM, Janeira M, Prior V (2011) Cloud to ground lightning activity over Portugal and its association with Circulation Weather Types. Atmospheric Research 101:84-101. doi: 10.1016/j.atmosres.2011.01

  14. Port Hamiltonian Formulation of Infinite Dimensional Systems II. Boundary Control by Interconnection

    NARCIS (Netherlands)

    Macchelli, Alessandro; Schaft, Arjan J. van der; Melchiorri, Claudio

    2004-01-01

    In this paper, some new results concerning the boundary control of distributed parameter systems in port Hamiltonian form are presented. The classical finite dimensional port Hamiltonian formulation of a dynamical system has been generalized to the distributed parameter and multi-variable case by

  15. On the reconstruction of boundary impedance of a heat conduction system from nonlocal measurement

    Science.gov (United States)

    Liu, Jijun; Wang, Yuchan

    2016-07-01

    We consider the reconstruction of the Robin impedance coefficient of a heat conduction system in a two-dimensional spatial domain from the time-average measurement specified on the boundary. By applying the potential representation of a solution, this nonlinear inverse problem is transformed into an ill-posed integral system coupling the density function for potential and the unknown boundary impedance. The uniqueness as well as the conditional stability of this inverse problem is established from the integral system. Then we propose to find the boundary impedance by solving a non-convex regularizing optimization problem. The well-posedness of this optimization problem together with the convergence property of the minimizer is analyzed. Finally, based on the singularity decomposition of the potential representation of the solution, two iteration schemes with their numerical realizations are proposed to solve this optimization problem.

  16. The effect of changes in surface winds and ocean stratification on coastal upwelling and sea surface temperatures in the Pliocene

    Science.gov (United States)

    Miller, Madeline D.; Tziperman, Eli

    2017-04-01

    Sea surface temperature (SST) in subtropical eastern boundary upwelling zones is shown to be affected by three main factors: large-scale ocean stratification, upwelling-favorable sea surface wind stress, and the surface concentration (baroclinicity) of the alongshore pressure gradient driving the incoming geostrophic flow which balances the Ekman surface outflow. Pliocene-aged SST proxies suggest that some combination of differences in upwelling forcing enable the sea surface temperatures in these zones to increase by up to 11°C. We find that large warming in SST in response to the three factors, of up to about 10°C in addition to a mean Pliocene ocean warming of 2-3°C, is concentrated in the direct upwelling zone. In the location of proxy sea surface temperatures, about 120 km away from the coast, and outside the coastal upwelling zone, the SST response to changes in wind and stratification is weaker, only accounting for up to 3.4°C above the mean Pliocene warming. Increased baroclinicity of the alongshore pressure gradient has a smaller effect, accounting for less than 2°C increases at both the coast and proxy site. The SST seaward (westward) of the upwelling zone is primarily determined by ocean-atmosphere heat exchange and basin-scale ocean forcing, rather than by changes in upwelling. The spatial pattern of SST change with each of the three forcing factors is similar, and therefore, all could contribute to the Pliocene-modern difference in coastal SST.

  17. Carbon and oxygen isotope time series records of planktonic and benthic foraminifera from the Arabian Sea: Implications on upwelling processes

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Niitsuma, N.

    ; upwelling; TerminationIB; climateshift 1. Introduction ThemonsoonsystemisoneoftheEarth’smost dynamic features, whichinteracts with theglobal atmospheric circulation that controls the heat budget in the Arabian Sea. Hence changes in the monsoon system may... is to infer the monsoon upwelling in£uence on the sur¢cial,subsurfaceanddeepwaterhydrographic variations and vertical chemical cycling in the western Arabian Sea during the Holocene and lastglaciation. 2. Oceanography Circulationinthe...

  18. On the System. Boundary Choices, Implications, and Solutions in Telecoupling Land Use Change Research

    Directory of Open Access Journals (Sweden)

    Cecilie Friis

    2017-06-01

    Full Text Available Land-based production provides societies with indispensable goods such as food, feed, fibre, and energy. Yet, with economic globalisation and global population growth, the environmental and social trade-offs of their production are ever more complex. This is particularly so since land use changes are increasingly embedded in networks of long-distance flows of, e.g., material, energy, and information. The resulting scientific and governance challenge is captured in the emerging telecoupling framework addressing socioeconomic and environmental interactions and feedbacks between distal human-environment systems. Understanding telecouplings, however, entails a number of fundamental analytical problems. When dealing with global connectivity, a central question is how and where to draw system boundaries between coupled systems. In this article, we explore the analytical implications of setting system boundaries in the study of a recent telecoupled land use change: the expansion of Chinese banana plantation investments in Luang Namtha Province, Laos. Based on empirical material from fieldwork in Laos in 2014 and 2015, and drawing on key concepts from the ‘systems thinking’ literature, we illustrate how treating the system and its boundaries as epistemological constructs enable us to capture the differentiated involvement of actors, as well as the socio-economic and environmental effects of this land use change. In discussing our results, the need for more explicit attention to the trade-offs and implications of scale and boundary choices when defining systems is emphasised.

  19. EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

    Science.gov (United States)

    Weikusat, Ilka; Kuiper, Ernst-Jan N.; Pennock, Gill M.; Kipfstuhl, Sepp; Drury, Martyn R.

    2017-09-01

    Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD), has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth) and Greenland (NEEM deep ice core at 719 m of depth). EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain boundaries that are not related to the

  20. EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

    Directory of Open Access Journals (Sweden)

    I. Weikusat

    2017-09-01

    Full Text Available Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD, has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth and Greenland (NEEM deep ice core at 719 m of depth. EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain

  1. On the presence of coastal upwelling along the northeastern Tyrrhenian coast

    Science.gov (United States)

    Martellucci, Riccardo; Melchiorri, Cristiano; Costanzo, Lorenzo; Marcelli, Marco

    2017-04-01

    The Mediterranean region shows a high climate variability due to the interactions between mid-latitude and tropical processes. This variability makes the Mediterranean a potentially vulnerable region to climatic changes. The present research aims to investigate the hydrographical response to Northerly wind in the northeastern Tyrrhenian coast, to identify the relations between upwelling events and teleconnection patterns. In the Tyrrhenian basin northerly winds flow between North-East and North-West and could be considered upwelling favorable winds. This atmospheric circulation can causes a divergent flow near the coast that generates a subsurface water flows inshore toward the coast up to the surface layer that is upwelling. This phenomenon strongly influence the marine ecosystems, contributing to the supply of nutrients and affecting the primary producers. In this context multi-platform observing system is an important tool to follow the evolution of these phenomena. Sea temperature and wind field acquired by the C-CEMS Observing system were used to identify upwelling phenomena between 2012 and 2016, in the coastal area of Civitavecchia, Northern Tyrrhenian sea, Italy. Moreover a thirty years' wind-driven upwelling conditions have been studied in the area. ERA-Interim (ECMWF) wind data for the period 1982-2012 have been used to compute the distribution of upwelling favorable wind events. These have been compared to "Copernicus Marine Environment Monitoring Service" Sea Surface Temperature (SST) to compute upwelling events. Upwelling favorable wind has been defined in the sector between Northwest and Northeast (Wd >330°N & Wd < 30°N). Wind speed has been divided into three classes: between 4 m/s and 6 m/s, between 6 m/s and 8 m/s and greater than 8 m/s. Sea Surface Temperature have been analyzed to define SST field for wind-driven coastal upwelling assessment. SST minima along the coast was used to identify upwelling from satellite imagery. The two datasets were

  2. Explicit formulation for natural frequencies of double-beam system with arbitrary boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mirzabeigy, Alborz; Madoliat, Reza [Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Dabbagh, Vahid [University of Malaya, Kuala Lumpur (Malaysia)

    2017-02-15

    In this paper, free transverse vibration of two parallel beams connected through Winkler type elastic layer is investigated. Euler- Bernoulli beam hypothesis has been applied and it is assumed that boundary conditions of upper and lower beams are similar while arbitrary without any limitation even for non-ideal boundary conditions. Material properties and cross-section geometry of beams could be different from each other. The motion of the system is described by a homogeneous set of two partial differential equations, which is solved by using the classical Bernoulli-Fourier method. Explicit expressions are derived for the natural frequencies. In order to verify accuracy of results, the problem once again solved using modified Adomian decomposition method. Comparison between results indicates excellent accuracy of proposed formulation for any arbitrary boundary conditions. Derived explicit formulation is simplest method to determine natural frequencies of double-beam systems with high level of accuracy in comparison with other methods in literature.

  3. A Numerical Iterative Method for Solving Systems of First-Order Periodic Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    Mohammed AL-Smadi

    2014-01-01

    Full Text Available The objective of this paper is to present a numerical iterative method for solving systems of first-order ordinary differential equations subject to periodic boundary conditions. This iterative technique is based on the use of the reproducing kernel Hilbert space method in which every function satisfies the periodic boundary conditions. The present method is accurate, needs less effort to achieve the results, and is especially developed for nonlinear case. Furthermore, the present method enables us to approximate the solutions and their derivatives at every point of the range of integration. Indeed, three numerical examples are provided to illustrate the effectiveness of the present method. Results obtained show that the numerical scheme is very effective and convenient for solving systems of first-order ordinary differential equations with periodic boundary conditions.

  4. Laplace Transform Methods for a Free Boundary Problem of Time-Fractional Partial Differential Equation System

    Directory of Open Access Journals (Sweden)

    Zhiqiang Zhou

    2017-01-01

    Full Text Available We study the pricing of the American options with fractal transmission system under two-state regime switching models. This pricing problem can be formulated as a free boundary problem of time-fractional partial differential equation (FPDE system. Firstly, applying Laplace transform to the governing FPDEs with respect to the time variable results in second-order ordinary differential equations (ODEs with two free boundaries. Then, the solutions of ODEs are expressed in an explicit form. Consequently the early exercise boundaries and the values for the American option are recovered using the Gaver-Stehfest formula. Numerical comparisons of the methods with the finite difference methods are carried out to verify the efficiency of the methods.

  5. Stratigraphic modeling of organic matter distribution and preservation in deep marine environment. Case of a margin with pelagic sedimentation: the coastal upwelling system of Benguela (Namibia, Western South Africa); Modelisation stratigraphique de la distribution et de la preservation de la matiere organique en milieu marin profond. Cas d'une marge a sedimentation pelagique: systeme d'upwelling cotier du Benguela (Namibie, Afrique du Sud Ouest)

    Energy Technology Data Exchange (ETDEWEB)

    Tranier, J.

    2006-06-15

    In order to develop stratigraphic modelling of organic matter distribution and preservation in marine environment, the methodology established, uses three modelling softwares. We make use of a 3D stratigraphic model, DIONISOS, which allows to build margin thanks to sediment input and transport and thanks to basin deformation. Biogenic sediments are introduced in DIONISOS after their production modelling by two coupled models, ROMS and NPZD. ROMS is a physical model which allows to simulate upwelling dynamics thanks to wind strength exerted on ocean surface and to margin morphology. NPZD models relationships (photosynthesis, grazing, excretion, mortality, re-mineralization, etc.) between four boxes: nutrients, phytoplankton, zooplankton and detritus. Nutrients availability (model inputs) and flux intensity between boxes are controlled by upwelling dynamics, i-e ROMS. Thanks to these three softwares, organic matter can be modelled from its production to its fossilization considering the influence of various factors as upwelling intensity, nutrients availability, chemical compounds of water mass and oxygenation of water column, species competition (diatoms and coccolithophoridae), margin morphology and eustatism. After testing sensibility of the various parameters of the three models, we study their capacity for reproduce biogenic sedimentation and simulate climatic cycle effect on organic matter distribution on a passive continental margin: the Namibian margin (Southwest Africa). They are validated comparing results with core data from this margin. (author)

  6. The Boundary Structure in the Analysis of Reversibly Interacting Systems by Sedimentation Velocity

    Science.gov (United States)

    Zhao, Huaying; Balbo, Andrea; Brown, Patrick H.; Schuck, Peter

    2011-01-01

    Sedimentation velocity (SV) experiments of heterogeneous interacting systems exhibit characteristic boundary structures that can usually be very easily recognized and quantified. For slowly interacting systems, the boundaries represent concentrations of macromolecular species and they can be interpreted directly with population models based solely on the mass action law. For fast reactions, migration and chemical reactions are coupled, and different, but equally easily discernable boundary structures appear. However, these features have not been commonly utilized for data analysis, for the lack of an intuitive and computationally simple model. The recently introduced effective particle theory (EPT) provides a suitable framework. Here, we review the motivation and theoretical basis of EPT, and explore practical aspects for its application. We introduce an EPT-based design tool for SV experiments of heterogeneous interactions in the software SEDPHAT. As a practical tool for the first step of data analysis, we describe how the boundary resolution can be further improved in c(s) with a Bayesian adjustment of maximum entropy regularization to the case of heterogeneous interactions between molecules that have been previously studied separately. This can facilitate extracting the characteristic boundary features by integration of c(s) and their assembly into isotherms as a function of total loading concentrations, which are fitted with EPT in a second stage. Methods for addressing concentration errors in isotherms are discussed. Finally, in an experimental model system of alpha-chymotrypsin interacting with soybean trypsin inhibitor, we show that EPT provides an excellent description of the experimental sedimentation boundary structure of fast interacting systems. PMID:21315155

  7. Effects of coastal upwelling on the structure of macrofaunal communities in SE Brazil

    Science.gov (United States)

    Quintana, Cintia O.; Bernardino, Angelo F.; de Moraes, Paula C.; Valdemarsen, Thomas; Sumida, Paulo Y. G.

    2015-03-01

    The effects of coastal upwelling on the structure of macrofaunal communities were investigated in two shallow bays in SE Brazil. Water, sediment and fauna samples were collected at four time-points corresponding to austral summer, fall, winter and spring, respectively. Water column temperature and salinity profiles indicated that upwelling occurred in summer-spring (December and November), but not in fall-winter (April and August). The structure of macrofaunal communities differed consistently between these periods. The sediment content of labile organic matter did not vary as a function of upwelling and could not explain the changes in macrofaunal communities. Rather it appeared that macrofaunal community structure was determined by organic matter quality (i.e. phytoplankton composition), physical disturbance regimes and bottom-water temperature. Physical disturbance caused by S-SE winds, warm water temperatures (up to 26 °C) and resuspension-driven phytoflagellate blooms during non-upwelling were associated to higher density (2511-2525 ind m- 2) and dominance of small opportunistic species such as spionid, paraonid and capitellid polychaetes. In contrast, stable hydrodynamic conditions, diatom blooms and lower water temperatures (down to 18 °C) during upwelling resulted in lower density of macrofauna (796-1387 ind m- 2) and a shift in species composition to relatively large-sized magelonids and carnivorous polychaetes. Therefore, organic matter quality, physical disturbance regimes, and bottom-water temperature were the major factors regulating the life-cycles, composition and density of macrofaunal communities in these less productive subtropical upwelling systems.

  8. The physical structure of an upwelling filament off the North-west ...

    African Journals Online (AJOL)

    Recent work in the Canary Current upwelling system highlights the role of previously uninvestigated filament structures. A filament located near 27°N in summer 1993 extended 150 km offshore with a width of ~20 km and surface temperature anomaly up to 2°C. The cool temperature signal was restricted to a shallow ...

  9. Initial boundary value problem for a system in elastodynamics with viscosity

    Directory of Open Access Journals (Sweden)

    Kayyunnapara Thomas Joseph

    2005-12-01

    Full Text Available In this paper we prove existence of global solutions to boundary-value problems for two systems with a small viscosity coefficient and derive estimates uniform in the viscosity parameter. We do not assume any smallness conditions on the data.

  10. Eigenvalues for Iterative Systems of (n,p-Type Fractional Order Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    K. R. Prasad

    2014-04-01

    Full Text Available In this paper, we determine the eigenvalue intervals of λ1, λ2, ..., λn for which the iterative system of (n,p-type fractional order two-point boundary value problem has a positive solution by an application of Guo-Krasnosel’skii fixed point theorem on a cone.

  11. Existence Results for a Coupled System of Nonlinear Fractional Boundary Value Problems at Resonance

    Directory of Open Access Journals (Sweden)

    Ruijuan Liu

    2013-01-01

    Full Text Available Some new Banach spaces are established. Based on those new Banach spaces and by using the coincidence degree theory, we present the existence results for a coupled system of nonlinear fractional differential equations with multipoint boundary value conditions at resonance case.

  12. Symplectic Hamiltonina formulation of Transmission Line Systems with Boundary Energy Flow

    NARCIS (Netherlands)

    van der Schaft, A.J.; Jeltsema, D

    2007-01-01

    The classical Langrangian and Hamiltonian formulation of an electrical transmission line is reviewed and extended to allow for varying boundary conditions. The method is based on the definition of an infinite-dimensional analogue of the affine Langrangian and Hamiltonian input-output systems

  13. Symplectic Hamiltonian Formulation of Transmission Line Systems with Boundary Energy Flow

    NARCIS (Netherlands)

    Jeltsema, Dimitri; Schaft, Arjan van der

    2008-01-01

    The classical Lagrangian and Hamiltonian formulation of an electrical transmission line is reviewed and extended to allow for varying boundary conditions. This extension is based on the definition of an infinite-dimensional analogue of the affine Lagrangian and Hamiltonian input-output systems

  14. Lagrangian and Hamiltonian Formulation of Transmission Line Systems with Boundary Energy Flow

    NARCIS (Netherlands)

    Jeltsema, Dimitri; Schaft, Arjan J. van der

    The classical Lagrangian and Hamiltonian formulation of an electrical transmission line is reviewed and extended to allow for varying boundary conditions, The method is based on the definition of an infinite-dimensional analogue of the affine Lagrangian and Hamiltonian input-output systems

  15. Flow system boundary by D'Agnese and others (1997) for the Death Valley regional ground-water flow system study, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the flow-system boundary encompassing the regional ground-water flow model by D'Agnese and others (1997). The boundary encompasses an...

  16. A bottom-landing water sampling system for the benthic boundary layer

    Science.gov (United States)

    Bale, A. J.; Barrett, C. D.

    A novel water sampling device which enables vertical profiles of water samples to be obtained within the benthic boundary layer in shelf sea waters is described. A maximum of ten samples spread over 2 m immediately above the seabed can be obtained on each deployment. The design of the sample bottles minimizes disturbances to particle aggregates and positive displacement sampling ensures that the samples are representative of the environment. Suspended-solids profiles sampled in the benthic boundary layer over 15-hour period at a station in the English Channel are presented to demonstrate the utility of the system.

  17. Coastal upwelling and downwelling forcing of circulation in a semi-enclosed bay: Ria de Vigo

    Science.gov (United States)

    Barton, E. D.; Largier, J. L.; Torres, R.; Sheridan, M.; Trasviña, A.; Souza, A.; Pazos, Y.; Valle-Levinson, A.

    2015-05-01

    Semi-enclosed bays in upwelling regions are exposed to forcing related to winds, currents and buoyancy over the shelf. The influence of this external forcing is moderated by factors such as connectivity to the open ocean, shelter by surrounding topography, dimensions of the bay, and freshwater outflows. Such bays, preferred locations for ports, mariculture, marine industry, recreational activities and coastal settlement, present a range of characteristics, understanding of which is necessary to their rational management. Observations in such a semi-enclosed bay, the Ria de Vigo in Spain, are used to characterize the influence of upwelling and downwelling pulses on its circulation. In this location, near the northern limit of the Iberian upwelling system, upwelling events dominate during a short summer season and downwelling events the rest of the year. The ria response to the external forcing is central to nutrient supply and resultant plankton productivity that supports its high level of cultured mussel production. Intensive field studies in September 2006 and June 2007 captured a downwelling event and an upwelling event, respectively. Data from eight current profiler moorings and boat-based MiniBat/ADCP surveys provided an unprecedented quasi-synoptic view of the distribution of water masses and circulation patterns in any ria. In the outer ria, circulation was dominated by the introduction of wind-driven alongshore flow from the external continental shelf through the ria entrances and its interaction with the topography. In the middle ria, circulation was primarily related to the upwelling/downwelling cycle, with a cool, salty and dense lower layer penetrating to the inner ria during upwelling over the shelf. A warmer, lower salinity and less dense surface layer of coastal waters flowed inward during downwelling. Without external forcing, the inner ria responded primarily to tides and buoyancy changes related to land runoff. Under both upwelling and downwelling

  18. Stability result of the Timoshenko system with delay and boundary feedback

    KAUST Repository

    Said-Houari, Belkacem

    2012-01-06

    Our interest in this paper is to analyse the asymptotic behaviour of a Timoshenko beam system together with two boundary controls, with delay terms in the first and second equation. Assuming the weights of the delay are small enough, we show that the system is well-posed using the semigroup theory. Furthermore, we introduce a Lyapunov functional that gives the exponential decay of the total energy. © 2012 The author.

  19. Upwelling filaments are cold, typically narrow features in surface ...

    African Journals Online (AJOL)

    spamer

    Where eddies draw recently upwelled water away from the coast, they create a surface temperature structure similar to a squirt. The last conceptual model consisted of a continuous equatorward jet, meandering offshore and onshore. During onshore excursions, the jet entrains coastally upwelled water and creates fila-.

  20. Ekman estimates of upwelling at cape columbine based on ...

    African Journals Online (AJOL)

    Cape Columbine is a prominent headland on the south-west coast of Africa at approximately 32°50´S, where there is a substantial upwelling tongue, enhancing the ambient upwelling on the shelf, produced by wind-stress curl. From hourly records of wind measured there, the longshore component of wind stress was ...

  1. Solutions Stability of Initial Boundary Problem, Modeling of Dynamics of Some Discrete Continuum Mechanical System

    Directory of Open Access Journals (Sweden)

    D. A. Eliseev

    2015-01-01

    Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.

  2. A system level boundary scan controller board for VME applications [to CERN experiments

    CERN Document Server

    Cardoso, N; Da Silva, J C

    2000-01-01

    This work is the result of a collaboration between INESC and LIP in the CMS experiment being conducted at CERN. The collaboration addresses the application of boundary scan test at system level namely the development of a VME boundary scan controller (BSC) board prototype and the corresponding software. This prototype uses the MTM bus existing in the VME64* backplane to apply the 1149.1 test vectors to a system composed of nineteen boards, called here units under test (UUTs). A top-down approach is used to describe our work. The paper begins with some insights about the experiment being conducted at CERN, proceed with system level considerations concerning our work and with some details about the BSC board. The results obtained so far and the proposed work is reviewed in the end of this contribution. (11 refs).

  3. Vibration analysis of multi-span beam system under arbitrary boundary and coupling conditions

    Directory of Open Access Journals (Sweden)

    ZHENG Chaofan

    2017-08-01

    Full Text Available In order to overcome the difficulties of studying the vibration analysis model of a multi-span beam system under various boundary and coupling conditions, this paper constructs a free vibration analysis model of a multi-span beam system on the basis of the Bernoulli-Euler beam theory. The vibration characteristics of a multi-span beam system under arbitrary boundary supports and elastic coupling conditions are investigated using the current analysis model. Unlike most existing techniques, the beam displacement function is generally sought as an improved Fourier cosine series, and four sine terms are introduced to overcome all the relevant discontinuities or jumps of elastic boundary conditions. On this basis, the unknown series coefficients of the displacement function are treated as the generalized coordinates and solved using the Rayleigh-Ritz method, and the vibration problem of multi-span bean systems is converted into a standard eigenvalue problem concerning the unknown displacement expansion coefficient. By comparing the free vibration characteristics of the proposed method with those of the FEA method, the efficiency and accuracy of the present method are validated, providing a reliable and theoretical basis for multi-span beam system structure in engineering applications.

  4. Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian sea shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, G.V.M.; Sudheesh, V.; Sudharma, K.V.; Saravanane, N.; Dhanya, V.; Dhanya, K.R.; Lakshmi, G.; Sudhakar, M.; Naqvi, S.W.A.

    ), southwest India and is the second modern one for the west coast of India after Candolim Time Series (CaTS, since 1997) off Goa (15.5°N). Perennial upwelling is associated with the eastern boundary currents in the Pacific (Humboldt and California currents...; Jayaram et al., 2010], but its biogeochemical effects were not studied in detail. Subsequently, the two other time series measurements being made off Goa since 1997 (Candolim Time Series, CaTS) in the AS [Maya et al., 2011] and off Visakhapatnam (since...

  5. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations

    Science.gov (United States)

    Bakun, Andrew

    2017-08-01

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring `dead zone' off the US State of Oregon. The evident `transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing `greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

  6. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations.

    Science.gov (United States)

    Bakun, Andrew

    2017-09-13

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring 'dead zone' off the US State of Oregon. The evident 'transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing 'greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

  7. The primary loop confinement and pressure boundary system of the HTR-10

    Energy Technology Data Exchange (ETDEWEB)

    He Shuyan; Zhang Zhengming E-mail: zhengmin@inet.tsinghua.edu.cn; Qin Zhenya

    2002-10-01

    The design philosophy and requirements of the HTR-10 reactor building and the primary loop confinement are introduced in this paper. Also introduced are the design, fabrication and the installation of the HTR-10 primary loop pressure boundary system. The primary loop confinement comprises the sealed cavities of the reinforced concrete structure. The main components and the connected gas systems of the primary loop pressure boundary system are contained in the confinement. Under normal operating condition, the inside pressure of the confinement is kept at negative pressure to ensure the sealing function of the confinement. There is a rupture disk of overpressure protection in the confinement wall. After a depressurization accident the pressure of the confinement increases and the rupture disk will break. The air of the confinement is discharged directly to the atmosphere through the accident discharge chimney which is connected to the rupture disk without filter. The main components of the primary loop pressure boundary system consist of the reactor pressure vessel, the steam generator pressure vessel and the hot gas duct vessel. All the above main components are installed in the reactor cavity and the steam generator cavity. They are all nuclear safety class 1 components, whose materials production, design, fabrication, and tests are carried out according to ASME Section III and relevant Chinese nuclear codes.

  8. The effect of system boundaries on the mean free path for confined gases

    Directory of Open Access Journals (Sweden)

    Sooraj K. Prabha

    2013-10-01

    Full Text Available The mean free path of rarefied gases is accurately determined using Molecular Dynamics simulations. The simulations are carried out on isothermal argon gas (Lennard-Jones fluid over a range of rarefaction levels under various confinements (unbounded gas, parallel reflective wall and explicit solid platinum wall bounded gas in a nanoscale domain. The system is also analyzed independently in constitutive sub-systems to calculate the corresponding local mean free paths. Our studies which predominate in the transition regime substantiate the boundary limiting effect on mean free paths owing to the sharp diminution in molecular free paths near the planar boundaries. These studies provide insight to the transport phenomena of rarefied gases through nanochannels which have established their potential in microscale and nanoscale heat transfer applications.

  9. Blow-up analysis for a system of heat equations coupled through a nonlinear boundary condition

    DEFF Research Database (Denmark)

    Pedersen, M.; Lin, Zhigui

    2001-01-01

    Consider the system of heat equations uit - Δui = 0 (i = 1 , . . . , k, uk+i := u1) in Ω x (0, T) coupled through nonlinear boundary conditions ∂ui/∂η = up1i+1 on ∂Ω x [0, T). The upper and lower bounds of the blow-up rate is derived. © 2000 Elsevier Science Ltd. All rights reserved.......Consider the system of heat equations uit - Δui = 0 (i = 1 , . . . , k, uk+i := u1) in Ω x (0, T) coupled through nonlinear boundary conditions ∂ui/∂η = up1i+1 on ∂Ω x [0, T). The upper and lower bounds of the blow-up rate is derived. © 2000 Elsevier Science Ltd. All rights reserved....

  10. Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

    Science.gov (United States)

    Felber, Raphael; Bretscher, Daniel; Münger, Andreas; Neftel, Albrecht; Ammann, Christof

    2016-05-01

    Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECBtot -27 ± 62 and NECBpast 23 ± 76 g C m-2 yr-1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH4 emissions from the cows to be the major contributor in terms of CO2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

  11. Stokes system with solution-dependent threshold slip boundary conditions: Analysis, approximation and implementation

    Czech Academy of Sciences Publication Activity Database

    Haslinger, Jaroslav; Kučera, R.; Šátek, V.

    2017-01-01

    Roč. 22, October 2017 (2017), s. 1-14 ISSN 1081-2865 R&D Projects: GA MŠk LQ1602; GA ČR(CZ) GA17-01747S Institutional support: RVO:68145535 Keywords : Stokes system * threshold slip boundary conditions * solution dependent slip function Subject RIV: BA - General Mathematics Impact factor: 2.953, year: 2016 http://journals.sagepub.com/doi/abs/10.1177/1081286517716222

  12. Positive Solution to Nonzero Boundary Values Problem for a Coupled System of Nonlinear Fractional Differential Equations

    Directory of Open Access Journals (Sweden)

    Jinhua Wang

    2010-01-01

    Full Text Available We consider the existence and uniqueness of positive solution to nonzero boundary values problem for a coupled system of fractional differential equations. The differential operator is taken in the standard Riemann-Liouville sense. By using Banach fixed point theorem and nonlinear differentiation of Leray-Schauder type, the existence and uniqueness of positive solution are obtained. Two examples are given to demonstrate the feasibility of the obtained results.

  13. Monotone methods for solving a boundary value problem of second order discrete system

    Directory of Open Access Journals (Sweden)

    Wang Yuan-Ming

    1999-01-01

    Full Text Available A new concept of a pair of upper and lower solutions is introduced for a boundary value problem of second order discrete system. A comparison result is given. An existence theorem for a solution is established in terms of upper and lower solutions. A monotone iterative scheme is proposed, and the monotone convergence rate of the iteration is compared and analyzed. The numerical results are given.

  14. Pre-service tightness tests of HTR-10 primary loop pressure boundary system

    Energy Technology Data Exchange (ETDEWEB)

    Liu Junjie; He Shuyan; Yu Suyuan. E-mail: suyuan@inet.tsinghua.edu.cn; Zhang Zhengming

    2003-06-01

    The main design and operating parameters for the 10 MW high temperature gas-cooled reactor (HTR-10) primary loop pressure boundary system are introduced in this paper. The component installations and the pneumatic and tightness test are also described, including the objectives and methods. The leakage rate test results are analyzed to show that the results meet the design requirements and have enough safety redundancy.

  15. New Boundary-Driven Twist States in Systems with Broken Spatial Inversion Symmetry

    Science.gov (United States)

    Hals, Kjetil M. D.; Everschor-Sitte, Karin

    2017-09-01

    A full description of a magnetic sample includes a correct treatment of the boundary conditions (BCs). This is in particular important in thin film systems, where even bulk properties might be modified by the properties of the boundary of the sample. We study generic ferromagnets with broken spatial inversion symmetry and derive the general micromagnetic BCs of a system with Dzyaloshinskii-Moriya interaction (DMI). We demonstrate that the BCs require the full tensorial structure of the third-rank DMI tensor and not just the antisymmetric part, which is usually taken into account. Specifically, we study systems with C∞ v symmetry and explore the consequences of the DMI. Interestingly, we find that the DMI already in the simplest case of a ferromagnetic thin film leads to a purely boundary-driven magnetic twist state at the edges of the sample. The twist state represents a new type of DMI-induced spin structure, which is completely independent of the internal DMI field. We estimate the size of the texture-induced magnetoresistance effect being in the range of that of domain walls.

  16. Boundary-equilibrium bifurcations in piecewise-smooth slow-fast systems.

    Science.gov (United States)

    Kowalczyk, P; Glendinning, P

    2011-06-01

    In this paper we study the qualitative dynamics of piecewise-smooth slow-fast systems (singularly perturbed systems) which are everywhere continuous. We consider phase space topology of systems with one-dimensional slow dynamics and one-dimensional fast dynamics. The slow manifold of the reduced system is formed by a piecewise-continuous curve, and the differentiability is lost across the switching surface. In the full system the slow manifold is no longer continuous, and there is an O(ɛ) discontinuity across the switching manifold, but the discontinuity cannot qualitatively alter system dynamics. Revealed phase space topology is used to unfold qualitative dynamics of planar slow-fast systems with an equilibrium point on the switching surface. In this case the local dynamics corresponds to so-called boundary-equilibrium bifurcations, and four qualitative phase portraits are uncovered. Our results are then used to investigate the dynamics of a box model of a thermohaline circulation, and the presence of a boundary-equilibrium bifurcation of a fold type is shown.

  17. Initial-boundary value problems for nearly incompressible vector fields, and applications to the Keyfitz and Kranzer system

    Science.gov (United States)

    Choudhury, Anupam Pal; Crippa, Gianluca; Spinolo, Laura V.

    2017-12-01

    We establish existence and uniqueness results for initial-boundary value problems with nearly incompressible vector fields. We then apply our results to establish well-posedness of the initial-boundary value problem for the Keyfitz and Kranzer system of conservation laws in several space dimensions.

  18. Existence of solutions for Riemann-Liouvillle type coupled systems of fractional integro-differential equations and boundary conditions

    Directory of Open Access Journals (Sweden)

    Ahmed Alsaedi

    2016-08-01

    Full Text Available In this article, we study a boundary value problem of coupled systems of nonlinear Riemann-Liouvillle fractional integro-differential equations supplemented with nonlocal Riemann-Liouvillle fractional integro-differential boundary conditions. Our results rely on some standard tools of the fixed point theory. An illustrative example is also discussed.

  19. IDENTIFICATION OF AN UNKNOWN PART OF THE BOUNDARY OF AN NAVIER-STOKES SYSTEM BY PUNCTUAL SENTINEL

    Directory of Open Access Journals (Sweden)

    IMAD REZZOUG

    2012-06-01

    Full Text Available In this work one interests a method for the identification of a part of the boundary in a parabolic equation (Navier-Stokes equations. By the means of the controllability of an adjoint system one has to identify this part while basing on an observation made on part of the boundary known.

  20. Boundary Ambiguity and Coparental Conflict after Divorce: An Empirical Test of a Family Systems Model of the Divorce Process.

    Science.gov (United States)

    Madden-Derdich, Debra A.; Leonard, Stacie A.; Christopher, F. Scott

    1999-01-01

    A family systems model of the divorce process was proposed and tested for divorced mothers and fathers using a series of multiple regression analysis. Findings support the hypothesized positive relationship between boundary ambiguity and coparental conflict. Reports factors that influence boundary ambiguity were found to be distinct for mothers…

  1. A Parameter Estimation Method for Nonlinear Systems Based on Improved Boundary Chicken Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Shaolong Chen

    2016-01-01

    Full Text Available Parameter estimation is an important problem in nonlinear system modeling and control. Through constructing an appropriate fitness function, parameter estimation of system could be converted to a multidimensional parameter optimization problem. As a novel swarm intelligence algorithm, chicken swarm optimization (CSO has attracted much attention owing to its good global convergence and robustness. In this paper, a method based on improved boundary chicken swarm optimization (IBCSO is proposed for parameter estimation of nonlinear systems, demonstrated and tested by Lorenz system and a coupling motor system. Furthermore, we have analyzed the influence of time series on the estimation accuracy. Computer simulation results show it is feasible and with desirable performance for parameter estimation of nonlinear systems.

  2. Effects from magnetic boundary conditions in superconducting-magnetic proximity systems

    Directory of Open Access Journals (Sweden)

    Thomas E. Baker

    2016-05-01

    Full Text Available A superconductor-magnetic proximity system displays singlet-triplet pair correlations in the magnetization as a function of inhomogeneities of the magnetic profile. We discuss how the magnetic boundary conditions affects differently the curvature and winding number of rotating magnetizations in the three commonly used structures to generate long range triplet components: an exchange spring, a helical structure and a misaligned magnetic multilayer. We conclude that the choice of the system is dictated by the goal one wishes to achieve in designing a spintronic device but note that only the exchange spring presently offers an experimentally realizable magnetic profile that is tunable.

  3. Single-File System with Absorbing Boundary: Tracer Dynamics and First-Passage Properties

    Science.gov (United States)

    Ryabov, Artem

    2015-03-01

    In this paper, we review the tagged particle dynamics in a semi-infinite system with an absorbing boundary. The emphasis is on an interplay between the hard-core interparticle interaction and the absorption process. The exact probability density function for the position of a tagged particle is derived by means of probabilistic arguments. First, the initially homogeneous system with constant density of particles is studied. In this setting, the dynamics of the tracer conditioned on nonabsorption becomes subdiffusive, the generalized diffusion coefficient being different from that reported for the system without absorbing boundary. Second, the case when the initial number of particles is finite is discussed. In this case, in the long time limit the tracer diffusion is normal and the hard-core interaction manifests itself through the renormalization of the tracer diffusion coefficient. The Gaussian distribution derived for infinite single-file systems is, in the present semi-infinite setting, replaced by the Rayleigh distribution. Special Issue Comments: This article presents results on the dynamics of a tagged particle in open systems, where the number of particles is not conserved in time. This article is related to the Special Issue articles about advanced statistical properties in single file dynamics,1 the calculation of correlations,2 files with force3 and the zig-zag patterns in files.4

  4. Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean

    Science.gov (United States)

    Wang, Li-Chiao; Jin, Fei-Fei; Wu, Chau-Ron; Hsu, Huang-Hsiung

    2017-04-01

    The annual upwelling is an important component of the equatorial Atlantic annual cycle. A simple theory is proposed using the framework of Zebiak-Cane (ZC) ocean model for insights into the dynamics of the upwelling annual cycle. It is demonstrated that in the Atlantic equatorial region this upwelling is dominated by Ekman processing in the west, whereas in the east it is primarily owing to shoaling and deepening of the thermocline resulting from equatorial mass meridional recharge/discharge and zonal redistribution processes associated with wind-driven equatorial ocean waves. This wind-driven wave upwelling plays an important role in the development of the annual cycle in the sea surface temperature of the cold tongue in the eastern equatorial Atlantic.

  5. An Examination of the Effect of Boundary Layer Ingestion on Turboelectric Distributed Propulsion Systems

    Science.gov (United States)

    Felder, James L.; Kim, Huyn Dae; Brown, Gerald V.; Chu, Julio

    2011-01-01

    A Turboelectric Distributed Propulsion (TeDP) system differs from other propulsion systems by the use of electrical power to transmit power from the turbine to the fan. Electrical power can be efficiently transmitted over longer distances and with complex topologies. Also the use of power inverters allows the generator and motors speeds to be independent of one another. This decoupling allows the aircraft designer to place the core engines and the fans in locations most advantageous for each. The result can be very different installation environments for the different devices. Thus the installation effects on this system can be quite different than conventional turbofans where the fan and core both see the same installed environments. This paper examines a propulsion system consisting of two superconducting generators, each driven by a turboshaft engine located so that their inlets ingest freestream air, superconducting electrical transmission lines, and an array of superconducting motor driven fan positioned across the upper/rear fuselage area of a hybrid wing body aircraft in a continuous nacelle that ingests all of the upper fuselage boundary layer. The effect of ingesting the boundary layer on the design of the system with a range of design pressure ratios is examined. Also the impact of ingesting the boundary layer on off-design performance is examined. The results show that when examining different design fan pressure ratios it is important to recalculate of the boundary layer mass-average Pt and MN up the height for each inlet height during convergence of the design point for each fan design pressure ratio examined. Correct estimation of off-design performance is dependent on the height of the column of air measured from the aircraft surface immediately prior to any external diffusion that will flow through the fan propulsors. The mass-averaged Pt and MN calculated for this column of air determine the Pt and MN seen by the propulsor inlet. Since the height

  6. Boundary Wall Shear Measurement with an Automated LDV-Based System

    Science.gov (United States)

    Modarress, Darius; Jeon, David; Svitek, Pavel; Gharib, Morteza

    2014-11-01

    Wall shear stress is one of the most important measurements in boundary layer flows. Getting wall shear measurements is generally quite difficult due to the need to measure very close to the wall, where poor optical access, particle seeding, and wall effects can bias the results. To simplify that process, a novel system was developed by Measurement Science Enterprise (MSE). The microPro consists of a 12 mm diameter miniLDV attached to a micro-translation stage assembled inside a sealed housing. The microPro automatically locates the wall and measures the mean flow speed profile from a point as close as 50 microns from the window. Accurate estimate of the mean wall shear is obtained from the calculation of the wall velocity gradient obtained from the velocity profile data. We measured wall shear stress on a boundary layer plate mounted in a water tunnel across a range of Reynolds numbers and compared the results against skin friction coefficient models. We also introduced bubbles into the boundary layer to measure the change in wall shear stress with changing void fraction. The measurements show good agreement with established data. This work is supported by the Office of Naval Research (Grant ONR-N00014-11-1-0031) and MSE.

  7. Space Oceanography for the Monitoring of Moroccan Upwelling Dynamic

    Science.gov (United States)

    Atillah, Abderrahman; Orbi, Abdellatif; Hilmi, Karim; Mangin, Antoine

    2005-03-01

    The Moroccan coastal upwelling is a complex physical and biological phenomenon which requires a regular and permanent monitoring to apprehend its dynamic in time and space. In order to meet this need and considering the influence of the upwelling events on the Moroccan marine resources fluctuations, the Royal Center for Remote Sensing (CRTS) in collaboration with the National Institute for Fisheries Research (INRH), has carried out GERMA (Management of Marines Resources) project to develop useful tools and applications to generate routine operational upwelling products for supporting fisheries. The characterizing and the monitoring of the upwelling fluctuations aim at exploiting Sea Surface Temperature (SST), ocean colour data and derived products combined with in situ data. The main objective is to provide users with operational products representing some environmental parameters and likely to help understanding the fish stock fluctuations. Indeed, methodologies and tools were set up to produce a derived upwelling index (CUI) from SST data. This synthetic product based on the thermal difference between Open Ocean and coastal cold water, is particularly adapted to monitor the upwelling phenomenon along Moroccan coast and to characterize the spatial and temporal variation of the cold water ascent, taking into account the local geographical specificities. In addition, another application is developed integrating several geophysical parameters, obtained both from satellites and in situ data, which allow the analysis of this phenomenon. This application permits the time series extraction of each parameter, separated or combined with others parameters, for a selected point along the coast thus allowing easy validation of satellite-derived products and analysis of long time series. The availability of the upwelling geophysical indicators time series supplies important information for the assessment of the upwelling evolution and fluctuations.

  8. Framework to Define Structure and Boundaries of Complex Health Intervention Systems: The ALERT Project.

    Science.gov (United States)

    Boriani, Elena; Esposito, Roberto; Frazzoli, Chiara; Fantke, Peter; Hald, Tine; Rüegg, Simon R

    2017-01-01

    Health intervention systems are complex and subject to multiple variables in different phases of implementation. This constitutes a concrete challenge for the application of translational science in real life. Complex systems as health-oriented interventions call for interdisciplinary approaches with carefully defined system boundaries. Exploring individual components of such systems from different viewpoints gives a wide overview and helps to understand the elements and the relationships that drive actions and consequences within the system. In this study, we present an application and assessment of a framework with focus on systems and system boundaries of interdisciplinary projects. As an example on how to apply our framework, we analyzed ALERT [an integrated sensors and biosensors' system (BEST) aimed at monitoring the quality, health, and traceability of the chain of the bovine milk], a multidisciplinary and interdisciplinary project based on the application of measurable biomarkers at strategic points of the milk chain for improved food security (including safety), human, and ecosystem health (1). In fact, the European food safety framework calls for science-based support to the primary producers' mandate for legal, scientific, and ethical responsibility in food supply. Because of its multidisciplinary and interdisciplinary approach involving human, animal, and ecosystem health, ALERT can be considered as a One Health project. Within the ALERT context, we identified the need to take into account the main actors, interactions, and relationships of stakeholders to depict a simplified skeleton of the system. The framework can provide elements to highlight how and where to improve the project development when project evaluations are required.

  9. Framework to Define Structure and Boundaries of Complex Health Intervention Systems: The ALERT Project

    Directory of Open Access Journals (Sweden)

    Elena Boriani

    2017-07-01

    Full Text Available Health intervention systems are complex and subject to multiple variables in different phases of implementation. This constitutes a concrete challenge for the application of translational science in real life. Complex systems as health-oriented interventions call for interdisciplinary approaches with carefully defined system boundaries. Exploring individual components of such systems from different viewpoints gives a wide overview and helps to understand the elements and the relationships that drive actions and consequences within the system. In this study, we present an application and assessment of a framework with focus on systems and system boundaries of interdisciplinary projects. As an example on how to apply our framework, we analyzed ALERT [an integrated sensors and biosensors’ system (BEST aimed at monitoring the quality, health, and traceability of the chain of the bovine milk], a multidisciplinary and interdisciplinary project based on the application of measurable biomarkers at strategic points of the milk chain for improved food security (including safety, human, and ecosystem health (1. In fact, the European food safety framework calls for science-based support to the primary producers’ mandate for legal, scientific, and ethical responsibility in food supply. Because of its multidisciplinary and interdisciplinary approach involving human, animal, and ecosystem health, ALERT can be considered as a One Health project. Within the ALERT context, we identified the need to take into account the main actors, interactions, and relationships of stakeholders to depict a simplified skeleton of the system. The framework can provide elements to highlight how and where to improve the project development when project evaluations are required.

  10. Determining system boundaries on commercial broiler chicken production system using ISO 14040/14044 guideline: A case Study

    Science.gov (United States)

    Sidek, ‘A. A.; Suffian, S. A.; Al-Hazza, M. H. F.; Yusof, H. M.

    2018-01-01

    The demand of poultry product in Malaysia market shows an escalation throughout the year and expected to increase in the future. The expansion of poultry production has led to environmental concern in relation to their operational impact to environmentAt present, assessment of waste management of poultry production in Malaysia is lacking. A case study research was conducted in a commercial broiler farm to identify and assess the system boundaries in the lifecycle supply chain of broiler chicken production using ISO 14040/44 guidelines. ISO 14040/44 standard includes Life Cycle Assessment (LCA) framework guidelines to evaluate environmental influence associated with a product/process throughout its life span. All attributes associated with broiler operation is defined and the system boundaries is determined to identify possible inputs and outputs in the case study. This paper discuss the initial stage in the LCA process, which set the context of the research and prepare for the stage of Life Cycle Inventory.

  11. Solvability for a Coupled System of Fractional Integrodifferential Equations with $m$ -Point Boundary Conditions on the Half-Line

    OpenAIRE

    Nasertayoob, Payam; Vaezpour, S. Mansour; Baleanu, Dumitru

    2014-01-01

    The aim of this paper is to study the solvability for a coupled system of fractional integrodifferential equations with multipoint fractional boundary value problems on the half-line. An example is given to demonstrate the validity of our assumptions.

  12. Existence and uniqueness for boundary-value problem with additional single point conditions of the Stokes-Bitsadze system

    Directory of Open Access Journals (Sweden)

    Muhammad Tahir

    2012-11-01

    Full Text Available This article shows the uniqueness of a solution to a Bitsadze system of equations, with a boundary-value problem that has four additional single point conditions. It also shows how to construct the solution.

  13. Boundary of the area contributing flow to the Death Valley regional ground-water flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the boundary of the area contributing ground-water flow to the Death Valley regional ground-water flow-system (DVRFS) model domain. The...

  14. An optimal control method for fluid structure interaction systems via adjoint boundary pressure

    Science.gov (United States)

    Chirco, L.; Da Vià, R.; Manservisi, S.

    2017-11-01

    In recent year, in spite of the computational complexity, Fluid-structure interaction (FSI) problems have been widely studied due to their applicability in science and engineering. Fluid-structure interaction systems consist of one or more solid structures that deform by interacting with a surrounding fluid flow. FSI simulations evaluate the tensional state of the mechanical component and take into account the effects of the solid deformations on the motion of the interior fluids. The inverse FSI problem can be described as the achievement of a certain objective by changing some design parameters such as forces, boundary conditions and geometrical domain shapes. In this paper we would like to study the inverse FSI problem by using an optimal control approach. In particular we propose a pressure boundary optimal control method based on Lagrangian multipliers and adjoint variables. The objective is the minimization of a solid domain displacement matching functional obtained by finding the optimal pressure on the inlet boundary. The optimality system is derived from the first order necessary conditions by taking the Fréchet derivatives of the Lagrangian with respect to all the variables involved. The optimal solution is then obtained through a standard steepest descent algorithm applied to the optimality system. The approach presented in this work is general and could be used to assess other objective functionals and controls. In order to support the proposed approach we perform a few numerical tests where the fluid pressure on the domain inlet controls the displacement that occurs in a well defined region of the solid domain.

  15. Eddy Surface properties and propagation at Southern Hemisphere western boundary current systems

    Science.gov (United States)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-02-01

    Oceanic eddies occur in all world oceans, but are more energetic when associated to western boundary currents (WBC) systems. In these regions, eddies play an important role on mixing and energy exchange. Therefore, it is important to quantify and qualify eddies occurring within these systems. Previous studies performed eddy censuses in Southern Hemisphere WBC systems. However, important aspects of local eddy population are still unknown. Main questions to be answered relate to eddies' spatial distribution, propagation and lifetime within each system. Here, we use a global eddy dataset to qualify eddies based on their surface characteristics at the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) Systems. We show that eddy propagation within each system is highly forced by the local mean flow and bathymetry. In the AC System, eddy polarity dictates its propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC System eddies from both polarities cross south of Tasmania, but only anticyclonics reach the Great Australian Bight. Eddies in all systems and from both polarities presented a geographical segregation according to size. Large eddies occur along the Agulhas Retroflection, the Agulhas Return Current, the Brazil-Malvinas Confluence and the Coral Sea. Small eddies occur in the systems southernmost domains. Understanding eddies' propagation helps to establish monitoring programs, and to better understand how these features would affect local mixing.

  16. Positive solutions for systems of nth order three-point nonlocal boundary value problems

    Directory of Open Access Journals (Sweden)

    Johnny Henderson

    2007-09-01

    Full Text Available Intervals of the parameter $\\lambda$ are determined for which there exist positive solutions for the system of nonlinear differential equations, $u^{(n} + \\lambda a(t f(v = 0, \\ v^{(n} +\\lambda b(t g(u = 0, $ for $0 < t <1$, and satisfying three-point nonlocal boundary conditions, $u(0 = 0, u'(0 = 0, \\ldots, u^{(n-2}(0 = 0, \\ u(1=\\alpha u(\\eta, v(0 = 0, v'(0 = 0, \\ldots, v^{(n-2}(0 = 0, \\ v(1=\\alpha v(\\eta$. A Guo-Krasnosel'skii fixed point theorem is applied.

  17. Upwelling Dynamics off Monterey Bay: Heat Flux and Temperature Variability, and their Sensitivities

    Science.gov (United States)

    2010-05-01

    WHOI Slocum gliders . The Princeton Glider Coordinated Control System (GCCS) was used for path planning to steer a fleet of underwater gliders to a...energy decayed and led to the development of mesoscale features within a warming upper thermocline. Shulman (2009) researched the impact of glider ...such as undersea gliders to study ocean processes associated with the upwelling of cold, deep water along the Central California Coast  Use the

  18. Interlaced, Nanostructured Interface with Graphene Buffer Layer Reduces Thermal Boundary Resistance in Nano/Microelectronic Systems.

    Science.gov (United States)

    Tao, Lei; Theruvakkattil Sreenivasan, Sreeprasad; Shahsavari, Rouzbeh

    2017-01-11

    Improving heat transfer in hybrid nano/microelectronic systems is a challenge, mainly due to the high thermal boundary resistance (TBR) across the interface. Herein, we focus on gallium nitride (GaN)/diamond interface-as a model system with various high power, high temperature, and optoelectronic applications-and perform extensive reverse nonequilibrium molecular dynamics simulations, decoding the interplay between the pillar length, size, shape, hierarchy, density, arrangement, system size, and the interfacial heat transfer mechanisms to substantially reduce TBR in GaN-on-diamond devices. We found that changing the conventional planar interface to nanoengineered, interlaced architecture with optimal geometry results in >80% reduction in TBR. Moreover, introduction of conformal graphene buffer layer further reduces the TBR by ∼33%. Our findings demonstrate that the enhanced generation of intermediate frequency phonons activates the dominant group velocities, resulting in reduced TBR. This work has important implications on experimental studies, opening up a new space for engineering hybrid nano/microelectronics.

  19. Artificial upwelling using the energy of surface waves

    Science.gov (United States)

    Soloviev, A.

    2016-02-01

    The ocean is an important component of climate and climate change, since the heat capacity of a few meters of the upper ocean is equivalent to the heat capacity of the entire atmosphere. (Solar radiation and IR balance in the atmosphere are of course major factors as well.) Artificial upwelling devices using the energy of surface waves, similar to those developed by Vershinskiy, Pshenichnyy, and Soloviev (1987), can bring cold water from below the thermocline to the sea surface. Their wave-inertia pump consisted of a vertical tube, a valve, and a buoy to keep the device afloat. The device operated by using energy of surface waves to create an upward flow of water in the tube. An outlet valve at the top of the unit synchronized the operation of the device with surface waves and prevented back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. This type of artificial upwelling can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from the deep layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps has been estimated for different environmental conditions using a computational fluid dynamics model. The cooled near-surface layer of the ocean will be getting more heat from the sun, which is a detrimental consequence. Cloud seeding can help to mitigate this extra warming. A synergistic approach to climate engineering can thus reduce detriments and increase potential benefits of this system to society.

  20. Initial boundary value problems for second order parabolic systems in cylinders with polyhedral base

    National Research Council Canada - National Science Library

    Luong, Vu Trong; Loi, Do Van

    2011-01-01

    The purpose of this article is to establish the well posedness and the regularity of the solution of the initial boundary value problem with Dirichlet boundary conditions for second-order parabolic...

  1. Open Innovation and the Erosion of the Traditional Information Systems Project's Boundaries

    Science.gov (United States)

    Elbanna, Amany

    This paper examines the notion of open innovation and its implication on information systems management. It investigates a project of an enterprise resource planning system implementation in an international organization to unravel the resemblance with the open innovation model. The study shows that the conceptualization of ERP project as an open innovation could reveal the complex architecture of today's organization from which the ERP project cannot be isolated. It argues that the traditional boundaries around IS projects are dissolving and the relationship between what used to be outside and what used to be inside the project is increasingly blurred. The study calls for a different perspective of project management that goes beyond single and multiple project management to scan the open space of innovation and actively look for partners, competitors, and collaborators.

  2. The effect of traffic light on accident probability in open and periodic boundaries system

    Science.gov (United States)

    Mhirech, Abdelaziz; Alaoui-Ismaili, Assia

    2015-09-01

    In this paper we numerically study the dependence of car accident probability Pac, per site and per time step on cycle time T of traffic light, both in open and periodic boundaries system. In this study one traffic light is placed in the middle of the system. This work is based on Nagel and Schreckenberg (NaSch) model (Nagel and Schreckenberg (1992)) in parallel dynamics. The Pac dependence on T and the (α, β) phase diagrams are established. α and β are the injecting and extracting rates of cars in the traffic lane respectively. The increase of the cycle time light T causes an important decrease of the accident probability Pac both in the open and periodic cases.

  3. Numerical continuation methods for dynamical systems path following and boundary value problems

    CERN Document Server

    Krauskopf, Bernd; Galan-Vioque, Jorge

    2007-01-01

    Path following in combination with boundary value problem solvers has emerged as a continuing and strong influence in the development of dynamical systems theory and its application. It is widely acknowledged that the software package AUTO - developed by Eusebius J. Doedel about thirty years ago and further expanded and developed ever since - plays a central role in the brief history of numerical continuation. This book has been compiled on the occasion of Sebius Doedel''s 60th birthday. Bringing together for the first time a large amount of material in a single, accessible source, it is hoped that the book will become the natural entry point for researchers in diverse disciplines who wish to learn what numerical continuation techniques can achieve. The book opens with a foreword by Herbert B. Keller and lecture notes by Sebius Doedel himself that introduce the basic concepts of numerical bifurcation analysis. The other chapters by leading experts discuss continuation for various types of systems and objects ...

  4. Computational Investigation of a Boundary-Layer Ingesting Propulsion System for the Common Research Model

    Science.gov (United States)

    Blumenthal, Brennan T.; Elmiligui, Alaa; Geiselhart, Karl A.; Campbell, Richard L.; Maughmer, Mark D.; Schmitz, Sven

    2016-01-01

    The present paper examines potential propulsive and aerodynamic benefits of integrating a Boundary-Layer Ingestion (BLI) propulsion system into a typical commercial aircraft using the Common Research Model (CRM) geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment is used to generate engine conditions for CFD analysis. Improvements to the BLI geometry are made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Previous studies have shown reductions of up to 25% in terms of propulsive power required for cruise for other axisymmetric geometries using the BLI concept. An analysis of engine power requirements, drag, and lift coefficients using the baseline and BLI geometries coupled with the NPSS model are shown. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown and any improvements between subsequent BLI designs presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet and an angle of attack of 2 deg for all geometries. A comparison between available wind tunnel data, previous computational results, and the original CRM model is presented for model verification purposes along with full results for BLI power savings. Results indicate a 14.4% reduction in engine power requirements at cruise for the BLI configuration over the baseline geometry. Minor shaping of the aft portion of the fuselage using CDISC has been shown to increase the benefit from Boundary-Layer Ingestion further, resulting in a 15.6% reduction in power requirements for cruise as well as a drag reduction of eighteen counts over the baseline geometry.

  5. Computational Investigation of a Boundary-Layer Ingestion Propulsion System for the Common Research Model

    Science.gov (United States)

    Blumenthal, Brennan

    2016-01-01

    This thesis will examine potential propulsive and aerodynamic benefits of integrating a boundary-layer ingestion (BLI) propulsion system with a typical commercial aircraft using the Common Research Model geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment will be used to generate engine conditions for CFD analysis. Improvements to the BLI geometry will be made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Previous studies have shown reductions of up to 25% in terms of propulsive power required for cruise for other axisymmetric geometries using the BLI concept. An analysis of engine power requirements, drag, and lift coefficients using the baseline and BLI geometries coupled with the NPSS model are shown. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown and any improvements between subsequent BLI designs presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet and an angle of attack of 2deg for all geometries. A comparison between available wind tunnel data, previous computational results, and the original CRM model is presented for model verification purposes along with full results for BLI power savings. Results indicate a 14.3% reduction in engine power requirements at cruise for the BLI configuration over the baseline geometry. Minor shaping of the aft portion of the fuselage using CDISC has been shown to increase the benefit from boundary-layer ingestion further, resulting in a 15.6% reduction in power requirements for cruise as well as a drag reduction of eighteen counts over the baseline geometry.

  6. Stochastic Well-posed Systems and Well-posedness of Some Stochastic Partial Differential Equations with Boundary Control and Observation

    OpenAIRE

    LU, Qi

    2015-01-01

    We generalize the concept "well-posed linear system" to stochastic linear control systems and study some basic properties of such kind systems. Under our generalized definition, we show the well-posedness of the stochastic heat equation and the stochastic Schr\\"odinger equation with suitable boundary control and observation operators, respectively.

  7. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Science.gov (United States)

    Hepach, Helmke; Quack, Birgit; Tegtmeier, Susann; Engel, Anja; Bracher, Astrid; Fuhlbrügge, Steffen; Galgani, Luisa; Atlas, Elliot L.; Lampel, Johannes; Frieß, Udo; Krüger, Kirstin

    2016-09-01

    Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L-1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L-1 and diiodomethane (CH2I2) of up to 32.4 pmol L-1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  8. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Directory of Open Access Journals (Sweden)

    H. Hepach

    2016-09-01

    Full Text Available Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3 and dibromomethane (CH2Br2 correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I of up to 35.4 pmol L−1, chloroiodomethane (CH2ClI of up to 58.1 pmol L−1 and diiodomethane (CH2I2 of up to 32.4 pmol L−1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt, CH2ClI (up to 2.5 ppt and CH2I2 (3.3 ppt above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  9. Influence of upwelling saline groundwater on iron and manganese cycling in the Rio Grande floodplain aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Matthew F. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States)], E-mail: matthew.f.kirk@gmail.com; Crossey, Laura J. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Takacs-Vesbach, Cristina [Department of Biology, University of New Mexico, Albuquerque, NM 87131 (United States); Newell, Dennis L. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Bowman, Robert S. [Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801 (United States)

    2009-03-15

    Salinity contributions from upwelling groundwater significantly degrade water quality in the Rio Grande, a major source of water for the southwestern USA. This study considers the influence of this upwelling water on the geochemistry and microbiology of the Rio Grande floodplain alluvial aquifer. The composition of surface water, groundwater, and floodplain sediment samples collected from three transects in the Socorro Basin was examined. Terminal-restriction fragment length polymorphism (T-RFLP) was also used to examine microbial biomass samples. The distribution of salinity in the floodplain groundwater largely reflects the configuration of local groundwater flow and mixing of two major water sources, deeply-sourced saline groundwater and river water. Microbial populations in the shallow aquifer consume O{sub 2} and NO{sub 3}{sup -} and serve to redistribute metal oxides from the saturated zone to locations of groundwater discharge at the surface and possibly near the water table. The upwelling saline groundwater affects floodplain microbial processes by transporting reduced metals and organic electron donors to the alluvial aquifer system. This enhances metal reduction in the saturated zone and ultimately metal oxidation at or near the surface. Geochemical modeling suggests that mixing of the saline groundwater with more dilute water in the floodplain creates conditions more favorable for metal oxidation to occur and thereby influences the distribution of metal oxides.

  10. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast.

    Directory of Open Access Journals (Sweden)

    Romeo Saldívar-Lucio

    Full Text Available The seasonal and interannual variability of vertical transport (upwelling/downwelling has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress. The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region.

  11. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast

    Science.gov (United States)

    Saldívar-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, Héctor; Lluch-Cota, Daniel; Del Monte-Luna, Pablo

    2016-01-01

    The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress). The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region. PMID:27893826

  12. An Earth system view on boundaries for human perturbation of the N and P cycles

    Science.gov (United States)

    Cornell, Sarah; de Vries, Wim

    2015-04-01

    The appropriation and transformation of land, water, and living resources can alter Earth system functioning, and potentially undermine the basis for the sustainability of our societies. Human activities have greatly increased the flows of reactive forms of nitrogen (N) and phosphorus (P) in the Earth system. These non-substitutable nutrient elements play a fundamental role in the human food system. Furthermore, the current mode of social and economic globalization, and its effect on the present-day energy system, also has large effects including large NOx-N emissions through combustion. Until now, this perturbation of N and P cycles has been treated largely as a local/regional issue, and managed in terms of direct impacts (water, land or air pollution). However, anthropogenic N and P cycle changes affect physical Earth system feedbacks (through greenhouse gas and aerosol changes) and biogeochemical feedbacks (via ecosystem changes, links to the carbon cycle, and altered nutrient limitation) with impacts that can be far removed from the direct sources. While some form of N and P management at the global level seems likely to be needed for continued societal development, the current local-level and sectorial management is often problematically simplistic, as seen in the tensions between divergent N management needs for climate change mitigation, air pollution control, food production, and ecosystem conservation. We require a step change in understanding complex biogeochemical, physical and socio-economic interactions in order to analyse these effects together, and inform policy trade-offs to minimize emergent systemic risks. Planetary boundaries for N and P cycle perturbation have recently been proposed. We discuss the current status of these precautionary boundaries and how we may improve on these preliminary assessments. We present an overview of the human perturbation of the global biogeochemical cycles of N and P and its interaction with the functioning of the

  13. Immersed Boundary Methods for Optimization of Strongly Coupled Fluid-Structure Systems

    Science.gov (United States)

    Jenkins, Nicholas J.

    Conventional methods for design of tightly coupled multidisciplinary systems, such as fluid-structure interaction (FSI) problems, traditionally rely on manual revisions informed by a loosely coupled linearized analysis. These approaches are both inaccurate for a multitude of applications, and they require an intimate understanding of the assumptions and limitations of the procedure in order to soundly optimize the design. Computational optimization, in particular topology optimization, has been shown to yield remarkable results for problems in solid mechanics using density interpolations schemes. In the context of FSI, however, well defined boundaries play a key role in both the design problem and the mechanical model. Density methods neither accurately represent the material boundary, nor provide a suitable platform to apply appropriate interface conditions. This thesis presents a new framework for shape and topology optimization of FSI problems that uses for the design problem the Level Set method (LSM) to describe the geometry evolution in the optimization process. The Extended Finite Element method (XFEM) is combined with a fictitiously deforming fluid domain (stationary arbitrary Lagrangian-Eulerian method) to predict the FSI response. The novelty of the proposed approach lies in the fact that the XFEM explicitly captures the material boundary defined by the level set iso-surface. Moreover, the XFEM provides a means to discretize the governing equations, and weak immersed boundary conditions are applied with Nitsche's Method to couple the fields. The flow is predicted by the incompressible Navier-Stokes equations, and a finite-deformation solid model is developed and tested for both hyperelastic and linear elastic problems. Transient and stationary numerical examples are presented to validate the FSI model and numerical solver approach. Pertaining to the optimization of FSI problems, the parameters of the discretized level set function are defined as explicit

  14. The Cottage Grove fault system (Illinois Basin): Late Paleozoic transpression along a Precambrian crustal boundary

    Science.gov (United States)

    Duchek, A.B.; McBride, J.H.; Nelson, W.J.; Leetaru, H.E.

    2004-01-01

    The Cottage Grove fault system in southern Illinois has long been interpreted as an intracratonic dextral strike-slip fault system. We investigated its structural geometry and kinematics in detail using (1) outcrop data, (2) extensive exposures in underground coal mines, (3) abundant borehole data, and (4) a network of industry seismic reflection profiles, including data reprocessed by us. Structural contour mapping delineates distinct monoclines, broad anticlines, and synclines that express Paleozoic-age deformation associated with strike slip along the fault system. As shown on seismic reflection profiles, prominent near-vertical faults that cut the entire Paleozoic section and basement-cover contact branch upward into outward-splaying, high-angle reverse faults. The master fault, sinuous along strike, is characterized along its length by an elongate anticline, ???3 km wide, that parallels the southern side of the master fault. These features signify that the overall kinematic regime was transpressional. Due to the absence of suitable piercing points, the amount of slip cannot be measured, but is constrained at less than 300 m near the ground surface. The Cottage Grove fault system apparently follows a Precambrian terrane boundary, as suggested by magnetic intensity data, the distribution of ultramafic igneous intrusions, and patterns of earthquake activity. The fault system was primarily active during the Alleghanian orogeny of Late Pennsylvanian and Early Permian time, when ultramatic igneous magma intruded along en echelon tensional fractures. ?? 2004 Geological Society of America.

  15. Dynamics of plankton populations in upwelling areas. [by remote sensors

    Science.gov (United States)

    Szekielda, K.

    1974-01-01

    Recent investigations of the upwelling area along the NW Coast of Africa which include studies with satellites are discussed. The detection of patchiness in temperature and plankton distribution in the upwelling area is of special interest because they can be investigated from space synoptically with repeated coverage. The recent satellite missions provide recordings in the infrared region of the electromagnetic spectrum (EMR) as well as in the visible part. The information from those two parts of the EMR is useful for establishing the sea surface temperature and plankton distribution in upwelling areas. The temperature distribution as observed with infrared sensors and the patchiness in plankton patterns are discussed as observed with the most recent satellites, namely the Earth Resources Technology Satellite (ERTS) and NOAA-2.

  16. An investigation of Ekman upwelling in the North Atlantic

    Science.gov (United States)

    Mcclain, Charles R.; Firestone, James

    1993-01-01

    The spatial and temporal variability of the North Atlantic Ekman upwelling fields on seasonal and interannual time scales is investigated on the basis of surface winds from the Fleet Numerical Oceanography Center for 1979-1986. A pronounced minimum in the basin-wide monthly mean vertical Ekman velocities during 1981-1982 is found. It is shown that the primary source of the interannual signal was the region off NW Africa in the vicinity of the Guinea Dome. Other sectors of the basin experienced no significant interannual trends. Hydrographic data and SST data from the NW Africa sector for 1981-1986 indicate a cooling trend beginning in late 1982, consistent with increased upwelling. The fall and winter seasons' mixed layers at the center of the Guinea Dome were deeper in 1984 and 1985 than in previous years. The potential impact of large interannual variations in Ekman upwelling on basin-wide primary productivity is discussed.

  17. Modelling Upwelling Irradiance using Secchi disk depth in lake ecosystems

    Directory of Open Access Journals (Sweden)

    Claudio ROSSI

    2009-02-01

    Full Text Available A simple model for upwelling irradiance has been developed. The model represents the relationship between Photosynthetically Active Radiation diffuse attenuation coefficients and Secchi disk depth described with a physical-mathematical expression. This physical mathematical expression allows the evaluation of the sub surface upwelling irradiance that was generated by the interaction between downwelling irradiance and the water column. The validation of the relation was performed using experimental data collected from five different aquatic ecosystems at different latitudes, solar elevations and irradiance levels. We found a good linear, positive correlation between the theoretical and measured upwelling irradiance (R2 = 0.96. The residues were well distributed, around the null value, according a Gaussian curve (R2 = 0.92. The results confirm the importance and the versatility of the Secchi disk measurements for aquatic optics.

  18. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries

    Science.gov (United States)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-01

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  19. Existence Results for a Coupled System of Nonlinear Fractional Hybrid Differential Equations with Homogeneous Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Josefa Caballero

    2014-01-01

    Full Text Available We study an existence result for the following coupled system of nonlinear fractional hybrid differential equations with homogeneous boundary conditions D0+α[x(t/f(t,x(t,y(t]=g(t,x(t,y(t,D0+αy(t/f(t,y(t,x(t=g(t,y(t,x(t,  0

  20. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries.

    Science.gov (United States)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-14

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  1. Performance improvement of 64-QAM coherent optical communication system by optimizing symbol decision boundary based on support vector machine

    Science.gov (United States)

    Chen, Wei; Zhang, Junfeng; Gao, Mingyi; Shen, Gangxiang

    2018-03-01

    High-order modulation signals are suited for high-capacity communication systems because of their high spectral efficiency, but they are more vulnerable to various impairments. For the signals that experience degradation, when symbol points overlap on the constellation diagram, the original linear decision boundary cannot be used to distinguish the classification of symbol. Therefore, it is advantageous to create an optimum symbol decision boundary for the degraded signals. In this work, we experimentally demonstrated the 64-quadrature-amplitude modulation (64-QAM) coherent optical communication system using support-vector machine (SVM) decision boundary algorithm to create the optimum symbol decision boundary for improving the system performance. We investigated the influence of various impairments on the 64-QAM coherent optical communication systems, such as the impairments caused by modulator nonlinearity, phase skew between in-phase (I) arm and quadrature-phase (Q) arm of the modulator, fiber Kerr nonlinearity and amplified spontaneous emission (ASE) noise. We measured the bit-error-ratio (BER) performance of 75-Gb/s 64-QAM signals in the back-to-back and 50-km transmission. By using SVM to optimize symbol decision boundary, the impairments caused by I/Q phase skew of the modulator, fiber Kerr nonlinearity and ASE noise are greatly mitigated.

  2. Upwelling Response to Hurricane Isaac in Geostrophic Oceanic Vortices

    Science.gov (United States)

    Jaimes, B.; Shay, L. K.; Brewster, J. K.; Schuster, R.

    2013-05-01

    As a tropical cyclone (TC) moves over the ocean, the cyclonic curl of the wind stress produces a region of upwelling waters under the TC center that is compensated by downwelling waters at regions outside the center. Direct measurements conducted during hurricane Rita and recent numerical studies indicate that this is not necessarily the case when TCs move over geostrophic oceanic features, where its background relative vorticity impacts wind-driven horizontal current divergence and the upwelling velocity. Modulation of the upwelling response in these energetic oceanic regimes impacts vertical mixing across the oceanic mixed layer base, air-sea fluxes into the atmosphere, and ultimately storm intensity. As part of NOAA Intensity Forecasting Experiment, an experiment was conducted during the passage of TC Isaac over the energetic geostrophic eddy field in the Gulf of Mexico in August 2012. Expendable bathythermographs, current profilers, and conductivity-temperature-depth probes were deployed in Isaac from NOAA WP-3D aircraft during four in-storm flights to measure oceanic variability and its impact on TC-driven upwelling and surface fluxes of heat and momentum. During intensification to hurricane, the cyclonic curl of the wind stress of Isaac extended over a region of more than 300 km in diameter (4 to 5 times the radius of maximum winds). Isaac's center moved over a cold cyclonic feature, while its right and left sides moved over warm anticyclones. Contrasting upwelling and downwelling regimes developed inside the region of cyclonic curl of the wind stress. Both positive (upwelling) and negative (downwelling) vertical displacements of 40 and 60 m, respectively, were measured inside the region of cyclonic curl of the wind stress, which are between 3 to 4 times larger than predicted vertical displacements for a quiescent ocean based on scaling arguments. Oceanic mixed layer (OML) currents of 0.2 to 0.7 m s-1 were measured, which are about 50% smaller than the

  3. The Ndynamics package—Numerical analysis of dynamical systems and the fractal dimension of boundaries

    Science.gov (United States)

    Avellar, J.; Duarte, L. G. S.; da Mota, L. A. C. P.; de Melo, N.; Skea, J. E. F.

    2012-09-01

    A set of Maple routines is presented, fully compatible with the new releases of Maple (14 and higher). The package deals with the numerical evolution of dynamical systems and provide flexible plotting of the results. The package also brings an initial conditions generator, a numerical solver manager, and a focusing set of routines that allow for better analysis of the graphical display of the results. The novelty that the package presents an optional C interface is maintained. This allows for fast numerical integration, even for the totally inexperienced Maple user, without any C expertise being required. Finally, the package provides the routines to calculate the fractal dimension of boundaries (via box counting). New version program summary Program Title: Ndynamics Catalogue identifier: %Leave blank, supplied by Elsevier. Licensing provisions: no. Programming language: Maple, C. Computer: Intel(R) Core(TM) i3 CPU M330 @ 2.13 GHz. Operating system: Windows 7. RAM: 3.0 GB Keywords: Dynamical systems, Box counting, Fractal dimension, Symbolic computation, Differential equations, Maple. Classification: 4.3. Catalogue identifier of previous version: ADKH_v1_0. Journal reference of previous version: Comput. Phys. Commun. 119 (1999) 256. Does the new version supersede the previous version?: Yes. Nature of problem Computation and plotting of numerical solutions of dynamical systems and the determination of the fractal dimension of the boundaries. Solution method The default method of integration is a fifth-order Runge-Kutta scheme, but any method of integration present on the Maple system is available via an argument when calling the routine. A box counting [1] method is used to calculate the fractal dimension [2] of the boundaries. Reasons for the new version The Ndynamics package met a demand of our research community for a flexible and friendly environment for analyzing dynamical systems. All the user has to do is create his/her own Maple session, with the system to

  4. Multi-domain boundary element method for axi-symmetric layered linear acoustic systems

    Science.gov (United States)

    Reiter, Paul; Ziegelwanger, Harald

    2017-12-01

    Homogeneous porous materials like rock wool or synthetic foam are the main tool for acoustic absorption. The conventional absorbing structure for sound-proofing consists of one or multiple absorbers placed in front of a rigid wall, with or without air-gaps in between. Various models exist to describe these so called multi-layered acoustic systems mathematically for incoming plane waves. However, there is no efficient method to calculate the sound field in a half space above a multi layered acoustic system for an incoming spherical wave. In this work, an axi-symmetric multi-domain boundary element method (BEM) for absorbing multi layered acoustic systems and incoming spherical waves is introduced. In the proposed BEM formulation, a complex wave number is used to model absorbing materials as a fluid and a coordinate transformation is introduced which simplifies singular integrals of the conventional BEM to non-singular radial and angular integrals. The radial and angular part are integrated analytically and numerically, respectively. The output of the method can be interpreted as a numerical half space Green's function for grounds consisting of layered materials.

  5. Random vibration analysis of axially compressed cylindrical shells under turbulent boundary layer in a symplectic system

    Science.gov (United States)

    Li, Yuyin; Zhang, Yahui; Kennedy, David

    2017-10-01

    A random vibration analysis of an axially compressed cylindrical shell under a turbulent boundary layer (TBL) is presented in the symplectic duality system. By expressing the cross power spectral density (PSD) of the TBL as a Fourier series in the axial and circumferential directions, the problem of structures excited by a random distributed pressure due to the TBL is reduced to solving the harmonic response function, which is the response of structures to a spatial and temporal harmonic pressure of unit magnitude. The governing differential equations of the axially compressed cylindrical shell are derived in the symplectic duality system, and then a symplectic eigenproblem is formed by using the method of separation of variables. Expanding the excitation vector and unknown state vector in symplectic space, decoupled governing equations are derived, and then the analytical solution can be obtained. In contrast to the modal decomposition method (MDM), the present method is formulated in the symplectic duality system and does not need modal truncation, and hence the computations are of high precision and efficiency. In numerical examples, harmonic response functions for the axially compressed cylindrical shell are studied, and a comparison is made with the MDM to verify the present method. Then, the random responses of the shell to the TBL are obtained by the present method, and the convergence problems induced by Fourier series expansion are discussed. Finally, influences of the axial compression on random responses are investigated.

  6. Upwelling along the western Indian continental margin and its geological record - a summary

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    Upwelling along the western Indian continental margin is recorded each year from Cape Comorin to Cochin and further north up to Goa from June to September during the southwest monsoon. During this upwelling heavy phytoplankton blooms develop which...

  7. Upwelling and associated hydrography along the west coast of india during southwest monsoon, 1999

    Digital Repository Service at National Institute of Oceanography (India)

    Maheswaran, P.A.; Rajesh, G.; Revichandran, C.; Nair, K.K.C.

    . Signatures of coastal under current were prominent which deepens, as moving towards north. Analysis of hydrographic characteristics reveals the presence of cool upwelled water by May itself. Strong signals of upwelling were observed off Kanyakumari...

  8. Arabian Sea upwelling - A comparison between coastal and open ocean regions

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; PrasannaKumar, S.

    Flux Studies (JGOFS) programme. Analysis of wind measurements indicated active upwelling along the southwest coast of India, which gradually propagates towards north. While the dominant long-shore component of the wind induces upwelling in the south...

  9. Observational evidence of upwelling off the southwest coast of India during June-July 2006

    Digital Repository Service at National Institute of Oceanography (India)

    Lekshmi, S.; Smitha, B.R.; Revichandran, C.

    upwelling parameters (isotherm slope towards the coast and local cooling) also reveal this contrast between local forcing and observed upwelling. The surface salinity off Koilam is comparatively lower (30.8-33.8 PSG) to that off Thiruvananthapuram (34...

  10. Propagation of Upwelling on Western-Coast Sumatera During MJO Event

    Directory of Open Access Journals (Sweden)

    Yosafat Donni Haryanto

    2018-01-01

    Full Text Available Madden-Julian oscillation (MJO is an atmospheric oscillation due to atmospheric phenomenon that occurs due to the uniformity of solar energy received at the surface of the earth, MJO is a natural occurrence in the sea-atmosphere system. When the MJO is active, in general there will be a disturbance in the upper air which is then followed by an anomaly at sea surface pressure causing the changes in the wind on the surface. The changes in the surface wind affectthe sea surface currents which then cause the occurrence of coastal upwelling downwelling. The upwelling process itself is a process whereby a sea mass is pushed upward along the continent, when the beach is to the left of the wind direction, the ecological transport leads to the mass of water away from the coast. As a result, there is a mass vacuum (divergence in the coastal area. This mass void will be filledby the mass of water from the inner layer that moves to the surface. Indonesian territory itself is passed by MJO in phases 3, 4 and 5, while for Sumatra region is passed by MJO phase 3 and 4. This research aims to identify the propagation of coastal upwelling during MJO on the west coast of Sumatera, therefore the data of geopotential height, surface pressure sea (MSLP, zonal and meridional components and sea surface temperature are used to analyze how the MJO effecton the coastal upwelling occurs in the research area. The analysis was conducted in June, July and August by comparing the atmospheric conditions at the time of strong MJO in phases 3 and 4 with normal viewing of anomaly geopotential height and MSLP and then seeing the anomaly surface wind changes from zonal wind (u and meridional wind (v and changes in SST in Sumatra region. The result shows that there is a change of GH and MSLP when MJO passes the west coast of Sumatra and then follows the change in the value of u and v and SST to identify the upwelling, while the anomaly change negative SST does not occur when MJO is

  11. Upwelling Index, 24N 113W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  12. Upwelling Index, 51N 131W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  13. Upwelling Index, 21N 107W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  14. Upwelling Index, 39N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  15. Upwelling Index, 45N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  16. Upwelling Index, 27N 116W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  17. Upwelling Index, 57N 137W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  18. Upwelling Index, 42N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  19. Dominant plankton sizes in response to various upwelling events.

    Science.gov (United States)

    Shin, J.; Jo, Y. H.

    2016-02-01

    Off the east coast of Korean Peninsula is known as regions of high primary production. One of the most important processes for the high primary productivity in coastal areas is, strong upwelling events. In this research, we investigated long-term changes of upwelling intensity and furthermore, examined corresponding Chlorophyll-a concentration (CHL). For the study area, off the east coast of Korea is divided into 9 areas along the coastal lines at 0.25° of intervals from 35.25°N to 37.25°N. Specifically, research is conducted for long-term tendency of CHL off the east coast of Korea with focus on upwelling events using `Upwelling Age (UA)'. For obtaining UA, we used wind-vector from The European Centre for Medium-Range Weather Forecasts (ECMWF), ocean temperature and salinity profile data from Hybrid Coordinate Ocean Model (HYCOM), and bathymetry data from a 1 arc-minute global relief model of Earth's surface that integrates land topography and ocean bathymetry (ETOPO1). The UA values are different along the regions of interests due to wind duration time, wind stress and continental shelf slopes, so do the dominant plankton size. In order to compare spatial changes of CHL, we used Moderate Resolution Imaging Spectroradiometer (MODIS) data. When UA is high, CHL is relatively higher and inversely sea surface temperature lower.

  20. Upwelling Index, 30N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  1. The winter St. Helena climate index and extreme Benguela upwelling

    Science.gov (United States)

    Hagen, Eberhard; Agenbag, Jacobus J.; Feistel, Rainer

    2005-09-01

    Climate changes in the subtropical South-east Atlantic turn out to be well described by the St. Helena Island Climate Index (HIX) and observed fluctuations are in good agreement with inter-decadal variability of the entire South Atlantic Ocean. Year-to-year variations of the averaged austral winter HIX (July-September), representative of the main upwelling season, were compared with (i) corresponding averages of the geostrophic alongshore component of the south-east trade wind (SET) between St. Helena Island in the south-west and Luanda/Angola in the north-east, (ii) the meridional distribution of surface waters colder than 13 °C to characterise intense Benguela upwelling (IBU), and (iii) the meridional position of the Angola-Benguela Frontal Zone (ABFZ) determined by means of sea surface temperature images for offshore distances between 50 and 400 km. Temporal changes of these parameters were investigated and showed that the frequency of consecutive years of strong and relaxed Benguela upwelling is characterised by a quasi-cycle of about 11-14 years. It is proposed that the index of the winter HIX may be used as a 'surveyor's rod' to describe interannual changes in the Benguela upwelling regime as well as those of the embedded marine ecosystem.

  2. Upwelling Index, 60N 149W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  3. Upwelling Index, 33N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  4. Upwelling Index, 48N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  5. Effects of translational symmetry breaking induced by the boundaries in a driven diffusive system

    DEFF Research Database (Denmark)

    Andersen, Jørgen Vitting; Leung, Kwan-tai

    1991-01-01

    We study the effects of the boundary conditions in a driven diffusive lattice-gas model which is known to display kinetic phase transitions. We find, in the case of attractive interaction, that a boundary-condition-induced symmetry breaking of the translational invariance, along the direction of ...

  6. A free boundary problem for a reaction-diffusion system with nonlinear memory

    DEFF Research Database (Denmark)

    Lin, Zhigui; Ling, Zhi; Pedersen, Michael

    2013-01-01

    We consider a integro-partial differential equation with a free boundary which appears in the theory of the nuclear dynamics. First, local existence and uniqueness are obtained by using the contraction mapping theorem. Then, the behavior of the free boundary and the blow-up criteria are obtained...

  7. Uncovering the Boundary-spanning Role of Information Systems Research in Trans-Disciplinary Knowledge Advancement

    DEFF Research Database (Denmark)

    Liu, Fei; Lim, Eric T. K.; Tan, Chee-Wee

    2017-01-01

    -Disciplinary Knowledge Advancement that posits a process that consists of three stages of thesis, antithesis, and synthesis with two transitions, namely knowledge liquidization and crystallization, in two modes, namely boundary-reinforcing and boundary-spanning. In light of this model, this study conducted...

  8. Mesoscale advection of Upogebia pusilla larvae through an upwelling filament in the Canaries Coastal Transition Zone (CTZ)

    Science.gov (United States)

    Landeira, José María; Lozano-Soldevilla, Fernando; Barton, Eric Desmond

    2012-12-01

    Larval transport has a strong influence on marine populations and ecosystem function. Traditional hypotheses establish that larvae of coastal species are swept offshore during strong upwelling periods producing low recruitment rates; however, recent studies have demonstrated that this hypothesis is not supported by larval distribution data. The present study examines the influence of upwelling filaments on larval advection and wastage. During August 1993, the transport of Upogebia pusilla was analysed in relation to an offshore filament off Northwest Africa. This mesoscale structure was generated by a trapped, quasi-permanent cyclonic eddy located between the Canary Islands and the African shelf and extended 150 km westward into the oligotrophic open ocean waters. The horizontal distribution depicted by U. pusilla larvae was strongly influenced by the oceanographic features of the Canaries Coastal Transition Zone (CTZ). Specifically, the larvae were closely associated with upwelling front and filament position, showing that these neritic larvae can be advected 10-100s of kilometres offshore through the filament. However, the low larval densities observed in the samples suggest that many larvae might remain close to the coast, thus avoiding seaward transport. This implies that filaments probably do not significantly affect the recruitment success of intertidal invertebrates such us U. pusilla in upwelling systems.

  9. System-size effects in ionic fluids under periodic boundary conditions

    Science.gov (United States)

    Thompson, Jeff P.; Sanchez, Isaac C.

    2016-12-01

    We investigate the system-size dependence of the thermodynamic properties of ionic fluids under periodic boundary conditions. Following an approach previously developed in the context of quantum Monte Carlo simulations of many-electron systems, we show that the leading-order finite-size artifact in the Coulomb energy per particle of a classical fluid of N structureless ions at given density and temperature is simply -kBT (2N ) -1 . Analytical approximations for the periodicity-induced size dependence of the excess thermodynamic properties of the fluid in the weak-coupling regime are obtained within the linearized Debye-Hückel theory. Theoretical results are compared with published simulations of the one-component plasma and our own simulations of a primitive-model electrolyte solution. Our work is directly relevant to estimating finite-size corrections in simulations of charged fluids comprising structureless ions embedded in continuous media. We outline in the Appendix how some of our formal results may be generalized to molecular fluids with mobile ions; e.g., electrolyte solutions with explicit solvent.

  10. The Unmanned Aerial System SUMO: an alternative measurement tool for polar boundary layer studies

    Science.gov (United States)

    Mayer, S.; Jonassen, M. O.; Reuder, J.

    2012-04-01

    Numerical weather prediction and climate models face special challenges in particular in the commonly stable conditions in the high-latitude environment. For process studies as well as for model validation purposes in-situ observations in the atmospheric boundary layer are highly required, but difficult to retrieve. We introduce a new measurement system for corresponding observations. The Small Unmanned Meteorological Observer SUMO consists of a small and light-weight auto-piloted model aircraft, equipped with a meteorological sensor package. SUMO has been operated in polar environments, among others during IPY on Spitsbergen in the year 2009 and has proven its capabilities for atmospheric measurements with high spatial and temporal resolution even at temperatures of -30 deg C. A comparison of the SUMO data with radiosondes and tethered balloons shows that SUMO can provide atmospheric profiles with comparable quality to those well-established systems. Its high data quality allowed its utilization for evaluation purposes of high-resolution model runs performed with the Weather Research and Forecasting model WRF and for the detailed investigation of an orographically modified flow during a case study.

  11. Planetary boundary layer as an essential component of the earth's climate system

    Science.gov (United States)

    Davy, Richard; Esau, Igor

    2015-04-01

    Following the traditional engineering approach proposed by Prandtl, the turbulent planetary boundary layers (PBLs) are considered in the climate science as complex, non-linear, essential but nevertheless subordinated components of the earth's climate system. Correspondingly, the temperature variations, dT - a popular and practically important measure of the climate variability, are seen as the system's response to the external heat forcing, Q, e.g. in the energy balance model of the type dT=Q/C (1). The moderation of this response by non-linear feedbacks embedded in the effective heat capacity, C, are to a large degree overlooked. The effective heat capacity is globally determined by the depth of the ocean mixed layer (on multi-decadal and longer time scales) but regionally, over the continents, C is much smaller and determined (on decadal time scales) by the depth, h, of the PBL. The present understanding of the climatological features of turbulent boundary layers is set by the works of Frankignoul & Hasselmann (1976) and Manabe & Stauffer (1980). The former explained how large-scale climate anomalies could be generated in the case of a large C (in the sea surface temperature) by the delta-correlated stochastic forcing (white noise). The latter demonstrated that the climate response to a given forcing is moderated by the depth, h, so that in the shallow PBL the signal should be significantly amplified. At present there are more than 3000 publications (ISI Web of Knowledge) which detail this understanding but the physical mechanisms, which control the boundary layer depth, and statistical relationships between the turbulent and climatological measures remain either unexplored or incorrectly attributed. In order to identify the climatic role of the PBL, the relationships between the PBL depth, h, - as the integral measure of the turbulent processes and micro-circulations due to the surface heterogeneity - and the climatic variability (variations and trends) of

  12. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    Science.gov (United States)

    Barbaro, E.; Vila-Guerau Arellano, J.; Ouwersloot, H. G.; Schroter, J.; Donovan, D. P.; Krol, M. C.

    2013-12-01

    We investigate the responses of the surface energy budget and the convective boundary-layer (CBL) dynamics to the presence of aerosols using a combination of observations and numerical simulations. A detailed observational dataset containing (thermo)dynamic variables observed at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions (IMPACT/EUCAARI) campaign is employed to design numerical experiments reproducing two prototype clear-sky days characterized by: (i) a well-mixed residual layer above a ground inversion and (ii) a continuously growing CBL. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, both coupled to a broadband radiative transfer code and a land-surface model, are used to study the impacts of aerosol scattering and absorption of shortwave radiation on the land-atmosphere system. We successfully validate our model results using the measurements of (thermo)dynamic variables and aerosol properties for the two different CBL prototypes studied here. Our findings indicate that in order to reproduce the observed surface energy budget and CBL dynamics, information of the vertical structure and temporal evolution of the aerosols is necessary. Given the good agreement between the LES and the MXL model results, we use the MXL model to explore the aerosol effect on the land-atmosphere system for a wide range of optical depths and single scattering albedos. Our results show that higher loads of aerosols decrease irradiance, imposing an energy restriction at the surface. Over the studied well-watered grassland, aerosols reduce the sensible heat flux more than the latent heat flux. As a result, aerosols increase the evaporative fraction. Moreover, aerosols also delay the CBL morning onset and anticipate its afternoon collapse. If also present above the CBL during the morning transition, aerosols maintain a persistent near

  13. On an upwelling front, propagation of upwelling and vertical velocity in the eastern Arabian sea during monsoon, 1987

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Unnikrishnan, A.S.

    A coastal upwelling front parallel to the coast and identifiable upto a depth of 75 m was observed between 12.5 and 16 degrees N along the eastern Arabian Sea in September, 1987 from closely spaced digital BT data. With a north-south slope...

  14. boundary dissipation

    Directory of Open Access Journals (Sweden)

    Mehmet Camurdan

    1998-01-01

    are coupled by appropriate trace operators. This overall model differs from those previously studied in the literature in that the elastic chamber floor is here more realistically modeled by a hyperbolic Kirchoff equation, rather than by a parabolic Euler-Bernoulli equation with Kelvin-Voight structural damping, as in past literature. Thus, the hyperbolic/parabolic coupled system of past literature is replaced here by a hyperbolic/hyperbolic coupled model. The main result of this paper is a uniform stabilization of the coupled PDE system by a (physically appealing boundary dissipation.

  15. Solvability for a Coupled System of Fractional Integrodifferential Equations with m-Point Boundary Conditions on the Half-Line

    Directory of Open Access Journals (Sweden)

    Payam Nasertayoob

    2014-01-01

    Full Text Available The aim of this paper is to study the solvability for a coupled system of fractional integrodifferential equations with multipoint fractional boundary value problems on the half-line. An example is given to demonstrate the validity of our assumptions.

  16. Existence results for a coupled system of nonlinear fractional differential equations with boundary value problems on an unbounded domain

    Directory of Open Access Journals (Sweden)

    Neda Khodabakhshi

    2013-12-01

    Full Text Available This paper deals with the existence results for solutions of coupled system of nonlinear fractional differential equations with boundary value problems on an unbounded domain. Also, we give an illustrative example in order to indicate the validity of our assumptions.

  17. Existence and Uniqueness Results for a Coupled System of Nonlinear Fractional Differential Equations with Antiperiodic Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Huina Zhang

    2014-01-01

    Full Text Available This paper studies the existence and uniqueness of solutions for a coupled system of nonlinear fractional differential equations of order α,β∈(4,5] with antiperiodic boundary conditions. Our results are based on the nonlinear alternative of Leray-Schauder type and the contraction mapping principle. Two illustrative examples are also presented.

  18. A Coupled System of Nonlinear Fractional Differential Equations with Multipoint Fractional Boundary Conditions on an Unbounded Domain

    Directory of Open Access Journals (Sweden)

    Guotao Wang

    2012-01-01

    Full Text Available This paper investigates the existence of solutions for a coupled system of nonlinear fractional differential equations with m-point fractional boundary conditions on an unbounded domain. Some standard fixed point theorems are applied to obtain the main results. The paper concludes with two illustrative examples.

  19. A Coupled System of Nonlinear Fractional Differential Equations with Multipoint Fractional Boundary Conditions on an Unbounded Domain

    OpenAIRE

    Guotao Wang; Bashir Ahmad; Lihong Zhang

    2012-01-01

    This paper investigates the existence of solutions for a coupled system of nonlinear fractional differential equations with m-point fractional boundary conditions on an unbounded domain. Some standard fixed point theorems are applied to obtain the main results. The paper concludes with two illustrative examples.

  20. Existence results for a coupled system of nonlinear fractional 2m-point boundary value problems at resonance

    Directory of Open Access Journals (Sweden)

    Wang Gang

    2011-01-01

    Full Text Available Abstract A 2m-point boundary value problem for a coupled system of nonlinear fractional differential equations is considered in this article. An existence result is obtained with the use of the coincidence degree theory. MSC: 34B17; 34L09.

  1. Boundary value problem for a coupled system of fractional differential equations with p-Laplacian operator at resonance

    Directory of Open Access Journals (Sweden)

    Lingling Cheng

    2014-02-01

    Full Text Available In this article, we discuss the existence of solutions to boundary-value problems for a coupled system of fractional differential equations with p-Laplacian operator at resonance. We prove the existence of solutions when $\\dim \\ker L\\geq 2$, using the coincidence degree theory by Mawhin.

  2. Well-posedness and regularity of hyperbolic boundary control systems on a one-dimensional spatial domain

    NARCIS (Netherlands)

    Zwart, Heiko J.; Le Gorrec, Yann; Maschke, B.M.; Villegas, J.A.

    2010-01-01

    We study a class of hyperbolic partial differential equations on a one dimensional spatial domain with control and observation at the boundary. Using the idea of feedback we show these systems are well-posed in the sense of Weiss and Salamon if and only if the state operator generates a

  3. Variational methods for boundary value problems for systems of elliptic equations

    CERN Document Server

    Lavrent'ev, M A

    2012-01-01

    Famous monograph by a distinguished mathematician presents an innovative approach to classical boundary value problems. The treatment employs the basic scheme first suggested by Hilbert and developed by Tonnelli. 1963 edition.

  4. Can upwelling signals be detected in intertidal fishes of different trophic levels?

    Science.gov (United States)

    Pulgar, J; Poblete, E; Alvarez, M; Morales, J P; Aranda, B; Aldana, M; Pulgar, V M

    2013-11-01

    For intertidal fishes belonging to three species, the herbivore Scartichthys viridis (Blenniidae), the omnivore Girella laevifrons (Kyphosidae) and the carnivore Graus nigra (Kyphosidae), mass and body size relationships were higher in individuals from an upwelling zone compared with those from a non-upwelling zone. RNA:DNA were higher in the herbivores and omnivores from the upwelling zone. Higher biomass and RNA:DNA in the upwelling intertidal fishes may be a consequence of an increased exposure to higher nutrient availability, suggesting that increased physiological conditioning in vertebrates from upwelling areas can be detected and measured using intertidal fishes of different trophic levels. © 2013 The Fisheries Society of the British Isles.

  5. Generalized Green's functions for higher order boundary value matrix differential systems

    Directory of Open Access Journals (Sweden)

    R. J. Villanueva

    1992-01-01

    Full Text Available In this paper, a Green's matrix function for higher order two point boundary value differential matrix problems is constructed. By using the concept of rectangular co-solution of certain algebraic matrix equation associated to the problem, an existence condition as well as an explicit closed form expression for the solution of possibly not well-posed boundary value problems is given avoiding the increase of the problem dimension.

  6. Motion of particles in solar and galactic systems by using Neumann boundary condition

    Science.gov (United States)

    Shenavar, Hossein

    2016-12-01

    A new equation of motion, which is derived previously by imposing Neumann boundary condition on cosmological perturbation equations (Shenavar in Astrophys. Space Sci., 2016a, doi: 10.1007/s10509-016-2676-5), is investigated. By studying the precession of perihelion, it is shown that the new equation of motion suggests a small, though detectable, correction in orbits of solar system objects. Then a system of particles is surveyed to have a better understanding of galactic structures. Also the general form of the force law is introduced by which the rotation curve and mass discrepancy of axisymmetric disks of stars are derived. In addition, it is suggested that the mass discrepancy as a function of centripetal acceleration becomes significant near a constant acceleration 2c1a0 where c1 is the Neumann constant and a0 = 6.59 ×10^{-10} m/s2 is a fundamental acceleration. Furthermore, it is shown that a critical surface density equal to σ0=a0/G, in which G is the Newton gravitational constant, has a significant role in rotation curve and mass discrepancy plots. Also, the specific form of NFW mass density profile at small radii, ρ∝1/r, is explained too. Finally, the present model will be tested by using a sample of 39 LSB galaxies for which we will show that the rotation curve fittings are generally acceptable. The derived mass to light ratios too are found within the plausible bound except for the galaxy F571-8.

  7. Coastal upwelling in the Gelendzhik area of the Black Sea: Effect of wind and dynamics

    Science.gov (United States)

    Silvestrova, K. P.; Zatsepin, A. G.; Myslenkov, S. A.

    2017-07-01

    Long series data of a thermistor chain in the Black Sea coastal zone near Gelendzhik were analyzed. A thermistor chain installed 1 km offshore and at a depth of 22 m. There are full and incomplete upwelling events observed. The study of upwelling genesis based on: wind speed data from the NCEP/CFSR reanalysis and Gelendzhik weather station, velocity and direction of coastal currents measured by ADCP profiler moored on the bottom near the thermistor chain. Over the whole observation period (warm seasons of 2013-2015), more than 40 events of upwelling were registered four of them were full upwellings, when presence of under-thermocline water was observed near the sea surface. For every upwelling event, conditions prior to the changes in thermic structure, were analyzed. It is found that full upwelling generally occur under synergistic wind and current forcing. Fairly strong forcing of one of these factors is sufficient for partial upwelling to occur.

  8. The active disturbance rejection control approach to stabilisation of coupled heat and ODE system subject to boundary control matched disturbance

    Science.gov (United States)

    Guo, Bao-Zhu; Liu, Jun-Jun; AL-Fhaid, A. S.; Younas, Arshad Mahmood M.; Asiri, Asim

    2015-08-01

    We consider stabilisation for a linear ordinary differential equation system with input dynamics governed by a heat equation, subject to boundary control matched disturbance. The active disturbance rejection control approach is applied to estimate, in real time, the disturbance with both constant high gain and time-varying high gain. The disturbance is cancelled in the feedback loop. The closed-loop systems with constant high gain and time-varying high gain are shown, respectively, to be practically stable and asymptotically stable.

  9. Method and system for detecting polygon boundaries of structures in images as particle tracks through fields of corners and pixel gradients

    Science.gov (United States)

    Paglieroni, David W [Pleasanton, CA; Manay, Siddharth [Livermore, CA

    2011-12-20

    A stochastic method and system for detecting polygon structures in images, by detecting a set of best matching corners of predetermined acuteness .alpha. of a polygon model from a set of similarity scores based on GDM features of corners, and tracking polygon boundaries as particle tracks using a sequential Monte Carlo approach. The tracking involves initializing polygon boundary tracking by selecting pairs of corners from the set of best matching corners to define a first side of a corresponding polygon boundary; tracking all intermediate sides of the polygon boundaries using a particle filter, and terminating polygon boundary tracking by determining the last side of the tracked polygon boundaries to close the polygon boundaries. The particle tracks are then blended to determine polygon matches, which may be made available, such as to a user, for ranking and inspection.

  10. Derivative matrices of a skew ray for spherical boundary surfaces and their applications in system analysis and design.

    Science.gov (United States)

    Lin, Psang Dain

    2014-05-10

    In a previous paper [Appl. Opt.52, 4151 (2013)], we presented the first- and second-order derivatives of a ray for a flat boundary surface to design prisms. In this paper, that scheme is extended to determine the Jacobian and Hessian matrices of a skew ray as it is reflected/refracted at a spherical boundary surface. The validity of the proposed approach as an analysis and design tool is demonstrated using an axis-symmetrical system for illustration purpose. It is found that these two matrices can provide the search direction used by existing gradient-based schemes to minimize the merit function during the optimization stage of the optical system design process. It is also possible to make the optical system designs more automatic, if the image defects can be extracted from the Jacobian and Hessian matrices of a skew ray.

  11. Reduced order models, inertial manifolds, and global bifurcations: searching instability boundaries in nuclear power systems

    Energy Technology Data Exchange (ETDEWEB)

    Suarez-Antola, Roberto, E-mail: roberto.suarez@miem.gub.u, E-mail: rsuarez@ucu.edu.u [Universidad Catolica del Uruguay, Montevideo (Uruguay). Fac. de Ingenieria y Tecnologias. Dept. de Matematica; Ministerio de Industria, Energia y Mineria, Montevideo (Uruguay). Direccion General de Secretaria

    2011-07-01

    One of the goals of nuclear power systems design and operation is to restrict the possible states of certain critical subsystems to remain inside a certain bounded set of admissible states and state variations. In the framework of an analytic or numerical modeling process of a BWR power plant, this could imply first to find a suitable approximation to the solution manifold of the differential equations describing the stability behavior, and then a classification of the different solution types concerning their relation with the operational safety of the power plant. Inertial manifold theory gives a foundation for the construction and use of reduced order models (ROM's) of reactor dynamics to discover and characterize meaningful bifurcations that may pass unnoticed during digital simulations done with full scale computer codes of the nuclear power plant. The March-Leuba's BWR ROM is generalized and used to exemplify the analytical approach developed here. A nonlinear integral-differential equation in the logarithmic power is derived. Introducing a KBM Ansatz, a coupled set of two nonlinear ordinary differential equations is obtained. Analytical formulae are derived for the frequency of oscillation and the parameters that determine the stability of the steady states, including sub- and supercritical PAH bifurcations. A Bautin's bifurcation scenario seems possible on the power-flow plane: near the boundary of stability, a region where stable steady states are surrounded by unstable limit cycles surrounded at their turn by stable limit cycles. The analytical results are compared with recent digital simulations and applications of semi-analytical bifurcation theory done with reduced order models of BWR. (author)

  12. Vertical Sampling Scales for Atmospheric Boundary Layer Measurements from Small Unmanned Aircraft Systems (sUAS

    Directory of Open Access Journals (Sweden)

    Benjamin L. Hemingway

    2017-09-01

    Full Text Available The lowest portion of the Earth’s atmosphere, known as the atmospheric boundary layer (ABL, plays an important role in the formation of weather events. Simple meteorological measurements collected from within the ABL, such as temperature, pressure, humidity, and wind velocity, are key to understanding the exchange of energy within this region, but conventional surveillance techniques such as towers, radar, weather balloons, and satellites do not provide adequate spatial and/or temporal coverage for monitoring weather events. Small unmanned aircraft, or aerial, systems (sUAS provide a versatile, dynamic platform for atmospheric sensing that can provide higher spatio-temporal sampling frequencies than available through most satellite sensing methods. They are also able to sense portions of the atmosphere that cannot be measured from ground-based radar, weather stations, or weather balloons and have the potential to fill gaps in atmospheric sampling. However, research on the vertical sampling scales for collecting atmospheric measurements from sUAS and the variabilities of these scales across atmospheric phenomena (e.g., temperature and humidity is needed. The objective of this study is to use variogram analysis, a common geostatistical technique, to determine optimal spatial sampling scales for two atmospheric variables (temperature and relative humidity captured from sUAS. Results show that vertical sampling scales of approximately 3 m for temperature and 1.5–2 m for relative humidity were sufficient to capture the spatial structure of these phenomena under the conditions tested. Future work is needed to model these scales across the entire ABL as well as under variable conditions.

  13. Surface circulation and upwelling patterns around Sri Lanka and formation of the Sri Lanka Dome

    Science.gov (United States)

    Pattiaratchi, C. B.; Wijeratne, S.; De Vos, A.

    2014-12-01

    Sri Lanka, a relatively large island (length 440 km; width 225 km), occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side and experiences bi-annually reversing monsoon winds. This allows for the Island to interact with the seasonally reversing monsoon currents leading to the the island mass effect and enhanced primary production. We will present elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 4 years to examine the inter-annual, seasonal and shorter term (~10 days) variability. The results confirmed the presence of the reversing current system, between the equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC) transporting 9.5 Sv during the Northeast (NE) monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast (see Figure). During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast resulting from southward flow converging along the south coast and subsequent divergence associated with the offshore transport of water(see Figure). Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and

  14. Seasonal variability of phytoplankton fluorescence in relation to the Straits of Messina (Sicily tidal upwelling

    Directory of Open Access Journals (Sweden)

    F. Azzaro

    2007-10-01

    Full Text Available In the Straits of Messina, large gradients of tidal displacements, as well as the topographic constrictions, determine the upwelling of deeper waters in the surface layer. This work describes the seasonal variability in the surface distribution of phytoplankton biomass depending on the upwelling phenomena. Temperature, salinity, nitrates and phytoplankton fluorescence were measured in 1994 and 1995 by continuous underway surface real-time measurements onboard dedicated research boats. Each survey was performed following the dynamic phases of flooding and ebbing tides. Tidal currents are essentially southward during high tide and northward during low tide.

    During the low water slack tide, large spatial gradients of physical-chemical and biological parameters were found, while at the high water slack tide, a diffused phytoplankton fluorescence was observed only in autumn due to a seasonal thermocline. Salinity, nitrate and chlorophyll-a fluorescence data revealed a significant positive intercorrelation, whereas they were inversely correlated with temperature. Generally, the upwelling distribution was limited to narrow zones during winter, while in summer it was found in the middle of the Straits and in the southern zones. During spring in the southern zone of the Straits, the maximum chlorophyll-a fluorescence was detected (May 1995, 0.32 μg-Chla l−1; in summer, when back and forth tidal movements between the Tyrrhenian and the Ionian seas intensify, decreased values were observed throughout the study area.

    The data set obtained through continuous and repeatable samplings has allowed the study of different time-space scales in the Straits of Messina, a very strong and dynamic environment.

    The Straits system could be compared to an "intermittent pump" which, during the different seasons, initially enriches itself and subsequently provides nutrients to the surrounding basins.

  15. Development of the Central-Afar volcanic margin, mantle upwelling and break-up processes

    Science.gov (United States)

    Pik, Raphaël; Bellahsen, Nicolas; Leroy, Sylvie; Stab, Martin; Ayalew, Dereje; Yirgu, Gezahegn

    2017-04-01

    Whereas the present day mantle dynamics is now well imaged by geophysical investigations, the long-term expression of mantle dynamics below rifted lithosphere is not directly recorded at the surface of the earth. Such information must therefore be extracted from non-direct manifestations of mantle upwelling, which are principally (i) the uplift of the upperlying lithosphere and (ii) the melts produced when the solidus of mantle mineral assemblages is crossed. These first order and unique evidences should therefore represent corner stones output of any geodynamic models used to deduce the interplay between mantle dynamics and surface deformations. For magmatism produced during extension of lithosphere, the dynamics of mantle upwelling can be recognized in the volumes of magmas and also in their geochremistry, which allow tracking the various types of mantle sources and the various types of mantle melting regime (P, T and intensity of partial melting). Volcanism has been closely associated with extension in the East African rift system. It is yet (and logically) heterogeneously distributed along the western, eastern and northern volcanic provinces. We have concentrated the efforts of a multidisciplinary team these last years in the northern Ethiopian volcanic province where the most important volumes of volcanism have been emplaced since 30 Ma, from Continental Flood Basalts episode to active extension along the Central Afar magmatic segment. These structural and geochemical data point out new constraints on the interplay between the upwelling of the Afar mantle plume and the style and mechanisms of extension, and imply to update and revise our understanding of the development of this volcanic margin.

  16. Phytoplankton stimulation in frontal regions of Benguela upwelling filaments by internal factors

    Directory of Open Access Journals (Sweden)

    Norbert Wasmund

    2016-11-01

    Full Text Available Filaments are intrusions of upwelling water into the sea, separated from the surrounding water by fronts. Current knowledge explains the enhanced primary production and phytoplankton growth found in frontal areas by external factors like nutrient input. The question is whether this enhancement is also caused by intrinsic factors, i.e. simple mixing without external forcing. In order to study the direct effect of frontal mixing on organisms, disturbing external influx has to be excluded. Therefore mixing was simulated by joining waters originating from inside and outside the filament in mesocosms (tanks. These experiments were conducted during two cruises in the northern Benguela upwelling system in September 2013 and January 2014. The mixed waters reached a much higher net primary production and chlorophyll a (chla concentration than the original waters already 2-3 days after their merging. The peak in phytoplankton biomass stays longer than the chla peak. After their maxima, primary production rates decreased quickly due to depletion of the nutrients. The increase in colored dissolved organic matter (CDOM may indicate excretion and degradation. Zooplankton is not quickly reacting on the changed conditions. We conclude that already simple mixing of two water bodies, which occurs generally at fronts between upwelled and ambient water, leads to a short-term stimulation of the phytoplankton growth. However, after the exhaustion of the nutrient stock, external nutrient supply is necessary to maintain the enhanced phytoplankton growth in the frontal area. Based on these data, some generally important ecological factors are discussed as for example nutrient ratios and limitations, silicate requirements and growth rates.

  17. Modeling of the upwelling hydrodynamics in the Aegean Sea

    Directory of Open Access Journals (Sweden)

    Y.G. SAVVIDIS

    2004-06-01

    Full Text Available The special features of the hydrodynamic circulation in the Aegean Sea referring to the development of regional upwelling coastal zones are studied by means of a mathematical model. The modeling effort is focused on the tracing of coastal areas, where upwelling events are frequently observed during the summer meteorological conditions. These areas are characterized by the enrichment of surface waters with nutrients and, consequently, increased fish production. The phenomenon is studied by the use of a two-layer mathematical model comprising the surface heated zone and the rest of the water column. The numerical solution of the model is based on the finite differences method. The wind shear applied over the stratified basin, with predefined density stratification and initial water-layers thickness, and the gravity and Coriolis forces taken into account, constitute the basic external factors for the generation of the hydrodynamic circulation in the area of the Aegean Sea. The calibration and the validation of the model are performed by the comparison of the model output to the data and observations reported in valid scientific sources. The aim of the paper is to demonstrate the significant contribution of numerical models to the better understanding of the hydrodynamics governing the Aegean water circulation as well as the tracing of upwelling zones.

  18. Artificial upwelling driven by salinity differences in the ocean

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D H; Decicco, J

    1983-12-01

    A concept for an artificial upwelling driven by salinity differences in the ocean to supply nutrients to a mariculture farm is described and analyzed. A long shell-and-tube counterflow heat exchanger built of inexpensive plastic and concrete is suspended vertically in the ocean. Cold, nutrient rich, but relatively fresh water from deep in the ocean flows up the shell side of the heat exchanger, and warm but relatively saline water from the surface flows down the tube side. The two flows exchange heat across the thin plastic walls of the tubes, maintaining a constant temperature difference along the heat exchanger. The plastic tubes are protected by the concrete outer shell of the heat exchanger. The flow is maintained by the difference in density between the deep and surface water due to their difference in salinity. This phenomenon was first recognized by the oceanographer Stommel, who termed it The Perpetual Salt Fountain. The heat transfer and flow rate as a function of tube number and diameter is analyzed and the size of the heat exchanger optimized for cost is determined for a given flow of nutrients for various locations. Reasonable sizes (outer diameter on the order of 5 m) are obtained. The incremental capital cost of the salinity-driven artificial upwelling is compared to the incremental capital cost and present value of the operating cost of an artificial upwell fueled by liquid hydrocarbons.

  19. Resolving the Mantle Heat Transfer Discrepancy by Reassessing Buoyancy Flux Estimates of Upwelling Plumes

    Science.gov (United States)

    Hoggard, Mark; Parnell-Turner, Ross; White, Nicky

    2017-04-01

    core-mantle boundary. If this higher estimate is correct, it suggests that upwelling plumes play a much more significant role in the transfer of heat through the Earth's mantle.

  20. An urban systems framework to assess the trans-boundary food-energy-water nexus: implementation in Delhi, India

    Science.gov (United States)

    Ramaswami, Anu; Boyer, Dana; Singh Nagpure, Ajay; Fang, Andrew; Bogra, Shelly; Bakshi, Bhavik; Cohen, Elliot; Rao-Ghorpade, Ashish

    2017-02-01

    This paper develops a generalizable systems framework to analyze the food-energy-water (FEW) nexus from an urban systems perspective, connecting in- and trans-boundary interactions, quantifying multiple environmental impacts of community-wide FEW provisioning to cities, and visualizing FEW supply-chain risks posed to cities by the environment. Delhi’s community-wide food demand includes household consumption by socio-economic-strata, visitors- and industrial food-use. This demand depends 90%, 76%, and 86% on trans-boundary supply of FEW, respectively. Supply chain data reveal unique features of trans-boundary FEW production regions (e.g. irrigation-electricity needs and GHG intensities of power-plants), yielding supply chain-informed coupled energy-water-GHG footprints of FEW provisioning to Delhi. Agri-food supply contributes to both GHG (19%) and water-footprints (72%-82%) of Delhi’s FEW provisioning, with milk, rice and wheat dominating these footprints. Analysis of FEW interactions within Delhi found >75% in-boundary water-use for food is for urban agriculture and >76% in-boundary energy-use for food is from cooking fuels. Food waste-to-energy and energy-intensity of commercial and industrial food preparation are key data gaps. Visualizing supply chains shows >75% of water embodied in Delhi’s FEW supply is extracted from locations over-drafting ground water. These baseline data enable evaluation of future urban FEW scenarios, comparing impacts of demand shifts, production shifts, and emerging technologies and policies, within and outside of cities.

  1. Theoretical and experimental studies on isotachophoresis in multi-moving chelation boundary system formed with metal ions and EDTA.

    Science.gov (United States)

    Zhang, Wei; Guo, Chen-Gang; Fan, Liu-Yin; Cao, Cheng-Xi

    2013-09-07

    In this paper, a general mode and theory of moving chelation boundary based isotachophoresis (MCB-based ITP), together with the concept of decisive metal ion (DMI) having the maximum complexation constant (lg Kmax) with the chelator, were developed from a multi-MCB (mMCB) system. The theoretical deductions were: (i) the reaction boundary velocities in the mMCB system at steady state were equal to each other, resulting in a novel MCB-based ITP separation of metal ions; (ii) the boundary directions and velocities in the system were controlled by the fluxes of chelator and DMI, rather than other metal ions; and (iii) a controllable stacking of metal ions could be simultaneously achieved in the developed system. To demonstrate the deductions, a series of experiments were conducted by using model chelator of EDTA and metal ions of Cu(II) and Co(II) due to characteristic colors of blue [Cu-EDTA](2-) and pink [Co-EDTA](2-) complexes. The experiments demonstrated the correctness of theoretical deductions, indicating the validity of the developed model and theory of ITP. These findings provide guidance for the development of MRB-based ITP separation and stacking of metal ions in biological sample matrix and heavy metal ions in environmental samples.

  2. Southeast Atlantic upwelling intensity changes influencing late Miocene C4 plant expansion?

    Science.gov (United States)

    Rommerskirchen, F.; Condon, T.; Mollenhauer, G.; Schefuß, E.

    2009-04-01

    The Late Miocene epoch (about 15 to 5 Myrs BP) is characterised by fundamental changes in Earth's climate system: turnovers in marine and terrestrial biota, sea-level variability, changes in surface- und deep-water circulations, and increase in upwelling intensities along the coasts [1,2]. During the transition period the Antarctic ice sheets expanded and were permanently established, while additionally ice volumes began to fluctuate [1]. Plants acting with the C4 concentrating mechanism of CO2 fixation for photosynthesis expanded nearly simultaneous at different places in the world, whereas the global CO2 levels exhibit no corresponding change [1,3]. However, C4 plants are also known to have a competitive advantage in habitats of higher temperature, light and fire intensities as well as of limited water supply, compared to the almost ubiquitous C3 plants. This study tries to give insights to Miocene climatic conditions in Southwest Africa and how these conditions may be linked to the C4 plant expansion. We focused on data from a sediment core of the Ocean Drilling Program (Leg 175, ODP 1085A), which span about 10 Myrs of the late Miocene. The core is situated in the Cape basin at the south-western African continental margin in the upwelling zone of the Benguela coastal current. The current brings cold, nutrient-rich waters from South Atlantic and the Antarctic circumpolar current to the surface water along the coast of Southwest Africa. Miocene sea surface temperatures (SST) were reconstructed by two indices, tetraether index (TEX86) and an alkenone based index (U37K'). Both trends exhibit a shift to cooler temperatures from around 27 to 18˚ C, but are different in rate and timing. Especially by TEX86 reconstructed SSTs exhibit a similar trend as found for ice volume changes shown by the δ18O curve [4]. These findings may reflect an intensification of the Benguela upwelling current during the late Miocene, probably in association with the formation of West

  3. Boltzmann’s Six-Moment One-Dimensional Nonlinear System Equations with the Maxwell-Auzhan Boundary Conditions

    Directory of Open Access Journals (Sweden)

    A. Sakabekov

    2016-01-01

    Full Text Available We prove existence and uniqueness of the solution of the problem with initial and Maxwell-Auzhan boundary conditions for nonstationary nonlinear one-dimensional Boltzmann’s six-moment system equations in space of functions continuous in time and summable in square by a spatial variable. In order to obtain a priori estimation of the initial and boundary value problem for nonstationary nonlinear one-dimensional Boltzmann’s six-moment system equations we get the integral equality and then use the spherical representation of vector. Then we obtain the initial value problem for Riccati equation. We have managed to obtain a particular solution of this equation in an explicit form.

  4. Can Vertical Migrations of Dinoflagellates Explain Observed Bioluminescence Patterns During an Upwelling Event in Monterey Bay, California?

    Science.gov (United States)

    2012-01-25

    of actual dinoflagellates swimming during the 2003 upwelling event represents a very challenging task and requires knowledge of their initial...Solid vertical lines indicate location of the Ml mooring. profiles derived from the Modular Ocean Data Assimilation System ( MODAS ) [Fox et al, 2002...to avoid strong advection by southward flow along the entrance to the Bay. [28] We want to stress here that the actual dinoflagellates swimming

  5. Existence of global solutions to free boundary value problems for bipolar Navier-Stokes-Possion systems

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2013-09-01

    Full Text Available In this article, we consider the free boundary value problem for one-dimensional compressible bipolar Navier-Stokes-Possion (BNSP equations with density-dependent viscosities. For general initial data with finite energy and the density connecting with vacuum continuously, we prove the global existence of the weak solution. This extends the previous results for compressible NS [27] to NSP.

  6. On preconditioning techniques for dense linear systems arising from singular boundary integral equations

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ke [Univ. of Liverpool (United Kingdom)

    1996-12-31

    We study various preconditioning techniques for the iterative solution of boundary integral equations, and aim to provide a theory for a class of sparse preconditioners. Two related ideas are explored here: singularity separation and inverse approximation. Our preliminary conclusion is that singularity separation based preconditioners perform better than approximate inverse based while it is desirable to have both features.

  7. Intermittent turbulence and oscillations in the stable boundary layer: a system dynamics approach

    NARCIS (Netherlands)

    Wiel, van de B.J.H.; Moene, A.F.; Hartogensis, O.K.; Ronda, R.J.; DeBruin, H.A.R.; Holtslag, A.A.M.

    2002-01-01

    The stable boundary layer (SBL) is often characterised by turbulence which is not continuous in space and time. This socalled intermittent turbulence may affect the whole depth of the SBL. In this study intermittent turbulence is studied from both theoretical and experimental point of view. The

  8. Exchanges across land-water-scape boundaries in urban systems: strategies for reducing nitrate pollution.

    Science.gov (United States)

    Cadenasso, M L; Pickett, S T A; Groffman, P M; Band, L E; Brush, G S; Galvin, M F; Grove, J M; Hagar, G; Marshall, V; McGrath, B P; O'Neil-Dunne, J P M; Stack, W P; Troy, A R

    2008-01-01

    Conservation in urban areas typically focuses on biodiversity and large green spaces. However, opportunities exist throughout urban areas to enhance ecological functions. An important function of urban landscapes is retaining nitrogen thereby reducing nitrate pollution to streams and coastal waters. Control of nonpoint nitrate pollution in urban areas was originally based on the documented importance of riparian zones in agricultural and forested ecosystems. The watershed and boundary frameworks have been used to guide stream research and a riparian conservation strategy to reduce nitrate pollution in urban streams. But is stream restoration and riparian-zone conservation enough? Data from the Baltimore Ecosystem Study and other urban stream research indicate that urban riparian zones do not necessarily prevent nitrate from entering, nor remove nitrate from, streams. Based on this insight, policy makers in Baltimore extended the conservation strategy throughout larger watersheds, attempting to restore functions that no longer took place in riparian boundaries. Two urban revitalization projects are presented as examples aimed at reducing nitrate pollution to stormwater, streams, and the Chesapeake Bay. An adaptive cycle of ecological urban design synthesizes the insights from the watershed and boundary frameworks, from new data, and from the conservation concerns of agencies and local communities. This urban example of conservation based on ameliorating nitrate water pollution extends the initial watershed-boundary approach along three dimensions: 1) from riparian to urban land-water-scapes; 2) from discrete engineering solutions to ecological design approaches; and 3) from structural solutions to inclusion of individual, household, and institutional behavior.

  9. Regularity results for quasilinear elliptic systems of power-law growth in nonsmooth domains : boundary, transmission and crack problems

    OpenAIRE

    Knees, Dorothee

    2005-01-01

    The thesis is devoted to the analysis of weak solutions of quasi-linear elliptic boundary transmission problems on nonsmooth domains. The focus lies on the following two classes of equations which are closely related: general systems of second order quasi-linear elliptic partial differential equations of p-structure with piecewise constant coefficients (e.g. the p-Laplace equation) and field equations for the displacement and stress fields of heterogeneous, physically nonlinear elastic bodies...

  10. Ground boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  11. Influence of ocean acidification and deep water upwelling on oligotrophic plankton communities in the subtropical North Atlantic

    DEFF Research Database (Denmark)

    Taucher, Jan; Bach, Lennart T.; Boxhammer, Tim

    2017-01-01

    and successfully simulated a deep water upwelling event that induced a pronounced plankton bloom. Our study revealed significant effects of OA on the entire food web, leading to a restructuring of plankton communities that emerged during the oligotrophic phase, and was further amplified during the bloom......Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. Increasing evidence indicates that these changes-summarized by the term ocean acidification (OA)-can significantly affect marine food webs and biogeochemical......, which regularly occur in response to upwelling of nutrient-rich deep water in the study region. Therefore, we specifically developed a deep water collection system that allowed us to obtain 85 m3 of seawater from 650 m depth. Thereby, we replaced 20% of each mesocosm's volume with deep water...

  12. Boundary Influences on HAB Phytoplankton Ecology in a Stratification-Enhanced Upwelling Shadow

    Science.gov (United States)

    2014-05-13

    specific features (Bird et al., 2007; Ryan etal., 2010b). In addition to propelled AUVs, we used a Slocum glider to provide a time-series of vertical...e MBARI ESP moorings n NRL moorings, gliders ɘ NSF LatMix array Fig. 1. Climatology-guided experiment design. Satellite-observed (a) sea...sections parallel to and ~1 km west of the NRL mooring array and E2 (Fig. 1c). Details of this glider and its sensors are published (Pcnta, 2011). To

  13. El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

    Directory of Open Access Journals (Sweden)

    W. E. Arntz

    2006-01-01

    Full Text Available To a certain degree, Eastern Boundary Current (EBC ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O2 exchange is restricted, it creates oxygen minimum zones (OMZs at shelf and upper slope (Humboldt and Benguela Current or slope depths (California Current. These hypoxic zones host a specifically adapted, small macro- and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H2S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between <100 and about 600 m, with decreasing thickness in a poleward direction. The OMZ merges into better oxygenated zones towards the deep sea, where large cold-water mega- and macrofauna occupy a dominant role as in the nearshore strip. The Benguela Current OMZ has a similar upper limit but remains shallower. It also hosts giant sulphur bacteria but little is known about the benthic fauna. However, sulphur eruptions and intense hypoxia might preclude the coexistence of significant mega- und macrobenthos. Conversely, off North America the upper limit of the OMZ is considerably deeper (e.g., 500–600 m off California and Oregon, and the lower boundary may exceed 1000m. The properties described are valid for very cold and cold (La Niña and "normal" ENSO conditions with effective upwelling of nutrient-rich bottom water. During warm (El Niño episodes, warm water masses of low oxygen concentration from oceanic and equatorial regions enter the upwelling

  14. Sources of new nitrogen in the Vietnamese upwelling region of the South China Sea

    DEFF Research Database (Denmark)

    Bombar, Deniz; Dippner, Joachim W.; Doan, Hai Nhu

    2010-01-01

    In the South China Sea, the southwest monsoon between June and September induces upwelling off the southern central Vietnamese coast. During field campaigns in July 2003 and 2004 we evaluated the importance of nitrate and nitrogen fixation as sources of new nitrogen for phytoplankton primary...... productivity, both in the actual upwelling zone and in the oligotrophic area farther offshore. Complementary to rate measurements of primary productivity, nitrate uptake, and nitrogen fixation, we determined vertical nitrate fluxes by Ekman upwelling (upwelling zone) and turbulent diffusion (offshore waters......). Because of the influence of El Nio, upwelling was weaker in July 2003, with an average primary productivity of 28 ± 18 mmol C m-2 d -1, compared to 103 ± 25 mmol C m-2 d-1 in July 2004. Calculated upwelling nitrate fluxes of 17 ± 2 mmol N m -2 d-1 in July 2004 are consistent with N demands of primary...

  15. Mathematical model of complex technical asymmetric system based on numerical-analytical boundary elements method

    Directory of Open Access Journals (Sweden)

    Dina V. Lazareva

    2015-06-01

    Full Text Available A new mathematical model of asymmetric support structure frame type is built on the basis of numerical-analytical boundary elements method (BEM. To describe the design scheme used is the graph theory. Building the model taken into account is the effect of frame members restrained torsion, which presence is due to the fact that these elements are thin-walled. The built model represents a real object as a two-axle semi-trailer platform. To implement the BEM algorithm obtained are analytical expressions of the fundamental functions and vector load components. The effected calculations are based on the semi-trailer two different models, using finite elements and boundary elements methods. The analysis showed that the error between the results obtained on the basis of two numerical methods and experimental data is about 4%, that indicates the adequacy of the proposed mathematical model.

  16. Vehicle cabin cooling system for capturing and exhausting heated boundary layer air from inner surfaces of solar heated windows

    Science.gov (United States)

    Farrington, Robert B.; Anderson, Ren

    2001-01-01

    The cabin cooling system includes a cooling duct positioned proximate and above upper edges of one or more windows of a vehicle to exhaust hot air as the air is heated by inner surfaces of the windows and forms thin boundary layers of heated air adjacent the heated windows. The cabin cooling system includes at least one fan to draw the hot air into the cooling duct at a flow rate that captures the hot air in the boundary layer without capturing a significant portion of the cooler cabin interior air and to discharge the hot air at a point outside the vehicle cabin, such as the vehicle trunk. In a preferred embodiment, the cooling duct has a cross-sectional area that gradually increases from a distal point to a proximal point to the fan inlet to develop a substantially uniform pressure drop along the length of the cooling duct. Correspondingly, this cross-sectional configuration develops a uniform suction pressure and uniform flow rate at the upper edge of the window to capture the hot air in the boundary layer adjacent each window.

  17. Random walks in the quarter plane algebraic methods, boundary value problems, applications to queueing systems and analytic combinatorics

    CERN Document Server

    Fayolle, Guy; Malyshev, Vadim

    2017-01-01

    This monograph aims to promote original mathematical methods to determine the invariant measure of two-dimensional random walks in domains with boundaries. Such processes arise in numerous applications and are of interest in several areas of mathematical research, such as Stochastic Networks, Analytic Combinatorics, and Quantum Physics. This second edition consists of two parts. Part I is a revised upgrade of the first edition (1999), with additional recent results on the group of a random walk. The theoretical approach given therein has been developed by the authors since the early 1970s. By using Complex Function Theory, Boundary Value Problems, Riemann Surfaces, and Galois Theory, completely new methods are proposed for solving functional equations of two complex variables, which can also be applied to characterize the Transient Behavior of the walks, as well as to find explicit solutions to the one-dimensional Quantum Three-Body Problem, or to tackle a new class of Integrable Systems. Part II borrows spec...

  18. DETERMINATION OF EFFICIENCY INDICES PERTAINING TO DEVELOPMENT AND OPERATION OF TRANS-BOUNDARY TRANSPORT AND LOGISTICS SYSTEM

    Directory of Open Access Journals (Sweden)

    Y. A. Kopko

    2011-01-01

    Full Text Available An investigation of the system efficiency requires a special approach in terms of its level, content and interrelations with an external environment. In this regard logistic  systems are rather complicated that consist of a number of service sub-systems and designed at various levels.  Such system complexity requires a development of an efficient mechanism for its design and operation of objects of the trans-boundary transport logistics. The efficiency of the trans-boundary transport and logistic systems (TTLS can be described by a number of cost and physical indicators reflecting both market and traditional approaches. The TTLS have their own peculiar features concerning determination of efficiency that are related with the state regulation set of processes occurring  at border crossings. In order to assess the current operational process it is necessary to apply an index system which pays a special attention to a transport capability due to the TTLS specificity. While planning a custom automotive processing at a border checkpoint there is no need to aspire for an immediate passage of all vehicles by all means. The basic requirement is to maintain a transport capability in the operational zone. Thus an irregularity of incoming vehicles at border crossing points is smoothed out by regulating priorities pertaining to requirements of custom processing while using an urgency function of cargo transportation thereby ensuring an optimal operation of a customs post.

  19. Isotopic evidences of past upwelling intensity in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    stream_size 29214 stream_content_type text/plain stream_name Global_Planet_Change_40_285.pdf.txt stream_source_info Global_Planet_Change_40_285.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8..., atmospheric CO 2 levels. In this manner, changes in the intensity of upwelling can exert a significant influence on the CO 2 budget of the atmosphere and consequently on the global climate. In view of welling zones are major sites for the sequestering of high...

  20. Jupiter's belts and zones: Contradictory evidence for upwelling and downwelling

    Science.gov (United States)

    Ingersoll, Andrew P.; Juno Science Team

    2017-10-01

    Early authors (Hess and Panofsky 1951, Ingersoll and Cuzzi 1969, Barcilon and Gierasch 1970) noted that the zonal winds are cyclonic in the belts and anticyclonic in the zones. From the thermal wind equation they concluded that the air below the clouds is colder at the belts and warmer at the zones. Hot air rising and cold air sinking led to the notion of downwelling in the belts and upwelling in the zones, which agreed with observations of clear air and low ammonia vapor in the belts and cloudy air and high ammonia vapor in the zones (Gierasch et al. 1986). However, lightning in the belts seemed to contradict that idea, based on the assumption that lightning and convection require upwelling of moist air from below (Little et al. 1999, Ingersoll et al. 2000). Convergence of the eddy momentum flux on the poleward sides of the zones (Salyk et al. 2006) supports the inference based on lightning by implying convergence of the meridional flow in the zones. Here we argue that lightning in the belts does not require upwelling. Instead, there is a threshold for moist convection that is triggered when the thickness of the weather layer drops below a critical value (Li and Ingersoll 2006, Thomson and McIntyre 2016). We also argue that the convergence of the eddy momentum flux does not require equatorward flow. Instead, the meridional flow is controlled by the sign of the potential vorticity (PV) gradient, which is southward on the equatorward sides of the zones (Ingersoll et al. 2017), implying divergence of the meridional flow in the zones. This is a new idea and is based on the observation that the predicted flat parts of the PV staircase (Dritschel and McIntyre 2008), might actually be sloping inward, since the curvature of the zonal velocity profile U_yy exceeds beta at the centers of the westward jets (Ingersoll and Cuzzi 1969, Ingersoll et al. 1981, Limaye et al. 1986, Li et al. 2004, Read et al. 2006). These arguments agree with observations of upwelling in the zones

  1. Coastal upwelling in Gelendzhik area of the Black sea: wind and dynamics influence.

    Science.gov (United States)

    Silvestrova, Ksenia

    2017-04-01

    This work presents the results of upwelling observations at the coastal zone of the Black Sea near Gelendzhik city. The long series of water temperature (thermochain from 6 to 18 m) were analyzed. The events of full and incomplete upwelling were selected. 5 events from 45 referred to the full upwelling. Under termocline water with a temperature of less than 10° C was observed near the surface. In order to analyze upwelling causes the wind speed from NCEP/CFSR reanalysis and data of the Acoustic Doppler Current Profiler (ADCP) over the period 2013-2015 (mostly warm season) were used. Special upwelling cryteria that consideres wind stress, local baroclinic Rossby radius and thickness of upper mixed layer was calculated. This cryteria allow to estimate role of the wind forcing. Conditions precedent change of the thermal structure are analyzed for each of the upwelling events. It is found that full upwelling preceded by a steady long (more than 2 days) northwest wind. Most of all fixed upwelling events (40%) happened with the synergetic effect of wind and currents. There is also a possibility of local rise of cold waters in submesoscale eddies and advection of these waters with current - such event of full upwelling was recorded in June 2015. This work was supported by Russian Science Founding, grant № 14-17-00382.

  2. Continued CO2 outgassing in an upwelling area off northern Chile during the development phase of El Niño 1997-1998 (July 1997)

    Science.gov (United States)

    Torres, Rodrigo; Turner, David R.; Rutllant, José; LefèVre, Nathalie

    2003-10-01

    Carbonate system parameters were measured in the upper 200 m of the water column during July 1997 in an upwelling area off northern Chile (22.6°-24°S), and the CO2 fluxes were estimated. At this time (during the onset of El Niño 1997-1998), the water column that feeds the coastal upwelling was less dense, warmer, and saltier than in non-El Niño winters. Nevertheless, the major vertical gradients in pH, total inorganic carbon (CT), carbon dioxide fugacity (fCO2), and apparent oxygen utilization (AOU) remained confined to the upper 100 m of the water column, so that the active upwelling forced by southerly winds caused the upwelling of CO2-rich water leading a CO2 flux from the ocean to the atmosphere. However, these fluxes were found to be highly variable. Grid surveys 2 weeks apart show a change in CO2 flux from +3.9 mol C m-2 yr-1 to +0.4 mol C m-2 yr-1: the change is thought to be associated with a pulsed upwelling forcing in combination with an active biological uptake of CO2. This high short-term variability of CO2 fluxes makes it difficult to assess the interannual variability of CO2 outgassing in this area based on low-frequency direct CO2 observations. The fact that the oxycline, whose location usually coincides with the carboncline, also remained within the upper 100 m during the remarkably warm 1972 and 1983 El Niño winters seems to imply that the CO2 outgassing during those warm periods can be as strong as we report for 1997 under similar upwelling favorable winds.

  3. Changing surface water conditions for the last 500ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

    NARCIS (Netherlands)

    Petrick, B.F.; McClymont, E.L.; Marret, F.; van der Meer, M.T.J.

    2015-01-01

    The Southeast Atlantic Ocean is an important component of global ocean circulation, as itincludes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productiveBenguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling

  4. Mixing between hyporheic flow cells and upwelling groundwater: laboratory simulations and implications for mixing-dependent reactions

    Science.gov (United States)

    Hester, E. T.; Nida, A.

    2014-12-01

    The hyporheic zone is the region where surface water and groundwater interact beneath and adjacent to stream and river systems. The hyporheic zone has been shown to affect water quality constituents such as heat, pollutants, and nutrients in this interfacial region. Recent modeling studies have shown that some compounds upwelling from groundwater toward surface water only react when water originating in surface water and groundwater mix at the edge of the hyporheic zone. These "mixing-dependent" reactions may be important for addressing upwelling pollution, yet depend on the extent of the mixing zone. Recent modeling studies have also shown this mixing zone to be thin, but this has not been confirmed in lab or field studies. Our current study took the first step toward such confirmation by simulating mixing between hyporheic flow cells and upwelling groundwater in a 1.7 m x 1m flow-through laboratory sediment mesocosm. We used tracer dyes and digital photographs taken through the glass wall of the mesocosm to quantify mixing zone thickness. We varied key hydraulic controls such as the surface water head drop that drives the hyporheic flow cells. Steady-state results confirm the thin mixing zones predicted by the earlier modeling. Mixing zone length increases with increasing surface water head drop, but mixing zone thickness appears to remain relatively constant. Furthermore, if the head drop in surface water changes rapidly, the mixing zone moves through riverbed sediments but does not appear to change appreciably in thickness. As a result, we conclude that mixing zones are probably thin under a range of field conditions. This has implications for one common definition of the hyporheic zone as an area of substantial mixing of surface water and groundwater. Thin mixing zones also may limit mixing-dependent reactions of upwelling contaminants, which bears further study.

  5. Ulam Type Stability for a Coupled System of Boundary Value Problems of Nonlinear Fractional Differential Equations

    Directory of Open Access Journals (Sweden)

    Aziz Khan

    2017-01-01

    Full Text Available We discuss existence, uniqueness, and Hyers-Ulam stability of solutions for coupled nonlinear fractional order differential equations (FODEs with boundary conditions. Using generalized metric space, we obtain some relaxed conditions for uniqueness of positive solutions for the mentioned problem by using Perov’s fixed point theorem. Moreover, necessary and sufficient conditions are obtained for existence of at least one solution by Leray-Schauder-type fixed point theorem. Further, we also develop some conditions for Hyers-Ulam stability. To demonstrate our main result, we provide a proper example.

  6. Multiple positive solutions to systems of nonlinear semipositone fractional differential equations with coupled boundary conditions

    Directory of Open Access Journals (Sweden)

    Chengjun Yuan

    2012-02-01

    where $\\lambda$ is a parameter, $a, b, \\xi,\\eta$ satisfy $\\xi,\\eta\\in(0,1$, $0boundary value problem has multiple positive solutions.

  7. Thickness of the Post-Perovskite Boundary in Fe2+ and Fe3+ Bearing Systems

    Science.gov (United States)

    Shim, S.; Catalli, K.; Prakapenka, V.

    2008-12-01

    Combined with seismic observations of the D" region, the perovskite (Pv) to postperovskite (PPv) transition provides new opportunities to constrain important parameters at the core-mantle boundary, such as heat flux from the core through the observation of the double crossing between the geotherm and the PPv transition. In the mantle, the PPv boundary should have a finite thickness. We have determined the PPv boundary thickness in 0.9MgSiO3-0.1FeSiO3 and 0.9MgSiO3-0.1Fe2O3 in the laser-heated diamond cell combined with in situ X-ray diffraction. In order to reduce thermal and pressure gradients, we use argon as a medium. In order to reduce the kinetic effect, we measured the boundary along both forward (from Pv to PPv) and reverse (from PPv to Pv) paths. Our data tightly constrain the transition depth and Clapeyron slope (+6.7±0.5 MPa/K in Fe2+ and +8.4±1.0 MPa/K in Fe3+) and the results are consistent with seismological observations. However, 10 mol% Fe2+ increases the thickness to 450±50 km which is significantly larger than the thickness of the D" discontinuity (≤80 km), whereas 10 mol% Fe3+ increases the thickness to only about 100±50 km. The discrepancy with the seismic observation for Fe2+ can be reconciled by assuming strong partitioning of Fe to ferropericlase (Fp) such that PPv is much more depleted in Fe than Pv. However, the partitioning of Fe among Pv, PPv, and Fp is highly controversial. An Fe3+-enriched lower mantle provides a natural explanation for the thickness of the D" discontinuity. These two models can be further examined for the high electrical conductivity required by the observation of the Earth's nutation. The low Fe2+ in Pv and PPv and high Fe2+ in Fp would result in very low electrical conductivity. However, an Fe3+-enriched lower mantle would have high electrical conductivity because Fe3+--O bonding becomes metallic in the PPv structure and the coexistence of Fe2+ and Fe3+ will enhance electron hopping between these two. Therefore

  8. Proposed Auxiliary Boundary Stratigraphic Section and Point (ASSP) for the base of the Ordovician System at Lawson Cove, Utah, USA

    Science.gov (United States)

    Miller, James F.; Evans, Kevin R.; Ethington, Raymond L.; Freeman, Rebecca; Loch, James D.; Repetski, John E.; Ripperdan, Robert; Taylor, John F.

    2016-01-01

    The Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System is at the First Appearance Datum (FAD) of the conodont Iapetognathus fluctivagus at Green Point in Newfoundland, Canada. Strata there are typical graptolitic facies that were deposited near the base of the continental slope.We propose establishing an Auxiliary boundary Stratotype Section and Point (ASSP) at the FAD of I. fluctivagus at the Lawson Cove section in the Ibex area of Millard County, Utah, USA. There, strata consist of typical shelly facies limestones that were deposited on a tropical carbonate platform and contain abundant conodonts, trilobites, brachiopods, and other fossil groups. Cambrian and Ordovician strata in this area are ~5300m thick, with the Lawson Cove section spanning 243m in three overlapping segments. Six other measured and studied sections in the area show stratigraphic relationships similar to those at Lawson Cove. Faunas have been used to divide these strata into 14 conodont and 7 trilobite zonal units. The widespread olenid trilobite Jujuyaspis occurs ~90cm above the proposed boundary at Lawson Cove; this genus is generally regarded as earliest Ordovician. Rhynchonelliform and linguliform brachiopods are common to abundant and are useful for correlation. The FAD of Iapetognathus fluctivagus and occurrences of Jujuyaspis and the Lower Ordovician planktonic graptolite Anisograptus matanensis all occur within a 2.4m interval of strata at a nearby section. Non-biological correlation tools include a detailed sequence stratigraphic classification and a detailed carbon-isotope profile. Especially useful for correlation is a positive 13C excursion peak ~15cm below the proposed boundary horizon. All of these correlation tools form an integrated framework that makes the Lawson Cove section especially useful as an ASSP for global correlation of strata with faunas typical of shallow, warm-water, shelly facies.

  9. 'Santa Ana' winds and upwelling filaments off Northern Baja California

    Science.gov (United States)

    Trasviña, A.; Ortiz-Figueroa, M.; Herrera, H.; Cosío, M. A.; González, E.

    2003-08-01

    An atmospheric condition known as a 'Santa Ana' wind occurred from 9 to 11 February 2002. Its effect was felt over a large portion of southern California and the northern half of the Baja California Peninsula. Santa Ana winds are dry, strong northwesterly through easterly mountain downslope winds, most common in winter. Satellite data from Quickscat show two large wind jets crossing the mountains of the peninsula and extending 300 km offshore. Data from a coastal station reveal that the event lasted over 52 h with average speeds of 11 m s -1 and gusts of 25 m s -1. The southernmost jet crosses the mountains at the San Matias mountain pass and generates a cold filament off Point Colonet. Satellite imagery shows this feature lasting at least two inertial periods ( Ti=22 h) and extending 100 km offshore during the observation period. Estimates of the stationary Ekman pumping produced vertical speeds of 20 m per day, consistent in time and location with the observed structures. The ocean off Point Colonet is well known for the existence of upwelling episodes. They occur mostly in the spring or early summer when persistent winds blow towards the equator and parallel to the coast. The events described here present a different phenomenon: upwelling filaments induced by short-lived, offshore winter winds.

  10. Effects of structural factors on upwelling fouling community, Southeast Brazil

    Directory of Open Access Journals (Sweden)

    Bruno Pereira Masi

    Full Text Available Abstract To assess the successional pattern of fouling organisms three hypotheses were tested: 1 a thermocline is caused by seasonal upwelling events, and therefore, depth influences the successional trajectory of the fouling community; 2 a reduction in the intensity of natural light of the substrate influences the fouling composition and the successional trajectory; 3 fish predation influences the community composition and its successional trajectory. During one year, up-facing and down-facing PVC panels on open, partially caged or fully caged, and placed at depths of 1.5 and 3.5 meters were monthly sampled by digital photograph to determine the community composition and by contact point to estimate the percent coverage of organisms. The upwelling impact provided different water masses, and light intensity was also a determining factor of the overall successional trajectory of the fouling community. After the installation of full and partial cages, differences were identified in the respective successional trajectories. The results of this study suggest that each physical factor or biological process can change the successional trajectory of the community, and the successional model (e.g., convergent, divergent, parallel, or cyclic depends on the magnitudes of the determinants that act on the community at each stage of its trajectory.

  11. Submesoscale CO2 variability across an upwelling front off Peru

    Science.gov (United States)

    Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

    2017-12-01

    As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

  12. Towards a management perspective for coastal upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Howe, S.O.; Walsh, J.J.

    1976-01-01

    Data are reviewed from studies on the general distribution of upwelling of coastal waters, associated current patterns, and first order biological effects. Field observations and theory are discussed. Recent research has shown that variability and dynamism are the predominant characteristic features of these regions. Populations related by nonlinear interactions occur in constantly moving patches and swirls subjected to variability in the winds, currents, water chemistry, and solar insolation. Gross stationary features of upwelling communities have been described, but the responses of critical components and their relationships to human or natural perturbations remain poorly defined in this and other types of coastal ecosystems. Large scale research programs recognize that the continental shelf ecosystems are complex event-oriented phenomena. It is postulated that assessment of living resources in an environmental vacuum may lead to mismanagement and hindcasting rather than prescient management. A growing data base encourages the development of computer simulation models of ecosystem relationships and responses will lead to better understanding and management of these and other marine ecosystems in the future. 80 references.

  13. Ground boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1990-01-01

    The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals. 10 refs., 1 fig.

  14. Acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of Hainan Island, Northern South China Sea

    Science.gov (United States)

    Dong, Xu; Huang, Haining; Zheng, Nan; Pan, Aijun; Wang, Sumin; Huo, Cheng; Zhou, Kaiwen; Lin, Hui; Ji, Weidong

    2017-09-01

    We investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in July 2014 and July 2015 at the east coast of Hainan Island where a fringing reef distributes inshore. By using a three end-member mixing model, we semiquantitatively estimated the removal of dissolved inorganic carbon (DIC) mediated by biological production in the river plume and upwelled water to be 13 ± 17 and 15 ± 16 μmol kg-1, respectively. The enhanced organic production was mainly responsible for these DIC consumptions in both two regimes, however, nearly a half of DIC removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system. Furthermore, the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of Hainan Island during cruises. In comparison, the biological contribution to acidification was limited for balancing between organic production and biocalcification during July 2014 cruise, whereas the acidification was greatly intensified by organic degradation during July 2015 cruise. It was verified that naturally local acidification (physical and biological processes) played a major role in great pH decreases on a short-term scale, leading to coastal waters more vulnerable to anthropogenic "ocean acidification" (uptake of atmospheric CO2) by reducing buffering capacity of waters. Finally, effects of acidification associated with other local threats on a fringing reef were further depicted with a conceptual model.

  15. Boundary element based 3D-crack growth module for finite element systems; Ein randelementbasiertes 3D-Rissfortschrittsmodul fuer Finite Elemente Systeme

    Energy Technology Data Exchange (ETDEWEB)

    Helldoerfer, Bastian

    2009-07-01

    Many technical failures are caused by cracks. As a consequence fracture mechanical assessment becomes more and more important during the design of security-relevant components. The simulation of stable crackgrowth provides an essential contribution for understanding these failures and as a consequence for preventing these. In order to benefit from the advantages of the Boundary Element Method (BEM) in the field of fracture mechanical problems as well as from the numerical advantages of the Finite Element Methode (FEM) a combined simulation technique is applied within this work. Here the domain containing the crackfront is discretized with boundary elements, the remaining structure is meshed with finite elements. The direct coupling of both techniques is achieved by applying the Symmetric Galerkin BEM (SGBEM) leading to a stiffness formulation for the boundary element domain. The nonlinearity of crackgrowth requires an incremental simulation procedure. In each increment the state of stress has to be obtained firstly, whereon the fracture mechanical assessment within the framework of linear elastic fracture mechanics is carried out based on the results of the boundary element domain only. The simulation of stable crackgrowth is implemented within a predictor/corrector scheme. For increasing the efficiency several approaches were put into practice, e.g. the parallelization of the SGBEM-code, integrated submodel computations and the adaptive enlargement of the boundary element domain. Using ABAQUS it is shown exemplarily how to combine the boundary element based crackgrowth module with commercial FE-Systems. A series of examples underline the efficiency of the presented simulation technique. (orig.)

  16. Existence of solutions for a coupled system with ∅-Laplacian operators and nonlinear coupled boundary conditions

    Directory of Open Access Journals (Sweden)

    Goli Konan Charles Etienne

    2017-12-01

    Full Text Available We study the existence of solutions of the system submitted to nonlinear coupled boundary conditions on [0, T] where ∅1, ∅2: (-a, a → ℝ, with 0 < a < +∞, are two increasing homeomorphisms such that ∅1(0 = ∅2(0 = 0, and fi : [0, T] × ℝ4 → ℝ, i ∈{1, 2} are two L1-Carathéodory functions. Using some new conditions and Schauder fixed point Theorem, we obtain solvability result.

  17. The Benguela upwelling system lying off southern Africa's west ...

    African Journals Online (AJOL)

    spamer

    the concept of a narrow jet of flowing northward, which provided the link between the spawning grounds for pelagic species on the western Agulhas Bank and their nursery grounds farther north on the West Coast. Boyd et al. (1992) built upon this concept using data from Acoustic Doppler Current Profiler (ADCP) surveys.

  18. Study on Movable gel Profiling/Flooding System Optimization at Boundary Temperature

    Science.gov (United States)

    Gao, Shanshan; Xie, Gang; Zhang, Tiantian; Wang, Zhiqiang; Jiang, Peijun; Wei, Junjie; Gu, Yi; Lei, Xiaoyang; Guo, Suzhen; Lei, Shi

    2017-12-01

    65-75°C is the boundary temperature of phenol-formaldehyde resin and organic chrome crosslink with HPAM to generate movable gel. Generally speaking, when the reservoir temperature is below 65-75°C, the crosslinking agent is Organic chrome. Phenol-formaldehyde resin is used when the temperature is above 65-75°C. In this paper the gelation properties of phenol-formaldehyde resin and organic chrome were compared at 70°C. The experiment results showed that the crosslinking time of phenol-formaldehyde resin gel was longer and more conducive to field injection. In addition the phenol-formaldehyde resin gel had greater viscosity, adhesion and shearing resistance compared with the organic chrome gel. So the phenol-formaldehyde resin was chosen for further optimization. The crosslinking time was shortened and the gel viscosity increased with the increase of the polymer concentration. As the polymer crosslinker proportion increased The crosslinking time was shortened and the gel viscosity increased first and then decreased. Reinforcer NC and stabilizer WG were added to improve the temperature and salt tolerance of the gel. The gel formula suitable for the boundary temperature was obtained. The optimum polymer concentration is 1200mg/L, the polymer crosslinker proportion is 1:1.1, the best reinforcer concentration is 400mg/L and the concentration of the stabilizer is 150mg/L. The crosslinking time is 31h, the gel viscosity is above 2100mPa·s. The gel did not shrink and no water separation was observed at 70°C for 150 days. The viscosity retention rate was more than 70%.

  19. Negotiating boundaries

    DEFF Research Database (Denmark)

    Aarhus, Rikke; Ballegaard, Stinne Aaløkke

    2010-01-01

    to maintain the order of the home when managing disease and adopting new healthcare technology. In our analysis we relate this boundary work to two continuums of visibility-invisibility and integration-segmentation in disease management. We explore five factors that affect the boundary work: objects......To move treatment successfully from the hospital to that of technology assisted self-care at home, it is vital in the design of such technologies to understand the setting in which the health IT should be used. Based on qualitative studies we find that people engage in elaborate boundary work......, activities, places, character of disease, and collaboration. Furthermore, the processes are explored of how boundary objects move between social worlds pushing and shaping boundaries. From this we discuss design implications for future healthcare technologies for the home....

  20. Boundary Spanning

    DEFF Research Database (Denmark)

    Zølner, Mette

    The paper explores how locals span boundaries between corporate and local levels. The aim is to better comprehend potentialities and challenges when MNCs draws on locals’ culture specific knowledge. The study is based on an in-depth, interpretive case study of boundary spanning by local actors...... in the period of post-acquisition when their organization is being integrated into the acquiring MNC. The paper contributes to the literature on boundary spanning in three ways: First, by illustrating that boundary spanning is performed by numerous organizational actors in a variety of positions in MNCs......, inclusively by locals in subsidiaries. Second, by showing that boundary spanning is ‘situated’ in the sense that its result depends on the kind of knowledge to be transmitted and the attitude of the receivers. A third contribution is methodological. The study illustrates that combining bottom-up grounded...

  1. Are large macroalgal blooms necessarily bad? Nutrient impacts on seagrass in upwelling-influenced estuaries.

    Science.gov (United States)

    Hessing-Lewis, Margot L; Hacker, Sally D; Menge, Bruce A; McConville, Sea-oh; Henderson, Jeremy

    2015-07-01

    Knowledge of nutrient pathways and their resulting ecological interactions can alleviate numerous environmental problems associated with nutrient increases in both natural and managed systems. Although not unique, coastal systems are particularly prone to complex ecological interactions resulting from nutrient inputs from both the land and sea. Nutrient inputs to coastal systems often spur ulvoid macroalgal blooms, with negative consequences for seagrasses, primarily through shading, as well as through changes in local biogeochemistry. We conducted complementary field and mesocosm experiments in an upwelling-influenced estuary, where marine-derived nutrients dominate, to understand the direct and indirect effects of nutrients on the macroalgal-eelgrass (Zostera marina L.) interaction. In the field experiment, we found weak evidence that nutrients and/or macroalgal treatments had a negative effect on eelgrass. However, in the mesocosm experiment, we found that a combination of nutrient and macroalgal treatments led to strongly negative eelgrass responses, primarily via indirect effects associated with macroalgal additions. Together, increased total light attenuation and decreased sediment oxygen levels were associated with larger effects on eelgrass than shading alone, which was evaluated using mimic algae treatments that did not alter sediment redox potential. Nutrient addition in the mesocosms directly affected seagrass density; biomass, and morphology, but not as strongly as macroalgae. We hypothesize that the contrary results from these parallel experiments are a consequence of differences in the hydrodynamics between field and mesocosm settings. We suggest that the high rates of water movement and tidal submersion of our intertidal field experiments alleviated the light reduction and negative biogeochemical changes in the sediment associated with macroalgal canopies, as well as the nutrient effects observed in the mesocosm experiments. Furthermore, adaptation

  2. A numerical investigation of the atmosphere-ocean thermal contrast over the coastal upwelling region of Cabo Frio, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Dourado, M. [Departamento de Meteorologia, Universidade Federal de Pelotas, Pelotas RS (Brazil)]. E-mail: marcelo_dourado@ufpel.edu.br; Pereira de Oliveira, A. [Departamento de Ciencias Atmosfericas, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, (Brazil)

    2008-01-15

    An one-dimensional atmospheric second order closure model, coupled to an oceanic mixed layer model, is used to investigate the short term variation of the atmospheric and oceanic boundary layers in the coastal upwelling area of Cabo Frio, Brazil (23 degrees Celsius S, 42 degrees Celsius 08' W). The numerical simulations were carried out to evaluate the impact caused by the thermal contrast between atmosphere and ocean on the vertical extent and other properties of both atmospheric and oceanic boundary layers. The numerical simulations were designed taking as reference the observations carried out during the passage of a cold front that disrupted the upwelling regime in Cabo Frio in July of 1992. The simulations indicated that in 10 hours the mechanical mixing, sustained by a constant background flow of 10 m s-1, increases the atmospheric boundary layer in 214 m when the atmosphere is initially 2 K warmer than the ocean (positive thermal contrast observed during upwelling regime). For an atmosphere initially -2 K colder than the ocean (negative thermal contrast observed during passage of the cold front), the incipient thermal convection intensifies the mechanical mixing increasing the vertical extent of the atmospheric boundary layer in 360 m. The vertical evolution of the atmospheric boundary layer is consistent with the observations carried out in Cabo Frio during upwelling condition. When the upwelling is disrupted, the discrepancy between the simulated and observed atmospheric boundary layer heights in Cabo Frio during July of 1992 increases considerably. During the period of 10 hours, the simulated oceanic mixed layer deepens 2 m and 5.4 m for positive and negative thermal contrasts of 2 K and -2 K, respectively. In the latter case, the larger vertical extent of the oceanic mixed layer is due to the presence of thermal convection in the atmospheric boundary layer, which in turn is associated to the absence of upwelling caused by the passage of cold fronts

  3. Differential responses of calcifying and non-calcifying epibionts of a brown macroalga to present-day and future upwelling pCO2.

    Directory of Open Access Journals (Sweden)

    Vincent Saderne

    Full Text Available Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida and Electra pilosa (Bryozoa and the non-calcifier Alcyonidium hirsutum (Bryozoa were maintained for 30 days under three pCO2 conditions: natural 460 ± 59 µatm, present-day upwelling1193 ± 166 µatm and future upwelling 3150 ± 446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic

  4. Seasonal patterns of wind-induced upwelling/downwelling in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Andrew Bakun

    2001-09-01

    Full Text Available The historical file of wind observations from maritime weather reports is summarized to identify the characteristic seasonal distributions of wind-induced Ekman upwelling and downwelling in the Mediterranean Sea. Both coastal upwelling/downwelling and wind-stress curl-driven open ocean upwelling/downwelling are treated in a unified description. Vigorous upwelling zones are found in the eastern Aegean Sea, off the west coast of Greece, and in the Gulf of Lyons. The southern coast of the Mediterranean is found to be primarily a downwelling area, although significant coastal upwelling does appear in the Gulf of Sidra during the spring and summer seasons, and along the Algerian coast during summer.

  5. Diurnal variability of inner-shelf circulation in the lee of a cape under upwelling conditions

    Science.gov (United States)

    Lamas, L.; Peliz, A.; Dias, J.; Oliveira, P. B.; Angélico, M. M.; Castro, J. J.; Fernandes, J. N.; Trindade, A.; Cruz, T.

    2017-07-01

    The nearshore circulation in the lee of a cape under upwelling conditions was studied using in-situ data from 3 consecutive summers (2006-2008). Focus was given to a period between 20 July and 04 August 2006 to study the diurnal variability of the cross-shelf circulation. This period was chosen because it had a steady upwelling-favourable wind condition modulated by a diurnal cycle much similar to sea breeze. The daily variability of the observed cross-shelf circulation consisted of three distinct periods: a morning period with a 3-layer vertical structure with onshore velocities at mid-depth, a mid-day period where the flow is reversed and has a 2-layer structure with onshore velocities at the surface and offshore flow below, and, lastly, in the evening, a 2-layer period with intensified offshore velocities at the surface and onshore flow at the bottom. The observed cross-shelf circulation showed a peculiar vertical shape and diurnal variability different from several other systems described in literature. We hypothesize that the flow reversal of the cross-shelf circulation results as a response to the rapid change of the wind magnitude and direction at mid-day with the presence of the cape north of the mooring site influencing this response. A numerical modelling experiment exclusively forced by winds simulated successfully most of the circulation at the ADCP site, especially the mid-day reversal and the evening's upwelling-type structure. This supports the hypothesis that the cross-shelf circulation at diurnal timescales is mostly wind-driven. By analysing the 3D circulation in the vicinity of Cape Sines we came to the conclusion that the diurnal variability of the wind and the flow interaction with topography are responsible for the circulation variability at the ADCP site, though only a small region in the south of the cape showed a similar diurnal variability. The fact that the wind diurnally undergoes relaxation and intensification strongly affects the

  6. Biological N2 Fixation in the Upwelling Region off NW Iberia: Magnitude, Relevance, and Players

    Directory of Open Access Journals (Sweden)

    Víctor Moreira-Coello

    2017-09-01

    Full Text Available The classical paradigm about marine N2 fixation establishes that this process is mainly constrained to nitrogen-poor tropical and subtropical regions, and sustained by the colonial cyanobacterium Trichodesmium spp. and diatom-diazotroph symbiosis. However, the application of molecular techniques allowed determining a high phylogenic diversity and wide distribution of marine diazotrophs, which extends the range of ocean environments where biological N2 fixation may be relevant. Between February 2014 and December 2015, we carried out 10 one-day samplings in the upwelling system off NW Iberia in order to: (1 investigate the seasonal variability in the magnitude of N2 fixation, (2 determine its biogeochemical role as a mechanism of new nitrogen supply, and (3 quantify the main diazotrophs in the region under contrasting hydrographic regimes. Our results indicate that the magnitude of N2 fixation in this region was relatively low (0.001 ± 0.002 – 0.095 ± 0.024 μmol N m−3 d−1, comparable to the lower-end of rates described for the subtropical NE Atlantic. Maximum rates were observed at the surface during both upwelling and relaxation conditions. The comparison with nitrate diffusive fluxes revealed the minor role of N2 fixation (<2% as a mechanism of new nitrogen supply into the euphotic layer. Small diazotrophs (<10 μm were responsible for all N2 fixation activity detected in the region. Quantitative PCR targeting the nifH gene revealed the highest abundances of two sublineages of Candidatus Atelocyanobacterium thalassa or UCYN-A (UCYN-A1 and UCYN-A2, mainly at surface waters during upwelling and relaxation conditions, and of Gammaproteobacteria γ-24774A11 at deep waters during downwelling. Maximum abundance for the three groups were up to 6.7 × 102, 1.5 × 103, and 2.4 × 104nifH copies L−1, respectively. Our findings demonstrate measurable N2 fixation activity and presence of diazotrophs throughout the year in a nitrogen

  7. IMPROVEMENT OF ACCURACY OF RADIATIVE HEAT TRANSFER DIFFERENTIAL APPROXIMATION METHOD FOR MULTI DIMENSIONAL SYSTEMS BY MEANS OF AUTO-ADAPTABLE BOUNDARY CONDITIONS

    Directory of Open Access Journals (Sweden)

    K. V. Dobrego

    2015-01-01

    Full Text Available Differential approximation is derived from radiation transfer equation by averaging over the solid angle. It is one of the more effective methods for engineering calculations of radia- tive heat transfer in complex three-dimensional thermal power systems with selective and scattering media. The new method for improvement of accuracy of the differential approximation based on using of auto-adaptable boundary conditions is introduced in the paper. The  efficiency  of  the  named  method  is  proved  for  the  test  2D-systems.  Self-consistent auto-adaptable boundary conditions taking into consideration the nonorthogonal component of the incident to the boundary radiation flux are formulated. It is demonstrated that taking in- to consideration of the non- orthogonal incident flux in multi-dimensional systems, such as furnaces, boilers, combustion chambers improves the accuracy of the radiant flux simulations and to more extend in the zones adjacent to the edges of the chamber.Test simulations utilizing the differential approximation method with traditional boundary conditions, new self-consistent boundary conditions and “precise” discrete ordinates method were performed. The mean square errors of the resulting radiative fluxes calculated along the boundary of rectangular and triangular test areas were decreased 1.5–2 times by using auto- adaptable boundary conditions. Radiation flux gaps in the corner points of non-symmetric sys- tems are revealed by using auto-adaptable boundary conditions which can not be obtained by using the conventional boundary conditions.

  8. Competition between Orography and SST in Creating Mesoscale Wind Anomalies in Subtropical Upwelling Zones

    Science.gov (United States)

    Hall, A. D.; Boe, J.; Colas, F.; Kurian, J.; McWilliams, J. C.; Kapnick, S. B.; Qu, X.

    2009-12-01

    Observational studies have shown that mesoscale variations in sea surface temperature may induce small-scale variations in wind. In eastern subtropical upwelling regions such as the Peru or California coasts, this coupling mechanism is mostly not captured by coupled models. Yet it could be of great importance for the evolution of the upwelling system and the coastal climate state. An additional element of complexity in these regions is the fact that coastal orography is also responsible for small-scale variations in wind, and the orographic effect may extend more than 100 km offshore. The respective roles of SST and coastal orography in shaping mesoscale wind variations in nearshore regions is not clear. This issue is difficult to address from a strictly observational point of view because the impossibility of completely separating the two mechanisms in limited observational data-sets. In this study, we use a high-resolution regional numerical modeling system coupling the WRF atmospheric model to the ROMS oceanic model, as well as additional uncoupled experiments to separate the effects of SST/wind coupling and coastal orography on small-scale wind variations. The experimental design allows the respective roles of SST/wind coupling and coastal orography on small-scale wind variations in the nearshore region to be quantified and compared. Even taking into account potential biases in the representation of the strength of the SST/ wind coupling by the model, our results suggest a dominant role for orography in small-scale wind variations within 100 km of the shore.

  9. Self-shading correction for oceanographic upwelling radiometers.

    Science.gov (United States)

    Leathers, Robert; Downes, Trijntje; Mobley, Cutris

    2004-10-04

    We present the derivation of an analytical model for the self-shading error of an oceanographic upwelling radiometer. The radiometer is assumed to be cylindrical and can either be a profiling instrument or include a wider cylindrical buoy for floating at the sea surface. The model treats both optically shallow and optically deep water conditions and can be applied any distance off the seafloor. We evaluate the model by comparing its results to those from Monte Carlo simulations. The analytical model performs well over a large range of environmental conditions and provides a significant improvement to previous analytical models. The model is intended for investigators who need to apply self-shading corrections to radiometer data but who do not have the ability to compute shading corrections with Monte Carlo simulations. The model also can provide guidance for instrument design and cruise planning.

  10. Grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1991-01-01

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  11. Grain boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990 to February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  12. A study on the role of grain boundary engineering in promoting high-cycle fatigue resistance and improving reliability in nickel base superalloys for propulsion systems

    Science.gov (United States)

    Gao, Yong

    High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a commercial polycrystalline nickel base gamma/gamma' superalloy, ME3, as a typical engine disk material, sequential thermomechanical processing, involving alternate cycles of strain and annealing, is used to (i) modify the proportion of special grain boundaries, and (ii) interrupt the connectivity of the random boundaries in the grain boundary network. The processed microstructures are then subjected to fracture-mechanics based high cycle fatigue testing to evaluate how the crack initiation and small- and large-crack growth properties are affected and to examine how the altered grain boundary population and connectivity can influence growth rates and overall lifetimes. The effect of such grain-boundary engineering on the fatigue-crack-propagation behavior of large (˜8 to 20 mm), through-thickness cracks at 25, 700, and 800°C was examined. Although there was little influence of an increased special boundary fraction at ambient temperatures, the resistance to near-threshold crack growth was definitively improved at elevated temperatures, with fatigue threshold-stress intensities some 10 to 20% higher than at 25°C, concomitant with a lower proportion (˜20%) of intergranular

  13. Artificial upwelling using offshore wind energy for mariculture applications

    Directory of Open Access Journals (Sweden)

    Álvaro Viúdez

    2016-09-01

    Full Text Available Offshore wind is proposed as an energy source to upwell nutrient-rich deep water to the ocean photic layers. A spar-buoy wind turbine with a rigid tube about 300 m long is proposed as a pipe to drive deep water up to the surface. The minimum energy required to uplift the water is the potential energy difference between surface waters inside and outside the pipe, which depends on the background density profile. The corresponding surface jump or hydraulic head, h, calculated for several analytical and experimental density profiles, is of the order of 10 cm. If the complete turbine power (of the order of several MW is used for raising the water (assuming a 100% pump efficiency, in a frictionless flow, very large water volumes, of the order of thousands of m3 s-1, will be transported to the photic layers. In a more realistic case, taking into account pipe friction in wide pipes, of the order of 10 m radius, and a power delivered to the fluid of 1 MW, the volume transport is still very large, about 500 m3 s-1. However, such a large amount of dense water could sink fast to aphotic layers due to vertical static instability (the fountain effect, ruining the enhancement of primary production. Hence, some ways to increase the turbulent entrainment and avoid the fountain effect are proposed. From the energetic viewpoint, artificial upwelling using offshore wind energy is a promising way to fertilize large open sea regions. This mariculture application is, however, severely subjected to atmosphere and ocean climatology, as well as to ecological dynamics. The general problem is multidisciplinary, and some important physical, engineering and ecological questions need to be seriously addressed to improve our confidence in the approach presented here.

  14. Using random boundary conditions to simulate disordered quantum spin models in two-dimensional systems

    Science.gov (United States)

    Yuste, A.; Moreno-Cardoner, M.; Sanpera, A.

    2017-05-01

    Disordered quantum antiferromagnets in two-dimensional compounds have been a focus of interest in the last years due to their exotic properties. However, with very few exceptions, the ground states of the corresponding Hamiltonians are notoriously difficult to simulate making their characterization and detection very elusive, both theoretically and experimentally. Here we propose a method to signal quantum disordered antiferromagnets by doing exact diagonalization in small lattices using random boundary conditions and averaging the observables of interest over the different disorder realizations. We apply our method to study the Heisenberg spin-1/2 model in an anisotropic triangular lattice. In this model, the competition between frustration and quantum fluctuations might lead to some spin-liquid phases as predicted from different methods ranging from spin-wave mean-field theory to 2D-DMRG or PEPS. Our method accurately reproduces the ordered phases expected of the model and signals quantum disordered phases by the presence of a large number of quasidegenerate ground states together with an undefined local order parameter. The method presents a weak dependence on finite-size effects.

  15. Le Chatelier Principle for Out-of-Equilibrium and Boundary-Driven Systems: Application to Dynamical Phase Transitions.

    Science.gov (United States)

    Shpielberg, O; Akkermans, E

    2016-06-17

    A stability analysis is presented for boundary-driven and out-of-equilibrium systems in the framework of the hydrodynamic macroscopic fluctuation theory. A Hamiltonian description is proposed which allows us to thermodynamically interpret the additivity principle. A necessary and sufficient condition for the validity of the additivity principle is obtained as an extension of the Le Chatelier principle. These stability conditions result from a diagonal quadratic form obtained using the cumulant generating function. This approach allows us to provide a proof for the stability of the weakly asymmetric exclusion process and to reduce the search for stability to the solution of two coupled linear ordinary differential equations instead of nonlinear partial differential equations. Additional potential applications of these results are discussed in the realm of classical and quantum systems.

  16. Height system unification based on the Fixed Geodetic Boundary Value Problem with limited availability of gravity data

    Science.gov (United States)

    Porz, Lucas; Grombein, Thomas; Seitz, Kurt; Heck, Bernhard; Wenzel, Friedemann

    2017-04-01

    Regional height reference systems are generally related to individual vertical datums defined by specific tide gauges. The discrepancies of these vertical datums with respect to a unified global datum cause height system biases that range in an order of 1-2 m at a global scale. One approach for unification of height systems relates to the solution of a Geodetic Boundary Value Problem (GBVP). In particular, the fixed GBVP, using gravity disturbances as boundary values, is solved at GNSS/leveling benchmarks, whereupon height datum offsets can be estimated by least squares adjustment. In spherical approximation, the solution of the fixed GBVP is obtained by Hotine's spherical integral formula. However, this method relies on the global availability of gravity data. In practice, gravity data of the necessary resolution and accuracy is not accessible globally. Thus, the integration is restricted to an area within the vicinity of the computation points. The resulting truncation error can reach several meters in height, making height system unification without further consideration of this effect unfeasible. This study analyzes methods for reducing the truncation error by combining terrestrial gravity data with satellite-based global geopotential models and by modifying the integral kernel in order to accelerate the convergence of the resulting potential. For this purpose, EGM2008-derived gravity functionals are used as pseudo-observations to be integrated numerically. Geopotential models of different spectral degrees are implemented using a remove-restore-scheme. Three types of modification are applied to the Hotine-kernel and the convergence of the resulting potential is analyzed. In a further step, the impact of these operations on the estimation of height datum offsets is investigated within a closed loop simulation. A minimum integration radius in combination with a specific modification of the Hotine-kernel is suggested in order to achieve sub-cm accuracy for the

  17. The coastal mosaic of ocean acidification: The influence of upwelling, riverine input, and geography along the US West Coast

    Science.gov (United States)

    Hill, T. M.; Gaylord, B.; Miller, S. H.; Russell, A. D.; Sanford, E.

    2011-12-01

    Ocean acidification shows clear potential to decrease calcification in a wide range of marine organisms. However, many questions remain about the natural temporal and spatial variability of the carbonate system, particularly in coastal systems. To understand the natural variability of the carbonate system in the California Current, we have developed a broad scale coastal transect (47 sites) from the US-Canada border to San Diego. These sites are sampled from the shore, where waters are interacting with rocky intertidal and sandy beach ecosystems. Our "coast wide" transect is sampled twice per year for a suite of water chemistry parameters (T, S, O2, pH, DIC, TA, oxygen isotopes). We observe seasonal differences in water chemistry, for example an overall decrease in pH during upwelling (May) vs. non-upwelling conditions (September). Additionally, the influence of riverine input is very apparent at the coast, with plumes of fresh, high pH, low alkalinity water observed at the San Francisco Bay and Columbia River mouths. We also observed a wide range of pH (7.6-8.6), with the most acidic waters found in the Northern California-Southern Oregon upwelling region (38N-45N). At individual sites along this transect, we are collecting carbonate system data at higher resolution. For example, an oceanographic mooring located 1 km offshore of BML has been monitoring pH and pCO2 on an hourly basis since November 2010. This mooring is coupled with intertidal pH and water chemistry measurements at the shore on Bodega Head. These linked mooring and shore-based investigations allow for direct comparisons of offshore water to intertidal conditions.

  18. Bifurcations of Eigenvalues of Gyroscopic Systems with Parameters Near Stability Boundaries

    DEFF Research Database (Denmark)

    Seyranian, Alexander P.; Kliem, Wolfhard

    1999-01-01

    The paper deals with stability problems of linear gyroscopic systems with finite or infinite degrees of freedom, where the system matrices or operators depend smoothly on several real parameters. Explicit formulae for the behavior of eigenvalues under a change of parameters are obtained. It is sh......The paper deals with stability problems of linear gyroscopic systems with finite or infinite degrees of freedom, where the system matrices or operators depend smoothly on several real parameters. Explicit formulae for the behavior of eigenvalues under a change of parameters are obtained...

  19. The effects of oppositely sloping boundaries with Ekman dissipation in a nonlinear baroclinic system

    Science.gov (United States)

    Weng, H.-Y.

    1990-01-01

    The present analytical and numerical examination of the effect of the slope Delta with dissipation delta on baroclinic flows in linear and nonlinear systems uses a modified Eady channel model with oppositely sloping top and bottom Ekman layers, and truncates the spectral wave solution up to six components. Comparisons are made wherever possible with results from beta-plane dissipative systems. In the linear system, the combined effect of Delta and delta strongly stabilizes long waves. In a nonlinear system without wave-wave interaction, Delta stabilizes the flow even for small delta and reduces the domain of vacillation while enlarging the domain of single-wave steady state.

  20. Using Remotely Piloted Aircraft System to Study the Evolution of the Boundary Layer Related to Fog Events

    Science.gov (United States)

    Roberts, G. C.; Cayez, G.; Ronflé-Nadaud, C.; Albrand, M.; Dralet, J. P.; Momboisse, G.; Nicoll, K.; Seity, Y.; Bronz, M.; Hattenberger, G.; Gorraz, M.; Bustico, A.

    2014-12-01

    Over the past decade, the scientific community has embraced the use of RPAS (remotely piloted aircraft system) as a tool to improve observations of the Earth's surface and atmospheric phenomena. The use of small RPAS (Remotely Piloted Aircraft System) in atmospheric research has increased because of their relative low-cost, compact size and ease of operation. Small RPAS are especially adapted for observing the atmospheric boundary layer processes at high vertical and temporal resolution. To this end, CNRM, ENAC, and ENM have developed the VOLTIGE (Vecteurs d'Observation de La Troposphere pour l'Investigation et la Gestion de l'Environnement) program to study the life cycle of fog with multiple, small RPAS. The instrumented RPAS flights have successfully observed the evolution of the boundary layer and dissipation of fog events. In addition, vertical profiles from the RPAS have been compared with Météo France forecast models, and the results suggest that forecast models may be improved using high resolution and frequent in-situ measurements. Within the VOLTIGE project, a flying-wing RPAS with four control surfaces was developed to separate elevator and aileron controls in order to reduce the pitch angle envelope and improve turbulence and albedo measurements. The result leads to a small RPAS with the capability of flying up to two hours with 150 grams of payload, while keeping the hand-launch capability as a constraint for regular atmospheric research missions. High frequency data logging has been integrated into the main autopilot in order to synchronize navigation and payload measurements, as well as allowing an efficient sensor-based navigation. The VOLTIGE program also encourages direct participation of students on the advancement of novel observing systems for atmospheric sciences, and provides a step towards deploying small RPAS in an operational network. VOLTIGE is funded by the Agence Nationale de Recherche (ANR-Blanc 2012) and supported by Aerospace

  1. A classification of ecological boundaries

    Science.gov (United States)

    Strayer, D.L.; Power, M.E.; Fagan, W.F.; Pickett, S.T.A.; Belnap, J.

    2003-01-01

    Ecologists use the term boundary to refer to a wide range of real and conceptual structures. Because imprecise terminology may impede the search for general patterns and theories about ecological boundaries, we present a classification of the attributes of ecological boundaries to aid in communication and theory development. Ecological boundaries may differ in their origin and maintenance, their spatial structure, their function, and their temporal dynamics. A classification system based on these attributes should help ecologists determine whether boundaries are truly comparable. This system can be applied when comparing empirical studies, comparing theories, and testing theoretical predictions against empirical results.

  2. Bioengineers and their associated fauna respond differently to the effects of biogeography and upwelling.

    Science.gov (United States)

    Cole, Victoria J; McQuaid, Christopher D

    2010-12-01

    Temperature and primary production (often linked to nutrient supply) are two of the few factors influencing species diversity and abundances across mesoscale gradients, while at smaller scales the habitat complexity offered by bioengineers is important. Previous studies have illustrated effects of upwelling and biogeography on intertidal bioengineers, but it is not known if these processes influence assemblages associated with those bioengineers in a similar way. We examined the habitat structure offered by two species of mussels and their associated fauna in five regions across 3000 km and three biogeographic provinces of the South African coast, replicating upwelling and non-upwelling areas within each region. Upwelling and region influenced the structure of mussel beds (the density and size of mussels). In contrast, upwelling did not influence mesoscale differences in composition, abundance, and numbers of species of crustaceans, mollusks, or polychaetes in mussel beds. Regardless of trophic level or mode of reproduction, mussel bed fauna were influenced only by region. Regional differences were strongly influenced by biogeography. The associated fauna was, however, also strongly correlated with the structure of the habitats created by mussels. Our results support the importance of upwelling to a critical ecosystem engineer, but show that these effects do not extend directly to the assemblages of associated fauna, which are more influenced by regional-scale effects and biogeography. We suggest that mesoscale patterns in the associated fauna of this bioengineered habitat are driven by the direct effects of biogeography, combined with the influence of biogeography and upwelling on mussel bed structure.

  3. Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Science Congress

    Directory of Open Access Journals (Sweden)

    Bogdan Ołdakowski

    2008-03-01

    Full Text Available The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions.

  4. Seasonal upwelling on the Western and Southern Shelves of the Gulf of Mexico

    Science.gov (United States)

    Zavala-Hidalgo, Jorge; Gallegos-García, Artemio; Martínez-López, Benjamín; Morey, Steven L.; O'Brien, James J.

    2006-07-01

    An 8-year database of sea surface temperature (SST), 7 years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color images, wind fields, and numerical model results are analyzed to identify regions and periods of coastal upwelling on the western and southern shelves of the Gulf of Mexico. On the seasonal scale, it is found that on the Tamaulipas, Veracruz, and southwestern Texas Louisiana shelves there are upwelling favorable winds from April to August, when southeasterly winds are dominant and cold SST anomalies associated with upwelling are observed along their coasts. However, during summer, values of chlorophyll-a concentration are lower than those in autumn and winter, which are high due to advection of old bloom biological material from upstream. During winter, there is a cold front on the Tamaulipas shelf produced by advection of cold water from the Texas Louisiana shelf and not due to upwelling. On the eastern Campeche Bank, persistent upwelling is observed due to favorable winds throughout the year with cold SST and large chlorophyll-a content along the inner shelf from May to September. On the Tamaulipas shelf, the summer upwelling delays the annual SST peak until September, while in most of the Gulf SST peaks in August. This difference is due to the end of the upwelling favorable wind conditions and the September seasonal current reversal.

  5. Examining Lagrangian surface transport during a coastal upwelling in the Gulf of Finland, Baltic Sea

    Science.gov (United States)

    Delpeche-Ellmann, Nicole; Mingelaitė, Toma; Soomere, Tarmo

    2017-07-01

    We employ in-situ surface drifters and satellite derived sea surface temperature data to examine the impact that an upwelling event may have on mixing and Lagrangian transport of surrounding surface waters. The test area is located near the southern coast of the Gulf of Finland where easterly winds are known to trigger intense coastal upwellings. The analysis is based on the comparison of motions of three drifters that follow the currents in the uppermost layer with a thickness of 2 m with MODIS-based sea surface temperature data and high-quality open sea wind time series. The presence of an upwelling event superseded the classic Ekman-type drift of the surface layer and considerably slowed down the average speed of surface currents in the region affected by the upwelled cold water jet and its filaments. The drifters tended to stay amidst the surrounding surface waters. The properties of mixing were evaluated using the daily rate of temperature change along several transects. The upwelled cooler water largely kept its identity during almost the entire duration of the upwelling event. Intense mixing started at a later stage of the upwelling and continued after the end of the event when the winds that have driven the entire process began to subside.

  6. Dynamics of ordering processes in annealed dilute systems: Island formation, vacancies at domain boundaries, and compactification

    DEFF Research Database (Denmark)

    Shah, Peter Jivan; Mouritsen, Ole G.

    1990-01-01

    . The results of the model study are relevant for the interpretation of experiments on ordering in impure systems and off-stochiometric alloys, grain growth in radiation-damaged materials, and may also shed light on aspects of sintering processes. The finding of a crossover from an algebraic growth law...... for the pure system to a slower, possibly logarithmic growth behavior in the dilute system is in accordance with recent high-resolution low-energy electron-diffraction experiments on the oxygen ordering on W(112) surfaces doped with nitrogen and time-resolved x-ray-scattering studies of the ordering in thin...

  7. Development of a Multi-Sensor System for Measurement of 4-D Atmospheric Boundary Layer Structures

    National Research Council Canada - National Science Library

    Knupp, Kevin

    2000-01-01

    ...) upgrade a WSR-74C Doppler radar, and (e) instrument a 30 m tower. The primary goal is to integrate measurements from these systems with those from other nearby instruments used by the Army for operations on Redstone Arsenal (RSA...

  8. Study area boundary for the Death Valley regional ground-water flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set represents the Death Valley regional ground-water flow system (DVRFS) study area which encompasses approximately 100,000-square kilometers in...

  9. On an approximation with prescribed zeros of SISO abstract boundary control systems

    NARCIS (Netherlands)

    Iftime, Orest; Ionescu, Tudor

    Finite-dimensional approximations of partial differential equations are used not only for simulation, but also for controller design. Modal truncation and numerical approximation are common practical methods for approximating distributed parameter systems. The modal approximation preserves the

  10. Positive solutions for a system of second-order boundary-value problems involving first-order derivatives

    Directory of Open Access Journals (Sweden)

    Kun Wang

    2012-08-01

    Full Text Available In this article we study the existence and multiplicity of positive solutions for the system of second-order boundary value problems involving first order derivatives $$displaylines{ -u''=f(t, u, u', v, v',cr -v''=g(t, u, u', v, v',cr u(0=u'(1=0,quad v(0=v'(1=0. }$$ Here $f,gin C([0,1]imes mathbb{R}_+^{4}, mathbb{R}_+(mathbb{R}_+:=[0,infty$. We use fixed point index theory to establish our main results based on a priori estimates achieved by utilizing Jensen's integral inequality for concave functions and $mathbb{R}_+^2$-monotone matrices.

  11. Challenging the planetary boundaries II: Assessing the sustainable global population and phosphate supply, using a systems dynamics assessment model

    Energy Technology Data Exchange (ETDEWEB)

    Sverdrup, Harald U., E-mail: harald.sverdrup@chemeng.lth.se [Applied Systems Analysis and Dynamics Group, Chemical Engineering, Lund University, Box 124, SE-221 00 Lund (Sweden); Ragnarsdottir, Kristin Vala [Institute of Earth Sciences, School of Engineering and Natural Sciences, University of Iceland, IS-101 Reykjavik (Iceland)

    2011-06-15

    Highlights: > Peak phosphorus supply behaviour. > Recycling essential for phosphorus supply. > Phosphorus supply is connected to food security. - Abstract: A systems dynamics model was developed to assess the planetary boundary for P supply in relation to use by human society. It is concluded that present day use rates and poor recycling rates of P are unsustainable at timescales beyond 100+ a. The predictions made suggest that P will become a scarce and expensive material in the future. The study shows clearly that market mechanisms alone will not be able to secure an efficient use before a large part of the resource will have been allowed to dissipate into the natural environment. It is suggested that population size management and effective recycling measures must be planned long term to avoid unpleasant consequences of hunger and necessary corrections imposed on society by mass balance and thermodynamics.

  12. Uniform regularity estimates in homogenization theory of elliptic systems with lower order terms on the Neumann boundary problem

    Science.gov (United States)

    Xu, Qiang

    2016-10-01

    In this paper, we mainly employed the idea of the previous paper [34] to study the sharp uniform W 1 , p estimates with 1 < p ≤ ∞ for more general elliptic systems with the Neumann boundary condition on a bounded C 1 , η domain, arising in homogenization theory. Based on the skills developed by Z. Shen in [27] and by T. Suslina in [31,32], we also established the L2 convergence rates on a bounded C 1 , 1 domain and a Lipschitz domain, respectively. Here we found a ;rough; version of the first order correctors (see (1.12)), which can unify the proof in [27] and [32]. It allows us to skip the corresponding convergence results on Rd that are the preconditions in [31,32]. Our results can be regarded as an extension of [23] developed by C. Kenig, F. Lin, Z. Shen, as well as of [32] investigated by T. Suslina.

  13. A Neumann problem for a system depending on the unknown boundary values of the solution

    Directory of Open Access Journals (Sweden)

    Pablo Amster

    2013-01-01

    Full Text Available A semilinear system of second order ODEs under Neumann conditions is studied. The system has the particularity that its nonlinear term depends on the (unknown Dirichlet values $y(0$ and $y(1$ of the solution. Asymptotic and non-asymptotic sufficient conditions of Landesman-Lazer type for existence of solutions are given. We generalize our previous results for a scalar equation, and a well known result by Nirenberg for a nonlinearity independent of $y(0$ and $y(1$.

  14. Leveraging a Statewide Clinical Data Warehouse to Expand Boundaries of the Learning Health System.

    Science.gov (United States)

    Turley, Christine B; Obeid, Jihad; Larsen, Rick; Fryar, Katrina M; Lenert, Leslie; Bjorn, Arik; Lyons, Genevieve; Moskowitz, Jay; Sanderson, Iain

    2016-01-01

    Learning Health Systems (LHS) require accessible, usable health data and a culture of collaboration-a challenge for any single system, let alone disparate organizations, with macro- and micro-systems. Recently, the National Science Foundation described this important setting as a cyber-social ecosystem. In 2004, in an effort to create a platform for transforming health in South Carolina, Health Sciences South Carolina (HSSC) was established as a research collaboration of the largest health systems, academic medical centers and research intensive universities in South Carolina. With work beginning in 2010, HSSC unveiled an integrated Clinical Data Warehouse (CDW) in 2013 as a crucial anchor to a statewide LHS. This CDW integrates data from independent health systems in near-real time, and harmonizes the data for aggregation and use in research. With records from over 2.7 million unique patients spanning 9 years, this multi-institutional statewide clinical research repository allows integrated individualized patient-level data to be used for multiple population health and biomedical research purposes. In the first 21 months of operation, more than 2,800 de-identified queries occurred through i2b2, with 116 users. HSSC has developed and implemented solutions to complex issues emphasizing anti-competitiveness and participatory governance, and serves as a recognized model to organizations working to improve healthcare quality by extending the traditional borders of learning health systems.

  15. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    Science.gov (United States)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  16. Biological and oceanographic upwelling indicators at Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Gleyci A. O. Moser

    1997-01-01

    Full Text Available Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ, Southeast Brazil, during summer (December 29 to 31, 1991 and winter (June 27 to 30, 1992. Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW, found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.A biomassa fitoplanctônica, parâmetros químicos e hidrologia foram estudadas em um transecto de 101,6 Km ao largo de Cabo Frio, (RJ Brasil, durante o verão (Dezembro 29 a 31, 1991 e inverno (Junho 27 a 30, 1992. Nesta área, eventos de ressurgência induzidos pelo vento são comuns durante o verão, tornando-se mais raros durante o inverno. Durante o período de verão uma floração de fitoplâncton foi observada na superfície próximo ao continente, apresentando um máximo de clorofila-a igual a 25,55 mg Cl-a m'3 desacoplado das águas frias e ricas em nutrientes da Água Central do Atlântico Sul (ACAS, presente abaixo de 40 m. Durante o inverno, a ACAS alcançou a superflcie em frente a Cabo Frio, caracterizando um evento de ressurgência. Entretanto, apesar das altas concentrações de nitrato na superf

  17. Stabilization of ODE-Schrodinger cascaded systems subject to boundary control matched disturbance

    Directory of Open Access Journals (Sweden)

    Ya-Ping Guo

    2015-09-01

    Full Text Available In this article, we consider the state feedback stabilization of ODE-Schrodinger cascaded systems with the external disturbance. We use the backstepping transformation to handle the unstable part of the ODE, then design a feedback control which is used to cope with the disturbance and stabilize the Schrodinger part. By active disturbance rejection control (ADRC approach, the disturbance is estimated by a constant high gain estimator, then the feedback control law can be designed. Next, we show that the resulting closed-loop system is practical stable, where the peaking value appears in the initial stage and the stabilized result requires that the derivative of disturbance be uniformly bounded. To avoid the peak phenomenon and to relax the restriction on the disturbance, a time varying high gain estimator is presented and asymptotical stabilization of the corresponding closed-loop system is proved. Finally, the effectiveness of the proposed control is verified by numerical simulations.

  18. Blurring Boundaries

    DEFF Research Database (Denmark)

    Neergaard, Ulla; Nielsen, Ruth

    2010-01-01

    This article builds on the results obtained in the so-called Blurring Boundaries project which was undertaken at the Law Department, Copenhagen Business School, in the period from 2007 to 2009. It looks at the sustainability of the Danish welfare state in an EU law context and on the integration...... of welfare functions into EU law both from an internal market law and a constitutional law perspective. The main problem areas covered by the Blurring Boundaries project were studied in sub-projects on: 1) Internal market law and welfare services; 2) Fundamental rights and non-discrimination law aspects......; and 3) Services of general interest. In the Blurring Boundaries project, three aspects of the European Social Model have been particularly highlighted: the constitutionalisation of the European Social Model, its multi-level legal character, and the clash between market access justice at EU level...

  19. Stability, Stochastic Stationarity and Generalized Lyapunov Equations for Two-Point Boundary-Value Descriptor Systems,

    Science.gov (United States)

    1988-03-03

    state regulation," IEEE Trans. Automat. Control, vol. AC-28, no. 5, pp. 601-611, May 1983. IT -49- 12. V. Kucera , "Stationary LQG control of singular...systems," IEEE Trans. % Automat. Control, vol. AC-31, no. 1, pp. 31-39, Jan . 1986. 13. D.J. Bender and A.J. Laub, "The linear-quadratic optimal...regulator for descrip- tor systems: discrete-time case," Autornatica, vol. 23, no. 1, pp. 71-85, Jan . 1987. 14. Z. Zhou, M.A. Shayman, and T.-J. Tarn

  20. Understanding the nature of mantle upwelling beneath East-Africa

    Science.gov (United States)

    Civiero, Chiara; Hammond, James; Goes, Saskia; Ahmed, Abdulhakim; Ayele, Atalay; Doubre, Cecile; Goitom, Berhe; Keir, Derek; Kendall, Mike; Leroy, Sylvie; Ogubazghi, Ghebrebrhan; Rumpker, Georg; Stuart, Graham

    2014-05-01

    The concept of hot upwelling material - otherwise known as mantle plumes - has long been accepted as a possible mechanism to explain hotspots occurring at Earth's surface and it is recognized as a way of removing heat from the deep Earth. Nevertheless, this theory remains controversial since no one has definitively imaged a plume and over the last decades several other potential mechanisms that do not require a deep mantle source have been invoked to explain this phenomenon, for example small-scale convection at rifted margins, meteorite impacts or lithospheric delamination. One of the best locations to study the potential connection between hotspot volcanism at the surface and deep mantle plumes on land is the East African Rift (EAR). We image seismic velocity structure of the mantle below EAR with higher resolution than has been available to date by including seismic data recorded by stations from many regional networks ranging from Saudi Arabia to Tanzania. We use relative travel-time tomography to produce P- velocity models from the surface down into the lower mantle incorporating 9250 ray-paths in our model from 495 events and 402 stations. We add smaller earthquakes (4.5 image structures of ~ 100-km length scales to ~ 1000 km depth beneath the northern East-Africa rift (Ethiopia, Eritrea, Djibouti, Yemen) with good resolution also in the transition zone and uppermost lower mantle. Our observations provide evidence that the shallow mantle slow seismic velocities continue trough the transition zone and into the lower mantle. In particular, the relatively slow velocity anomaly beneath the Afar Depression extends up to depths of at least 1000 km depth while another low-velocity anomaly beneath the Main Ethiopian Rift seems to be present in the upper mantle only. These features in the lower mantle are isolated with a diameter of about 400 km indicating deep multiple sources of upwelling that converge in broader low-velocity bodies along the rift axis at shallow

  1. Boundary Conditions of the High-Investment Human Resource Systems-Small-Firm Labor Productivity Relationship

    Science.gov (United States)

    Chadwick, Clint; Way, Sean A.; Kerr, Gerry; Thacker, James W.

    2013-01-01

    Although a few published, multiindustry, firm-level, empirical studies have linked systems of high-investment or high-performance human resource management practices to enhanced small-firm performance, this stream of strategic human resource management research is underdeveloped and equivocal. Accordingly, in this study, we use a sample of…

  2. Multipoint Singular Boundary-Value Problem for Systems of Nonlinear Differential Equations

    Directory of Open Access Journals (Sweden)

    Zdeněk Šmarda

    2009-01-01

    Full Text Available A singular Cauchy-Nicoletti problem for a system of nonlinear ordinary differential equations is considered. With the aid of combination of Ważewski's topological method and Schauder's principle, the theorem concerning the existence of a solution of this problem (having the graph in a prescribed domain is proved.

  3. Working the Boundaries between Education and Work: Transformations of the German Educational System Reconsidered

    Science.gov (United States)

    Niemeyer, Beatrix

    2014-01-01

    The Lisbon commitment for a European knowledge society together with the subsequently implemented policy of lifelong learning and social inclusion has significantly affected the German educational system and its teaching practices. This article examines the impact of these policy reforms on educational work in Germany through an analysis of the…

  4. Enabling System Evolution through Configuration Management on the Hardware/Software Boundary

    NARCIS (Netherlands)

    Krikhaar, R.L.; Mosterman, W.; Veerman, N.P.; Verhoef, C.

    2009-01-01

    As the use of software and electronics in modern products is omnipresent and continuously increasing, companies in the embedded systems industry face increasing complexity in controlling and enabling the evolution of their IT-intensive products. Traditionally, product configurations and their

  5. Shifting boundaries of volunteered geographic information systems and modalities : learning from PGIS

    NARCIS (Netherlands)

    McCall, M.K.; Martinez Martin, Javier; Verplanke, J.J.

    2015-01-01

    This paper develops a framework for assessing how Volunteered Geographical Information (VGI)[1] systems, modalities and practices perform, as measured against principles of good governance and participation; the framework is applied to two case studies. From this, we argue for a shift towards

  6. Topology of sustainable management of dynamical systems with desirable states: from defining planetary boundaries to safe operating spaces in the Earth System

    Science.gov (United States)

    Heitzig, Jobst; Kittel, Tim; Donges, Jonathan; Molkenthin, Nora

    2016-04-01

    To keep the Earth System in a desirable region of its state space, such as defined by the recently suggested "tolerable environment and development window", "guardrails", "planetary boundaries", or "safe (and just) operating space for humanity", one not only needs to understand the quantitative internal dynamics of the system and the available options for influencing it (management), but also the structure of the system's state space with regard to certain qualitative differences. Important questions are: Which state space regions can be reached from which others with or without leaving the desirable region? Which regions are in a variety of senses "safe" to stay in when management options might break away, and which qualitative decision problems may occur as a consequence of this topological structure? In this work, we develop a mathematical theory of the qualitative topology of the state space of a dynamical system with management options and desirable states, as a complement to the existing literature on optimal control which is more focussed on quantitative optimization and is much applied in both the engineering and the integrated assessment literature. We suggest a certain terminology for the various resulting regions of the state space and perform a detailed formal classification of the possible states with respect to the possibility of avoiding or leaving the undesired region. Our results indicate that before performing some form of quantitative optimization such as of indicators of human well-being for achieving certain sustainable development goals, a sustainable and resilient management of the Earth System may require decisions of a more discrete type that come in the form of several dilemmas, e.g., choosing between eventual safety and uninterrupted desirability, or between uninterrupted safety and larger flexibility. We illustrate the concepts and dilemmas drawing on conceptual models from climate science, ecology, coevolutionary Earth System modeling

  7. Trophic modeling of Eastern Boundary Current Systems: a review and prospectus for solving the “Peruvian Puzzle”

    Directory of Open Access Journals (Sweden)

    Marc H. Taylor

    2013-04-01

    Full Text Available Eastern Boundary Current systems (EBCSs are among the most productive fishing areas in the world. High primary and secondary productivity supports a large biomass of small planktivorous pelagic fish, “small pelagics”, which are important drivers of production to the entire system whereby they can influence both higher and lower trophic levels. Environmental variability causes changes in plankton (food quality and quantity, which can affect population sizes, distribution and domi-nance among small pelagics. This variability combined with impacts from the fishery complicate the development of management strategies. Consequently, much recent work has been in the development of multispecies trophic models to better understand interdependencies and system dynamics. Despite similarities in extent, structure and primary productivity between EBCSs, the Peruvian system greatly differs from the others in the magnitude of fish catches, due mainly to the incredible production of the anchovy Engraulis ringens. This paper reviews literature concerning EBCSs dynamics and the state-of-the-art in the trophic modeling of EBCSs. The objective is to critically analyze the potential of this approach for system understanding and management and to adapt existing steady-state models of the Peruvian system for use in (future dynamic simulations. A guideline for the construction of trophodynamic models is presented taking into account the important trophic and environmental interactions. In consideration of the importance of small pelagics for the system dynamics, emphasis is placed on developing appropriate model compartmentalization and spatial delineation that facilitates dynamic simulations. Methods of model validation to historical changes are presented to support hypotheses concerning EBCS dynamics and as a critical step to the development of predictive models. Finally, the identification of direct model links to easily obtainable abiotic parameters is

  8. Coda Q and its Frequency Dependence in the Eastern Himalayan and Indo-Burman Plate Boundary Systems

    Science.gov (United States)

    Mitra, S.; Kumar, A.

    2015-12-01

    We use broadband waveform data for 305 local earthquakes from the Eastern Himalayan and Indo-Burman plate boundary systems, to model the seismic attenuation in NE India. We measure the decay in amplitude of coda waves at discreet frequencies (between 1 and 12Hz) to evaluate the quality factor (Qc) as a function of frequency. We combine these measurements to evaluate the frequency dependence of Qc of the form Qc(f)=Qof η, where Qo is the quality factor at 1Hz and η is the frequency dependence. Computed Qo values range from 80-360 and η ranges from 0.85-1.45. To study the lateral variation in Qo and η, we regionalise the Qc by combining all source-receiver measurements using a back-projection algorithm. For a single back scatter model, the coda waves sample an elliptical area with the epicenter and receiver at the two foci. We parameterize the region using square grids. The algorithm calculates the overlap in area and distributes Qc in the sampled grids using the average Qc as the boundary value. This is done in an iterative manner, by minimising the misfit between the observed and computed Qc within each grid. This process is repeated for all frequencies and η is computed for each grid by combining Qc for all frequencies. Our results reveal strong variation in Qo and η across NE India. The highest Qo are in the Bengal Basin (210-280) and the Indo-Burman subduction zone (300-360). The Shillong Plateau and Mikir Hills have intermediate Qo (~160) and the lowest Qo (~80) is observed in the Naga fold thrust belt. This variation in Qo demarcates the boundary between the continental crust beneath the Shillong Plateau and Mikir Hills and the transitional to oceanic crust beneath the Bengal Basin and Indo-Burman subduction zone. Thick pile of sedimentary strata in the Naga fold thrust belt results in the low Qo. Frequency dependence (η) of Qc across NE India is observed to be very high, with regions of high Qo being associated with relatively higher η.

  9. Unmanned aircraft system measurements of the atmospheric boundary layer over Terra Nova Bay, Antarctica

    Directory of Open Access Journals (Sweden)

    S. L. Knuth

    2013-02-01

    Full Text Available In September 2009, a series of long-range unmanned aircraft system (UAS flights collected basic atmospheric data over the Terra Nova Bay polynya in Antarctica. Air temperature, wind, pressure, relative humidity, radiation, skin temperature, GPS, and operational aircraft data were collected and quality controlled for scientific use. The data have been submitted to the United States Antarctic Program Data Coordination Center (USAP-DCC for free access (doi:10.1594/USAP/0739464.

  10. Solving Boundary Value Problem for a Nonlinear Stationary Controllable System with Synthesizing Control

    Directory of Open Access Journals (Sweden)

    Alexander N. Kvitko

    2017-01-01

    Full Text Available An algorithm for constructing a control function that transfers a wide class of stationary nonlinear systems of ordinary differential equations from an initial state to a final state under certain control restrictions is proposed. The algorithm is designed to be convenient for numerical implementation. A constructive criterion of the desired transfer possibility is presented. The problem of an interorbital flight is considered as a test example and it is simulated numerically with the presented method.

  11. Evidence of upwelling events at the northern Patagonian shelf break

    Science.gov (United States)

    Valla, Daniel; Piola, Alberto R.

    2015-11-01

    The Patagonian shelf break marks a transition between relative warm-fresh shelf waters and relative cold-salty Subantarctic Water advected northward by the Malvinas Current. From early spring to late autumn, the outer shelf region is characterized by a band of high chlorophyll concentration that sustains higher trophic levels, including significant fisheries. We analyze time series of current and water mass property observations collected at two moorings deployed at the shelf edge at 41°S and 43.8°S to investigate what mechanisms lead to temperature variability at the shelf break, and their role on the nutrient supply to the upper layer. The in situ data are combined with satellite-derived observations of sea surface temperature and chlorophyll a to analyze a sharp cooling event at the outer shelf that lasted 10 days and extended ˜500 km along the outer shelf. The event is consistent with upwelling of cold waters through the base of the mixed layer. The vertical velocity required to explain the observed cooling is 13-29 m d-1. Satellite-derived sea surface temperature reveals additional cooling events of similar characteristics. Seventy-five percent of these events are concurrent with surface chlorophyll increase over a 5 day period suggesting that cooling events observed at the shelf break are associated with nutrient fluxes that promote the growth of phytoplankton.

  12. Near-surface temperature gradient in a coastal upwelling regime

    Science.gov (United States)

    Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

    2014-08-01

    In oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

  13. Climatic control of upwelling variability along the western North-American coast

    National Research Council Canada - National Science Library

    Macias, Diego; Landry, Michael R; Gershunov, Alexander; Miller, Arthur J; Franks, Peter J S

    2012-01-01

    .... Here, we use Singular Spectral Analysis (SSA) to reveal, for the first time, low-frequency concordance between the time series of climatic indices and upwelling intensity along the coast of western North America...

  14. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  15. Ekman Upwelling, METOP ASCAT, 0.25 degrees, Global, Near Real Time

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  16. On an upwelling front along the west coast of India during later part of southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Antony, M.K.

    A coastal front, associated with upwelling, is identified from the observed thermal field along the west coast of India during September, 1987. The front, which is seen very clearly upto a depth of about 75 m, has a horizontal gradient...

  17. Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Rao, R.R.; Nisha, K.; GirishKumar, M.S.; Pankajakshan, T.; Ravichandran, M.; Johnson, Z.; Girish, K.; Aneeshkumar, N.; Srinath, M.; Rajesh, S.; Rajan, C.K.

    of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005...

  18. Chasing boundaries and cascade effects in a coupled barrier-marsh-lagoon system

    Science.gov (United States)

    Lorenzo-Trueba, Jorge; Mariotti, Giulio

    2017-08-01

    The long-term dynamic evolution of an idealized barrier-marsh-lagoon system experiencing sea-level rise is studied by coupling two existing numerical models. The barrier model accounts for the interaction between shoreface dynamics and overwash flux, which allows the occurrence of barrier drowning. The marsh-lagoon model includes both a backbarrier marsh and an interior marsh, and accounts for the modification of the wave regime associated with changes in lagoon width and depth. Overwash, the key process that connects the barrier shoreface with the marsh-lagoon ecosystems, is formulated to account for the role of the backbarrier marsh. Model results show that a number of factors that are not typically associated with the dynamics of coastal barriers can enhance the rate of overwash-driven landward migration by increasing backbarrier accommodation space. For instance, lagoon deepening could be triggered by marsh edge retreat and consequent export of fine sediment via tidal dispersion, as well as by an expansion of inland marshes and consequent increase in accommodation space to be filled in with sediment. A deeper lagoon results in a larger fraction of sediment overwash being subaqueous, which coupled with a slow shoreface response sending sediment onshore can trigger barrier drowning. We therefore conclude that the supply of fine sediments to the back-barrier and the dynamics of both the interior and backbarrier marsh can be essential for maintaining the barrier system under elevated rates of sea-level rise. Our results highlight the importance of considering barriers and their associated backbarriers as part of an integrated system in which sediment is exchanged.

  19. Cross-categorization of legal concepts across boundaries of legal systems: in consideration of inferential links

    DEFF Research Database (Denmark)

    Glückstad, Fumiko Kano; Herlau, Tue; Schmidt, Mikkel Nørgaard

    2014-01-01

    -IRM (n-IRM) proposed by Herlau et al. (IEEE International Workshop on Machine Learning for Signal Processing, 2012). We apply our cross-categorization approach to datasets where legal concepts related to educational systems are respectively defined by the Japanese- and the Danish authorities according...... to the International Standard Classification of Education. The main contribution of this work is the proposal of a conceptual framework of the cross-categorization approach that, inspired by Sartor (Artif Intell Law 17:217–251, 2009), attempts to explain reasoner’s inferential mechanisms....

  20. Determination of mantle upwelling rate beneath Taiyuan basin by using absolute gravity, GPS, groundwater and GLDAS data

    Science.gov (United States)

    Xing, Lelin; Wang, Linhai; Hu, Minzhang

    2017-03-01

    The Taiyuan basin is in the Shanxi rift system of China. Results of tectonic studies indicate that the Moho is uplifted by 2-3 km under the Taiyuan basin. However, there is no quantitative evidence showing whether the rift is still in the status of mantle upwelling. Herein, we estimated mantle upwelling rate of Taiyuan basin by using absolute gravity, GPS, groundwater and GLDAS data in this paper. In order to utilize the absolute gravity measurements in terms of tectonic study it is necessary to reduce all disturbing environmental effects. Many of those can be modeled, such as tide, polar motion, ocean tidal loading and atmospheric mass components. The Taiyuan station located in the Taiyuan basin, and absolute gravity measurements with a FG5 instrument were performed from 2009 to 2014, a secular trend was obtained. In-situ GPS data was used to estimate the vertical motion rate since 2011, and the result indicated a land subsidence. In-situ groundwater level was collected with daily surveys from 2009 to 2015, and local hydrology impact on effect was made. The global terrestrial water storage loading effect on gravity at Taiyuan station was computed by using GLDAS global hydrology model. Furthermore there is a good agreement between GRACE results and GLDAS hydrological model results. Subtracting the gravity change rate attributable to the land subsidence, groundwater level and global hydrology from the absolute gravity change rate, the residual gravity change rate was obtained. It reflects mantle upwelling about 2.1 ± 2.6 cm/yr beneath Taiyuan basin.

  1. Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

    Science.gov (United States)

    Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

    2016-02-01

    Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

  2. Transacting generation attributes across market boundaries: Compatible information systems and the treatment of imports and exports

    Energy Technology Data Exchange (ETDEWEB)

    Grace, Robert; Wiser, Ryan

    2002-11-01

    Voluntary markets for ''green'' power, and mandatory policies such as fuel source disclosure requirements and renewables portfolio standards, each rely on the ability to differentiate electricity by the ''attributes'' of the generation. Throughout North America, electricity markets are devising accounting and verification systems for generation ''attributes'': those characteristics of a power plant's production such as fuel source and emissions that differentiate it from undifferentiated (or ''commodity'') electricity. These accounting and verification systems are intended to verify compliance with market mandates, create accurate disclosure labels, substantiate green power claims, and support emissions markets. Simultaneously, interest is growing in transacting (importing or exporting) generation attributes across electricity market borders, with or without associated electricity. Cross-border renewable attribute transactions have advantages and disadvantages. Broad access to markets may encourage more renewable generation at lower cost, but this result may conflict with desires to assure that at least some renewable resources are built locally to achieve either local policy goals or purchaser objectives. This report is intended to serve as a resource document for those interested in and struggling with cross-border renewable attribute transactions. The report assesses the circumstances under which renewable generation attributes from a ''source'' region might be recognized in a ''sink'' region. The report identifies several distinct approaches that might be used to account for and verify attribute import and export transactions, and assesses the suitability of these alternative approaches. Because policymakers have often made systems ''compatibility'' between market areas a pre-requisite to allowing cross

  3. Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium

    Science.gov (United States)

    Steinfeldt, R.; Sültenfuß, J.; Dengler, M.; Fischer, T.; Rhein, M.

    2015-07-01

    Oceanic upwelling velocities are too small to be measured directly. The surface disequilibrium of the 3He/4He ratio provides an indirect method to infer vertical velocities at the base of the mixed layer. Samples of helium isotopes were taken from two coastal upwelling regions, off Peru on cruise M91, and off Mauritania on 3 cruises. The helium-3 flux into the mixed layer also depends on the diapycnal mixing. Direct observations of the vertical diffusivity have been performed on all 4 cruises and are also used in this study. The resulting upwelling velocities in the coastal regions vary between 1.1 × 10-5 and 2.8 × 10-5 m s-1 for all cruises. Vertical velocities off the equator can also be inferred from the divergence of the wind driven Ekman transport. In the coastal regimes, the agreement between wind and helium derived upwelling is fairly good at least for the mean values. Further offshore, the helium derived upwelling still reaches 1 × 10-5 m s-1, whereas the wind driven upwelling from Ekman suction is smaller by at least one order of magnitude. One reason for this difference might be eddy induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium derived vertical velocities and the measured vertical diffusivities. The advective part of these fluxes makes up at least 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 g C m2 d-1 off Peru and 1.6-1.9 g C m2 d-1 off Mauritania.

  4. Spatial distribution of upwelling off the central east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.V.N.

    ), Stommel and Wooster (1965), Panikkar and Jayaraman (1966) and Hsueh and Coastal upwelling along the east coast of India has received considerable attention over the past three decades both in theoretical and observational studies (LaFond, 1954, 1957... coast has been reported by LaFond (1954). The lowering of sea surface tempera- ture in August along the east coast prompted LaFond (1958) to infer the possibility of a secondary period of upwelling. A theoretical study by Varadachari (1961) indicates...

  5. Comparison of floating and thermalized multilayer insulation systems at low boundary temperature

    CERN Document Server

    Ferlin, G; Lebrun, P; Peón-Hernández, G; Riddone, G; Szeless, Balázs

    1997-01-01

    The Large Hadron Collider (LHC) is 26.7 km circumference particle collider using high-field superconducting magnets operating in superfluid helium. An efficient and robust thermal insulation system is therefore required to minimize the residual heat in leak to the large surface area at 1.9 K constituted by the stainless steel wall of the helium enclosure. The baseline solution uses "floating" multilayer reflective insulation. Moreover, an alternative consists of a combination of multilayer reflective films and a soft screen, partially thermalized to the 5 K level and supported away from the cold wall by net-type insulating spacers. This chapter establishes the improvement potential of the alternative over the baseline solution, and compares their insulation performance on the basis of measured characteristics of thermal contacts and spacers.

  6. Mapping the Environmental Boundaries for Methanogenesis in Serpentinizing Systems using a Cell-scale Numerical Model

    Science.gov (United States)

    Alperin, M. J.; Hoehler, T. M.; McCollom, T.

    2011-12-01

    Serpentinizing systems occur where liquid water reacts with ultramafic minerals. The reaction releases heat and produces an alkaline fluid that is rich in H2. The abundant H2 suggests that the energetics of methane production by CO2 reduction is highly favorable (ΔG ~ -102 kJ/mol CH4 for [H2] ~ 10-2 M). Given the possibility of subsurface water and ultramafic minerals on Mars, methanogenesis in serpentinizing systems has been considered as a possible model for photosynthesis-independent, extraterrestrial life. However, the high pH (9 - 11) and possibly elevated temperature have a negative impact on the overall cellular energy balance by increasing the cell's maintenance energy and reducing the concentration of CO2 substrate. We developed a reaction-transport model on the scale of a methanogen cell to investigate how the overall bioenergetics of methane production is influenced by the interplay between pH, temperature, and H2 and CO2 concentration. The model differentiates the cell into three basic structural units (cell wall, cell membrane with gated ion channels, and cytoplasm) and employs both thermodynamic and kinetic controls to estimate an upper-limit energy yield as a function of environmental conditions. The model provides a map of the range of environmental extremes for which the energy balance for microbial methane production is positive. The model also provides a tool for exploring the energetics of different metabolic strategies that methanogens could use to cope with stresses associated with life in an alkaline, low-CO2 environment.

  7. Dynamic features of successive upwelling events in the Baltic Sea - a numerical case study

    Directory of Open Access Journals (Sweden)

    Kai Myrberg

    2010-03-01

    Full Text Available Coastal upwelling often reveals itself during the thermal stratification season as an abrupt sea surface temperature (SST drop. Its intensity depends not only on the magnitude of an upwelling-favourablewind impulse but also on the temperature stratification of the water column during the initial stage of the event. When a "chain" of upwelling events is taking place, one event may play a part in forming the initial stratification for the next one; consequently, SST may drop significantly even with a reduced wind impulse.    Two upwelling events were simulated on the Polish coast in August 1996 using a three-dimensional, baroclinic prognostic model. The model results proved to be in good agreement with in situobservations and satellite data. Comparison of the simulated upwelling events show that the first one required a wind impulse of 28000 kg m-1 s-1 to reach its mature, full form, whereasan impulse of only 7500 kg m-1 s-1 was sufficient to bring about a significant drop in SST at the end of the second event. In practical applications like operational modelling, the initial stratification conditions prior to an upwelling event should be described with care in order to be able to simulate the coming event with very good accuracy.

  8. Observations of the Hawaiian Mesopelagic Boundary Community in Daytime and Nighttime Habitats Using Estimated Backscatter

    Directory of Open Access Journals (Sweden)

    Comfort CM

    2017-07-01

    Full Text Available The Hawaiian mesopelagic boundary community is a slope-associated assemblage of micronekton that undergoes diel migrations along the slopes of the islands, residing at greater depths during the day and moving upslope to forage in shallower water at night. The timing of these migrations may be influenced by environmental factors such as moon phase or ambient light. To investigate the movements of this community, we examined echo intensity data from acoustic Doppler current profilers (ADCPs deployed at shallow and deep sites on the southern slope of Oahu, Hawaii. Diel changes in echo intensity (and therefore in estimated backscatter were observed and determined to be caused, at least in part, by the horizontal migration of the mesopelagic boundary community. Generalized additive modeling (GAM was used to assess the impact of environmental factors on the migration timing. Sunset time and lunar illumination were found to be significant factors. Movement speeds of the mesopelagic boundary community were estimated at 1.25–1.99 km h-1 (35–55 cm s-1. The location at which the migrations were observed is the future site of a seawater air conditioning system, which will cause artificial upwelling at our shallow observation site and may cause animal entrainment at the seawater intake near our deep water observation site. This study is the first to observe the diel migration of the mesopelagic boundary community on southern Oahu in both deep and shallow parts of the habitat, and it is also the first to examine migration trends over long time scales, which allows a better assessment of the effects of seasons and lunar illumination on micronekton migrations. Understanding the driving mechanisms of mesopelagic boundary community behavior will increase our ability to assess and manage coastal ecosystems in the face of increasing anthropogenic impacts.

  9. Horizontal wind estimation within the planetary boundary layer by sounding with unmanned aerial systems

    Science.gov (United States)

    Petersen, Erik; Philipp, Andreas; Junkermann, Wolfgang; Emeis, Stefan; Groos, Alexander; Ferenci, Pia; Engerer, Stefan; Jacobeit, Jucundus

    2017-04-01

    Measurements of wind speed and wind direction with conventional equipment and remote sensing methods are often limited with respect to the three-dimensional range. For that reason, unmanned aerial systems (UAS) were introduced about 15 to 20 years ago to measure meteorological variables such as air-temperature, humidity and wind, besides ground based remote sensing techniques. However, there are still challenges when measuring the wind components speed and direction due to the complexity of measuring the airspeed of UAS. In addition to the fact that devices such as five hole probes are expensive and fragile, the limited take-off-weight is another reason for these challenges. Thus, wind estimation from GPS data by using the Best-Curve-Fitting (BCF) method is presented in this poster. The BCF method was first introduced by Bonin et al. (2013) and has been modified for the purposes of this research. The method enables us to calculate wind direction and wind speed with respect to differences between headwind GPS speeds and tailwind GPS speeds of UAS. It has to be shown that estimated wind data is valid and can be compared to traditional methods of wind measurements. For that reason, wind estimations using the BCF method were compared to a SODAR-RASS and to a measurement flight with a manned microlight aircraft. The gained data has got a high vertical resolution. Furthermore, the quality of these estimations is shown during the interpretation of datasets from an international field campaign and other measurement campaigns.

  10. Geosfear? - Overcoming System Boundaries by Open-source Based Monitoring of Spatio-temporal Processes

    Science.gov (United States)

    Brandt, T.; Schima, R.; Goblirsch, T.; Paschen, M.; Francyk, B.; Bumberger, J.; Zacharias, S.; Dietrich, P.; Rubin, Y.; Rinke, K.; Fleckenstein, J. H.; Schmidt, C.; Vieweg, M.

    2016-12-01

    The impact of global change, intensive agriculture and complex interactions between humans and the environment show different effects on different scales. However, the desire to obtain a better understanding of ecosystems and process dynamics in nature accentuates the need for observing these processes at higher temporal and spatial resolutions. Especially with regard to the process dynamics and heterogeneity of rivers and catchment areas, a comprehensive monitoring of the ongoing processes and effects remains to be a challenging issue. What we need are monitoring systems which can collect most diverse data across different environmental compartments and scales. Today, open-source based electronics and innovative sensors and sensor components are offering a promising approach to investigate new possibilities of mobile data acquisition to improve our understanding of the geosphere. To start with, we have designed and implemented a multi-operable, embedded Linux platform for fast integration of different sensors within a single infrastructure. In addition, a GPS module in combination with a GSM transmitter ensures the synchronization and geo-referencing of all data, no matter how old-fashioned the sensors are. To this end, initial field experiments were conducted at a 3rd order stream in the Central German Lowland. Here, we linked in-stream DOC inputs with subsurface metabolism by coupling miniaturized DOC sensor probes with a modified vertical oxygen profiler in situ. Starting from metrological observations to water quality and subsurface conditions, the overarching goal is the detection of interlinked process dynamics across highly reactive biogeochemical interfaces. Overall, the field experiments demonstrated the feasibility of this emerging technology and its potential towards a cutting-edge strategy based on a holistic and integrated process. Now, we are only a few steps away from realizing adaptive and event-triggered observations close to real

  11. Albedo Boundary

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-510, 11 October 2003The sharp, nearly straight line that runs diagonally across the center of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an albedo boundary. Albedois a term that refers to reflectance of sunlight. A surface with a low albedo is one that appears dark because it reflects less light than a high albedo (bright) surface. On Mars, albedo boundaries occur between two materials of differing texture, particle size, or composition, or some combination of these three factors. The boundary shown here is remarkable because it is so sharp and straight. This is caused by wind. Most likely, the entire surface was once covered with the lower-albedo (darker) material that is now seen in the upper half of the image. At some later time, wind stripped away this darker material from the surfaces in the lower half of the image. The difference in albedo here might be related to composition, and possibly particle size. This picture is located near the southwest rim of Schiaparelli Basin at 5.5oS, 345.9oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  12. Ice Cloud Property Retrievals Using Far Infrared Upwelling Radiance Spectra

    Science.gov (United States)

    Merrelli, A. J.; Turner, D. D.

    2012-12-01

    Spectral measurements of the upwelling radiance in the mid-infrared (MIR, 8 - 12 μm wavelength) have proven sensitivity to microphysical and macrophysical parameters of ice clouds. This sensitivity is caused by the spectrally varying index of refraction, as well as the ice crystal shape and particle size parameter. Many methods have been demonstrated that utilize this sensitivity to retrieve bulk ice cloud microphysical properties such as effective ice particle size, and macrophysical properties such as optical depth and height. By extending the spectral observations into the far-infrared (FIR, 17 - 50 μm wavelength), additional information can be retrieved due to the different sensitivities exhibited by cloud ice at these longer wavelengths. Typically, in the far-infrared, ice exhibits stronger scattering across all particle sizes, due to a smaller complex index of refraction, and weaker forward scattering due to the smaller size parameter. In this research, a modeling framework is used to quantify the information content of the FIR spectrum for ice cloud property retrieval. The information content is quantitatively compared to the MIR, to show how ice cloud retrievals could be improved with FIR spectral measurements. For cases where the MIR spectrum contains a high amount of information (e.g., moderate optical depths with small particle size), the FIR spectrum adds only a marginal amount of information. In other cases where the MIR spectrum contains low information (e.g., high optical depth clouds), the FIR spectrum is shown to add significant information. The FIR spectrum can thus be shown to extend the region in state space where passive infrared measurements can effectively constrain ice cloud properties.

  13. An observational study of the evolution of the atmospheric boundary-layer over Cabo Frio, Brazil

    Directory of Open Access Journals (Sweden)

    S. H. Franchito

    2007-08-01

    Full Text Available The effect of coastal upwelling on the evolution of the atmospheric boundary layer (ABL in Cabo Frio (Brazil is investigated. For this purpose, radiosounding data collected in two experiments made during the austral summer (upwelling case and austral winter (no upwelling case are analysed. The results show that during the austral summer, cold waters that crop up near the Cabo Frio coast favour the formation of an atmospheric stable layer, which persists during the upwelling episode. Due to the low SSTs, the descending branch of the sea-breeze circulation is located close to the coast, inhibiting the development of a mixed layer mainly during the day. At night, with the reduction of the land-sea thermal contrast the descending motion is weaker, allowing a vertical mixing. The stable ABL favours the formation of a low level jet, which may also contribute to the development of a nocturnal atmospheric mixed layer. During the austral winter, due to the higher SSTs observed near the coast, the ABL is less stable compared with that in the austral summer. Due to warming, a mixed layer is observed during the day. The observed vertical profiles of the zonal winds show that the easterlies at low levels are stronger in the austral summer, indicating that the upwelling modulates the sea-breeze signal, thus confirming model simulations.

  14. Existence and smoothness of solutions to second initial boundary value problems for Schrodinger systems in cylinders with non-smooth bases

    Directory of Open Access Journals (Sweden)

    Nguyen Manh Hung

    2008-03-01

    Full Text Available In this paper, we consider the second initial boundary value problem for strongly general Schrodinger systems in both the finite and the infinite cylinders $Q_T, 0

  15. Implementation of non-local boundary layer schemes in the Regional Atmospheric Modeling System and its impact on simulated mesoscale circulations

    NARCIS (Netherlands)

    Gómez, I.; Ronda, R.J.; Caselles, V.; Estrela, M.J.

    2016-01-01

    This paper proposes the implementation of different non-local Planetary Boundary Layer schemes within the Regional Atmospheric Modeling System (RAMS) model. The two selected PBL parameterizations are the Medium-Range Forecast (MRF) PBL and its updated version, known as the Yonsei University (YSU)

  16. Synthesis of Automatic Control System of Step-Up DC Voltage Converter Operating in Boundary-Continuous Current Conduction Mode

    Directory of Open Access Journals (Sweden)

    A. V. Mironovich

    2007-01-01

    Full Text Available The paper investigates an operation of a step-up DC voltage converter in the mode of boundary-continuous restrictor current. Functional diagram of a logic unit ensuring boundary-continuous mode has been developed. A mathematical model of a converter operating in a boundary-continuous mode, has been built in the paper. Comparative transient simulation in a linear structure and a model on the basis of power element library have been carried out with the help of a computer.

  17. Boundaries and Boundary Marks - Substantive Cultural Heritage of Extensive Importance

    Science.gov (United States)

    Waldhaeusl, P.; Koenig, H.; Mansberger, R.

    2015-08-01

    The Austrian Society for surveying and Geoinformation (ASG) has proposed to submit "Boundaries and Boundary Marks" for the UNESCO World Heritage title. It was time that boundaries, borders and limits of all types as well as ownership rights would find the proper attention in the global public. Landmarks symbolize the real property and the associated rights and obligations, in a figurative sense, the property generally and all legal limits. A democratic state of law is impossible at today's population density without a functioning land administration system with surveying and jurisdiction. As monumental World Heritage representatives of the geodetic artwork "Boundaries and Boundary Marks" are specifically proposed: remaining monuments of the original cadastral geodetic network, the first pan-Austrian surveying headquarters in Vienna, and a specific selection of outstanding boundary monuments. Landmarks are monuments to the boundaries which separate rights and obligations, but also connect the neighbors peacefully after written agreement. "And cursed be he who does not respect the boundaries" you wrote already 3000 years ago. Boundaries and Boundary Marks are a real thing; they all belong to the tangible or material heritage of human history. In this context also the intangible heritage is discussed. This refers to oral tradition and expressions, performing arts; social practices, rituals and festive events; as well as to knowledge and practices handling nature and the universe. "Boundaries and Boundary Marks" do not belong to it, but clearly to the material cultural world heritage. "Boundary and Boundary Marks" is proposed to be listed according to the criteria (ii),(iv),(vi).

  18. Multiple Positive Solutions for a Coupled System of p-Laplacian Fractional Order Two-Point Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    K. R. Prasad

    2014-01-01

    Full Text Available This paper establishes the existence of at least three positive solutions for a coupled system of p-Laplacian fractional order two-point boundary value problems, D0+β1(ϕp(D0+α1u(t=f1(t,u(t,v(t, t∈(0,1, D0+β2(ϕp(D0+α2v(t=f2(t,u(t,v(t, t∈(0,1, u(0=D0+q1u(0=0, γu(1+δD0+q2u(1=0, D0+α1u(0=D0+α1u(1=0, v(0=D0+q1v(0=0, γv(1+δD0+q2v(1=0, D0+α2v(0=D0+α2v(1=0, by applying five functionals fixed point theorem.

  19. Observations of Near-Surface Relative Humidity in a Wind Turbine Array Boundary Layer Using an Instrumented Unmanned Aerial System

    Science.gov (United States)

    Adkins, K. A.; Sescu, A.

    2016-12-01

    Simulation and modeling have shown that wind farms have an impact on the near-surface atmospheric boundary layer (ABL) as turbulent wakes generated by the turbines enhance vertical mixing. These changes alter downstream atmospheric properties. With a large portion of wind farms hosted within an agricultural context, changes to the environment can potentially have secondary impacts such as to the productivity of crops. With the exception of a few observational data sets that focus on the impact to near-surface temperature, little to no observational evidence exists. These few studies also lack high spatial resolution due to their use of a limited number of meteorological towers or remote sensing techniques. This study utilizes an instrumented small unmanned aerial system (sUAS) to gather in-situ field measurements from two Midwest wind farms, focusing on the impact that large utility-scale wind turbines have on relative humidity. Wind turbines are found to differentially alter the relative humidity in the downstream, spanwise and vertical directions under a variety of atmospheric stability conditions.

  20. Distributed Tuning of Boundary Resources

    DEFF Research Database (Denmark)

    Eaton, Ben; Elaluf-Calderwood, Silvia; Sørensen, Carsten

    2015-01-01

    in the context of a paradoxical tension between the logic of generative and democratic innovations and the logic of infrastructural control. Boundary resources play a critical role in managing the tension as a firm that owns the infrastructure can secure its control over the service system while independent...... firms can participate in the service system. In this study, we explore the evolution of boundary resources. Drawing on Pickering’s (1993) and Barrett et al.’s (2012) conceptualizations of tuning, the paper seeks to forward our understanding of how heterogeneous actors engage in the tuning of boundary...... resources within Apple’s iOS service system. We conduct an embedded case study of Apple’s iOS service system with an in-depth analysis of 4,664 blog articles concerned with 30 boundary resources covering 6 distinct themes. Our analysis reveals that boundary resources of service systems enabled by digital...

  1. Modelling an alkenone-like proxy record in the NW African upwelling

    Directory of Open Access Journals (Sweden)

    X. Giraud

    2006-01-01

    Full Text Available A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy, alkenones, are produced at the sea surface and recorded in the slope sediments. The biogeochemical model has two phytoplankton groups: an alkenone producer group, considered to be coccolithophores, and a group comprising other phytoplankton. The Regional Ocean Modelling System (ROMS is used to simulate the ocean circulation and takes advantage of the Adaptive Grid Refinement in Fortran (AGRIF package to set up an embedded griding system. In the simulations the alkenone temperature records in the sediments are between 1.1 and 2.3°C colder than the annual mean SSTs. Despite the seasonality of the coccolithophore production, this temperature difference is not mainly due to a seasonal bias, nor to the lateral advection of phytoplankton and phytodetritus seaward from the cold near-shore waters, but to the production depth of the coccolithophores. If coretop alkenone temperatures are effectively recording the annual mean SSTs, the amount of alkenone produced must vary among the coccolithophores in the water column and depend on physiological factors (e.g. growth rate, nutrient stress.

  2. Gulf-Wide Information System, Environmental Sensitivity Index Survey Boundaries, Geographic NAD83, LDWF (2001) [esi_survey_LDWF_2001

    Data.gov (United States)

    Louisiana Geographic Information Center — This data set contains vector polygons representing survey boundaries for the various data collection efforts used as sources in the larger Louisiana G-WIS database....

  3. Province, Total Petroleum System and Assessment Unit Boundaries from the 2009-2011 World Petroleum Resources Project

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The boundaries illustrated by these Assessment Units are the result of geologic studies conducted by the World Petroleum Resources Project, 2009-2011 (Project). The...

  4. Does upwelling intensity influence feeding habits and trophic position of planktivorous fish?

    Science.gov (United States)

    Lopez-Lopez, Lucia; Preciado, Izaskun; Muñoz, Isabel; Decima, Moira; Molinero, Juan Carlos; Tel, Elena

    2017-04-01

    Food web configuration is shaped by many factors, including primary production patterns and oceanographic features, such as upwelling events. In this study, we investigate variability in the trophic position, food web interlinks and energy pathways of four planktivorous demersal fish in the Southern Bay of Biscay- NE Atlantic. The study area is exposed to upwelling events of varying intensity and shows a significant spatial gradient along the coast. The two sampling years were characterized by markedly different conditions, with weak summer upwelling in 2012 and an intense upwelling season in 2013. We used a complementary approach based on stomach content analysis (SCA) and stable isotope analysis (SIA) to test the effects of upwelling intensity and persistence on the food-web. In particular we investigated whether different intensities shift the main flow of energy between the pelagic and benthic energy pathways. We found conspicuous interannual changes in the isotopic POM, whose δ15N was 2.5‰ lower during the productive 2013 season. Interannual changes in the isotopic signature of the fish species were also detected, although their values did not mirror variability at the basal level. The SCA results did not match the isotopic changes, which likely reflected dietary adjustments of the species during summer. The upwelling intensity gradient along the coast did not affect the nitrogen isotopic ratio of any group, however there was a significant effect of such gradient on the carbon isotopic ratio of the fish and euphausiid species. This effect was likely related to the higher primary production associated with intense upwelling conditions.

  5. Decadal resolution record of Oman upwelling indicates solar forcing of the Indian summer monsoon (9-6 ka)

    Science.gov (United States)

    Munz, Philipp M.; Steinke, Stephan; Böll, Anna; Lückge, Andreas; Groeneveld, Jeroen; Kucera, Michal; Schulz, Hartmut

    2017-05-01

    The Indian summer monsoon (ISM) is an important conveyor in the ocean-atmosphere coupled system on a trans-regional scale. Here we present a study of a sediment core from the northern Oman margin, revealing early to mid-Holocene ISM conditions on a near-20-year resolution. We assess multiple independent proxies indicative of sea surface temperatures (SSTs) during the upwelling season together with bottom-water conditions. We use geochemical parameters, transfer functions of planktic foraminiferal assemblages and Mg /  Ca palaeothermometry, and find evidence corroborating previous studies showing that upwelling intensity varies significantly in coherence with solar sunspot cycles. The dominant ˜ 80-90-year Gleissberg cycle apparently also affected bottom-water oxygen conditions. Although the interval from 8.4 to 5.8 ka BP is relatively short, the gradually decreasing trend in summer monsoon conditions was interrupted by short events of intensified ISM conditions. Results from both independent SST proxies are linked to phases of weaker oxygen minimum zone (OMZ) conditions and enhanced carbonate preservation. This indicates that atmospheric forcing was intimately linked to bottom-water properties and state of the OMZ on decadal timescales.

  6. Characteristics of Middle and Deep Crustal Expression of an Arc - Forearc Boundary Strike-Slip Fault System

    Science.gov (United States)

    Roeske, S.; Mulcahy, S. R.; McClelland, W.; Cain, J.

    2008-12-01

    Strike-slip faults below the seismogenic zone are commonly assumed to widen with depth into broad region of distributed strain or flatten into subhorizontal shear zones within the middle crust. While this may occur in some continental strike-slip systems, we propose that strike-slip faults at a major rheologic boundary, such as an arc-forearc transition, remain relatively narrow at depth, with localized high strain zones separating discrete packages of less-deformed metamorphic rock. Strain localization allows for greater displacements and explains the juxtaposition of significantly different crustal levels exposed in such strike-slip systems. We present metamorphic and geochronologic evidence for the initiation of one such strike slip system in western Argentina. The Valle Fertil, Desaguadero-Bermejo lineament is a prominent high angle lineament which currently accommodates significant shortening in the western Sierra Pampeanas of Argentina. The lineament is characterized geophysically as a high-angle to steeply east-dipping boundary with denser and more magnetic rocks on the east. The fault zone is bounded by the Cambrian-Ordovician Famatina arc, an intermediate composition batholith, to the east and an arc-forearc package of predominantly metasedimentary rocks intruded by Ordovician mafic to intermediate composition plutonic rocks to the west. The two packages currently expose markedly different crustal levels; those to the east expose rocks metamorphosed at 2-8 kbar, while those to the west expose rocks metamorphosed 11-14 kbar. Both units experienced high-grade metamorphism and granulite facies migmatization between ~470-450 Ma. Separate isolated packages within the fault/ shear zone record separate histories from those exposed to the east and west of the lineament. Low grade-limestone as well as 1.1 Ga and 845 Ma granitoids are overprinted by low-grade shear zones and show no significant thermal effect of the Ordovician magmatism and metamorphism. Regional

  7. Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

    Science.gov (United States)

    De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio L.

    2017-11-01

    The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.

  8. Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

    Science.gov (United States)

    De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio L.

    2017-05-01

    The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.

  9. Distributed sounding of the boundary layer using multiple unmanned aerial systems during the ScaleX campaign 2016

    Science.gov (United States)

    Philipp, Andreas; Petersen, Erik; Groos, Alexander; Ferenci, Pia; Engerer, Stefan; Fiedler, Benedikt; Emeis, Stefan; Schäfer, Klaus; Brosy, Caroline; Zeeman, Matthias; Jacobeit, Jucundus

    2017-04-01

    In order to observe and better understand micro scale processes of interaction between the surface and the atmosphere and to relate them to meso and macro scale processes, an intensive measurement campaign at the TERENO (Terrestrial Environmental Observatories) site Fendt in southern Germany was organized in summer 2016 by IMK-IFU (Institute of Meteorology and Climate Research - Atmospheric Environmental Research) / KIT (Karlsruher Institute for Technology) under participation of a large number of cooperation partners. While several ground based remote sensing systems were implemented beside already installed long-term observing instruments for turbulence, soil moisture, trace gas emission etc., several flight campaigns with unmanned aerial systems took place. IGUA (Institute for Geography at the Universiy of Augsburg) contributed with spiral profile flights up to 1000 meters above ground level simultaneously at five locations, covering an 1 km x 1 km large area, corresponding to a WRF (Weather and Research Forecast model) grid box. Starting in the afternoon of 6th of July and ending in the morning of 7th of July each full hour an ascent was launched. While there were several technical problems leading to missing values, an all together useful dataset was produced covering the distribution of temperature, humidity and wind for the diurnal cycle. The contribution presents the interpretation of the profiles in respect to stratification of the planetary boundary layer and comparison to the cooperated instruments. An interesting aspect of the observation data is the modification of the wind field by an nearby terrain step which also influences cold air flow near the ground. These observations are compared to mesoscale model data (METRAS and later WRF) in order to check whether the principle mechanisms can be simulated.

  10. Grain boundary melting in ice

    OpenAIRE

    Thomson, E. S.; Hansen-Goos, Hendrik; Wilen, L. A.; Wettlaufer, J. S.

    2012-01-01

    We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentr...

  11. Boundary issues

    Science.gov (United States)

    Townsend, Alan R.; Porder, Stephen

    2011-03-01

    What is our point of no return? Caesar proclaimed 'the die is cast' while crossing the Rubicon, but rarely does modern society find so visible a threshold in our continued degradation of ecosystems and the services they provide. Humans have always used their surroundings to make a living— sometimes successfully, sometimes not (Diamond 2005)—and we intuitively know that there are boundaries to our exploitation. But defining these boundaries has been a challenge since Malthus first prophesied that nature would limit the human population (Malthus 1798). In 2009, Rockström and colleagues tried to quantify what the 6.8 billion (and counting) of us could continue to get away with, and what we couldn't (Rockström et al 2009). In selecting ten 'planetary boundaries', the authors contend that a sustainable human enterprise requires treating a number of environmental thresholds as points of no return. They suggest we breach these Rubicons at our own peril, and that we've already crossed three: biodiversity loss, atmospheric CO2, and disruption of the global nitrogen (N) cycle. As they clearly hoped, the very act of setting targets has provoked scientific inquiry about their accuracy, and about the value of hard targets in the first place (Schlesinger 2009). Such debate is a good thing. Despite recent emphasis on the science of human-ecosystem interactions, understanding of our planetary boundaries is still in its infancy, and controversy can speed scientific progress (Engelhardt and Caplan 1987). A few weeks ago in this journal, Carpenter and Bennett (2011) took aim at one of the more controversial boundaries in the Rockström analysis: that for human alteration of the global phosphorus (P) cycle. Rockström's group chose riverine P export as the key indicator, suggesting that humans should not exceed a value that could trigger widespread marine anoxic events—and asserting that we have not yet crossed this threshold. There are defensible reasons for a marine

  12. Modelling of upwelling in the coastal area of Cabo Frio (Rio de Janeiro - Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Carbonel

    1998-01-01

    Full Text Available A 1 1/2 reduced-gravity model is proposed to study the hydrodynamic and thermodynamic features of the coastal upwelling area of Cabo Frio (Rio de Janeiro-Brazil. The vertical structure of the model is described by an active layer overlaying a deep inert layer where the pressure gradient is set to zero. For the upper layer, the model includes the turbulent version of the momentum. continuity and heat equations. The conservation of heat is represented by a transport equation to describe the thermodynamic changes of the sea surface temperature (SST. The solution domain includes open boundaries in which weakly-retlective conditions are prescribed. Solutions are found numerically on a uniform grid and the fundamental equations are approximated by the finite difference method. Numerical experiments are performed to evaluate the dynamic response of the coastal area of Cabo Frio forced by uniform and non-uniform wind fields. The solutions differ considerably depending on the orientation of the winds. East and northeast winds correlate with colder waters in the zonal coastline of this area and the presence of tlows toward Cabo Frio correlates with north wind components. The proposed model is validated with the numerical simulation of an observed event of upwelling, where a time­-dependent and non-uniform wind ficld develops a SST pattern similar as the observations, particularly the extension of the cool water plume in south-west direction and the rapid time variation of the SST.Um modelo de gravidade reduzida de 1 1/2 camada é proposto para estudar as características hidrodinmicas e termodinmicas da área costeira de Cabo Frio (Rio de Janeiro ­Brasil. A estrutura vertical do modelo é descrita por uma camada ativa sobre uma camada profunda sem movimento onde o gradicnte de pressão é zero. Para a camada superior. o modelo incluí a versão turbulenta das equações de momentum, continuidade e calor. A conservação do calor é representada por uma

  13. Expression of the Middle-Late Miocene "Carbonate Crash" and "Biogenic Bloom" in the Benguela Current Upwelling Area of the South Atlantic Ocean

    Science.gov (United States)

    Diester-Haass, L.; Meyers, P. A.; Bauman, S. C.

    2001-05-01

    The middle-late Miocene "carbonate crash" - several episodes with significant drops in concentrations and accumulation rates of CaCO3 - occurred between 13 and 9 Ma in the equatorial Pacific and Indian Oceans and the Carribean Sea (Lyle et al., 1995; Roth et al., 2000). This event is followed by a "biogenic bloom" - a strong increase in biogenous production that has been described in the equatorial Pacific and Indian Oceans. In order to explain these two events, the questions of whether they are confined to tropical upwelling areas, whether they also occur in coastal upwelling areas, or whether they are global phenomena must be answered. We have explored the expression of these events during the evolution of the Benguela Current upwelling system. Sediment sequences from ODP Sites 1085 and 1087 record several drops in carbonate concentrations in the middle and early late Miocene that culminate in a major depression at 9.5-9.0 Ma and that are synchronous with the "carbonate crash" in the equatorial Pacific (Lyle et al., 1995). Climatic changes in SW Africa, reflected by an increase in delivery terrigenous sediment components and by a larger proportion of kaolinite, and oceanic changes, indicated by an expansion of the oxygen minimum zone, accompany this event. Oxygen depletion starts during early carbonate depressions and has a maximum during the major CaCO3 depression. Marine biological productivity, as reconstructed from concentrations of organic carbon and benthic foraminiferal accumulation rates, is at a minimum in the middle-early late Miocene. However, it increases 3-6 fold at 6.5 Ma, a shift that is synchronous with the "biogenic bloom" in the equatorial Pacific Ocean (Farrell et al., 1995). We attribute this important paleoceanographic change to a strengthening of latitudinal temperature gradients and corresponding vertical mixing by zonal winds during the onset of North Atlantic Deep Water flow, which led to more vigorous deep ventilation and emergence of

  14. Boundaries of the universe

    CERN Document Server

    Glasby, John S

    2013-01-01

    The boundaries of space exploration are being pushed back constantly, but the realm of the partially understood and the totally unknown is as great as ever. Among other things this book deals with astronomical instruments and their application, recent discoveries in the solar system, stellar evolution, the exploding starts, the galaxies, quasars, pulsars, the possibilities of extraterrestrial life and relativity.

  15. Geothermal system boundary at the northern edge of Patuha Geothermal Field based on integrated study of volcanostratigraphy, geological field mapping, and cool springs contamination by thermal fluids

    Science.gov (United States)

    Suryantini; Rachmawati, C.; Abdurrahman, M.

    2017-12-01

    Patuha Geothermal System is a volcanic hydrothermal system. In this type of system, the boundary of the system is often determined by low resistivity (10 ohm.m) anomaly from Magnetotelluric (MT) or DC-Resistivity survey. On the contrary, during geothermal exploration, the system boundary often need to be determined as early as possible even prior of resistivity data available. Thus, a method that use early stage survey data must be developed properly to reduce the uncertainty of the geothermal area extent delineation at the time the geophysical data unavailable. Geological field mapping, volcanostratigraphy analysis and fluid chemistry of thermal water and cold water are the data available at the early stage of exploration. This study integrates this data to delineate the geothermal system boundary. The geological mapping and volcanostratigraphy are constructed to limit the extent of thermal and cold springs. It results that springs in the study area are controlled hydrologically by topography of Patuha Volcanic Crown (complex) or so called PVC, the current geothermal field and Masigit Volcanic Crown (complex) or so called MVC, the dormant volcano not associated with active geothermal system. Some of the cold springs at PVC are contaminated by subsurface steam heated outflow while others are not contaminated. The contaminated cold springs have several characteristics such as higher water temperature than ambient temperature at the time it was measured, higher total disolved solid (TDS), and lower pH. The soluble elements analysis support the early contamination indication by showing higher cation and anion, and positive oxygen shifting of stable isotope of these cool springs. Where as the uncontaminated spring shows similar characteristic with cool springs occur at MVC. The boundary of the system is delineated by an arbitrary line drawn between distal thermal springs from the upflow or contaminated cool springs with the cool uncontaminated springs. This boundary is

  16. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    Science.gov (United States)

    Bayraktarov, Elisa; Hauffe, Torsten; Pizarro, Valeria; Wilke, Thomas; Wild, Christian

    2014-01-01

    In Tayrona National Natural Park (Colombian Caribbean), abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn) and gross production (Pg) of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos) at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1), and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively). At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef communities is

  17. The Influence of Somalia and Oman Upwellings on the Indian Summer Monsoon

    Science.gov (United States)

    Izumo, T.; de Boyer Montégut, C.; Luo, J.; Behera, S. K.; Masson, S.; Yamagata, T.

    2006-12-01

    What controls the strength of the Indian summer monsoon is not well known yet. The Somalia and Oman upwellings peak during the summer monsoon and strongly cool the Sea Surface Temperature (SST) in the Western Arabian Sea. A slight change in their strength can thus have strong impacts on the SST and extent of the Indian ocean warm pool, which is the main source of moisture for the monsoon. Here the role of Somalia and Oman upwellings on the strength of the Indian monsoon is evidenced using both observations and the high resolution SINTEX-F Coupled Global Circulation Model (CGCM), which accurately simulates the monsoon. Within the CGCM, the spring increase and summer maximum of the Western Arabian Sea coastal upwellings are removed in a sensitivity experiment (SENS) by imposing over the Indian Ocean the mean windstress, instead of the temporally varying one of the control experiment (CTL). The ocean circulation becomes nearly stationnary. In summer, the main change in SST in SENS is a strong warming (up to 2°C) along the East African coast where coastal upwelling and off-shore horizontal advection of upwelled waters usually cool SST. This SST warming leads to a strong increase in the monsoon extent and strength along the West coast of India up to 5 mm/day (about 25% of CTL). The mechanism is as follow: in SENS, summer SST warming in the upwelling region causes anomalous evaporation, which increases specific humidity of the air masses going over the upwelling region. The humidity transport thus increases all over the Arabian sea towards the coastal Ghats mountains of India. This finally leads to enhanced moisture convergence and precipitations along the West coast of India. This role of coastal upwelling and associated SST variations on the Indian monsoon is confirmed by observations since 1980. Correlation analysis shows that enhanced summer precipitations on the West Indian coast are usually associated with warmer SST in summer East of Somalia-Oman and North

  18. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    Directory of Open Access Journals (Sweden)

    Corvin Eidens

    2014-09-01

    Full Text Available In Tayrona National Natural Park (Colombian Caribbean, abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn and gross production (Pg of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1, and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively. At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef

  19. Sporadic Groundwater Upwelling in Deep Martian Craters: Evidence for Lacustrine Clays and Carbonates

    Science.gov (United States)

    Michalski, J. R.; Rogers, A. D.; Wright, S. P.; Niles, P.; Cuadros, J.

    2012-01-01

    While the surface of Mars may have had an active hydrosphere early in its history [1], it is likely that this water retreated to the subsurface early on due to loss of the magnetic field and early atmosphere [2]. This likely resulted in the formation of two distinct aqueous regimes for Mars from the Late Noachian onward: one dominated by redistribution of surface ice and occasional melting of snow/ice [3], and one dominated by groundwater activity [4]. The excavation of alteration minerals from deep in the crust by impact craters points to an active, ancient, deep hydrothermal system [5]. Putative sapping features [6] may occur where the groundwater breached the surface. Upwelling groundwater may also have played a critical role in the formation of massive, layered, cemented sediments in Sinus Meridiani [7,8], in the Valles Marineris [9], and possibly in Gale Crater [10], where the Curiosity Rover will land later this year. Understanding the past distribution, geochemistry, and significance of groundwater on Mars is critical to untangling the origins of deep alteration minerals, Hesperian sulfate deposits, and crater fill deposits at Gale Crater or in other locations.

  20. Adaptive Sentence Boundary Disambiguation

    CERN Document Server

    Palmer, D D; Palmer, David D.; Hearst, Marti A.

    1994-01-01

    Labeling of sentence boundaries is a necessary prerequisite for many natural language processing tasks, including part-of-speech tagging and sentence alignment. End-of-sentence punctuation marks are ambiguous; to disambiguate them most systems use brittle, special-purpose regular expression grammars and exception rules. As an alternative, we have developed an efficient, trainable algorithm that uses a lexicon with part-of-speech probabilities and a feed-forward neural network. After training for less than one minute, the method correctly labels over 98.5\\% of sentence boundaries in a corpus of over 27,000 sentence-boundary marks. We show the method to be efficient and easily adaptable to different text genres, including single-case texts.

  1. Direct measurement of anisotropy of interfacial free energy from grain boundary groove morphology in transparent organic metal analong systems

    Energy Technology Data Exchange (ETDEWEB)

    Rustwick, Bryce A. [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    Both academia and industry alike have paid close attention to the mechanisms of microstructural selection during the solidification process. The forces that give rise to and the principles which rule the natural selection of particular morphologies are important to understanding and controlling new microstructures. Interfacial properties play a very crucial role to the selection of such microstructure formation. In the solidification of a metallic alloy, the solid-liquid interface is highly mobile and responds to very minute changes in the local conditions. At this interface, the driving force must be large enough to drive solute diffusion, maintain local curvature, and overcome the kinetic barrier to move the interface. Therefore, the anisotropy of interfacial free energy with respect to crystallographic orientation is has a significant influence on the solidification of metallic systems. Although it is generally accepted that the solid-liquid interfacial free energy and its associated anisotropy are highly important to the overall selection of morphology, the confident measurement of these particular quantities remains a challenge, and reported values are scarce. Methods for measurement of the interfacial free energy include nucleation experiments and grain boundary groove experiments. The predominant method used to determine anisotropy of interfacial energy has been equilibrium shape measurement. There have been numerous investigations involving grain boundaries at a solid-liquid interface. These studies indicated the GBG could be used to describe various interfacial energy values, which affect solidification. Early studies allowed for an estimate of interfacial energy with respect to the GBG energy, and finally absolute interfacial energy in a constant thermal gradient. These studies however, did not account for the anisotropic nature of the material at the GBG. Since interfacial energy is normally dependent on orientation of the crystallographic plane of the

  2. Variabilidad estacional de cadmio en un sistema de surgencia costera del norte de Chile (Bahía Mejillones del Sur, 23° S Seasonal variability of cadmium in a coastal upwelling system off northern Chile (Mejillones bay, 23° S

    Directory of Open Access Journals (Sweden)

    JORGE VALDÉS

    2006-12-01

    observada en esta razón pueden ser explicados ya sea por una mayor eficiencia en la remoción de PO4 que de Cadmio en las aguas superficiales o una mayor remineralización de cadmio en las aguas subsuperficialesTotal and dissolved cadmium were measured from surface to 100 m water depth, between June 2002 and April 2003, in Mejillones bay. Total and dissolved cadmium range concentration was 0.41-10.7 and 0.08-1.61 nM, respectively. Cadmium profiles and water structure were used to study seasonal variability patterns of this metal in this upwelling system. Oceanographic conditions during this period correspond to a normal (non-El Niño year. Water masses present in this bay correspond to subantartic superficial water, subtropical superficial water and Equatorial subsuperficial water with different degree of mixture and stratification during sampling period. Cadmium profiles showed a classic nutrient-type distribution. Whereas some differences in this profiles could be attributed to a water masses mixing condition into the bay. Multivariate analysis indicates that temporal cadmium variations were associated with chlorophyll-a concentration and temperature fluctuation, indicating that, at this temporal resolution, phytoplanktonic biomass production is the principal factor controlling cadmium concentration in surface waters of Mejillones bay. By other hand, in spite of cadmium being a redox-sensitive metal, any significant influence of dissolved oxygen on this metal were founded, thus microxic condition of bottom water of Mejillones bay is not the principal factor that promotes cadmium flux to the sediments. Cd/PO4 ratio is in agreement with normal values reported for the Chilean coast, and its low values, compared with the northeast Pacific coast, can be explained either by the fact that PO4 is more efficiently removed than cadmium from the surface layer, or that cadmium remineralization is occurring much faster than in the case of PO4

  3. Application of remotely piloted aircraft systems in observing the atmospheric boundary layer over Antarctic sea ice in winter

    Directory of Open Access Journals (Sweden)

    Marius O. Jonassen

    2015-10-01

    Full Text Available The main aim of this paper is to explore the potential of combining measurements from fixed- and rotary-wing remotely piloted aircraft systems (RPAS to complement data sets from radio soundings as well as ship and sea-ice-based instrumentation for atmospheric boundary layer (ABL profiling. This study represents a proof-of-concept of RPAS observations in the Antarctic sea-ice zone. We present first results from the RV Polarstern Antarctic winter expedition in the Weddell Sea in June–August 2013, during which three RPAS were operated to measure temperature, humidity and wind; a fixed-wing small unmanned meteorological observer (SUMO, a fixed-wing meteorological mini-aerial vehicle, and an advanced mission and operation research quadcopter. A total of 86 RPAS flights showed a strongly varying ABL structure ranging from slightly unstable temperature stratification near the surface to conditions with strong surface-based temperature inversions. The RPAS observations supplement the regular upper air soundings and standard meteorological measurements made during the campaign. The SUMO and quadcopter temperature profiles agree very well and, excluding cases with strong temperature inversions, 70% of the variance in the difference between the SUMO and quadcopter temperature profiles can be explained by natural, temporal, temperature fluctuations. Strong temperature inversions cause the largest differences, which are induced by SUMO's high climb rates and slow sensor response. Under such conditions, the quadcopter, with its slower climb rate and faster sensor, is very useful in obtaining accurate temperature profiles in the lowest 100 m above the sea ice.

  4. Breaking Boundaries

    DEFF Research Database (Denmark)

    produce desperate attempts to maintain old or create new differences. Political and sociological research into these complex processes has been mainly guided by structural and normative concerns. Faced with growing evidence about the instability of world order and domestic social structures alike, policy....... As a fundamental human experience, liminality transmits cultural practices, codes, rituals, and meanings in-between aggregate structures and uncertain outcomes. As a methodological tool it is well placed to overcome disciplinary boundaries, which often direct attention to specific structures or sectors of society....... Its capacity to provide explanatory accounts of seemingly unstructured situations provides an opportunity to link experience-based and culture-oriented approaches not only to contemporary problems but also to undertake comparisons across historical periods. From a perspective of liminality...

  5. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea.

    Science.gov (United States)

    Kok, Poh Heng; Mohd Akhir, Mohd Fadzil; Tangang, Fredolin; Husain, Mohd Lokman

    2017-01-01

    This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM) is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW) indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST) was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast.

  6. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea.

    Directory of Open Access Journals (Sweden)

    Poh Heng Kok

    Full Text Available This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast.

  7. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea

    Science.gov (United States)

    Mohd Akhir, Mohd Fadzil; Tangang, Fredolin; Husain, Mohd Lokman

    2017-01-01

    This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM) is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW) indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST) was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast. PMID:28187215

  8. El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

    Science.gov (United States)

    Arntz, W. E.; Gallardo, V. A.; Gutiérrez, D.; Isla, E.; Levin, L. A.; Mendo, J.; Neira, C.; Rowe, G. T.; Tarazona, J.; Wolff, M.

    2006-03-01

    To a certain degree, Eastern Boundary Current (EBC) ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O2 exchange is restricted, it creates oxygen minimum zones (OMZs) at shelf and upper slope (Humboldt and Benguela Current) or slope depths (California Current). These hypoxic zones host a specifically adapted, small macro- and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H2S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between nutrient-rich bottom water. During warm (El Niño) episodes, warm water masses of low oxygen concentration from oceanic and equatorial regions enter the upwelling zones, bringing a variety of (sub)tropical immigrants. The autochthonous benthic fauna emigrates to deeper water or poleward, or suffers mortality. However, some local macrofaunal species experience important population proliferations, presumably due to improved oxygenation (in the southern hemisphere), higher temperature tolerance, reduced competition or the capability to use different food. Both these negative and positive effects of El Niño influence local artisanal fisheries and the livelihood of coastal populations. In the Humboldt Current system the hypoxic seafloor at outer shelf depths receives important flushing from the equatorial zone, causing havoc on the sulphur bacteria mats and immediate recolonisation of the sediments by mega- and macrofauna. Conversely, off California, the intruding

  9. Gradients in microbial methanol uptake: productive coastal upwelling waters to oligotrophic gyres in the Atlantic Ocean

    Science.gov (United States)

    Dixon, Joanna L; Sargeant, Stephanie; Nightingale, Philip D; Colin Murrell, J

    2013-01-01

    Methanol biogeochemistry and its importance as a carbon source in seawater is relatively unexplored. We report the first microbial methanol carbon assimilation rates (k) in productive coastal upwelling waters of up to 0.117±0.002 d−1 (∼10 nmol l−1 d−1). On average, coastal upwelling waters were 11 times greater than open ocean northern temperate (NT) waters, eight times greater than gyre waters and four times greater than equatorial upwelling (EU) waters; suggesting that all upwelling waters upon reaching the surface (⩽20 m), contain a microbial population that uses a relatively high amount of carbon (0.3–10 nmol l−1 d−1), derived from methanol, to support their growth. In open ocean Atlantic regions, microbial uptake of methanol into biomass was significantly lower, ranging between 0.04–0.68 nmol l−1 d−1. Microbes in the Mauritanian coastal upwelling used up to 57% of the total methanol for assimilation of the carbon into cells, compared with an average of 12% in the EU, and 1% in NT and gyre waters. Several methylotrophic bacterial species were identified from open ocean Atlantic waters using PCR amplification of mxaF encoding methanol dehydrogenase, the key enzyme in bacterial methanol oxidation. These included Methylophaga sp., Burkholderiales sp., Methylococcaceae sp., Ancylobacter aquaticus, Paracoccus denitrificans, Methylophilus methylotrophus, Methylobacterium oryzae, Hyphomicrobium sp. and Methylosulfonomonas methylovora. Statistically significant correlations for upwelling waters between methanol uptake into cells and both chlorophyll a concentrations and methanol oxidation rates suggest that remotely sensed chlorophyll a images, in these productive areas, could be used to derive total methanol biological loss rates, a useful tool for atmospheric and marine climatically active gas modellers, and air–sea exchange scientists. PMID:23178665

  10. Plume-subduction interaction in southern Central America: Mantle upwelling and slab melting

    Science.gov (United States)

    Gazel, Esteban; Hoernle, Kaj; Carr, Michael J.; Herzberg, Claude; Saginor, Ian; den Bogaard, Paul van; Hauff, Folkmar; Feigenson, Mark; Swisher, Carl

    2011-01-01

    The volcanic front in southern Central America is well known for its Galapagos OIB-like geochemical signature. A comprehensive set of geochemical, isotopic and geochronological data collected on volumetrically minor alkaline basalts and adakites were used to better constrain the mantle and subduction magma components and to test the different models that explain this OIB signature in an arc setting. We report a migration of back-arc alkaline volcanism towards the northwest, consistent with arc-parallel mantle flow models, and a migration towards the southeast in the adakites possibly tracking the eastward movement of the triple junction where the Panama Fracture Zone intersects the Middle America Trench. The adakites major and trace element compositions are consistent with magmas produced by melting a mantle-wedge source metasomatized by slab derived melts. The alkaline magmas are restricted to areas that have no seismic evidence of a subducting slab. The geochemical signature of the alkaline magmas is mostly controlled by upwelling asthenosphere with minor contributions from subduction components. Mantle potential temperatures calculated from the alkaline basalt primary magmas increased from close to ambient mantle (~ 1380-1410 °C) in the Pliocene to ~ 1450 °C in the younger units. The calculated initial melting pressures for these primary magmas are in the garnet stability field (3.0-2.7 GPa). The average final melting pressures range between 2.7 and 2.5 GPa, which is interpreted as the lithosphere-asthenosphere boundary at ~ 85-90 km. We provide a geotectonic model that integrates the diverse observations presented here. The slab detached after the collision of the Galapagos tracks with the arc (~ 10-8 Ma). The detachment allowed hotter asthenosphere to flow into the mantle wedge. This influx of hotter asthenosphere explains the increase in mantle potential temperatures, the northwest migration in the back-arc alkaline lavas that tracks the passage of the

  11. Distribution of upwelling index planktonic foraminifera in the sediments of the western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    d'UllC zone d'upwelling, marge continentale de I'Indc I Les foraminifcrcs planctoniques. radiolaires. carhonates et Ie carhone organique. ont etc analyses dans vingt et un cchantillons de sediments. La repartition de ces parame tres revcle que les... sediments contienncnt la signature d'un upwelling. L'ahondance relative des foraminitcres planctoniques, des radiolaires et les teneurs en carbonates et en c

  12. Larval fish assemblages across an upwelling front: Indication for active and passive retention

    Science.gov (United States)

    Tiedemann, Maik; Brehmer, Patrice

    2017-03-01

    In upwelling areas, enrichment, concentration and retention are physical processes that have major consequences for larval fish survival. While these processes generally increase larval survival, strong upwelling can also increase mortality due to an offshore transport of larvae towards unfavorable habitats. In 2013 a survey was conducted along the Senegalese coast to investigate the upwelling effect with regard to larval fish assemblages and possible larval fish retention. According to water column characteristics two distinct habitats during an upwelling event were discriminated, i.e. the inshore upwelled water and the transition area over the deepest part of the Senegalese shelf. Along the two areas 42,162 fish larvae were collected representing 133 species within 40 families. Highest larval fish abundances were observed in the inshore area and decreasing abundances towards the transition, indicating that certain fish species make use of the retentive function of the inner shelf area as spawning grounds. Two larval fish assemblages overlap both habitats, which are sharply delimited by a strong upwelling front. One assemblage inhabited the inshore/upwelling area characterized by majorly neritic and pelagic species (Sparidae spp., Sardinella aurita), that seem to take the advantage of a passive retention on the shelf. The second assemblage consisted of a mix of pelagic and mesopelagic species (Engraulis encrasicolus, Carangidae spp. and Myctophidae spp.). Some species of the second assemblage, e.g. horse mackerels (Trachurus trachurus and Trachurus trecae), large finned-lantern fish (Hygophum macrochir) and foureyed sole (Microchirus ocellatus), revealed larval peak occurrences at intermediate and deep water layers, where the near-ground upwelling layer is able to transport larvae back to the shelf. This indicates active larval retention for species that are dominant in the transition area. Diel vertical migration patterns of S. aurita, E. encrasicolus and M

  13. Coccolithophores in the upwelling waters of Portugal: Four years of weekly distribution in Lisbon bay

    Science.gov (United States)

    Silva, A.; Palma, S.; Moita, M. T.

    2008-10-01

    From July 2001 to May 2005, seawater samples were collected once a week at a fixed station in Lisbon bay (38°41'N, 09°24'W) in order to describe the ecological dynamics of the coccolithophore community. The seasonal and interannual distribution patterns of the different species and their relationships with environmental parameters are addressed. The present work aimed to identify potential proxies for different local water bodies and environmental conditions. Throughout the period of study, the upwelling events were weak and progressively more persistent. High sea surface temperatures (SST) were observed earlier in the year; summers and winters were gradually warmer and colder, respectively. Salinity variations reflected the different weather conditions as they are strongly influenced by rainfall and thus by the Tagus river flow. The extended periods of weak upwelling and the overall increase in SST resulted in the development of phytoplankton populations as measured by chlorophyll a. However, the persistence of the upwelling, and thus shorter convergence periods, favoured other phytoplankton groups than coccolithophore populations as these decreased towards the end of the sampling period. The annual structure of the coccolithophore assemblage showed a pronounced and recurrent seasonal variability, mainly related with the intensity and persistence of upwelling. The highest cell densities were recorded from spring to autumn. An overall preference by most species for mature upwelled waters and low turbulent conditions was observed associated with high temperatures and salinities, although the species develop in different windows with mismatching maxima. The coccolithophores observed were capable of withstanding coastal processes such as turbulence and were well adapted to an environment rich in nutrients provided by both continental runoff and upwelling. The consistency of the results enabled local oceanographic tracers to be defined. Emiliania huxleyi and

  14. Variaciones del sistema de surgencia de Punta Angamos (23 S y la Zona de Mínimo Oxígeno durante el pasado reciente: Una aproximación desde el registro sedimentario de la Bahía Mejillones del Sur Variations of Punta Angamos upwelling system (23 S and the Oxygen Minimum Zone during the recent past: An approximation from sedimentary record of Mejillones del Sur Bay

    Directory of Open Access Journals (Sweden)

    JORGE VALDÉS

    2003-09-01

    Full Text Available Parámetros geoquímicos (carbono orgánico, sílice biogénica y cadmio y petrográficos (materia orgánica estudiados en un testigo de sedimento de la Bahía Mejillones del Sur fueron utilizados para inferir variaciones en la productividad biológica superficial y la oxigenación subsuperficial durante los últimos 2.000 años. Este estudio demuestra que al interior de la bahía la productividad ha disminuido hacia el presente mientras que la Zona de Mínimo Oxígeno se ha intensificado. Se plantea que las variaciones de la productividad se deben a un desplazamiento del centro de surgencia de Punta Angamos, más cerca o más lejos de la bahía y/o a cambios en su intensidad asociados al régimen de vientos locales. Por su parte, la oxigenación estaría influenciada por el ascenso o descenso de la Zona de Mínimo Oxígeno presente en el área. Una correlación de estos resultados con estudios de bioindicadores realizados en otros testigos de la Bahía Mejillones permiten reforzar la hipótesis de que eventos como la Pequeña Edad del Hielo y el Episodio Cálido de la Edad Media han quedado registrados en esta bahía del norte de Chile. Según el presente estudio, el primer periodo estaría caracterizado por un aumento de la productividad superficial y un descenso en la oxigenación subsuperficial de la bahía, mientras que el segundo periodo presentaría características opuestas.Geochemical (organic carbon, biogenic silica and cadmium and petrographic (organic matter parameters analyzed in a sediment core of Mejillones del Sur Bay, have been used to reconstruct past variations in superficial biological productivity and subsuperficial oxygenation, during the last 2,000 years. This study tends to demonstrate that into the bay, the productivity has diminished up to the present, while the Oxygen Minimum Zone has intensified. Productivity variations can be attributed to changes in the upwelling intensity associated to changes in local wind system

  15. 75 FR 82362 - Nonfederal Oil and Gas Development Within the Boundaries of Units of the National Park System...

    Science.gov (United States)

    2010-12-30

    ... directional drilling operations sited on lands outside park boundaries. The existing regulations are not... drilling operations are regulated to retain incentives for operators to site operations outside of parks... operators, visitor experience and public safety, adjacent lands, and park operations will also be analyzed...

  16. Prediction of dislocation boundary characteristics

    DEFF Research Database (Denmark)

    Winther, Grethe

    Plastic deformation of both fcc and bcc metals of medium to high stacking fault energy is known to result in dislocation patterning in the form of cells and extended planar dislocation boundaries. The latter align with specific crystallographic planes, which depend on the crystallographic....... Crystal plasticity calculations combined with the hypothesis that these boundaries separate domains with local differences in the slip system activity are introduced to address precise prediction of the experimentally observed boundaries. The presentation will focus on two cases from fcc metals...... orientation of the grain [1]. For selected boundaries it has been experimentally verified that the boundaries consist of fairly regular networks of dislocations, which come from the active slip systems [2]. The networks have been analyzed within the framework of Low-Energy-Dislocation-Structures (LEDS...

  17. The Boundary Function Method. Fundamentals

    Science.gov (United States)

    Kot, V. A.

    2017-03-01

    The boundary function method is proposed for solving applied problems of mathematical physics in the region defined by a partial differential equation of the general form involving constant or variable coefficients with a Dirichlet, Neumann, or Robin boundary condition. In this method, the desired function is defined by a power polynomial, and a boundary function represented in the form of the desired function or its derivative at one of the boundary points is introduced. Different sequences of boundary equations have been set up with the use of differential operators. Systems of linear algebraic equations constructed on the basis of these sequences allow one to determine the coefficients of a power polynomial. Constitutive equations have been derived for initial boundary-value problems of all the main types. With these equations, an initial boundary-value problem is transformed into the Cauchy problem for the boundary function. The determination of the boundary function by its derivative with respect to the time coordinate completes the solution of the problem.

  18. Coastal upwelling fluxes of O2, N2O, and CO2 assessed from continuous atmospheric observations at Trinidad, California

    Directory of Open Access Journals (Sweden)

    T. J. Lueker

    2004-01-01

    Full Text Available Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed. Regional air-sea fluxes of O2/N2, N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.

  19. Development of upwelling on pathway and freshwater transport of Pearl River plume in northeastern South China Sea

    Science.gov (United States)

    Chen, Zhaoyun; Jiang, Yuwu; Liu, James T.; Gong, Wenping

    2017-08-01

    In situ observations, satellite images, and numerical modeling results have shown that the Pearl River plume axis extends alongshore and passes through two separate upwelling regions—one off the Guangdong and Fujian coasts (the Yuedong upwelling) and the other in the Taiwan Bank during the initial and medium stages of the Yuedong upwelling, while it is directed offshore when the Yuedong upwelling is strong. Model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the Pearl River plume. The baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern South China Sea. The freshwater transport flux is further decomposed into advection, vertical shear, and tidal pumping components, and advection is the dominant contributor. As the Yuedong upwelling develops, the zone with a relatively high-pressure gradient moves offshore due to offshore Ekman transport and the shift in the upwelling front, which is responsible for the offshore transport of the river plume. When the river plume is transported to the outer-shelf, sometimes it can be further entrained into eddies, allowing its export to the open sea.

  20. Examining coastal upwellings from a Lagrangian perspective in the Gulf of Finland, Baltic Sea

    Science.gov (United States)

    Delpeche-Ellmann, Nicole; Mingelaitė, Toma; Soomere, Tarmo

    2017-04-01

    This study examines from a Lagrangian perspective the impact that an upwelling event may have on mixing and the Lagrangian transport of surrounding surface waters. To accomplish this we employ in-situ surface drifters (that follow the currents in the uppermost layer with a thickness of 2 m), satellite derived sea surface temperature data (obtained from the MODIS Aqua satellite), and high-quality open sea wind time series. The study area is located near the southern coast of the Gulf of Finland where easterly winds are known to trigger intense coastal upwellings. The properties of mixing were evaluated using the daily rate of temperature change along several transects. Results show that unlike classical upwelling events that normally show cooler water hugging the coastline in a longitudinal direction, this upwelling event instead took the form of transverse jets that protruded as much as 40-45 km from the coastline at distinct locations. Interestingly, the surface drifters show that the presence of the upwelling event superseded classic Ekman-type drift of the surface layer and in effect slowed down the average speed of surface currents in the surrounding waters. It was discovered that intense and long-lasting upwelling events may contain three distinct stages, which was clearly influenced by the wind intensity: During the first stage (strong winds) the cooler water is brought to the surface. The second stage (strong winds) is characterized by the presence of coherent cooler water transverse jets that protrude some distance from the coast at two distinct locations and that lasted 5 days, during this stage very little mixing took place it was mainly the advection of colder water to the open sea. Whilst the third stage encompasses the presence of filaments/squirts and eventually the disintegration of these structures and intense mixing of upwelled and surrounding waters under weaker winds. Thus the upwelled cooler water largely kept its identity during almost the

  1. Spatial and Temporal Evolution of Rift Systems: Implication for the Nature, Kinematics and Timing of the Iberian-European Plate Boundary

    Science.gov (United States)

    Tugend, J.; Manatschal, G.; Kusznir, N. J.

    2014-12-01

    The mechanisms of continental lithosphere deformation that control the formation and evolution of rift systems leading to continental breakup and the creation of divergent plate boundaries represent a long-standing problem in tectonics. Studies conducted in present-day rifted margins and their onshore fossil analogues reveal variable crustal architecture emphasizing the complex spatial and temporal evolution of rift systems. The Bay of Biscay and Pyrenees, at the transition between the Iberian and European plates, correspond to a Late Jurassic to Mid Cretaceous rift system. The transition from preserved oceanic and rift domains to the West to their complete inversion in the East enables the investigation of seismically imaged, drilled and exposed parts of a rift system. We combine observations from seismic reflection data, gravity inversion results and field mapping to identify and map former rift domains from the Bay of Biscay margins to onshore fossil analogues preserved in the Pyrenean orogen. The results of this mapping emphasize the existence of spatially disconnected and strongly segmented rift systems preserved along the paleo Iberian-European plate boundary. Based on their restoration, subsidence and deformation history, we illustrate the evolution of strain partitioning between them and present the implications at the scale of the Iberian-European plate boundary. The deformation history suggested is more complex than previously assumed, highlighting the polyphased evolution of this plate boundary. We propose that the onset of the Late Jurassic to Early Cretaceous rifting was partitioned between a set of distinct left-lateral transtensional rift systems. A plate kinematic reorganization at Aptian-Albian time resulted in the onset of seafloor spreading in the Western Bay of Biscay and extreme crustal and lithosphere thinning in intra-continental rift basins to the east. Finally, the results of this work may provide insights on: (1) processes preceding break

  2. Fine-scale recognition and use of mesoscale fronts by foraging Cape gannets in the Benguela upwelling region

    Science.gov (United States)

    Sabarros, Philippe S.; Grémillet, David; Demarcq, Hervé; Moseley, Christina; Pichegru, Lorien; Mullers, Ralf H. E.; Stenseth, Nils C.; Machu, Eric

    2014-09-01

    Oceanic structures such as mesoscale fronts may become hotspots of biological activity through concentration and enrichment processes. These fronts generally attract fish and may therefore be targeted by marine top-predators. In the southern Benguela upwelling system, such fronts might be used as environmental cues by foraging seabirds. In this study we analyzed high-frequency foraging tracks (GPS, 1 s sampling) of Cape gannets Morus capensis from two colonies located on the west and east coast of South Africa in relation to mesoscale fronts detected on daily high-resolution chlorophyll-a maps (MODIS, 1 km). We tested the association of (i) searching behavior and (ii) diving activity of foraging birds with mesoscale fronts. We found that Cape gannets shift from transiting to area-restricted search mode (ARS) at a distance from fronts ranging between 2 and 11 km (median is 6.7 km). This suggests that Cape gannets may be able to sense fronts (smell or vision) or other predators, and that such detection triggers an intensified investigation of their surroundings (i.e. ARS). Also we found that diving probability increases near fronts in 11 out of 20 tracks investigated (55%), suggesting that Cape gannets substantially use fronts for feeding; in the remaining cases (45%), birds may have used other cues for feeding including fishing vessels, particularly for gannets breeding on the west coast. We demonstrated in this study that oceanographic structures such as mesoscale fronts are important environmental cues used by a foraging seabird within the rich waters of an upwelling system. There is now need for further investigations on how Cape gannets actually detect these fronts.

  3. Technology for Boundaries

    DEFF Research Database (Denmark)

    Bødker, Susanne; Kristensen, Jannie Friis; Nielsen, Christina

    2003-01-01

    This paper presents a study of an organisation, which is undergoing a process transforming organisational and technological boundaries. In particular, we shall look at three kinds of boundaries: the work to maintain and change the boundary between the organisation and its customers; boundaries.......After analysing the history and the current boundary work, the paper will propose new technological support for boundary work. In particular the paper will suggest means of supporting boundaries when these are productive and for changing boundaries when this seems more appropriate. In total, flexible technologies...... seem a core issue when dealing with technology for boundaries....

  4. Melt-peridotite reactions in upwelling EM1-type eclogite bodies

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin

    2013-01-01

    the Payenia volcanic province (34–38 °S) in Argentina, for which Sr, Nd and double-spike Pb isotope ratios are presented, and from other north Patagonian volcanic fields may provide details of the eclogite melt–peridotite reactions taking place in the melting column of an upwelling OIB-type mantle...

  5. Fish larvae retention linked to abrupt bathymetry at Mejillones Bay (northern Chile during coastal upwelling events

    Directory of Open Access Journals (Sweden)

    Pablo M Rojas

    2014-11-01

    Full Text Available The influence of oceanic circulation and bathymetry on the fish larvae retention inside Mejillones Bay, northern Chile, was examined. Fish larvae were collected during two coastal upwelling events in November 1999 and January 2000. An elevated fish larvae accumulation was found near an oceanic front and a zone of low-speed currents. Three groups of fish larvae were identified: the coastal species (Engraulis ringens and Sardinops sagax, associated with high chlorophyll-a levels; larvae from the families Phosichthyidae (Vinciguerria lucetia and Myctophidae (Diogenichthys laternatus and Triphoturus oculeus, associated with the thermocline (12°C, and finally, larvae of the families Myctophidae (Diogenichthys atlanticus and Bathylagidae (Bathylagus nigrigenys, associated with high values of temperature and salinity. The presence of a seamount and submarine canyon inside Mejillones Bay appears to play an important role in the circulation during seasonal upwelling events. We propose a conceptual model of circulation and particles retention into Mejillones Bay. The assumption is that during strong upwelling conditions the flows that move along the canyon emerge in the centre of Mejillones Bay, producing a fish larvae retention zone. Understanding the biophysical interactions responsible to trap and/or concentrate particles is essential to protect these fragile upwelling ecosystems.

  6. The "Rocket Experiment for Neutral Upwelling 2 (RENU2)" Sounding Rocket

    Science.gov (United States)

    Lessard, M.; Bekkeng, T. A.; Clausen, L. B. N.; Clemmons, J. H.; Crowley, G.; Ellingsen, P. G.; Fritz, B.; Harrington, M. I.; Hatch, S.; Hecht, J. H.; Hysell, D. L.; Kenward, D. R.; Labelle, J. W.; Lynch, K. A.; Moen, J.; Oksavik, K.; Otto, A.; Partamies, N.; Powell, S. P.; Sadler, B.; Sigernes, F.; Syrjäsuo, M.; Yeoman, T. K.

    2016-12-01

    Thermospheric upwelling has been known to exist since the earliestdays of the space program, when observers noted increased satellite dragassociated with solar activity. Scientists quickly attributed the upwelling toJoule heating effects, explaining that increased solar activity results inincreased Joule heating, which can couple energy to the ambient neutral gasesto cause the upwelling. Observations by the CHAMP satellite, however, haveshown that neutral upwelling often occurs on much smaller scales and is highlycorrelated with small-scale field-aligned currents in the vicinity of the cuspregion. Several theories have since been put forward that seek to explain thisphenomenon. Motivated by these competing theories and outfitted with acomprehensive suite of instruments, the RENU2 sounding rocket was launched intoa Poleward Moving Auroral Form (PMAF) in the cusp region on December 13, 2015.In this highly successful mission, instruments on the payload did, in fact,record neutral atomic oxygen above the payload at 350 km as it passed throughthe PMAF. In addition, signatures of N2+ ions also appeared above the PMAF,evidence of so-called "sunlit aurora". In this presentation, initial resultswill be presented from this mission and discussed in the context describedabove.

  7. Coastal upwelling ecosystems are known to be parts of the most ...

    African Journals Online (AJOL)

    spamer

    Spawning of the Peruvian anchoveta Engraulis ringens ... mixed layer off Peru in winter is taken into account, the speed of surface offshore drift is ..... LITERATURE CITED. BAKUN, A. 1973 — Coastal upwelling indices, west coast of. North America, 1946–71. NOAA tech. Rep. NMFS SSRF-. 671: 103 pp. BAKUN, A. 1978 ...

  8. Foraminiferal production and monsoonal upwelling in the Arabian sea: evidence from sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Curry, W.B.; Ostermann, D.R.; Guptha, M.V.S.; Ittekkot, V.

    of foraminifera increased in flux shortly after the advent of the southwest monsoon. G. bulloides increased its production rate by three orders of magnitude. The isotopic chemistry of G. ruber recorded the increase in monsoon upwelling by increasing its delta sup...

  9. On the upwelling off the Southern Tip and along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Smitha, B.R.; Sanjeevan, V.N.; VimalKumar, K.G.; Revichandran, C.

    ; the latter is forced by the longshore wind stress. Moderate to relatively intense upwelling occurs along the Kollam to Mangalore coast (9 degrees N to 13 degrees N) due to the combined action of the longshore wind stress, the coastally trapped Kelvin waves...

  10. Coastal upwelling along the southwest coast of India – ENSO modulation

    Directory of Open Access Journals (Sweden)

    K. Muni Krishna

    2008-06-01

    Full Text Available An index of El Niño Southern Oscillation (ENSO in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold ENSO events being associated with relaxation (intensification of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

  11. Separation of a coastal upwelling jet at Cape Blanco, Oregon, USA ...

    African Journals Online (AJOL)

    Current Profiler, satellite sea surface temperature maps and satellite-tracked surface drifters during three cruises: August 1994, May and August 1995. Results demonstrate that the baroclinic coastal upwelling jet (and associated front), which was over the shelf poleward of Cape Blanco in all three cruises, separates from the ...

  12. Observations and mechanisms of upwelling in the northern KwaZulu ...

    African Journals Online (AJOL)

    The 11-month inshore bottom-temperature record revealed five substantial upwelling events lasting 5–10 days each where temperatures decreased by about 7 °C to 17–18 °C. Satellite sea surface temperature data showed these events to coincide with cold-water plumes occupying the northern wedge of the ...

  13. An upwelling-induced retention area off Senegal: A mechanism to ...

    African Journals Online (AJOL)

    However, in areas such as Peru, Senegal and Côte d'Ivoire-Ghana, spawning and upwelling occur simultaneously. What are the mechanisms that allow such reproductive strategies to be successful? To attempt to answer this question, some environmental characteristics of the spawning ground of Sardinella aurita in the ...

  14. Spanning maternal, newborn and child health (MNCH) and health systems research boundaries: conducive and limiting health systems factors to improving MNCH outcomes in West Africa.

    Science.gov (United States)

    Agyepong, Irene Akua; Kwamie, Aku; Frimpong, Edith; Defor, Selina; Ibrahim, Abdallah; Aryeetey, Genevieve C; Lokossou, Virgil; Sombie, Issiaka

    2017-07-12

    interventions is needed. This requires multi-level, multi-sectoral and multi-stakeholder engagement approaches that span current geographical, language, research and practice community boundaries in West Africa, and effectively link the efforts of actors interested in health systems strengthening with those of actors interested in MNCH outcome improvement.

  15. Multiple Positive Solutions to Multipoint Boundary Value Problem for a System of Second-Order Nonlinear Semipositone Differential Equations on Time Scales

    Directory of Open Access Journals (Sweden)

    Gang Wu

    2013-01-01

    Full Text Available We study a system of second-order dynamic equations on time scales (p1u1∇Δ(t-q1(tu1(t+λf1(t,u1(t,u2(t=0,t∈(t1,tn,(p2u2∇Δ(t-q2(tu2(t+λf2(t,u1(t, u2(t=0, satisfying four kinds of different multipoint boundary value conditions, fi is continuous and semipositone. We derive an interval of λ such that any λ lying in this interval, the semipositone coupled boundary value problem has multiple positive solutions. The arguments are based upon fixed-point theorems in a cone.

  16. Land Boundary Conditions for the Goddard Earth Observing System Model Version 5 (GEOS-5) Climate Modeling System: Recent Updates and Data File Descriptions

    Science.gov (United States)

    Mahanama, Sarith P.; Koster, Randal D.; Walker, Gregory K.; Takacs, Lawrence L.; Reichle, Rolf H.; De Lannoy, Gabrielle; Liu, Qing; Zhao, Bin; Suarez, Max J.

    2015-01-01

    The Earths land surface boundary conditions in the Goddard Earth Observing System version 5 (GEOS-5) modeling system were updated using recent high spatial and temporal resolution global data products. The updates include: (i) construction of a global 10-arcsec land-ocean lakes-ice mask; (ii) incorporation of a 10-arcsec Globcover 2009 land cover dataset; (iii) implementation of Level 12 Pfafstetter hydrologic catchments; (iv) use of hybridized SRTM global topography data; (v) construction of the HWSDv1.21-STATSGO2 merged global 30 arc second soil mineral and carbon data in conjunction with a highly-refined soil classification system; (vi) production of diffuse visible and near-infrared 8-day MODIS albedo climatologies at 30-arcsec from the period 2001-2011; and (vii) production of the GEOLAND2 and MODIS merged 8-day LAI climatology at 30-arcsec for GEOS-5. The global data sets were preprocessed and used to construct global raster data files for the software (mkCatchParam) that computes parameters on catchment-tiles for various atmospheric grids. The updates also include a few bug fixes in mkCatchParam, as well as changes (improvements in algorithms, etc.) to mkCatchParam that allow it to produce tile-space parameters efficiently for high resolution AGCM grids. The update process also includes the construction of data files describing the vegetation type fractions, soil background albedo, nitrogen deposition and mean annual 2m air temperature to be used with the future Catchment CN model and the global stream channel network to be used with the future global runoff routing model. This report provides detailed descriptions of the data production process and data file format of each updated data set.

  17. Distribution of 226Ra Radionuclide in Upwelling Event Off Ulsan, Gampo and Pohang, Korea

    Directory of Open Access Journals (Sweden)

    Muslim

    2009-07-01

    Full Text Available Upwelling is an important event in the sea for it makes the area to become more productive. The objective of this study is to determine the distribution of radium-226 as radiotoxic in the upwelling area in the summer season. Measurements of the horizontal and vertical activities of 226Ra in the Ulsan, Gampo and Pohang waters were conducted in June, August 1999 and June 2000 when the upwelling event was expected to occur. Water temperature, salinity and dissolved oxygen (DO were also measured concurrently. The thermocline layer or the layer where the temperature decreased drastically occurred at a depth between 30 m to 100 m for samples dated June 1999 and 30 m to more than 100 m for samples dated August 1999 and June 2000. The salinity decreased with depth but the DO concentration increased in this layer. The condition affected the vertical distribution of 226Ra in the study area, where the 226Ra activities showed to be relatively homogeneous vertically in each station. This indicates that the upwelling which occurred in the study area was capable to distribute the 226Ra activities from the bottom to the surface. Thus, the 226Ra distribution at that time did not increase with depth, opposite to what usually occurs in the ocean at normal condition. The 226Ra activities also did not decrease after elapsed time of one year, in fact, it increased. However, horizontally the 226Ra activities decreased with increasing distance from the coastal zone. Based on these results, it can be concluded that the upwelling event in the Ulsan, Gampo and Pohang was effective for increasing the 226Ra activities and was capable to create homogeneous 226Ra activities from the bottom to the surface in the water column, and the source of 226Ra was likely to originate from outside area (i.e. coastal zone and bottom area.

  18. Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Gouveia, A.D.; Michael, G.S.; Sundar, D.; Nampoothiri, G.

    mechanism that can provide this is the interaction between the lighter, fresher surface waters and the coast. Laboratory experiments by STERN et al. (1982) showed that when light rotating fluid spreads over heavier fluid in the vicinity of a vertical wall..., A. M. ALMEIDA and K. SANTANAM (1990) Hydrography and circulation off the west coast of India during the Southwest monsoon 1987. Journal of Marine Research, 48, 359-378. STERN M. E., J. A. WHITEHEAD and BACH-LIEN HUA (1982) Intrusion of a density...

  19. Impact of recently upwelled water on productivity investigated using in situ and incubation-based methods in Monterey Bay

    Science.gov (United States)

    Manning, Cara C.; Stanley, Rachel H. R.; Nicholson, David P.; Smith, Jason M.; Timothy Pennington, J.; Fewings, Melanie R.; Squibb, Michael E.; Chavez, Francisco P.

    2017-03-01

    Photosynthetic conversion of CO2 to organic carbon and the transport of this carbon from the surface to the deep ocean is an important regulator of atmospheric CO2. To understand the controls on carbon fluxes in a productive region impacted by upwelling, we measured biological productivity via multiple methods during a cruise in Monterey Bay, California. We quantified net community production and gross primary production from measurements of O2/Ar and O2 triple isotopes (17Δ), respectively. We simultaneously conducted incubations measuring the uptake of 14C, 15NO3-, and 15NH4+, and nitrification, and deployed sediment traps. At the start of the cruise (Phase 1) the carbon cycle was at steady state and the estimated net community production was 35(10) and 35(8) mmol C m-2 d-1 from O2/Ar and 15N incubations, respectively, a remarkably good agreement. During Phase 1, net primary production was 96(27) mmol C m-2 d-1 from C uptake, and gross primary production was 209(17) mmol C m-2 d-1 from 17Δ. Later in the cruise (Phase 2), recently upwelled water with higher nutrient concentrations entered the study area, causing 14C and 15NO3- uptake to increase substantially. Continuous O2/Ar measurements revealed submesoscale variability in water mass structure and likely productivity in Phase 2 that was not evident from the incubations. These data demonstrate that O2/Ar and 15N incubation-based NCP estimates can give equivalent results in an N-limited, coastal system, when the nonsteady state O2 fluxes are negligible or can be quantified.

  20. Imaging a Fault Boundary System Using Controlled-Source Data Recorded on a Large-N Seismic Array

    Science.gov (United States)

    Paschall, O. C.; Chen, T.; Snelson, C. M.; Ralston, M. D.; Rowe, C. A.

    2016-12-01

    The Source Physics Experiment (SPE) is a series of chemical explosions conducted in southern Nevada with an objective of improving nuclear explosion monitoring. Five chemical explosions have occurred thus far in granite, the most recent being SPE-5 on April 26, 2016. The SPE series will improve our understanding of seismic wave propagation (primarily S-waves) due to explosions, and allow better discrimination of background seismicity such as earthquakes and explosions. The Large-N portion of the project consists of 996 receiver stations. Half of the stations were vertical component and the other half were three-component geophones. All receivers were deployed for 30 days and recorded the SPE-5 shot, earthquakes, noise, and an additional controlled-source: a large weight-drop, which is a 13,000 kg modified industrial pile driver. In this study, we undertake reflection processing of waveforms from the weight-drop, as recorded by a line of sensors extracted from the Large-N array. The profile is 1.2 km in length with 25 m station spacing and 100 m shot point spacing. This profile crosses the Boundary Fault that separates granite body and an alluvium basin, a strong acoustic impedance boundary that scatters seismic energy into S-waves and coda. The data were processed with traditional seismic reflection processing methods that include filtering, deconvolution, and stacking. The stack will be used to extract the location of the splays of the Boundary Fault and provide geologic constraints to the modeling and simulation teams within the SPE project.