WorldWideScience

Sample records for boundary upwelling systems

  1. A comparative study of biological production in eastern boundary upwelling systems using an artificial neural network

    OpenAIRE

    Z. Lachkar; Gruber, N.

    2012-01-01

    Eastern Boundary Upwelling Systems (EBUS) are highly productive ocean regions. Yet, substantial differences in net primary production (NPP) exist within and between these systems for reasons that are still not fully understood. Here, we explore the leading physical processes and environmental factors controlling NPP in EBUS through a comparative study of the California, Canary, Benguela, and Humboldt Current systems. The NPP drivers are identified with the aid of an artifici...

  2. A comparative study of biological production in eastern boundary upwelling systems using an artificial neural network

    OpenAIRE

    Z. Lachkar; Gruber, N.

    2011-01-01

    Eastern Boundary Upwelling Systems (EBUS) are highly productive ocean regions. Yet, substantial differences in net primary production (NPP) exist within and between these systems for reasons that are still not fully understood. Here, we explore the leading physical processes and environmental factors controlling NPP in EBUS through a comparative study of the California, Canary, Benguela, and Humboldt Current systems. The identification of NPP drivers is done with the aid of an artificial neur...

  3. A comparative study of biological production in eastern boundary upwelling systems using an artificial neural network

    Science.gov (United States)

    Lachkar, Z.; Gruber, N.

    2012-01-01

    Eastern Boundary Upwelling Systems (EBUS) are highly productive ocean regions. Yet, substantial differences in net primary production (NPP) exist within and between these systems for reasons that are still not fully understood. Here, we explore the leading physical processes and environmental factors controlling NPP in EBUS through a comparative study of the California, Canary, Benguela, and Humboldt Current systems. The NPP drivers are identified with the aid of an artificial neural network analysis based on self-organizing-maps (SOM). Our results suggest that in addition to the expected NPP enhancing effect of stronger equatorward alongshore wind, three factors have an inhibiting effect: (1) strong eddy activity, (2) narrow continental shelf, and (3) deep mixed layer. The co-variability of these 4 drivers defines in the context of the SOM a continuum of 100 patterns of NPP regimes in EBUS. These are grouped into 4 distinct classes using a Hierarchical Agglomerative Clustering (HAC) method. Our objective classification of EBUS reveals important variations of NPP regimes within each of the four EBUS, particularly in the Canary and Benguela Current systems. Our results show that the Atlantic EBUS are generally more productive and more sensitive to upwelling favorable winds because of weaker factors inhibiting NPP. Perturbations of alongshore winds associated with climate change may therefore lead to contrasting biological responses in the Atlantic and the Pacific EBUS.

  4. A comparative study of biological production in eastern boundary upwelling systems using an artificial neural network

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-10-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are highly productive ocean regions. Yet, substantial differences in net primary production (NPP exist within and between these systems for reasons that are still not fully understood. Here, we explore the leading physical processes and environmental factors controlling NPP in EBUS through a comparative study of the California, Canary, Benguela, and Humboldt Current systems. The identification of NPP drivers is done with the aid of an artificial neural network analysis based on self-organizing-maps (SOMs. We show that in addition to the expected NPP enhancing effect of stronger alongshore wind, three factors have an inhibiting effect: (1 strong eddy activity, (2 narrow continental shelf, and (3 deep mixed layer. The co-variability of these 4 drivers defines in the context of the SOM a continuum of 100 patterns of NPP regimes in EBUS. These are grouped into 4 distinct classes using a Hierarchical Agglomerative Clustering (HAC method. Our objective classification of EBUS reveals important variations of NPP regimes within each of the four EBUS, particularly in the Canary and Benguela Current systems. Our results show that the Atlantic EBUS are generally more productive and more sensitive to upwelling favorable winds because of a weaker factors inhibiting NPP. Perturbations of alongshore winds associated with climate change may therefore lead to contrasting biological responses in the Atlantic and the Pacific EBUS.

  5. 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.

  6. Ocean-Atmosphere-Land interactions and their consequences on the biogeochemical variability in Eastern Boundary Upwelling System

    Science.gov (United States)

    Renault, L.; McWilliams, J. C.; Deutsch, C.; Molemaker, M. J.

    2015-12-01

    Coastal winds and upwelling of deep water along Eastern Boundary Upwelling System (EBUS) yield some of the ocean's most productive ecosystems, but the effect of coastal wind shape and ocean-atmosphere interactions on regional Net Primary Production (NPP) is not well known. Here, we first show how the spatial and temporal variability of nearshore winds in EBUS is affected by orography, coastline shape, and air-sea interaction. Using regional atmospheric simulations over the US West Coast, we determine monthly characteristics of the wind drop-off, and show that when the mountain orography is combined with the coastline shape of a cape, it has the biggest influence on wind drop-off. Then, using a realistic ocean model of the California Current System, we show that the slackening of the winds near the coast has little effect on near-shore phytoplankton productivity, despite a large reduction in upwelling velocity. On a regional scale, the wind drop-off leads to a substantially higher NPP, especially when it occurs over a broad swath, even when the total upwelling rate remains the same. This partial decoupling of NPP from upwelling is effected by alongshore currents and the eddies they generate. When peak winds extend all the way to the coast, alongshore current shear is stronger, and a more energetic eddy field subducts nutrients offshore and out of the photic zone, reducing overall productivity. This causal sequence is supported by satellite remote sensing. Finally, using a interanual coupled simulation over the US West Coast, we show the ocean-atmosphere interactions can also reduce the eddy activity by pumping energy out from the eddies, reducing their amplitude and rotation speed, and leading to more realistic eddies characteristics. This may also reduce the eddy quenching and therefore increase the NPP. This complex ocean-atmosphere-land interactions imply that simple wind indices are incomplete predictors of productivity in EBUS.

  7. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    Directory of Open Access Journals (Sweden)

    E. Gutknecht

    2013-06-01

    Full Text Available The Eastern Boundary Upwelling Systems (EBUS contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs, EBUS represent key regions for the oceanic nitrogen (N cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen

  8. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2012-10-01

    Full Text Available The Eastern Boundary Upwelling Systems (EBUS contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs, EBUS represent key regions for the oceanic nitrogen (N cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial, due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (Northern Benguela using the high-resolution hydrodynamical model ROMS. We present here a validation using in situ and satellite data as well as diagnostic metrics, and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate and Chl a concentrations, and the rates of microbial processes (e.g. NH4+ and NO2− oxidation, NO3− reduction and anammox as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking and nitrification play a key role for the low-oxygen water content, N loss and N2O concentrations in the OMZ. Moreover, the importance of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is highlighted to improve the representation of microbial activity linked with OMZ. The simulated minimum oxygen concentrations are driven by the

  9. Nitrogen dynamics in a Western Boundary Upwelling System (Cabo Frio, Brazil) based on δ15N-nitrate and δ15N of sinking particle signals

    Science.gov (United States)

    Fontana, L.; Belem, A. L.; Venancio, I.; Duarte, C.; Chiara, S. D.; Albuquerque, A. L.

    2014-12-01

    To improve the efficiency of upwelling to control nitrogen dynamic in the ocean, better understanding of the occurring processes is necessary. This research explores δ15N of nitrate and sinking particles on a western boundary upwelling System (Cabo Frio, Brazil). The Continental Shelf of southeastern Brazil is dominated by the oligotrophic Brazil Current, whose instabilities promote the coastal upwelling of South Atlantic Central Water (SACW), and consequently increases of primary productivity. The coastal upwelling system plays an important role in the nitrogen dynamics on the Cabo Frio Upwelling System (CFUS). However, the interactions between biological induced processes, including biological N-fixation and nitrate inputs from upwelled waters in CFUS still have not been well explored. Then, this study aims clarify N-dynamics on CFUS based on a cross-shelf approach. δ15N-nitrate was characterized for each water masses present on the shelf (South Atlantic Central Water, Tropical Water and Coastal Water) and associated with physicochemical parameters (T/S, nutrients), as well as the δ15N of sinking particles at different depths (from surface to the bottom water). Samples were collected in a time interval of 1 month during ~4 years (2011 to 2014). Cross-shelf gradients of nitrogen species concentration (ammonium + nitrite + nitrate) and stable isotopes were observed. The δ15N of nitrate and sinking particles were interpreted according to the prevailing processes of the N-transformations. Considering the region as N-limited (N:P global average of deep ocean (5-6‰) characterizing the inner and mid-shelf conditions, where the input of new nitrate from upwelling is rapidly used by organisms in the euphotic zone without any fractionation. On the other hands, the dominance of N-limited Tropical Waters on the outer shelf provide a δ15N-nitrate and δ15N-sinking particles signals (-2.0 to 3.0‰) lower than the global average of deep ocean range indicating the

  10. Eastern Boundary Upwelling Ecosystems: Review and Observing Needs

    Science.gov (United States)

    Chavez, F.; Garçon, V. C.; Dewitte, B.; Montes, I.

    2015-12-01

    Eastern Boundary Upwelling Systems (EBUS) cover less than 3% of the world ocean surface but play a significant role in the climate system, and contribute disproportionately to ocean biological productivity with up to 40% of the reported global fish catch. Coupled with the vast coastal human populations, these regions play key socio-economic roles. Human pressure on these productive ecosystems and their services is increasing, requiring new and evolving scientific approaches to collect information and use it in management. Here we review and compare the physical, chemical and biological characteristics of the four major EBUS: Benguela, California, Northwest Africa and Peru/Chile. Long-term trends and climate variability are emphasized. Technologies and systems for observing and understanding the changing marine ecosystems of EBUS are discussed.

  11. Retention controls on-shelf hypoxia in coastal upwelling systems

    Science.gov (United States)

    Harrison, C. S.; Long, M. C.; Hales, B. R.; Siedlecki, S. A.; Samelson, R. M.

    2015-12-01

    A maximally simple, coupled physical-biogeochemical box model is used to examine interactions controlling seasonal hypoxia over the continental shelf in an idealized Eastern Boundary upwelling system (EBUS). On-shelf bottom oxygen drawdown is controlled by the balance between flushing with offshore source waters and the degree to which surface particulate organic carbon (POC) production and its subsequent sinking and respiration are retained over the shelf and focused on the bottom. In the model, POC production is controlled by wind-driven upwelling of a generic nutrient to the surface, balanced by respiration and sinking. The degree to which this production occurs over shelf is a balance between the net POC growth rate η, and the upwelling driven shelf flushing rate λ, equivalent to the Ekman upwelling index scaled by the shelf width and surface layer depth. Initial oxygen drawdown follows this exponential rate of surface POC accumulation over shelf (α=η-λ), and so is slower for rapid upwelling (large λ) or nutrient limited conditions (small η). Retention efficiency indicates that up to 40% or more of upwelled nutrients can be retained over the shelf and contribute to oxygen drawdown. Fluctuations in the amplitude of the upwelling forcing can systematically reduce the potential for oxygen depletion below these estimates, especially when surface sinking export is rapid or forcing is strong.

  12. What controls biological production in coastal upwelling systems? Insights from a comparative modeling study

    OpenAIRE

    Z. Lachkar; Gruber, N.

    2011-01-01

    The magnitude of net primary production (NPP) in Eastern Boundary Upwelling Systems (EBUS) is traditionally viewed as directly reflecting the wind-driven upwelling intensity. Yet, different EBUS show different sensitivities of NPP to upwelling-favorable winds (Carr and Kearns, 2003). Here, using a comparative modeling study of the California Current System (California CS) and Canary Current System (Canary CS), we show how physical and environmental factors, such as light,...

  13. What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

    OpenAIRE

    Z. Lachkar; Gruber, N.

    2011-01-01

    The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS) is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003). Here, using a comparative modeling study of the California Current System (California CS) and Canary Current System (Canary CS), we show how physical and environmental factors, such as light, temperature and c...

  14. Upwelling processes along a western boundary current in the Abrolhos-Campos region of Brazil

    Science.gov (United States)

    Aguiar, A. L.; Cirano, M.; Pereira, J.; Marta-Almeida, M.

    2014-08-01

    Upwelling events observed from the years 2003 to 2011 were analyzed. Our focus was on the Abrolhos-Campos region (ACR, 15°S-23°S), which is located along the Brazilian Margin and influenced by a western boundary current, the Brazil Current (BC). Satellite sea surface temperature, National Centers for Environmental Prediction (NCEP) and Global Forecast System (GFS) wind data were used to complement the results of a high-resolution regional oceanic model to investigate the occurrence of and the mechanisms responsible for intense upwelling events in this region. These events were more frequent from 20°S to 23°S. Over 90% of the identified upwelling events were influenced by favorable wind stress. Surface Ekman transport was found to be more important for the region from Prado (17°S) to Marataízes (21°S), whereas upward Ekman pumping played a more important role from 22°S to 23°S. Current-driven upwelling processes associated with the location of the BC as well as its velocity and meso-scale activity were also analyzed. The results showed that these mechanisms are highly influenced by the local topography. Topographic effects exerted via the acceleration of the BC are more obvious in the southern ACR, while in the Prado region, BC cyclonic meanders tend to be more relevant. Moreover, eddy-driven upwelling increases in the southward direction after the passage of the Vitória-Trindade Ridge (20°S), an important submarine chain, which acts to constrain and modulate the southward flow of the BC.

  15. Behaviorally Mediated Larval Transport in Upwelling Systems

    OpenAIRE

    Morgan, Steven G.

    2014-01-01

    Highly advective upwelling systems along the western margins of continents are widely believed to transport larvae far offshore in surface currents resulting in larval wastage, limited recruitment, and increased population connectivity. However, suites of larval behaviors effectively mediate interspecific differences in the extent of cross-shelf migrations between nearshore adult habitats and offshore larval habitats. Interspecific differences in behavior determining whether larvae complete d...

  16. Controls on Primary Productivity and its Measurement in Coastal Upwelling Systems

    OpenAIRE

    Jacox, Michael

    2012-01-01

    Eastern Boundary Current systems, running along the west coasts of Africa and the Americas, are among the most biologically productive oceanic ecosystems. Their disproportionately large contributions to global marine primary productivity (photosynthesis) and fish catch are supported by upwelling of deep, nutrient rich water, a process driven by the interaction of surface winds and Earth's rotation. Upwelling in these systems may be forced by two mechanisms: equatorward winds at the coastal bo...

  17. Modelling the impact of Baltic Sea upwelling on the atmospheric boundary layer

    OpenAIRE

    Sproson, David; Sahlée, Erik

    2014-01-01

    Coastal upwelling, with a strong sea-surface temperature (SST) signal, is extremely common in the Baltic Sea during the summer months. Although the spatial scale of upwelling is small, its high frequency of occurrence in the semi-enclosed basin may allow the SST signature to have significant feedback onto the lower atmosphere. In this paper, we develop a method to remove the signature of upwelling from SST fields, and use these modified SST fields as the lower boundary condition of an atmosph...

  18. Lithostratigraphic Summary For Leg 175: Angola-Benguela Upwelling System

    OpenAIRE

    Anderson, L; Maslin, M.A.; Jansen, F.; H. Lin; Pufahl, P.K.; Pérez, M.; Brüchert, V.; Vidal, L.

    1998-01-01

    During Ocean Drilling Program Leg 175, 40 holes were drilled at 13 sites, and 8003 m were recovered with the aim of reconstructing the late Neogene history of the Angola-Benguela upwelling system on the southwest African margin. This system is one of the great upwelling regions of the world and is characterized by organic-rich sediments that provide an excellent record of productivity back to the middle Miocene. Understanding the sedimentology and stratigraphy of these sediments will...

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

    OpenAIRE

    Hassan Ebrahiem Ismail; Johannes Jacobus Agenbag; Stephanie de Villiers; Bhekumusa Jabulani Ximba

    2015-01-01

    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 ch...

  20. Poleward displacement of coastal upwelling-favorable winds in the ocean's eastern boundary currents through the 21st century

    Science.gov (United States)

    Rykaczewski, Ryan R.; Dunne, John P.; Sydeman, William J.; García-Reyes, Marisol; Black, Bryan A.; Bograd, Steven J.

    2015-08-01

    Upwelling is critical to the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A leading conceptual hypothesis projects that the winds that induce coastal upwelling will intensify in response to increased land-sea temperature differences associated with anthropogenic global warming. We examine this hypothesis using an ensemble of coupled, ocean-atmosphere models and find limited evidence for intensification of upwelling-favorable winds or atmospheric pressure gradients in response to increasing land-sea temperature differences. However, our analyses reveal consistent latitudinal and seasonal dependencies of projected changes in wind intensity associated with poleward migration of major atmospheric high-pressure cells. Summertime winds near poleward boundaries of climatological upwelling zones are projected to intensify, while winds near equatorward boundaries are projected to weaken. Developing a better understanding of future changes in upwelling winds is essential to identifying portions of the oceans susceptible to increased hypoxia, ocean acidification, and eutrophication under climate change.

  1. Partial decoupling of primary productivity from upwelling in the California Current system

    Science.gov (United States)

    Renault, Lionel; Deutsch, Curtis; McWilliams, James C.; Frenzel, Hartmut; Liang, Jun-Hong; Colas, François

    2016-07-01

    Coastal winds and upwelling of deep nutrient-rich water along subtropical eastern boundaries yield some of the ocean's most productive ecosystems. Simple indices of coastal wind strength have been extensively used to estimate the timing and magnitude of biological productivity on seasonal and interannual timescales and underlie the prediction that anthropogenic climate warming will increase the productivity by making coastal winds stronger. The effect of wind patterns on regional net primary productivity is not captured by such indices and is poorly understood. Here we present evidence, using a realistic model of the California Current system and satellite measurements, that the observed slackening of the winds near the coast has little effect on near-shore phytoplankton productivity despite a large reduction in upwelling velocity. On the regional scale the wind drop-off leads to substantially higher production even when the total upwelling rate remains the same. This partial decoupling of productivity from upwelling results from the impact of wind patterns on alongshore currents and the eddies they generate. Our results imply that productivity in eastern boundary upwelling systems will be better predicted from indices of the coastal wind that account for its offshore structure.

  2. 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.

  3. What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-06-01

    Full Text Available The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003. Here, using a comparative modeling study of the California Current System (California CS and Canary Current System (Canary CS, we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of biological productivity to upwelling strength. To this end, we made a series of eddy-resolving simulations of the California CS and Canary CS using the Regional Ocean Modeling System (ROMS, coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD ecosystem model. We find the nutrient content of the euphotic zone to be 20 % smaller in the Canary CS relative to the California CS. Yet, the biological productivity is 50 % smaller in the latter. This is due to: (1 a faster nutrient-replete growth in the Canary CS relative to the California CS, related to a more favorable light and temperature conditions in the Canary CS, and (2 the longer nearshore water residence times in the Canary CS which lead to larger buildup of biomass in the upwelling zone, thereby enhancing the productivity. The longer residence times in the Canary CS appear to be associated with the wider continental shelves and the lower eddy activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and enhancing the coupling between new and export production in the Northwest African system. Our results suggest that climate change induced perturbations such as upwelling favorable wind intensification might lead to contrasting biological responses in the California CS and the Canary CS, with major implications for the biogeochemical cycles

  4. Shelf/Offshore interactions in the Benguela upwelling system using a 3-D coupled physical/biogeochemical model

    OpenAIRE

    Gutknecht, E.

    2011-01-01

    The main objective of this PhD thesis is the study of the shelf/offshore interactions in the Benguela upwelling system, off South African and Namibian coasts, using a numerical model as well as satellite and in-situ data. A Biogeochemical model adapted for the Benguela Upwelling System (BioBUS), taking into account the main processes linked with eastern boundary upwelling systems and associated oxygen minimum zones, has been developed and coupled with the ROMS hydrodynamical model, in order t...

  5. Does mesoscale matters in decadal changes observed in the northern Canary upwelling system?

    Science.gov (United States)

    Relvas, P.; Luís, J.; Santos, A. M. P.

    2009-04-01

    The Western Iberia constitutes the northern limb of the Canary Current Upwelling System, one of the four Eastern Boundary Upwelling Systems of the world ocean. The strong dynamic link between the atmosphere and the ocean makes these systems highly sensitive to global change, ideal to monitor and investigate its effects. In order to investigate decadal changes of the mesoscale patterns in the Northern Canary upwelling system (off Western Iberia), the field of the satellite-derived sea surface temperature (SST) trends was built at the pixel scale (4x4 km) for the period 1985-2007, based on the monthly mean data from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA series satellites, provided by the NASA Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory. The time series were limited to the nighttime passes to avoid the solar heating effect and a suite of procedures were followed to guarantee that the temperature trends were not biased towards the seasonally more abundant summer data, when the sky is considerably clear. A robust linear fit was applied to each individual pixel, crossing along the time the same pixel in all the processed monthly mean AVHRR SST images from 1985 until 2007. The field of the SST trends was created upon the slopes of the linear fits applied to each pixel. Monthly mean SST time series from the one degree enhanced International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and from near-shore measurements collected on a daily basis by the Portuguese Meteorological Office (IM) are also used to compare the results and extend the analysis back until 1960. A generalized warming trend is detected in the coastal waters off Western Iberia during the last decades, no matter which data set we analyse. However, significant spatial differences in the warming rates are observed in the satellite-derived SST trends. Remarkably, off the southern part of the Western Iberia the known

  6. Influence of external climate forcing on coastal upwelling systems analysed in ensemble of past millennium climate simulations

    Science.gov (United States)

    Tim, Nele; Zorita, Eduardo; Hünicke, Birgit; Yi, Xin; Emeis, Kay

    2016-04-01

    Eastern Boundary Upwelling Systems are highly productive coastal ocean areas where nutrient rich, cold water upwells by the action of favorable winds. Observations over the 20th century and ocean sediment records, which may be indicative of upwelling, display an intensification due to stronger external climate forcing, such as increasing greenhouse gas concentrations or changes in solar irradiance. This intensification is compatible with the hypothesis put forward by Bakun (1990) that a stronger external radiative forcing should lead to a more intense coastal upwelling. Here, we analyze ensemble of simulations covering the past millennium with the aim of identifying and quantifying the role of external climate forcing on upwelling in the major Eastern Boundary Upwelling System. We analyse the decadal variability and centennial trends of upwelling in ensemble of simulations with the global climate model MPI-ESM covering the past millennium, the last 150 years and the next 100 years. The future simulations were driven by three IPCC scenarios of concentrations of anthropogenic greenhouse gases, RCP2.5, RCP4.5 and RCP 8.5. For the past millennium and the last 150 years, coastal upwelling does not show any imprint of external forcing. This result indicates that chaotic internal variability has dominated upwelling intensity in major upwelling regions over the last thousand years and even since industrialisation up to present. For the 21st century, all ensemble members show a consistent and significant intensification of upwelling in the strongest scenario RCP8.5 for the Benguela upwelling region, consistent and significant weakening for Morocco and California, and no significant change for the Peruvian upwelling. Weaker scenarios do not produce consistent long-term trends that are replicated in all ensemble members. The results are confirmed by analysing another ensemble of past millennium simulations with the model CESM-CAM5 (Community Earth System Model

  7. Implementation of an end-to-end coupled model including small pelagic fish in the Canary Current Upwelling System

    OpenAIRE

    Sanchez Garrido, Jose Carlos

    2016-01-01

    Eastern Boundary Current Upwelling Systems are extraordinary productive regions of the World Ocean that are essential to the world’s fisheries. These upwelling ecosystems are subject to substantial variability ranging from few days to decades, and are sensitive to the expected climate change via modification of the global wind patterns. Due to their broad biological and commercial relevance, understanding the source of fluctuations and the likely climate drift of these regions is of major int...

  8. What controls biological production in coastal upwelling systems? Insights from a comparative modeling study

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-10-01

    Full Text Available The magnitude of net primary production (NPP in Eastern Boundary Upwelling Systems (EBUS is traditionally viewed as directly reflecting the wind-driven upwelling intensity. Yet, different EBUS show different sensitivities of NPP to upwelling-favorable winds (Carr and Kearns, 2003. Here, using a comparative modeling study of the California Current System (California CS and Canary Current System (Canary CS, we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of NPP to upwelling strength. To this end, we made a series of eddy-resolving simulations of the two upwelling systems using the Regional Oceanic Modeling System (ROMS, coupled to a nitrogen-based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD ecosystem model. Using identical ecological/biogeochemical parameters, our coupled model simulates a level of NPP in the California CS that is 50 % smaller than that in the Canary CS, in agreement with observationally based estimates. We find this much lower NPP in the California CS despite phytoplankton in this system having nearly 20 % higher nutrient concentrations available to fuel their growth. This conundrum can be explained by: (1 phytoplankton having a faster nutrient-replete growth in the Canary CS relative to the California CS; a consequence of more favorable light and temperature conditions in the Canary CS, and (2 the longer nearshore water residence times in the Canary CS, which permit a larger buildup of biomass in the upwelling zone, thereby enhancing NPP. The longer residence times in the Canary CS appear to be a result of the wider continental shelves and the lower mesoscale activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and reducing the spatial decoupling between new and export production in the Canary CS. Our results suggest that climate change

  9. Estimates of potential new production in the Java-Sumatra upwelling system

    Institute of Scientific and Technical Information of China (English)

    WEI Xing; LIAO Xiaomei; ZHAN Haigang; LIU Hailong

    2012-01-01

    The Java-Sumatra upwelling is one of the most important upwelling systems in the Indian Ocean,with maximum upwelling intensity in July through August.To estimate the nitrate supplied by upwelling,we developed a three-dimensional hydrodynamic model to calculate the mean vertical speed and determine the depth of upwelling.We used in-situ vertical nitrate profiles to assess nitrate concentration in the upwelled waters,and calculated the nitrate supply as the product of nitrate concentration and vertical transport obtained from the numerical model.The calculated result represents potential new production generated in the upwelling region.We found that on the event time scale (monthly) of Java-Sumatra upwelling,water brought to the surface originated from locations 100-m deep,giving a nitrate supply of 93.77× 103 mol/s and potential new production of 1.02× 1014 gC/a.

  10. Sea-Breeze and Topographic Influences on the Planetary Boundary Layer in the Coastal Upwelling Area of Cabo Frio (Brazil)

    Science.gov (United States)

    Ribeiro, F. N. D.; Soares, J.; Oliveira, A. P.

    2016-01-01

    We use a fully coupled oceanic-atmospheric model to investigate the sources and sinks of turbulent kinetic energy in the Cabo Frio coastal area and to determine the role of topography and the sea breeze in planetary boundary-layer (PBL) development. The study area presents similar boundary-layer characteristics than other coastal upwelling areas with complex topography, such as increased stability and low-level jets. The results show that the major effect of upwelling, over the investigated area, is to maintain low temperatures in the lower atmosphere over the coastal zone, sustaining a strong temperature inversion that precludes the vertical PBL development. Therefore, the cooling effect reduces the horizontal thermal contrast between land and water, generating a negative feedback between the intensity of the sea breeze and the intensity of the upwelling. The topography at Cabo Frio prevents this cooling effect from propagating inland, since it limits the penetration of the sea-breeze circulation.

  11. Variability of the upwelling system in the southeastern Brazilian margin for the last 110,000 years

    Science.gov (United States)

    Portilho-Ramos, Rodrigo da Costa; Ferreira, Fabricio; Calado, Leandro; Frontalini, Fabrizio; de Toledo, Mauro Bevilacqua

    2015-12-01

    Western boundary upwelling systems such as those found in the southeastern Brazilian margin (SBM) are promoted by special atmospheric and oceanographic interactions with topography of the coastline. In order to investigate the evolution of the upwelling system in SBM over the past 110 kyr, the abundance of Globigerina bulloides (a planktonic foraminiferal species typically associated with upwelling waters) from two marine cores was combined with estimates of upper water thermal structure derived from Modern Analog Technique based on planktonic foraminifera. High abundances (up to 35%) of large specimens of G. bulloides (≥ 250 μm) associated with cooling subsurface waters reveal the occurrence of an intense coastal upwelling system between 110 kyr and 88 kyr. Changes in coastline orientation due to lower sea level stand (20-70 m lower than today) and a longer season of vigorous Brazil Current (BC) and prevailing northeasterly winds maintained permanently the cold and nutrient-rich South Atlantic Central Waters (SACW) over the shelf promoting the strongest upwelling system of the Brazilian coast over the past 110 kyr. At 88 kyr, a sharp reduction of 14% in abundance of G. bulloides and a 2.6 °C warming of the water column indicates an abrupt weakening of the coastal upwelling, probably caused by a disturbance in SACW formation. During the last glaciation, longer current winter-like conditions of prevailing southwesterly winds and a weakened Brazil Current suppressed the upwelling system in SBM. At this time, constant and relatively high abundance of G. bulloides (up to 10%) suggest that the coastal upwelling was restricted to a short period of months year-round, when the BC and northeasterly winds were relatively vigorous despite the glacial context. The predominance of warm and oligotrophic Tropical Waters due to the shutdown of coastal upwelling in northern SBM was inferred for the last 20 kyr. Despite vigorous northeasterly winds and BC strength, high sea

  12. Pliocene-Pleistocene variability of upwelling activity, productivity and nutrient cycle in the Benguela Upwelling System and the Eastern Equatorial Pacific

    OpenAIRE

    Etourneau, Johan

    2009-01-01

    The focus of this study is to explore the long term Plio-Pleistocene variability of coastal and open ocean upwelling systems by reconstructing for the last ~3.5 Ma, sea surface temperature (SST), primary productivity and nutrient cycling in the Benguela Upwelling System (BUS) and the Eastern Equatorial Pacific (EEP), two areas particularly sensible and influential to climate change.

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

    OpenAIRE

    Prego, R; Varela, Manuel; De Castro, M.; Ospina-Álvarez, Natalia; García-Soto, Carlos; Gómez-Gesteira, M.

    2012-01-01

    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 ther...

  14. Evidence of a large seasonal coastal upwelling system along the southern shelf of Australia

    Science.gov (United States)

    Kämpf, Jochen; Doubell, Mark; Griffin, David; Matthews, Roger L.; Ward, Tim M.

    2004-05-01

    We report observational existence of a large seasonal coastal upwelling system that establishes in austral summer (December-April) along Australian southern shelves. Wind-driven upwelling events occur simultaneously in three upwelling centres spanning a distance of ~800 km. During each summer period there are ~2-3 major upwelling events, each lasting ~1 week. The simultaneous, rapid response of SST to wind forcing in the upwelling centres, which display vastly different shelf widths, points to the existence of a larger-scale process that carries cold water onto the shelf prior to the upwelling season. Exploration of a major upwelling event in March 1998 shows the evolution of peak surface chlorophyll-a concentrations of >4 μg/L lagging the onset of upwelling by ~1 week. The associated (exponential) growth rate can be estimated at 0.4 d-1. Another week later we found a distinct sub-surface chlorophyll-a maximum at a depth of 50 m centred along the upwelling front. Reasons for the formation of this maximum are not fully understood.

  15. 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.

  16. How will Somali coastal upwelling evolve under future warming scenarios?

    Science.gov (United States)

    Decastro, M.; Sousa, M. C.; Santos, F.; Dias, J. M.; Gómez-Gesteira, M.

    2016-07-01

    Somali upwelling system, the fifth in the world, presents some unique features compared with the other major upwelling systems: 1) it is a Western Boundary Upwelling System located near the Equator and 2) upwelling affects the moisture responsible for monsoon rainfall. The intensity of Somali coastal upwelling during summer was projected for the twenty first century by means of an ensemble of Global Climate Models and Regional Climate Models within the framework of CMIP5 and CORDEX projects, respectively. Regardless global or regional circulation models and the chosen greenhouse warming scenario, the strengthening of Somali coastal upwelling, which increases with latitude, is even higher than observed for the Eastern Boundary Upwelling System. In addition, coastal upwelling strengthening is mainly due to Ekman transport since Ekman pumping shows no clear trend for most of the latitudes. Projected land-sea air temperature and pressure show a clear intensification of land-sea thermal and pressure gradient as a consequence of the global warming, which is likely to affect the strengthening of Somali upwelling verifying the hypothesis of Bakun. As a consequence, projected sea surface temperature warming is less intense nearshore than at oceanic locations, especially at latitudes where upwelling strengthening is more intense.

  17. How will Somali coastal upwelling evolve under future warming scenarios?

    Science.gov (United States)

    deCastro, M; Sousa, M C; Santos, F; Dias, J M; Gómez-Gesteira, M

    2016-01-01

    Somali upwelling system, the fifth in the world, presents some unique features compared with the other major upwelling systems: 1) it is a Western Boundary Upwelling System located near the Equator and 2) upwelling affects the moisture responsible for monsoon rainfall. The intensity of Somali coastal upwelling during summer was projected for the twenty first century by means of an ensemble of Global Climate Models and Regional Climate Models within the framework of CMIP5 and CORDEX projects, respectively. Regardless global or regional circulation models and the chosen greenhouse warming scenario, the strengthening of Somali coastal upwelling, which increases with latitude, is even higher than observed for the Eastern Boundary Upwelling System. In addition, coastal upwelling strengthening is mainly due to Ekman transport since Ekman pumping shows no clear trend for most of the latitudes. Projected land-sea air temperature and pressure show a clear intensification of land-sea thermal and pressure gradient as a consequence of the global warming, which is likely to affect the strengthening of Somali upwelling verifying the hypothesis of Bakun. As a consequence, projected sea surface temperature warming is less intense nearshore than at oceanic locations, especially at latitudes where upwelling strengthening is more intense. PMID:27440455

  18. 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.

  19. 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

  20. Upwelling velocity and ventilation in the Mauritanian upwelling system estimated by CFC-12 and SF6 observations

    Science.gov (United States)

    Tanhua, Toste; Liu, Mian

    2015-11-01

    Transient tracer data (CFC-12 and SF6) from three oceanographic field campaigns to the Mauritanian Upwelling area conducted during winter, spring and summer from 2005 to 2007 is presented. The transient tracers are used to constrain a possible solution to the transient time distribution (TTD) along 18°N and to quantify the mean ages in vertical sections perpendicular to the coast. We found that an Inverse Gaussian distribution where the ratio of the moments Δ and Γ equals 1.2 is a possible solution (Δ/Γ = 1.2) of the TTD. The transient tracers further show considerable under-saturation in the mixed layer during the winter and spring cruises that can only be maintained by mixing or upwelling by tracer-poor water from below the mixed layer. We use dissipation data from microstructure measurements and the tracer depth distribution to quantify the flux of tracers to the mixed layer by vertical diffusivity and wind data from the ship to quantify the air-sea flux. We then use the magnitude of the under-saturation in the mixed layer to estimate the advective upwelling velocity which is the balance the first two processes, in a steady state assumption. We find that the upwelling velocities range from less than 1 to 5.6 × 10- 5 m s- 1 (SF6 transient tracer data for calculating upwelling velocity, and found an overall uncertainty of roughly ± 50%.

  1. Decadal variability and trends of the Benguela upwelling system as simulated in a high-resolution ocean simulation

    OpenAIRE

    N. Tim; E. Zorita; B. Hünicke

    2015-01-01

    Detecting the atmospheric drivers of the Benguela upwelling systems is essential to understand its present variability and its past and future changes. We present a statistical analysis of a high-resolution (0.1°) ocean-only simulation driven by observed atmospheric fields over the last 60 years with the aim of identifying the large-scale atmospheric drivers of upwelling variability and trends. The simulation is found to reproduce well the seasonal cycle of upwelling intens...

  2. Decadal variability and trends of the Benguela Upwelling System as simulated in a high-resolution ocean simulation

    OpenAIRE

    N. Tim; E. Zorita; B. Hünicke

    2015-01-01

    Detecting the atmospheric drivers of the Benguela Upwelling Systems is essential to understand its present variability and its past and future changes. We present a statistical analysis of an ocean-only simulation driven by observed atmospheric fields over the last decades with the aim of identifying the large-scale atmospheric drivers of upwelling variability and trends. The simulation is found to reproduce well the seasonal cycle of upwelling intensity, with a maximum in t...

  3. Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

    Science.gov (United States)

    Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

    2016-07-01

    Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

  4. Exploring system boundaries

    OpenAIRE

    Webb, Tom

    2013-01-01

    Autopoiesis is normally considered to be the systems theory in law. In this paper complexity theory is presented as an alternative systems approach. In order to position complexity theory as a plausible alternative to autopoiesis I discuss the differing understanding of boundary within each theory, and use this as a vehicle to critique autopoiesis. My critique is situated within systems theory thinking but is external to both autopoiesis and complexity theory (although I must oscillate betwee...

  5. 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

  6. 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.

  7. 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

    2015-10-01

    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.

  8. 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.

  9. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

    Directory of Open Access Journals (Sweden)

    E. Gutknecht

    2013-06-01

    Full Text Available Eastern boundary upwelling systems (EBUS are regions of high primary production often associated with oxygen minimum zones (OMZs. They represent key regions for the oceanic nitrogen (N cycle. By exporting organic matter (OM and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS, especially the Walvis Bay area (between 22° S and 24° S where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1 the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2 export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 2 m−3; and (3 the N2O emission to the atmosphere in the upwelling area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr−1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m−2 yr−1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary

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

    OpenAIRE

    Belmadani, A.; Echevin, Vincent; Codron, F.; Takahashi, K; Junquas, Clémentine

    2014-01-01

    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 co...

  11. Particle fluxes in the NW Iberian coastal upwelling system: Hydrodynamical and biological control

    Science.gov (United States)

    Zúñiga, D.; Villacieros-Robineau, N.; Salgueiro, E.; Alonso-Pérez, F.; Rosón, G.; Abrantes, F.; Castro, C. G.

    2016-07-01

    To better understand sources and transport of particulate material in the NW Iberian coastal upwelling system, a mooring line dotted with an automated PPS 4/3 sediment trap was deployed off Cape Silleiro at the base of the photic zone. The samples were collected from November 2008 through June 2012 over sampling periods of 4-12 days. Our study represents the first automated sediment trap database for the NW Iberian margin. The magnitude and composition of the settling material showed strong seasonal variability with the highest fluxes during the poleward and winter mixing periods (averages of 12.9±9.6 g m-2 d-1 and 5.6±5.6 g m-2 d-1 respectively), and comparatively lower fluxes (3.6±4.1 g m-2 d-1) for the upwelling season. Intensive deposition events registered during poleward and winter mixing periods were dominated by the lithogenic fraction (80±3%). They were associated to high energy wave-driven resuspension processes, due to the occurrence of south-westerly storms, and intense riverine inputs of terrestrial material from Minho and Douro rivers. On the other hand, during the spring - summer upwelling season, the share of biogenic compounds (organic matter, calcium carbonate (CaCO3), biogenic silica (bSiO2)) to downward fluxes was higher, reflecting an increase in pelagic sedimentation due to the seasonal intensification of primary production and negligible river inputs and wave-driven resuspended material. Otherwise, the large variations of biogenic settling particles were mainly modulated by upwelling intensity, which by means of upwelling filaments ultimately controlled the offshore transport of the organic carbon fixed by primary producers towards the adjacent ocean. Based on the average downward flux of organic carbon (212 mg C m-2 d-1) and considering an average primary production of 1013 mg C m-2 d-1 from literature, we estimated that about 21% of the fixed carbon is vertically exported during the upwelling season.

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

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    remineralization associated with nitrate reduction to nitrite. Secondly, the coupled model was used to simulate upwelling and iogeochemical cycles associated with different continental shelf geometries. In particular the generalized effect of shelf width was investigated. Anoxic/euxinic conditions in bottom waters...... active but cryptic sulfur cycle possibly is coupled to the nitrogen cycle in an oxygen-minimum-zone (OMZ), 2) what is the relation between the shelf–ocean exchange, continental shelf width and development of the observed bottom water anoxia/euxinia associated with different configurations of continental...... calibrated to reproduce the observed coupling between nitrogen and sulfur cycles in OMZ of the northern Chile upwelling systems. The model results show that sulfate reduction contribute significantly to organic matter remineralization in the OMZ water depths, along with nitrate reduction. In the model...

  13. Intensification and spatial homogenization of coastal upwelling under climate change.

    Science.gov (United States)

    Wang, Daiwei; Gouhier, Tarik C; Menge, Bruce A; Ganguly, Auroop R

    2015-02-19

    The timing and strength of wind-driven coastal upwelling along the eastern margins of major ocean basins regulate the productivity of critical fisheries and marine ecosystems by bringing deep and nutrient-rich waters to the sunlit surface, where photosynthesis can occur. How coastal upwelling regimes might change in a warming climate is therefore a question of vital importance. Although enhanced land-ocean differential heating due to greenhouse warming has been proposed to intensify coastal upwelling by strengthening alongshore winds, analyses of observations and previous climate models have provided little consensus on historical and projected trends in coastal upwelling. Here we show that there are strong and consistent changes in the timing, intensity and spatial heterogeneity of coastal upwelling in response to future warming in most Eastern Boundary Upwelling Systems (EBUSs). An ensemble of climate models shows that by the end of the twenty-first century the upwelling season will start earlier, end later and become more intense at high but not low latitudes. This projected increase in upwelling intensity and duration at high latitudes will result in a substantial reduction of the existing latitudinal variation in coastal upwelling. These patterns are consistent across three of the four EBUSs (Canary, Benguela and Humboldt, but not California). The lack of upwelling intensification and greater uncertainty associated with the California EBUS may reflect regional controls associated with the atmospheric response to climate change. Given the strong linkages between upwelling and marine ecosystems, the projected changes in the intensity, timing and spatial structure of coastal upwelling may influence the geographical distribution of marine biodiversity. PMID:25693571

  14. Plio-Pleistocene glacial-interglacial productivity changes in the eastern equatorial Pacific upwelling system

    Science.gov (United States)

    Jakob, Kim A.; Wilson, Paul A.; Bahr, André; Bolton, Clara T.; Pross, Jörg; Fiebig, Jens; Friedrich, Oliver

    2016-03-01

    The eastern equatorial Pacific Ocean (EEP) upwelling system supports >10% of the present-day global ocean primary production, making it an important component in Earth's atmospheric and marine carbon budget. Traditionally, it has been argued that since intensification of Northern Hemisphere glaciation (iNHG, ~2.7 Ma), changes in EEP productivity have predominantly depended on trade wind strength-controlled upwelling intensity. An alternative hypothesis suggests that EEP productivity is primarily controlled by nutrient supply from the high southern latitudes via mode waters. Here we present new high-resolution data for the latest Pliocene/early Pleistocene from Ocean Drilling Program Site 849, located within the equatorial divergence system in the heart of the EEP upwelling regime. We use carbon isotopes in benthic and planktic foraminiferal calcite and sand accumulation rates to investigate glacial-interglacial (G-IG) productivity fluctuations between 2.65 and 2.4 Ma (marine isotope stages (MIS) G1 to 94). This interval includes MIS 100, 98, and 96, three large-amplitude glacials (~1‰ in benthic δ18O) representing the culmination of iNHG. Our results suggest that latest Pliocene/early Pleistocene G-IG productivity changes in the EEP were strongly controlled by nutrient supply from Southern Ocean-sourced mode waters. Our records show a clear G-IG cyclicity from MIS 100 onward with productivity levels increasing from full glacial conditions and peaking at glacial terminations. We conclude that enhanced nutrient delivery from high southern latitudes during full glacial conditions together with superimposed intensified regional upwelling toward glacial terminations strongly regulated primary productivity rates in the EEP from MIS 100 onward.

  15. Response of the Southern Benguela upwelling system to fine-scale modifications of the coastal wind

    Science.gov (United States)

    Desbiolles, F.; Blanke, B.; Bentamy, A.; Roy, C.

    2016-04-01

    We analyze the results of a regional model of the Southern Benguela upwelling system forced by wind stress fields derived from QuikSCAT observations. Two different horizontal resolutions are considered for the wind stress: QS25 and QS50, corresponding to native 25 and 50 km grids, respectively. The differences between both products highlight the primary importance of fine-scale momentum fluxes for both the structure and intensity of the wind- and wind-curl-driven upwelling. Using QS25, we show that the coastal Ekman transport is reduced, leading to a warmer SST and a reduced oceanic coastal jet. QS25 finer wind stress curl patterns also favor the development of a stronger and shallower poleward undercurrent. The addition of a coastal wind correction to QS25 lets us investigate the possible implications of an imbalance between Ekman transport and Ekman pumping: a wind reduction in the coastal band often reduces the SST cooling, but the two mechanisms compensate each other when the characteristic length scales of the coastal upwelling and the orography-induced wind drop-off are similar.

  16. 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. PMID:25641504

  17. A physical view of La Guajira Upwelling System, Colombian Basin, Caribbean Sea

    Science.gov (United States)

    Bernal, G.; Beier, E.; Barton, E. D.; Ruiz-Ochoa, M.; Correa, J. G.

    2013-05-01

    La Guajira Peninsula lies within a large upwelling system along the South Caribbean Coast, created by the NE trade winds. In this location, sea surface temperature (SST) exhibits the lowest mean value and the highest variability in the whole Colombian Basin. The seasonal variation of SST explains up to 75 % of the total variability. La Guajira coastal zone also experiences the highest values of wind stress and wind stress curl, with the greatest annual and semiannual variability in the Colombian Basin. It has been shown that wind stress curl enhances the upwelling over the region. Near 90% of the variability of SST in La Guajira can be explained by the seasonality plus the first three EOFs interannual modes: the first, synchronous throughout the Basin, is dominant, and consists of a uniform interannual variation in phase with the North Tropical Atlantic Index; the second co-varies strongly with the second mode of wind stress curl; and the third reflects the role of the vertical atmospheric circulation cell associated with the Caribbean Low Level Jet off Central America. The inclusion of wind stress curl with its maximum offshore of La Guajira explains in part the extension of cool coastal water into the Colombian Basin, with advection in filaments, eddies and meanders. In order to complement the physical knowledge of La Guajira upwelling system, an analysis of water masses, sea surface height, Ekman suction, Ekman transport and coastal upwelling index (CUI) was performed. Hydrographic data was obtained from gridded climatologies from the National Oceanographic Data Center (WOD01); sea surface height anomalies from the Archiving, Validation, and Interpretation of Satellite Oceanography (AVISO) data; and wind data from the Cross-Calibrated Multi-Platform Ocean Surface Wind Velocity Product for Meteorological and Oceanographic Applications (CCMP). The upwelling forms a local water mass, La Guajira surface water (LGSW), with the mixing of subtropical underwater and

  18. Ionospheric heating, upwelling, and depletions in auroral current systems

    Science.gov (United States)

    Zettergren, M. D.; Semeter, J. L.

    2010-12-01

    This research investigates aspects of ionospheric dynamics relevant to magnetosphere-ionosphere coupling in auroral arc current systems. Auroral electric fields and particle precipitation deposit energy in the ionosphere, often resulting in enhanced ion or electron temperatures. This heating has a wide variety of consequences for the ionosphere. High ion temperatures alter chemical balance in the lower F-region, resulting in conversion to a molecular ion plasma, faster recombination, and plasma depletions. Pressure enhancements resulting from both ion and electron heating are capable of generating intense ion upflows. Ion upflow and depletion processes redistribute and structure the auroral plasma in ways that are likely of consequence to wave coupling of the magnetosphere and ionosphere. These implications are examined through the use of a fluid-kinetic model of the auroral ionosphere and new incoherent scatter radar data analysis techniques. Results indicate that enhanced recombination of molecular ions in auroral downward current regions may work in concert with well-known electrodynamic depletion processes, in the F-region ionosphere. Furthermore, ionospheric upflows in auroral upward and downward current regions may be quite different in terms of intensity and types of upflowing ions.

  19. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

    Science.gov (United States)

    Gutknecht, E.; Dadou, I.; Marchesiello, P.; Cambon, G.; Le Vu, B.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2013-06-01

    Eastern boundary upwelling systems (EBUS) are regions of high primary production often associated with oxygen minimum zones (OMZs). They represent key regions for the oceanic nitrogen (N) cycle. By exporting organic matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O) to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS) is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS), especially the Walvis Bay area (between 22° S and 24° S) where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1) the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2) export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr-1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m-2 yr-1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary production estimated for the South Atlantic subtropical gyre. Export production (16

  20. Observations of Upwelling Filaments in the Southern North-West African Upwelling System : a Joint Effect of the Bottom Topography and the Offshore Eddy Field?

    Science.gov (United States)

    Meunier, T.; Barton, E. D.; Torres, R.; Barreiro, B.

    2010-12-01

    The nature and dynamics of the long filaments forming in the southern edge of the West-African upwelling system are investigated using data from the SOLAS-ICON cruise, that took place in April-May 2009 offshore of Cap Blanc, between 19.5 and 22.5 °N and 17 and 19 °W. Two synoptic hydrographic surveys using a Moving Vessel Profiler were performed at a 15 days interval on two distinct upwelling filaments at different stages of development. The first survey showed the presence of a large anticyconic eddy North of the filament, also evident in the satellite imagery. Two transects were performed across the tip of the filament, showing a steep rising of the isohalines and the isotherms, with horizontal gradients of 3.10-2 psu km-1 and 10 -1 °C km-1. The density compensation of temperature and salinity in this part of the North West African upwelling system resulted in a weaker doming of the isopycnals across the filament. The second filament developed during a strong wind episode directly following a 2 days wind relaxation period. 8 cross sections were performed, all showing a steeper doming of the isohalines and isotherms than during the first survey, resulting in horizontal gradients of 8.10-2 psu km-1 and 5.10-1 °C km-1 near the surface. The hydrographic signature of the filament was evident as deep as 300 m. Satellite imagery showed the persistence between the two surveys of a shorter and colder filament West of Cap Blanc , rolling around a small anticyclonic eddy, in spite of the relaxation of the wind. The surveyed filaments both appeared to emerge from this struc ture. A process study using a simple two layer shallow water isopycnic numerical model (MICOM) and an idealized topography was carried out to elucidate the development and stationarity of the anticyclone and cold filament at the root of the longer structures. Potential vorticity anomalies generated by topographic effects were shown to play a major role in the filament formation, when interacting with

  1. Hamiltonian systems with boundaries

    International Nuclear Information System (INIS)

    Lately, to provide a solid ground for quantization of the open string theory with a constant B-field it has been proposed to treat the boundary conditions as hamiltonian constraints. It seems that this proposal is quite general and it should be applicable to a wide range of models defined on manifolds with boundaries. The goal of the present paper is to show how the boundary conditions can arise as constraints in a purely algebraic fashion within the Hamiltonian approach without any reference to the Lagrangian formulation of the theory. The construction of the boundary Dirac brackets is also given and some subtleties are pointed out. We consider four examples of field theories with boundaries: the topological sigma model, the open string theory with and without a constant B-field and electrodynamics with topological term. A curious result about electrodynamics on a manifold with boundaries is presented. (author)

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

    Science.gov (United States)

    Clark, D. R.; Widdicombe, C. E.; Rees, A. P.; Woodward, E. M. S.

    2015-11-01

    The lagrangian progression of biogeochemical processes was followed in a filament of the Mauritanian upwelling system, North West Africa, during offshore advection. Inert duel tracers sulphur 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 (NO3- = 9.0 ± 0.1 μmol L-1; PO43- = 0.7 ± 0.1 μmol L-1; Si = 2.7 ± 0.1 μmol L-1) but was depleted in N compared to Redfield stoichiometry (N:P = 13.9:1). A maximum primary productivity rate of 0.7 mol C m-2 d-1 was measured on the continental shelf, associated with N-assimilation rates of 43.8 nmol L-1 h-1 for NO3-, 32.8 nmol L-1 h-1 for NH4+ 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, primary productivity rates of 0.1 mol C m-2 d-1 were measured, associated with N-assimilation rates of 3.9 nmol L-1 h-1 for NO3-, 6.1 nmol L-1 h-1 for NH4+ and lower nutrient concentrations (NO3- = 4.6 ± 0.3 μmol L-1; PO43- = 0.4 ± 0.1 μmol L-1; Si = 0.9 ± 0.1 μmol L-1). Nitrogen regeneration and assimilation took place simultaneously; NH4+ was regenerated at 9.4-85.0 nmol L-1 h-1; NH4+ was oxidised at 0.30-8.75 nmol L-1 h-1; NO2- was oxidised at 25.55-81.11 nmol L-1 h-1. Results highlight 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

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

    Directory of Open Access Journals (Sweden)

    D. R. Clark

    2015-11-01

    Full Text Available The lagrangian progression of biogeochemical processes was followed in a filament of the Mauritanian upwelling system, North West Africa, during offshore advection. Inert duel tracers sulphur 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 (NO3− = 9.0 ± 0.1 μmol L−1; PO43− = 0.7 ± 0.1 μmol L−1; Si = 2.7 ± 0.1 μmol L−1 but was depleted in N compared to Redfield stoichiometry (N:P = 13.9:1. A maximum primary productivity rate of 0.7 mol C m−2 d−1 was measured on the continental shelf, associated with N-assimilation rates of 43.8 nmol L−1 h−1 for NO3−, 32.8 nmol L−1 h−1 for NH4+ 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, primary productivity rates of 0.1 mol C m−2 d−1 were measured, associated with N-assimilation rates of 3.9 nmol L−1 h−1 for NO3−, 6.1 nmol L−1 h−1 for NH4+ and lower nutrient concentrations (NO3− = 4.6 ± 0.3 μmol L−1; PO43− = 0.4 ± 0.1 μmol L−1; Si = 0.9 ± 0.1 μmol L−1. Nitrogen regeneration and assimilation took place simultaneously; NH4+ was regenerated at 9.4–85.0 nmol L−1 h−1; NH4+ was oxidised at 0.30–8.75 nmol L−1 h−1; NO2− was oxidised at 25.55–81.11 nmol L−1 h−1. Results highlight 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

  4. 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.

    , the longshore component of the wind stress was 0.45 dyne cm -2, which corresponds to an Ekman transport of 120 m 3 s -1 per 100 m of the coast. The winds were most favourable to upwelling when leg E of the track (Fig. 1) was covered. Here the Ekman transport... 88 90E -IO N Fig. 2. Winds measured on board the vessel every 3 h during the cruise (some of the wind vectors are not shown, to avoid confusion). Wind stress (F) was calculated using the bulk aerodynamic formula -Fffi CDp\\[~IV, where CD was taken...

  5. Egg production and hatching success of Calanus chilensis and Acartia tonsa in the northern Chile upwelling zone (23°S), Humboldt Current System

    Science.gov (United States)

    Ruz, Paula M.; Hidalgo, Pamela; Yáñez, Sonia; Escribano, Rubén; Keister, Julie E.

    2015-08-01

    Oxygen Minimum Zones (OMZ's) are expanding and intensifying as result of climate change, affecting Eastern Boundary Upwelling Systems. Local effects of vertical movements of OMZ's that result from changes in upwelling intensity could reduce or expand the oxygenated surface layer that most zooplanktonic species inhabit in coastal areas. Using the copepods Calanus chilensis and Acartia tonsa as model organisms, an experimental test of the impact of different dissolved oxygen (DO) concentrations (between 0.5 and 5 ml L- 1) on egg production and hatching success was carried out and compared with field estimations of egg production, female and egg abundance in Mejillones Bay (23°S). Abundance of C. chilensis was highly variability and no consistent pattern in egg production and hatching success was found across DO levels, whereas A. tonsa egg production had maximum values between 2.6 and 4.7 ml O2 L- 1 and hatching success was positively correlated with DO (r = 0.75). In the field, temperature was the main factor controlling the dynamics of both species, while Chl-a and DO were also correlated with C. chilensis and A. tonsa, respectively. Principal Component Analysis showed that abundances of both copepods were controlled by temperature, stratification, OMZ depth, and Ekman transport, which together explained more than 70% of the total variance and were the main factors that modulated the populations of C. chilensis and A. tonsa in the upwelling zone of northern Chile (23°S). The differential responses of C. chilensis and A. tonsa to changes in DO concentrations associated with vertical movements of the OMZ suggest that C. chilensis may be better adapted to hypoxic conditions than A. tonsa, however both species are successful and persistent all year-round. We suggest that physiological responses of copepods could be used to evaluate population dynamics affected by the shoaling of OMZ's and the repercussions to trophic food webs of eastern boundary current systems.

  6. Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation RID B-8834-2011

    DEFF Research Database (Denmark)

    Kuypers, MMM; Lavik, G.; Woebken, D.;

    2005-01-01

    the world ocean, the Benguela upwelling system. Our in situ experiments indicate that nitrate is not directly converted to N-2 by heterotrophic denitrification in the suboxic zone. In the Benguela system, nutrient profiles, anammox rates, abundances of anammox cells, and specific biomarker lipids...

  7. Reactive Halogen Species in the Marine Boundary Layer: A Comparision of the Mauretanian and the Peruvian upwelling regions

    Science.gov (United States)

    Lampel, Johannes; Tschritter, Jens; Pöhler, Denis; Großmann, Katja; Horbanski, Martin; Frieß, Udo; Platt, Ulrich

    2013-04-01

    Reactive halogen species (RHS) such as bromine oxide (BrO) or iodine oxide (IO) play a major role in the chemistry of ozone in both, the troposphere, and the stratosphere and possibly influence the ozone budget on a global scale. In order to estimate the amount of RHS release from marine sources DOAS measurements in three different upwelling regions (Mauritanian, African equatorial and Peruvian) as well as long-term-observations at the Cape Verde Atmospheric Observatory (CVAO) were performed within the SOPRAN Project (BMBF Förderkennzeichen 03F0611F). In 2010 the HaloCaVe campaign with a set of DOAS instruments on the CVAO and RV Poseidon allowed for an intercomparision of Long-Path-DOAS (LP), Multi-Axis-DOAS (MAX) and Cavity-Enhanced-DOAS (CE) measurements on shore as well as for extending these observations to a larger area with the simultaneous ship-borne MAX-DOAS measurements during the DRIVE campaign from Gran Canaria to Cape Verde and back along the mauretanian coast. A re-evaluation of the entire data set is presented. LP- and MAX-DOAS observations show significant BrO concentrations of several ppt with strong variations from day to day and a diurnal cycle with a maximum at sunrise and sunset and a minimum during noon. In opposite to previous measurements, IO was below the detection limit of 0.5 ppt for the LP-DOAS and CE-DOAS instrument. From the ship (DRIVE campaign) locally restricted BrO hotspots with mixing ratios of up to 10ppt were observed in the Mauritanian costal upwelling. These findings allow new conclusions on the relevance of halogens on this marine environment which will be presented. Within the SOPRAN cruise M91 on RV Meteor the upwelling region along the coast of Peru has been investigated in December 2012. First results from MAX-DOAS and CE-DOAS measurements will be presented and compared to those from the Atlantic. Both instruments measured NO2, IO and glyoxal mixing ratios, the MAX-DOAS additionally BrO and formaldehyde. We observed

  8. Coastal Upwelling.

    Science.gov (United States)

    Clark, Steve

    1998-01-01

    Features a three-part activity designed to teach students about coastal upwelling, the upward movement of cooler, more nutrient-rich water along a coast. Activity includes a mapping exercise, a graphing exercise, and questions for analyzing the map and graph. (Author/WRM)

  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...

  10. 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

  11. Octopus vulgaris paralarvae vertical distribution in a fluctuating upwelling-downwelling system

    Directory of Open Access Journals (Sweden)

    Lorena Olmos Pérez

    2014-06-01

    - Upwelling situation: superficial waters (0-20m enter through the northern mouth of the Ría and are washed through the southern mouth. This water movement promotes the entrance of cold, bottom upwelled water through the southern mouth of the Ría. Under this scenario, Octopus paralarvae are concentrated at the surface (10-0m, thus leaving the Ría. This difference is bigger after strong upwelling during the previous days. Abundances inside the Ría are the highest, maybe because it acts as a temporal retention area, or because cold upwelled waters might stimulate hatching inside the Ría. Day/night changes under strong upwelling conditions: paralarvae abundance in both mouths was quite similar, except that during the day they were in sub-surficial waters (10-5 m, while at night paralarvae were mainly found close to the surface (0-5 m. This vertical distribution during the day is remarkable because paralarvae may select offward surface waters.

  12. Aragonite saturation state in a monsoonal upwelling system off Java, Indonesia

    Science.gov (United States)

    Xue, Liang; Wang, Huiwu; Jiang, Li-Qing; Cai, Wei-Jun; Wei, Qinsheng; Song, Hongjun; Kuswardani, Rita Tisiana Dwi; Pranowo, Widodo S.; Beck, Brian; Liu, Lin; Yu, Weidong

    2016-01-01

    Aragonite saturation state (Ωarag) and its influence from upwelling along the southern coast of Java, Indonesia were examined using carbonate and hydrographic data collected from 22 September to 2 October 2013. Results showed that sea surface Ωarag was lower in the upwelling area (2.97-3.44) than in the nonupwelling area (3.45-3.57), with the lowest value in the eastern part of the study area. We used a two end-member mixing model to separate contributions on Ωarag from two processes associated with upwelling: physical transport vs. biological production. Results indicated that physical transport induced at least a Ωarag decrease of 0.8, whereas biological production caused Ωarag to increase by up to 0.6. Additionally, the influence on Ωarag of interannual upwelling variability modulated by the Indian Ocean Dipole (IOD), a unique climate phenomenon in the Indian Ocean, was roughly estimated. We argue that the effect of interannual upwelling variability modulated by IOD events was possibly larger than what was imposed on Ωarag by increasing atmospheric CO2 levels over the past decade.

  13. Complex trophic interactions of calanoid copepods in the Benguela upwelling system

    Science.gov (United States)

    Schukat, Anna; Auel, Holger; Teuber, Lena; Lahajnar, Niko; Hagen, Wilhelm

    2014-01-01

    Life-cycle adaptations, dietary preferences and trophic levels of calanoid copepods from the northern Benguela Current off Namibia were determined via lipid classes, marker fatty acids and stable isotope analyses, respectively. Trophic levels of copepod species were compared to other zooplankton and top consumers. Lipid class analyses revealed that three of the dominant calanoid copepod species stored wax esters, four accumulated triacylglycerols and another three species were characterised by high phospholipid levels. The two biomarker approaches (via fatty acids and stable isotopes) revealed a complex pattern of trophic positions for the various copepod species, but also highlighted the dietary importance of diatoms and dinoflagellates. Calanoides carinatus and Nannocalanus minor occupied the lowest trophic level (predominantly herbivorous) corresponding to high amounts of fatty acid markers for diatoms (e.g. 16:1(n - 7)) and dinoflagellates (e.g. 18:4(n - 3)). These two copepod species represent the classical link between primary production and higher trophic levels. All other copepods belonged to secondary or even tertiary (some deep-sea copepods) consumers. The calanoid copepod species cover the entire range of δ15N ratios, as compared to δ15N ratios of all non-calanoid taxa investigated, from salps to adult fish. These data emphasise that the trophic roles of calanoid copepods are far more complex than just interlinking primary producers with pelagic fish, which should also be considered in the process of developing realistic food-web models of coastal upwelling systems.

  14. Seasonal and interannual phytoplankton dynamics and forcing mechanisms in the Northern Benguela upwelling system

    Science.gov (United States)

    Louw, Deon C.; van der Plas, Anja K.; Mohrholz, Volker; Wasmund, Norbert; Junker, Tim; Eggert, Anja

    2016-05-01

    Seasonal phytoplankton blooms are one of the key features of the productive northern Benguela upwelling system (nBUS), however they are not well described thus far. In this study twelve years (2000-2012) of in situ chlorophyll-a data from a monitoring transect off the Namibian coast were analysed to assess the long-term and seasonal variability in chlorophyll-a as a measure of phytoplankton biomass and the occurrence of phytoplankton blooms. On the shelf, low chlorophyll-a concentrations were identified in 2001/2002, 2005/2006, and 2011/2012. The concentrations on the shelf were highest in 2008/2009 and 2010/2011. Major phytoplankton blooms defined at chlorophyll-a concentrations > 18 mg m- 3 occurred in five of the 12 years (2002/2003, 2004/2005, 2008/2009, 2009/2010 and 2010/2011) while minor blooms (> 13 mg m- 3) occurred in almost every year. The calculated climatology of the chlorophyll-a time series revealed a clear seasonality. Three chlorophyll-a maxima typically develop inshore over the year: an austral winter peak (August), an early austral summer peak (December) and a late summer/autumn peak (April). The analysis of synoptic hydrographic, nutrient and wind data revealed three different forcing mechanisms that all initiate an influx of nutrients into the surface mixed layer.

  15. 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.

  16. Cadmium in the California Current system: Tracer of past and present upwelling

    Science.gov (United States)

    VanGeen, A.; Husby, D.M.

    1996-01-01

    Over 100 samples were collected off the west coast of North America during 1991-1993 to determine the relation between wind-driven upwelling and nearshore concentrations of dissolved silicate (Si), phosphate (P), and cadmium (Cd). Highly enriched in deep water offshore, these constituents are sensitive indicators of upwelling. Coastal water was sampled from the shore in January and June 1992 at 12 sites distributed between 36?? and 48??N latitude. In January the composition of nearshore water along this transect was fairly uniform: 5-15 ??mol/kg for Si, 0.5 to 1.0 ??mol/kg for P, and 0.1-0.3 nmol/kg for Cd. In June, elevated concentrations of Si (30 ??mol/kg), P (2.0 ??mol/kg), and Cd (0.6 nmol/kg) revealed a region of intense upwelling between 38?? and 40??N. The pattern is broadly consistent with meridional gradients in coastal upwelling calculated from the long-term mean of alongshore winds compiled from ship reports. Nearshore water was also collected biweekly to monthly at two sites 3 km apart near San Francisco Bay (37.5??N) during 1991-1993. The variability seen in the time series suggests that the composition of nearshore water integrates the effect of alongshore winds over timescales of several weeks. Seasonal variations in Si (5-50 ??mol/kg), P (0.5-2.5 ??mol/kg), and Cd (0.1-0.8 nmol/kg) concentrations were consistent with upwelling during spring and summer. Maximum Si, P, and Cd concentrations reached in May 1991 were consistent with advection to the very nearshore region from a depth of about 300 m relative to a vertical profile at a distance of 200 km from the coast. Nearshore Si, P, and Cd concentrations were reduced relative to 1991 in 1992 and, to a lesser extent, in 1993 due to weaker upwelling linked to the warm phase of the El Nin???o-Southern Oscillation. During periods of weaker upwelling or downwelling, variations in P, Si, and Cd concentrations became uncoupled. There is a good correlation between the coastal Cd time series near San

  17. Fungal parasites infect marine diatoms in the upwelling ecosystem of the Humboldt current system off central Chile.

    Science.gov (United States)

    Gutiérrez, Marcelo H; Jara, Ana M; Pantoja, Silvio

    2016-05-01

    This is the first report of fungal parasitism of diatoms in a highly productive coastal upwelling ecosystem, based on a year-round time series of diatom and parasitic Chytridiomycota abundance in the Humboldt Current System off Chile (36°30.80'S-73°07.70'W). Our results show co-variation in the presence of Skeletonema, Thalassiosira and Chaetoceros diatoms with attached and detached chytrid sporangia. High abundance of attached sporangia was observed during the austral spring, coinciding with a predominance of Thalassiosira and Skeletonema under active upwelling conditions. Towards the end of austral spring, a decreasing proportion of attached sporangia was accompanied by a decline in abundance of Skeletonema and Thalassiosira and the predominance of Chaetoceros, suggesting specificity and host density dependence of chytrid infection. The new findings on fungal parasitism of diatoms provide further support for the inclusion of Fungi in the current model of the role played by the marine microbial community in the coastal ocean. We propose a conceptual model where Fungi contribute to controlling the dynamics of phytoplankton populations, as well as the release of organic matter and the transfer of organic carbon through the pelagic trophic web in coastal upwelling ecosystems. PMID:26914416

  18. An improved coastal upwelling index from sea surface temperature using satellite-based approach : the case of the Canary Current upwelling system

    OpenAIRE

    Benazzouz, A.; Mordane, S.; Orbi, A.; Chagdali, M.; Hilmi, K; A. Atillah; Pelegri, J. L.; Demarcq, Hervé

    2014-01-01

    A new methodology to derive an SST-based upwelling index was based on a rigorous spatial analysis of satellite SST fields and their variability, by referring to previous works, from Wooster et al. (1976) to Santos et al. (2011). The data was precautiously processed by considering data quality aspects (including cloud cover) and the best way to derive accurate coastal SST and its offshore reference. The relevance of the developed index was evaluated by comparing its spatial and seasonal consis...

  19. Community response of zooplankton to oceanographic changes (2002-2012) in the central/southern upwelling system of Chile

    Science.gov (United States)

    Medellín-Mora, Johanna; Escribano, Ruben; Schneider, Wolfgang

    2016-03-01

    A 10-year time series (2002-2012) at Station 18 off central/southern Chile allowed us to study variations in zooplankton along with interannual variability and trends in oceanographic conditions. We used an automated analysis program (ZooImage) to assess changes in the mesozooplankton size structure and the composition of the taxa throughout the entire community. Oceanographic conditions changed over the decade: the water column became less stratified, more saline, and colder; the mixed layer deepened; and the oxygen minimum zone became shallower during the second half of the time series (2008-2012) in comparison with the first period (2002-2007). Both the size structure and composition of the zooplankton were significantly associated with oceanographic changes. Taxonomic and size diversity of the zooplankton community increased to the more recent period. For the second period, small sized copepods (1.5 mm) and medium size copepods (1-1.5 mm), whereas euphausiids, decapod larvae, appendicularian and ostracods increased their abundance during the second period. These findings indicated that the zooplankton community structure in this eastern boundary ecosystem was strongly influenced by variability of the upwelling process. Thus, climate-induced forcing of upwelling trends can alter the zooplankton community in this highly productive region with potential consequences for the ecosystem food web.

  20. 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.

  1. (abstract) Seasonal Variability in Coastal Upwelling: A Comparison of Four Coastal Upwelling Sites from Space

    Science.gov (United States)

    Carr, Mary-Elena

    1996-01-01

    Coastal upwelling of subsurface nutrient-rich water occurs along the eastern boundary of the ocean basins and leads to high primary production and fish catches. In this study satellite observations are used to compare the seasonal cycle in wind forcing and in the oceanic and biological response of the major coastal upwelling regions associated with the Canary, Benguela, California, and Humboldt Currents.

  2. Meeting reproductive demands in a dynamic upwelling system: Foraging strategies of a pursuit-diving seabird, the marbled murrelet

    Science.gov (United States)

    Peery, M.Z.; Newman, S.H.; Storlazzi, C.D.; Beissinger, S.R.

    2009-01-01

    Seabirds maintain plasticity in their foraging behavior to cope with energy demands and foraging constraints that vary over the reproductive cycle, but behavioral studies comparing breeding and nonbreeding individuals are rare. Here we characterize how Marbled Murrelets (Brachyramphus marmoratus) adjust their foraging effort in response to changes in reproductive demands in an upwelling system in central California. We radio-marked 32 murrelets of known reproductive status (9 breeders, 12 potential breeders, and 11 nonbreeders) and estimated both foraging ranges and diving rates during the breeding season. Murrelets spent more time diving during upwelling than oceanographic relaxation, increased their foraging ranges as the duration of relaxation grew longer, and reduced their foraging ranges after transitions to upwelling. When not incubating, murrelets moved in a circadian pattern, spending nighttime hours resting near flyways used to reach nesting habitat and foraging during the daytime an average of 5.7 km (SD 6.7 km) from nighttime locations. Breeders foraged close to nesting habitat once they initiated nesting and nest attendance was at a maximum, and then resumed traveling longer distances following the completion of nesting. Nonbreeders had similar nighttime and daytime distributions and tended to be located farther from inland flyways. Breeders increased the amount of time they spent diving by 71-73% when they had an active nest by increasing the number of dives rather than by increasing the frequency of anaerobiosis. Thus, to meet reproductive demands during nesting, murrelets adopted a combined strategy of reducing energy expended commuting to foraging sites and increasing aerobic dive rates. ?? 2009 by The Cooper Ornithological Society. All rights reserved.

  3. Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria.

    Science.gov (United States)

    Maisch, Markus; Wu, Wenfang; Kappler, Andreas; Swanner, Elizabeth D

    2016-01-01

    A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling from hydrothermal sources in the Precambrian ocean was oxidized by molecular oxygen [O2] produced by cyanobacteria. The oldest BIFs, deposited prior to the Great Oxidation Event (GOE) at about 2.4 billion years (Gy) ago, could have formed by direct oxidation of Fe(II) by anoxygenic photoferrotrophs under anoxic conditions. As a method for testing the geochemical and mineralogical patterns that develop under different biological scenarios, we designed a 40 cm long vertical flow-through column to simulate an anoxic Fe(II)-rich marine upwelling system representative of an ancient ocean on a lab scale. The cylinder was packed with a porous glass bead matrix to stabilize the geochemical gradients, and liquid samples for iron quantification could be taken throughout the water column. Dissolved oxygen was detected non-invasively via optodes from the outside. Results from biotic experiments that involved upwelling fluxes of Fe(II) from the bottom, a distinct light gradient from top, and cyanobacteria present in the water column, show clear evidence for the formation of Fe(III) mineral precipitates and development of a chemocline between Fe(II) and O2. This column allows us to test hypotheses for the formation of the BIFs by culturing cyanobacteria (and in the future photoferrotrophs) under simulated marine Precambrian conditions. Furthermore we hypothesize that our column concept allows for the simulation of various chemical and physical environments - including shallow marine or lacustrine sediments. PMID:27500924

  4. 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

  5. The interplay between the surface and bottom water environment within the Benguela Upwelling System over the last 70 ka

    NARCIS (Netherlands)

    McKay, C.L.; Filipsson, H.L.; Romero, O.E.; Stuut, J.-B. W.; Bjorck, S.

    2016-01-01

    The Benguela Upwelling System (BUS), located between 30 and 20°S, is one of the fundamentalhigh-productivity systems of the world ocean. The BUS has previously been studied in terms of primaryproductivity and ecology over glacial-interglacial timescales; however, the response and coupling with thebe

  6. The interplay between the surface and bottom water environment within the Benguela Upwelling System over the last 70 ka

    Science.gov (United States)

    McKay, C. L.; Filipsson, H. L.; Romero, O. E.; Stuut, J.-B. W.; Björck, S.

    2016-02-01

    The Benguela Upwelling System (BUS), located between 30 and 20°S, is one of the fundamental high-productivity systems of the world ocean. The BUS has previously been studied in terms of primary productivity and ecology over glacial-interglacial timescales; however, the response and coupling with the benthic environment have received little attention. Here, for the first time, we present a high-resolution reconstruction of the BUS highlighting the link between surface and benthic productivity and their response to climatic and oceanographic changes over the last 70 ka. The study is based on benthic foraminiferal faunal analysis together with analyses of diatom assemblages, grain size of the terrigenous fraction, and stable O and C isotopic and bulk biogenic components of core GeoB3606-1. We reveal significant shifts in benthic foraminiferal assemblage composition. Tight coupling existed between the surface and bottom water environment especially throughout marine isotope stages 4 and 3 (MIS4 and MIS3). Due to the high export production, the site has essentially experienced continuous low oxygen conditions; however, there are time periods where the hypoxic conditions were even more notable. Two of these severe hypoxic periods were during parts of MIS4 and MIS3 where we find an inverse relationship between diatom and benthic foraminifera accumulation, meaning that during times of extremely high phytodetritus export we note strongly suppressed benthic productivity. We also stress the importance of food source for the benthos throughout the record. Shifts in export productivity are attributed not only to upwelling intensity and filament front position, but also, regional-global climatic and oceanographic changes had significant impact on the BUS dynamics.

  7. A modeling study of the effects of river runoff, tides, and surface wind-wave mixing on the Eastern and Western Hainan upwelling systems of the South China Sea, China

    Science.gov (United States)

    Wang, Daoru; Yang, Yi; Wang, Jia; Bai, Xuezhi

    2015-08-01

    This study investigates the variation of eastern Hainan (or Qiongdong) and western Hainan upwelling systems during the East Asia summer monsoon (EASM) season using a state-of-the-art finite-volume coastal model and reveals the impacts of tidal mixing, surface wind-wave mixing, and river runoff on the Hainan upwellings in terms of the spatial and temporal variations, intensification, and vertical structure. It is found that (1) river runoff, a stabilizer of the water column, suppresses the upwelling beneath it from reaching the surface, although strong upwelling still occurs in the lower layer of the water column; (2) tidal mixing, a mechanism of forming bottom mixed layer, promotes upwelling, leading to strengthening of the upwelling; (3) surface wind-wave mixing, a major mechanism for formation of the upper mixed layer and a sharp thermocline, inhibits the upwelling from crossing the thermocline to reach the surface; and (4) unlike the east coast upwelling, the upwelling on the west coast is tidally induced.

  8. Mixed basin boundary structures of chaotic systems

    International Nuclear Information System (INIS)

    Motivated by recent numerical observations on a four-dimensional continuous-time dynamical system, we consider different types of basin boundary structures for chaotic systems. These general structures are essentially mixtures of the previously known types of basin boundaries where the character of the boundary assumes features of the previously known boundary types at different points arbitrarily finely interspersed in the boundary. For example, we discuss situations where an everywhere continuous boundary that is otherwise smooth and differentiable at almost every point has an embedded uncountable, zero Lebesgue measure set of points at which the boundary curve is nondifferentiable. Although the nondifferentiable set is only of zero Lebesgue measure, the curve close-quote s fractal dimension may (depending on parameters) still be greater than one. In addition, we discuss bifurcations from such a mixed boundary to a 'pure' boundary that is a fractal nowhere differentiable curve or surface and to a pure nonfractal boundary that is everywhere smooth. copyright 1999 The American Physical Society

  9. 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.

  10. The importance of external climate forcing for the variability and trends of coastal upwelling in past and future climate

    Science.gov (United States)

    Tim, Nele; Zorita, Eduardo; Hünicke, Birgit; Yi, Xing; Emeis, Kay-Christian

    2016-06-01

    The eastern boundary upwelling systems, located in the subtropics at the eastern boundary of the Atlantic and Pacific oceans and mainly driven by the trade winds, are the major coastal upwelling regions. Previous studies have suggested that the intensity of upwelling in these areas in the past centuries may have been influenced by the external radiative forcing, for instance by changes in solar irradiance, and it will also be influenced in the future by the increasing atmospheric greenhouse gases. Here, we analyse the impact of the external climate forcing on these upwelling systems in ensembles of simulations of two Earth system models. The ensembles contain three simulations for each period covering the past millennium (900-1849) and the 20th century (1850-2005). One of these Earth system models additionally includes the near future (2006-2100). Using a set of simulations, differing only in their initial conditions, enables us to test whether the observed variability and trends are driven by the external radiative forcing. Our analysis shows that the variability of the simulated upwelling is largely not affected by the external forcing and that, generally, there are no significant trends in the periods covering the past and future. Only in future simulations with the strongest increase of greenhouse gas concentrations the upwelling trends are significant and appear in all members of the ensemble.

  11. Life in the sea of plenty: Seasonal and regional comparison of physiological performance of Euphausia hanseni in the northern Benguela upwelling system

    Science.gov (United States)

    Werner, Thorsten; Buchholz, Cornelia; Buchholz, Friedrich

    2015-09-01

    Variability in upwelling events may lead to periods of constrained food availability in the northern Benguela upwelling system (NBUS), thereby affecting the physiological state and metabolic activity of euphausiids. Most attention has so far been paid to seasonal effects but little is known about regional variability. Metabolic activity (expressed by respiration and excretion rates) and physiological state (expressed by reproductive effort and moult activity) in Euphausia hanseni were examined at different stations during austral summer (minimum upwelling) and austral winter (maximum upwelling). Overall, regional differences in physiological state, influencing metabolic activity, were greater than seasonal ones, indicating favourable conditions for growth and reproduction year-round. Higher respiration rates were found for females in more advanced stages of sexual development. Moult stage did not affect oxygen consumption rates, however. The physiological state of E. hanseni at the time of capture may serve as a meaningful indicator of the associated hydrographic conditions in the NBUS, to be further used in eco-system analysis on seasonal or long-term time scales. A latitudinal comparison of species highlights the extraordinary physiological plasticity of euphausiids.

  12. 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.

  13. 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.

  14. 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.

  15. Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal.

    Science.gov (United States)

    Puccinelli, Eleonora; McQuaid, Christopher David; Noyon, Margaux

    2016-01-01

    Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA) signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI) and Gonad Index (GI) differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while nearshore

  16. 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.

  17. Wireless boundary monitor system and method

    International Nuclear Information System (INIS)

    A wireless boundary monitor system used to monitor the integrity of a boundary surrounding an area uses at least two housings having at least one transmitting means for emitting ultrasonic pressure waves to a medium. Each of the housings has a plurality of receiving means for sensing the pressure waves in the medium. The transmitting means and the receiving means of each housing are aimable and communicably linked. At least one of the housings is equipped with a local alarm means for emitting a first alarm indication whereby, when the pressure waves propagating from a transmitting means to a receiving means are sufficiently blocked by an object a local alarm means or a remote alarm means or a combination thereof emit respective alarm indications. The system may be reset either manually or automatically. This wireless boundary monitor system has useful applications in both indoor and outdoor environments. 4 figs

  18. 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

    A model of trophic flows through the northern Benguela between 1980 and 1989 was constructed using the ECOPATH approach. The model serves to close the temporal gap between models of the system for the 1970s and 1990s. The aim is to provide a workable model, with the intention of encouraging scien...

  19. Dehumidification of Iberia by enhanced summer upwelling

    Science.gov (United States)

    Miranda, P. M.; Costa, V.; Nogueira, M.; Semedo, A.

    2015-12-01

    Dehumidification of Iberia by enhanced summer upwelling Miranda PMA, Costa V, Semedo AIDL, Faculdade de Ciências, University of LisbonA 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. Aknowledgements: Study supported by FCT Grant RECI/GEO-MET/0380/2012Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245.Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.xHoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189.Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric

  20. The future of coastal upwelling ecosystems: the impact of potential wind changes on ocean acidification and coastal hypoxia

    Science.gov (United States)

    Lachkar, Z.; Gruber, N.

    2012-04-01

    The upwelling of deep, low pH, and low oxygen water to the surface makes eastern boundary upwelling systems (EBUS) naturally prone to global change induced perturbations such as ocean acidification and ocean deoxygentation related to decreased ocean ventilation. The severity of these chemical perturbations may further be exacerbated in EBUS by the potential increase in upwelling favorable winds induced by global warming. Here, we explore the impact of upwelling-favorable wind changes on modern and future ocean acidification and coastal hypoxia through a comparative study of the California Current System (California CS) and the Canary Current System (Canary CS). To this end, we undertook a series of idealized wind perturbation studies for present-day and year 2050 conditions with eddy-resolving setups of the Regional Oceanic Modeling System - ROMS- to which a nitrogen-based Nutrient-Phytoplankton-Detritus-Zooplankton (NPDZ) biogeochemical model was coupled. Our results show that the increase of upwelling favorable winds leads to a substantial shoaling of the hypoxic boundary in the California CS, while the same wind perturbation results in a reduction of the hypoxic water volume in the Canary CS. This is because coastal hypoxia is driven by local remineralization of organic matter on the shelf in the Canary CS, while it is essentially driven by large-scale advection of low oxygen water in the California CS. The intensification of upwelling tends to acerbate ocean acidification in the surface ocean, but mediates it below it, leading to complex change pattern reflecting the intricate interplay between biologically and physically -driven changes in calcium carbonate saturation state. Additionally, our results reveal differential biogeochemical responses to upwelling intensification in the water column and on the continental shelf with, therefore, contrasting implications for the benthic and the pelagic communities of these ecosystems.

  1. Environmental proteomics of microbial plankton in a highly productive coastal upwelling system

    Energy Technology Data Exchange (ETDEWEB)

    Sowell, Sarah [Oregon State University, Corvallis; Abraham, Paul E [ORNL; Shah, Manesh B [ORNL; Verberkmoes, Nathan C [ORNL; Smith, Daniel [Oregon State University, Corvallis; Barofsky, Douglas [Oregon State University, Corvallis; Giovannoni, Stephen [Oregon State University, Corvallis

    2011-01-01

    Metaproteomics is one of a suite of new approaches providing insights into the activities of microorganisms in natural environments. Proteins, the final products of gene expression, indicate cellular priorities, taking into account both transcriptional and posttranscriptional control mechanisms that control adaptive responses. Here, we report the proteomic composition of the o 1.2 lm fraction of a microbial community from Oregon coast summer surface waters, detected with two-dimensional liquid chromatography coupled with electrospray tandem mass spectrometry. Spectra corresponding to proteins involved in protein folding and biosynthesis, transport, and viral capsid structure were the most frequently detected. A total of 36% of all the detected proteins were best matches to the SAR11 clade, and other abundant coastal microbial clades were also well represented, including the Roseobacter clade (17%), oligotrophic marine gammaproteobacteria group (6%), OM43 clade (1%). Viral origins were attributed to 2.5% of proteins. In contrast to oligotrophic waters, phosphate transporters were not highly detected in this nutrient-rich system. However, transporters for amino acids, taurine, polyamines and glutamine synthetase were among the most highly detected proteins, supporting predictions that carbon and nitrogen are more limiting than phosphate in this environment. Intriguingly, one of the highly detected proteins was methanol dehydrogenase originating from the OM43 clade, providing further support for recent reports that the metabolism of one-carbon compounds by these streamlined methylotrophs might be an important feature of coastal ocean biogeochemistry.

  2. Pervasive multidecadal variations in productivity within the Peruvian Upwelling System over the last millennium

    Science.gov (United States)

    Fleury, S.; Martinez, P.; Crosta, X.; Charlier, K.; Billy, I.; Hanquiez, V.; Blanz, T.; Schneider, R. R.

    2015-10-01

    There is no agreement on the pluri-decadal expression of El Niño-Southern Oscillation (ENSO) in the Pacific over the last millennium. Marine records from the Peruvian margin indicate humid conditions (El Niño-like mean conditions) over the Little Ice Age, while precipitation records from the eastern equatorial Pacific infer arid conditions (La Niña-like mean conditions) for the same period. We here studied diatom assemblages, nitrogen isotopes, and major and minor elements at the lamination level in three laminated trigger cores located between 11°S and 15°S on the Peruvian shelf within the oxygen minimum zone (OMZ) to reconstruct precipitation and ocean productivity at the multiannual to multidecadal timescales over the last millennium. We respected the sediment structure, thus providing the first records of the mean climatic conditions at the origin of the lamination deposition, which ones represent several years. Light laminations were deposited under productive and dry conditions, indicative of La Niña-like mean conditions in the system, while dark laminations were deposited under non-productive and humid conditions, representative of El Niño-like mean conditions. La Niña-like mean conditions were predominant during the Medieval Warm Period (MWP; 1000-600 years BP) and Current Warm Period (CWP; 150 years BP to present), while El Niño-like mean conditions prevailed over the Little Ice Age (LIA; 600-150 years BP). We provide evidence for persistent multidecadal variations in productivity over the last millennium, which were disconnected from the mean climate state. Multidecadal variability has been stronger over the last 450 years concomitantly to increased variability in the NAO index. Two intervals of strong multidecadal variability were also observed over the MWP, congruent to decreased solar irradiance and increased volcanic activity.

  3. Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

    Science.gov (United States)

    Laudien, Jürgen; Rojo, Manuel E.; Oliva, Marcelo E.; Arntz, Wolf E.; Thatje, Sven

    2007-06-01

    The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m-2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m-2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H', Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-m-zone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997-1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system.

  4. Entanglement Entropies in Conformal Systems with Boundaries

    OpenAIRE

    Taddia, L.; Xavier, J. C.; Alcaraz, F. C.; Sierra, G.

    2013-01-01

    We study the entanglement entropies in one-dimensional open critical systems, whose effective description is given by a conformal field theory with boundaries. We show that for pure-state systems formed by the ground state or by the excited states associated to primary fields, the entanglement entropies have a finite-size behavior that depends on the correlation of the underlying field theory. The analytical results are checked numerically, finding excellent agreement for the quantum chains r...

  5. A global system view of firm boundaries

    OpenAIRE

    Peter J Buckley; Niron Hashai

    2004-01-01

    This paper applies the global system view to the location and control strategies of firms. This approach envisages the world as a grid of potential locations for value-adding activities, connected by flows of information and products. The simplified model provides a basis for testing new hypotheses on the number of firms that will exist in the global system, their locations, and their organisational boundaries. The paper provides a rigorous and formal exposition of the theories of internation...

  6. Magnetopause Boundary Processes Throughout the Solar System

    Science.gov (United States)

    Masters, A.

    2014-12-01

    Earth is not the only planet in the Solar System with a natural magnetic shield. Mercury, Jupiter, Saturn, Uranus, and Neptune are similarly protected from the solar wind and cosmic rays. However, like our planet, the magnetic shielding of each of these magnetized planets can break down, driving energy flow through each planetary magnetosphere. Although studies of the magnetopause boundary of Earth's magnetosphere have shed considerable light on the processes that lead to this breakdown, the extent to which we can apply this understanding to the diverse space plasma environments surrounding other planets remains unclear. Here we review what we have learnt so far about the operation of magnetopause boundary processes at all the magnetized planets in the Solar System, and outline some of the relevant outstanding questions. We start by consolidating present understanding of terrestrial magnetopause processes, which is our reference when considering other boundaries. We focus on selected processes (magnetic reconnection, Kelvin-Helmholtz instability), compare how we expect them to operate at each planetary magnetopause, and assess whether or not this is consistent with in situ spacecraft observations. For each planetary magnetosphere we then discuss the nature of the total interaction with the solar wind, and whether this is expected to be dominant over internal drivers of magnetospheric dynamics. A combination of further spacecraft exploration and dedicated numerical modeling is required in order to address the many outstanding questions concerning this topic. Progress in this direction would have broad implications for other space plasma systems, in our solar system and beyond.

  7. Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology

    OpenAIRE

    Reddin, Carl J.; Felipe Docmac; Nessa E O'Connor; Bothwell, John H; Chris Harrod

    2015-01-01

    Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchi...

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

    OpenAIRE

    Ospina-Álvarez, Natalia; Varela, Manuel; Doval, M. Dolores; Gómez-Gesteira, M.; Cervantes-Duarte, Rafael; Prego, R

    2014-01-01

    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 20...

  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 processes of upwelling off the southern tip (the Kanyakumari coast) and the west coast of India are highly localized features with different forcing mechanisms, and they cannot be treated as a uniform wind-driven upwelling system. Off...

  10. Transmission of the haplosporidian parasite MSX Haplosporidium nelsoni to the eastern oyster Crassostrea virginica in an upweller system.

    Science.gov (United States)

    Sunila, I; Karolus, J; Lang, E P; Mroczka, M E; Volk, J

    2000-08-31

    The haplosporidian oyster parasite MSX (Multinucleated Sphere X) Haplosporidium nelsoni was transmitted to eastern oysters Crassostrea virginica. Hatchery-raised, MSX-free juvenile oysters were placed in upweller tanks. Water to the tanks was filtered through a screen with 1 mm2 openings and originated from the water column overlaying naturally infected oysters beds (MSX prevalence 17 to 57%). MSX was diagnosed by histopathological analysis. MSX-disease (57% prevalence) with increased mortality (19%) was observed 11 wk after the beginning of the exposure and mortality of 80% after 16 wk. The study demonstrates transmission of MSX via water-borne infectious agents capable of passing through a 1 mm filter. PMID:11023255

  11. New boundary conditions for the c=-2 ghost system

    International Nuclear Information System (INIS)

    We investigate a novel boundary condition for the bc system with central charge c=-2. Its boundary state is constructed and tested in detail. It appears to give rise to the first example of a local logarithmic boundary sector within a bulk theory whose Virasoro zero modes are diagonalizable. (orig.)

  12. New boundary conditions for the c=-2 ghost system

    Energy Technology Data Exchange (ETDEWEB)

    Creutzig, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quella, T. [Amsterdam Univ. (Netherlands). KdV Inst. for Mathematics; Schomerus, V. [Center for Mathematical Physics, Hamburg (Germany)]|[King' s College London (United Kingdom). Dept. of Mathematics

    2006-12-15

    We investigate a novel boundary condition for the bc system with central charge c=-2. Its boundary state is constructed and tested in detail. It appears to give rise to the first example of a local logarithmic boundary sector within a bulk theory whose Virasoro zero modes are diagonalizable. (orig.)

  13. ON STABILITY BOUNDARY OF LINEAR MULTI-PARAMETER HAMILTONIAN SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Qi Zhaohui(齐朝晖); Alexander P.Seyranian

    2002-01-01

    In this paper an approximate equation is derived to describe smoothparts of the stability boundary for linear Hamiltonian systems, depending on arbitrarynumber of parameters. With this equation, we can obtain parameters correspondingto the stability boundary, as well as to the stability and instability domains, pro-vided that one point on the stability boundary is known. Then differential equationsdescribing the evolution of eigenvalues and eigenvectors along a curve on the sta-bility boundary surface are derived. These equations also allow us to obtain curvesbelonging to the stability boundary. Applications to linear gyroscopic systems areconsidered and studied with examples.

  14. HETERO PHASE BOUNDARIES IN THE SILVER-NICKEL SYSTEM

    OpenAIRE

    Maurer, R; Fischmeister, H.

    1988-01-01

    Using Gleiter's sphere rotation technique, the orientation relations of preferred heterophase boundaries have been determined in the system silver/nickel. Comparison with other sphere rotation studies shows great similarities between all systems studied so far, which include metals on oxides and on alkali halides. In all, 33 orientation types have been found : these can be reduced to 10 "elementary" boundary types if facetting and twinning at the boundary are admitted. In almost al1 systems. ...

  15. 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...... 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...

  16. Random error analysis of marine xCO2 measurements in a coastal upwelling region

    Science.gov (United States)

    Reimer, Janet J.; Cueva, Alejandro; Gaxiola-Castro, Gilberto; Lara-Lara, Ruben; Vargas, Rodrigo

    2016-04-01

    Quantifying and identifying measurement error is an ongoing challenge for carbon cycle science to constrain measurable uncertainty related to the sources and sinks of CO2. One source of uncertainty in measurements is derived from random errors (ε); thus, it is important to quantify their magnitude and their relationship to environmental variability in order to constrain local-to-global carbon budgets. We applied a paired-observation method to determine ε associated with marine xCO2 in a coastal upwelling zone of an eastern boundary current. Continuous data (3-h resolution) from a mooring platform during upwelling and non-upwelling seasons was analyzed off of northern Baja California in the California Current. To test the rigor of the algorithm to calculate ε we propose a method for determining daily mean time series values that may be affected by ε. To do this we used either two or three variables in the function, but no significant differences for ε mean values were found due to the large variability in ε (-0.088 ± 27 ppm for two variables and -0.057 ± 28 ppm for three variables). Mean ε values were centered on zero, with low values of ε more frequent than greater values, and follow a double exponential distribution. Random error variability increased with higher magnitudes of xCO2, and in general, ε variability increased in relation to upwelling conditions (up to ∼9% of measurements). Increased ε during upwelling suggests the importance of meso-scale processes on ε variability and could have a large influence seasonal to annual CO2 estimates. This approach could be extended and modified to other marine carbonate system variables as part of data quality assurance/quality control and to quantify uncertainty (due to ε) from a wide variety of continuous oceanographic monitoring platforms.

  17. Salinity driven oceanographic upwelling

    Science.gov (United States)

    Johnson, David H.

    1986-01-01

    The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water.

  18. Analytical determination of distillation boundaries for ternary azeotropic systems

    OpenAIRE

    Marcilla Gomis, Antonio; Reyes Labarta, Juan Antonio; Velasco, Raúl; Serrano Cayuelas, María Dolores; Olaya López, María del Mar

    2009-01-01

    A new straight forward algorithm to calculate distillation boundaries in ternary azeotropic systems has been developed. The proposed method allows, using cubic splines, the calculation of distillation trajectories and the calculation of that corresponding to the searched distillation boundaries. The algorithm is applied to 4 ternary liquid-vapour systems to test its validity.

  19. Electrostatics of solvated systems in periodic boundary conditions

    OpenAIRE

    Andreussi, Oliviero; Marzari, Nicola

    2014-01-01

    Continuum solvation methods can provide an accurate and inexpensive embedding of quantum simulations in liquid or complex dielectric environments. Notwithstanding a long history and manifold applications to isolated systems in open boundary conditions, their extension to materials simulations --- typically entailing periodic-boundary conditions --- is very recent, and special care is needed to address correctly the electrostatic terms. We discuss here how periodic-boundary corrections develop...

  20. Boundary Layer to a System of Viscous Hyperbolic Conservation Laws

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, we investigate the large-time behavior of solutions to the initial-boundary value problem for nxn hyperbolic system of conservation laws with artificial viscosity in the half line (0, ∞). We first show that a boundary layer exists if the corresponding hyperbolic part contains at least one characteristic field with negative propagation speed. We further show that such boundary layer is nonlinearly stable under small initial perturbation. The proofs are given by an elementary energy method.

  1. 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

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

    DEFF Research Database (Denmark)

    Winther, Grethe

    2009-01-01

    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...... 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...... phenomena are coupled through their common dependence on the slip systems....

  3. Slip systems, lattice rotations and dislocation boundaries

    DEFF Research Database (Denmark)

    Winther, Grethe

    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......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...... these discrepancies is discussed. Finally, the implications of the relations between slip and dislocation structures for the modelling of mechanical properties are discussed....

  4. Cross-shelf structure of coastal upwelling : a two - dimensional extension of Ekman's theory and a mechanism for inner shelf upwelling shut down

    OpenAIRE

    Estrade, P.; Marchesiello, Patrick; Verdière de, A. C.; Roy, Claude

    2008-01-01

    Sea-surface temperature images of the coastal upwelling regions off Northwest Africa show that the core of upwelling is sometimes located far from the coast. This has been documented in three regions that share a common feature, namely a wide and shallow continental shelf. This upwelling feature plays a key role in the ecology of the Canary Current System. It creates an innerfront which provides retention for biological material, e.g. fish eggs and larvae, in the highly productive nearshore e...

  5. Inverse Boundary Problems for Systems in Two Dimensions

    CERN Document Server

    Albin, Pierre; Tzou, Leo; Uhlmann, Gunther

    2011-01-01

    We prove identification of coefficients up to gauge by Cauchy data at the boundary for elliptic systems on oriented compact surfaces with boundary or domains of $\\mathbb{C}$. In the geometric setting, we fix a Riemann surface with boundary, and consider both a Dirac-type operator plus potential acting on sections of a Clifford bundle and a connection Laplacian plus potential (i.e. Schr\\"odinger Laplacian with external Yang-Mills field) acting on sections of a Hermitian bundle. In either case we show that the Cauchy data determines both the connection and the potential up to a natural gauge transformation: conjugation by an endomorphism of the bundle which is the identity at the boundary. For domains of $\\mathbb{C}$, we recover zeroth order terms up to gauge from Cauchy data at the boundary in first order elliptic systems.

  6. Boundary Controllability of Integrodifferential Systems in Banach Spaces

    Indian Academy of Sciences (India)

    K Balachandran; E R Anandhi

    2001-02-01

    Sufficient conditions for boundary controllability of integrodifferential systems in Banach spaces are established. The results are obtained by using the strongly continuous semigroup theory and the Banach contraction principle. Examples are provided to illustrate the theory.

  7. 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...

  8. A realization theory for autonomous boundary-value linear systems

    OpenAIRE

    Nikoukhah, Ramine

    1989-01-01

    A frequency-domain realization theory is developed for the class of autonomous- , but not necessarily stationary, boundary-value linear systems. It is shown that this realization problem, which consists of constructing autonomous boundary-value linear systems from prescribed weighting patterns, reduces to the factorization of several rational matrices in two variables having separable denominators. This factorization problem is examined and a method is given for constructing minimal factoriza...

  9. Pliocene Warm Period Upwelling in the Southern Benguela Region

    Science.gov (United States)

    Petrick, B. F.; McClymont, E.; Felder, S.; Leng, M. J.; Rosell Mele, A.; Rueda, G.

    2014-12-01

    The mid-Pliocene has been proposed as a possible analogue for understanding future climate change and testing climate models. Previous work has shown that during the Pliocene the major upwelling systems were relatively warm, and thus either inactive, contracted, or upwelling warmer waters than present. Here we examine evidence from a core site located on the margins of the modern Benguela upwelling system, to test whether the upwelling cells had migrated or contracted relative to present during the Pliocene. We applied several organic geochemistry proxies and foraminiferal analyses to reconstruct the Pliocene history of ODP site 1087 (31º28'S, 15º19'E, 1374m water depth), including the UK37' index and TEX86 index (for reconstructing sea surface temperatures), chlorins (for estimating primary productivity) and planktonic foraminifera assemblages (for inferring water mass changes). These proxies show that between 3.5 and 3.0 Ma the southern Benguela region was significantly cooler than the northern Benguela region, the latter where the main upwelling cells are found today. Coupled with higher primary production, a shift in planktonic foraminifera assemblage, and an offset between the UK37' index and TEX86 index, we infer that more extensive upwelling was present in the southern Benguela region during the Pliocene. We infer that the main Benguela upwelling cells had shifted southward relative to today, as a result of changes in the local wind field. We find evidence for pronounced cooling and a shift in the planktonic foraminifera assemblage during the M2 and KM2 glacial stages, showing a sensitivity of Benguela upwelling to these short-lived climate events.

  10. Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific

    Science.gov (United States)

    Toth, Lauren T.; Aronson, Richard B.; Cheng, Hai; Edwards, R. Lawrence

    2015-01-01

    Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from ~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at ~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño–Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene.

  11. Combining shipboard in situ data with satellite data to estimate daily primary production in a coastal upwelling system: A data mining approach

    Science.gov (United States)

    Williamson, Robert I.; Field, John G.; Shillington, Frank A.; Jarre, Astrid; Potgieter, Anet

    2015-11-01

    This study classifies coastal time-series data according to subsurface phytoplankton vertical distributions to be able to capture the variability of primary production at fine spatial and temporal scales. Our method uses algorithms developed to extract patterns in large datasets of time-sequential data. We use short time-series of QuikSCAT surface winds, MODIS sea surface temperature and surface chlorophyll a associated with each in situ chlorophyll a profile, as well as the season and bottom depth of the in situ station to discover patterns that can be used to classify new data into 12 profile classes. We first fill in missing MODIS data using a conditional random field model so that cloudy days are not excluded. The most likely profile is then predicted using all the available data. We apply our method to the St Helena Bay area, a region within the productive Benguela Current upwelling system. A profile is predicted for each day and each pixel of 4 km resolution satellite image for 16 consecutive months. Each profile is used in a broad-band photosynthesis model to produce a daily three-dimensional estimate of gross primary production. An average production rate of 3.2 g C m-2 day-1 was obtained for the area, which shows very good agreement with other estimates from the region. The results show persistent high productivity near the surface throughout the year with the exception of the winter months. Deeper in the water column productivity is more seasonal. The 16 month time-series highlights the interannual, seasonal and daily variability of the system. By linking physical processes to the distribution of phytoplankton at appropriate spatio-temporal scales, we can now more rigorously investigate bottom-up driven impacts on ecosystems characterised by short-term variability.

  12. Emergy analysis of coastal systems influenced by upwelling in northern Chile: Estimation of ecological-economic sustainability at multiple scales

    Science.gov (United States)

    Numerous studies carried out in a variety of environments have suggested that coastal marine systems generate a variety of goods and services for humanity. However, in recent decades there has been a marked degradation of these ecosystems, as well as over-exploitation of natural ...

  13. 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...

  14. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

    Science.gov (United States)

    Siedlecki, Samantha A.; Kaplan, Isaac C.; Hermann, Albert J.; Nguyen, Thanh Tam; Bond, Nicholas A.; Newton, Jan A.; Williams, Gregory D.; Peterson, William T.; Alin, Simone R.; Feely, Richard A.

    2016-06-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA’s Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

  15. Upwelling in the Gulf of Lions

    OpenAIRE

    Millot, Claude; Wald, Lucien

    1981-01-01

    International audience The hydrological and meteorological characteristics of the Gulf of Lions are such that upwelling occurs with no bias due to tides or strong longshore circulation. The sky is generally cloud-free, an uncommon feature in an upwelling area that allows extensive use of satellite infrared data. The observations are adequate to compute mean maps of the sea-surface temperature during upwelling events. Undoubtedly upwelling is much more intense along straitght coastal segmen...

  16. Upwelling limitation by onshore geostrophic flow

    OpenAIRE

    Marchesiello, Patrick; Estrade, P.

    2010-01-01

    Although coastal upwelling has now been the subject of many studies. the only available dynamical upwelling index is derived from a simple relation between upwelling intensity and alongshore winds stress In this study. we first present a primitive equation model simulation of the New Caledonia island legion to show that upwelling intensity can be limited by onshore geostrophic flow Then, we propose a new analytical model accounting for the effect of onshore geostrophic flow on the structure o...

  17. Nimbus observation of oceanic upwelling

    Science.gov (United States)

    Szekielda, K.

    1972-01-01

    Observing the development of upwelling on the northeast coast of Africa by measuring ocean surface emission with infrared radiometers on Nimbus satellites is reported. Using the temperature of the ocean as telemetered by the satellite, the biological potential of an area is estimated, and consequently the highest potential for fisheries.

  18. Driven nonequilibrium lattice systems with shifted periodic boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Valles, J.L. (New York Univ., NY (USA)); Leung, K.; Zia, R.K.P. (Virginia Polytechnic Institute and State Univ., Blacksburg (USA))

    1989-07-01

    The authors present the first study of a driven nonequilibrium lattice system in the two-phase region, with shifted periodic boundary conditions, forcing steps into the interface. When the shift corresponds to small angles with respect to the driving field, they find nonanalytic behavior in the (internal) energy of the system, supporting numerical evidence that interface roughness is suppressed by the field. For larger shifts, the competition between the driving field and the boundary induces the breakup of a single strip with tilted interfaces into many narrower strips with aligned interfaces. The size and temperature dependences of the critical angles of such breakup transitions are studied.

  19. Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Tiselius, P.; Mitchell-Innes, B.;

    1998-01-01

    The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling...... center. We therefore hypothesized that upwelling diatom blooms are terminated by aggregate formation and rapid sedimentation. We monitored the development of a maturing diatom (mainly Chaetoceros spp.) bloom in the Benguela upwelling current during 7 d in February. Chlorophyll concentrations remained...

  20. Dynamic stability boundaries of a liquid metal cooled reactor system

    International Nuclear Information System (INIS)

    Part of the reactor design process is the assessment of the impact of different design changes on predefined performance criteria including stability of the reactor system under different conditions. This work focuses on the stability analysis of a combined reactor and primary heat transport system where system parameters are free to vary, with particular interest in low reactor power, low reactor coolant flow conditions. Such conditions might be encountered, for example, after a loss-of-flow without scram in some passively safe reactor designs. Linear stability analysis based methods are developed to find the stability regions, stability boundary surface in system parameter space, and frequency of oscillation at oscillatory instability boundaries. Models are presented for the reactor, detailed thermal hydraulic reactivity feedback associated with coolant outlet and inlet temperatures, decay heat, and primary system. Developed stability analysis tools are applied to the system model. System parameters include integral reactivity parameters, decay heat primary system mass, coolant flow, and natural circulation flow. The resulting stability boundary surface and its associated frequency of oscillation surface in multidimensional system parameter space show the effect of system parameter changes. By adopting model parameters for a reactor design, a stability prediction procedure is illustrated

  1. Boundary Spanning in Offshored Information Systems Development Projects

    Science.gov (United States)

    Krishnan, Poornima

    2010-01-01

    Recent growth in offshore outsourcing of information systems (IS) services is accompanied by managing the offshore projects successfully. Much of the project failures can be attributed to geographic and organizational boundaries which create differences in culture, language, work patterns, and decision making processes among the offshore project…

  2. On Nonlinear Coupled System with Nonlocal Boundary Conditions

    Directory of Open Access Journals (Sweden)

    U. R. Soares

    2003-11-01

    Full Text Available We discuss the existence, uniqueness and stability exponential andpolynomial of global solutions for a nonlinear coupled system with nonlocal boundary conditions. We show that such dissipation is strong enough to produce uniform rate of decay. Besides, the coupled is nonlinear which brings up some additional difficulties, which makes the problem interesting.

  3. 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.

  4. The thermodynamic cost of driving quantum systems by their boundaries

    OpenAIRE

    Felipe Barra

    2015-01-01

    The laws of thermodynamics put limits to the efficiencies of thermal machines. Analogues of these laws are now established for quantum engines weakly and passively coupled to the environment providing a framework to find improvements to their performance. Systems whose interaction with the environment is actively controlled do not fall in that framework. Here we consider systems actively and locally coupled to the environment, evolving with a so-called boundary-driven Lindblad equation. Start...

  5. Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Tiselius, P.; Mitchell-Innes, B.; Hansen, J.L.S.; Visser, Andre; Mari, X.

    1998-01-01

    The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling...

  6. Intense submesoscale upwelling in anticyclonic eddies

    Science.gov (United States)

    Brannigan, L.

    2016-04-01

    Observations from around the global ocean show that enhanced biological activity can be found in anticyclonic eddies. This may mean that upwelling of nutrient-rich water occurs within the eddy, but such upwelling is not captured by models that resolve mesoscale processes. High-resolution simulations presented here show intense submesoscale upwelling from the thermocline to the mixed layer in anticyclonic eddies. The properties of the upwelling are consistent with a process known as symmetric instability. A simple limiting nutrient experiment shows that this upwelling can drive much higher biological activity in anticyclonic eddies when there is a high nutrient concentration in the thermocline. An estimate for the magnitude of upwelling associated with symmetric instability in anticyclonic eddies in the Sargasso Sea shows that it may be of comparable magnitude to other processes, though further work is required to understand the full implications for basin-scale nutrient budgets.

  7. System, Subsystem, Hive: Boundary Problems in Computational Theories of Consciousness

    Science.gov (United States)

    Fekete, Tomer; van Leeuwen, Cees; Edelman, Shimon

    2016-01-01

    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. PMID:27512377

  8. Electrostatics of solvated systems in periodic boundary conditions

    Science.gov (United States)

    Andreussi, Oliviero; Marzari, Nicola

    2014-12-01

    Continuum solvation methods can provide an accurate and inexpensive embedding of quantum simulations in liquid or complex dielectric environments. Notwithstanding a long history and manifold applications to isolated systems in open boundary conditions, their extension to materials simulations, typically entailing periodic boundary conditions, is very recent, and special care is needed to address correctly the electrostatic terms. We discuss here how periodic boundary corrections developed for systems in vacuum should be modified to take into account solvent effects, using as a general framework the self-consistent continuum solvation model developed within plane-wave density-functional theory [O. Andreussi et al., J. Chem. Phys. 136, 064102 (2012), 10.1063/1.3676407]. A comprehensive discussion of real- and reciprocal-space corrective approaches is presented, together with an assessment of their ability to remove electrostatic interactions between periodic replicas. Numerical results for zero- and two-dimensional charged systems highlight the effectiveness of the different suggestions, and underline the importance of a proper treatment of electrostatic interactions in first-principles studies of charged systems in solution.

  9. 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...

  10. Applying twisted boundary conditions for few-body nuclear systems

    Science.gov (United States)

    Körber, Christopher; Luu, Thomas

    2016-05-01

    We describe and implement twisted boundary conditions for the deuteron and triton systems within finite volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twist angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length L ≈8 -14 fm. Of particular importance is our derivation and numerical verification of three-body analogs of "i-periodic" twist angles that eliminate the leading-order finite-volume effects to the three-body binding energy.

  11. Applying Twisted Boundary Conditions for Few-body Nuclear Systems

    CERN Document Server

    Körber, Christopher

    2015-01-01

    We describe and implement twisted boundary conditions for the deuteron and triton systems within finite-volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twists angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length $L\\approx8-14$ fm. Of particular importance is our derivation and numerical verification of three-body analogue of `i-periodic' twist angles that eliminate the leading order finite-volume effects to the three-body binding energy.

  12. Comparaisons des systèmes productifs de l'Atlantique tropical est : dômes thermiques, upwellings côtiers et upwelling équatorial

    OpenAIRE

    Voituriez, B; Herbland, Alain

    1982-01-01

    All the high-productive systems of the Eastern tropical Atlantic between 20°N and 15°S - coastal upwelling, equatorial upwelling, and thermal domes-are partly controlled by the subsuperficial equatorial countercurrent system, which feeds all of them with Southern Atlantic Central Water. However, the enrichment processes in the systems are quite different, and thus the structures differ from one another. Two types have to be considered : 1) the quasi geostrophic ones which are two-layered syst...

  13. Some Notes on Reaction Diffusion Systems with Nonlinear Boundary Conditions

    Institute of Scientific and Technical Information of China (English)

    Wen-jun Sun

    2003-01-01

    This paper deals with the existence and nonexistence of global positive solution to a semilinear reaction-diffusion system with nonlinear boundary conditions. For the heat diffusion case, the necessary and sufficient conditions on the global existence of all positive solutions are obtained. For the general fast diffusion case, we get some conditions on the global existence and nonexistence of positive solutions. The results of this paper fill the some gaps which were left in this field.

  14. Theoretical principles of capillary isotachophoresis in moving-boundary systems

    Czech Academy of Sciences Publication Activity Database

    Gebauer, Petr; Malá, Zdeňka; Boček, Petr

    University of Pécs, 2014 - (Kiliár, F.; Kiss, I.; Nagy, L.; Pap, V.). s. 97-97 ISBN 978-963-642-599-9. [International Symposium on MicroScale Bioseparations /30./. 27.04.2014-01.05.2014, Pécs] R&D Projects: GA ČR(CZ) GA13-05762S Institutional support: RVO:68081715 Keywords : capillary isotachophoresis * moving-boundary systems * CE-ESI MS Subject RIV: CB - Analytical Chemistry, Separation

  15. Coastal-offshore exchange of organic matter across the Cape Ghir filament (NW Africa) during moderate upwelling

    Science.gov (United States)

    Santana-Falcón, Yeray; Benavides, Mar; Sangrà, Pablo; Mason, Evan; Barton, Eric Desmond; Orbi, Abdellatif; Arístegui, Javier

    2016-02-01

    The net coastal-ocean export of particulate organic carbon (POC), dissolved organic carbon (DOC) and chlorophyll a is studied in August 2009 at the Cape Ghir filament, a recurrent feature located within the NW African upwelling system. The estimated flux of excess total organic carbon (the non-refractory pools of DOC and POC) is about 2.1 × 109 kg C y- 1. DOC represents ~ 70% of the excess organic carbon in August 2009, during moderate upwelling. Assuming that this flux is representative of the range within a typical year, the yearly offshore net transport of total organic carbon would represent at least 29% of the primary production in this area. Since the Cape Ghir filament may extend hundreds of kilometers offshore, the associated seaward flux of organic carbon would contribute to the high microbial respiration rates reported from the nearby oligotrophic open ocean region. Our results illustrate that, when considering the regional carbon budgets of eastern boundary regions, it is imperative to take account of the offshore transport of organic matter in the numerous and recurrent upwelling filaments.

  16. 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.

  17. Nutrients, Recycling, and Biological Populations in Upwelling Ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T. E.

    1980-01-01

    Nutrient recycling has been studied in the upwelling areas of Baja California, Northwest Africa, and Peru. Regeneration by biological populations in these areas contributes significant quantities of recycled nitrogen which is utilized in productivity processes. Each area has a different combination of organisms which leads to differences in the relative contributions of zooplankton, nekton, or benthos to the nutrient cycles. Comparisons of ammonium regeneration rates of zooplankton and nekton-micronekton populations in the three upwelling areas show that zooplankton recycle relatively less nitrogen in the Baja California and Peru systems than nekton. In the Northwest Africa upwelling region, however, zooplankton, fish, and benthic inputs are all substantial. In recent years the Peruvian upwelling system has been altered with the decline of the anchoveta population and an increase in the importance of zooplankton in nutrient recycling. The distribution of recycled nitrogen (ammonium and urea) in transects across the shelf at 10°S and 15°S indicates that regeneration is relatively more important at 10°S in the region of the wide shelf. In both areas the distribution of ammonium and urea are not entirely coincident thereby indicating differences in their production and/or utilization.

  18. Theoretical principles of capillary isotachophoresis in moving boundary systems

    Czech Academy of Sciences Publication Activity Database

    Gebauer, Petr; Malá, Zdeňka; Boček, Petr

    Brno : Institute of Analytical Chemistry AS CR, 2014 - (Foret, F.; Křenková, J.; Drobníková, I.; Guttman, A.; Klepárník, K.), s. 205-208 ISBN 978-80-904959-2-0. [CECE 2014. International Interdisciplinary Meeting on Bioanalysis /11./. Brno (CZ), 20.10.2014-22.10.2014] R&D Projects: GA ČR(CZ) GA13-05762S Institutional support: RVO:68081715 Keywords : capillary isotachophoresis * moving boundary system * stacking capability Subject RIV: CB - Analytical Chemistry, Separation http://www.ce-ce.org/CECE2014/CECE%202014%20proceedings_full.pdf

  19. Turing Instability in a Boundary-fed System

    CERN Document Server

    Setayeshgar, S

    1998-01-01

    The formation of localized structures in the chlorine dioxide-idodine-malonic acid (CDIMA) reaction-diffusion system is investigated numerically using a realistic model of this system. We analyze the one-dimensional patterns formed along the gradients imposed by boundary feeds, and study their linear stability to symmetry-breaking perturbations (Turing instability) in the plane transverse to these gradients. We establish that an often-invoked simple local linear analysis which neglects longitudinal diffusion is inappropriate for predicting the linear stability of these patterns. Using a fully nonuniform analysis, we investigate the structure of the patterns formed along the gradients and their stability to transverse Turing pattern formation as a function of the values of two control parameters: the malonic acid feed concentration and the size of the reactor in the dimension along the gradients. The results from this investigation are compared with existing experiments.

  20. Solutions to a hyperbolic system of conservation laws on two boundaries

    Institute of Scientific and Technical Information of China (English)

    JIA Zhi; YAO Ai-di

    2009-01-01

    This paper studies the interaction of elementary waves including delta-shock waves on two boundaries for a hyperbolic system of conservation laws. The solutions of the initial-boundary value problem for the system are constructively obtained. In the problem the initial-boundary data are in piecewise constant states.

  1. Two-Baryon Systems with Twisted Boundary Conditions

    CERN Document Server

    Briceno, Raul A; Luu, Thomas C; Savage, Martin J

    2013-01-01

    We explore the use of twisted boundary conditions in extracting the nucleon mass and the binding energy of two-baryon systems, such as the deuteron, from Lattice QCD calculations. Averaging the results of calculations performed with periodic and anti-periodic boundary conditions imposed upon the light-quark fields, or other pair-wise averages, improves the volume dependence of the deuteron binding energy from ~exp(-kappa*L)/L to ~exp(-sqrt(2)kappa*L)/L. However, a twist angle of pi/2 in each of the spatial directions improves the volume dependence from ~exp(-kappa*L)/L to ~exp(-2kappa*L)/L. Twist averaging the binding energy with a random sampling of twist angles improves the volume dependence from ~exp^(-kappa*L)/L to ~exp(-2kappa*L)/L, but with a standard deviation of ~exp(-kappa*L)/L, introducing a signal-to-noise issue in modest lattice volumes. Using the experimentally determined phase shifts and mixing angles, we determine the expected energies of the deuteron states over a range of cubic lattice volume...

  2. The Nonlinear Predator-Prey Singularly Perturbed Robin Initial Boundary Value Problems for Reaction Diffusion System

    Institute of Scientific and Technical Information of China (English)

    莫嘉琪

    2003-01-01

    The nonlinear predator-prey singularly perturbed Robin initial boundary value problems for reaction diffusion systems were considered. Under suitable conditions, using theory of differential inequalities the existence and asymptotic behavior of solution for initial boundary value problems were studied.

  3. A survey of upwelling ion event characteristics

    Science.gov (United States)

    Pollock, C. J.; Chandler, M. O.; Moore, T. E.; Chappell, C. R.; Waite, J. H., Jr.

    1990-01-01

    Quasi-static electric field data collected by the DE-1 spacecraft were used to study ionospheric ion upwelling events observed in the vicinity of the dayside cleft. Bulk plasma parameters such as ion-species density and field-aligned bulk velocity and flux were derived at points within several upwelling ion events for the H(+), He(+), O(+), and O(2+), and the ion-species bulk parameters near the source altitude were compared. It was found that O(+) ions comprise about 90 percent of the upwelling particle density, followed by H(+) at less than 10 percent; He(+) and O(2+) contribute about 1 percent each. The upwelling O(+) flux is also dominant, followed by upward H(+) flux, which is relatively more significant than the fractional H(+) density, due to its high upward flow velocity.

  4. Coastal Upwelling off Chile: Ocean Productivity and Surface Sediments

    Science.gov (United States)

    Hebbeln, D.; Lamy, F.

    2002-12-01

    The coastal upwelling system of the Peru-Chile Current belongs to the most productive regions in the world oceans. In spite of this fact only very little is known about the sediment distribution in its southern part off the coast of Chile. To increase the knowledge about this region a multi-parameter study of the surface sediment distribution at over 100 sampling sites along the Chilean continental slope between 23°S and 45°S has been carried out. Detailed analyses of sedimentary data (TOC, carbonate, and biogenic opal contents, delta 15N) reveal a close relation to environmental conditions in the region. Coastal upwelling along the Chilean coast, centered around main upwelling centers such as off Antofagasta (23°S), off Lengua de Vaca (30°S), off Valparaiso (33°S), and off Concepci¢n (35-38°S), sustains the high productivity observed in satellite pigment data and in sediment data. However, the highest pigment concentrations are found south of 40°S where prevailing onshore winds of the Southern Westerlies generally prevent coastal upwelling. There, also highest estimated accumulation rates of organic carbon and biogenic opal at the sea floor are found. Thus, the general pattern of a southward increase of surface water productivity known from satellite data is closely reflected in the organic carbon, biogenic opal and ?15N data, although the observation of highest productivity south of the upwelling area is surprising. Probably, this high productivity in the south can be attributed to the advection of (macro-) nutrients by the Antarctic Circumpolar Current, supplying so-called high nutrient-low chlorophyll (HNLC) waters to the Chilean margin. Impinging on the Chilean margin these waters can take up micronutrients such as iron from the strong riverine input and from benthic exchange processes. The combination of macro- and micro-nutrients in this area most likely results in the high productivity of the area between 40°S and 45°S. From there these fertile

  5. The thermodynamic cost of driving quantum systems by their boundaries

    Science.gov (United States)

    Barra, Felipe

    2015-10-01

    The laws of thermodynamics put limits to the efficiencies of thermal machines. Analogues of these laws are now established for quantum engines weakly and passively coupled to the environment providing a framework to find improvements to their performance. Systems whose interaction with the environment is actively controlled do not fall in that framework. Here we consider systems actively and locally coupled to the environment, evolving with a so-called boundary-driven Lindblad equation. Starting from a unitary description of the system plus the environment we simultaneously obtain the Lindblad equation and the appropriate expressions for heat, work and entropy-production of the system extending the framework for the analysis of new, and some already proposed, quantum heat engines. We illustrate our findings in spin 1/2 chains and explain why an XX chain coupled in this way to a single heat bath relaxes to thermodynamic-equilibrium while and XY chain does not. Additionally, we show that an XX chain coupled to a left and a right heat baths behaves as a quantum engine, a heater or refrigerator depending on the parameters, with efficiencies bounded by Carnot efficiencies.

  6. Mechanisms for tropical upwelling in the stratosphere

    OpenAIRE

    Semeniuk, Kirill; Shepherd, Theodore G.

    2001-01-01

    The dynamics of the tropical upwelling branch of the stratospheric Brewer–Dobson circulation are examined, with a particular focus on the role of the middle-atmosphere Hadley circulation. Upwelling is examined in terms of both the diabatic circulation and Lagrangian trajectories using a zonally symmetric balance model. The behavior of the wave-driven circulation in the presence of angular momentum redistribution by the Hadley circulation is also considered. The results of the zonally symmetri...

  7. Possible upwelling phenomenon off the Nigerian coast

    OpenAIRE

    Ibe, A.C.; Ajayi, T.O.

    1985-01-01

    Published information favour the occurrence in certain years of wind related upwelling in Nigeria's inshore waters especially between July and September. This is corroborated by the prevalence of petroleum source beds, glauconite, phosphorite and periodic abundance of some fish including Engraulis encrassicolus, Sardinella maderensis and the bonga Ethalmosa fimbriata which are pelagic and are associated with upwelling phenomena. Examination of temperature and salinity data for 1978 - 81 sug...

  8. The linking number in systems with Periodic Boundary Conditions

    Science.gov (United States)

    Panagiotou, E.

    2015-11-01

    Periodic Boundary Conditions (PBC) are often used for the simulation of complex physical systems. Using the Gauss linking number, we define the periodic linking number as a measure of entanglement for two oriented curves in a system employing PBC. In the case of closed chains in PBC, the periodic linking number is an integer topological invariant that depends on a finite number of components in the periodic system. For open chains, the periodic linking number is an infinite series that accounts for all the topological interactions in the periodic system. In this paper we give a rigorous proof that the periodic linking number is defined for the infinite system, i.e., that it converges for one, two, and three PBC models. It gives a real number that varies continuously with the configuration and gives a global measure of the geometric complexity of the system of chains. Similarly, for a single oriented chain, we define the periodic self-linking number and prove that it also is defined for open chains. In addition, we define the cell periodic linking and self-linking numbers giving localizations of the periodic linking numbers. These can be used to give good estimates of the periodic linking numbers in infinite systems. We also define the local periodic linking number associated to chains in the immediate cell neighborhood of a chain in order to study local linking measures in contrast to the global linking measured by the periodic linking numbers. Finally, we study and compare these measures when applied to a PBC model of polyethylene melts.

  9. Spatial and temporal seasonal trends in the major global upwelling areas during the last 30 years

    Directory of Open Access Journals (Sweden)

    Rubén Varela Rodríguez

    2014-05-01

    Full Text Available Winds at the ocean surface are a key element in the Earth system having a great impact on many economic activities and becoming really important to several oceanographic and atmospheric applications. Thus, wind above sea surface constitutes a critical parameter to analyze coastal phenomena as upwelling events. Upwelling regions are areas of high productivity compared to other areas of the ocean. In fact, over 20% of global fish catches occur in upwelling areas, although these areas occupy less than 1% of the surface of the world's oceans. Therefore, accurate surface wind datasets are needed to better analyze these processes. In this study wind data obtained from NCEP Climate Forecast System Reanalysis (CFSR database was used to analyse the four most important upwelling systems (Benguela, Canarias, Peru and California. Wind data are available for the whole world at a spatial resolution of 0.3 x 0.3 degrees and a temporal resolution of 6h from January 1982 to December 2010. Alongshore wind stress was considered to analyse variations in upwelling intensity and trends were analysed on these upwelling regions. Comparison with previous studies showed the highly dependence of the results of the length of the time series, the selected areas, the season considered for the analysis and the resolution of the used database.

  10. Peru-Chile upwelling dynamics under climate change

    Science.gov (United States)

    Oerder, Véra; Colas, Francois; Echevin, Vincent; Codron, Francis; Tam, Jorge; Belmadani, Ali

    2015-02-01

    The consequences of global warming on the Peru-Chile Current System (PCCS) ocean circulation are examined with a high-resolution, eddy-resolving regional oceanic model. We performed a dynamical downscaling of climate scenarios from the IPSL-CM4 Coupled General Circulation Model (CGCM), corresponding to various levels of CO2 concentrations in the atmosphere. High-resolution atmospheric forcing for the regional ocean model are obtained from the IPSL atmospheric model run on a stretched grid with increased horizontal resolution in the PCCS region. When comparing future scenarios to preindustrial (PI) conditions, the circulation along the Peru and Chile coasts is strongly modified by changes in surface winds and increased stratification caused by the regional warming. While the coastal poleward undercurrent is intensified, the surface equatorial coastal jet shoals and the nearshore mesoscale activity are reinforced. Reduction in alongshore wind stress and nearshore wind stress curl drive a year-round reduction in upwelling intensity off Peru. Modifications in geostrophic circulation mitigate this upwelling decrease in late austral summer. The depth of the upwelling source waters becomes shallower in warmer conditions, which may have a major impact on the system's biological productivity.

  11. Asymptotic profile of a parabolic-hyperbolic system with boundary effect arising from tumor angiogenesis

    Science.gov (United States)

    Mei, Ming; Peng, Hongyun; Wang, Zhi-An

    2015-11-01

    This paper concerns a parabolic-hyperbolic system on the half space R+ with boundary effect. The system is derived from a singular chemotaxis model describing the initiation of tumor angiogenesis. We show that the solution of the system subject to appropriate boundary conditions converges to a traveling wave profile as time tends to infinity if the initial data is a small perturbation around the wave which is shifted far away from the boundary but its amplitude can be arbitrarily large.

  12. COMPLEX SYSTEM SELF-ORGANIZATION AND BOUNDARY OF ITS PERCEPTION

    Directory of Open Access Journals (Sweden)

    DUBROV Ju. I.

    2016-04-01

    Full Text Available Stipulations. The term “complex system” (CS is rather frequently utilized, therefore, we will take an effort to give a detailed explanation of what is understood by this term. In order to do that, we will not cite a variety of interpretations existing for this term, instead, we are intended to give a notion to this term that would provide for a more visual interpretation. Basic problem statement. Using the abovementioned Stipulation and Hypotheses it is necessary to determine a quality criterion of a self-organizing system functioning as well as to give its formal description. Certain SC subclasses. In order to detect qualitative peculiarities of the considered model the following numerical investigations were conducted. In a new equilibrium state we obtain an absolutely new evolvable system that again, with the change of a load parameter, initiates the process of its development similar. Facts confirming presence of information perception boundary (IPB with self-organizing systems. Given analysis shows that any system, capable of perceiving information, possesses its own IPB. This fact comes well enough to an agreement with data that prove the possibilities of self-organization on the basis of the existing principles of physics and biology. According to the abovementioned it can be concluded that the task of a qualitative survey of evolvable system may lie in determination of its IPB, depending on determining parameters, such as quantity and quality of information coming into the system as well as speed rate of its organization. Such survey is aimed at the description of all possible bifurcations, plotting of a range of bifurcation set at a range with various type of phase portraits and to indicate a phase portrait corresponding to every range with IPB domain. Using the words of great I.P. Pavlov “all types of life, from the simplest to the most complex organisms, including human, is a long line of ever complicating to the highest degree

  13. Convective upwelling in the mantle beneath the Gulf of California.

    Science.gov (United States)

    Wang, Yun; Forsyth, Donald W; Savage, Brian

    2009-11-26

    In the past six million years, Baja California has rifted obliquely apart from North America, opening up the Gulf of California. Between transform faults, seafloor spreading and rifting is well established in several basins. Other than hotspot-dominated Iceland, the Gulf of California is the only part of the world's seafloor-spreading system that has been surrounded by enough seismometers to provide horizontal resolution of upper-mantle structure at a scale of 100 kilometres over a distance great enough to include several spreading segments. Such resolution is needed to address the long-standing debate about the relative importance of dynamic and passive upwelling in the shallow mantle beneath spreading centres. Here we use Rayleigh-wave tomography to image the shear velocity in the upper 200 kilometres or so of the mantle. Low shear velocities similar to those beneath the East Pacific Rise oceanic spreading centre underlie the entire length of the Gulf, but there are three concentrated locations of anomalously low velocities spaced about 250 kilometres apart. These anomalies are 40 to 90 kilometres beneath the surface, at which depths petrological studies indicate that extensive melting of passively upwelling mantle should begin. We interpret these seismic velocity anomalies as indicating that partial melting triggers dynamic upwelling driven by either the buoyancy of retained melt or by the reduced density of depleted mantle. PMID:19940924

  14. A local upwelling controls viral and microbial community structure in South Australian continental shelf waters

    Science.gov (United States)

    Paterson, James S.; Nayar, Sasi; Mitchell, James G.; Seuront, Laurent

    2012-01-01

    Despite the increasing awareness of the role of viruses and heterotrophic bacteria in microbial dynamics and biogeochemical cycles, there is still a critical lack of information on their community composition and dynamics, especially in relation to upwellings. We investigated, within surface waters and the Deep Chlorophyll Max, the community composition and dynamics of flow cytometrically defined sub-populations of heterotrophic bacteria and virus-like particles in nearby water masses that were affected and unaffected by a localised wind-driven coastal upwelling. In contrast to previous studies we uniquely identified a 4-fold increase in total viral abundance and a decrease in bacterial abundance, from upwelled to offshore waters. Individual viral sub-populations were seen to correlate significantly to both bacterial populations and chlorophyll a, suggesting the possibility of individual viral populations infecting multiple host species rather than the often assumed single host species. The percentage of HDNA bacteria was high (84.3-93.4%) within upwelled waters, in accordance with the highest recorded values within an upwelling system, and decreased down to 35.5-42.6% away from the upwelling. Additionally, changes in the community composition of individual bacterial sub-populations suggest individual populations might be better adapted to distinct environments. We suggest that each flow cytometrically defined bacterial population may possess its own environmental niche where favourable conditions for that population result in an increase in abundance, cellular activity and productivity.

  15. Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian Sea shelf

    Science.gov (United States)

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

    2016-01-01

    Observations along 10 shelf transects in 2012 near 10°N in the southeastern Arabian Sea revealed the usual warm oligotrophic conditions during the winter monsoon and upwelling of oxygen-deficient, nutrient-rich cool water during the summer monsoon (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major process that regulates the biogeochemistry of this shelf. Its onset is perceptible at 100 m depth between January and March. The upwelling reaches the surface layer in May and intensifies during June-July but withdraws completely and abruptly by October. Despite the nutrient injection, the primary production during SM, integrated for euphotic zone, is comparable to that during the preceding spring intermonsoon (SIM). Again, as usual, the high oxygen demand coupled with low concentration in the upwelled subsurface waters causes severe oxygen depletion below the shallow pycnocline. The oxygen concentrations/saturations of 2012 on the midshelf are similar from those of mid-1958 to early 1960, except for marginally higher values during the peak upwelling period due to relatively weak upwelling in 2012. This implies little anthropogenic influence on coastal hypoxia unlike many other coastal regions. In 2012, the inner shelf system shifted from net autotrophy in SIM to net heterotrophy in SM but on an annual basis it was net autotrophic (gross primary production to community respiration ratio, GPP/R:1.11 ± 0.84) as organic production exceeded consumption.

  16. Surface circulation and upwelling patterns around Sri Lanka

    Directory of Open Access Journals (Sweden)

    A. de Vos

    2013-09-01

    Full Text Available 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

  17. A FREE-BOUNDARY PROBLEM TO DYNAMIC SYSTEM FOR PURE FOREST

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A free-boundary model of nonlinear dynamic system for pure forest is presented, in which the felling rate is unbounded nearby the free boundary. The effiect of unbounded function on a priori estimate and analysis of regularity is overcome, and the existence and uniqueness of the global classical solution to this system are proved.

  18. Upwelling to Outflowing Oxygen Ions at Auroral Latitudes during Quiet Times: Exploiting a New Satellite Database

    Science.gov (United States)

    Redmon, Robert J.

    The mechanisms by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere are not fully understood even with 30 years of active research. This thesis introduces a new database, builds a simulation framework around a thermospheric model and exploits these tools to gain new insights into the study of O+ ion outflows. A dynamic auroral boundary identification system is developed using Defense Meteorological Satellite Program (DMSP) spacecraft observations at 850 km to build a database characterizing the oxygen source region. This database resolves the ambiguity of the expansion and contraction of the auroral zone. Mining this new dataset, new understanding is revealed. We describe the statistical trajectory of the cleft ion fountain return flows over the polar cap as a function of activity and the orientation of the interplanetary magnetic field y-component. A substantial peak in upward moving O+ in the morning hours is discovered. Using published high altitude data we demonstrate that between 850 and 6000 km altitude, O+ is energized predominantly through transverse heating; and acceleration in this altitude region is relatively more important in the cusp than at midnight. We compare data with a thermospheric model to study the effects of solar irradiance, electron precipitation and neutral wind on the distribution of upward O+ at auroral latitudes. EUV irradiance is shown to play a dominant role in establishing a dawn-focused source population of upwelling O+ that is responsible for a pre-noon feature in escaping O+ fluxes. This feature has been corroborated by observations on platforms including the Dynamics Explorer 1 (DE-1), Polar, and Fast Auroral Snapshot SnapshoT (FAST) spacecraft. During quiet times our analysis shows that the neutral wind is more important than electron precipitation in establishing the dayside O+ upwelling distribution. Electron precipitation is found to play a relatively modest role in controlling dayside, and a

  19. Free Boundary Problems for a Lotka-Volterra Competition System

    Science.gov (United States)

    Wang, Mingxin; Zhao, Jingfu

    2014-09-01

    In this paper we investigate two free boundary problems for a Lotka-Volterra type competition model in one space dimension. The main objective is to understand the asymptotic behavior of the two competing species spreading via a free boundary. We prove a spreading-vanishing dichotomy, namely the two species either successfully spread to the entire space as time t goes to infinity and survive in the new environment, or they fail to establish and die out in the long run. The long time behavior of the solutions and criteria for spreading and vanishing are also obtained. This paper is an improvement and extension of J. Guo and C. Wu.

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

    DEFF Research Database (Denmark)

    Wei, Yili; Godfrey, A.; Liu, W.; Liu, Q.; Huang, Xiaoxu; Hansen, Niels; Winther, Grethe

    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 the...... boundaries investigated lie in the longitudinal plane. Practically all dislocations have screw character, with Burgers vectors corresponding to the slip systems predicted active. The dislocations arrange in a regular grid and the boundaries are most likely low-energy dislocation structures....

  1. Molecular Dynamics ofa Coulomb System with Deformable Periodic Boundary Conditions

    OpenAIRE

    Totsuji, Hiroo; Shirokoshi, Hideki; Nara, Shigetoshi

    1991-01-01

    Variable shape molecular dynamics is formulated for the one-component plasma and the structural transition from the fcc lattice to the bcc lattice has been observed. It is emphasized that the condition of constant volume should be imposed when deformations of periodic boundary conditions are taken into account.

  2. A Wind-Derived Upwelling Index for Lake Michigan

    OpenAIRE

    Davis, Stephen B; Essig, Rebecca; Troy, Cary

    2014-01-01

    Coastal upwelling is a phenomenon that occurs along coastlines throughout the world, and has been shown to be strongly correlated with large fish populations in these areas. Coastal upwelling occurs when strong coastal winds drive water transport away from the coast, causing colder, often nutrient-rich water to upwell in its place. While coastal upwellings can be detected with satellite imagery or in situ temperature measurements, these datasets are neither continuous nor long-term. A wind-...

  3. Synoptic conditions governing upwelling along the Polish Baltic coast

    OpenAIRE

    Bartosz Czernecki; Ewa Bednorz; Marek Półrolniczak

    2013-01-01

    The study analyses atmospheric feedback to the occurrence of upwelling along the Polish Baltic coast. Upwelling events were identified on the basis of daily mean sea surface temperature (SST) maps from the period 1982-2010 derived from the NOAA OI SST V2 High Resolution Dataset. Synoptic conditions favourable to the occurrence of upwelling were determined on the basis of the NCEP/NCAR reanalysis data. On average, there are approximately 23 days with upwelling each year along the Polish Baltic...

  4. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    YAN BangLiang

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is examined by using a mixed-mode model. The results show that the positive feedback process of the effects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Ni(n)a event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal variation of the upwelling mean on the ENSO cycle in previous studies.

  5. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is ex-amined by using a mixed-mode model. The results show that the positive feedback process of the ef-fects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Nia event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal varia-tion of the upwelling mean on the ENSO cycle in previous studies.

  6. Mass spectrometric study of the phase boundaries of the CdS-CdTe system

    Energy Technology Data Exchange (ETDEWEB)

    Nunoue, S.Y.; Hemmi, T.; Kato, E. (Dept. of Materials Science and Engineering, Waseda Univ., Shinjuku-ku Tokyo 160 (JP))

    1990-04-01

    An isothermal evaporation method by means of a Knudsen cell-mass spectrometer combination has been applied to the determination of the phase boundaries in the CdS-CdTe system in the temperature range of 650{degrees}--720{degrees}C. The phase boundaries obtained were compared with published phase boundaries. The advantages of the present method over the x-ray diffraction technique are discussed.

  7. 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.

  8. On the boundaries of solvability and unsolvability in tag systems. Theoretical and Experimental Results

    CERN Document Server

    De Mol, Liesbeth

    2009-01-01

    Several older and more recent results on the boundaries of solvability and unsolvability in tag systems are surveyed. Emphasis will be put on the significance of computer experiments in research on very small tag systems.

  9. On the boundaries of solvability and unsolvability in tag systems. Theoretical and experimental results.

    OpenAIRE

    Liesbeth De Mol

    2008-01-01

    Several older and more recent results on the boundaries of solvability and unsolvability in tag systems are surveyed. Emphasis will be put on the significance of computer experiments in research on very small tag systems.

  10. A boundary value problem for first order strictly hyperbolic systems on the plane

    Science.gov (United States)

    Soldatov, Alexander P.; Zhura, Nikolay A.

    2015-11-01

    Boundary value problems, more precisely Dirichlet's problem for a string equation, or for an equivalent system of first order equations have been first studied in the first half of last century ([1] - [9]). The interest to these problems has been big ever since, see e.g. [10, 11]. All these papers have looked into the boundary value problems in a finite domains in the plane. Strictly hyperbolic systems with more than two characteristics in infinite domains, have been studied in [12, 13]. The question of boundary value problems for a hyperbolic system of equations with more than two characteristics in finite domain on the plane, when a boundary conditions are prescribed at a whole boundary of the domain, evidently remained open. In this paper, we study this problem in a finite domain on the plane for a hyperbolic system of equations of the first order with constant coefficients and with three mutually distinct characteristics.

  11. A comparison of Globigerinoides ruber calcification between upwelling and non-upwelling regions in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Godad, S.P.; Naidu, P.D.; Ramaswamy, V.

    Shell weights of planktonic foraminifera species Globigerinoides ruber in the size range of 300–355 mew m were measured from sediment traps in the western and eastern Arabian Sea which represent upwelling and non-upwelling conditions respectively...

  12. Remote sensing and ichthyoplankton ecology of coastal upwelling fronts off central California

    Science.gov (United States)

    Bjorkstedt, Eric Peter

    1998-11-01

    Recruitment to many marine populations is determined by processes affecting survival and transport of planktonic larvae. Coastal upwelling poses a trade-off between larval access to high productivity supported by upwelled nutrients and increased risk of offshore transport and failure to return to coastal habitats. I used plankton surveys, remote sensing, and a simple model to investigate the role of coastal upwelling fronts and behavior in pelagic ecology and recruitment success, focussing on rockfish (Sebastes spp.) off central California. Distributions of early stage larvae suggest that coastal upwelling fronts reduce offshore transport of rockfish larvae, in contrast to distributions of taxa with life histories that minimize larval exposure to strong upwelling. Coincident distributions of larval fish, prey (i.e., small copepods and invertebrate eggs) and phytoplankton patches indicate that coastal upwelling fronts provide enhanced foraging conditions for larvae. Thus, coastal upwelling fronts may allow coastal taxa to successfully exploit high productivity during the upwelling season while reducing the risk of offshore transport. I developed a novel method for utilizing a single HF radar to resolve currents and detect fronts that matched sea surface temperature fronts generated by coastal upwelling. Fronts and currents detected with NF radar affect distributions and transport of planktonic larval fish and intertidal barnacle larvae, demonstrating that remote sensing with HF radar can support field and modelling research on ecological dynamics in coastal marine systems. I used an empirically-based model that incorporated the advection-foraging trade-off and long-distance swimming as an active settlement behavior to investigate optimal settlement strategies as a function of pelagic transport and growth. For parameters loosely describing pelagic stages of rockfish, the model predicts optimal settling strategies (ages and sizes) for pelagic juveniles that roughly

  13. The effect of coastal upwelling on the sea-breeze circulation at Cabo Frio, Brazil: a numerical experiment

    Directory of Open Access Journals (Sweden)

    S. H. Franchito

    Full Text Available The effect of coastal upwelling on sea-breeze circulation in Cabo Frio (Brazil and the feedback of sea-breeze on the upwelling signal in this region are investigated. In order to study the effect of coastal upwelling on sea-breeze a non-linear, three-dimensional, primitive equation atmospheric model is employed. The model considers only dry air and employs boundary layer formulation. The surface temperature is determined by a forcing function applied to the Earth's surface. In order to investigate the seasonal variations of the circulation, numerical experiments considering three-month means are conducted: January-February-March (JFM, April-May-June (AMJ, July-August-September (JAS and October-November-December (OND. The model results show that the sea-breeze is most intense near the coast at all the seasons. The sea-breeze is stronger in OND and JFM, when the upwelling occurs, and weaker in AMJ and JAS, when there is no upwelling. Numerical simulations also show that when the upwelling occurs the sea-breeze develops and attains maximum intensity earlier than when it does not occur. Observations show a similar behavior. In order to verify the effect of the sea-breeze surface wind on the upwelling, a two-layer finite element ocean model is also implemented. The results of simulations using this model, forced by the wind generated in the sea-breeze model, show that the sea-breeze effectively enhances the upwelling signal.

    Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; ocean-atmosphere interactions · Oceanography (numerical modeling

  14. Boundary conditions for star matter and other periodic fermionic systems

    OpenAIRE

    Gulminelli, F.; Furuta, T.; Juillet, O.; Leclercq, C

    2011-01-01

    International audience Bulk fermionic matter, as it can be notably found in supernova matter and neutrons stars, is subject to correlations of infinite range due to the antisymmetrisation of the N-body wave function, which cannot be explicitly accounted for in a practical simulation. This problem is usually addressed in condensed matter physics by means of the so-called Twist Averaged Boundary Condition method. A different ansatz based on the localized Wannier representation has been propo...

  15. Influence of ocean winds on the pelagic ecosystem in upwelling regions

    OpenAIRE

    Rykaczewski, Ryan R.; Checkley, David M.

    2008-01-01

    Upwelling of nutrient-rich, subsurface water sustains high productivity in the ocean's eastern boundary currents. These ecosystems support a rate of fish harvest nearly 100 times the global mean and account for >20% of the world's marine fish catch. Environmental variability is thought to be the major cause of the decadal-scale biomass fluctuations characteristic of fish populations in these regions, but the mechanisms relating atmospheric physics to fish production remain unexplained. Two at...

  16. The role of open ocean boundary forcing on seasonal to decadal-scale variability and long-term change of natural shelf hypoxia

    International Nuclear Information System (INIS)

    In this study we investigate the possible reasons for the widespread differences between the seasonal cycles of carbon production and export compared to those of hypoxia in eastern boundary upwelling systems. An idealized model is proposed that qualitatively characterizes the relative roles of physics and biogeochemical fluxes. The model is tested on three contrasting upwelling systems: the Benguela (from relatively aerated to interannual anoxic), the Humboldt (sub-oxic and interannually anoxic) and the Cariaco (permanently anoxic). Overall we propose that shelf hypoxia variability can be explained on the basis of the interaction between ventilation by ocean boundary forcing through ocean-shelf exchange and the role of shelf geometry in the retention of shelf-based particulate organic carbon (POC) fluxes. We aim to identify the hypoxia regimes associated with low ventilation-wide-shelf systems and high ventilation-narrow-shelf systems, considering them as extremes of conditions controlled by the two factors. We propose that this may help to explain differences in the seasonal cycles of the biogeochemical drivers and responses as well as difference between upwelling systems and within individual upwelling systems. It is suggested that when seasonal hypoxia emerges it does so preferentially at a wide-shelf part of a system.

  17. REGULARITY THEORY FOR SYSTEMS OF PARTIAL DIFFERENTIAL EQUATIONS WITH NEUMANN BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The objective of this paper is to consider the theory of regularity of systems of partial differential equations with Neumann boundary conditions. It complements previous works of the authors for the Dirichlet case. This type of problem is motivated by stochastic differential games. The Neumann case corresponds to stochastic differential equations with reflection on boundary of the domain.

  18. Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

    Science.gov (United States)

    Hoetzel, Sebastian; Dupont, Lydie M.; Marret, Fabienne; Jung, Gerlinde; Wefer, Gerold

    2016-03-01

    Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

  19. Miocene–Pliocene stepwise intensification of the Benguela upwelling over the Walvis Ridge off Namibia

    Directory of Open Access Journals (Sweden)

    S. Hoetzel

    2015-05-01

    Full Text Available Upwelling is a significant part of the ocean circulation controlling largely the transport of cold waters to the surface and therefore influences ocean productivity and global climate. The Benguela Upwelling System (BUS is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the organic-walled dinoflagellate cyst record of ODP Site 1081 from the Late Miocene to the Pliocene we reconstruct and discuss the upwelling history on the Walvis Ridge with a special focus on the movement of the Angola–Benguela Front (ABF. We show that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.4 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Also effects of Cunene River discharge into the South Atlantic are recorded since 4.4 Ma. Our results show a northward migration of the ABF and the initial stepwise intensification of the BUS.

  20. Heat kernel for the elliptic system of linear elasticity with boundary conditions

    OpenAIRE

    Taylor, Justin; Kim, Seick; Brown, Russell

    2013-01-01

    We consider the elliptic system of linear elasticity with bounded measurable coefficients in a domain where the second Korn inequality holds. We construct heat kernel of the system subject to Dirichlet, Neumann, or mixed boundary condition under the assumption that weak solutions of the elliptic system are H\\"older continuous in the interior. Moreover, we show that if weak solutions of the mixed problem are H\\"older continuous up to the boundary, then the corresponding heat kernel has a Gauss...

  1. Chaotic Dynamics of One-Dimensional Systems with Periodic Boundary Conditions

    OpenAIRE

    Kumar, Pankaj; Miller, Bruce N.

    2014-01-01

    We provide appropriate tools for the analysis of dynamics and chaos for one-dimensional systems with periodic boundary conditions. Our approach allows for the investigation of the dependence of the largest Lyapunov exponent on various initial conditions of the system. The method employs an effective approach for defining the phase-space distance appropriate for systems with periodic boundary and allows for an unambiguous test-orbit rescaling in the phase space required to calculate the Lyapun...

  2. Structural Stability of Boundary Equilibria in a class of hybrid systems : Analysis and Use for Control System Design

    NARCIS (Netherlands)

    Bernardo, Mario di; Camlibel, Kanat

    2005-01-01

    This paper is concerned with the structural stability of boundary equilibria in a class of hybrid systems, that of piecewise linear continuous systems. Specifically, we study the structural stability under parameter variations of equilibria lying on discontinuity boundaries in phase space dividing r

  3. Manganese content records seasonal upwelling in Lake Tanganyika mussels

    Science.gov (United States)

    Langlet, D.; Alleman, L. Y.; Plisnier, P.-D.; Hughes, H.; André, L.

    2007-03-01

    Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system.

  4. Manganese content records seasonal upwelling in Lake Tanganyika mussels

    Directory of Open Access Journals (Sweden)

    D. Langlet

    2007-01-01

    Full Text Available Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system.

  5. Temperature and salinity shaping life-history traits and long-term population stability of Mesodesma donacium in the Humboldt Upwelling System

    OpenAIRE

    Riascos, José; Carstensen, Daniel; Laudien, Jürgen; Arntz, Wolf; Oliva, M.; Günter, A.; Heilmayer, Olaf

    2009-01-01

    Large-scale environmental patterns in the Humboldt Current System (HCS) show major changes during strong El Niño episodes, leading to the mass mortality of dominant species in coastal ecosystems. Here we explore how these changes affect the life-history traits of the surf clam Mesodesma donacium. Growth and mortality rates under normal temperature and salinity were compared to those under anomalous (El Niño) higher temperature and reduced salinity. Moreover, the reproductivespatialtemporal pa...

  6. Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007-2013

    Science.gov (United States)

    Kikas, Villu; Lips, Urmas

    2016-07-01

    Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a predefined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criteria, 33 coastal upwelling events were identified in May-September 2007-2013. The number of events, as well as the frequency of their occurrence and intensity expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coasts. Nevertheless, the wind impulse, which was needed to generate upwelling events of similar intensity, differed between the northern and southern coastal areas. It is suggested that the general thermohaline structure adapted to the prevailing forcing and the estuarine character of the basin weaken the upwelling created by the westerly to southwesterly (up-estuary) winds and strengthen the upwelling created by the easterly to northeasterly (down-estuary) winds. Two types of upwelling events were identified - one characterized by a strong temperature front and the other revealing gradual decrease in temperature from the open sea to the coastal area, with maximum temperature deviation close to the shore.

  7. 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

  8. Molecular dynamics simulation of mechanical behavior of a system including both a crack and grain boundaries under cyclic loading

    International Nuclear Information System (INIS)

    The evaluation of material properties has been recently executed using a molecular dynamics simulation for the purpose of the application to the analysis of semiconductor manufacture process and structural design of a micro machine. The effect of grain boundaries on the mechanical behaviors of material has been examined. These studies, however, dealt with the initial phase of brittle fracture such as crack propagation in a polycrystalline materials. On the other hand, the effect of grain boundaries on ductile fracture is not enough to be examined. Therefore, in order to observe the initial phase of ductile fracture of a material with grain boundaries, we performed a molecular dynamics simulation for a system including both a crack and two tilt grain boundaries under uniaxial tension. Three kinds of the grain boundaries were examined. The {112} grain boundary has the lowest grain boundary energy among all tilt grain boundaries. The {111} grain boundary is one of the grain boundaries which have a local-maximum grain boundary energy. The {332} grain boundary has a grain boundary energy between the preceding two grain boundaries. In a system including both the crack and the {112} grain boundaries, not only a phase transition from bcc to hcp but also ductile deformation such as dislocations and twin deformation were observed around the crack tip in order to relax stress concentration. Then, two dislocation pile-ups near the grain boundaries were formed after the dislocations reached the grain boundaries. In a system including both the crack and the {111} grain boundaries, a new crack was generated at the grain boundaries and intergranular fracture occurred. In a system including both the crack and the {332} grain boundaries, dislocations were emitted not only from the crack tip but also from contact points of a free surface and the grain boundary, then complex dislocation structure was formed. Refs. 3 (author)

  9. 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...

  10. Integrable systems on so(4) related to XXX spin chains with boundaries

    International Nuclear Information System (INIS)

    We consider two-site XXX Heisenberg magnets with different boundary conditions, which are integrable systems on so(4) possessing additional cubic and quartic integrals of motion. The separated variables for these models are constructed using the Sklyanin method

  11. 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...

  12. THE DYNAMICS OF SINE-GORDON SYSTEM WITH DIRICHLET BOUNDARY CONDITION

    Institute of Scientific and Technical Information of China (English)

    Liu Yingdong; Li Zhengyuan

    2000-01-01

    We prove the existence of the global attractor of Sine-Gordon system with Dirichlet boundary condition and show the attractor is the unique steady state when the damping constant and the diffusion constant are sufficiently large.

  13. What shapes mesoscale wind anomalies in coastal upwelling zones?

    Energy Technology Data Exchange (ETDEWEB)

    Boe, Julien [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); CNRS/CERFACS, URA 1875, Toulouse (France); Hall, Alex; Qu, Xin; Kapnick, Sarah B. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Colas, Francois; McWilliams, James C.; Kurian, Jaison [University of California, Institute of Geophysics and Planetary Physics, Los Angeles, CA (United States)

    2011-06-15

    Observational studies have shown that mesoscale variations in sea surface temperature may induce mesoscale variations in wind. In eastern subtropical upwelling regions such as the California coast, this mechanism could be of great importance for the mean state and variability of the climate system. In coastal regions orography also creates mesoscale variations in wind, and the orographic effect may extend more than 100 km offshore. The respective roles of SST/wind links and coastal orography in shaping mesoscale wind variations in nearshore regions is not clear. We address this question in the context of the California Upwelling System, using a high-resolution regional numerical modeling system coupling the WRF atmospheric model to the ROMS oceanic model, as well as additional uncoupled experiments to quantify and separate the effects of SST/wind links and coastal orography on mesoscale wind variations. After taking into account potential biases in the representation of the strength of SST/wind links by the model, our results suggest that the magnitude of mesoscale wind variations arising from the orographic effects is roughly twice that of wind variations associated with mesoscale SST anomalies. This indicates that even in this region where coastal orography is complex and leaves a strong imprint on coastal winds, the role of SST/winds links in shaping coastal circulation and climate cannot be neglected. (orig.)

  14. 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. PMID:26560464

  15. Boundary conditions for star matter and other periodic fermionic systems

    Science.gov (United States)

    Gulminelli, F.; Furuta, T.; Juillet, O.; Leclercq, C.

    2011-12-01

    Bulk fermionic matter, as can be notably found in supernova matter and neutrons stars, is subject to correlations of infinite range due to the antisymmetrization of the N-body wave function, which cannot be explicitly accounted for in a practical simulation. This problem is usually addressed in condensed matter physics by means of the so-called twist averaged boundary condition method. A different ansatz based on the localized Wannier representation has been proposed in the context of antisymmetrized molecular dynamics. In this paper we work out the formal relation between the two approaches. We show that, while the two coincide when working with exact eigenstates of the N-body Hamiltonian, differences appear in the case of variational approaches, which are currently used for the description of stellar matter. Some model applications with fermionic molecular dynamics are shown.

  16. Numerical Bifurcation Diagram for the Two-Dimensional Boundary-fed CDIMA System

    CERN Document Server

    Setayeshgar, S

    1999-01-01

    We present numerical solution of the chlorine dioxide-iodine-malonic acid reaction-diffusion system in two dimensions in a boundary-fed system using a realistic model. The bifurcation diagram for the transition from non-symmetry breaking structures along boundary feed gradients to transverse symmetry breaking patterns in a single layer is numerically determined. We find this transition to be discontinuous. We make connection with earlier results and discuss prospects for future work.

  17. On incompressible limits for the Navier-Stokes system on unbounded domains under slip boundary conditions

    OpenAIRE

    Donatelli, D.; Feireisl, E.; Novotný, A.

    2010-01-01

    We study the low Mach number limit for the compressible Navier-Stokes system supplemented with Navier's boundary condition on an unbounded domain with compact boundary. Our main result asserts that the velocities converge pointwise to a solenoidal vector field - a weak solution of the incompressible Navier-Stokes system - while the fluid density becomes constant. The proof is based on a variant of local energy decay property for the underlying acoustic equation established by Kato.

  18. Exact Synchronization for a Coupled System of Wave Equations with Dirichlet Boundary Controls

    Institute of Scientific and Technical Information of China (English)

    Tatsien LI; Bopeng RAO

    2013-01-01

    In this paper,the exact synchronization for a coupled system of wave equations with Dirichlet boundary controls and some related concepts are introduced.By means of the exact null controllability of a reduced coupled system,under certain conditions of compatibility,the exact synchronization,the exact synchronization by groups,and the exact null controllability and synchronization by groups are all realized by suitable boundary controls.

  19. Tracking "Large" or "Smal": Boundaries and their Consequences for Veterinary Students within the Tracking System

    Science.gov (United States)

    Vermilya, Jenny R.

    In this dissertation, I use 42 in-depth qualitative interviews with veterinary medical students to explore the experience of being in an educational program that tracks students based on the species of non-human animals that they wish to treat. Specifically, I examine how tracking produces multiple boundaries for veterinary students. The boundaries between different animal species produce consequences for the treatment of those animals; this has been well documented. Using a symbolic interactionist perspective, my research extends the body of knowledge on species boundaries by revealing other consequences of this boundary work. For example, I analyze the symbolic boundaries involved in the gendering of animals, practitioners, and professions. I also examine how boundaries influence the collective identity of students entering an occupation segmented into various specialties. The collective identity of veterinarian is one characterized by care, thus students have to construct different definitions of care to access and maintain the collective identity. The tracking system additionally produces consequences for the knowledge created and reproduced in different areas of animal medicine, creating a system of power and inequality based on whose knowledge is privileged, how, and why. Finally, socially constructed boundaries generated from tracking inevitably lead to cases that do not fit. In particular, horses serve as a "border species" for veterinary students who struggle to place them into the tracking system. I argue that border species, like other metaphorical borders, have the potential to challenge discourses and lead to social change.

  20. Invariance of decay rate with respect to boundary conditions in thermoelastic Timoshenko systems

    Science.gov (United States)

    Alves, M. S.; Jorge Silva, M. A.; Ma, T. F.; Muñoz Rivera, J. E.

    2016-06-01

    This paper is mainly concerned with the polynomial stability of a thermoelastic Timoshenko system recently introduced by Almeida Júnior et al. (Z Angew Math Phys 65(6):1233-1249, 2014) that proved, in the general case when equal wave speeds are not assumed, different polynomial decay rates depending on the boundary conditions, namely, optimal rate {t^{-1/2}} for mixed Dirichlet-Neumann boundary condition and rate {t^{-1/4}} for full Dirichlet boundary condition. Here, our main achievement is to prove the same polynomial decay rate {t^{-1/2}} (corresponding to the optimal one) independently of the boundary conditions, which improves the existing literature on the subject. As a complementary result, we also prove that the system is exponentially stable under equal wave speeds assumption. The technique employed here can probably be applied to other kind of thermoelastic systems.

  1. Habitable Zone Boundaries: Implications for our Solar System and Beyond

    Science.gov (United States)

    Kasting, J. F.; Kopparapu, R.; Harman, C.; Batalha, N. E.; Haqq-Misra, J. D.

    2015-12-01

    The successful completion of NASA's Kepler Mission has led to renewed interest in the definition and boundaries of the circumstellar habitable zone (HZ), where liquid water can be stable on a planet's surface. Goldblatt et al. [1] showed that the runaway greenhouse effect, which defines the inner edge of the HZ, depends critically on absorption coefficients of H2O obtained from the new HITEMP database. Kopparapu et al. [2,3] followed up on this observation by recalculating HZ boundaries using HITEMP coefficients. This caused the inner edge to move out to 0.99 AU in their (fully saturated, cloud-free) 1-D climate model. Leconte et al. [4] then used a 3-D climate model to show that the inner edge moves back in to 0.95 AU when relative humidity and clouds are taken into account. In their model, however, the upper stratosphere remained cold and dry, making it difficult to explain how Venus lost its water. But Leconte et al. only looked at surface temperatures up to ~330 K. At somewhat higher surface temperatures (350 K), our own 1-D model predicts that the stratosphere should indeed become wet [5]. Towards the outer edge of the HZ, it now appears that planets should undergo limit cycles involving global glaciation, CO2 buildup from volcanism, and CO2 drawdown from weathering [6,7]. If supplemented with volcanic H2 [8], such cycles could explain how early Mars could have been cold much of the time and yet have experienced enough warm periods to carve the observed fluvial features. Results from a new model of this process will be discussed. Refs: 1. Goldblatt, C., Robinson, T. D., Zahnle, K. J., & Crisp, D. 2013, Nature Geoscience, 6, 661 2. Kopparapu, R. K., et al. 2013, Astrophysical Journal, 765 3. ---. 2013, Astrophysical Journal, 770 4. Leconte, J., Forget, F., Charnay, B., Wordsworth, R., & Pottier, A. 2013, Nature, 504, 268 5. Kasting, J. F., Chen, H., & Kopparapu, R. K. in prep., Ap J Lett 6. Kadoya, S., & Tajika, E. 2014, Astrophysical Journal, 790 7. Menou, K

  2. Upwelling radiance at 976 nm measured from space using the OPALS CCD camera on the ISS

    Science.gov (United States)

    Biswas, Abhijit; Kovalik, Joseph M.; Oaida, Bogdan V.; Abrahamson, Matthew; Wright, Malcolm W.

    2015-03-01

    The Optical Payload for Lasercomm Science (OPALS) Flight System on-board the International Space Station uses a charge coupled device (CCD) camera to detect a beacon laser from Earth. Relative measurements of the background contributed by upwelling radiance under diverse illumination conditions and varying surface terrain is presented. In some cases clouds in the field-of-view allowed a comparison of terrestrial and cloud-top upwelling radiance. In this paper we will report these measurements and examine the extent of agreement with atmospheric model predictions.

  3. Bio-optical characteristics of phytoplankton populations in the upwelling system off the coast of Chile Características (bio-ópticas) de poblaciones de fitoplancton en el sistema de surgencia de la costa de Chile

    OpenAIRE

    VENETIA STUART; OSVALDO ULLLOA; GADIEL ALARCÓN; SHUBHA SATHYENDRANATH; HEATHER MAJOR; Head, Erica J.H; TREVOR PLATT

    2004-01-01

    Phytoplankton samples collected from two cruises off the coast of Chile were analysed for pigment composition and absorption characteristics. High pigment concentrations (up to 20 mg chl-a m-3) were found in the upwelled waters over the shelf break off the coast of Concepción during spring (October 1998), but relatively oligotrophic conditions were found further offshore. Similarly, stations further north (between Coquimbo and Iquique), sampled during the austral summer (February 1999), also ...

  4. A NON-UNIFORM SEDIMENT TRANSPORT MODEL WITH THE BOUNDARY-FITTING ORTHOGONAL COORDINATE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A 2-D non-uniform sediment mathmatical model in the boundary-fitting orthogonal coordinate system was developed in this paper. The governing equations, the numerical scheme, the boundary conditions, the movable boundary technique and the numerical solutions were presented. The model was verified by the data of the reach 25km upstream the Jialingjiang estuary and the 44km long main stream of the Chongqing reach of the Yangtze river. The calculated results show that, the water elevation, the velocity distribution and the river bed deformation are in agreement with the measured data.

  5. ALmost EXact boundary conditions for transient Schrödinger-Poisson system

    Science.gov (United States)

    Bian, Lei; Pang, Gang; Tang, Shaoqiang; Arnold, Anton

    2016-05-01

    For the Schrödinger-Poisson system, we propose an ALmost EXact (ALEX) boundary condition to treat accurately the numerical boundaries. Being local in both space and time, the ALEX boundary conditions are demonstrated to be effective in suppressing spurious numerical reflections. Together with the Crank-Nicolson scheme, we simulate a resonant tunneling diode. The algorithm produces numerical results in excellent agreement with those in Mennemann et al. [1], yet at a much reduced complexity. Primary peaks in wave function profile appear as a consequence of quantum resonance, and should be considered in selecting the cut-off wave number for numerical simulations.

  6. Convergence in comparable almost periodic reaction-diffusion systems with Dirichlet boundary conditions

    OpenAIRE

    Feng Cao; Yelai Fu

    2014-01-01

    In this article, we study the asymptotic dynamics in nonmonotone comparable almost periodic reaction-diffusion systems with Dirichlet boundary condition, which are comparable with uniformly stable strongly order-preserving system. By appealing to the theory of skew-product semiflows, we obtain the asymptotic almost periodicity of uniformly stable solutions to the comparable reaction-diffusion system.

  7. Convergence in comparable almost periodic reaction-diffusion systems with Dirichlet boundary conditions

    Directory of Open Access Journals (Sweden)

    Feng Cao

    2014-04-01

    Full Text Available In this article, we study the asymptotic dynamics in nonmonotone comparable almost periodic reaction-diffusion systems with Dirichlet boundary condition, which are comparable with uniformly stable strongly order-preserving system. By appealing to the theory of skew-product semiflows, we obtain the asymptotic almost periodicity of uniformly stable solutions to the comparable reaction-diffusion system.

  8. Pilot project of measuring and computing system for mesoscale monitoring of atmospheric boundary layer

    Science.gov (United States)

    Korolkov, V. A.; Tikhomirov, A. A.; Telminov, A. E.; Komarov, A. I.; Kobzev, A. A.

    2015-11-01

    Conception of design of measuring and computing system for monitoring atmospheric boundary layer is proposed. The system includes: stationary measuring complex consisting of four multiple-elevation ultrasonic weather stations and mobile measuring complex consisting of transportable weather station, touch probing system of weather data profile based on unmanned aerial vehicle and also Raman scattering gas analyzer, and new modification mercury gas analyzer.

  9. Artificial ocean upwelling utilizing the energy of surface waves

    Science.gov (United States)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents 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 10 oC 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. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper 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 and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  10. Solvability of the Navier-Stokes System with L2 Boundary Data

    International Nuclear Information System (INIS)

    We prove the existence of the very weak solution of the Dirichlet problem for the Navier-Stokes system with L2 boundary data. Under the small data assumption we also prove the uniqueness. We use the penalization method to study the linearized problem and then apply Banach's fixed point theorem for the nonlinear problem with small boundary data. We extend our result to the case with no small data assumption by splitting the data on a large regular and small irregular part

  11. LOCAL CLASSICAL SOLUTION OF FREE BOUNDARY PROBLEM FOR A COUPLED SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Wang Xiaohua; Yi Fahuai; Yang Zhou

    2005-01-01

    This paper considers a two-phase free boundary problem for coupled system including one parabolic equation and two elliptic equations. The problem comes from the discussion of a growth model of self-maintaining protocell in multidimensional case. The local classical solution of the problem with free boundary Γ:y = g(x, t) between two domains is being seeked. The local existence and uniqueness of the problem will be proved in multidimensional case.

  12. Upwelling of Arctic pycnocline associated with shear motion of sea ice

    Science.gov (United States)

    McPhee, M. G.; Kwok, R.; Robins, R.; Coon, M.

    2006-01-01

    High-resolution radar imagery shows that the dynamic response of winter sea ice to gradients in large-scale surface wind stress is often localized along quasi-linear fractures hundreds of kilometers long. Relative shearing motion across these narrow fractures can exceed 10 cm/s. In one event recorded during the drift of the SHEBA ice camp, we observed an intense zone of pycnocline upwelling (approx.14 m) associated with significant shear motion near the camp, while upward turbulent heat flux in the ocean boundary layer reached nearly 400 W/sq m, an order of magnitude greater than at any other time during the year-long drift. We attribute the upwelling to Ekman pumping associated with concentrated ice shear. Over the entire Arctic Ocean sea ice cover, this process could be responsible for significant heat exchange between the cold surface layer and warmer subsurface water at the ubiquitous fractures resulting from large-scale atmosphere-ice interactions.

  13. Has upwelling strengthened along worldwide coasts over 1982-2010?

    OpenAIRE

    Varela, R; Álvarez, I.; Santos, F.;  deCastro, M.; Gómez-Gesteira, M.

    2015-01-01

    Changes in coastal upwelling strength have been widely studied since 1990 when Bakun proposed that global warming can induce the intensification of upwelling in coastal areas. Whether present wind trends support this hypothesis remains controversial, as results of previous studies seem to depend on the study area, the length of the time series, the season, and even the database used. In this study, temporal and spatial trends in the coastal upwelling regime worldwide were investigated during ...

  14. Paleoenvironmental changes across the Cretaceous/Tertiary boundary in the northern Clarence valley, southeastern Marlborough, New Zealand

    International Nuclear Information System (INIS)

    Strata outcropping in Mead and Branch Streams, northern Clarence valley, provide important records of pelagic-hemipelagic sedimentation through the Cretaceous-Paleocene transition in a southern high-latitude, upwelling system flanking a carbonate platform. The two stream sections, 13C) indicate that high biological productivity continued across the K/T boundary and through the biosiliceous episode. Siliceous plankton thrived in the Marlborough upwelling zone during the Early Paleocene. Fluctuations in abundance and lithofacies can be related to significant changes in sea level, which may be the result of local tectonic or global climate changes. The delayed recovery of calcareous plankton after mass extinction at the K/T boundary, in both outer neritic and bathyal settings, indicates a relatively cool oceanic regime for the first 1.5 m.y. of the Paleocene. (author). 68 refs., 11 figs., 6 tabs

  15. Role of Ekman Transport Versus Ekman Pumping in Driving Summer Upwelling in the South China Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Dakui; WANG Hui; LI Ming; LIU Guimei; WU Xiangyu

    2013-01-01

    Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea (SCS) are examined using QuikSCAT scatterometer wind data.The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam (UESEV),east and southeast of Hainan Island (UESEH),and southeast of Guangdong province (USEG).It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems.In UESEV,Ekman pumping and Ekman transport are equally important in generating upwelling.The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August,while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period.In UESEH,the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv,respectively,indicating that 33% of the total wind-driven upwelling is due to Ekman pumping.In USEG,the mean Ekman transport is 0.041 Sv with the peak occurring in July,while Ekman pumping is much smaller (0.003 on average),indicating that the upwelling in this area is primarily driven by Ekman transport.In the summers of 2003 and 2007 following E1 Ni(n)o-Southem Oscillation (ENSO) events,both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon.During the same events,however,Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.

  16. 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.

  17. 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)

  18. Hydra, a model system to trace the emergence of boundaries in developing eumetazoans.

    Science.gov (United States)

    Böttger, Angelika; Hassel, Monika

    2012-01-01

    In developing embryos, boundary formation between neighbouring groups of cells is essential to establish compartments which later fulfil specialized functions. The ability to form such boundaries has likely developed early in animal evolution - due to functional requirements imposed by the necessity to separate tissues which protect the animal, take up food or ensure propagation. Essential for boundary formation are local cues which may be provided by the intersection of diffusible molecules or set locally by activation of membrane-bound receptors and transcription factors. In the simple diploblastic Hydra, a representative of the basally branching metazoan Cnidaria, tissue boundaries are morphologically detectable between the body column and terminally differentiated head and foot structures. In adult polyps, these borders correspond to sharp lines of differential gene expression. They form de novo during regeneration and budding of a young polyp. Functional studies strongly suggest the involvement of FGFR/Notch signalling in the establishment of the parent-bud boundary, and it is very likely that these pathways interact with the WNT and BMP systems. How boundaries in the head and foot regions are generated is still unclear. Expression patterns of transcription factors like Cngsc, HyAlx, HyBra, HyOtx, Prdl-a, CnNK2 and Manacle show strong position dependency and may be involved in regulating gene expression on either side of the boundaries, by interpreting positional information during their formation and maintenance. Due to its simplicity, the easy accessibility to pharmacological interference and, recently, transgenesis, Hydra is an interesting prebilaterian model system to study the emergence of boundary-forming mechanisms during evolution. PMID:22689360

  19. Quasilinearization for the periodic boundary value problem for systems of impulsive differential equations

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available The method of generalized quasilinearization for the system of nonlinear impulsive differential equations with periodic boundary conditions is studied. As a byproduct, the result for the system without impulses can be obtained, which is a new result as well.

  20. Triple fixed-sign solutions in modelling a system with Hermite boundary conditions

    OpenAIRE

    Wong Patricia JY; Soh YC

    2005-01-01

    We consider the following system of differential equations , , together with Hermite boundary conditions , , , , where , for , and . By using different fixed point theorems, we offer criteria for the existence of three solutions of the system which are of "prescribed signs" on the interval .

  1. Boundaries of the homologous phases in Sb–Te and Bi–Te binary alloy systems

    Energy Technology Data Exchange (ETDEWEB)

    Kifune, K., E-mail: k.kifune.yw@cc.it-hiroshima.ac.jp [Hiroshima Institute of Technology, Research Center for Condensed Matter Physics, 2-1-1 Miyake, Saeki-ku, Hiroshima 731-5193 (Japan); Tachizawa, T.; Kanaya, H.; Kubota, Y. [Osaka Prefecture University, Graduate School of Science, Osaka 599-8531 (Japan); Yamada, N. [Kyoto University, Department of Materials Science & Engineering, Kyoto 606-8501 (Japan); Matsunaga, T. [Panasonic Corporation, Advanced Research Division, Osaka 571-8501 (Japan)

    2015-10-05

    Highlights: • Phase boundary of the homologous phase in Sb–Te is fixed at Sb{sub 20}Te{sub 3} compound. • Crystal structure of Sb{sub 20}Te{sub 3} is refined by the 4D structure analysis. • Phase boundary of the homologous phase in Bi–Te is fixed at Bi{sub 8}Te{sub 3} compound. • Crystal structure of Bi{sub 8}Te{sub 3} is refined by the 4D structure analysis. • Difference between Sb–Te and Bi–Te systems are proposed. - Abstract: Sb–Te and Bi–Te binary systems have long-period stacking structures called homologous phases. Within these structures, two types of fundamental structural units change their numbers according to their composition, and the stacking periods also change systematically. X-ray powder diffraction data on bulk specimens with different compositions reveal both the phase boundaries of the homologous phases and the structures of the boundary phases. The boundary phases are Sb{sub 20}Te{sub 3} in the Sb–Te system and Bi{sub 8}Te{sub 3} in the Bi–Te system.

  2. Boundary Work: Engaging Knowledge Systems in Co-management of Feral Animals on Indigenous Lands

    Directory of Open Access Journals (Sweden)

    Tabatha J. Wallington

    2012-06-01

    Full Text Available The integration and use of Indigenous knowledge to inform contemporary environmental policy decisions and management solutions is a growing global phenomenon. However, there is little critical inquiry about how the interactions between scientific and Indigenous knowledge (IK systems can be effectively negotiated for the joint management of social-ecological systems. Such issues are urgent on Indigenous lands where co-management efforts respond to pressing conservation agendas and where the contribution of scientific knowledge and IK is required to better understand and manage complex social-ecological systems. We draw on the notion of boundary work to examine how interaction at the boundaries of scientific and IK systems can be managed effectively as a contribution to co-management. The case study of feral animal co-management in Australia's Kakadu National Park illuminates the work required for local co-managers to bridge the divide between scientific and IK systems and to ensure the translation of knowledge for management decisions. Attributes of effective boundary work demonstrated in this case include: meaningful participation in agenda setting and joint knowledge production to enable co-managers to translate available knowledge into joint feral animal programs, Indigenous and non-Indigenous ranger efforts to broker interactions between knowledge systems that are supported by co-governance arrangements to ensure that boundary work remains accountable, and the production of collaboratively built boundary objects (e.g., feral animal impact assessment data that helps to coordinate local action between co-managers. This case study illustrates the contribution of boundary work to local co-manager efforts to translate across knowledge systems and across the knowledge-action divide, even when consensus is difficult to achieve.

  3. Orographic shaping of US West Coast wind profiles during the upwelling season

    Science.gov (United States)

    Renault, Lionel; Hall, Alex; McWilliams, James C.

    2016-01-01

    Spatial and temporal variability of nearshore winds in eastern boundary current systems is affected by orography, coastline shape, and air-sea interaction. These lead to a weakening of the wind close to the coast: the so-called wind drop-off. In this study, regional atmospheric simulations over the US West Coast are used to demonstrate monthly characteristics of the wind drop-off and assess the mechanisms controlling it. Using a long-term simulation, we show the wind drop-off has spatial and seasonal variability in both its offshore extent and intensity. The offshore extent varies from around 10 to 80 km from the coast and the wind reduction from 10 to 80 %. We show that when the mountain orography is combined with the coastline shape of a cape, it has the biggest influence on wind drop-off. The primary associated processes are the orographically-induced vortex stretching and the surface drag related to turbulent momentum flux divergence that has an enhanced drag coefficient over land. Orographically-induced tilting/twisting can also be locally significant in the vicinity of capes. The land-sea drag difference acts as a barrier to encroachment of the wind onto the land through turbulent momentum flux divergence. It turns the wind parallel to the shore and slightly reduces it close to the coast. Another minor factor is the sharp coastal sea surface temperature front associated with upwelling. This can weaken the surface wind in the coastal strip by shallowing the marine boundary layer and decoupling it from the overlying troposphere.

  4. Nonlinear second order system of Neumann boundary value problems at resonance

    Directory of Open Access Journals (Sweden)

    Chaitan P. Gupta

    1989-01-01

    Full Text Available Let f:[0,π]×ℝN→ℝN, (N≥1 satisfy Caratheodory conditions, e(x∈L1([0,π];ℝN. This paper studies the system of nonlinear Neumann boundary value problems x″(t+f(t,x(t=e(t, 0boundary value problem x″(t=λx(t, 0systems. The methods apply to the corresponding system of Lienard-type periodic boundary value problems.

  5. Bifurcation for Second-Order Hamiltonian Systems with Periodic Boundary Conditions

    OpenAIRE

    Francesca Faraci; Antonio Iannizzotto

    2008-01-01

    Through variational methods, we study nonautonomous systems of second-order ordinary differential equations with periodic boundary conditions. First, we deal with a nonlinear system, depending on a function $u$ , and prove that the set of bifurcation points for the solutions of the system is not ${\\sigma{}} $ -compact. Then, we deal with a linear system depending on a real parameter ${\\lambda{}}>0$ and on a function $u$ , and prove that there exists ${{\\lambda{}}}^{{_\\ast}} $ such that the se...

  6. Stabilization of the Gas Flow in Networks: Boundary Feedback Stabilization of Quasilinear Hyperbolic Systems on Networks

    OpenAIRE

    Dick, Markus

    2012-01-01

    We study the stabilization of quasilinear hyperbolic PDE systems on networks. To do so we develop stabilizing boundary feedback controls. We study feedback controls without and with time-varying delays. To analyze the system evolution we introduce strict Lyapunov functions which are weighted and squared L2- and H1-norms of the solutions of the quasilinear systems. The exponential weights in the Lyapunov functions contain the system eigenvalues. The feedback controls with time delay are repres...

  7. Investigation on the choice of boundary conditions and shape functions for flexible multi-body system

    Institute of Scientific and Technical Information of China (English)

    Ke-Qi Pan; Jin-Yang Liu

    2012-01-01

    The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems.The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference (FFR) formulation.The deformations obtained by the absolute nodal coordinate (ANC) formulation which are transformed by two sets of reference coordinates are introduced as a criterion to verify the accuracy of the simulation results by using the FFR formulation.The relationship between the deformations obtained from different boundary conditions is revealed.Numerical simulation examples demonstrate that the assumed modes with cantilevered-free,simply-supported and freefree boundary conditions without inclusion of rigid body modes are suitable for simulation of flexible multi-body system with large over all motion,and the same physical deformation can be obtained using those mode functions,differ only by a coordinate transformation.It is also shown that when using mode shapes with statically indeterminate boundary conditions,significant error may occur.Furthermore,the slider crank mechanism with rigid crank is accurate enough for investigating boundary condition problem of flexible multi-body system,which cost significant less simulating time.

  8. Investigation on the choice of boundary conditions and shape functions for flexible multi-body system

    Science.gov (United States)

    Pan, Ke-Qi; Liu, Jin-Yang

    2012-02-01

    The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems. The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference (FFR) formulation. The deformations obtained by the absolute nodal coordinate (ANC) formulation which are transformed by two sets of reference coordinates are introduced as a criterion to verify the accuracy of the simulation results by using the FFR formulation. The relationship between the deformations obtained from different boundary conditions is revealed. Numerical simulation examples demonstrate that the assumed modes with cantilevered-free, simply-supported and free-free boundary conditions without inclusion of rigid body modes are suitable for simulation of flexible multi-body system with large over all motion, and the same physical deformation can be obtained using those mode functions, differ only by a coordinate transformation. It is also shown that when using mode shapes with statically indeterminate boundary conditions, significant error may occur. Furthermore, the slider crank mechanism with rigid crank is accurate enough for investigating boundary condition problem of flexible multi-body system, which cost significant less simulating time. The project was supported by the National Natural Science Foundation of China (10872126) and the Research Fund of the Doctoral Program of Higher Education of China (20100073110007).

  9. Upwelling features near Sri Lanka in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    ShreeRam, P.; Rao, L.V.G.

    , the southwest monsoon in summer and the northeast monsoon in winter. The wind stress associated with these winds cause mass drift of oceanic waters leading to upwelling and downwelling. The upwelling features in the Bay of Bengal with a special mention about...

  10. A study on the development of automatic economic profit and loss calculation system for maritime boundary delimitation

    International Nuclear Information System (INIS)

    As the maritime boundary delimitation is important for the purpose of securing marine resources, in addition to the aspect of maritime security, interest in maritime boundary delimitation to help national benefits are increasing over the world. In Korea, the importance of maritime boundary delimitation with the neighbouring countries is also increasing in practice. The quantity of obtainable marine resources depending on maritime boundary acts as an important factor for maritime boundary delimitation. Accordingly, a study is required to calculate quantity of our obtainable marine resources depending on maritime boundary delimitation. This study intends to calculate obtainable marine resources depending on various maritime boundary scenarios insisted by several countries. It mainly aims at developing a GIS-based automation system to be utilized for decision making of the maritime boundary delimitation. For this target, it has designed a module using spatial analysis technique to automatically calculate profit and loss waters area of each country upon maritime boundary and another module to estimate economic profits and losses obtained by each country using the calculated waters area and pricing information of the marine resources. By linking both the designed modules, it has implemented an automatic economic profit and loss calculation system for the GIS-based maritime boundary delimitation. The system developed from this study automatically calculate quantity of the obtainable marine resources of a country for the maritime boundary to be added and created in the future. Thus, it is expected to support decision making for the maritime boundary negotiators

  11. On the boundaries of quantum integrability for the spin-1/2 Richardson–Gaudin system

    International Nuclear Information System (INIS)

    We discuss a generalised version of Sklyanin's Boundary Quantum Inverse Scattering Method applied to the spin-1/2, trigonometric sl(2) case, for which both the twisted-periodic and boundary constructions are obtained as limiting cases. We then investigate the quasi-classical limit of this approach leading to a set of mutually commuting conserved operators which we refer to as the trigonometric, spin-1/2 Richardson–Gaudin system. We prove that the rational limit of the set of conserved operators for the trigonometric system is equivalent, through a change of variables, rescaling, and a basis transformation, to the original set of trigonometric conserved operators. Moreover, we prove that the twisted-periodic and boundary constructions are equivalent in the trigonometric case, but not in the rational limit

  12. Chaotic dynamics of one-dimensional systems with periodic boundary conditions

    Science.gov (United States)

    Kumar, Pankaj; Miller, Bruce N.

    2014-12-01

    We provide appropriate tools for the analysis of dynamics and chaos for one-dimensional systems with periodic boundary conditions. Our approach allows for the investigation of the dependence of the largest Lyapunov exponent on various initial conditions of the system. The method employs an effective approach for defining the phase-space distance appropriate for systems with periodic boundaries and allows for an unambiguous test-orbit rescaling in the phase space required to calculate the Lyapunov exponents. We elucidate our technique by applying it to investigate the chaotic dynamics of a one-dimensional plasma with periodic boundaries. Exact analytic expressions are derived for the electric field and potential using Ewald sums, thereby making it possible to follow the time evolution of the plasma in simulations without any special treatment of the boundary. By employing a set of event-driven algorithms, we calculate the largest Lyapunov exponent, the radial distribution function, and the pressure by following the evolution of the system in phase space without resorting to numerical manipulation of the equations of motion. Simulation results are presented and analyzed for the one-dimensional plasma with a view to examining the dynamical and chaotic behavior exhibited by small and large versions of the system.

  13. Parallel striatal and hippocampal systems for landmarks and boundaries in spatial memory.

    Science.gov (United States)

    Doeller, Christian F; King, John A; Burgess, Neil

    2008-04-15

    How the memory systems centered on the hippocampus and dorsal striatum interact to support behavior remains controversial. We used functional MRI while people learned the locations of objects by collecting and replacing them over multiple trials within a virtual environment comprising a landmark, a circular boundary, and distant cues for orientation. The relative location of landmark and boundary was occasionally changed, with specific objects paired with one or other cue, allowing dissociation of learning and performance relative to either cue. Right posterior hippocampal activation reflected learning and remembering of boundary-related locations, whereas right dorsal striatal activation reflected learning and remembering of landmark-related locations. Within the right hippocampus, anterior processing of environmental change (spatial novelty) was dissociated from posterior processing of location. Behavioral studies show that landmark-related learning obeys associative reinforcement, whereas boundary-related learning is incidental [Doeller CF, Burgess N (2008) Proc Natl Acad Sci USA 105:5909-5914]. The distinct incidental hippocampal processing of boundaries is suggestive of a "geometric module" or "cognitive map" and may explain the hippocampal support of incidental/observational learning in "declarative" or "episodic" memory versus the striatal support of trial-and-error learning in "procedural" memory. Finally, the hippocampal and striatal systems appear to combine "bottom-up," simply influencing behavior proportional to their activations, without direct interaction, with "top-down" ventromedial prefrontal involvement when both are similarly active. PMID:18408152

  14. Systemic effects of geoengineering by terrestrial carbon dioxide removal on carbon related planetary boundaries

    Science.gov (United States)

    Heck, Vera; Donges, Jonathan; Lucht, Wolfgang

    2015-04-01

    The planetary boundaries framework as proposed by Rockström et al. (2009) provides guidelines for ecological boundaries, the transgression of which is likely to result in a shift of Earth system functioning away from the relatively stable Holocene state. As the climate change boundary is already close to be transgressed, several geoengineering (GE) methods are discussed, aiming at a reduction of atmospheric carbon concentrations to control the Earth's energy balance. One of the proposed GE methods is carbon extraction from the atmosphere via biological carbon sequestration. In case mitigation efforts fail to substantially reduce greenhouse gas emissions, this form of GE could act as potential measure to reduce atmospheric carbon dioxide concentrations. We here study the possible influences of human interactions in the Earth system on carbon related planetary boundaries in the form of geoengineering (terrestrial carbon dioxide removal). We use a conceptual model specifically designed to investigate fundamental carbon feedbacks between land, ocean and atmosphere (Anderies et al., 2013) and modify it to include an additional geoengineering component. With that we analyze the existence and stability of a safe operating space for humanity, which is here conceptualized in three of the 9 proposed dimensions, namely climate change, ocean acidification and land-use. References: J. M. Anderies et al., The topology of non-linear global carbon dynamics: from tipping points to planetary boundaries. Environ. Res. Lett., 8(4):044048 (2013) J. Rockström et al., A safe operating space for humanity. Nature 461 (7263), 472-475 (2009)

  15. Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems

    OpenAIRE

    O'Connor, William; Zhu, Ming

    2013-01-01

    A companion paper in this conference considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and sp...

  16. Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems

    OpenAIRE

    O'Connor, William; Zhu, Ming

    2012-01-01

    A companion paper considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and to maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and spring values can ...

  17. Trophic interactions in northern Chile upwelling ecosystem, year 1997

    Directory of Open Access Journals (Sweden)

    Mónica E Barros

    2014-11-01

    Full Text Available A food web model is constructed to describe predator-prey interactions, community structure and trophic flows in northern Chile upwelling ecosystem (18°20'S, 24°S, for the year 1997. The model is built using the Ecopath with Ecosim software version 6.4, and encompasses 21 functional groups, ranging from primary producers (phytoplankton to top predators (birds and marine mammals, the principal fishing resources and the fishery. Input parameters required to build the model were gathered from specialized literature, grey literature and our own estimates. The results indicated that the total biomass (B T was estimated at 624.7 ton km-2. The combined biomass of small pelagic fish represented 26% of B T, while the combined biomass of demersal fish represented only 0.1% of B T. These results highlight the importance of pelagic fish in this system. Predation mortality resulted to be the main source of mortality. Nevertheless, fishing mortality was important in anchovy, mackerel, common dolphinfish and jack mackerel. The mean trophic level of the fishery was estimated as 3.7, with landings sustained mainly by anchovy. Primary production required to sustain the landings (PPR was estimated at 7.5% of calculated total net primary production, which is lower than PPR estimates in other upwelling ecosystems. The average trophic transfer efficiency was 18%, which is in the range (10-20% informed for marine ecosystems. Results indicate that in 1997 the northern Chile marine ecosystem was characterized for being a system far from maturity, dominated in terms of biomass and flows by the pelagic realm.

  18. Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition.

    Science.gov (United States)

    Gregoracci, Gustavo Bueno; Soares, Ana Carolina Dos Santos; Miranda, Milene Dias; Coutinho, Ricardo; Thompson, Fabiano L

    2015-01-01

    Although previous studies have described opposing states in upwelling regions, i.e., the rise of cold nutrient-rich waters and prevalence of surface warm nutrient-poor waters, few have addressed the transition from one state to the other. This study aimed to describe the microbial and viral structure during this transition and was able to obtain the taxonomic and metabolic compositions as well as physical-chemical data. This integrated approach allowed for a better understanding of the dynamics of the downwelling upwelling transition, suggesting that a wealth of metabolic processes and ecological interactions are occurring in the minute fractions of the plankton (femto, pico, nano). These processes and interactions included evidence of microbial predominance during downwelling (with nitrogen recycling and aerobic anoxygenic photosynthesis), different viral predation pressures over primary production in different states (cyanobacteria vs eukaryotes), and a predominance of diatoms and selected bacterial and archaeal groups during upwelling (with the occurrence of a wealth of nitrogen metabolism involving ammonia). Thus, the results provided insights into which microbes, viruses and microbial-mediated processes are probably important in the functioning of upwelling systems. PMID:26327119

  19. Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition.

    Directory of Open Access Journals (Sweden)

    Gustavo Bueno Gregoracci

    Full Text Available Although previous studies have described opposing states in upwelling regions, i.e., the rise of cold nutrient-rich waters and prevalence of surface warm nutrient-poor waters, few have addressed the transition from one state to the other. This study aimed to describe the microbial and viral structure during this transition and was able to obtain the taxonomic and metabolic compositions as well as physical-chemical data. This integrated approach allowed for a better understanding of the dynamics of the downwelling upwelling transition, suggesting that a wealth of metabolic processes and ecological interactions are occurring in the minute fractions of the plankton (femto, pico, nano. These processes and interactions included evidence of microbial predominance during downwelling (with nitrogen recycling and aerobic anoxygenic photosynthesis, different viral predation pressures over primary production in different states (cyanobacteria vs eukaryotes, and a predominance of diatoms and selected bacterial and archaeal groups during upwelling (with the occurrence of a wealth of nitrogen metabolism involving ammonia. Thus, the results provided insights into which microbes, viruses and microbial-mediated processes are probably important in the functioning of upwelling systems.

  20. Multiple Positive Solutions of Boundary Value Problems for Systems of Nonlinear Third-Order Differential Equations

    Institute of Scientific and Technical Information of China (English)

    Yaohong LI; Xiaoyan ZHANG

    2013-01-01

    In this paper,we consider boundary value problems for systems of nonlinear thirdorder differential equations.By applying the fixed point theorems of cone expansion and compression of norm type and Leggett-Williams fixed point theorem,the existence of multiple positive solutions is obtained.As application,we give some examples to demonstrate our results.

  1. Trigonometric series adapted for the study of Dirichlet boundary-value problems of Lame systems

    Directory of Open Access Journals (Sweden)

    Boubakeur Merouani

    2015-07-01

    Full Text Available Several authors have used trigonometric series for describing the solutions to elliptic equations in a plane sector; for example, the study of the biharmonic operator with different boundary conditions, can be found in [2,9,10]. The main goal of this article is to adapt those techniques for the study of Lame systems in a sector.

  2. Trigonometric series adapted for the study of Dirichlet boundary-value problems of Lame systems

    OpenAIRE

    Boubakeur Merouani; Razika Boufenouche

    2015-01-01

    Several authors have used trigonometric series for describing the solutions to elliptic equations in a plane sector; for example, the study of the biharmonic operator with different boundary conditions, can be found in [2,9,10]. The main goal of this article is to adapt those techniques for the study of Lame systems in a sector.

  3. Positive Solutions for a Class of Coupled System of Singular Three-Point Boundary Value Problems

    OpenAIRE

    Naseer Ahmad Asif; Rahmat Ali Khan

    2009-01-01

    Existence of positive solutions for a coupled system of nonlinear three-point boundary value problems of the type , , , , , , , is established. The nonlinearities , are continuous and may be singular at , and/or , while the parameters , satisfy . An example is also included to show the applicability of our result.

  4. Methodology for identifying boundaries of systems important to safety in CANDU nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Therrien, S.; Komljenovic, D.; Therrien, P.; Ruest, C.; Prevost, P.; Vaillancourt, R. [Hydro-Quebec, Nuclear Generating Station Gentilly-2, Becancour, Quebec (Canada)

    2007-07-01

    This paper presents a methodology developed to identify the boundaries of the systems important to safety (SIS) at the Gentilly-2 Nuclear Power Plant (NPP), Hydro-Quebec. The SIS boundaries identification considers nuclear safety only. Components that are not identified as important to safety are systematically identified as related to safety. A global assessment process such as WANO/INPO AP-913 'Equipment Reliability Process' will be needed to implement adequate changes in the management rules of those components. The paper depicts results in applying the methodology to the Shutdown Systems 1 and 2 (SDS 1, 2), and to the Emergency Core Cooling System (ECCS). This validation process enabled fine tuning the methodology, performing a better estimate of the effort required to evaluate a system, and identifying components important to safety of these systems. (author)

  5. The minimal habitat size for spreading in a weak competition system with two free boundaries

    Science.gov (United States)

    Wu, Chang-Hong

    2015-08-01

    In this paper, we focus on the dynamics for a Lotka-Volterra type weak competition system with two free boundaries, where free boundaries which may intersect each other as time evolves are used to describe the spreading of two competing species, respectively. In the weak competition case, the dynamics of this model can be classified into four cases, which forms a spreading-vanishing quartering. The notion of the minimal habitat size for spreading is introduced to determine if species can always spread. Some sufficient conditions for spreading and vanishing are established. Also, when spreading occurs, some rough estimates for spreading speed and the long-time behavior of solutions are established.

  6. Dynamic boundary controls of a rotating body-beam system with time-varying angular velocity

    OpenAIRE

    Boumediène Chentouf

    2004-01-01

    This paper deals with feedback stabilization of a flexible beam clamped at a rigid body and free at the other end. We assume that there is no damping and the rigid body rotates with a nonconstant angular velocity. To stabilize this system, we propose a feedback law which consists of a control torque applied on the rigid body and either a dynamic boundary control moment or a dynamic boundary control force or both of them applied at the free end of the beam. Then it is ...

  7. 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...

  8. Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems

    Science.gov (United States)

    O'Connor, William J.; Zhu, Ming

    2013-08-01

    A companion paper considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and to maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and spring values can be arbitrary. A special "bi-uniform" case is first studied, consisting of two different uniform cascaded systems in series, with an obvious, uncontrolled, impedance mismatch where they meet. The paper shows how boundary actuator control systems can be designed to establish, and robustly maintain, apparently pure travelling waves of constant amplitude in either the first or the second uniform section, in each case with an appropriate, partial, standing wave pattern in the other section. Then a more general non-uniform case is studied. A definition of a "pure travelling wave" in non-uniform systems is proposed. Curiously, it does not imply constant amplitude motion. It does however yield maximum power transfer between boundary actuators. The definition, and its implementation in a control system, involves extending the notions of "pure" travelling waves, of standing waves, and of input and output impedances of sources and loads, when applied to non-uniform lumped systems. Practical, robust control strategies are presented for all cases.

  9. 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...

  10. Bifurcation for Second-Order Hamiltonian Systems with Periodic Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Francesca Faraci

    2008-02-01

    Full Text Available Through variational methods, we study nonautonomous systems of second-order ordinary differential equations with periodic boundary conditions. First, we deal with a nonlinear system, depending on a function u, and prove that the set of bifurcation points for the solutions of the system is not σ-compact. Then, we deal with a linear system depending on a real parameter λ>0 and on a function u, and prove that there exists λ∗ such that the set of the functions u, such that the system admits nontrivial solutions, contains an accumulation point.

  11. R\\'enyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    CERN Document Server

    Taddia, Luca; Pálmai, Tamás

    2016-01-01

    We discuss the R\\'enyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories (CFT) in the scaling limit. We unify the previous CFT approaches to describe primary and descendant states in systems with both open and closed boundaries. We apply the technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and compare the results to numerical data obtained on finite spin chains.

  12. Computational quantum-classical boundary of complex and noisy quantum systems

    OpenAIRE

    Fujii, Keisuke; Tamate, Shuhei

    2014-01-01

    It is often said that the transition from quantum to classical worlds is caused by decoherence originated from an interaction between a system of interest and its surrounding environment. Here we establish a computational quantum-classical boundary from the viewpoint of classical simulatability of a quantum system under decoherence. Specifically, we consider commuting quantum circuits being subject to decoherence. Or equivalently, we can regard them as measurement-based quantum computation on...

  13. Cooperative Behavior in Driven Lattice Systems with Shifted Periodic Boundary Conditions

    OpenAIRE

    Anderson, Mark Jule Jr.

    1998-01-01

    We explore the nature of driven stochastic lattice systems with non-periodic boundary conditions. The systems consist of particle and holes which move by exchanges of nearest neighbor particle-hole pairs. These exchanges are controlled by the energetics associated with an internal Hamiltonian, an external drive and a stochastic coupling to a heat reservoir. The effect of the drive is to bias particle-hole exchanges along the field in such a way that a particle current ...

  14. On angular momentum balance for particle systems with periodic boundary conditions

    OpenAIRE

    Kuzkin, Vitaly A.

    2013-01-01

    The well-known issue with the absence of conservation of angular momentum in classical particle systems with periodic boundary conditions is addressed. It is shown that conventional theory based on Noether's theorem fails to explain the simplest possible example, notably jumps of angular momentum in the case of single particle moving in a periodic cell. It is suggested to consider the periodic cell as an open system, exchanging mass, momentum, angular momentum, and energy with surrounding cel...

  15. 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.

  16. Analysis of optimal boundary control for radiative heat transfer modeled by the $SP_{n}$-system

    OpenAIRE

    Pinnau, René

    2007-01-01

    We present an analytic study of an optimal boundary control problem for the diffusive $SP_{1}$-system modeling radiative heat transfer. The cost functional is of tracking-type and the control problem is considered as a constrained optimization problem, where the constraint is given by the nonlinear parabolic/elliptic $SP_{1}$-system. We prove the existence, uniqueness and regularity of bounded states, which allows for the introduction of the reduced cost functional. Further, we sh...

  17. To a sustainable energy supply system in the Netherlands. Energetic, economic, and environmental boundaries

    International Nuclear Information System (INIS)

    In this essay energetic, economic, and environmental boundaries are presented, for the use of the renewable energy source biomass for CHP production in the Netherlands. After a general overview of global fossil fuel demand/reserves, its resulting environmental consequences, and the substituting possibilities for renewable energy sources (section 2), the possibilities for a new technological (r)evolution are presented in section 3. In this section items such as sustainable development and industrial ecology are introduced, which result to criteria for a global sustainable energy supply system. The specific Dutch energy supply/power production system, together with the Dutch governmental policy concerning the introduction of renewable energy sources, is presented in section 4. The potential role of the most promising renewable energy source in the Netherlands, viz. biomass, in the future Dutch sustainable energy supply system, together with its energetic, economic, and environmental boundaries, is presented in section 5., closing this essay. 22 refs

  18. 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).

  19. Effects of grain boundaries on superconductivity in multi-phase systems

    International Nuclear Information System (INIS)

    The experimental results presented show that there are three types of effects of grain boundaries on Tc in multi-phase systems studied. The critical current density (Jc) can raise apparently by improving the properties of the boundary between the two superconducting grains. The first type is that the grain boundary is beneficial to Tc, e.g., in the Ba-Ln-Cu-O system, Tc of the multi-phase superconductors is often found higher than that of the corresponding single phase ones. The second type shows that Tc degrades, e.g., in Ba-Sr-Y-Cu-O system. The third type is zero, as in the system with nominal composition Ba2-xCaxYCu3Oy, Tc remains 78K when x is larger than 0.25. In the system with nominal composition Ba2YCu3-xPbxOy, Tc keeps constant, but Jc increases obviously when a suitable amount of Pb is doped

  20. 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....

  1. 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....

  2. Upwelling Index, 54N 134W, 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....

  3. 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....

  4. 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....

  5. 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....

  6. Upwelling Index, 36N 122W, 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....

  7. 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....

  8. 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....

  9. 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....

  10. 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....

  11. 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....

  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....

  13. 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....

  14. Upwelling Index, 60N 146W, 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....

  15. 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.

  16. The relationship between Arabian Sea upwelling and Indian monsoon revisited

    OpenAIRE

    Yi, X; B. Hünicke; N. Tim; E. Zorita

    2015-01-01

    Studies based on upwelling indices (sediment records, sea-surface temperature and wind) suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM). In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 ...

  17. Interannual variability in the PFEG coastal upwelling indices

    OpenAIRE

    Parker, Heather A.

    1996-01-01

    Numerous studies examine decadal-scale variability in basin-scale parameters in the Northern Pacific. Characterizing such interannual-to-interdecadal variability is essential to identifying long-term climate changes. The Pacific Fisheries Environmental Group (PFEG) coastal upwelling indices display variability on these time scales and may help explain the mechanisms responsible for such climate variability. ... In this study, examination of 49-year time series of monthly mean upwelling indice...

  18. Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007-2013

    Science.gov (United States)

    Kikas, V.; Lips, U.

    2015-11-01

    Ferrybox measurements are carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) in a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a pre-defined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criterion, 33 coastal upwelling events were identified in May-September 2007-2013. The number of events as well as frequency of their occurrence and intensity, expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coast. It is shown that the wind impulse needed to generate upwelling events of similar intensity differ between the two coastal areas whereas this difference is related to the average wind forcing in the area. Two types of upwelling events were identified - one characterized by a strong temperature front and the other revealing gradual decrease of temperature from the open to coastal area with maximum temperature deviation close to the shore.

  19. Numerical Analysis of Dynamical Systems and the Fractal Dimension of Boundaries

    OpenAIRE

    Duarte, L. G. S.; da Mota, L. A. C. P.; H.P. Oliveira; Ramos, R. O.; Skea, J. E. F.

    1998-01-01

    A set of MapleV R.4/5 software routines for calculating the numerical evolution of dynamical systems and flexibly plotting the results is presented. The package consists of an initial condition generator (on which the user can impose quite general constraints), a numerical solving manager, plotting commands that allow the user to locate and focus in on regions of possible interest and, finally, a set of routines that calculate the fractal dimension of the boundaries of those regions. A specia...

  20. 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.

  1. Periodic Solutions of the Vlasov-Poisson System with Boundary Conditions

    OpenAIRE

    Bostan, Mihai; Poupaud, Frédéric

    1998-01-01

    We study the Vlasov-Poisson system with time periodic boundary conditions. For small data we prove existence of weak periodic solutions in any space dimension. In the one dimensional case the result is stronger: we obtain existence of mild solution and uniqueness of this solution when the data are smooth. It is necessary to impose a non vanishing condition for the incoming velocities in order to control the life-time of particles in the domain.

  2. Periodic Solutions of the 1D Vlasov-Maxwell System with Boundary Conditions

    OpenAIRE

    Bostan, Mihai

    1998-01-01

    We study the 1D Vlasov-Maxwell system with time periodic boundary conditions in its classical and relativistic form. For small data we prove existence of weak periodic solutions. It is necessary to impose non vanishing conditions for the incoming velocities in order to control the life-time of particles in the domain. In order to preserve the periodicity, another condition of vanishing the time average of the incoming current is imposed.

  3. Blowup for a Non-Newtonian Polytropic Filtration System Coupled via Nonlinear Boundary Flux

    OpenAIRE

    Mu Chunlai; Li Yuhuan; Li Zhongping

    2008-01-01

    We study the global existence and the global nonexistence of a non-Newtonian polytropic filtration system coupled via nonlinear boundary flux. We first establish a weak comparison principle, then discuss the large time behavior of solutions by using modified upper and lower solution methods and constructing various upper and lower solutions. Necessary and sufficient conditions on the global existence of all positive (weak) solutions are obtained.

  4. Blowup for a Non-Newtonian Polytropic Filtration System Coupled via Nonlinear Boundary Flux

    Directory of Open Access Journals (Sweden)

    Mu Chunlai

    2008-01-01

    Full Text Available We study the global existence and the global nonexistence of a non-Newtonian polytropic filtration system coupled via nonlinear boundary flux. We first establish a weak comparison principle, then discuss the large time behavior of solutions by using modified upper and lower solution methods and constructing various upper and lower solutions. Necessary and sufficient conditions on the global existence of all positive (weak solutions are obtained.

  5. Blowup for a Non-Newtonian Polytropic Filtration System Coupled via Nonlinear Boundary Flux

    Directory of Open Access Journals (Sweden)

    Yuhuan Li

    2008-04-01

    Full Text Available We study the global existence and the global nonexistence of a non-Newtonian polytropic filtration system coupled via nonlinear boundary flux. We first establish a weak comparison principle, then discuss the large time behavior of solutions by using modified upper and lower solution methods and constructing various upper and lower solutions. Necessary and sufficient conditions on the global existence of all positive (weak solutions are obtained.

  6. 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.

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

    Science.gov (United States)

    Felber, R.; Bretscher, D.; Münger, A.; Neftel, A.; Ammann, C.

    2015-12-01

    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 non-significant C loss: NECBtot - 13 ± 61 g C m-2 yr-1 and NECBpast - 17 ± 81 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 associated GHG budget revealed CH4 emissions from the cows to be the major contributor, but with much lower uncertainty compared to NECB. Although only one year of data limit the representativeness of the carbon budget results, they demonstrated 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.

  8. Existence of solutions for boundary value problem of fractional order impulsive differential equations systems

    Directory of Open Access Journals (Sweden)

    Weihua JIANG

    2015-04-01

    Full Text Available By defining appropriate linear space and norm, giving the appropriate operator, using the contraction mapping principle and krasnoselskii fixed point theorem respectively, the existence and uniqueness of solutions for boundary value problem of fractional order impulsive differential equations systems are investigated under certain condition that nonlinear term and pulse value are satisfied. An example is given to illustrate that the required conditions can be satisfied.

  9. Higher integrability of solutions to generalized Stokes system under perfect slip boundary conditions

    Czech Academy of Sciences Publication Activity Database

    Mácha, Václav; Tichý, J.

    2014-01-01

    Roč. 16, č. 4 (2014), s. 823-845. ISSN 1422-6928 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : generalized Stokes system * perfect slip boundary conditions * Lq theory Subject RIV: BA - General Math ematics Impact factor: 1.186, year: 2014 http://link.springer.com/article/10.1007%2Fs00021-014-0190-5

  10. GLOBAL C1 SOLUTION TO THE INITIAL-BOUNDARY VALUE PROBLEM FOR DIAGONAL HYPERBOLIC SYSTEMS WITH LINEARLY DEGENERATE CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    Li Ta-tsien(李大潜); Peng Yue-Jun

    2003-01-01

    Abstract We prove that the C0 boundedness of solution impliesthe global existence and uniqueness of C1 solution to the initial-boundary value problem for linearly degenerate quasilinear hyperbolic systems of diagonal form with nonlinear boundary conditions. Thus, if the C1 solution to the initial-boundary value problem blows up in a finite time, then the solution itself must tend to the infinity at the starting point of singularity.

  11. PROGS2H4-the program for solving the boundary problem for the system of differential equations

    International Nuclear Information System (INIS)

    The description of the computational scheme and procedure realizing the sweep method for solving the system of two ordinary differential equations with 2nd type boundary conditions at the ends points of given interval is represented. The boundary problem is approximated with the help of the difference scheme of O(h4) precision on the mesh with constant step h. This problem occurs in schemes of linearity of nonlinear boundary problems (for example, in Newtonian iterative schemes), and represented. (author)

  12. Blow up at the hyperbolic boundary for a 2x2 system arising from chemical engineering

    OpenAIRE

    Bourdarias, Christian; Gisclon, Marguerite; Junca, Stéphane

    2009-01-01

    We consider an initial boundary value problem for a 2x2 system of conservation laws modeling heatless adsorption of a gaseous mixture with two species and instantaneous exchange kinetics, close to the system of Chromatography. In this model the velocity is not constant because the sorption effect is taken into account. Exchanging the roles of the x, t variables we obtain a strictly hyperbolic system with a zero eigenvalue. Our aim is to construct a solution with a velocity which blows up at t...

  13. Phytoplankton community and environmental correlates in a coastal upwelling zone along western Taiwan Strait

    Science.gov (United States)

    Wang, Yu; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

    2016-02-01

    Upwelling system in western Taiwan Strait is important for facilitating the fishery production. This study investigated hydro-chemical properties, phytoplankton biomass, phytoplankton species composition, three-dimensional (horizontal, vertical and transect) distribution of phytoplankton abundance, as well as phytoplankton annual variation and the correlation of phytoplankton community with the upwelling of underlying current and nutrients according to samples of Fujian-Guangdong coastal upwelling zone in western Taiwan Strait from August 27 to September 8, 2009. The results manifest that the nutrient-rich cold and high salinity current on the continental shelf of South China Sea upwells to the Fujian-Guangdong coastal waters through Taiwan Bank and the surging strength to surface is weak while strong at 30-m layer. The thermohaline center of coastal upwelling shifts to the east of Dongshan Island and expanded to offshore waters in comparison with previous records. A total of 137 phytoplankton species belonging to 59 genera in 4 phyla are identified excluding the unidentified species. Diatom is the first major group and followed by dinoflagellate. Cyanobacteria mainly composed by three Trichodesmium species account for a certain proportions, while Chrysophyta are only found in offshore waters. The dominant species include Thalassionema nitzschioides, Pseudo-nitzschia pungens, Thalassionema frauenfeldii, Pseudo-nitzschia delicatissima, Rhizosolenia styliformis, Chaetoceros curvisetus, Diplopsalis lenticula and Trichodesmium thiebautii. Phytoplankton community mainly consists of eurythermal and eurytopic species, followed by warm-water species, tropic high-salinity species and oceanic eurythermic species in order. Phytoplankton abundance ranges from 1.00 × 102 ind./L ~ 437.22 × 102 ind./L with an average of 47.36 × 102 ind./L. For vertical distribution, maximum abundance is found at 30 m-depth and the surface comes second. Besides, the abundance below 30 m

  14. Hydrobiology in the Cabo Frio (Brazil) upwelling: two-dimensional structure and variability during a wind cycle

    Science.gov (United States)

    Valentin, Jean L.; Andre, Dalmo L.; Jacob, Salvador A.

    1987-01-01

    A study of the variability of hydrobiological parameters in a vertical section during .. wind cycle allowed us to investigate the structure and dynamics of the upwelling ecosystem at Cabo Frio (Brazil). This coastal upwelling system is extremely sensitive to wind changes with nutrient-rich water reaching the surface under NE winds along a coastal belt less than 5 km wide. This narrow strip is dominated by great hydrological instability. Above the continental shelf the upwelling of cold water is characterized by the inclination of the thermocline, whose vertical oscillation determines the main factors of planktonic fluctuations through the water column. After reaching the surface the deep water induces new production which spreads up to 20 km offshore. From a general point of view, pigment richness would fit a quadratic function of general hydrologic conditions. However, this function is only useful at the given collecting point, and within the limits of the amplitude of the hydrological variations.

  15. Parallel channel instabilities in boiling water reactor systems: boundary conditions for out of phase oscillations

    International Nuclear Information System (INIS)

    In this paper we study the boundary conditions during out of phase oscillations, in a system formed by two parallel channels coupled to multimodal neutron kinetics. The fact that the pressure drop can change with time, but remains the same in all the parallel channels, leads us to analytical integration of the time derivative term of the channel momentum equation, in order to get a dynamic equation for the inlet mass flux to each channel. From these inlet mass flux dynamic equations plus the appropriate boundary conditions, we have obtained the expression of the time dependent common pressure drop to all the channels. Finally the oscillations in the pressure drop and in the inlet mass flux to the channels have been investigated when out of phase oscillations take place

  16. A study of the entanglement in systems with periodic boundary conditions

    OpenAIRE

    Panagiotou, E.; Tzoumanekas, C.; Lambropoulou, S.; Millett, K. C.; Theodorou, D. N.

    2010-01-01

    We define the local periodic linking number, LK, between two oriented closed or open chains in a system with three-dimensional periodic boundary conditions. The properties of LK indicate that it is an appropriate measure of entanglement between a collection of chains in a periodic system. Using this measure of linking to assess the extent of entanglement in a polymer melt we study the effect of CReTA algorithm on the entanglement of polyethylene chains. Our numerical results show that the sta...

  17. Many-body position operator in lattice fermionic systems with periodic boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hetenyi, Balazs [Institut fuer Theoretische Physik, Technische Universitaet Graz, Petersgasse 16, A-8010 Graz (Austria); Mathematisches Institut, Fakultaet fuer Mathematik, Informatik und Statistik, Ludwig Maximilians Universitaet, Theresienstrasse 39, Muenchen 80333 (Germany)], E-mail: hetenyi@itp.tugraz.at

    2009-10-16

    A total position operator X in the position representation is derived for lattice fermionic systems with periodic boundary conditions. The operator is shown to be Hermitian, the generator of translations in momentum space, and its time derivative is shown to correspond to the total current operator in a periodic system. The operator is such that its moments can be calculated up to any order. To demonstrate its utility finite size scaling is applied to the Brinkman-Rice transition as well as to metallic and insulating Gutzwiller wavefunctions. (fast track communication)

  18. Characteristic finite difference method and application for moving boundary value problem of coupled system

    Institute of Scientific and Technical Information of China (English)

    YUAN Yi-rang; LI Chang-feng; YANG Cheng-shun; HAN Yu-ji

    2008-01-01

    The coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution. It is of great value in rational evaluation of prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. A kind of characteristic finite difference schemes is put forward, from which optimal order estimates in l2 norm are derived for the error in the approximate solutions. The research is important both theoretically and practically for the model analysis in the field, the model numerical method and software development.

  19. 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.

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

    Science.gov (United States)

    Baker, Thomas E.; Bill, Andreas

    2016-05-01

    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.

  1. Modelling the upwelling offthe east Hainan Island coast in summer 2010

    Science.gov (United States)

    Bai, Peng; Gu, Yanzhen; Li, Peiliang; Wu, Kejian

    2016-03-01

    A synoptic-scale upwelling event that developed offthe east coast of the Hainan Island (EHIU) in the summer of 2010 is defined well via processing the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data. The Regional Ocean Modeling System (ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo float profiles and MODIS SST, it is confirmed that the ROMS reproduces the EHIU well. The cooler-water core (CWC) distinguished by waters stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2-0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefit the development of the CWC.

  2. Boundary Layer

    Science.gov (United States)

    Loitsianskii. L. G.

    1956-01-01

    The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the boundary layer. The presence of a boundary layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of boundary layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work "On the Form of Ships" published as early as 1890. In his book "Theoretical Foundations of Air Navigation," Joukowsky gave an account of the most important properties of the boundary layer and pointed out the part played by it in the production of the resistance of bodies to motion. The fundamental differential equations of the motion of a fluid in a laminar boundary layer were given by Prandtl in 1904; the first solutions of these equations date from 1907 to 1910. As regards the turbulent boundary layer, there does not exist even to this day any rigorous formulation of this problem because there is no closed system of equations for the turbulent motion of a fluid. Soviet scientists have done much toward developing a general theory of the boundary layer, and in that branch of the theory which is of greatest practical importance at the present time, namely the study of the boundary layer at large velocities of the body in a compressed gas, the efforts of the scientists of our country have borne fruit in the creation of a new theory which leaves far behind all that has been done previously in this direction. We shall herein enumerate the most important results by Soviet scientists in the development of the theory of the boundary layer.

  3. Lagrangian studies of phytoplankton growth and grazing relationships in a coastal upwelling ecosystem off Southern California

    Science.gov (United States)

    Landry, Michael R.; Ohman, Mark D.; Goericke, Ralf; Stukel, Michael R.; Tsyrklevich, Kate

    2009-12-01

    Experimental studies of phytoplankton growth and grazing processes were conducted in the coastal upwelling system off Point Conception, California to test the hypothesis that phytoplankton growth and grazing losses determine, to first order, the local dynamics of phytoplankton in the upwelling circulation. Eight experiments of 3-5 days each were conducted over the course of two cruises in May-June 2006 and April 2007 following the trajectories of satellite-tracked drifters. Rates of phytoplankton growth and microzooplankton grazing were determined by daily in situ dilution incubations at 8 depths spanning the euphotic zone. Mesozooplankton grazing was assessed by gut fluorescence analysis of animals collected from net tows through the euphotic zone. We compared directly the net rates of change observed for the ambient phytoplankton community to the net growth rates predicted from experimental determinations of each process rate. The resulting relationship accounted for 91% of the variability observed, providing strong support for the growth-grazing hypothesis. In addition, grazing by mesozooplankton was unexpectedly high and variable, driving a substantial positive to negative shift in phytoplankton net rate of change between years despite comparable environmental conditions and similar high growth rates and suggesting strong top-down control potential. The demonstrated agreement between net ambient and experimental community changes is an important point of validation for using field data to parameterize models. Data sets of this type may provide an important source of new information and rate constraints for developing better coupled biological-physical models of upwelling system dynamics.

  4. Changes in optical characteristics of surface microlayers hint to photochemically and microbially-mediated DOM turnover in the upwelling region off Peru

    Science.gov (United States)

    Galgani, L.; Engel, A.

    2015-12-01

    The coastal upwelling system off Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. During the Meteor (M91) cruise to the Peruvian upwelling system in 2012, we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples at 38 stations determining DOC concentration, amino acid composition, marine gels, CDOM and bacterial and phytoplankton abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. We identified five fluorescent components of the CDOM pool, of which two had excitation/emission characteristics of protein-like fluorophores and were highly enriched in the SML. CDOM composition and changes in spectral slope properties suggested a local microbial release of HMW DOM directly in the SML as a response to light exposure in this extreme environment. Our results suggest that microbial and photochemical processes play an important role for the production, alteration and loss of optically active substances in the SML.

  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. Solution Transformations and Their Effects on the Systems with Open Boundary Conditions

    Institute of Scientific and Technical Information of China (English)

    JU Guo-Xing; ZHAO Xian-Lin

    2002-01-01

    The solution transformations and properties of the R-matrices for two-component systems uner these transformations are analyzed in details.Not all transformed R-matrices can be put into the Skalyanin's formalism.For those R-matrices with all required properties,the effects of solution transformations to the six- and eight-vertex systems with open boundary conditions are discussed.These effects can be one of the following types: The Hamiltonian is invariant or transposition-invariant or made in a similarity transformation,or its coupling coefficients are multiplied by an overall factor,or the spin of the system is rotated around the z axis or/and reflected with respect to some plane.In these cases,the transformed systems remain to be integrable.

  8. Isotopic and enzymatic analyses of planktonic nitrogen utilisation in the vicinity of Cape Sines (Portugal) during weak upwelling activity

    Science.gov (United States)

    Slawyk, Gerd; Coste, Bernard; Collos, Yves; Rodier, Martine

    1997-01-01

    ) absolute and Chl a-specific nitrate uptake rates (10.4 nM h -1, 7.5 nmol μ -1 h -1) compared to the mean rates during weak upwelling (1.7 nM h -1, 1.5 nmol μ -1 h -1). From a comparison with the neighbouring Moroccan upwelling, it is assumed that new production in the Portuguese upwelling averages 50 nM h -1. Thus, this upwelling would rank with the northwest African upwelling system off Cape Blanc or with the Californian upwelling at Point Conception for the capacity of new production, but seems to be much less efficient (seven-fold) than the highly permanent Peru upwelling.

  9. Chemical hydrography of coastal upwelling in the East China Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Baodong; WANG Xiulin

    2007-01-01

    Based on the field data obtained during cruises on the shelf of the East China Sea from 1997 to 1999, seasonal variations of coastal upwelling on the inner shelf are discussed by using cross-shelf transect profiles and horizontal distributions of chemical and hydrographic variables. Results show that the coastal upwelling was year-round, but the areas and intensities of the upwelling were quite different in season. The coastal upwelling occurred in all of the coastal areas of the region in spring and summer, but in autumn only in the area off Zhejiang Province, and in winter in the area off Fujian Province. It was the strongest in summer and the weakest in winter. Geographically, it was the strongest in the area off Zhejiang Province and the weakest in the southmost or northmost parts of the East China Sea.The estimated nutrient fluxes upward into euphotic zone through coastal upwelling were quite large, especially for phosphate, which contributed significantly to primary production and improved the nutrient structure of the coastal ecosystem in the East China Sea.

  10. Methane emissions from the upwelling area off Mauritania (NW Africa

    Directory of Open Access Journals (Sweden)

    A. Kock

    2008-08-01

    Full Text Available Coastal upwelling regions have been identified as sites of enhanced CH4 emissions to the atmosphere. The coastal upwelling area off Mauritania (NW Africa is one of the most biologically productive regions of the world's ocean but its CH4 emissions have not been quantified so far. More than 1000 measurements of atmospheric and dissolved CH4 in the surface layer in the upwelling area off Mauritania were performed as part of the German SOPRAN (Surface Ocean Processes in the Anthropocene study during two cruises in March/April 2005 (P320/1 and February 2007 (P348. During P348 enhanced CH4 saturations of up to 200% were found close to the coast and were associated with upwelling of South Atlantic Central Water. An area-weighted, seasonally adjusted estimate yielded overall annual CH4 emissions in the range from 1.6 to 2.9 Gg CH4. Thus the upwelling area off Mauritania represents a regional hot spot of CH4 emissions but seems to be of minor importance for the global oceanic CH4 emissions.

  11. Methane emissions from the upwelling area off Mauritania (NW Africa

    Directory of Open Access Journals (Sweden)

    A. Kock

    2008-01-01

    Full Text Available Coastal upwelling regions have been indentified as sites of enhanced CH4 emissions to the atmosphere. The coastal upwelling area off Mauritania (NW Africa is one of the most biologically productive regions of the world's ocean but its CH4 emissions have not been quantified so far. More than 1000 measurements of atmospheric and dissolved CH4 in the surface layer in the upwelling area off Mauritania were performed as part of the German SOPRAN (Surface Ocean Processes in the Anthropocene study during two cruises in March/April 2005 (P320/1 and February 2007 (P348. During P348 enhanced CH4 saturations of up to 179% were found close to the coast and were associated with upwelling of South Atlantic Central Water. An area-weighted, seasonally adjusted estimate yielded overall annual CH4 emissions in the range from 0.7 to 1.4 Gg CH4. Thus the upwelling area off Mauritania represents a regional hot spot of CH4 emissions but seems to be of minor importance for the global oceanic CH4 emissions.

  12. How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

    DEFF Research Database (Denmark)

    Niggemann, Jutta; Ferdelman, Timothy G.; Lomstein, Bente Aagaard;

    2007-01-01

    Chilean coastal upwelling system and have an extended oxygen minimum zone in the water column. However, the northern site (23°S) borders the Atacama Desert, while the southern site (36°S) has a humid hinterland. Eight surface sediment cores (up to 30 cm long) from water depths of 126‑1350 m were...

  13. THE DEVELOPMENT OF LOGISTIC STRATEGY IN THE BOUNDARIES OF LOGISTIC BUSINESS PROCESS IMPROVEMENT OF ENERGY SYSTEM COMPANIES

    OpenAIRE

    Sankov, V.; Tayakina, E.

    2010-01-01

    This article considers the problems concerning the methods of logistic strategy development in the boundaries of logistic business process improvement of energy system companies. It is stated that logistic methods in solving the strategy problems are important.

  14. 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....

  15. On the Existence of Hydrodynamic Instability in Single Diffusive Bottom Heavy Systems with Permeable Boundaries

    Indian Academy of Sciences (India)

    A K Gupta; R G Shandil

    2011-11-01

    We utilize the reformulated equations of the classical theory, as derived by Banerjee et al.(J. Math. Anal. Appl. 175 (1993) 458), to establish mathematically, the existence of hydrodynamic instability in single diffusive bottom heavy systems, when considered in the more general framework of the boundary conditions of the type specified by Beavers and Joseph (J. Fluid Mech. 30 (1967) 197), in the parameter regime $T_0_2>1$, where $T_0$ and 2 being some properly chosen mean temperature and coefficient of specific heat (at constant volume) variation due to temperature variation respectively.

  16. Multiple solutions for systems of multi-point boundary value problems

    Directory of Open Access Journals (Sweden)

    John R. Graef

    2013-01-01

    Full Text Available In this paper, we establish the existence of at least three solutions of the multi-point boundary value system \\[\\left\\{\\begin{array}{ll} -(\\phi_{p_i}(u'_{i}'=\\lambda F_{u_{i}}(x,u_{1},\\ldots,u_{n},\\ t\\in(0,1,\\\\ u_{i}(0=\\sum_{j=1}^m a_ju_i(x_j,\\ u_{i}(1=\\sum_{j=1}^m b_ju_i(x_j, \\end{array}\\right. i=1,\\ldots,n.\\] The approaches used are based on variational methods and critical point theory.

  17. Nonlinear systems of differential inequalities and solvability of certain boundary value problems

    Directory of Open Access Journals (Sweden)

    Tvrdý Milan

    2001-01-01

    Full Text Available In the paper we present some new existence results for nonlinear second order generalized periodic boundary value problems of the form These results are based on the method of lower and upper functions defined as solutions of the system of differential inequalities associated with the problem and their relation to the Leray–Schauder topological degree of the corresponding operator. Our main goal consists in a fairly general definition of these functions as couples from . Some conditions ensuring their existence are indicated, as well.

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

    International Nuclear Information System (INIS)

    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 O2 and NO3- 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

  19. Numerical bifurcation diagram for the two-dimensional boundary-fed chlorine-dioxide–iodine–malonic-acid system

    OpenAIRE

    Setayeshgar, S.; Cross, M. C.

    1999-01-01

    We present a numerical solution of the chlorine-dioxide–iodine–malonic-acid reaction-diffusion system in two dimensions in a boundary-fed system using a realistic model. The bifurcation diagram for the transition from nonsymmetry-breaking structures along boundary feed gradients to transverse symmetry-breaking patterns in a single layer is numerically determined. We find this transition to be discontinuous. We make a connection with earlier results and discuss prospects for future work.

  20. Why productive upwelling areas are often sources rather than sinks of CO2? – a comparative study on eddy upwellings in the South China Sea

    Directory of Open Access Journals (Sweden)

    N. Jiao

    2013-08-01

    Full Text Available Marine upwelling regions are known to be productive in carbon fixation and thus thought to be sinks of CO2, whereas many upwelling areas in the ocean are actually sources rather than sinks of CO2. To address this paradox, multiple biogeochemical parameters were investigated at two cyclonic-eddy-induced upwelling sites CE1 and CE2 in the western South China Sea. The results showed that upwelling can exert significant influences on biological activities in the euphotic zone and can either increase or decrease particulate organic carbon (POC export flux depending on upwelling conditions such as the magnitude, timing, and duration of nutrient input and consequent microbial activities. At CE2 the increase of phytoplankton biomass caused by the upwelled nutrients resulted in increase of POC export flux compared to non-eddy reference sites, while at CE1 the microbial respiration of organic carbon stimulated by the upwelled nutrients significantly contributed to the attenuation of POC export flux, aggravating outgassing of CO2. These results suggest that on top of upwelled dissolved inorganic carbon release, microbial activities stimulated by upwelled nutrients and phytoplankton labile organic carbon can play a critical role for a marine upwelling area to be a source rather than a sink of CO2. Meanwhile, we point out that even though an upwelling region is outgassing, carbon sequestration still takes place through the POC-based biological pump as well as the refractory dissolved organic carbon (RDOC-based microbial carbon pump.

  1. Solution of linear systems in arterial fluid mechanics computations with boundary layer mesh refinement

    Science.gov (United States)

    Manguoglu, Murat; Takizawa, Kenji; Sameh, Ahmed H.; Tezduyar, Tayfun E.

    2009-10-01

    Computation of incompressible flows in arterial fluid mechanics, especially because it involves fluid-structure interaction, poses significant numerical challenges. Iterative solution of the fluid mechanics part of the equation systems involved is one of those challenges, and we address that in this paper, with the added complication of having boundary layer mesh refinement with thin layers of elements near the arterial wall. As test case, we use matrix data from stabilized finite element computation of a bifurcating middle cerebral artery segment with aneurysm. It is well known that solving linear systems that arise in incompressible flow computations consume most of the time required by such simulations. For solving these large sparse nonsymmetric systems, we present effective preconditioning techniques appropriate for different stages of the computation over a cardiac cycle.

  2. Mn seasonal upwellings recorded in Lake Tanganyika mussels

    Science.gov (United States)

    Langlet, D.; Alleman, L. Y.; Plisnier, P.-D.; Hughes, H.; André, L.

    2006-09-01

    Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition.

  3. Mn seasonal upwellings recorded in Lake Tanganyika mussels

    Directory of Open Access Journals (Sweden)

    D. Langlet

    2006-09-01

    Full Text Available Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition.

  4. Evaluation of upwelling infrared radiance in a nonequilibrium nonhomogeneous atmosphere

    Science.gov (United States)

    Tiwari, S. N.; Subramanian, S. V.

    1982-01-01

    The influence of vibrational nonequilibrium upon upwelling infrared radiance from the earth's atmosphere is investigated. By employing the line-by-line model for spectral absorption, heating rates and upwelling radiances are calculated for equilibrium and nonequilibrium conditions in the spectral range of 4.7 micron CO and 3.3 micron CH4 bands. Heating rates are calculated also for the 15 micron CO2 band and are compared with other available results in the literature. For the spectral range of the CO fundamental band, the influence of different parameters on the upwelling radiance is investigated. It is found that for CO the assumption of local thermodynamic equilibrium (LTE) is not justified at tropospheric temperatures and pressures. If the resonance effects of CO-N2 collisions are considered, then the assumption of LTE is justified up to 60 kilometers. This information is very useful for measurement of atmospheric pollutants, earth radiation budget studies and climate modeling, and infrared signature works.

  5. Evaluation of upwelling infrared radiance from earth's atmosphere

    Science.gov (United States)

    Gupta, S. K.; Tiwari, S. N.

    1975-01-01

    Basic equations for calculating the upwelling atmospheric radiation are presented which account for various sources of radiation coming out at the top of the atmosphere. The theoretical formulation of the transmittance models (line-by-line and quasi-random band model) and the computational procedures used for the evaluation of the transmittance and radiance are discussed in detail. By employing the Lorentz line-by-line and quasi-random computer programs, model calculations were made to determine the upwelling radiance and signal change in the wave number interval of CO fundamental band. These results are useful in determining the effects of different interfering molecules, water vapor profiles, ground temperatures, and ground emittances on the upwelling radiance and signal change. This information is of vital importance in establishing the feasibility of measuring the concentrations of pollutants in the atmosphere from a gas filter correlation instrument flown on an aircraft or mounted on a satellite.

  6. 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.

  7. THE ARTIFICIAL BOUNDARY CONDITIONS FOR NUMERICAL SIMULATIONS OF THE COMPLEX AMPLITUDE IN A COUPLED BAY-RIVER SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Hou-de Han; Xin Wen

    2004-01-01

    We consider the numerical approximations of the complex amplitude in a coupled bay-river system in this work. One half-circumference is introduced as the artificial boundary in the open sea, and one segment is introduced as the artificial boundary in the river if the river is semi-infinite. On the artificial boundary a sequence of high-order artificial boundary conditions are proposed. Then the original problem is solved in a finite computational domain, which is equivalent to a variational problem. The numerical approximations for the original problem are obtained by solving the variational problem with the finite element method. The numerical examples show that the artificial boundary conditions given in this work are very effective.

  8. THE UPWIND FINITE DIFFERENCE METHOD FOR MOVING BOUNDARY VALUE PROBLEM OF COUPLED SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Yuan Yirang

    2011-01-01

    Coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution. It is of great value in rational evaluation of prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. The upwind finite difference schemes applicable to parallel arith- metic are put forward and two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques, such as change of variables, calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order dif- ference operators and prior estimates, are adopted. The estimates in 12 norm are derived to determine the error in the approximate solution. This method was already applied to the numerical simulation of migration-accumulation of oil resources.

  9. 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 ...

  10. Brunet-Derrida particle systems, free boundary problems and Wiener-Hopf equations

    CERN Document Server

    Durrett, Rick

    2009-01-01

    We consider a branching-selection system in $\\rr$ with $N$ particles which give birth independently at rate 1 and where after each birth the leftmost particle is erased, keeping the number of particles constant. We show that, as $N\\to\\infty$, the empirical measure process associated to the system converges in distribution to a deterministic measure-valued process whose densities solve a free boundary integro-differential equation. We also show that this equation has a unique traveling wave solution traveling at speed $c$ or no such solution depending on whether $c>a$ or $c\\leq a$, where $a$ is the asymptotic speed of the branching random walk obtained by ignoring the removal of the leftmost particles in our process. The traveling wave solutions correspond to solutions of Wiener-Hopf equations.

  11. On the Boundaries of Trust and Security in Computing and Communications Systems

    CERN Document Server

    Pathan, Al-Sakib Khan

    2012-01-01

    This article analyzes trust and security in computing and communications systems. While in human-life, trust usually has some kind of commonly understood meaning, in the realm of computing and communications systems, it could be interpreted differently in different environments and settings. On the other hand, security is about making sure that the participating entities are legitimate in a communication event or incident so that the core requirements of privacy, integrity, and authenticity are maintained. This notion is also true for our human life, even for example entering a house needs legitimacy of a person. Some boundary lines preserve the security; otherwise an unwanted access is called a 'security breach'. The intent of this article is to compare and discuss these two terms with our societal behavior and understanding amongst entities. To illustrate these issues especially in computing and communications world, some of the innovating and recent technologies are discussed which demand trust and securit...

  12. 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.

  13. Dynamical property of nucleation in spin crossover depending on the system boundary

    Energy Technology Data Exchange (ETDEWEB)

    Nishino, Masamichi [Computational Materials Science Center, National Institute of Material Science, Tsukuba 305-0047 (Japan); Boukheddaden, Kamel; Varret, Francois [Groupe d' Etudes de la Matiere Condensee, CNRS-Universite de Versailles/St. Quentin en Yvelines, F78035 Versailles Cedex (France); Miyashita, Seiji, E-mail: nishino.masamichi@nims.go.j [Department of Physics, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan)

    2009-02-01

    We investigate dynamical properties of nucleation from a photoinduced excited high-spin state. Applying a molecular dynamics method to a model with elastic interactions, we found that the boundary condition plays an important role in the nucleation. Different from the periodic boundary, in which no clustering occurs, when the boundary is open, clustering tends to occur from the boundary. It can induce domain structures as phase separation.

  14. 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.

  15. Bifurcations of Eigenvalues of Gyroscopic Systems with Parameters Near Stability Boundaries

    DEFF Research Database (Denmark)

    Seyranian, Alexander P.; Kliem, Wolfhard

    1999-01-01

    shown that the bifurcation (splitting) of double eigenvalues is closely related to the stability, flutter and divergence boundaries in the parameter space. Normal vectors to these boundaries are derived using only information at a boundary point: eigenvalues, eigenvectors and generalized eigenvectors...

  16. UPWELLING AND SEDIMENTATION DYNAMICS Ⅲ: COINCIDENCE OF UPWELLING AREAS WITH MUD PATCHES IN NORTH HEMISPHERE SHELF SEAS

    Institute of Scientific and Technical Information of China (English)

    庞重光; 胡敦欣

    2002-01-01

    The determinant role of upwelling in fine sediment patches is examined from the viewpoints of physical process and biological process respectively. It is pointed out that physical and biological processes are usually coexistent and interact with each other during the sedimentation of suspended matters. This study used available figures showing the circulation pattern and surface sediment distribution in the whole China Seas, the Gulf of Maine, the Irish Sea and the North Sea, and additional data to verify that wherever upwelling exists on the continental shelf, mud must occur; and that wherever downwelling occurs, coarse sediment substitutes for mud.

  17. Effects of interface width scaling and spatial correlations on Ising systems with rough boundaries

    Science.gov (United States)

    Reis, F. D. A. Aarão

    2001-03-01

    We studied the ferromagnetic Ising model on two-dimensional systems with rough boundaries and several thickness distributions. First, we considered very long strips with discretized Gaussian distributions of widths with mean 3⩽ L⩽12. Systems with fixed interface width W and with increasing roughness ( W∼ Lβ, with 0⩽ β⩽1) were analysed. We also considered strips with columns’ heights correlations, where the difference in the heights of neighbouring columns was 0 or 1, with 0⩽ β≲0.5. Free energies per spin, fL, and initial susceptibilities, χL, were calculated using transfer matrix techniques at the critical temperature of the two-dimensional Ising model. The scaling of fL and of the finite-size estimates of the ratio of exponents ( γ/ ν) L was analysed. In systems with small and slowly increasing W ( β<0.2), correlated or not, extrapolations of fL and ( γ/ ν) L to L→∞ give accurate estimates of the critical parameters f∞ and γ/ ν. In systems with rapidly increasing roughness, the deviations of those estimates from the exact values indicate the presence of large corrections in finite-size scaling relations. The comparison of systems with nearly the same β shows that spatial correlations have no systematic effect on corrections to scaling. It suggests the reliability of uncorrelated models or related approximate systems for the description of scaling properties of thin magnetic films and other low-dimensional structures.

  18. Coastal upwelling activity on the Pacific shelf of the Baja California Peninsula

    OpenAIRE

    O. Zaytsev; Cervantes Duarte, Rafael; Montante, Orzo; Gallegos García, A.

    2003-01-01

    High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m3/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local wi...

  19. Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

    OpenAIRE

    M. Abalos; W. J. Randel; E. Serrano

    2012-01-01

    Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal timescales, and the three estimates show reasonably good agreement. Tropical upwelling should exer...

  20. Mechanisms of near-surface current and upwelling variability in the tropical Atlantic

    OpenAIRE

    Hüttl, Sabine

    2006-01-01

    The upwelling regions of the eastern equatorial oceans provide not only sources of cold water in a relatively warm environment but also influence the atmospheric circulation and the biological productivity in the tropics. However, the sources of the upwelling waters are well known only for the equatorial upwelling but remained unclear for the off-equatorial upwelling in the Guinea and Angola Dome. A main aspect of this work is to contribute to the understanding of the mean pathways into these...

  1. Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

    OpenAIRE

    M. Abalos; W. J. Randel; E. Serrano

    2012-01-01

    Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal time scales, and the three estimates show reasonably good agreement. Tropical upwelling sho...

  2. 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

  3. Coastal upwelling observed by multi-satellite sensors

    Institute of Scientific and Technical Information of China (English)

    LI XiaoMing; LI XiaoFeng; HE MingXia

    2009-01-01

    Coastal upwelling phenomenon along the China coast in the Yellow Sea during August 2007 is studied using ENVISAT Advanced Synthetic Aperture Radar (ASAR) data, NOAA Advanced AVHRR series Sea Surface Temperature (SST) data, and NASA QuikSCAT Scatterometer ocean surface wind data. A dark pattern in an ASAR image is interpreted as coastal upwelling. This is because the natural biogenic slicks associated with coastal upwelling damp the Bragg waves on the sea surface and thus make the surface smoother. Most of the incoming radar energy is reflected in the forward direction. As a result, the radar backscatter signal is very weak. Analyzing the concurrent AVHRR SST Image, we find that the dark pattern in the ASAR image is indeed corresponding to the low SST area. The wind retrieval in the slicks dominant region is biased due to the low Normaliced Radar Cross Section (NRCS) associated with the coastal upwelling. We applied a SST correction to the NRCS values to improve the accuracy of wind retrieval from ASAR data.

  4. Upwelling O(+) ion source characteristics. [in polar magnetosphere

    Science.gov (United States)

    Moore, T. E.; Lockwood, M.; Chandler, M. O.; Waite, J. H., Jr.; Chappell, C. R.; Persoon, A.; Sugiura, M.

    1986-01-01

    The characteristics of an upwelling ion source are discussed. A typical upwelling event is analyzed using Dynamic Explorer 1 satellite retarding ion mass spectrometer (RIMS) observations of the low-energy plasma, and energetic ion and local electromagnetic field observations. The RIMS spectrograms of the O(+) ion species, radial and axial head data for O(+), and spin plan O(+) distribution functions are examined. The features of the upwelling observed include: (1) transverse ion heating to temperature of 100,000 K, (2) large outward flows of O(+), (3) enhanced flow of H(+) and He (+), (4) moderately strong field-aligned current sheets, (5) an associated intense eastward convection channel, and (6) strong wave emissions in the range near and below the proton gyrofrequency. The association between the upwelling O(+) signature and auroral current is investigated. Plasma wave and electric field environments are studied and plasma flows and densities are derived. It is noted that the mechanism for ion heating which defines the source region for these polar ion outflows is related to field-aligned currents and an associated auroral convection channel or jet.

  5. Evaluation of upwelling infrared radiance from the earth's troposphere

    Science.gov (United States)

    Tiwari, S. N.; Gupta, S. K.

    1976-01-01

    Basic equations for calculating the upwelling atmospheric radiance are presented. Theoretical formulation of the transmittance models (line-by-line and quasi-random band) and computational procedures for the evaluation of transmittance and radiance are discussed. This information is useful in the interpretation of the data obtained from measuring gaseous pollutants in the troposphere.

  6. Coastal upwelling observed by multi-satellite sensors

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Coastal upwelling phenomenon along the China coast in the Yellow Sea during August 2007 is studied using ENVISAT Advanced Synthetic Aperture Radar (ASAR) data, NOAA Advanced AVHRR series Sea Surface Temperature (SST) data,and NASA QuikSCAT Scatterometer ocean surface wind data. A dark pattern in an ASAR image is interpreted as coastal upwelling. This is because the natural biogenic slicks associated with coastal upwelling damp the Bragg waves on the sea surface and thus make the surface smoother. Most of the incoming radar energy is reflected in the forward direction. As a result, the radar backscatter signal is very weak. Analyzing the concurrent AVHRR SST image, we find that the dark pattern in the ASAR image is indeed corresponding to the low SST area. The wind retrieval in the slicks dominant region is biased due to the low Normalised Radar Cross Section (NRCS) associated with the coastal upwelling. We applied a SST correction to the NRCS values to improve the accuracy of wind retrieval from ASAR data.

  7. Lipid biomarker patterns of phosphogenic sediments from upwelling regions

    DEFF Research Database (Denmark)

    Arning, Esther T.; Birgel, Daniel; Schultz-Vogt, Heide N.;

    2008-01-01

    Sediments of upwelling regions off Namibia, Peru, and Chile contain dense populations of large nitrate-storing sulfide-oxidizing bacteria, Thiomargarita, Beggiatoa, and Thioploca. Increased contents of monounsaturated C16 and C18 fatty acids have been found at all stations studied, especially when...

  8. Strongly coupled dynamics of fluids and rigid-body systems with the immersed boundary projection method

    Science.gov (United States)

    Wang, Chengjie; Eldredge, Jeff D.

    2015-08-01

    A strong coupling algorithm is presented for simulating the dynamic interactions between incompressible viscous flows and rigid-body systems in both two- and three-dimensional problems. In this work, the Navier-Stokes equations for incompressible flow are solved on a uniform Cartesian grid by the vorticity-based immersed boundary projection method of Colonius and Taira. Dynamical equations for arbitrary rigid-body systems are also developed. The proposed coupling method attempts to unify the treatment of constraints in the fluid and structure-the incompressibility of the fluid, the linkages in the rigid-body system, and the conditions at the interface-through the use of Lagrange multipliers. The resulting partitioned system of equations is solved with a simple relaxation scheme, based on an identification of virtual inertia from the fluid. The scheme achieves convergence in only 2 to 5 iterations per time step for a wide variety of mass ratios. The formulation requires that only a subset of the discrete fluid equations be solved in each iteration. Several two- and three-dimensional numerical tests are conducted to validate and demonstrate the method, including a falling cylinder, flapping of flexible wings, self-excited oscillations of a system of many linked plates in a free stream, and passive pivoting of a finite aspect ratio plate under the influence of gravity in a free stream. The results from the current method are compared with previous experimental and numerical results and good agreement is achieved.

  9. Formation of magnetic filaments at the boundaries of the magnetospheres of solar system planets

    International Nuclear Information System (INIS)

    The theory of localized spontaneous reconnection at the boundaries of the magnetospheres of solar-system planets with strong intrinsic magnetic field is given in the paper. Such forms of reconnection (flux transfer events - FTE) resulting in formation of magnetic filaments are observed by sattelites near the magnetosphgeres of Mercury, Earth and Jupiter. The physical factors controlling the temporal and spatial scales of this phenomenon in dependence on the distance from the Sun (the parameters of the solar wind) and the planetary magnetic dipole moment are discussed. the theoretical estimates of characteristic diameters of magnetic filaments λE ∼ 5000 km, λM ∼ 500 km, λJ ∼ 13000 km for the Earth, Mercury and Jupiter agree satisfactorily with the experimental data. In conclusion, the typical FTE parameters for Saturn and some other astrophysical objects are evaluated

  10. Magnetic properties on the grain boundary of high Tc Bi-system films

    International Nuclear Information System (INIS)

    The tunneling spectrum was observed on the grain boundary of the small bridge which was patterned mechanically on polycrystalline high Tc Bi-system films. The spectrum at 15 K gives 4Δ=54 meV and 2Δ0/kTc=4.2 using Tc=75 K. The quantum interference pattern and the Fraunhofer-like pattern were observed under the magnetic field on the reannealed bridge. The periods of the quantum interference pattern were 0.56 and 0.66 Oe which were modulated and they give the loop areas respectively 36 and 30 μm2. The effective areas of the junction obtained from the Fraunhofer-like pattern was about 2.5 μm2. (orig.)

  11. ADFE METHOD WITH HIGH ACCURACY FOR NONLINEAR PARABOLIC INTEGRO-DIFFERENTIAL SYSTEM WITH NONLINEAR BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    崔霞

    2002-01-01

    Alternating direction finite element (ADFE) scheme for d-dimensional nonlinear system of parabolic integro-differential equations is studied. By using a local approximation based on patches of finite elements to treat the capacity term qi(u), decomposition of the coefficient matrix is realized; by using alternating direction, the multi-dimensional problem is reduced to a family of single space variable problems, calculation work is simplified; by using finite element method, high accuracy for space variant is kept; by using inductive hypothesis reasoning, the difficulty coming from the nonlinearity of the coefficients and boundary conditions is treated; by introducing Ritz-Volterra projection, the difficulty coming from the memory term is solved. Finally, by using various techniques for priori estimate for differential equations, the unique resolvability and convergence properties for both FE and ADFE schemes are rigorously demonstrated, and optimal H1 and L2norm space estimates and O((△t)2) estimate for time variant are obtained.

  12. Stability and Hopf bifurcation for a delayed cooperation diffusion system with Dirichlet boundary conditions

    International Nuclear Information System (INIS)

    This paper is concerned with a delayed cooperation diffusion system with Dirichlet boundary conditions. By applying the implicit function theorem, the normal form theory and the center manifold reduction, the asymptotic stability of positive equilibrium and Hopf bifurcation are investigated. It is shown that an increase in delay will destabilize the positive equilibrium and lead to the occurrence of a supercritical Hopf bifurcation when the delay crosses through a sequence of critical values. Based on the normal form theory and the center manifold reduction for partial functional differential equations (PFDEs), we find that the bifurcating periodic solution occurring from the first Hopf bifurcation point is stable on the center manifold and those occurring from the other bifurcation points are unstable. Finally, some numerical simulations are given to illustrate our results

  13. Stability and Hopf bifurcation for a delayed cooperation diffusion system with Dirichlet boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Li Wantong [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China)], E-mail: wtli@lzu.edu.cn; Yan Xiangping; Zhang Cunhua [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China); Department of Mathematics, Lanzhou Jiaotong University, Lanzhou 730070 (China)

    2008-10-15

    This paper is concerned with a delayed cooperation diffusion system with Dirichlet boundary conditions. By applying the implicit function theorem, the normal form theory and the center manifold reduction, the asymptotic stability of positive equilibrium and Hopf bifurcation are investigated. It is shown that an increase in delay will destabilize the positive equilibrium and lead to the occurrence of a supercritical Hopf bifurcation when the delay crosses through a sequence of critical values. Based on the normal form theory and the center manifold reduction for partial functional differential equations (PFDEs), we find that the bifurcating periodic solution occurring from the first Hopf bifurcation point is stable on the center manifold and those occurring from the other bifurcation points are unstable. Finally, some numerical simulations are given to illustrate our results.

  14. Dual nature of localization in guiding systems with randomly corrugated boundaries: Anderson-type versus entropic

    International Nuclear Information System (INIS)

    A unified theory for the conductance of an infinitely long multimode quantum wire whose finite segment has randomly rough lateral boundaries is developed. It enables one to rigorously take account of all feasible mechanisms of wave scattering, both related to boundary roughness and to contacts between the wire rough section and the perfect leads within the same technical frameworks. The rough part of the conducting wire is shown to act as a mode-specific randomly modulated effective potential barrier whose height is governed essentially by the asperity slope. The mean height of the barrier, which is proportional to the average slope squared, specifies the number of conducting channels. Under relatively small asperity amplitude this number can take on arbitrary small, up to zero, values if the asperities are sufficiently sharp. The consecutive channel cut-off that arises when the asperity sharpness increases can be regarded as a kind of localization, which is not related to the disorder per se but rather is of entropic or (equivalently) geometric origin. The fluctuating part of the effective barrier results in two fundamentally different types of guided wave scattering, viz., inter- and intramode scattering. The intermode scattering is shown to be for the most part very strong except in the cases of (a) extremely smooth asperities, (b) excessively small length of the corrugated segment, and (c) the asperities sharp enough for only one conducting channel to remain in the wire. Under strong intermode scattering, a new set of conducting channels develops in the corrugated waveguide, which have the form of asymptotically decoupled extended modes subject to individual solely intramode random potentials. In view of this fact, two transport regimes only are realizable in randomly corrugated multimode waveguides, specifically, the ballistic and the localized regime, the latter characteristic of one-dimensional random systems. Two kinds of localization are thus shown to

  15. Research on a Small Signal Stability Region Boundary Model of the Interconnected Power System with Large-Scale Wind Power

    Directory of Open Access Journals (Sweden)

    Wenying Liu

    2015-03-01

    Full Text Available For the interconnected power system with large-scale wind power, the problem of the small signal stability has become the bottleneck of restricting the sending-out of wind power as well as the security and stability of the whole power system. Around this issue, this paper establishes a small signal stability region boundary model of the interconnected power system with large-scale wind power based on catastrophe theory, providing a new method for analyzing the small signal stability. Firstly, we analyzed the typical characteristics and the mathematic model of the interconnected power system with wind power and pointed out that conventional methods can’t directly identify the topological properties of small signal stability region boundaries. For this problem, adopting catastrophe theory, we established a small signal stability region boundary model of the interconnected power system with large-scale wind power in two-dimensional power injection space and extended it to multiple dimensions to obtain the boundary model in multidimensional power injection space. Thirdly, we analyzed qualitatively the topological property’s changes of the small signal stability region boundary caused by large-scale wind power integration. Finally, we built simulation models by DIgSILENT/PowerFactory software and the final simulation results verified the correctness and effectiveness of the proposed model.

  16. Feasibility of developing risk-based rankings of pressure boundary systems for inservice inspection

    Energy Technology Data Exchange (ETDEWEB)

    Vo, T.V.; Smith, B.W.; Simonen, F.A.; Gore, B.F.

    1994-08-01

    The goals of the Evaluation and Improvement of Non-destructive Examination Reliability for the In-service Inspection of Light Water Reactors Program sponsored by the Nuclear Regulatory Commission at Pacific Northwest Laboratory (PNL) are to (1) assess current ISI techniques and requirements for all pressure boundary systems and components, (2) determine if improvements to the requirements are needed, and (3) if necessary, develop recommendations for revising the applicable ASME Codes and regulatory requirements. In evaluating approaches that could be used to provide a technical basis for improved inservice inspection plans, PNL has developed and applied a method that uses results of probabilistic risk assessment (PRA) to establish piping system ISI requirements. In the PNL program, the feasibility of generic ISI requirements is being addressed in two phases. Phase I involves identifying and prioritizing the systems most relevant to plant safety. The results of these evaluations will be later consolidated into requirements for comprehensive inservice inspection of nuclear power plant components that will be developed in Phase II. This report presents Phase I evaluations for eight selected plants and attempts to compare these PRA-based inspection priorities with current ASME Section XI requirements for Class 1, 2 and 3 systems. These results show that there are generic insights that can be extrapolated from the selected plants to specific classes of light water reactors.

  17. Feasibility of developing risk-based rankings of pressure boundary systems for inservice inspection

    International Nuclear Information System (INIS)

    The goals of the Evaluation and Improvement of Non-destructive Examination Reliability for the In-service Inspection of Light Water Reactors Program sponsored by the Nuclear Regulatory Commission at Pacific Northwest Laboratory (PNL) are to (1) assess current ISI techniques and requirements for all pressure boundary systems and components, (2) determine if improvements to the requirements are needed, and (3) if necessary, develop recommendations for revising the applicable ASME Codes and regulatory requirements. In evaluating approaches that could be used to provide a technical basis for improved inservice inspection plans, PNL has developed and applied a method that uses results of probabilistic risk assessment (PRA) to establish piping system ISI requirements. In the PNL program, the feasibility of generic ISI requirements is being addressed in two phases. Phase I involves identifying and prioritizing the systems most relevant to plant safety. The results of these evaluations will be later consolidated into requirements for comprehensive inservice inspection of nuclear power plant components that will be developed in Phase II. This report presents Phase I evaluations for eight selected plants and attempts to compare these PRA-based inspection priorities with current ASME Section XI requirements for Class 1, 2 and 3 systems. These results show that there are generic insights that can be extrapolated from the selected plants to specific classes of light water reactors

  18. 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...

  19. EXISTENCE OF POSITIVE SOLUTION TO TWO-POINT BOUNDARY VALUE PROBLEM FOR A SYSTEM OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, we consider a two-point boundary value problem for a system of second order ordinary differential equations. Under some conditions, we show the existence of positive solution to the system of second order ordinary differential equa-tions.

  20. Casimir Force of Piston Systems with Arbitrary Cross Sections under Different Boundary Conditions

    Institute of Scientific and Technical Information of China (English)

    XIONG Ai-Min; CHEN Xiao-Song

    2009-01-01

    We study the Casimir force between two pistons under different boundary conditions inside an infinite cylinder with arbitrary cross section.It is found that the attractive or repulsive character of the Casimir force for a scalar field is determined only by the boundary condition along the longitudinal direction and is independent of the cross section,transverse boundary conditions and the mass of the field.Under symmetric Dirichlet-Dirichlet,Neumann-Neumann and periodic longitudinal boundary conditions the Casimir force is always attractive,but is repulsive under non-symmetric Dirichlet-Neumann and anti-periodic longitudinal boundary conditions.The Casimir force of the electromagnetic field in an ideal conductive piston is also investigated.This force is always attractive regardless of the shape of the cross section and the transverse boundary conditions.

  1. The influence of a scaled boundary response on integral system transient behavior

    International Nuclear Information System (INIS)

    Scaling relationships associated with the thermal-hydraulic response of a closed-loop system are applied to a calculational assessment of a feed-and-bleed recovery in a nuclear reactor integral effects test. The analysis demonstrates both the influence of scale on the system response and the ability of the thermal-hydraulics code to represent those effects. The qualitative response of the fluid is shown to be coupled to the behavior of the bounding walls through the energy equation. The results of the analysis described in this paper influence the determination of computer code applicability. The sensitivity of the code response to scaling variations introduced in the analysis is found to be appropriate with respect to scaling criteria determined from the scaling literature. Differences in the system response associated with different scaling criteria are found to be plausible and easily explained using well-known principles of heat transfer. Therefore, it is concluded that RELAP5/MOD2 can adequately represent the scaled effects of heat transfer boundary conditions of the thermal-hydraulic calculations through the mechanism of communicating walls. The results of the analysis also serve to clarify certain aspects of experiment and facility design

  2. The Response of Phytoplankton Size Spectra and Chlorophyll Biomass to Wind-driven Coastal Upwelling off Northern California During the CoOP-WEST Study.

    Science.gov (United States)

    Wilkerson, F. P.; Dugdale, R. C.; Marchi, A.; Hogue, V.; Lassiter, A.; Lew, K.; Lorenzi, A.

    2002-12-01

    During the WEST (Wind Events and Shelf Transport) summer studies of the coastal upwelling region off Bodega Bay, CA, chlorophyll concentrations consistently reached phytoplankton bloom levels following wind driven upwelling events that resulted in high concentrations of pCO2 and nutrients. In most coastal upwelling areas, upwelled nitrate and high rates of new production lie close to the coast in a distinct plume, and their consequences (a band of enhanced chlorophyll) are propagated seaward far beyond the point where upwelled nutrients have been exhausted. Most likely grazing on advected diatoms results in release of regenerated N (ammonium and urea) that is taken up by the small-sized phytoplankton that out-compete diatoms for ammonium and consequently carry coastal new production offshore in the upper layer current system. However in the WEST study area the growing phytoplankton (showing high rates of new production) and productivity are retained on the shelf, and apparently transported alongshore rather than offshore most of the time. The elevated chlorophyll (reaching over 30 μg/l in June 2000) is made up of mostly larger phytoplankton cells with the diatom Chaetoceros spp. dominating during the bloom events. These cells may be grazed or sink and be carried in sub surface currents and re-entrained in the undercurrent, unlike smaller cells that remain in the upper layer. Surface distributions of chlorophyll and phytoplankton size spectra and fluorescence obtained using a CytoSense flow cytometer will be compared between upwelling spring cruises and a non upwelling winter cruise to the CoOP-WEST study site off Bodega Bay, CA.

  3. Bio-optical characteristics of phytoplankton populations in the upwelling system off the coast of Chile Características (bio-ópticas de poblaciones de fitoplancton en el sistema de surgencia de la costa de Chile

    Directory of Open Access Journals (Sweden)

    VENETIA STUART

    2004-03-01

    Full Text Available Phytoplankton samples collected from two cruises off the coast of Chile were analysed for pigment composition and absorption characteristics. High pigment concentrations (up to 20 mg chl-a m-3 were found in the upwelled waters over the shelf break off the coast of Concepción during spring (October 1998, but relatively oligotrophic conditions were found further offshore. Similarly, stations further north (between Coquimbo and Iquique, sampled during the austral summer (February 1999, also showed low pigment concentrations, characterised by the presence of prymnesiophytes, and cyanobacteria including Prochlorococcus sp. The specific absorption coefficient of phytoplankton at 443 nm (a*ph(443 was much higher for the offshore population than the inshore population, which was dominated by large diatoms. These differences are attributed to changes in pigment packaging and pigment composition. The relative proportion of non-photosynthetic carotenoids to chl-a, together with the ratio of the peak height of the Gaussian bands in the blue and red regions of the spectrum, p(435/p(676, (an indicator of the importance of the packaging effect could account for up to 92 % of the total variation in a*ph(443. Blue/green absorption ratios were strongly related to the relative concentration of 19'-hexanoyloxyfucoxanthin and fucoxanthin. A reasonable agreement was found between in situ and satellite estimates of chl-a (SeaWiFS data despite the large variability in phytoplankton specific absorption coefficients, suggesting that the `global' absorption-to-chlorophyll relationships encompass the regional variations observed off the coast of Chile. Satellite chl-a was overestimated in oligotrophic water when compared to HPLC chl-a measurements, apparently because of the high specific absorption coefficients of phytoplankton in the offshore waters. On the other hand, ship and satellite data were in closer agreement when in situ fluorometric chl-a data was used. It is

  4. Distribution and respiration of the high-latitude pelagic amphipod Themisto gaudichaudi in the Benguela Current in relation to upwelling intensity

    Science.gov (United States)

    Auel, Holger; Ekau, Werner

    2009-12-01

    The cold and highly productive waters of coastal upwelling areas provide habitats for marine species usually occurring at higher latitudes and allow those species to extend their distribution ranges towards the equator into regions otherwise characterised by warm and oligotrophic sub-tropical waters. The pelagic hyperiid amphipod Themisto gaudichaudi has a circum-Antarctic epipelagic distribution pattern generally south of 35°S and plays an important role in Antarctic food webs as effective link from zooplankton secondary production to higher trophic levels including seabirds and marine mammals. In the cold and productive waters of the Benguela Current coastal upwelling system, the distribution range of the species extents far northward into the subtropics. The present study focuses on the distribution of T. gaudichaudi at the northernmost limit of its range in the Benguela upwelling system in relation to upwelling intensity and hydrographic conditions (sea surface temperature) based on time-series data from 2002 to 2008. Moreover, field data on life-history traits and respiration rates in relation to water temperature are combined to elucidate the environmental and physiological factors limiting the distribution range. Compared to Themisto populations from higher latitudes, the relatively higher water temperatures in the coastal upwelling region lead to higher respiration rates, faster growth, earlier sexual maturity and smaller body size.

  5. The role of Equatorial Undercurrent in sustaining the Eastern Indian Ocean upwelling

    Science.gov (United States)

    Chen, Gengxin; Han, Weiqing; Shu, Yeqiang; Li, Yuanlong; Wang, Dongxiao; Xie, Qiang

    2016-06-01

    By combining volume transport and salinity analysis from 1958 to 2014, this paper investigates how the transient Equatorial Undercurrent (EUC) sustains the summer-fall equatorial eastern Indian Ocean (EIO) upwelling. On seasonal time scales, the EIO upwelling is mainly supplied by the salty water from the western basin through a buffering process: The winter-spring EUC carries the salty water from the western basin eastward, induces downwelling in the EIO, and pushes portion of the salty water below the central thermocline, which subsequently upwells to the central thermocline during summer-fall and sustains the EIO upwelling. On interannual time scales, enhanced upwelling occurs during positive Indian Ocean Dipole (+IOD) years. The strong summer-fall EUC associated with the +IOD supplies water for the intensified upwelling. This research provides new knowledge for basin-scale mass and property exchanges associated with the EIO upwelling, contributing to our understanding of three-dimensional ocean circulation and climate variability.

  6. The Effects of Climate Change on the Planting Boundary and Potential Yield for Different Rice Cropping Systems in Southern China

    Institute of Scientific and Technical Information of China (English)

    YE Qing; YANG Xiao-guang; LIU Zhi-juan; DAI Shu-wei; LI Yong; XIE Wen-juan; CHEN Fu

    2014-01-01

    Based on climate data from 254 meteorological stations, this study estimated the effects of climate change on rice planting boundaries and potential yields in the southern China during 1951-2010. The results indicated a signiifcant northward shift and westward expansion of northern boundaries for rice planting in the southern China. Compared with the period of 1951-1980, the average temperature during rice growing season in the period of 1981-2010 increased by 0.4°C, and the northern planting boundaries for single rice cropping system (SRCS), early triple cropping rice system (ETCRS), medium triple cropping rice system (MTCRS), and late triple cropping rice system (LTCRS) moved northward by 10, 30, 52 and 66 km, respectively. In addition, compared with the period of 1951-1980, the suitable planting area for SRCS was reduced by 11%during the period of 1981-2010. However, the suitable planting areas for other rice cropping systems increased, with the increasing amplitude of 3, 8, and 10%for ETCRS, MTCRS and LTCRS, respectively. In general, the light and temperature potential productivity of rice decreased by 2.5%. Without considering the change of rice cultivars, the northern planting boundaries for different rice cropping systems showed a northward shift tendency. Climate change resulted in decrease of per unit area yield for SRCS and the annual average yields of ETCRS and LTCRS. Nevertheless, the overall rice production in the entire research area showed a decreasing trend even with the increasing trend of annual average yield for MTCRS.

  7. Implementation of a boundary layer heat flux parameterization into the Regional Atmospheric Modeling System (RAMS

    Directory of Open Access Journals (Sweden)

    E. L. McGrath-Spangler

    2008-07-01

    Full Text Available The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the boundary layer. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the lower layer through the insertion of energy and mass. This alters the surface energy budget by changing the Bowen ratio and thereby altering the vegetative response and the surface boundary conditions. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. A parameterization to include the effects of boundary layer entrainment was introduced into a coupled ecosystem-atmosphere model (SiB-RAMS. The parameterization is based on a downward heat flux at the top of the boundary layer that is proportional to the heat flux at the surface. Results with the parameterization show that the boundary layer simulated is deeper, warmer, and drier than when the parameterization is turned off. These results alter the vegetative stress factors thereby changing the carbon flux from the surface. The combination of this and the deeper boundary layer change the concentration of carbon dioxide in the boundary layer.

  8. 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....

  9. Applying different quality and safety models in healthcare improvement work: Boundary objects and system thinking

    International Nuclear Information System (INIS)

    A number of theoretical models can be applied to help guide quality improvement and patient safety interventions in hospitals. However there are often significant differences between such models and, therefore, their potential contribution when applied in diverse contexts. The aim of this paper is to explore how two such models have been applied by hospitals to improve quality and safety. We describe and compare the models: (1) The Organizing for Quality (OQ) model, and (2) the Design for Integrated Safety Culture (DISC) model. We analyze the theoretical foundations of the models, and show, by using a retrospective comparative case study approach from two European hospitals, how these models have been applied to improve quality and safety. The analysis shows that differences appear in the theoretical foundations, practical approaches and applications of the models. Nevertheless, the case studies indicate that the choice between the OQ and DISC models is of less importance for guiding the practice of quality and safety improvement work, as they are both systemic and share some important characteristics. The main contribution of the models lay in their role as boundary objects directing attention towards organizational and systems thinking, culture, and collaboration

  10. DESIGN OF LOW COST MARITIME BOUNDARY IDENTIFICATION DEVICE USING GPS SYSTEM

    Directory of Open Access Journals (Sweden)

    K. Suresh Kumar,

    2010-09-01

    Full Text Available GPS (Global Positioning System is increasingly being used for a wide range of applications. It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on or near the Earth. GPS is made up of three segments: Space, Control and User. GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, tracking and surveillance, and hobbies such as geocaching and way marking. None of the present GPS systems satisfy the requirements for the safety of civilian navigation in the sea as the maritime boundary of a country cannotbe marked. This paper deals on the versatility and the usefulness of a GPS device in the sea. The main objective of the paper is to help the fishermen not to navigate beyond other country’s border. If a fisherman navigates beyond the country’s border, an alarm is generated indicating that the fisherman has crossed the border. Additionally, a GSM transmitter interface will send a message to base station located on the shore indicating that a vessel has crossed the border. Thus guards in the shore can assist and provide additional help to those fishermen if needed. Keeping in mind about lives of Indian fishermen, this device has been created to help them not to move beyond Indian. On the whole, it is an attempt to build a suitable device for the fishermen at a reasonably low cost.

  11. Nitrogen transfers and air-sea N2O fluxes in the upwelling off Namibia within the oxygen minimum zone: a 3-D model approach

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2011-04-01

    Full Text Available As regions of high primary production and being often associated to Oxygen Minimum Zones (OMZs, Eastern Boundary Upwelling Systems (EBUS represent key regions for the oceanic nitrogen (N cycle. Indeed, by exporting the Organic Matter (OM and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. Losses of fixed inorganic N, through denitrification and anammox processes and through nitrous oxide (N2O emissions to the atmosphere, take place in oxygen depleted environments such as EBUS, and alleviate the role of these regions as a source of N. In the present study, we developed a 3-D coupled physical/biogeochemical (ROMS/BioBUS model for investigating the full N budget in the Namibian sub-system of the Benguela Upwelling System (BUS. The different state variables of a climatological experiment have been compared to different data sets (satellite and in situ observations and show that the model is able to represent this biogeochemical oceanic region. The N transfer is investigated in the Namibian upwelling system using this coupled model, especially in the Walvis Bay area between 22° S and 24° S where the OMZ is well developed (O2 2 l−1. The upwelling process advects 24.2 × 1010 mol N yr−1 of nitrate enriched waters over the first 100 m over the slope and over the continental shelf. The meridional advection by the alongshore Benguela current brings also nutrient-rich waters with 21.1 × 1010 mol N yr−1. 10.5 × 1010 mol N yr−1 of OM are exported outside of the continental shelf (between 0 and 100-m depth. 32.4% and 18.1% of this OM are exported by advection in the form of Dissolved and Particulate Organic Matters (DOM and POM, respectively, however vertical sinking of POM represents the main contributor (49.5% to OM export outside of the first 100-m depth of the water column on the continental shelf. The continental slope also represents a net N

  12. Stress relaxation in thin film/substrate systems by grain boundary diffusion: a discrete dislocation framework

    International Nuclear Information System (INIS)

    The relaxation of stress in a thin film due to grain boundary diffusion is investigated in terms of a new discrete dislocation framework. Discrete dislocations along grain boundaries are nucleated from the free surface and are then driven to 'climb' by the Peach–Koehler force, with a mobility that is determined by the grain boundary diffusivity. Application to a planar film/substrate problem with (sub-) micrometer scale columnar grains shows that the amount of relaxation is dependent on the initial stress and on the grain aspect ratio. For thin columnar grains the relaxation is faster and more effective and the opening displacements along the grain boundary are more uniform, an effect that is not captured by current continuum models. When the initial stress is low and and the grain size is small, it is necessary to account for variations in the threshold stress for diffusion among different grain boundaries to achieve realistic results

  13. Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle.

    Science.gov (United States)

    Rosenthal, Anja; Yaxley, Gregory M; Green, David H; Hermann, Joerg; Kovács, István; Spandler, Carl

    2014-01-01

    Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. Here we show with an experimental study that these residual eclogites continuously melt during upwelling of such heterogeneous mantle and we characterize the melting reactions and compositional changes in the residue minerals. The chemical exchange between these partial melts and more refractory peridotite leads to a variably metasomatised mantle. Re-melting of these metasomatised peridotite lithologies at given pressures and temperatures results in diverse melt compositions, which may contribute to the observed heterogeneity of oceanic basalt suites. We also show that heterogeneous upwelling mantle is subject to diverse local freezing, hybridization and carbonate-carbon-silicate redox reactions along a mantle adiabat. PMID:25130275

  14. 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

  15. The Asymptotic Behavior and the Quasineutral Limit for the Bipolar Euler-Poisson System with Boundary Effects and a Vacuum

    Institute of Scientific and Technical Information of China (English)

    Yeping LI

    2013-01-01

    In this paper,a one-dimensional bipolar Euler-Poisson system (a hydrodynamic model) from semiconductors or plasmas with boundary effects is considered.This system takes the form of Euler-Poisson with an electric field and frictional damping added to the momentum equations.The large-time behavior of uniformly bounded weak solutions to the initial-boundary value problem for the one-dimensional bipolar Euler-Poisson system is firstly presented.Next,two particle densities and the corresponding current momenta are verified to satisfy the porous medium equation and the classical Darcy's law time asymptotically.Finally,as a by-product,the quasineutral limit of the weak solutions to the initial-boundary value problem is investigated in the sense that the bounded L∞ entropy solution to the one-dimensional bipolar Euler-Poisson system converges to that of the corresponding one-dimensional compressible Euler equations with damping exponentially fast as t → +∞.As far as we know,this is the first result about the asymptotic behavior and the quasineutral limit for the one-dimensional bipolar Euler-Poisson system with boundary effects and a vacuum.

  16. Mn seasonal upwellings recorded in Lake Tanganyika mussels

    OpenAIRE

    D. Langlet; Alleman, L. Y.; P.-D. Plisnier; Hughes, H; André, L.

    2006-01-01

    International audience Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragon...

  17. Manganese content records seasonal upwelling in Lake Tanganyika mussels

    OpenAIRE

    D. Langlet; Alleman, L. Y.; Plisnier, P.-D.; Hughes, H; André, L.

    2007-01-01

    International audience Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profil...

  18. Surface circulation and upwelling patterns around Sri Lanka

    OpenAIRE

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

    2013-01-01

    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...

  19. Offshore Wind Farm Wake Effect on Stratification and Coastal Upwelling

    OpenAIRE

    Bakhoday Paskyabi, Mostafa

    2015-01-01

    In this study, the interactions between an offshore wind farm, upper-ocean currents, and stratification are examined under shallow water conditions from a two-dimensional modeling standpoint. The modeling results from two numerical simulation runs provide new insights on the formation of downwind vortex streets and the adjustment of coastal processes, such as upwelling and stratification. The distorted farm-induced wind deficits are calculated by the concept of single- and multiple-wake model...

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

    Directory of Open Access Journals (Sweden)

    F. Azzaro

    2007-05-01

    Full Text Available In the Straits of Messina the 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 of surface distribution of phytoplankton biomass depending on upwelling phenomena. Temperature, salinity, nitrates and phytoplankton fluorescence were measured in 1994 and 1995 by continuous underway surface real-time measurements on board dedicated research boats. Each survey was performed following the dynamic phases of flooding and ebbing tides. Tidal currents are essentially southward during the high tide and northward during the low tide.

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

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

    The Straits system can be compared to an "intermittent pump" which, during the different seasons, before enriched itself and then it provides nutrients to the surrounding basins.

  1. Large Topographic Rises on Venus: Implications for Mantle Upwelling

    Science.gov (United States)

    Stofan, Ellen R.; Smrekar, Suzanne E.; Bindschandler, Duane L.; Senske, David A.

    1995-01-01

    Topographic rises on Venus have been identified that are interpreted to be the surface manifestation of mantle upwellings. These features are classified into groups based on their dominant morphology. Atla and Beta Regiones are classified as rift-dominated, Dione, western Eistla, Bell, and Imdr Regiones as volcano-dominated, and Themis, eastern Eistla, and central Eistla Regiones as corona-dominated. At several topographic rises, geologic indicators were identified that may provide evidence of uplifted topography (e.g., volcanic flow features trending upslope). We assessed the minimum contribution of volcanic construction to the topography of each rise, which in general represents less than 5% of the volume of the rise, similar to the volumes of edifices at terrestrial hotspot swells. The total melt volume at each rise is approximated to be 10(exp 4) - 10(exp 6) cu km. The variations in morphology, topography, and gravity signatures at topographic rises are not interpreted to indicate variations in stage of evolution of a mantle upwelling. Instead, the morphologic variations between the three classes of topographic rises are interpreted to indicate the varying influences of lithospheric structure, plume characteristics, and regional tectonic environment. Within each class, variations in topography, gravity, and amount of volcanism may be indicative of differing stages of evolution. The similarity between swell and volcanic volumes for terrestrial and Venusian hotspots implies comparable time-integrated plume strengths for individual upwellings on the two planets.

  2. Aragonite saturation state dynamics in a coastal upwelling zone

    Science.gov (United States)

    Harris, Katherine E.; Degrandpre, Michael D.; Hales, Burke

    2013-06-01

    upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state (ΩAr) waters to the surface that are further suppressed by anthropogenic CO2. ΩAr was calculated with pH, pCO2, and salinity-derived alkalinity time series data from autonomous pH and pCO2 instruments moored on the Oregon shelf and shelf break during different seasons from 2007 to 2011. Surface ΩAr values ranged between 0.66 ± 0.04 and 3.9 ± 0.04 compared to an estimated pre-industrial range of 1.0 ± 0.1 to 4.7 ± 0.1. Upwelling of high-CO2 water and subsequent removal of CO2 by phytoplankton imparts a dynamic range to ΩAr from ~1.0 to ~4.0 between spring and autumn. Freshwater input also suppresses saturation states during the spring. Winter ΩAr is less variable than during other seasons and is controlled primarily by mixing of the water column.

  3. Modeling of the upwelling hydrodynamics in the Aegean Sea

    Directory of Open Access Journals (Sweden)

    Y.G. SAVVIDIS

    2012-12-01

    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.

  4. Blueschist Blocks in the Shale-matrix Melange of the Franciscan Complex of California: Metamorphic Aureoles and Subduction Channel Upwelling

    Science.gov (United States)

    Cloos, Mark; Ukar, Estibalitz

    2014-05-01

    The subduction channel concept postulates that where oceanic lithosphere converges faster than ~2 cm/yr, the plate boundary is best approximated as a viscous shear zone. Channel capacity can abruptly decrease where there is a sharp increase in the pressure gradient along the top of the shear zone. Where this occurs, subducted sediment can upwell and flow back towards the inlet. The Central Belt of the Franciscan Complex is up to tens of km wide and extends from where subduction continues in Oregon southwards to the Nacimiento Block, west of the San Andreas fault. The scaly shale matrix outcrops poorly along the 1500+ km belt because it is weakly metamorphosed (blueschists (e.g., Tiburon, Jenner Beach). How these high-T blocks, the oldest metamorphics in the Franciscan and the more voluminous lower-T blueschists became rounded fragments encased in shale-matrix has been the subject of much discussion. Uplift in serpentine diapirs is widely invoked, but the scarcity of these blocks in serpentinite where exposures are good is problematic. Explaining the blocks as sedimentary olistoliths requires both a phantom source terrane and exhumation mechanism. The simplest explanation is that the coarse blueschists are fragments of a metamorphic aureole formed during subduction initiation that were later detached from the base of the ophiolitic leading edge of the North American plate. Later, tectonic melange was generated by subduction-driven shearing that caused upwelling of shale-rich sediment. Slabs of blueschist were boudinaged and mixed with fragments of greenstone and chert detached from seamounts. Blueschist block incorporation into upwelling mélange is a kind of subduction erosion akin to plucking by glaciers. The exposure of the blueschist along the roof of the subduction channel may have been mostly localized to near where normal faults formed in the overriding block as Farallon plate dip flattened from 80 to 40 Ma. Only blocks of the appropriate size and density can

  5. GLOBAL EXISTENCE AND BLOW-UP OF SOLUTIONS TO A NONLOCAL EVOLUTION p-LAPLACE SYSTEM WITH NONLINEAR BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    Wu Xuesong; Gao Wenjie; Cao Jianwen

    2011-01-01

    In this paper, the authors discuss the global existence and blow-up of the solution to an evolution ρ-Laplace system with nonlinear sources and nonlinear boundary condition. The authors first establish the local existence of solutions, then give a necessary and sufficient condition on the global existence of the positive solution.

  6. Electrostatic interactions in finite systems treated with periodic boundary conditions: Application to linear-scaling density functional theory

    Science.gov (United States)

    Hine, Nicholas D. M.; Dziedzic, Jacek; Haynes, Peter D.; Skylaris, Chris-Kriton

    2011-11-01

    We present a comparison of methods for treating the electrostatic interactions of finite, isolated systems within periodic boundary conditions (PBCs), within density functional theory (DFT), with particular emphasis on linear-scaling (LS) DFT. Often, PBCs are not physically realistic but are an unavoidable consequence of the choice of basis set and the efficacy of using Fourier transforms to compute the Hartree potential. In such cases the effects of PBCs on the calculations need to be avoided, so that the results obtained represent the open rather than the periodic boundary. The very large systems encountered in LS-DFT make the demands of the supercell approximation for isolated systems more difficult to manage, and we show cases where the open boundary (infinite cell) result cannot be obtained from extrapolation of calculations from periodic cells of increasing size. We discuss, implement, and test three very different approaches for overcoming or circumventing the effects of PBCs: truncation of the Coulomb interaction combined with padding of the simulation cell, approaches based on the minimum image convention, and the explicit use of open boundary conditions (OBCs). We have implemented these approaches in the ONETEP LS-DFT program and applied them to a range of systems, including a polar nanorod and a protein. We compare their accuracy, complexity, and rate of convergence with simulation cell size. We demonstrate that corrective approaches within PBCs can achieve the OBC result more efficiently and accurately than pure OBC approaches.

  7. GLOBAL WEAKLY DISCONTINUOUS SOLUTIONS TO A KIND OF MIXED INITIAL-BOUNDARY VALUE PROBLEM FOR INHOMOGENEOUS QUASILINEAR HYPERBOLIC SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    GUO Fei

    2007-01-01

    In this paper we study the mixed initial-boundary value problem for inhomogeneous quasilinear hyperbolic systems in the domain D={(t,x)| t≥O,x≥O}.Under the assumption that the source term satisfies the matching condition,a sufficient condition to guarantee the existence and uniqueness of global weakly discontinuous solution is given.

  8. Glacial/Interglacial Record of Planktic Foraminifera From the Upwelling Area off Chile

    Science.gov (United States)

    Mohtadi, M.; Hebbeln, D.; Wefer, G.

    2002-12-01

    The southern part of the Peru-Chile Current (PCC) is among the least studied regions of the world ocean compared to other Eastern Boundary Currents (EBC). The PCC stands out as the EBC with the longest N-S extension (over 20° of latitude) and a strong continuous upwelling regime resulting in a very high biological productivity and an intense cycling of carbon making the PCC to an important part of the global carbon cycle. We analyzed three gravity cores from the Chilean continental margin between 24° and 30° S to observe the intensity of upwelling and productivity in the PCC during the LGM and the Holocene deduced from planktic foraminifera assemblages. Core GeoB 3375-1 was recovered during the CHIPAL-Expedition of RV Sonne (SO-102) off the Norte Chico, while cores GeoB 7112-5 off Antofagasta and GeoB 7139-2 off Coquimbo were retrieved during the PUCK-Expedition of RV Sonne (SO-156). The age models for the cores are based on accelerator mass spectrometry (AMS) 14C dates and stable oxygen isotope data correlated with the SPECMAP stack. Examination of the faunal composition showed the dominance of six species, which account on average for more than 90% of the total planktic foraminiferal assemblage. The dominant species are N. pachyderma dex. (~30%), G. bulloides (~27%), N. pachyderma sin. (~25%), N. dutertrei (~2%), G. glutinata (~2%) and G. inflata (~6%). Absolute concentrations of planktic foraminifera show a distinct maximum during the LGM. After lower levels during the early Holocene, the concentration drops to very low middle-late Holocene levels. The total planktic foraminifera assemblage shows a considerable change in the species composition between 14 and 12 kyr BP manifested by the distinct relative decrease of the cold water species N. pachyderma sin. and G. inflata opposed by the increase of the relatively warmer water species N. pachyderma dex. and N. dutertrei. Thus, warmer water species become dominant at 12 kyr BP. During the LGM, the species

  9. Inversion formulas for complex Radon transform on projective varieties and boundary value problems for systems of linear PDE

    CERN Document Server

    Henkin, Gennadi M

    2011-01-01

    Let $G\\subset \\C P^n$ be a linearly convex compact with smooth boundary, $D={\\C}P^n\\setminus G$, and let $D^* \\subset (\\C P^n)^*$ be the dual domain. Then for an algebraic, not necessarily reduced, complete intersection subvariety $V$ of dimension $d$ we construct an explicit inversion formula for the complex Radon transform $R_V:\\ H^{d,d-1}(V\\cap D)\\to H^{1,0}(D^*)$, and explicit formulas for solutions of an appropriate boundary value problem for the corresponding system of differential equations with constant coefficients on $D^*$.

  10. Outer boundary of major discharge areas of Death Valley regional flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The digital data set delineates the outer boundary of each major discharge area evaluated as part of the study. These areas were used to refine estimates of...

  11. Development of ion diagnostic system based on electrostatic probe in the boundary plasma of the JFT-2M tokamak

    International Nuclear Information System (INIS)

    An ion diagnostic system using electrostatic probes for measurements in the JFT-2M tokamak boundary plasma has been developed under the collaboration program between KFA and JAERI. The rotating double probe system, on which the Hoethker double probe and Amemiya asymmetric probe can mounted, are manufactured at KFA workshop while the linear driver to support the rotating double probe, the ion toothbrush probe, the Katsumata probe and the cubic Mach probe are developed at JAERI. This report describes the hardware of this probe system for ion diagnostics in the boundary plasma and preliminary data obtained by means of this system. Furthermore, results on the transport are estimated on the basis of these probe data. (author)

  12. Positive Solutions for (n-1,1-Type Singular Fractional Differential System with Coupled Integral Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Ying Wang

    2014-01-01

    Full Text Available We study the positive solutions of the (n-1,1-type fractional differential system with coupled integral boundary conditions. The conditions for the existence of positive solutions to the system are established. In addition, we derive explicit formulae for the estimation of the positive solutions and obtain the unique positive solution when certain additional conditions hold. An example is then given to demonstrate the validity of our main results.

  13. 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)

  14. Long-term Variability of NorthWest African coastal upwelling

    Science.gov (United States)

    Wade, Malick; Rodríguez-Fonseca, Belen; Lazar, Alban

    2014-05-01

    The NorthWest African sea surface temperature variability can be due to changes in the coastal upwelling system, which in turn can be due to alterations in local winds, global winds induced by teleconnections and propagation of waves from wind burst in remote regions. The two last processes could be due in turn to changes in the sea surface temperature in extended regions remote from the upwelling region, as changes in Pacific SSTs associated with ENSO, or in the Equatorial Atlantic SSTs. This work demonstrates that the whole signal cannot be explained by local wind/Ekman pumping and large scale winds induced by teleconnections play an important role. Using observational data of SSTs and winds from atmospheric reanalysis, and applying different statistical technics, as correlation analysis, filtering and discriminant analysis, the different influences and its stationarity along the observational period are tested pointing to the non stationarity of El Niño influence in FMA and to other possible predictors influencing in the region.

  15. Narrowing of the Upwelling Branch of the Brewer-Dobson Circulation and Hadley Cell in Chemistry-Climate Model Simulations of the 21st Century

    Science.gov (United States)

    Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn

    2010-01-01

    Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley cell's rising branch. Model results suggest that eddy forcing may also play a part in the narrowing of the rising branch of the Hadley cell.

  16. Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current

    OpenAIRE

    John A. Barth; Menge, Bruce A.; Lubchenco, Jane; Chan, Francis; Bane, John M.; Kirincich, Anthony R.; McManus, Margaret A.; Nielsen, Karina J.; Pierce, Stephen D.; Washburn, Libe

    2007-01-01

    Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255–257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We sh...

  17. Simulation of nutrient transport from different depths during an upwelling event in the Gulf of Finland

    OpenAIRE

    Germo Väli; Victor Zhurbas; Jaan Laanemets; Jüri Elken

    2011-01-01

    Numerical simulation experiments with a high-resolution circulation model were carried out to study nutrient transport from different depths to the surface 10-m layer during an upwelling event along the northern coast of the Gulf of Finland in July 1999. The initial nutrient distribution is based on field measurements performed in the north-western part of the Gulf. Wind forcing covering the period of the upwelling along the northern coast was turned through 180° to simulate an upwelling alon...

  18. Contribution à l'étude de l'upwelling du Pérou Chili

    OpenAIRE

    Croquette, Marie

    2007-01-01

    The upwelling and associated alongshore coastal currents variability (CPCC, Chile Peru coastal Current and PCUC, Peru-Chile Undercurrent) has been studied with satellite data and two numerical models. This study covers a large meridional extend: from Peru to Southern Chile (50°S). Variability characteristics in Peru and Chile are separated by a transition zone around 20°S where winds, upwelling and the PCUC are particularly weak. The origins of upwelling and PCUC waters have also been studied...

  19. 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

  20. 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 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 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

  1. Estimation of velocity boundaries in basement - sedimentary layer system of Yokohama region by means of nonstationary ray decomposition method

    Science.gov (United States)

    Takagishi, M.; Kinoshita, S.

    2011-12-01

    We estimated the velocity boundaries in a sedimentary layer-basement system in Yokohama by applying nonstationary ray decomposition method (NRDM) to the strong motion data recorded at the Yokohama dense strong motion array (YKH array). NRDM is a method to estimate the velocity boundaries of real layered structure from surface recordings by decomposing power of an SH-wave into instantaneous power of wave associated with rays in a homogeneous half space. The estimated results obtained by applying this method to seismograms are represented as a function of lapse time and depth time, which is travel time from surface toward depth-direction. A total of 10080 surface seismograms obtained at the YKH array for the 128 earthquakes that occurred in the Kanto area from 2000 to 2010 were used. The recordings were measured by acceleration seismometers. The data were obtained for the events having JMA magnitudes in the range of from 2.8 to 6.5. NRDM was applied to the transverse component data of velocity seismogram. Since the seismograms obtained at the YKH array predominate in high frequencies due to the weak subsurface structure, we applied bandpass filtering to the seismograms by using several intrinsic mode functions that are narrowband signals with different center frequencies. After such a processing, the data were converted to analytic signals, and then, the signals were used to estimate the instantaneous power by means of Wigner-Ville distribution. We have estimated the velocity boundaries in sediment in Yokohama region using 37 sites which were located in a rectangular area with a width of 4 km and a length of 40 km south-southeast of the FCH array. We were able to estimate two velocity boundaries, one in sediment (K-M) and the other being the upper boundary of the pre-Tertiary basement (M-B). On the whole, the upper boundary of the pre-Tertiary basement is dipping toward the south-southeast. The estimated depth times at K-M and M-B were from 1.5 to 2.2 s and from 2

  2. Domoic acid production near California coastal upwelling zones, June 1998

    Energy Technology Data Exchange (ETDEWEB)

    Trainer, V L.(National Marine Fisheries Service); Adams, Nicolaus G.(National Marine Fisheries Service); Bill, Brian D.(National Marine Fisheries Service); Stehr, Carla M.(National Marine Fisheries Service); Wekell, John C.(National Marine Fisheries Service); Moeller, Peter (National Ocean Service, Marine Biotoxins Program); Busman, Mark (National Ocean Service, Marine Biotoxins Program); Woodruff, Dana L.(BATTELLE (PACIFIC NW LAB))

    2000-01-01

    Sea lion mortalities in central California during May and June 1998 were traced to their ingestion of sardines and anchovies that had accumulated the neurotoxin domoic acid. The detection of toxin in urine, feces, and stomach contents of several sea lions represents the first proven occurrence of domoic acid transfer through the food chain to a marine mammal. The pennate diatoms, Pseudo-nitzschia multiseries and P. australis, were the dominant, toxin-producing phytoplankton constituting algal blooms near Monterey Bay, Half Moon Bay, and Oceano Dunes, areas where sea lions with neurological symptoms stranded. Toxic Pseudo-nitzschia were also found near Morrow Bay, Point Conception, Point Arguello, and Santa Barbara, demonstrating that these species were widespread along the central California coast in June 1998. Measurements of domoic acid during three cruises in early June showed the highest cellular toxin levels in P. multiseries near Point A?o Nuevo and in P. australis from Morro w Bay. Maximum cellular domoic acid levels were observed within 20 km of the coast between 0 and 5 m depth, although toxin was also measured to depths of 40 m. Hydrographic data indicated that the highest toxin levels and greatest numbers of toxic cells were positioned in water masses associated with upwelling zones near coastal headlands. Nutrient levels at these sites were less than those typically measured during periods of active upwelling, due to the 1998 El Ni?o event. The flow of cells and/or nutrients from coastal headlands into embayments where cells can multiply in a stratified environment is a possible mechanism of bloom development along the central California coast. This coupling of toxic Pseudo-nitzschia growth near upwelling zones with physical processes involved in cell transport will be understood only when long-term measurements are made at several key coastal locations, aiding in our capability to predict domoic-acid producing algal blooms.

  3. Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981-2012

    OpenAIRE

    Cropper, T.E; Hanna, E; Bigg, G.R.

    2014-01-01

    Seasonal coastal upwelling was analyzed along the NW African coastline (11-35°N) from 1981 to 2012. Upwelling magnitudes are calculated by wind speed indices, sea-surface temperature indices and inferred from meteorological station, sea-surface height and vertical water column transport data. A permanent annual upwelling regime is documented across 21-35°N and a seasonal regime across 12-19°N, in accordance with the climatology of previous studies. Upwelling regions were split into three zone...

  4. Trophic connectivity between offshore upwelling and the inshore food web of Banc d'Arguin (Mauritania): New insights from isotopic analysis

    Science.gov (United States)

    Carlier, Antoine; Chauvaud, Laurent; van der Geest, Matthijs; Le Loc'h, François; Le Duff, Michel; Vernet, Marc; Raffray, Jean; Diakhaté, Djibril; Labrosse, Pierre; Wagué, Abdoulaye; Le Goff, Clément; Gohin, Francis; Chapron, Bertrand; Clavier, Jacques

    2015-11-01

    Banc d'Arguin (BA), Mauritania, is a nationally protected shallow gulf > 10,000 km2 between the Sahara desert and the upwelling system off the Mauritanian coast. In the southeast, BA consists of a 500 km2 tidal flat, the most important wintering site for shorebirds using the East Atlantic Flyway. The Mauritanian upwelling-driven phytoplankton production supports the most productive fisheries worldwide, but little is known about its trophic role in the functioning of the inshore BA food web. Using stable isotopes as trophic tracers to distinguish between upwelling-driven phytoplankton, open ocean phytoplankton, and benthic primary producers, we assessed the spatial extent to which the inshore BA food web is fuelled by upwelling-driven phytoplankton production. The δ13C and δ15N signals were characterized in dominant primary producers, benthic invertebrate taxa, and various fish species along an offshore-inshore (northwest-southeast) gradient. We also monitored the spatial and temporal extent of upwelling entering BA during 2008 with remote sensing of sea surface temperature and chlorophyll a data. The results suggest that benthic invertebrates and fishes living in the northwestern part of BA depend on the nearby upwelling phytoplankton production, but this food source does not support the intertidal benthic community in southeast BA. Furthermore, the isotopic signatures of fishes suggest weak trophic connectivity between the northern subtidal and southeastern intertidal BA. Our results support the hypothesis that the southeastern tidal flat region functions as a distinct ecosystem with a food web supported mainly by local benthic primary production, which is crucial knowledge for effective management of the pristine BA national park.

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

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    : divakar@csnio.ren.nic.in (P.D. Naidu). intensity in the Sea Naidu * Paula 403 004, Goa, India 2003 www.elsevier.com/locate/gloplacha (2004) 285–293 the important role played by the upwelling zones on the ocean carbon cycle, it is important to identify... flux (Fig. 2a,b).Furthermore,G. bulloides flux and Dd 18 O obl-bul show significant in- verse ranking correlation coefficient (r=C00.56) (pV0.1). 5.2. Dd 13 C sac-dut G.bulloides d 13 Cvaluesarestronglyeffectedbythe vital effects (Naidu and Niitsuma...

  6. The profile of upwelling 11-micron radiance through the atmospheric boundary layer overlying the ocean

    Science.gov (United States)

    Hagen, Denise E.

    1988-01-01

    Measurements of the gradient of 11-micron radiance from the ocean surface were made with spaceborne AVHRR and with radiometers carried on research vessels in California and east Florida waters. The results obtained for the radiance gradient at a variety of atmospheric conditions are in good agreement with radiative transfer calculations, suggesting that there was no significant error in the water vapor absorption parameters used in the calculations. The results confirm earlier predictions that, for a typical viewing factor (i.e., zenith angle 60 deg) and for mid-latitude standard water vapor conditions, the 11-micron radiant flux measured by a spaceborne sensor will be dominated by the atmospheric contribution to the total outgoing radiation in this 'window' region.

  7. Trophic connectivity between offshore upwelling and the inshore food web of Banc d'Arguin (Mauritania): New insights from isotopic analysis

    NARCIS (Netherlands)

    Carlier, A.; Chauvaud, L.; van der Geest, M.; Le Loc'h, F.; Le Duff, M.; Vernet, M.; Raffray, J.; Diakhate, D.; Labrosse, P.; Wagué, A.; Le Goff, C.; Gohin, F.; Chapron, B.; Clavier, J.

    2015-01-01

    Banc d'Arguin (BA), Mauritania, is a nationally protected shallow gulf > 10,000 km2 between the Sahara desert and the upwelling system off the Mauritanian coast. In the southeast, BA consists of a 500 km2 tidal flat, the most important wintering site for shorebirds using the East Atlantic Flyway. Th

  8. Potential contribution of planktonic components to ammonium cycling in the coastal area off central-southern Chile during non-upwelling conditions

    Science.gov (United States)

    Molina, Veronica; Morales, Carmen E.; Farías, Laura; Cornejo, Marcela; Graco, Michelle; Eissler, Yoanna; Cuevas, Luis A.

    2012-01-01

    The potential contributions of different microbial components (chemosynthesis (0.005 g C m -2 d -1) represented a large proportion (51%) of the total dark carbon fixation during the non-upwelling season when integrated rates of photosynthesis are relatively low (0.42 g C m -2 d -1) and microbial food webs dominate the transfer of carbon within this coastal system.

  9. 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.

  10. Fredholm-type theorem for boundary value problems for systems of nonlinear functional differential equations

    Czech Academy of Sciences Publication Activity Database

    Hakl, Robert; Zamora, M.

    -, May 2014 (2014), s. 113. ISSN 1687-2770 Institutional support: RVO:67985840 Keywords : functional-differential equations * boundary value problems * existence of solutions Subject RIV: BA - General Mathematics Impact factor: 1.014, year: 2014 http://www.boundaryvalueproblems.com/content/2014/1/113

  11. 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.

  12. The boundary condition model for three-particle system and nonzero partial waves

    International Nuclear Information System (INIS)

    The three-particle bound state problem in the 'boundary condition model' case is solved in the framework of Faddeev integral equations. An interaction in nonzero partial waves is shown to be necessarily taken into account due to its essential role in the model. 8 refs

  13. 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.

  14. Alkaline phosphatase activity at the southwest coast of India: A comparison of locations differently affected by upwelling

    Science.gov (United States)

    Mamatha, S. S.; Malik, Ashish; Varik, Sandesh; Parvathi, V.; Jineesh, V. K.; Gauns, Mangesh U.; LokaBharathi, P. A.

    2015-01-01

    The realization of the potential importance of phosphorus (P) as a limiting nutrient in marine ecosystem is increasing globally. Hence, the contribution of biotic variables in mobilizing this nutrient would be relevant especially in productive coastal waters. As alkaline phosphatase activity (APA) indicates the status of P for primary production in aquatic environments, we asked the following question: is the level of APA indicative of P sufficiency or deficiency in coastal waters, especially, where upwelling is a regular phenomenon? Therefore, we have examined the total APA, chlorophyll a along with phosphatase producing bacteria (PPB) and related environmental parameters from nearshore to offshore in coastal waters off Trivandrum and Kochi regions differently affected by upwelling during the onset of monsoon. Off Trivandrum, APA in the offshore waters of 5-m layer at 2.23 μM P h- 1 was > 4 times higher than nearshore. Thus, low APA could be indicative of P sufficiency in coastal waters and higher activity suggestive of deficiency in offshore waters off Trivandrum. In contrast, there was less difference in APA between near and offshore surface waters off Kochi. Our results show that the regions differently affected by upwelling respond differently according to ambient P concentration, distance from shore or depth of water. These observations could apparently be applicable to other coastal systems as well, where gradients in upwelling and phosphate runoff have been noticed. Further studies on other transects would throw more light on the extent and direction of the relationship between APA and ambient P concentration. Such studies would help in understanding the level of control of this nutrient on the productivity of coastal waters.

  15. The EarthScope Plate Boundary Observatory Distributed Data Management System

    Science.gov (United States)

    Anderson, G.; Eakins, J.; Hodgkinson, K.; Matykiewicz, J.; Beldyk, M.; Blackman, B.; Boler, F.; Henderson, B.; Hoyt, B.; Lee, E.; Persson, E.; Smith, J.; Torrez, D.; Wright, J.; Jackson, M.; Meertens, C.

    2007-05-01

    EarthScope is an ambitious multi-year project funded by the United States National Science Foundation to explore the structure and dynamics of the North American continent using a wide range of geophysical methods. The Plate Boundary Observatory (PBO), being built by UNAVCO, is the geodetic component of EarthScope, and will comprise 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters; in addition, PBO will manage data for 209 existing GPS stations and 11 GPS stations installed by the USArray segment of EarthScope. As of February 2007, 561 of these stations have been installed. PBO data flow is managed from the PBO Boulder Network Operations Center (NOC), located at UNAVCO Headquarters. Automated systems at the NOC retrieve data from our stations at least daily, monitor the status of the network and alert operators to problems, and pass data on for analysis, archiving, and distribution. Real-time network status can be found at http:pboweb.unavco.org/soh_map. PBO's analysis centers generate high-quality derived data products from PBO raw data. Two centers, at Central Washington University and the New Mexico Institute of Mining and Technology, process raw GPS data to produce initial PBO GPS products including network solutions and station position time series, andthese products are combined by the Analysis Center Coordinator at MIT to produce the official PBO GPS products. Two analysis centers, at UNAVCO's Socorro office and the University of California, San Diego, process data from the PBO borehole and laser strainmeter networks and produce cleaned time series of shear, areal, and linear strain, Earth tides, pore fluid pressure, and other parameters. The UNAVCO Facility archives and distributes all PBO GPS data products and runs a secondary archive offsite; to date, these centers hold more than 2.5 TB of PBO products. The IRIS Data Management Center and Northern California Earthquake Data Center archive and

  16. Nitrogen transfers and air-sea N2O fluxes in the upwelling off Namibia within the oxygen minimum zone: a 3-D model approach

    Science.gov (United States)

    Gutknecht, E.; Dadou, I.; Le Vu, B.; Cambon, G.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2011-04-01

    As regions of high primary production and being often associated to Oxygen Minimum Zones (OMZs), Eastern Boundary Upwelling Systems (EBUS) represent key regions for the oceanic nitrogen (N) cycle. Indeed, by exporting the Organic Matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. Losses of fixed inorganic N, through denitrification and anammox processes and through nitrous oxide (N2O) emissions to the atmosphere, take place in oxygen depleted environments such as EBUS, and alleviate the role of these regions as a source of N. In the present study, we developed a 3-D coupled physical/biogeochemical (ROMS/BioBUS) model for investigating the full N budget in the Namibian sub-system of the Benguela Upwelling System (BUS). The different state variables of a climatological experiment have been compared to different data sets (satellite and in situ observations) and show that the model is able to represent this biogeochemical oceanic region. The N transfer is investigated in the Namibian upwelling system using this coupled model, especially in the Walvis Bay area between 22° S and 24° S where the OMZ is well developed (O2 nutrient-rich waters with 21.1 × 1010 mol N yr-1. 10.5 × 1010 mol N yr-1 of OM are exported outside of the continental shelf (between 0 and 100-m depth). 32.4% and 18.1% of this OM are exported by advection in the form of Dissolved and Particulate Organic Matters (DOM and POM), respectively, however vertical sinking of POM represents the main contributor (49.5%) to OM export outside of the first 100-m depth of the water column on the continental shelf. The continental slope also represents a net N export (11.1 × 1010 mol N yr-1) between 0 and 100-m depth: advection processes export 14.4% of DOM and 1.8% of POM, and vertical sinking of POM contributes to 83.8%. Between 100 and 600-m depth, water column denitrification and anammox constitute

  17. The reduction of biological production induced by mesoscale mixing: a modelling study in the Benguela upwelling

    CERN Document Server

    Hernández-Carrasco, Ismael; Hernández-García, Emilio; Garçon, Veronique; López, Cristóbal

    2013-01-01

    Recent studies, both based on remote sensed data and coupled models, showed a reduction of biological productivity due to vigorous horizontal mixing in upwelling systems. In order to better understand this phenomenon, we have considered a system of oceanic flow in the Benguela area coupled with a simple biogeochemical model of Nutrient-Phyto-Zooplankton (NPZ) type. For the flow three different surface velocity fields are considered: one derived from satellite altimetry data, and the other two from a regional numerical model at two different spatial resolutions. We computed horizontal particle dispersion in terms of Lyapunov Exponents, and analyzed their correlations with phytoplankton concentrations. Our modelling approach confirms that in the south Benguela, there is a reduction of biological activity when stirring is increased. Two-dimensional offshore advection seems to be the dominant process involved. In the northern area, other factors not taken into account in our simulation are influencing the ecosyst...

  18. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport

    Science.gov (United States)

    Armour, Kyle C.; Marshall, John; Scott, Jeffery R.; Donohoe, Aaron; Newsom, Emily R.

    2016-07-01

    The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns--of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north--are fundamentally shaped by the Southern Ocean's meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.

  19. Seismic tomographic evidence for upwelling mantle plume in NE China

    Science.gov (United States)

    He, Chuansong; Santosh, M.

    2016-05-01

    In this study, we collected teleseismic data recorded by permanent and mobile seismic stations and carried out a teleseismic P-wave tomographic study. The results reveal low velocity perturbation regions at the central part of NE China and specifically in the Songliao basin at different depths, which correspond to the location of a proposed upwelling mantle plume identified by receiver function in a recent study. Receiver function data show a predominantly mafic/ultra-mafic lower crust in the Songliao basin, in contrast to the predominantly felsic lower crust in the other regions. The vestige of upwelling mantle plume is well defined at the mantle transition region. Based on the above results, we suggest that the volcanism in NE China and the Songliao basin formation might be related to Mesozoic mantle plume beneath NE China. We also evaluate alternate models on lower crustal delamination contributing to the volcanism in NE China following collision and amalgamation between the Siberia craton and the North China-Mongolian block during late Jurassic and early Cretaceous.

  20. Zooplankton Responses to Low-Oxygen Condition upon a Shallow Oxygen Minimum Zone in the Upwelling Region off Chile

    Science.gov (United States)

    Hidalgo, P.; Escribano, R.

    2015-12-01

    A shallow oxygen minimum zone (OMZ) is a critical component in the coastal upwelling ecosystem off Chile. This OMZ causes oxygen-deficient water entering the photic layer and affecting plankton communities having low tolerance to hypoxia. Variable, and usually species-dependent, responses of zooplankton to hypoxia condition can be found. Most dominant species avoid hypoxia by restricting their vertical distribution, while others can temporarily enter and even spent part of their life cycle within the OMZ. Whatever the case, low-oxygen conditions appear to affect virtually all vital rates of zooplankton, such as mortality, fecundity, development and growth and metabolism, and early developmental stages seem more sensitive, with significant consequences for population and community dynamics. For most study cases, these effects are negative at individual and population levels. Observations and predictions upon increasing upwelling intensity over the last 20-30 years indicate a gradual shoaling of the OMZ, and so that an expected enhancement of these negative effects of hypoxia on the zooplankton community. Unknown processes of adaptation and community-structure adjustments are expected to take place with uncertain consequences for the food web of this highly productive eastern boundary current ecosystem.

  1. Changes in optical characteristics of surface microlayers hint to photochemically and microbially mediated DOM turnover in the upwelling region off the coast of Peru

    Science.gov (United States)

    Galgani, Luisa; Engel, Anja

    2016-04-01

    The coastal upwelling system off the coast of Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. From 3 to 23 December 2012, R/V Meteor (M91) cruise took place in the Peruvian upwelling system between 4.59 and 15.4° S, and 82.0 to 77.5° W. During M91 we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like chromophoric dissolved organic matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. We analyzed SML and underlying water (ULW) samples at 38 stations focusing on CDOM spectral characteristics as indicator of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and excitation-emission matrix fluorescence (EEMs), which allow us to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. Spectral slope S varied between 0.012 to 0.043 nm-1 and was quite similar between SML and ULW, with no significant differences between the two compartments. Higher S values were observed in the ULW of the southern stations below 15° S. By EEMs, we identified five fluorescent components (F1-5) of the CDOM pool, of which two had excitation/emission characteristics of amino-acid-like fluorophores (F1, F4) and were highly enriched in the SML, with a median ratio SML : ULW of 1.5 for both fluorophores. In the study region, values for CDOM absorption ranged from 0.07 to 1.47 m-1. CDOM was generally highly concentrated in the SML, with a median enrichment with respect to the ULW of 1.2. CDOM composition and changes in spectral slope properties suggested a local

  2. 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.

  3. Microprobe determination of the α/(α+β) boundary for the Zr-Nb system

    International Nuclear Information System (INIS)

    Electron probe microanalysis has been used to locate the position of the α/(α+β) boundary in the Zr-Nb phase diagram by measuring the phase compositions in specimens of a Zr-2.5 wt.% Nb-0.12 wt% 0 alloy annealed at temperatures in the range 600-850oC. The solubility of Nb in α-Zr at 600oC is shown to be 1.1 ± 0.1 wt.%. The concentration of Nb in the a-phase annealed for short intervals at 850oC is also close to 1%, decreasing to 0.85 ± 0.05 wt.% with prolonged annealing at this temperature. A precise determination of the (α+β)/β boundary has not been made; extrapolation of non-equilibrium compositions indicate that the monotectoid composition is close to 20 wt.% Nb, as shown in earlier phase diagram work. (author)

  4. First-order Phase Transitions in Finite Systems I: Periodic Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Igor Medved

    2005-01-01

    Full Text Available We briefly review rigorous results on the finite-size effect near first-order phase transitions at which a two-phase coexistence takes place. We consider a large class of statistical mechanical models in (hypercubic volumes with periodic boundary conditions at low temperatures. The results show a universal behavior of the asymptotic smoothing of the phase transition discontinuities. The determination of the transition point from

  5. First-order Phase Transitions in Finite Systems I: Periodic Boundary Conditions

    OpenAIRE

    Igor Medved

    2005-01-01

    We briefly review rigorous results on the finite-size effect near first-order phase transitions at which a two-phase coexistence takes place. We consider a large class of statistical mechanical models in (hyper)cubic volumes with periodic boundary conditions at low temperatures. The results show a universal behavior of the asymptotic smoothing of the phase transition discontinuities. The determination of the transition point from

  6. Transient Pressure Analysis of Horizontal Wells in a MultiBoundary System

    Directory of Open Access Journals (Sweden)

    S. Al Rbeawi

    2013-01-01

    Full Text Available Horizontal wells can greatly increase the contact area of the wellbore and the pay zone; so they are commonly applied in oil reservoirs to enhance the production and ultimate recovery of oil and gas, especially, in low permeability formations. The purpose of this study is to develop a technique for the interpretation of transient pressure based on dimensionless pressure and pressure derivative. Type curve matching is one of the techniques that can be used to interpret the pressure data of horizontal wells in finite reservoirs. Starting from very short horizontal wells to extra-long wells, the pressure behavior of the wells has been analyzed for different conditions. The effect of the outer boundaries of the reservoir on the pressure behavior of the horizontal wells has been investigated for different configurations. Rectangular shape reservoirs with different dimensions have been used to study the pressure response in the well. Five flow regimes have been observed for regular length horizontal wells; early radial, early linear flow, pseudo radial flow, channel flow or late linear flow, and pseudosteady state flow. Four flow regimes have been observed for the extra-long wells: linear flow, pseudo radial flow, channel flow, and pseudo-steady state or boundary-affected flow. Of course, those flow regimes do not always take place under all conditions. Pseudo-steady state flow is expected to occur after long production time. A pressure drawdown test was solved using the proposed type curve matching technique. The study has shown that the effect of the boundary on the pressure response of the horizontal wells and the type of flow regimes depend on the length of the horizontal wells and the distance to the nearest boundary.

  7. On the Robin-Transmission Boundary Value Problems for the Nonlinear Darcy-Forchheimer-Brinkman and Navier-Stokes Systems

    Science.gov (United States)

    Kohr, Mirela; de Cristoforis, Massimo Lanza; Wendland, Wolfgang L.

    2016-06-01

    The purpose of this paper is to study a boundary value problem of Robin-transmission type for the nonlinear Darcy-Forchheimer-Brinkman and Navier-Stokes systems in two adjacent bounded Lipschitz domains in {{{R}}n (nin {2,3})}, with linear transmission conditions on the internal Lipschitz interface and a linear Robin condition on the remaining part of the Lipschitz boundary. We also consider a Robin-transmission problem for the same nonlinear systems subject to nonlinear transmission conditions on the internal Lipschitz interface and a nonlinear Robin condition on the remaining part of the boundary. For each of these problems we exploit layer potential theoretic methods combined with fixed point theorems in order to show existence results in Sobolev spaces, when the given data are suitably small in {L^2}-based Sobolev spaces or in some Besov spaces. For the first mentioned problem, which corresponds to linear Robin and transmission conditions, we also show a uniqueness result. Note that the Brinkman-Forchheimer-extended Darcy equation is a nonlinear equation that describes saturated porous media fluid flows.

  8. Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ).

    Science.gov (United States)

    Coelho-Souza, Sergio A; Araújo, Fábio V; Cury, Juliano C; Jesus, Hugo E; Pereira, Gilberto C; Guimarães, Jean R D; Peixoto, Raquel S; Dávila, Alberto M R; Rosado, Alexandre S

    2015-09-01

    Upwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling. PMID:26375020

  9. 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

    2014-11-01

    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.

  10. Response of Mytilus edulis to enhanced phytoplankton availibility by controlled upwelling in an oligographic fjord

    NARCIS (Netherlands)

    Strohmeier, T.; Strand, Ø.; Alunno-Bruscia, M.; Duinker, A.; Rosland, R.; Jansen, H.M.

    2015-01-01

    The controlled upwelling of nutrient-rich deep water in oligotrophic coastal regions has been proposed as a means of increasing phytoplankton and, subsequently, bivalve aquaculture production. This was tested as part of a large-scale upwelling experiment in an oligotrophic environment (Lysefjord, No

  11. Seasonality in Planktic Foraminifera of the Central California Coastal Upwelling Region

    OpenAIRE

    Davis, C.V.; Russell, A. D.; Gaylord, B. P.; Jahncke, J.; Hill, T M

    2016-01-01

    The association between planktic foraminiferal assemblages and local hydrography make foraminifera invaluable proxies for environmental conditions. Modern foraminiferal seasonality is important for interpreting fossil distributions and shell geochemistry as paleoclimate proxies. Understanding this seasonality in an active upwelling area is also critical for anticipating which species may be vulnerable to future changes in upwelling intensity and ocean acidification. Two ye...

  12. The potential role of mass balance models for the management of upwelling ecosystems

    DEFF Research Database (Denmark)

    Jarre, Astrid

    1998-01-01

    Upwelling ecosystems are productive fishing grounds, contributing >30% to the world's catch of marine fish. A set of seven trophic mass balance models of productive subsystems of the four largest upwelling areas is used to demonstrate key features of the modeling process and the analysis of the...

  13. Simulations of membranes and other interfacial systems using P2(1) and Pc periodic boundary conditions.

    OpenAIRE

    Dolan, Elizabeth A.; Venable, Richard M.; Pastor, Richard W.; Brooks, Bernard R.

    2002-01-01

    We demonstrate the ease and utility of simulating heterogeneous interfacial systems with P2(1) and Pc periodic boundary conditions which allow, for example, lipids in a membrane to switch leaflets. In preliminary tests, P2(1) was shown to yield equivalent results to P1 in simulations of bulk water, a water/vacuum interface, and pure DPPC bilayers with an equal number of lipids per leaflet; equivalence of Pc and P1 was also demonstrated for the former two systems. P2(1) was further tested in s...

  14. 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

  15. Initial observation of upwelling along east coast of Peninsular Malaysia musica gratis

    Science.gov (United States)

    Akhir, M.; Tanggang, F.

    2013-12-01

    There is no published evidence of upwelling in coastal area along the east coast of Peninsular Malaysia. However numbers of recent cruise data collected during the southwest monsoon found features of thermocline lifting and isolated cooler temperature water along the coast, These sign was observed along the 104°E from numbers of parallel transects. To confirm the presence of upwelling, satellite remote sensing data was used, and numerical model experiments were conducted. Cooler sea-surface temperature along the coast was observed from both in-situ and satellite data, while upward movement in the vertical profiles agreed with the location of upwelling from both in-situ and satellite data. Moreover, these data also show that the upwelled water band along the 104°E longitude stretch approximately 650 km long. Initially, southwesterly wind during this season is believed to be the important mechanism that contributed to this wind-induced Ekman upwelling. musica gratis

  16. Stable isotope analysis challenges wasp-waist food web assumptions in an upwelling pelagic ecosystem.

    Science.gov (United States)

    Madigan, Daniel J; Carlisle, Aaron B; Dewar, Heidi; Snodgrass, Owyn E; Litvin, Steven Y; Micheli, Fiorenza; Block, Barbara A

    2012-01-01

    Eastern boundary currents are often described as 'wasp-waist' ecosystems in which one or few mid-level forage species support a high diversity of larger predators that are highly susceptible to fluctuations in prey biomass. The assumption of wasp-waist control has not been empirically tested in all such ecosystems. This study used stable isotope analysis to test the hypothesis of wasp-waist control in the southern California Current large marine ecosystem (CCLME). We analyzed prey and predator tissue for δ¹³C and δ¹⁵N and used Bayesian mixing models to provide estimates of CCLME trophic dynamics from 2007-2010. Our results show high omnivory, planktivory by some predators, and a higher degree of trophic connectivity than that suggested by the wasp-waist model. Based on this study period, wasp-waist models oversimplify trophic dynamics within the CCLME and potentially other upwelling, pelagic ecosystems. Higher trophic connectivity in the CCLME likely increases ecosystem stability and resilience to perturbations. PMID:22977729

  17. Regulation of bacterial sulfate reduction and hydrogen sulfide fluxes in the central Namibian coastal upwelling zone

    DEFF Research Database (Denmark)

    Bruchert, V.; Jørgensen, BB; Neumann, K.;

    2003-01-01

    low capacity to oxidize and trap sulfide. The inner shelf break marks the seaward border of sulfidic bottom waters, and separates two different regimes of bacterial sulfate reduction. In the sulfidic bottom waters on the shelf, up to 55% of sulfide oxidation is mediated by the large nitrate......The coastal upwelling system off central Namibia is one of the most productive regions of the oceans and is characterized by frequently occurring shelf anoxia with severe effects for the benthic life and fisheries. We present data on water column dissolved oxygen, sulfide, nitrate and nitrite, pore...... water profiles for dissolved,sulfide and sulfate, S-35-sulfate reduction rates, as well as bacterial counts of large sulfur bacteria from 20 stations across the continental shelf and slope. The stations covered two transects and included the inner shelf with its anoxic and extremely oxygen...

  18. 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

  19. Productivity cycles in the coastal upwelling area off Concepción: The importance of diatoms and bacterioplankton in the organic carbon flux

    Science.gov (United States)

    Montero, Paulina; Daneri, Giovanni; Cuevas, L. Antonio; González, Humberto E.; Jacob, Bárbara; Lizárraga, Lorena; Menschel, Eduardo

    2007-11-01

    Recurrent coastal upwelling is recognized as one of the main factors promoting the exceptionally high productivity of the Humboldt Current System. Herein, we study time series data of gross primary production (2003-2006) and its fluctuation in relation to seasonal changes in the light and nutrient field of the Concepción upwelling ecosystem. Concurrent measurements of gross primary production, community respiration, bacterial secondary production, and sedimentation rates allowed a characterization of the main carbon fluxes and pathways in the study area. The integrated values of gross primary production were higher during the upwelling period (>1 g C m -2 d -1; October-April; that is, early spring to early austral fall). Seasonal changes in the system were also reflected in community respiration, organic matter sedimentation, and bacterial production rates, which varied along with the gross primary production. The significant correlation between gross primary production and community respiration (Spearman, r = 0.7; p 6 g C m -2 d -1) were consistently associated with maximum biomass levels of Skeletonema costatum and Thalassiosira subtilis. We observed a positive correlation between gross primary production and the sedimentation of intact diatom cells (Spearman, r = 0.5, p < 0.05, n = 17). Our data suggest that, in the Concepción upwelling ecosystem, bacteria utilize an important fraction of the gross primary production. If our interpretations are correct, they leave unanswered the question of how the system supports the extremely high fish biomass levels, therein pointing out the system’s limited capacity to buffer the evasion of CO 2 following upwelling.

  20. Tidally induced upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    MASNUM wave-tide-circulation coupled numerical model (MASNUM coupled model, hereinafter) is de-veloped based on the Princeton Ocean Model (POM). Both POM and MASNUM coupled model are ap-plied in the numerical simulation of the upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer. The upwelling mechanisms are analyzed from the viewpoint of tide, and a new mechanism is proposed. The study suggests that the tidally inducing mechanism of the upwelling in-cludes two dynamic aspects: the barotropic and the baroclinic process. On the one hand, the residual currents induced by barotropic tides converge near the seabed, and upwelling is generated to maintain mass conservation. The climbing of the residual currents along the sea bottom slope also contributes to the upwelling. On the other hand, tidal mixing plays a very important role in inducing the upwelling in the baroclinic sea circumstances. Strong tidal mixing leads to conspicuous front in the coastal waters. The considerable horizontal density gradient across the front elicits a secondary circulation clinging to the tidal front, and the upwelling branch appears near the frontal zone. Numerical experiments are de-signed to determine the importance of tide in inducing the upwelling. The results indicate that tide is a key and dominant inducement of the upwelling. Experiments also show that coupling calculation of the four main tidal constituents (M2, S2, K1, and O1), rather than dealing with the single M2 constituent, im-proves the modeling precision of the barotropic tide-induced upwelling.

  1. Tidally induced upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer

    Institute of Scientific and Technical Information of China (English)

    L(ü) XinGang; QIAO FangLi; XIA ChangShui; YUAN YeLi

    2007-01-01

    MASNUM wave-tide-circulation coupled numerical model(MASNUM coupled model,hereinafter)is developed based on the Princeton Ocean Model (POM).Both POM and MASNUM coupled model are applied in the numerical simulation of the upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer.The upwelling mechanisms are analyzed from the viewpoint of tide,and a new mechanism is proposed.The study suggests that the tidally inducing mechanism of the upwelling includes two dynamic aspects:the barotropic and the baroclinic process.On the one hand,the residual currents induced by barotropic tides converge near the seabed,and upwelling is generated to maintain mass conservation.The climbing of the residual currents along the sea bottom slope also contributes to the upwelling.On the other hand,tidal mixing plays a very important role in inducing the upwelling in the baroclinic sea circumstances.Strong tidal mixing leads to conspicuous front in the coastal waters.The considerable horizontal density gradient across the front elicits a secondary circulation clinging to the tidal front,and the upwelling branch appears near the frontal zone.Numerical experiments are designed to determine the importance of tide in inducing the upwelling.The results indicate that tide is a key and dominant inducement of the upwelling.Experiments also show that coupling calculation of the four main tidal constituents (M2,S2,K1,and O1),rather than dealing with the single M2 constituent,improves the modeling precision of the barotropic tide-induced upwelling.

  2. Triple junction and grain boundary diffusion in the Ni/Cu system

    International Nuclear Information System (INIS)

    Atomic transport along triple junctions (TJs) and grain boundaries (GBs) has been measured by atom probe tomography in nanocrystalline Ni/Cu bilayers. Heat treatment was chosen in the kinetic C-B regime according to generalized Harrison categories for the hierarchy of volume, GB and TJ transport. Diffusion coefficients at 623 K were found to be 4.65 x 10-20 and 1.65 x 10-17 m2 s-1 for the GB and TJ, respectively. Thus, TJs represent a significantly faster diffusion route than GBs.

  3. WELL-POSEDNESS OF A FREE BOUNDARY PROBLEM IN THE LIMIT OF SLOW-DIFFUSION FAST-REACTION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Chen Xinfu; Gao Congyu

    2006-01-01

    We consider a free boundary problem obtained from the asymptotic limit of a FitzHugh-Nagumo system, or more precisely, a slow-diffusion, fast-reaction equation governing a phase indicator, coupled with an ordinary differential equation governing a control variable v. In the range (-1, 1), the v value controls the speed of the propagation of phase boundaries (interfaces) and in the mean time changes with dynamics depending on the phases. A new feature included in our formulation and thus made our model different from most of the contemporary ones is the nucleation phenomenon: a phase switch occurs whenever v elevates to 1 or drops to -1. For this free boundary problem, we provide a weak formulation which allows the propagation,annihilation, and nucleation of interfaces, and excludes interfaces from having (spacetime) interior points. We study, in the one space dimension setting, the existence,uniqueness, and non-uniqueness of weak solutions. A few illustrating examples are also included.

  4. The intraplate Euphrates fault system-Palmyrides mountain belt junction and relationship to Arabian plate boundary tectonics

    Directory of Open Access Journals (Sweden)

    T. Sawaf

    1995-06-01

    Full Text Available We interpret seismic data and well logs to indicate that the Euphrates graben, intersecting orthogonally with the Palmyride mountains, is an intraplate transtensional feature that probably developed in response to plate boundary stress created by a latest Cretaceous convergence event along the present-day northern boundary of the Arabian plate. The principal stress direction is proposed to lie generally parallel to the graben; hence, it may have formed as a tear in the Arabian crust while, as previously documented, the Palmyride region under- went shortening and uplift. Arabian plate boundary tectonism as well as shorteningin the Palmyrides were pe- riodically active during the entire Cenozoic, especially in Neogene and Quaternary time. However, the normal fault motions that formed the Euphrates graben were not active within the study area after the end of the Cre- taceous, and were most active during the Campanian-Maastl.ichtian. A broad, Cenozoic depression overlying the Euphrates graben and most of Eastern Syria is possibly related to the Mesopotamian foredeep that devel- oped in response to the nearby Zagros continental collision zone during Neogene and Quaternary time. Cenozoic strike-slip faults lie between the Euphrates graben and the Palmyrides belt and may kinematically separate the Palmyrides from the Euphrates system.

  5. Dissolved Rare Earth Element Concentrations in the Upwelling area off Peru

    Science.gov (United States)

    Grasse, P.; Plass, A.; Hathorne, E. C.; Frank, M.

    2012-12-01

    Rare earth elements (REEs) are powerful tracers of continental input, particle exchange and scavenging processes, as well as for water mass transport in the ocean. We present a first data set of dissolved REE distributions in filtered seawater covering the major gradients of bio-productivity and oxygen concentrations in the upwelling area off Peru. A total of 22 stations were analyzed along a shelf, a nearshore and an offshore transect to investigate the influence of local inputs versus water mass mixing. The Peruvian coastal upwelling area is a highly dynamic system characterized by intense upwelling of nutrient-rich subsurface water and therefore high productivity that leads to one of the globally largest Oxygen Minimum Zones (OMZ). The upwelling area off Peru is of particular interest for understanding the biogeochemical cycling of REEs and other redox-sensitive metals because anoxic conditions are expected to release of REEs from the shelf, whereas high particle densities and fluxes efficiently remove the REEs from the water column. Despite their high potential as tracers few systematic investigations of seawater REEs have been carried out so far because the low concentrations of REEs (pM) are difficult to measure. In this study an online preconcentration (OP) system (seaFast, Elemental Scientific Inc.) was used with a technique slightly modified from Hathorne et al. (2012). The OP system efficiently separates seawater matrix elements from the REEs and elutes the preconcentrated sample directly into the spray chamber of the ICP-MS instrument. Repeated measurements of a seawater reference sample (n= 20) during this study gave a reproducibility of between 5% and 15% (2σ), with the worst reproducibility for Sm, Eu, and Gd (12% to 15%). In general, the REEs, except Ce, show a nutrient-like behavior in seawater increasing in concentration with water depth. However, such distributions were not observed for some stations on the shelf where the highest concentrations

  6. Abundancia estacional y distribución vertical del zooplancton gelatinoso carnívoro en una área de surgencia en el norte del Sistema de la Corriente de Humboldt Seasonal abundance and vertical distribution of the carnivorous gelatinous zooplankton in an upwelling area of the northern Humboldt Current System

    Directory of Open Access Journals (Sweden)

    Sergio Palma

    2004-01-01

    Full Text Available Se analizó la abundancia estacional y distribución vertical del zooplancton gelatinoso colectado en cuatro cruceros efectuados frente a la bahía de Mejillones. En esta zona se identificaron 44 especies macroplanctónicas distribuidas en 23 de sifonóforos, 17 de hidromedusas, y 4 de ctenóforos, de las cuales 8 especies, Sphaeronectes irregularis, Rhizophysa eysenhardti, Amphogona apicata, Proboscidactyla stellata, Sarsia coccometra, Pleurobrachia bachei, Thalassocalyce inconstans y Velamen parallelum, se registran por primera vez para el Sistema de la Corriente de Humboldt. Se determinó un incremento de abundancia en primavera y verano, con densas agregaciones (> 2.600 ind·100 m-3 en octubre de Aglaura hemistoma, Solmundella bitentaculata, Muggiaea atlantica y Pleurobrachia bachei, y en febrero de Obelia spp. Las mayores densidades se determinaron en la estación más costera y en el frente oceánico, mientras que en la estación oceánica se registró una fuerte disminución de abundancia. La mayoría de las especies dominantes se encontraron en los primeros 100 m de la columna de agua, con una mayor concentración de ejemplares en los primeros 25 o 50 m de profundidad. Esta distribución vertical estaría limitada por la capa de mínimo oxígeno (The seasonal abundance and vertical distribution of gelatinous zooplankton collected during four cruises off Mejillones bay were analyzed. In this area we identified 44 species of macroplankton distributed in 23 siphonophores, 17 hydromedusae, and 4 ctenophores. Eight species, Sphaeronectes irregularis, Rhizophysa eysenhardti, Amphogona apicata, Proboscidactyla stellata, Sarsia coccometra, Pleurobrachia bachei, Thalassocalyce inconstans and Velamen parallelum, are the first records in the Humboldt Current System. The seasonal distribution showed an increase in abundance in spring and summer, with the highest aggregations (> 2600 ind·100 m-3 of Aglaura hemistoma, Solmundella bitentaculata

  7. Decadal changes in Gulf of Alaska upwelling source waters

    Science.gov (United States)

    Pozo Buil, Mercedes; Di Lorenzo, Emanuele

    2015-03-01

    Decadal changes in sea surface temperature (SST) in the Gulf of Alaska are linked to long-term transitions in the marine ecosystem. While previous studies have identified the atmospheric variability of the Aleutian Low as an important driver of Ekman pumping and low-frequency SST anomalies, the role of subsurface gyre-scale dynamics remains unexplored. Using a set of reanalysis data sets from 1958 to the present, we find that subsurface temperature anomalies generated along the North Pacific Current significantly contribute through mean upwelling to decadal changes of SST in the Gulf of Alaska. This influence is comparable to the contribution associated with variations in atmospheric winds. Given the exceptional low-frequency character of the propagation of subsurface anomalies (e.g., multidecadal) along the gyre, monitoring subsurface temperature anomalies up stream along the North Pacific Current may enhance the decadal predictability of SST in the Gulf of Alaska and its impact on local marine ecosystems.

  8. Quantum group approach to steady states of boundary-driven open quantum systems

    International Nuclear Information System (INIS)

    We present a systematic approach for constructing steady state density operators of Markovian dissipative evolution for open quantum chain models with integrable bulk interaction and boundary incoherent driving. The construction is based on fundamental solutions of the quantum Yang–Baxter equation pertaining to quantum algebra symmetries and their quantizations (q-deformations). In particular, we facilitate a matrix-product state description, by resorting to generic spin-s infinite-dimensional solutions associated with non-compact spins, serving as ancillary degrees of freedom. After formally deriving already known steady states for the anisotropic spin-1/2 Heisenberg chain from first symmetry principles, we obtain a class of solutions belonging to interacting quantum gases with SU(N)-symmetric Hamiltonians, using a restricted set of incoherent boundary jump processes, and point out how new non-trivial generalizations emerge from twists of quantum group structures. Finally, we discuss the possibilities for the analytical calculation of observables by employing the algebraic properties of associated auxiliary vertex operators. (paper)

  9. Hot mantle upwelling across the 660 beneath Yellowstone

    Science.gov (United States)

    Schmandt, Brandon; Dueker, Kenneth; Humphreys, Eugene; Hansen, Steven

    2012-05-01

    P-to-s receiver functions mapped to depth through P and S body-wave tomography models image continuous 410 and 660 km discontinuities beneath the area covered by USArray prior to the year 2011. Mean depths to the 410 and 660 km discontinuities of 410 and 656 km imply a mantle transition zone that is about 4 km thicker than the global average and hence has a slightly cooler mean temperature and/or enhanced water content. Compared to the mean 660 depth beneath this ~ 2000 km wide area, the 660 beneath the Yellowstone hotspot is deflected upward by 12-18 km over an area about 200 km wide. This is the most anomalous shallowing of the 660 imaged and its horizontal extent is similar to the area where P and S tomography image low-velocity mantle extending from the top of the transition zone to about 900 km depth. Together, these results indicate a high-temperature, plume-like upwelling extending across the 660. The depth of 410 km discontinuity beneath the Yellowstone region is within 5 km of the mean depth implying that the plume is vertically heterogeneous and possibly discontinuous. Tomography indicates a similar vertically heterogeneous thermal plume. The irregular plume structure may be intrinsic to the dynamics of upwelling through the transition zone, or distortion may be caused by subduction-induced mantle flow. Topography of the 410 and 660 confirms that subducted slabs beneath the western U.S. are highly segmented, as inferred from recent tomography studies. We find no evidence of regionally pervasive velocity discontinuities between 750 and 1400 km depth. The plume's depth of origin within the lower mantle remains uncertain.

  10. Identification of upwelling areas in the Oman Sea Using Satellite Data

    Science.gov (United States)

    Moradi, Masoud

    2016-07-01

    Satellite-derived sea-surface temperature, TOPEX/POSEIDON (T/P) sea-level anomalies (SLAs), modeled wind data, and hydrodynamic data from World Ocean Database were used to characterize the upwelling along the Oman Sea coasts during 2002 - 2012. Principal Component Analysis (PCA) of the satellite-derived sea-surface temperature (SST) shows the first mode affected by upwelling processes, which represents a biannual variability. In addition, the SST shows the upwelling front moving offshore with the development of Southwest (SW) Monsoon in early June. SST shows the persistence of cold upwelling waters for nearly a month after the end of the SW Monsoon within the bays along the Oman coast. TOPEX/POSEIDON SLAs indicate that with the onset of the SW Monsoon, a 30-cm drop in height is observed along the Oman coast associated the presence of the cool upwelled waters. This drop in height sets up a horizontal pressure gradient and results in a compensating along-shore, northeastward flowing, geostrophic current (East Arabian Current) during the SW Monsoon. Similarly, the altimeter data slow an offshore decrease in height during the Northeast (NE) Monsoon, indicating a seasonal reversal in direction of the East Oman Currents with flow to the southwest. The following upwelling characteristics are identified for the Oman upwelling zone: 1- Upwelling zones have seen along Oman and Pakistan coasts and in the western coasts, like Iran, persistent upwelling zones are not available. 2- Upwelling zones along Oman coasts are more persistent and developed than in Pakistan coastal area. 3- Upwelling in the Oman and East Pakistan coasts starts with SW-Monsoon and will developed in the mid-August, adjusted with summer cooling. 4- Along Oman Sea, upwelling zones were developed between Rasal-Haddad and the southern bay. Mean SST during SW-Monsoon is about 22 °C. 5-Waters with temperature about 23°C were upwelled from depth 50-75 m along Oman coasts, and about 50 m along Pakistan coasts. 6

  11. The Mono Arch, eastern Sierra region, California: Dynamic topography associated with upper-mantle upwelling?

    Science.gov (United States)

    Jayko, A.S.

    2009-01-01

    A broad, topographic flexure localized east of and over the central and southern Sierra Nevada, herein named the Mono Arch, apparently represents crustal response to lithospheric and/or upper-mantle processes, probably dominated by mantle upwelling within the continental interior associated Pacific-North American plate-boundary deformation. This zone of flexure is identified through comparison between the topographic characteristics of the active Cascade volcanic arc and backarc regions with the analogous former arc and backarc in the Sierra Nevada and eastern Sierra Nevada. Serial topographic profiles measured normal to the modern Cascade backarc reveal an accordance of topographic lows defined by valley floors with an average minimum elevation of ???1400-1500m for over 175km to the southeast. Although the accordance drops in elevation slightly to the south, the modern Cascade backarc region is remarkably level, and is characterized by relief up to ???750m above this baseline elevation. By contrast, serial topographic profiles over the former arc and backarc transitions of the eastern Sierra region exhibit a regional anticlinal warping defined by accordant valley floors and by a late Miocene-early Pliocene erosion surface and associated deposits. The amplitude of this flexure above regionally flat baseline elevations to the east varies spatially along the length of the former Sierran arc, with a maximum of ???1000m centred over the Bridgeport Basin. The total zone of flexure is approximately 350km long N-S and 100km wide E-W, and extends from Indian Wells Valley in the south to the Sonora Pass region in the north. Previous geophysical, petrologic, and geodetic studies suggest that the Mono Arch overlies a zone of active mantle upwelling. This region also represents a zone crustal weakness formerly exploited by the middle-to-late Miocene arc and is presently the locus of seismic and volcanic activities. This seismic zone, which lies east of the Sierra Nevada block

  12. MULTIGRID ALGORITHM FOR THE COUPLING SYSTEM OF NATURAL BOUNDARY ELEMENT METHOD AND FINITE ELEMENT METHOD FOR UNBOUNDED DOMAIN PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Sheng Zhang; Dehao Yu

    2007-01-01

    In this paper, some V-cycle multigrid algorithms are presented for the coupling system arising from the discretization of the Dirichlet exterior problem by coupling the natural boundary element method and finite element method. The convergence of these multigrid algorithms is obtained even with only one smoothing on all levels. The rate of convergence is found uniformly bounded independent of the number of levels and the mesh sizes of all levels, which indicates that these multigrid algorithms are optimal. Some numerical results are also reported.

  13. High temperature metamorphism in the conductive boundary layer adjacent to a rhyolite intrusion in the Krafla geothermal system, Iceland

    OpenAIRE

    P. Schiffman; Zierenberg, RA; Mortensen, AK; Frioleifsson, GO; Elders, WA

    2014-01-01

    A rhyolite magma body within the Krafla geothermal system that was encountered at a depth of 2.1km during drilling of the IDDP-1 borehole is producing high temperature metamorphism within a conductive boundary layer (CBL) in adjacent host rocks. Cuttings recovered during drilling within a few meters of the intrusive contact in IDDP-1 are mainly comprised of granoblastic hornfelses, the rock type which confirms the presence of the CBL at the base of the IDDP-1 bore hole. The two pyroxenes in t...

  14. Solution of the Stokes system by boundary integral equations and fixed point iterative schemes

    International Nuclear Information System (INIS)

    The solution to the exterior three dimensional Stokes problem is sought in the form of a single layer potential of unknown density. This reduces the problem to a boundary integral equation of the first kind whose operator is the velocity component of the single layer potential. It is shown that this component is an isomorphism between two appropriate Sobolev spaces containing the unknown densities and the data respectively. The isomorphism corresponds to a variational problem with coercive bilinear form. The latter property allows us to consider various fixed point iterative schemes that converge to the unique solution of the integral equation. Explicit error estimates are also obtained. The successive approximations are also considered in a more computable form by using the product integration method of Atkinson. (author). 47 refs

  15. Transient dynamics in electric power system with dc transmission: Fractal growth in stability boundary

    OpenAIRE

    Susuki, Yoshihiko; Hikihara, Takashi

    2005-01-01

    The paper is concerned with transient dynamics and stability of an electric power system with DC transmission. Nowadays, DC transmission systems are widely applied to conventional electric power systems. However, the transient dynamics of AC/DC power systems, affected by the active power that flows into DC transmissions, is not entirely understood. The paper derives a non-symmetrical swing equation system to analyse the transient dynamics of an AC/DC power system. The non-symmetry implies a u...

  16. Boundary transfer matrices and boundary quantum KZ equations

    Energy Technology Data Exchange (ETDEWEB)

    Vlaar, Bart, E-mail: Bart.Vlaar@nottingham.ac.uk [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2015-07-15

    A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.

  17. Anode flooding characteristics as design boundary for a hydrogen supply system for automotive polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Jenssen, Dirk; Berger, Oliver; Krewer, Ulrike

    2015-12-01

    An automotive fuel cell is investigated to define the design boundaries for an automotive hydrogen supply system with regard to anode flooding. The flooding characteristics of the fuel cell anode at various operating conditions (hydrogen flow rate, pressure, temperature, current density) are analyzed by in-situ and ex-situ measurements. Stable operation conditions are identified and a relation to the operating conditions is established. For adequate water removal, a minimum Reynolds number in the gas channels has to be adjusted. Using this information, different hydrogen supply system designs are compared in their compliance with the stability requirements. It is shown that passive hydrogen supply systems do not achieve all fuel cell requirements regarding power density, lifetime and robustness.

  18. Response of Mytilus edulis to enhanced phytoplankton availability by controlled upwelling in an oligotrophic fjord

    OpenAIRE

    Strohmeier, Tore; Strand, Oivind; ALUNNO-BRUSCIA, Marianne; Duinker, Arne; Rosland, Rune; Aure, Jan; Erga, Svein R.; Naustvoll, Lars J.; Jansen, Henrice M.; Cranford, Peter J.

    2015-01-01

    The controlled upwelling of nutrient-rich deep water in oligotrophic coastal regions has been proposed as a means of increasing phytoplankton and, subsequently, bivalve aquaculture production. This was tested as part of a large-scale upwelling experiment in an oligotrophic environment (Lysefjord, Norway). The mean chlorophyll a concentration in the upwelling area was consistently higher than at the control site (mean ± SD: 3.3 ± 1.9 and 1.5 ± 0.6 mg Chl a m-3, respectively) during the 4 mo of...

  19. Global uniqueness in inverse boundary value problems for the Navier–Stokes equations and Lamé system in two dimensions

    International Nuclear Information System (INIS)

    We consider inverse boundary value problems for the Navier–Stokes equations and the isotropic Lamé system in two dimensions. The question of global uniqueness for these inverse problems, without any smallness assumptions on unknown coefficients, has been a longstanding open problem for the Navier–Stokes equations and the isotropic Lamé system in two dimensions. We prove the global uniqueness for both inverse boundary value problems. Our methodology is the same for both systems. The key is the construction of complex geometric optics solutions after decoupling the systems into weakly coupling systems. (papers)

  20. Exploring the potential of the RPA system SUMO for multipurpose boundary-layer missions during the BLLAST campaign

    Science.gov (United States)

    Reuder, Joachim; Båserud, Line; Jonassen, Marius O.; Kral, Stephan T.; Müller, Martin

    2016-06-01

    In June and July 2011 the RPAS (Remotely Piloted Aircraft System) SUMO (Small Unmanned Meteorological Observer) performed a total number of 299 scientific flights during the BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) campaign in southern France. Three different types of missions were performed: vertical profiling of the mean meteorological parameters (temperature, humidity and wind), horizontal surveys of the surface temperature and horizontal transects for the estimation of turbulence. The manuscript provides an introduction to the corresponding SUMO operations, including regulatory issues and the coordination of manned and unmanned airborne operations for boundary-layer research that have been pioneered during the BLLAST campaign. The main purpose of the SUMO flight strategy was atmospheric profiling at high temporal resolution. A total of 168 profile flights were performed during the campaign with typically more than 10 flights per Intensive Observational Period (IOP) day. The collected data allow for a detailed study of boundary-layer structure and dynamics and will be used for further analysis, e.g. the determination of profiles of sensible and latent heat fluxes. First, tests of a corresponding method have shown very promising results and have provided surface-flux values in close agreement with those from ground-based eddy-covariance measurements. In addition, 74 horizontal surveys of the IR emission of the surface were performed at altitudes of around 65 m. Each of those surveys covers a typical area of around 1 km2 and allows for an estimation of the surface-temperature variability, important information for the assessment of the heterogeneity of the surface forcing as a function of soil and vegetation properties. The comparison with other surface-temperature measurements shows that the raw data of the airborne and ground observations can differ considerably, but that even a very simple multiple regression method can reduce those

  1. Reconstruction of upwelling intensity and paleo-nutrient gradients in the northwest Arabian Sea derived from stable carbon and oxygen isotopes of planktic foraminifera.

    OpenAIRE

    C. Moos

    2000-01-01

    The Asian Monsoon system dominates the climate over large areas of the Asian and Indian continents and the rainfall prevailing during SW-monsoon is decisive for the agriculture of the entire region. The atmospheric monsoon system dominates the oceanographic surface circulation of the northern Indian Ocean and causes strong upwelling off Somalia and Arabia during SW-monsoon and makes the northwestern Arabian Sea to one of the most productive areas in the world oceans. Thus, productivity and nu...

  2. Asymptotic investigation of the nonlinear boundary value dynamic problem for the systems with finite sizes

    International Nuclear Information System (INIS)

    Asymptotic approaches for nonlinear dynamics of continual system are developed well for the infinite in spatial variables. For the systems with finite sizes we have an infinite number of resonance, and Poincare-Lighthill-Go method does riot work. Using of averaging procedure or method of multiple scales leads to the infinite systems of nonlinear algebraic or ordinary differential equations systems and then using truncation method. which does not gives possibility to obtain all important properties of the solutions

  3. 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

  4. Modelling of Continental Lithosphere Breakup and Rifted Margin Formation in Response to an Upwelling Divergent Flow Field Incorporating a Temperature Dependent Rheology

    Science.gov (United States)

    Tymms, V. J.; Kusznir, N. J.

    2005-05-01

    We numerically model continental lithosphere deformation leading to breakup and sea floor spreading initiation in response to an imposed upwelling and divergent flow field applied to continental lithosphere and asthenosphere. The model is used to predict rifted continental margin lithosphere thinning and temperature structure. Model predictions are compared with observed rifted margin structure for four diverse case studies. Prior to application of the upwelling divergent flow field the continental lithosphere is undeformed with a uniform temperature gradient. The upwelling divergent flow field is defined kinematically using boundary conditions consisting of the upwelling velocity Vz at the divergence axis and the half divergence rate Vx . The resultant velocity field throughout the continuum is computed using finite element (FE) code incorporating a Newtonian temperature dependent rheology. The flow field is used to advect the continental lithosphere material and lithospheric and asthenospheric temperatures. Viscosity structure is hence modified and the velocities change correspondingly in a feedback loop. We find the kinematic boundary conditions Vz and Vx to be of first order importance. A high Vz/Vx (greater than10), corresponding to buoyancy assisted flow, leads to minimal mantle exhumation and a well defined continent ocean transition consistent with observations at volcanic margins. For Vz/Vx near unity, corresponding to plate boundary driven divergence, mantle exhumation over widths of up to 100 km is predicted which is consistent with observations at non-volcanic margins. The FE method allows the upwelling velocity Vz to be propagated upwards from the top of the asthenosphere to the Earth's surface without the requirement of imposing Vx. When continental breakup is achieved the half divergence velocity Vx can be applied at the lithosphere surface and the upwelling velocity Vz left free. We find this time and space dependent set of boundary conditions is

  5. 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. PMID:27367375

  6. Simulations of membranes and other interfacial systems using P2(1) and Pc periodic boundary conditions.

    Science.gov (United States)

    Dolan, Elizabeth A; Venable, Richard M; Pastor, Richard W; Brooks, Bernard R

    2002-01-01

    We demonstrate the ease and utility of simulating heterogeneous interfacial systems with P2(1) and Pc periodic boundary conditions which allow, for example, lipids in a membrane to switch leaflets. In preliminary tests, P2(1) was shown to yield equivalent results to P1 in simulations of bulk water, a water/vacuum interface, and pure DPPC bilayers with an equal number of lipids per leaflet; equivalence of Pc and P1 was also demonstrated for the former two systems. P2(1) was further tested in simulations involving the spreading of an octane film on water, and equilibration of a DPPC bilayer from an initial condition containing different numbers of lipids in the two leaflets. Lastly, a simulation in P2(1) of a DOPC/melittin membrane showed significant passage of lipids to the melittin-containing leaflet from the initial distribution, and lends insight into the condensation of lipids by melittin. PMID:11964222

  7. 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

  8. An immersed-boundary method for flow-structure interaction in biological systems with application to phonation.

    Science.gov (United States)

    Luo, Haoxiang; Mittal, Rajat; Zheng, Xudong; Bielamowicz, Steven A; Walsh, Raymond J; Hahn, James K

    2008-11-20

    A new numerical approach for modeling a class of flow-structure interaction problems typically encountered in biological systems is presented. In this approach, a previously developed, sharp-interface, immersed-boundary method for incompressible flows is used to model the fluid flow and a new, sharp-interface Cartesian grid, immersed boundary method is devised to solve the equations of linear viscoelasticity that governs the solid. The two solvers are coupled to model flow-structure interaction. This coupled solver has the advantage of simple grid generation and efficient computation on simple, single-block structured grids. The accuracy of the solid-mechanics solver is examined by applying it to a canonical problem. The solution methodology is then applied to the problem of laryngeal aerodynamics and vocal fold vibration during human phonation. This includes a three-dimensional eigen analysis for a multi-layered vocal fold prototype as well as two-dimensional, flow-induced vocal fold vibration in a modeled larynx. Several salient features of the aerodynamics as well as vocal-fold dynamics are presented. PMID:19936017

  9. 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...

  10. A Comparison of the Role of Episode Nutrient Supply on Pathways of Carbon in Upwelling Regimes

    Science.gov (United States)

    Carr, M. E.

    1997-01-01

    Nutrient supply is episode in the ocean even in regions of fairly high and continuous nutrient supply, such as coastal upwelling regimes. The structure of the ecosystem depends on nutrient availability and the different requirements of phytoplankton cells.

  11. Upwelling at the ice edge - A mechanism for deep water formation?

    Science.gov (United States)

    Hakkinen, Sirpa

    1987-01-01

    This study sets forward a hypothesis which anticipates deep water formation due to ice edge upwelling. The upwelling can raise thermocline waters (the lower Arctic Intermediate Water) to the surface or near it, where the water is exposed to cooling, evaporation, mixing, and oxygenation. Thus, upwelling can act as a preconditioning mechanism for deep convection. The conjecture would also explain the salinity range of the Greenland Sea Deep Water if the upper and lower Arctic Intermediate Water masses are mixed so that the latter has at least an 80-percent contribution. It is also anticipated that the convection events induced by ice edge upwelling during winter season could give rise to a new deep water annual production rate consistent with observations.

  12. 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...

  13. 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.

    Considerable latitudinal variability exists in the forcing mechanisms and intensity of coastal upwelling along the southwest coast of India. Present work is based on the insitu observations conducted onboard FORV Sagar Sampada for 12 days along two...

  14. 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...... approach with pattern matching is a way to shed light on the tacit local knowledge that organizational actors cannot articulate and that an exclusively inductive research is not likely to unveil....

  15. 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.

  16. 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

  17. An Efficient Tool for Automatic Delimitation of Moroccan Coastal Upwelling Using SST Images

    OpenAIRE

    Tamim, Ayoub; Minaoui, Khalid; Daoudi, Khalid; Yahia, Hussein; Atillah, Abderrahman; Aboutajdine, Driss

    2014-01-01

    International audience An unsupervised classification method is developed for the coarse segmentation of Moroccan coastal upwelling using the Sea Surface Temperature (SST) satellite images. The algorithm is started with the generation of c-partitioned labeled image using Otsu's method for the purpose of finding regions of homogenous temperatures. Then two well-known validity indices are used to select the c-partition which best reproduce the shape of upwelling area. A region-growing algori...

  18. Practical limitations on the use of diurnal temperature signals to quantify groundwater upwelling

    Science.gov (United States)

    Briggs, Martin; Lautz, Laura K.; Buckley, Sean F.; Lane, Jr., John W.

    2014-01-01

    Groundwater upwelling to streams creates unique habitat by influencing stream water quality and temperature; upwelling zones also serve as vectors for contamination when groundwater is degraded. Temperature time series data acquired along vertical profiles in the streambed have been applied to simple analytical models to determine rates of vertical fluid flux. These models are based on the downward propagation characteristics (amplitude attenuation and phase-lag) of the surface diurnal signal. Despite the popularity of these models, there are few published characterizations of moderate-to-strong upwelling. We attribute this limitation to the thermodynamics of upwelling, under which the downward conductive signal transport from the streambed interface occurs opposite the upward advective fluid flux. Governing equations describing the advection–diffusion of heat within the streambed predict that under upwelling conditions, signal amplitude attenuation will increase, but, counterintuitively, phase-lag will decrease. Therefore the extinction (measurable) depth of the diurnal signal is very shallow, but phase lag is also short, yielding low signal to noise ratio and poor model sensitivity. Conversely, amplitude attenuation over similar sensor spacing is strong, yielding greater potential model sensitivity. Here we present streambed thermal time series over a range of moderate to strong upwelling sites in the Quashnet River, Cape Cod, Massachusetts. The predicted inverse relationship between phase-lag and rate of upwelling was observed in the field data over a range of conditions, but the observed phase-lags were consistently shorter than predicted. Analytical solutions for fluid flux based on signal amplitude attenuation return results consistent with numerical models and physical seepage meters, but the phase-lag analytical model results are generally unreasonable. Through numerical modeling we explore reasons why phase-lag may have been over-predicted by the

  19. Hydrous upwelling across the mantle transition zone beneath the Afar Triple Junction

    OpenAIRE

    Thompson, D A; Hammond, J.O.S.; Kendall, J-M; Stuart, G.W.; Helffrich, G.R.; Keir, D.; Ayele, A.; Goitom, B.

    2015-01-01

    The mechanisms that drive the upwelling of chemical heterogeneity from the lower to upper mantle (e.g., thermal versus compositional buoyancy) are key to our understanding of whole mantle con- vective processes. We address these issues through a receiver function study on new seismic data from recent deployments located on the Afar Triple Junction, a location associated with deep mantle upwelling. The detailed images of upper mantle and mantle transition zone structure illuminate features tha...

  20. Detection of Moroccan Coastal Upwelling in SST images using the Expectation-Maximization

    OpenAIRE

    Tamim, Ayoub; Minaoui, Khalid; Daoudi, Khalid; Atillah, Abderrahman; Aboutajdine, Driss

    2014-01-01

    International audience This paper proposes an unsupervised algorithm for automatic detection and segmentation of upwelling region in Moroccan Atlantic coast using the Sea Surface Temperature (SST) satellite images. This has been done by exploring the Expectation-Maximization algorithm. The good number of clus- ters that best reproduces the shape of upwelling areas is selected by using the two popular Davies-Bouldin and Dunn indices. Area opening technique is developed that is used to remov...