WorldWideScience

Sample records for test ocean tidal

  1. Ocean renewable energy : Tidal power in the Yellow Sea

    OpenAIRE

    Lee, Han Soo

    2011-01-01

    Ocean renewable energy sources are briefly introduced in this review article. Special focus on tidal energy from ocean renewable energy in the Yellow Sea and its practical utilization in South Korea are illustrated with several examples. Among them, the Sihwa Lake tidal power plant, the Garolim Bay tidal power project, the Incheon tidal power project, and the Uldolmok tidal current power station were introduced with more details. A numerical modelling system, Regional Ocean Tide Simulator, is...

  2. Investigating oceanic tidal energy dissipation on deep time scales using short tidal deposit sequences

    Science.gov (United States)

    Coughenour, C.

    2012-12-01

    One of the enduring problems in physical oceanography has been that of tidal dynamics and the effective tidal torque that serves to slow Earth's axial rotation. In the late 20th century, with the aid of satellite altimetry and other technologies, a suite of reliable estimates was finally placed on the magnitude of this torque and other, related parameters in the current epoch. Tidal drag accounts for a 20 microsecond/year increase in mean day length, a 3.5 terawatt dissipation of energy in the oceans (Kantha et al., 1998), and a lunar retreat rate of 3.82 cm/yr (Dickey et al., 1994). Despite these significant advances, however, the problem of tidal dissipation in the geologic past remains largely unresolved. This is due, in part, to difficulties in numerical modeling of past tidal regimes that stem from uncertainties in ocean basin configurations and lunar distances. Tidal deposits can record, to high resolution, the primary astronomical periodicities responsible for the generation of the tidal currents under which transport and deposition occur. With reliable lunar orbital period data obtained from tidal deposits, the past Earth-Moon distance and length of day can be calculated. This task requires careful spectral analysis and consideration of sedimentological factors that may add noise and/or discontinuities to the signal. For deposits representing less than one year of deposition, the necessary assumptions are that Earth's moment of inertia has not changed significantly over the time interval of interest and that the solar component of tidal dissipation can be well-approximated. With consideration of the total angular momentum of the Earth-Moon couplet, we derive a method to calculate lunar distance and length of day. The efficacy of this method and its assumptions is tested via the multi-year sequence of data obtained from the late Precambrian Elatina Formation of Australia and comparing results obtained from the full suite of data by Williams (2000). We go on

  3. How Tidal Forces Cause Ocean Tides in the Equilibrium Theory

    Science.gov (United States)

    Ng, Chiu-king

    2015-01-01

    We analyse why it is erroneous to think that a tidal bulge is formed by pulling the water surface directly up by a local vertical tidal force. In fact, ocean tides are caused by the global effect of the horizontal components of the tidal forces.

  4. NS begins tidal power test with 1 turbine

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2009-11-15

    The Bay of Fundy holds huge potential as a source of clean renewable tidal energy. This article announced the successful installation of a turbine that will test the potential of tidal power in the Bay of Fundy. Rather than requiring any dams or head ponds, new tidal power technologies include offshore floating tidal turbines and turbines that are anchored to the ocean floor to take advantage of natural tidal flows. In September 2009, Nova Scotia Power unveiled the 1 MW Open-Centre tidal turbine that was manufactured in Ireland by OpenHydro. The 10-metre turbine will be deployed in the Minas Passage as part of the Fundy Ocean Research Centre for Energy (FORCE) tidal test site. The turbine will rest directly on the ocean floor using a subsea gravity base made in Dartmouth by Cherubini Metal Works. It has several design features that minimize the impact on marine life. A large open centre provides a safe passage for marine life and the turbine's clean hydrodynamic lines ensure that fish will not become entangled. The use of oils, greases and other lubricants has also been avoided. The unit produces only very low levels of mechanical noise. A detailed turbine and environmental monitoring program will begin upon completion of the installation. Nova Scotia Power's involvement with the tidal energy test facility is supported by Sustainable Development Technology Canada. Nova Scotia Hydro owns and operates 1 of only 3 tidal power plants in the world, and the only one in the western hemisphere. The Annapolis Tidal Power plant, which came online in 1984, has a capacity of 20 MW and a daily output of about 80 to 100 megawatt hours.

  5. A new high resolution tidal model in the arctic ocean

    DEFF Research Database (Denmark)

    Cancet, M.; Andersen, Ole Baltazar; Lyard, F.

    The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence, the accu...... for assimilation and validation. This paper presents the performances of this new regional tidal model in the Arctic Ocean, compared to the existing global tidal models.......The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence......-growing maritime and industrial activities in this region. NOVELTIS and DTU Space have developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of the CryoSat Plus for Ocean (CP4O) ESA project. In particular, this atlas benefits from the assimilation of the most complete satellite...

  6. New estimates of oceanic tidal energy dissipation from satellite altimetry

    Science.gov (United States)

    Cartwright, David E.; Ray, Richard D.

    1989-01-01

    As a novel approach to computing the flux of tidal power into shelf areas, tidal maps of an oceanic area near the Patagonian Shelf are derived from 11 months of altimetry records from the GEOSAT satellite. Power fluxes are computed from the maps through Laplace's tidal equations. Flux vectors for M2 clearly show a convergence on to the southern portion of the shelf sea and their total is nearly twice the loss computed by Miller for that area. A decrease of 'quality factor' with frequency from M2 to S2 is in keeping with Webb's hypothesis of shelf resonances at frequencies a little higher than the tidal band.

  7. Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary

    DEFF Research Database (Denmark)

    Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.

    2016-01-01

    , there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. Themodel derived from more than 12 years of satellite data reveals...

  8. Tidal dissipation in the ice-ocean system on Enceladus

    Science.gov (United States)

    Hellard, H.; Sohl, F.; Van der Wal, W.; Steinke, T.; Hußmann, H.

    2017-09-01

    We investigate how the interior structure and dissipation of tidal energy on Enceladus affect the lateral layering of its outer ice shell. Structural models are created that satisfy the satellite's mean density and polar moment-of-inertia factor as derived from Cassini gravity field data. We particularly consider variations in core density, ice shell thickness and ocean composition. A partly dehydrated core is found to be consistent with current ice shell thickness estimates and power output measurements for Enceladus.

  9. Ocean tidal loading affecting precise geodetic observations on Greenland: Error account of surface deformations by tidal gravity measurements

    DEFF Research Database (Denmark)

    Jentzsch, G.; Knudsen, Per; Ramatschi, M.

    2000-01-01

    observations. Near the coast ocean tidal loading causes additional vertical deformations in the order of 1 to 10 cm Therefore, tidal gravity measurements were carried out at four fiducial sites around Greenland in order to provide corrections for the kinematic part of the coordinates of these sites. Starting...

  10. The dynamic tidal response of a subsurface ocean on Titan and the associated dissipative heat generated

    Science.gov (United States)

    Tyler, Robert

    2012-04-01

    The tidal flow response and associated dissipative heat generated in a satellite ocean depends strongly on the ocean configuration parameters as these parameters control the form and frequencies of the ocean's natural modes of oscillation; if there is a near match between the form and frequency of one of these natural modes and that of one of the available tidal forcing constituents, the ocean can be resonantly excited, producing strong tidal flow and appreciable dissipative heat. Of primary interest in this study are the ocean parameters that can be expected to evolve (notably, the ocean depth in an ocean attempting to freeze, and the stratification in an ocean attempting to cool) because this evolution can cause an ocean to be pushed into a resonant configuration where the increased dissipative heat of the resonant response halts further evolution and a liquid ocean can be maintained by ocean tidal heat. In this case the resonant ocean tidal response is not only allowed but may be inevitable. Previous work on this topic is extended to describe the resonant configurations in both unstratified and stratified cases for an assumed global ocean on Titan subject to both obliquity and eccentricity tidal forces. Results indicate first that the assumption of an equilibrium tidal response is not justified and the correct dynamical response must be considered. Second, the ocean tidal dissipation will be appreciable if the ocean configuration is near that producing a resonant state. The parameters values required for this resonance are provided in this study, and examples/movies of calculated ocean tidal flow are also presented.

  11. Energy supply technologies. Hydro, ocean, wave and tidal

    Energy Technology Data Exchange (ETDEWEB)

    Fenhann, J.; Larsen, Hans [Risoe National Lab. - DTU (Denmark)

    2007-11-15

    This chapter presents an overview of current hydro, ocean, wave and tidal initiatives. Large hydro remains one of the lowest-cost generating technologies, although environmental constraints, resettlement impacts and the limited availability of sites have restricted further growth in many countries. Large hydro supplied 16 % of global electricity in 2004, down from 19 % a decade ago. Large hydro capacity totalled about 720 GW worldwide in 2004 and has grown historically at slightly more than 2 % annually. China installed nearly 8 GW of large hydro in 2004, taking the country to number one in terms of installed capacity (74 GW). With the completion of the Three Gorges Dam, China will add some 18.2 GW of hydro capacity in 2009. The socio-economic benefits of hydro include improved flood control and water supply. The socio-economic benefits of hydro include improved flood control and water supply. The socio-economic cost of hydro includes displacements and submergence. Further hydro can improve peak-capacity management. Ocean currents, some of which runs close to European coasts, carry a lot of kinetic energy. Part of this energy can be captured by sub-marine windmills and converted into electricity. These are more compact than the wind turbines used on land, simply because water is much denser than air. The main European countries with useful current power potential are France and the UK. Ocean tides are driven by the gravitational pull of the moon. With one high tide every 12 hours, a tidal power plant can operate for only four or five hours per cycle, so power from a single plant is intermittent. A suitably-designed tidal plant can, however, operate as a pimped storage system, using electricity during periods of low demand to store energy that can be recovered later. The only large, modern example of a tidal power plant is the 240 MW La Rance plant, built in France in the 1960s, which represents 91 % of the world tidal power capacity. Wave energy can be seen as

  12. Tidal Energy Available for Deep Ocean Mixing: Bounds From Altimetry Data

    Science.gov (United States)

    Egbert, Gary D.; Ray, Richard D.

    1999-01-01

    Maintenance of the large-scale thermohaline circulation has long presented a problem to oceanographers. Observed mixing rates in the pelagic ocean are an order of magnitude too small to balance the rate at which dense bottom water is created at high latitudes. Recent observational and theoretical work suggests that much of this mixing may occur in hot spots near areas of rough topography (e.g., mid-ocean ridges and island arcs). Barotropic tidal currents provide a very plausible source of energy to maintain these mixing processes. Topex/Poseidon satellite altimetry data have made precise mapping of open ocean tidal elevations possible for the first time. We can thus obtain empirical, spatially localized, estimates of barotropic tidal dissipation. These provide an upper bound on the amount of tidal energy that is dissipated in the deep ocean, and hence is available for deep mixing. We will present and compare maps of open ocean tidal energy flux divergence, and estimates of tidal energy flux into shallow seas, derived from T/P altimetry data using both formal data assimilation methods and empirical approaches. With the data assimilation methods we can place formal error bars on the fluxes. Our results show that 20-25% of tidal energy dissipation occurs outside of the shallow seas, the traditional sink for tidal energy. This suggests that up to 1 TW of energy may be available from the tides (lunar and solar) for mixing the deep ocean. The dissipation indeed appears to be concentrated over areas of rough topography.

  13. Tidal simulation using regional ocean modeling systems (ROMS)

    Science.gov (United States)

    Wang, Xiaochun; Chao, Yi; Li, Zhijin; Dong, Changming; Farrara, John; McWilliams, James C.; Shum, C. K.; Wang, Yu; Matsumoto, Koji; Rosenfeld, Leslie K.; hide

    2006-01-01

    The purpose of our research is to test the capability of ROMS in simulating tides. The research also serves as a necessary exercise to implement tides in an operational ocean forecasting system. In this paper, we emphasize the validation of the model tide simulation. The characteristics and energetics of tides of the region will be reported in separate publications.

  14. Impact of oceanic warming on electromagnetic oceanic tidal signals: A CMIP5 climate model-based sensitivity study

    Science.gov (United States)

    Saynisch, J.; Petereit, J.; Irrgang, C.; Thomas, M.

    2017-05-01

    In contrast to ocean circulation signals, ocean tides are already well detectable by electromagnetic measurements. Oceanic electric conductivities from the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate simulations are combined with tidal currents of M2 and O1 to estimate electromagnetic tidal signals and their sensitivity to global warming. Ninety-four years of global warming leads to differences of ±0.3 nT in tidal magnetic amplitudes and ±0.1 mV/km in the tidal electric amplitudes at sea level. Locally, the climate-induced changes can be much higher, e.g., +1 nT in the North Atlantic. In general, all studied electromagnetic tidal amplitudes show large-scale climate-induced anomalies that are strongest in the Northern Hemisphere and amount to 30% of their actual values. Consequently, changes in oceanic electromagnetic tidal amplitudes should be detectable in electromagnetic records. Electric and magnetic signals, as well as tides of different frequencies, contain complementary regional information.

  15. 3-D modelling the electric field due to ocean tidal flow and comparison with observations

    DEFF Research Database (Denmark)

    Kuvshinov, A.; Junge, A.; Utada, H.

    2006-01-01

    The tidal motion of the ocean water through the ambient magnetic field, generates secondary electric field. This motionally induced electric field can be detected in the sea or inland and has a potential for electrical soundings of the Earth. A first goal of the paper is to gain an understanding...... that in some coastal regions the amplitudes of the electric field can reach 100 mV/km and 10 mV/km for M2 and O1 tides respectively. The changes of lithosphere resistance produce detectable changes in the tidal electric signals. We show that our predictions are in a good agreement with observations....... of the global distribution of the electric signal due to tidal ocean flow. We simulate the electric signals for two tidal constituents - lunar semidiurnal (M2) and diurnal (O1) tides. We assume a realistic Earth's conductivity model with a surface thin shell and 1-D mantle underneath. Simulations demonstrate...

  16. Design and analysis of a global sub-mesoscale and tidal dynamics admitting virtual ocean.

    Science.gov (United States)

    Menemenlis, D.; Hill, C. N.

    2016-02-01

    We will describe the techniques used to realize a global kilometerscale ocean model configuration that includes representation of sea-ice and tidal excitation, and spans scales from planetary gyres to internal tides. A simulation using this model configuration provides a virtual ocean that admits some sub-mesoscale dynamics and tidal energetics not normally represented in global calculations. This extends simulated ocean behavior beyond broadly quasi-geostrophic flows and provides a preliminary example of a next generation computational approach to explicitly probing the interactions between instabilities that are usually parameterized and dominant energetic scales in the ocean. From previous process studies we have ascertained that this can lead to a qualitative improvement in the realism of many significant processes including geostrophic eddy dynamics, shelf-break exchange and topographic mixing. Computationally we exploit high-degrees of parallelism in both numerical evaluation and in recording model state to persistent disk storage. Together this allows us to compute and record a full three-dimensional model trajectory at hourly frequency for a timeperiod of 5 months with less than 9 million core hours of parallel computer time, using the present generation NASA Ames Research Center facilities. We have used this capability to create a 5 month trajectory archive, sampled at high spatial and temporal frequency for an ocean configuration that is initialized from a realistic data-assimilated state and driven with reanalysis surface forcing from ECMWF. The resulting database of model state provides a novel virtual laboratory for exploring coupling across scales in the ocean, and for testing ideas on the relationship between small scale fluxes and large scale state. The computation is complemented by counterpart computations that are coarsened two and four times respectively. In this presentation we will review the computational and numerical technologies employed

  17. Sounding the Earth's electrical structure with satellite-detected ocean tidal magnetic signals

    Science.gov (United States)

    Grayver, Alexander; Schnepf, Neesha; Kuvshinov, Alexey; Sabaka, Terence; Nair, Manoj; Olsen, Nils

    2016-04-01

    Over the last decade, the quality of satellite data, processing and modeling methods have experienced substantial improvements leading to a stage where satellite-observed tidal magnetic signals can be used to image electrical conductivity of the subsurface. In 2015, a collaborative project supported by ESA's STSE program was kicked off with the primary goal of performing the necessary data processing and their inversion. We present the first radial electrical conductivity model of the oceanic lithosphere and upper mantle obtained by inverting ocean tidal magnetic signals on the global scale. Specifically, the oceanic M2 tidal magnetic field was extracted as a part of the comprehensive magnetic field model (CM5) based on the twelve years of data from pre-Swarm satellite missions and magnetic observatories. The magnetic field was shown to exhibit structure on multiple spatial scales providing uniform global spatial coverage. In order to accurately model the tidal signal, we built the source by using the latest generation of the high-resolution HAMTIDE oceanic tide model and also derived laterally variable electrical conductivity of the world ocean. A surface conductance map that takes into account continent/ocean conductivity and sea-bottom sediment conductivity was used to account for the near-surface inhomogeneous layer. The integral equation forward solver was combined with a global stochastic optimization method and random sampling to carry out the inversion and uncertainty quantification. The obtained model is consistent with the existing regional models and provides a view on global lithosphere-asthenosphere boundary.

  18. Significant Dissipation of Tidal Energy in the Deep Ocean Inferred from Satellite Altimeter Data

    Science.gov (United States)

    Egbert, G. D.; Ray, R. D.

    2000-01-01

    How and where the ocean tides dissipate their energy are longstanding questions that have consequences ranging from the history of the Moon to the mixing of the oceans. Historically, the principal sink of tidal energy has been thought to be bottom friction in shallow seas. There has long been suggestive however, that tidal dissipation also occurs in the open ocean through the scattering by ocean-bottom topography of surface tides into internal waves, but estimates of the magnitude of this possible sink have varied widely. Here we use satellite altimeter data from Topex/Poseidon to map empirically the tidal energy dissipation. We show that approximately 10(exp 12) watts-that is, 1 TW, representing 25-30% of the total dissipation-occurs in the deep ocean, generally near areas of rough topography. Of the estimated 2 TW of mixing energy required to maintain the large-scale thermohaline circulation of the ocean, one-half could therefore be provided by the tides, with the other half coming from action on the surface of the ocean.

  19. Ocean tidal signals in observatory and satellite magnetic measurements

    DEFF Research Database (Denmark)

    Maus, S.; Kuvshinov, A.

    2004-01-01

    Ocean flow moves sea water through the Earth's magnetic field, inducing electric fields, currents and secondary magnetic fields. These motionally induced magnetic fields have a potential for the remote sensing of ocean flow variability. A first goal must be to gain a better understanding of magne...

  20. Electrical design for ocean wave and tidal energy systems

    CERN Document Server

    Alcorn, Raymond

    2013-01-01

    Provides an electrical engineering perspective on offshore power stations and their integration to the grid. With contributions from a panel of leading international experts, this book is essential reading for those working in ocean energy development and renewable energy.

  1. Testing the tidal alignment model of galaxy intrinsic alignment

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Seljak, Uroš [Department of Physics and Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); McQuinn, Matthew, E-mail: blazek@berkeley.edu, E-mail: mmcquinn@berkeley.edu, E-mail: useljak@berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

    2011-05-01

    Weak gravitational lensing has become a powerful probe of large-scale structure and cosmological parameters. Precision weak lensing measurements require an understanding of the intrinsic alignment of galaxy ellipticities, which can in turn inform models of galaxy formation. It is hypothesized that elliptical galaxies align with the background tidal field and that this alignment mechanism dominates the correlation between ellipticities on cosmological scales (in the absence of lensing). We use recent large-scale structure measurements from the Sloan Digital Sky Survey to test this picture with several statistics: (1) the correlation between ellipticity and galaxy overdensity, w{sub g+}; (2) the intrinsic alignment auto-correlation functions; (3) the correlation functions of curl-free, E, and divergence-free, B, modes, the latter of which is zero in the linear tidal alignment theory; (4) the alignment correlation function, w{sub g}(r{sub p},θ), a recently developed statistic that generalizes the galaxy correlation function to account for the angle between the galaxy separation vector and the principle axis of ellipticity. We show that recent measurements are largely consistent with the tidal alignment model and discuss dependence on galaxy luminosity. In addition, we show that at linear order the tidal alignment model predicts that the angular dependence of w{sub g}(r{sub p},θ) is simply w{sub g+}(r{sub p})cos (2θ) and that this dependence is consistent with recent measurements. We also study how stochastic nonlinear contributions to galaxy ellipticity impact these statistics. We find that a significant fraction of the observed LRG ellipticity can be explained by alignment with the tidal field on scales ∼> 10 \\hMpc. These considerations are relevant to galaxy formation and evolution.

  2. Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska final report

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Bruce Albert [Aleutian Pribilof Islands Association, Inc., Anchorage, AK (United States)

    2014-05-07

    The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutian Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and electrical data

  3. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars

    Science.gov (United States)

    Hu, Yongyun; Yang, Jun

    2014-01-01

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere–ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an “eyeball.” For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs’ habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets. PMID:24379386

  4. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars.

    Science.gov (United States)

    Hu, Yongyun; Yang, Jun

    2014-01-14

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere-ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an "eyeball." For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs' habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets.

  5. Revised predictions of long-period ocean tidal effects on Earth's rotation rate

    Science.gov (United States)

    Dickman, S. R.; Nam, Young S.

    1995-01-01

    The rotational response of Earth to long-period tidal forces, embodied in a 'zonal response function,' can be expected to vary with frequency because of variable contributions by the oceans, mantle, and core. The zonal response function has been estimated from 9 years of International Radio Interferometric Surveying (IRIS) universal time (UT1) data and compared with theoretical predictions, using a spherical harmonic tide model to compute the oceans' dynamic response, at semiannual, monthly, fortnightly, and 9-day lunisolar tidal frequencies. Different amounts of mantle anelasticity have been considered for both the oceanic and soild earth responses; predictions have been made assuming axial core-mantle coupling which is either complete or absent. Additionally, an extensive recalibration of the ocean model's frictional parameters was performed using constraints derived in part from Space92 polar motion data; zonal response function predictions have also been made employing this recalibrated ocean tide model. Our results indicate that any amount of core coupling can be ruled out at a fortnightly period and probably at a 9-day period, but not at a monthly period. Our results also suggest that the mantle responds purely elastically at a 9-day period but may behave increasingly anelastically at longer periods. A simple dispersive rule is postulated for periods ranging up to the 14-month Chandler wobble period.

  6. Testing ocean tide models using GGP superconducting gravimeter observations

    Science.gov (United States)

    Baker, T.; Bos, M.

    2003-04-01

    Observations from the global network of superconducting gravimeters in the Global Geodynamics Project (GGP) are used to test 10 ocean tide models (SCHW; FES94.1, 95.2, 98, 99; CSR3.0, 4.0; TPXO.5; GOT99.2b; and NAO.99b). In addition, observations are used from selected sites with LaCoste and Romberg gravimeters with electrostatic feedback, where special attention has been given to achieving a calibration accuracy of 0.1%. In Europe, there are several superconducting gravimeter stations in a relatively small area and this can be used to advantage in testing the ocean (and body) tide models and in identifying sites with anomalous observations. At some of the superconducting gravimeter sites there are anomalies in the in-phase components of the main tidal harmonics, which are due to calibration errors of up to 0.3%. It is shown that the recent ocean tide models are in better agreement with the tidal gravity observations than were the earlier models of Schwiderski and FES94.1. However, no single ocean tide model gives completely satisfactory results in all areas of the world. For example, for M2 the TPXO.5 and NAO99b models give anomalous results in Europe, whereas the FES95.2, FES98 and FES99 models give anomalous results in China and Japan. It is shown that the observations from this improved set of tidal gravity stations will provide an important test of the new ocean tide models that will be developed in the next few years. For further details see Baker, T.F. and Bos, M.S. (2003). "Validating Earth and ocean tide models using tidal gravity measurements", Geophysical Journal International, 152.

  7. Tidal constituent database. West Coast of the United States and Eastern North pacific ocean. Technical note

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-01-01

    This technical note describes a database of tidal elevation boundary condition information generated in support of the `Long-Term Fate of Dredged Material Disposed in Open Water` research of the Dredging Research Program (DRP), being conducted at the U.S. Army Engineer Waterways Experiment Station. The database, described in detail by Hench and others (1994), allows the user to manually generate time series of tidal elevations or to use a program to access the full database to generate time series of both tidal elevations and currents for any location along the West Coast of the United States and Eastern North Pacific Ocean, extending from Seal Cape on Unimak Island, Alaska, in the North to Punta Parada, Peru, in the South. The land boundary includes the Pacific shorelines of Alaska, Canada, mainland United States, Mexico, Guatemala, El Salvador, Nicaragua, Costa Rica, Panama, Columbia, and Northern Peru. Although the capability to generate these time series was developed to provide input to the Long-Term Fate and Stability Model (LTFATE), the generated time series can be used for any application requiring tidal forcing data.

  8. Testing Ocean Tide Models Using Superconducting Gravimeter Observations

    Science.gov (United States)

    Baker, T. F.; Bos, M. S.

    2002-12-01

    Observations from the global network of superconducting gravimeters in the Global Geodynamics Project (GGP) are used to test 10 recent ocean tide models. In addition, observations are used from selected sites with LaCoste and Romberg gravimeters with electrostatic feedback, where special attention has been given to achieving a calibration accuracy of 0.1%. At some superconducting gravimeter sites there are anomalies in the in-phase components of the main tidal harmonics, which are due to calibration errors of up to 0.3%. It is shown that the recent ocean tide models are in better agreement with the tidal gravity observations than were the earlier models of Schwiderski and FES94.1. However, no single ocean tide model gives completely satisfactory results in all areas of the world. For example, for M2 the TPXO.5 and NAO99b models give anomalous results in Europe, whereas the FES95.2, FES98 and FES99 models give anomalous results in China and Japan. It is shown that the observations from this improved set of tidal gravity stations will provide an important test of the new ocean tide models that will be developed in the next few years.

  9. A robust interpolation procedure for producing tidal current ellipse inputs for regional and coastal ocean numerical models

    Science.gov (United States)

    Byun, Do-Seong; Hart, Deirdre E.

    2017-04-01

    Regional and/or coastal ocean models can use tidal current harmonic forcing, together with tidal harmonic forcing along open boundaries in order to successfully simulate tides and tidal currents. These inputs can be freely generated using online open-access data, but the data produced are not always at the resolution required for regional or coastal models. Subsequent interpolation procedures can produce tidal current forcing data errors for parts of the world's coastal ocean where tidal ellipse inclinations and phases move across the invisible mathematical "boundaries" between 359° and 0° degrees (or 179° and 0°). In nature, such "boundaries" are in fact smooth transitions, but if these mathematical "boundaries" are not treated correctly during interpolation, they can produce inaccurate input data and hamper the accurate simulation of tidal currents in regional and coastal ocean models. These avoidable errors arise due to procedural shortcomings involving vector embodiment problems (i.e., how a vector is represented mathematically, for example as velocities or as coordinates). Automated solutions for producing correct tidal ellipse parameter input data are possible if a series of steps are followed correctly, including the use of Cartesian coordinates during interpolation. This note comprises the first published description of scenarios where tidal ellipse parameter interpolation errors can arise, and of a procedure to successfully avoid these errors when generating tidal inputs for regional and/or coastal ocean numerical models. We explain how a straightforward sequence of data production, format conversion, interpolation, and format reconversion steps may be used to check for the potential occurrence and avoidance of tidal ellipse interpolation and phase errors. This sequence is demonstrated via a case study of the M2 tidal constituent in the seas around Korea but is designed to be universally applicable. We also recommend employing tidal ellipse parameter

  10. Testing strong-field gravity with tidal Love numbers

    Science.gov (United States)

    Cardoso, Vitor; Franzin, Edgardo; Maselli, Andrea; Pani, Paolo; Raposo, Guilherme

    2017-04-01

    The tidal Love numbers (TLNs) encode the deformability of a self-gravitating object immersed in a tidal environment and depend significantly both on the object's internal structure and on the dynamics of the gravitational field. An intriguing result in classical general relativity is the vanishing of the TLNs of black holes. We extend this result in three ways, aiming at testing the nature of compact objects: (i) we compute the TLNs of exotic compact objects, including different families of boson stars, gravastars, wormholes, and other toy models for quantum corrections at the horizon scale. In the black-hole limit, we find a universal logarithmic dependence of the TLNs on the location of the surface. (ii) We compute the TLNs of black holes beyond vacuum general relativity, including Einstein-Maxwell, Brans-Dicke, and Chern-Simons gravity. (iii) We assess the ability of present and future gravitational-wave detectors to measure the TLNs of these objects, including the first analysis of TLNs with LISA. Both LIGO, ET, and LISA can impose interesting constraints on boson stars, while LISA is able to probe even extremely compact objects. We argue that the TLNs provide a smoking gun of new physics at the horizon scale and that future gravitational-wave measurements of the TLNs in a binary inspiral provide a novel way to test black holes and general relativity in the strong-field regime.

  11. Nova Scotia Power shows how to generate electricity from ocean. [Annapolis Tidal Generating station

    Energy Technology Data Exchange (ETDEWEB)

    1986-02-01

    The first tidal power plant in North America has completed a successful first year of operation, reports Nova Scotia Power Corp., the utility that built it and operates it. Rated at 19 MW, it's the largest tidal generating plant in the world, but the Canadians consider it a pilot-scale installation built to test the feasibility of harnessing the unusually large tides in the Bay of Fundy on Canada's east coast. Called the Annapolis Tidal Generating station it's located on a narrow neck of land separating the Annapolis River from the Bay of Fundy. The tides there range from 15 to 25 feet, averaging 21 feet. In the average tidal cycle the plant generates electricity for about six hours, sluices water into the reservoir for about three hours, and is at a standstill for about three hours. During the first year of operation the plant produced 25 million kWh. Reported availability was 99%. It missed only eight tides out of a possible 728.

  12. Extracting Ocean-Generated Tidal Magnetic Signals from Swarm Data Through Satellite Gradiometry

    Science.gov (United States)

    Sabaka, Terence J.; Tyler, Robert H.; Olsen, Nils

    2016-01-01

    Ocean-generated magnetic field models of the Principal Lunar, M2, and the Larger Lunar elliptic, N2, semidiurnal tidal constituents were estimated through a "Comprehensive Inversion" of the first 20.5 months of magnetic measurements from European Space Agency's (ESA) Swarm satellite constellation mission. While the constellation provides important north-south along-track gradiometry information, it is the unique low-spacecraft pair that allows for east-west cross-track gradiometry. This latter type is crucial in delivering an M2 estimate of similar quality with that derived from over 10 years of CHAMP satellite data but over a shorter interval, at higher altitude, and during more magnetically disturbed conditions. Recovered N2 contains nonoceanic signal but is highly correlated with theoretical models in regions of maximum oceanic amplitude. Thus, satellite magnetic gradiometry may eventually enable the monitoring of ocean electrodynamic properties at temporal resolutions of 1 to 2 years, which may have important implications for the inference of ocean temperature and salinity.

  13. Extracting Ocean-Generated Tidal Magnetic Signals from Swarm Data through Satellite Gradiometry

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Tyler, Robert H.; Olsen, Nils

    2016-01-01

    Ocean-generated magnetic field models of the Principal Lunar, M2, and the Larger Lunar elliptic, N2, semi-diurnal tidal constituents were estimated through a “Comprehensive Inversion" of the first 20.5 months of magnetic measurements from ESA's Swarm satellite constellation mission. While the con...

  14. Observations of ocean tidal load response in South America from subdaily GPS positions

    Science.gov (United States)

    Martens, Hilary R.; Simons, Mark; Owen, Susan; Rivera, Luis

    2016-06-01

    We explore Earth's elastic deformation response to ocean tidal loading (OTL) using kinematic Global Positioning System (GPS) observations and forward-modelled predictions across South America. Harmonic coefficients are extracted from up to 14 yr of GPS-inferred receiver locations, which we estimate at 5 min intervals using precise point positioning. We compare the observed OTL-induced surface displacements against predictions derived from spherically symmetric, non-rotating, elastic and isotropic (SNREI) Earth models. We also compare sets of modelled predictions directly for various ocean-tide and Earth-model combinations. The vector differences between predicted displacements computed using separate ocean-tide models reveal uniform-displacement components common to all stations in the South America network. Removal of the network-mean OTL-induced displacements from each site substantially reduces the vector differences between observed and predicted displacements. We focus on the dominant astronomical tidal harmonics from three distinct frequency bands: semidiurnal (M2), diurnal (O1) and fortnightly (Mf). In each band, the observed OTL-induced surface displacements strongly resemble the modelled displacement-response patterns, and the residuals agree to about 0.3 mm or better. Even with the submillimetre correspondence between observations and predictions, we detect regional-scale spatial coherency in the final set of residuals, most notably for the M2 harmonic. The spatial coherency appears relatively insensitive to the specific choice of ocean-tide or SNREI-Earth model. Varying the load model or 1-D elastic structure yields predicted OTL-induced displacement differences of order 0.1 mm or less for the network. Furthermore, estimates of the observational uncertainty place the noise level below the magnitude of the residual displacements for most stations, supporting our interpretation that random errors cannot account for the entire misfit. Therefore, the

  15. Spectral analysis of one-way and two-way downscaling applications for a tidally driven coastal ocean forecasting system

    Science.gov (United States)

    Solano, Miguel; Gonzalez, Juan; Canals, Miguel; Capella, Jorge; Morell, Julio; Leonardi, Stefano

    2017-04-01

    A prevailing problem for a tidally driven coastal ocean has been the adequate imposition of open boundary conditions. This study aims at assessing the role of open boundary conditions and tidal forcing for one and two way downscaling applications at high resolution. The operational system is based on the Caribbean Coastal Ocean Forecasting System (COFS) that uses the Regional Ocean Modeling System (ROMS), a split-explicit ocean model in which the barotropic (2D) and baroclinic (3D) modes advance separately. This COFS uses a uniform horizontal grid with 1km resolution, but a grid sensitivity analysis is performed for both one and two way downscaling methodologies with horizontal resolutions up to 700m. Initial and lateral boundary conditions are derived from the U.S Naval Oceanographic Office (NAVOCEANO) operational AmSeas model forecast, a 3-km resolution of the regional Navy Coastal Ocean Model (NCOM) that encompasses the Gulf of Mexico and Caribbean Sea. Meteorological conditions are interpolated from the Navy's COAMPS model with the exception of surface stresses, which are computed from a 2-km application of the WRF model used by NCEP's National Digital Forecast Database. Tidal forcing is performed in two different ways: 1) tidal and sub-tidal variability is imposed to the barotropic and baroclinic modes by downscaling from the AmSeas NCOM regional model and 2) tidal variability is imposed using ROMS harmonic tidal forcing from OTPS and sub-tidal conditions are imposed by filtering high frequencies out the NCOM regional solution. Special focus is given to the latter approach, where the nudging time scales and the boundary update frequency play an important role in the evolution of the ocean state for short 3-day forecasts. A spectral analysis of the sea surface height and barotropic velocity is performed via Fourier's transform, continuous 1-D wavelet transforms, and classic harmonic analysis. Tide signals are then reconstructed and removed from the OBC's in 3

  16. Computational Fluid Dynamics and Visualisation of Coastal Flows in Tidal Channels Supporting Ocean Energy Development

    Directory of Open Access Journals (Sweden)

    Enayatollah Zangiabadi

    2015-06-01

    Full Text Available Flow characteristics in coastal regions are strongly influenced by the topography of the seabed and understanding the fluid dynamics is necessary before installation of tidal stream turbines (TST. In this paper, the bathymetry of a potential TST deployment site is used in the development of the a CFD (Computational Fluid Dynamics model. The steady state k-ϵ and transient Large Eddy Simulation (LES turbulence methods are employed and compared. The simulations are conducted with a fixed representation of the ocean surface, i.e., a rigid lid representation. In the vicinity of Horse Rock a study of the pressure difference shows that the small change in height of the water column is negligible, providing confidence in the simulation results. The stream surface method employed to visualise the results has important inherent characteristics that can enhance the visual perception of complex flow structures. The results of all cases are compared with the flow data transect gathered by an Acoustic Doppler Current Profiler (ADCP. It has been understood that the k-ϵ method can predict the flow pattern relatively well near the main features of the domain and the LES model has the ability to simulate some important flow patterns caused by the bathymetry.

  17. Development, installation and testing of a large-scale tidal current turbine

    Energy Technology Data Exchange (ETDEWEB)

    Thake, J.

    2005-10-15

    This report summarises the findings of the Seaflow project to investigate the feasibility of building and operating a commercial scale marine current horizontal axis tidal turbine and to evaluate the long-term economics of producing electricity using tidal turbines. Details are given of competitive tidal stream technologies and their commercial status, the selection of the site on the North Devon coast of the UK, and the evaluation of the turbine design, manufacture, testing, installation, commissioning, and maintenance of the turbine. The organisations working on the Seaflow project and cost estimations are discussed.

  18. A new high-resolution model of non-tidal atmosphere and ocean mass variability for de-aliasing of satellite gravity observations: AOD1B RL06

    Science.gov (United States)

    Dobslaw, H.; Bergmann-Wolf, I.; Dill, R.; Poropat, L.; Thomas, M.; Dahle, C.; Esselborn, S.; König, R.; Flechtner, F.

    2017-10-01

    The release 06 (RL06) of the Gravity Recovery and Climate Experiment (GRACE) Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) product has been prepared for use as a time-variable background model in global gravity research. Available since the year 1976 with a temporal resolution of 3 hr, the product is provided in Stokes coefficients up to degree and order 180. RL06 separates tidal and non-tidal signals, and has an improved long-term consistency due to the introduction of a time-invariant reference orography in continental regions. Variance reduction tests performed with globally distributed in situ ocean bottom pressure recordings and sea-surface height anomalies from Jason-2 over a range of different frequency bands indicate a generally improved performance of RL06 compared to its predecessor. Orbit tests for two altimetry satellites remain inconclusive, but GRACE K-band residuals are reduced by 0.031 nm s-2 in a global average, and by more than 0.5 nm s-2 at numerous places along the Siberian shelf when applying the latest AOD1B release. We therefore recommend AOD1B RL06 for any upcoming satellite gravimetry reprocessing effort.

  19. Design and test of 1/5th scale horizontal axis tidal current turbine

    Science.gov (United States)

    Liu, Hong-wei; Zhou, Hong-bin; Lin, Yong-gang; Li, Wei; Gu, Hai-gang

    2016-06-01

    Tidal current energy is prominent and renewable. Great progress has been made in the exploitation technology of tidal current energy all over the world in recent years, and the large scale device has become the trend of tidal current turbine (TCT) for its economies. Instead of the similarity to the wind turbine, the tidal turbine has the characteristics of high hydrodynamic efficiency, big thrust, reliable sealing system, tight power transmission structure, etc. In this paper, a 1/5th scale horizontal axis tidal current turbine has been designed, manufactured and tested before the full scale device design. Firstly, the three-blade horizontal axis rotor was designed based on traditional blade element momentum theory and its hydrodynamic performance was predicted in numerical model. Then the power train system and stand-alone electrical control unit of tidal current turbine, whose performances were accessed through the bench test carried out in workshop, were designed and presented. Finally, offshore tests were carried out and the power performance of the rotor was obtained and compared with the published literatures, and the results showed that the power coefficient was satisfactory, which agrees with the theoretical predictions.

  20. Permeability of the Lucky Strike deep-sea hydrothermal system: Constraints from the poroelastic response to ocean tidal loading

    Science.gov (United States)

    Barreyre, Thibaut; Escartin, Javier; Sohn, Robert; Cannat, Mathilde

    2014-12-01

    We use the time delay between tidal loading and the induced subsurface flow response to constrain the poroelastic behavior and permeability of the Lucky Strike hydrothermal field on the Mid-Atlantic Ridge. We demonstrate that high-temperature (T > 200 °C) exit-fluid discharge records from four hydrothermal sites across the field are highly coherent with contemporaneously acquired bottom pressure records at tidal periods, with the thermal response lagging pressure by ∼155° (5.3 h) on average across all sites for the semi-diurnal (M2) frequency over a three-year observation period. In a one-dimensional poroelastic model of ocean tidal loading this phase lag corresponds to a high-permeability system where pore pressure perturbations at the seafloor rapidly propagate downward from the seafloor interface until they encounter a permeability boundary. Our results suggest that at the Lucky Strike field this tidal pumping is largely restricted to the ∼600 m thick extrusive layer (i.e., seismic layer 2A). Under a plausible set of matrix elastic parameters, the ∼5.3 h lag between pressure and exit-fluid temperature is consistent with an effective matrix permeability of ∼10-10 m2 and an average vertical flow velocity of ∼0.02 m/s within the extrusive layer. Our results argue against tidal pumping of the entire crustal section between the seafloor and the axial magma chamber (at ∼3.4 kmbsf) because this scenario requires unrealistically high effective permeabilities (∼10-9 m2) and average vertical flow velocities (∼0.15 m/s) over this depth range. Our effective permeability estimate for the extrusive layer is broadly consistent with previous results, and indicates that flow must be channeled in discrete permeable pathways (e.g., faults, fissures) that cut through the extrusive volcanic layer.

  1. Geochemical behavior of phosphorus and iron in porewater in a mangrove tidal flat and associated phosphorus input into the ocean

    Science.gov (United States)

    Pan, Feng; Liu, Huatai; Guo, Zhanrong; Li, Zhiwei; Wang, Bo; Gao, Aiguo

    2017-11-01

    A thorough understanding of the distribution and geochemical behavior of phosphorus (P) and iron (Fe) across the sediment-water interface (SWI) is essential for estimating the exchange flux between sediment porewater and overlying seawater. In this study, in situ high-resolution diffusive gradients in thin films (DGT) technique, ZrO-Chelex DGT, were applied to investigate the depth profiles of dissolved reactive phosphorus (DRP) and ferrous iron (Fe2+) in sediment porewater in a mangrove tidal flat of the Jiulong River estuary, China. The concentrations of DRP and Fe2+, which ranged from 0.014 to 0.288 mg L-1 and 0.003-0.619 mg L-1, respectively, were highly heterogeneous across these profiles. The positive correlation between DRP and Fe2+ concentrations in most parts of the profiles verified the key role of Fe-redox cycling in controlling DRP variations. However, in some parts of the profiles, this coupling relationship was disturbed by the enrichment of mangrove organic matter or biological activity, such as that of macrobenthos and microorganisms. The recirculated seawater fluxes driven by tides and wave setups were calculated to be 23.15 m3 m-1 d-1 and 1.49 × 10-3 m3 m-1 d-1, respectively. Based on these calculated fluxes and end-member concentrations, the net DRP flux into the ocean was calculated to be approximately 1.57 mmol m-2 d-1, which is much larger than the molecular diffusion flux of DRP (1.79 × 10-3 mmol m-2 d-1). These results indicate that the advection of recirculated seawater is a significant pathway to deliver DRP into the ocean and that this kind of internal phosphorus from mangrove tidal flats or muddy coastal zones should be considered in future nutrient budgets of estuaries or coastal oceans.

  2. High-frequency non-linear motions induced by non-tidal ocean loading and their effect on estimating the geocenter motion from a geodetic network

    Science.gov (United States)

    Memin, A.; Watson, C. S.; Tregoning, P.

    2013-12-01

    We investigate the influence of high-frequency non-tidal ocean loading on the displacement induced at a global set of geodetic stations and on estimating the geocenter motion from a geodetic network. Ground displacements of each geodetic site induced by atmospheric and ocean loading are computed by convolving surface mass or pressure variations with Green functions for the vertical and horizontal displacement. The displacements resulting from atmospheric loading are computed using the surface pressure variations provided by the European Center for Medium-range Weather Forecasts model (1.5° space and 3h time sampling). The ocean response is taken into account assuming an inverted barometer and a non-inverted barometer response of the ocean to changes in the atmosphere. The first one is derived from the atmospheric model. The latter is computed using the sea height variations from the global barotropic ocean model named Toulouse Unstructured Grid Ocean model (0.25° grid and 3h time sampling). To examine the spatial and temporal effects of the high-frequency non-tidal atmospheric and ocean deformations spanning the network, made of 157 stations, from 2002 to 2011, we remove a seasonal component from the loading and geodetic time series. We find that high-frequency non-tidal ocean loading induces a larger long term variability (mean increase of 25% and up to 80%) in the vertical displacement than the non-tidal atmospheric loading at 131 stations. A similar conclusion holds for the induced sub-daily scatter at 127 stations (mean increase of 37% and up to 90%). Using the dynamic ocean's response, when correcting the geodetic time series for non-tidal ocean loading, reduces the weighted variance of the geodetic time series at 118 sites, the largest reductions (> 11%) are obtained along the Baltic sea. We compute the deformation in a center of mass and center of figure reference frame and estimate the time series of the translation of the geocenter. Comparing the

  3. ENPAC 2003: A Tidal Constituent Database for Eastern North Pacific Ocean

    Science.gov (United States)

    2004-09-01

    tidal model. The model domain for this project extended from Unimak Island, AK, to Punta Parada, Peru, covering an area of approximately 2.1 X 107 km and...redefining the domain. The new domain began at the same location, Unimak Island, AK, but extended only to Acapulco, Mexico, stopping short of...domain are shown in Figure 3. This domain extends from Unimak Island, AK, to Chamela, Mexico, approximately 650 km north of Acapulco, Mexico, along the

  4. Puget Sound Tidal Energy In-Water Testing and Development Project Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Collar, Craig W

    2012-11-16

    Tidal energy represents potential for the generation of renewable, emission free, environmentally benign, and cost effective energy from tidal flows. A successful tidal energy demonstration project in Puget Sound, Washington may enable significant commercial development resulting in important benefits for the northwest region and the nation. This project promoted the United States Department of Energy's Wind and Hydropower Technologies Program's goals of advancing the commercial viability, cost-competitiveness, and market acceptance of marine hydrokinetic systems. The objective of the Puget Sound Tidal Energy Demonstration Project is to conduct in-water testing and evaluation of tidal energy technology as a first step toward potential construction of a commercial-scale tidal energy power plant. The specific goal of the project phase covered by this award was to conduct all activities necessary to complete engineering design and obtain construction approvals for a pilot demonstration plant in the Admiralty Inlet region of the Puget Sound. Public Utility District No. 1 of Snohomish County (The District) accomplished the objectives of this award through four tasks: Detailed Admiralty Inlet Site Studies, Plant Design and Construction Planning, Environmental and Regulatory Activities, and Management and Reporting. Pre-Installation studies completed under this award provided invaluable data used for site selection, environmental evaluation and permitting, plant design, and construction planning. However, these data gathering efforts are not only important to the Admiralty Inlet pilot project. Lessons learned, in particular environmental data gathering methods, can be applied to future tidal energy projects in the United States and other parts of the world. The District collaborated extensively with project stakeholders to complete the tasks for this award. This included Federal, State, and local government agencies, tribal governments, environmental groups, and

  5. Experimental Test Plan DOE Tidal and River Reference Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Neary, Vincent S [ORNL; Hill, Craig [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414; Chamorro, Leonardo [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414; Gunawan, Budi [ORNL

    2012-09-01

    Our aim is to provide details of the experimental test plan for scaled model studies in St. Anthony Falls Laboratory (SAFL) Main Channel at the University of Minnesota, including a review of study objectives, descriptions of the turbine models, the experimental set-up, instrumentation details, instrument measurement uncertainty, anticipated experimental test cases, post-processing methods, and data archiving for model developers.

  6. Detection and Modeling of Non-Tidal Oceanic Effects on the Earth's Rotation Rate

    Science.gov (United States)

    Marcus, S. L.; Chao, Y.; Dickey, J. O.; Gegout, P.

    1998-01-01

    Sub-decadal changes in the Earth's rotation rate, and hence in the length-of-day (LOD), are largely controlled by variations in atmospheric angular momentum. Results from two oceanic general circulation models (OGCMs), forced by observed wind stress and heat flux for the years 1992-1994, show that ocean current and mass distribution changes also induce detectable LOD variations.

  7. The ocean response at multiple space and time scales to tidal stream energy extraction by a large-scale turbine array.

    Science.gov (United States)

    De Dominicis, Michela; O'Hara Murray, Rory; Wolf, Judith

    2017-04-01

    A comprehensive assessment of the tidal energy resource realistically available for electricity generation and the study of the potential environmental impacts associated with its extraction in the Pentland Firth (Scottish Waters, UK) are presented. In order to examine both local (100 km) spatial scales, the Scottish Shelf Model (SSM), an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) model implementation has been used, since it covers the entire NW European Shelf, with a high resolution where the tidal stream energy is extracted. A large theoretical array of tidal stream turbines has been designed and implemented in the model using the momentum sink approach, in which a momentum sink term represents the loss of momentum due to tidal energy extraction. The estimate of the maximum available power for electricity generation from the Pentland Firth is 1.64 GW, which requires thousands of turbines to be deployed. This estimate takes into account the tidal stream energy extraction feedbacks on the flow and considers, for the first time, the realistic operation of a generic tidal stream turbine, which is limited to operate in a range of flow velocities due to technological constraints. The ocean response to the extraction of 1.64 GW of energy has been examined by comparing a typical annual cycle of the NW European Shelf hydrodynamics reproduced by the SSM with the same period perturbed by tidal stream energy extraction. The changes were analysed at the temporal scale of a spring-neap tidal cycle and, for the first time, on longer term seasonal timescales. Tidal elevation mainly increases in the vicinity of the tidal farm, while far-field effects show a decrease in the mean spring tidal range of the order of 2 cm along the whole east coast of the UK, possibly counteracting some part of the predicted sea level rise due to climate change. Marine currents, both tidal and residual flows, are also affected. They can slow down due to the

  8. Phytoplankton community composition and primary production in the tropical tidal ecosystem, Maputo Bay (the Indian Ocean)

    Science.gov (United States)

    Olofsson, Malin; Karlberg, Maria; Lage, Sandra; Ploug, Helle

    2017-07-01

    Maputo Bay is highly affected by large tidal changes and riverine freshwater input with a phytoplankton biomass peak during March each year. Microscopy analysis was used to describe how the phytoplankton community composition was affected by tidal changes, during four in situ incubation experiments. Using stable isotope tracers, new and total primary production, based on nitrate (15NO3-)- and carbon (13C-bicarbonate)-assimilation were estimated. The highest biovolume of phytoplankton (> 2 μm) and also the highest C- and NO3--assimilation rates (nM h-1) were found at spring-high tide. The C:N (mol:mol) ratio of particulate organic matter (POM) varied between 6.0 and 8.2. The proportion of diatoms in the phytoplankton community was higher at spring-high tide as compared to neap-low tide, whereas dinoflagellates were found in a reverse pattern. New production ranged between 6.3% and 10.4% of total primary production and was thus within the range previously reported for tropical regions. The largest proportion of NO3--based new production relative to total production was estimated during calm conditions and spring-high tide. Concordantly, a large fraction of the microplanktonic community covered their N-demand by other sources of N than NO3-.

  9. Potential of High Spatial and Temporal Ocean Color Satellite Data to Study the Dynamics of Suspended Particles in a Micro-Tidal River Plume

    Directory of Open Access Journals (Sweden)

    Anouck Ody

    2016-03-01

    Full Text Available Ocean color satellite sensors are powerful tools to study and monitor the dynamics of suspended particulate matter (SPM discharged by rivers in coastal waters. In this study, we test the capabilities of Landsat-8/Operational Land Imager (OLI, AQUA&TERRA/Moderate Resolution Imaging Spectroradiometer (MODIS and MSG-3/Spinning Enhanced Visible and Infrared Imager (SEVIRI sensors in terms of spectral, spatial and temporal resolutions to (i estimate the seawater reflectance signal and then SPM concentrations and (ii monitor the dynamics of SPM in the Rhône River plume characterized by moderately turbid surface waters in a micro-tidal sea. Consistent remote-sensing reflectance (Rrs values are retrieved in the red spectral bands of these four satellite sensors (median relative difference less than ~16% in turbid waters. By applying a regional algorithm developed from in situ data, these Rrs are used to estimate SPM concentrations in the Rhône river plume. The spatial resolution of OLI provides a detailed mapping of the SPM concentration from the downstream part of the river itself to the plume offshore limits with well defined small-scale turbidity features. Despite the low temporal resolution of OLI, this should allow to better understand the transport of terrestrial particles from rivers to the coastal ocean. These details are partly lost using MODIS coarser resolutions data but SPM concentration estimations are consistent, with an accuracy of about 1 to 3 g·m−3 in the river mouth and plume for spatial resolutions from 250 m to 1 km. The MODIS temporal resolution (2 images per day allows to capture the daily to monthly dynamics of the river plume. However, despite its micro-tidal environment, the Rhône River plume shows significant short-term (hourly variations, mainly controlled by wind and regional circulation, that MODIS temporal resolution failed to capture. On the contrary, the high temporal resolution of SEVIRI makes it a powerful tool to

  10. Towing Tank and Flume Testing of Passively Adaptive Composite Tidal Turbine Blades: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Murray, Robynne [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Ordonez-Sanchez, Stephanie [University of Strathclyde; Porter, Kate E. [University of Strathclyde; Johnstone, Cameron M. [University of Strathclyde; Doman, Darrel A. [Dalhousie University; Pegg, Michael J. [Dalhousie University

    2017-09-28

    Composite tidal turbine blades with bend-twist (BT) coupled layups allow the blade to self-adapt to local site conditions by passively twisting. Passive feathering has the potential to increase annual energy production and shed thrust loads and power under extreme tidal flows. Decreased hydrodynamic thrust and power during extreme conditions meann that the turbine support structure, generator, and other components can be sized more appropriately, resulting in a higher utilization factor and increased cost effectiveness. This paper presents new experimental data for a small-scale turbine with BT composite blades. The research team tested the turbine in the Kelvin Hydrodynamics Laboratory towing tank at the University of Strathclyde in Glasgow, United Kingdom, and in the recirculating current flume at the l Institut Francais de Recherche pour l Exploitation de la Mer Centre in Boulogne-sur-Mer, France. Tests were also performed on rigid aluminum blades with identical geometry, which yielded baseline test sets for comparison. The results from both facilities agreed closely, supporting the hypothesis that increased blade flexibility can induce load reductions. Under the most extreme conditions tested the turbine with BT blades had up to 11 percent lower peak thrust loads and a 15 percent reduction in peak power compared to the turbine with rigid blades. The load reductions varied as a function of turbine rotational velocity and ambient flow velocity.

  11. Application of the Geostationary Ocean Color Imager to Mapping the Diurnal and Seasonal Variability of Surface Suspended Matter in a Macro-Tidal Estuary

    Directory of Open Access Journals (Sweden)

    Zhixin Cheng

    2016-03-01

    Full Text Available Total suspended particulate matter (TSM in estuarine and coastal regions usually exhibits significant natural variations. The understanding of such variations is of great significance in coastal waters. The aim of this study is to investigate and assess the diurnal and seasonal variations of surface TSM distribution and its mechanisms in coastal waters based on Geostationary Ocean Color Imager (GOCI data. As a case study, dynamic variations of TSM in the macro-tidal Yalu River estuary (YRE of China were analysed. With regard to diurnal variability, there were usually two peaks of TSM in a tidal cycle corresponding to the maximum flood and ebb current. Tidal action appears to play a vital role in diurnal variations of TSM. Both the processes of tidal re-suspension and advection could be identified; however, the diurnal variation of TSM was mainly affected by a re-suspension process. In addition, spring-neap tides can affect the magnitude of TSM diurnal variations in the YRE. The GOCI-retrieved TSM results clearly showed the seasonal variability of surface TSM in this area, with the highest level occurring in winter and the lowest in summer. Moreover, although river discharge to the YRE was much greater in the wet season than the dry season, TSM concentrations were significantly higher in the dry season. Wind waves were considered to be the main factor affecting TSM seasonal variation in the YRE.

  12. Tidal Creek Sentinel Habitat Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ecological Research, Assessment and Prediction's Tidal Creeks: Sentinel Habitat Database was developed to support the National Oceanic and Atmospheric...

  13. Model Testing - Bringing the Ocean into the Laboratory

    DEFF Research Database (Denmark)

    Aage, Christian

    2000-01-01

    Hydrodynamic model testing, the principle of bringing the ocean into the laboratory to study the behaviour of the ocean itself and the response of man-made structures in the ocean in reduced scale, has been known for centuries. Due to an insufficient understanding of the physics involved, however...

  14. Hydrological exchanges and Organic Matter dynamics in highly vulnerable tidal wetland ecosystems at the land-ocean interface

    Science.gov (United States)

    Tzortziou, M.; Neale, P.; Megonigal, P.; Loughner, C.

    2014-12-01

    Occupying a critical interface between the land and the sea, tidal wetlands are amongst the most ecologically valuable and economically important ecosystems on Earth, but also especially vulnerable to human pressures and climate change. These rich in biodiversity and highly productive ecosystems are hot spots of biogeochemical transformations, consistently exchanging Organic Matter with adjacent estuarine waters through tidal flushing. Here we discuss new results on the amount and directions of biogeochemical exchanges at the tidal wetland-estuary interface. Detailed microbial and photochemical degradation experiments and high resolution bio-optical observations in tidal freshwater and salt marsh systems of the Eastern US coast provide insights on the quality and fate of the organic compounds exported from tidal marshes and their influence on near-shore biological processes, biogeochemical cycles and optical variability. Impacts of anthropogenic activities and resulting air-pollution are also discussed. High resolution model runs were performed using the Community Multi-scale Air Quality (CMAQ) model, to examine atmospheric composition along the shoreline where processes such as sea and bay breeze circulations often favor the accumulation and air-deposition of atmospheric pollutants, impacting biogeochemical processes in sensitive tidal wetland ecosystems.

  15. Seafloor tilt induced by ocean tidal loading inferred from broadband seismometer data from the Cascadia subduction zone and Juan de Fuca Ridge

    Science.gov (United States)

    Davis, Earl E.; Heesemann, Martin; Lambert, Anthony; He, Jianheng

    2017-04-01

    Mass-balancing voltages from four buried broadband seismometers connected to the NEPTUNE Canada seafloor cable are being recorded at 24-bit resolution. Sites are located on the Vancouver Island continental shelf, the nearby Cascadia accretionary prism, the eastern flank of the Juan de Fuca Ridge, and the western flank close to the Juan de Fuca Ridge axis. Tidal variations are present throughout the records. Variations in vertical acceleration at three of the sites match predicted gravitational attraction variations very well; those at the fourth site show a small residual that is probably caused by sensitivity to tilt resulting from sensor inclination. Horizontal accelerations, which at tidal periods are sensitive primarily to tilt, are anomalously large relative to standard-earth model results. After removal of predicted tidal body and ocean attraction and loading terms, the residuals are seen to follow ocean pressure variations. Responses range from 0.4 μrad dbar-1 (0.04 μrad kPa-1) at 10° true (down under positive load) at the continental shelf site, to 0.6 μrad dbar-1 at 243° at the Cascadia prism, 0.4 μrad dbar-1 at 90° at the eastern Juan de Fuca Ridge flank, and 0.2 μrad dbar-1 at 116° true on the western ridge flank. Except at the continental shelf site, tilts are roughly perpendicular to structural strike. The tilt observations can be explained by loading-induced deformation in the presence of local lithologic gradients or by the influence of faults or structurally controlled anisotropic elastic properties. The observations highlight the utility of using mass position data from force-feedback broad-band seismometers for geodynamic studies.

  16. Observations of Tidal Straining Within Two Different Ocean Environments in the East China Sea: Stratification and Near-Bottom Turbulence

    Science.gov (United States)

    Yang, Wei; Wei, Hao; Zhao, Liang

    2017-11-01

    Tidal straining describes the straining effect induced by the vertical shear of oscillatory tidal currents that act on horizontal density gradients. It tends to create tidal periodic stratification and modulate the turbulence in the bottom boundary layer (BBL). Here, we present observations of current, hydrology and turbulence obtained at two mooring stations that are characterized by two typical hydrological environments in the East China Sea (ECS). One is located adjacent to the Changjiang River's mouth, and the other is located over a sloping shelf which is far from the freshwater sources. Tidal straining induces a semidiurnal switching between stable and unstable stratification at both stations. Near-bottom high-frequency velocity measurements further reveal that the dissipation rate of turbulent kinetic energy (TKE) is highly elevated during periods when unstable stratification occurs. A comparison between the TKE dissipation rate (ɛ) and the shear production (P) further reveals that the near-bottom mixing is locally shear-induced most of the time except during the unstable stratification period. Within this period, the magnitude of dissipation exceeds the expected value based on the law of the wall by an order of magnitude. The buoyancy flux that calculated by the balance method is too small to compensate for the existing discrepancy between the dissipation and shear production. Another plausible candidate is the advection of TKE, which may play an important role in the TKE budget during the unstable stratification period.

  17. Salinity Changes in a Tidal River. A Learning Experience for Coastal and Oceanic Awareness Studies, No. 308. [Project COAST].

    Science.gov (United States)

    Delaware Univ., Newark. Coll. of Education.

    The materials in this packet are designed to aid teachers in the implementation of a science field studies unit concerning tidal rivers. The packet consists of the following: (1) background material for the teacher; (2) lab exercises; (3) field activities; and (4) classroom activities. The overall purpose of this packet is to provide information…

  18. Maine Tidal Power Initiative: Environmental Impact Protocols For Tidal Power

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Michael Leroy [Univ. of Maine, Orono, ME; Zydlewski, Gayle Barbin [Univ. of Maine, Orono, ME; Xue, Huijie [Univ. of Maine, Orono, ME; Johnson, Teresa R. [Univ. of Maine, Orono, ME

    2014-02-02

    The Maine Tidal Power Initiative (MTPI), an interdisciplinary group of engineers, biologists, oceanographers, and social scientists, has been conducting research to evaluate tidal energy resources and better understand the potential effects and impacts of marine hydro-kinetic (MHK) development on the environment and local community. Project efforts include: 1) resource assessment, 2) development of initial device design parameters using scale model tests, 3) baseline environmental studies and monitoring, and 4) human and community responses. This work included in-situ measurement of the environmental and social response to the pre-commercial Turbine Generator Unit (TGU®) developed by Ocean Renewable Power Company (ORPC) as well as considering the path forward for smaller community scale projects.

  19. Guidelines for Using Eastcoast 2001 Database of Tidal Constituents within Western North Atlantic Ocean, Gulf of Mexico and Caribbean Sea

    Science.gov (United States)

    2002-03-01

    important regions such as the Great Bahama Bank for which ETOPO5 indicates depths of hundreds of meters whereas DNC indicates depths on the order of...data are obtained from several sources: International Hydrographic Organization (IHO) Tidal Constituent Bank , 1991; U.S. Geological Survey, 1984...94.411667 IHO GOM -- -- 57 Campeche , Mexico 19.833333 -90.533333 IHO GOM -- -- 58 Progreso, Yucatan, Mexico 21.300000 -89.650000 IHO GOM -- -- 59 Middle

  20. The electrical conductivity of the upper mantle and lithosphere from the magnetic signal due to ocean tidal flow

    DEFF Research Database (Denmark)

    Schnepf, Neesha Regmi; Kuvshinov, Alexey; Grayver, Alexander

    Oceans cover about seventy percent of the Earth and yet the overwhelming majority of seismological or electromagnetic (EM) observatories are found on continents. This provides a challenge for understanding composition, structure, and dynamics of Earth’s lithosphere and upper mantle in oceanic reg...... satellite and seafloor magnetic signals from the M2 ocean tide. With these data we also make an attempt to detect lateral variability of the Earth’s conductivity....

  1. Marine Hydrokinetic (MHK) Energy Conversion Research at UNH: From Fundamental Studies of Hydrofoil Sections, to Moderate Reynolds Number Turbine Tests in a Tow Tank, to Open Water Deployments at Tidal Energy Test Sites (Invited)

    Science.gov (United States)

    Wosnik, M.; Bachant, P.; Nedyalkov, I.; Rowell, M.; Dufresne, N.; Lyon, V.

    2013-12-01

    We report on research related to MHK turbines at the Center for Ocean Renewable Energy (CORE) at the University of New Hampshire (UNH). The research projects span varies scales, levels of complexity and environments - from fundamental studies of hydrofoil sections in a high speed water tunnel, to moderate Reynolds number turbine tests with inflow and wake studies in a large cross-section tow tank, to deployments of highly instrumented process models at tidal energy test sites in New England. A concerted effort over the past few years has brought significant new research infrastructure for marine hydrokinetic energy conversion online at UNH-CORE. It includes: a high-speed cavitation tunnel with independent control of velocity and pressure; a highly accurate tow mechanism, turbine test bed and wake traversing system for the 3.7m x 2.4m cross-section UNH tow tank; a 10.7m x 3.0m tidal energy test platform which can accommodate turbines up to 1.5m in diameter, for deployments at the UNH-CORE Tidal Energy Test Site in Great Bay Estuary, NH, a sheltered 'nursery site' suitable for intermediate scale tidal energy conversion device testing with peak currents typically above 2 m/s during each tidal cycle. Further, a large boundary layer wind tunnel, the new UNH Flow Physics Facility (W6.0m x H2.7m xL72m) is being used for detailed turbine wake studies, producing data and insight also applicable to MHK turbines in low Froude number deployments. Bi-directional hydrofoils, which perform equally well in either flow direction and could avoid the use of complex and maintenance-intensive yaw or blade pitch mechanisms, are being investigated theoretically, numerically and experimentally. For selected candidate shapes lift, drag, wake, and cavitation inception/desinence are measured. When combined with a cavitation inception model for MHK turbines, this information can be used to prescribe turbine design/operational parameters. Experiments were performed with a 1m diameter and 1m

  2. Tidal energy site - Tidal energy site mammal/bird survey

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A vessel-based line visual transect survey was conducted for birds and marine mammals near the proposed Snohomish County PUD Admiralty Inlet tidal energy site...

  3. Oscillating Hydrofoils for Tidal Energy Extraction: Experiments, Simulations and Salt Water Field Tests

    Science.gov (United States)

    Mandre, S.; Franck, J.; Breuer, K.; Fawzi, A.; Cardona, J.; Miller, M. J.; Su, Y.; Medina, A.; Loera Loera, C.; Junquera, E.; Simeski, F.; Volkmann, K.; Lorick, R.; Cowles, S.; Luiz Rocha Ribeiro, B.; Winckler, S.; Derecktor, T.

    2015-12-01

    We report on the development of a new oscillating hydrofoil technology for tidal flow energy harvesting. A series of flume experiments and computational fluid dynamics (CFD) simulations have been performed over a wide range of frequencies, f, heave amplitudes, h, and pitch angles, θ. The flume model has chord, c, of 10 cm and aspect ratio of 4.5. Mechanical power extracted is estimated from the foil trajectory, force and moment data. A robust real-time algorithm has been developed to identify the kinematics that optimizes either the total power or the Betz efficiency. Optimal efficiency is found when the pitch and heave cycles are 90 degrees out of phase, oscillating at a reduced frequency, fc/U, of approximately 0.15, with a heave amplitude of approximately 1c, and a pitch amplitude of θ=75 degrees. The high pitch amplitude and sharp leading edge of the foil generates a transient leading edge vortex on the suction side of the foil, significantly enhancing the vertical force and power. The optimal frequency ensures that the vortex generation and ultimate shedding maximize these unsteady hydrodynamic effects. The flume results, including power and efficiency, as well as flow visualization and particle image velocimetry (PIV) exhibit excellent agreement with the CFD. Furthermore, extensive CFD and physical experiments have been performed to investigate the effects of operating in confined or shallow channels. It is found that the efficiency and power generation can significantly increase in confined areas due to the acceleration of the freestream flow around the device. Finally, the Leading Edge team has designed, built, and as of this date, is currently field-testing a 1kW prototype device consisting of two foils operating in parallel. The prototype is attached to the underside of a pontoon boat, and testing is currently underway in the Narragansett Bay near Providence RI. On completion of the field tests, in October 2015, data from the prototype will be analyzed

  4. Monthly and Fortnightly Tidal Variations of the Earth's Rotation Rate Predicted by a TOPEX/POSEIDON Empirical Ocean Tide Model

    Science.gov (United States)

    Desai, S.; Wahr, J.

    1998-01-01

    Empirical models of the two largest constituents of the long-period ocean tides, the monthly and the fortnightly constituents, are estimated from repeat cycles 10 to 210 of the TOPEX/POSEIDON (T/P) mission.

  5. Tidal and atmospheric forcing of the upper ocean in the Gulf of California. 2: Surface heat flux

    Science.gov (United States)

    Paden, Cynthia A.; Winant, Clinton D.; Abbott, Mark R.

    1993-01-01

    Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual surface heat flux for the area north of Guaymas and Santa Rosalia is estimated to be +74 W/sq m for the 1984-1985 time period. This is comparable to the +20-50 W/sq m previously obtained from heat and freshwater transport estimates made with hydrographic surveys from different years and months. The spatial distribution of the net surface heat flux shows a net gain of heat over the whole northern gulf. Except for a local maximum near San Esteban Island, the largest heat gain (+110-120 W/sq m) occurs in the Ballenas and Salsipuedes channels, where strong tidal mixing produces anomalously cold sea surface temperatures (SSTs) over much of the year. The lowest heat gain occurs in the Guayamas Basin (+40-50 W/sq m), where SSTs are consistently warmer. In the relatively shallow northern basin the net surface heat flux is farily uniform, with a net annual gain of approxmately +70 W/sq m. A local minimum in heat gain (approximately +60 W/sq m) is observed over the shelf in the northwest, where spring and summer surface temperatures are particularly high. A similar minimum in heat gain over the shelf was observed in a separate study in which historical SSTs and 7 years (1979-1986) of meteorological data from Puerto Penasco were used to estimate the net surface heat flux for the northern basin. In that study, however, the heat fluxes were higher, with a gain of +100 W/sq m over the shelf and +114 W/sq m in the northern basin. These larger values are directly attributable to the higher humidities in the 1979-1986 study compared to the 1984-1985 satellite study. High humidities reduce evaporation and the associated latent heat loss, promoting a net annual heat gain. In the norther Gulf of California, however, tidal mixing appears to play a key role in the observed gain of

  6. Tidal volume single breath washout of two tracer gases--a practical and promising lung function test.

    Directory of Open Access Journals (Sweden)

    Florian Singer

    Full Text Available BACKGROUND: Small airway disease frequently occurs in chronic lung diseases and may cause ventilation inhomogeneity (VI, which can be assessed by washout tests of inert tracer gas. Using two tracer gases with unequal molar mass (MM and diffusivity increases specificity for VI in different lung zones. Currently washout tests are underutilised due to the time and effort required for measurements. The aim of this study was to develop and validate a simple technique for a new tidal single breath washout test (SBW of sulfur hexafluoride (SF(6 and helium (He using an ultrasonic flowmeter (USFM. METHODS: The tracer gas mixture contained 5% SF(6 and 26.3% He, had similar total MM as air, and was applied for a single tidal breath in 13 healthy adults. The USFM measured MM, which was then plotted against expired volume. USFM and mass spectrometer signals were compared in six subjects performing three SBW. Repeatability and reproducibility of SBW, i.e., area under the MM curve (AUC, were determined in seven subjects performing three SBW 24 hours apart. RESULTS: USFM reliably measured MM during all SBW tests (n = 60. MM from USFM reflected SF(6 and He washout patterns measured by mass spectrometer. USFM signals were highly associated with mass spectrometer signals, e.g., for MM, linear regression r-squared was 0.98. Intra-subject coefficient of variation of AUC was 6.8%, and coefficient of repeatability was 11.8%. CONCLUSION: The USFM accurately measured relative changes in SF(6 and He washout. SBW tests were repeatable and reproducible in healthy adults. We have developed a fast, reliable, and straightforward USFM based SBW method, which provides valid information on SF(6 and He washout patterns during tidal breathing.

  7. Newtonian wormholes with spherical symmetry and tidal forces on test particles

    CERN Document Server

    Luz, Paulo

    2015-01-01

    A spherically symmetric wormhole in Newtonian gravitation in curved space, enhanced with a connection between the mass density and the Ricci scalar, is presented. The wormhole, consisting of two connected asymptotically flat regions, inhabits a spherically symmetric curved space. The gravitational potential, gravitational field and the pressure that supports the fluid that permeates the Newtonian wormhole are computed. Particle dynamics and tidal effects in this geometry are studied. The possibility of having Newtonian black holes in this theory is sketched.

  8. Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric Pressure, Ocean Tidal, and Surface Water Excitation

    Science.gov (United States)

    Dong, D,; Gross, R.S.; Dickey, J.

    1996-01-01

    Monthly mean gravitational field parameters (denoted here as C(sub even)) that represent linear combinations of the primarily even degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National meteorological center (NMC) spanning 1983-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant cause of observed annual C(sub even) variations. Closure with observations is seen at the 1sigma level when atmospheric pressure, ocean tide and surface water effects are include. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C(sub even) variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

  9. Dissipation of Tidal Energy

    Science.gov (United States)

    2002-01-01

    The moon's gravity imparts tremendous energy to the Earth, raising tides throughout the global oceans. What happens to all this energy? This question has been pondered by scientists for over 200 years, and has consequences ranging from the history of the moon to the mixing of the oceans. Richard Ray at NASA's Goddard Space Flight Center, Greenbelt, Md. and Gary Egbert of the College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Ore. studied six years of altimeter data from the TOPEX/Poseidon satellite to address this question. According to their report in the June 15 issue of Nature, about 1 terawatt, or 25 to 30 percent of the total tidal energy dissipation, occurs in the deep ocean. The remainder occurs in shallow seas, such as on the Patagonian Shelf. 'By measuring sea level with the TOPEX/Poseidon satellite altimeter, our knowledge of the tides in the global ocean has been remarkably improved,' said Richard Ray, a geophysicist at Goddard. The accuracies are now so high that this data can be used to map empirically the tidal energy dissipation. (Red areas, above) The deep-water tidal dissipation occurs generally near rugged bottom topography (seamounts and mid-ocean ridges). 'The observed pattern of deep-ocean dissipation is consistent with topographic scattering of tidal energy into internal motions within the water column, resulting in localized turbulence and mixing', said Gary Egbert an associate professor at OSU. One important implication of this finding concerns the possible energy sources needed to maintain the ocean's large-scale 'conveyor-belt' circulation and to mix upper ocean heat into the abyssal depths. It is thought that 2 terawatts are required for this process. The winds supply about 1 terawatt, and there has been speculation that the tides, by pumping energy into vertical water motions, supply the remainder. However, all current general circulation models of the oceans ignore the tides. 'It is possible that properly

  10. NOAA Historical Tidal Current Data for the Coastal United States

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Knowledge of the timing and strength of tidal currents is extremely important for safe navigation in coastal waters. Tidal currents are almost always the strongest...

  11. NOAA Tidal Current Data for the Coastal United States

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Knowledge of the timing and strength of tidal currents is extremely important for safe navigation in coastal waters. Tidal currents are almost always the strongest...

  12. Tidal Energy.

    Science.gov (United States)

    Impact of Science on Society, 1987

    1987-01-01

    States that tidal power projects are feasible in a relatively limited number of locations around the world. Claims that together they could theoretically produce the energy equivalent to more than one million barrels of oil per year. (TW)

  13. Tidal power

    Energy Technology Data Exchange (ETDEWEB)

    Baker, A.C.

    1987-05-01

    The principal tidal power sites around the world are summarised, showing that the UK is fortunate in having three major potential sites. The first use of tidal power for generating electricity was a small scheme near Bristol built 56 years ago. Since then, the 240 MW Rance barrage and the recent 20 MW pilot 'Straflo' turbine installed at Annapolis Royal in the Bay of Funday are the main schemes built to date. These were built 'in the dry'. For an inlet off the White sea, North Russia, a samll tidal power plant was prefabricated complete and towed into position in the early 1960s. Alternative methods of operation are discussed and the economics of tidal power compared with thermal stations. Overall, the tides could be a highly predictable and substantial source of renewable energy whose development involves proven technology.

  14. Tidal Power Exploitation in Korea

    Science.gov (United States)

    Choi, Byung Ho; Kim, Kyeong Ok; Choi, Jae Cheon

    The highest tides in South Korea are found along the northwest coast between latitudes 36-38 degrees and the number of possible sites for tidal range power barrages to create tidal basins is great due to irregular coastlines with numerous bays. At present Lake Sihwa tidal power plant is completed. The plant is consisted of 10 bulb type turbines with 8 sluice gates. The installed capacity of turbines and generators is 254MW and annual energy output expected is about 552.7 GWh taking flood flow generation scheme. Three other TPP projects are being progressed at Garolim Bay (20 turbines with 25.4MW capacity), Kangwha (28 turbines with 25.4MW capacity), Incheon (44 or 48 turbines with 30 MW capacity) and project features will be outlined here. The introduction of tidal barrages into four major TPP projects along the Kyeonggi bay will render wide range of potential impacts. Preliminary attempts were performed to quantify these impacts using 2 D hydrodynamic model demonstrating the changes in tidal amplitude and phase under mean tidal condition, associated changes in residual circulation (indicator for SPM and pollutant dispersion), bottom stress (indicator for bedload movement), and tidal front (positional indicator for bio-productivity) in both shelf scale and local context. Tidal regime modeling system for ocean tides in the seas bordering the Korean Peninsula is designed to cover an area that is broad in scope and size, yet provide a high degree of resolution in strong tidal current region including off southwestern tip of the Peninsula (Uldolmok , Jangjuk, Wando-Hoenggan), Daebang Sudo (Channel) and Kyeonggi Bay. With this simulation system, real tidal time simulation of extended springneap cycles was performed to estimate spatial distribution of tidal current power potentials in terms of power density, energy density and then extrapolated annual energy density.

  15. The Kislaya Guba tidal power plant

    National Research Council Canada - National Science Library

    Bernshtein, L.B; Gavrilov, V.G; Gel'fer, S.L; Nehoroshev, N.N; Suponitskii, L.I; Usachev, I.N; Monosov, M.L; Silakov, V.N; Pylev, I.M; Platov, V.I; Vestfal, V.L; Trifel, M.S

    1977-01-01

    This book examines the experience of designing, constructing, and testing the experimental Kislaya Guba tidal power plant, which was created in order to examine new methods of utilizing tidal energy...

  16. Tides and tidal currents

    NARCIS (Netherlands)

    Roos, A.

    1997-01-01

    Basic phenomena, origin and generation of tides, analysis and prediction of tides, basic equation and types of long waves in one dimension, tidal propagation in one dimension, tidal propagation in two directions, analytical tidal computation, numerical tidal computation.

  17. DTP: a Tidal Power Revolution

    Science.gov (United States)

    Steijn, Robbert; Hulsbergen, Kees; van Banning, Gijs

    2013-04-01

    shape of the dam, on hmax. DTP deliberately causes a significant dynamic change in local tidal parameters. Consequently it will change large-scale flow, transport processes, waves, morphodynamics and biogeochemistry in its proximity and surroundings. Examples of morphodynamic responses are coastline re-adjustment, seafloor scouring and changes in seabed composition. This study will present an inventory of these effects, including a preliminary assessment for a hypothetical schematised case. References: Hulsbergen, K., e.a., 2012 Dynamic Tidal Power for Korea, 1st Asian Wave and Tidal Energy Conference (AWTECT), Nov. 2012 Mei, C.C., 2012 Note on tidal diffraction by a coastal barrier, Applied Ocean Research 36 (2012)

  18. Non-Tidal Ocean Loading Correction for the Argentinean-German Geodetic Observatory Using an Empirical Model of Storm Surge for the Río de la Plata

    Science.gov (United States)

    Oreiro, F. A.; Wziontek, H.; Fiore, M. M. E.; D'Onofrio, E. E.; Brunini, C.

    2017-08-01

    The Argentinean-German Geodetic Observatory is located 13 km from the Río de la Plata, in an area that is frequently affected by storm surges that can vary the level of the river over ±3 m. Water-level information from seven tide gauge stations located in the Río de la Plata are used to calculate every hour an empirical model of water heights (tidal + non-tidal component) and an empirical model of storm surge (non-tidal component) for the period 01/2016-12/2016. Using the SPOTL software, the gravimetric response of the models and the tidal response are calculated, obtaining that for the observatory location, the range of the tidal component (3.6 nm/s2) is only 12% of the range of the non-tidal component (29.4 nm/s2). The gravimetric response of the storm surge model is subtracted from the superconducting gravimeter observations, after applying the traditional corrections, and a reduction of 7% of the RMS is obtained. The wavelet transform is applied to the same series, before and after the non-tidal correction, and a clear decrease in the spectral energy in the periods between 2 and 12 days is identify between the series. Using the same software East, North and Up displacements are calculated, and a range of 3, 2, and 11 mm is obtained, respectively. The residuals obtained after applying the non-tidal correction allow to clearly identify the influence of rain events in the superconducting gravimeter observations, indicating the need of the analysis of this, and others, hydrological and geophysical effects.

  19. Tidal variations of earth rotation

    Science.gov (United States)

    Yoder, C. F.; Williams, J. G.; Parke, M. E.

    1981-01-01

    The periodic variations of the earths' rotation resulting from the tidal deformation of the earth by the sun and moon were rederived including terms with amplitudes of 0.002 millisec and greater. The series applies to the mantle, crust, and oceans which rotate together for characteristic tidal periods; the scaling parameter is the ratio of the fraction of the Love number producing tidal variations in the moment of inertia of the coupled mantle and oceans (k) to the dimensionless polar moment of inertia of the coupled moments (C). The lunar laser ranging data shows that k/C at monthly and fortnightly frequencies equals 0.99 + or - 0.15 and 0.99 + or - 0.20 as compared to the theoretical value of 0.94 + or - 0.04.

  20. Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Valeria Castellucci

    2015-04-01

    Full Text Available The power production of the linear generator wave energy converter developed at Uppsala University is affected by variations of mean sea level. The reason is that these variations change the distance between the point absorber located on the surface and the linear generator located on the seabed. This shifts the average position of the translator with respect to the center of the stator, thereby reducing the generator output power. A device mounted on the point absorber that compensates for tides of small range by regulating the length of the connection line between the buoy at the surface and the linear generator has been constructed and tested. This paper describes the electro-mechanical, measurement, communication and control systems installed on the buoy and shows the results obtained before its connection to the generator. The adjustment of the line was achieved through a linear actuator, which shortens the line during low tides and vice versa. The motor that drives the mechanical device was activated remotely via SMS. The measurement system that was mounted on the buoy consisted of current and voltage sensors, accelerometers, strain gauges and inductive and laser sensors. The data collected were transferred via Internet to a Dropbox server. As described within the paper, after the calibration of the sensors, the buoy was assembled and tested in the waters of Lysekil harbor, a few kilometers from the Uppsala University research site. Moreover, the performance of the sensors, the motion of the mechanical device, the power consumption, the current control strategy and the communication system are discussed.

  1. Salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

  2. Tidal phenomena in reservoirs; Fenomeno de mare em reservatorios

    Energy Technology Data Exchange (ETDEWEB)

    Pinilla Cortes, John Freddy

    1997-06-01

    This work models the oceanic tidal effect on reservoirs by coupling geomechanic principles with equations for fluid in a deformable porous media. The coupling revealed the importance of establishing properly the system compressibility under the various possible configurations of the loading system. The basic models for infinite reservoir, constant outer-pressure reservoir and closed reservoir were considered. It was verified that it was possible to apply the superposition of effects on the solution for the basic models by carrying a simple transformation on the solution variable. The problem was treated by in the context of test analysis, concerning dimensionless form of variables and the inclusion of well effects. The solution for the infinite reservoir including tidal effects. The solution for the infinite reservoir including tidal effects was obtained in the Laplace space and was inverted numerically by using Crump's routine. The results were incorporated to conventional type curves, and were validated by comparison with real and simulated pressure test data. Finally, alternate practices were suggested to integrate the well test analysis in reservoirs affected by the tidal effect. (author)

  3. University of Washington/ Northwest National Marine Renewable Energy Center Tidal Current Technology Test Protocol, Instrumentation, Design Code, and Oceanographic Modeling Collaboration: Cooperative Research and Development Final Report, CRADA Number CRD-11-452

    Energy Technology Data Exchange (ETDEWEB)

    Driscoll, Frederick R. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-11-01

    The University of Washington (UW) - Northwest National Marine Renewable Energy Center (UW-NNMREC) and the National Renewable Energy Laboratory (NREL) will collaborate to advance research and development (R&D) of Marine Hydrokinetic (MHK) renewable energy technology, specifically renewable energy captured from ocean tidal currents. UW-NNMREC is endeavoring to establish infrastructure, capabilities and tools to support in-water testing of marine energy technology. NREL is leveraging its experience and capabilities in field testing of wind systems to develop protocols and instrumentation to advance field testing of MHK systems. Under this work, UW-NNMREC and NREL will work together to develop a common instrumentation system and testing methodologies, standards and protocols. UW-NNMREC is also establishing simulation capabilities for MHK turbine and turbine arrays. NREL has extensive experience in wind turbine array modeling and is developing several computer based numerical simulation capabilities for MHK systems. Under this CRADA, UW-NNMREC and NREL will work together to augment single device and array modeling codes. As part of this effort UW NNMREC will also work with NREL to run simulations on NREL's high performance computer system.

  4. Trans World Tidal Gravity Profile.

    Science.gov (United States)

    1984-12-31

    2 :Areas added or modified in the SchwidersKi maps. 7 Asin’m AC TB, 6 R A cos a Figure 3 A observed vector (A amplitude, = : phase) R tidal vector ...for an elastic non-viscous earth with liquid core but oceanless (R : amplitude, zero phase) L ocean attraction and loading vector (L : amplitude, X...3M D 80KM CENTRO POLITECNICO- GEODESIA -U.F*PR. PROF. CGEMAEL GRAVIMETRE GEODYNAMICS 783 PMELCHIOR - OBSERVATOIRE ROYAL DC BCLGIQUE CALIBRATION

  5. Tidal power in Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Aisiks, E.G.

    1993-03-01

    This presentation describes the tidal power potential of Argentina and the current status of its utilization. The topics of the presentation include tidal power potential, electric production of the region and the Argentine share of production and consumption, conventional hydroelectric potential, economic feasibility of tidal power production, and the general design and feasibility of a tidal power plant planned for the San Jose Gulf.

  6. Testing Predictions of Continental Insulation using Oceanic Crustal Thicknesses

    Science.gov (United States)

    Hoggard, Mark; Shorttle, Oliver; White, Nicky

    2016-04-01

    The thermal blanketing effect of continental crust has been predicted to lead to elevated temperatures within the upper mantle beneath supercontinents. Initial break-up is associated with increased magmatism and the generation of flood basalts. Continued rifting and sea-floor spreading lead to a steady reduction of this thermal anomaly. Recently, evidence in support of this behaviour has come from the major element geochemistry of mid-ocean ridge basalts, which suggest excess rifting temperatures of ˜ 150 °C that decay over ˜ 100 Ma. We have collated a global inventory of ˜ 1000 seismic reflection profiles and ˜ 500 wide-angle refraction experiments from the oceanic realm. Data are predominantly located along passive margins, but there are also multiple surveys in the centres of the major oceanic basins. Oceanic crustal thickness has been mapped, taking care to avoid areas of secondary magmatic thickening near seamounts or later thinning such as across transform faults. These crustal thicknesses are a proxy for mantle potential temperature at the time of melt formation beneath a mid-ocean ridge system, allowing us to quantify the amplitude and duration of thermal anomalies generated beneath supercontinents. The Jurassic break-up of the Central Atlantic and the Cretaceous rifting that formed the South Atlantic Ocean are both associated with excess temperatures of ˜ 50 °C that have e-folding times of ˜ 50 Ma. In addition to this background trend, excess temperatures reach > 150 °C around the region of the Rio Grande Rise, associated with the present-day Tristan hotspot. The e-folding time of this more local event is ˜ 10 Ma, which mirrors results obtained for the North Atlantic Ocean south of Iceland. In contrast, crustal thicknesses from the Pacific Ocean reveal approximately constant potential temperature through time. This observation is in agreement with predictions, as the western Pacific was formed by rifting of an oceanic plate. In summary

  7. Numerical study of the effects of mangrove areas and tidal flats on tides: A case study of Darwin Harbour, Australia

    Science.gov (United States)

    Li, Li; Wang, Xiao Hua; Williams, David; Sidhu, Harvinder; Song, Dehai

    2012-06-01

    The tidal dynamics of Darwin Harbour, Australia, are simulated using a finite volume coastal ocean model. The calibrated model agreed well with the observed sea surface elevation and current velocity. Results indicate that the harbor's hydrodynamics are driven mainly by the tides, with wind and river inputs playing only small roles. The M2 tide is dominant, with amplitude 1.7 m and peak current speed 3.0 m s-1. Sensitivity tests using the model indicate that the mangrove areas and tidal flats play crucial roles in modulating tidal amplitudes and phases in the embayments, especially for the shallow water tides such as M4. Removal of the mangrove areas and tidal flats from Darwin Harbour would dampen the M2 amplitude due to decreased shoaling effects but generate a 75.0% greater M4 amplitude in parts of the harbor. Mangrove areas and tidal flats also affect tidal asymmetry through the changing amplitudes and phases of mainly the M2 and M4 tides. In Darwin Harbour, tidal asymmetry, measured by elevation and current skewness, would increase by up to 100% if the mangrove areas were removed. If the tidal flats were removed as well, the increase would be 120%. Therefore, reclamation of the mangrove areas and tidal flats may cause sediment siltation as a result of increased flood dominance. Although this study is site-specific, the model and our findings have a wider applicability to the effects of mangrove areas and tidal flats on tides and sediment transport in harbors and estuaries.

  8. Bathymetric Control of Front Generation in a Tidal River

    Science.gov (United States)

    2012-06-01

    important linkages between the land margin and the coastal ocean serving as major export pathways for terrigenous sediment (Childers and Day, 1990a... sediment dynamics (Largier, 1993). Tidal creeks are small costal inlets or else side channels or tributaries of tidal rivers, the flow in which is...relative strengths of the tidal flows and the river flows. As the river water picks up much sediment in the shallow side creek, the action of the shoals

  9. Tidal Energy Dissipation from Topex/Poseidon

    Science.gov (United States)

    Ray, Richard D.; Egbert, G. D.; Smith, David E. (Technical Monitor)

    2000-01-01

    In a recent paper ({\\it Nature, 405,} 775, 2000) we concluded that 25 to 30\\% of the ocean's tidal energy dissipation, or about 1 terawatt, occurs in the deep ocean, with the remaining 2.6 TW in shallow seas. The physical mechanism for deep-ocean dissipation is apparently scattering of the surface tide into internal modes; Munk and Wunsch have suggested that this mechanism may provide half the power needed for mixing the deep-ocean. This paper builds further evidence for $1\\pm 0.2$ TW of deep-ocean dissipation. The evidence is extracted from tidal elevations deduced from seven years of Topex/Poseidon satellite altimeter data. The dissipation rate Is formed as a balance between the rate of working by tidal forces and the energy flux divergence. While dynamical assumptions are required to compute fluxes, area integrals of the energy balance are, owing to the tight satellite constraints, remarkably insensitive to these assumptions. A large suite of tidal solutions based on a wide range of dynamical assumptions, on perturbations to bathymetric models, and on simulated elevation data are used to assess this sensitivity. These and Monte Carlo error fields from a generalized inverse model are used to establish error uncertainties.

  10. Tidal Energy Research

    Energy Technology Data Exchange (ETDEWEB)

    Stelzenmuller, Nickolas [Univ of Washington; Aliseda, Alberto [Univ of Washington; Palodichuk, Michael [Univ of Washington; Polagye, Brian [Univ of Washington; Thomson, James [Univ of Washington; Chime, Arshiya [Univ of Washington; Malte, Philip [Univ of washington

    2014-03-31

    This technical report contains results on the following topics: 1) Testing and analysis of sub-scale hydro-kinetic turbines in a flume, including the design and fabrication of the instrumented turbines. 2) Field measurements and analysis of the tidal energy resource and at a site in northern Puget Sound, that is being examined for turbine installation. 3) Conceptual design and performance analysis of hydro-kinetic turbines operating at high blockage ratio, for use for power generation and flow control in open channel flows.

  11. Global Ocean Forecast System 3.1 Validation Test

    Science.gov (United States)

    2017-05-04

    mission (Kurtz et al., 2013) collects airborne remote sensing measurements to bridge the gap between NASA’s Ice , Cloud and land Elevation Satellite...Forecast System (GOFS) 3.1 is comprised of the 1/12° HYbrid Coordinate Ocean Model that is two-way coupled to the Community Ice CodE in a daily update...structure, the surface mixed layer, the location of mesoscale features, and ice concentration, thickness and drift in both hemispheres. It is scheduled to

  12. Inundation Mapping Tidal Surface - Mean Higher High Water

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data are a derived product of the NOAA VDatum tool and they extend the tool's Mean Higher High Water (MHHW) tidal datum conversion inland beyond its original...

  13. Estuary-wide genetic stock distribution and salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

  14. Testing river surveying techniques in tidal environments: example from an actively meandering channel surveyed with TLS (Mont Saint-Michel bay, France)

    Science.gov (United States)

    Leroux, J.; Lague, D.

    2013-12-01

    factor 2 during summer/autumn spring tides at the peak of pioneer vegetation development. Bank erosion and channel dynamics show a marked difference for tides reaching the salt marsh elevation. For tides below marsh elevation, bank erosion is negligible and the channel is systematically aggrading at a rate proportional to HWL. For tides flooding the marsh, mean bank erosion increases linearly with HWL and the channel shifts to erosion for over-marsh tides. Using flow velocity and SSC data we show that sedimentation on the inner bar results from the penetration of the turbid flood onto the inner bar. Spatial variability in sedimentation results from local interactions between flow and vegetation. On the contrary, bank erosion is dominated by the very large ebb peak velocity developing during spring tides. The very non-linear sensitivity to HWL of bank erosion and channel erosion means that the rate of evolution is largely controlled by the largest tides of the year. This in turn yields very large annual fluctuations in the rates of meander evolution. These results demonstrate that mega-tidal environment can offer an alternative setting to test new survey techniques aimed at river monitoring and can shed light in the elementary processes governing biogeomorphological interactions.

  15. Slow Strain Rate Testing for Hydrogen Embrittlement Susceptibility of Alloy 718 in Substitute Ocean Water

    Science.gov (United States)

    LaCoursiere, M. P.; Aidun, D. K.; Morrison, D. J.

    2017-05-01

    The hydrogen embrittlement susceptibility of near-peak-aged UNS N07718 (Alloy 718) was evaluated by performing slow strain rate tests at room temperature in air and substitute ocean water. Tests in substitute ocean water were accomplished in an environmental cell that enabled in situ cathodic charging under an applied potential of -1.1 V versus SCE. Some specimens were cathodically precharged for 4 or 16 weeks at the same potential in a 3.5 wt.% NaCl-distilled water solution at 50 °C. Unprecharged specimens tested in substitute ocean water exhibited only moderate embrittlement with plastic strain to failure decreasing by about 20% compared to unprecharged specimens tested in air. However, precharged specimens exhibited significant embrittlement with plastic strain to failure decreasing by about 70%. Test environment (air or substitute ocean water with in situ charging) and precharge time (4 or 16 weeks) had little effect on the results of the precharged specimens. Fracture surfaces of precharged specimens were typical of hydrogen embrittlement and consisted of an outer brittle ring related to the region in which hydrogen infused during precharging, a finely dimpled transition zone probably related to the region where hydrogen was drawn in by dislocation transport, and a central highly dimpled ductile region. Fracture surfaces of unprecharged specimens tested in substitute ocean water consisted of a finely dimpled outer ring and heavily dimpled central region typical of ductile fracture.

  16. VISCOELASTIC MODELS OF TIDALLY HEATED EXOMOONS

    Energy Technology Data Exchange (ETDEWEB)

    Dobos, Vera [Konkoly Thege Miklos Astronomical Institute, Research Centre of Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Konkoly Thege Miklós út 15-17, Budapest (Hungary); Turner, Edwin L., E-mail: dobos@konkoly.hu [Department of Astrophysical Sciences, Princeton University, 08544, 4 Ivy Lane, Peyton Hall, Princeton, NJ (United States)

    2015-05-01

    Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life has been intensely studied on solar system moons such as Europa or Enceladus where the surface ice layer covers a tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. To study the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than the widely used, so-called fixed Q models because it takes into account the temperature dependence of the tidal heat flux and the melting of the inner material. Using this model, we introduced the circumplanetary Tidal Temperate Zone (TTZ), which strongly depends on the orbital period of the moon and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ using both models. We have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ with orbital periods between 0.1 and 3.5 days than the fixed Q model for plausible distributions of physical and orbital parameters. The viscoelastic model provides more promising results in terms of habitability because the inner melting of the body moderates the surface temperature, acting like a thermostat.

  17. Research Article. Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata

    Directory of Open Access Journals (Sweden)

    Richter A.

    2017-02-01

    Full Text Available We present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory’s future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loads.

  18. Experimentally Testing Hydrothermal Vent Origin of Life on Enceladus and Other Icy/Ocean Worlds.

    Science.gov (United States)

    Barge, Laura M; White, Lauren M

    2017-09-01

    We review various laboratory strategies and methods that can be utilized to simulate prebiotic processes and origin of life in hydrothermal vent systems on icy/ocean worlds. Crucial steps that could be simulated in the laboratory include simulations of water-rock chemistry (e.g., serpentinization) to produce hydrothermal fluids, the types of mineral catalysts and energy gradients produced in vent interfaces where hydrothermal fluids interface with the surrounding seawater, and simulations of biologically relevant chemistry in flow-through gradient systems (i.e., far-from-equilibrium experiments). We describe some examples of experimental designs in detail, which are adaptable and could be used to test particular hypotheses about ocean world energetics or mineral/organic chemistry. Enceladus among the ocean worlds provides an ideal test case, since the pressure at the ocean floor is more easily simulated in the lab. Results for Enceladus could be extrapolated with further experiments and modeling to understand other ocean worlds. Key Words: Enceladus-Ocean worlds-Icy worlds-Hydrothermal vent-Iron sulfide-Gradient. Astrobiology 17, 820-833.

  19. Short period tidal variations of earth rotation

    Science.gov (United States)

    Yoder, C. F.; Williams, J. G.; Parke, M. E.; Dickey, J. O.

    1981-01-01

    It is explained that the tidal deformation of the earth's polar moment of inertia by the moon and sun cause periodic variations in rotation. The short period oscillations give rise to a meter-sized, diurnal signature in the lunar laser ranging data obtained at McDonald Observatory. A solution is given for the scale parameter k/C at fortnightly and monthly tidal frequencies. The results are compared with those obtained by other investigators and with a theoretical estimate which includes the effect of oceans and a decoupled fluid core.

  20. Tidal Energy Update 2009

    OpenAIRE

    O'Rourke, Fergal; Boyle, Fergal; Reynolds, Anthony

    2010-01-01

    Tidal energy has the potential to play a valuable part in a sustainable energy future. It is an extremely predictable energy source, depending only on the gravitational pull of the moon and the sun and the centrifugal forces created by the rotation of the earth-moon system. Tidal energy has been exploited on a significant scale since the construction of the La Rance tidal barrage in France in 1967. A tidal barrage utilises the potential energy of the tide and has proven to be very successful,...

  1. Reedsport PB150 Deployment and Ocean Test Project

    Energy Technology Data Exchange (ETDEWEB)

    Hart, Phil [Ocean Power Technologies Inc., Pennington, NJ (United States)

    2016-06-03

    As the first utility scale wave power project in the US, the Wave Power Demonstration Project at Reedsport (OR) was planned to consist of 10 PowerBuoys (Phase II)1, located 2.5 miles off the coast. U.S. Department of Energy (DOE) funding under a prior DOE Grant (DE-FG36-08GO88017) along with funding from PNGC Power, an Oregon-based electric power cooperative, was utilized for the design completion, fabrication, assembly and factory testing of the first PowerBuoy for the Reedsport project. The design and fabrication of the first PowerBuoy and factory testing of the power take-off subsystem were completed, and the power take-off subsystem was successfully integrated into the spar at the fabricator’s facility in Oregon. The objectives of this follow-on grant were: advance PB150B design from TRL 5/6 to TRL 7/8; deploy a single PB150 and operate autonomously for 2 years; establish O&M costs; collect environmental information; and establish manufacturing methodologies.

  2. The origin of neap-spring tidal cycles

    Science.gov (United States)

    Kvale, E.P.

    2006-01-01

    The origin of oceanic tides is a basic concept taught in most introductory college-level sedimentology/geology, oceanography, and astronomy courses. Tides are typically explained in the context of the equilibrium tidal theory model. Yet this model does not take into account real tides in many parts of the world. Not only does the equilibrium tidal model fail to explicate amphidromic circulation, it also does not explain diurnal tides in low latitude positions. It likewise fails to explain the existence of tide-dominated areas where neap-spring cycles are synchronized with the 27.32-day orbital cycle of the Moon (tropical month), rather than with the more familiar 29.52-day cycle of lunar phases (synodic month). Both types of neap-spring cycles can be recognized in the rock record. A complete explanation of the origin of tides should include a discussion of dynamic tidal theory. In the dynamic tidal model, tides resulting from the motions of the Moon in its orbit around the Earth and the Earth in its orbit around the Sun are modeled as products of the combined effects of a series of phantom satellites. The movement of each of these satellites, relative to the Earth's equator, creates its own tidal wave that moves around an amphidromic point. Each of these waves is referred to as a tidal constituent. The geometries of the ocean basins determine which of these constituents are amplified. Thus, the tide-raising potential for any locality on Earth can be conceptualized as the result of a series of tidal constituents specific to that region. A better understanding of tidal cycles opens up remarkable opportunities for research on tidal deposits with implications for, among other things, a more complete understanding of the tidal dynamics responsible for sediment transport and deposition, changes in Earth-Moon distance through time, and the possible influences tidal cycles may exert on organisms. ?? 2006 Elsevier B.V. All rights reserved.

  3. Long-Period Tidal Variations of the Earth's Rotation Rate

    Science.gov (United States)

    Desai, S.; Gross, R.; Wahr, J.

    1999-01-01

    Long-period tidal variations of the Earth's rotation rate are caused by the redistribution of mass associated with the respective elastic solid Earth tides, the ocean tide heights, and the anelasticity of the Earth's mantle, and by the relative angular momentum associated with the long-period ocean tide currents.

  4. An equilibrium profile model for tidal environments

    Directory of Open Access Journals (Sweden)

    A. M. Bernabeu

    2002-12-01

    Full Text Available During a full tidal cycle, the beach profile is exposed to continuously changing hydrodynamical conditions. Consequently, the profile evolves constantly to adapt to these changes. The equilibrium condition on tidal beaches is defined in terms of the relative occurrence of swash, surf zone and shoaling processes. We have assumed that the tidal beach profile is in equilibrium when the net sediment transport along a tidal cycle is zero. In this model the contribution of swash is considered negligible. A simple and easy-to-apply equilibrium profile formulation is proposed. This model is based on the assumption that surf zone processes dominate the profile morphology wherever wave breaking occurs during the tidal cycle. The obtained equilibrium profile is valid from the high tide level to the breaker point at low tide level. The tidal influence on the profile morphology is the lengthening of the surf profile. The higher the tidal range, the longer the surf profile. The model was tested against field and laboratory data, showing reasonable predictions of measured beach profiles.

  5. Greenland Tidal Pools as Hot Spots for Ecosystem Metabolism and Calcification

    KAUST Repository

    Duarte, Carlos M.

    2018-01-18

    The hypothesis that Arctic tidal pools provide environmental conditions suitable for calcifiers during summer, thereby potentially providing refugia for calcifiers in an acidifying Arctic Ocean, was tested on the basis of measurements conducted during two midsummers (2014 and 2016) in tidal pools colonised by a community composed of macroalgae and calcifiers in Disko Bay, Greenland (69° N). The tidal pools exhibited steep diurnal variations in temperature from a minimum of about 6 °C during the night to a maximum of almost 18 °C in the afternoon, while the temperature of the surrounding shore water was much lower, typically in the range 3 to 8 °C. O2 concentrations in the tidal pools were elevated relative to those in the adjacent open waters, by up to 11 mg O2 L−1, and exhibited heavy super-saturation (up to > 240%) during daytime emersion, reflecting intense and sustained photosynthetic rates of the tidal macroalgae. The intense photosynthetic activity of the seaweeds resulted in the drawdown of pCO2 concentrations in the pools during the day to levels down to average (±SE) values of 66 ± 18 ppm, and a minimum recorded value of 14.7 ppm, corresponding to pH levels as high as 8.69 ± 0.08, as compared to CO2 levels of 256 ± 4 and pH levels of 8.14 ± 0.01 in the water flooding the pools during high tide. The corresponding Ωarag reached 5.04 ± 0.49 in the pools as compared to 1.55 ± 0.02 in the coastal waters flooding the pools. Net calcification averaged 9.6 ± 5.6 μmol C kg−1 h−1 and was strongly and positively correlated with calculated net ecosystem production rates, which averaged 27.5 ± 8.6 μmol C kg−1 h−1. Arctic tidal pools promote intense metabolism, creating conditions suitable for calcification during the Arctic summer, and can, therefore, provide refugia from ocean acidification to vulnerable calcifiers as extended periods of continuous light during summer are conducive to suitable conditions

  6. Results from Tests of Direct Wave Mixing in the Ocean’s Surface Mixed Layer

    Science.gov (United States)

    2012-11-16

    The parameterization of direct wave mixing proposed by Qiao et al. (2004) was tested with data from the Ocean Weathership Station (OWS) Papa in the...improved the agreement between the predicted and observed sea-surface temperature (SST) at Papa . However, the results of the tests showed two significant...problems with the parameterization of the wave mixing. At OWS Papa , the wave mixing caused too much diffusion of heat through the seasonal

  7. Tidal Love numbers of membrane worlds: Europa, Titan, and Co

    CERN Document Server

    Beuthe, Mikael

    2015-01-01

    Under tidal forcing, icy satellites with subsurface oceans deform as if the surface were a membrane stretched around a fluid layer. `Membrane worlds' is thus a fitting name for these bodies and membrane theory provides the perfect toolbox to predict tidal effects. I describe here a new membrane approach to tidal perturbations based on the general theory of viscoelastic-gravitational deformations of spherically symmetric bodies. The massive membrane approach leads to explicit formulas for viscoelastic tidal Love numbers which are exact in the limit of zero crust thickness. The accuracy on $k_2$ and $h_2$ is better than one percent if the crust thickness is less than five percents of the surface radius, which is probably the case for Europa and Titan. The new approach allows for density differences between crust and ocean and correctly includes crust compressibility. This last feature makes it more accurate than the propagation matrix method. Membrane formulas factorize shallow and deep interior contributions, ...

  8. 33 CFR 334.590 - Atlantic Ocean off Cape Canaveral, Fla.; Air Force missile testing area, Patrick Air Force Base...

    Science.gov (United States)

    2010-07-01

    ..., Fla.; Air Force missile testing area, Patrick Air Force Base, Fla. 334.590 Section 334.590 Navigation... RESTRICTED AREA REGULATIONS § 334.590 Atlantic Ocean off Cape Canaveral, Fla.; Air Force missile testing area, Patrick Air Force Base, Fla. (a) The danger zone. An area in the Atlantic Ocean immediately offshore from...

  9. Tidal viscosity of Enceladus

    Science.gov (United States)

    Efroimsky, Michael

    2018-01-01

    In the preceding paper (Efroimsky, 2017), we derived an expression for the tidal dissipation rate in a homogeneous near-spherical Maxwell body librating in longitude. Now, by equating this expression to the outgoing energy flux due to the vapour plumes, we estimate the mean tidal viscosity of Enceladus, under the assumption that the Enceladean mantle behaviour is Maxwell. This method yields a value of 0.24 × 1014 Pa s for the mean tidal viscosity, which is very close to the viscosity of ice near the melting point.

  10. Slope-induced tidal straining: Analysis of rotational effects

    Science.gov (United States)

    Schulz, Kirstin; Endoh, Takahiro; Umlauf, Lars

    2017-03-01

    Tidal straining is known to be an important factor for the generation of residual currents and transports of suspended matter in the coastal ocean. Recent modeling studies and field experiments have revealed a new type of "slope-induced" tidal straining, in which the horizontal density gradient required for this process is induced by the presence of a slope rather than by river runoff (as in classical tidal straining). Slope-induced tidal straining is investigated here with the help of an idealized numerical model, and results are compared to a recent data set from the East China Sea providing first direct observational evidence. The focus of this study is on the effect of rotation that was ignored in previous investigations. The model is shown to reproduce the key features of the observations, in particular the strain-induced generation of unstable stratification in the bottom boundary layer during periods of upslope flow. Rotation effects are found to significantly reduce the upslope tidal pumping of suspended material and also give rise to a newly identified pumping mechanism that results in a vigorous transport of suspended material along the slope. It is shown that slope-induced tidal straining is likely to be relevant for a wide range of oceanic slopes exposed to tidal motions.

  11. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  12. Sustainable tidal power

    Energy Technology Data Exchange (ETDEWEB)

    Walsum, E. van

    2003-07-01

    North America is increasingly searching for ways to achieve energy self-sufficiency. This paper discussed the tidal power potential of the Upper Bay of Fundy, located on Canada's east coast. The Bay of Fundy has the largest tides in the world. It is also close to a major electricity market. Tidal power plants could mean substantial quantities of clean, renewable energy. Some of the environmental concerns with the development of tidal power plants on the Bay of Fundy include: siltation, shorebird survival, fish-stock survival, sea-mammal survival, drainage of agricultural lands, and changes in the tidal regime of the Bay of Fundy-Gulf of Maine Basin. In this paper, the author proved that it is possible to qualitatively assess those concerns, but that the quantitative assessment is more complex. A quantitative assessment of the effect on living organisms would require assessing the overall performance of an ecologically designed, built and operated pilot tidal power plant. The author argued that a full-fledged tidal power plant construction can take place once a pilot plant has been proven to operate symbiotically with a thriving marine shore-based flora and fauna. 18 refs., 2 tabs., 6 figs.

  13. NOAA Water Level (Tidal) Data of 205 Stations for the Coastal United States and Other Non-U.S. Sites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The National Ocean Service (NOS) maintains a long-term database containing water level measurements and derived tidal data for coastal waters of the United States...

  14. Design and analysis of a natural-gradient ground-water tracer test in a freshwater tidal wetland, West Branch Canal Creek, Aberdeen Proving Ground, Maryland

    Science.gov (United States)

    Olsen, Lisa D.; Tenbus, Frederick J.

    2005-01-01

    A natural-gradient ground-water tracer test was designed and conducted in a tidal freshwater wetland at West Branch Canal Creek, Aberdeen Proving Ground, Maryland. The objectives of the test were to characterize solute transport at the site, obtain data to more accurately determine the ground-water velocity in the upper wetland sediments, and to compare a conservative, ionic tracer (bromide) to a volatile tracer (sulfur hexafluoride) to ascertain whether volatilization could be an important process in attenuating volatile organic compounds in the ground water. The tracer test was conducted within the upper peat unit of a layer of wetland sediments that also includes a lower clayey unit; the combined layer overlies an aquifer. The area selected for the test was thought to have an above-average rate of ground-water discharge based on ground-water head distributions and near-surface detections of volatile organic compounds measured in previous studies. Because ground-water velocities in the wetland sediments were expected to be slow compared to the underlying aquifer, the test was designed to be conducted on a small scale. Ninety-seven ?-inch-diameter inverted-screen stainless-steel piezometers were installed in a cylindrical array within approximately 25 cubic feet (2.3 cubic meters) of wetland sediments, in an area with a vertically upward hydraulic gradient. Fluorescein dye was used to qualitatively evaluate the hydrologic integrity of the tracer array before the start of the tracer test, including verifying the absence of hydraulic short-circuiting due to nonnatural vertical conduits potentially created during piezometer installation. Bromide and sulfur hexafluoride tracers (0.139 liter of solution containing 100,000 milligrams per liter of bromide ion and 23.3 milligrams per liter of sulfur hexafluoride) were co-injected and monitored to generate a dataset that could be used to evaluate solute transport in three dimensions. Piezometers were sampled 2 to 15 times

  15. Thermal Coupling Between the Ocean and Mantle of Europa: Implications for Ocean Convection

    Science.gov (United States)

    Soderlund, Krista M.; Schmidt, Britney E.; Wicht, Johannes; Blankenship, Donald D.

    2015-11-01

    Magnetic induction signatures at Europa indicate the presence of a subsurface ocean beneath the cold icy crust. The underlying mantle is heated by radioactive decay and tidal dissipation, leading to a thermal contrast sufficient to drive convection and active dynamics within the ocean. Radiogenic heat sources may be distributed uniformly in the interior, while tidal heating varies spatially with a pattern that depends on whether eccentricity or obliquity tides are dominant. The distribution of mantle heat flow along the seafloor may therefore be heterogeneous and impact the regional vigor of ocean convection. Here, we use numerical simulations of thermal convection in a global, Europa-like ocean to test the sensitivity of ocean dynamics to variations in mantle heat flow patterns. Towards this end, three end-member cases are considered: an isothermal seafloor associated with dominant radiogenic heating, enhanced seafloor temperatures at high latitudes associated with eccentricity tides, and enhanced equatorial seafloor temperatures associated with obliquity tides. Our analyses will focus on convective heat transfer since the heat flux pattern along the ice-ocean interface can directly impact the ice shell and the potential for geologic activity within it.

  16. 33 CFR 334.1410 - Pacific Ocean, at Makapuu Point, Waimanalo, Island of Oahu, Hawaii, Makai Undersea Test Range.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean, at Makapuu Point, Waimanalo, Island of Oahu, Hawaii, Makai Undersea Test Range. 334.1410 Section 334.1410 Navigation and... RESTRICTED AREA REGULATIONS § 334.1410 Pacific Ocean, at Makapuu Point, Waimanalo, Island of Oahu, Hawaii...

  17. Tidal Heating in Multilayered Terrestrial Exoplanets

    Science.gov (United States)

    Henning, Wade G.; Hurford, Terry

    2014-01-01

    The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R(sub E) is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

  18. Tidal heating in multilayered terrestrial exoplanets

    Energy Technology Data Exchange (ETDEWEB)

    Henning, Wade G.; Hurford, Terry, E-mail: wade.g.henning@nasa.gov [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

    2014-07-01

    The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R{sub E} is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

  19. Tidal Love numbers of membrane worlds: Europa, Titan, and Co.

    Science.gov (United States)

    Beuthe, Mikael

    2015-09-01

    Under tidal forcing, icy satellites with subsurface oceans deform as if the surface were a membrane stretched around a fluid layer. 'Membrane worlds' is thus a fitting name for these bodies and membrane theory provides the perfect toolbox to predict tidal effects. I describe here a new membrane approach to tidal perturbations based on the general theory of viscoelastic-gravitational deformations of spherically symmetric bodies. The massive membrane approach leads to explicit formulas for viscoelastic tidal Love numbers which are exact in the limit of zero crust thickness. Formulas for load Love numbers come as a bonus. The accuracy on k2 and h2 is better than one percent if the crust thickness is less than five percents of the surface radius, which is probably the case for Europa and Titan. The new approach allows for density differences between crust and ocean and correctly includes crust compressibility. This last feature makes it more accurate than the incompressible propagator matrix method. Membrane formulas factorize shallow and deep interior contributions, the latter affecting Love numbers mainly through density stratification. I show that a screening effect explains why ocean stratification typically increases Love numbers instead of reducing them. For Titan, a thin and dense liquid layer at the bottom of a light ocean can raise k2 by more than ten percents. The membrane approach can also deal with dynamical tides in a non-rotating body. I show that a dynamical resonance significantly decreases the tilt factor and may thus lead to underestimating Europa's crust thickness. Finally, the dynamical resonance increases tidal deformations and tidal heating in the crust if the ocean thickness is of the order of a few hundred meters.

  20. On the superposition of bedforms in a tidal channel

    DEFF Research Database (Denmark)

    Winter, C; Vittori, G.; Ernstsen, V.B.

    2008-01-01

    High resolution bathymetric measurements reveal the super-imposition of bedforms in the Grådyb tidal inlet in the Danish Wadden Sea. Preliminary results of numerical model simulations are discussed: A linear stability model was tested to explain the large bedforms as being caused by tidal system ...

  1. Design and Performance of an Enhanced Bioremediation Pilot Test in a Tidal Wetland Seep, West Branch Canal Creek, Aberdeen Proving Ground, Maryland

    Science.gov (United States)

    Majcher, Emily H.; Lorah, Michelle M.; Phelan, Daniel J.; McGinty, Angela L.

    2009-01-01

    Because of a lack of available in situ remediation methods for sensitive wetland environments where contaminated groundwater discharges, the U.S. Geological Survey, in cooperation with the U.S. Army Garrison, Aberdeen Proving Ground, Maryland, conceived, designed, and pilot tested a permeable reactive mat that can be placed horizontally at the groundwater/surface-water interface. Development of the reactive mat was part of an enhanced bioremediation study in a tidal wetland area along West Branch Canal Creek at Aberdeen Proving Ground, where localized areas of preferential discharge (seeps) transport groundwater contaminated with carbon tetrachloride, chloroform, tetrachloroethene, trichloroethene, and 1,1,2,2-tetrachloroethane from the Canal Creek aquifer to land surface. The reactive mat consisted of a mixture of commercially available organic- and nutrient-rich peat and compost that was bioaugmented with a dechlorinating microbial consortium, WBC-2, developed for this study. Due to elevated chlorinated methane concentrations in the pilot test site, a layer of zero-valent iron mixed with the peat and compost was added at the base of the reactive mat to promote simultaneous abiotic and biotic degradation. The reactive mat for the pilot test area was designed to optimize chlorinated volatile organic compound degradation efficiency without altering the geotechnical and hydraulic characteristics, or creating undesirable water quality in the surrounding wetland area, which is referred to in this report as achieving geotechnical, hydraulic, and water-quality compatibility. Optimization of degradation efficiency was achieved through the selection of a sustainable organic reactive matrix, electron donor, and bioaugmentation method. Consideration of geotechnical compatibility through design calculations of bearing capacity, settlement, and geotextile selection showed that a 2- to 3-feet tolerable thickness of the mat was possible, with 0.17 feet settlement predicted for

  2. Tidal power plants in Russia

    Energy Technology Data Exchange (ETDEWEB)

    Bernshtein, L.B. (Hydroproject Assoc., Moscow (Russian Federation))

    1994-01-01

    This article examines the performance of tidal power plants in Russia and the expansion of tidal plant to new sites. The topics of the article include remote construction and transport techniques, pilot plant performance, economics and payback, and a review of global tidal power plant designs that are on hold due to economic problems relating to the global economy.

  3. In-stream PIT detection, estuary wetlands - Columbia River Estuary Tidal Habitats

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

  4. Operational Review of the First Wireline In Situ Stress Test in Scientific Ocean Drilling

    Directory of Open Access Journals (Sweden)

    Casey Moore

    2012-04-01

    Full Text Available Scientific ocean drilling’s first in situ stress measurement was made at Site C0009A during Integrated Ocean Drilling Program (IODP Expedition 319 as part of Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE Stage 2. The Modular Formation Dynamics Tester (MDT, Schlumbergerwireline logging tool was deployed in riser Hole C0009A to measure in situ formation pore pressure, formation permeability (often reported as mobility=permeability/viscosity, and the least principal stress (S3 at several isolated depths (Saffer et al., 2009; Expedition 319 Scientists, 2010. The importance of in situ stress measurements is not only for scientific interests in active tectonic drilling, but also for geomechanical and well bore stability analyses. Certain in situ tools were not previously available for scientific ocean drilling due to the borehole diameter and open hole limits of riserless drilling. The riser-capable drillship, D/V Chikyu,now in service for IODP expeditions, allows all of the techniques available to estimate the magnitudes and orientations of 3-D stresses to be used. These techniques include downhole density logging for vertical stress, breakout and caliper log analyses for maximum horizontal stress, core-based anelastic strain recovery (ASR, used in the NanTroSEIZE expeditions in 2007–2008, and leak-off test (Lin et al., 2008 and minifrac/hydraulic fracturing (NanTroSEIZE Expedition319 in 2009. In this report, the whole operational planning process related to in situ measurements is reviewed, and lessons learned from Expedition 319 are summarized for efficient planning and testing in the future.

  5. A calcium isotope test of end-Permian ocean acidification using biogenic apatite

    Science.gov (United States)

    Hinojosa, J.; Brown, S. T.; DePaolo, D. J.; Paytan, A.; Shen, S.; Chen, J.; Payne, J.

    2011-12-01

    Submarine erosional truncation of uppermost Permian carbonate strata has been interpreted to reflect ocean acidification coincident with the end-Permian mass extinction. Although this scenario is consistent with carbon isotope and paleontological data, several alternative scenarios, such as ocean overturn or collapse of the biological pump, can also account for the carbon isotope and paleontological evidence. Calcium isotopes provide a geochemical proxy to test between acidification and alternative scenarios. Specifically, a negative shift in the calcium isotope composition (δ44/40Ca) of seawater is predicted under the acidification scenario but not the alternatives. The δ44/40Ca of carbonate rocks from south China exhibits a negative excursion of approximately 0.3%, but this shift could result from either a change in the δ44/40Ca of seawater or a change in carbonate mineralogy because calcite and aragonite exhibit substantially different fractionation factors relative to seawater. To test whether the negative shift in δ44/40Ca reflects seawater δ44/40Ca or carbonate mineralogy, we measured the δ44/40Ca of conodont microfossils (calcium hydroxyapatite) from the global stratotype section for the Permian-Triassic boundary at Meishan, China. The conodont δ44/40Ca record shows a negative excursion similar in stratigraphic position and magnitude to that previously observed in carbonate rocks. Parallel negative excursions in the δ44/40Ca of carbonate rocks and conodont microfossils cannot be accounted for by a change in carbonate mineralogy but are consistent with a negative shift in the δ44/40Ca of seawater. These data add further support for the ocean acidification scenario, pointing toward strong similarities between the greatest catastrophe in the history of animal life and anticipated global change during the 21st century.

  6. Nested high resolution models for the coastal areas of the North Indian Ocean

    Science.gov (United States)

    Wobus, Fred; Shapiro, Georgy

    2017-04-01

    . Due to the lack of effective detiding methods and the prevailing view that harmonics-derived SSH provide a cleaner tidal signal over the SSH taken from a tidal parent model it has traditionally only been the last model in a nesting chain that is tidal. But to our knowledge these assumptions haven't been sufficiently tested and need to be re-visited. Furthermore, the lack of tides in the larger-scale regional models limits their capability and we would like to push for a nesting chain where all regional models (including the intermediate ones) are tidal. In this study we have conducted a number of numerical experiments where we have tested whether a tidal regional model can effectively force a tidal nested model without resorting to detiding techniques and the use of a dedicated tidal model such as TPXO. We have tested whether it's possible to use a tidal parent model and use the total SSH (combined geostrophic SSH and tidal component) to force the child model at the boundary. We call this strategy "tidal nesting" as opposed to TPXO tidal forcing which is used in "traditional nesting". For our experiments we have developed 2 models based on the same NEMO 3.6 codebase. The medium resolution AS20 model covers the Arabian Sea at 1/20 ̊ with 50 layers using a hybrid s-on-top-of-z vertical discretisation scheme (Shapiro et al., 2013); and the high resolution AG60 model covers the Arabian/Persian Gulf at 1/60 ̊ with 50 layers. The AS20 model is "traditionally" nested within the UK Met Office non-tidal large-scale Indian Ocean model at 1/12 ̊ resolution and tidal constituents at the boundary are taken from the TPXO7.2 Global Tidal Solution. Our "tidal nesting" experiments use different forcing frequencies at which the tidal SSH is fed from the larger-scale AS20 into the smaller-scale AG60 model. These strategies are compared with "traditional nesting" where the inner AG60 uses boundary conditions from a non-tidal AS20 parent model and tides are computed from TPXO harmonics

  7. Tidal dynamics and their influence on the climate system from the Cretaceous to present day

    Science.gov (United States)

    Weber, Tobias; Thomas, Maik

    2017-11-01

    Global numerical ocean models used for paleo-climate reconstructions commonly only consider the ocean's general circulation but neglect tidal dynamics. However, tidal dynamics affect the ocean's mean general circulation, in particular by vertical mixing and tidal residual mean currents. Through feedback loops the whole climate system is affected. Plate tectonics modify geometric resonance conditions in ocean basins and thereby tidal dynamics. We study the influence of ocean tides on the ocean general circulation and atmospheric parameters by forcing the coupled atmosphere-ocean model ECHAM5/MPIOM with the complete lunisolar tidal potential. Simulations have been performed for five tectonically important time-slices: the Early Albian (ca. 110 million years ago, Ma), the Cenomanian-Turonian Boundary (ca. 93 Ma, CTB), the Early Eocene (ca. 55 Ma), the Early Pliocene (ca. 3.5 Ma), and a pre-industrial period (ca. 1850 CE). The model results suggest that the global mean tidal potential energy in the Early Eocene is almost three times larger than in the CTB. The large potential energy input in the Early Eocene leads to a tripling of current velocities in 10% of the deep ocean. Although the effect of tides on the general ocean circulation is less pronounced in the other time-slices, horizontal velocities are modified by more than 20% in 55% of the deep ocean. The tidally induced shifts of ocean currents and vertical mixing also have an effect on the three-dimensional temperature distribution in the ocean. The impact of tidal dynamics on atmospheric temperatures is particularly strong in the Southern Ocean of the Early Pliocene and the pre-industrial period. By a feedback loop with the atmosphere, tidal forcing locally reduces sea-ice concentration by up to 30% and local atmospheric 2 m temperatures by up to 4°C. Although uncertainties in bathymetry reconstructions limit the significance of quantitative analysis, the qualitative conclusions suggest that the impacts of

  8. CFD for wind and tidal offshore turbines

    CERN Document Server

    Montlaur, Adeline

    2015-01-01

    The book encompasses novel CFD techniques to compute offshore wind and tidal applications. Computational fluid dynamics (CFD) techniques are regarded as the main design tool to explore the new engineering challenges presented by offshore wind and tidal turbines for energy generation. The difficulty and costs of undertaking experimental tests in offshore environments have increased the interest in the field of CFD which is used to design appropriate turbines and blades, understand fluid flow physical phenomena associated with offshore environments, predict power production or characterise offshore environments, amongst other topics.

  9. Tidal propagation off the central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.

    and phases from a global tidal model in the open ocean and those at the coast are used to construct co-amplitude and co-phase lines of M2 and K1, which are the largest among the semi-diurnal and diurnal constituents respectively. One of the characteristic...

  10. Developments in tidal power

    Science.gov (United States)

    Charlier, R. H.

    Successful, planned, and potential tidal power plants and sites are discussed. Units are in operation in France and Russia, with the French plant using reversible blade turbines being used as a design guide for plants in Argentina and Australia. The U.S. is studying the feasibility of a plant in Passamaquaddy Bay, and Canada is pursuing construction of a plant in the Bay of Fundy. The Severn River in Great Britain is receiving a site study, and over a hundred plants have been built as local power systems in China. Bulb-type turbines, which enhance the volume emptying and filling the retaining basin, are considered as the highest performing power unit. Simpler one-way flow turbines have been suggested as more economical to install. Governmental, institutional, and investor impediments to tidal power plant are explored.

  11. Relativistic tidal disruption events

    Directory of Open Access Journals (Sweden)

    Levan A.

    2012-12-01

    Full Text Available In March 2011 Swift detected an extremely luminous and long-lived outburst from the nucleus of an otherwise quiescent, low luminosity (LMC-like galaxy. Named Swift J1644+57, its combination of high-energy luminosity (1048 ergs s−1 at peak, rapid X-ray variability (factors of >100 on timescales of 100 seconds and luminous, rising radio emission suggested that we were witnessing the birth of a moderately relativistic jet (Γ ∼ 2 − 5, created when a star is tidally disrupted by the supermassive black hole in the centre of the galaxy. A second event, Swift J2058+0516, detected two months later, with broadly similar properties lends further weight to this interpretation. Taken together this suggests that a fraction of tidal disruption events do indeed create relativistic outflows, demonstrates their detectability, and also implies that low mass galaxies can host massive black holes. Here, I briefly outline the observational properties of these relativistic tidal flares observed last year, and their evolution over the first year since their discovery.

  12. Are Wave and Tidal Energy Plants New Green Technologies?

    Science.gov (United States)

    Douziech, Mélanie; Hellweg, Stefanie; Verones, Francesca

    2016-07-19

    Wave and tidal energy plants are upcoming, potentially green technologies. This study aims at quantifying their various potential environmental impacts. Three tidal stream devices, one tidal range plant and one wave energy harnessing device are analyzed over their entire life cycles, using the ReCiPe 2008 methodology at midpoint level. The impacts of the tidal range plant were on average 1.6 times higher than the ones of hydro-power plants (without considering natural land transformation). A similar ratio was found when comparing the results of the three tidal stream devices to offshore wind power plants (without considering water depletion). The wave energy harnessing device had on average 3.5 times higher impacts than offshore wind power. On the contrary, the considered plants have on average 8 (wave energy) to 20 (tidal stream), or even 115 times (tidal range) lower impact than electricity generated from coal power. Further, testing the sensitivity of the results highlighted the advantage of long lifetimes and small material requirements. Overall, this study supports the potential of wave and tidal energy plants as alternative green technologies. However, potential unknown effects, such as the impact of turbulence or noise on marine ecosystems, should be further explored in future research.

  13. Evidences of Seasonal Variation in Altimetry Derived Ocean Tides in the Subarctic Ocean

    Directory of Open Access Journals (Sweden)

    Hok Sum Fok

    2013-01-01

    Full Text Available While the barotropic ocean tides in the deep ocean are well modeled to ~2 cm RMS, accurate tidal prediction in the ice-covered polar oceans and near coastal regions remain elusive. A notable reason is that the most accurate satellite altimeters (TOPEX/Jason-1/-2, whose orbits are optimized to minimize the tidal aliasing effect, have spatial coverage limited to largely outside of the polar ocean. Here, we update the assessment of tidal models using 7 contemporary global and regional models, and show that the altimetry sea surface height (SSH anomaly residual after tidal correction is 9 - 12 cm RMS in the Subarctic Ocean. We then address the hypothesis whether plausible evidence of variable tidal signals exist in the seasonally ice-covered Subarctic Ocean, where the sea ice cover is undergoing rapid thinning. We first found a difference in variance reduction for multi-mission altimeter SSH anomaly residuals during the summer and winter seasons, with the residual during winter season 15 - 30% larger than that during the summer season. Experimental seasonal ocean tide solutions derived from satellite altimetry reveals that the recovered winter and summer tidal constituents generally differ by a few cm in amplitude and tens of degrees in phase. Relatively larger seasonal tidal patterns, in particular for M2, S2 and K1 tides, have been identified in the Chukchi Sea study region near eastern Siberia, coincident with the seasonal presence and movement of sea ice.

  14. Structural and tidal models of Titan and inferences on cryovolcanism

    Science.gov (United States)

    Sohl, F.; Solomonidou, A.; Wagner, F. W.; Coustenis, A.; Hussmann, H.; Schulze-Makuch, D.

    2014-05-01

    Titan, Saturn's largest satellite, is subject to solid body tides exerted by Saturn on the timescale of its orbital period. The tide-induced internal redistribution of mass results in tidal stress variations, which could play a major role for Titan's geologic surface record. We construct models of Titan's interior that are consistent with the satellite's mean density, polar moment-of-inertia factor, obliquity, and tidal potential Love number k2 as derived from Cassini observations of Titan's low-degree gravity field and rotational state. In the presence of a global liquid reservoir, the tidal gravity field is found to be consistent with a subsurface water-ammonia ocean more than 180 km thick and overlain by an outer ice shell of less than 110 km thickness. The model calculations suggest comparatively low ocean ammonia contents of less than 5 wt % and ocean temperatures in excess of 255 K, i.e., higher than previously thought, thereby substantially increasing Titan's potential for habitable locations. The calculated diurnal tidal stresses at Titan's surface amount to 20 kPa, almost comparable to those expected at Enceladus and Europa. Tidal shear stresses are concentrated in the polar areas, while tensile stresses predominate in the near-equatorial, midlatitude areas of the sub- and anti-Saturnian hemispheres. The characteristic pattern of maximum diurnal tidal stresses is largely compliant with the distribution of active regions such as cryovolcanic candidate areas. The latter could be important for Titan's habitability since those may provide possible pathways for liquid water-ammonia outbursts on the surface and the release of methane in the satellite's atmosphere.

  15. Spatiotemporal Information Organization and Visualization on Tidal Level

    Science.gov (United States)

    Huang, B.; Zhang, Y.; Wang, Y.; Liu, Q.

    2015-07-01

    The amount and location of oceanographic stations vary in different time and the observation information of the same station shows temporality. Hence, ocean observation information has strong spatiotemporal characteristics. This article firstly introduces storage strategy and representation method of spatiotemporal information on tidal level. Then the prototype system was built with the ability of storing, updating, analyzing, and early warning of tidal level in Shandong Peninsula of China. The system achieves the inquiry and visualization of realtime and historical information of oceanographic stations, which provides technical support for oceanographers and decisionmakers.

  16. Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

    Science.gov (United States)

    Gatto, Vincenzo Marco; van Prooijen, Bram Christiaan; Wang, Zheng Bing

    2017-11-01

    Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats' morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats' equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

  17. Tidal Venuses: triggering a climate catastrophe via tidal heating.

    Science.gov (United States)

    Barnes, Rory; Mullins, Kristina; Goldblatt, Colin; Meadows, Victoria S; Kasting, James F; Heller, René

    2013-03-01

    Traditionally, stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here, we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high-enough levels to induce a runaway greenhouse for a long-enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets "Tidal Venuses" and the phenomenon a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits (i.e., with negligible tidal heating) in the habitable zone (HZ). However, these planets are not habitable, as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. We simulated the evolution of hypothetical planetary systems in a quasi-continuous parameter distribution and found that we could constrain the history of the system by statistical arguments. Planets orbiting stars with masseswater via tidal heating, as orbital stability is unlikely for the high eccentricities required for the tidal greenhouse. As the inner edge of the HZ is defined by the onset of a runaway or moist greenhouse powered by radiation, our results represent a fundamental revision to the HZ for noncircular orbits. In the appendices we review (a) the moist and runaway greenhouses, (b) hydrogen escape, (c) stellar mass-radius and mass-luminosity relations, (d) terrestrial planet mass-radius relations, and (e) linear tidal theories.

  18. Tidal and subtidal hydrodynamics and energetics in a constricted estuary

    Science.gov (United States)

    Zarzuelo, Carmen; López-Ruiz, Alejandro; Díez-Minguito, Manuel; Ortega-Sánchez, Miguel

    2017-02-01

    The dynamics of coastal plain estuaries are mainly associated with variable tidal forcing and local winds in combination with bathymetric complexity and coastline irregularity. Specific features, such as constricted areas, can potentially affect and energize the hydrodynamics of these types of systems. Particularly, tidal range and tidal currents can be significantly amplified where the incoming tidal wave becomes constricted. In this work, the impact of a narrow constriction on a mesotidal estuary was analysed at tidal and subtidal time scales. Tidal hydrodynamics, energy fluxes and energy dissipation were determined for the entire Cádiz Bay (southwestern Spain) using the Delft3D numerical model. Field observations were used to analyse tidal propagation and energy dissipation along the bay constriction and to calibrate and test the numerical model. The results indicate that the presence of the constriction transformed and distorted the tide and increased the tidal range and flow velocities along the channel, with implications on energy dissipation. The tidal currents were oriented along-channel at the central part of the constriction, although abrupt bathymetric changes at the channel inner boundary provoked a sudden rotation of the flow. Although the energy fluxes were higher for spring tides and were strongly influenced by winds, the energy dissipation was controlled by bed shear stresses and vertical dispersion. The significance of this energy dissipation was that it destabilized the water column, which resulted in a weakly stratified system with implications on water quality. At a subtidal scale, the residual water volume exchange was the result of the combined effects of the neap/spring tides, wind and waves, whereas tides were dominant at the tidal scale.

  19. Characterization of U.S. Wave Energy Converter (WEC) Test Sites: A Catalogue of Met-Ocean Data.

    Energy Technology Data Exchange (ETDEWEB)

    Dallman, Ann Renee; Neary, Vincent Sinclair

    2014-10-01

    This report presents met - ocean data and wave energy characteristics at three U.S. wave energy converter (WEC) test and potential deployment sites . Its purpose is to enable the compari son of wave resource characteristics among sites as well as the select io n of test sites that are most suitable for a developer's device and that best meet their testing needs and objectives . It also provides essential inputs for the design of WEC test devices and planning WEC tests, including the planning of deployment and op eration s and maintenance. For each site, this report catalogues wave statistics recommended in the (draft) International Electrotechnical Commission Technical Specification (IEC 62600 - 101 TS) on Wave Energy Characterization, as well as the frequency of oc currence of weather windows and extreme sea states, and statistics on wind and ocean currents. It also provides useful information on test site infrastructure and services .

  20. Europa: Perspectives on an Ocean World

    Science.gov (United States)

    Singer, K. N.; McKinnon, W. B.; Pappalardo, R. T.; Khurana, K. K.

    2009-12-01

    over the age of the surface. From a dynamical perspective, it is not implausible that Europa, like Io, is evolving away from a geologically recent state of higher eccentricity and greater tidal dissipation. While total shell thickness is unlikely to vary significantly over local or regional scales, the brittle lithosphere thickness certainly does. And it may simply have been the limited data return from Galileo, in type and quantity, that prevented the discovery of Enceladus-like activity there. We have come a long way from the criticisms of one of Galileo’s contemporaries, who argued that the moons of Jupiter could not even exist. Not only do they exist, but one of these moons, Europa, bears more than a passing resemblance to a smaller but more water-rich Earth. In time, this ocean world should offer a test of one of Science’s greatest questions: whether there was a second, independent origin of life.

  1. Ocean energy resource systems

    Energy Technology Data Exchange (ETDEWEB)

    Bregman, R.; Knapp, R.H.; Takahashi, P.K. [Univ. of Hawaii, Honolulu, HI (United States)

    1996-08-01

    The oceans occupy nearly three-quarters of the Earth`s surface and represent a potentially large source of renewable energy. While many industrialized nations have conducted exploratory research and development, the total power currently available from ocean energy resource systems, with the exception of a French tidal power plant, is less that 100 megawatts. A number of ocean energy conversion technologies are approaching an acceptable stage of development for commercial utilization. Factors important to the design and development of such systems-including wave, tide and thermal gradient sources are discussed.

  2. The gravitational self-interaction of the Earth's tidal bulge

    Science.gov (United States)

    Norsen, Travis; Dreese, Mackenzie; West, Christopher

    2017-09-01

    According to a standard, idealized analysis, the Moon would produce a 54 cm equilibrium tidal bulge in the Earth's oceans. This analysis omits many factors (beyond the scope of the simple idealized model) that dramatically influence the actual height and timing of the tides at different locations, but it is nevertheless an important foundation for more detailed studies. Here, we show that the standard analysis also omits another factor—the gravitational interaction of the tidal bulge with itself—which is entirely compatible with the simple, idealized equilibrium model and which produces a surprisingly non-trivial correction to the predicted size of the tidal bulge. Our analysis uses ideas and techniques that are familiar from electrostatics, and should thus be of interest to teachers and students of undergraduate E&M, Classical Mechanics (and/or other courses that cover the tides), and geophysics courses that cover the closely related topic of Earth's equatorial bulge.

  3. Guidance for Performing Tests on Dredged Material Proposed for Ocean Disposal at the Historic Area Remediation Site

    Science.gov (United States)

    Guidance presents the sediment testing guidelines and requirements to be used by applicants who wish to obtain a Department of the Army permit from the USACE-New York District for dredging and placement of dredged material at the HARS in the Atlantic Ocean

  4. Estimates of M2 Tidal Energy Dissipation from TOPEX/Poseidon Altimeter Data

    Science.gov (United States)

    Egbert, Gary D.; Ray, Richard D.

    2001-01-01

    Most of the tidal energy dissipation in the ocean occurs in shallow seas, as has long been recognized. However, recent work has suggested that a significant fraction of the dissipation, perhaps 1 TW or more, occurs in the deep ocean. This paper builds further evidence for that conclusion. More than 6 years of data from the TOPEX/Poseidon satellite altimeter are used to map the tidal dissipation rate throughout the world ocean. The dissipation rate is estimated as a balance between the rate of working by tidal forces and the energy flux divergence, computed using currents derived by least squares fitting of the altimeter data and the shallow water equations. Such calculations require dynamical assumptions, in particular about the nature of dissipation. To assess sensitivity of dissipation estimates to input assumptions, a large suite of tidal inversions based on a wide range of drag parameterizations and employing both real and synthetic altimeter data are compared. These experiments and Monte Carlo error fields from a generalized inverse model are used to establish error uncertainties for the dissipation estimates. Owing to the tight constraints on tidal elevation fields provided by the altimeter, area integrals of the energy balance are remarkably insensitive to required dynamical assumptions. Tidal energy dissipation is estimated for all major shallow seas (excluding individual polar seas) and compared with previous model and data-based estimates. Dissipation in the open ocean is significantly tnhanced around major bathymetric features, in a manner consistent with simple theories the generation of baroclinic tides.

  5. Tidal and subtidal exchange flows at an inlet of the Wadden Sea

    Science.gov (United States)

    Valle-Levinson, Arnoldo; Stanev, Emil; Badewien, Thomas H.

    2018-03-01

    Observations of underway velocity profiles during complete spring and neap tidal cycles were used to determine whether the spatial structures of tidal and subtidal flows at a tidal inlet in a multiple-inlet embayment are consistent with those observed at single-inlet embayments. Measurements were obtained at the Otzumer Balje, one of the multiple inlets among the East Frisian Islands of the Wadden Sea. The 1.5 km-wide inlet displayed a bathymetric profile consisting of a channel ∼15 m deep flanked by frictional effects from bathymetry molded tidal flows. Spatial distributions of semidiurnal tidal current amplitude and phase conform to those predicted by an analytical model for a basin with one inlet. Maximum semidiurnal flows appear at the surface in the channel, furthest away from bottom friction effects. Therefore, Otzumer Balje displays tidal hydrodynamics that are independent of the other inlets of the embayment. Subtidal exchange flows are laterally sheared, with residual inflow in the channel combined with outflow over shoals. The spatial distribution of these residual flows follow theoretical expectations of tidally driven flows interacting with bathymetry. Such distribution is similar to the tidal residual circulation at other inlets with only one communication to the ocean, suggesting that at subtidal scales the Otzumer Balje responds to tidal forcing independently of the other inlets.

  6. High-resolution modeling assessment of tidal stream resource in Western Passage of Maine, USA

    Science.gov (United States)

    Yang, Zhaoqing; Wang, Taiping; Feng, Xi; Xue, Huijie; Kilcher, Levi

    2017-04-01

    Although significant efforts have been taken to assess the maximum potential of tidal stream energy at system-wide scale, accurate assessment of tidal stream energy resource at project design scale requires detailed hydrodynamic simulations using high-resolution three-dimensional (3-D) numerical models. Extended model validation against high quality measured data is essential to minimize the uncertainties of the resource assessment. Western Passage in the State of Maine in U.S. has been identified as one of the top ranking sites for tidal stream energy development in U.S. coastal waters, based on a number of criteria including tidal power density, market value and transmission distance. This study presents an on-going modeling effort for simulating the tidal hydrodynamics in Western Passage using the 3-D unstructured-grid Finite Volume Community Ocean Model (FVCOM). The model domain covers a large region including the entire the Bay of Fundy with grid resolution varies from 20 m in the Western Passage to approximately 1000 m along the open boundary near the mouth of Bay of Fundy. Preliminary model validation was conducted using existing NOAA measurements within the model domain. Spatial distributions of tidal power density were calculated and extractable tidal energy was estimated using a tidal turbine module embedded in FVCOM under different tidal farm scenarios. Additional field measurements to characterize resource and support model validation were discussed. This study provides an example of high resolution resource assessment based on the guidance recommended by the International Electrotechnical Commission Technical Specification.

  7. Workshop on tidal power and the environment in the 21. century : summary report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-15

    There is substantial interest in marine renewable energy development, particularly in ocean energy from waves, tidal power barrages, or from tidal stream turbines. This document provided a summary of the issues discussed at a workshop held by the Offshore Energy Environmental Research Association (OEER) on tidal research issues and priorities. The purpose of the workshop was to discuss the opportunities and implications of using tidal stream generators to capture energy from the Bay of Fundy tides in Nova Scotia. Workshop participants included proponents, engineers, environmental scientists, regulators and non-government organizations. This summary report reviewed the opportunities presented for tidal power generation. It also identified and discussed the environmental implications of new proposals and suggested research strategies to address these implications. The workshop considered the issue of a strategic environmental assessment (SEA) and the appropriateness of OEER doing the SEA. The first day of the workshop involved a public forum on tidal energy. Participants discussed ecological issues; socioeconomic and community issues; physical processes and technology; policy and assessment processes; governance; resources; and modeling. The history of tidal power in the Bay of Fundy was also presented along with a review of in-stream tidal energy technology; general environmental issues for an in-stream tidal power plant feasibility study; and a regulatory overview. tabs., figs.

  8. Tidally induced lateral dispersion of the Storfjorden overflow plume

    Directory of Open Access Journals (Sweden)

    F. Wobus

    2013-10-01

    Full Text Available We investigate the flow of brine-enriched shelf water from Storfjorden (Svalbard into Fram Strait and onto the western Svalbard Shelf using a regional set-up of NEMO-SHELF, a 3-D numerical ocean circulation model. The model is set up with realistic bathymetry, atmospheric forcing, open boundary conditions and tides. The model has 3 km horizontal resolution and 50 vertical levels in the sh-coordinate system which is specially designed to resolve bottom boundary layer processes. In a series of modelling experiments we focus on the influence of tides on the propagation of the dense water plume by comparing results from tidal and non-tidal model runs. Comparisons of non-tidal to tidal simulations reveal a hotspot of tidally induced horizontal diffusion leading to the lateral dispersion of the plume at the southernmost headland of Spitsbergen which is in close proximity to the plume path. As a result the lighter fractions in the diluted upper layer of the plume are drawn into the shallow coastal current that carries Storfjorden water onto the western Svalbard Shelf, while the dense bottom layer continues to sink down the slope. This bifurcation of the plume into a diluted shelf branch and a dense downslope branch is enhanced by tidally induced shear dispersion at the headland. Tidal effects at the headland are shown to cause a net reduction in the downslope flux of Storfjorden water into the deep Fram Strait. This finding contrasts previous results from observations of a dense plume on a different shelf without abrupt topography.

  9. Water Stage Forecasting in Tidal streams during High Water Using EEMD

    Science.gov (United States)

    Chen, Yen-Chang; Kao, Su-Pai; Su, Pei-Yi

    2017-04-01

    There are so many factors may affect the water stages in tidal streams. Not only the ocean wave but also the stream flow affects the water stage in a tidal stream. During high water, two of the most important factors affecting water stages in tidal streams are flood and tide. However the hydrological processes in tidal streams during high water are nonlinear and nonstationary. Generally the conventional methods used for forecasting water stages in tidal streams are very complicated. It explains the accurately forecasting water stages, especially during high water, in tidal streams is always a difficult task. The study makes used of Ensemble Empirical Model Decomposition (EEMD) to analyze the water stages in tidal streams. One of the advantages of the EEMD is it can be used to analyze the nonlinear and nonstationary data. The EEMD divides the water stage into several intrinsic mode functions (IMFs) and a residual; meanwhile, the physical meaning still remains during the process. By comparing the IMF frequency with tidal frequency, it is possible to identify if the IMF is affected by tides. Then the IMFs is separated into two groups, affected by tide or not by tide. The IMFs in each group are assembled to become a factor. Therefore the water stages in tidal streams are only affected by two factors, tidal factor and flood factor. Finally the regression analysis is used to establish the relationship between the factors of the gaging stations in the tidal stream. The available data during 15 typhoon periods of the Tanshui River whose downstream reach is in estuary area is used to illustrate the accuracy and reliability of the proposed method. The results show that the simple but reliable method is capable of forecasting water stages in tidal streams.

  10. Ocean energies

    Energy Technology Data Exchange (ETDEWEB)

    Charlier, R.H. (Univ. of Brussels (Belgium)); Justus, J.R. (The Library of Congress, CRS/SPRD, Washington, DC (United States))

    1993-09-01

    This timely volume provides a comprehensive review of current technology for all ocean energies. It opens with an analysis of ocean thermal energy conversion (OTEC), with and without the use of an intermediate fluid. The historical and economic background is reviewed, and the geographical areas in which this energy could be utilized are pinpointed. The production of hydrogen as a side product, and environmental consequences of OTEC plants are considered. The competitiveness of OTEC with conventional sources of energy is analysed. Optimisation, current research and development potential are also examined. Separate chapters provide a detailed examination of other ocean energy sources. The possible harnessing of solar ponds, ocean currents, and power derived from salinity differences is considered. There is a fascinating study of marine winds, and the question of using the ocean tides as a source of energy is examined, focussing on a number of tidal power plant projects, including data gathered from China, Australia, Great Britain, Korea and the USSR. Wave energy extraction has excited recent interest and activity, with a number of experimental pilot plants being built in northern Europe. This topic is discussed at length in view of its greater chance of implementation. Finally, geothermal and biomass energy are considered, and an assessment of their future is given. The authors also distinguished between energy schemes which might be valuable in less-industrialized regions of the world, but uneconomical in the developed countries. A large number of illustrations support the text. This book will be of particular interest to energy economists, engineers, geologists and oceanographers, and to environmentalists and environmental engineers

  11. Compilation of ocean circulation and other data from ADCP current meters, CTD casts, tidal gauges, and other instruments from a World-Wide distribution by Oregon State University and other institutions as part of World Ocean Circulation Experiment (WOCE) and other projects from 24 November 1985 to 30 December 2000 (NODC Accession 0000649)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Compilation of ocean circulation and other data were collected from a World-Wide distribution by Oregon State University (OSU) and other institutions as part of...

  12. Biodiversity crisis and recovery during the Triassic-Jurassic greenhouse interval: testing ocean acidification hypotheses

    OpenAIRE

    Jacobsen, Nikita Danielle

    2014-01-01

    The Late Rhaetian (Late Triassic) extinction event is characterised by shelled species showing a reduction in size, and thickness, which together with changed mineralogy is thought to be as a result of increased atmospheric pCO2 levels. Similar morphological changes have been demonstrated for extant species exposed experimentally to high CO2 leading to the hypothesis that Late Triassic extinctions were linked with global ocean acidification and increased oceanic palaeotemperatures. Consequent...

  13. Tidal Power Plant Energy Estimation

    OpenAIRE

    Silva–Casarín R.; Hiriart–Le Bert G.; López–González J.

    2010-01-01

    In this paper a methodology is presented which allows a quick and simple means of estimating the potential energy that can be obtained from a tidal power plant. The evaluation is made using a normalised nomograph, which is a function of the area of the tidal basin against the electricity installed capacity to thus obtain the potential energy for any location. The results describe two means of operation, one of "flow tide" and the other "flow–ebb tides", with two tidal basin systems operating:...

  14. Tidal controls on riverbed denitrification along a tidal freshwater zone

    Science.gov (United States)

    Knights, Deon; Sawyer, Audrey H.; Barnes, Rebecca T.; Musial, Cole T.; Bray, Samuel

    2017-01-01

    In coastal rivers, tidal pumping enhances the exchange of oxygen-rich river water across the sediment-water interface, controlling nitrogen cycling in riverbed sediment. We developed a one-dimensional, fluid flow and solute transport model that quantifies the influence of tidal pumping on nitrate removal and applied it to the tidal freshwater zone (TFZ) of White Clay Creek (Delaware, USA). In field observations and models, both oxygenated river water and anoxic groundwater deliver nitrate to carbon-rich riverbed sediment. A zone of nitrate removal forms beneath the aerobic interval, which expands and contracts over daily timescales due to tidal pumping. At high tide when oxygen-rich river water infiltrates into the bed, denitrification rates decrease by 25% relative to low tide. In the absence of tidal pumping, our model predicts that the aerobic zone would be thinner, and denitrification rates would increase by 10%. As tidal amplitude increases toward the coast, nitrate removal rates should decrease due to enhanced oxygen exchange across the sediment-water interface, based on sensitivity analysis. Denitrification hot spots in TFZs are more likely to occur in less permeable sediment under lower tidal ranges and higher rates of ambient groundwater discharge. Our models suggest that tidal pumping is not efficient at removing surface water nitrate but can remove up to 81% of nitrate from discharging groundwater in the TFZ of White Clay Creek. Given the high population densities of coastal watersheds, the reactive riverbeds of TFZs play a critical role in mitigating new nitrogen loads to coasts.

  15. Ocean acidification effect on prokaryotic metabolism tested in two diverse trophic regimes in the Mediterranean Sea

    Science.gov (United States)

    Celussi, Mauro; Malfatti, Francesca; Annalisa, Franzo; Gazeau, Frédéric; Giannakourou, Antonia; Pitta, Paraskevi; Tsiola, Anastasia; Del Negro, Paola

    2017-02-01

    Notwithstanding the increasing amount of researches on the effect of ocean acidification (OA) on marine ecosystems, no consent has emerged on its consequences on many prokaryote-mediated processes. Two mesocosm experiments were performed in coastal Mediterranean areas with different trophic status: the summer oligotrophic Bay of Calvi (BC, Corsica, France) and the winter mesotrophic Bay of Villefranche (BV, France). During these experiments, nine enclosures (∼54 m3) were deployed: 3 unamended controls and 6 elevated CO2, following a gradient up to 1250 μatm. We present results involving free-living viral and prokaryotic standing stocks, bacterial carbon production, abundance of highly active cells (CTC+), and degradation processes (beta-glucosidase, chitinase, leucine-aminopeptidase, lipase and alkaline phosphatase activities). The experiments revealed clear differences in the response of the two prokaryotic communities to CO2 manipulation. Only abundances of heterotrophic prokaryotes, viruses and lipase activity were not affected by CO2 manipulation at both locations. On the contrary, the percent of CTC+ was positively correlated to CO2 only in BC, concomitantly to a bulk reduction of [3H]-leucine uptake. The other tested parameters showed a different response at the two sites suggesting that the trophic regime of the systems plays a fundamental role on the effect of OA on prokaryotes through indirect modifications of the available substrate. Modified degradation rates may affect considerably the export of organic matter to the seafloor and thus ecosystem functioning within the water column. Our results highlight the need to further analyse the consequences of OA in oligotrophic ecosystems with particular focus on dissolved organic matter.

  16. Ocean Health X-Prize testing of a Simplified Spectrophotometric pH Sensor

    Science.gov (United States)

    Darlington, R. C.; DeGrandpre, M. D.; Spaulding, R. S.; Beck, J. C.

    2016-02-01

    Since the Industrial Revolution, the world's oceans have absorbed increasing amounts of CO2, resulting in a >0.1 reduction in the pH of surface waters. This acidification of the oceans has many far reaching impacts on marine life. There is, therefore, great need of quality instrumentation to assess and follow the changing carbonate system. To address this need, we have developed a simplified spectrophotometric pH sensor with accuracy and precision suitable for sea surface measurements with special emphasis on reduced size and cost. The reduced size will allow deployment of sensors on a much wider variety of platforms than are currently possible, and the reduced cost will make the instruments available to a broader research community. This prototype pH instrument was entered into the Wendy Schmidt Ocean Health X-Prize, an incentivized global competition to spur innovation in sensors to monitor ocean acidification's impact on marine ecosystems. Results from the three phases of competition which explored accuracy, precision, and stability culminating in a one month field trial are detailed. The prototype proved to be highly accurate (+/-0.009), with good precision (+/-0.004) and stability showing drift indistinguishable from that of the validation measurements. The innovations that enabled this sensor to succeed in the competition could allow for deployment of spectrophotometric sensors on new platforms such as NOAAs Global Drifter Program, a network of non-recovered surface drifting buoys, which would greatly extend the spatial and temporal resolution of ocean acidification measurements.

  17. On luminescence bleaching of tidal channel sediments

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel; Pejrup, Morten; Murray, Andrew S.

    2015-01-01

    We investigate the processes responsible for bleaching of the quartz OSL signal from tidal channel sediment. Tidal dynamics are expected to play an important role for complete bleaching of tidal sediments. However, no studies have examined the amount of reworking occurring in tidal channels...... and on tidal flats due to the mixing caused by currents and waves. We apply bed level data to evaluate the amount of vertical sediment reworking in modern tidal channels and at a tidal flat. Cycles of deposition and erosion are measured with a bed level sensor, and the results show that gross sedimentation...... was several times higher than net sedimentation. We propose that tidal channel sediment is bleached either on the tidal flat before it is transported to the tidal channels and incorporated in channel-fill successions or, alternatively, on the shallow intertidal part of the channel banks. Based...

  18. Computational modeling of unsteady loads in tidal boundary layers

    Science.gov (United States)

    Alexander, Spencer R.

    As ocean current turbines move from the design stage into production and installation, a better understanding of oceanic turbulent flows and localized loading is required to more accurately predict turbine performance and durability. In the present study, large eddy simulations (LES) are used to measure the unsteady loads and bending moments that would be experienced by an ocean current turbine placed in a tidal channel. The LES model captures currents due to winds, waves, thermal convection, and tides, thereby providing a high degree of physical realism. Probability density functions, means, and variances of unsteady loads are calculated, and further statistical measures of the turbulent environment are also examined, including vertical profiles of Reynolds stresses, two-point correlations, and velocity structure functions. The simulations show that waves and tidal velocity had the largest impact on the strength of off-axis turbine loads. By contrast, boundary layer stability and wind speeds were shown to have minimal impact on the strength of off- axis turbine loads. It is shown both analytically and using simulation results that either transverse velocity structure functions or two-point transverse velocity spatial correlations are good predictors of unsteady loading in tidal channels.

  19. Tidal locking of habitable exoplanets

    Science.gov (United States)

    Barnes, Rory

    2017-10-01

    Potentially habitable planets can orbit close enough to their host star that the differential gravity across their diameters can produce an elongated shape. Frictional forces inside the planet prevent the bulges from aligning perfectly with the host star and result in torques that alter the planet's rotational angular momentum. Eventually the tidal torques fix the rotation rate at a specific frequency, a process called tidal locking. Tidally locked planets on circular orbits will rotate synchronously, but those on eccentric orbits will either librate or rotate super-synchronously. Although these features of tidal theory are well known, a systematic survey of the rotational evolution of potentially habitable exoplanets using classic equilibrium tide theories has not been undertaken. I calculate how habitable planets evolve under two commonly used models and find, for example, that one model predicts that the Earth's rotation rate would have synchronized after 4.5 Gyr if its initial rotation period was 3 days, it had no satellites, and it always maintained the modern Earth's tidal properties. Lower mass stellar hosts will induce stronger tidal effects on potentially habitable planets, and tidal locking is possible for most planets in the habitable zones of GKM dwarf stars. For fast-rotating planets, both models predict eccentricity growth and that circularization can only occur once the rotational frequency is similar to the orbital frequency. The orbits of potentially habitable planets of very late M dwarfs ([InlineEquation not available: see fulltext.]) are very likely to be circularized within 1 Gyr, and hence, those planets will be synchronous rotators. Proxima b is almost assuredly tidally locked, but its orbit may not have circularized yet, so the planet could be rotating super-synchronously today. The evolution of the isolated and potentially habitable Kepler planet candidates is computed and about half could be tidally locked. Finally, projected TESS planets

  20. Tidal locking of habitable exoplanets

    Science.gov (United States)

    Barnes, Rory

    2017-12-01

    Potentially habitable planets can orbit close enough to their host star that the differential gravity across their diameters can produce an elongated shape. Frictional forces inside the planet prevent the bulges from aligning perfectly with the host star and result in torques that alter the planet's rotational angular momentum. Eventually the tidal torques fix the rotation rate at a specific frequency, a process called tidal locking. Tidally locked planets on circular orbits will rotate synchronously, but those on eccentric orbits will either librate or rotate super-synchronously. Although these features of tidal theory are well known, a systematic survey of the rotational evolution of potentially habitable exoplanets using classic equilibrium tide theories has not been undertaken. I calculate how habitable planets evolve under two commonly used models and find, for example, that one model predicts that the Earth's rotation rate would have synchronized after 4.5 Gyr if its initial rotation period was 3 days, it had no satellites, and it always maintained the modern Earth's tidal properties. Lower mass stellar hosts will induce stronger tidal effects on potentially habitable planets, and tidal locking is possible for most planets in the habitable zones of GKM dwarf stars. For fast-rotating planets, both models predict eccentricity growth and that circularization can only occur once the rotational frequency is similar to the orbital frequency. The orbits of potentially habitable planets of very late M dwarfs ([InlineEquation not available: see fulltext.]) are very likely to be circularized within 1 Gyr, and hence, those planets will be synchronous rotators. Proxima b is almost assuredly tidally locked, but its orbit may not have circularized yet, so the planet could be rotating super-synchronously today. The evolution of the isolated and potentially habitable Kepler planet candidates is computed and about half could be tidally locked. Finally, projected TESS planets

  1. The distribution and tapping tidal energy

    OpenAIRE

    Zygmunt Kowalik

    2004-01-01

    Tidal power along tidal shores has been used for centuries to run small tidal mills. Generating electricity by tapping tidal power proved to be very successful only in the last century through the tidal power plant constructed in 1967 in La Rance, France. This used a large barrier to generate the sea level head necessary for driving turbines. Construction of such plants evolved very slowly because of prohibitive costs and concerns about the environmental impact. Developments in the...

  2. Tidal Power Plant Energy Estimation

    Directory of Open Access Journals (Sweden)

    Silva–Casarín R.

    2010-04-01

    Full Text Available In this paper a methodology is presented which allows a quick and simple means of estimating the potential energy that can be obtained from a tidal power plant. The evaluation is made using a normalised nomograph, which is a function of the area of the tidal basin against the electricity installed capacity to thus obtain the potential energy for any location. The results describe two means of operation, one of "flow tide" and the other "flow–ebb tides", with two tidal basin systems operating: single and double reservoir systems. To obtain the normalised nomograph the numerical results for simulations of several tidal power plants under differing operational conditions over a period of one year. These conditions were established by varying the electricity installed capacity, the hydraulic conditions in "flow tide", "ebb tides" or both and with single or double reservoir systems and using sea level information taken every 15 minutes. To validate the model information from the tidal power plant at Rance, France, was used, which includes data concerning production, electricity installed capacity, turbine characteristics and tidal ranges. A very good correlation was found between the results of the numerical model and those reported in various technical reports.

  3. DIRECTLY IMAGING TIDALLY POWERED MIGRATING JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Dong Subo; Katz, Boaz; Socrates, Aristotle [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2013-01-10

    Upcoming direct-imaging experiments may detect a new class of long-period, highly luminous, tidally powered extrasolar gas giants. Even though they are hosted by {approx} Gyr-'old' main-sequence stars, they can be as 'hot' as young Jupiters at {approx}100 Myr, the prime targets of direct-imaging surveys. They are on years-long orbits and presently migrating to 'feed' the 'hot Jupiters'. They are expected from 'high-e' migration mechanisms, in which Jupiters are excited to highly eccentric orbits and then shrink semimajor axis by a factor of {approx}10-100 due to tidal dissipation at close periastron passages. The dissipated orbital energy is converted to heat, and if it is deposited deep enough into the atmosphere, the planet likely radiates steadily at luminosity L {approx} 100-1000 L{sub Jup}(2 Multiplication-Sign 10{sup -7}-2 Multiplication-Sign 10{sup -6} L{sub Sun }) during a typical {approx} Gyr migration timescale. Their large orbital separations and expected high planet-to-star flux ratios in IR make them potentially accessible to high-contrast imaging instruments on 10 m class telescopes. {approx}10 such planets are expected to exist around FGK dwarfs within {approx}50 pc. Long-period radial velocity planets are viable candidates, and the highly eccentric planet HD 20782b at maximum angular separation {approx}0.''08 is a promising candidate. Directly imaging these tidally powered Jupiters would enable a direct test of high-e migration mechanisms. Once detected, the luminosity would provide a direct measurement of the migration rate, and together with mass (and possibly radius) estimate, they would serve as a laboratory to study planetary spectral formation and tidal physics.

  4. Development and Test of a Medium Voltage Converter for Ocean Observatories

    Science.gov (United States)

    2010-06-01

    shark bites, tangles, and fouling – just to name a few. It is little wonder that the ocean remains largely unexplored, even though it potentially...energy production, climate prediction, disaster warning, pollution, fishery collapses, and species extinctions . ACKNOWLEDGMENT The authors would like to

  5. Breakdown of Hydrostatic Assumption in Tidal Channel with Scour Holes

    Directory of Open Access Journals (Sweden)

    Chunyan Li

    2016-10-01

    Full Text Available Hydrostatic condition is a common assumption in tidal and subtidal motions in oceans and estuaries.. Theories with this assumption have been largely successful. However, there is no definite criteria separating the hydrostatic from the non-hydrostatic regimes in real applications because real problems often times have multiple scales. With increased refinement of high resolution numerical models encompassing smaller and smaller spatial scales, the need for non-hydrostatic models is increasing. To evaluate the vertical motion over bathymetric changes in tidal channels and assess the validity of the hydrostatic approximation, we conducted observations using a vessel-based acoustic Doppler current profiler (ADCP. Observations were made along a straight channel 18 times over two scour holes of 25 m deep, separated by 330 m, in and out of an otherwise flat 8 m deep tidal pass leading to the Lake Pontchartrain over a time period of 8 hours covering part of the diurnal tidal cycle. Out of the 18 passages over the scour holes, 11 of them showed strong upwelling and downwelling which resulted in the breakdown of hydrostatic condition. The maximum observed vertical velocity was ~ 0.35 m/s, a high value in a tidal channel, and the estimated vertical acceleration reached a high value of 1.76×10-2 m/s2. Analysis demonstrated that the barotropic non-hydrostatic acceleration was dominant. The cause of the non-hydrostatic flow was the that over steep slopes. This demonstrates that in such a system, the bathymetric variation can lead to the breakdown of hydrostatic conditions. Models with hydrostatic restrictions will not be able to correctly capture the dynamics in such a system with significant bathymetric variations particularly during strong tidal currents.

  6. Ocean Bottom Seismometer: Design and Test of a Measurement System for Marine Seismology

    Directory of Open Access Journals (Sweden)

    Javier Cadena

    2012-03-01

    Full Text Available The Ocean Bottom Seismometer (OBS is a key instrument for the geophysical study of sea sub-bottom layers. At present, more reliable autonomous instruments capable of recording underwater for long periods of time and therefore handling large data storage are needed. This paper presents a new Ocean Bottom Seismometer designed to be used in long duration seismic surveys. Power consumption and noise level of the acquisition system are the key points to optimize the autonomy and the data quality. To achieve our goals, a new low power data logger with high resolution and Signal–to-Noise Ratio (SNR based on Compact Flash memory card is designed to enable continuous data acquisition. The equipment represents the achievement of joint work from different scientific and technological disciplines as electronics, mechanics, acoustics, communications, information technology, marine geophysics, etc. This easy to handle and sophisticated equipment allows the recording of useful controlled source and passive seismic data, as well as other time varying data, with multiple applications in marine environment research. We have been working on a series of prototypes for ten years to improve many of the aspects that make the equipment easy to handle and useful to work in deep-water areas. Ocean Bottom Seismometers (OBS have received growing attention from the geoscience community during the last forty years. OBS sensors recording motion of the ocean floor hold key information in order to study offshore seismicity and to explore the Earth’s crust. In a seismic survey, a series of OBSs are placed on the seabed of the area under study, where they record either natural seismic activity or acoustic signals generated by compressed air-guns on the ocean surface. The resulting data sets are subsequently used to model both the earthquake locations and the crustal structure.

  7. Ocean bottom seismometer: design and test of a measurement system for marine seismology.

    Science.gov (United States)

    Mànuel, Antoni; Roset, Xavier; Del Rio, Joaquin; Toma, Daniel Mihai; Carreras, Normandino; Panahi, Shahram Shariat; Garcia-Benadí, A; Owen, Tim; Cadena, Javier

    2012-01-01

    The Ocean Bottom Seismometer (OBS) is a key instrument for the geophysical study of sea sub-bottom layers. At present, more reliable autonomous instruments capable of recording underwater for long periods of time and therefore handling large data storage are needed. This paper presents a new Ocean Bottom Seismometer designed to be used in long duration seismic surveys. Power consumption and noise level of the acquisition system are the key points to optimize the autonomy and the data quality. To achieve our goals, a new low power data logger with high resolution and Signal-to-Noise Ratio (SNR) based on Compact Flash memory card is designed to enable continuous data acquisition. The equipment represents the achievement of joint work from different scientific and technological disciplines as electronics, mechanics, acoustics, communications, information technology, marine geophysics, etc. This easy to handle and sophisticated equipment allows the recording of useful controlled source and passive seismic data, as well as other time varying data, with multiple applications in marine environment research. We have been working on a series of prototypes for ten years to improve many of the aspects that make the equipment easy to handle and useful to work in deep-water areas. Ocean Bottom Seismometers (OBS) have received growing attention from the geoscience community during the last forty years. OBS sensors recording motion of the ocean floor hold key information in order to study offshore seismicity and to explore the Earth's crust. In a seismic survey, a series of OBSs are placed on the seabed of the area under study, where they record either natural seismic activity or acoustic signals generated by compressed air-guns on the ocean surface. The resulting data sets are subsequently used to model both the earthquake locations and the crustal structure.

  8. The ocean as the eternal energy source; De oceaan als eeuwige energiebron

    Energy Technology Data Exchange (ETDEWEB)

    Laban, C.; Speelman, H. [Nederlands Instituut voor Toegepaste Geowetenschappen TNO NITG-TNO, Delft (Netherlands)

    1998-06-01

    The oceans contain enormous reserves of fossil fuels. Also use can be made of sustainable energy in the form of wave energy, tidal power and heat. The options to use the oceans as an energy source are outlined. 4 refs.

  9. Ocean energy; L'energie marine

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-12-15

    This annual evaluation is a synthesis of works published in 2006. Comparisons are presented between the wind power performances and European Commission White Paper and Biomass action plan objectives. The sector covers the energy exploitation of all energy flows specifically supplied by the seas and oceans. At present, most efforts in both research and development and in experimental implementation are concentrated on tidal currents and wave power. 90% of today worldwide ocean energy production is represented by a single site: the Rance Tidal Power Plant. Ocean energies must face up two challenges: progress has to be made in finalizing and perfecting technologies and costs must be brought under control. (A.L.B.)

  10. Ocean circulation generated magnetic signals

    DEFF Research Database (Denmark)

    Manoj, C.; Kuvshinov, A.; Maus, S.

    2006-01-01

    Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and magnetic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of importance for geomagnetism and oceanography. Motivated by the clear identification...... of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM numerical solution. The required velocity data are from the ECCO ocean circulation experiment and alternatively from the OCCAM model for higher resolution. We assume...... of the magnetic field, as compared to the ECCO simulation. Besides the expected signatures of the global circulation patterns, we find significant seasonal variability of ocean magnetic signals in the Indian and Western Pacific Oceans. Compared to seasonal variation, interannual variations produce weaker signals....

  11. A Dynamic Programming Algorithm for Optimal Design of Tidal Power Plants

    Science.gov (United States)

    Nag, B.

    2013-03-01

    A dynamic programming algorithm is proposed and demonstrated on a test case to determine the optimum operating schedule of a barrage tidal power plant to maximize the energy generation over a tidal cycle. Since consecutive sets of high and low tides can be predicted accurately for any tidal power plant site, this algorithm can be used to calculate the annual energy generation for different technical configurations of the plant. Thus an optimal choice of a tidal power plant design can be made from amongst different design configurations yielding the least cost of energy generation. Since this algorithm determines the optimal time of operation of sluice gate opening and turbine gates opening to maximize energy generation over a tidal cycle, it can also be used to obtain the annual schedule of operation of a tidal power plant and the minute-to-minute energy generation, for dissemination amongst power distribution utilities.

  12. Tidal effects on stellar activity

    Science.gov (United States)

    Poppenhaeger, K.

    2017-10-01

    The architecture of many exoplanetary systems is different from the solar system, with exoplanets being in close orbits around their host stars and having orbital periods of only a few days. We can expect interactions between the star and the exoplanet for such systems that are similar to the tidal interactions observed in close stellar binary systems. For the exoplanet, tidal interaction can lead to circularization of its orbit and the synchronization of its rotational and orbital period. For the host star, it has long been speculated if significant angular momentum transfer can take place between the planetary orbit and the stellar rotation. In the case of the Earth-Moon system, such tidal interaction has led to an increasing distance between Earth and Moon. For stars with Hot Jupiters, where the orbital period of the exoplanet is typically shorter than the stellar rotation period, one expects a decreasing semimajor axis for the planet and enhanced stellar rotation, leading to increased stellar activity. Also excess turbulence in the stellar convective zone due to rising and subsiding tidal bulges may change the magnetic activity we observe for the host star. I will review recent observational results on stellar activity and tidal interaction in the presence of close-in exoplanets, and discuss the effects of enhanced stellar activity on the exoplanets in such systems.

  13. The Changes in Pulse Pressure Variation or Stroke Volume Variation After a "Tidal Volume Challenge" Reliably Predict Fluid Responsiveness During Low Tidal Volume Ventilation.

    Science.gov (United States)

    Myatra, Sheila Nainan; Prabu, Natesh R; Divatia, Jigeeshu Vasishtha; Monnet, Xavier; Kulkarni, Atul Prabhakar; Teboul, Jean-Louis

    2017-03-01

    Stroke volume variation and pulse pressure variation do not reliably predict fluid responsiveness during low tidal volume ventilation. We hypothesized that with transient increase in tidal volume from 6 to 8 mL/kg predicted body weight, that is, "tidal volume challenge," the changes in pulse pressure variation and stroke volume variation will predict fluid responsiveness. Prospective, single-arm study. Medical-surgical ICU in a university hospital. Adult patients with acute circulatory failure, having continuous cardiac output monitoring, and receiving controlled low tidal volume ventilation. The pulse pressure variation, stroke volume variation, and cardiac index were recorded at tidal volume 6 mL/kg predicted body weight and 1 minute after the "tidal volume challenge." The tidal volume was reduced back to 6 mL/kg predicted body weight, and a fluid bolus was given to identify fluid responders (increase in cardiac index > 15%). The end-expiratory occlusion test was performed at tidal volumes 6 and 8 mL/kg predicted body weight and after reducing tidal volume back to 6 mL/kg predicted body weight. Thirty measurements were obtained in 20 patients. The absolute change in pulse pressure variation and stroke volume variation after increasing tidal volume from 6 to 8 mL/kg predicted body weight predicted fluid responsiveness with areas under the receiver operating characteristic curves (with 95% CIs) being 0.99 (0.98-1.00) and 0.97 (0.92-1.00), respectively. The best cutoff values of the absolute change in pulse pressure variation and stroke volume variation after increasing tidal volume from 6 to 8 mL/kg predicted body weight were 3.5% and 2.5%, respectively. The pulse pressure variation, stroke volume variation, central venous pressure, and end-expiratory occlusion test obtained during tidal volume 6 mL/kg predicted body weight did not predict fluid responsiveness. The changes in pulse pressure variation or stroke volume variation obtained by

  14. Korea tidal power and beyond

    Science.gov (United States)

    Song, W. O.; van Walsum, E.

    A study evaluating the tidal power potential on the west coast of Korea is presented. The tidal power plant concept applied to all sites features prefabricated caissons from which the powerhouse and the sluice sections of the plant are built up. In the screening process, all 13 potential sites were compared on the basis of a single basin and single effect schemes operated to produce the maximum amount of energy. The four sites identified as having potential for development (the inner Asan Bay, the outer Asan Bay, the Incheon Bay, and the Garorim Bay) are economically evaluated. It is noted that harbor development and land reclamation can proceed in conjunction with tidal power development.

  15. Properties of active tidal bedforms

    DEFF Research Database (Denmark)

    Winter, Christian; Lefebvre, Alice; Becker, Marius

    2016-01-01

    Bedforms of various shapes and sizes are ubiquitous in tidal channels, inlets and estuaries. They constitute a form roughness which has a large scale effect on the hydrodynamics and sediment transport of coastal environments. It has been shown that this form roughness can be expressed in terms...... of the lee side slope of bedforms. This study compiles data on the topography and hydraulics of compound dunes from different settings in the German Bight to discuss implications of a critical lee slope in tidal environments with reversing flow. Data from the Weser estuary is used to exemplify and quantify...

  16. Combined impacts of tidal energy extraction and sea level rise in the Gulf of Maine

    Science.gov (United States)

    Hashemi, M. R.; Kresning, B.

    2016-12-01

    The objective of this study was to assess the combined effects of SLR and tidal energy extraction on the dynamics of tides in the Gulf of Maine in both US and Canadian waters. The dynamics of tides in the Gulf of Maine is dominated by tidal resonance, which generates one of the largest tidal ranges in the world. Further, sea level rise (SLR) is affecting tidal circulations globally, and in the Gulf of Maine. A large tidal energy resource is available in the Gulf of Maine, particularly in the Bay of Fundy, and is expected to be harvested in the future. Currently, more than 6 projects are operational or under development in this region (in both US and Canadian waters). Understanding the far-field impacts of tidal-stream arrays is important for future development of tidal energy extraction. The impacts include possible changes in water elevation, which can potentially increase flooding in coastal areas. Further, SLR can affect tidal energy resources and the impacts of tidal energy extraction during the project lifetime - which is usually more than 25 years. A tidal model of the Gulf of Maine was developed using Regional Ocean Model System (ROMS) at one arcminute scale. An array of turbines were simulated in the model. After validation of the model at NOAA tidal gauge stations and NERACOOS buoys, several scenarios; including SLR scenario, and tidal extraction scenario, were examined. In particular, the results of a recent research was used to assess the impacts of SLR on the boundary of the model domain, which was neglected in previous studies. The results of the impacts of the tidal energy extraction with and without the SLR were presented, and compared with those from literature. This includes the decrease of tidal range and M2 amplitude in Minas Basin due to the 2.5 GW extraction scenario, and possible changes in Massachusetts coastal area. The impacts were compared with the level of uncertainty in the model. It was shown that the impact of SLR on the dynamics of

  17. The distribution and tapping tidal energy

    Directory of Open Access Journals (Sweden)

    Zygmunt Kowalik

    2004-09-01

    Full Text Available Tidal power along tidal shores has been used for centuries to run small tidal mills. Generating electricity by tapping tidal power proved to be very successful only in the last century through the tidal power plant constructed in 1967 in La Rance, France. This used a large barrier to generate the sea level head necessary for driving turbines. Construction of such plants evolved very slowly because of prohibitive costs and concerns about the environmental impact. Developments in the construction of small, efficient and inexpensive underwater turbines admit the possibility of small scale operations that will use local tidal currents to bring electricity to remote locations. Since the generation of such electricity is concerned with the tidal energy in local water bodies, it is important to understand the site-specific energy balance, i.e., the energy flowing in through open boundaries, and the energy generated and dissipated within the local domain. The question is how to tap the tidal energy while keeping possible changes in the present tidal regimes to a minimum. The older approach of constructing barrages may still be quite useful in some locations. The basics of such tidal power plants constructed in a small bay are analyzed in order to understand the principal parameter for tidal plant evaluation, i.e., the power produced.     The new approach is to place turbines - devices similar to windmills - in the pathway of tidal currents. Theoretically, the amount of power available by such turbines for electricity generation is proportional to the water density and velocity cubed of the tidal flow. The naturally dissipated tidal power due to bottom friction forces is also proportional to the cube of the velocity. Because of this similarity, the exploitation of tidal energy can be directed to reinvesting the naturally dissipated power into tidal power for the generation of electricity. This approach to tidal power exploitation is better tuned

  18. Pacific deep circulation and ventilation controlled by tidal mixing away from the sea bottom.

    Science.gov (United States)

    Oka, Akira; Niwa, Yoshihiro

    2013-01-01

    Vertical mixing in the ocean is a key driver of the global ocean thermohaline circulation, one of the most important factors controlling past and future climate change. Prior observational and theoretical studies have focused on intense tidal mixing near the sea bottom (near-field mixing). However, ocean general circulation models that employ a parameterization of near-field mixing significantly underestimate the strength of the Pacific thermohaline circulation. Here we demonstrate that tidally induced mixing away from the sea bottom (far-field mixing) is essential in controlling the Pacific thermohaline circulation. Via the addition of far-field mixing to a widely used tidal parameterization, we successfully simulate the Pacific thermohaline circulation. We also propose that far-field mixing is indispensable for explaining the presence of the world ocean's oldest water in the eastern North Pacific Ocean. Our findings suggest that far-field mixing controls ventilation of the deep Pacific Ocean, a process important for ocean carbon and biogeochemical cycles.

  19. Energy potential of a tidal fence deployed near a coastal headland.

    Science.gov (United States)

    Draper, S; Borthwick, A G L; Houlsby, G T

    2013-02-28

    Enhanced tidal streams close to coastal headlands appear to present ideal locations for the deployment of tidal energy devices. In this paper, the power potential of tidal streams near an idealized coastal headland with a sloping seabed is investigated using a near-field approximation to represent a tidal fence, i.e. a row of tidal devices, in a two-dimensional depth-averaged numerical model. Simulations indicate that the power extracted by the tidal fence is limited because the flow will bypass the fence, predominantly on the ocean side, as the thrust applied by the devices increases. For the dynamic conditions, fence placements and headland aspect ratios considered, the maximum power extracted at the fence is not related in any obvious way to the local undisturbed kinetic flux or the natural rate of energy dissipation due to bed friction (although both of these have been used in the past to predict the amount of power that may be extracted). The available power (equal to the extracted power net of vertical mixing losses in the immediate wake of devices) is optimized for devices with large area and small centre-to-centre spacing within the fence. The influence of energy extraction on the natural flow field is assessed relative to changes in the M2 component of elevation and velocity, and residual bed shear stress and tidal dispersion.

  20. Tidal Datum Changes Induced by Morphological Changes of North Carolina Coastal Inlets

    Directory of Open Access Journals (Sweden)

    Jindong Wang

    2016-11-01

    Full Text Available In support of the National Oceanic and Atmospheric Administration’s VDatum program, a new version of a tidal datum product for the North Carolina coastal waters has been developed to replace the initial version released in 2004. Compared with the initial version, the new version used a higher resolution grid to cover more areas and incorporated up-to-date tide, bathymetry, and shoreline data. Particularly, the old bathymetry datasets that were collected from the 1930s to the 1970s and were used in the initial version have been replaced by the new bathymetry datasets collected in the 2010s in the new version around five North Carolina inlets. This study aims at evaluating and quantifying tidal datum changes induced by morphological changes over about 40 to 80 years around the inlets. A series of tidal simulations with either the old or new bathymetry datasets used around five inlets were conducted to quantify the consequent tidal datum changes. The results showed that around certain inlets, approximately 10% change in the averaged depth could result in over 30% change in the tidal datum magnitude. Further investigation also revealed that tidal datum changes behind the barrier islands are closely associated with the cross-inlet tidal flux changes.

  1. Turning the tide : tidal power in the UK

    OpenAIRE

    Sustainable Development Commission

    2007-01-01

    Contents: Turning the tide : tidal power in the UK -- Executive summary -- Tidal power in the UK : research report 1 : UK tidal resource assessment -- Tidal power in the UK : research report 2 : tidal technologies overview -- Tidal power in the UK : research report 3 : Severn barrage proposals -- Tidal power in the UK : research report 4 : Severn non-barrage options -- Tidal power in the UK : research report 5 : UK case studies. Summarised in the Welsh language version of the executive ...

  2. Validation Test Report for the Coupled Ocean/Atmosphere MesoscalePrediction System (COAMPS) Version 5.0: Ocean/Wave Component Validation

    Science.gov (United States)

    2012-12-31

    following mechanisms: 1) Stokes drift current ( SDC ) in which a particle floating at the free surface experiences a net drift velocity in the...forcing fields are passed from SWAN to NCOM. SDC causes ocean current speeds to increase, but enhanced vertical mixing in the surface mixed layer...increased shear) will decrease currents. The SDC also tends to increase bottom stress. Ocean model water levels can modify the water depth used in wave

  3. Cost Assessment Methodology and Economic Viability of Tidal Energy Projects

    Directory of Open Access Journals (Sweden)

    Eva Segura

    2017-11-01

    Full Text Available The exploitation of technologies with which to harness the energy from ocean currents will have considerable possibilities in the future thanks to their enormous potential for electricity production and their high predictability. In this respect, the development of methodologies for the economic viability of these technologies is fundamental to the attainment of a consistent quantification of their costs and the discovery of their economic viability, while simultaneously attracting investment in these technologies. This paper presents a methodology with which to determine the economic viability of tidal energy projects, which includes a technical study of the life-cycle costs into which the development of a tidal farm can be decomposed: concept and definition, design and development, manufacturing, installation, operation and maintenance and dismantling. These cost structures are additionally subdivided by considering their sub-costs and bearing in mind the main components of the tidal farm: the nacelle, the supporting tidal energy converter structure and the export power system. Furthermore, a technical study is developed in order to obtain an estimation of the annual energy produced (and, consequently, the incomes generated if the electric tariff is known by considering its principal attributes: the characteristics of the current, the ability of the device to capture energy and its ability to convert and export the energy. The methodology has been applied (together with a sensibility analysis to the particular case of a farm composed of first generation tidal energy converters in one of the Channel Island Races, the Alderney Race, in the U.K., and the results have been attained by means of the computation of engineering indexes, such as the net present value, the internal rate of return, the discounted payback period and the levelized cost of energy, which indicate that the proposed project is economically viable for all the case studies.

  4. Modeling Interactions between Backbarrier Marshes, Tidal Inlets, Ebb-deltas, and Adjacent Barriers Exposed to Rising Sea Levels

    Science.gov (United States)

    Hanegan, K.; Georgiou, I. Y.; FitzGerald, D.

    2016-02-01

    Along barrier island chains, tidal exchange between the backbarrier and the coastal ocean supports unique saltwater and brackish ecosystems and is responsible for exporting sediment and nutrients to the surrounding coast. Tidal prism, basement controls, and wave and tidal energy dictate the size and number of tidal inlets and the volume of sand sequestered in ebb-tidal deltas. The inlet tidal prism is a function of bay area, tidal range, and secondary controls, including flow inertia, basinal hypsometry, and frictional factors. Sea- level rise (SLR) is threatening coastal environments, causing mainland flooding, changes in sediment supply, and conversion of wetlands and tidal flats to open water. These factors are impacting basinal hypsometry and increasing open water area, resulting in enlarging tidal prisms, increased dimensions of tidal inlets and ebb-tidal deltas, and erosion along adjacent barrier shorelines. Although the effects of SLR on coastal morphology are difficult to study by field observations alone, physics-based numerical models provide a sophisticated means of analyzing coastal processes over decadal time-scales and linking process causation to long term development. Here, we use a numerical model that includes relevant features in the barrier/tidal basin system, linking back-barrier marsh degradation, inlet expansion, and ebb-delta growth to barrier erosion through long-term hydrodynamic and morphology simulations. Sediment exchange and process interactions are investigated using an idealized domain resembling backbarrier basins of mixed energy coasts so that the sensitivity to varying SLR rates, interior marsh loss, sediment supply, and hydrodynamic controls can be more easily analyzed. Model runs explore these processes over geologic time scales, demonstrating the vulnerability of backbarrier systems to projected SLR and marsh loss. Results demonstrate the links between changing basin morphology and shoreface sedimentation patterns that initiate

  5. General relativistic tidal heating for Moller pseudotensor

    CERN Document Server

    So, Lau Loi

    2015-01-01

    Thorne elucidated that the relativistic tidal heating is the same as the Newtonian theory. Moreover, Thorne also claimed that the tidal heating is independent of how one localizes gravitational energy and is unambiguously given by a certain formula. Purdue and Favata calculated the tidal heating for different classical pseudotensors including Moller and obtained the results all matched with the Newtonian perspective. After re-examined this Moller pseudotensor, we find that there does not exist any tidal heating value. Thus we claim that the relativistic tidal heating is pseudotensor independent under the condition that if the peusdotensor is a Freud typed superpotential.

  6. Patterns of fracture and tidal stresses on Europa

    Science.gov (United States)

    Helfenstein, P.; Parmentier, E. M.

    1983-01-01

    A comparison of dark band, triple band, and cuspate ridge orientations with the fracture patterns predicted for tidal distortion due to orbital recession and eccentricity is undertaken, to test the hypothesized identification of Europa's lineaments as tidal distortion and planetary volume change fractures. Short, reticule dark bands near the anti-Jove point could be tension cracks caused by orbital eccentricity. Long, arcuate dark bands and triple bands peripheral to the anti-Jove point may be strike-slip faults due to orbital recession. The orientation and distribution of cuspate ridges, if they are compressional, suggests their formation in response to a combination of orbital recession and planetary volume decrease. If surface fracturing is due to tidal deformation, important constraints are exerted by it on Europa's orbital evolution.

  7. Using Principal Component and Tidal Analysis as a Quality Metric for Detecting Systematic Heading Uncertainty in Long-Term Acoustic Doppler Current Profiler Data

    Science.gov (United States)

    Morley, M. G.; Mihaly, S. F.; Dewey, R. K.; Jeffries, M. A.

    2015-12-01

    Ocean Networks Canada (ONC) operates the NEPTUNE and VENUS cabled ocean observatories to collect data on physical, chemical, biological, and geological ocean conditions over multi-year time periods. Researchers can download real-time and historical data from a large variety of instruments to study complex earth and ocean processes from their home laboratories. Ensuring that the users are receiving the most accurate data is a high priority at ONC, requiring quality assurance and quality control (QAQC) procedures to be developed for all data types. While some data types have relatively straightforward QAQC tests, such as scalar data range limits that are based on expected observed values or measurement limits of the instrument, for other data types the QAQC tests are more comprehensive. Long time series of ocean currents from Acoustic Doppler Current Profilers (ADCP), stitched together from multiple deployments over many years is one such data type where systematic data biases are more difficult to identify and correct. Data specialists at ONC are working to quantify systematic compass heading uncertainty in long-term ADCP records at each of the major study sites using the internal compass, remotely operated vehicle bearings, and more analytical tools such as principal component analysis (PCA) to estimate the optimal instrument alignments. In addition to using PCA, some work has been done to estimate the main components of the current at each site using tidal harmonic analysis. This paper describes the key challenges and presents preliminary PCA and tidal analysis approaches used by ONC to improve long-term observatory current measurements.

  8. Oceanography of Wadge bank - current measurements over a tidal cycle off the south coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rama; RameshBabu, V.; Anto, A

    current over a tidal cycle is observed to flow parallel to the coast directed southeastward off Muttam Point in the Arabian Sea, east to southeastward in the area south of Cape Comorin in the Indian Ocean and northeastward parallel to the coast line...

  9. Sudden increase in tidal response linked to calving and acceleration at a large Greenland outlet glacier

    DEFF Research Database (Denmark)

    de Juan, Julia; Elósegui, Pedro; Nettles, Meredith

    2010-01-01

    Large calving events at Greenland's largest outlet glaciers are associated with glacial earthquakes and near-instantaneous increases in glacier flow speed. At some glaciers and ice streams, flow is also modulated in a regular way by ocean tidal forcing at the terminus. At Helheim Glacier, analysi...

  10. Tidal and subtidal flow patterns o a tropical continental shelf semi-insulated by coral reefs

    NARCIS (Netherlands)

    Tarya, A.; Hoitink, A.J.F.; Vegt, van der M.

    2010-01-01

    The present study sets out to describe the tidal and subtidal water motion at the Berau coastal shelf, which represents a tropical continental shelf area of variable width hosting a complex of barrier reefs along its oceanic edge. Moored and shipboard measurements on currents and turbulence were

  11. On-Shore Central Hydraulic Power Generation for Wind and Tidal Energy

    Science.gov (United States)

    Jones, Jack A.; Bruce, Allan; Lim, Steven; Murray, Luke; Armstrong, Richard; Kimbrall, Richard; Cook-Chenault, Kimberly; DeGennaro, Sean

    2012-01-01

    Tidal energy, offshore wind energy, and onshore wind energy can be converted to electricity at a central ground location by means of converting their respective energies into high-pressure hydraulic flows that are transmitted to a system of generators by high-pressure pipelines. The high-pressure flows are then efficiently converted to electricity by a central power plant, and the low-pressure outlet flow is returned. The Department of Energy (DOE) is presently supporting a project led by Sunlight Photonics to demonstrate a 15 kW tidal hydraulic power generation system in the laboratory and possibly later submerged in the ocean. All gears and submerged electronics are completely eliminated. A second portion of this DOE project involves sizing and costing a 15 MW tidal energy system for a commercial tidal energy plant. For this task, Atlantis Resources Corporation s 18-m diameter demonstrated tidal blades are rated to operate in a nominal 2.6 m/sec tidal flow to produce approximately one MW per set of tidal blades. Fifteen units would be submerged in a deep tidal area, such as in Maine s Western Passage. All would be connected to a high-pressure (20 MPa, 2900 psi) line that is 35 cm ID. The high-pressure HEPG fluid flow is transported 500-m to on-shore hydraulic generators. HEPG is an environmentally-friendly, biodegradable, watermiscible fluid. Hydraulic adaptations to ORPC s cross-flow turbines are also discussed. For 15 MW of wind energy that is onshore or offshore, a gearless, high efficiency, radial piston pump can replace each set of top-mounted gear-generators. The fluid is then pumped to a central, easily serviceable generator location. Total hydraulic/electrical efficiency is 0.81 at full rated wind or tidal velocities and increases to 0.86 at 1/3 rated velocities.

  12. Ocean Thermal Energy Conversion (OTEC) test facilities study program. Final report. Volume I

    Energy Technology Data Exchange (ETDEWEB)

    None

    1977-01-17

    A comprehensive test program has been envisioned by ERDA to accomplish the OTEC program objectives of developing an industrial and technological base that will lead to the commercial capability to successfully construct and economically operate OTEC plants. This study was performed to develop alternative non-site specific OTEC test facilities/platform requirements for an integrated OTEC test program including both land and floating test facilities. A progression of tests was established in which OTEC power cycle component designs proceed through advanced research and technology, component, and systems test phases. This progression leads to the first OTEC pilot plant and provides support for following developments which potentially reduce the cost of OTEC energy. It also includes provisions for feedback of results from all test phases to enhance modifications to existing designs or development of new concepts. The tests described should be considered as representative of generic types since specifics can be expected to change as the OTEC plant design evolves. Emphasis is placed on defining the test facility which is capable of supporting the spectrum of tests envisioned. All test support facilities and equipment have been identified and included in terms of space, utilities, cost, schedule, and constraints or risks. A highly integrated data acquisition and control system has been included to improve test operations and facility effectiveness through a centralized computer system capable of automatic test control, real-time data analysis, engineering analyses, and selected facility control including safety alarms. Electrical power, hydrogen, and ammonia are shown to be technically feasible as means for transmitting OTEC power to a land-based distribution point. (WHK)

  13. Population genetic structure in Atlantic and Pacific Ocean common murres (Uria aalge): natural replicate tests of post-Pleistocene evolution.

    Science.gov (United States)

    Morris-Pocock, J A; Taylor, S A; Birt, T P; Damus, M; Piatt, J F; Warheit, K I; Friesen, V L

    2008-11-01

    Understanding the factors that influence population differentiation in temperate taxa can be difficult because the signatures of both historic and contemporary demographics are often reflected in population genetic patterns. Fortunately, analyses based on coalescent theory can help untangle the relative influence of these historic and contemporary factors. Common murres (Uria aalge) are vagile seabirds that breed in the boreal and low arctic waters of the Northern Hemisphere. Previous analyses revealed that Atlantic and Pacific populations are genetically distinct; however, less is known about population genetic structure within ocean basins. We employed the mitochondrial control region, four microsatellite loci and four intron loci to investigate population genetic structure throughout the range of common murres. As in previous studies, we found that Atlantic and Pacific populations diverged during the Pleistocene and do not currently exchange migrants. Therefore, Atlantic and Pacific murre populations can be used as natural replicates to test mechanisms of population differentiation. While we found little population genetic structure within the Pacific, we detected significant east-west structuring among Atlantic colonies. The degree that population genetic structure reflected contemporary population demographics also differed between ocean basins. Specifically, while the low levels of population differentiation in the Pacific are at least partially due to high levels of contemporary gene flow, the east-west structuring of populations within the Atlantic appears to be the result of historic fragmentation of populations rather than restricted contemporary gene flow. The contrasting results in the Atlantic and Pacific Oceans highlight the necessity of carefully considering multilocus nonequilibrium population genetic approaches when reconstructing the demographic history of temperate Northern Hemisphere taxa.

  14. Ocean Thermal Energy Conversion (OTEC) test facilities study program. Final report. Volume II. Part A

    Energy Technology Data Exchange (ETDEWEB)

    1977-01-17

    Results are presented of an 8-month study to develop alternative non-site-specific OTEC facilities/platform requirements for an integrated OTEC Test Program which may include land and floating test facilities. The document, Volume II - Appendixes is bound in three parts (A, B, and C) which together comprise a compendium of the most significant detailed data developed during the study. Part A contains definitions, baseline revisions, test plans, and energy utilization sections.

  15. Changes in surf zone morphodynamics driven by multi-decadal contraction of a large ebb-tidal delta

    Science.gov (United States)

    Hansen, J. E.; Barnard, P.; Elias, E.

    2012-12-01

    The impact of large-scale deflation (76 million m3 of sediment loss) and contraction (~1 km) of a 150 km2 ebb-tidal delta over a half-century on hydrodynamics and sediment transport at Ocean Beach in San Francisco, CA (USA), onshore of the delta, is examined using a coupled wave and circulation model. The model is forced with representative wave and tidal conditions using recent (2005) and historic (1956) ebb-tidal delta bathymetry data sets. Comparison of the simulations indicate that along north/south trending Ocean Beach the contraction and deflation of the ebb-tidal delta has resulted in significant differences in the flow and sediment dynamics. Between 1956 and 2005 the transverse bar (the shallow attachment point of the ebb-tidal delta to the shoreline) migrated north ~1 km toward the inlet while a persistent alongshore flow and transport divergence point migrated south by ~500 m (Figure 1). Alongshore migration of these features has resulted in an increasing portion of onshore migrating sediment from the ebb-tidal delta, inferred by the contraction, to be transported north along the beach in 2005 versus south in 1956. The northerly migrating sediment is then trapped by Pt. Lobos, a rocky headland at the northern extreme of the beach, consistent with the observed shoreline accretion in this area. Conversely, alongshore migration of the transverse bar and divergence point has decreased the sediment supply to southern Ocean Beach, consistent with the observed erosion of the shoreline in this area. The approach described here is broadly applicable for investigating the causes of long-term morphological changes along urbanized beaches adjacent to inlet mouths worldwide.Figure 1. Ebb-tidal delta bathymetry in 1956 (A) and 2005 (B), 2 m contour interval to 20 m. Schematized pattern of alongshore transport along Ocean Beach and transport of onshore migrating sediment from the ebb-tidal delta in 1956 (C) and 2005 (D).

  16. Ocean Thermal Energy Conversion (OTEC) test facilities study program. Final report. Volume II. Part C

    Energy Technology Data Exchange (ETDEWEB)

    None

    1977-01-17

    Results are presented of an 8-month study to develop alternative non-site-specific OTEC facilities/platform requirements for an integrated OTEC Test Program which may include land and floating test facilities. Volume II--Appendixes is bound in three parts (A, B, and C) which together comprise a compendium of the most significant detailed data developed during the study. Part C describes test facility support, data acquisition and control system design, cost data, energy self-sufficiency, and test facility applications.

  17. Atlantic Ocean Acidification Test-Bed -- OA Time-Series, Cheeca Rocks, Florida Reef Tract FY2012

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The AOAT project is engaged in monitoring/modeling efforts designed to: a) establish methodologies for monitoring, assessing, and modeling the impacts of Ocean...

  18. Atlantic Ocean Acidification Test-Bed -- Net Ecosystem Calcification and Net Ecosystem Productivity, Flower Garden Banks, FY2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The AOAT project is engaged in monitoring/modeling efforts designed to: a) establish methodologies for monitoring, assessing, and modeling the impacts of Ocean...

  19. A dynamical picture of the oceanic tides

    Science.gov (United States)

    Butikov, Eugene I.

    2002-10-01

    A detailed treatment of tide-generating forces is given, followed by a simplified dynamic theory of tidal waves. To clarify the underlying physics, we use a simple model of the ocean that consists of a water shell of uniform depth completely covering the globe. The treatment is appropriate for college and university undergraduate students studying introductory geophysics or astronomy, general physics, or intermediate mechanics. A computer simulation is developed to aid in understanding the properties of sun- or moon-induced tide-generating forces and of the stationary tidal waves created by these forces in the open ocean.

  20. Developing a test-bed for robust research governance of geoengineering: the contribution of ocean iron biogeochemistry

    Science.gov (United States)

    Boyd, Philip W.; Bressac, Matthieu

    2016-11-01

    Geoengineering to mitigate climate change has long been proposed, but remains nebulous. Exploration of the feasibility of geoengineering first requires the development of research governance to move beyond the conceptual towards scientifically designed pilot studies. Fortuitously, 12 mesoscale (approx. 1000 km2) iron enrichments, funded to investigate how ocean iron biogeochemistry altered Earth's carbon cycle in the geological past, provide proxies to better understand the benefits and drawbacks of geoengineering. The utility of these iron enrichments in the geoengineering debate is enhanced by the GEOTRACES global survey. Here, we outline how GEOTRACES surveys and process studies can provide invaluable insights into geoengineering. Surveys inform key unknowns including the regional influence and magnitude of modes of iron supply, and stimulate iron biogeochemical modelling. These advances will enable quantification of interannual variability of iron supply to assess whether any future purposeful multi-year iron-fertilization meets the principle of `additionality' (sensu Kyoto protocol). Process studies address issues including upscaling of geoengineering, and how differing iron-enrichment strategies could stimulate wide-ranging biogeochemical outcomes. In summary, the availability of databases on both mesoscale iron-enrichment studies and the GEOTRACES survey, along with modelling, policy initiatives and legislation have positioned the iron-enrichment approach as a robust multifaceted test-bed to assess proposed research into climate intervention. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

  1. Tidal Evolution and Hydrothermal Activity in IcyWorlds

    Science.gov (United States)

    Vance, S.; Hussmann, H.

    2008-09-01

    The tidal heating that sustains a subsurface ocean in Europa likely varied in intensity through the moons history due to the exchange of orbital angular momentum with the innermost Galilean satellite, Io [1]. Tidal interactions elsewhere in the solar system — e.g. in Neptunes moon Triton, and in Kuiper belt systems such as Pluto-Charon and the 2003 EL61 system (Santa-Rudolph-Blitzen) — highlight the potential for vigorously heated subsurface oceans and thus the existence of hydrothermal systems in icy worlds. Understanding the extent and nature of hydrothermal activity in such systems is important for assessing the availability of essential elements and organic compounds necessary sustain and, possibly, originate life [2, 3, 4, 5, 6, 7]. During periods of low tidal heating in such systems, hydrothermalism driven by serpentinization (reaction of water with ultramafic rock) may be extensive, with implications for seafloor production of hydrogen, methane and other potential nutrients, and elements necessary to originate and support life in icy world oceans. For Enceladus, an anomalously dense satellite for its size, radiogenic heating and overburden pressure in the mantle are sufficiently low to permit fracturing of the entirety of the moons rocky interior on long time scales [8]. Estimates of methane production from serpentinization of Enceladus interior, based on measured fluxes from the Lost City Hydrothermal Field [9], are an order of magnitude greater than fluxes observed at Enceladuss south polar plume by the Cassini Ion Neutral Mass Spectrometer [10]. For the largest icy worlds in the Solar System — Titan, Ganymede and Callisto—pressures at and below the H2Orock interface are likely too high to permit the formation of microfractures, so an alternative explanation is required if methane is endogenous. Aqueous alteration may be augmented from the above estimates if altered crust is rejuvenated during periods of increased tidal dissipation. Crustal

  2. Limits to tidal current power

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, Chris [Department of Physics and Astronomy, University of Victoria, Victoria, BC (Canada); Cummins, Patrick [Institute of Ocean Sciences, Fisheries and Oceans (Canada)

    2008-11-15

    Estimating the extractable power of tidal currents in channels is a practical question that has received attention recently. Analysis has clearly shown that the power potential is not given by the flux of kinetic energy, as has been commonly assumed. A general formula for the maximum available power is reviewed, along with assessments of the reduction if only partial fences are used, as would be required for navigational and ecological reasons. In typical situations, the maximum power obtainable may be achieved with a surprisingly small number of turbines, especially if allowance is made for the flow reduction caused by drag on the supporting structures of turbines which reduces the maximum power available. Finally, the flow through tidal turbines is compared with the cooling water demands of nuclear reactors generating the same power. (author)

  3. Tidal energy, a renewable energy within hand reach; Les marees, une energie renouvelable a portee de lune

    Energy Technology Data Exchange (ETDEWEB)

    Danielo, O.

    2011-06-15

    Tide energy and oceanic current energy represent a strong potentiality for a few countries in the world including France. In the domain of tidal energy there are 2 strategies. The first one is based on the search for the lowest power production cost in order to contribute efficiently to the country's energy mix. Generally this strategy leads to the construction of tidal dams. The second strategy is based on the search for the lowest environmental impact. This strategy is economically competitive only in places where electrical power is expensive like isolated islands. This strategy is illustrated by the tidal power station of the Alderney island. In fact the amount of energy delivered by a tidal power station depends on the rise of the tide and on the surface of the dam. It appears that tidal dams require less surface that hydroelectric power plants. The energy of oceanic currents like Gulf Stream or the thermal energy of oceans or wave power are very little exploited now but represent a potentiality higher by several orders of magnitude than tidal energy. (A.C.)

  4. Tidal peritoneal dialysis: preliminary experience.

    Science.gov (United States)

    Flanigan, M J; Doyle, C; Lim, V S; Ullrich, G

    1992-01-01

    To determine the feasibility of home tidal peritoneal dialysis (TPD) and to assess whether eight hours of TPD can achieve uremia control and urea removal equal to that of continuous cycling peritoneal dialysis (CCPD). An open enrollment pilot study. The Home Dialysis Training Center of the University of Iowa Hospitals and Clinics, a tertiary care teaching hospital. Nine patients experienced with CCPD and living 80 km to 280 km from the dialysis center began TPD, because they wished to decrease their dialysis time. Following baseline measurements, each patient was taught to perform TPD. TPD consisted of an initial fill volume of 40 mL/kg, a residual volume approximately 20 mL/kg, and tidal exchanges of 10 to 20 mL/kg to achieve the desired hourly flow rate. Clinic assessments took place every four to six weeks, and prescriptions were subsequently altered to attain urea removal equal to that of CCPD. Patient interviews were used to determine TPD acceptance. Prior to each clinic visit, dialysate effluent volume and dialysis duration were recorded, and a sterile sample of the effluent was obtained for urea, creatinine, and total nitrogen measurement. Urea and creatinine clearances increased with dialysate flow. Dialysate nonurea nitrogen was 3.0 +/- 0.2 mmol/kg/D and changed minimally with increasing dialysate volumes. Eight hours of TPD (initial fill: 40 mL/kg; residual volume: 20 mL/kg; tidal inflow: 20 mL/kg) with hourly tidal flow exceeding 40 mL/kg/hr and no daytime volume achieved urea removal equal to that of the patient's prior CCPD prescription. TPD can provide dialysis equal to that of CCPD within a shorter amount of time (eight vs ten hours), but uses a greater volume of dialysate (16.0 L for TPD vs 9.5 L for CCPD).

  5. Tidal Dissipation in WASP-12

    Science.gov (United States)

    Weinberg, Nevin N.; Sun, Meng; Arras, Phil; Essick, Reed

    2017-11-01

    WASP-12 is a hot Jupiter system with an orbital period of P = 1.1 days, making it one of the shortest-period giant planets known. Recent transit timing observations by Maciejewski et al. and Patra et al. found a decreasing period with P/| \\dot{P}| = 3.2 Myr. This has been interpreted as evidence of either orbital decay due to tidal dissipation or a long-term oscillation of the apparent period due to apsidal precession. Here, we consider the possibility that it is orbital decay. We show that the parameters of the host star are consistent with either a M * ≃ 1.3 M ⊙ main sequence star or a M * ≃ 1.2 M ⊙ subgiant. We find that if the star is on the main sequence, the tidal dissipation is too inefficient to explain the observed \\dot{P}. However, if it is a subgiant, the tidal dissipation is significantly enhanced due to nonlinear wave-breaking of the dynamical tide near the star’s center. The subgiant models have a tidal quality factor Q{{\\prime} }* ≃ 2× {10}5 and an orbital decay rate that agrees well with the observed \\dot{P}. It would also explain why the planet survived for ≃3 Gyr while the star was on the main sequence and yet is now inspiraling on a 3 Myr timescale. Although this suggests that we are witnessing the last ∼0.1% of the planet’s life, the probability of such a detection is a few percent given the observed sample of ≃30 hot Jupiters in P 1.2 M ⊙ hosts.

  6. Test results of heat-exchanger cleaning in support of ocean thermal energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Lott, D F

    1980-12-01

    These tests evaluated flow-driven brushes, recirculating sponge rubber balls, chlorination, and mechanical system/chlorination combinations for in-situ cleaning of two potential heat exchanger materials: titanium and aluminum alloy 5052. Tests were successful when fouling resistance was <3.0 x 10/sup -4/ ft/sup 2/ hr-/sup 0/F/Btu. Results indicated systems and cleaning techniques using brushes, soft sponge balls, and various concentrations of chlorine had some potential for maintaining heat transfer efficiency.

  7. Effect of tidal triggering on seismicity in Taiwan revealed by the empirical mode decomposition method

    Directory of Open Access Journals (Sweden)

    H.-J. Chen

    2012-07-01

    Full Text Available The effect of tidal triggering on earthquake occurrence has been controversial for many years. This study considered earthquakes that occurred near Taiwan between 1973 and 2008. Because earthquake data are nonlinear and non-stationary, we applied the empirical mode decomposition (EMD method to analyze the temporal variations in the number of daily earthquakes to investigate the effect of tidal triggering. We compared the results obtained from the non-declustered catalog with those from two kinds of declustered catalogs and discuss the aftershock effect on the EMD-based analysis. We also investigated stacking the data based on in-phase phenomena of theoretical Earth tides with statistical significance tests. Our results show that the effects of tidal triggering, particularly the lunar tidal effect, can be extracted from the raw seismicity data using the approach proposed here. Our results suggest that the lunar tidal force is likely a factor in the triggering of earthquakes.

  8. Near-bed turbulence and sediment flux measurements in tidal channels

    Science.gov (United States)

    Wright, S.A.; Whealdon-Haught, D.R.

    2012-01-01

    Understanding the hydrodynamics and sediment transport dynamics in tidal channels is important for studies of estuary geomorphology, sediment supply to tidal wetlands, aquatic ecology and fish habitat, and dredging and navigation. Hydrodynamic and sediment transport data are essential for calibration and testing of numerical models that may be used to address management questions related to these topics. Herein we report preliminary analyses of near-bed turbulence and sediment flux measurements in the Sacramento-San Joaquin Delta, a large network of tidal channels and wetlands located at the confluence of the Sacramento and San Joaquin Rivers, California, USA (Figure 1). Measurements were made in 6 channels spanning a wide range of size and tidal conditions, from small channels that are primarily fluvial to large channels that are tidally dominated. The results of these measurements are summarized herein and the hydrodynamic and sediment transport characteristics of the channels are compared across this range of size and conditions.

  9. Results of scoping tests for open-cycle OTEC (ocean thermal energy conversion) components operating with seawater

    Energy Technology Data Exchange (ETDEWEB)

    Zangrando, F; Bharathan, D; Green, H J; Link, H F; Parsons, B K; Parsons, J M; Pesaran, A A [Solar Energy Research Inst., Golden, CO (USA); Panchal, C B [Argonne National Lab., IL (USA)

    1990-09-01

    This report presents comprehensive documentation of the experimental research conducted on open-cycle ocean thermal energy conversion (OC-OTEC) components operating with seawater as a working fluid. The results of this research are presented in the context of previous analysis and fresh-water testing; they provide a basis for understanding and predicting with confidence the performance of all components of an OC-OTEC system except the turbine. Seawater tests have confirmed the results that were obtained in fresh-water tests and predicted by the analytical models of the components. A sound technical basis has been established for the design of larger systems in which net power will be produced for the first time from OC-OTEC technology. Design and operation of a complete OC-OTEC system that produces power will provide sufficient confidence to warrant complete transfer of OC-OTEC technology to the private sector. Each components performance is described in a separate chapter written by the principal investigator responsible for technical aspects of the specific tests. Chapters have been indexed separately for inclusion on the data base.

  10. Tidal characteristics in the Wenzhou offshore waters and changes resulting from the Wenzhou Shoal Reclamation Project

    Science.gov (United States)

    Bao, Min; Bao, Xianwen; Yu, Huaming; Ding, Yang

    2015-12-01

    The Wenzhou Shoal Reclamation Project is the core part of Wenzhou Peninsula Engineering which is a big comprehensive development project to expand the city space. The dynamics of the surrounding area was proved to suffer little effect in response to the Lingni north dyke since it was built approximately along the current direction. Therefore, this paper focuses firstly on the tidal characteristics in the Wenzhou and Yueqing bays with the Lingni north dyke being built and then on the changes resulting from the implementation of the on-going Wenzhou Shoal Reclamation Project (WSRP) which will reclaim land from the whole Wenzhou Shoal. To simulate the tidal dynamics, a high-resolution coastal ocean model with unstructured triangular grids was set up for the Wenzhou and Yueqing Bays. The model resolved the complicated tidal dynamics with the simulated tidal elevation and current in good agreement with observations. In the study area, M2 is the predominant tidal component, which means the tide is semidiurnal. The new reclamation project hardly affects the Yueqing Bay and the open ocean, but there are concentrated effects on the mouth of the southern branch of the Oujiang River and the southwest of Wenzhou Shoal. This study provides an indicative reference to the local government and helps to weigh the advantages and disadvantages of the project.

  11. Effects of gas composition on the delivered tidal volume of the Avance Carestation.

    Science.gov (United States)

    Miyaji, Tetsuya; Fukakura, Yoshimasa; Usuda, Yutaka; Maruyama, Koichi; Hirabayashi, Go; Yamada, Rieko; Akihisa, Yuki; Nishioka, Hiroko; Andoh, Tomio

    2015-10-01

    Measurements with various flowmeters are affected by changes in gas mixture density. The Avance Carestation incorporates ventilator feedback controlled by a built-in flowmeter with a variable orifice sensor. We hypothesised that changes in the composition of delivered gas may cause changes in the delivered tidal volume by affecting the flow measurement unless appropriate corrections are made. We used 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O as carrier gases with/without sevoflurane and desflurane. We measured delivered tidal volume using the FlowAnalyzer™ PF 300 calibrated with the corresponding gas mixtures during volume control ventilation with 500-ml tidal volume using the Avance Carestation connected to a test lung. Change of carrier gas and addition of sevoflurane and desflurane significantly altered delivered tidal volume. Desflurane 6 % reduced delivered tidal volume by 7.6, 3.6 and 16 % of the pre-set volume at 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O, respectively. Importantly, the Carestation panel indicator did not register these changes in measured expired tidal volume. Ratios of delivered tidal volume to 500 ml correlated inversely with the square root of the delivered gas density. These results support our hypothesis and suggest that changing gas composition may alter delivered tidal volume of anesthesia machines with built-in ventilators that are feedback-controlled by uncorrected flowmeters due to changes in gas mixture density.

  12. Tidally-forced flow in a rotating, stratified, shoaling basin

    Science.gov (United States)

    Winters, Kraig B.

    2015-06-01

    Baroclinic flow of a rotating, stratified fluid in a parabolic basin is computed in response to barotropic tidal forcing using the nonlinear, non-hydrostatic, Boussinesq equations of motion. The tidal forcing is derived from an imposed, boundary-enhanced free-surface deflection that advances cyclonically around a central amphidrome. The tidal forcing perturbs a shallow pycnocline, sloshing it up and down over the shoaling bottom. Nonlinearities in the near-shore internal tide produce an azimuthally independent 'set-up' of the isopycnals that in turn drives an approximately geostrophically balanced, cyclonic, near-shore, sub-surface jet. The sub-surface cyclonic jet is an example of a slowly evolving, nearly balanced flow that is excited and maintained solely by forcing in the fast, super-inertial frequency band. Baroclinic instability of the nearly balanced jet and subsequent interactions between eddies produce a weak transfer of energy back into the inertia-gravity band as swirling motions with super-inertial vorticity stir the stratified fluid and spontaneously emit waves. The sub-surface cyclonic jet is similar in many ways to the poleward flows observed along eastern ocean boundaries, particularly the California Undercurrent. It is conjectured that such currents may be driven by the surface tide rather than by winds and/or along-shore pressure gradients.

  13. River-tide dynamics: Exploration of nonstationary and nonlinear tidal behavior in the Yangtze River estuary

    Science.gov (United States)

    Guo, Leicheng; van der Wegen, Mick; Jay, David A.; Matte, Pascal; Wang, Zheng Bing; Roelvink, Dano; He, Qing

    2015-05-01

    River-tide dynamics remain poorly understood, in part because conventional harmonic analysis (HA) does not cope effectively with nonstationary signals. To explore nonstationary behavior of river tides and the modulation effects of river discharge, this work analyzes tidal signals in the Yangtze River estuary using both HA in a nonstationary mode and continuous wavelet transforms (CWT). The Yangtze is an excellent natural laboratory to analyze river tides because of its high and variable flow, its length, and the fact that there are do dams or reflecting barriers within the tidal part of the system. Analysis of tidal frequencies by CWT and analysis of subtidal water level and tidal ranges reveal a broad range of subtidal variations over fortnightly, monthly, semiannual, and annual frequencies driven by subtidal variations in friction and by variable river discharges. We employ HA in a nonstationary mode (NSHA) by segregating data within defined flow ranges into separate analyses. NSHA quantifies the decay of the principal tides and the modulation of M4 tide with increasing river discharges. M4 amplitudes decrease far upriver (landward portion of the estuary) and conversely increase close to the ocean as river discharge increases. The fortnightly frequencies reach an amplitude maximum upriver of that for over tide frequencies, due to the longer wavelength of the fortnightly constituents. These methods and findings should be applicable to large tidal rivers globally and have broad implications regarding management of navigation channels and ecosystems in tidal rivers.

  14. Estimating Coastal Lagoon Tidal Flooding and Repletion with Multidate ASTER Thermal Imagery

    Directory of Open Access Journals (Sweden)

    Thomas R. Allen

    2012-10-01

    Full Text Available Coastal lagoons mix inflowing freshwater and tidal marine waters in complex spatial patterns. This project sought to detect and measure temperature and spatial variability of flood tides for a constricted coastal lagoon using multitemporal remote sensing. Advanced Spaceborne Thermal Emission Radiometer (ASTER thermal infrared data provided estimates of surface temperature for delineation of repletion zones in portions of Chincoteague Bay, Virginia. ASTER high spatial resolution sea-surface temperature imagery in conjunction with in situ observations and tidal predictions helped determine the optimal seasonal data for analyses. The selected time series ASTER satellite data sets were analyzed at different tidal phases and seasons in 2004–2006. Skin surface temperatures of ocean and estuarine waters were differentiated by flood tidal penetration and ebb flows. Spatially variable tidal flood penetration was evaluated using discrete seed-pixel area analysis and time series Principal Components Analysis. Results from these techniques provide spatial extent and variability dynamics of tidal repletion, flushing, and mixing, important factors in eutrophication assessment, water quality and resource monitoring, and application of hydrodynamic modeling for coastal estuary science and management.

  15. TIDAL FRICTION AND TIDAL LAGGING. APPLICABILITY LIMITATIONS OF A POPULAR FORMULA FOR THE TIDAL TORQUE

    Energy Technology Data Exchange (ETDEWEB)

    Efroimsky, Michael; Makarov, Valeri V., E-mail: michael.efroimsky@usno.navy.mil, E-mail: vvm@usno.navy.mil [US Naval Observatory, Washington, DC 20392 (United States)

    2013-02-10

    Tidal torques play a key role in rotational dynamics of celestial bodies. They govern these bodies' tidal despinning and also participate in the subtle process of entrapment of these bodies into spin-orbit resonances. This makes tidal torques directly relevant to the studies of habitability of planets and their moons. Our work begins with an explanation of how friction and lagging should be built into the theory of bodily tides. Although much of this material can be found in various publications, a short but self-consistent summary on the topic has been lacking in the hitherto literature, and we are filling the gap. After these preparations, we address a popular concise formula for the tidal torque, which is often used in the literature, for planets or stars. We explain why the derivation of this expression, offered in the paper by Goldreich and in the books by Kaula (Equation (4.5.29)) and Murray and Dermott (Equation (4.159)), implicitly sets the time lag to be frequency independent. Accordingly, the ensuing expression for the torque can be applied only to bodies having a very special (and very hypothetical) rheology which makes the time lag frequency independent, i.e., the same for all Fourier modes in the spectrum of tide. This expression for the torque should not be used for bodies of other rheologies. Specifically, the expression cannot be combined with an extra assertion of the geometric lag being constant, because at finite eccentricities the said assumption is incompatible with the constant-time-lag condition.

  16. Observations of a tidal intrusion front in a tidal channel

    Science.gov (United States)

    Lu, Shasha; Xia, Xiaoming; Thompson, Charlie E. L.; Cao, Zhenyi; Liu, Yifei

    2017-11-01

    A visible front indicated by a surface colour change, and sometimes associated with foam or debris lines, was observed in a tidal channel during neap tide. This is an example of a tidal intrusion front occurring in the absence of sudden topographical changes or reversing flows, typically reported to be associated with such fronts. Detailed Acoustic Doppler Current Profiler and conductivity/temperature/depth measurements were taken on repeated transects both with fronts apparent and with fronts absent. The results indicated that the front occurred as a result of stratification, which was sustained by the buoyancy flux and the weak tide-induced mixing during neap ebb tide. The stronger tide-induced mixing during spring tide restrained stratification, leading to the absence of a front. The mechanism of the frontogenesis was the density gradient between the stratified water formed during neap ebb tide, and the more mixed seawater during neap flood tide; thus, the water on the landward (southwestern) side of the front was stratified, and that on the seaward side (northeastern) of the front was vertically well mixed. Gradient Richardson number estimates suggest that the flow between the stratified and mixed water was near the threshold 0.25 for shear instability. Meanwhile, the density gradient would provide an initial baroclinic contribution to velocity convergence, which is indicated by the accumulation of buoyant matter such as foam, grass, and debris into a sharply defined line along the surface. The front migrates with the flood current, with a local maximum towards the eastern side of the channel, leading to an asymmetrical shape with the eastern side of the front driven further into the Tiaozhoumen tidal channel.

  17. Eddy Generation and Shedding in a Tidally Energetic Channel

    Science.gov (United States)

    McIlvenny, J.; Gillibrand, P. A.; Walters, R. A.

    2016-02-01

    The Pentland Firth in northern Scotland, and its subsidiary channel the Inner Sound, are currently under scrutiny as the first tidal energy array in the world is installed during 2016. The tidal flows in the channel and sound have been intensively observed and modelled in recent years, and the turbulent nature of the flow, with features of eddy generation and shedding, is becoming increasingly well known. Turbulence and eddies pose potential risks to the turbine infrastructure through enhanced stress on the blades, while understanding environmental effects of energy extraction also requires accurate simulation of the hydrodynamics of the flow. Here, we apply a mixed finite element/finite volume hydrodynamic model to the northern Scottish shelf, with a particular focus on flows through the Pentland Firth and the Inner Sound. We use an unstructured grid model, which allows the open boundaries to be far removed from the region of interest, while still allowing a grid spacing of 40m in the Inner Sound. The model employs semi-implicit techniques to solve the momentum and free surface equations, and semi-Lagrangian methods to solve the material derivative in the momentum equation, making it fast, robust and accurate and suitable for simulating flows in irregular coastal ocean environments. The model is well suited to address questions relating to tidal energy potential. We present numerical simulations of tidal currents in The Pentland Firth and Inner Sound. Observed velocities in the Inner Sound, measured by moored ADCP deployments, reach speeds of up to 5 m s-1 and the model successfully reproduces these strong currents. In the simulations, eddies are formed by interactions between the strong flow and the northern and southern headlands on the island of Stroma; some of these eddies are trapped and remain locked in position, whereas others are shed and transported away from the generation zone. We track the development and advection of eddies in relation to the site of

  18. Reversing tidal flow and estuarine morphodynamics in the Metronome laboratory flume

    NARCIS (Netherlands)

    Kleinhans, M.G.; Leuven, J.R.F.W.; Braat, L.; van der Vegt, M.; van Maarseveen, M.C.G.; Markies, H.; Roosendaal, C.; van Eijk, A.M.

    2016-01-01

    Our objective is to test a novel experimental principle for creating reversing tidal flows of sufficient strength to cause estuarine morphodynamics. The study of estuarine morphodynamics has hitherto been limited to field observation and numerical modelling, whilst fluvial morphodynamics have

  19. Dynamics of tidal and non-tidal currents along the southwest continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Aruna, C.; Ravichandran, C.; Srinivas, K.; Rasheed, P.A.A; Lekshmi, S.

    The tidal regimes over the continental shelves are often less documented due to lack of coastal water level data. This is of concern since continental shelves rule the global dissipation of tidal energy. The tides along the Southwest Indian shelf...

  20. Interactions between wind and tidally induced currents in coastal and shelf basins

    Science.gov (United States)

    Jacob, Benjamin; Stanev, Emil Vassilev

    2017-10-01

    This paper addresses the impact of atmospheric variability on ocean circulation in tidal and non-tidal basins. The data are generated by an unstructured-grid numerical model resolving the dynamics in the coastal area, as well as in the straits connecting the North Sea and Baltic Sea. The model response to atmospheric forcing in different frequency intervals is quantified. The results demonstrate that the effects of the two mechanical drivers, tides and wind, are not additive, yet non-linear interactions play an important role. There is a tendency for tidally and wind-driven circulations to be coupled, in particular in the coastal areas and straits. High-frequency atmospheric variability tends to amplify the mean circulation and modify the exchange between the North and the Baltic Sea. The ocean response to different frequency ranges in the wind forcing is area-selective depending on specific local dynamics. The work done by wind on the oceanic circulation depends strongly upon whether the regional circulation is tidally or predominantly wind-driven. It has been demonstrated that the atmospheric variability affects the spring-neap variability very strongly.

  1. Array Optimization for Tidal Energy Extraction in a Tidal Channel – A Numerical Modeling Analysis

    OpenAIRE

    Yang, Zhaoqing; Wang, Taiping; Copping, Andrea

    2014-01-01

    This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in a tidal dominated estuary in the Pacific Northwest coast. A series of numerical experiments were carried out to simulate tidal energy extraction with different turbine array configurations, including location, spacing and array size. Preliminary model results suggest that array optimization for tidal energy extraction in a real-world site is a very complex process that requires consideration of m...

  2. Characterization of U.S. Wave Energy Converter (WEC) Test Sites: A Catalogue of Met-Ocean Data, 2nd Edition

    Energy Technology Data Exchange (ETDEWEB)

    Dallman, Ann R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Water Power Technologies; Neary, Vincent S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Water Power Technologies

    2015-09-01

    This report presents met-ocean data and wave energy characteristics at eight U.S. wave energy converter (WEC) test and potential deployment sites. Its purpose is to enable the comparison of wave resource characteristics among sites as well as the selection of test sites that are most suitable for a developer's device and that best meet their testing needs and objectives. It also provides essential inputs for the design of WEC test devices and planning WEC tests, including the planning of deployment, and operations and maintenance. For each site, this report catalogues wave statistics recommended in the International Electrotechnical Commission Technical Speci cation (IEC 62600-101 TS) on Wave Energy Characterization, as well as the frequency of occurrence of weather windows and extreme sea states, and statistics on wind and ocean currents. It also provides useful information on test site infrastructure and services.

  3. Validation Test Report for the Improved Synthetic Ocean Profile (ISOP) System, Part I: Synthetic Profile Methods and Algorithm

    Science.gov (United States)

    2013-03-15

    Naval Research for funding the Naval Research Laboratory project The Impact of Spice on Ocean Circulation , program element 61153N. The authors also... Thermohaline Strucure from Fields Mearuable by Satellite." J. Atmos. Ocean. Tech., 1994: 551-566. Cummings, J. A. "Operational multivariate ocean data...34Relationship of TOPEX/Poseidon altimetric height to steric height and circulation in the North Pacific." J. Geophys. Res., 1998: 27,947- 27,965

  4. Twenty Years of Progress on Global Ocean Tides: The Impact of Satellite Altimetry

    Science.gov (United States)

    Egbert, Gary; Ray, Richard

    2012-01-01

    At the dawn of the era of high-precision altimetry, before the launch of TOPEX/Poseidon, ocean tides were properly viewed as a source of noise--tidal variations in ocean height would represent a very substantial fraction of what the altimeter measures, and would have to be accurately predicted and subtracted if altimetry were to achieve its potential for ocean and climate studies. But to the extent that the altimetry could be severely contaminated by tides, it also represented an unprecedented global-scale tidal data set. These new data, together with research stimulated by the need for accurate tidal corrections, led to a renaissance in tidal studies in the oceanographic community. In this paper we review contributions of altimetry to tidal science over the past 20 years, emphasizing recent progress. Mapping of tides has now been extended from the early focus on major constituents in the open ocean to include minor constituents, (e.g., long-period tides; non-linear tides in shelf waters, and in the open ocean), and into shallow and coastal waters. Global and spatially local estimates of tidal energy balance have been refined, and the role of internal tide conversion in dissipating barotropic tidal energy is now well established through modeling, altimetry, and in situ observations. However, energy budgets for internal tides, and the role of tidal dissipation in vertical ocean mixing remain controversial topics. Altimetry may contribute to resolving some of these important questions through improved mapping of low-mode internal tides. This area has advanced significantly in recent years, with several global maps now available, and progress on constraining temporally incoherent components. For the future, new applications of altimetry (e.g., in the coastal ocean, where barotropic tidal models remain inadequate), and new mission concepts (studies of the submesoscale with SWOT, which will require correction for internal tides) may bring us full circle, again pushing

  5. General relativistic tidal work for Papapetrou, Weinberg and Goldberg pseudotensors

    CERN Document Server

    So, Lau Loi

    2015-01-01

    In 1998 Thorne claimed that all pseudotensors give the same tidal work as the Newtonian theory. In 1999, Purdue used the Landau-Lifshitz pseudotensor to calculate the tidal heating and the result matched with the Newtonian gravity. Soon after in 2001, Favata employed the same method to examine the Einstein, Bergmann-Thomson and M{\\o}ller pseudotensors, all of them give the same result as Purdue did. Inspired by the work of Purdue and Favata, for the completeness, here we manipulate the tidal work for Papapetrou, Weinberg and Goldberg pseudotensors. We obtained the same tidal work as Purdue achieved. In addition, we emphasize that a suitable gravitational energy-momentum pseudotensor requires fulfill the inside matter condition and all of the classical pseudotensors pass this test except M$\\o$ller. Moreover, we constructed a general pseudotesnor which is modified by 13 linear artificial higher order terms combination with Einstein pseudotensor. We find that the result agrees with Thorne's prediction, i.e., rel...

  6. Global Ocean Forecast System V3.0 Validation Test Report Addendum: Provision of Boundary Conditions to the Relocatable Navy Coastal Ocean Model (NCOM)

    Science.gov (United States)

    2012-03-21

    Model (NLOM) and 1/8º Modular Ocean Data Assimilation ( MODAS )). This document can be viewed as both a User’s Manual and an addendum to the Phase II...8217 = experiment number x10 (000=from archive file) 3 ’yrflag’ = days in year flag (0=360J16,1=366J16,2=366J01,3- actual ) $NX ’idm...366J01,3- actual ) $NX ’idm ’ = longitudinal array size $NY ’jdm ’ = latitudinal array size 32 ’kdm ’ = number of layers 34.0

  7. Storm surge and tidal range energy

    Science.gov (United States)

    Lewis, Matthew; Angeloudis, Athanasios; Robins, Peter; Evans, Paul; Neill, Simon

    2017-04-01

    The need to reduce carbon-based energy sources whilst increasing renewable energy forms has led to concerns of intermittency within a national electricity supply strategy. The regular rise and fall of the tide makes prediction almost entirely deterministic compared to other stochastic renewable energy forms; therefore, tidal range energy is often stated as a predictable and firm renewable energy source. Storm surge is the term used for the non-astronomical forcing of tidal elevation, and is synonymous with coastal flooding because positive storm surges can elevate water-levels above the height of coastal flood defences. We hypothesis storm surges will affect the reliability of the tidal range energy resource; with negative surge events reducing the tidal range, and conversely, positive surge events increasing the available resource. Moreover, tide-surge interaction, which results in positive storm surges more likely to occur on a flooding tide, will reduce the annual tidal range energy resource estimate. Water-level data (2000-2012) at nine UK tide gauges, where the mean tidal amplitude is above 2.5m and thus suitable for tidal-range energy development (e.g. Bristol Channel), were used to predict tidal range power with a 0D modelling approach. Storm surge affected the annual resource estimate by between -5% to +3%, due to inter-annual variability. Instantaneous power output were significantly affected (Normalised Root Mean Squared Error: 3%-8%, Scatter Index: 15%-41%) with spatial variability and variability due to operational strategy. We therefore find a storm surge affects the theoretical reliability of tidal range power, such that a prediction system may be required for any future electricity generation scenario that includes large amounts of tidal-range energy; however, annual resource estimation from astronomical tides alone appears sufficient for resource estimation. Future work should investigate water-level uncertainties on the reliability and

  8. New ERP predictions based on (sub-)daily ocean tides from satellite altimetry data

    Science.gov (United States)

    Madzak, Matthias; Böhm, Sigrid; Böhm, Johannes; Bosch, Wolfgang; Schuh, Harald

    2013-04-01

    A new model for Earth rotation variations based on ocean tide models is highly desirable in order to close the gap between geophysical Earth rotation models and geodetic observations. We have started a project, SPOT (Short Period Ocean Tidal variations in Earth Rotation), with the goal to develop a new model of short period Earth rotation variations based on one of the best currently available empirical ocean tide models obtained from satellite altimetry. We employ the EOT11a model which is an upgrade of EOT08a, developed at DGFI, Munich. As EOT11a does not provide the tidal current velocities which are fundamental contributors to Earth rotation excitation, the calculation of current velocities from the tidal elevations is one of three main areas of research in project SPOT. The second key aspect is the conversion from ocean tidal angular momentum to the corresponding ERP variations using state-of-the-art transfer functions. A peculiar innovation at this step will be to consider the Earth's response to ocean tidal loading based on a realistic Earth model, including an anelastic mantle. The third part of the project deals with the introduction of the effect of minor tides. Ocean tide models usually only provide major semi-diurnal and diurnal tidal terms and the minor tides have to be inferred through admittance assumptions. Within the proposed project, selected minor tidal terms and the corresponding ERP variations shall be derived directly from satellite altimetry data. We determine ocean tidal angular momentum of four diurnal and five sub-daily tides from EOT11a and apply the angular momentum approach to derive a new model of ocean tidal Earth rotation variations. This poster gives a detailed description of project SPOT as well as the status of work progress. First results are presented as well.

  9. Annual Energy Production (AEP) optimization for tidal power plants based on Evolutionary Algorithms - Swansea Bay Tidal Power Plant AEP optimization

    Science.gov (United States)

    Kontoleontos, E.; Weissenberger, S.

    2016-11-01

    In order to be able to predict the maximum Annual Energy Production (AEP) for tidal power plants, an advanced AEP optimization procedure is required for solving the optimization problem which consists of a high number of design variables and constraints. This efficient AEP optimization procedure requires an advanced optimization tool (EASY software) and an AEP calculation tool that can simulate all different operating modes of the units (bidirectional turbine, pump and sluicing mode). The EASY optimization software is a metamodel-assisted Evolutionary Algorithm (MAEA) that can be used in both single- and multi-objective optimization problems. The AEP calculation tool, developed by ANDRITZ HYDRO, in combination with EASY is used to maximize the tidal annual energy produced by optimizing the plant operation throughout the year. For the Swansea Bay Tidal Power Plant project, the AEP optimization along with the hydraulic design optimization and the model testing was used to evaluate all different hydraulic and operating concepts and define the optimal concept that led to a significant increase of the AEP value. This new concept of a triple regulated “bi-directional bulb pump turbine” for Swansea Bay Tidal Power Plant (16 units, nominal power above 320 MW) along with its AEP optimization scheme will be presented in detail in the paper. Furthermore, the use of an online AEP optimization during operation of the power plant, that will provide the optimal operating points to the control system, will be also presented.

  10. Microbial quality of a marine tidal pool

    CSIR Research Space (South Africa)

    Genthe, Bettina

    1995-01-01

    Full Text Available tidal pool water was compared to South African and other marine water quality guidelines. The microbial quality of a marine tidal pool on South Africa's Atlantic coast was found to be inferior to that of the adjoining seawater (the latter Complying...

  11. Organic matter processing in tidal estuaries

    NARCIS (Netherlands)

    Middelburg, J.J.; Herman, P.M.J.

    2007-01-01

    Processing of organic matter in tidal estuaries modifies its transfer from the river to the sea. We examined the distribution and the elemental and isotopic composition of organic matter in nine tidal estuaries along the Atlantic coast of Europe (Elbe, Ems, Thames, Rhine, Scheldt, Loire, Gironde,

  12. Tidal power from the Bay of Fundy

    Energy Technology Data Exchange (ETDEWEB)

    van Walsum, W.

    1998-10-01

    The potential for tidal power development in New Brunswick`s Bay of Fundy was discussed. Alternative methods of tidal plant operation, suitable for the site conditions of the head of the Bay (where there are two continuous basins), were described. Tidal power is strongly influenced by site conditions. A simple mathematical model has shown that for the location at the head of the Bay, a linked-basins plant could produce 5 per cent more energy with only 53 per cent of the power generating machinery that would be required for a conventional paired basins scheme. The challenge is to find an economical, environmentally friendly way of extracting power and energy from the tides. An early study series from 1966 to 1988 has shown that tidal power can be economical, yet nothing has materialized beyond an 18 MW pilot plant at Annapolis because of environmental concerns. In 1977, this single basin tidal power plant was found to increase the tidal range at Boston by 30 cm. It was suggested that a `tidal fence` may be an ecologically acceptable solution to this problem. Attention was drawn to the need to draft a master plan for the development of Fundy`s tidal power potential, making sure that early development does not jeopardize optimum development of the total resource. 8 refs., 6 figs.

  13. Tidal power plant prototype achieves 99% availability

    Energy Technology Data Exchange (ETDEWEB)

    DeLory, R.P.

    1987-01-01

    In 1984 the Annapolis Royal tidal power plant (Canada) was connected to the national grid and achieved 99% availability in its first year. It is the first tidal power plant built in North America and the first in the world which operates a large-diameter Straflo turbine.

  14. Prototype tidal power plant achieves 99% availability

    Energy Technology Data Exchange (ETDEWEB)

    De Lory, R.P.

    1987-01-01

    The Annapolis Royal (Canada) tidal power plant officially came on line in 1984. In its first year it achieved 99% availability. It is the first tidal power plant in North America and the first plant in the world to employ a large diameter Straflo turbine. The performance of the prototype plant is discussed.

  15. Tidal constraints on the interior of Venus

    Science.gov (United States)

    Dumoulin, Caroline; Tobie, Gabriel; Verhoeven, Olivier; Rosenblatt, Pascal; Rambaux, Nicolas

    2016-10-01

    As a prospective study for a future exploration of Venus, we propose to systematically investigate the signature of the internal structure in the gravity field and the rotation state of Venus, through the determination of the moment of inertia and the tidal Love number.We test various mantle compositions, core size and density as well as temperature profiles representative of different scenarios for formation and evolution of Venus. The mantle density ρ and seismic vP and vS wavespeeds are computed in a consistent manner from given temperature and composition using the Perple X program. This method computes phase equilibria and uses the thermodynamics of mantle minerals developped by Stixrude and Lithgow-Bertelloni (2011).The viscoelastic deformation of the planet interior under the action of periodic tidal forces are computed following the method of Tobie et al. (2005).For a variety of interior models of Venus, the Love number, k2, and the moment of inertia factor are computed following the method described above. The objective is to determine the sensitivity of these synthetic results to the internal structure. These synthetic data are then used to infer the measurement accuracies required on the time-varying gravitational field and the rotation state (precession rate, nutation and length of day variations) to provide useful constraints on the internal structure.We show that a better determination of k2, together with an estimation of the moment of inertia, the radial displacement, and of the time lag, if possible, will refine our knowledge on the present-day interior of Venus (size of the core, mantle temperature, composition and viscosity). Inferring these quantities from a future ex- ploration mission will provide essential constraints on the formation and evolution scenarios of Venus.

  16. Seasonal, diel, and tidal CO2 variation in the Bay of Fundy

    Science.gov (United States)

    Horwitz, Rachel; Burt, William J.; Hay, Alex; Thomas, Helmuth

    2017-04-01

    Anthropogenic CO2 emissions acidify the oceans and have potentially adverse effects for ecosystems, living marine resources, and the fisheries and mariculture industries that depend on them. Assessing the vulnerability of these resources to ocean acidification requires a detailed understanding of both the system's natural variability and its response to the ocean's uptake of anthropogenic CO2. A cabled-to-shore observatory was installed in Grand Passage, a tidal channel in the Bay of Fundy, Nova Scotia. Measurements from a CO2 sensor, CTD, and ADCP provide year-long time series of pCO2, temperature, salinity, and currents. The dominant seasonal cycle of pCO2 indicates a spring bloom in April and May, and net respiration from November through March. This seasonal cycle is modulated by a large diel cycle in summertime, and by equal contributions from diel and tidal variation in winter. The oceanic CO2 partial pressure (pCO2) is higher than the atmospheric pCO2 for most of the year, indicating an annual average balance between respiration and outgassing at this site. Further analysis aims to link observations in this tidal channel to the larger Bay of Fundy - Gulf of Maine carbon system.

  17. Pressure-gradient-driven nearshore circulation on a beach influenced by a large inlet-tidal shoal system

    Science.gov (United States)

    Shi, F.; Hanes, D. M.; Kirby, J. T.; Erikson, L.; Barnard, P.; Eshleman, J.

    2011-04-01

    The nearshore circulation induced by a focused pattern of surface gravity waves is studied at a beach adjacent to a major inlet with a large ebb tidal shoal. Using a coupled wave and wave-averaged nearshore circulation model, it is found that the nearshore circulation is significantly affected by the heterogeneous wave patterns caused by wave refraction over the ebb tidal shoal. The model is used to predict waves and currents during field experiments conducted near the mouth of San Francisco Bay and nearby Ocean Beach. The field measurements indicate strong spatial variations in current magnitude and direction and in wave height and direction along Ocean Beach and across the ebb tidal shoal. Numerical simulations suggest that wave refraction over the ebb tidal shoal causes wave focusing toward a narrow region at Ocean Beach. Due to the resulting spatial variation in nearshore wave height, wave-induced setup exhibits a strong alongshore nonuniformity, resulting in a dramatic change in the pressure field compared to a simulation with only tidal forcing. The analysis of momentum balances inside the surf zone shows that, under wave conditions with intensive wave focusing, the alongshore pressure gradient associated with alongshore nonuniform wave setup can be a dominant force driving circulation, inducing heterogeneous alongshore currents. Pressure-gradient-forced alongshore currents can exhibit flow reversals and flow convergence or divergence, in contrast to the uniform alongshore currents typically caused by tides or homogeneous waves.

  18. Pressure-gradient-driven nearshore circulation on a beach influenced by a large inlet-tidal shoal system

    Science.gov (United States)

    Shi, F.; Hanes, D.M.; Kirby, J.T.; Erikson, L.; Barnard, P.; Eshleman, J.

    2011-01-01

    The nearshore circulation induced by a focused pattern of surface gravity waves is studied at a beach adjacent to a major inlet with a large ebb tidal shoal. Using a coupled wave and wave-averaged nearshore circulation model, it is found that the nearshore circulation is significantly affected by the heterogeneous wave patterns caused by wave refraction over the ebb tidal shoal. The model is used to predict waves and currents during field experiments conducted near the mouth of San Francisco Bay and nearby Ocean Beach. The field measurements indicate strong spatial variations in current magnitude and direction and in wave height and direction along Ocean Beach and across the ebb tidal shoal. Numerical simulations suggest that wave refraction over the ebb tidal shoal causes wave focusing toward a narrow region at Ocean Beach. Due to the resulting spatial variation in nearshore wave height, wave-induced setup exhibits a strong alongshore nonuniformity, resulting in a dramatic change in the pressure field compared to a simulation with only tidal forcing. The analysis of momentum balances inside the surf zone shows that, under wave conditions with intensive wave focusing, the alongshore pressure gradient associated with alongshore nonuniform wave setup can be a dominant force driving circulation, inducing heterogeneous alongshore currents. Pressure-gradient- forced alongshore currents can exhibit flow reversals and flow convergence or divergence, in contrast to the uniform alongshore currents typically caused by tides or homogeneous waves.

  19. Effects of ocean acidification and diet on thickness and carbonate elemental composition of the test of juvenile sea urchins.

    Science.gov (United States)

    Asnaghi, Valentina; Mangialajo, Luisa; Gattuso, Jean-Pierre; Francour, Patrice; Privitera, Davide; Chiantore, Mariachiara

    2014-02-01

    Continuous anthropogenic CO2 emissions to the atmosphere and uptake by the oceans will cause a reduction of seawater pH and saturation state (Ω) of CaCO3 minerals from which marine calcifiers build their shells and skeletons. Sea urchins use the most soluble form of calcium carbonate, high-magnesium calcite, to build their skeleton, spines and grazing apparatus. In order to highlight the effects of increased pCO2 on the test thickness and carbonate elemental composition of juvenile sea urchins and potential differences in their responses linked to the diet, we performed a laboratory experiment on juvenile Paracentrotus lividus, grazing on calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea, Dictyota dichotoma) macroalgae, under different pH (corresponding to pCO2 values of 390, 550, 750 and 1000 μatm). Results highlighted the importance of the diet in determining sea urchin size irrespectively of the pCO2 level, and the relevance of macroalgal diet in modulating urchin Mg/Ca ratio. The present study provides relevant clues both in terms of the mechanism of mineral incorporation and in terms of bottom-up processes (algal diet) affecting top-down ones (fish predation) in rocky subtidal communities. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Does elevation matter? Living foraminiferal distribution in a hyper tidal salt marsh (Canche Estuary, Northern France)

    Science.gov (United States)

    Francescangeli, F.; Bouchet, V. M. P.; Trentesaux, A.; Armynot du Chatelet, E.

    2017-07-01

    In the present study we investigate the ecology and distribution of living benthic foraminifera to test the effect of hyper tidal exposure and their suitability as sea level indicators. Within a salt marsh area along the Canche Estuary (northern France), four transects were sampled to see the effects of maximal tidal constraints (shore transects) and minimal tidal constraints (alongshore transects). Multivariate analyses have been performed to determine the correlations between biotic (foraminiferal absolute abundances) and abiotic factors (elevation, grain-size, TOC and total sulphur). For each of the principal benthic foraminiferal species the tolerance to subaerial exposure have been estimated as well. Two distinctive foraminiferal zones have been identified along the vertical tidal gradient: a zone I in the higher part of the salt marsh dominated by agglutinated and porcelaneous taxa, and a zone II in the lower one dominated by hyaline specimens. Hyper tidal exposure constraints the foraminiferal vertical zonation in accordance with the tidal frame. However it does not constitute a threshold parameter able by itself to explain all the faunal variations in the Canche Estuary. For sea level indicators, foraminifera should be considered relative to tidal subaerial exposure rather than to absolute altitude.

  1. Enceladus's crust as a non-uniform thin shell: I tidal deformations

    Science.gov (United States)

    Beuthe, Mikael

    2018-03-01

    The geologic activity at Enceladus's south pole remains unexplained, though tidal deformations are probably the ultimate cause. Recent gravity and libration data indicate that Enceladus's icy crust floats on a global ocean, is rather thin, and has a strongly non-uniform thickness. Tidal effects are enhanced by crustal thinning at the south pole, so that realistic models of tidal tectonics and dissipation should take into account the lateral variations of shell structure. I construct here the theory of non-uniform viscoelastic thin shells, allowing for depth-dependent rheology and large lateral variations of shell thickness and rheology. Coupling to tides yields two 2D linear partial differential equations of the fourth order on the sphere which take into account self-gravity, density stratification below the shell, and core viscoelasticity. If the shell is laterally uniform, the solution agrees with analytical formulas for tidal Love numbers; errors on displacements and stresses are less than 5% and 15%, respectively, if the thickness is less than 10% of the radius. If the shell is non-uniform, the tidal thin shell equations are solved as a system of coupled linear equations in a spherical harmonic basis. Compared to finite element models, thin shell predictions are similar for the deformations due to Enceladus's pressurized ocean, but differ for the tides of Ganymede. If Enceladus's shell is conductive with isostatic thickness variations, surface stresses are approximately inversely proportional to the local shell thickness. The radial tide is only moderately enhanced at the south pole. The combination of crustal thinning and convection below the poles can amplify south polar stresses by a factor of 10, but it cannot explain the apparent time lag between the maximum plume brightness and the opening of tiger stripes. In a second paper, I will study the impact of a non-uniform crust on tidal dissipation.

  2. 77 FR 1674 - Ocean Renewable Power Company Maine, LLC; Notice of Availability of Environmental Assessment for...

    Science.gov (United States)

    2012-01-11

    ... Renewable Power Company, LLC's application for an 8-year pilot license for the proposed Cobscook Bay Tidal... Energy Regulatory Commission Ocean Renewable Power Company Maine, LLC; Notice of Availability of Environmental Assessment for the Proposed Cobscook Bay Tidal Energy Project In accordance with the National...

  3. Tidal current and tidal energy changes imposed by a dynamic tidal power system in the Taiwan Strait, China

    Science.gov (United States)

    Dai, Peng; Zhang, Jisheng; Zheng, Jinhai

    2017-12-01

    The Taiwan Strait has recently been proposed as a promising site for dynamic tidal power systems because of its shallow depth and strong tides. Dynamic tidal power is a new concept for extracting tidal potential energy in which a coast-perpendicular dike is used to create water head and generate electricity via turbines inserted in the dike. Before starting such a project, the potential power output and hydrodynamic impacts of the dike must be assessed. In this study, a two-dimensional numerical model based on the Delft3D-FLOW module is established to simulate tides in China. A dike module is developed to account for turbine processes and estimate power output by integrating a special algorithm into the model. The domain decomposition technique is used to divide the computational zone into two subdomains with grid refinement near the dike. The hydrodynamic processes predicted by the model, both with and without the proposed construction, are examined in detail, including tidal currents and tidal energy flux. The predicted time-averaged power yields with various opening ratios are presented. The results show that time-averaged power yield peaks at an 8% opening ratio. For semidiurnal tides, the flow velocity increases in front of the head of the dike and decreases on either side. For diurnal tides, these changes are complicated by the oblique incidence of tidal currents with respect to the dike as well as by bathymetric features. The dike itself blocks the propagation of tidal energy flux.

  4. A Framework for Optimizing the Placement of Tidal Turbines

    Science.gov (United States)

    Nelson, K. S.; Roberts, J.; Jones, C.; James, S. C.

    2013-12-01

    Power generation with marine hydrokinetic (MHK) current energy converters (CECs), often in the form of underwater turbines, is receiving growing global interest. Because of reasonable investment, maintenance, reliability, and environmental friendliness, this technology can contribute to national (and global) energy markets and is worthy of research investment. Furthermore, in remote areas, small-scale MHK energy from river, tidal, or ocean currents can provide a local power supply. However, little is known about the potential environmental effects of CEC operation in coastal embayments, estuaries, or rivers, or of the cumulative impacts of these devices on aquatic ecosystems over years or decades of operation. There is an urgent need for practical, accessible tools and peer-reviewed publications to help industry and regulators evaluate environmental impacts and mitigation measures, while establishing best sitting and design practices. Sandia National Laboratories (SNL) and Sea Engineering, Inc. (SEI) have investigated the potential environmental impacts and performance of individual tidal energy converters (TECs) in Cobscook Bay, ME; TECs are a subset of CECs that are specifically deployed in tidal channels. Cobscook Bay is the first deployment location of Ocean Renewable Power Company's (ORPC) TidGenTM unit. One unit is currently in place with four more to follow. Together, SNL and SEI built a coarse-grid, regional-scale model that included Cobscook Bay and all other landward embayments using the modeling platform SNL-EFDC. Within SNL-EFDC tidal turbines are represented using a unique set of momentum extraction, turbulence generation, and turbulence dissipation equations at TEC locations. The global model was then coupled to a local-scale model that was centered on the proposed TEC deployment locations. An optimization frame work was developed that used the refined model to determine optimal device placement locations that maximized array performance. Within the

  5. Regional Ocean Data Assimilation

    KAUST Repository

    Edwards, Christopher A.

    2015-01-03

    This article reviews the past 15 years of developments in regional ocean data assimilation. A variety of scientific, management, and safety-related objectives motivate marine scientists to characterize many ocean environments, including coastal regions. As in weather prediction, the accurate representation of physical, chemical, and/or biological properties in the ocean is challenging. Models and observations alone provide imperfect representations of the ocean state, but together they can offer improved estimates. Variational and sequential methods are among the most widely used in regional ocean systems, and there have been exciting recent advances in ensemble and four-dimensional variational approaches. These techniques are increasingly being tested and adapted for biogeochemical applications.

  6. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions.

    Science.gov (United States)

    Driscoll, P E; Barnes, R

    2015-09-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the "tidal zone," where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life.

  7. Estimation of energy potential and power generation from tidal basin in coastal area of malaysia

    Directory of Open Access Journals (Sweden)

    Nazri Nazani

    2016-01-01

    Full Text Available This paper presents the potential of tidal energy in Malaysia. Malaysia is heavily depending on the fossil fuel to satisfy the energy demand. However, this reserve energy is reported will be depleted. The population growth also caused the demand on energy increase over the year. This situation can lead to the global warming and climate change that be a major concern around the world. As an alternative, renewable energy become a solution in order to reduce the usage of conventional energy such as fossil fuel, coal and gas. One of the renewable energy that can be used is from ocean energy. Since the tidal energy is not study thoroughly in Malaysia and Malaysia has a potential sites that can implement this tidal energy for electricity generation to meet the local demand. This tidal energy can be harnessed in several approach such as by using tidal barrage single basin with single mode generation consist ebb-mode and flood-mode of generation and the other approach of single mode is double-mode of generation. In order to meet the local demand, single-mode generation and double-mode generation was studied by getting the number of population at that area, the electricity demand then from that data the basin area is estimated for power generation. The result shows that double-mode generation is one of the approaches that meet the local demand for electricity.

  8. Tidal breathing flow-volume loops in bronchiolitis in infancy: the effect of albuterol [ISRCTN47364493].

    Science.gov (United States)

    Totapally, Balagangadhar R; Demerci, Cem; Zureikat, George; Nolan, Brian

    2002-04-01

    To evaluate the effect of nebulized albuterol on tidal breathing flow-volume loops in infants with bronchiolitis due to respiratory syncytial virus. A randomized, double-blind, control study. Pediatric unit in a community teaching hospital. Twenty infants younger than 1 year of age (mean age, 5.8 +/- 2.8 months) with a first episode of wheezing due to respiratory syncytial virus bronchiolitis. Chloral hydrate (50 mg/kg) was administered orally for sedation. One dose each of nebulized albuterol (0.15 mg/kg in 3 ml saline) and saline (3 ml) were given at 6 hour intervals in a random order. Tidal breathing flow-volume loops were obtained before and after each aerosol treatment with a Neonatal/Pediatric Pulmonary Testing System (Model 2600; Sensor Medics, Anaheim, CA, USA). At the same time, the fraction of tidal volume exhaled at peak tidal expiratory flow (PTEF) to total tidal volume (VPTEF/VE), and the fraction of exhaled time at PTEF to total expiratory time (tPTEF/tE) were measured. The PTEF, the tidal expiratory flows at 10%, 25%, and 50% of the remaining tidal volume (TEF10, TEF25, and TEF50), and the wheeze score were also determined. There were no significant changes in VPTEF/VE and tPTEF/tE after albuterol or saline treatment. PTEF increased significantly both after albuterol and saline treatments but the difference between the two treatments was not significant (P = 0.6). Both TEF10 and the ratio of the tidal expiratory flow at 25% of the remaining tidal volume to PTEF (25/PT) decreased significantly (P bronchiolitis due to respiratory syncytial virus did not improve VPTEF/VE and tPTEF/tE but did decrease TEF10 and 25/PT.

  9. Improvements for the Western North Atlantic, Caribbean and Gulf of Mexico ADCIRC Tidal Database (EC2015

    Directory of Open Access Journals (Sweden)

    Christine Szpilka

    2016-11-01

    Full Text Available This research details the development and validation of an updated constituent tidal database for the Western North Atlantic, Caribbean and Gulf of Mexico (WNAT region, referred to as the EC2015 database. Regional databases, such as EC2015, provide much higher resolution than global databases allowing users to more accurately define the tidal forcing on smaller sub-region domains. The database last underwent major updates in 2001 and was developed using the two-dimensional, depth-integrated form of the coastal hydrodynamic model, ADvanced CIRCulation (ADCIRC, which solves the shallow-water equations in the generalized wave continuity equation form. Six main areas of improvement are examined: (1 placement of the open ocean boundary; (2 higher coastal resolution using Vertical Datum (VDatum models; (3 updated bathymetry from global databases; (4 updated boundary forcing compared using two global tidal databases; (5 updated bottom friction formulations; and (6 improved model physics by incorporating the advective terms in ADCIRC. The skill of the improved database is compared to that of its predecessor and is calculated using harmonic data from the National Oceanic and Atmospheric Administration Center for Operational Oceanographic Products and Services (NOAA CO-OPS stations and historic International Hydrographic Organization (IHO data. Overall, the EC2015 database significantly reduces errors realized in the EC2001 database and improves the quality of coastal tidal constituents available for smaller sub-regional models in the Western North Atlantic, Caribbean and Gulf of Mexico (WNAT region.

  10. The impact of wind energy turbine piles on ocean dynamics

    Science.gov (United States)

    Grashorn, Sebastian; Stanev, Emil V.

    2016-04-01

    The small- and meso-scale ocean response to wind parks has not been investigated in the southern North Sea until now with the help of high-resolution numerical modelling. Obstacles such as e.g. wind turbine piles may influence the ocean current system and produce turbulent kinetic energy which could affect sediment dynamics in the surrounding area. Two setups of the unstructured-grid model SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) have been developed for an idealized channel including a surface piercing cylindrical obstacle representing the pile and a more realistic test case including four exemplary piles. Experiments using a constant flow around the obstacles and a rotating M2 tidal wave are carried out. The resulting current and turbulence patterns are investigated to estimate the influence of the obstacles on the surrounding ocean dynamics. We demonstrate that using an unstructured ocean model provides the opportunity to embed a high-resolution representation of a wind park turbine pile system into a coarser North Sea setup, which is needed in order to perform a seamless investigation of the resulting geophysical processes.

  11. No Snowball on Habitable Tidally Locked Planets

    Science.gov (United States)

    Checlair, Jade; Menou, Kristen; Abbot, Dorian S.

    2017-08-01

    The TRAPPIST-1, Proxima Centauri, and LHS 1140 systems are the most exciting prospects for future follow-up observations of potentially inhabited planets. All of the planets orbit nearby M-stars and are likely tidally locked in 1:1 spin-orbit states, which motivates the consideration of the effects that tidal locking might have on planetary habitability. On Earth, periods of global glaciation (snowballs) may have been essential for habitability and remote signs of life (biosignatures) because they are correlated with increases in the complexity of life and in the atmospheric oxygen concentration. In this paper, we investigate the snowball bifurcation (sudden onset of global glaciation) on tidally locked planets using both an energy balance model and an intermediate-complexity global climate model. We show that tidally locked planets are unlikely to exhibit a snowball bifurcation as a direct result of the spatial pattern of insolation they receive. Instead, they will smoothly transition from partial to complete ice coverage and back. A major implication of this work is that tidally locked planets with an active carbon cycle should not be found in a snowball state. Moreover, this work implies that tidally locked planets near the outer edge of the habitable zone with low CO2 outgassing fluxes will equilibrate with a small unglaciated substellar region rather than cycling between warm and snowball states. More work is needed to determine how the lack of a snowball bifurcation might affect the development of life on a tidally locked planet.

  12. Seasonal dynamics of adjoining tidal coastal inlet on east coast of India ­measurements and modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Reddy, N.A.; Ramanamurty, M.V.; ManiMurali, R.; ArunaKumar, A.; Rao, S.

    The opening and closure of coastal tidal inlets play a major role in regulating the water and sediment exchange between the river and ocean as well as in the interruption of the longshore sediment transport. The present work is an effort...

  13. Climate change impacts on the stability of small tidal inlets : A numerical modelling study using Realistic Analogue approach

    NARCIS (Netherlands)

    Duong, T.; Ranasinghe, R.; Luijendijk, A.; Dastgheib, A.; Roelvink, D.

    2012-01-01

    Tidal inlets are of great societal importance as they are often associated with ports and harbours, industry, tourism, recreation and prime waterfront real estate. Their behaviour is governed by the delicate balance of oceanic processes (tides, waves and mean sea level), and fluvial/estuarine

  14. Tides, tidal currents and their effects on the intertidal ecosystem of the southern bay, Inhaca Island, Mozambique

    NARCIS (Netherlands)

    Boer, de W.F.; Rydberg, L.; Saide, V.

    2000-01-01

    Sediment characteristics and tidal currents were studied in the 1500 ha intertidal area south of Inhaca Island, Mozambique. The tide is semi-diurnal with a range at spring of about 3 m. The area connects directly to the ocean through the Ponta Torres Strait and (indirectly) through several narrow

  15. Tidal power in Norway; Maanekraft fra dypet

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    The world's first tidal power station is scheduled for stat-up in the spring of 2003. It is located in Kvalsundet, off Hammerfest, Norway. This is a pilot installation of a 300 kW tidal turbine at a depth of 50 metres. When fully developed in 2007, the tidal power plant will deliver 32 GWh per year. Hammerfest Stroem has patented the energy and the company hopes to be able to install similar power stations both in Norway and abroad. The potential worldwide is claimed to be more than 450 TWh per year.

  16. A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum

    Directory of Open Access Journals (Sweden)

    Laura Sordo

    2016-09-01

    Full Text Available Most ocean acidification (OA experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA that measures pCO2 and conveys this value to a Proportional-Integral-Derivative (PID controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients.

  17. A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

    Science.gov (United States)

    Sordo, Laura; Santos, Rui; Reis, Joao; Shulika, Alona; Silva, Joao

    2016-01-01

    Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO2 and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients.

  18. Numerical and experimental investigation on novel systems for harvesting tidal current energy

    Energy Technology Data Exchange (ETDEWEB)

    Coiro, D.P. [Naples Univ., Naples (Italy). Dept. of Aerospace Engineering

    2008-07-01

    Theoretical and experimental tidal current energy investigations currently being conducted at an aerospace engineering department in Italy were presented. The department has set up a test site to harness marine and river current energy in the Messina Strait. A vertical axis hydro turbine developed by the department has been installed at the site. This presentation provided details of unsteady viscous numerical studies conducted to examine flow curvature effects on the turbine's airfoils and rotor design. Numerical studies were also conducted to develop a new generator and optimize the hydrodynamic efficiency of the turbine's rotor. The use of flow increasers to double output power was also examined. The aim of the study was to prove that the vertical axis turbine is capable of reaching the same efficiency levels as horizontal axis turbines. The department is also designing a 300 kW horizontal axis turbine that operates as an underwater ocean kite anchored at the bottom with a winched chain. Details of studies conducted to measure rotational speed, rotor torque, and thrust were presented, as well as details of tests performed at various depths and velocities in order to obtain cavitation numbers for the full-scale turbine. Details of computational fluid dynamics (CFD) studies of the turbine modelled as an actuator disk were also included. tabs., figs.

  19. The oceanic tides in the South Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    M. L. Genco

    Full Text Available The finite element ocean tide model of Le Provost and Vincent (1986 has been applied to the simulation of the M2 and K1 components over the South Atlantic Ocean. The discretisation of the domain, of the order of 200 km over the deep ocean, is refined down to 15 km along the coasts, such refinement enables wave propagation and damping over the continental shelves to be correctly solved. The marine boundary conditions, from Dakar to Natal, through the Drake passage and from South Africa to Antarctica, are deduced from in situ data and from Schwiderski's solution and then optimised following a procedure previously developed by the authors. The solutions presented are in very good agreement with in situ data: the root mean square deviations from a standard subset of 13 pelagic stations are 1.4 cm for M2 and 0.45 cm for K1, which is significantly better overall than solutions published to date in the literature. Zooms of the M2 solution are presented for the Falkland Archipelago, the Weddell Sea and the Patagonian Shelf. The first zoom allows detailing of the tidal structure around the Falklands and its interpretation in terms of a stationary trapped Kelvin wave system. The second zoom, over the Weddell Sea, reveals for the first time what must be the tidal signal under the permanent ice shelf and gives a solution over that sea which is generally in agreement with observations. The third zoom is over the complex Patagonian Shelf. This zoom illustrates the ability of the model to simulate the tides, even over this area, with a surprising level of realism, following purely hydrodynamic modelling procedures, within a global ocean tide model. Maps of maximum associated tidal currents are also given, as a first illustration of a by-product of these simulations.

  20. Exploitation of tidal power in the Bay of Cadiz: ancient tidal mills

    Directory of Open Access Journals (Sweden)

    José J. Alonso del Rosario

    2006-03-01

    Full Text Available Tidal mills were the main industrial activity in the Bay of Cadiz for centuries. They were the last step in the production of salt and flour made by grinding grains. They were installed along the shallow channels, called “caños”, around the Bay, where the frictional and geometrical effects are very strong. The authors have analyzed the propagation of the semidiurnal tidal waves along the Caño de Sancti Petri and the available tidal power in the area. The ancient tidal mills were located where the available tidal potential energy is highest, which ensured productivity for grinding salt and wheat in ancient times. Some considerations about the possibility of installing tidal power plants in the Bay of Cadiz now are given, which show that it could be a real and renewal alternative source of energy for the area.

  1. Relativistic tidal effects in non standard Kerr space-time

    CERN Document Server

    Maselli, Andrea; Laguna, Pablo

    2016-01-01

    Astrophysical phenomena involving massive black holes (BHs) in close binaries are expected to leave detectable signatures in the electromagnetic and gravitational-wave spectrum. Such imprints may provide precious information to probe the space-time around rotating BHs, and to reveal new insights on the nature of gravity in the strong-field regime. To support this observational window it is crucial to develop suitable tests to verify the predictions of General Relativity (GR). In this framework, the metric recently proposed by Johannsen and Psaltis parametrises strong field deviations from a Kerr space-time in a theory-independent way. In the following, we make use of this approach to describe the tidal field produced by spinning BHs. We compute the gravito-magnetic and gravito-electric tidal tensors for particles moving on equatorial circular geodesics, comparing our results with those obtained in the standard GR scenario. Our calculations show significant differences even for distances far form the last stab...

  2. Downstream hydraulic geometry of a tidally influenced river delta

    NARCIS (Netherlands)

    Sassi, M.G.; Hoitink, A.J.F.; Brye, de B.; Deleersnijder, E.

    2012-01-01

    Channel geometry in tidally influenced river deltas can show a mixed scaling behavior between that of river and tidal channel networks, as the channel forming discharge is both of river and tidal origin. We present a method of analysis to quantify the tidal signature on delta morphology, by

  3. Stingray tidal stream energy device - phase 3

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    The 150 kW Stingray demonstrator was designed, built and installed by The Engineering Business (EB) in 2002, becoming the world's first full-scale tidal stream generator. The concept and technology are described in the reports from Phases 1 and 2 of the project. This report provides an overview of Phase 3 - the re-installation of Stingray in Yell Sound in the Shetland Isles between July and September 2003 for further testing at slack water and on the flood tide to confirm basic machine characteristics, develop the control strategy and to demonstrate performance and power collection through periods of continuous operation. The overall aim was to demonstrate that electricity could be generated at a potentially commercially viable unit energy cost; cost modelling indicated a future unit energy cost of 6.7 pence/kWh when 100 MW capacity had been installed. The report describes: project objectives, targets and activities; design and production; marine operations including installation and demobilisation; environmental monitoring and impact, including pre-installation and post-decommissioning surveys; stakeholder involvement; test results on machine characteristics, sensor performance, power cycle analysis, power collection, transmission performance and efficiency, current data analysis; validation of the mathematical model; the background to the economic model; cost modelling; and compliance with targets set by the Department of Trade and Industry (DTI).

  4. Accelerated tidal circularization via resonance locking in KIC 8164262

    Science.gov (United States)

    Fuller, Jim; Hambleton, Kelly; Shporer, Avi; Isaacson, Howard; Thompson, Susan

    2017-11-01

    Tidal dissipation in binary star and planetary systems is poorly understood. Fortunately, eccentric binaries known as heartbeat stars often exhibit tidally excited oscillations, providing observable diagnostics of tidal circularization mechanisms and time-scales. We apply tidal theories to observations of the heartbeat star KIC 8164262, which contains an F-type primary in a very eccentric orbit that exhibits a prominent tidally excited oscillation. We demonstrate that the prominent oscillation is unlikely to result from a chance resonance between tidal forcing and a stellar oscillation mode. However, the oscillation has a frequency and amplitude consistent with the prediction of resonance locking, a mechanism in which coupled stellar and orbital evolution maintain a stable resonance between tidal forcing and a stellar oscillation mode. The resonantly excited mode produces efficient tidal dissipation (corresponding to an effective tidal quality factor Q ∼ 5 × 104), such that tidal orbital decay/circularization proceeds on a stellar evolution time-scale.

  5. Tides and tidal harmonics at Umbharat, Gujarat

    Digital Repository Service at National Institute of Oceanography (India)

    Suryanarayana, A.; Swamy, G.N.

    A part of the data on tides recorded at Machiwada near Umbharat, Gulf of Cambay during April 1978 was subjected to harmonic analysis following the Admiralty procedure. The general tidal characteristics and the value of four major harmonic...

  6. Tidal mixing in Dahej creek waters

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.; Sarma, R.V.

    of effluent discharge has been worked out. The allowable duration of discharge of the hypothetical effluent over a tidal cycle ensuring a specified minimum dilution has also been indicated to help optimise the degree of inplant treatment. The results suggested...

  7. Internal wave generation by tidal flow over periodically and randomly distributed seamounts

    Science.gov (United States)

    Zhang, Likun; Buijsman, Maarten C.; Comino, Eva; Swinney, Harry L.

    2017-06-01

    We examine numerically the conversion of barotropic tidal energy into internal waves by flow over an isolated seamount and over systems of periodically and randomly distributed 1100 m tall seamounts with Gaussian profiles. The simulations use the Massachusetts Institute of Technology general circulation model (MITgcm) to calculate for an infinitely deep ocean the dependence of the energy conversion on seamount slope, seamount separation, tidal direction, and the size and aspect ratio of the simulation domain. For neighboring seamounts with a slope greater than the internal wave beam slope, wave interference reduces the conversion relative to that calculated for an isolated seamount, and relative to that predicted by linear theory for a seamount of slope less than the beam slope. The conversion by an individual seamount in a system of random seamounts separated by an average distance of 18 km is found to be suppressed by 16% relative to the conversion by an isolated seamount. This study provides insight into tidal conversion by ocean seamounts modeled as Gaussian mountains with slopes both smaller and larger than the beam slope. We conclude that the total energy conversion by all seamounts (peak height ≥1000 m) and knolls (peak height 500-1000 m), taking into account interference affects, is of the order of 1% of the total barotropic to baroclinic energy conversion in the oceans, which is about twice as large as previous estimates.

  8. Hydrogen as an activating fuel for a tidal power plant

    Science.gov (United States)

    Gorlov, A. M.

    Tidal projects, offering a clean, inexhaustible, and fairly predictable energy source, require a system for accumulating energy for off-peak periods. Hydrogen produced by electrolysis during off-peak power plant operation can be used as an activating fuel to furnish the plant during peak load demands. Tidal energy is converted into compressed air energy by special chambers on the ocean bed. This compressed air can be heated by combustion of the stored hydrogen and expanded through high speed gas turbine generators. For off-peak periods, the energy of non-heated compressed air is used for the production of hydrogen fuel. The amount of fuel produced at this time is enough for power plant operation during two peak hours, with three times greater plant capacity. The hydrogen fuel storage method does have energy losses and requires extra capital investment for electrolysis and hydrogen storage equipment. It does not, however, require a gas turbine oil fuel, as does the air compressed storage method, nor a low-speed heavy hydro-turbine, as does the hydro-pumped method. Moreover, the gas turbine can be used for both production and consumption of hydrogen fuel.

  9. Morphodynamics of tidal networks: advances and challenges

    Science.gov (United States)

    Coco, G.; Olabarrieta, M.; van Maanen, B.; Zhou, Z.; Tinoco, R.

    2012-12-01

    Tidal embayments are complex environments at the boundary between land and sea. Their evolution, natural or human-induced, feeds back onto ecological, economic and societal functions. Overall, the ability to manage tidal embayments successfully and maintain their value hinges on our knowledge of the system. The morphological behaviour of tidal embayments, however, is very complex because of the variety of feedback mechanisms which lead to morphological change. In recent years, numerical studies have highlighted that the feedback between the hydrodynamics, sediment transport and morphological evolution can lead to the development of tidally-forced morphological networks characterized by slowly-evolving bifurcating channels. Both tidal range and the initial bathymetry appear to have a strong control on the morphological characteristics of the tidal network by affecting final basin hypsometry and channel patterns. Although promising, none of the numerical models presented in the literature and capable of simulating the growth of a tidal network have been scrutinized against field or laboratory data. Here, we show and discuss the performance of one of those numerical models against detailed laboratory data. Preliminary results indicate that numerical simulations can reproduce the general features of pattern development but that a better description of many fast- and small-scale processes is needed to achieve better model-data agreement. Unsurprisingly, the model shows a strong sensitivity to frictional effects and resuspension parameterizations. Numerical models of morphodynamics tend to neglect some physical or biological processes that affect the short- and long-term evolution of tidal networks. In terms of physical processes, wind waves, interacting with the ebb shoal and tidal currents at the mouth of the embayment can significantly affect hydro- and morphodynamics. Under high wave conditions waves can break in the inlet area producing wave induced circulation

  10. Tidal Dissipation in Hot Jupiter Atmospheres

    Science.gov (United States)

    Johnson, Eric T.

    2009-01-01

    Short-period extrasolar giant planets (hot Jupiters) experience periods of strong tidal dissipation. It is not well known whether tidal energy is deposited primarily in the deep interior or the surface layers of these planets, or what effect the location of tidal heating has on their evolution and observable properties (e.g. radii, spectra, and rate of mass loss in a planetary wind). I present a study of the local tidal heating rate as a function of latitude and depth in the radiative envelope and atmosphere (between pressure levels of about 1 kilobar and 0.001 microbars). Results are based on a nonadiabatic linear analysis of the tide in this region, which takes the form of an upward-propagating train of inertial-gravity waves excited at the interface between the convective interior and the stably-stratified envelope. Radiative damping dominates the dissipation. Careful attention is paid to the computation of the radiative relaxation timescale, using nongray radiative transfer to transition smoothly from the optically thick to the optically thin regime. The potential exists for conversion from inertial-gravity waves to pure inertial waves in the presence of strong radiative damping. This raises the possibility that a significant tidal energy flux can be transported as high as the base of the thermosphere, where it would contribute to driving atmospheric escape. Results can be used to chart local tidal heating rates over the lifetime of a hot Jupiter as its orbit and rotation rate evolve. Although the potential for high-altitude tidal heating is intriguing, I find that over a wide range of orbital parameters the bulk of the energy flux is dissipated nearer the IR photosphere. Tidal heating at those heights (around 0.1-10 bars) has the greatest potential to affect the emergent spectrum, and is least likely to slow the planet's rate of contraction.

  11. Spatial patterns of tidal heating

    CERN Document Server

    Beuthe, Mikael

    2012-01-01

    In a body periodically strained by tides, heating produced by viscous friction is far from homogeneous. I show here that the distribution of the dissipated power within a spherically stratified body is a linear combination of three angular functions. These angular functions depend only on the tidal potential whereas the radial weights are specified by the internal structure of the body. The 3D problem of predicting spatial patterns of dissipation at all radii is thus reduced to the 1D problem of computing weight functions. I compute spatial patterns in various toy models without assuming a specific rheology: a viscoelastic thin shell stratified in conductive and convective layers, an incompressible homogeneous body and a two-layer model of uniform density with a liquid or rigid core. For a body in synchronous rotation undergoing eccentricity tides, dissipation in a mantle surrounding a liquid core is highest at the poles. Within a softer layer (asthenosphere or icy layer), the same tides generate maximum heat...

  12. Cassini Can Constrain Tidal Dissipation in Saturn

    Science.gov (United States)

    Luan, Jing; Fuller, Jim; Quataert, Eliot

    2017-10-01

    Tidal dissipation inside giant planets is important for the orbital evolution of their natural satellites. It is conventionally treated by parameterized equilibrium tidal the- ory, in which the tidal torque declines rapidly with distance, and orbital expansion was faster in the past. However, Lainey et al. (2017) find that some Saturnian satellites are currently migrating outward faster than predicted by equilibrium tidal theory. Reso- nance locking between satellites and internal oscillations of Saturn, proposed by Fuller et al. (2016), naturally matches the observed migration rates. Here, we show that the resonance locking theory predicts dynamical tidal perturbations to Saturn’s gravita- tional field in addition to those produced by equilibrium tidal bulges. We show that these perturbations can likely be detected during Cassini’s proximal orbits if migra- tion of satellites results from resonant gravity modes, but will likely be undetectable if migration results from inertial wave attractors or dissipation of the equilibrium tide. Additionally, we show that the detection of gravity modes would place constraints on the size of the hypothetical stably stratified region in Saturn.

  13. Half Moon Cove Tidal Project. Feasibility report

    Energy Technology Data Exchange (ETDEWEB)

    1980-11-01

    The proposed Half Moon Cove Tidal Power Project would be located in a small cove in the northern part of Cobscook Bay in the vicinity of Eastport, Maine. The project would be the first tidal electric power generating plant in the United States of America. The basin impounded by the barrier when full will approximate 1.2 square miles. The average tidal range at Eastport is 18.2 feet. The maximum spring tidal range will be 26.2 feet and the neap tidal range 12.8 feet. The project will be of the single pool-type single effect in which generation takes place on the ebb tide only. Utilizing an average mean tidal range of 18.2 feet the mode of operation enables generation for approximately ten and one-half (10-1/2) hours per day or slightly in excess of five (5) hours per tide. The installed capacity will be 12 MW utilizing 2 to 6 MW units. An axial flow, or Bulb type of turbine was selected for this study.

  14. Managing Ocean Dumping in EPA Region 1

    Science.gov (United States)

    Overview of ocean dumping in New England, US. Includes materials dumped in the Region, ocean dumping permits issues, dredged material testing guidance, ocean disposal site descriptions and information, regional dredging teams and other partnerships.

  15. Managing Ocean Dumping in EPA Region 3

    Science.gov (United States)

    Overview of ocean dumping in Mid Atlantic, US. Includes materials dumped in the Region, ocean dumping permits issues, dredged material testing guidance, ocean disposal site descriptions and information, regional dredging teams and other partnerships.

  16. Development of Ocean Energy Technologies: A Case Study of China

    Directory of Open Access Journals (Sweden)

    Qin Guodong

    2013-01-01

    Full Text Available For the energy shortage in China's coastal areas, which has exerted severe impact on economy development, a growing number of attentions have been paid to ocean energy utilization. In this paper, a review of related researches as well as development of ocean energy in China is given. The main part of this paper is the investigation into ocean energy distribution and technology status of tidal energy, wave energy, and thermal energy, especially that of the tidal energy and wave energy. Finally, some recommendations for the future development of ocean energy in China are also provided. For further research in this field and development of ocean energy utilization in China, this review can be taken as reference.

  17. Sensitivity of palaeo-ice-stream retreat patterns to ice-ocean interactions and topography: a test of the marine ice sheet instability hypothesis

    Science.gov (United States)

    Jamieson, S.; Vieli, A.; Livingstone, S. J.; O'Cofaigh, C.; Stokes, C. R.; Hillenbrand, C.

    2011-12-01

    The aim is to understand the long-term controls on marine ice stream retreat. Short-term observations combined with modelling are helping decipher the controls driving contemporary mass loss via dynamic thinning and grounding-line retreat. However, ice-stream response times are likely to be longer than the timescales for which contemporary observations are available. We therefore focus on century to millenial timescales by investigating the retreat of Marguerite Bay palaeo-ice stream in Antarctica after the LGM. Our approach is to use high-resolution mapping of glacial landforms on the sea floor to constrain a numerical ice stream model. Mapped positions of grounding-zone wedges indicate that the palaeo-ice stream paused multiple times during its rapid retreat over a bed that deepens inland. The geomorphic record not only questions the marine ice sheet instability hypothesis but also provides geometrical and dynamical constraints for retreat experiments using numerical ice stream models. To understand the controls on the retreat pattern in Marguerite Bay, we test the sensitivity of the ice stream to a range of forcing regimes using a 1-dimensional numerical flow-line model that incorporates basal, lateral and longitudinal stresses and a self-refining grid scheme. Ice-ocean interactions are incorporated via a fixed-length ice shelf, the inclusion of an ice-ocean boundary condition and the calculation of ocean-driven melt. We test modelled retreat sensitivity to a range of external forcing patterns including sea-level, temperature, accumulation and ocean-driven melt. In addition, the importance of the topographic setting of the ice drainage basin is also examined. We find that the modelled ice stream naturally re-creates the pauses observed in the geomorphic record and that the pattern of palaeo-grounding-line retreat in Marguerite Bay can only be achieved within the chronological timeframe by including ocean-driven melt. Sensitivity tests indicate that the

  18. Tidal disruption of asteroids by supermassive black holes

    Directory of Open Access Journals (Sweden)

    Gomboc A.

    2012-12-01

    Full Text Available The compact radio source Sgr A* at the centre of our Galaxy harbours a super-massive black hole, and is therefore the nearest laboratory for testing the super-massive black hole astrophysics and environment. Since it is not an active galactic nucleus, it also offers the possibility of observing the capture of low-mass objects, such as comets or asteroids, that may orbit the central black hole. In this paper we discuss conditions for tidal disruption of low-mass objects and predictions of the appearance and light curve of such events, as well as their relevance for the X-ray and infra-red flares detected in Sgr A*. The modelled light curves of such tidal disruption events bear marks of the strong gravitational field: tidal squeezing and elongation of the object, gravitational lensing, aberration of light, and Doppler effects. Finally, we show that this model is able to reproduce and fit X-ray flares.

  19. Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

    Science.gov (United States)

    Schnepf, N. R.; Kuvshinov, A.; Sabaka, T.

    2015-01-01

    A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

  20. Tidal Modulation of Ice-shelf Flow: a Viscous Model of the Ross Ice Shelf

    Science.gov (United States)

    Brunt, Kelly M.; MacAyeal, Douglas R.

    2014-01-01

    Three stations near the calving front of the Ross Ice Shelf, Antarctica, recorded GPS data through a full spring-neap tidal cycle in November 2005. The data revealed a diurnal horizontal motion that varied both along and transverse to the long-term average velocity direction, similar to tidal signals observed in other ice shelves and ice streams. Based on its periodicity, it was hypothesized that the signal represents a flow response of the Ross Ice Shelf to the diurnal tides of the Ross Sea. To assess the influence of the tide on the ice-shelf motion, two hypotheses were developed. The first addressed the direct response of the ice shelf to tidal forcing, such as forces due to sea-surface slopes or forces due to sub-ice-shelf currents. The second involved the indirect response of ice-shelf flow to the tidal signals observed in the ice streams that source the ice shelf. A finite-element model, based on viscous creep flow, was developed to test these hypotheses, but succeeded only in falsifying both hypotheses, i.e. showing that direct tidal effects produce too small a response, and indirect tidal effects produce a response that is not smooth in time. This nullification suggests that a combination of viscous and elastic deformation is required to explain the observations.

  1. Mining CANDELS for Tidal Features to Measure Major Merging at Cosmic High Noon

    Science.gov (United States)

    McIntosh, Daniel

    2017-08-01

    The importance of major merging at z>1 remains in question despite the rapid buildup and development of massive galaxies at these epochs. New theories and observations suggest that non-merging processes like disk instabilities may be even more important than previously thought at assembling bulges, producing clumps, and inducing morphological disturbances that may be misinterpreted as the product of major merging. We propose a novel search for tidal features on a complete sample of nearly 6000 massive z>1 galaxies from CANDELS. Our novel approach will use improved residual maps from multi-component fits to archival WFC3 images, and a new machine learning classification pipeline to robustly identify transient and faint tidal signatures: the hallmark sign of major merging. We will repeat this analysis on synthetic mock images to thoroughly quantify the impacts of cosmological dimming, and calibrate the observability timescale of tidal feature detections. Our study will yield (1) definitive census of massive z>1 galaxies with merger tidal signatures from CANDELS, (2) critically important calibrations for converting tidal detections into merger rates, (3) two novel software pipelines, (4) new stringent tidal-based merger rates that will provide critical tests of theoretical predictions on the relative importance of ex-situ (hierarchical merging) vs. in-situ (gas accretion, cooling, and star formation) assembly of massive galaxies.

  2. THE SHAPES OF MILKY WAY SATELLITES: LOOKING FOR SIGNATURES OF TIDAL STIRRING

    Energy Technology Data Exchange (ETDEWEB)

    Lokas, Ewa L. [Nicolaus Copernicus Astronomical Center, 00-716 Warsaw (Poland); Majewski, Steven R.; Nidever, David L. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Kazantzidis, Stelios [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Mayer, Lucio [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland); Carlin, Jeffrey L. [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180-3590 (United States); Moustakas, Leonidas A., E-mail: lokas@camk.edu.pl [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-05-20

    We study the shapes of Milky Way satellites in the context of the tidal stirring scenario for the formation of dwarf spheroidal galaxies. The standard procedures used to measure shapes involve smoothing and binning of data and thus may not be sufficient to detect structural properties such as bars, which are usually subtle in low surface brightness systems. Taking advantage of the fact that in nearby dwarfs photometry of individual stars is available, we introduce discrete measures of shape based on the two-dimensional inertia tensor and the Fourier bar mode. We apply these measures of shape first to a variety of simulated dwarf galaxies formed via tidal stirring of disks embedded in dark matter halos and orbiting the Milky Way. In addition to strong mass loss and randomization of stellar orbits, the disks undergo morphological transformation that typically involves the formation of a triaxial bar after the first pericenter passage. These tidally induced bars persist for a few Gyr before being shortened toward a more spherical shape if the tidal force is strong enough. We test this prediction by measuring in a similar way the shape of nearby dwarf galaxies, satellites of the Milky Way. We detect inner bars in Ursa Minor, Sagittarius, Large Magellanic Cloud, and possibly Carina. In addition, 6 out of 11 dwarfs that we studied show elongated stellar distributions in the outer parts that may signify transition to tidal tails. We thus find the shapes of Milky Way satellites to be consistent with the predictions of the tidal stirring model.

  3. Modelling of the impact of biofouling on hydrodynamics downstream of a tidal turbine

    Science.gov (United States)

    Bennis, A. C.; Rivier, A.; Dauvin, J. C.

    2016-02-01

    Biological organisms, like barnacles, mussels or bryozoans, colonize rapidly an immersed surface and could form a thickness until several centimeters on it. This biofouling could modify hydrodynamics around tidal turbine by increasing drag and hence resistance and could be detrimental to the performance of turbine (e.g. Orme et al., 2001; Khor and Xiao, 2011). Our work focuses on modifications of vortices downstream of a tidal turbine due to biofouling using CFD. Fixed biological organisms are solved explicitly by the model and are considered by modifying the blade profile. Firstly an airfoil colonized by barnacles is modelled for various fouling height and spacing and results are compared to experimental and simulated data (Orme et al., 2001; Khor and Xiao, 2011) in order to assess the capacity of the model to reproduce the flow around a blade with biofouling. Then a Darrieus vertical axis tidal turbine is modelled using a dynamic mesh. Configuration with smooth clean blades is assessed by comparison with experiments and simulations made by Roa (2011) and Bossard (2012). Biological organisms with various heights, spacing and shapes are fixed on blades and wakes downstream of clean and colonized tidal turbine are compared. Vorticity fields around the tidal turbine are clearly modified when blades are colonized. Samples will be taken from location where farms are planned to be built (Alderney Race/Raz Blanchard) to characterize more precisely the characteristics of species which are liable to fix on tidal turbine.Reference:Bossard (2012). Doctoral dissertation, Université de Grenoble.Khor & Xiao. (2011). Ocean Eng, 38(10), 1065-1079. Orme et al. (2001). Marine Renewable Energy Conference, Newcastle.Roa (2011).Doctoral dissertation, Université de Grenoble.

  4. A SURVEY ON TIDAL ANALYSIS AND FORECASTING METHODS FOR TSUNAMI DETECTION

    Directory of Open Access Journals (Sweden)

    Diego Reforgiato Recupero

    2014-01-01

    Full Text Available Accurate analysis and forecasting of tidal level are very important tasks for human activities in oceanic and coastal areas. They can be crucial in catastrophic situations like occurrences of Tsunamis in order to provide a rapid alerting to the human population involved and to save lives. Conventional tidal forecasting methods are based on harmonic analysis using the least squares method to determine harmonic parameters. However, a large number of parameters and long-term measured data are required for precise tidal level predictions with harmonic analysis. Furthermore, traditional harmonic methods rely on models based on the analysis of astronomical components and they can be inadequate when the contribution of non-astronomical components, such as the weather, is significant. Other alternative approaches have been developed in the literature in order to deal with these situations and provide predictions with the desired accuracy, with respect also to the length of the available tidal record. These methods include standard high or band pass filtering techniques, although the relatively deterministic character and large amplitude of tidal signals make special techniques, like artificial neural networks and wavelets transform analysis methods, more effective. This paper is intended to provide the communities of both researchers and practitioners with a broadly applicable, up to date coverage of tidal analysis and forecasting methodologies that have proven to be successful in a variety of circumstances, and that hold particular promise for success in the future. Classical and novel methods are reviewed in a systematic and consistent way, outlining their main concepts and components, similarities and differences, advantages and disadvantages.

  5. Deep-ocean Internal Wave Spectra

    Science.gov (United States)

    van Haren, H.

    Details of the internal wave frequency band (IWB) are studied using yearlong current observations in the lowest 1000 m above the bottom of the continental slope into the abyssal plain of the Bay of Biscay. It is shown that the first half decade of the IWB is dominated by forced phase- locked motions rather than random free waves, except at fundamental inertial (f) and semidiurnal tidal frequencies. A finestructure of non- linear motions fills the spectrum. All non-linear motions are induced by an interaction between the tidal and atmospherically induced near-inertial motions. Using a simple model it is shown that such interactions imply maximum wave steepness in a balance between forcing and dissipation. Above the abyssal plain tidal and inertial motions are equally important factors in non-linear internal wave interactions, suggesting equal importance for deep-ocean mixing.

  6. CLIMATE INSTABILITY ON TIDALLY LOCKED EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Kite, Edwin S.; Manga, Michael [Department of Earth and Planetary Science, University of California at Berkeley, CA 94720 (United States); Gaidos, Eric, E-mail: edwin.kite@gmail.com [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2011-12-10

    Feedbacks that can destabilize the climates of synchronously rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable planets maintain stable surface liquid water over geologic time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering, and greenhouse-gas resupply by other processes. Detected small-radius exoplanets, and anticipated M-dwarf habitable-zone rocky planets, are expected to be in synchronous rotation (tidally locked). In this paper, we investigate two hypothetical feedbacks that can destabilize climate on planets in synchronous rotation. (1) If small changes in pressure alter the temperature distribution across a planet's surface such that the weathering rate goes up when the pressure goes down, a runaway positive feedback occurs involving increasing weathering rate near the substellar point, decreasing pressure, and increasing substellar surface temperature. We call this feedback enhanced substellar weathering instability (ESWI). (2) When decreases in pressure increase the fraction of surface area above the melting point (through reduced advective cooling of the substellar point), and the corresponding increase in volume of liquid causes net dissolution of the atmosphere, a further decrease in pressure will occur. This substellar dissolution feedback can also cause a runaway climate shift. We use an idealized energy balance model to map out the conditions under which these instabilities may occur. In this simplified model, the weathering runaway can shrink the habitable zone and cause geologically rapid 10{sup 3}-fold atmospheric pressure shifts within the habitable zone. Mars may have undergone a weathering runaway in the past. Substellar dissolution is usually a negative feedback or weak positive feedback on changes in atmospheric pressure. It can only cause runaway changes for small, deep oceans and highly soluble atmospheric

  7. Do new anesthesia ventilators deliver small tidal volumes accurately during volume-controlled ventilation?

    Science.gov (United States)

    Bachiller, Patricia R; McDonough, Joseph M; Feldman, Jeffrey M

    2008-05-01

    During mechanical ventilation of infants and neonates, small changes in tidal volume may lead to hypo- or hyperventilation, barotrauma, or volutrauma. Partly because breathing circuit compliance and fresh gas flow affect tidal volume delivery by traditional anesthesia ventilators in volume-controlled ventilation (VCV) mode, pressure-controlled ventilation (PCV) using a circle breathing system has become a common approach to minimizing the risk of mechanical ventilation for small patients, although delivered tidal volume is not assured during PCV. A new generation of anesthesia machine ventilators addresses the problems of VCV by adjusting for fresh gas flow and for the compliance of the breathing circuit. In this study, we evaluated the accuracy of new anesthesia ventilators to deliver small tidal volumes. Four anesthesia ventilator systems were evaluated to determine the accuracy of volume delivery to the airway during VCV at tidal volume settings of 100, 200, and 500 mL under different conditions of breathing circuit compliance (fully extended and fully contracted circuits) and lung compliance. A mechanical test lung (adult and infant) was used to simulate lung compliances ranging from 0.0025 to 0.03 L/cm H(2)O. Volumes and pressures were measured using a calibrated screen pneumotachograph and custom software. We tested the Smartvent 7900, Avance, and Aisys anesthesia ventilator systems (GE Healthcare, Madison, WI) and the Apollo anesthesia ventilator (Draeger Medical, Telford, PA). The Smartvent 7900 and Avance ventilators use inspiratory flow sensors to control the volume delivered, whereas the Aisys and Apollo ventilators compensate for the compliance of the circuit. We found that the anesthesia ventilators that use compliance compensation (Aisys and Apollo) accurately delivered both large and small tidal volumes to the airway of the test lung under conditions of normal and low lung compliance during VCV (ranging from 95.5% to 106.2% of the set tidal volume

  8. Three-dimensional semi-idealized model for tidal motion in tidal estuaries

    NARCIS (Netherlands)

    Kumar, M.; Schuttelaars, H.M.; Roos, P.C.; Möller, M.

    2015-01-01

    In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the

  9. Seasonal variability of tidal and non-tidal currents off Beypore, SW coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DineshKumar, P.K.; Srinivas, K.; AnilKumar, N.

    Analyses of current meter records generated in the coastal waters off Beypore (11 degrees 10 minutes S; 75 degrees 48 minutes E) on the southwest coast of India have been made to understand the tidal and non-tidal variability during premonsoon...

  10. A comparative study of nitrogen and phosphorus cycling in tidal and non-tidal riverine wetlands

    NARCIS (Netherlands)

    Verhoeven, J. T.A.; Whigham, D.F.; van Logtestijn, R.; O'Neill, J.K.

    2001-01-01

    This paper describes a study of nutrient dynamics in 12 tidal and non-tidal freshwater riverine wetlands in The Netherlands, Belgium, and Maryland (USA). The purpose of the study was to investigate the relationships between nutrient cycling processes in riverine wetlands that were geographically

  11. Bio-geomorphic effects on tidal channel evolution: impact of vegetation establishment and tidal prism change

    NARCIS (Netherlands)

    Vandenbruwaene, W.; Meire, P.; Temmerman, S.; Bouma, T.J.

    2013-01-01

    The long-term (10–100 years) evolution of tidal channels is generally considered to interact with the bio-geomorphic evolution of the surrounding intertidal platform. Here we studied how the geometric properties of tidal channels (channel drainage density and channel width) change as (1) vegetation

  12. Changes in surfzone morphodynamics driven by multi-decadel contraction of a large ebb-tidal delta

    Science.gov (United States)

    Hansen, Jeff E.; Elias, Edwin; Barnard, Patrick L.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    The impact of multi-decadal, large-scale deflation (76 million m3 of sediment loss) and contraction (~ 1 km) of a 150 km2 ebb-tidal delta on hydrodynamics and sediment transport at adjacent Ocean Beach in San Francisco, CA (USA), is examined using a coupled wave and circulation model. The model is forced with representative wave and tidal conditions using recent (2005) and historic (1956) ebb-tidal delta bathymetry data sets. Comparison of the simulations indicates that along north/south trending Ocean Beach the contraction and deflation of the ebb-tidal delta have resulted in significant differences in the flow and sediment dynamics. Between 1956 and 2005 the transverse bar (the shallow attachment point of the ebb-tidal delta to the shoreline) migrated northward ~ 1 km toward the inlet while a persistent alongshore flow and transport divergence point migrated south by ~ 500 m such that these features now overlap. A reduction in tidal prism and sediment supply over the last century has resulted in a net decrease in offshore tidal current-generated sediment transport at the mouth of San Francisco Bay, and a relative increase in onshore-directed wave-driven transport toward the inlet, accounting for the observed contraction of the ebb-tidal delta. Alongshore migration of the transverse bar and alongshore flow divergence have resulted in an increasing proportion of onshore migrating sediment from the ebb-tidal delta to be transported north along the beach in 2005 versus south in 1956. The northerly migrating sediment is then trapped by Pt. Lobos, a rocky headland at the northern extreme of the beach, consistent with the observed shoreline accretion in this area. Conversely, alongshore migration of the transverse bar and divergence point has decreased the sediment supply to southern Ocean Beach, consistent with the observed erosion of the shoreline in this area. This study illustrates the utility of applying a high-resolution coupled circulation-wave model for

  13. 76 FR 42122 - Ocean Renewable Power Company, LLC; Notice Concluding Pre-Filing Process and Approving Process...

    Science.gov (United States)

    2011-07-18

    ... By: Ocean Renewable Power Company, LLC. e. Name of Project: Cobscook Bay Tidal Energy Project. f... Energy Regulatory Commission Ocean Renewable Power Company, LLC; Notice Concluding Pre-Filing Process and... R. Sauer, Ocean Renewable Power Company, LLC, 120 Exchange Street, Suite 508, Portland, Maine 04101...

  14. The Europa Ocean Discovery mission

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, B.C. [Los Alamos National Lab., NM (United States); Chyba, C.F. [Univ. of Arizona, Tucson, AZ (United States); Abshire, J.B. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center] [and others

    1997-06-01

    Since it was first proposed that tidal heating of Europa by Jupiter might lead to liquid water oceans below Europa`s ice cover, there has been speculation over the possible exobiological implications of such an ocean. Liquid water is the essential ingredient for life as it is known, and the existence of a second water ocean in the Solar System would be of paramount importance for seeking the origin and existence of life beyond Earth. The authors present here a Discovery-class mission concept (Europa Ocean Discovery) to determine the existence of a liquid water ocean on Europa and to characterize Europa`s surface structure. The technical goal of the Europa Ocean Discovery mission is to study Europa with an orbiting spacecraft. This goal is challenging but entirely feasible within the Discovery envelope. There are four key challenges: entering Europan orbit, generating power, surviving long enough in the radiation environment to return valuable science, and complete the mission within the Discovery program`s launch vehicle and budget constraints. The authors will present here a viable mission that meets these challenges.

  15. Joint inversion of satellite-detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone

    DEFF Research Database (Denmark)

    Grayver, Alexander V.; Munch, F. D.; Kuvshinov, Alexey V.

    2017-01-01

    We present a new global electrical conductivity model of Earth's mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin...... and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three-dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic...

  16. Carbon sequestration by Australian tidal marshes

    KAUST Repository

    Macreadie, Peter I.

    2017-03-10

    Australia\\'s tidal marshes have suffered significant losses but their recently recognised importance in CO2 sequestration is creating opportunities for their protection and restoration. We compiled all available data on soil organic carbon (OC) storage in Australia\\'s tidal marshes (323 cores). OC stocks in the surface 1 m averaged 165.41 (SE 6.96) Mg OC ha-1 (range 14-963 Mg OC ha-1). The mean OC accumulation rate was 0.55 ± 0.02 Mg OC ha-1 yr-1. Geomorphology was the most important predictor of OC stocks, with fluvial sites having twice the stock of OC as seaward sites. Australia\\'s 1.4 million hectares of tidal marshes contain an estimated 212 million tonnes of OC in the surface 1 m, with a potential CO2-equivalent value of $USD7.19 billion. Annual sequestration is 0.75 Tg OC yr-1, with a CO2-equivalent value of $USD28.02 million per annum. This study provides the most comprehensive estimates of tidal marsh blue carbon in Australia, and illustrates their importance in climate change mitigation and adaptation, acting as CO2 sinks and buffering the impacts of rising sea level. We outline potential further development of carbon offset schemes to restore the sequestration capacity and other ecosystem services provided by Australia tidal marshes.

  17. On the migration rate of tidal meanders

    Science.gov (United States)

    D'Alpaos, A.; Finotello, A.; Ghinassi, M.; Lanzoni, S.; Marani, M.; Rinaldo, A.

    2016-12-01

    Sinuous channels shaped by periodically reversing tidal flows are a ubiquitous feature of tidal landscapes. Despite their fundamental role on the morphology and sedimentary patterns of these landscapes, tidal meanders have received less attention than their fluvial counterparts, particularly as far as migration processes are concerned. We have analyzed the migration of about 300 meander bends in the Northern Venice Lagoon (Italy), from 1968 to nowadays, through observations and modeling interpretation. Similarities with fluvial meanders occur, although important difference also emerge. Meanders cutting through salt-marshes in the Venice Lagoon follow the relationship between Cartesian length and channel width, typical of meanders developed within different settings. We find a mean migration rate of about 0.20 m/year. However, the potential migration rate can reach values of about 0.20 channel widths per year thus suggesting similarities with fluvial meanders. In addition, tidal channel migration dynamics displays features which qualitatively agree with theories developed for the fluvial setting. We deem our results are valuable for the understanding of the morphological evolution and architecture of tidal landscapes, with implications for restoration strategies, also in the face of changes in environmental conditions.

  18. Carbon sequestration by Australian tidal marshes

    Science.gov (United States)

    Macreadie, Peter I.; Ollivier, Q. R.; Kelleway, J. J.; Serrano, O.; Carnell, P. E.; Ewers Lewis, C. J.; Atwood, T. B.; Sanderman, J.; Baldock, J.; Connolly, R. M.; Duarte, C. M.; Lavery, P. S.; Steven, A.; Lovelock, C. E.

    2017-03-01

    Australia’s tidal marshes have suffered significant losses but their recently recognised importance in CO2 sequestration is creating opportunities for their protection and restoration. We compiled all available data on soil organic carbon (OC) storage in Australia’s tidal marshes (323 cores). OC stocks in the surface 1 m averaged 165.41 (SE 6.96) Mg OC ha-1 (range 14-963 Mg OC ha-1). The mean OC accumulation rate was 0.55 ± 0.02 Mg OC ha-1 yr-1. Geomorphology was the most important predictor of OC stocks, with fluvial sites having twice the stock of OC as seaward sites. Australia’s 1.4 million hectares of tidal marshes contain an estimated 212 million tonnes of OC in the surface 1 m, with a potential CO2-equivalent value of $USD7.19 billion. Annual sequestration is 0.75 Tg OC yr-1, with a CO2-equivalent value of $USD28.02 million per annum. This study provides the most comprehensive estimates of tidal marsh blue carbon in Australia, and illustrates their importance in climate change mitigation and adaptation, acting as CO2 sinks and buffering the impacts of rising sea level. We outline potential further development of carbon offset schemes to restore the sequestration capacity and other ecosystem services provided by Australia tidal marshes.

  19. Estimating hydraulic properties from tidal attenuation in the Northern Guam Lens Aquifer, territory of Guam, USA

    Science.gov (United States)

    Rotzoll, Kolja; Gingerich, Stephen B.; Jenson, John W.; El-Kadi, Aly I.

    2013-05-01

    Tidal-signal attenuations are analyzed to compute hydraulic diffusivities and estimate regional hydraulic conductivities of the Northern Guam Lens Aquifer, Territory of Guam (Pacific Ocean), USA. The results indicate a significant tidal-damping effect at the coastal boundary. Hydraulic diffusivities computed using a simple analytical solution for well responses to tidal forcings near the periphery of the island are two orders of magnitude lower than for wells in the island's interior. Based on assigned specific yields of ˜0.01-0.4, estimated hydraulic conductivities are ˜20-800 m/day for peripheral wells, and ˜2,000-90,000 m/day for interior wells. The lower conductivity of the peripheral rocks relative to the interior rocks may best be explained by the effects of karst evolution: (1) dissolutional enhancement of horizontal hydraulic conductivity in the interior; (2) case-hardening and concurrent reduction of local hydraulic conductivity in the cliffs and steeply inclined rocks of the periphery; and (3) the stronger influence of higher-conductivity regional-scale features in the interior relative to the periphery. A simple numerical model calibrated with measured water levels and tidal response estimates values for hydraulic conductivity and storage parameters consistent with the analytical solution. The study demonstrates how simple techniques can be useful for characterizing regional aquifer properties.

  20. Estimating hydraulic properties from tidal attenuation in the Northern Guam Lens Aquifer, territory of Guam, USA

    Science.gov (United States)

    Rotzoll, Kolja; Gingerich, Stephen B.; Jenson, John W.; El-Kadi, Aly I.

    2013-01-01

    Tidal-signal attenuations are analyzed to compute hydraulic diffusivities and estimate regional hydraulic conductivities of the Northern Guam Lens Aquifer, Territory of Guam (Pacific Ocean), USA. The results indicate a significant tidal-damping effect at the coastal boundary. Hydraulic diffusivities computed using a simple analytical solution for well responses to tidal forcings near the periphery of the island are two orders of magnitude lower than for wells in the island’s interior. Based on assigned specific yields of ~0.01–0.4, estimated hydraulic conductivities are ~20–800 m/day for peripheral wells, and ~2,000–90,000 m/day for interior wells. The lower conductivity of the peripheral rocks relative to the interior rocks may best be explained by the effects of karst evolution: (1) dissolutional enhancement of horizontal hydraulic conductivity in the interior; (2) case-hardening and concurrent reduction of local hydraulic conductivity in the cliffs and steeply inclined rocks of the periphery; and (3) the stronger influence of higher-conductivity regional-scale features in the interior relative to the periphery. A simple numerical model calibrated with measured water levels and tidal response estimates values for hydraulic conductivity and storage parameters consistent with the analytical solution. The study demonstrates how simple techniques can be useful for characterizing regional aquifer properties.

  1. Tidal creeks as hot spots for submarine groundwater discharge on barrier islands: an example from Spiekeroog

    Science.gov (United States)

    Gilfedder, Benjamin; Glaser, Clarissa

    2017-04-01

    Submarine groundwater discharge can be a controlling factor in water and nutrient cycles in coastal ecosystems. Groundwater discharge and associated nutrient fluxes are controlled by both geomorphology of coastal catchments as well as dynamics at the land-ocean interface e.g. tidal magnitude. The Wadden Sea of Northern Germany is one of the largest regions shaped by tides in the world as well as having active biogeochemistry in the organic-rich mud flats. The aim of this work was to characterize and quantify groundwater discharge to the coastal zone in space and time, with a particular focus on tidal creeks, using the noble gas 222Rn. We have conducted two field campaigns on the barrier island Spiekeroog, which is an ideal field laboratory due to its well defined hydrological boundary conditions. The investigations took place from February 22 to 26 2016, and from March 14 to 20 2016 in a selected branched tidal creek and its catchment in the eastern part of the island (Ostplate). We have mapped the tidal creek using 222Rn activities as well as biogeochemical parameters (e.g. EC, DOC, Fe, SO42-). A continuous measurement station was set-up at the creek mouth and measured 222Rn, O2 and EC in 15 min resolution for 5 days. The mapping results show that groundwater discharge is highest in areas closed to the dune systems and decreases towards the tidal flat areas. While all samples in the creek had a high salt concentration (EC>30 ms/cm), the samples were also close to the dunes had the largest proportion of salt compared to areas close to the mud flats. The continuous 222Rn measurements showed that the largest groundwater discharge occurred during low tide, when hydrological gradients are likely to be largest towards the sea. While the discharge could be very high over short periods ( 1 m/d), which is likely due to the large tidal amplitude in the Norther German sea, when averaged over the whole tidal cycle it was similar to previous studies (15-26 cm/d). Our work on

  2. The wave and tidal resource of Scotland

    Science.gov (United States)

    Neill, Simon; Vogler, Arne; Lewis, Matt; Goward-Brown, Alice

    2017-04-01

    As the marine renewable energy industry evolves, in parallel with an increase in the quantity of available data and improvements in validated numerical simulations, it is occasionally appropriate to re-assess the wave and tidal resource of a region. This is particularly true for Scotland - a leading nation that the international community monitors for developments in the marine renewable energy industry, and which has witnessed much progress in the sector over the last decade. With 7 leased wave and 17 leased tidal sites, Scotland is well poised to generate significant levels of electricity from its abundant natural marine resources. In this review of Scotland's wave and tidal resource, I present the theoretical and technical resource, and provide an overview of commercial progress. I also discuss issues that affect future development of the marine energy seascape in Scotland, applicable to other regions of the world, including the potential for developing lower energy sites, and grid connectivity.

  3. TIDAL TURBULENCE SPECTRA FROM A COMPLIANT MOORING

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, Jim; Kilcher, Levi; Richmond, Marshall C.; Talbert, Joe; deKlerk, Alex; Polagye, Brian; Guerra, Maricarmen; Cienfuegos, Rodrigo

    2013-06-13

    A compliant mooring to collect high frequency turbulence data at a tidal energy site is evaluated in a series of short demon- stration deployments. The Tidal Turbulence Mooring (TTM) improves upon recent bottom-mounted approaches by suspend- ing Acoustic Doppler Velocimeters (ADVs) at mid-water depths (which are more relevant to tidal turbines). The ADV turbulence data are superior to Acoustic Doppler Current Profiler (ADCP) data, but are subject to motion contamination when suspended on a mooring in strong currents. In this demonstration, passive stabilization is shown to be sufficient for acquiring bulk statistics of the turbulence, without motion correction. With motion cor- rection (post-processing), data quality is further improved; the relative merits of direct and spectral motion correction are dis- cussed.

  4. Circumbinary discs from tidal disruption events

    Science.gov (United States)

    Coughlin, Eric R.; Armitage, Philip J.

    2017-10-01

    Tidal disruption events, which occur when a star is shredded by the tidal field of a supermassive black hole (SMBH), provide a means of fuelling black hole accretion. Here we show, using a combination of three-body orbit integrations and hydrodynamic simulations, that these events are also capable of generating circumbinary rings of gas around tight SMBH binaries with small mass ratios. Depending on the thermodynamics, these rings can either fragment into clumps that orbit the binary, or evolve into a gaseous circumbinary disc. We argue that tidal disruptions provide a direct means of generating circumbinary discs around SMBH binaries and, more generally, can replenish the reservoir of gas on very small scales in galactic nuclei.

  5. Oceanographic data collected during the EX1401 (Ship Shakedown and Patch Test Exploration) expedition on NOAA Ship OKEANOS EXPLORER in the North Atlantic Ocean from 2014-02-06 to 2014-02-09 (NODC Accession 0116846)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — To begin the 2014 NOAA Ship Okeanos Explorer field season, a ship shakedown and multibeam patch test was performed off the coast of Rhode Island over Veatch Canyon....

  6. Oceanographic data collected during the EX1601 Transit and Mission Patch Test on NOAA Ship OKEANOS EXPLORER in the North Pacific Ocean from 2016-01-20 to 2016-02-07 (NCEI Accession 0145341)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Normal underway operations and mapping patch testing. Bathymetric mapping of either the Murray or Molokai Fracture Zones during the transit to Hawaii was planned, as...

  7. Correlation between seismicity and barometric tidal exalting

    Directory of Open Access Journals (Sweden)

    D. N. Arabelos

    2008-10-01

    Full Text Available Changes of barometric pressure in the area of Thessaloniki in Northern Greece were studied by analyzing a sample of 31 years of hourly measurements. The results of this analysis on the periodicities of tidal components are expressed in terms of amplitude and phases variability. An earlier investigation revealed a detectable correlation between the exalting of the amplitude parameters of the tidal waves with strong seismic events. A problem of this work was that we had compared the tidal parameters resulting from the analysis of data covering the period of one year with instantaneous seismic events, although the earthquake is the final result of a tectonic process of the upper lithosphere. Consequently, in order to increase the resolution of our method we had analyzed our data in groups of 3-months extent and the resulted amplitudes were compared with seismicity index for corresponding time periods. A stronger correlation was found in the last case. However, the estimation of tidal parameters in this case was restricted to short period (from one day down to eight hours constituents. Therefore, a new analysis was performed, retaining the one-year length of each data block but shifting the one year window by steps of three months from the beginning to the end of the 31 years period. This way, we are able to estimate again tidal parameters ranging from periods of one year (Sa down to eight hours (M3. The resulting correlation between these tidal parameters with a cumulative seismicity index for corresponding time intervals was remarkably increased.

  8. Vital Signs: Seismology of Icy Ocean Worlds

    Science.gov (United States)

    Vance, Steven D.; Kedar, Sharon; Panning, Mark P.; Stähler, Simon C.; Bills, Bruce G.; Lorenz, Ralph D.; Huang, Hsin-Hua; Pike, W. T.; Castillo, Julie C.; Lognonné, Philippe; Tsai, Victor C.; Rhoden, Alyssa R.

    2018-01-01

    Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with the Moon, that detectable seismic activity should occur frequently on tidally flexed ocean worlds. Their ices fracture more easily than rocks and dissipate more tidal energy than the seismology investigations of the Moon or Mars.

  9. Shape Design of the Duct for Tidal Converters Using Both Numerical and Experimental Approaches (pre-2015

    Directory of Open Access Journals (Sweden)

    Chul H. Jo

    2016-03-01

    Full Text Available Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Among the various ocean energy sources, tidal current power (TCP is recognized as the most promising energy source in terms of predictability and reliability. The enormous energy potential in TCP fields has been exploited by installing TCP systems. The flow velocity is the most important factor for power estimation of a tidal current power system. The kinetic energy of the flow is proportional to the cube of the flow’s velocity, and velocity is a critical variable in the performance of the system. Since the duct can accelerate the flow velocity, its use could expand the applicable areas of tidal devices to relatively low velocity sites. The inclined angle of the duct and the shapes of inlet and outlet affect the acceleration rates of the flow inside the duct. In addition, the volume of the duct can affect the flow velocity amplification performance. To investigate the effects of parameters that increase the flow velocity, a series of simulations are performed using the commercial computational fluid dynamics (CFD code ANSYS-CFX. Experimental investigations were conducted using a circulation water channel (CWC.

  10. WATER TRAPPING ON TIDALLY LOCKED TERRESTRIAL PLANETS REQUIRES SPECIAL CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jun; Abbot, Dorian S. [Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Liu, Yonggang [Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 (United States); Hu, Yongyun, E-mail: junyang28@uchicago.edu [Laboratory for Climate and Atmosphere-Ocean Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing (China)

    2014-12-01

    Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld, we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, nightside sea ice remains O(10 m) thick and nightside water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete dayside dessiccation. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth's would be susceptible to complete water trapping.

  11. Combining local lithofacies and global geochemical signals to test the acidification hypothesis for the onset of Oceanic Anoxic Event 2 in the U.S. Western Interior Basin

    Science.gov (United States)

    Jones, M. M.; Sageman, B. B.; Selby, D. S.; Oakes, R. L.; Bralower, T. J.; Parker, A. L.; Leckie, R. M.; Sepulveda, J.

    2015-12-01

    Strata preserving Oceanic Anoxic Event 2 (OAE2), which span the Cenomanian-Turonian (C/T; Late Cretaceous), exhibit evidence of widespread anoxia, a major perturbation to the global carbon cycle, and increased biotic turnover rates. It has been hypothesized that a major volcanic (LIP) eruption, increased CO2 levels, and significant climate warming triggered the event. Recently, OAE2 has also been cited as a potential example of ocean acidification in Earth history and therefore has potential to offer predictive insights on impacts of increasing modern pCO2 levels. As part of an effort to test this hypothesis, the 131-m Smoky Hollow #1 (SH-1) core was drilled near Big Water, Utah during the summer of 2014. The core recovered an expanded stratigraphic record of OAE2 from the mud-rich western margin of the Western Interior Seaway. A high-resolution stable carbon isotope record from bulk organic carbon (δ13Corg) indicates near-continuous preservation of OAE2 with a sustained +2.5‰ excursion that is over 5 times the thickness of the same excursion at the C/T GSSP in Pueblo, Colorado. Notably, this record is characterized by a 1-m thick carbonate-barren interval at the δ13C excursion's onset. This may indicate an episode of ocean acidification driving suppressed carbonate sedimentation or carbonate dissolution. An alternative interpretation is that variations in carbonate concentrations are unrelated to changes in ocean chemistry and are instead driven by changes in local sedimentation patterns (e.g. transgressive-regressive parasequences). To test these hypotheses, a regional lithostratigraphic correlation to the nearshore Cottonwood Canyon section is constructed to assess whether prograding sandy parasequences may have altered carbonate sedimentation rates at the SH-1 locality. Initial osmium and δ13C chemostratigraphies are also developed to constrain the timing of perturbations in global geochemical cycles at the initiation of OAE2, including the onset of large

  12. Tidal forces in Kiselev black hole

    Energy Technology Data Exchange (ETDEWEB)

    Shahzad, M.U. [University of Central Punjab, CAMS, UCP Business School, Lahore (Pakistan); Jawad, Abdul [COMSATS Institute of Information Technology, Department of Mathematics, Lahore (Pakistan)

    2017-06-15

    The aim of this paper is to examine the tidal forces occurring in a Kiselev black hole surrounded by radiation and dust fluids. It is noted that the radial and angular components of the tidal force change the sign between event and Cauchy horizons. We solve the geodesic deviation equation for radially free-falling bodies toward Kiselev black holes. We explain the geodesic deviation vector graphically and point out the location of the event and Cauchy horizons for specific values of the radiation and dust parameters. (orig.)

  13. Validation Test Report for the 1/8 deg Global Navy Coastal Ocean Model Nowcast/Forecast System

    Science.gov (United States)

    2007-01-24

    equation of state, and the adaptation by Mellor (1991) of the United Nations Educational Scientific and Cultural Organization (UNESCO) equation of state...Sigma Z-level Model TAO Tropical Atmosphere Ocean UNESCO United Nations Educational Scientific and Cultural Organization USACE United States Army...0.5 Atl. Trn. 40.0N 40N,5-71.6W -0.8 2.9 Yucatan Channel 21.3N,86.7W– 23.2 N, 80.7W 22.2 2.1 Atl. Trn. 34.0N 34N, 7.6-80.7W 0.0 0.0 Windward

  14. Tidal disruptions by rotating black holes: relativistic hydrodynamics with Newtonian codes

    Science.gov (United States)

    Tejeda, Emilio; Gafton, Emanuel; Rosswog, Stephan; Miller, John C.

    2017-08-01

    We propose an approximate approach for studying the relativistic regime of stellar tidal disruptions by rotating massive black holes. It combines an exact relativistic description of the hydrodynamical evolution of a test fluid in a fixed curved space-time with a Newtonian treatment of the fluid's self-gravity. Explicit expressions for the equations of motion are derived for Kerr space-time using two different coordinate systems. We implement the new methodology within an existing Newtonian smoothed particle hydrodynamics code and show that including the additional physics involves very little extra computational cost. We carefully explore the validity of the novel approach by first testing its ability to recover geodesic motion, and then by comparing the outcome of tidal disruption simulations against previous relativistic studies. We further compare simulations in Boyer-Lindquist and Kerr-Schild coordinates and conclude that our approach allows accurate simulation even of tidal disruption events where the star penetrates deeply inside the tidal radius of a rotating black hole. Finally, we use the new method to study the effect of the black hole spin on the morphology and fallback rate of the debris streams resulting from tidal disruptions, finding that while the spin has little effect on the fallback rate, it does imprint heavily on the stream morphology, and can even be a determining factor in the survival or disruption of the star itself. Our methodology is discussed in detail as a reference for future astrophysical applications.

  15. The Concentric Maclaurin Spheroid method with tides and a rotational enhancement of Saturn's tidal response

    Science.gov (United States)

    Wahl, Sean M.; Hubbard, William B.; Militzer, Burkhard

    2017-01-01

    We extend to three dimensions the Concentric Maclaurin Spheroid method for obtaining the self-consistent shape and gravitational field of a rotating liquid planet, to include a tidal potential from a satellite. We exhibit, for the first time, an important effect of the planetary rotation rate on tidal response of gas giants, whose shape is dominated by the centrifugal potential from rapid rotation. Simulations of planets with fast rotation rates like those of Jupiter and Saturn, exhibit significant changes in calculated tidal love numbers knm when compared with non-rotating bodies. A test model of Saturn fitted to observed zonal gravitational multipole harmonics yields k2 = 0.413 , consistent with a recent observational determination from Cassini astrometry data (Lainey et al., 2016.). The calculated love number is robust under reasonable assumptions of interior rotation rate, satellite parameters, and details of Saturn's interior structure. The method is benchmarked against several published test cases.

  16. Ocean Acoustic Propagation and Coherence Studies

    Science.gov (United States)

    2015-09-30

    and Engineering Department, MS 11 Woods Hole Oceanographic Institution, Woods Hole , MA 02543 phone: (508) 289-2495 fax: (508) 457-2194 email...Simulations are at one-hour intervals. The ocean structure contains mainly tidal frequency fluctuations, which are resolves at this sampling rate. Some...Hz sound going down Coronado Canyon from left to right (150 dB source is 40 m deep at the [x,y] origin. Black lines are depth contours as in Figure 1

  17. Spatial tidal asymmetry of Cochin estuary, West Coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Vinita, J.; Shivaprasad, A.; Manoj, N.T.; Revichandran, C.; Naveenkumar, K.R.; Jineesh, V.K.

    tidal amplitude and currents get attenuated towards upstream through frictional dissipation The results showed that the tidal momentum balance along the main axis of the channel was dominated by pressure gradient and friction The influence of advection...

  18. Tidal flow characteristics at Kasheli (Kalwa/ Bassein creek), Bombay

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.; Suryanarayana, A.

    Tidal flow characteristics of waters at Kasheli, connected to the sea through Thane and Bassein Creeks in Bombay, Maharashtra, India are investigated based on tide and current observations carried out in 1980-81. The results establish that the tidal...

  19. Correcting GRACE gravity fields for ocean tide effects

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar

    2002-01-01

    [1] The GRACE mission will be launch in early 2002 and will map the Earth's gravity fields and its variations with unprecedented accuracy during its 5-year lifetime. Unless ocean tide signals and their load upon the solid earth are removed from the GRACE data, their long period aliases obscure more...... subtle climate signals which GRACE aims at. The difference between two existing ocean tide models can be used as an estimate of current tidal model error for the M-2,S-2,K-1, and O-1 constituents. When compared with the expected accuracy of the GRACE system, both expressed as spherical harmonic degree...... variances, we find that the current ocean tide models are not accurate enough to correct GRACE data at harmonic degrees lower that 35. The accumulated tidal errors may affect the GRACE data up to harmonic degree 56. Furthermore, the atmospheric (radiation) tides may cause significant errors in the ocean...

  20. SUITABLE POWERHOUSE DESIGN FOR KUCHING BARRAGE TIDAL POWER SCHEME

    OpenAIRE

    Kamran Ahmed Samo*1, Andrew Ragai Henry Rigit2, Imran Ahmed Samo3, Abid Ali Shah Bukhari 4, Ahsanullah Soomro5, Azhaili Baharun6

    2017-01-01

    Renewable energy is the best solution and alternative to overcome the world growing energy demand and fossil fuels deficiency. Tidal energy is also renewable energy that uses barrage and tide height difference to extract energy. Kuching Barrage located in Sarawak was built to mitigate flood in the city of Kuching and has the potential for development into tidal power station. The purpose of this paper is to offer suitable tidal power plant system for tidal energy harnessing at Kuching Barrage...

  1. Quantification of tidal parameters from Solar system data

    OpenAIRE

    Lainey, Valéry

    2016-01-01

    Tidal dissipation is the main driver of orbital evolution of natural satellites and a key point to understand the exoplanetary system configurations. Despite its importance, its quantification from observations still remains difficult for most objects of our own Solar system. In this work, we overview the method that has been used to determine, directly from observations, the tidal parameters, with emphasis on the Love number k2 and the tidal quality factor Q. Up-to-date values of these tidal...

  2. Tidal Power Potential in the Submerged Channels of Dar es

    African Journals Online (AJOL)

    Results from in-situ measurements show that currents on the sandbank and the tidal flat, in water depths from 0.5 m to 3.0 m, are directed opposite the main tidal current in the deeper waters. Current velocities vary during a tidal cycle and are strongest in the middle of the cycle. Generally, velocities on the tidal flat are around ...

  3. Ocean tide models for satellite geodesy and Earth rotation

    Science.gov (United States)

    Dickman, Steven R.

    1991-01-01

    A theory is presented which predicts tides in turbulent, self-gravitating, and loading oceans possessing linearized bottom friction, realistic bathymetry, and continents (at coastal boundaries no-flow conditions are imposed). The theory is phrased in terms of spherical harmonics, which allows the tide equations to be reduced to linear matrix equations. This approach also allows an ocean-wide mass conservation constraint to be applied. Solutions were obtained for 32 long and short period luni-solar tidal constituents (and the pole tide), including the tidal velocities in addition to the tide height. Calibrating the intensity of bottom friction produces reasonable phase lags for all constituents; however, tidal amplitudes compare well with those from observation and other theories only for long-period constituents. In the most recent stage of grant research, traditional theory (Liouville equations) for determining the effects of angular momentum exchange on Earth's rotation were extended to encompass high-frequency excitations (such as short-period tides).

  4. Acoustic Monitoring of Beluga Whale Interactions with Cook Inlet Tidal Energy Project

    Energy Technology Data Exchange (ETDEWEB)

    Worthington, Monty [ORPC Alaska, LLC, Anchorage, AK (United States)

    2014-02-05

    Cook Inlet, Alaska is home to some of the greatest tidal energy resources in the U.S., as well as an endangered population of beluga whales (Delphinapterus leucas). Successfully permitting and operating a tidal power project in Cook Inlet requires a biological assessment of the potential and realized effects of the physical presence and sound footprint of tidal turbines on the distribution, relative abundance, and behavior of Cook Inlet beluga whales. ORPC Alaska, working with the Project Team—LGL Alaska Research Associates, University of Alaska Anchorage, TerraSond, and Greeneridge Science—undertook the following U.S. Department of Energy (DOE) study to characterize beluga whales in Cook Inlet – Acoustic Monitoring of Beluga Whale Interactions with the Cook Inlet Tidal Energy Project (Project). ORPC Alaska, LLC, is a wholly-owned subsidiary of Ocean Renewable Power Company, LLC, (collectively, ORPC). ORPC is a global leader in the development of hydrokinetic power systems and eco-conscious projects that harness the power of ocean and river currents to create clean, predictable renewable energy. ORPC is developing a tidal energy demonstration project in Cook Inlet at East Foreland where ORPC has a Federal Energy Regulatory Commission (FERC) preliminary permit (P-13821). The Project collected baseline data to characterize pre-deployment patterns of marine mammal distribution, relative abundance, and behavior in ORPC’s proposed deployment area at East Foreland. ORPC also completed work near Fire Island where ORPC held a FERC preliminary permit (P-12679) until March 6, 2013. Passive hydroacoustic devices (previously utilized with bowhead whales in the Beaufort Sea) were adapted for study of beluga whales to determine the relative abundance of beluga whale vocalizations within the proposed deployment areas. Hydroacoustic data collected during the Project were used to characterize the ambient acoustic environment of the project site pre-deployment to inform the

  5. Anisotropic dissipation of the global internal tide from a higher-order multiscale barotropic tidal simulation

    Science.gov (United States)

    Salehipour, Hesam; Peltier, W. Richard

    2013-04-01

    Increasing recognition of the importance of the diapycnal mixing induced by the dissipation of internal tides excited by the interaction of the barotropic tide with bottom topography has begun to attract increasing attention. The partition of the dissipation of the barotropic tide between that related to the internal tide and that related to bottom friction is also of considerable interest as this partition has been shown to shift significantly between the modern and Last Glacial Maximum tidal regimes [Griffiths and Peltier, 2008, 2009] . Ocean general circulation models, though clearly unable to explicitly resolve small scale mixing processes, currently rely on the introduction of an appropriate parameterization of the contribution to such mixing due to dissipation of the internal tidal. One widely-used parameterization of this kind (which is currently employed in POP2) is that proposed by Jayne and St. Laurent [GRL 2001] and is based on topographic roughness. This contrasts with the parameterization of Carrere and Lyard [GRL 2003] and Lyard [Ocean Dynamics, 2006] which also considers the flow direction with respect to the topographic features. Both of these parameterizations require the tuning of parameters to arrive at sensible tidal amplitudes. We have developed an original higher order barotropic tidal model based on the discontinuous Galerkin finite element method applied on global triangular grids [Salehipour et al., submitted to Ocean Modelling] in which we parameterize the energy conversion to baroclinic tides by introducing an anisotropic internal tide drag [Griffiths and Peltier GRL 2008, Griffiths and Peltier J Climate 2009] which also considers the time dependent angle of attack of the barotropic tidal flow on abyssal topographic features but requires no tuning parameters. The model is massively parallelized which enables very high resolution modeling of global barotropic tides as well as the implementation of local grid refinement. In this paper we

  6. Novel approach to the exploitation of the tidal energy. Volume 1: Summary and discussion

    Science.gov (United States)

    Gorlov, A. M.

    1981-12-01

    The hydropneumatic concept in the approach to harnessing low tidal hydropower is discussed. The energy of water flow is converted into the energy of an air jet by a specialized air chamber which is placed on the ocean floor across a flowing watercourse. Water passes through the chamber where it works as a natural piston compressing air in the upper part of the closure. Compressed air is used as a new working plenum to drive air turbines. The kinetic energy of an air jet provided by the air chamber is sufficient for stable operation of industrial air turbines. It is possible to use light plastic barriers instead of conventional rigid dams (the water sail concept). It is confirmed that the concept can result in a less expensive and more effective tidal power plant project than the conventional hydroturbine approach.

  7. Ocean Fertilization and Ocean Acidification

    Science.gov (United States)

    Cao, L.; Caldeira, K.

    2008-12-01

    It has been suggested that ocean fertilization could help diminish ocean acidification. Here, we quantitatively evaluate this suggestion. Ocean fertilization is one of several ocean methods proposed to mitigate atmospheric CO2 concentrations. The basic idea of this method is to enhance the biological uptake of atmospheric CO2 by stimulating net phytoplankton growth through the addition of iron to the surface ocean. Concern has been expressed that ocean fertilization may not be very effective at reducing atmospheric CO2 concentrations and may produce unintended environmental consequences. The rationale for thinking that ocean fertilization might help diminish ocean acidification is that dissolved inorganic carbon concentrations in the near-surface equilibrate with the atmosphere in about a year. If ocean fertilization could reduce atmospheric CO2 concentrations, it would also reduce surface ocean dissolved inorganic carbon concentrations, and thus diminish the degree of ocean acidification. To evaluate this line of thinking, we use a global ocean carbon cycle model with a simple representation of marine biology and investigate the maximum potential effect of ocean fertilization on ocean carbonate chemistry. We find that the effect of ocean fertilization on ocean acidification depends, in part, on the context in which ocean fertilization is performed. With fixed emissions of CO2 to the atmosphere, ocean fertilization moderately mitigates changes in ocean carbonate chemistry near the ocean surface, but at the expense of further acidifying the deep ocean. Under the SRES A2 CO2 emission scenario, by year 2100 simulated atmospheric CO2, global mean surface pH, and saturation state of aragonite is 965 ppm, 7.74, and 1.55 for the scenario without fertilization and 833 ppm, 7.80, and 1.71 for the scenario with 100-year (between 2000 and 2100) continuous fertilization for the global ocean (For comparison, pre-industrial global mean surface pH and saturation state of

  8. Subtidal flow division at a shallow tidal junction

    NARCIS (Netherlands)

    Buschman, F.A.; Hoitink, A.J.F.; Vegt, van der M.; Hoekstra, P.

    2010-01-01

    Tides influence distribution of river discharge at tidally affected channel junctions. At the apex of a channel network in an Indonesian delta, observations of flow division suggest that tidally averaged flow division depends on the tidal range. To understand the mechanisms governing the subtidal

  9. Sedimentary signatures of tidal bores: a brief synthesis

    Science.gov (United States)

    Tessier, Bernadette; Furgerot, Lucille; Mouazé, Dominique

    2017-08-01

    This article aims at presenting a brief synthesis of sedimentary signatures assigned to tidal bore dynamics and impacts. According to the few studies published until now on tidal bore-induced facies within inner estuarine tidal channel infilling successions, only two major signatures can be reported: (1) soft sediment deformations (SSDs) due to overpressure linked to sudden water level elevation, high shear stress and vertical velocity acceleration below the tidal bore front and secondary waves; SSDs may be present throughout the channel infill succession, with the general exception of the uppermost part; tidal bore-induced SSDs have been described only in modern facies; (2) tidal bore couplets (TBCs) formed by an erosional surface overlain by massive sand drapes, related to the reworking of the sediment bottom during tidal bore passage; TBCs were first described in the ancient record. Studies in modern estuaries demonstrate that TBCs evolve towards tidal bore sequences from the tidal channel bottom (subtidal to low intertidal facies) to tidal channel bank (low to mid intertidal facies). In mid to upper intertidal facies, the occurrence of thicker-than-average tidal rhythmites, reflecting higher-than-average suspended sediment concentrations, are also considered as a possible signature of tidal bore dynamics.

  10. Ecological consequences of diurnal flooding in tidal freshwater wetlands

    NARCIS (Netherlands)

    Barendregt, A.; Wassen, M.J.

    2010-01-01

    Diurnal flooding can be observed in the upper end of tidal estuaries, where flooding water originating from the river is constantly fresh. Here, the input from the river is confronted with a tidal wave, so that the sand banks, mud flats, low and high marshes and tidal forests are flooded mostly

  11. 77 FR 5791 - Ocean Renewable Power Company Maine, LLC; Notice of Staff Participation in Meeting

    Science.gov (United States)

    2012-02-06

    ... Energy Regulatory Commission Ocean Renewable Power Company Maine, LLC; Notice of Staff Participation in... representatives from Ocean Renewable Power Company Maine, LLC at the Federal Energy Regulatory Commission's... environmental assessment issued on January 4, 2012, for the Cobscook Bay Tidal Energy Project No. 12711. A...

  12. 76 FR 18750 - Ocean Renewable Power Company, LLC; Notice of Change in Docket Number

    Science.gov (United States)

    2011-04-05

    ... Energy Regulatory Commission Ocean Renewable Power Company, LLC; Notice of Change in Docket Number On July 24, 2009, Ocean Renewable Power Company, LLC (ORPC) filed a draft hydrokinetic pilot license application (DLA) for the proposed Eastport Tidal Energy Project, a proposal that unified two preliminary...

  13. 76 FR 63917 - Ocean Renewable Power Company, LLC; Notice of Application Accepted for Filing, Soliciting Motions...

    Science.gov (United States)

    2011-10-14

    .... d. Applicant: Ocean Renewable Power Company, LLC. e. Name of Project: Cobscook Bay Tidal Energy... Federal Energy Regulatory Commission Ocean Renewable Power Company, LLC; Notice of Application Accepted.... The project does not affect federal lands. g. Filed Pursuant to: Federal Power Act, 16 U.S.C. 791(a...

  14. Evolution and Termination of Oceanic Anoxic Event 2: Testing the impact of organic matter sulfurization on benthic-pelagic coupling during OAE2

    Science.gov (United States)

    Hülse, D.; Arndt, S.; Ridgwell, A.

    2016-12-01

    Oceanic Anoxic Events (OAEs) represent severe disturbances of the global carbon, oxygen and nutrient cycles of the ocean. The archetypal example is OAE2 ( 93.5 Ma), which is characterized by widespread bottom water anoxia and photic zone euxinia. One way to explain these conditions is via increased oxygen demand in the water column resulting from enhanced primary productivity (PP), itself fuelled by increased nutrient availability for instance from the sediments as the burial efficiency of phosphorus declines when bottom waters become anoxic. The recovery from OAE like conditions is thought to involve the permanent removal of excess CO2 from the atmosphere and ocean by burying carbon in the form of organic matter (OM) in marine sediments, which is consistent with the geological record of widespread black shale formation. A number of possible controls on enhanced OM burial have previously been proposed and assessed, such as elevated depositional fluxes, higher clay mineral availability, or reduced oxygenation. Here we explore a 4th possible mechanism - organic matter sulfurization. During sulfurization, reduced inorganic sulfur species (e.g. H2S) react with OM, resulting in the formation of organic sulfur compounds which are less prone to bacterial degradation. Although studies indicate the global significance of this process for OAE2, its implications on Cretaceous benthic-pelagic coupling and thus OAE2 evolution and recovery has not yet been quantified and tested with a 3D Earth system model. The major hurdle is the high computational cost of simulating the essential redox reactions in marine sediments, which are critical to quantify the burial of OM and benthic recycling fluxes of chemical compounds. In order to close this knowledge gap, we developed a new, mechanistic representation of OM preservation in marine sediments (OMEN-SED) and coupled it to a 3D Earth system model (cGENIE). Using this new model we explore the impact of organic matter sulfurization on

  15. A review of ocean energy converters, with an Australian focus

    OpenAIRE

    Chris Knight; Scott McGarry; Jennifer Hayward; Peter Osman; Sam Behrens

    2014-01-01

    The requirement to move away from carbon based fossil fuels has led to a renewed interest in unconventional energy sources. Of interest in this article are ocean waves and current and tidal flows. This paper reviews the numerous options for ocean energy conversion systems that are currently available. A basic nomenclature for the variety of systems is utilized to classify the devices. A variety of issues including competing use, boating, fishing, commercial shipping and tourism are discussed ...

  16. Geometry of tidal inlet systems : A key factor for the net sediment transport in tidal inlets

    National Research Council Canada - National Science Library

    Ridderinkhof, W; de Swart, H. E; van der Vegt, M; Alebregtse, N. C; Hoekstra, P

    2014-01-01

    .... Earlier studies showed that in a short basin, tidal flats favor peak ebb-currents stronger than peak flood currents, implying export of coarse sediment, while shallow basins favor stronger flood currents...

  17. Tidal reorientation and the fracturing of Jupiter's moon Europa

    Science.gov (United States)

    McEwen, A.S.

    1986-01-01

    The most striking characteristic of Europa is the network of long linear albedo markings over the surface, suggestive of global-scale tectonic processes. Various explanations for the fractures have been proposed: Freezing and expansion of an early liquid water ocean1, planetary expansion due to dehydration of hydrated silicates2, localization by weak points in the crust generated by impacts3, and a combination of stresses due to planetary volume change and tidal distortions from orbital recession and orbital eccentricity4,5. Calculations by Yoder6 and Greenberg and Weidenschilling7 have shown that Europa may rotate slightly more rapidly than the synchronous rate, with a rotation period (reorientation through 360??) ranging from 20 to >103 yr if a liquid mantle is present, or up to 1010 yr if the satellite is essentially solid7. Helfen-stein and Parmentier8 modelled the stresses due to nonsynchronous rotation, and concluded that this could explain the long fractures in part of the anti-jovian hemisphere. In this note, I present a global map of lineaments with long arc lengths (>20?? or 550 km), and compare the lineament orientations to the tensile stress trajectories due to tidal distortions (changes in the lengths of three principal semiaxes) and to nonsynchronous rotation (longitudinal reorientation of two of the principal semiaxes). An excellent orthogonal fit to the lineaments is achieved by the stresses due to nonsynchronous rotation with the axis radial to Jupiter located 25?? east of its present position. This fit suggests that nonsynchronous rotation occurred at some time in Europa's history. ?? 1986 Nature Publishing Group.

  18. Predictions of Bedforms in Steady, Tidal and Oscillatory Flows

    Science.gov (United States)

    Gallagher, E. L.

    2016-02-01

    Bedforms are ubiquitous in unconsolidated sediments. They range in size from small orbital ripples (l 5-50 cm) to megaripples (l 1-5 m) to large dunes (l 10-100 m). Bedforms are important because they affect sediment transport, flow energy dissipation, and larger-scale hydro- and morpho-dynamics. Bedforms in different environments (eg, deserts, rivers and oceans) are thought to be dynamically similar, therefore modeling approaches from one environment can be used to predicted features in another (Gallagher 2011). Here, a self-organization model is used to simulate the formation and development of bedforms in the combined flows of the surf zone, tidal inlets and river mouths. Sediment flux is determined from combined wave and current flows using different formulations, but, interestingly, the transport formulation has little effect on model results. Random bed irregularities, either imposed or resulting from small variations in the flow representing turbulence, are seeds for bedform development. Feedback between the bed and the flow in the form of a shadow zone downstream of a bedform and increasing flow velocity with elevation over bedform crests alter the transport such that organized bedforms emerge. The model has been used to predict surf zone megaripples and bedforms in tidal inlets and river mouths. Many bedform models (e.g., Hulscher et al. 1996, Nielsen 1981, Clifton 1976, Wiberg and Harris 1994), predict specific bedform characteristics for a given flow condition. However, many observations report multiple scales existing simultaneously. A recent study by Lefevbre et al (2013) found that the boundary layer thickness and resulting bedform-induced roughness was different for single and multiple bedform fields. The present model predicts multiple bedform scales. In this study, predictions of different time and length scales of bedform evolution and roughness, as a function of flow magnitude, direction and variability are being examined.

  19. Methane emission from tidal freshwater marshes

    NARCIS (Netherlands)

    Van der Nat, F.J.; Middelburg, J.J.

    2000-01-01

    In two tidal freshwater marshes, methane emission, production and accumulation in the pore-water have been studied. The two sites differ in their dominant vegetation, i.e., reed and bulrush, and in their heights above sea level. The reed site was elevated in relation to the bulrush site and had

  20. Palaemon pacijicus (Stimpson) in eastern Cape tidal

    African Journals Online (AJOL)

    1984-09-25

    Sep 25, 1984 ... study of marine benthos, IBP Handbook 16: 197 - 279, (eds). Holme, N.A. & Mcintyre, A.D., Blackwell, Oxford. DAY, J.H. 1980. A guide to marine life on South African shores,. A.A. Balkema, Cape Town. EMMERSON, W.D. 1983. Tidal exchange of two decapod larvae. Palaemon pacijicus (Caridea) and ...

  1. Reinterpreting The Sagittarius Dwarf Tidal Debris

    Science.gov (United States)

    Newby, Matthew T.; Newberg, Heidi Jo; Thompson, Jeffery M.; Weiss, Jake

    2015-01-01

    Tidal debris from the Sagittarius dwarf galaxy (Sgr) has been used as a primary constraint in several determinations of the Milky Way Galaxy's total mass and dark matter distribution. However, the apparent "bifurcation" of both the leading and trailing tidal tails has never been satisfactorily explained. Using the powerful MilkyWay@home volunteer computing platform, we were surprised that the apparently fainter of the bifurcated tidal tails required an extremely wide stream to fit the observed stellar densities. Here, through additional analysis, we show that both the primary and secondary tidal tails of Sgr, as well as the Virgo overdensity, are all wider than previously thought, and dominate star counts in the Galactic halo. Additionally, we present evidence of a stellar "envelope" about the primary Sgr stream, which may be direct evidence for a subhalo-rich (or "lumpy") dark matter distribution. This research was supported by the NSF through grant AST 10-09670, and crowd funding from the MilkyWay@home volunteers.

  2. Tidal dwarf galaxies in cosmological simulations

    Science.gov (United States)

    Ploeckinger, Sylvia; Sharma, Kuldeep; Schaye, Joop; Crain, Robert A.; Schaller, Matthieu; Barber, Christopher

    2018-02-01

    The formation and evolution of gravitationally bound, star forming substructures in tidal tails of interacting galaxies, called tidal dwarf galaxies (TDG), has been studied, until now, only in idealized simulations of individual pairs of interacting galaxies for pre-determined orbits, mass ratios and gas fractions. Here, we present the first identification of TDG candidates in fully cosmological simulations, specifically the high-resolution simulations of the EAGLE suite. The finite resolution of the simulation limits their ability to predict the exact formation rate and survival time-scale of TDGs, but we show that gravitationally bound baryonic structures in tidal arms already form in current state-of-the-art cosmological simulations. In this case, the orbital parameter, disc orientations as well as stellar and gas masses and the specific angular momentum of the TDG forming galaxies are a direct consequence of cosmic structure formation. We identify TDG candidates in a wide range of environments, such as multiple galaxy mergers, clumpy high-redshift (up to z = 2) galaxies, high-speed encounters and tidal interactions with gas-poor galaxies. We present selection methods, the properties of the identified TDG candidates and a road map for more quantitative analyses using future high-resolution simulations.

  3. Methane distribution in European tidal estuaries

    NARCIS (Netherlands)

    Middelburg, J.J.; Nieuwenhuize, J.; Iversen, N.; Høgh, N.; De Wilde, H.; Helder, W.; Seifert, R.; Christof, O.

    2002-01-01

    Methane concentrations have been measured along salinity profiles in nine tidal estuaries in Europe (Elbe, Ems, Thames, Rhine, Scheldt, Loire, Gironde, Douro and Sado). The Rhine, Scheldt and Gironde estuaries have been studied seasonally. A number of different methodologies have been used and they

  4. Estuaries and Tidal Marshes. Habitat Pac.

    Science.gov (United States)

    Fish and Wildlife Service (Dept. of Interior), Washington, DC.

    This educational packet consists of an overview, three lesson plans, student data sheets, and a poster. The overview examines estuaries and tidal or salt marshes by discussing the plants and animals in these habitats, marsh productivity, benefits and management of the habitats, historical aspects, and development and pollution. A glossary and list…

  5. Development trends in ocean energy. Concepts and projects; Entwicklungstrends in der Meeresenergienutzung. Konzepte und Projekte

    Energy Technology Data Exchange (ETDEWEB)

    Riegebauer, Philipp; Stenzel, Peter; Volkmann, Lukas [Fachhochschule Duesseldorf (DE). Zentrum fuer Innovative Energiesysteme (ZIES)

    2011-05-15

    The use of ocean energy by means of tidal mills has been known for centuries. The era of modern, industrial-scale production of ocean energy began in the mid-1960s when a tidal power plant was commissioned at the mouth of the River Rance in France. In recent years there has been a resurgence in development efforts in the area of ocean energy which is driven by the ongoing climate change and associated demands for greater use of renewable energies. Today many promising concepts are being pursued all over the world and are increasingly being implemented in concrete projects.

  6. Modelling the far field hydro-environmental impacts of tidal farms - A focus on tidal regime, inter-tidal zones and flushing

    Science.gov (United States)

    Nash, S.; O'Brien, N.; Olbert, A.; Hartnett, M.

    2014-10-01

    The introduction of tidal stream turbines into water bodies can have an impact on the environment due to changes in the hydrodynamic flow fields resulting from the extraction of energy by the tidal turbines. Water levels, tidal currents and flushing characteristics could potentially be significantly altered with the introduction of tidal turbine farms, which could lead to possible loss of habitat and a change in the tidal regime. Therefore, planning of tidal turbines field deployments must take into account possible hydro-environmental impacts. This paper describes research undertaken by the authors in the Shannon Estuary to predict changes in the tidal regime and flushing characteristics, with the introduction of tidal turbine farms of different array configurations. The model was simulated using a 2D hydrodynamic model that was modified to incorporate the effects of tidal turbine fields. Water levels are shown to have been affected with the inclusion of turbines, especially in areas upstream of the turbine farm where inter-tidal zones could become predominately inundated resulting in loss of habitat in the estuary. Flushing parameters were also shown to be altered with the inclusion of turbines, with residence time shown to be increased, which could change pollutant transport in the region.

  7. Estimating effects of tidal power projects and climate change on threatened and endangered marine species and their food web.

    Science.gov (United States)

    Busch, D Shallin; Greene, Correigh M; Good, Thomas P

    2013-12-01

    Marine hydrokinetic power projects will operate as marine environments change in response to increased atmospheric carbon dioxide concentrations. We considered how tidal power development and stressors resulting from climate change may affect Puget Sound species listed under the U.S. Endangered Species Act (ESA) and their food web. We used risk tables to assess the singular and combined effects of tidal power development and climate change. Tidal power development and climate change posed risks to ESA-listed species, and risk increased with incorporation of the effects of these stressors on predators and prey of ESA-listed species. In contrast, results of a model of strikes on ESA-listed species from turbine blades suggested that few ESA-listed species are likely to be killed by a commercial-scale tidal turbine array. We applied scenarios to a food web model of Puget Sound to explore the effects of tidal power and climate change on ESA-listed species using more quantitative analytical techniques. To simulate development of tidal power, we applied results of the blade strike model. To simulate environmental changes over the next 50 years, we applied scenarios of change in primary production, plankton community structure, dissolved oxygen, ocean acidification, and freshwater flooding events. No effects of tidal power development on ESA-listed species were detected from the food web model output, but the effects of climate change on them and other members of the food web were large. Our analyses exemplify how natural resource managers might assess environmental effects of marine technologies in ways that explicitly incorporate climate change and consider multiple ESA-listed species in the context of their ecological community. Estimación de los Efectos de Proyectos de Energía de las Mareas y el Cambio Climático sobre Especies Marinas Amenazadas y en Peligro y su Red Alimentaria. © 2013 Society for Conservation Biology No claim to original US government works.

  8. Strategies for the Use of Tidal Stream Currents for Power Generation

    Science.gov (United States)

    Orhan, Kadir; Mayerle, Roberto

    2015-04-01

    Indonesia is one of the priority countries in Southeast Asia for the development of ocean renewable energy facilities and The National Energy Council intends to increase the role of ocean energy significantly in the energy mix for 2010-2050. To this end, the joint German-Indonesian project "Ocean Renewable Energy ORE-12" aims at the identification of marine environments in the Indonesian Archipelago, which are suitable for the efficient generation of electric power by converter facilities. This study, within the ORE-12 project, is focused on the tidal stream currents on the straits between the Indian Ocean and Flores Sea to estimate the energy potentials and to develop strategies for producing renewable energy. FLOW module of Delft3D has been used to run hydrodynamic models for site assessment and design development. In site assessment phase, 2D models have been operated for a-month long periods and with a resolution of 500 m. Later on, in design development phase, detailed 3D models have been developed and operated for three-month long periods and with a resolution of 50 m. Bathymetric data for models have been obtained from the GEBCO_08 Grid and wind data from the Global Forecast System of NOAA's National Climatic Data Center. To set the boundary conditions of models, tidal forcing with 11 harmonic constituents was supplied from TPXO Indian Ocean Atlas (1/12° regional model) and data from HYCOM+NCODA Global 1/12° Analysis have been used to determine salinity and temperature on open boundaries. After the field survey is complete, water level time-series supplied from a tidal gauge located in the domain of interest (8° 20΄ 9.7" S, 122° 54΄ 51.9" E) have been used to verify the models and then energy potentials of the straits have been estimated. As a next step, correspondence between model outputs and measurements taken by the radar system of TerraSAR-X satellite (DLR) will be analysed. Also for the assessment of environmental impacts caused by tidal stream

  9. Submesoscale tidal eddies in the wake of coral islands and reefs: satellite data and numerical modelling

    Science.gov (United States)

    Delandmeter, Philippe; Lambrechts, Jonathan; Marmorino, George O.; Legat, Vincent; Wolanski, Eric; Remacle, Jean-François; Chen, Wei; Deleersnijder, Eric

    2017-07-01

    Interaction of tidal flow with a complex topography and bathymetry including headlands, islands, coral reefs and shoals create a rich submesoscale field of tidal jets, vortices, unsteady wakes, lee eddies and free shear layers, all of which impact marine ecology. A unique and detailed view of the submesoscale variability in a part of the Great Barrier Reef lagoon, Australia, that includes a number of small islands was obtained by using a "stereo" pair of 2-m-resolution visible-band images that were acquired just 54 s apart by the WorldView-3 satellite. Near-surface current and vorticity were extracted at a 50-m-resolution from those data using a cross-correlation technique and an optical-flow method, each yielding a similar result. The satellite-derived data are used to test the ability of the second-generation Louvain-la-Neuve ice-ocean model (SLIM), an unstructured-mesh, finite element model for geophysical and environmental flows, to reproduce the details of the currents in the region. The model succeeds in simulating the large-scale (> 1 km) current patterns, such as the main current and the width and magnitude of the jets developing in the gaps between the islands. Moreover, the order of magnitude of the vorticity and the occurrence of some vortices downstream of the islands are correctly reproduced. The smaller scales (< 500 m) are resolved by the model, although various discrepancies with the data are observed. The smallest scales (< 50 m) are unresolved by both the model- and image-derived velocity fields. This study shows that high-resolution models are able to a significant degree to simulate accurately the currents close to a rugged coast. Very-high-resolution satellite oceanography stereo images offer a new way to obtain snapshots of currents near a complex topography that has reefs, islands and shoals, and is a potential resource that could be more widely used to assess the predictive ability of coastal circulation models.

  10. Gravitational tidal effects on galactic open clusters

    Science.gov (United States)

    Bergond, G.; Leon, S.; Guibert, J.

    2001-10-01

    We have investigated the 2-D stellar distribution in the outer parts of three nearby open clusters: NGC 2287 (equiv M 41), NGC 2516, and NGC 2548 (equiv M 48). Wide-field star counts have been performed in two colours on pairs of digitized ESO and SRC Schmidt plates, allowing us to select likely cluster members in the colour-magnitude diagrams. Cluster tidal extensions were emphasized using a wavelet transform. Taking into account observational biases, namely the galaxy clustering and differential extinction in the Galaxy, we have associated these stellar overdensities with real open cluster structures stretched by the galactic gravitational field. As predicted by theory and simulations, and despite observational limitations, we detected a general elongated (prolate) shape in a direction parallel to the galactic Plane, combined with tidal tails extended perpendicularly to it. This geometry is due both to the static galactic tidal field and the heating up of the stellar system when crossing the Disk. The time varying tidal field will deeply affect the cluster dynamical evolution, and we emphasize the importance of adiabatic heating during the Disk-shocking. In the case of NGC 2548, our dating of the last shocking with the Plane (based on a tidal clump) is consistent with its velocity. During the 10-20 Z-oscillations experienced by a cluster before its dissolution in the Galaxy, crossings through the galactic Disk contribute to at least 15% of the total mass loss. Using recent age estimations published for open clusters, we find a destruction time-scale of about 600 Myr for clusters in the solar neighbourhood. Plate scanning was done at the Centre d'Analyse des Images (CAI) with M.A.M.A. (Machine Automatique àMesurer pour l'Astronomie), a facility located at the Observatoire de Paris, developed and operated by INSU (Institut National des Sciences de l'Univers, CNRS). Web site http://dsmama.obspm.fr

  11. Tidal Tales II: Molecular Gas and Star Formation in the Tidal Tails of Minor Mergers

    Science.gov (United States)

    Knierman, Karen A.; Scowen, Paul A.; Groppi, Christopher E.

    2017-01-01

    While major mergers and their tidal debris are well studied, equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio pivotal role in the formation of most large galaxies. Tidal debris regions have large amounts of neutral gas but a lower gas density and may have higher turbulence. We use star formation tracers such as young star cluster populations and H-alpha and CII emission to determine the different factors that may influence star formation in tidal debris. These tracers were compared to the reservoirs of molecular and neutral gas available for star formation to estimate the star formation efficiency (SFE). The SFR in tidal debris can reach up to 50% of the total star formation in the system. The SFE of tidal tails in minor mergers can range over orders of magnitude on both local and global scales. From the tidal debris environments in our study, this variance appears to stem from the formation conditions of the debris. Current surveys of the 2.12 micron line of molecular hydrogen, CO(1-0), and HI for 15 minor mergers, are providing a larger sample of environments to study the threshold for star formation that can inform star formation models, particularly at low densities.

  12. Tidal Tales of Minor Mergers: Star Formation in the Tidal Tails of Minor Mergers

    Science.gov (United States)

    Knierman, Karen A.; Monkiewicz, Jacqueline A.; Scowen, Paul A.; Groppi, Christopher E.

    2017-06-01

    While major mergers and their tidal debris are well studied, equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio pivotal role in the formation of most large galaxies. Tidal debris regions have large amounts of neutral gas but a lower gas density and may have higher turbulence. We use star formation tracers such as young star cluster populations and H-alpha and CII emission to determine the different factors that may influence star formation in tidal debris. These tracers were compared to the reservoirs of molecular and neutral gas available for star formation to estimate the star formation efficiency (SFE). The SFR in tidal debris can reach up to 50% of the total star formation in the system. The SFE of tidal tails in minor mergers can range over orders of magnitude on both local and global scales, and include several star forming regions with higher than normal SFE. From the tidal debris environments in our study, this variance appears to stem from the formation conditions of the debris. Current surveys of the 2.12 micron line of molecular hydrogen, CO(1-0), and HI for 15 minor mergers, are providing a larger sample of environments to study the threshold for star formation that can inform star formation models, particularly at low densities.

  13. A Sediment Testing Reference Area Database for the San Francisco Deep Ocean Disposal Site (SF-DODS)

    Science.gov (United States)

    EPA established and maintains a SF-DODS reference area database of previously-collected sediment test data. Several sets of sediment test data have been successfully collected from the SF-DODS reference area.

  14. Stellar tidal disruption flares provide evidence for a black hole event horizon

    Science.gov (United States)

    Van Velzen, Sjoert

    2017-08-01

    The tidal disruption of a star by a massive black is expected to yield a luminous flare of thermal emission. Optical transient surveys have collected about two dozen similar-looking nuclear transients that are consider examples of these stellar tidal disruption flares (TDFs). However, explaining the observed properties of these events within the tidal disruption paradigm is challenging. For example, there is no consensus on the origin of the optical emission. This theoretical ambiguity leaves open the possibility that the flares we call TDFs are instead due to a completely different process, such a nuclear supernovae or accretion disk instabilities. Fortunately, the number of discovered TDFs recently became large enough to test a fundamental prediction of the stellar tidal disruption paradigm. At high black hole mass (greater than 108 M⊙), the star will be swallowed whole before being disrupted. Using a recently compiled catalog of candidate TDFs with black hole mass measurements, plus a careful treatment of selection effects in this flux-limited sample, we robustly detect a suppression of flares from high-mass black holes. This dearth of observed TDFs from the upper end of the black hole mass distribution is naturally explained by suppression due the event horizon and implies a moderate mean spin of these black holes (a > 0.5). Conversely, if we start by assuming that current TDF candidates are indeed due to stellar tidal disruptions, our sample can be used to constrain the existence of naked singularities.

  15. Quantifying vegetation and nekton response to tidal restoration of a New England salt marsh

    Science.gov (United States)

    Roman, C.T.; Raposa, K.B.; Adamowicz, S.C.; James-Pirri, M.J.; Catena, J.G.

    2002-01-01

    Tidal flow to salt marshes throughout the northeastern United States is often restricted by roads, dikes, impoundments, and inadequately sized culverts or bridge openings, resulting in altered ecological structure and function. In this study we evaluated the response of vegetation and nekton (fishes and decapod crustaceans) to restoration of full tidal flow to a portion of the Sachuest Point salt marsh, Middletown, Rhode Island. A before, after, control, impact study design was used, including evaluations of the tide-restricted marsh, the same marsh after reintroduction of tidal flow (i.e., tide-restored marsh), and an unrestricted control marsh. Before tidal restoration vegetation of the 3.7-ha tide-restricted marsh was dominated by Phragmites australis and was significantly different from the adjacent 6.3-ha Spartina -dominated unrestricted control marsh (analysis of similarities randomization test, p nekton compared with the tide-restricted marsh (analysis of variance, p nekton density was equivalent. A similar trend was documented for nekton species richness. Nekton density and species richness from marsh surface samples were similar between the tide-restored marsh and unrestricted control marsh. Fundulus heteroclitus and Palaemonetes pugio were the numerically dominant fish and decapod species in all sampled habitats. This study provides an example of a quantitative approach for assessing the response of vegetation and nekton to tidal restoration.

  16. A review of methods of extrapolating tidal model predictions to long term siltation effects in estuaries

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    Sites which have prospects for tidal power generation almost invariably have large expanses of potentially mobile sand banks, mud shoals and intertidal sand or mud flats. The construction and operation of a tidal power plant alters the tidal regime and hence the pattern of sediment transport within the sphere of influence of the engineering works. At present, there is no generally accepted method of predicting the long term effects of a major tidal power barrage on the equilibrium distribution of sediment in a large wide estuary. Detailed multi-dimension mathematical models are criticised because they appear only to predict the immediate impact of the proposed engineering works on the sediment regime. The largely empirical regime technique is commonly used to predict changes in the cross-sectional area of the estuary. However, there is a less widely used, but much more powerful, technique whereby the results from short term predictions are extrapolated in an interactive process to predict long term siltation. There are no established, tested theories or standard methods for extrapolating results from short term siltation models. For this reason this review is based on an analysis of a number of case studies, which represent the only readily available source of experience with the problem. The case studies do not relate to tidal barrage projects, but they do illustrate and demonstrate the basic principles and problems associated with the extrapolation of short term predictions. (author).

  17. Flow paths of water and sediment in a tidal marsh: relations with marsh developmental stage and tidal inundation height

    NARCIS (Netherlands)

    Temmerman, S.; Bouma, T.J.; Govers, G.; Lauwaet, D.

    2005-01-01

    This study provides new insights in the relative role of tidal creeks and the marsh edge in supplying water and sediments to and from tidal marshes for a wide range of tidal inundation cycles with different high water levels and for marsh zones of different developmental stage. Net import or export

  18. Circalunidian clocks control tidal rhythms of locomotion in the American horseshoe crab, Limulus polyphemus

    Science.gov (United States)

    Chabot, Christopher C.; Ramberg-Pihl, Nicole C.; Watson, Winsor H.

    2016-01-01

    While many intertidal animals exhibit circatidal rhythms, the nature of the underlying endogenous clocks that control these rhythms has been controversial. In this study American horseshoe crabs, Limulus polyphemus, were used to test the circalunidian hypothesis by exposing them to four different tidal regimes. Overall, the results obtained support the circalunidian hypothesis: each of the twice-daily rhythms of activity appears to be controlled by a separate clock, each with an endogenous period of approximately 24.8h. First, spontaneous “skipping” of one of the daily bouts was observed under several different conditions. Second, the presence of two bouts of activity/day, with different periods, was observed. Lastly, we were able to separately synchronize bouts of activity to two artificial tidal regimes with different periods. These results, taken together, argue in favor of two separate circalunidian clocks in Limulus, each of which controls one of the two bouts of their daily tidal activity rhythms. PMID:27559270

  19. Testing of toxicology and emissions-sampling methodology for ocean incineration of hazardous wastes. Final report, January 1985-January 1986

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, P.; Cooke, M.; Carr, S.; Piispanen, W.; Werme, C.

    1988-05-01

    This report addresses the development and testing of a system to expose marine organisms to hazardous-waste emissions in order to assess the potential toxicity of incinerator plumes at sea as they contact the marine environment through air-sea exchange and initial mixing. A sampling train was designed and tested at EPA's land-based hazardous-waste incinerator, using transformer oil as a waste feed. The incinerator was operated under conditions which would be appropriate for at-sea incinerators. The sampling train (Marine Incineration Biological Assessment Sampler--MIBAS) provides a sea-water sample containing a plume emission for the marine organisms testing. Five toxicity-test protocols were refined and/or developed for use in the program: (1) a sea-urchin fertilization test; (2) a chronic test using macroalgae Champia parvula; (3) a 7-day chronic test using growth and reproduction of the crustacean Mysidopsis bahia; (4) a 7-day growth and survival test with the fish Menidia beryllina; and (5) a 7-day life-cycle test using the archiannelid worm Dinophilus gyrocilatus. The results of applying these tests during a hazardous-waste burn are given.

  20. VLT observations of NGC 1097's ``dog-leg'' tidal stream. Dwarf spheroidals and tidal streams

    Science.gov (United States)

    Galianni, P.; Patat, F.; Higdon, J. L.; Mieske, S.; Kroupa, P.

    2010-10-01

    Aims: We investigate the structure and stellar population of two large stellar condensations (knots A & B) along one of the faint optical “jet-like” tidal streams associated with the spiral NGC 1097, with the goal of establishing their physical association with the galaxy and their origin. Methods: We use the VLT/FORS2 to get deep V-band imaging and low-resolution optical spectra of two knots along NGC 1097's northeast “dog-leg” tidal stream. With this data, we explore their morphology and stellar populations. Results: Spectra were obtained for eleven sources in the field surrounding the tidal stream. The great majority of them turned out to be background or foreground sources, but the redshift of knot A (and perhaps of knot B) is consistent with that of NGC 1097. Using the V-band image of the “dog-leg” tidal feature we find that the two knots match the photometric scaling relations of canonical dwarf spheroidal galaxies (dSph) very well. Spectral analysis shows that knot A is mainly composed of stars near G-type, with no signs of ongoing star formation. Comparing its spectrum with a library of high resolution spectra of galactic globular clusters (GCs), we find that the stellar population of this dSph-like object is most similar to intermediate to metal rich galactic GCs. We find moreover, that the tidal stream shows an “S” shaped inflection as well as a pronounced stellar overdensity at knot A's position. This suggests that knot A is being tidally stripped, and populating the stellar stream with its stars. Conclusions: We have discovered that two knots along NGC 1097's northeast tidal stream share most of their spectral and photometric properties with ordinary dwarf spheroidal galaxies (dSph). Moreover, we find strong indications that the “dog-leg” tidal stream arises from the tidal disruption of knot A. Since it has been demonstrated that tidally stripping dSph galaxies need to loose most of their dark matter before starting to loose stars

  1. Characterization of the Vertical Structure of Tidal Currents in the Golden Gate (San Francisco) Inlet

    Science.gov (United States)

    2012-12-01

    to resolve the spatial resolution of tidal currents from shipboard surveys was tested in the Yellow sea ( Candela , Beardsley, & Limeburner, 1990). This... Candela , J., Beardsley, R. C., & Limeburner, R. (1990). Removing Tides from Ship- Mounted ADCP data with application to the Yellow Sea. Third working

  2. Evaluation of a transportable capnometer for monitoring end-tidal carbon dioxide

    DEFF Research Database (Denmark)

    Hildebrandt, T; Tobiasen, Malene Espelund; Olsen, K S

    2010-01-01

    to two of the nine EMMAs tested. Using batteries with reduced voltage did not influence the measurements. The 95% CI of the medians of the differences were -0.4 to -0.2. We conclude that the EMMA can slightly under-read the end-tidal carbon dioxide but is generally comparable with a free-standing monitor...

  3. Salicornia strobilacea (synonym of Halocnemum strobilaceum) Grown Under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth

    KAUST Repository

    Marasco, Ramona

    2016-04-01

    Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum) plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the PGP potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i) stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii) are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes.

  4. Salicornia strobilacea (Synonym of Halocnemum strobilaceum) Grown under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth

    KAUST Repository

    Marasco, Ramona

    2016-08-22

    Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum) plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the plant growth promoting (PGP) potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i) stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii) are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes.

  5. Salicornia strobilacea (synonym of Halocnemum strobilaceum Grown Under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth

    Directory of Open Access Journals (Sweden)

    Ramona Marasco

    2016-08-01

    Full Text Available Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the PGP potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes.

  6. Ocean technology

    Digital Repository Service at National Institute of Oceanography (India)

    Peshwe, V.B.

    stream_size 2 stream_content_type text/plain stream_name Voices_Oceans_1996_113.pdf.txt stream_source_info Voices_Oceans_1996_113.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  7. Ocean acidification

    National Research Council Canada - National Science Library

    Gattuso, J.P; Hansson, L

    2011-01-01

    The fate of much of the CO 2 we produce will be to enter the ocean. In a sense, we are fortunate that ocean water is endowed with the capacity to absorb far more CO 2 per litre than were it salt free...

  8. Oceanic archipelagos

    DEFF Research Database (Denmark)

    Triantis, Kostas A.; Whittaker, Robert James; Fernández-Palacios, José María

    2016-01-01

    Since the contributions of Charles Darwin and Alfred Russel Wallace, oceanic archipelagos have played a central role in the development of biogeography. However, despite the critical influence of oceanic islands on ecological and evolutionary theory, our focus has remained limited to either the i...

  9. Tidal synchronization of an anelastic multi-layered body: Titan's synchronous rotation

    Science.gov (United States)

    Folonier, Hugo A.; Ferraz-Mello, Sylvio

    2017-12-01

    Tidal torque drives the rotational and orbital evolution of planet-satellite and star-exoplanet systems. This paper presents one analytical tidal theory for a viscoelastic multi-layered body with an arbitrary number of homogeneous layers. Starting with the static equilibrium figure, modified to include tide and differential rotation, and using the Newtonian creep approach, we find the dynamical equilibrium figure of the deformed body, which allows us to calculate the tidal potential and the forces acting on the tide generating body, as well as the rotation and orbital elements variations. In the particular case of the two-layer model, we study the tidal synchronization when the gravitational coupling and the friction in the interface between the layers is added. For high relaxation factors (low viscosity), the stationary solution of each layer is synchronous with the orbital mean motion ( n) when the orbit is circular, but the rotational frequencies increase if the orbital eccentricity increases. This behavior is characteristic in the classical Darwinian theories and in the homogeneous case of the creep tide theory. For low relaxation factors (high viscosity), as in planetary satellites, if friction remains low, each layer can be trapped in different spin-orbit resonances with frequencies n/2,n,3n/2,2n,\\ldots . When the friction increases, attractors with differential rotations are destroyed, surviving only commensurabilities in which core and shell have the same velocity of rotation. We apply the theory to Titan. The main results are: (i) the rotational constraint does not allow us to confirm or reject the existence of a subsurface ocean in Titan; and (ii) the crust-atmosphere exchange of angular momentum can be neglected. Using the rotation estimate based on Cassini's observation (Meriggiola et al. in Icarus 275:183-192, 2016), we limit the possible value of the shell relaxation factor, when a deep subsurface ocean is assumed, to γ _s≲ 10^{-9} s^{-1}, which

  10. Power Generation for River and Tidal Generators

    Energy Technology Data Exchange (ETDEWEB)

    Muljadi, Eduard [National Renewable Energy Lab. (NREL), Golden, CO (United States); Wright, Alan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Donegan, James [Ocean Renewable Power Company (ORPC), Portland, ME (United States); Marnagh, Cian [Ocean Renewable Power Company (ORPC), Portland, ME (United States); McEntee, Jarlath [Ocean Renewable Power Company (ORPC), Portland, ME (United States)

    2016-06-01

    Renewable energy sources are the second largest contributor to global electricity production, after fossil fuels. The integration of renewable energy continued to grow in 2014 against a backdrop of increasing global energy consumption and a dramatic decline in oil prices during the second half of the year. As renewable generation has become less expensive during recent decades, and it becomes more accepted by the global population, the focus on renewable generation has expanded from primarily wind and solar to include new types with promising future applications, such as hydropower generation, including river and tidal generation. Today, hydropower is considered one of the most important renewable energy sources. In river and tidal generation, the input resource flow is slower but also steadier than it is in wind or solar generation, yet the level of water turbulent flow may vary from one place to another. This report focuses on hydrokinetic power conversion.

  11. Toward a Global 1/25 deg HYCOM Ocean Prediction System with Tides

    Science.gov (United States)

    2011-09-30

    with new target densities (Figure 7) indicates marked improvement in simulation of the Atlantic Water circulation and thermohaline structure in the...to extract the mesoscale circulation , 2) data assimilation using the de-tided forward model, 3) combine tidal and the corrected non-tidal component...topography (experiment “NRL-ST”, Table 1) revealed noticeable biases in the simulated temperature and salinity as well as ocean circulation in the

  12. Stratification on the Skagit Bay Tidal Flats

    Science.gov (United States)

    2012-09-01

    shore Skagit Bay a Camano Island -1 0 1 -2-1012 0.5 -0.5 1 -1 C ro ss -s ho re (k m ) Alongshore (km) 0 b 1 0 -1 Bed level (m ) 18 2.2 Modeled...shadowed by Camano Island, which forms the southern border of the tidal flats (Fig. 2-3c). Saline water has propagated onshore and a roughly

  13. Integrating tidal and nontidal ecological assessments

    Science.gov (United States)

    Mark Southerland; Roberto Llanso

    2016-01-01

    The Maryland Department of Natural Resources (DNR) has a long history of conducting rigorous assessments of ecological conditions in both tidal and nontidal waters. The Long-Term Benthic (LTB) Monitoring Program and the Maryland Biological Stream Survey (MBSS) both use reference-based indicators of benthic invertebrate communities to provide areawide estimates of ...

  14. Tidally driven evolution of differentiated terrestrial exoplanets

    Science.gov (United States)

    Walterova, M.; Behounkova, M.

    2017-09-01

    We present a numerical model of tidally driven orbital evolution based on the solution of continuum mechanics equations for a differentiated spherical body, whose mantle is governed by either the Maxwell or the Andrade viscoelastic rheology. The model enables generally heterogeneous structure of the mantle, making thus possible the analysis of coupling between the internal and the orbital evolution of terrestrial exoplanets or icy moons.

  15. Super-Eddington Accreting Tidal Disruption Events

    Science.gov (United States)

    Lin, Dacheng; Guillochon, James; Komossa, St.; Ramirez-Ruiz, Enrico; Irwin, Jimmy; Maksym, W. Peter; Grupe, Dirk; Godet, Olivier; Webb, Natalie; Barret, Didier; Zauderer, Bevin; Duc, Pierre-Alain; Carrasco, Eleazar R.; Gwyn, Stephen

    2017-08-01

    Multiwavelength flares from tidal disruption and subsequent accretion of stars are important for study of otherwise dormant massive black holes in galactic nuclei. Previous well-monitored candidate flares were short-lived, with most emission confined to within ~1 year. Here, we report our discovery of a well observed super-long (>11 years) luminous X-ray flare from the nuclear region of a dwarf starburst galaxy. After an apparently fast rise within ~4 months a decade ago, the X-ray luminosity, though showing a weak trend of decay, has been persistently high at around the Eddington limit. The X-ray spectra are soft and can be described with Comptonized emission from an optically thick low-temperature corona, a super-Eddington accretion signature often observed in accreting stellar-mass black holes. Dramatic spectral softening was also caught in one recent observation, implying either a temporary transition from the super-Eddington accretion state to the standard thermal state, or the presence of a transient highly blueshifted (~0.36c) warm absorber. All these properties in concert suggest a tidal disruption event with an unusually long super-Eddington accretion phase that has never before been observed. We also found two additional events showing similar X-ray spectra characteristic of super-Eddington accretion from two otherwise quiescent galaxies. Therefore these events seem to form a new, super-Eddington accreting class of tidal disruption events.

  16. Tidal controls on river delta morphology

    Science.gov (United States)

    Hoitink, A. J. F.; Wang, Z. B.; Vermeulen, B.; Huismans, Y.; Kästner, K.

    2017-09-01

    River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology. Tides interacting with river discharge can play a crucial role in the morphodynamic development of deltas under pressure. Emerging insights into tidal controls on river delta morphology suggest that--despite the active morphodynamics in tidal channels and mouth bar regions--tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing non-linear interactions between river discharge and the tide. These interactions lead to flow changes within channels, and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.

  17. Tidal energy extraction: renewable, sustainable and predictable.

    Science.gov (United States)

    Nicholls-Lee, R F; Turnock, S R

    2008-01-01

    The tidal flow of sea water induced by planetary motion is a potential source of energy if suitable systems can be designed and operated in a cost-effective manner This paper examines the physical origins of the tides and how the local currents are influenced by the depth of the seabed and presence of land mass and associated coastal features. The available methods of extracting energy from tidal movement are classified into devices that store and release potential energy and those that capture kinetic energy directly. A survey is made of candidate designs and, for the most promising, the likely efficiency of energy conversion and methods of installing them are considered. Overall, the need to reduce CO2 emissions, a likely continued rise in fossil fuel cost will result in a significantly increased use of tidal energy. What is still required, especially for kinetic energy devices, is a much greater understanding of how they can be designed to withstand long-term immersion in the marine environment.

  18. The effects of tidal range on saltmarsh morphology

    Science.gov (United States)

    Goodwin, Guillaume; Mudd, Simon

    2017-04-01

    Saltmarshes are highly productive coastal ecosystems that act simultaneously as flood barriers, carbon storage, pollutant filters and nurseries. As halophytic plants trap suspended sediment and decay in the settled strata, innervated platforms emerge from the neighbouring tidal flats, forming sub-vertical scarps on their eroding borders and sub-horizontal pioneer zones in areas of seasonal expansion. These evolutions are subject to two contrasting influences: stochastically generated waves erode scarps and scour tidal flats, whereas tidally-generated currents transport sediment to and from the marsh through the channel network. Hence, the relative power of waves and tidal currents strongly influences saltmarsh evolution, and regional variations in tidal range yield marshes of differing morphologies. We analyse several sheltered saltmarshes to determine how their morphology reflects variations in tidal forcing. Using tidal, topographic and spectral data, we implement an algorithm based on the open-source software LSDTopoTools to automatically identify features such as marsh platforms, tidal flats, erosion scarps, pioneer zones and tidal channels on local Digital Elevation Models. Normalised geometric properties are then computed and compared throughout the spectrum of tidal range, highlighting a notable effect on channel networks, platform geometry and wave exposure. We observe that micro-tidal marshes typically display jagged outlines and multiple islands along with wide, shallow channels. As tidal range increases, we note the progressive disappearance of marsh islands and linearization of scarps, both indicative of higher hydrodynamic stress, along with a structuration of channel networks and the increase of levee volume, suggesting higher sediment input on the platform. Future research will lead to observing and modelling the evolution of saltmarshes under various tidal forcing in order to assess their resilience to environmental change.

  19. An initial assessment of Ocean Energy Resources in the Western Indian Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Hammar, Linus; Ehnberg, Jimmy

    2011-07-01

    The demand for modern energy is accelerating in the Western Indian Ocean (coastal East Africa). A mixture of different energy sources will by necessity be the option for the long-term future and the most adequate solutions naturally vary between locations. The vast coastlines and many islands of the region make ocean energy (OE) a relevant field to explore. With an early understanding of the resources strategic planning towards sustainable development is facilitate. Moreover, early awareness facilitates a respectful integration of new technologies in the fragile and for local people invaluable ecosystems. This study provides a first assessment of the frontier OE technologies and corresponding resources in the region. Five renewable Ocean Energy technologies have been reviewed and the physical resource abundance for respective energy source has been screened based on available literature and databases. The Western Indian Ocean is shared between nine African countries and two French departments. The studied countries are the Comoros, Kenya, Madagascar, Mauritius, Mayotte, Mozambique, the Seychelles, Tanzania, and Reunion. The energy situation is insufficient throughout the region, either as consequence of lacking domestic energy sources or rudimentary grid extension. The results indicate that ocean energy resources are abundant in much of the region, but different sources have potential in different areas. Several countries have favourable physical conditions for extracting energy from waves and from the temperature gradient between the surface and deep water. Wave power is a young but currently available technology which can be utilized for both large- and small-scale applications. Ocean Thermal Energy Conversion is a technology under development that, once proven, may be applicable for large-scale power production. The physical conditions for small-scale tidal barrage power, tidal stream power, and ocean current power are less pronounced but may be of interest at

  20. Europa the ocean moon : search for an alien biosphere

    CERN Document Server

    Greenberg, Richard

    2004-01-01

    Europa - The Ocean Moon tells the story of the Galileo spacecraft probe to Jupiter's moon, Europa. It provides a detailed description of the physical processes, including the dominating tidal forces that operate on Europa, and includes a comprehensive tour of Europa using images taken by Galileo's camera. The book reviews and evaluates the interpretative work carried out to date, providing a philosophical discussion of the scientific process of analyzing results and the pitfalls that accompany it. It also examines the astrobiological constraints on this possible biosphere, and implications for future research, exploration and planetary biological protection. Europa - The Ocean Moon provides a unique understanding of the Galileo images of Europa, discusses the theory of tidal processes that govern its icy ridged and disrupted surface, and examines in detail the physical setting that might sustain extra-terrestrial life in Europa's ocean and icy crust.

  1. A year-by-year record of 236-U/238-U in coral as a step towards establishing 236-U from nuclear weapons testing fall-out as oceanic tracer

    Energy Technology Data Exchange (ETDEWEB)

    Winkler, Stephan; Steier, Peter [University of Vienna, Faculty of Physics, Vienna (Austria); Carilli, Jessica [Australian Nuclear Science and Technology Organisation, Lucas Heights (Australia)

    2012-07-01

    Since uranium is known to behave conservatively in ocean waters, 236-U has great potential in application as oceanic tracer. 236-U (t1/2=23.4 Ma) was introduced into the oceans by atmospheric nuclear weapon testing with amount estimates ranging from 700 kg to 1500 kg. Thus a resulting initial average 236-U/238-U ratio of at least 5e-9 is expected for an oceanic mixed layer depth of 100 m. This ratio is already higher than the natural pre-nuclear background, which is expected to be at 10e-14 levels. Even the elevated ratios of global stratospheric fall-out are beyond the capabilities of ICPMS and TIMS methods. However, the exceptional sensitivity and ultra-low background for 236-U of the Vienna Environmental Research Accelerator's Accelerator Mass Spectrometry system allows us to measure down to 10-13 detection limits. We present a year-by-year record of 236-U/238-U for a Caribbean coral core covering years 1944 to 2006, thus allowing to us put constraints on the oceanic input of 236-U by atmospheric testing. Moreover modeling of the results also demonstrates the capabilities of 236-U as oceanic tracer.

  2. Tidal Mixing and Buoyancy Advection: Joint Influences on Lobster Distribution in Coastal Maine

    Science.gov (United States)

    Brooks, D. A.

    2004-12-01

    The Eastern Maine Coastal Current (EMCC) flows southwestward from the mouth of the Bay of Fundy to Penobscot Bay on the central Maine coast. Maximum non-tidal surface speeds reach 20-30 cm/s about 20 km offshore during April-May when the outflow from the Saint John River is strongest. Vigorous tides cause strong vertical and horizontal mixing, so that dispersal of neutral particles is influenced both by advection and tidal mixing. To survive, planktonic lobsters carried southwestward in the surface flow must settle to a nearshore cobble substrate. Larvae hatched near the Bay of Fundy can be advected to the central coast in 2-3 weeks, roughly the time needed to reach settlement stage. Over the same period, transverse tidal mixing is sufficient to raise nearshore larval concentrations to about half that offshore in the axis of the EMCC. Both processes may be necessary to explain the observed lobster distribution, which exhibits a distinct maximum in the central coastal region. The seasonal development of the EMCC is also influenced by winds and the larger circulation of the Gulf of Maine. This work is part of a multidisciplinary synthesis study funded by the NOAA Coastal Ocean Program.

  3. M2 tidal parameter modulation revealed by superconducting gravimeter time series

    Science.gov (United States)

    Meurers, Bruno; Van Camp, Michel; Francis, Olivier; Pálinkáš, Vojtech

    2016-04-01

    Analyzing consecutive and independent 1-yr data sets of 10 European superconducting gravimeters (SG) reveals statistically significant temporal variations of M2 tidal parameters. Both common short-term ( 2 yr) features are identified in all SG time series but one. The averaged variations of the amplitude factor are about 0.2 per mille. The path of load vector variations equivalent to the temporal changes of tidal parameters suggests the presence of an 8.85 yr modulation (lunar perigee). The tidal waves having the potential to modulate M2 with this period belong to the 3rd degree constituents. Their amplitude factors turn out to be much closer to body tide model predictions than that of the main 2nd degree M2, which indicates ocean loading for 3rd degree waves to be less prominent than for 2nd degree waves within the M2 group. These two different responses to the loading suggest that the observed long-term modulation is more due to insufficient frequency resolution of limited time series rather than to time variable loading. Presently, SG gravity time series are still too short to prove if time variable loading processes are involved too as in case of the annual M2 modulation known to appear for analysis intervals of less than 1 yr. The observed variations provide an upper accuracy limit for Earth model validation and permit estimating the temporal stability of SG scale factors and assessing the quality of gravity time series.

  4. Temporal variation of tidal parameters in superconducting gravimeter time-series

    Science.gov (United States)

    Meurers, Bruno; Van Camp, Michel; Francis, Olivier; Pálinkáš, Vojtech

    2016-04-01

    Analysing independent 1-yr data sets of 10 European superconducting gravimeters (SG) reveals statistically significant temporal variations of M2 tidal parameters. Both common short-term (2 yr) features are identified in all SG time-series but one. The averaged variations of the amplitude factor are about 0.2‰. The path of load vector variations equivalent to the temporal changes of tidal parameters suggests the presence of an 8.85 yr modulation (lunar perigee). The tidal waves having the potential to modulate M2 with this period belong to the 3rd degree constituents. Their amplitude factors turn out to be much closer to body tide model predictions than that of the main 2nd degree M2, which indicates ocean loading for 3rd degree waves to be less prominent than for 2nd degree waves within the M2 group. These two different responses to the loading suggest that the observed modulation is more due to insufficient frequency resolution of limited time-series rather than to time variable loading. Presently, SG gravity time-series are still too short to prove if time variable loading processes are involved too as in case of the annual M2 modulation known to appear for analysis intervals of less than 1 yr. Whatever the variations are caused by, they provide the upper accuracy limit for earth model validation and permit estimating the temporal stability of SG scale factors and assessing the quality of gravity time-series.

  5. Monthly Variation in the M2 Tidal Characteristics in the South Atlantic Bight

    Science.gov (United States)

    Blanton, B. O.; Seim, H.; Muglia, M.; Werner, F. E.

    2002-12-01

    Barotropic tides in the South Atlantic Bight of the eastern United States coast are examined using a combination of recent observations of pressure and velocity from a permanent coastal ocean observing system and shorter term instrument deployments in the region. The data extent from near-shore to shelf-break and cover the region from Onslow Bay, North Carolina, to St. Augustine, Florida. The principal tidal elevation and depth-averaged velocity ellipse characteristics are described. Monthly variation in the tidal elevation and depth-averaged velocity is assessed from the longest available records. Cross-shelf semi-diurnal water level amplification and phase lag associated with shelf width changes are observed. Maximum M2 amplification and cross-shelf phase lag occurs at the widest part of the shelf and decrease to the north and south. Monthly variability of the M2 tidal elevation and depth-averaged velocity ellipse phase appears significant. Monthly analysis indicates M2 elevation phase variation of about 5 degrees. Diurnal constituent variability is generally below the error estimates. Comparison with a baroclinic numerical model is discussed.

  6. Tidal Tales of Minor Mergers: Star Formation in the Tidal Tails of Minor Mergers

    Science.gov (United States)

    Knierman, Karen; Monkiewicz, Jacqueline; Scowen, Paul; Groppi, Christopher

    2018-01-01

    While major mergers and their tidal debris are well studied, equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio tails in minor mergers can range over orders of magnitude on both local and global scales, and include several star forming regions with higher than normal SFE. From the tidal debris environments in our study, this variance appears to stem from the formation conditions of the debris. New results from the first survey of molecular hydrogen in minor merger tidal debris will be presented. Current surveys of the 2.12 micron line of molecular hydrogen, CO(1-0), and HI for 15 minor mergers, are providing a larger sample of environments to study the threshold for star formation that can inform star formation models, particularly at low densities.

  7. Tidal tomography constrains Earth’s deep-mantle buoyancy

    Science.gov (United States)

    Lau, Harriet C. P.; Mitrovica, Jerry X.; Davis, James L.; Tromp, Jeroen; Yang, Hsin-Ying; Al-Attar, David

    2017-11-01

    Earth’s body tide—also known as the solid Earth tide, the displacement of the solid Earth’s surface caused by gravitational forces from the Moon and the Sun—is sensitive to the density of the two Large Low Shear Velocity Provinces (LLSVPs) beneath Africa and the Pacific. These massive regions extend approximately 1,000 kilometres upward from the base of the mantle and their buoyancy remains actively debated within the geophysical community. Here we use tidal tomography to constrain Earth’s deep-mantle buoyancy derived from Global Positioning System (GPS)-based measurements of semi-diurnal body tide deformation. Using a probabilistic approach, we show that across the bottom two-thirds of the two LLSVPs the mean density is about 0.5 per cent higher than the average mantle density across this depth range (that is, its mean buoyancy is minus 0.5 per cent), although this anomaly may be concentrated towards the very base of the mantle. We conclude that the buoyancy of these structures is dominated by the enrichment of high-density chemical components, probably related to subducted oceanic plates or primordial material associated with Earth’s formation. Because the dynamics of the mantle is driven by density variations, our result has important dynamical implications for the stability of the LLSVPs and the long-term evolution of the Earth system.

  8. Effects of increasing seawater circulation by tidal power plant operation on the water quality in the Shihwa coastal reservoir, Republic of Korea

    Science.gov (United States)

    Lee, B. Y.; Lee, C. H.; KIm, K. T.

    2016-02-01

    Since 2012 to present, the Tidal Power Plant (TPP) has been operated in Shihwa Coastal Reservoir (SCR) to improve the water quality. The tidal mixing volume increased about 5 times from 0.03 to 0.16 billion ton/day which represents about 50% of the SCR water volume. Water quality monitoring data showed that it break a strong stratification and hypoxia (≤3 mg/L Dissolved Oxygen) during summer season in main tidal channel. In addition, Total Phosphorus (TP), Total Nitrogen (TN) and Chemical Oxygen Demand concentrations in the main tidal channel reached to similar level with outside SCR concentrations. However, inner area with limited tidal mixing has not experienced improvement in TN and TP concentrations after the TPP operation. Trophic State Index (TSI) which was composite index of trophic condition also kept high score (>50) and remained in eutrophic state especially in summer season. Overall, an increase of seawater circulation has a positive effect on water quality in main tidal channel but not in inner area because of limited seawater mixing and effects of stormwater runoff. The stormwater runoff should be properly managed in this case because most point source pollution load is discharged outside of SCR. Acknowledgement : This research was a part of the project titled 'Development of integrated estuarine management system', funded by the Ministry of Oceans and Fisheries, Korea

  9. Tidal Energy System for On-Shore Power Generation

    Energy Technology Data Exchange (ETDEWEB)

    Bruce, Allan J

    2012-06-26

    Addressing the urgent need to develop LCOE competitive renewable energy solutions for US energy security and to replace fossil-fuel generation with the associated benefits to environment impacts including a reduction in CO2 emissions, this Project focused on the advantages of using hydraulic energy transfer (HET) in large-scale Marine Hydrokinetic (MHK) systems for harvesting off-shore tidal energy in US waters. A recent DOE resource assessment, identifies water power resources have a potential to meet 15% of the US electric supply by 2030, with MHK technologies being a major component. The work covered a TRL-4 laboratory proof-in-concept demonstration plus modeling of a 15MW full scale system based on an approach patented by NASA-JPL, in which submerged high-ratio gearboxes and electrical generators in conventional MHK turbine systems are replaced by a submerged hydraulic radial pump coupled to on-shore hydraulic motors driving a generator. The advantages are; first, the mean-time-between-failure (MTBF), or maintenance, can be extended from approximately 1 to 5 years and second, the range of tidal flow speeds which can be efficiently harvested can be extended beyond that of a conventional submerged generator. The approach uses scalable, commercial-off-the-shelf (COTS) components, facilitating scale-up and commercialization. All the objectives of the Project have been successfully met (1) A TRL4 system was designed, constructed and tested. It simulates a tidal energy turbine, with a 2-m diameter blade in up to a 2.9 m/sec flow. The system consists of a drive motor assembly providing appropriate torque and RPM, attached to a radial piston pump. The pump circulates pressurized, environmentally-friendly, HEES hydraulic fluid in a closed loop to an axial piston motor which drives an electrical generator, with a resistive load. The performance of the components, subsystems and system were evaluated during simulated tidal cycles. The pump is contained in a tank for

  10. A review of ocean energy converters, with an Australian focus

    Directory of Open Access Journals (Sweden)

    Chris Knight

    2014-08-01

    Full Text Available The requirement to move away from carbon based fossil fuels has led to a renewed interest in unconventional energy sources. Of interest in this article are ocean waves and current and tidal flows. This paper reviews the numerous options for ocean energy conversion systems that are currently available. A basic nomenclature for the variety of systems is utilized to classify the devices. A variety of issues including competing use, boating, fishing, commercial shipping and tourism are discussed with respect to impacts on and from ocean renewable energy.

  11. Salinity structure of a tidal freshwater ecosystem under multiple tidal conditions, Mission River, TX, USA

    Science.gov (United States)

    Jones, A.; Befus, K. M.; Cardenas, M.; McClelland, J. W.; Moffett, K. B.

    2013-12-01

    The ecological health and integrity of coastal estuaries critically depends on the balance between the quantity, quality, and timing of freshwater inflow. This balance may be upset by subtle changes in numerous hydrologic conditions, including precipitation rates and frequencies, runoff conditions, and tides. Certain hydrologic conditions will create an abnormally long freshwater residence time in a lower river reach--on the order of months between episodic storms--which will drastically alter the quantity, quality, and timing of estuarine freshwater inflow. We term this fresh, tidal, lentic river reach the 'tidal freshwater ecosystem' (TFE) and find that it remains largely overlooked by hydrologic and estuarine sciences. We hypothesize that TFEs occur in coastal rivers with small bed slope and riverine discharge, enabling denser saltwater intruding inland via tidal motion to impede freshwater discharge to the estuary. However, the balance of forces governing the relative rates and volumes of freshwater discharge, saltwater intrusion, and freshwater-saltwater mixing are not well understood in TFEs, especially with regard to the influence of vertical salinity structure (whether stratified, well-mixed, or a combination) on the retardation of freshwater discharge. In this study we sought to empirically characterize the salinity structure of a river known to contain a tidal freshwater reach, the Mission River of southern Texas. During high and low spring and neap tides, we surveyed a ~ 22 km-long tidal section of the river by towing two instruments: a multi-parameter probe measuring temperature, electrical conductivity (EC), and dissolved oxygen (DO) at mid-channel depth; and, at the water surface, an electrical resistivity geophysical cable measuring water and channel bed sediment electrical resistivity. We also profiled the water column every 0.25 km using a second multi-parameter probe. The data successfully resolved longitudinal and vertical salinity variations

  12. Geometric properties of hydraulic-relevant tidal bedforms

    DEFF Research Database (Denmark)

    Winter, Christian; Ferret, Yann; Lefebvre, Alice

    2013-01-01

    Large compound tidal bedforms (also termed dunes, sandwaves, megaripples by different authors) constitute prominent roughness elements in tidal channels and estuaries. Quantitative knowledge on their geometry, dynamics and hydraulic effect is crucial for coastal system understanding and process...... to technical constraints and data reduction the (historic) data bases mostly are restricted to information on mean geometrical states, whereas individual bedform properties are often not reported. Recently Lefebvre et al. (2011) showed that the hydraulic effect of asymmetric compound tidal bedforms depends...... on the tidal stage: Whereas the secondary bedforms act as roughness elements throughout the tidal cycle, the large primary bedforms dominate the hydraulics when the tidal flow is in the (dominant) direction of the bedform orientation (e.g. ebb-directed primary bedforms act during ebb currents) when...

  13. Tidal bending of glaciers: a linear viscoelastic approach

    DEFF Research Database (Denmark)

    Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph

    2003-01-01

    In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating....... This suggests that ice creep may have a significant influence on tidal bending of glaciers. Moreover, detailed tidal-deflection and tilt data from Nioghalvfjerdsfjorden glacier, northeast Greenland, cannot be explained by elastic-beam theory. We present a theory of tidal bending of glaciers based on linear...... glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values...

  14. How Cassini can constrain tidal dissipation in Saturn

    Science.gov (United States)

    Luan, Jing; Fuller, Jim; Quataert, Eliot

    2018-02-01

    Tidal dissipation inside giant planets is important for the orbital evolution of their natural satellites. It is conventionally treated by parametrized equilibrium tidal theory, in which the tidal torque declines rapidly with distance, and orbital expansion was faster in the past. However, some Saturnian satellites are currently migrating outward faster than predicted by equilibrium tidal theory. Resonance locking between satellites and internal oscillations of Saturn naturally matches the observed migration rates. Here, we show that the resonance locking theory predicts dynamical tidal perturbations to Saturn's gravitational field in addition to those produced by equilibrium tidal bulges. We show that these perturbations can likely be detected during Cassini's proximal orbits if migration of satellites results from resonant gravity modes, but will likely be undetectable if migration results from inertial wave attractors or dissipation of the equilibrium tide. Additionally, we show that the detection of gravity modes would place constraints on the size of the hypothetical stably stratified region in Saturn.

  15. Synthesis study of an erosion hot spot, Ocean Beach, California

    Science.gov (United States)

    Barnard, Patrick L.; Hansen, Jeff E.; Erikson, Li H.

    2012-01-01

    A synthesis of multiple coastal morphodynamic research efforts is presented to identify the processes responsible for persistent erosion along a 1-km segment of 7-km-long Ocean Beach in San Francisco, California. The beach is situated adjacent to a major tidal inlet and in the shadow of the ebb-tidal delta at the mouth of San Francisco Bay. Ocean Beach is exposed to a high-energy wave climate and significant alongshore variability in forcing introduced by varying nearshore bathymetry, tidal forcing, and beach morphology (e.g., beach variably backed by seawall, dunes, and bluffs). In addition, significant regional anthropogenic factors have influenced sediment supply and tidal current strength. A variety of techniques were employed to investigate the erosion at Ocean Beach, including historical shoreline and bathymetric analysis, monthly beach topographic surveys, nearshore and regional bathymetric surveys, beach and nearshore grain size analysis, two surf-zone hydrodynamic experiments, four sets of nearshore wave and current experiments, and several numerical modeling approaches. Here, we synthesize the results of 7 years of data collection to lay out the causes of persistent erosion, demonstrating the effectiveness of integrating an array of data sets covering a huge range of spatial scales. The key findings are as follows: anthropogenic influences have reduced sediment supply from San Francisco Bay, leading to pervasive contraction (i.e., both volume and area loss) of the ebb-tidal delta, which in turn reduced the regional grain size and modified wave focusing patterns along Ocean Beach, altering nearshore circulation and sediment transport patterns. In addition, scour associated with an exposed sewage outfall pipe causes a local depression in wave heights, significantly modifying nearshore circulation patterns that have been shown through modeling to be key drivers of persistent erosion in that area.

  16. Impact of tidal heating on the onset of convection in Enceladus' ice shell

    Science.gov (United States)

    Behounkova, Marie; Tobie, Gabriel; Choblet, Gael; Cadek, Ondrej

    2013-04-01

    southern hemisphere as long as the ocean width is smaller than Δ < 240°. Furthermore, we show that the onset of convection is associated with internal melting for tidal heating rate larger than ~ 0.5 - 1 ? 10-6Wm-3 and that increasing the heating rate above 10-6Wm-3 does not influence anymore the critical grain size for the initiation of convection.

  17. A Tidally Averaged Sediment-Transport Model for San Francisco Bay, California

    Science.gov (United States)

    Lionberger, Megan A.; Schoellhamer, David H.

    2009-01-01

    A tidally averaged sediment-transport model of San Francisco Bay was incorporated into a tidally averaged salinity box model previously developed and calibrated using salinity, a conservative tracer (Uncles and Peterson, 1995; Knowles, 1996). The Bay is represented in the model by 50 segments composed of two layers: one representing the channel (>5-meter depth) and the other the shallows (0- to 5-meter depth). Calculations are made using a daily time step and simulations can be made on the decadal time scale. The sediment-transport model includes an erosion-deposition algorithm, a bed-sediment algorithm, and sediment boundary conditions. Erosion and deposition of bed sediments are calculated explicitly, and suspended sediment is transported by implicitly solving the advection-dispersion equation. The bed-sediment model simulates the increase in bed strength with depth, owing to consolidation of fine sediments that make up San Francisco Bay mud. The model is calibrated to either net sedimentation calculated from bathymetric-change data or measured suspended-sediment concentration. Specified boundary conditions are the tributary fluxes of suspended sediment and suspended-sediment concentration in the Pacific Ocean. Results of model calibration and validation show that the model simulates the trends in suspended-sediment concentration associated with tidal fluctuations, residual velocity, and wind stress well, although the spring neap tidal suspended-sediment concentration variability was consistently underestimated. Model validation also showed poor simulation of seasonal sediment pulses from the Sacramento-San Joaquin River Delta at Point San Pablo because the pulses enter the Bay over only a few days and the fate of the pulses is determined by intra-tidal deposition and resuspension that are not included in this tidally averaged model. The model was calibrated to net-basin sedimentation to calculate budgets of sediment and sediment-associated contaminants. While

  18. Ocean Acidification

    Science.gov (United States)

    Ocean and coastal acidification is an emerging issue caused by increasing amounts of carbon dioxide being absorbed by seawater. Changing seawater chemistry impacts marine life, ecosystem services, and humans. Learn what EPA is doing and what you can do.

  19. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... In ocean transportation economics we present investment and operating costs as well as the results of a study of financing of shipping. Similarly, a discussion of government aid to shipping is presented.

  20. Ocean Color

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellite-derived Ocean Color Data sets from historical and currently operational NASA and International Satellite missions including the NASA Coastal Zone Color...

  1. What is Enhancing the Tidal Disruption Rate of Stars in Post-Starburst Galaxies?

    Science.gov (United States)

    Arcavi, Iair

    2016-10-01

    The search for the tidal disruption of stars by supermassive black holes (tidal disruption events; TDEs) is now yielding exciting results. Recently, we tied several events together into a coherent class of outbursts. This picture offers a surprising new insight: TDEs show a strong (200x) preference for post-starburst galaxies. Why is this? As likely post-merger galaxies, they could harbor a binary black hole in their center, which is expected to increase the rate of TDEs, but only at certain ages after the merger and for certain merger mass ratios. Alternatively, a disturbed central potential or nuclear gas reservoirs may be affecting stellar orbits in the core of the galaxy. Finally, a nuclear over-abundance of A stars (which dominate ground-based galaxy-integrated spectra), evolving to giants, could increase the global cross section for tidal disruption. HST spatial resolution and low surface brightness sensitivity allows us to test each of these options for four post-starburst TDE host galaxies. We will measure post-merger tidal tails, age-date the starburst using individual star cluster colors, map the luminosity profile of the inner 100pc to test for asphericity or double nuclei, and localize the weak line emission and A-star population seen in our galaxy-integrated spectra. We will also perform bulge-disk decompositions to estimate the mass of the central black hole, a crucial test of TDE emission models. Our group has successfully carried out HST analyses of the star cluster populations, tidal tails, and core surface brightness profiles of (non-TDE-host) post-starburst galaxies, a sample which will serve as a control for the observations proposed here.

  2. Progress in developing tidal electric power plants reported

    Science.gov (United States)

    Blokhnin, A.

    1984-12-01

    The natural energy potential of tides on the shores of the U.S.S.R. is equal to about a third of the world's total. The Achilles heel of tidal power plants is their pulsating operation. One solution to this problem was to build a hydroelectric power plant for use in tandem with the tidal power plant. During lulls in the tidal plant, the hydraulic power plant switches on at full power. Possible sites for dual plants were discussed.

  3. The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

    Science.gov (United States)

    Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

    2012-06-01

    Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

  4. Improving Sediment Transport Prediction by Assimilating Satellite Images in a Tidal Bay Model of Hong Kong

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2014-03-01

    Full Text Available Numerical models being one of the major tools for sediment dynamic studies in complex coastal waters are now benefitting from remote sensing images that are easily available for model inputs. The present study explored various methods of integrating remote sensing ocean color data into a numerical model to improve sediment transport prediction in a tide-dominated bay in Hong Kong, Deep Bay. Two sea surface sediment datasets delineated from satellite images from the Moderate Resolution Imaging Spectra-radiometer (MODIS were assimilated into a coastal ocean model of the bay for one tidal cycle. It was found that remote sensing sediment information enhanced the sediment transport model ability by validating the model results with in situ measurements. Model results showed that root mean square errors of forecast sediment both at the surface layer and the vertical layers from the model with satellite sediment assimilation are reduced by at least 36% over the model without assimilation.

  5. 76 FR 59671 - Ocean Renewable Power Company, LLC; Notice of Application Tendered for Filing With the Commission...

    Science.gov (United States)

    2011-09-27

    ... Energy Regulatory Commission Ocean Renewable Power Company, LLC; Notice of Application Tendered for... License. b. Project No.: 12711-005. c. Date Filed: September 1, 2011. d. Applicant: Ocean Renewable Power Company, LLC. e. Name of Project: Cobscook Bay Tidal Energy Project. f. Location: The proposed project...

  6. On tidal migration in the shrimp Crangon crangon

    Science.gov (United States)

    Janssen, G. M.; Kuipers, B. R.

    The length-frequency distribution of the shrimp population in the tidal flat area Balgzand in the western Wadden Sea shows a spatial separation between the adult shrimps, that inhibit the subtidal, and the juveniles (< 2.5 cm) that are restricted to the tidal zone. Observations in the tidal channel through the tides indicate that the juvenile population does not show migration of any importance from the tidal zone during ebb. Samples on the emerged flats during LW proof the presence of these juveniles in about the same densities as observed during HW.

  7. Turbulent viscosity and Jupiter's tidal Q. [energy dissipation function

    Science.gov (United States)

    Goldreich, P.; Nicholson, P. D.

    1977-01-01

    A recent estimate of tidal dissipation by turbulent viscosity in Jupiter's convective interior predicts that the current value of the planet's tidal Q is roughly 5 million. We point out a fundamental error in this calculation, and show that turbulent dissipation alone implies that at present Q is about 50 trillion. Our reduced estimate for the rate of tidal dissipation shows conclusively that tidal torques have produced only negligible modifications of the orbits of the Galilean satellites over the age of the solar system.

  8. Effect of tidal stream power generation on the region-wide circulation in a shallow sea

    Directory of Open Access Journals (Sweden)

    G. I. Shapiro

    2011-02-01

    Full Text Available This paper quantifies the backward effect on the ocean currents caused by a tidal stream farm located in the open shallow sea. Recent studies in channels with 1-D models have indicated that the power potential is not given purely by the flux of kinetic energy, as has been commonly assumed. In this study, a 3-D ocean circulation model is used to estimate (i practically extractable energy resource at different levels of rated generation capacity of the farm, (ii changes in the strength of currents due to energy extraction, and (iii alterations in the pattern of residual currents and the pathways of passive tracers. As well as tidal streams, the model also takes into account the wind-driven and density-driven ocean currents. Numerical modelling has been carried out for a hypothetical tidal farm located in the Celtic Sea north of Cornwall, an area known for its high level of tidal energy. Modelling results clearly indicate that the extracted power does not grow linearly with the increase in the rated capacity of the farm. For the case study covered in this paper, a 100-fold increase in the rated generation capacity of the farm results in only 7-fold increase in extracted power. In the case of a high power farm, kinetic energy of currents is altered significantly as far as 10–20 km away from the farm. At high levels of extracted energy the currents tend to avoid flowing through the farm, an effect which is not captured with 1-D models. Residual currents are altered as far as a hundred kilometres away. The magnitude of changes in the dispersion of tracers is highly sensitive to the location. Some of the passive drifters analysed in this study experience significant variations in the end-to-start distance due to energy extraction ranging from 13% to 238% while others are practically unaffected. This study shows that both energy extraction estimates and effects on region wide circulation depend on a complex combination of factors, and the specific

  9. Effect of tidal stream power generation on the region-wide circulation in a shallow sea

    Science.gov (United States)

    Shapiro, G. I.

    2011-02-01

    This paper quantifies the backward effect on the ocean currents caused by a tidal stream farm located in the open shallow sea. Recent studies in channels with 1-D models have indicated that the power potential is not given purely by the flux of kinetic energy, as has been commonly assumed. In this study, a 3-D ocean circulation model is used to estimate (i) practically extractable energy resource at different levels of rated generation capacity of the farm, (ii) changes in the strength of currents due to energy extraction, and (iii) alterations in the pattern of residual currents and the pathways of passive tracers. As well as tidal streams, the model also takes into account the wind-driven and density-driven ocean currents. Numerical modelling has been carried out for a hypothetical tidal farm located in the Celtic Sea north of Cornwall, an area known for its high level of tidal energy. Modelling results clearly indicate that the extracted power does not grow linearly with the increase in the rated capacity of the farm. For the case study covered in this paper, a 100-fold increase in the rated generation capacity of the farm results in only 7-fold increase in extracted power. In the case of a high power farm, kinetic energy of currents is altered significantly as far as 10-20 km away from the farm. At high levels of extracted energy the currents tend to avoid flowing through the farm, an effect which is not captured with 1-D models. Residual currents are altered as far as a hundred kilometres away. The magnitude of changes in the dispersion of tracers is highly sensitive to the location. Some of the passive drifters analysed in this study experience significant variations in the end-to-start distance due to energy extraction ranging from 13% to 238% while others are practically unaffected. This study shows that both energy extraction estimates and effects on region wide circulation depend on a complex combination of factors, and the specific figures given in the

  10. Waves and tides responsible for the intermittent closure of the entrance of a small, sheltered tidal wetland at San Francisco, CA

    Science.gov (United States)

    Hanes, D.M.; Ward, K.; Erikson, L.H.

    2011-01-01

    Crissy Field Marsh (CFM; http://www.nps.gov/prsf/planyourvisit/crissy-field-marsh-and-beach.htm) is a small, restored tidal wetland located in the entrance to San Francisco Bay just east of the Golden Gate. The marsh is small but otherwise fairly typical of many such restored wetlands worldwide. The marsh is hydraulically connected to the bay and the adjacent Pacific Ocean by a narrow sandy channel. The channel often migrates and sometimes closes completely, which effectively blocks the tidal connection to the ocean and disrupts the hydraulics and ecology of the marsh. Field measurements of waves and tides have been examined in order to evaluate the conditions responsible for the intermittent closure of the marsh entrance. The most important factor found to bring about the entrance channel closure is the occurrence of large ocean waves. However, there were also a few closure events during times with relatively small offshore waves. Examination of the deep-water directional wave spectra during these times indicates the presence of a small secondary peak corresponding to long period swell from the southern hemisphere, indicating that CFM and San Francisco Bay in general may be more susceptible to long period ocean swell emanating from the south or southwest than the more common ocean waves coming from the northwest. The tidal records during closure events show no strong relationship between closures and tides, other than that closures tend to occur during multi-day periods with successively increasing high tides. It can be inferred from these findings that the most important process to the intermittent closure of the entrance to CFM is littoral sediment transport driven by the influence of ocean swell waves breaking along the CFM shoreline at oblique angles. During periods of large, oblique waves the littoral transport of sand likely overwhelms the scour potential of the tidal flow in the entrance channel. ?? 2011.

  11. ADCIRC: An Advanced Three-Dimensional Circulation Model for Shelves, Coasts, and Estuaries. Report 3. Development of a Tidal Constituent DataBase for the Western North Atlantic and Gulf of Mexico

    Science.gov (United States)

    1993-06-01

    Bank . (1991). "Station Catalogue." Ocean and Aquatic Sciences, Department of Fisheries and Oceans, Ottawa. Kinnmark, I. P. E. (1984). "The shallow water...8217 - 28°56’ Coast IHO, GOM (Continued) Sources of Tidal Data: IHO-Internalional Hydrographic Organization Tidal Constituent Bank (1991); USGS: U.S...Ciudad Madero, Mexico 97051’ - 22013’ Coast GOM 34 Coatzacoalcos, Mexico 94025, - 1809’ Coast IHO, GOM 35 Campeche , Mexico 90032’ - 19050’ Coast IHO

  12. Development of an interdisciplinary model cluster for tidal water environments

    Science.gov (United States)

    Dietrich, Stephan; Winterscheid, Axel; Jens, Wyrwa; Hartmut, Hein; Birte, Hein; Stefan, Vollmer; Andreas, Schöl

    2013-04-01

    Global climate change has a high potential to influence both the persistence and the transport pathways of water masses and its constituents in tidal waters and estuaries. These processes are linked through dispersion processes, thus directly influencing the sediment and solid suspend matter budgets, and thus the river morphology. Furthermore, the hydrologic regime has an impact on the transport of nutrients, phytoplankton, suspended matter, and temperature that determine the oxygen content within water masses, which is a major parameter describing the water quality. This project aims at the implementation of a so-called (numerical) model cluster in tidal waters, which includes the model compartments hydrodynamics, morphology and ecology. For the implementation of this cluster it is required to continue with the integration of different models that work in a wide range of spatial and temporal scales. The model cluster is thus suggested to lead to a more precise knowledge of the feedback processes between the single interdisciplinary model compartments. In addition to field measurements this model cluster will provide a complementary scientific basis required to address a spectrum of research questions concerning the integral management of estuaries within the Federal Institute of Hydrology (BfG, Germany). This will in particular include aspects like sediment and water quality management as well as adaptation strategies to climate change. The core of the model cluster will consist of the 3D-hydrodynamic model Delft3D (Roelvink and van Banning, 1994), long-term hydrodynamics in the estuaries are simulated with the Hamburg Shelf Ocean Model HAMSOM (Backhaus, 1983; Hein et al., 2012). The simulation results will be compared with the unstructured grid based SELFE model (Zhang and Bapista, 2008). The additional coupling of the BfG-developed 1D-water quality model QSim (Kirchesch and Schöl, 1999; Hein et al., 2011) with the morphological/hydrodynamic models is an

  13. Improvement of ocean loading correction for superconducting gravimeter data of GGP including Syowa Station, Antarctica, and the effect on fluid core resonance (FCR) parameters

    Science.gov (United States)

    Kim, Taehee; Shibuya, Kazuo; Doi, Koichiro; Aoyama, Yuichi; Hayakawa, Hideaki

    2010-05-01

    The free core nutation (FCN), also refered to as the nearly diurnal free wobble, is due to the pressure coupling between the liquid core and the solid mantle. The FCN enhances the resonance with the diurnal earth tide. Investigation of resonance parameters of FCR (eigenperiod, quality factor Q, and resonance strength) is essential for the Earth's deep interior dynamics and structure. The eigenperiod directly depends on the core-mantle boundary (CMB) ellipticity and on the mantle's inelasticity. The quality factor Q is a direct consequence of damping mechanisms inside the Earth (Sasao et al., 1980; Sasao and Wahr, 1981; Florsch and Hinderer, 2000). For determining theseresonance parameters, the tidal gravimetric factor based on superconducting gravimeter (SG) data is used. We used the gravity data of 4 stations, from 1992 through 2002 at Syowa Station, from 1997 through 2007 at Strasbourg, from 1998 through 2007 at Metsahovi, from 2000 through 2006 at Sutherland, of the GGP Data Center. The tidal gravity parameters were determined using the BAYTAP-G software package (Ishiguro et al., 1981; Tamura et al., 1991). In this study, we focused on the influence of ocean loading effect on precise estimation of FCN parameters. The global ocean tidal models, CSR4.0 (Eanes and Bettadpur, 1999), GOT99.2b (Ray, 1999), FES2004 (Lyard et al., 2006) and TPXO7.1 (Egbert and Erofeeva, 2002) models are tested. These models are accomodated to the GOTIC2 for ocean loading estimation program (Matsumoto et al. 2001). The quality factor Q is dependent on the phase delay of the tidal waves, that means the imaginary part of gravimetric factor corrected for ocean loading effect is an important point for this inverse problem(Florsch and Hinderer, 2000). We present how much the accuracy of FCR parameters can be improved by adopting proper ocean models to each station (Le provost et al., 2001). For this work, we have applied minor waves for ocean loading correction (Matsumoto, 2003), and the

  14. Linking human impacts within an estuary to ebb-tidal delta evolution

    Science.gov (United States)

    Dallas, Kate L.; Barnard, Patrick L.

    2009-01-01

    San Francisco Bay, California, USA is among the most anthropogenically altered estuaries in the entire United States, but the impact on sediment transport to the coastal ocean has not been quantified. Analysis of four historic bathymetric surveys has revealed large changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of the San Francisco Bay. From 1873 to 2005 the bar eroded an average of 80 cm, which equates to a total volume loss of 100 + 65 x 106 m3 of sediment. Comparison of the surveys indicates the entire ebb delta has contracted radially while its crest has moved landward an average of 1 km. Compilation of historic records reveals that 130 x 106 m3 of sediment has been permanently removed from the San Francisco Bay and adjacent coastal ocean. Constriction of the bar is hypothesized to be from a decrease in sediment supply from San Francisco Bay, a reduction in the tidal prism of the estuary, and/or a reduction in the input of hydraulic mining debris. Changes to the morphology of the San Francisco Bar have likely altered wave refraction and focusing patterns on adjacent beaches and may be a factor in persistent beach erosion occurring in the area.

  15. Uranium and barium cycling in a salt wedge subterranean estuary: The influence of tidal pumping

    Science.gov (United States)

    Santos, I.R.; Burnett, W.C.; Misra, S.; Suryaputra, I.G.N.A.; Chanton, J.P.; Dittmar, T.; Peterson, R.N.; Swarzenski, P.W.

    2011-01-01

    The contribution of submarine groundwater discharge (SGD) to oceanic metal budgets is only beginning to be explored. Here, we demonstrate that biogeochemical processes in a northern Florida subterranean estuary (STE) significantly alter U and Ba concentrations entering the coastal ocean via SGD. Tidal pumping controlled the distribution of dissolved metals in shallow beach groundwater. Hourly observations of intertidal groundwaters revealed high U and low Ba concentrations at high tide as a result of seawater infiltration into the coastal aquifer. During ebb tide, U decreased and Ba increased due to freshwater dilution and, more importantly, biogeochemical reactions that removed U and added Ba to solution. U removal was apparently a result of precipitation following the reduction of U(VI) to U(IV). A significant correlation between Ba and dissolved organic carbon (DOC) in shallow beach groundwaters implied a common source, likely the mineralization of marine particulate organic matter driven into the beach face by tidal pumping. In deeper groundwaters, where the labile organic matter had been depleted, Ba correlated with Mn. We estimate that net SGD fluxes were − 163 and + 1660 μmol m− 1 d− 1 for U and Ba, respectively (or − 1 and + 8 μmol m− 2 d− 1 if a 200-m wide seepage area is considered). Our results support the emerging concept that subterranean estuaries are natural biogeochemical reactors where metal concentrations are altered relative to conservative mixing between terrestrial and marine endmembers. These deviations from conservative mixing significantly influence SGD-derived trace metal fluxes.

  16. Waddenfonds Tidal Texel Demonstration project. BlueTEC Texel Tidal Project: Environmental measurement and performance analysis

    NARCIS (Netherlands)

    Ponsoni, L.; Nauw, J.J.; Smit, M.; Ober, S.; Nichols, C.; Kenkhuis, J.; Schmidt, C.; Buatois, A.; de Haas, P.

    2016-01-01

    In the context of the BlueTEC project, this report starts by introducing theBlueTEC tidal energy platform and reviewing the patterns of circulation of theMarsdiep inlet. The energy resource assessment and the site selection for theplatform's deployment are reported. This document analyses di?erent

  17. Stellar binaries in galactic nuclei: tidally stimulated mergers followed by tidal disruptions

    Science.gov (United States)

    Bradnick, B.; Mandel, I.; Levin, Y.

    2017-08-01

    We investigate interactions of stellar binaries in galactic nuclear clusters with a massive black hole (MBH). We consider binaries on highly eccentric orbits around the MBH that change due to random gravitational interactions with other stars in the nuclear stellar cluster. The pericentres of the orbits perform a random walk, and we consider cases where this random walk slowly brings the binary to the Hills tidal separation radius (the so-called empty loss-cone regime). However, we find that in a majority of cases, the expected separation does not occur and instead the members of the binary merge together. This happens because the binary's eccentricity is excited by tidal interactions with the MBH, and the relative excursions of the internal eccentricity of the binary far exceed those in its internal semimajor axis. This frequently reduces the pericentre separation to values below typical stellar diameters, which induces a significant fraction of such binaries to merge (≳75 per cent in our set of numerical experiments). Stellar tides do not appreciably change the total rate of mergers but circularize binaries, leading to a significant fraction of low-eccentricity, low-impact-velocity mergers. Some of the stellar merger products will then be tidally disrupted by the MBH within ∼106 yr. If the merger strongly enhances the magnetic field of the merger product, this process could explain observations of prompt relativistic jet formation in some tidal disruption events.

  18. Atmospheric dynamics of tidally synchronized extrasolar planets.

    Science.gov (United States)

    Cho, James Y-K

    2008-12-13

    Tidally synchronized planets present a new opportunity for enriching our understanding of atmospheric dynamics on planets. Subject to an unusual forcing arrangement (steady irradiation on the same side of the planet throughout its orbit), the dynamics on these planets may be unlike that on any of the Solar System planets. Characterizing the flow pattern and temperature distribution on the extrasolar planets is necessary for reliable interpretation of data currently being collected, as well as for guiding future observations. In this paper, several fundamental concepts from atmospheric dynamics, likely to be central for characterization, are discussed. Theoretical issues that need to be addressed in the near future are also highlighted.

  19. Tidal Dynamics and Mixing Over Steep Topography

    Science.gov (United States)

    1994-06-01

    of tidal vorticity is the mechanism by which residual vorticity is generated. Also by running simplified numerical solutions in a Eulerian sense...In the case of Monterey Bay, depths range from 1O00m to lOOm over distances of 5000m , corresponding to very large slopes of approximately 15% and 100...experiment were UT=O.Oss/s, dh/dxuO.1S (slope) with depths ranging from h(O)=1OOm to hb=lOOOu over a 5000m horizontal distance across the slope. Figure

  20. Interactions Between Wetlands and Tidal Inlets

    Science.gov (United States)

    2008-08-01

    and γ = 2). Depth is relative to mean sea level, and square cells represent inactive regions. 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 A’ h’ — r...represent a vegetation density of 320 stems/m2 and square cells represent inactive regions. where αc is a correction factor for the presence of a tidal...velocities at four observation stations are shown in Figure 5 for the idealized estuaries with shape factors equal to 2 and 5, which represent vege

  1. The high resolution mapping of the Venice Lagoon tidal network

    Science.gov (United States)

    Madricardo, Fantina; Foglini, Federica; Kruss, Aleksandra; Bellafiore, Debora; Trincardi, Fabio

    2017-04-01

    One of the biggest challenges of the direct observation of the ocean is to achieve a high resolution mapping of its seafloor morphology and benthic habitats. So far, sonars have mapped just 0.05% of the ocean floor with less than ten-meter resolution. The recent efforts of the scientific community have been devoted towards the mapping of both Deep Ocean and very shallow coastal areas. Coastal and transitional environments in particular undergo strong morphological changes due to natural and anthropogenic pressure. Nowadays, only about 5% of the seafloor of these environments † have been mapped: the shallowness of these environments has prevented the use of underwater acoustics to reveal their morphological features. The recent technological development of multibeam echosounder systems, however, enables these instruments to achieve very high performances also in such shallow environments. In this work, we present results and case studies of an extensive multibeam survey carried out in the Lagoon of Venice in 2013. The Lagoon of Venice is the biggest lagoon in the Mediterranean Sea with a surface of about 550 km2 and with an average depth of about 1 m. In the last century, the morphological and ecological properties of the lagoon changed dramatically: the surface of the salt marshes was reduced by 60% and some parts of the lagoon are deepening with a net sediment flux exiting from the inlets. Moreover, major engineering interventions are currently ongoing at the inlets (MOSE project). These changes at the inlets could affect substantially the lagoon environment. To understand and monitor the future evolution of the Lagoon of Venice, ISMAR within the project RITMARE (a National Research Programme funded by the Italian Ministry of University and Research) carried out an extensive survey, involving a team of more than 25 scientists, to collect high resolution (0.5 m) bathymetry of key study areas such as the tidal inlets and channels. Following a broad

  2. Impact of Tidal Level Variations on Wave Energy Absorption at Wave Hub

    Directory of Open Access Journals (Sweden)

    Valeria Castellucci

    2016-10-01

    Full Text Available The energy absorption of the wave energy converters (WEC characterized by a limited stroke length —like the point absorbers developed at Uppsala University—depends on the sea level variation at the deployment site. In coastal areas characterized by high tidal ranges, the daily energy production of the generators is not optimal. The study presented in this paper quantifies the effects of the changing sea level at the Wave Hub test site, located at the south-west coast of England. This area is strongly affected by tides: the tidal height calculated as the difference between the Mean High Water Spring and the Mean Low Water Spring in 2014 was about 6.6 m. The results are obtained from a hydro-mechanic model that analyzes the behaviour of the point absorber at the Wave Hub, taking into account the sea state occurrence scatter diagram and the tidal time series at the site. It turns out that the impact of the tide decreases the energy absorption by 53%. For this reason, the need for a tidal compensation system to be included in the design of the WEC becomes compelling. The economic advantages are evaluated for different scenarios: the economic analysis proposed within the paper allows an educated guess to be made on the profits. The alternative of extending the stroke length of the WEC is investigated, and the gain in energy absorption is estimated.

  3. Assessing the Performance of a Northern Gulf of Mexico Tidal Model Using Satellite Imagery

    Directory of Open Access Journals (Sweden)

    Stephen C. Medeiros

    2013-11-01

    Full Text Available Tidal harmonic analysis simulations along with simulations spanning four specific historical time periods in 2003 and 2004 were conducted to test the performance of a northern Gulf of Mexico tidal model. A recently developed method for detecting inundated areas based on integrated remotely sensed data (i.e., Radarsat-1, aerial imagery, LiDAR, Landsat 7 ETM+ was applied to assess the performance of the tidal model. The analysis demonstrates the applicability of the method and its agreement with traditional performance assessment techniques such as harmonic resynthesis and water level time series analysis. Based on the flooded/non-flooded coastal areas estimated by the integrated remotely sensed data, the model is able to adequately reproduce the extent of inundation within four sample areas from the coast along the Florida panhandle, correctly identifying areas as wet or dry over 85% of the time. Comparisons of the tidal model inundation to synoptic (point-in-time inundation areas generated from the remotely sensed data generally agree with the results of the traditional performance assessment techniques. Moreover, this approach is able to illustrate the spatial distribution of model inundation accuracy allowing for targeted refinement of model parameters.

  4. A new relativistic model for tidal stream evolution during tidal disruption events

    Science.gov (United States)

    Servin, Juan; Kesden, Michael

    2018-01-01

    When stars are tidally disrupted by a supermassive black hole, approximately half of their original mass becomes gravitationally bound and may eventually produce a tidal flare. The stellar debris evolves into streams that can self-intersect due to relativistic pericenter precession. Energy loss in these inelastic collisions both circularizes the stream and contributes to the tidal flare. Models of this process often assume that all elements of the tidal stream have the same specific energy and angular momentum as the most bound debris element. Real tidal debris possesses a distribution of binding energies, however, which grants it a distribution of orbits. We propose a new treatment for this debris, wherein we evolve the elements of the stream individually. We determine the radial distance (from the black hole) and the time (after the disruption) of the stream collisions as a function of black-hole mass under both Newtonian gravity (N+1PN) and general relativity (GR). We also use the Lane-Emden equation to account for the mass differences among the debris elements when calculating the energy loss in the inelastic collisions. For the N+1PN method, we evolve the stream using Newtonian orbital mechanics and apply pericenter precession after each pericenter passage using a first-order post-Newtonian approximation. Our relativistic method directly integrates the geodesic equations of motion. We see that the higher precession in the fully relativistic method results in more prompt collisions, and that assuming equal masses for the colliding debris elements greatly overestimates the energy loss resulting from these collisions. We also provide light curves for the corresponding flares and compare our predictions to those of previous models.

  5. Field Observations and Model Predictions of Wave Transformation, Setup, Runup, and Turbulence on a Macro-tidal Beach, Korea

    Science.gov (United States)

    Yoo, J.; Shin, S.; Jun, K.; Shim, J.

    2011-12-01

    Surf-zone wave dynamics are one of important driving forces in coastal morphology by inducing beach erosions and sediment transports in inter-tidal shallow water areas, due to active wave breaking, energetic turbulence and violent near-bed velocities. Morphological beach changes are also considerably associated with other surf-zone hydro-dynamics such as nearshore wave transformation, water levels, wave run-up, set-up and coastal currents. In earlier studies, the COBRAS model (a RANS model, developed by Lin and Liu of Cornell University) has been used to investigate such beach processes with reasonable success, mostly, in wave dominant micro-tidal environments. The model solves the RANS equations using VOF method and k-epsilon closure scheme. Recently, intensive field experiments were carried out at a macro-tide environment (i.e. the Mallipo sand beach located in the west coast of Korea, having a large inter-tidal range of 7 m to investigate the complicated surf zone hydro-dynamics under interactions of coastal waves, strong tidal currents, and nearshore bathymetries. The field observation data are used to evaluate the capability of the RANS model to predict the cross-shore variations of free surface, wave set-up, wave run-up, and velocities on the Mallipo Beach. Since the dataset of water surface elevations includes both waves and tides, the COBRAS model was tried to simulate waves accompanied with tidal currents. The measured water surface elevation data were divided into wave and tidal components, in order to be used as inputs of the model. Comparisons of the measurements and the predictions show (1) performance of the model for the wave transformation, wave set-up, and wave run-up on the macro-tidal beach, (2) predictive capability for the turbulence closure scheme in the surf and swash zones, and (3) overall skills to predict under-tows and tidal currents. Acknowledgement This work was supported by the KORDI (Grant PE98572, PE98573 and PM56300). This work was

  6. Recognition of Tidal Bore Deposits in the Stratigraphic Record

    Science.gov (United States)

    Fielding, C. R.; Joeckel, M.

    2015-12-01

    Tidal bores are upstream-propagating hydraulic jumps that episodically form the leading edge of flood tides in upstream-narrowing, gently sloping, coastal rivers which experience high tidal ranges (6 m+, typically). They attain 9 m in height and can penetrate more than 100 km inboard of a shoreline. The deposits of tidal bores, if they can be confidently diagnosed in ancient successions, constitute an unequivocal line of evidence in support of deposition within the tidal-fluvial zone of a lowland river. Deposits of modern tidal bores have been documented, and two recent studies have interpreted tidal bore deposits in ancient (Jurassic and Pennsylvanian) sedimentary rocks. The ancient tidal bore deposits recognized thus far comprise laterally discontinuous, erosionally-based beds of massive to faintly stratified sand, locally muddy and rich in detrital plant debris. Paleoflow structures, where preserved, indicate upstream-directed flow. The beds are enclosed by other, more pervasively stratified sandstones that were the product of ebb and flood-oriented currents in the ancient tidal rivers. The interpreted bore deposits are anomalous in the context of these normal current deposits, and indicate erosive scouring of the substrate followed by the en masse deposition of sand from suspension and upstream advection. Multiple horizons of putative tidal bore deposits are recognized in both the Jurassic and Pennsylvanian examples, suggesting that they were not the product of low-frequency, high-magnitude events such as tsunami or debris flows. It is anticipated that more examples of ancient tidal bore deposits will come to light now that diagnostic criteria are available, and that these will contribute to the fuller recognition of tidally-modulated fluvial deposits in the rock record.

  7. Tidal instability in exoplanetary systems evolution

    Directory of Open Access Journals (Sweden)

    Le Gal P.

    2011-02-01

    Full Text Available A new element is proposed to play a role in the evolution of extrasolar planetary systems: the tidal (or elliptical instability. It comes from a parametric resonance and takes place in any rotating fluid whose streamlines are (even slightly elliptically deformed. Based on theoretical, experimental and numerical works, we estimate the growth rate of the instability for hot-jupiter systems, when the rotation period of the star is known. We present the physical process, its application to stars, and preliminary results obtained on a few dozen systems, summarized in the form of a stability diagram. Most of the systems are trapped in the so-called "forbidden zone", where the instability cannot grow. In some systems, the tidal instability is able to grow, at short timescales compared to the system evolution. Implications are discussed in the framework of misaligned transiting systems, as the rotational axis of the star would be unstable in systems where this elliptical instability grows.

  8. Study of a Tidal Disruption Event Candidate

    Science.gov (United States)

    Hampel, J.; Reiprich, T.; Freyberg, M.; Greiner, J.; Komossa, S.

    2017-10-01

    During the close encounter of a star with a supermassive black hole, the star might get disrupted by the black hole's tidal forces (tidal disruption events, TDE). The accretion of the stellar material onto the black hole creates luminous emission at different wavelength, including X-rays. We will report the results of an investigation of a bright X-ray source in a set of five ROSAT PSPC observations. The light curve of this event shows an increase in brightness by a factor of nine within eight days, followed by a strong fading over the following 165 days. This observation seems inconsistent with common X-ray source variability, such as active galactic nuclei, and more in favor of a TDE. In order to investigate the possible TDE origin, optical and X-ray spectra have been analyzed. An expected absence of emission lines in the optical and a very soft X-ray spectrum are confirmed. Detailed comparisons with known TDEs show discrepancies in the light curves. Particularly, the increase in brightness happens over a shorter timescale than comparable events. The study of this TDE candidate might help to gain a better understanding of such events, especially for the expected TDE discoveries with the upcoming eROSITA all-sky survey.

  9. Tidal Dwarf Galaxies and Missing Baryons

    Directory of Open Access Journals (Sweden)

    Frederic Bournaud

    2010-01-01

    Full Text Available Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

  10. Evaluation the effect of breathing filters on end-tidal carbon dioxide during inferior abdominal surgery in infants and changes of tidal volume and respiratory rate needs for preventing of increasing end-tidal carbon dioxide

    Directory of Open Access Journals (Sweden)

    Parvin Sajedi

    2016-01-01

    Full Text Available Background: The aim of this study was to prevent of increasing end-tidal carbon dioxide (ETCO2with changing of vital capacity and respiratory rate when using of birthing filter in infants. Materials and Methods: In a randomized clinical trial study, ninety-four infant' patients were studied in three groups. Basic values, such as peak inspiratory pressure, tidal volume, minute ventilation, respiratory rate, and partial pressure of ET CO2 (PETCO2 level had been evaluated after intubation, 10 min after intubation and 10 min after filter insertion. In the first group, patients only observed for changing in ETCO2level. In the second and the third groups, respiratory rates and tidal volume had been increased retrospectively, until that ETCO2 ≤35 mmHg was received. We used ANOVA, Chi-square, and descriptive tests for data analysis. P< 0.05 was considered statistically significant. Results: Tidal volume 10 min after filter insertion was statistically higher in Group 3 (145.0 ± 26.3 ml versus 129.3 ± 38.9 ml in Group 1 and 118.7 ± 20.8 ml in Group 2 (P = 0.02. Furthermore, respiratory rate at this time was statistically higher in Group 2 (25.82 ± 0.43 versus Groups 1 and 3 (21.05 ± 0.20 ml and 21.02 ± 0.60 ml, respectively (P = 0.001. Minute volume and PETCO2level were statistically significant between Group 1 and the other two groups after filter insertion (P = 0.01 and P = 0.00,1 respectively. Conclusion: With changing the vital capacity and respiratory rate we can control PETCO2level ≤35 mmHg during using of birthing filters in infants. We recommend this instrument during anesthesia of infants.

  11. Oceans Past

    DEFF Research Database (Denmark)

    Based on research for the History of Marine Animal Populations project, Oceans Past examines the complex relationship our forebears had with the sea and the animals that inhabit it. It presents eleven studies ranging from fisheries and invasive species to offshore technology and the study of marine...... environmental history, bringing together the perspectives of historians and marine scientists to enhance understanding of ocean management of the past, present and future. In doing so, it also highlights the influence that changes in marine ecosystems have upon the politics, welfare and culture of human...

  12. Oceans Past

    DEFF Research Database (Denmark)

    environmental history, bringing together the perspectives of historians and marine scientists to enhance understanding of ocean management of the past, present and future. In doing so, it also highlights the influence that changes in marine ecosystems have upon the politics, welfare and culture of human......Based on research for the History of Marine Animal Populations project, Oceans Past examines the complex relationship our forebears had with the sea and the animals that inhabit it. It presents eleven studies ranging from fisheries and invasive species to offshore technology and the study of marine...

  13. Tidal exchange of larvae of Sesarma catenata (Decapoda, Brachyura)

    African Journals Online (AJOL)

    1992-10-02

    Oct 2, 1992 ... bimonthly during spring and neap tides from October to March at the tidal inlet. Samples were collected hourly for 25 h in February, and for 13 h in all other months. Hourly estimates of water flux through the tidal inlet of the estuary were calculated using a generalized one-dimensional hydrodynamic model ...

  14. Wave and tidal generation devices reliability and availability

    CERN Document Server

    Tavner, Peter John

    2017-01-01

    To some extent the wave and tidal generation industry is following in the wake of the wind industry, learning from the growing experience of offshore wind farm deployment. This book combines wind industry lessons with wave and tidal field knowledge to explore the main reliability and availability issues facing this growing industry.

  15. The Simulation Of Residual Tidal Phenomena In The White Sea

    Science.gov (United States)

    May, R. I.

    2004-12-01

    Residual tidal phenomena (residual tidal circulation and residual tidal level) in the White Sea play a significant role in energy contribution to the formation of the hydrological regime. Non-linear residual tidal currents and sea level due to energy exchanges from the basic harmonics to the high frequency part of the spectrum have been poorly investigated in the White Sea until now. But residual tidal phenomena play an important role in the general circulation, which affects the temperature distribution and the drift of ice, plankton, pollution and other conservative tracers. We carried out numerical experiments with a non-linear hydrodynamic model to estimate the contributions of (shallow, friction and convective) nonlinearities to the residual tidal phenomena of White Sea's, using a `consecutive realisation' technique. The model grid's spatio-temporal resolution is more detailed than before: the Earth's geoid is approximated by the Krasovskiy rotation ellipsoid. A residual tidal level is observed in the low frequency part of spectrum of model results. In the linear approximation, the spectral density has a dominant peak at the frequencies of the basic harmonics in all parts of the sea, and the residual level was absent; overtones were not expressed. The experiments revealed that the residual circulation was defined by the convective non-linearity. The Earth's rotation does not change the current structure: only the circulation intensity decreases. These results will enhance the knowledge of tidal phenomena in the White Sea, and can be used for navigation, ecology and fisheries research.

  16. Ammonium transformation in a nitrogen-rich tidal freshwater marsh

    NARCIS (Netherlands)

    Gribsholt, B.; Struyf, E.; Tramper, A.; Andersson, M.G.I.; Brion, N.; de Brabandere, L.; van Damme, S.; Meire, P.; Middelburg, J.J.; Dehairs, F.; Boschker, H.T.S.

    2006-01-01

    The fate and transport of watershed-derived ammonium in a tidal freshwater marsh fringing the nutrient rich Scheldt River, Belgium, was quantified in a whole ecosystem 15N labeling experiment. In late summer (September) we added 15N-NH 4 + to the flood water entering a 3477 m2 tidal freshwater marsh

  17. Carbon dioxide uptake by a temperate tidal sea

    NARCIS (Netherlands)

    Klaassen, Wim

    2007-01-01

    Carbon dioxide (CO2) exchange between the atmosphere and the Wadden Sea, a shallow coastal region along the northern Netherlands, has been measured from April 2006 onwards on a tidal flat and over open water. Tidal flat measurements were done using a flux chamber, and ship borne measurements using

  18. Optical discovery of probable stellar tidal discruption flares

    NARCIS (Netherlands)

    van Velzen, S.; Farrar, G.R.; Gezari, S.; Morrell, N.; Zaritsky, D.; Ostman, L.; Smith, M.; Gelfand, J.; Drake, A.J.

    2012-01-01

    Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures

  19. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application ...

  20. Simulating tidal turbines with multi-scale mesh optimisation techniques

    NARCIS (Netherlands)

    Abolghasemi, M.A.; Piggott, M.D.; Spinneken, J; Viré, A.C.; Cotter, CJ; Crammond, S.

    2016-01-01

    Embedding tidal turbines within simulations of realistic large-scale tidal flows is a highly multi-scale problem that poses significant computational challenges. Here this problem is tackled using actuator disc momentum (ADM) theory and Reynolds-averaged Navier–Stokes (RANS) with, for the first

  1. Modeling of channel patterns in short tidal basins

    NARCIS (Netherlands)

    Marciano, R.; Wang, Z.B.; Hibma, A.; De Vriend, H.J.; Defina, A.

    2005-01-01

    We model branching channel patterns in short tidal basins with two methods. A theoretical stability analysis leads to a relationship between the number of channels and physical parameters of the tidal system. The analysis reveals that width and spacing of the channels should decrease as the slope of

  2. Temporal bed level variations in the Yangtze tidal flats (abstract)

    NARCIS (Netherlands)

    Yan, H.; Van Prooijen, B.C.

    2013-01-01

    The Yangtze River is one of the largest rivers in the world and the longest one in Asia. Its estuary forms an important entrance for shipping, but is also a key ecological system. Especially the inter-tidal flats are valuable habitats. The health and integrity of the estuarine tidal flat are however

  3. A stand-alone tidal prediction application for mobile devices

    Science.gov (United States)

    Tsai, Cheng-Han; Fan, Ren-Ye; Yang, Yi-Chung

    2017-04-01

    It is essential for people conducting fishing, leisure, or research activities at the coasts to have timely and handy tidal information. Although tidal information can be found easily on the internet or using mobile device applications, this information is all applicable for only certain specific locations, not anywhere on the coast, and they need an internet connection. We have developed an application for Android devices, which allows the user to obtain hourly tidal height anywhere on the coast for the next 24 hours without having to have any internet connection. All the necessary information needed for the tidal height calculation is stored in the application. To develop this application, we first simulate tides in the Taiwan Sea using the hydrodynamic model (MIKE21 HD) developed by the DHI. The simulation domain covers the whole coast of Taiwan and the surrounding seas with a grid size of 1 km by 1 km. This grid size allows us to calculate tides with high spatial resolution. The boundary conditions for the simulation domain were obtained from the Tidal Model Driver of the Oregon State University, using its tidal constants of eight constituents: M2, S2, N2, K2, K1, O1, P1, and Q1. The simulation calculates tides for 183 days so that the tidal constants for the above eight constituents of each water grid can be extracted by harmonic analysis. Using the calculated tidal constants, we can predict the tides in each grid of our simulation domain, which is useful when one needs the tidal information for any location in the Taiwan Sea. However, for the mobile application, we only store the eight tidal constants for the water grids on the coast. Once the user activates the application, it reads the longitude and latitude from the GPS sensor in the mobile device and finds the nearest coastal grid which has our tidal constants. Then, the application calculates tidal height variation based on the harmonic analysis. The application also allows the user to input location and

  4. Confusion around the tidal force and the centrifugal force

    CERN Document Server

    Matsuda, Takuya; Boffin, Henri M J

    2015-01-01

    We discuss the tidal force, whose notion is sometimes misunderstood in the public domain literature. We discuss the tidal force exerted by a secondary point mass on an extended primary body such as the Earth. The tidal force arises because the gravitational force exerted on the extended body by the secondary mass is not uniform across the primary. In the derivation of the tidal force, the non-uniformity of the gravity is essential, and inertial forces such as the centrifugal force are not needed. Nevertheless, it is often asserted that the tidal force can be explained by the centrifugal force. If we literally take into account the centrifugal force, it would mislead us. We therefore also discuss the proper treatment of the centrifugal force.

  5. Quantification of tidal parameters from Solar System data

    Science.gov (United States)

    Lainey, Valéry

    2016-11-01

    Tidal dissipation is the main driver of orbital evolution of natural satellites and a key point to understand the exoplanetary system configurations. Despite its importance, its quantification from observations still remains difficult for most objects of our own Solar System. In this work, we overview the method that has been used to determine, directly from observations, the tidal parameters, with emphasis on the Love number k_2 and the tidal quality factor Q. Up-to-date values of these tidal parameters are summarized. Last, an assessment on the possible determination of the tidal ratio k_2/Q of Uranus and Neptune is done. This may be particularly relevant for coming astrometric campaigns and future space missions focused on these systems.

  6. Too Little, Too Late: How the Tidal Evolution of Hot Jupiters Affects Transit Surveys of Clusters

    Science.gov (United States)

    Debes, John H.; Jackson, Brian

    2010-01-01

    The tidal evolution of hot Jupiters may change the efficiency of transit surveys of stellar clusters. The orbital decay that hot Jupiters suffer may result in their destruction, leaving fewer transiting planets in older clusters. We calculate the impact tidal evolution has for different assumed stellar populations, including that of 47 Tuc, a globular cluster that was the focus of an intense HST search for transits. We find that in older clusters one expects to detect fewer transiting planets by a factor of two for surveys sensitive to Jupiter-like planets in orbits out to 0.5 AU, and up to a factor of 25 for surveys sensitive to Jupiter-like planets in orbits out to 0.08 AU. Additionally, tidal evolution affects the distribution of transiting planets as a function of semi-major axis, producing larger orbital period gaps for transiting planets as the age of the cluster increases. Tidal evolution can explain the lack of detected exoplanets in 47 Tuc without invoking other mechanisms. Four open clusters residing within the Kepler fields of view have ages that span 0.4-8 Gyr-if Kepler can observe a significant number of planets in these clusters, it will provide key tests for our tidal evolution hypothesis. Finally, our results suggest that observers wishing to discover transiting planets in clusters must have sufficient accuracy to detect lower mass planets, search larger numbers of cluster members, or have longer observation windows to be confident that a significant number of transits will occur for a population of stars.

  7. Methods for monitoring tidal flushing in large animal burrows in tropical mangrove swamps

    Science.gov (United States)

    Hollins, Suzanne E.; Heron, Scott F.; Ridd, Peter V.

    2009-05-01

    The typically anaerobic nature of mangrove sediments provides significant challenges to the mangrove trees and biota inhabiting them. The burrowing activities and flow of water through the numerous and complex animal burrows perforating the sediments of mangroves have a major influence on the biogeochemistry of the sediments and are important to the enhancement of nutrient and oxygen exchange. Two new methods are presented for monitoring the tidal flushing of Sesarma messa and Alpheus cf macklay burrows in a Rhizophora stylosa mangrove forest - by measuring oxygen content of burrow water and by determining the change in fluorescence of a dye tracer through tidal inundation. A case study using the first of these showed oxygen consumption rates at the burrow wall deep within the burrow were found to be between 210 and 460 μmol O 2 m -2 h -1. The influx of oxygen during a flood tide was found to be significant and indicated that approximately 40% of the burrow water is flushed during a single tidal event. However, the high consumption rate of oxygen within the burrow resulted in the oxygen concentration remaining at or below one-third of the oxygen content of the flooding tidal water. A test application of the second method, using rhodamine dye as a tracer, indicated that the exchange of water between the burrow and the flooding tide was found to be in the order of 30% of the burrow volume. These new techniques provide a means to further study the nutrient exchange within these burrow systems and verify the initial findings that several tidal inundations are necessary to completely flush the burrows.

  8. Nitrogen fertilizer management for tidal submergence tolerant landrace rice (Oryza sativa L. cultivars

    Directory of Open Access Journals (Sweden)

    M.A.A. Mamun

    2017-12-01

    Full Text Available In tidal submergence ecosystem, nitrogen (N is a crucial nutrient for improved and sustainable rice production. Therefore, a series of on-farm and on-station field experiments were conducted to develop a suitable N management practice for tidal submergence tolerant landrace aman rice. In on-farm, urea deep placement (UDP through urea super granule before panicle initiation (PI stage was compared with no fertilizer application. Similarly, five N fertilizer management practices viz. (i. two splits of prilled urea (PU, (ii. UDP at 10 DAT, (iii. UDP before PI, (iv. full dose PU before PI and (v. No urea (control were compared at on-station trial. Tidal submergence tolerance aman rice varieties (Rajashail, Kutiagni, Sadamota and Lalmota were used as testing materials. In on farm experiment, aman cultivars produced 2.0–2.5 t ha−1 grain without N fertilizer. But, cultivated Rajashail, Kutiagni, Sadachikon, Sadapajam, Lalmota and Sadamota gave 3.0–3.5 t ha−1 grain yield with the UDP before PI in tidal prone areas. Though UDP required fertilizer and application cost but it gave profit upto 22,000 BDT ha−1 (Bangladeshi Taka. In on-station experiment, UDP before PI stage significantly increased rice yield and economic return although it was comparable to two splits of PU and top dressing of PU before PI stage. However, UDP at 10 DAT increased straw yield but failed to increase grain yield even compared to control. It could be concluded that UDP before PI stage of rice is an effective method for increasing rice yield and farm income in tidal prone areas.

  9. Sea-level rise and refuge habitats for tidal marsh species: can artificial islands save the California Ridgway's rail?

    Science.gov (United States)

    Overton, Cory T.; Takekawa, John Y.; Casazza, Michael L.; Bui, Thuy-Vy D.; Holyoak, Marcel; Strong, Donald R.

    2014-01-01

    Terrestrial species living in intertidal habitats experience refuge limitation during periods of tidal inundation, which may be exacerbated by seasonal variation in vegetation structure, tidal cycles, and land-use change. Sea-level rise projections indicate the severity of refuge limitation may increase. Artificial habitats that provide escape cover during tidal inundation have been proposed as a temporary solution to alleviate these limitations. We tested for evidence of refuge habitat limitation in a population of endangered California Ridgway's rail (Rallus obsoletus obsoletus; hereafter California rail) through use of artificial floating island habitats provided during two winters. Previous studies demonstrated that California rail mortality was especially high during the winter and periods of increased tidal inundation, suggesting that tidal refuge habitat is critical to survival. In our study, California rail regularly used artificial islands during higher tides and daylight hours. When tide levels inundated the marsh plain, use of artificial islands was at least 300 times more frequent than would be expected if California rails used artificial habitats proportional to their availability (0.016%). Probability of use varied among islands, and low levels of use were observed at night. These patterns may result from anti-predator behaviors and heterogeneity in either rail density or availability of natural refuges. Endemic saltmarsh species are increasingly at risk from habitat change resulting from sea-level rise and development of adjacent uplands. Escape cover during tidal inundation may need to be supplemented if species are to survive. Artificial habitats may provide effective short-term mitigation for habitat change and sea-level rise in tidal marsh environments, particularly for conservation-reliant species such as California rails.

  10. Modeling mid-ocean ridge hydrothermal response to earthquakes, tides, and ocean currents: a case study at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge

    Science.gov (United States)

    Xu, G.; Bemis, K. G.

    2014-12-01

    Seafloor hydrothermal systems feature intricate interconnections among oceanic, geological, hydrothermal, and biological processes. The advent of the NEPTUNE observatory operated by Ocean Networks Canada at the Endeavour Segment, Juan de Fuca Ridge enables scientists to study these interconnections through multidisciplinary, continuous, real-time observations. The multidisciplinary observatory instruments deployed at the Grotto Mound, a major study site of the NEPTUNE observatory, makes it a perfect place to study the response of a seafloor hydrothermal system to geological and oceanic processes. In this study, we use the multidisciplinary datasets recorded by the NEPTUNE Observatory instruments as observational tools to demonstrate two different aspects of the response of hydrothermal activity at the Grotto Mound to geological and oceanic processes. First, we investigate a recent increase in venting temperature and heat flux at Grotto observed by the Benthic and Resistivity Sensors (BARS) and the Cabled Observatory Vent Imaging Sonar (COVIS) respectively. This event started in Mar 2014 and is still evolving by the time of writing this abstract. An initial interpretation in light of the seismic data recorded by a neighboring ocean bottom seismometer on the NEPTUNE observatory suggests the temperature and heat flux increase is probably triggered by local seismic activities. Comparison of the observations with the results of a 1-D mathematical model simulation of hydrothermal sub-seafloor circulation elucidates the potential mechanisms underlying hydrothermal response to local earthquakes. Second, we observe significant tidal oscillations in the venting temperature time series recorded by BARS and the acoustic imaging of hydrothermal plumes by COVIS, which is evidence for hydrothermal response to ocean tides and currents. We interpret the tidal oscillations of venting temperature as a result of tidal loading on a poroelastic medium. We then invoke poroelastic

  11. Evaluation of streambed scour at bridges over tidal waterways in Alaska

    Science.gov (United States)

    Conaway, Jeffrey S.; Schauer, Paul V.

    2012-01-01

    The potential for streambed scour was evaluated at 41 bridges that cross tidal waterways in Alaska. These bridges are subject to several coastal and riverine processes that have the potential, individually or in combination, to induce streambed scour or to damage the structure or adjacent channel. The proximity of a bridge to the ocean and water-surface elevation and velocity data collected over a tidal cycle were criteria used to identify the flow regime at each bridge, whether tidal, riverine, or mixed, that had the greatest potential to induce streambed scour. Water-surface elevations measured through at least one tide cycle at 32 bridges were correlated to water levels at the nearest tide station. Asymmetry of the tidal portion of the hydrograph during the outgoing tide at 12 bridges indicated that riverine flows were stored upstream of the bridge during the tidal exchange. This scenario results in greater discharges and velocities during the outgoing tide compared to those on the incoming tide. Velocity data were collected during outgoing tides at 10 bridges that experienced complete flow reversals, and measured velocities during the outgoing tide exceeded the critical velocity required to initiate sediment transport at three sites. The primary risk for streambed scour at most of the sites considered in this study is from riverine flows rather than tidal fluctuations. A scour evaluation for riverine flow was completed at 35 bridges. Scour from riverine flow was not the primary risk for six tidally-controlled bridges and therefore not evaluated at those sites. Field data including channel cross sections, a discharge measurement, and a water-surface slope were collected at the 35 bridges. Channel instability was identified at 14 bridges where measurable scour and or fill were noted in repeated surveys of channel cross sections at the bridge. Water-surface profiles for the 1-percent annual exceedance probability discharge were calculated by using the Hydrologic

  12. Oceans Past

    DEFF Research Database (Denmark)

    Based on research for the History of Marine Animal Populations project, Oceans Past examines the complex relationship our forebears had with the sea and the animals that inhabit it. It presents eleven studies ranging from fisheries and invasive species to offshore technology and the study of mari...

  13. Oceans Past

    DEFF Research Database (Denmark)

    environmental history, bringing together the perspectives of historians and marine scientists to enhance understanding of ocean management of the past, present and future. In doing so, it also highlights the influence that changes in marine ecosystems have upon the politics, welfare and culture of human...

  14. Three-dimensional semi-idealized model for tidal motion in tidal estuaries: an application to the Ems estuary

    NARCIS (Netherlands)

    Kumar, Mohit; Schuttelaars, H.M.; Roos, Pieter C.; Möller, M.

    2016-01-01

    In this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the

  15. A process study of the interaction of tidal currents, tidal mixing and density gradients in a region of freshwater influence

    Science.gov (United States)

    Xing, Jiuxing; Chen, Shengli

    2017-08-01

    A three dimensional unstructured grid model of the west coast of Britain is used to study the process of the interaction of tidal currents, tidal mixing and density gradient in the Liverpool Bay region. Calculations with M2 tidal forcing and omitting freshwater discharge show that tidal currents in the region are strong (of order 1 ms- 1), with tidal current ellipses essentially rectilinear in the surface and bottom. In the absence of tidal forcing, the freshwater is confined to a thin surface layer. With the inclusion of tidal mixing the surface layer thickens, and in the shallow water area mixed layer occupies the whole water depth. This has a significant effect of reducing its lateral spread. A detailed study of time series of velocity, salinity and turbulence reveals that at flood tide, more saline water is advected into the coastal region and rapid vertical mixing occurs, whereas at ebb tide, fresher water is advected over more saline water. The induced strong pycnocline uncouples surface and bottom layers leading to more circular tidal ellipses which rotate in opposite directions in the vertical, as found in observations. The three dimensional nature of the model reveals that this process involves both horizontal and vertical density gradients, and shows significant horizontal variability in the Liverpool Bay region.

  16. Development of a Multi-Site and Multi-Device Webgis-Based Tool for Tidal Current Energy Development

    Science.gov (United States)

    Ang, M. R. C. O.; Panganiban, I. K.; Mamador, C. C.; De Luna, O. D. G.; Bausas, M. D.; Cruz, J. P.

    2016-06-01

    A multi-site, multi-device and multi-criteria decision support tool designed to support the development of tidal current energy in the Philippines was developed. Its platform is based on Geographic Information Systems (GIS) which allows for the collection, storage, processing, analyses and display of geospatial data. Combining GIS tools with open source web development applications, it becomes a webGIS-based marine spatial planning tool. To date, the webGIS-based tool displays output maps and graphs of power and energy density, site suitability and site-device analysis. It enables stakeholders and the public easy access to the results of tidal current energy resource assessments and site suitability analyses. Results of the initial development showed that it is a promising decision support tool for ocean renewable energy project developments.

  17. Ultraviolet Spectroscopy of Tidal Disruption Flares

    Science.gov (United States)

    Cenko, Stephen B.

    2017-08-01

    When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics,TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies.In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths.Here I present recent attempts to obtain UV spectra of tidal disruption flares. I describe the UV spectrum of ASASSN-14li, in which we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by 250-400 km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will

  18. Effect of the Free Core Resonance derived from tidal strain data

    Science.gov (United States)

    Amoruso, Antonella; Crescentini, Luca; Milyukov, Vadim; Mironov, Aleksey; Myasnikov, Andrey

    2017-04-01

    To investigate the effect of the Free Core Resonance (FCR) we use the data from two European strain stations: Baksan (Russia), and Gran Sasso (Italy). Eight years of strain recorded by two crossed 90-m long laser interferometers (BA and BC) at Gran Sasso underground observatory, and six years of strain recorded by the 75-m long laser interferometer at Baksan underground observatory, have been analysed. For the FCR parameter estimation we use 8 diurnal tidal constituents (namely Q1, O1, P1, K1, Ψ1, Φ1, J1, OO1) and compare measurements and model predictions through a joint fit on BAKSAN, BA, and BC tidal parameters minimizing the £1 misfit function. As measurements we use the amplitudes of the sine and cosine terms of the observed tides, obtained from the output amplitudes and phases of the VAV03 code [Venedikov et al., 2003] applied on the pre-whitened strain series. Retrieved tidal parameters are corrected for ocean loading and local effects. Measured tidal parameters for the three interferometers in the diurnal band have been compared with predicted SNRE tides. The out-of-phase Φ1wave discrepancies are outside the uncertainties for all interferometers, and the Baksan out-of-phase J1wave discrepancy is outside the uncertainty too. The results of analysis show that at the 80% (50%) confidence level the period of the Free Core Nutation (TFCN) is between 413.5 (421.2) and 436.8 (431.0) sidereal days. The quality factor is badly constrained because of the large uncertainty on the Ψ1 phase. Probability density function of Q-factor shows a peak around 18000. The joint analysis confirms the results obtained from the analysis of the Gran Sasso strain tides only [Amoruso et al., 2012] and are comparable to those from gravity tides. This work is partly supported by the Russian Foundation for Basic Research under Grant No 16-05-00122. References Amoruso, A., Botta, V., Crescentini, L., 2012. Free Core Resonance parameters from strain data: sensitivity analysis and

  19. Tidally modulated eruptions on Enceladus: Cassini ISS observations and models

    Energy Technology Data Exchange (ETDEWEB)

    Nimmo, Francis [Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064 (United States); Porco, Carolyn; Mitchell, Colin, E-mail: carolyn@ciclops.org [CICLOPS, Space Science Institute, Boulder, CO 80304 (United States)

    2014-09-01

    We use images acquired by the Cassini Imaging Science Subsystem (ISS) to investigate the temporal variation of the brightness and height of the south polar plume of Enceladus. The plume's brightness peaks around the moon's apoapse, but with no systematic variation in scale height with either plume brightness or Enceladus' orbital position. We compare our results, both alone and supplemented with Cassini near-infrared observations, with predictions obtained from models in which tidal stresses are the principal control of the eruptive behavior. There are three main ways of explaining the observations: (1) the activity is controlled by right-lateral strike slip motion; (2) the activity is driven by eccentricity tides with an apparent time delay of about 5 hr; (3) the activity is driven by eccentricity tides plus a 1:1 physical libration with an amplitude of about 0.°8 (3.5 km). The second hypothesis might imply either a delayed eruptive response, or a dissipative, viscoelastic interior. The third hypothesis requires a libration amplitude an order of magnitude larger than predicted for a solid Enceladus. While we cannot currently exclude any of these hypotheses, the third, which is plausible for an Enceladus with a subsurface ocean, is testable by using repeat imaging of the moon's surface. A dissipative interior suggests that a regional background heat source should be detectable. The lack of a systematic variation in plume scale height, despite the large variations in plume brightness, is plausibly the result of supersonic flow; the details of the eruption process are yet to be understood.

  20. Hawaii Ocean Mixing Experiment: Program Summary

    Science.gov (United States)

    Ray, Richard D.; Chao, Benjamin F. (Technical Monitor)

    2002-01-01

    It is becoming apparent that insufficient mixing occurs in the pelagic ocean to maintain the large scale thermohaline circulation. Observed mixing rates fall a factor of ten short of classical indices such as Munk's "Abyssal Recipe." The growing suspicion is that most of the mixing in the sea occurs near topography. Exciting recent observations by Polzin et al., among others, fuel this speculation. If topographic mixing is indeed important, it must be acknowledged that its geographic distribution, both laterally and vertically, is presently unknown. The vertical distribution of mixing plays a critical role in the Stommel Arons model of the ocean interior circulation. In recent numerical studies, Samelson demonstrates the extreme sensitivity of flow in the abyssal ocean to the spatial distribution of mixing. We propose to study the topographic mixing problem through an integrated program of modeling and observation. We focus on tidally forced mixing as the global energetics of this process have received (and are receiving) considerable study. Also, the well defined frequency of the forcing and the unique geometry of tidal scattering serve to focus the experiment design. The Hawaiian Ridge is selected as a study site. Strong interaction between the barotropic tide and the Ridge is known to take place. The goals of the Hawaiian Ocean Mixing Experiment (HOME) are to quantify the rate of tidal energy loss to mixing at the Ridge and to identify the mechanisms by which energy is lost and mixing generated. We are challenged to develop a sufficiently comprehensive picture that results can be generalized from Hawaii to the global ocean. To achieve these goals, investigators from five institutions have designed HOME, a program of historic data analysis, modeling and field observation. The Analysis and Modeling efforts support the design of the field experiments. As the program progresses, a global model of the barotropic (depth independent) tide, and two models of the

  1. Wave and tidal flushing in a near-equatorial mesotidal atoll

    Science.gov (United States)

    Costa, Mirella B.; Macedo, Eduardo C.; Valle-Levinson, Arnoldo; Siegle, Eduardo

    2017-03-01

    Most of the atolls found worldwide are under microtidal regimes, and their circulation mechanisms are widely documented and well known. Here, we describe the flushing mechanisms of a small-sized mesotidal atoll, based on water-level, wave and current data obtained during two different periods (total of 60 d). Rocas is the only atoll in the South Atlantic Ocean and is built primarily of coralline algae. Two reef passages connect the atoll lagoon to the ocean. Synchronous current profilers were deployed at the two reef passages, one inside and one outside the atoll, to characterize the influence of tides and waves on the circulation. Results showed that wind waves drove a setup on the exposed side of the atoll and that currents were predominately downwind, causing outflow at both reef passages. Waves breaking on the windward side supplied water to the atoll causing the lagoon water level to rise above ocean water level, driving the outflow. However, unlike microtidal atolls, at Rocas Atoll the water level drops significantly below the reef rim during low tides. This causes the reef rim to act as a barrier to water pumping into the lagoon by waves, resulting in periodic activation of the wave pumping mechanism throughout a tidal cycle. As result, inflow occurs in the wider passage during 27% of each tidal cycle, starting at low tides and reversing direction during mid-flood tide when the water level exceeded approximately 1.6 m (while overtopping the atoll's rim). Our findings show that tides play a direct role in driving circulation on a mesotidal atoll, not only by modulating wave setup but also by determining the duration of wave pumping into the lagoon.

  2. Reversing tidal flow and estuarine morphodynamics in the Metronome laboratory flume

    OpenAIRE

    Kleinhans, M. G.; Leuven, J.R.F.W.; L. Braat; Vegt, M.; van Maarseveen, M.C.G.; Markies, H.; Roosendaal, C.; Eijk, A.M.

    2016-01-01

    Our objective is to test a novel experimental principle for creating reversing tidal flows of sufficient strength to cause estuarine morphodynamics. The study of estuarine morphodynamics has hitherto been limited to field observation and numerical modelling, whilst fluvial morphodynamics have additionally been studied by scale experiments with the same sediment mobility as the prototype, here defined by the Shields number. The most important reason is the difficulty of downscaling sediment si...

  3. Waddenfonds Tidal Texel Demonstration project. BlueTEC Texel Tidal Project: Environmental measurement and performance analysis

    OpenAIRE

    Ponsoni, L.; Nauw, J. J.; Smit, M.; Ober, S.; Nichols, C; Kenkhuis, J.; Schmidt, C.; Buatois, A.; Haas, P.

    2016-01-01

    In the context of the BlueTEC project, this report starts by introducing theBlueTEC tidal energy platform and reviewing the patterns of circulation of theMarsdiep inlet. The energy resource assessment and the site selection for theplatform's deployment are reported. This document analyses di?erent datasetssampled during the project, including current speeds, wave parameters, turbinepower output, platform excursions, and environmental parameters. Most of thedata was measured by instruments ins...

  4. Slow Rotating Trojans: Tidally Synchronized Binaries?

    Science.gov (United States)

    Noll, Keith

    2017-08-01

    We propose HST observations of six slow-rotating Trojans to search for tidally synchronous binaries similar to the Patroclus binary system. A significant excess of slow rotators over Maxwellian suggests that additional binaries may be present. If any of the targets are binary, they can be resolved by HST. This target selection strategy has recently yielded the third known resolved Trojan binary, detected in a sample of seven slow-rotating Trojans. We wish to extend this successful strategy with another similarly selected sample. Even one additional resolved binary in the Trojans, which would become the fourth, would be of extreme interest. The discovery of no binaries among this group of slow rotators would challenge the understanding of the source of the excess slow rotators in the Trojans.

  5. Coastal Downscaling Experiments: Can CESM Fields Successfully Force Regional Coastal Ocean Simulations with Strong Freshwater Forcing?

    Science.gov (United States)

    MacCready, P.; Bryan, F.; Tseng, Y. H.; Whitney, M. M.

    2014-12-01

    The coastal ocean accounts for about half of the global fish harvest, but is poorly resolved in global climate models (a one-degree grid barely sees the continental shelf). Moreover, coastal ocean circulation is strongly modified by river freshwater sources, often coming from estuarine systems that are completely unresolved in the coarse grid. River freshwater input in CESM is added in a practical but ad hoc way, by imposing a surface salinity sink over a region of the ocean approximating the plume area of a given river. Here we present results from a series of model experiments using a high-resolution (1.5 km) ROMS model of the NE Pacific, including the Columbia River and the inland waters of Puget Sound. The base model does multi-year hindcasts using the best available sources of atmospheric (MM5/WRF), ocean (NCOM), river (USGS), and tidal forcing. It has been heavily validated against observations of all sorts, and performs well, so it is an ideal test bed for downscaling experiments. The model framework also does biogeochemistry, including oxygen, and carbon chemistry is being added to make forecasts of Ocean Acidification.This high-resolution ROMS model is systematically run in downscaling experiments for the year 2005 with combinations of CESM forcing (CAM, POP, and rivers) swapped in. Skill is calculated using observations. It is found that the runs with CESM forcing generally retain much of the skill of the base model. A compact metric of response to freshwater forcing is used, which is the mechanical energy required to destratify a shallow coastal volume. This, along with the average temperature and salinity of the volume, are used to characterize and compare runs, including the original CESM-POP fields. Finally the model is run with projected CESM simulation forcing at the end of 21st century based on a set of RCP scenarios, and the compact metrics are used to quantify differences from 2005.

  6. Testing the alkenone D/H ratio as a paleo indicator of sea surface salinity in a coastal ocean margin (Mozambique Channel)

    NARCIS (Netherlands)

    Kasper, S.; van der Meer, M.T.J.; Castañeda, I.S; Tjallingii, R.; Brummer, G.J.A.; Sinninghe Damsté, J.S.; Schouten, S.

    2015-01-01

    Reconstructing past ocean salinity is important for assessing paleoceanographic change and therefore past climatic dynamics. Commonly, sea water salinity reconstruction is based on planktonic foraminifera oxygen isotope values combined with sea surface temperature reconstruction. However, the

  7. Multimission empirical ocean tide modeling for shallow waters and polar seas

    DEFF Research Database (Denmark)

    Cheng, Yongcun; Andersen, Ole Baltazar

    2011-01-01

    A new global ocean tide model named DTU10 (developed at Technical University of Denmark) representing all major diurnal and semidiurnal tidal constituents is proposed based on an empirical correction to the global tide model FES2004 (Finite Element Solutions), with residual tides determined using...... to recover twice the spatial variations of the tidal signal which is particularly important in shallow waters where the spatial scale of the tidal signal is scaled down. Outside the +/- 66 degrees parallel combined Envisat, GEOSAT Follow-On, and ERS-2, data sets have been included to solve for the tides up...... to the +/- 82 degrees parallel. A new approach to removing the annual sea level variations prior to estimating the residual tides significantly improved tidal determination of diurnal constituents from the Sun-synchronous satellites (e. g., ERS-2 and Envisat) in the polar seas. Extensive evaluations with six...

  8. Magnetic field evolution in tidal disruption events

    Science.gov (United States)

    Bonnerot, Clément; Price, Daniel J.; Lodato, Giuseppe; Rossi, Elena M.

    2017-08-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to pervade its debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of ˜10. However, this value represents a lower limit since it increases with numerical resolution. For an initial field strength of 1 G, the magnetic field never becomes dynamically important. Instead, the disruption of a star with a strong 1 MG magnetic field produces a debris stream within which magnetic pressure becomes similar to gas pressure a few tens of hours after disruption. If the remnant of one or multiple partial disruptions is eventually fully disrupted, its magnetic field could be large enough to magnetically power the relativistic jet detected from Swift J1644+57. Magnetized streams could also be significantly thickened by magnetic pressure when it overcomes the confining effect of self-gravity.

  9. Dynamics of Tidally Locked, Ultrafast Rotating Atmospheres

    Science.gov (United States)

    Tan, Xianyu; Showman, Adam P.

    2017-10-01

    Tidally locked gas giants, which exhibit a novel regime of day-night thermal forcing and extreme stellar irradiation, are typically in several-day orbits, implying slow rotation and a modest role for rotation in the atmospheric circulation. Nevertheless, there exist a class of gas-giant, highly irradiated objects - brown dwarfs orbiting white dwarfs in extremely tight orbits - whose orbital and hence rotation periods are as short as 1-2 hours. Spitzer phase curves and other observations have already been obtained for this fascinating class of objects, which raise fundamental questions about the role of rotation in controlling the circulation. So far, most modeling studies have investigated rotation periods exceeding a day, as appropriate for typical hot Jupiters. In this work we investigate the dynamics of tidally locked atmospheres in shorter rotation periods down to about two hours. With increasing rotation rate (decreasing rotation period), we show that the width of the equatorial eastward jet decreases, consistent with the narrowing of wave-mean-flow interacting region due to decrease of the equatorial deformation radius. The eastward-shifted equatorial hot spot offset decreases accordingly, and the westward-shifted hot regions poleward of the equatorial jet associated with Rossby gyres become increasingly distinctive. At high latitudes, winds becomes weaker and more geostrophic. The day-night temperature contrast becomes larger due to the stronger influence of rotation. Our simulated atmospheres exhibit small-scale variability, presumably caused by shear instability. Unlike typical hot Jupiters, phase curves of fast-rotating models show an alignment of peak flux to secondary eclipse. Our results have important implications for phase curve observations of brown dwarfs orbiting white dwarfs in ultra tight orbits.

  10. Ambient Noise in an Urbanized Tidal Channel

    Science.gov (United States)

    Bassett, Christopher

    In coastal environments, when topographic and bathymetric constrictions are combined with large tidal amplitudes, strong currents (> 2 m/s) can occur. Because such environments are relatively rare and difficult to study, until recently, they have received little attention from the scientific community. However, in recent years, interest in developing tidal hydrokinetic power projects in these environments has motivated studies to improve this understanding. In order to support an analysis of the acoustic effects of tidal power generation, a multi-year study was conducted at a proposed project site in Puget Sound (WA) are analyzed at a site where peak currents exceeded 3.5 m/s. From these analyses, three noise sources are shown to dominate the observed variability in ambient noise between 0.02-30 kHz: anthropogenic noise from vessel traffic, sediment-generated noise during periods of strong currents, and flow-noise resulting from turbulence advected over the hydrophones. To assess the contribution of vessel traffic noise, one calendar year of Automatic Identification System (AIS) ship-traffic data was paired with hydrophone recordings. The study region included inland waters of the Salish Sea within a 20 km radius of the hydrophone deployment site in northern Admiralty Inlet. The variability in spectra and hourly, daily, and monthly ambient noise statistics for unweighted broadband and M-weighted sound pressure levels is driven largely by vessel traffic. Within the one-year study period, at least one AIS transmitting vessel is present in the study area 90% of the time and over 1,363 unique vessels are recorded. A noise budget for vessels equipped with AIS transponders identifies cargo ships, tugs, and passenger vessels as the largest contributors to noise levels. A simple model to predict received levels at the site based on an incoherent summation of noise from different vessel types yields a cumulative probability density function of broadband sound pressure

  11. Dwarf Galaxies Swimming in Tidal Tails

    Science.gov (United States)

    2005-01-01

    This false-color infrared image from NASA's Spitzer Space Telescope shows little 'dwarf galaxies' forming in the 'tails' of two larger galaxies that are colliding together. The big galaxies are at the center of the picture, while the dwarfs can be seen as red dots in the red streamers, or tidal tails. The two blue dots above the big galaxies are stars in the foreground. Galaxy mergers are common occurrences in the universe; for example, our own Milky Way galaxy will eventually smash into the nearby Andromeda galaxy. When two galaxies meet, they tend to rip each other apart, leaving a trail, called a tidal tail, of gas and dust in their wake. It is out of this galactic debris that new dwarf galaxies are born. The new Spitzer picture demonstrates that these particular dwarfs are actively forming stars. The red color indicates the presence of dust produced in star-forming regions, including organic molecules called polycyclic aromatic hydrocarbons. These carbon-containing molecules are also found on Earth, in car exhaust and on burnt toast, among other places. Here, the molecules are being heated up by the young stars, and, as a result, shine in infrared light. This image was taken by the infrared array camera on Spitzer. It is a 4-color composite of infrared light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). Starlight has been subtracted from the orange and red channels in order to enhance the dust features.

  12. Validation Test Report for the Global Ocean Forecast System V3.0 - 1/12 deg HYCOM-NCODA: Phase II

    Science.gov (United States)

    2010-02-23

    Coastal Ocean Observing Lab at Rutgers University attempted two trans-Atlantic flights using Slocum gliders . These began off the U.S. 26 East...surface temperature, and e) a velocity comparison against glider and drifting buoy observations. Overall, this report has determined that GOFS V3.0 is...upper-ocean velocity using glider and drifter observations. They are discussed below. 3.2.1 Provision of boundary conditions to a regional nested model

  13. Tidal River Management (TRM and Tidal Basin Management (TBM: A case study on Bangladesh

    Directory of Open Access Journals (Sweden)

    Talchabhadel Rocky

    2016-01-01

    Full Text Available Bangladesh is the biggest delta of the world. Construction of numbers of polders is one of the flood resilient approach. But the presence of coastal polders de-linked the flood plain. The siltation in river causes riverbeds to become higher than the adjacent crop lands, and vast area under the polders became permanently water logged rendering large tract of land uncultivable. The current practice is temporarily de-poldering by cutting embankment. This is a natural water management process with very little human interventions but it needs strong participation and consensus with a great deal of sacrifice by the stakeholders for a specific period (3 to 5 years or even more[1]. An attempt has been made to study the phenomena of tidal basin management reviewing some secondary data and processes involved in successfully operated tidal basins of Bangladesh. And preliminary laboratory experiments are carried out to precisely look into the suspended sediment transport. With varying outflow discharge and sediment supply, the transport processes are investigated. 3D sediment transport model developed using openFOAM has good agreement with experimental result and can be used to better understand effectiveness of tidal basin management.

  14. Variations in tidal level in the Gulf of Mexico and implications for tidal wetlands

    Science.gov (United States)

    Stumpf, R.P.; Haines, J.W.

    1998-01-01

    Tidal wetland environments have an ecological zonation that corresponds with tide levels, in particular with mean high water. However, mean sea level (MSL), which has shown a persistent rise in the Gulf of Mexico during this century, is the most common reference for water level change. We examine here the relationship between mean sea level and mean high water in describing water level changes in the Gulf of Mexico. The records of monthly mean water level for four stations, Galveston, Pensacola, Cedar Key and Key West, are partitioned into the annual cycle, the long-term trend, and a low-frequency (> 10 year period) fluctuation. The trend is the same for MSL and mean higher high water (MHHW) for all stations investigated except Cedar Key, Florida, where MHHW has increased more rapidly than MSL. The low-frequency fluctuations are similar between the stations and the tidal datums. MSL can predict MHHW with discrepancies of up to 5 cm owing to the lunar nodal cycle and an annual tidal signal. Low-frequency climatic fluctuations produce greater variations than the nodal cycle, but the difference in frequency can lead to interference between the two in MHHW. The combination of the two can produce sea-level rises in excess of 1 cm year-1 over several year periods, even in areas having long-term trends of 0.2 cm year-1 or less.

  15. Environmental extremes and biotic interactions facilitate depredation of endangered California Ridgway’s rail in a San Francisco Bay tidal marsh

    Science.gov (United States)

    Overton, Cory T.; Bobzien, Steven; Grefsrud, Marcia

    2016-01-01

    On 23 December 2015 while performing a high tide population survey for endangered Ridgway’s rails (Rallus obsoletus obsoletus; formerly known as the California clapper rail) and other rail species at Arrowhead Marsh, Martin Luther King Jr. Regional Shoreline, Oakland, California, the authors observed a series of species interactions resulting in the predation of a Ridgway’s rail by an adult female peregrine falcon (Falco peregrinus). High tide surveys are performed during the highest tides of the year when tidal marsh vegetation at Arrowhead Marsh becomes inundated, concentrating the tidal marsh obligate species into the limited area of emergent vegetation remaining as refuge cover. Annual mean tide level (elevation referenced relative to mean lower low water) at Arrowhead Marsh is 1.10 m, mean higher high water is 2.04 m (NOAA National Ocean Service 2014) and the average elevation of the marsh surface is 1.60 m (Overton et al. 2014). Tidal conditions on the day of the survey were predicted to be 2.42 m. Observed tides at the nearby Alameda Island tide gauge were 8 cm higher than predicted due to a regional low-pressure system and warmer than average sea surface temperatures (NOAA National Ocean Service 2014). The approximately 80 cm deep inundation of the marsh plain was sufficient to completely submerge tidal marsh vegetation and effectively remove 90% of refugia habitats.

  16. Assessment of tidal circulation and tidal current asymmetry in the Iroise sea with specific emphasis on characterization of tidal energy resources around the Ushant Island.

    Science.gov (United States)

    Thiébaut, Maxime; Sentchev, Alexei

    2015-04-01

    We use the current velocity time series recorded by High Frequency Radars (HFR) to study circulation in highly energetic tidal basin - the Iroise sea. We focus on the analysis of tidal current pattern around the Ushant Island which is a promising site of tidal energy. The analysis reveals surface current speeds reaching 4 m/s in the North of Ushant Island and in the Fromveur Strait. In these regions 1 m/s is exceeded 60% of time and up to 70% of time in center of Fromveur. This velocity value is particularly interesting because it represents the cut-in-speed of the most of marine turbine devices. Tidal current asymmetry is not always considered in tidal energy site selection. However, this quantity plays an important role in the quantification of hydrokinetic resources. Current velocity times series recorded by HFR highlights the existence of a pronounced asymmetry in current magnitude between the flood and ebb tide ranging from -0.5 to more 2.5. Power output of free-stream devices depends to velocity cubed. Thus a small current asymmetry can generate a significant power output asymmetry. Spatial distribution of asymmetry coefficient shows persistent pattern and fine scale structure which were quantified with high degree of accuracy. The particular asymmetry evolution on both side of Fromveur strait is related to the spatial distribution of the phase lag of the principal semi-diurnal tidal constituent M2 and its higher order harmonics. In Fromveur, the asymmetry is reinforced due to the high velocity magnitude of the sixth-diurnal tidal harmonics. HF radar provides surface velocity speed, however the quantification of hydrokinetic resources has to take into account the decreasing of velocity with depth. In order to highlight this phenomenon, we plot several velocity profiles given by an ADCP which was installed in the HFR study area during the same period. The mean velocity in the water column calculated by using the ADCP data show that it is about 80% of the

  17. Magnetic fields driven by tidal mixing in radiative stars

    Science.gov (United States)

    Vidal, J.; Cébron, D.; Schaeffer, N.; Hollerbach, R.

    2018-01-01

    Stellar magnetism plays an important role in stellar evolution theory. Approximatively 10 % of observed main sequence (MS) and pre-main-sequence (PMS) radiative stars exhibit surface magnetic fields above the detection limit, raising the question of their origin. These stars host outer radiative envelopes, which are stably stratified. Therefore, they are assumed to be motionless in standard models of stellar structure and evolution. We focus on rapidly rotating, radiative stars which may be prone to the tidal instability, due to an orbital companion. Using direct numerical simulations in a sphere, we study the interplay between a stable stratification and the tidal instability, and assess its dynamo capability. We show that the tidal instability is triggered regardless of the strength of the stratification (Brunt-Väisälä frequency). Furthermore, the tidal instability can lead to both mixing and self-induced magnetic fields in stably stratified layers (provided that the Brunt-Väisälä frequency does not exceed the stellar spin rate in the simulations too much). The application to stars suggests that the resulting magnetic fields could be observable at the stellar surfaces. Indeed, we expect magnetic field strengths up to several Gauss. Consequently, tidally driven dynamos should be considered as a (complementary) dynamo mechanism, possibly operating in radiative MS and PMS stars hosting orbital companions. In particular, tidally driven dynamos may explain the observed magnetism of tidally deformed and rapidly rotating Vega-like stars.

  18. Spatial Assessment of a Biocriteria Applied to Texas Tidal Streams

    Directory of Open Access Journals (Sweden)

    James M. Tolan

    2013-01-01

    Full Text Available This study reports on a derived multivariate method for assessing ecosystem health within tidally influenced portions of river basins and coastal basins. These tidally influenced areas are highly productive transitional areas which serve as important nursery areas for many fish and shellfish species. Numerous Texas tidal streams under varying degrees of anthropogenic stressors were analyzed jointly with this new, standardized methodology. Physical and chemical constituents of the tidal systems, as well as their resident nekton communities, were compared with nonparametric ordination techniques in order to uncover a biocriteria that might have general applicability over large spatial scales. All of the tidal stream communities were dominated by only a few taxa that each displays tremendous euryhaline/physiological tolerances, and these abilities allow taxa utilizing tidal streams to adapt to a wide variety of environmental stressors. The absence of any clear connections between degraded water-bodies and any impaired nektonic communities should not automatically be viewed as a constraint inherent to the techniques of the methodology presented, but rather a verification that impaired tidal streams are not that common of an occurrence along the Texas coast, at least not when using nekton communities as the degradation indicator.

  19. Tidal volume and alveolar clearance of insoluble particles.

    Science.gov (United States)

    John, J; Wollmer, P; Dahlbäck, M; Luts, A; Jonson, B

    1994-02-01

    We studied the effect of 3 h of large tidal volume ventilation on alveolar clearance of 0.63-micron fluorescent latex particles in rabbits during pentobarbital anesthesia. After particle deposition, six animals were killed as controls, six were subjected to large tidal volume ventilation with a peak pressure of 27 cmH2O, and six were subjected to conventional ventilation with a peak pressure of 11 cmH2O. Mean tidal volumes were 30.2 +/- 6.1 and 8.4 +/- 1.6 ml/kg in the large tidal volume and conventional groups, respectively. End-expiratory pressure was 2 cmH2O in all groups. Compliance decreased only after large tidal ventilation (P = 0.0036). Compared with controls the conventional ventilation group showed no alveolar clearance, but more particles were clustered within macrophages (P = 0.01). Compared with other groups the large tidal volume group had fewer alveolar particles (P = 0.0005), most of which were single particles. Accordingly, large tidal volumes enhance alveolar particle clearance, which is possibly related to distension-related evacuation of surfactant to proximal airways. Clearance may be due to accelerated motion of the particle-loaded macrophage in response to the fast film motion. Alternatively, single particles embedded in the surfactant film may be dragged by the fast-moving film toward the airways.

  20. Tidal day organic and inorganic material flux of ponds in the Liberty Island freshwater tidal wetland.

    Science.gov (United States)

    Lehman, Peggy W; Mayr, Shawn; Liu, Leji; Tang, Alison

    2015-01-01

    The loss of inorganic and organic material export and habitat produced by freshwater tidal wetlands is hypothesized to be an important contributing factor to the long-term decline in fishery production in San Francisco Estuary. However, due to the absence of freshwater tidal wetlands in the estuary, there is little information on the export of inorganic and organic carbon, nutrient or phytoplankton community biomass and the associated mechanisms. A single-day study was conducted to assess the potential contribution of two small vegetated ponds and one large open-water pond to the inorganic and organic material flux within the freshwater tidal wetland Liberty Island in San Francisco Estuary. The study consisted of an intensive tidal day (25.5 h) sampling program that measured the flux of inorganic and organic material at three ponds using continuous monitoring of flow, chlorophyll a, turbidity and salt combined with discrete measurements of phytoplankton community carbon, total and dissolved organic carbon and nutrient concentration at 1.5 h intervals. Vegetated ponds had greater material concentrations than the open water pond and, despite their small area, contributed up to 81% of the organic and 61% of the inorganic material flux of the wetland. Exchange between ponds was important to wetland flux. The small vegetated pond in the interior of the wetland contributed as much as 72-87% of the total organic carbon and chlorophyll a and 10% of the diatom flux of the wetland. Export of inorganic and organic material from the small vegetated ponds was facilitated by small-scale topography and tidal asymmetry that produced a 40% greater material export on ebb tide. The small vegetated ponds contrasted with the large open water pond, which imported 29-96% of the inorganic and 4-81% of the organic material into the wetland from the adjacent river. This study identified small vegetated ponds as an important source of inorganic and organic material to the wetland and the

  1. A summary of the San Francisco tidal wetlands restoration series

    Directory of Open Access Journals (Sweden)

    Larry R. Brown

    2003-10-01

    Full Text Available The four topical articles of the Tidal Wetlands Restoration Series summarized and synthesized much of what is known about tidal wetlands and tidal wetland restoration in the San Francisco Estuary (hereafter “Estuary”. Despite a substantial amount of available information, major uncertainties remain. A major uncertainty with regard to fishes is the net benefit of restored tidal wetlands relative to other habitats for native fishes in different regions of the Estuary given the presence of numerous invasive alien species. With regard to organic carbon, a major uncertainty is the net benefit of land use change given uncertainty about the quantity and quality of different forms of organic carbon resulting from different land uses. A major challenge is determining the flux of organic carbon from open systems like tidal wetlands. Converting present land uses to tidal wetlands will almost certainly result in increased methylation of mercury at the local scale with associated accumulation of mercury within local food webs. However, it is unclear if such local accumulation is of concern for fish, wildlife or humans at the local scale or if cumulative effects at the regional scale will emerge. Based on available information it is expected that restored tidal wetlands will remain stable once constructed; however, there is uncertainty associated with the available data regarding the balance of sediment accretion, sea-level rise, and sediment erosion. There is also uncertainty regarding the cumulative effect of many tidal restoration projects on sediment supply. The conclusions of the articles highlight the need to adopt a regional and multidisciplinary approach to tidal wetland restoration in the Estuary. The Science Program of the CALFED effort provides an appropriate venue for addressing these issues.

  2. A simple approach to adjust tidal forcing in fjord models

    Science.gov (United States)

    Hjelmervik, Karina; Kristensen, Nils Melsom; Staalstrøm, André; Røed, Lars Petter

    2017-07-01

    To model currents in a fjord accurate tidal forcing is of extreme importance. Due to complex topography with narrow and shallow straits, the tides in the innermost parts of a fjord are both shifted in phase and altered in amplitude compared to the tides in the open water outside the fjord. Commonly, coastal tide information extracted from global or regional models is used on the boundary of the fjord model. Since tides vary over short distances in shallower waters close to the coast, the global and regional tidal forcings are usually too coarse to achieve sufficiently accurate tides in fjords. We present a straightforward method to remedy this problem by simply adjusting the tides to fit the observed tides at the entrance of the fjord. To evaluate the method, we present results from the Oslofjord, Norway. A model for the fjord is first run using raw tidal forcing on its open boundary. By comparing modelled and observed time series of water level at a tidal gauge station close to the open boundary of the model, a factor for the amplitude and a shift in phase are computed. The amplitude factor and the phase shift are then applied to produce adjusted tidal forcing at the open boundary. Next, we rerun the fjord model using the adjusted tidal forcing. The results from the two runs are then compared to independent observations inside the fjord in terms of amplitude and phases of the various tidal components, the total tidal water level, and the depth integrated tidal currents. The results show improvements in the modelled tides in both the outer, and more importantly, the inner parts of the fjord.

  3. Alternative concept for tidal power plant with reservoir restrictions

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Rafael M.; Estefen, Segen F. [Department of Ocean Engineering, COPPE/Federal University of Rio de Janeiro, P.O. Box 68508, 21945-970 Rio de Janeiro, RJ (Brazil)

    2009-04-15

    The Brazilian North and Northeast regions have possibilities on harnessing tidal power, where the greatest tidal amplitudes are to be found. In the 1970s, a barrage constructed in the Bacanga estuary, a civil construction project for reducing the distance between the city of Sao Luis do Maranhao and the port of Itaqui, was planned to be the first Brazilian tidal power plant. The favorable conditions associated with the considerable tidal heights, which can be as much as 6.5 m, made this an ideal place for building a pilot plant. Although, a scheme had been proposed to harness tidal energy in a conventional way with the use of the reservoir, the tidal plant in its original form was not implemented due economic and technical restrictions originated from the turbo generators chosen at that time. This paper presents an alternative concept for tidal power plant when the reservoir presents limitations caused by urban occupation, silting up and deterioration of the original structures. These limitations have been verified following the construction of the Bacanga barrage which led to an alternative proposal for the future installation of a pilot tidal power plant. The power generation possible to be harnessed was simulated through a model for each hour from the water head data, outflow, levels, areas and volumes of the reservoir and estuary. The development of the conceptual project, with the utilization of low-head turbines, a floating platform for the turbines and, particularly, taking into consideration those restrictions to be found at the present time, it can be concluded that Bacanga tidal power plant of is technically viable. (author)

  4. Ocean bowling

    Science.gov (United States)

    Showstack, Randy

    Coach Scott Carpenter, a biology teacher at Lexington High School in Massachusetts, says that “some [students] want to show that they can win on a football field, and some want to show that they know science better than anyone else.”His team of four sophomores and one senior proved their mettle when they won the 1998 National Ocean Science Bowl on April 27.

  5. A computer software system for the generation of global ocean tides including self-gravitation and crustal loading effects

    Science.gov (United States)

    Estes, R. H.

    1977-01-01

    A computer software system is described which computes global numerical solutions of the integro-differential Laplace tidal equations, including dissipation terms and ocean loading and self-gravitation effects, for arbitrary diurnal and semidiurnal tidal constituents. The integration algorithm features a successive approximation scheme for the integro-differential system, with time stepping forward differences in the time variable and central differences in spatial variables. Solutions for M2, S2, N2, K2, K1, O1, P1 tidal constituents neglecting the effects of ocean loading and self-gravitation and a converged M2, solution including ocean loading and self-gravitation effects are presented in the form of cotidal and corange maps.

  6. Joint inversion of satellite-detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone

    Science.gov (United States)

    Grayver, A. V.; Munch, F. D.; Kuvshinov, A. V.; Khan, A.; Sabaka, T. J.; Tøffner-Clausen, L.

    2017-06-01

    We present a new global electrical conductivity model of Earth's mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three-dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic signals results in a model with much improved resolution. Comparison with laboratory-based conductivity profiles shows that obtained models are compatible with a pyrolytic composition and a water content of 0.01 wt % and 0.1 wt % in the upper mantle and transition zone, respectively.

  7. Tidal analysis of data recorded by a superconducting gravimeter

    Directory of Open Access Journals (Sweden)

    F. Palmonari

    1995-06-01

    Full Text Available A superconducting gravimeter was used to monitor the tidal signal for a period of five months. The instrument was placed in a site (Brasimone station, Italy chat-acterized by a low noise level, and was calibrated with a precision of 0.2%. Then tidal analysis on hourly data was performed and the results presented in this paper; amplitudes, gravimetric factors, phase differences for the main tidal waves, M2, S2, N2, 01, Pl, K1, QI, were calculated together with barometric pressure admittance and long term instrumental drift.

  8. Motion of particles near a magnetized tidal charged black hole

    Science.gov (United States)

    Sharif, M.; Kousar, Lubna

    2017-07-01

    This paper is devoted to study the effects of tidal charge on the motion of both neutral as well as charged particles around a magnetized tidal charged black hole. We analyze the innermost stable circular orbits and conditions for escape velocity. In order to discuss stability of orbits, we explore Lyapunov exponent and effective force on the particle. The center of mass energy of the interacting particles is studied in the presence/absence of external magnetic field. We conclude that the external magnetic field as well as tidal charge has a great influence on the particle's motion.

  9. Fortnightly Earth Rotation, Ocean Tides, and Mantle Anelasticity

    Science.gov (United States)

    Ray, Richard D.; Egbert, Gary D.

    2011-01-01

    Sustained accurate measurements of earth rotation are one of the prime goals of Global Geodetic Observing System (GGOS). We here concentrate on the fortnightly (Mf) tidal component of earth-rotation data to obtain new results concerning anelasticity of the mantle at this period. The study comprises three parts: (1) a new determination of the Mf component of polar motion and length-of-day from a multi-decade time series of space-geodetic data; (2) the use of the polar-motion determination as one constraint in the development of a hydrodynamic ocean model of the Mf tide; and (3) the use of these results to place new constraints on mantle anelasticity. Our model of the Mf ocean tide assimilates more than fourteen years of altimeter data from the Topex/Poseidon and Jason-1 satellites. The polar motion data, plus tide-gauge data and independent altimeter data, give useful additional information, with only the polar motion putting constraints on tidal current velocities. The resulting ocean-tide model, plus the dominant elastic body tide, leaves a small residual in observed length-of-day caused by mantle anelasticity. The inferred effective tidal 0 of the anelastic body tide is 90 and is in line with a omega-alpha frequency dependence with alpha in the range 0.2--0.3.

  10. Accuracy Assessment of Recent Global Ocean Tide Models around Antarctica

    Science.gov (United States)

    Lei, J.; Li, F.; Zhang, S.; Ke, H.; Zhang, Q.; Li, W.

    2017-09-01

    Due to the coverage limitation of T/P-series altimeters, the lack of bathymetric data under large ice shelves, and the inaccurate definitions of coastlines and grounding lines, the accuracy of ocean tide models around Antarctica is poorer than those in deep oceans. Using tidal measurements from tide gauges, gravimetric data and GPS records, the accuracy of seven state-of-the-art global ocean tide models (DTU10, EOT11a, GOT4.8, FES2012, FES2014, HAMTIDE12, TPXO8) is assessed, as well as the most widely-used conventional model FES2004. Four regions (Antarctic Peninsula region, Amery ice shelf region, Filchner-Ronne ice shelf region and Ross ice shelf region) are separately reported. The standard deviations of eight main constituents between the selected models are large in polar regions, especially under the big ice shelves, suggesting that the uncertainty in these regions remain large. Comparisons with in situ tidal measurements show that the most accurate model is TPXO8, and all models show worst performance in Weddell sea and Filchner-Ronne ice shelf regions. The accuracy of tidal predictions around Antarctica is gradually improving.

  11. Assessing the potential for measuring Europa's tidal Love number h2 using radar sounder and topographic imager data

    Science.gov (United States)

    Steinbrügge, G.; Schroeder, D. M.; Haynes, M. S.; Hussmann, H.; Grima, C.; Blankenship, D. D.

    2018-01-01

    The tidal Love number h2 is a key geophysical measurement for the characterization of Europa's interior, especially of its outer ice shell if a subsurface ocean is present. We performed numerical simulations to assess the potential for estimating h2 using altimetric measurements with a combination of radar sounding and stereo imaging data. The measurement principle exploits both delay and Doppler information in the radar surface return in combination with topography from a digital terrain model (DTM). The resulting radar range measurements at cross-over locations can be used in combination with radio science Doppler data for an improved trajectory solution and for estimating the h2 Love number. Our simulation results suggest that the absolute accuracy of h2 from the joint analysis of REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface) surface return and EIS (Europa Imaging System) DTM data will be in the range of 0.04-0.17 assuming full radio link coverage. The error is controlled by the SNR budget and DTM quality, both dependent on the surface properties of Europa. We estimate that this would unambiguously confirm (or reject) the global ocean hypothesis and, in combination with a nominal radio-science based measurement of the tidal Love number k2, constrain the thickness of Europa's outer ice shell to up to ±15 km.

  12. Plant growth under salinity and inundation stress: implications for sea-level rise on tidal wetland function

    Science.gov (United States)

    Climate change and sea-level rise (SLR) may increase salinity or inundation duration for tidal wetland organisms. To test the effects of these stressors on wetland productivity, we transplanted seedlings of seven common plant species to polyhaline, mesohaline and oligohaline tida...

  13. Analysis of Tidal Data for Dagang Tidal Gauge and Study of the Changes for the National Height Datum

    Directory of Open Access Journals (Sweden)

    WU Fumei

    2015-07-01

    Full Text Available The main tides affecting Dagang sea level are analyzed and the national height datum is studied by analyzing 1980—2011 hourly tidal data and 1952—2007 monthly mean tidal data. Firstly, the frequencies and amplitudes of main tides including 180 short-period tides and 6 long-period tides are gained by the Fouirer transform. Then the actual amplitudes and their variations of main tides are obtained by the harmonic analysis of the 1980—2011 hourly tidal data, and the changes with about 19 year period can easily be found in the amplitudes of Q1、O1、M2、K1、K2. And then the changes of the mean sea level at Dagang tidal gauge defining national height datum during the period of 1952—2011 are studied by the harmonic analysis and the shifting average of 18.61 year tidal heights. The results of these methods show that the mean sea level at Dagang tidal gauge descended with the speed of 1.07 mm/a and 0.76 mm/a respectively during 1952—1980, and that it ascended with the speed of 1.59 mm/a and 1.62 mm/a respectively during 1980—2011. And finally the difference of 0.14 cm is achieved by the shifting average of 18.61 year tidal heights for 1985 National Height Datum.

  14. Scales of Marine Turbulence in Cook Strait (New Zealand) in the Context of Tidal Energy Turbines

    Science.gov (United States)

    Stevens, Craig

    2017-04-01

    Cook Strait, the channel separating New Zealand's North and South Islands, is at it's narrowest around 22 km across with flows driven by a semidiurnal tide, wind and a baroclinic pressure gradient. Water depths are around 250-300 m in the main part of the channel, with shoals to the south and the submerged Fishermans Rock (aka pinnacle) in the centre northwest of the Strait. The substantial tidal flow speed is due to the tide being nearly out of phase comparing the ends of the strait and further enhanced by a narrowing of the strait. It has significant potential for a tidal energy resource suitable for extraction due to both its significant energy levels but also its proximity to electricity infrastructure and nationally high uptake of renewable energy in general. Here we describe recent flow and turbulence data and contextualise them in terms of scales relevant to marine energy extraction. With flow speeds reaching 3 m s-1 in a water column of > 200 m depth the setting is heuristically known to be highly turbulent. Turbulent energy dissipation rates are modest but high for oceans, around 5x10-5 W kg-1. Thorpe scales, the observed quantity representing the energy-bearing scale, are often as much as one quarter of the water depth. This means eddy sizes can potentially be larger than blade length. A boundary-layer structure was apparent but highly variable. This has implications for both operation of tidal turbines, as well as modulating their effect on the environment. Fishermans Rock itself is interesting as if can be considered a proxy for a larger array of turbines.

  15. Effect of the tiger stripes on the tidal deformation of Enceladus

    Science.gov (United States)

    Soucek, Ondrej; Hron, Jaroslav; Behounkova, Marie; Cadek, Ondrej

    2016-10-01

    The south polar region of Saturn's moon Enceladus has been subjected to a thorough scientific scrutiny since the Cassini mission discovery of an enigmatic system of fractures informally known as "tiger stripes". This fault system is possibly connected to the internal water ocean and exhibits a striking geological activity manifesting itself in the form of active water geysers on the moon's surface.The effect of the faults on periodic tidal deformation of the moon has so far been neglected because of the difficulties associated with the implementation of fractures in continuum mechanics models. Employing an open source finite element FEniCS package, we provide a numerical estimate of the maximum possible impact of the tiger stripes on the tidal deformation and the heat production in Enceladus's ice shell by representing the faults as narrow zones with negligible frictional and bulk resistance passing vertically through the whole shell.For a uniform ice shell thickness of 25 km, consistent with the recent estimate of libration, and for linear elastic rheology, we demonstrate that the faults can dramatically change the distribution of stress and strain in Enceladus's south polar region, leading to a significant increase of the heat flux and to a complex deformation pattern in this area. We also present preliminary results studying the effects of (i) variable ice-shell thickness, based on the recent topography, gravity and libration inversion model by Čadek et al. (2016) and (ii) Maxwell viscoelastic rheology on the global tidal deformation of the ice shell.O.S. acknowledges support by the Grant Agency of the Czech Republic through the project 15-14263Y.

  16. Optical dating of young tidal sediments in the Danish Wadden Sea

    DEFF Research Database (Denmark)

    Madsen, Anni Tindahl; Murray, A. S.; Andersen, Thorbjørn Joest

    2007-01-01

     We have tested the applicability of optically stimulated luminescence (OSL) to the dating of young estuarine sediments (210Pb dating. The degree of bleaching before deposition...... is investigated by examining the age trend in various sediment cores, and where possible, by comparison with independent age control provided by 210Pb dating. The consistency between optical ages and 210Pb ages is shown to be satisfactory on a time-scale down to only a few years. We conclude that OSL provides...... reliable and reproducible results in cores from sub-, inter- and supra-tidal sediments, ranging from only a few years up to ~1000 years old, confirming its value in the estimation of estuarine accretion rates. With OSL it is, for the first time, possible to date sediment cores from silty and sandy tidal...

  17. Decomposition of plant litter in Pacific coast tidal marshes, 2014-2015

    Science.gov (United States)

    Janousek, Christopher; Buffington, Kevin J.; Guntenspergen, Glenn R.; Thorne, Karen M.; Dugger, Bruce D.; Takekawa, John Y.

    2017-01-01

    Decomposition of plant matter is one of the key processes affecting carbon cycling and storage in tidal wetlands. In this study, we evaluated the effects of factors related to climate change (temperature, inundation) and vegetation composition on rates of litter decay in seven tidal marsh sites along the Pacific coast. In 2014 we conducted manipulative experiments to test inundation effects on litter decay at Siletz Bay, OR and Petaluma marsh, CA. In 2015 we studied decay of litter in high and low elevation marshes at seven Pacific coast sites.These data support the following publication: Janousek, C.N., Buffington, K.J., Guntenspergen, G.R. et al. Ecosystems (2017). doi:10.1007/s10021-017-0111-6. http://link.springer.com/article/10.1007/s10021-017-0111-6

  18. Numerical Simulation of Admiralty Inlet, WA, with Tidal Hydrokinetic Turbine Siting Application

    Science.gov (United States)

    Thyng, Kristen M.

    Tidal hydrokinetic energy has been recognized as a potential source of sustainable, renewable energy. In order to properly site turbines for commercial-scale development, the complex flow conditions in a potential deployment region must be understood. Viable locations for turbines are limited by many factors, including underwater space that is above the bottom boundary layer, below shipping traffic, within areas of strong currents, and yet avoids additional fatiguing stresses. The primary area of interest in the Puget Sound for commercial tidal energy development is Admiralty Inlet, which includes potentially disruptive flow features such as vortices and strong turbulence. This dissertation seeks to increase the body of knowledge of these features both from an oceanographic perspective and as they pertain to turbine site characterization. The primary means of studying Admiralty Inlet in this document is through numerical simulation of the region using the Regional Ocean Modeling System (ROMS). The model output is found to compare well with field data, capturing eddy fields, turbulence properties, relative tidal phases, and illuminating many flow features. Horizontal velocities in the simulation are, on average, approximately 75% the size of those found in the data. This speed deficiency is inherited from the forcing model in which the Admiralty Inlet simulation is nested. The model output also shows that the flow field of this fjord-like estuary is largely affected by a headland on the northeast side of the Inlet. Vortices generated by this headland, Admiralty Head, are found to vary considerably depending on the tidal cycle. The eddies can persist beyond the half-cycle of generation to significantly affect the horizontal speed and other flow field properties in the subsequent half-cycle. Detailed analysis of the vertical vorticity governing equation shows that advection, tilting, stretching, and boundary generation are the most significant processes dictating the

  19. The Effects of the Impedance of the Flow Source on the Design of Tidal Stream Generators

    Science.gov (United States)

    Salter, S.

    2011-12-01

    The maximum performance of a wind turbine is set by the well-known Betz limit. If the designer of a wind turbine uses too fast a rotation, too large a blade chord or too high an angle of blade pitch, the air flow can take an easier path over or around the rotor. Most estimates of the tidal stream resource use equations borrowed from wind and would be reasonably accurate for a single unit. But water cannot flow through the seabed or over rotors which reach to the surface. If contra-rotating, vertical-axis turbines with a rectangular flow-window are placed close to one another and reach from the surface close to the seabed, the leakage path is blocked and they become more like turbines in a closed duct. Instead of an equation with area times velocity-cubed we should use the first power of volume flow rate though the rotor times the pressure difference across it. A long channel with a rough bed will already be losing lots of energy and will behave more like a high impedance flow. Attempts to block it with closely-packed turbines will increase the head across the turbines with only a small effect on flow rate. The same thing will occur if a close-packed line of turbines is built out to sea from a headland. It is necessary to understand the impedance of the flow source all the way out to mid-ocean. In deep seas where the current velocities at the seabed are too slow to disturb the ooze the friction coefficients will be similar to those of gloss paint, perhaps 0.0025. But the higher velocities in shallow water will remove ooze and quite large sediments leaving rough, bare rock and leading to higher friction-coefficients. Energy dissipation will be set by the higher friction coefficients and the cube of the higher velocities. The presence of turbines will reduce seabed losses and about one third of the present loss can be converted to electricity. The velocity reduction would be about 10%. In many sites the energy output will be far higher than the wind turbine equations

  20. Linking freshwater tidal hydrology to carbon cycling in bottomland hardwood wetlands

    Science.gov (United States)

    Carl C. Trettin; Brooke J. Czwartacki; Craig J. Allan; Devendra M. Amatya

    2016-01-01

    Hydrology is recognized as one of the principal factors regulating soil biogeochemical processes in forested wetlands. However, the consequences of tidally mediated hydrology are seldom considered within forested wetlands that occur along tidal water bodies. These tidal water bodies may be either fresh or brackish, and the tidal streams function as a reservoir to...