SPREADING OF ANTARCTIC BOTTOM WATER IN THE ATLANTIC OCEAN

Directory of Open Access Journals (Sweden)

Eugene Morozov

2012-01-01

Full Text Available This paper describes the transport of bottom water from its source region in the Weddell Sea through the abyssal channels of the Atlantic Ocean. The research brings together the recent observations and historical data. A strong flow of Antarctic Bottom Water through the Vema Channel is analyzed. The mean speed of the flow is 30 cm/s. A temperature increase was found in the deep Vema Channel, which has been observed for 30 years already. The flow of bottom water in the northern part of the Brazil Basin splits. Part of the water flows through the Romanche and Chain fracture zones. The other part flows to the North American Basin. Part of the latter flow propagates through the Vema Fracture Zone into the Northeast Atlantic. The properties of bottom water in the Kane Gap and Discovery Gap are also analyzed.

A perfectly matched layer for fluid-solid problems: Application to ocean-acoustics simulations with solid ocean bottoms

DEFF Research Database (Denmark)

Xie, Zhinan; Matzen, René; Cristini, Paul

2016-01-01

A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range-dependent a......A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range......-dependent and depth-dependent wave speed and density, as well as steep ocean floor topography. For truncation of the infinite domain, to efficiently absorb outgoing waves, a fluid-solid complex-frequency-shifted unsplit perfectly matched layer is introduced based on the complex coordinate stretching technique....... The complex stretching is rigorously taken into account in the derivation of the fluid-solid matching condition inside the absorbing layer, which has never been done before in the time domain. Two implementations are designed: a convolutional formulation and an auxiliary differential equation formulation...

Distribution of 137Cs in samples of ocean bottom sediments of the baltic sea in 1982-1983

International Nuclear Information System (INIS)

Gedenov, L.I.; Flegontov, V.M.; Ivanova, L.M.; Kostandov, K.A.

1986-01-01

The concentration of Cs-137 in samples of ocean bottom sediments picked up in 1979 in the Gulf of Finland with a geological nozzle pipe varied within a wide interval of values. The results could indicate nonuniformity of the Cs-137 distribution in ocean bottom sediments as well as the penetration of significant amounts of Cs-137 to large depths. The main error resulted from the sampling technique employed because the upper part of the sediment could be lost. In 1982, a special ground-sampling device, with which the upper layer of sediments in the water layer close to the ocean bottom could be sampled, was tested in the Gulf of Finland and the Northeastern part of the Baltic Sea. The results of a layerwise determination of the Cs-137 concentration in samples of ocean bottom sediments of the Gulf of Finland and of the Baltic Sea are listed. The new soil-sampling device for picking samples of ocean sediments of undisturbed stratification will allow a correct determination of the radionuclide accumulation in the upper layers of ocean bottom sediments in the Baltic Sea

Ocean Bottom Deformation Due To Present-Day Mass Redistribution and Its Impact on Sea Level Observations

Science.gov (United States)

Frederikse, Thomas; Riva, Riccardo E. M.; King, Matt A.

2017-12-01

Present-day mass redistribution increases the total ocean mass and, on average, causes the ocean bottom to subside elastically. Therefore, barystatic sea level rise is larger than the resulting global mean geocentric sea level rise, observed by satellite altimetry and GPS-corrected tide gauges. We use realistic estimates of mass redistribution from ice mass loss and land water storage to quantify the resulting ocean bottom deformation and its effect on global and regional ocean volume change estimates. Over 1993-2014, the resulting globally averaged geocentric sea level change is 8% smaller than the barystatic contribution. Over the altimetry domain, the difference is about 5%, and due to this effect, barystatic sea level rise will be underestimated by more than 0.1 mm/yr over 1993-2014. Regional differences are often larger: up to 1 mm/yr over the Arctic Ocean and 0.4 mm/yr in the South Pacific. Ocean bottom deformation should be considered when regional sea level changes are observed in a geocentric reference frame.

14 CFR 25.533 - Hull and main float bottom pressures.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float bottom pressures. 25... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Water Loads § 25.533 Hull and main float bottom pressures. (a) General. The hull and main float structure, including frames and bulkheads...

A non-hydrostatic flat-bottom ocean model entirely based on Fourier expansion

Science.gov (United States)

Wirth, A.

2005-01-01

We show how to implement free-slip and no-slip boundary conditions in a three dimensional Boussinesq flat-bottom ocean model based on Fourier expansion. Our method is inspired by the immersed or virtual boundary technique in which the effect of boundaries on the flow field is modeled by a virtual force field. Our method, however, explicitly depletes the velocity on the boundary induced by the pressure, while at the same time respecting the incompressibility of the flow field. Spurious spatial oscillations remain at a negligible level in the simulated flow field when using our technique and no filtering of the flow field is necessary. We furthermore show that by using the method presented here the residual velocities at the boundaries are easily reduced to a negligible value. This stands in contradistinction to previous calculations using the immersed or virtual boundary technique. The efficiency is demonstrated by simulating a Rayleigh impulsive flow, for which the time evolution of the simulated flow is compared to an analytic solution, and a three dimensional Boussinesq simulation of ocean convection. The second instance is taken form a well studied oceanographic context: A free slip boundary condition is applied on the upper surface, the modeled sea surface, and a no-slip boundary condition to the lower boundary, the modeled ocean floor. Convergence properties of the method are investigated by solving a two dimensional stationary problem at different spatial resolutions. The work presented here is restricted to a flat ocean floor. Extensions of our method to ocean models with a realistic topography are discussed.

14 CFR 23.533 - Hull and main float bottom pressures.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float bottom pressures. 23... Water Loads § 23.533 Hull and main float bottom pressures. (a) General. The hull and main float....00213; K2=hull station weighing factor, in accordance with figure 2 of appendix I of this part; VS1...

Microbial diversity from chlorophyll maximum, oxygen minimum and bottom zones in the southwestern Atlantic Ocean

Science.gov (United States)

Medina-Silva, Renata; de Oliveira, Rafael R.; Pivel, Maria A. G.; Borges, Luiz G. A.; Simão, Taiz L. L.; Pereira, Leandro M.; Trindade, Fernanda J.; Augustin, Adolpho H.; Valdez, Fernanda P.; Eizirik, Eduardo; Utz, Laura R. P.; Groposo, Claudia; Miller, Dennis J.; Viana, Adriano R.; Ketzer, João M. M.; Giongo, Adriana

2018-02-01

Conspicuous physicochemical vertical stratification in the deep sea is one of the main forces driving microbial diversity in the oceans. Oxygen and sunlight availability are key factors promoting microbial diversity throughout the water column. Ocean currents also play a major role in the physicochemical stratification, carrying oxygen down to deeper zones as well as moving deeper water masses up towards shallower depths. Water samples within a 50-km radius in a pockmark location of the southwestern Atlantic Ocean were collected and the prokaryotic communities from different water depths - chlorophyll maximum, oxygen minimum and deep-sea bottom (down to 1355 m) - were described. At phylum level, Proteobacteria were the most frequent in all water depths, Cyanobacteria were statistically more frequent in chlorophyll maximum zone, while Thaumarchaeota were significantly more abundant in both oxygen minimum and bottom waters. The most frequent microorganism in the chlorophyll maximum and oxygen minimum zones was a Pelagibacteraceae operational taxonomic unit (OTU). At the bottom, the most abundant genus was the archaeon Nitrosopumilus. Beta diversity analysis of the 16S rRNA gene sequencing data uncovered in this study shows high spatial heterogeneity among water zones communities. Our data brings important contribution for the characterisation of oceanic microbial diversity, as it consists of the first description of prokaryotic communities occurring in different oceanic water zones in the southwestern Atlantic Ocean.

Ocean Bottom Seismometers technology: current state and future outlook

Science.gov (United States)

Ilinskiy, Dmitry; Ganzha, Oleg

2016-04-01

The beginning of 2000s was marked by a significant progress in the development and use of self-pop-up sea-bottom seismic recorders (Ocean Bottom Seismometers). In Russia it was a novel solution developed by the Russian Academy of Sciences Experimental Design Bureau of Oceanological Engineering. This recorder and its clones have been widely used not only for the Earth crust studies, but also for investigations of sub-basalt structures and gas hydrate exploration. And what has happened over the last 10 years? Let us look closely at the second generation of ocean bottom stations developed by Geonodal Solutions (GNS) as an illustration of the next step forward in the sea-bottom acquisition technology. First of all, hardware components have changed dramatically. The electronic components became much smaller, accordingly, the power consumption and electronic self-noise were dropped down significantly. This enabled development of compact station 330 mm in diameter instead of previous 450mm. The weight fell by half, while the autonomy increased up to 90 days due to both decreased energy consumption and increased capacity of the batteries. The dynamic range of recorded seismic data has expended as a result of decreased set noise and the application of 24-bit A/D converters. The instruments dimensions have been reduced, power consumption decreased, clock accuracy was significantly improved. At the same time, development of advanced time reference algorithms enabled to retain instrument accuracy around 1 ms during all the autonomous recording period. The high-speed wireless data transfer technology offered a chance to develop "maintenance-free" station throughout its operation time. The station can be re-used at the different sea bottom locations without unsealing of the deep-water container for data download, battery re-charge, clock synchronization. This noticeably reduces the labor efforts of the personnel working with the stations. This is critically important in field

Improved estimation of geocenter motion and changes in the Earth's dynamic oblateness from GRACE data and an ocean bottom pressure model

Science.gov (United States)

Sun, Y.; Ditmar, P.; Riva, R.

2015-12-01

The Gravity Recovery and Climate Experiment (GRACE) satellite mission, since the launch in 2002, has enabled the monitoring of mass transport in the Earth's system on a monthly basis. In spite of continuous improvements in data processing techniques, an estimation of very low-degree spherical harmonic coefficients remains problematic. GRACE is insensitive to variations in the degree-1 coefficients (ΔC11, ΔS11 and ΔC10), which reflect the motion of the geocenter. The variations of C20 coefficients, which characterize changes in the Earth's dynamic oblateness (Δ J2) are corrupted by ocean tide aliases and usually replaced with estimates from other techniques.In this study, the methodology proposed by Swenson et al. (2008) to estimate geocenter motion is updated and extended to co-estimate changes in the Earth's dynamic oblateness. The algorithm uses monthly GRACE gravity solutions (in the form of spherical harmonic coefficients), an ocean bottom pressure model (over the oceans), and a glacial isostatic adjustment (GIA) model (globally). GRACE solutions over coastal areas may suffer from signal leakage due to their limited spectral content and to filtering. We effectively avoid the influence of this effect by introducing a carefully chosen buffer zone. We also take into account self-attraction and loading effects when dealing with water redistribution in the oceans. The estimated annual amplitude of ΔC10 , i.e. the Z component of the geocenter motion, is significantly amplified compared to the original estimations of Swenson et al. (2008) and it is in line with estimates from other techniques, such as the global GPS inversion. The resulting ΔC20 time-series agree remarkably well with a solution based on satellite laser ranging data, which is currently believed to be one of the most accurate sources of information on changes in the Earth's dynamic oblateness. Trends in both geocenter position and the Earth's oblateness are estimated as well. The results show a

Ocean Bottom Pressure Seasonal Cycles and Decadal Trends from GRACE Release-05: Ocean Circulation Implications

Science.gov (United States)

Johnson, G. C.; Chambers, D. P.

2013-12-01

Ocean mass variations are important for diagnosing sea level budgets, the hydrological cycle and global energy budget, as well as ocean circulation variability. Here seasonal cycles and decadal trends of ocean mass from January 2003 to December 2012, both global and regional, are analyzed using GRACE Release 05 data. The trend of global flux of mass into the ocean approaches 2 cm decade-1 in equivalent sea level rise. Regional trends are of similar magnitude, with the North Pacific, South Atlantic, and South Indian oceans generally gaining mass and other regions losing mass. These trends suggest a spin-down of the North Pacific western boundary current extension and the Antarctic Circumpolar Current in the South Atlantic and South Indian oceans. The global average seasonal cycle of ocean mass is about 1 cm in amplitude, with a maximum in early October and volume fluxes in and out of the ocean reaching 0.5 Sv (1 Sv = 1 × 106 m3 s-1) when integrated over the area analyzed here. Regional patterns of seasonal ocean mass change have typical amplitudes of 1-4 cm, and include maxima in the subtropics and minima in the subpolar regions in hemispheric winters. The subtropical mass gains and subpolar mass losses in the winter spin up both subtropical and subpolar gyres, hence the western boundary current extensions. Seasonal variations in these currents are order 10 Sv, but since the associated depth-averaged current variations are only order 0.1 cm s-1, they would be difficult to detect using in situ oceanographic instruments. a) Amplitude (colors, in cm) and b) phase (colors, in months of the year) of an annual harmonic fit to monthly GRACE Release 05 CSR 500 km smoothed maps (concurrently with a trend and the semiannual harmonic). The 97.5% confidence interval for difference from zero is also indicated (solid black line). Data within 300 km of coastlines are not considered.

Temperature correction and usefulness of ocean bottom pressure data from cabled seafloor observatories around Japan for analyses of tsunamis, ocean tides, and low-frequency geophysical phenomena

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Inazu, D.; Hino, R.

2011-11-01

Ocean bottom pressure (OBP) data obtained by cabled seafloor observatories deployed around Japan, are known to be significantly affected by temperature changes. This paper examines the relationship between the OBP and temperature records of six OBP gauges in terms of a regression coefficient and lag at a wide range of frequencies. No significant temperature dependency is recognized in secular variations, while substantial increases, at rates of the order of 1 hPa/year, are commonly evident in the OBP records. Strong temperature dependencies are apparent for periods of hours to days, and we correct the OBP data based on the estimated OBP-temperature relationship. At periods longer than days, the temperature corrections work well for extracting geophysical signals for OBP data at a station off Hokkaido (KPG2), while other corrected data show insufficient signal-to-noise ratios. At a tsunami frequency, the correction can reduce OBP fluctuations, due to rapid temperature changes, by as much as millimeters, and is especially effective for data at a station off Shikoku (MPG2) at which rapid temperature changes most frequently occur. A tidal analysis shows that OBP data at a station off Honshu (TM1), and at KPG2, are useful for studies on the long-term variations of tidal constituents.

An analytical evaluation for the pressure drop characteristics of bottom nozzle flow holes

International Nuclear Information System (INIS)

Yang, S. G.; Kim, H. J.; Lim, H. T.; Park, E. J.; Jeon, K. L.

2002-01-01

An analytical evaluation for the bottom nozzle flow holes was performed to find a best design concept in terms of pressure drop. For this analysis, Computational Fluid Dynamics (CFD), FLUENT 5.5, code was selected as an analytical evaluation tool. The applicability of CFD code was verified by benchmarking study with Vibration Investigation of Small-scale Test Assemblies (VISTA) test data in several flow conditions and typical flow hole shape. From this verification, the analytical data were benchmarked roughly within 17% to the VISTA test data. And, overall trend under various flow conditions looked very similar between both cases. Based on the evaluated results using CFD code, it is concluded that the deburring and multiple chamfer hole features at leading edge are the excellent design concept to decrease pressure drop across bottom nozzle plate. The deburring and multiple chamfer hole features at leading edge on the bottom nozzle plate have 12% and 17% pressure drop benefit against a single chamfer hole feature on the bottom nozzle plate, respectively. These design features are meaningful and applicable as a low pressure drop design concept of bottom nozzle for Pressurized Water Reactor (PWR) fuel assembly

Bottom Pressure Tides Along a Line in the Southeast Atlantic Ocean and Comparisons with Satellite Altimetry

Science.gov (United States)

Ray, Richard D.; Byrne, Deidre A.

2010-01-01

Seafloor pressure records, collected at 11 stations aligned along a single ground track of the Topex/Poseidon and Jason satellites, are analyzed for their tidal content. With very low background noise levels and approximately 27 months of high-quality records, tidal constituents can be estimated with unusually high precision. This includes many high-frequency lines up through the seventh-diurnal band. The station deployment provides a unique opportunity to compare with tides estimated from satellite altimetry, point by point along the satellite track, in a region of moderately high mesoscale variability. That variability can significantly corrupt altimeter-based tide estimates, even with 17 years of data. A method to improve the along-track altimeter estimates by correcting the data for nontidal variability is found to yield much better agreement with the bottom-pressure data. The technique should prove useful in certain demanding applications, such as altimetric studies of internal tides.

Characterizing the Seismic Ocean Bottom Environment of the Bransfield Strait

Science.gov (United States)

Washington, B.; Lekic, V.; Schmerr, N. C.

2017-12-01

Ocean bottom seismometers record ground motions that result from earthquakes, anthropogenic sound sources (e.g. propellers, air gun sources, etc.), ocean waves and currents, biological activity, as well as surface processes on the sea and coastal land. Over a two-week span in April, 2001 - the Austral late fall -ten stations arranged in eleven lines were deployed beneath the Bransfield Strait along the Antarctica Peninsula to passively record data before and after an active source seismic survey. The goal of this study is to understand ocean bottom seismicity, identify centers of seismic activity and characterize possible glaciological mechanisms of icequakes and tremors. The instruments were sampled at 200Hz, allowing signals of ice-quakes, small earthquakes, and other high frequency sources to be detected and located. By visualizing the data as spectrograms, we identify and document ground vibrations excited by local earthquakes, whale songs, and those potentially due to surface processes, such as the cracking and movement of icebergs or ice shelves, including possible harmonic tremors from the ice or the volcanic arc nearby. Using relative timing of P-wave arrivals, we locate the hypocenters of nearby earthquakes and icequakes, and present frequency-dependent polarization analysis of their waveforms. Marine mammal sounds were detected in a substantial part of the overall acoustic environment-late March and Early April are the best months to hear whales such as humpback, sperm and orca communicating amongst each other because they are drawn to the cold, nutrient-rich Antarctic waters. We detect whales communicating for several hours in the dataset. Other extensively recorded sources resemble harmonic tremors, and we also identify signals possibly associated with waves set up on the notoriously stormy seas.

Near real-time noise removal for the Monterey Ocean Bottom Broadband (MOBB) seismic station data

Science.gov (United States)

Guinois, M.; Zheng, Z.; Taira, T.; Romanowicz, B. A.

2012-12-01

The Monterey Ocean Bottom Broadband (MOBB) observatory, located 40 km offshore central California, at a water depth of 1000 m, provides important complementary coverage of the San Andreas Fualt system to the land-based network. First installed in 2002, it is arguably the longest lived ocean bottom broadband seismic station. It includes a three-component broadband Guralp CMG-1T seismometer and a collocated differential pressure gauge (DPG) to measure the local water pressure continuously, as well as a current meter. After 7 years of autonomous operation, in February 2009, MOBB was successfully connected to the MARS cable (http://www.mbari.org/mars), and the data have been available in real time at the Northern California Earthquake Data Center (Romanowicz et al., 2009). However, the usage of MOBB data has been limited because of the noisy character of the data, in particular at periods of interest for regional moment tensor studies (20-100 sec), due to the ocean infragravity waves. Crawford and Webb (2000) demonstrated that there is a strong correlation between the water pressure and the vertical component of seafloor ground velocity in the infragravity wave band. Applying this to MOBB vertical component data, a transfer function (TF) was determined and utilized to successfully deconvolve the pressure-correlated noise from the vertical component of MOBB seismograms (Dolenc et al., 2007) in the period band 20-200 sec. Romanowicz et al. (2003, 2009) presented examples of how the cleaned MOBB data contribute to the determination of source parameters and regional structure. These past efforts, however, have been mostly case studies for illustration purpose. In this study, we systematically process all the available MOBB data since 2009 (because the cable was trawled, about a year of data is missing from February 2010 to June 2011). We calculate the TF over time and find that it is generally very stable, except for one change in 2010 due to an instrument replacement. Two

High-frequency bottom-pressure and acoustic variations in a sea strait: internal wave turbulence

NARCIS (Netherlands)

van Haren, H.

2012-01-01

During a period of 3 days, an accurate bottom-pressure sensor and a four-beam acoustic Doppler current profiler (ADCP) were mounted in a bottom frame at 23 m in a narrow sea strait with dominant near-rectilinear tidal currents exceeding 1 m s(-1) in magnitude. The pressure record distinguishes small

Transport of Antarctic bottom water through the Kane Gap, tropical NE Atlantic Ocean

NARCIS (Netherlands)

Morozov, E.G.; Tarakanov, R.Y.; van Haren, H.

2013-01-01

We study low-frequency properties of the Antarctic Bottom Water (AABW) flow through the Kane Gap (9° N) in the Atlantic Ocean. The measurements in the Kane Gap include five visits with CTD (Conductivity-Temperature-Depth) sections in 2009–2012 and a year-long record of currents on a mooring using

Application of ocean bottom cable as a new tool in offshore 3-D ...

African Journals Online (AJOL)

Application of ocean bottom cable as a new tool in offshore 3-D seismic data acquisition. CC Ugbor, KM Onuoha, LI Mamah. Abstract. No Abstract. Journal of Mining and Geology Vol. 43 (1) 2007: pp. 63-69. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Excess bottom radon 222 distribution in deep ocean passages

International Nuclear Information System (INIS)

Sarmiento, J.L.; Broecker, W.S.; Biscaye, P.E.

1978-01-01

Radon 222 and STD profiles were obtained as part of the Geosecs program in the Vema Channel in the southwest Atlantic Ocean and in the Samoan, Clarion, and Wake Island passages in the Pacific Ocean. The standing crop of excess radon 222 is higher in the passages than at other nearby locations. The most likely explanation for this is that there is a high flux of radon 222 from the floor of the passages. Since much of the floor is covered with manganese nodules and encrustations, the high flux of radon 222 may be attributable to the high concentrations of radium 226 in the outer few millimeters of such deposits. Laboratory measurements of radon 222 emissivity from maganese encrustations obtained in Vema Channel support this hypothesis. The excess radon 222 in the Vema Channel and Wake Island Passage is found in substantial quantities at heights above bottom greatly exceeding the heights at which excess radon 222 is found in nonpassage areas. The horizontal diffusion of radon emanating from the walls of the passages is unlikely to be the cause of the observed concentrations because the ratio of wall surface area to water volume is very low. The profiles must therefore be a result of exceptionally high apparent vertical mixing in the passages. Further work is needed to determine the nature of this apparent vertical mixing. The excess radon 222 and STD data in all four passages have been fit with an empirical model in which it is assumed that the bouyancy flux is constant with distance above bottom. The fits are very good and yield apparent buoyancy fluxes that are between 1 and 3 orders of magnitude greater than those obtained at nearby stations outside the passages for three of the four passages

Possible Significance of Early Paleozoic Fluctuations in Bottom Current Intensity, Northwest Iapetus Ocean

Science.gov (United States)

Lash, Gary G.

1986-06-01

Sedimentologic and geochemical characteristics of red and green deep water mudstone exposed in the central Appalachian orogen define climatically-induced fluctuations in bottom current intensity along the northwest flank of the Iapetus Ocean in Early and Middle Ordovician time. Red mudstone accumulated under the influence of moderate to vigorous bottom current velocities in oxygenated bottom water produced during climatically cool periods. Interbedded green mudstone accumulated at greater sedimentation rates, probably from turbidity currents, under the influence of reduced thermohaline circulation during global warming periods. The close association of green mudstone and carbonate turbidites of Early Ordovician (late Tremadocian to early Arenigian) age suggests that a major warming phase occurred at this time. Increasing temperatures reduced bottom current velocities and resulted in increased production of carbonate sediment and organic carbon on the carbonate platform of eastern North America. Much of the excess carbonate sediment and organic carbon was transported into deep water by turbidity currents. Although conclusive evidence is lacking, this eustatic event may reflect a climatic warming phase that followed the postulated glacio-eustatic Black Mountain event. Subsequent Middle Ordovician fluctuations in bottom current intensity recorded by thin red-green mudstone couplets probably reflect periodic growth and shrinkage of an ice cap rather than major glacial episodes.

Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean.

Science.gov (United States)

Menezes, Viviane V; Macdonald, Alison M; Schatzman, Courtney

2017-01-01

Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade -1 ), warmer (0.06° ± 0.01°C decade -1 ), and less dense (0.011 ± 0.002 kg/m 3 decade -1 ). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade -1 ) compared to the 0.002 ± 0.001 kg/g decade -1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.

Spatiotemporal distribution of interplate slip following the 2003 Tokachi-oki earthquake deduced from ocean bottom pressure gauges and onland GNSS data

Science.gov (United States)

Itoh, Y.; Nishimura, T.; Ariyoshi, K.; Matsumoto, H.

2017-12-01

The 2003 Tokachi-oki earthquake (Mw 8.0) is an interplate earthquake along the Kurile trench. Its co- and post-seismic deformation has been observed by onland GNSS [e.g., Miyazaki et al. 2004] and modeled with afterslip and/or viscoelastic relaxation [e.g., Itoh and Nishimura 2016]. In the offshore region, two ocean bottom pressure gauges (OBPs) are operated by JAMSTEC since July 1999 [Hirata et al. 2002] and they have continuously observed the pre-, co- and post-seismic pressure change of the 2003 event [Baba et al. 2006]. The observed pressure change can be interpreted as vertical displacement, and the resolution of slip beneath the seafloor far from the land was improved by incorporating these pressure data into onland GNSS data [Baba et al. 2006]. However, no previous studies used postseismic pressure data for several years to estimate an interplate slip. Because, in this region, an M8 class event similar to the 2003 event has occurred in 1952, it is important to clarify a healing process of an interplate coupling which may lead to a next M8 class event in terms of the earthquake cycle. Itoh and Nishimura [2017, JpGU-AGU Joint Meeting] estimated it but used only onland GNSS data. In this study, we use both onland GNSS and OBP data. For OBP data analysis, we first removed the tidal component using BAYTAP08 [Tamura et al. 1991; Tamura and Agnew 2008]. Next, we corrected the temporal fluctuation of data correlating with temperature [Baba et al. 2006]. We estimated the linear trend before the 2003 event using the corrected time series from 2002 Jan. 1 to 2003 Sep. 1 and remove the estimated trend from the data after the 2003 event. Here, we assumed a non-linear drift could be ignored. Finally, we down-sampled the remained time series with an interval of 1 month. For the onland GNSS data, we used the same data set of Itoh and Nishimura [2017, JpGU-AGU Joint Meeting]. We constructed the model consisting of coseismic slip of the 2003 and M6-7 events in the postseismic

Development of Real-time Tsunami Inundation Forecast Using Ocean Bottom Tsunami Networks along the Japan Trench

Science.gov (United States)

Aoi, S.; Yamamoto, N.; Suzuki, W.; Hirata, K.; Nakamura, H.; Kunugi, T.; Kubo, T.; Maeda, T.

2015-12-01

In the 2011 Tohoku earthquake, in which huge tsunami claimed a great deal of lives, the initial tsunami forecast based on hypocenter information estimated using seismic data on land were greatly underestimated. From this lesson, NIED is now constructing S-net (Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench) which consists of 150 ocean bottom observatories with seismometers and pressure gauges (tsunamimeters) linked by fiber optic cables. To take full advantage of S-net, we develop a new methodology of real-time tsunami inundation forecast using ocean bottom observation data and construct a prototype system that implements the developed forecasting method for the Pacific coast of Chiba prefecture (Sotobo area). We employ a database-based approach because inundation is a strongly non-linear phenomenon and its calculation costs are rather heavy. We prepare tsunami scenario bank in advance, by constructing the possible tsunami sources, and calculating the tsunami waveforms at S-net stations, coastal tsunami heights and tsunami inundation on land. To calculate the inundation for target Sotobo area, we construct the 10-m-mesh precise elevation model with coastal structures. Based on the sensitivities analyses, we construct the tsunami scenario bank that efficiently covers possible tsunami scenarios affecting the Sotobo area. A real-time forecast is carried out by selecting several possible scenarios which can well explain real-time tsunami data observed at S-net from tsunami scenario bank. An advantage of our method is that tsunami inundations are estimated directly from the actual tsunami data without any source information, which may have large estimation errors. In addition to the forecast system, we develop Web services, APIs, and smartphone applications and brush them up through social experiments to provide the real-time tsunami observation and forecast information in easy way to understand toward urging people to evacuate.

Adsorption of 90Sr and 90Y by bottom-set beds in the Atlantic ocean

International Nuclear Information System (INIS)

Gromov, V.V.; Shakhova, N.F.; Emel'yanov, E.M.

1978-01-01

The behaviour of 90 Sr and 90 Y has been studied in an adsorption system of sea water-bottom-set beds of the Atlantic ocean (red clay; pelitic silt). It has been shown that strontium is present in the sea water in one form, viz, Sr 2+ . Adsorption of 90 Sr with bottom-set beds follows the ion-exchange mechanism. Yttrium is present in the sea water at least three forms (two absorbable and one non-absorbable). Yttrium-90 adsorption is an irreversible process and only about 10% 90 Y is desorbed by the sea water from red clay and silt

Accurate ocean bottom seismometer positioning method inspired by multilateration technique

Science.gov (United States)

Benazzouz, Omar; Pinheiro, Luis M.; Matias, Luis M. A.; Afilhado, Alexandra; Herold, Daniel; Haines, Seth S.

2018-01-01

The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data.

Improving ambient noise cross-correlations in the noisy ocean bottom environment of the Juan de Fuca plate

Science.gov (United States)

Tian, Ye; Ritzwoller, Michael H.

2017-09-01

Ambient noise tomography exploits seismic ground motions that propagate coherently over long interstation distances. Such ground motions provide information about the medium of propagation that is recoverable from interstation cross-correlations. Local noise sources, which are particularly strong in ocean bottom environments, corrupt ambient noise cross-correlations and compromise the effectiveness of ambient noise tomography. Based on 62 ocean bottom seismometers (OBSs) located on Juan de Fuca (JdF) plate from the Cascadia Initiative experiment and 40 continental stations near the coast of the western United States obtained in 2011 and 2012, we attempt to reduce the effects of local noise on vertical component seismic records across the plate and onto US continent. The goal is to provide better interstation cross-correlations for use in ambient noise tomography and the study of ambient noise directionality. As shown in previous studies, tilt and compliance noise are major sources of noise that contaminate the vertical channels of the OBSs and such noise can be greatly reduced by exploiting information on the horizontal components and the differential pressure gauge records, respectively. We find that ambient noise cross-correlations involving OBSs are of significantly higher signal-to-noise ratio at periods greater than 10 s after reducing these types of noise, particularly in shallow water environments where tilt and compliance noise are especially strong. The reduction of tilt and compliance noise promises to improve the accuracy and spatial extent of ambient noise tomography, allowing measurements based on coherently propagating ambient noise to be made at stations in the shallower parts of the JdF plate and at longer periods than in previous studies. In addition such local noise reduction produces better estimates of the azimuthal content of ambient noise.

The Role of Rough Topography in Mediating Impacts of Bottom Drag in Eddying Ocean Circulation Models.

Science.gov (United States)

Trossman, David S; Arbic, Brian K; Straub, David N; Richman, James G; Chassignet, Eric P; Wallcraft, Alan J; Xu, Xiaobiao

2017-08-01

Motivated by the substantial sensitivity of eddies in two-layer quasi-geostrophic (QG) turbulence models to the strength of bottom drag, this study explores the sensitivity of eddies in more realistic ocean general circulation model (OGCM) simulations to bottom drag strength. The OGCM results are interpreted using previous results from horizontally homogeneous, two-layer, flat-bottom, f-plane, doubly periodic QG turbulence simulations and new results from two-layer β -plane QG turbulence simulations run in a basin geometry with both flat and rough bottoms. Baroclinicity in all of the simulations varies greatly with drag strength, with weak drag corresponding to more barotropic flow and strong drag corresponding to more baroclinic flow. The sensitivity of the baroclinicity in the QG basin simulations to bottom drag is considerably reduced, however, when rough topography is used in lieu of a flat bottom. Rough topography reduces the sensitivity of the eddy kinetic energy amplitude and horizontal length scales in the QG basin simulations to bottom drag to an even greater degree. The OGCM simulation behavior is qualitatively similar to that in the QG rough bottom basin simulations in that baroclinicity is more sensitive to bottom drag strength than are eddy amplitudes or horizontal length scales. Rough topography therefore appears to mediate the sensitivity of eddies in models to the strength of bottom drag. The sensitivity of eddies to parameterized topographic internal lee wave drag, which has recently been introduced into some OGCMs, is also briefly discussed. Wave drag acts like a strong bottom drag in that it increases the baroclinicity of the flow, without strongly affecting eddy horizontal length scales.

Novel compact tiltmeter for ocean bottom and other frontier observations

International Nuclear Information System (INIS)

Takamori, Akiteru; Araya, Akito; Kanazawa, Toshihiko; Shinohara, Masanao; Bertolini, Alessandro; DeSalvo, Riccardo

2011-01-01

Long-term observations conducted with large arrays of tiltmeters deployed in ocean-bottom boreholes, on the seafloor and in other hazardous regions are expected to provide rich information useful in geosciences, social engineering, resource monitoring and other applications. To facilitate such observations, we designed and built a compact, highly sensitive tiltmeter with sufficient performance, comparable to that of much larger instruments that are difficult to operate in the target locations. The new tiltmeter is suitable for observations requiring multiple instruments because its design is optimized for low-cost mass production. This paper describes its key technologies, including a very compact folded pendulum and an optical fiber readout. Preliminary results of test observations conducted using a prototype tiltmeter are compared with a conventional water-tube tiltmeter

Development of a GPS buoy system for monitoring tsunami, sea waves, ocean bottom crustal deformation and atmospheric water vapor

Science.gov (United States)

Kato, Teruyuki; Terada, Yukihiro; Nagai, Toshihiko; Koshimura, Shun'ichi

2010-05-01

We have developed a GPS buoy system for monitoring tsunami for over 12 years. The idea was that a buoy equipped with a GPS antenna and placed offshore may be an effective way of monitoring tsunami before its arrival to the coast and to give warning to the coastal residents. The key technology for the system is real-time kinematic (RTK) GPS technology. We have successfully developed the system; we have detected tsunamis of about 10cm in height for three large earthquakes, namely, the 23 June 2001 Peru earthquake (Mw8.4), the 26 September 2003 Tokachi earthquake (Mw8.3) and the 5 September 2004 earthquake (Mw7.4). The developed GPS buoy system is also capable of monitoring sea waves that are mainly caused by winds. Only the difference between tsunami and sea waves is their frequency range and can be segregated each other by a simple filtering technique. Given the success of GPS buoy experiments, the system has been adopted as a part of the Nationwide Ocean Wave information system for Port and HArborS (NOWPHAS) by the Ministry of Land, Infrastructure, Transport and Tourism of Japan. They have established more than eight GPS buoys along the Japanese coasts and the system has been operated by the Port and Airport Research Institute. As a future scope, we are now planning to implement some other additional facilities for the GPS buoy system. The first application is a so-called GPS/Acoustic system for monitoring ocean bottom crustal deformation. The system requires acoustic waves to detect ocean bottom reference position, which is the geometrical center of an array of transponders, by measuring distances between a position at the sea surface (vessel) and ocean bottom equipments to return the received sonic wave. The position of the vessel is measured using GPS. The system was first proposed by a research group at the Scripps Institution of Oceanography in early 1980's. The system was extensively developed by Japanese researchers and is now capable of detecting ocean

Numerical simulations of the stratified oceanic bottom boundary layer

Science.gov (United States)

Taylor, John R.

Numerical simulations are used to consider several problems relevant to the turbulent oceanic bottom boundary layer. In the first study, stratified open channel flow is considered with thermal boundary conditions chosen to approximate a shallow sea. Specifically, a constant heat flux is applied at the free surface and the lower wall is assumed to be adiabatic. When the surface heat flux is strong, turbulent upwellings of low speed fluid from near the lower wall are inhibited by the stable stratification. Subsequent studies consider a stratified bottom Ekman layer over a non-sloping lower wall. The influence of the free surface is removed by using an open boundary condition at the top of the computational domain. Particular attention is paid to the influence of the outer layer stratification on the boundary layer structure. When the density field is initialized with a linear profile, a turbulent mixed layer forms near the wall, which is separated from the outer layer by a strongly stable pycnocline. It is found that the bottom stress is not strongly affected by the outer layer stratification. However, stratification reduces turbulent transport to the outer layer and strongly limits the boundary layer height. The mean shear at the top of the boundary layer is enhanced when the outer layer is stratified, and this shear is strong enough to cause intermittent instabilities above the pycnocline. Turbulence-generated internal gravity waves are observed in the outer layer with a relatively narrow frequency range. An explanation for frequency content of these waves is proposed, starting with an observed broad-banded turbulent spectrum and invoking linear viscous decay to explain the preferential damping of low and high frequency waves. During the course of this work, an open-source computational fluid dynamics code has been developed with a number of advanced features including scalar advection, subgrid-scale models for large-eddy simulation, and distributed memory

Pressure drop performance evaluation for test assemblies with the newly developed top and bottom nozzles

International Nuclear Information System (INIS)

Lee, S. K.; Park, N. K.; Su, J. M.; Kim, H. K.; Lee, J. N.; Kim, K. T.

2003-01-01

To perform the hydraulic test for the newly developed top and bottom nozzles, two kinds of test assemblies were manufactured i. e. one is the test assembly which has the newly developed top and bottom nozzles and the other is Guardian test assembly which is commercially in mass production now. The test results show that the test assembly with one top nozzle and two bottom nozzles has a greater pressure loss coefficient than Guardian test assembly by 60.9% and 90.4% at the bottom nozzle location. This cause is due to the debris filtering plate for bottom nozzle to improve a filtering efficiency aginst foreign material. In the region of mid grid and top nozzle, there is no difference in pressure loss coefficient between the test assemblies since the componet features in these regions are very similar or same each other. The loss coefficients are 14.2% and 21.9% for model A and B respectively in the scale of test assembly, and the value would be within the 10% in the scale of real fuel assembly. As a result of hydraulic performance evaluation, model A is superior to model B

The Bottom Boundary Layer.

Science.gov (United States)

Trowbridge, John H; Lentz, Steven J

2018-01-03

The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

The Bottom Boundary Layer

Science.gov (United States)

Trowbridge, John H.; Lentz, Steven J.

2018-01-01

The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

The updated bottom up solution applied to atmospheric pressure photoionization and electrospray ionization mass spectrometry

Science.gov (United States)

The Updated Bottom Up Solution (UBUS) was recently applied to atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) of triacylglycerols (TAGs). This report demonstrates that the UBUS applies equally well to atmospheric pressure photoionization (APPI) MS and to electrospray ionizatio...

Torricelli and the ocean of air: the first measurement of barometric pressure.

Science.gov (United States)

West, John B

2013-03-01

The recognition of barometric pressure was a critical step in the development of environmental physiology. In 1644, Evangelista Torricelli described the first mercury barometer in a remarkable letter that contained the phrase, "We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight." This extraordinary insight seems to have come right out of the blue. Less than 10 years before, the great Galileo had given an erroneous explanation for the related problem of pumping water from a deep well. Previously, Gasparo Berti had filled a very long lead vertical tube with water and showed that a vacuum formed at the top. However, Torricelli was the first to make a mercury barometer and understand that the mercury was supported by the pressure of the air. Aristotle stated that the air has weight, although this was controversial for some time. Galileo described a method of measuring the weight of the air in detail, but for reasons that are not clear his result was in error by a factor of about two. Torricelli surmised that the pressure of the air might be less on mountains, but the first demonstration of this was by Blaise Pascal. The first air pump was built by Otto von Guericke, and this influenced Robert Boyle to carry out his classical experiments of the physiological effects of reduced barometric pressure. These were turning points in the early history of high-altitude physiology.

HOBIT-The new Hamburg Ocean Bottom Tiltmeter: A First Deployment at Columbo Seamount, Aegean Sea

Science.gov (United States)

Hort, M.; Hensch, M.; Winter, S.; Dahm, T.

2007-12-01

Assessing the state of activity of subaerial volcanoes is already quite a difficult task, but assessing the activity of submarine seamounts is even more complicated due to the difficulty of deploying instruments. At land various techniques can be used including seismic networks, deformation studies, gas measurements and others. At sea, it is mainly seismological observations, which are used to assess volcanic activity safe for some measurements with tiltmeters. However, especially at land deformation studies using INSAR have proven to be very valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling ocean bottom tiltmeter mounted in a 17 inch glass sphere to observe deformation on the ocean floor. For measuring tilt signals we use a two component high resolution tiltmeter manufactured by Lipmann Geophysikalische Messgeräte (www.l-gm.de). The instrument has a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045 rad (0.5°) can be detected. It is mounted on a levelling stage, which can relevel the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling purposes the instrument can be pulled up by very thin nylon strings and then is looked to a gimbal system in order to compensate for tilt >5°. This releveling procedure is done once every 48 hours. The data are recorded on an 18bit (at 50Hz sampling rate) MLS Geolon logger (www.send.de). Once deployed the instruments sleeps for a prescribed amount of time before the first levelling procedure is initiated. In addition to the tiltmeter and a hydrophone for receiving seismic signals, temperature, absolute pressure (paroscientific pressure sensor) to measure possible uplift or subsidence, and orientation (electronic compass mounted to the system) are monitored. 4 HOBIT systems were deployed for ten months (Jun06-Mar07) at Columbo seamount, a submarine

Debris filtering effectiveness and pressure drop tests of debris resistance-bottom end piece

International Nuclear Information System (INIS)

Chung, Moon Ki; Song, Chul Hwa; Chung, Heung June; Won, Soon Yeun; Cho, Young Ro; Kim, Bok Deuk

1992-03-01

In this final report, described are the test conditions and test procedures for the debris filtering effectiveness and pressure drop tests for developing the Debris Resistance-Bottom End Piece (DR-BEP). And the test results are tabulated for later evaluation. (Author)

Development of automated ultrasonic device for in-service inspection of ABWR pressure vessel bottom head

International Nuclear Information System (INIS)

Kojima, Y.; Matsuyama, A.

1995-01-01

An automated device and its controller have been developed for the bottom head weld examination of pressure vessel of Advanced Boiling Water Reactor (ABWR). The internal pump casings and the housings of control rod prevent a conventional ultrasonic device from scanning the required inspection zone. With this reason, it is required to develop a new device to examine the bottom head area of ABWR. The developed device is characterized by the following features. (1) Composed of a mother vehicle and a compact inspection vehicle. They are connected only by an electric wire without using the conventional arm mechanism. (2) The mother vehicle travels on a track and lift up the inspection vehicle to the vessel. (3) The mother vehicle can automatically attach the inspection vehicle to the bottom head, and detach the inspection vehicle from it. (4) Collision avoidance control function with a touch sensor is installed at the front of the inspection vehicle. The device was successfully demonstrated using a mock-up of reactor pressure vessel

The new Hamburg Ocean Bottom Tiltmeter: A First Deployment at Columbo Seamount (Aegean Sea, Greece)

Science.gov (United States)

Hensch, M.; Hort, M.; Dahm, T.; Winter, S.; Klawonn, M.

2009-04-01

Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17" glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt >5°. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 and March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short-period deformations associated with local earthquakes and also observe long-period deformation processes

The 2010 Southern California Ocean Bottom Seismometer Deployment

Science.gov (United States)

Booth, C. M.; Kohler, M. D.; Weeraratne, D. S.

2010-12-01

Subduction, mid-ocean ridge spreading, and transpressional deformation are all processes that played important roles in the evolution of the diffuse Pacific-North America plate boundary offshore Southern California. Existing seismic data for the boundary typically end at the coastline due to the fact that onshore data collection is easier and more feasible. As a result, current models for plate boundary deformation and mantle flow lack data from nearly half the plate boundary offshore. In August 2010, twenty-four broadband and ten short period ocean bottom seismometers (OBS) were deployed on a research cruise as part of a year-long passive OBS experiment off the coast of Southern California. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) will study local seismicity, and crustal and upper mantle seismic structure. Studies using onshore data have shown a high velocity anomaly that exists in the region of convergence under the Transverse Ranges. The Transverse Ranges belong to a large crustal block that experienced clockwise rotation of at least ninety degrees. Geologic studies indicate that the entire Channel Islands on the western end belongs to the region of convergence and have been a part of this rotation. In anticipation of OBS data analysis, a hypothetical velocity model is being developed for the crust and uppermost mantle for the region under the Channel Islands. P-wave arrival times are predicted by propagating teleseismic waves through the model. Different possible P-wave arrival patterns are explored by varying the lithospheric thickness. The long-term goal for developing this model will be to compare it with the actual OBS travel-time residual data to assess the best-fitting model. In preparation for the ALBACORE cruise, existing gravity data near the Channel Island region were examined for correlations with geologic features. Gravity data collected during the ALBACORE cruise will help

Acoustic Travel Time and Hydrostatic Pressure in Sermilik Fjord in Southeastern Greenland from 2011-08-23 to 2016-08-11 (NCEI Accession 0163212)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — These data records are time series of (1) round trip surface to bottom acoustic travel time, (2) bottom pressure and (3) bottom temperature (with the latter internal...

High Performance Simulation of Large-Scale Red Sea Ocean Bottom Seismic Data on the Supercomputer Shaheen II

KAUST Repository

Tonellot, Thierry

2017-02-27

A combination of both shallow and deepwater, plus islands and coral reefs, are some of the main features contributing to the complexity of subsalt seismic exploration in the Red Sea transition zone. These features often result in degrading effects on seismic images. State-of-the-art ocean bottom acquisition technologies are therefore required to record seismic data with optimal fold and offset, as well as advanced processing and imaging techniques. Numerical simulations of such complex seismic data can help improve acquisition design and also help in customizing, validating and benchmarking the processing and imaging workflows that will be applied on the field data. Subsequently, realistic simulation of wave propagation is a computationally intensive process requiring a realistic model and an efficient 3D wave equation solver. Large-scale computing resources are also required to meet turnaround time compatible with a production time frame. In this work, we present the numerical simulation of an ocean bottom seismic survey to be acquired in the Red Sea transition zone starting in summer 2016. The survey\\'s acquisition geometry comprises nearly 300,000 unique shot locations and 21,000 unique receiver locations, covering about 760 km2. Using well log measurements and legacy 2D seismic lines in this area, a 3D P-wave velocity model was built, with a maximum depth of 7 km. The model was sampled at 10 m in each direction, resulting in more than 5 billion cells. Wave propagation in this model was performed using a 3D finite difference solver in the time domain based on a staggered grid velocity-pressure formulation of acoustodynamics. To ensure that the resulting data could be generated sufficiently fast, the King Abdullah University of Science and Technology (KAUST) supercomputer Shaheen II Cray XC40 was used. A total of 21,000 three-component (pressure and vertical and horizontal velocity) common receiver gathers with a 50 Hz maximum frequency were computed in less

High Performance Simulation of Large-Scale Red Sea Ocean Bottom Seismic Data on the Supercomputer Shaheen II

KAUST Repository

Tonellot, Thierry; Etienne, Vincent; Gashawbeza, Ewenet; Curiel, Emesto Sandoval; Khan, Azizur; Feki, Saber; Kortas, Samuel

2017-01-01

A combination of both shallow and deepwater, plus islands and coral reefs, are some of the main features contributing to the complexity of subsalt seismic exploration in the Red Sea transition zone. These features often result in degrading effects on seismic images. State-of-the-art ocean bottom acquisition technologies are therefore required to record seismic data with optimal fold and offset, as well as advanced processing and imaging techniques. Numerical simulations of such complex seismic data can help improve acquisition design and also help in customizing, validating and benchmarking the processing and imaging workflows that will be applied on the field data. Subsequently, realistic simulation of wave propagation is a computationally intensive process requiring a realistic model and an efficient 3D wave equation solver. Large-scale computing resources are also required to meet turnaround time compatible with a production time frame. In this work, we present the numerical simulation of an ocean bottom seismic survey to be acquired in the Red Sea transition zone starting in summer 2016. The survey's acquisition geometry comprises nearly 300,000 unique shot locations and 21,000 unique receiver locations, covering about 760 km2. Using well log measurements and legacy 2D seismic lines in this area, a 3D P-wave velocity model was built, with a maximum depth of 7 km. The model was sampled at 10 m in each direction, resulting in more than 5 billion cells. Wave propagation in this model was performed using a 3D finite difference solver in the time domain based on a staggered grid velocity-pressure formulation of acoustodynamics. To ensure that the resulting data could be generated sufficiently fast, the King Abdullah University of Science and Technology (KAUST) supercomputer Shaheen II Cray XC40 was used. A total of 21,000 three-component (pressure and vertical and horizontal velocity) common receiver gathers with a 50 Hz maximum frequency were computed in less than

The monterey bay broadband ocean bottom seismic observatory

Directory of Open Access Journals (Sweden)

R. Uhrhammer

2006-06-01

Full Text Available We report on the installation of a long-term buried ocean-floor broadband seismic station (MOBB in Monterey Bay, California (USA, 40km off-shore, at a water depth of 1000 m. The station was installed in April 2002 using a ship and ROV, in a collaborative effort between the Monterey Bay Aquarium Research Institute (MBARI and the Berkeley Seismological Laboratory (BSL. The station is located on the western side of the San Gregorio Fault, a major fault in the San Andreas plate boundary fault system. In addition to a 3-component CMG-1T seismometer package, the station comprises a current meter and Differential Pressure Gauge, both sampled at high-enough frequency (1 Hz to allow the study of relations between background noise on the seismometers and ocean waves and currents. The proximity of several land-based broadband seismic stations of the Berkeley Digital Seismic Network allows insightful comparisons of land/ocean background seismic noise at periods relevant to regional and teleseismic studies. The station is currently autonomous. Recording and battery packages are exchanged every 3 months during scheduled one day dives. Ultimately, this station will be linked to shore using continuous telemetry (cable and/or buoy and will contribute to the earthquake notification system in Northern California. We present examples of earthquake and noise data recorded during the first 6 months of operation of MOBB. Lessons learned from these and continued recordings will help understand the nature and character of background noise in regional off-shore environments and provide a reference for the installation of future off-shore temporary and permanent broadband seismic stations.

Pressure and temperature data from bottom-mounted pressure recorders to assist in the definition of net circulation through the Florida Keys, 2001-2003 (NODC Accession 0000826)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using pressure gauge in the Northwest Atlantic Ocean and Florida Bay from 11 September 2001 to 23 April 2003....

The new Hamburg Ocean-Bottom-Tiltmeter (OBT): A first deployment at Columbo Seamount (Aegean Sea, Greece)

Science.gov (United States)

Huebscher, C.; Hensch, M.; Hort, M.; Dahm, T.; Klawonn, M.; Winter, S.

2008-12-01

Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17~inch glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 - March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis σ_1 of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short- period deformations associated with local earthquakes and also observe long-period deformation processes

SMART MONITORING AND DECISION MAKING FOR REGULATING ANNULUS BOTTOM HOLE PRESSURE WHILE DRILLING OIL WELLS

Directory of Open Access Journals (Sweden)

M. P. Vega

Full Text Available Abstract Real time measurements and development of sensor technology are research issues associated with robustness and safety during oil well drilling operations, making feasible the diagnosis of problems and the development of a regulatory strategy. The major objective of this paper is to use an experimental plant and also field data, collected from a basin operation, offshore Brazil, for implementing smart monitoring and decision making, in order to assure drilling inside operational window, despite the commonly observed disturbances that produce fluctuations in the well annulus bottom hole pressure. Using real time measurements, the performance of a continuous automated drilling unit is analyzed under a scenario of varying levels of rate of penetration; aiming pressure set point tracking (inside the operational drilling window and also rejecting kick, a phenomenon that occurs when the annulus bottom hole pressure is inferior to the porous pressure, producing the migration of reservoir fluids into the annulus region. Finally, an empirical model was built, using real experimental data from offshore Brazil basins, enabling diagnosing and regulating a real drilling site by employing classic and advanced control strategies.

Preventive protection device and method for bottom of reactor pressure vessel

International Nuclear Information System (INIS)

Hayashi, Eisaku; Kurosawa, Koichi; Furukawa, Hideyasu; Morinaka, Ren; Enomoto, Kunio; Otaka, Masahiro; Yoshikubo, Fujio; Chiba, Noboru; Sato, Kazunori.

1995-01-01

In a preventive protection device for improving stresses in reactor structural components by jetting highly pressurized water with cavitation bubbles from a jetting nozzle toward structural components in a reactor pressure vessel, a fixed structure to a CRD housing is provided with a rotational body attached to the structure, a multi joint arm and a jetting nozzle supported to the multi joint arm. The jetting nozzle is disposed at a position where the center of the jetting deviates from the center of the CRD housing. In addition, a monitoring camera is disposed for displaying the target for preventive protection. The state of stresses on a plurality of targets for preventive protection can be improved by the preventive protection device at a fixed position in the bottom of a reactor pressure vessel where housings stand densely, thereby enabling to attain the preventive protection operation easily and rapidly. (N.H.)

The Vertical Profile of Ocean Mixing

Science.gov (United States)

Ferrari, R. M.; Nikurashin, M.; McDougall, T. J.; Mashayek, A.

2014-12-01

The upwelling of bottom waters through density surfaces in the deep ocean is not possible unless the sloping nature of the sea floor is taken into account. The bottom--intensified mixing arising from interaction of internal tides and geostrophic motions with bottom topography implies that mixing is a decreasing function of height in the deep ocean. This would further imply that the diapycnal motion in the deep ocean is downward, not upwards as is required by continuity. This conundrum regarding ocean mixing and upwelling in the deep ocean will be resolved by appealing to the fact that the ocean does not have vertical side walls. Implications of the conundrum for the representation of ocean mixing in climate models will be discussed.

Partial pressure of carbon dioxide, pH, oxygen and other variables collected from time series observations using SAMI-CO2, SAMI-pH, and other instruments from Buoy NH-10 off the coast of Newport, Oregon, United States, at the near bottom depth of ~80 meters from 2011-08-16 to 2015-08-25 (NCEI Accession 0145162)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains time series measurements of near bottom partial pressure of carbon dioxide, pH, dissolved oxygen that are measured from SAMI-CO2, and...

Fall Bottom Trawl Survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The standardized NEFSC Fall Bottom Trawl Survey was initiated in 1963 and covered an area from Hudson Canyon, NY to Nova Scotia, Canada. Throughout the years,...

Winter Bottom Trawl Survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The standardized NEFSC Winter Bottom Trawl Survey was initiated in 1992 and covered offshore areas from the Mid-Atlantic to Georges Bank. Inshore strata were covered...

Summer Bottom Trawl Survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Sampling the coastal waters of the Gulf of Maine using the Northeast Fishery Science Center standardized bottom trawl has been problematic due to large areas of hard...

Spring Bottom Trawl Survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The standardized NEFSC Spring Bottom Trawl Survey was initiated in 1968 and covered an area from Cape Hatteras, NC, to Nova Scotia, Canada, at depths >27m....

Assessing the quality of bottom water temperatures from the Finite-Volume Community Ocean Model (FVCOM) in the Northwest Atlantic Shelf region

Science.gov (United States)

Li, Bai; Tanaka, Kisei R.; Chen, Yong; Brady, Damian C.; Thomas, Andrew C.

2017-09-01

The Finite-Volume Community Ocean Model (FVCOM) is an advanced coastal circulation model widely utilized for its ability to simulate spatially and temporally evolving three-dimensional geophysical conditions of complex and dynamic coastal regions. While a body of literature evaluates model skill in surface fields, independent studies validating model skill in bottom fields over large spatial and temporal scales are scarce because these fields cannot be remotely sensed. In this study, an evaluation of FVCOM skill in modeling bottom water temperature was conducted by comparison to hourly in situ observed bottom temperatures recorded by the Environmental Monitors on Lobster Traps (eMOLT), a program that attached thermistors to commercial lobster traps from 2001 to 2013. Over 2 × 106 pairs of FVCOM-eMOLT records were evaluated by a series of statistical measures to quantify accuracy and precision of the modeled data across the Northwest Atlantic Shelf region. The overall comparison between modeled and observed data indicates reliable skill of FVCOM (r2 = 0.72; root mean squared error = 2.28 °C). Seasonally, the average absolute errors show higher model skill in spring, fall and winter than summer. We speculate that this is due to the increased difficulty of modeling high frequency variability in the exact position of the thermocline and frontal zones. The spatial patterns of the residuals suggest that there is improved similarity between modeled and observed data at higher latitudes. We speculate that this is due to increased tidal mixing at higher latitudes in our study area that reduces stratification in winter, allowing improved model accuracy. Modeled bottom water temperatures around Cape Cod, the continental shelf edges, and at one location at the entrance to Penobscot Bay were characterized by relatively high errors. Constraints for future uses of FVCOM bottom water temperature are provided based on the uncertainties in temporal-spatial patterns. This study is

Open ocean tide modelling

Science.gov (United States)

Parke, M. E.

1978-01-01

Two trends evident in global tidal modelling since the first GEOP conference in 1972 are described. The first centers on the incorporation of terms for ocean loading and gravitational self attraction into Laplace's tidal equations. The second centers on a better understanding of the problem of near resonant modelling and the need for realistic maps of tidal elevation for use by geodesists and geophysicists. Although new models still show significant differences, especially in the South Atlantic, there are significant similarities in many of the world's oceans. This allows suggestions to be made for future locations for bottom pressure gauge measurements. Where available, estimates of M2 tidal dissipation from the new models are significantly lower than estimates from previous models.

Bottom Trawl Survey Protocol Development (HB0706, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Cruise objectives include: 1) Investigate performance characteristics of new research bottom trawl; 2) Develop standard operating procedures for the NEFSC Bottom...

Seismic Structure of the Oceanic Plate Entering the Central Part of the Japan Trench Obtained from Ocean-Bottom Seismic Data

Science.gov (United States)

Ohira, A.; Kodaira, S.; Fujie, G.; No, T.; Nakamura, Y.; Miura, S.

2017-12-01

In trench-outer rise regions, the normal faults develop due to the bending of the incoming plate, which cause numerous normal-faulting earthquakes and systematic structural variations toward trenches. In addition to the effects on the bend-related normal fault, structural variations which are interpreted to be attributed to pseudofaults, a fracture zone, and petit-spot volcanic activities are observed in the oceanic plate entering the central part of the Japan Trench, off Miyagi. In May-June 2017, to understand detail structural variations and systematic structural changes of the oceanic plate toward the trench, we conducted an active-source seismic survey off Miyagi using R/V Kaimei, a new research vessel of JAMSTEC. Along a 100 km-long seismic profile which is approximately perpendicular to the trench axis, we deployed 40 ocean-bottom seismometers at intervals of 2 km and fired a large airgun array (total volume 10,600 cubic inches) with 100 m shooting intervals. Multi-channel seismic reflection data were also collected along the profile. On OBS records we observed refractions from the sedimentary layer and the oceanic crust (Pg), wide-angle reflections from the crust-mantle boundary (PmP), and refractions from the uppermost mantle (Pn). Pg is typically observed clearly at near offsets (approximately 20 km) but it highly attenuates at far offsets (> 20 km). A triplication of Pg-PmP-Pn with strong amplitudes is observed at ranges from 30 km to 60 km offsets. Pn is typically weak and its apparent velocity is approximately 8 km/sec. High attenuation of Pg and weak Pn may indicate the complex crustal structure related to petit-spot volcanic activities and/or a fracture zone, which are recognized in bathymetry data around the profile.

Organic carbon and nitrogen in the surface sediments of world oceans and seas: distribution and relationship to bottom topography

Energy Technology Data Exchange (ETDEWEB)

Premuzic, E.T.

1980-06-01

Information dealing with the distribution of organic carbon and nitrogen in the top sediments of world oceans and seas has been gathered and evaluated. Based on the available information a master chart has been constructed which shows world distribution of sedimentary organic matter in the oceans and seas. Since organic matter exerts an influence upon the settling properties of fine inorganic particles, e.g. clay minerals and further, the interaction between organic matter and clay minerals is maximal, a relationship between the overall bottom topography and the distribution of clay minerals and organic matter should be observable on a worldwide basis. Initial analysis of the available data indicates that such a relationship does exist and its significance is discussed.

Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

Science.gov (United States)

Rohr, Tyler; Long, Matthew C.; Kavanaugh, Maria T.; Lindsay, Keith; Doney, Scott C.

2017-05-01

A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed "disturbance-recovery" hypothesis relative to more traditional, exclusively "bottom-up" frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S-65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.

Low parameter model to monitor bottom hole pressure in vertical multiphase flow in oil production wells

Directory of Open Access Journals (Sweden)

Mohammad Ali Ahmadi

2016-09-01

Full Text Available The importance of the flow patterns through petroleum production wells proved for upstream experts to provide robust production schemes based on the knowledge about flow behavior. To provide accurate flow pattern distribution through production wells, accurate prediction/representation of bottom hole pressure (BHP for determining pressure drop from bottom to surface play important and vital role. Nevertheless enormous efforts have been made to develop mechanistic approach, most of the mechanistic and conventional models or correlations unable to estimate or represent the BHP with high accuracy and low uncertainty. To defeat the mentioned hurdle and monitor BHP in vertical multiphase flow through petroleum production wells, inventive intelligent based solution like as least square support vector machine (LSSVM method was utilized. The evolved first-break approach is examined by applying precise real field data illustrated in open previous surveys. Thanks to the statistical criteria gained from the outcomes obtained from LSSVM approach, the proposed least support vector machine (LSSVM model has high integrity and performance. Moreover, very low relative deviation between the model estimations and the relevant actual BHP data is figured out to be less than 6%. The output gained from LSSVM model are closed the BHP while other mechanistic models fails to predict BHP through petroleum production wells. Provided solutions of this study explicated that implies of LSSVM in monitoring bottom-hole pressure can indicate more accurate monitoring of the referred target which can lead to robust design with high level of reliability for oil and gas production operation facilities.

Ocean Futures Under Ocean Acidification, Marine Protection, and Changing Fishing Pressures Explored Using a Worldwide Suite of Ecosystem Models

Directory of Open Access Journals (Sweden)

Erik Olsen

2018-03-01

Full Text Available Ecosystem-based management (EBM of the ocean considers all impacts on and uses of marine and coastal systems. In recent years, there has been a heightened interest in EBM tools that allow testing of alternative management options and help identify tradeoffs among human uses. End-to-end ecosystem modeling frameworks that consider a wide range of management options are a means to provide integrated solutions to the complex ocean management problems encountered in EBM. Here, we leverage the global advances in ecosystem modeling to explore common opportunities and challenges for ecosystem-based management, including changes in ocean acidification, spatial management, and fishing pressure across eight Atlantis (atlantis.cmar.csiro.au end-to-end ecosystem models. These models represent marine ecosystems from the tropics to the arctic, varying in size, ecology, and management regimes, using a three-dimensional, spatially-explicit structure parametrized for each system. Results suggest stronger impacts from ocean acidification and marine protected areas than from altering fishing pressure, both in terms of guild-level (i.e., aggregations of similar species or groups biomass and in terms of indicators of ecological and fishery structure. Effects of ocean acidification were typically negative (reducing biomass, while marine protected areas led to both “winners” and “losers” at the level of particular species (or functional groups. Changing fishing pressure (doubling or halving had smaller effects on the species guilds or ecosystem indicators than either ocean acidification or marine protected areas. Compensatory effects within guilds led to weaker average effects at the guild level than the species or group level. The impacts and tradeoffs implied by these future scenarios are highly relevant as ocean governance shifts focus from single-sector objectives (e.g., sustainable levels of individual fished stocks to taking into account competing

MUG-OBS - Multiparameter Geophysical Ocean Bottom System : a new instrumental approach to monitor earthquakes.

Science.gov (United States)

hello, yann; Charvis, Philippe; Yegikyan, Manuk; verfaillie, Romain; Rivet, Diane

2016-04-01

Real time monitoring of seismic activity is a major issue for early warning of earthquakes and tsunamis. It can be done using regional scale wired nodes, such as Neptune in Canada and in the U.S, or DONET in Japan. Another approach to monitor seismic activity at sea is to deploying repeatedly OBS array like during the amphibious Cascadia Initiative (four time 1-year deployments), the Japanese Pacific Array (broadband OBSs "ocean-bottom broadband dispersion survey" with 2-years autonomy), the Obsismer program in the French Lesser Antilles (eight time 6-months deployments) and the Osisec program in Ecuador (four time 6-months deployments). These autonomous OBSs are self-recovered or recovered using an ROV. These systems are costly including ship time, and require to recover the OBS before to start working on data. Among the most recent alternative we developed a 3/4 years autonomy ocean bottom system with 9 channels (?) allowing the acquisition of different seismic or environmental parameters. MUG-OBS is a free falling instrument rated down to 6000 m. The installation of the sensor is monitored by acoustic commands from the surface and a health bulletin with data checking is recovered by acoustic during the installation. The major innovation is that it is possible to recover the data any time on demand (regularly every 6-months or after a crisis) using one of the 6 data-shuttles released from the surface by acoustic command using a one day fast cruise boat of opportunity. Since sensors stayed at the same location for 3 years, it is a perfect tool to monitor large seismic events, background seismic activity and aftershock distribution. Clock, drift measurement and GPS localization is automatic when the shuttle reaches the surface. For remote areas, shuttles released automatically and a seismic events bulletin is transmitted. Selected data can be recovered by two-way Iridium satellite communication. After a period of 3 years the main station is self-recovered by

Three-Dimensional Adjustment of Stratified Flow Over a Sloping Bottom

National Research Council Canada - National Science Library

Chapman, David

2002-01-01

.... Results indicate the simple theories are relevant to the ocean and that the bottom boundary layer plays an important role in the behavior of ocean currents, even when the boundary layer is thin...

Autonomous BBOBS-NX (NX-2G) for New Era of Ocean Bottom Broadband Seismology

Science.gov (United States)

Shiobara, H.; Ito, A.; Sugioka, H.; Shinohara, M.

2017-12-01

The broadband ocean bottom seismometer (BBOBS) and its new generation system (BBOBS-NX) have been developed in Japan, and we performed several test and practical observations to create and establish a new category of the ocean floor broadband seismology, since 1999. Now, the data obtained by our BBOBS and BBOBS-NX is proved to be adequate for broadband seismic analyses. Especially, the BBOBS-NX can obtain the horizontal data comparable to land sites in longer periods (10 s -). Moreover, the BBOBST-NX is in practical evaluation for the mobile tilt observation that enables dense geodetic monitoring. The BBOBS-NX system is a powerful tool, although, it has intrinsic limitation of the ROV operation. If this system can be used without the ROV, like as the BBOBS, it should lead us a true breakthrough of ocean bottom seismology. Hereafter, the new autonomous BBOBS-NX is noted as NX-2G in short. The main problem to realize the NX-2G is a tilt of the sensor unit on landing, which exceed the acceptable limit (±8°) in about 50%. As we had no evidence at which moment and how this tilt occurred, we tried to observe it during the BBOBST-NX landing in 2015 by attaching a video camera and an acceleration logger. The result shows that the tilt on landing was determined by the final posture of the system at the penetration into the sediment, and the large oscillating tilt more than ±10° was observed in descending. The function of the NX-2G system is based on 3 stage operations as shown in the image. The glass float is aimed not only to obtain enough buoyancy to extract the sensor unit, but also to suppress the oscillating tilt of the system in descending. In Oct. 2016, we made the first in-situ test of the NX-2G system with a ROV. It was dropped from the sea surface with the video camera and the acceleration logger. The ROV was used to watch the operation of the system at the seafloor. The landing looked well and it was examined from the acceleration data. As the maximum tilt in

Improvement of Blood Pressure, Glucose Metabolism, and Lipid Profile by the Intake of Powdered Asparagus (蘆筍 Lú Sǔn Bottom-stems and Cladophylls

Directory of Open Access Journals (Sweden)

Mie Nishimura

2013-10-01

Full Text Available Asparagus (蘆筍 Lú Sǔn; Asparagus officinalis L. is a common vegetable, long used as an herbal medicine. The cladophylls and bottom-stems of asparagus have various pharmacological effects, but they are generally discarded at harvesting. The present open clinical trial was performed to examine the effects of the intake of cladophylls and bottom-stems on the improvement of metabolic syndrome characterized by hypertension, hyperglycemia, and dyslipidemia. Twenty-eight healthy volunteers ingested either cladophyll or bottom-stem powder (6 g/day daily for 10 weeks. The cladophyll intake resulted in significant reduction in the subjects’ diastolic blood pressure and fasting plasma glucose (FPG, and decreased both the left cardio-ankle vascular index score and the total cholesterol level (T-CHO. The bottom-stem intake significantly reduced the subjects’ systolic and diastolic blood pressure and FPG as well as T-CHO. These results suggest the possibility that asparagus cladophylls and bottom-stems differentially improve hypertension, hyperglycemia, and dyslipidemia.

Changing Arctic Ocean freshwater pathways.

Science.gov (United States)

Morison, James; Kwok, Ron; Peralta-Ferriz, Cecilia; Alkire, Matt; Rigor, Ignatius; Andersen, Roger; Steele, Mike

2012-01-04

Freshening in the Canada basin of the Arctic Ocean began in the 1990s and continued to at least the end of 2008. By then, the Arctic Ocean might have gained four times as much fresh water as comprised the Great Salinity Anomaly of the 1970s, raising the spectre of slowing global ocean circulation. Freshening has been attributed to increased sea ice melting and contributions from runoff, but a leading explanation has been a strengthening of the Beaufort High--a characteristic peak in sea level atmospheric pressure--which tends to accelerate an anticyclonic (clockwise) wind pattern causing convergence of fresh surface water. Limited observations have made this explanation difficult to verify, and observations of increasing freshwater content under a weakened Beaufort High suggest that other factors must be affecting freshwater content. Here we use observations to show that during a time of record reductions in ice extent from 2005 to 2008, the dominant freshwater content changes were an increase in the Canada basin balanced by a decrease in the Eurasian basin. Observations are drawn from satellite data (sea surface height and ocean-bottom pressure) and in situ data. The freshwater changes were due to a cyclonic (anticlockwise) shift in the ocean pathway of Eurasian runoff forced by strengthening of the west-to-east Northern Hemisphere atmospheric circulation characterized by an increased Arctic Oscillation index. Our results confirm that runoff is an important influence on the Arctic Ocean and establish that the spatial and temporal manifestations of the runoff pathways are modulated by the Arctic Oscillation, rather than the strength of the wind-driven Beaufort Gyre circulation.

Modeling selective pressures on phytoplankton in the global ocean.

Directory of Open Access Journals (Sweden)

Jason G Bragg

Full Text Available Our view of marine microbes is transforming, as culture-independent methods facilitate rapid characterization of microbial diversity. It is difficult to assimilate this information into our understanding of marine microbe ecology and evolution, because their distributions, traits, and genomes are shaped by forces that are complex and dynamic. Here we incorporate diverse forces--physical, biogeochemical, ecological, and mutational--into a global ocean model to study selective pressures on a simple trait in a widely distributed lineage of picophytoplankton: the nitrogen use abilities of Synechococcus and Prochlorococcus cyanobacteria. Some Prochlorococcus ecotypes have lost the ability to use nitrate, whereas their close relatives, marine Synechococcus, typically retain it. We impose mutations for the loss of nitrogen use abilities in modeled picophytoplankton, and ask: in which parts of the ocean are mutants most disadvantaged by losing the ability to use nitrate, and in which parts are they least disadvantaged? Our model predicts that this selective disadvantage is smallest for picophytoplankton that live in tropical regions where Prochlorococcus are abundant in the real ocean. Conversely, the selective disadvantage of losing the ability to use nitrate is larger for modeled picophytoplankton that live at higher latitudes, where Synechococcus are abundant. In regions where we expect Prochlorococcus and Synechococcus populations to cycle seasonally in the real ocean, we find that model ecotypes with seasonal population dynamics similar to Prochlorococcus are less disadvantaged by losing the ability to use nitrate than model ecotypes with seasonal population dynamics similar to Synechococcus. The model predictions for the selective advantage associated with nitrate use are broadly consistent with the distribution of this ability among marine picocyanobacteria, and at finer scales, can provide insights into interactions between temporally varying

Modeling selective pressures on phytoplankton in the global ocean.

Science.gov (United States)

Bragg, Jason G; Dutkiewicz, Stephanie; Jahn, Oliver; Follows, Michael J; Chisholm, Sallie W

2010-03-10

Our view of marine microbes is transforming, as culture-independent methods facilitate rapid characterization of microbial diversity. It is difficult to assimilate this information into our understanding of marine microbe ecology and evolution, because their distributions, traits, and genomes are shaped by forces that are complex and dynamic. Here we incorporate diverse forces--physical, biogeochemical, ecological, and mutational--into a global ocean model to study selective pressures on a simple trait in a widely distributed lineage of picophytoplankton: the nitrogen use abilities of Synechococcus and Prochlorococcus cyanobacteria. Some Prochlorococcus ecotypes have lost the ability to use nitrate, whereas their close relatives, marine Synechococcus, typically retain it. We impose mutations for the loss of nitrogen use abilities in modeled picophytoplankton, and ask: in which parts of the ocean are mutants most disadvantaged by losing the ability to use nitrate, and in which parts are they least disadvantaged? Our model predicts that this selective disadvantage is smallest for picophytoplankton that live in tropical regions where Prochlorococcus are abundant in the real ocean. Conversely, the selective disadvantage of losing the ability to use nitrate is larger for modeled picophytoplankton that live at higher latitudes, where Synechococcus are abundant. In regions where we expect Prochlorococcus and Synechococcus populations to cycle seasonally in the real ocean, we find that model ecotypes with seasonal population dynamics similar to Prochlorococcus are less disadvantaged by losing the ability to use nitrate than model ecotypes with seasonal population dynamics similar to Synechococcus. The model predictions for the selective advantage associated with nitrate use are broadly consistent with the distribution of this ability among marine picocyanobacteria, and at finer scales, can provide insights into interactions between temporally varying ocean processes and

Modes of Arctic Ocean Change from GRACE, ICESat and the PIOMAS and ECCO2 Models of the Arctic Ocean

Science.gov (United States)

Peralta Ferriz, C.; Morison, J. H.; Bonin, J. A.; Chambers, D. P.; Kwok, R.; Zhang, J.

2012-12-01

EOF analysis of month-to-month variations in GRACE derived Arctic Ocean bottom pressure (OBP) with trend and seasonal variation removed yield three dominant modes. The first mode is a basin wide variation in mass associated with high atmospheric pressure (SLP) over Scandinavia mainly in winter. The second mode is a shift of mass from the central Arctic Ocean to the Siberian shelves due to low pressure over the basins, associated with the Arctic Oscillation. The third mode is a shift in mass between the Eastern and Western Siberian shelves, related to strength of the Beaufort High mainly in summer, and to eastward alongshore winds on the Barents Sea in winter. The PIOMAS and ECCO2 modeled OBP show fair agreement with the form of these modes and provide context in terms of variations in sea surface height SSH. Comparing GRACE OBP from 2007 to 2011 with GRACE OBP from 2002 to 2006 reveals a rising trend over most of the Arctic Ocean but declines in the Kara Sea region and summer East Siberian Sea. ECCO2 bears a faint resemblance to the observed OBP change but appears to be biased negatively. In contrast, PIOMAS SSH and ECCO2 especially, show changes between the two periods that are muted but similar to ICESat dynamic ocean topography and GRACE-ICESat freshwater trends from 2005 through 2008 [Morison et al., 2012] with a rising DOT and freshening in the Beaufort Sea and a trough with decreased freshwater on the Russian side of the Arctic Ocean. Morison, J., R. Kwok, C. Peralta-Ferriz, M. Alkire, I. Rigor, R. Andersen, and M. Steele (2012), Changing Arctic Ocean freshwater pathways, Nature, 481(7379), 66-70.

Effects of High-Pressure Treatment on the Muscle Proteome of Hake by Bottom-Up Proteomics.

Science.gov (United States)

Carrera, Mónica; Fidalgo, Liliana G; Saraiva, Jorge A; Aubourg, Santiago P

2018-05-02

A bottom-up proteomics approach was applied for the study of the effects of high-pressure (HP) treatment on the muscle proteome of fish. The performance of the approach was established for a previous HP treatment (150-450 MPa for 2 min) on frozen (up to 5 months at -10 °C) European hake ( Merluccius merluccius). Concerning possible protein biomarkers of quality changes, a significant degradation after applying a pressure ≥430 MPa could be observed for phosphoglycerate mutase-1, enolase, creatine kinase, fructose bisphosphate aldolase, triosephosphate isomerase, and nucleoside diphosphate kinase; contrary, electrophoretic bands assigned to tropomyosin, glyceraldehyde-3-phosphate dehydrogenase, and beta parvalbumin increased their intensity after applying a pressure ≥430 MPa. This repository of potential protein biomarkers may be very useful for further HP investigations related to fish quality.

Three dimensional investigation of oceanic active faults. A demonstration survey

Energy Technology Data Exchange (ETDEWEB)

Nakao, Seizo; Kishimoto, Kiyoyuki; Kuramoto, Shinichi; Sato, Mikio [Geological Survey of Japan, Tsukuba, Ibaraki (Japan)

1998-02-01

In order to upgrade probability of activity and action potential evaluation of oceanic active faults which have some important effects on nuclear facilities, trench type oceanic active fault was investigated three dimensionally. Contents of the investigation were high precision sea bottom topographic survey and sea bottom back scattering wave image data observation by using a sea bottom topography acoustic imaginator. And, by high resolution earthquake wave survey, high precision survey of an active fault under sea bottom was conducted to detect oceanic active faults three-dimensionally. Furthermore, the generally issued data were summarized to promote to construct a data base for evaluating the active faults. (G.K.)

Three dimensional investigation of oceanic active faults. A demonstration survey

International Nuclear Information System (INIS)

Nakao, Seizo; Kishimoto, Kiyoyuki; Kuramoto, Shinichi; Sato, Mikio

1998-01-01

In order to upgrade probability of activity and action potential evaluation of oceanic active faults which have some important effects on nuclear facilities, trench type oceanic active fault was investigated three dimensionally. Contents of the investigation were high precision sea bottom topographic survey and sea bottom back scattering wave image data observation by using a sea bottom topography acoustic imaginator. And, by high resolution earthquake wave survey, high precision survey of an active fault under sea bottom was conducted to detect oceanic active faults three-dimensionally. Furthermore, the generally issued data were summarized to promote to construct a data base for evaluating the active faults. (G.K.)

A Novel Thermal-Mechanical Detection System for Reactor Pressure Vessel Bottom Failure Monitoring in Severe Accidents

International Nuclear Information System (INIS)

Bi, Daowei; Bu, Jiangtao; Xu, Dongling

2013-06-01

Following the Fukushima Daiichi nuclear accident in Japan, there is an increased need of enhanced capabilities for severe accident management (SAM) program. Among others, a reliable method for detecting reactor pressure vessel (RPV) bottom failure has been evaluated as imperative by many utility owners. Though radiation and/or temperature measurement are potential solutions by tradition, there are some limitations for them to function desirably in such severe accident as that in Japan. To provide reliable information for assessment of accident progress in SAM program, in this paper we propose a novel thermal-mechanical detection system (TMDS) for RPV bottom failure monitoring in severe accidents. The main components of TMDS include thermally sensitive element, metallic cables, tension controlled switch and main control room annunciation device. With TMDS installed, there shall be a reliable means of keeping SAM decision-makers informed whether the RPV bottom has indeed failed. Such assurance definitely guarantees enhancement of severe accident management performance and significantly improve nuclear safety and thus protect the society and people. (authors)

Bottom fauna of the Malacca Strait

Digital Repository Service at National Institute of Oceanography (India)

Parulekar, A.H.; Ansari, Z.A.

Bottom fauna of Malacca Strait (connecting the Indian Ocean with Pacific) in the depth range of 80 to 1350 m, is dominated by meiofauna which exceeds macrofauna by 12.5 times in weight and by more than 780 times in population density. Standing crop...

Pressing technology for large bottoms

International Nuclear Information System (INIS)

Jilek, L.

1986-01-01

The technology has been selected of a circular plate bent into the shape of a trough, for pressing bottoms of pressure vessels from a circular plate of large diameter. The initial sheet is first bent in the middle by heating with the edges remaining straight. These are then welded longitudinally by electroslag welding and the circular shape is flame cut. The result will be a plate with a straight surface in the middle with raised edges which may be pressed into the desired shape. In this manner it is also possible to press pressure vessel bottoms with tube couplings from plates which are thickened in the middle and drilled; additional welding is then eliminated. Deformation from heat treatment may be avoided by the use of a fixture in the shape of a ring with a groove into which is fixed the edge of the bottom. During hardening of the bottom it will be necessary to care for the withdrawal of vapours and gases which would hamper uniform cooling. Bottom hardening with the grill and the cupola downwards has been proven. Deformation which occurs during treatment may to a certain extent be removed by calibration which cannot, however, be made without special fixtures and instruments. (J.B.)

Ocean circulation code on machine connection

International Nuclear Information System (INIS)

Vitart, F.

1993-01-01

This work is part of a development of a global climate model based on a coupling between an ocean model and an atmosphere model. The objective was to develop this global model on a massively parallel machine (CM2). The author presents the OPA7 code (equations, boundary conditions, equation system resolution) and parallelization on the CM2 machine. CM2 data structure is briefly evoked, and two tests are reported (on a flat bottom basin, and a topography with eight islands). The author then gives an overview of studies aimed at improving the ocean circulation code: use of a new state equation, use of a formulation of surface pressure, use of a new mesh. He reports the study of the use of multi-block domains on CM2 through advection tests, and two-block tests

NMFS Bottom Longline Analytical Dataset Provided to NRDA

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Southeast Fisheries Science Center Mississippi Laboratories has conducted standardized bottom longline surveys in the Gulf of Mexico and South Atlantic since...

The impact of Indian Ocean high pressure system on rainfall and stream flow

International Nuclear Information System (INIS)

Rehman, S.; Nasir, H.; Zia, S.S.; Ansari, W.A.; Salam, K.; Tayyab, N.

2012-01-01

Centre of Action approach is very useful in getting insight of rainfall and stream flow variability of specific region. Hameed et al. showed that Inter-annual variability of Gulf Stream north wall is influenced by low Icelandic pressure system and has more statistically significant correlation than North Atlantic Oscillation (NAO) with longitude of Icelandic low. This study also aims to explore possible relationships between rainfall and stream flow in Collie river catchment in Southwest Western Australia (SWWA) with Indian Ocean high pressure dynamics. The relationship between rainfall and stream flow with Indian Ocean high pressure system have been investigated using correlation analysis for early winter season (MJJA), lag correlation for MJJA versus SOND rainfall and stream flow are also calculated and found significant at 95% confidence level. By investigating the relationship between COA indices with rainfall and stream flow over the period 1976-2008, significant correlations suggests that rainfall and stream flow in Collie river basin is strongly influenced by COA indices. Multiple correlations between rainfall and stream flow with Indian Ocean high pressure (IOHPS and IOHLN) is 0.7 and 0.6 respectively. Centers of Action (COA) indices explain 51% and 36% of rainfall and stream flow respectively. The correlation between rainfall and stream flow with IOHPS is -0.4 and -0.3 whereas, with IOHLN is -0.47 and -0.52 respectively. (author)

Gear Selectivity of a Longfin Squid Bottom Trawl

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Loligo pealeii (longfin inshore squid) co-occurs with Atlantic butterfish (Peprilus triacanthus) throughout the year and discarding in the L. pealeii bottom trawl...

Development of compact long-term broadband ocean bottom seismometer for seafloor observation of slow earthquakes

Science.gov (United States)

Yamashita, Y.; Shinohara, M.; Yamada, T.; Shiobara, H.

2017-12-01

It is important to understand coupling between plates in a subduction zone for studies of earthquake generation. Recently low frequency tremor and very low frequency earthquake (VLFE) were discovered in plate boundary near a trench. These events (slow earthquakes) in shallow plate boundary should be related to slow slip on a plate boundary. For observation of slow earthquakes, Broad Band Ocean Bottom Seismometer (BBOBS) is useful, however a number of BBOBSs are limited due to cost. On the other hand, a number of Long-term OBSs (LT-OBSs) with recording period of one year are available. However, the LT-OBS has seismometer with a natural period of 1 second. Therefore frequency band of observation is slightly narrow for slow earthquakes. Therefore we developed a compact long-term broad-band OBS by replacement of the seismic sensor of the LT-OBSs to broadband seismometer.We adopted seismic sensor with natural period of 20 seconds (Trillium Compact Broadband Seismometer, Nanometrics). Because tilt of OBS on seafloor can not be controlled due to free-fall, leveling system for seismic sensor is necessary. The broadband seismic senor has cylinder shape with diameter of 90 mm and height of 100 mm, and the developed levelling system can mount the seismic sensor with no modification of shape. The levelling system has diameter of 160 mm and height of 110 mm, which is the same size as existing levelling system of the LT-OBS. The levelling system has two horizontal axes and each axis is driven by motor. Leveling can be performed up to 20 degrees by using micro-processor (Arduino). Resolution of levelling is less than one degree. The system immediately starts leveling by the power-on of controller. After levelling, the the seismic senor is powered and the controller records angles of levelling to SD RAM. Then the controller is shut down to consume no power. Compact long-term broadband ocean bottom seismometer is useful for observation of slow earthquakes on seafloor. In addition

Distribution of shallow very low frequency earthquakes in the eastern Nankai trough influenced by a subducted oceanic ridge: Results from cluster analysis applied to ocean bottom seismographs

Science.gov (United States)

To, A.; Obana, K.; Araki, E.

2016-12-01

The activity of very low frequency earthquakes (VLFEs) in the shallow accretionary prism of the eastern Nankai trough has been observed frequently in the past. In this study, we investigated the distribution of VLFEs that occurred in October 2015, which were recorded by an array of broadband ocean bottom seismometers (BBOBSs) of DONET1 network. The size of the network is much wider (>80 km) compared to previous BBOBS networks that were used for close-in observations of VLFEs; therefore the new dataset provides a broader overview of the VLFE distribution of this region. We first located the detected events using conventional methods such as the envelope correlation method. However, the results seemed to be largely scattered due to noise and the effect of 3D structures that could not be properly handled. Then, we introduced hierarchal clustering analysis, based on measured travel time patterns among stations obtained for each event. The analyses enabled the assessment of relative locations among events. Finally, the locations of event-clusters were estimated, instead of individual events, so that the obtained locations seemed less scattered. The obtained results indicate that the VLFE distribution is strongly influenced by a subducted ridge (Park et al., 2003) that exists beneath the northeastern side of the DONET1 network. Though the VLFEs are distributed from an area near the outer ridge toward the trench axis in the region with a smooth plate boundary, they are clustered at a shallow depth near the outer ridge in the region of the rough plate boundary. The VLFEs are clustered on the landward side of the peak of the subducted ridge; this could be explained by an elevated pore pressure in the region caused by the low-permeability oceanic ridge that may clog the up-dip pathway of the fluid along the decollement zone. The along-strike variation of the stress state, inferred from the VLFE distribution, should be an important factor in assessing the strain release

Measuring device for water quality at reactor bottom

Energy Technology Data Exchange (ETDEWEB)

Urata, Hidehiro; Takagi, Jun-ichi

1995-10-27

The present invention concerns measurement for water quality at the bottom of a reactor of a BWR type plant, in which reactor water is sampled and analyzed in a state approximate to conditions in a pressure vessel. Based on the result, hydrogen injection amount is controlled during hydrogen injection operation. Namely, a monitor for water quality is disposed to a sampling line in communication with the bottom of a pressure vessel. A water quality monitor is disposed to a drain sampling line in communication with the bottom of the pressure vessel. A corrosion potentiometer is disposed to the pressure sampling line or the drain sampling line. A dissolved oxygen measuring device is disposed to the pressure vessel sampling line or the drain sampling line. With such a constitution, the reactor water can be sampled and analyzed in a state approximate to the conditions in the pressure vessel. In addition, signals from the water quality monitor are inputted to a hydrogen injection amount control device. As a result, the amount of hydrogen injected to primary coolants can be controlled in a state approximate to the conditions in the pressure vessel. (I.S.).

Measuring device for water quality at reactor bottom

International Nuclear Information System (INIS)

Urata, Hidehiro; Takagi, Jun-ichi.

1995-01-01

The present invention concerns measurement for water quality at the bottom of a reactor of a BWR type plant, in which reactor water is sampled and analyzed in a state approximate to conditions in a pressure vessel. Based on the result, hydrogen injection amount is controlled during hydrogen injection operation. Namely, a monitor for water quality is disposed to a sampling line in communication with the bottom of a pressure vessel. A water quality monitor is disposed to a drain sampling line in communication with the bottom of the pressure vessel. A corrosion potentiometer is disposed to the pressure sampling line or the drain sampling line. A dissolved oxygen measuring device is disposed to the pressure vessel sampling line or the drain sampling line. With such a constitution, the reactor water can be sampled and analyzed in a state approximate to the conditions in the pressure vessel. In addition, signals from the water quality monitor are inputted to a hydrogen injection amount control device. As a result, the amount of hydrogen injected to primary coolants can be controlled in a state approximate to the conditions in the pressure vessel. (I.S.)

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.

Ocean tides for satellite geodesy

Science.gov (United States)

Dickman, S. R.

1990-01-01

Spherical harmonic tidal solutions have been obtained at the frequencies of the 32 largest luni-solar tides using prior theory of the author. That theory was developed for turbulent, nonglobal, self-gravitating, and loading oceans possessing realistic bathymetry and linearized bottom friction; the oceans satisfy no-flow boundary conditions at coastlines. In this theory the eddy viscosity and bottom drag coefficients are treated as spatially uniform. Comparison of the predicted degree-2 components of the Mf, P1, and M2 tides with those from numerical and satellite-based tide models allows the ocean friction parameters to be estimated at long and short periods. Using the 32 tide solutions, the frequency dependence of tidal admittance is investigated, and the validity of sideband tide models used in satellite orbit analysis is examined. The implications of admittance variability for oceanic resonances are also explored.

Mapping The Brightness Of The Ocean Bottoms

Energy Technology Data Exchange (ETDEWEB)

Milazzo, Damien Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-03-25

This is a presentation that describes some of the work LANL is doing in the way of; describing the lithology of the ocean floor; use of data to describe natural radioisotopes; and the determination of minerals that can be neutron activated.

Summertime calcium carbonate undersaturation in shelf waters of the western Arctic Ocean – how biological processes exacerbate the impact of ocean acidification

OpenAIRE

N. R. Bates; M. I. Orchowska; R. Garley; J. T. Mathis

2013-01-01

The Arctic Ocean accounts for only 4% of the global ocean area, but it contributes significantly to the global carbon cycle. Recent observations of seawater CO2-carbonate chemistry in shelf waters of the western Arctic Ocean, primarily in the Chukchi Sea, from 2009 to 2011 indicate that bottom waters are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Nearly 40% of sampled bottom waters on the shelf have saturation states...

Gulf of Maine Cooperative Bottom Longline Survey Database

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This database is for a bottom longline (fixed gear) survey executed in the western and central Gulf of Maine targeting complex rocky habitats. The survey is operated...

Effect of water flow rate and water chemistry on corrosion environment in reactor pressure vessel bottom of BWRs

Energy Technology Data Exchange (ETDEWEB)

Ichikawa, Nagayoshi; Hemmi, Yukio; Takagi, Junichi; Urata, Hidehiro [Toshiba Corp., Kawasaki, Kanagawa (Japan)

1999-07-01

To evaluate the corrosion environment at the bottom of the reactor pressure vessel in a BWR and the effect of hydrogen water chemistry on the corrosion of materials in the region, measurements of the corrosion potential of Type-304 stainless steel and nickel base alloy were made in a laboratory test loop. The effect of water chemistry on the corrosion potential of nickel base alloy is found to be similar to the effect on Type-304 stainless steel. Flow analysis and precise evaluations of the corrosion potential of materials in the bottom region were implemented. Corrosion potentials throughout the region were evaluated from the flow analysis results. At the jet pump outlet and shroud support leg, a rather large amount of hydrogen had to be added to reduce the potential. Conversely, a small amount of hydrogen was enough in the case of the stub tube of the control rod drive guide tubing and the ICM housings located in the center of the bottom region. (author)

Effect of water flow rate and water chemistry on corrosion environment in reactor pressure vessel bottom of BWRs

International Nuclear Information System (INIS)

Ichikawa, Nagayoshi; Hemmi, Yukio; Takagi, Junichi; Urata, Hidehiro

1999-01-01

To evaluate the corrosion environment at the bottom of the reactor pressure vessel in a BWR and the effect of hydrogen water chemistry on the corrosion of materials in the region, measurements of the corrosion potential of Type-304 stainless steel and nickel base alloy were made in a laboratory test loop. The effect of water chemistry on the corrosion potential of nickel base alloy is found to be similar to the effect on Type-304 stainless steel. Flow analysis and precise evaluations of the corrosion potential of materials in the bottom region were implemented. Corrosion potentials throughout the region were evaluated from the flow analysis results. At the jet pump outlet and shroud support leg, a rather large amount of hydrogen had to be added to reduce the potential. Conversely, a small amount of hydrogen was enough in the case of the stub tube of the control rod drive guide tubing and the ICM housings located in the center of the bottom region. (author)

Constructing bottom barriers with met grouting

International Nuclear Information System (INIS)

Shibazaki, M.; Yoshida, H.

1997-01-01

Installing a bottom barrier using conventional high pressure jetting technology and ensuring barrier continuity is challenging. This paper describes technology that has been developed and demonstrated for the emplacement of bottom barriers using pressures and flow rates above the conventional high pressure jetting parameters. The innovation capable of creating an improved body exceeding 5 meters in diameter has resulted in the satisfying connection and adherence between the treated columns. Besides, the interfaces among the improved bodies obtain the same strength and permeability lower than 1 x 10 -7 cm/sec as body itself. A wide variety of the thickness and the diameter of the improved mass optimizes the application, and the method is nearing completion. The paper explains an aspect and briefs case histories

Ultrasonic test results for the reactor pressure vessel of the HTTR. Longitudinal welding line of bottom dome

International Nuclear Information System (INIS)

Nojiri, Naoki; Ohwada, Hiroyuki; Kato, Yasushi

2008-06-01

This paper describes the inspection method, the measured area, etc. of the ultrasonic test of the in-service inspection (ISI) for welding lines of the reactor pressure vessel of the HTTR and the inspection results of the longitudinal welding line of the bottom dome. The pre-service inspection (PSI) results for estimation of occurrence and progression of defects to compare the ISI results is described also. (author)

Atmospheric and oceanic excitation of decadal-scale Earth orientation variations

Science.gov (United States)

Gross, Richard S.; Fukumori, Ichiro; Menemenlis, Dimitris

2005-09-01

The contribution of atmospheric wind and surface pressure and oceanic current and bottom pressure variations during 1949-2002 to exciting changes in the Earth's orientation on decadal timescales is investigated using an atmospheric angular momentum series computed from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis project and an oceanic angular momentum series computed from a near-global ocean model that was forced by surface fluxes from the NCEP/NCAR reanalysis project. Not surprisingly, since decadal-scale variations in the length of day are caused mainly by interactions between the mantle and core, the effect of the atmosphere and oceans is found to be only about 14% of that observed. More surprisingly, it is found that the effect of atmospheric and oceanic processes on decadal-scale changes in polar motion is also only about 20% (x component) and 38% (y component) of that observed. Therefore redistribution of mass within the atmosphere and oceans does not appear to be the main cause of the Markowitz wobble. It is also found that on timescales between 10 days and 4 years the atmospheric and oceanic angular momentum series used here have very little skill in explaining Earth orientation variations before the mid to late 1970s. This is attributed to errors in both the Earth orientation observations prior to 1976 when measurements from the accurate space-geodetic techniques became available and to errors in the modeled atmospheric fields prior to 1979 when the satellite era of global weather observing systems began.

Climate change, pink salmon, and the nexus between bottom-up and top-down forcing in the subarctic Pacific Ocean and Bering Sea.

Science.gov (United States)

Springer, Alan M; van Vliet, Gus B

2014-05-06

Climate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem.

/sup 226/Ra in the western Indian Ocean

Energy Technology Data Exchange (ETDEWEB)

Chung, Y.

1987-09-01

/sup 226/Ra profiles have been measured in the western Indian Ocean as part of the 1977-78 Indian Ocean GEOSECS program. These profiles show a general increase in deep and bottom water Ra concentration from the Circumpolar region to the Arabian Sea. A deep Ra maximum which originates in the Arabian Sea and in the Somali basin at about 3000 m depth spreads southward into the Mascarene basin and remains discernible in the Madagascar and Crozet basins. In the western Indian Ocean, the cold Antarctic Bottom Water spreads northward under the possibly southward-flowing deep water, forming a clear benthic front along the Crozet basin across the Southwest Indian Ridge into the Madagascar and Mascarene basins. The Antarctic Bottom Water continues to spread farther north to the Somali basin through the Amirante Passage at 10/sup 0/S as a western boundary current. The benthic front and other characteristic features in the western Indian Ocean are quite similar to those observed in the western Pacific where the benthic front as a distinctive feature was first described by Craig et al. Across the Mid-Indian Ridge toward the Ceylon abyssal plain near the triple junction, Ra profiles display a layered structure, reflecting the topographic effect of the mid-ocean ridge system on the mixing and circulation of the deep and bottom waters. Both Ra and Si show a deep maximum north of the Madagascar Basin. Linear relationships between these two elements are observed in the deep and bottom water with slopes increasing northward. This suggests a preferential input of Ra over Si from the bottom sediments of the Arabian Sea and also from the flank sediments of the Somali basin.

Nonlinear and hysteretic twisting effects in ocean cable laying

International Nuclear Information System (INIS)

Shashaty, A.J.

1983-01-01

Armored ocean cable unlays under the action of installation tensions and restraining moments applied by the ocean bottom and the ship's bow sheave. The process of elongation and twist is nonlinear and hysteretic. This process has often been assumed linear and reversible. The equations describing the moment which is developed in laying cable on the ocean bottom are worked out, without assuming linearity and reversibility. These equations are applied to some cases likely to arise. For a typical armored coaxial cable laid in 3700m (2,000 fathoms) depth without bottom tension, a steady-state laying-up moment of 134Nm (99 lbs. ft.) is developed. For the reversible case, no moment is developed. If the bottom tension is increased from zero to 33,375N (7500 lbs.) and then returned to zero, a peak moment of 198Nm (146 lbs. ft.) is developed

Ocean Sense: Student-Led, Real-Time Research at the Bottom of the Ocean - Without Leaving the Classroom

Science.gov (United States)

Pelz, M.; Hoeberechts, M.; McLean, M. A.; Riddell, D. J.; Ewing, N.; Brown, J. C.

2016-12-01

This presentation outlines the authentic research experiences created by Ocean Networks Canada's Ocean Sense program, a transformative education program that connects students and teachers with place-based, real-time data via the Internet. This program, developed in collaboration with community educators, features student-centric activities, clearly outlined learning outcomes, assessment tools and curriculum aligned content. Ocean Networks Canada (ONC), an initiative of the University of Victoria, develops, operates, and maintains cabled ocean observatory systems. Technologies developed on the world-leading NEPTUNE and VENUS observatories have been adapted for small coastal installations called "community observatories," which enable community members to directly monitor conditions in the local ocean environment. Data from these observatories are fundamental to lessons and activities in the Ocean Sense program. Marketed as Ocean Sense: Local observations, global connections, the program introduces middle and high school students to research methods in biology, oceanography and ocean engineering. It includes a variety of resources and opportunities to excite students and spark curiosity about the ocean environment. The program encourages students to connect their local observations to global ocean processes and the observations of students in other geographic regions. Connection to place and local relevance of the program is enhanced through an emphasis on Indigenous and place-based knowledge. The program promotes of cross-cultural learning with the inclusion of Indigenous knowledge of the ocean. Ocean Sense provides students with an authentic research experience by connecting them to real-time data, often within their own communities. Using the freely accessible data portal, students can curate the data they need from a range of instruments and time periods. Further, students are not restricted to their local community; if their question requires a greater range of

ULF/VLF (0.001 to 50 Hz) Seismo-Acoustic Noise in the Ocean. Proceedings of a Workshop Held at Austin, Texas on November 29-December 1, 1988

Science.gov (United States)

1989-08-03

holes drilled in the seafloor from the D/V JOIDES Resolution through petrological , geochemical and paleomagnetic studies of the samples and logging...seismome- ters and/or hydrophones (or differential pressure gauges , DPG). Testing of the new instruments at very early stages is important to ensure...resolved using ocean bottom seismometers, suspended hydrophones and differential pressure gauges assisted by an orbiting radar altimeter (GEOSAT

Bottom Dissolved Oxygen Maps From SEAMAP Summer Groundfish/Shrimp Surveys

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Bottom dissolved oxygen (DO) data was extracted from environmental profiles acquired during the Southeast Fisheries Science Center Mississippi Laboratories summer...

Bursting Events in Pressure Flushing with Expanding Bottom Outlet Channel within Dam Reservoir

Directory of Open Access Journals (Sweden)

soheila Tofighi

2017-01-01

Full Text Available Introduction: Currently, large dams in the world, due to the high amount of sediments in the reservoir, especially around the intake, have operational problems. One of the solutions for this problem is pressure flushing. In this type of flushing, a mixture of water and sediment is removed from bottom outlets form dam reservoir and a funnel shaped crater is created in the vicinity of the outlet opening. In laboratory experiments carried out in this study, pressure flushing with the expansion of bottom outlet within the reservoir and its statistical analysis of bursting events were investigated. The structure of the turbulent flow is not fully understood due to their complexity and random nature. Klein et al. Introduced the turbulence bursting in this kind of flow and Nezo and Nakagora suggested that the events resulting from turbulence bursting has a significant effect of transferring the sediment particles. Materials and Methods: For the purposes of this study, the experiments were conducted with a physical model with 7m length, 1.4m width, and 1.5m height, consisting of three parts namely the inlet of the model, the main reservoir, and settling basin. The main reservoir of the model was 5m long and the sediments were placed within this part of the model. The sediment particles were non-cohesive silica with uniform size and with median diameter (d50 1.15mm and geometrics standard deviation (σg 1.37. Experiments carried out with different discharges and water depths above the bottom outlet in different expansion size of outlet channel in constant sediment level of 20cm above the center of the outlet channel. The model was slowly filled with water until the water surface elevation reached to a desired level. The bottom outlet was manually opened, after a while sedimentwere discharged with the water flow in very high concentrations through the outlet channel (sudden discharge and a funnel shaped crater was formed in front of it. After the run of

Ecological and Economic Prerequisites for the Extraction of Solid Minerals from the Bottom of the Arctic Seas

Directory of Open Access Journals (Sweden)

Myaskov Alexander

2017-01-01

Full Text Available The world ocean has huge reserves of minerals that are contained directly in the water, as well as on the surface of its bottom and in its subsoils. The deposits of solid minerals on the surface of the bottom of the World Ocean are considered the most promising for industrial extraction. The deposits of ferromanganese nodules, cobalt-manganese crusts and polymetallic sulphides are considered as an object of extracting more often than others. There are the largest deposits of ferromanganese nodules in the central and southern parts of the Pacific Ocean, in the central part of the Indian Ocean, and in the seas of the Arctic Ocean near Russia. The deposits of ferromanganese nodules are a serious alternative to deposits of manganese ore on land. However, there are many factors influencing the efficiency of the development of ferromanganese deposits, the most significant are: the content of the useful component in the ore, the depth of the bottom and the distance from the seaports. It is also necessary to take into account the possible environmental consequences of underwater mining.

Nonlocal impacts of the Loop Current on cross-slope near-bottom flow in the northeastern Gulf of Mexico

Science.gov (United States)

Nguyen, Thanh-Tam; Morey, Steven L.; Dukhovskoy, Dmitry S.; Chassignet, Eric P.

2015-04-01

Cross-slope near-bottom motions near De Soto Canyon in the northeastern Gulf of Mexico are analyzed from a multidecadal ocean model simulation to characterize upwelling and downwelling, important mechanisms for exchange between the deep ocean and shelf in the vicinity of the 2010 BP Macondo well oil spill. Across the continental slope, large-scale depression and offshore movement of isopycnals (downwelling) occur more frequently when the Loop Current impinges upon the West Florida Shelf slope farther south. Upwelling and onshore movement of isopycnals occurs with roughly the same likelihood regardless of Loop Current impingement on the slope. The remote influence of Loop Current on the De Soto Canyon region downwelling is a consequence of a high-pressure anomaly that extends along the continental slope emanating from the location of Loop Current impact.

NEFSC 2002 Winter Bottom Trawl Survey (AL0203, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2002 Fall Bottom Trawl Survey (AL0210, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2011 Fall Bottom Trawl Survey (HB1105, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2008 Spring Bottom Trawl Survey (AL0801, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2008 Spring Bottom Trawl Survey (HB0802, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2015 Fall Bottom Trawl Survey (HB1506, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2011 Spring Bottom Trawl Survey (HB1102, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2007 Bottom Trawl Survey Calibration (HB0711, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2003 Spring Bottom Trawl Survey (DE0303, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2008 Fall Bottom Trawl Survey (AL0803, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2004 Winter Bottom Trawl Survey (AL0401, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2005 Fall Bottom Trawl Survey (AL0508, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 1998 Fall Bottom Trawl Survey (AL9811, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2009 Spring Bottom Trawl Survey (HB0901, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2012 Spring Bottom Trawl Survey (HB1201, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2015 Spring Bottom Trawl Survey (HB1501, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2004 Spring Bottom Trawl Survey (AL0403, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 1999 Fall Bottom Trawl Survey (AL9911, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2005 Fall Bottom Trawl Survey (AL0509, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2012 Fall Bottom Trawl Survey (HB1206, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2013 Fall Bottom Trawl Survey (HB1304, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2010 Spring Bottom Trawl Survey (HB1002, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2016 Fall Bottom Trawl Survey (HB1604, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2000 Fall Bottom Trawl Survey (Al0006, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2000 Fall Bottom Trawl Survey (AL0007, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2005 Winter Bottom Trawl Survey (AL0502, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2009 Fall Bottom Trawl Survey (HB0905, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2004 Fall Bottom Trawl Survey (AL0409, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2013 Spring Bottom Trawl Survey (HB1301, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2014 Fall Bottom Trawl Survey (HB1405, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2014 Spring Bottom Trawl Survey (HB1401, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2007 Bottom Trawl Survey Calibration (HB0710, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2005 Spring Bottom Trawl Survey (AL0504, EK500)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2016 Spring Bottom Trawl Survey (HB1601, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

NEFSC 2008 Fall Bottom Trawl Survey (HB0807, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

Some Approaches to the Analysis and Interpretation of Wide-Angle Bottom Loss Data.

Science.gov (United States)

1982-02-15

different mechanisms which cause acoustic energy to be lost in the ocean bottom. It is, however, a very significant parameter in predicting bottom loss...Model Based on Numerical Integration," J. Acoust. Soc. Am. 64, 1470. Helmberger, D. V., G. Engen , and P. Scott, 1979. "A Note on Velocity, Density, and

Probing magnetic bottom and crustal temperature variations along the Red Sea margin of Egypt

Science.gov (United States)

Ravat, D.; Salem, A.; Abdelaziz, A.M.S.; Elawadi, E.; Morgan, P.

2011-01-01

Over 50 magnetic bottom depths derived from spectra of magnetic anomalies in Eastern Egypt along the Red Sea margin show variable magnetic bottoms ranging from 10 to 34. km. The deep magnetic bottoms correspond more closely to the Moho depth in the region, and not the depth of 580??C, which lies significantly deeper on the steady state geotherms. These results support the idea of Wasilewski and coworkers that the Moho is a magnetic boundary in continental regions. Reduced-to-pole magnetic highs correspond to areas of Younger Granites that were emplaced toward the end of the Precambrian. Other crystalline Precambrian units formed earlier during the closure of ocean basins are not strongly magnetic. In the north, magnetic bottoms are shallow (10-15. km) in regions with a high proportion of these Younger Granites. In the south, the shoaling of the magnetic bottom associated with the Younger Granites appears to be restricted to the Aswan and Ras Banas regions. Complexity in the variation of magnetic bottom depths may arise due to a combination of factors: i) regions of Younger (Precambrian) Granites with high magnetite content in the upper crust, leaving behind low Curie temperature titanomagnetite components in the middle and lower crust, ii) rise in the depth of 580??C isotherm where the crust may have been heated due to initiation of intense magmatism at the time of the Red Sea rifting (~. 20. Ma), and iii) the contrast of the above two factors with respect to the neighboring regions where the Moho and/or Curie temperature truncates lithospheric ferromagnetism. Estimates of fractal and centroid magnetic bottoms in the oceanic regions of the Red Sea are significantly below the Moho in places suggesting that oceanic uppermost mantle may be serpentinized to the depth of 15-30 km in those regions. ?? 2011 Elsevier B.V.

The last stage of Earth's formation: Increasing the pressure

Science.gov (United States)

Lock, S. J.; Stewart, S. T.; Mukhopadhyay, S.

2017-12-01

A range of high-energy, high-angular momentum (AM) giant impacts have been proposed as a potential trigger for lunar origin. High-energy, high-AM collisions create a previously unrecognized planetary object, called a synestia. Terrestrial synestias exceed the corotation limit for a rocky planet, forming an extended structure with a corotating inner region and disk-like outer region. We demonstrate that the internal pressures of Earth-like planets do not increase monotonically during the giant impact stage, but can vary substantially in response to changes in rotation and thermal state. The internal pressures in an impact-generated synestia are much lower than in condensed, slowly rotating planets of the same mass. For example, the core-mantle boundary (CMB) pressure can be as low as 60 GPa for a synestia with Earth mass and composition, compared to 136 GPa in the present-day Earth. The lower pressures are due to the low density and rapid rotation of the post-impact structure. After a high-AM Moon-forming impact, the internal pressures in the interior of the synestia would have increased to present-day Earth values in two stages: first by vapor condensation and second by removal of AM from the Earth during the tidal evolution of the Moon. The pressure evolution of the Earth has several implications. Metal-silicate equilibration after the impact would have occurred at much lower pressures than has previously been assumed. The observed moderately siderophile element abundances in the mantle may be consistent with equilibration at the bottom of a deep, lower-pressure magma ocean. In addition, the pressure at the CMB during cooling is coincident with, or lower than, the proposed intersection of liquid adiabats with the mantle liquidus. The mantle would hence freeze from the bottom up and there would be no basal magma ocean. The subsequent pressure increase and tidal heating due to the Moon's orbital evolution likely induces melting in the lowermost mantle. Increasing

Strong Flows of Bottom Water in Abyssal Channels of the Atlantic

Science.gov (United States)

Morozov, E. G.

Analysis of bottom water transport through the abyssal channels of the Atlantic Ocean is presented. The study is based on recent observations in the Russian expeditions and historical data. A strong flow of Antarctic Bottom Water from the Argentine Basin to the Brazil Basin through the Vema Channel is observed on the basis of lowered profilers and anchored buoys with current meters. The further flow of bottom water in the Brazil Basin splits in the northern part of the basin. Part of the bottom water flows to the East Atlantic through the Romanche and Chain fracture zones. The other part follows the bottom topography and flows to the northwester into the North American Basin. Part of the northwesterly flow propagates through the Vema Fracture Zone into the Northeastern Atlantic. This flow generally fills the bottom layer in the Northeastern Atlantic basins. The flows of bottom waters through the Romanche and Chain fracture zones do not spread to the Northeast Atlantic due to strong mixing in the equatorial zone and enhanced transformation of bottom water properties.

Phased array concept for the ultrasonic inservice inspection of the spherical bottom of BWR-pressure vessels

International Nuclear Information System (INIS)

Brekow, G.; Wuestenberg, H.; Moehrle, W.; Schulz, E.

1989-01-01

The spherical bottom of BWR-pressure vessels contains holes for the nozzles of control rods and instrumentation. Up to now the detectable areas for the ultrasonic inspection are the accessible ligaments between the nozzles with an orientation parallel and transverse to the manipulator rails. Some licensing authorities demand an inspection technique capable of reliably detecting significant crack initiation in all critical areas near the cladding of the spherical inner surface. By order and in cooperation with the HEW we have developed a computer controlled equipment with two ultrasonic probes containing four linear arrays and a digitized A-scan storage for documentation and evaluation of inspection results. The manipulator guided probe movement in the paths between the nozzles of the spherical bottom is controlled by a computer program. This program determines for each array system and for each coupling position the beam angle as a function of the variable skewing angle to realize detection conditions suited to possible crack positions at the longitudinal, transverse and diagonal ligaments between the nozzles for control rods and instrumentation. (orig./HP)

Rapid shelf-wide cooling response of a stratified coastal ocean to hurricanes.

Science.gov (United States)

Seroka, Greg; Miles, Travis; Xu, Yi; Kohut, Josh; Schofield, Oscar; Glenn, Scott

2017-06-01

Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead-of-eye-center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation-validated, high-resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U.S. Mid-Atlantic hurricanes were investigated: Hurricane Irene (2011)-with an inshore Mid-Atlantic Bight (MAB) track during the late summer stratified coastal ocean season-and Tropical Storm Barry (2007)-with an offshore track during early summer. For both storms, the critical ahead-of-eye-center depth-averaged force balance across the entire MAB shelf included an onshore wind stress balanced by an offshore pressure gradient. This resulted in onshore surface currents opposing offshore bottom currents that enhanced surface to bottom current shear and turbulent mixing across the thermocline, resulting in the rapid cooling of the surface layer ahead-of-eye-center. Because the same baroclinic and mixing processes occurred for two storms on opposite ends of the track and seasonal stratification envelope, the response appears robust. It will be critical to forecast these processes and their implications for a wide range of future storms using realistic 3-D coupled atmosphere-ocean models to lower the uncertainty in predictions of TC intensities and impacts and enable coastal populations to better respond to increasing rapid intensification threats in an era of rising sea levels.

Rapid shelf‐wide cooling response of a stratified coastal ocean to hurricanes

Science.gov (United States)

Miles, Travis; Xu, Yi; Kohut, Josh; Schofield, Oscar; Glenn, Scott

2017-01-01

Abstract Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead‐of‐eye‐center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation‐validated, high‐resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U.S. Mid‐Atlantic hurricanes were investigated: Hurricane Irene (2011)—with an inshore Mid‐Atlantic Bight (MAB) track during the late summer stratified coastal ocean season—and Tropical Storm Barry (2007)—with an offshore track during early summer. For both storms, the critical ahead‐of‐eye‐center depth‐averaged force balance across the entire MAB shelf included an onshore wind stress balanced by an offshore pressure gradient. This resulted in onshore surface currents opposing offshore bottom currents that enhanced surface to bottom current shear and turbulent mixing across the thermocline, resulting in the rapid cooling of the surface layer ahead‐of‐eye‐center. Because the same baroclinic and mixing processes occurred for two storms on opposite ends of the track and seasonal stratification envelope, the response appears robust. It will be critical to forecast these processes and their implications for a wide range of future storms using realistic 3‐D coupled atmosphere‐ocean models to lower the uncertainty in predictions of TC intensities and impacts and enable coastal populations to better respond to increasing rapid intensification threats in an era of rising sea levels. PMID:28944132

The bottom water exchange between the Singapore Strait and the West Johor Strait

Science.gov (United States)

Sun, Yunfang; Eltahir, Elfatih; Malanotte-Rizzoli, Paola

2017-08-01

As a part of the border between Singapore and Malaysia, the West Johor Strait (WJS) suffered newly from harmful algal blooms. There is no previous study showing the source of the nutrients in the WJS. This paper is investigating the possible water exchange between the water in the WJS and the bottom water in Singapore Strait. This paper adopts a two-level nesting atmosphere-ocean coupled models to downscale the global atmosphere-ocean model into the Singapore coastal water, keeping the large-scale and long-term ocean and climate circulation signals and the advantages of the high-resolution. Based on the high-resolution ocean circulation fields, a Lagrangian particle tracking model is used to trace the Singapore Strait's bottom water movement and the water mixing in the WJS. The results showed that the numerical models well resolved the Singapore coastal water regional circulation. There is a small but significant bottom water (1.25%) transport from the Singapore Strait to the WJS, which occurs from the southwest coastline of Singapore. The bottom water in the Singapore Strait prefers to enter the WJS during the spring tide and the flood period, and stay in Johor Strait for 6.4 days. The spring tide is the first-order factor for the water vertical mixing in the WJS, the wind is also very important for the vertical mixing especially in neap tide condition. An overall very important factor is the light perturbation. With the strongest vertical mixing of nutrients and bottom sediments due to the spring tide, the latter ones may inhibit the light penetration during the spring tide and reduce the algal bloom. The light penetration otherwise is greater during the neap tide, when the winds are the most important factor and hence favor the algal bloom. With the strongest wind in February and the longest permanence time in June and the sufficient nutrient supply in February and June, the most serious algal blooms may happen in February and June in the WJS.

Experiments on melt dispersion with lateral failure in the bottom head of the pressure vessel

Energy Technology Data Exchange (ETDEWEB)

Meyer, L.; Gargallo, M. [Forschungszentrum Karlsruhe, Institut fur Kern-und Energietechnik, Karlsruhe (Germany)

2001-07-01

Melt dispersion experiments with lateral failure in the bottom head were carried out in a 1:18 scaled annular cavity design under low pressure conditions. Water and a bismuth alloy were used as melt simulant material and nitrogen as driving gas. With lateral breaches the liquid height in the lower head relative to the upper and lower edge of the breach is an additional parameter for the dispersion process. Shifting the break from the central position towards the side of the lower head leads to smaller melt dispersion, and a larger breach size does not necessarily lead to a larger dispersed melt fraction. (author)

Improvement of the free-surface tension model in shallow water basin by using in-situ bottom-friction measurements

Science.gov (United States)

Alekseenko, Elena; Kuznetsov, Konstantin; Roux, Bernard

2016-04-01

Wind stress on the free surface is the main driving force behind the circulation of the upper part of the ocean, which in hydrodynamic models are usually defined in terms of the coefficient of surface tension (Zhang et al., 2009, Davies et al., 2003). Moreover, wave motion impacts local currents and changes sea level, impacts the transport and the stratification of the entire water column. Influence of surface waves at the bottom currents is particularly pronounced in the shallow coastal systems. However, existing methods of parameterization of the surface tension have significant limits, especially in strong wind waves (Young et al., 2001, Jones et al., 2004) due to the difficulties of measuring the characteristics of surface waves in stormy conditions. Thus, the formula for calculating the coefficient of surface tension in our day is the actual problem in modeling fluid dynamics, particularly in the context of strong surface waves. In the hydrodynamic models usually a coefficient of surface tension is calculated once at the beginning of computation as a constant that depends on the averaged wind waves characteristic. Usually cases of strongly nonlinear wind waves are not taken into account, what significantly reduces the accuracy of the calculation of the flow structures and further calculation of the other processes in water basins, such as the spread of suspended matter and pollutants. Thus, wave motion influencing the pressure on the free surface and at the bottom must be considered in hydrodynamic models particularly in shallow coastal systems. A method of reconstruction of a free-surface drag coefficient based on the measured in-situ bottom pressure fluctuations is developed and applied in a three-dimensional hydrodynamic model MARS3D, developed by the French laboratory of IFREMER (IFREMER - French Research Institute for Marine Dynamics). MARS3D solves the Navier-Stokes equations for incompressible fluid in the Boussinesq approximation and with the

Role of Effective Density in improving the accuracy of bottom pressure based sea level measurements - A case study from Gulf of Guinea

Digital Repository Service at National Institute of Oceanography (India)

Joseph, A.; Mehra, P.; Desai, R.G.P.; Dotse, J.; Odametey, J.T.; Nkebi, E.K.; Vijaykumar, K.; Prabhudesai, S.P.

of the sea water, as a result of turbulence induced by wind forcing and impact of rain drops, is suspected to be responsible for the observed effective reduction in the in situ density of this shallow water body The accuracy of bottom-pressure based sea level...

Explicit Modeling of Solid Ocean Floor in Shallow Underwater Explosions

Directory of Open Access Journals (Sweden)

A.P. Walters

2013-01-01

Full Text Available Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. For simplicity, elastic materials were used in this current effort, though multiple constitutive soil models can be applied to improve the overall accuracy of the model. Even though this method is unable to account for soil cratering effects, it does however provide the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The study conducted here showed significant differences among the initial bottom reflections for the different solid bottom contours that were modeled. The most important bottom contour effect was the distortion to the gas bubble and its associated first pulse timing. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains.

Inversion for Sound Speed Profile by Using a Bottom Mounted Horizontal Line Array in Shallow Water

International Nuclear Information System (INIS)

Feng-Hua, Li; Ren-He, Zhang

2010-01-01

Ocean acoustic tomography is an appealing technique for remote monitoring of the ocean environment. In shallow water, matched field processing (MFP) with a vertical line array is one of the widely used methods for inverting the sound speed profile (SSP) of water column. The approach adopted is to invert the SSP with a bottom mounted horizontal line array (HLA) based on MFP. Empirical orthonormal functions are used to express the SSP, and perturbation theory is used in the forward sound field calculation. This inversion method is applied to the data measured in a shallow water acoustic experiment performed in 2003. Successful results show that the bottom mounted HLA is able to estimate the SSP. One of the most important advantages of the inversion method with bottom mounted HLA is that the bottom mounted HLA can keep a stable array shape and is safe in a relatively long period. (fundamental areas of phenomenology (including applications))

New model and field data on estimates of Antarctic Bottom Water flow through the deep Vema Channel

Science.gov (United States)

Frey, D. I.; Fomin, V. V.; Diansky, N. A.; Morozov, E. G.; Neiman, V. G.

2017-05-01

We used a numerical model of the ocean circulation with a high spatial resolution to obtain estimates of the kinematic characteristics of Antarctic Bottom Water flow through the abyssal Vema Channel in the southwestern part of the Atlantic Ocean. The results of simulations correspond to the data of direct velocity measurements made at several locations in the channel. The high horizontal and vertical resolution of the model in the bottom layer allowed us to study in detail the hydrodynamics of this flow over its entire length.

Rapid bottom melting widespread near Antarctic ice sheet grounding lines

Science.gov (United States)

Rignot, E.; Jacobs, S.

2002-01-01

As continental ice from Antartica reaches the grounding line and begins to float, its underside melts into the ocean. Results obtained with satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.

Summertime calcium carbonate undersaturation in shelf waters of the western Arctic Ocean – how biological processes exacerbate the impact of ocean acidification

Directory of Open Access Journals (Sweden)

N. R. Bates

2013-08-01

Full Text Available The Arctic Ocean accounts for only 4% of the global ocean area, but it contributes significantly to the global carbon cycle. Recent observations of seawater CO2-carbonate chemistry in shelf waters of the western Arctic Ocean, primarily in the Chukchi Sea, from 2009 to 2011 indicate that bottom waters are seasonally undersaturated with respect to calcium carbonate (CaCO3 minerals, particularly aragonite. Nearly 40% of sampled bottom waters on the shelf have saturation states less than one for aragonite (i.e., Ωaragonite 3-secreting organisms, while 80% of bottom waters present had Ωaragonite values less than 1.5. Our observations indicate seasonal reduction of saturation states (Ω for calcite (Ωcalcite and aragonite (Ωaragonite in the subsurface in the western Arctic by as much as 0.8 and 0.5, respectively. Such data indicate that bottom waters of the western Arctic shelves were already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in Ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air–sea gas exchange of CO2. Combined, these processes either increase or enhance in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA on Ω in surface and subsurface waters, respectively. Future monitoring of the western Arctic shelves is warranted to assess the present and future impact of ocean acidification and seasonal physico-biogeochemical processes on Ω values and Arctic marine ecosystems.

Conditions for the occurrence of intense turbidity currents in the benthic boundary layer over a sloping bottom

NARCIS (Netherlands)

Zhmur, VV

2003-01-01

The evolution of density currents over the continental slope of the ocean is investigated with allowance for the entrainment of the bottom sediments and background liquid in motion. A simple criterion is proposed for determining the possibility of evolving initially weak density currents into bottom

Importance of the Gulf of Aqaba for the formation of bottom water in the Red Sea

Science.gov (United States)

Plähn, Olaf; Baschek, Burkard; Badewien, Thomas H.; Walter, Maren; Rhein, Monika

2002-08-01

Conductivity-temperature-depth tracer and direct current measurements collected in the northern Red Sea in February and March 1999 are used to study the formation of deep and bottom water in that region. Historical data showed that open ocean convection in the Red Sea can contribute to the renewal of intermediate or deep water but cannot ventilate the bottom water. The observations in 1999 showed no evidence for open ocean convection in the Red Sea during the winter 1998/1999. The overflow water from the Gulf of Aqaba was found to be the densest water mass in the northern Red Sea. An anomaly of the chlorofluorocarbon component CFC-12 observed in the Gulf of Aqaba and at the bottom of the Red Sea suggests a strong contribution of this water mass to the renewal of bottom water in the Red Sea. The CFC data obtained during this cruise are the first available for this region. Because of the new signal, it is possible for the first time to subdivide the deep water column into deep and bottom water in the northern Red Sea. The available data set also shows that the outflow water from the Gulf of Suez is not dense enough to reach down to the bottom of the Red Sea but was found about 250 m above the bottom.

An inventory of Arctic Ocean data in the World Ocean Database

Science.gov (United States)

Zweng, Melissa M.; Boyer, Tim P.; Baranova, Olga K.; Reagan, James R.; Seidov, Dan; Smolyar, Igor V.

2018-03-01

The World Ocean Database (WOD) contains over 1.3 million oceanographic casts (where cast refers to an oceanographic profile or set of profiles collected concurrently at more than one depth between the ocean surface and ocean bottom) collected in the Arctic Ocean basin and its surrounding marginal seas. The data, collected from 1849 to the present, come from many submitters and countries, and were collected using a variety of instruments and platforms. These data, along with the derived products World Ocean Atlas (WOA) and the Arctic Regional Climatologies, are exceptionally useful - the data are presented in a standardized, easy to use format and include metadata and quality control information. Collecting data in the Arctic Ocean is challenging, and coverage in space and time ranges from excellent to nearly non-existent. WOD continues to compile a comprehensive collection of Arctic Ocean profile data, ideal for oceanographic, environmental and climatic analyses (https://doi.org/10.7289/V54Q7S16" target="_blank">https://doi.org/10.7289/V54Q7S16).

Re-initiation of bottom water formation in the East Sea (Japan Sea) in a warming world.

Science.gov (United States)

Yoon, Seung-Tae; Chang, Kyung-Il; Nam, SungHyun; Rho, TaeKeun; Kang, Dong-Jin; Lee, Tongsup; Park, Kyung-Ae; Lobanov, Vyacheslav; Kaplunenko, Dmitry; Tishchenko, Pavel; Kim, Kyung-Ryul

2018-01-25

The East Sea (Japan Sea), a small marginal sea in the northwestern Pacific, is ventilated deeply down to the bottom and sensitive to changing surface conditions. Addressing the response of this marginal sea to the hydrological cycle and atmospheric forcing would be helpful for better understanding present and future environmental changes in oceans at the global and regional scales. Here, we present an analysis of observations revealing a slowdown of the long-term deepening in water boundaries associated with changes of water formation rate. Our results indicate that bottom (central) water formation has been enhanced (reduced) with more (less) oxygen supply to the bottom (central) layer since the 2000s. This paper presents a new projection that allows a three-layered deep structure, which retains bottom water, at least until 2040, contrasting previous results. This projection considers recent increase of slope convections mainly due to the salt supply via air-sea freshwater exchange and sea ice formation and decrease of open-ocean convections evidenced by reduced mixed layer depth in the northern East Sea, resulting in more bottom water and less central water formations. Such vigorous changes in water formation and ventilation provide certain implications on future climate changes.

Sensitivity of the Arctic Ocean gas hydrate to climate changes in the period of 1948-2015

Science.gov (United States)

Malakhova, Valentina V.; Golubeva, Elena N.; Iakshina, Dina F.

2017-11-01

The objective of the present study is to analyze the interactions between a methane hydrates stability zone and the ocean temperature variations and to define the hydrate sensitivity to the contemporary warming in the Arctic Ocean. To obtain the spatial-temporary variability of the ocean bottom temperature we employ the ICMMG regional Arctic-North Atlantic ocean model that has been developed in the Institute of Computational Mathematics and Mathematical Geophysics. With the ice-ocean model the Arctic bottom water temperatures were analyzed. The resulting warming ocean bottom water is spatially inhomogeneous, with a strong impact by the Atlantic inflow on shallow regions of 200-500 m depth. Results of the mathematical modeling of the dynamics of methane hydrate stability zone in the Arctic Ocean sediment are reported. We find that the reduction of the methane hydrate stability zone occurs in the Arctic Ocean between 250 and 400 m water depths within the upper 100 m of sediment in the area influenced by the Atlantic inflow. We have identified the areas of the Arctic Ocean where an increase in methane release is probable to occur at the present time.

Does deep ocean mixing drive upwelling or downwelling of abyssal waters?

Science.gov (United States)

Ferrari, R. M.; McDougall, T. J.; Mashayek, A.; Nikurashin, M.; Campin, J. M.

2016-02-01

It is generally understood that small-scale mixing, such as is caused by breaking internal waves, drives upwelling of the densest ocean waters that sink to the ocean bottom at high latitudes. However the observational evidence that the turbulent fluxes generated by small-scale mixing in the stratified ocean interior are more vigorous close to the ocean bottom than above implies that small-scale mixing converts light waters into denser ones, thus driving a net sinking of abyssal water. Using a combination of numerical models and observations, it will be shown that abyssal waters return to the surface along weakly stratified boundary layers, where the small-scale mixing of density decays to zero. The net ocean meridional overturning circulation is thus the small residual of a large sinking of waters, driven by small-scale mixing in the stratified interior, and a comparably large upwelling, driven by the reduced small-scale mixing along the ocean boundaries.

Ocean Thermal Conversion (OTEC) Project Bottom Cable Protection Study: Environmental Characteristics and Hazards Analysis,

Science.gov (United States)

1981-10-01

Chesaneake Division, Naval Facilities Engineering Command, Washington, DC) 34. "Strait of Belle Isle Crossing HVDC Transmission - Submarine Cable...phenomena; such as wind storm generated wave action, bottom currents, bottom mudslides, or seismic activity; as well as human activity, such as...engaging a cable. Ship anchors are used to develop holding power on the seafloor for mooring a floating body permanently or temporary on site. The major

NEFSC 2008 Spring Bottom Trawl Survey - Site Specific Calibration (HB0803, EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC bottom trawl survey is a fisheries independent, multi-species survey that provides the primary scientific data for fisheries assessments in the U.S....

A Synoptic View of the Ventilation and Circulation of Antarctic Bottom Water from Chlorofluorocarbons and Natural Tracers

Science.gov (United States)

Purkey, Sarah G.; Smethie, William M.; Gebbie, Geoffrey; Gordon, Arnold L.; Sonnerup, Rolf E.; Warner, Mark J.; Bullister, John L.

2018-01-01

Antarctic Bottom Water (AABW) is the coldest, densest, most prolific water mass in the global ocean. AABW forms at several distinct regions along the Antarctic coast and feeds into the bottom limb of the meridional overturning circulation, filling most of the global deep ocean. AABW has warmed, freshened, and declined in volume around the globe in recent decades, which has implications for the global heat and sea level rise budgets. Over the past three decades, the use of tracers, especially time-varying tracers such as chlorofluorocarbons, has been essential to our understanding of the formation, circulation, and variability of AABW. Here, we review three decades of temperature, salinity, and tracer data and analysis that have led to our current knowledge of AABW and how the southern component of deep-ocean ventilation is changing with time.

Ice-­Ocean Thermodynamic Interface and Small-­Scale Issues

Energy Technology Data Exchange (ETDEWEB)

Turner, Adrian K. [Los Alamos National Laboratory

2012-07-02

This presentation discusses: (1) Stefan condition, (2) lower boundary condition of mushy layers, (3) salt flux to ocean from gravity drainage, (4) distribution of salt flux in the ocean, (5) under ice melt ponds and false bottoms, and (6) basal ablation.

Topographic control of oceanic flows in deep passages and straits

Science.gov (United States)

Whitehead, J. A.

1998-08-01

Saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next, depending on the source of bottom water. Flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next. Examples in the Atlantic include flow in the Romanche Fracture Zone, the Vema Channel, the Ceara Abyssal Plain, the Anegada-Jungfern passage, and the Discovery Gap, but there are many more. Theoretical predictions of volume flux using a method that requires only conductivity-temperature-depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and/or geostrophic estimates for seven cases. The ratio of prediction to volume flux estimate ranges from 1.0 to 2.7. Some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins. Theory of the influence of rotation on such critical flows is reviewed. Predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods.

The oceanic chemistry of the U- and Th-series nuclides

International Nuclear Information System (INIS)

Cochran, J.K.

1982-01-01

The subject is discussed under the headings: input and removal of U- and Th-series nuclides in the oceans; uranium (input to the oceans; in the coastal ocean; in the open ocean; in sediment pore water; removal from the oceans; sources and sinks of 234 U in the oceans); thorium (scavenging in the deep sea; 230 Th and 231 Pa balance; removal from the coastal and surface ocean); Ra-226 and Ra-228; radon (in surface waters; near bottom 222 Rn as a tracer for vertical mixing); lead-210; polonium-210. (U.K.)

Bottom pressure, vertical acoustic round-trip travel time, and near-bottom currents data collected by Current-and-Pressure-recording Inverted Echo Sounders (CPIES), as part of the Kuroshio Extension System Study (KESS), from 26 April 2004 to 25 June 2006 in the Kuroshio Extension east of Japan (NODC Accession 0073269)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains Current and Pressure recording Inverted Echo Sounder (CPIES) measurements collected during the Kuroshio Extension System Study (KESS) under...

Deep ice and salty oceans of icy worlds, how high pressures influence their thermodynamics and provide constrains on extraterrestrial habitability

Science.gov (United States)

Journaux, B.; Brown, J. M.; Bollengier, O.; Abramson, E.

2017-12-01

As in Earth arctic and Antarctic regions, suspected extraterrestrial deep oceans in icy worlds (i.e. icy moons and water-rich exoplanets) chemistry and thermodynamic state will strongly depend on their equilibrium with H2O ice and present solutes. Na-Mg-Cl-SO4 salt species are currently the main suspected ionic solutes to be present in deep oceans based on remote sensing, magnetic field measurements, cryovolcanism ice grains chemical analysis and chondritic material aqueous alteration chemical models. Unlike on our planet, deep extraterrestrial ocean might also be interacting at depth with high pressure ices (e.g. III, V, VI, VI, X) which have different behavior compared to ice Ih. Unfortunately, the pressures and temperatures inside these hydrospheres differ significantly from the one found in Earth aqueous environments, so most of our current thermodynamic databases do not cover the range of conditions relevant for modeling realistically large icy worlds interiors. Recent experimental results have shown that the presence of solutes, and more particularly salts, in equilibrium with high pressure ices have large effects on the stability, buoyancy and chemistry of all the phases present at these extreme conditions. High pressure in-situ measurements using diamond anvil cell apparatus were operated both at the University of washington and at the European Synchrotron Radiation Facility on aqueous systems phase diagrams with Na-Mg-Cl-SO4 species, salt incorporation in high pressure ices and density inversions between the solid and the fluids. These results suggest a more complex picture of the interior structure, dynamic and chemical evolution of large icy worlds hydrospheres when solutes are taken into account, compared to current models mainly using pure water. Based on our in-situ experimental measurements, we propose the existence of new liquid environments at greater depths and the possibility of solid state transport of solute through the high pressure ices

Dynamics of the Antarctic Circumpolar Current as seen by GRACE (Invited)

Science.gov (United States)

Thomas, M.; Dobslaw, H.; Bergmann, I.

2010-12-01

The Antarctic Circumpolar Current, being the strongest and longest ocean current on Earth, connects the three great ocean basins and contributes substantially to the global re-distribution of water masses, with a significant impact on global climate. Observational coverage from in-situ measurements is sparse due to the harsh environmental conditions, and satellite altimetry does not capture the full extent of the current due to seasonal sea-ice coverage. Ocean bottom pressure variations as sensed with the satellite gravity mission GRACE provide a promising way to broaden our observational basis. Besides monthly mean gravity fields that provide ocean bottom pressure variations averaged over 30 days, several alternative GRACE products with higher temporal resolution have been developed during the most recent years. These include 10-day solutions from GRGS Toulouse, weekly solutions from the GFZ Potsdam as well as constrained daily solutions from the University of Bonn which have been obtained by means of a Kalman filtering approach. In this presentation, ocean bottom pressure derived from these alternative GRACE releases will be contrasted against both in-situ observations and output from a numerical ocean model, highlighting the additional information contained in these GRACE solutions with respect to the standard monthly fields. By means of statistical analyses of ocean bottom pressure variations and barotropic transports it will be demonstrated how these new GRACE releases are contributing to our understanding of this highly dynamic great ocean conveyor.

Controls on the global distribution of contourite drifts: Insights from an eddy-resolving ocean model

Science.gov (United States)

Thran, Amanda C.; Dutkiewicz, Adriana; Spence, Paul; Müller, R. Dietmar

2018-05-01

Contourite drifts are anomalously high sediment accumulations that form due to reworking by bottom currents. Due to the lack of a comprehensive contourite database, the link between vigorous bottom water activity and drift occurrence has yet to be demonstrated on a global scale. Using an eddy-resolving ocean model and a new georeferenced database of 267 contourites, we show that the global distribution of modern contourite drifts strongly depends on the configuration of the world's most powerful bottom currents, many of which are associated with global meridional overturning circulation. Bathymetric obstacles frequently modify flow direction and intensity, imposing additional finer-scale control on drift occurrence. Mean bottom current speed over contourite-covered areas is only slightly higher (2.2 cm/s) than the rest of the global ocean (1.1 cm/s), falling below proposed thresholds deemed necessary to re-suspend and redistribute sediments (10-15 cm/s). However, currents fluctuate more frequently and intensely over areas with drifts, highlighting the role of intermittent, high-energy bottom current events in sediment erosion, transport, and subsequent drift accumulation. We identify eddies as a major driver of these bottom current fluctuations, and we find that simulated bottom eddy kinetic energy is over three times higher in contourite-covered areas in comparison to the rest of the ocean. Our work supports previous hypotheses which suggest that contourite deposition predominantly occurs due to repeated acute events as opposed to continuous reworking under average-intensity background flow conditions. This suggests that the contourite record should be interpreted in terms of a bottom current's susceptibility to experiencing periodic, high-speed current events. Our results also highlight the potential role of upper ocean dynamics in contourite sedimentation through its direct influence on deep eddy circulation.

Measuring ocean acidification: new technology for a new era of ocean chemistry.

Science.gov (United States)

Byrne, Robert H

2014-05-20

Human additions of carbon dioxide to the atmosphere are creating a cascade of chemical consequences that will eventually extend to the bottom of all the world's oceans. Among the best-documented seawater effects are a worldwide increase in open-ocean acidity and large-scale declines in calcium carbonate saturation states. The susceptibility of some young, fast-growing calcareous organisms to adverse impacts highlights the potential for biological and economic consequences. Many important aspects of seawater CO2 chemistry can be only indirectly observed at present, and important but difficult-to-observe changes can include shifts in the speciation and possibly bioavailability of some life-essential elements. Innovation and invention are urgently needed to develop the in situ instrumentation required to document this era of rapid ocean evolution.

On anisotropy and internal pressure errors in numerical ocean models and processes near the shelf edge

Energy Technology Data Exchange (ETDEWEB)

Thiem, Oeyvind A.

2004-12-01

In this thesis the focus has been on anisotropy, internal pressure errors and shelf edge/slope processes. Anisotropy is a common problem in ocean models. Especially where a rectangular grid is used to discretize the horizontal. Selecting a horizontal grid, which reduces the anisotropy, will therefore probably be important when new ocean models are being developed. Hexagonal grid discretization in the horizontal has the desired property of reducing anisotropy, and therefore this grid should be considered as a reasonable choice for new ocean models. In sigma coordinate models internal pressure errors occur in areas with steep topography. In the second paper in this thesis, it is shown that the internal pressure errors depend on the grid orientation. It is further shown that the erroneous velocities in the sea mount test case of Beckmann and Haidvogel (1993) can be reduced significantly by first computing the internal pressure gradients in both the original and a coordinate system where the axis are rotated 45 degrees to the original. Then a normalized weighted linear combination of the two estimates is used as the internal pressure gradients in the simulation. A following up paper where this method is used on a real ocean should be performed to investigate how well this method performs in domains with irregular topography. In such an experiment the boundary should be closed and the initial velocities set to zero. The occurring currents should then be compared with a corresponding experiment, where the initial pressure gradients are computed in the original grid only. In the third and fourth paper the focus is on the use of BOM in along shelf barotropic flow. First the generation of eddies is investigated. This is done in the third paper and two simulations are performed. The first simulation is a barotropic simulation, and the second is a two layer simulation. The results from both simulations show development of eddies, but the strength of the eddies depend on the

Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

Energy Technology Data Exchange (ETDEWEB)

Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.

2017-05-01

Experiments establishing the effect of pressure on the Fe³⁺/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO₂ were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe³⁺/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe³⁺/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe³⁺ ions of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe²⁺ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe³⁺/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe³⁺/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe²⁺ ions from ~5.5 to ~6, with negligible effects evident for Fe³⁺ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe³⁺/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe³⁺/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations

Performance of an autonomously deployable telemetered deep ocean seismic observatory

Science.gov (United States)

Berger, Jonathan; Laske, Gabe; Orcutt, John; Babcock, Jeffrey

2016-04-01

We describe a transformative technology that can provide near real-time telemetry of sensor data from the ocean bottom without a moored buoy or a cable to shore. The breakthrough technology that makes this system possible is an autonomous surface vehicle called a Wave Glider developed by Liquid Robotics, which harvests wave and solar energy for motive and electrical power. For navigation, the wave glider is equipped with a small computer, a GPS receiver, a rudder, solar panels and batteries, AIS ship detection receiver, weather station, and an Iridium satellite modem. Wave gliders have demonstrated trans-oceanic range and long-term station keeping capabilities. We present results from several deployments of a prototype system that demonstrate the feasibility of this concept. The system comprises ocean bottom package (OBP) and an ocean surface gateway (OSG). Acoustic communications connect the OBP instruments with OSG while communications between the gateway and land are provided by the Iridium satellite constellation. The most recent deployment of the OBP was off the edge of the Patton Escarpment some 300 km west of San Diego in 4000 m of water. The OSG was launched about 30 km west of San Diego harbor and programmed to navigate to the site of the ocean bottom package. Arriving after 161 hours, the OSG then commenced holding station at the site for the next 68 days. Speeds over-the-ground varied with wind, wave, and surface current conditions but averaged 0.5 m/s while winds varied between 0 m/s and 17 m/s and wave heights between 0.2 m and 5.9 m. Over this period the median total data latency was 260 s and the data loss less that 0.2% when the wave glider was within 1.5 km of the central point. We have also tested a full-scale model of a towable ocean bottom package, which demonstrated that a wave glider could tow and navigate an autonomously deployable ocean bottom package. Taken together, these tests have demonstrated that the concept is viable for long

Refinement of the bottom boundary of the INES scale

International Nuclear Information System (INIS)

Ferjencik, Milos

2010-01-01

No existing edition of the International Nuclear Events Scale (INES) Manual addresses in depth the determination of the bottom boundary of the Scale, although a need for a definition is felt. The article introduces a method for determining the INES bottom boundary applicable to pressurized water reactors. This bottom boundary is put identical with the threshold of degradation of the installation's nuclear safety assurance. A comprehensive flowchart has been developed as the main outcome of the analysis of the nuclear safety assurance violation issue. The use of this flowchart in INES classification to replace the introductory question in the General INES Rating Procedure in the INES Manual is recommended. (orig.)

Connecting an Ocean-Bottom Broadband Seismometer to a Seafloor Cabled Observatory: A Prototype System in Monterey Bay

Science.gov (United States)

McGill, P.; Neuhauser, D.; Romanowicz, B.

2008-12-01

The Monterey Ocean-Bottom Broadband (MOBB) seismic station was installed in April 2003, 40 km offshore from the central coast of California at a seafloor depth of 1000 m. It comprises a three-component broadband seismometer system (Guralp CMG-1T), installed in a hollow PVC caisson and buried under the seafloor; a current meter; and a differential pressure gauge. The station has been operating continuously since installation with no connection to the shore. Three times each year, the station is serviced with the aid of a Remotely Operated Vehicle (ROV) to change the batteries and retrieve the seismic data. In February 2009, the MOBB system will be connected to the Monterey Accelerated Research System (MARS) seafloor cabled observatory. The NSF-funded MARS observatory comprises a 52 km electro-optical cable that extends from a shore facility in Moss Landing out to a seafloor node in Monterey Bay. Once installation is completed in November 2008, the node will provide power and data to as many as eight science experiments through underwater electrical connectors. The MOBB system is located 3 km from the MARS node, and the two will be connected with an extension cable installed by an ROV with the aid of a cable-laying toolsled. The electronics module in the MOBB system is being refurbished to support the connection to the MARS observatory. The low-power autonomous data logger has been replaced with a PC/104 computer stack running embedded Linux. This new computer will run an Object Ring Buffer (ORB), which will collect data from the various MOBB sensors and forward it to another ORB running on a computer at the MARS shore station. There, the data will be archived and then forwarded to a third ORB running at the UC Berkeley Seismological Laboratory. Timing will be synchronized among MOBB's multiple acquisition systems using NTP, GPS clock emulation, and a precise timing signal from the MARS cable. The connection to the MARS observatory will provide real-time access to

Influence of internal tides on Antarctic Bottom Water propagation through abyssal channels

Science.gov (United States)

Morozov, Eugene

2010-05-01

Antarctic Bottom Water (AABW) propagates in the Atlantic Ocean from the Weddell Sea to the north through narrow passages in submarine ridges. Submarine ridges are regions of strong internal tide generation in the ocean that causes mixing and eventually AABW loses its distinguishing properties such as low temperature and salinity. The Vema Fracture Zone (11 N) and Romanche Fracture Zone (equator) in the Mid-Atlantic Ridge (MAR) are pathways for AABW to the Northeast Atlantic. The deep basin of the Northeast Atlantic (Canary Basin and Gambia Abyssal Plain) are filled with the bottom water propagating through the Vema FZ rather than through the equatorial fracture zones because strong internal tides and mixing over the slopes of the MAR near the equator cause warming of AABW and decrease of its density. Further propagation of AABW through the Kane Gap is low. Recent field measurements in the fracture zones confirm this concept based on modeling results. Results of recent cruises are presented.

Bottom friction optimization for a better barotropic tide modelling

Science.gov (United States)

Boutet, Martial; Lathuilière, Cyril; Son Hoang, Hong; Baraille, Rémy

2015-04-01

At a regional scale, barotropic tides are the dominant source of variability of currents and water heights. A precise representation of these processes is essential because of their great impacts on human activities (submersion risks, marine renewable energies, ...). Identified sources of error for tide modelling at a regional scale are the followings: bathymetry, boundary forcing and dissipation due to bottom friction. Nevertheless, bathymetric databases are nowadays known with a good accuracy, especially over shelves, and global tide models performances are better than ever. The most promising improvement is thus the bottom friction representation. The method used to estimate bottom friction is the simultaneous perturbation stochastic approximation (SPSA) which consists in the approximation of the gradient based on a fixed number of cost function measurements, regardless of the dimension of the vector to be estimated. Indeed, each cost function measurement is obtained by randomly perturbing every component of the parameter vector. An important feature of SPSA is its relative ease of implementation. In particular, the method does not require the development of tangent linear and adjoint version of the circulation model. Experiments are carried out to estimate bottom friction with the HYbrid Coordinate Ocean Model (HYCOM) in barotropic mode (one isopycnal layer). The study area is the Northeastern Atlantic margin which is characterized by strong currents and an intense dissipation. Bottom friction is parameterized with a quadratic term and friction coefficient is computed with the water height and the bottom roughness. The latter parameter is the one to be estimated. Assimilated data are the available tide gauge observations. First, the bottom roughness is estimated taking into account bottom sediment natures and bathymetric ranges. Then, it is estimated with geographical degrees of freedom. Finally, the impact of the estimation of a mixed quadratic/linear friction

Combining Top-down and Bottom-up Accountability: Evidence from a Bribery Experiment.

OpenAIRE

Danila Serra

2008-01-01

Monitoring corruption typically relies on top-down interventions aimed at increasing the probability of external controls and the severity of punishment. An alternative approach to fighting corruption is to induce bottom-up pressure for reform. Recent studies have shown that both top-down and bottom-up mechanisms are rarely able to keep service providers accountable. This paper investigates the effectiveness of an accountability system that combines bottom-up monitoring and top-down auditing ...

Global assessment of benthic nepheloid layers and linkage with upper ocean dynamics

Science.gov (United States)

Gardner, Wilford D.; Richardson, Mary Jo; Mishonov, Alexey V.

2018-01-01

Global maps of the maximum bottom concentration, thickness, and integrated particle mass in benthic nepheloid layers are published here to support collaborations to understand deep ocean sediment dynamics, linkage with upper ocean dynamics, and assessing the potential for scavenging of adsorption-prone elements near the deep ocean seafloor. Mapping the intensity of benthic particle concentrations from natural oceanic processes also provides a baseline that will aid in quantifying the industrial impact of current and future deep-sea mining. Benthic nepheloid layers have been mapped using 6,392 full-depth profiles made during 64 cruises using our transmissometers mounted on CTDs in multiple national/international programs including WOCE, SAVE, JGOFS, CLIVAR-Repeat Hydrography, and GO-SHIP during the last four decades. Intense benthic nepheloid layers are found in areas where eddy kinetic energy in overlying waters, mean kinetic energy 50 m above bottom (mab), and energy dissipation in the bottom boundary layer are near the highest values in the ocean. Areas of intense benthic nepheloid layers include the Western North Atlantic, Argentine Basin in the South Atlantic, parts of the Southern Ocean and areas around South Africa. Benthic nepheloid layers are weak or absent in most of the Pacific, Indian, and Atlantic basins away from continental margins. High surface eddy kinetic energy is associated with the Kuroshio Current east of Japan. Data south of the Kuroshio show weak nepheloid layers, but no transmissometer data exist beneath the Kuroshio, a deficiency that should be remedied to increase understanding of eddy dynamics in un-sampled and under-sampled oceanic areas.

Temperature profile, pressure, and nutrients data from bottle in South Atlantic Ocean from 24 November 1987 to 12 March 1989 (NODC Accession 0000196)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile, pressure, and nutrients data were collected using bottle in the South Atlantic Ocean from 24 November 1987 to 12 March 1989. Data were collected...

Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

Science.gov (United States)

Zhang, H.; Hirschmann, M. M.

2014-12-01

The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

Water level measurements (bottom hydrostatic pressure) data from the Gulf of Alaska from 02 April 1983 to 25 October 1989 (NODC Accession 0000339)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Depth, pressure, and water temperature data were collected at fixed platforms in the Gulf of Mexico from April 2, 1983 to October 25, 1989. Data were submitted...

Development of built-in debris-filter bottom nozzle for PWR fuel assemblies

International Nuclear Information System (INIS)

Juntaro Shimizu; Kazuki Monaka; Masaji Mori; Kazuo Ikeda

2005-01-01

Mitsubishi Heavy Industries, Ltd. (MHI) has worked to improve the capability of anti debris bottom nozzle for a PWR fuel assembly. The Current debris filter bottom nozzle (DFBN) having 4mm diameter flow holes can capture the larger size of debris than the flow hole inner diameter. MHI has completed the development of the built-in debris filter bottom nozzle, which is the new idea of the debris-filter for high burnup (55GWd/t assembly average burnup). Built-in debris filter bottom nozzle consists of the blades and nozzle body. The blades made from inconel strip are embedded and welded on the grooved top surface of the bottom nozzle adapter plate. A flow hole is divided by the blade and the trap size of the debris is reduced. Because the blades block the coolant flow, it was anticipated to increase the pressure loss of the nozzle, however, adjusting the relation between blade and taper shape of the flow hole, the pressure loss has been successfully maintained the satisfactory level. Grooves are cut on the nozzle plate; nevertheless, the additional skirts on the four sides of the nozzle compensate the structural strength. (authors)

Diurnal tides in the Arctic Ocean

Science.gov (United States)

Kowalik, Z.; Proshutinsky, A. Y.

1993-01-01

A 2D numerical model with a space grid of about 14 km is applied to calculate diurnal tidal constituents K(1) and O(1) in the Arctic Ocean. Calculated corange and cotidal charts show that along the continental slope, local regions of increased sea level amplitude, highly variable phase and enhanced currents occur. It is shown that in these local regions, shelf waves (topographic waves) of tidal origin are generated. In the Arctic Ocean and Northern Atlantic Ocean more than 30 regions of enhanced currents are identified. To prove the near-resonant interaction of the diurnal tides with the local bottom topography, the natural periods of oscillations for all regions have been calculated. The flux of energy averaged over the tidal period depicts the gyres of semitrapped energy, suggesting that the shelf waves are partially trapped over the irregularities of the bottom topography. It is shown that the occurrence of near-resonance phenomenon changes the energy flow in the tidal waves. First, the flux of energy from the astronomical sources is amplified in the shelf wave regions, and afterwards the tidal energy is strongly dissipated in the same regions.

Temperature, pressure, and other data from FIXED PLATFORMS in the North Atlantic Ocean from 29 April 1975 to 26 January 1976 (NODC Accession 7700668)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, pressure, and other data were collected from FIXED PLATFORMS in the North Atlantic Ocean. Data were collected by the Massachusetts Institute of...

Oceanic diffusion in the coastal area

International Nuclear Information System (INIS)

Rukuda, Masaaki

1980-03-01

Described in this paper is the eddy diffusion in the area off Tokai Village investigated by means of dye diffusion experiment and of oceanic observation. In order to assess the oceanic diffusion in coastal areas, improved methods effective in complex field were developed. The oceanic diffusion was separated in two groups, horizontal and vertical diffusion respectively. Both these diffusions are combined and their analysis together is difficult. The oceanic diffusion is thus considered separately. Instantaneous point release is the basis of horizontal diffusion analysis. Continuous release is then the overlap of numerous instantaneous releases. It was shown that the diffusion parameters derived from the results of diffusion experiment or oceanic observation vary widely with time and place and with sea conditions. A simple diffusion equation was developed from the equation of continuity. The results were in good agreement with seasonal mean horizontal distribution of river water in the sea area. The vertical observation in diffusion experiment is difficult and the vertical structure of oceanic condition is complex, so that the research on vertical diffusion generally is not advanced yet. With river water as the tracer, a method of estimating vertical diffusion parameters with a Gaussian model or one-dimensional model was developed. The vertical diffusion near sea bottom was numerically analized with suspended particles in seawater as the tracer. Diffusion was computed for each particle size, and by summing up the vertical distribution of beam attenuation coefficient was estimated. By comparing the results of estimation and those of observation the vertical diffusivity and the particle size distribution at sea bottom could be estimated. (author)

The Hamburg oceanic carbon cycle circulation model. Cycle 1

International Nuclear Information System (INIS)

Maier-Reimer, E.; Heinze, C.

1992-02-01

The carbon cycle model calculates the prognostic fields of oceanic geochemical carbon cycle tracers making use of a 'frozen' velocity field provided by a run of the LSG oceanic circulation model (see the corresponding manual, LSG=Large Scale Geostrophic). The carbon cycle model includes a crude approximation of interactions between sediment and bottom layer water. A simple (meridionally diffusive) one layer atmosphere model allows to calculate the CO 2 airborne fraction resulting from the oceanic biogeochemical interactions. (orig.)

Peach Bottom transient analysis with BWR TRACB02

International Nuclear Information System (INIS)

Alamgir, M.; Sutherland, W.A.

1984-01-01

TRAC calculations have been performed for a Turbine Trip transient (TT1) in the Peach Bottom BWR power plant. This study is a part of the qualification of the BWR-TRAC code. The simulation is aimed at reproducing the observed thermal hydraulic behavior in a pressurization transient. Measured core power is an input to the calculation. Comparison with data show the code reasonably well predicts the generation and propagation of the pressure waves in the main steam line and associated pressurization of the reactor vessel following the closure of the turbine stop valve

AFSC/RACE/GAP/vonSzalay: The Eastern Bering Sea Shelf, Gulf of Alaska, and Aleutian Islands Simrad ES 60 Acoustic Data Collected on Bottom Trawl Surveys

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Calibrated midwater and bottom backscatter data collected continuously with ES-60 echosounders throughout the bottom trawlsurvey period, continuing a time series of...

Near-inertial waves and deep ocean mixing

Science.gov (United States)

Shrira, V. I.; Townsend, W. A.

2013-07-01

For the existing pattern of global oceanic circulation to exist, there should be sufficiently strong turbulent mixing in the abyssal ocean, the mechanisms of which are not well understood as yet. The review discusses a plausible mechanism of deep ocean mixing caused by near-inertial waves in the abyssal ocean. It is well known how winds in the atmosphere generate near-inertial waves in the upper ocean, which then propagate downwards losing their energy in the process; only a fraction of the energy at the surface reaches the abyssal ocean. An open question is whether and, if yes, how these weakened inertial motions could cause mixing in the deep. We review the progress in the mathematical description of a mechanism that results in an intense breaking of near-inertial waves near the bottom of the ocean and thus enhances the mixing. We give an overview of the present state of understanding of the problem covering both the published and the unpublished results; we also outline the key open questions. For typical ocean stratification, the account of the horizontal component of the Earth's rotation leads to the existence of near-bottom wide waveguides for near-inertial waves. Due to the β-effect these waveguides are narrowing in the poleward direction. Near-inertial waves propagating poleward get trapped in the waveguides; we describe how in the process these waves are focusing more and more in the vertical direction, while simultaneously their group velocity tends to zero and wave-induced vertical shear significantly increases. This causes the development of shear instability, which is interpreted as wave breaking. Remarkably, this mechanism of local intensification of turbulent mixing in the abyssal ocean can be adequately described within the framework of linear theory. The qualitative picture is similar to wind wave breaking on a beach: the abyssal ocean always acts as a surf zone for near-inertial waves.

Near-inertial waves and deep ocean mixing

International Nuclear Information System (INIS)

Shrira, V I; Townsend, W A

2013-01-01

For the existing pattern of global oceanic circulation to exist, there should be sufficiently strong turbulent mixing in the abyssal ocean, the mechanisms of which are not well understood as yet. The review discusses a plausible mechanism of deep ocean mixing caused by near-inertial waves in the abyssal ocean. It is well known how winds in the atmosphere generate near-inertial waves in the upper ocean, which then propagate downwards losing their energy in the process; only a fraction of the energy at the surface reaches the abyssal ocean. An open question is whether and, if yes, how these weakened inertial motions could cause mixing in the deep. We review the progress in the mathematical description of a mechanism that results in an intense breaking of near-inertial waves near the bottom of the ocean and thus enhances the mixing. We give an overview of the present state of understanding of the problem covering both the published and the unpublished results; we also outline the key open questions. For typical ocean stratification, the account of the horizontal component of the Earth's rotation leads to the existence of near-bottom wide waveguides for near-inertial waves. Due to the β-effect these waveguides are narrowing in the poleward direction. Near-inertial waves propagating poleward get trapped in the waveguides; we describe how in the process these waves are focusing more and more in the vertical direction, while simultaneously their group velocity tends to zero and wave-induced vertical shear significantly increases. This causes the development of shear instability, which is interpreted as wave breaking. Remarkably, this mechanism of local intensification of turbulent mixing in the abyssal ocean can be adequately described within the framework of linear theory. The qualitative picture is similar to wind wave breaking on a beach: the abyssal ocean always acts as a surf zone for near-inertial waves. (paper)

Searching for conditions of observation of subduction seismogenic zone transients on Ocean Bottom Seismometers deployed at the Lesser Antilles submerged fore-arc

Science.gov (United States)

Bécel, Anne; Laigle, Mireille; Diaz, Jordi; Hirn, Alfred; Flueh, Ernst; Charvis, Philippe

2010-05-01

In the frame of the European Union « THALES WAS RIGHT » and French ANR CATTELL SUBSISMANTI funding, an unprecedented array of 80 OBS, Ocean Bottom Seismometers of Géoazur Nice, INSU/IPGP Paris, IfM-GEOMAR Kiel, AWI Bremerhaven could gathered. They have been deployed for continuous recording over four months on the fore-arc domain of the Lesser Antilles subduction zone offshore Martinique, Dominica, Guadeloupe and Antigua Islands, by scientific cruises of N/O ATALANTE, F/S M. A. MERIAN and N/O ANTEA. One of the aims of this OBS array was the feasibility study of detecting at sea-bottom the seismological part of recently discovered phenomena such as NVT non-volcanic tremors and LP, for Long-Period events. The ability of detecting such transient signals is of importance, since they are possibly related to potential mega-thrust earthquakes and their preparation zone. At the Lesser Antilles subduction zone, the fore-arc domain overlying the seismogenic part of the interplate is located offshore, covered by as much as 4000 m of water. In this case, transient signals can be accessible only from OBS observations. Hence, there is a major difference, in the sense of the instrumental and logistical effort, with the subductions under NW US-Canada and under Central Japan where these signals have been discovered. There, the subduction zones have an emerged fore-arc that has allowed the chance discovery of those phenomena by regular instrument maintained routinely on land. Over 20 of the instruments were BB-OBS, with broadband seismic sensors, possibly the largest such gathering at the time of the experiment among the OBS types. Among those broadband OBS designed or used by different Institutions, there were at least three different seismometer brands and acoustical sensors, as well as different mechanical mounting and technical solutions for coupling them to ground. This did not facilitate data recovery and processing, but on the other hand, as planned by interweaving the

The footprint of bottom trawling in European waters

NARCIS (Netherlands)

Eigaard, Ole R.; Bastardie, Francois; Hintzen, Niels T.; Buhl-Mortensen, Lene; Buhl-Mortensen, Pål; Catarino, Rui; Dinesen, Grete E.; Egekvist, Josefine; Fock, Heino O.; Geitner, Kerstin; Gerritsen, Hans D.; González, Manuel Marín; Jonsson, Patrik; Kavadas, Stefanos; Laffargue, Pascal; Lundy, Mathieu; Gonzalez-Mirelis, Genoveva; Nielsen, J.R.; Papadopoulou, Nadia; Posen, Paulette E.; Pulcinella, Jacopo; Russo, Tommaso; Sala, Antonello; Silva, Cristina; Smith, Christopher J.; Vanelslander, Bart; Rijnsdorp, Adriaan D.

2017-01-01

Mapping trawling pressure on the benthic habitats is needed as background to support an ecosystem approach to fisheries management. The extent and intensity of bottom trawling on the European continental shelf (0-1000 m) was analysed from logbook statistics and vessel monitoring system data for

Ferromanganese nodules from the Central Indian Ocean Basin

Digital Repository Service at National Institute of Oceanography (India)

Jauhari, P.; Pattan, J.N.

In order to delineate a mine site for ferromanganese nodules, extensive surveys were conducted in Central Indian Ocean Basin. Mapping of the basin by multibeam swath bathymetry (Hydrosweep) has revealed many new bottom relief features...

Experimental investigation of slamming impact acted on flat bottom bodies and cumulative damage

Directory of Open Access Journals (Sweden)

Hyunkyoung Shin

2018-05-01

Full Text Available Most offshore structures including offshore wind turbines, ships, etc. suffer from the impulsive pressure loads due to slamming phenomena in rough waves. The effects of elasticity & plasticity on such slamming loads are investigated through wet free drop test results of several steel unstiffened flat bottom bodies in the rectangular water tank. Also, their cumulative deformations by consecutively repetitive free drops from 1000 mm to 2000 mm in height are measured. Keywords: Slamming phenomena, Impulsive pressure load, Wet free drop test, Flat bottom body, Cumulative damage

EPOCA/EUR-OCEANS data compilation on the biological and biogeochemical responses to ocean acidification

NARCIS (Netherlands)

Nisumaa, A.-M.; Pesant, S.; Bellerby, R.G.J.; Delille, B.; Middelburg, J.J.; Orr, J.C.; Riebesell, U.; Tyrrell, T.; Wolf-Gladrow, D.; Gattuso, J.P.

2010-01-01

The uptake of anthropogenic CO2 by the oceans has led to a rise in the oceanic partial pressure of CO2, and to a decrease in pH and carbonate ion concentration. This modification of the marine carbonate system is referred to as ocean acidification. Numerous papers report the effects of ocean

Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

DEFF Research Database (Denmark)

Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V.

2014-01-01

The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are re......The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid...... caused massive organic-carbon burial on the Arctic shelf in general, with important implications for hydrocarbon source-rock distribution in the Arctic region....

Assimilation of TOPEX/Poseidon altimeter data into a global ocean circulation model: How good are the results?

Science.gov (United States)

Fukumori, Ichiro; Raghunath, Ramanujam; Fu, Lee-Lueng; Chao, Yi

1999-11-01

The feasibility of assimilating satellite altimetry data into a global ocean general circulation model is studied. Three years of TOPEX/Poseidon data are analyzed using a global, three-dimensional, nonlinear primitive equation model. The assimilation's success is examined by analyzing its consistency and reliability measured by formal error estimates with respect to independent measurements. Improvements in model solution are demonstrated, in particular, properties not directly measured. Comparisons are performed with sea level measured by tide gauges, subsurface temperatures and currents from moorings, and bottom pressure measurements. Model representation errors dictate what can and cannot be resolved by assimilation, and its identification is emphasized.

The analysis of bottom forming process for hybrid heating device

Science.gov (United States)

Bałon, Paweł; Świątoniowski, Andrzej; Kiełbasa, Bartłomiej

2017-10-01

In this paper the authors present an unusual method for bottom forming applicable for various industrial purposes including the manufacture of water heaters or pressure equipment. This method allows for the fabrication of the bottom of a given piece of stainless steel into a pre-determined shape conforming to the DIN standard which determines the most advantageous dimensions for the bottom cross section in terms of working pressure loading. The authors checked the validity of the method in a numerical and experimental way generating a tool designed to produce bottoms of specified geometry. Many problems are encountered during the design and production of parts, especially excessive sheet wrinkling over a large area of the part. The experiment showed that a lack of experience and numerical analysis in the design of such elements would result in the production of highly wrinkled parts. This defect would render the parts impossible to assemble with the cylindrical part. Many tool shops employ a method for drawing elements with a spherical surface which involves additional spinning, stamping, and grading operations, which greatly increases the cost of parts production. The authors present and compare two forming methods for spherical and parabolic objects, and experimentally confirm the validity of the sheet reversing method with adequate pressure force. The applied method produces parts in one drawing operation and in a following operation that is based on laser or water cutting to obtain a round blank. This reduces the costs of tooling manufacturing by requiring just one tool which can be placed on any hydraulic press with a minimum force of 2 000 kN.

AFSC/RACE/SAP: Detailed Crab Data From NOAA Fisheries Service 2012 Chukchi Sea Bottom Trawl Surveys

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains detailed crab data collected from the 2012 NOAA/NMFS/AFSC/RACE crab-groundfish bottom trawl survey of the Chukchi Sea. 71 survey stations were...

Temperature profile and barometric pressure data collected in North Atlantic Ocean using XBT casts from 01 January 1993 to 26 April 1993 (NODC Accession 9600142)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and barometric pressure data were collected using XBT casts from the GRAND BASSAM and other platforms in the North Atlantic OCean. Data were collected...

Effects of Rotation on the Differentiation of a terrestrial Magma Ocean

Science.gov (United States)

Maas, C.; Hansen, U.

2014-12-01

It is widely accepted that the Earth experienced several large impacts during its early evolution which led to the formation of one or more magma oceans. Differentiation processes in such a magma ocean are of great importance for the initial conditions of mantle convection and for the subsequent mantle structure. Convection in a magma ocean is most likely very vigorous. Further, rotation of the early Earth is supposed to be very fast. Therefore, and due to the small viscosity, it can be assumed that differentiation is strongly affected by rotation.To study the influence of rotation on the crystallization of a magma ocean, we employed a 3D Cartesian numerical model with low Prandtl number and used a discrete element method to describe silicate crystals.Our results show a crucial dependence on crystal density, rotation rate and latitude. Low rotation at the pole leads to a large fraction of suspended particles. With increasing rotation the particles settle at the bottom and form a stable stratified layer. In contrast to that at the equator at low rotation all particles settle at the bottom, at higher rotation they form a layer of significant thickness and at the highest rotation rate the particles accumulate in the middle of the magma ocean. In addition to that, we observe that due to the Coriolis force silicate crystals with different densities separate from each other. While lighter particles are at the bottom, denser particles accumulate at mid-depth at the same rotation rate. This could result in an unstable stratified mantle in the equatorial region after magma ocean solidification.All in all, rotation could lead to an asymmetrical crystallization of the magma ocean, with a contrary layering at the pole and the equator. This affects the composition of the early mantle and could explain the development of a localized magma ocean at the core-mantle boundary and the development of phase transitions observed in seismology, like the mantle transition zone.

West Coast Groundfish Bottom Trawl Survey Data - Annual West Coast time series groundfish trawl data collection survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Members of the Fishery Resource Analysis and Monitoring Division Survey Team conduct an annual West Coast Groundfish Bottom Trawl Survey from May - October each...

Variability at Multiple Scales: Using an Array of Current- and Pressure-Sensor Equipped Inverted Echo Sounders to Measure the Ocean

Science.gov (United States)

2016-11-29

of Current- and Pressure - Sensor Equipped Inverted Echo Sounders to Measure the Ocean 5b. GRANT NUMBER NOOO 14-15-1-2857 5c. PROGRAM ELEMENT NUMBER...inverted echo sounders (lESs) equipped with pressure and current sensors (CPIESs). CPIESs are moored instruments that measure the round-trip acoustic...at a range of spatial and temporal scales. The goals of this project were to enhance the pool of pressure - sensor equipped lESs available at the

Variability at Multiple Scales: Using an Array of Current and Pressure Sensor Equipped Inverted Echo Sounders to Measure the Ocean

Science.gov (United States)

2016-11-29

of Current- and Pressure - Sensor Equipped Inverted Echo Sounders to Measure the Ocean 5b. GRANT NUMBER NOOO 14-15-1-2857 5c. PROGRAM ELEMENT NUMBER...inverted echo sounders (lESs) equipped with pressure and current sensors (CPIESs). CPIESs are moored instruments that measure the round-trip acoustic...at a range of spatial and temporal scales. The goals of this project were to enhance the pool of pressure - sensor equipped lESs available at the

A numerical study of wave-current interaction through surface and bottom stresses: Coastal ocean response to Hurricane Fran of 1996

Science.gov (United States)

Xie, L.; Pietrafesa, L. J.; Wu, K.

2003-02-01

A three-dimensional wave-current coupled modeling system is used to examine the influence of waves on coastal currents and sea level. This coupled modeling system consists of the wave model-WAM (Cycle 4) and the Princeton Ocean Model (POM). The results from this study show that it is important to incorporate surface wave effects into coastal storm surge and circulation models. Specifically, we find that (1) storm surge models without coupled surface waves generally under estimate not only the peak surge but also the coastal water level drop which can also cause substantial impact on the coastal environment, (2) introducing wave-induced surface stress effect into storm surge models can significantly improve storm surge prediction, (3) incorporating wave-induced bottom stress into the coupled wave-current model further improves storm surge prediction, and (4) calibration of the wave module according to minimum error in significant wave height does not necessarily result in an optimum wave module in a wave-current coupled system for current and storm surge prediction.

Construction for holding together a cylindrical high pressure reactor vessel with hemispherical bottom and lid

International Nuclear Information System (INIS)

Desmarchais, W.E.; Braun, H.E.

1972-01-01

The construction shall prevent that in case of ruptures of the vessel rupture pieces may damage the secondary shielding system. The construction consists of two yokes fitting to the bottom and the lid of the vessel and held together by means of pull rods. The yokes are designed as truncated conshaped shells. The smaller end of the cone shells supports the hemispherical bottom and the lid of the vessel. The larger cone shell ends are tied together by the pull rods. As further improvements there may be arranged hemispherical protective shields between the hemispherical bottom and the lid of the vessel and the smaller end of the cone shells. (P.K.)

Ocean acidification buffering effects of seagrass in Tampa Bay

Science.gov (United States)

Yates, Kimberly K.; Moyer, Ryan P.; Moore, Christopher; Tomasko, David A.; Smiley, Nathan A.; Torres-Garcia, Legna; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana; Smiley, Nathan; Torres-Garcia, Legna M.; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana

2016-01-01

The Intergovernmental Panel on Climate Change has identified ocean acidification as a critical threat to marine and estuarine species in ocean and coastal ecosystems around the world. However, seagrasses are projected to benefit from elevated atmospheric pCO2, are capable of increasing seawater pH and carbonate mineral saturation states through photosynthesis, and may help buffer against the chemical impacts of ocean acidification. Additionally, dissolution of carbonate sediments may also provide a mechanism for buffering seawater pH. Long-term water quality monitoring data from the Environmental Protection Commission of Hillsborough County indicates that seawater pH has risen since the 1980‘s as seagrass beds have continued to recover since that time. We examined the role of seagrass beds in maintaining and elevating pH and carbonate mineral saturation state in northern and southern Tampa Bay where the percent of carbonate sediments is low (40%), respectively. Basic water quality and carbonate system parameters (including pH, total alkalinity, dissolved inorganic carbon, partial pressure of CO2, and carbonate mineral saturation state) were measured over diurnal time periods along transects (50-100 m) including dense and sparse Thalassia testudinum. seagrass beds, deep edge seagrass, and adjacent bare sand bottom. Seagrass density and productivity, sediment composition and hydrodynamic parameters were also measured, concurrently. Results indicate that seagrass beds locally elevate pH by up to 0.5 pH unit and double carbonate mineral saturation states relative to bare sand habitats. Thus, seagrass beds in Tampa Bay may provide refuge for marine organisms from the impacts of ocean acidification.

Deep oceans may acidify faster than anticipated due to global warming

Science.gov (United States)

Chen, Chen-Tung Arthur; Lui, Hon-Kit; Hsieh, Chia-Han; Yanagi, Tetsuo; Kosugi, Naohiro; Ishii, Masao; Gong, Gwo-Ching

2017-12-01

Oceans worldwide are undergoing acidification due to the penetration of anthropogenic CO2 from the atmosphere1-4. The rate of acidification generally diminishes with increasing depth. Yet, slowing down of the thermohaline circulation due to global warming could reduce the pH in the deep oceans, as more organic material would decompose with a longer residence time. To elucidate this process, a time-series study at a climatically sensitive region with sufficient duration and resolution is needed. Here we show that deep waters in the Sea of Japan are undergoing reduced ventilation, reducing the pH of seawater. As a result, the acidification rate near the bottom of the Sea of Japan is 27% higher than the rate at the surface, which is the same as that predicted assuming an air-sea CO2 equilibrium. This reduced ventilation may be due to global warming and, as an oceanic microcosm with its own deep- and bottom-water formations, the Sea of Japan provides an insight into how future warming might alter the deep-ocean acidification.

Pressure suppression device

International Nuclear Information System (INIS)

Mizumachi, Wataru; Fukuda, Akira; Kitaguchi, Hidemi; Shimizu, Toshiaki.

1976-01-01

Object: To relieve and absorb impact wave vibrations caused by steam and non-condensed gases releasing into the pressure suppression chamber at the time of an accident. Structure: The reactor container is filled with inert gases. A safety valve attached main steam pipe is provided to permit the excessive steam to escape, the valve being communicated with the pressure suppression chamber through an exhaust pipe. In the pressure suppression chamber, a doughnut-like cylindrical outer wall is filled at its bottom with pool water to condense the high temperature vapor released through the exhaust pipe. A head portion of a vent tube which leads the exhaust pipe is positioned at the top, and a down comer and an exhaust vent tube are locked by means of steady rests. At the bottom is mounted a pressure adsorber device which adsorbs a pressure from the pool water. (Kamimura, M.)

AFSC/RACE/GAP/Palsson: Gulf of Alaska and Aleutian Islands Biennial Bottom Trawl Survey estimates of catch per unit effort, biomass, population at length, and associated tables

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The GOA/AI Bottom Trawl Estimate database contains abundance estimates for the Alaska Biennial Bottom Trawl Surveys conducted in the Gulf of Alaska and the Aleutian...

Nuclear reactor construction with bottom supported reactor vessel

International Nuclear Information System (INIS)

Sharbaugh, J.E.

1987-01-01

This patent describes an improved liquid metal nuclear reactor construction comprising: (a) a nuclear reactor core having a bottom platform support structure; (b) a reactor vessel for holding a large pool of low pressure liquid metal coolant and housing the core; (c) a containment structure surrounding the reactor vessel and having a sidewall spaced outwardly from the reactor vessel side wall and having a base mat spaced below the reactor vessel bottom end wall; (d) a central small diameter post anchored to the containment structure base mat and extending upwardly to the reactor vessel to axially fix the bottom end wall of the reactor vessel and provide a center column support for the lower end of the reactor core; (e) annular support structure disposed in the reactor vessel on the bottom end wall and extending about the lower end of the core; (f) structural support means disposed between the containment structure base mat and bottom end of the reactor vessel wall and cooperating for supporting the reactor vessel at its bottom end wall on the containment structure base mat to allow the reactor vessel to expand radially but substantially prevent any lateral motions that might be imposed by the occurrence of a seismic event; (g) a bed of insulating material disposed between the containment structure base mat and the bottom end wall of the reactor vessel and uniformly supporting the reactor vessel at its bottom end wall; freely expand radially from the central post as it heats up while providing continuous support thereof; (h) a deck supported upon the wall of the containment vessel above the top open end of the reactor vessel; and (i) extendible and retractable coupling means extending between the deck and the top open end of the reactor vessel and flexibly and sealably interconnecting the reactor vessel at its top end to the deck

Five Year Mean Bottom to Surface Temperature Differences in the Northern Gulf of Mexico for 2005 through 2009

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — These images were created by combining the estimates of the mean bottom to surface temperature differences to produce seasonal representations for winter, spring,...

Bottom Dissolved Oxygen Maps From SEAMAP Summer and Fall Groundfish/Shrimp Surveys from 1982 to 1998 (NCEI Accession 0155488)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Bottom dissolved oxygen (DO) data was extracted from environmental profiles acquired during the Southeast Fisheries Science Center Mississippi Laboratories summer...

Bottom Sediment Granulometric Data for the Continental Margins of the Bering, Chukchi, East Siberia, Laptev, and Beaufort Seas

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — These data are part of Roberts, Richard W., University of Washington, Department of Oceanography Special Report No. 70, Bottom Sediment Granulometric Data for the...

Small break loss of coolant accidents: Bottom and side break

International Nuclear Information System (INIS)

Hardy, P.G.; Richter, H.J.

1987-01-01

A LOCA can be caused, e.g. by a small break in the primary cooling system. The rate of fluid escaping through such a break will define the time until the core will be uncovered. Therefore the prediction of fluid loss and pressure transient is of major importance to plan for timely action in response to such an event. Stratification of the two phases might be present upstream of the break, thus, the location of the break relative to the vapor-liquid interface and the overall upstream fluid conditions are relevant for the calculation of fluid loss. Experimental results and analyses are presented here for small breaks at the bottom or at the side of a small pressure vessel. It was found that in such a case the onset of the so-called ''vapor pull through'' is important but swelling at sufficient depressurization rates of the liquid due to flashing is also of significance. It was also discovered that in the bottom break the flow rate is strongly dependent on the break entrance quality of the vapour-liquid mixture. The side break can be treated similarly to the bottom break if the interface level is above the break. The analyses developed on the basis of experimental observations showed reasonable agreement of predicted and measured pressure transients. It was possible to calculate the changing interface level and mixture void fraction history in a way compatible with the behavior observed during the experiments. Even though the experiments were performed at low pressures, this work should help to get a better understanding of physical phenomena occurring in a full scale small break LOCA. (orig./HP)

Dispersion of tracers by the oceanic eddy field modelling programme

International Nuclear Information System (INIS)

Richards, K.J.

1986-01-01

A numerical model has been developed to study the dispersion of tracers by the oceanic eddy field. The study is designed to investigate the horizontal and vertical structure of the eddies and how this structure is influenced by the bottom topography. It is found that hills and valleys have a strong effect on the eddies above them. The flow close to the bottom has a tendency to be steered by the height contours. The surface and bottom flows become decorrelated and the vertical variation of the kinetic energy of the eddies is increased with higher topographic features. (author)

Designing a framework to design a business model for the 'bottom of the pyramid' population

NARCIS (Netherlands)

Ver loren van Themaat, Tanye; Schutte, Cornelius S.L.; Lutters, Diederick

2013-01-01

This article presents a framework for developing and designing a business model to target the bottom of the pyramid (BoP) population. Using blue ocean strategy and business model literature, integrated with research on the BoP, the framework offers a systematic approach for organisations to analyse

Temperature regulation of marine heterotrophic prokaryotes increases latitudinally as a breach between bottom-up and top-down controls

KAUST Repository

Moran, Xose Anxelu G.; Gasol, Josep M.; Pernice, Massimo C.; Mangot, Jean-Franç ois; Massana, Ramon; Lara, Elena; Vaqué , Dolors; Duarte, Carlos M.

2017-01-01

Planktonic heterotrophic prokaryotes make up the largest living biomass and process most organic matter in the ocean. Determining when and where the biomass and activity of heterotrophic prokaryotes are controlled by resource availability (bottom

SWIM: A Semi-Analytical Ocean Color Inversion Algorithm for Optically Shallow Waters

Science.gov (United States)

McKinna, Lachlan I. W.; Werdell, P. Jeremy; Fearns, Peter R. C. S.; Weeks, Scarla J.; Reichstetter, Martina; Franz, Bryan A.; Shea, Donald M.; Feldman, Gene C.

2014-01-01

Ocean color remote sensing provides synoptic-scale, near-daily observations of marine inherent optical properties (IOPs). Whilst contemporary ocean color algorithms are known to perform well in deep oceanic waters, they have difficulty operating in optically clear, shallow marine environments where light reflected from the seafloor contributes to the water-leaving radiance. The effect of benthic reflectance in optically shallow waters is known to adversely affect algorithms developed for optically deep waters [1, 2]. Whilst adapted versions of optically deep ocean color algorithms have been applied to optically shallow regions with reasonable success [3], there is presently no approach that directly corrects for bottom reflectance using existing knowledge of bathymetry and benthic albedo.To address the issue of optically shallow waters, we have developed a semi-analytical ocean color inversion algorithm: the Shallow Water Inversion Model (SWIM). SWIM uses existing bathymetry and a derived benthic albedo map to correct for bottom reflectance using the semi-analytical model of Lee et al [4]. The algorithm was incorporated into the NASA Ocean Biology Processing Groups L2GEN program and tested in optically shallow waters of the Great Barrier Reef, Australia. In-lieu of readily available in situ matchup data, we present a comparison between SWIM and two contemporary ocean color algorithms, the Generalized Inherent Optical Property Algorithm (GIOP) and the Quasi-Analytical Algorithm (QAA).

Trace elements distribution in bottom sediments from Amazon River estuary

International Nuclear Information System (INIS)

Lara, L.B.L.S.; Nadai Fernandes, E. de; Oliveira, H. de; Bacchi, M.A.

1994-01-01

The Amazon River discharges into a dynamic marine environment where there have been many interactive processes affecting dissolved and particulate solids, either those settling on the shelf or reaching the ocean. Trace elemental concentration, especially of the rare earth elements, have been determined by neutron activation analysis in sixty bottom sediment samples of the Amazon River estuary, providing information for the spatial and temporal variation study of those elements. (author). 16 refs, 6 figs, 3 tabs

Geochemical behavior of beryllium isotopes in the ocean

International Nuclear Information System (INIS)

Kusakabe, M.; Ku, T.L.; Cusimano, G.L.; Southon, J.R.; Measures, C.I.

1989-01-01

9 Be and 10 Be have been measured in a variety of geological samples: sea water, marine particulate, bottom sediment and river water. While the 10 Be/ 9 Be ratio in the Pacific deep water seems to be constant, ∼ 1 x 10 -7 , the deep water in the Atlantic Ocean has significantly lower and variable ratio (0.7 x 10 -7 or less), reflecting larger input of riverine 9 Be to the Atlantic Ocean. The study of Be isotopes in river water, sea water, and sediment pore water from the southern California borderland shows that coastal areas play an important role in the removal of Be isotopes from the ocean. The behavior of particulate Be isotopes in the ocean is also discussed

Pressure Dependence of Komatiite Liquid Viscosity and Implications for Magma Ocean Rheology

Science.gov (United States)

O'Dwyer Brown, L.; Lesher, C. E.; Terasaki, H. G.; Yamada, A.; Sakamaki, T.; Shibazaki, Y.; Ohtani, E.

2009-12-01

temperature and pressure on ultramafic liquids suggests that changes in viscosity are likely modest and viscosity will decrease with depth. Stiffening and isolation of the lower regions of a magma ocean due to increasing melt viscosity seem unlikely. [1] PEPI (2003) 139, 45 [2] EPSL (2005) 240, 589

Temperature regulation of marine heterotrophic prokaryotes increases latitudinally as a breach between bottom-up and top-down controls

KAUST Repository

Moran, Xose Anxelu G.

2017-04-19

Planktonic heterotrophic prokaryotes make up the largest living biomass and process most organic matter in the ocean. Determining when and where the biomass and activity of heterotrophic prokaryotes are controlled by resource availability (bottom-up), predation and viral lysis (top-down) or temperature will help in future carbon cycling predictions. We conducted an extensive survey across subtropical and tropical waters of the Atlantic, Indian and Pacific Oceans during the Malaspina 2010 Global Circumnavigation Expedition and assessed indices for these three types of controls at 109 stations (mostly from the surface to 4000 m depth). Temperature control was approached by the apparent activation energy in eV (ranging from 0.46 to 3.41), bottom-up control by the slope of the log-log relationship between biomass and production rate (ranging from -0.12 to 1.09) and top-down control by an index that considers the relative abundances of heterotrophic nanoflagellates and viruses (ranging from 0.82 to 4.83). We conclude that temperature becomes dominant (i.e. activation energy >1.5 eV) within a narrow window of intermediate values of bottom-up (0.3-0.6) and top-down 0.8-1.2) controls. A pervasive latitudinal pattern of decreasing temperature regulation towards the Equator, regardless of the oceanic basin, suggests that the impact of global warming on marine microbes and their biogeochemical function will be more intense at higher latitudes. Our analysis predicts that 1°C ocean warming will result in increased biomass of heterotrophic prokaryoplankton only in waters with <26°C of mean annual surface temperature. This article is protected by copyright. All rights reserved.

A Bottom Gravity Survey of the Continental Shelf Between Point Lobos and Point Sur, California.

Science.gov (United States)

From an occupation of 68 ocean bottom and 38 land gravity stations between Pt. Lobos and Pt. Sur, California, a complete Bouguer anomaly map was...produced and analyzed. The steps in data reduction leading to the complete Bouguer anomaly field are presented, unique features of which are associated

The desorption of caesium from Peach Bottom HTGR steam generator materials

International Nuclear Information System (INIS)

Clark, M.J.

1979-03-01

The work at Harwell on the Peach Bottom End-of-Life Program in co-operation with the General Atomic Company (U.S.A.) is described. Materials taken from the Economiser, Evaporator and Superheater Sections of the Peach Bottom Unit No. 1. High Temperature Gas Cooled Reactor (HTGR) Heat Exchanger were placed in a reducing atmosphere comparable to the composition of an HTGR helium coolant gas, and the desorption of caesium isotopes measured under known conditions of flow, temperature and oxygen pressure. (author)

Evidence for infragravity wave-tide resonance in deep oceans.

Science.gov (United States)

Sugioka, Hiroko; Fukao, Yoshio; Kanazawa, Toshihiko

2010-10-05

Ocean tides are the oscillatory motions of seawater forced by the gravitational attraction of the Moon and Sun with periods of a half to a day and wavelengths of the semi-Pacific to Pacific scale. Ocean infragravity (IG) waves are sea-surface gravity waves with periods of several minutes and wavelengths of several dozen kilometres. Here we report the first evidence of the resonance between these two ubiquitous phenomena, mutually very different in period and wavelength, in deep oceans. The evidence comes from long-term, large-scale observations with arrays of broadband ocean-bottom seismometers located at depths of more than 4,000 m in the Pacific Ocean. This observational evidence is substantiated by a theoretical argument that IG waves and the tide can resonantly couple and that such coupling occurs over unexpectedly wide areas of the Pacific Ocean. Through this resonant coupling, some of ocean tidal energy is transferred in deep oceans to IG wave energy.

Temperature profile and pressure data collected using moored buoy from the Atlantic Ocean with support from the IDOE/POLYMODE (International Decade of Ocean Exploration / combination of USSR POLYGON project and US MODE) from 04 May to 18 December 1975 (NODC Accession 7601247)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using moored buoy from the Atlantic Ocean from May 4, 1975 to December 18, 1975. Data were submitted by...

Bottom head assembly

International Nuclear Information System (INIS)

Fife, A.B.

1998-01-01

A bottom head dome assembly is described which includes, in one embodiment, a bottom head dome and a liner configured to be positioned proximate the bottom head dome. The bottom head dome has a plurality of openings extending there through. The liner also has a plurality of openings extending there through, and each liner opening aligns with a respective bottom head dome opening. A seal is formed, such as by welding, between the liner and the bottom head dome to resist entry of water between the liner and the bottom head dome at the edge of the liner. In the one embodiment, a plurality of stub tubes are secured to the liner. Each stub tube has a bore extending there through, and each stub tube bore is coaxially aligned with a respective liner opening. A seat portion is formed by each liner opening for receiving a portion of the respective stub tube. The assembly also includes a plurality of support shims positioned between the bottom head dome and the liner for supporting the liner. In one embodiment, each support shim includes a support stub having a bore there through, and each support stub bore aligns with a respective bottom head dome opening. 2 figs

Integrated hard and soft bottom seafloor substrate maps at select islands in American Samoa and the Mariana Archipelago

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Seafloor substrate (i.e., hard vs. soft bottom) from 0 to 50 m depths around islands in American Samoa and Mariana Archipelago produced by the NOAA Coral Reef...

Pigment species, depth, and pressure data from bottle and CTD casts in the North Atlantic Ocean as part of the Joint Global Ocean Flux Study / Time Series Site "BATS" (JGOFS/BATS) project, from 1993-10-01 to 1996-12-31 (NODC Accession 9800186)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Pigment species, depth, and pressure data were collected using bottle and CTD casts from the R/V WEATHERBIRD in the North Atlantic Ocean from October 1, 1993 to...

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

Science.gov (United States)

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

2017-12-01

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

An accurate estimation and optimization of bottom hole back pressure in managed pressure drilling

Directory of Open Access Journals (Sweden)

Boniface Aleruchi ORIJI

2017-06-01

Full Text Available Managed Pressure Drilling (MPD utilizes a method of applying back pressure to compensate for wellbore pressure losses during drilling. Using a single rheological (Annular Frictional Pressure Losses, AFPL model to estimate the backpressure in MPD operations for all sections of the well may not yield the best result. Each section of the hole was therefore treated independently in this study as data from a case study well were used. As the backpressure is a function of hydrostatic pressure, pore pressure and AFPL, three AFPL models (Bingham plastic, Power law and Herschel Bulkley models were utilized in estimating the backpressure. The estimated backpressure values were compared to the actual field backpressure values in order to obtain the optimum backpressure at the various well depths. The backpressure values estimated by utilizing the power law AFPL model gave the best result for the 12 1/4" hole section (average error % of 1.855% while the back pressures estimated by utilizing the Herschel Bulkley AFPL model gave the best result for the 8 1/2" hole section (average error % of 12.3%. The study showed that for hole sections of turbulent annular flow, the power law AFPL model fits best for estimating the required backpressure while for hole sections of laminar annular flow, the Herschel Bulkley AFPL model fits best for estimating the required backpressure.

Occurrence of @iNeogloboquadrina pachyderma@@ new subspecies in the shelf-slope sediments of northern Indian Ocean

Digital Repository Service at National Institute of Oceanography (India)

Setty, M.G.A.P.

~'N in the Bay of Bengal. Studies of hydrological conditions in the Indian Ocean reveal that the Subtropical Subsurface Water Mass is traceable as far north as the Gulf of Aden, and the Indian Ocean Deep Bottom Water Mass originating in the deepest...

EPOCA/EUR-OCEANS data compilation on the biological and biogeochemical responses to ocean acidification

OpenAIRE

Nisumaa Anne-Marin; Pesant Stephane; Bellerby Richard G J; Delille Bruno; Middelburg Jack J; Orr James C; Riebesell Ulf; Tyrrell Toby; Wolf-Gladrow Dieter A; Gattuso Jean-Pierre

2010-01-01

The uptake of anthropogenic CO₂ by the oceans has led to a rise in the oceanic partial pressure of CO₂, and to a decrease in pH and carbonate ion concentration. This modification of the marine carbonate system is referred to as ocean acidification. Numerous papers report the effects of ocean acidification on marine organisms and communities but few have provided details concerning full carbonate chemistry and complementary observations. Additional...

Diet of invasive lionfish on hard bottom reefs of the Southeast USA: insights from stomach contents and stable isotopes

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Stomach contents and stable isotope analyses were used to determine the diet of lionfish in the warm-temperate hard bottom reef community in theSoutheast US Atlantic...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Dome Reef, 2007 (NODC Accession 0093023)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Wellwood, 2006 - 2009 (NODC Accession 0093067)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at 7-mile Bridge (NODC Accession 0002750)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Bottom head failure program plan

International Nuclear Information System (INIS)

Meyer, R.O.

1989-01-01

Earlier this year the NRC staff presented a Revised Severe Accident Research Program Plan (SECY-89-123) to the Commission and initiated work on that plan. Two of the near-term issues in that plan involve failure of the bottom head of the reactor pressure vessel. These two issues are (1) depressurization and DCH and (2) BWR Mark I Containment Shell Meltthrough. ORNL has developed models for several competing failure mechanisms for BWRs. INEL has performed analytical and experimental work directly related to bottom head failure in connection with several programs. SNL has conducted a number of analyses and experimental activities to examine the failure of LWR vessels. In addition to the government-sponsored work mentioned above, EPRI and FAI performed studies on vessel failure for the Industry Degraded Core Rulemaking Program (IDCOR). EPRI examined the failure of a PWR vessel bottom head without penetrations, as found in some Combustion Engineering reactors. To give more attention to this subject as called for by the revised Severe Accident Research Plan, two things are being done. First, work previously done is being reviewed carefully to develop an overall picture and to determine the reliability of assumptions used in those studies. Second, new work is being planned for FY90 to try to complete a reasonable understanding of the failure process. The review and planning are being done in close cooperation with the ACRS. Results of this exercise will be presented in this paper

A comparison of high-frequency noise levels on Cascadia Initiative ocean-bottom seismometers

Science.gov (United States)

Hilmo, R.; Wilcock, W. S. D.; Roland, E. C.; Bodin, P.; Connolly, J.

2017-12-01

The Cascadia Initiative (CI) included a four-year deployment of 70 ocean bottom seismometers (OBSs) on the Cascadia subduction zone and the Juan de Fuca plate for the purposes of characterizing seismicity and imaging the Earth's interior. The Cascadia subduction zone megathrust exhibits very low rates of seismicity relative to most other subduction zones, and there is great motivation to understand deformation on the megathrust because of its potential to produce a catastrophic M9 earthquake. An understanding of earthquake detectability of the CI network, based on knowledge of noise levels, could contribute to the interpretation of earthquake catalogs derived from the experiment and aid in the design of future networks. This project is aimed at estimating these thresholds of local earthquake detectability and how they change across the array both geographically and temporally. We characterize background noise levels recorded from 0.1 to 20 Hz with an emphasis on the frequency band used to detect local seismicity ( 3-15 Hz) to understand how noise levels depend on instrument design and environmental parameters including seafloor depth, season and oceanographic conditions. Our initial analysis of 3 weeks of vertical channel data in September, January, and May 2012-2013 shows that noise increase significantly moving from the continental shelf to deeper water. Noise levels at a given depth vary with instrument type but further analysis is required to determine whether this reflects variations in instrumental noise and ground coupling noise or errors in the scaling of the instrument response. There is also a strong seasonality in recorded noise levels at some frequencies, with winter noise levels exceeding spring and fall noise levels by up to 10 decibels in both the microseism band and in the fin whale calling band (15-20 Hz). In contrast, the seasonal noise level in the local seismicity band for a given instrument type and location shows smaller noise variation

Nanocomposite-Based Microstructured Piezoresistive Pressure Sensors for Low-Pressure Measurement Range

Directory of Open Access Journals (Sweden)

Vasileios Mitrakos

2018-01-01

Full Text Available Piezoresistive pressure sensors capable of detecting ranges of low compressive stresses have been successfully fabricated and characterised. The 5.5 × 5 × 1.6 mm3 sensors consist of a planar aluminium top electrode and a microstructured bottom electrode containing a two-by-two array of truncated pyramids with a piezoresistive composite layer sandwiched in-between. The responses of two different piezocomposite materials, a Multiwalled Carbon Nanotube (MWCNT-elastomer composite and a Quantum Tunneling Composite (QTC, have been characterised as a function of applied pressure and effective contact area. The MWCNT piezoresistive composite-based sensor was able to detect pressures as low as 200 kPa. The QTC-based sensor was capable of detecting pressures as low as 50 kPa depending on the contact area of the bottom electrode. Such sensors could find useful applications requiring the detection of small compressive loads such as those encountered in haptic sensing or robotics.

Better well control through safe drilling margin identification, influx analysis and direct bottom hole pressure control method for deep water

Energy Technology Data Exchange (ETDEWEB)

Veeningen, Daan [National Oilwell Varco IntelliServ (NOV), Houston, TX (United States)

2012-07-01

Currently, well control events are almost exclusively detected by using surface measurements. Measuring a volume increase in the 'closed loop' mud circulation system; a standpipe pressure decrease; or changes in a variety of drilling parameters provide indicators of a kick. Especially in deep water, where the riser comprises a substantial section of the well bore, early kick detection is paramount for limiting the severity of a well bore influx and improve the ability to regain well control. While downhole data is presently available from downhole tools nearby the bit, available data rates are sparse as mud pulse telemetry bandwidth is limited and well bore measurements compete with transmission of other subsurface data. Further, data transfer is one-directional, latency is significant and conditions along the string are unknown. High-bandwidth downhole data transmission system, via a wired or networked drill string system, has the unique capability to acquire real-time pressure and temperature measurement at a number of locations along the drill string. This system provides high-resolution downhole data available at very high speed, eliminating latency and restrictions that typically limit the availability of downhole data. The paper describes well control opportunities for deep water operations through the use of downhole data independent from surface measurements. First, the networked drill string provides efficient ways to identify pore pressure, fracture gradient, and true mud weight that comprise the safe drilling margin. Second, the independent measurement capability provides early kick detection and improved ability to analyze an influx even with a heterogeneous mud column through distributed along-string annular pressure measurements. Third, a methodology is proposed for a direct measurement method using downhole real-time pressure for maintaining constant bottom hole pressure during well kills in deep water. (author)

AFSC/RACE/SAP: Detailed Crab Data From NOAA Fisheries Service Annual Eastern Bering Sea Summer Bottom Trawl Surveys 1975 - 2015

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains detailed crab data collected from the annual NOAA/NMFS/AFSC/RACE crab-groundfish bottom trawl survey of the eastern Bering Sea continental...

Turbidity distribution in the Atlantic Ocean

Science.gov (United States)

Eittreim, S.; Thorndike, E.M.; Sullivan, L.

1976-01-01

The regional coverage of Lamont nephelometer data in the North and South Atlantic can be used to map seawater turbidity at all depths. At the level of the clearest water, in the mid-depth regions, the turbidity distribution primarily reflects the pattern of productivity in the surface waters. This suggests that the 'background' turbidity level in the oceans is largely a function of biogenic fallout. The bottom waters of the western Atlantic generally exhibit large increases in turbidity. The most intense benthic nepheloid layers are in the southwestern Argentine basin and northern North American basin; the lowest bottom water turbidity in the western Atlantic is in the equatorial regions. Both the Argentine and North American basin bottom waters appear to derive their high turbidity largely from local resuspension of terrigenous input in these basins. In contrast to the west, the eastern Atlantic basins show very low turbidities with the exception of three regions: the Mediterranean outflow area, the Cape basin, and the West European basin. ?? 1976.

East Greenland Ridge in the North Atlantic Ocean

DEFF Research Database (Denmark)

Andreasen, Arne Døssing; Dahl-Jensen, T.; Thybo, Hans

2008-01-01

The combined Greenland-Senja Fracture Zones (GSFZ) represent a first-order plate tectonic feature in the North Atlantic Ocean. The GSFZ defines an abrupt change in the character of magnetic anomalies with well-defined seafloor spreading anomalies in the Greenland and Norwegian basins to the south...... but ambiguous and weak magnetic anomalies in the Boreas Basin to the north. Substantial uncertainty exists concerning the plate tectonic evolution of the latter area, including the role of the East Greenland Ridge, which is situated along the Greenland Fracture Zone. In 2002, a combined ocean-bottom seismometer...

The Effect of Pressure on Iron Speciation in Silicate Melts at a Fixed Oxygen Fugacity: The Possibility of a Redox Profile Through a Terrestrial Magma Ocean

Science.gov (United States)

Armstrong, K.; Frost, D. J.; McCammon, C. A.; Rubie, D. C.; Boffa Ballaran, T.

2017-12-01

As terrestrial planets accreted, mantle silicates equilibrated with core-forming metallic iron, which would have imposed a mantle oxygen fugacity below the iron-wüstite oxygen buffer. Throughout Earth's history, however, the oxygen fugacity of at least the accessible portions of the upper mantle has been 4-5 orders of magnitude higher. The process that caused the rapid increase in the redox state of the mantle soon after core formation is unclear. Here we test the possibility that pressure stabilises ferric iron in silicate melts, as has been observed in silicate minerals. A deep magma ocean, which would have likely existed towards the end of accretion, could then develop a gradient in oxygen fugacity for a fixed ferric-ferrous ratio as a result of pressure. We have equilibrated an andesitic melt with a Ru-RuO2 buffer in a multianvil press between 5 and 24 GPa. Further experiments were performed on the same melt in equilibrium with iron metal. The recovered melts were then analysed using Mössbauer spectroscopy to determine the ferric/ferrous ratio. The results show that for the Ru-RuO2 buffer at lower pressures, the ferric iron content decreases with pressure, due to a positive volume change of the reaction FeO + 1/4O2 = FeO1.5. Ferric iron content also appears to be sensitive to water content at lower pressures. However, above 15 GPa this trend apparently reverses and the ferric iron content increases with pressure. This reversal in pressure dependence would drive the oxygen fugacity of a deep magma ocean with a fixed ferric/ferrous ratio down with increasing depth. This would create a redox gradient, where the magma ocean could potentially be in equilibrium with metallic iron at its base but more oxidised in its shallower regions. Crystallisation of this magma ocean could render an upper mantle oxygen fugacity similar to that in the Earth's accessible mantle today.

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.

Science.gov (United States)

Righter, K; Ghiorso, M S

2012-07-24

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO(2) that is based on the ratio of Fe and FeO [called "ΔIW (ratio)" hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO(2) + O(2) = Fe(2)SiO(4) to calculate absolute fO(2) and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO(2) in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO(2) may evolve from high to low fO(2) during Earth (and other differentiated bodies) accretion. Any

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Dome Reef, 1989 - 2003 (NODC Accession 0002809)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Dome Reef, 2006 - 2007 (NODC Accession 0029107)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Dome Reef, 2005 - 2006 (NODC Accession 0014268)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Alligator Reef, 2005 - 2007 (NODC Accession 0019351)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Grecian Rocks, 2005 - 2007 (NODC Accession 0039973)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Track at Tennessee Reef, 1990 - 2004 (NODC Accession 0002749)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Triumph Reef, 1990 - 2006 (NODC accession 0013166)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Grecian Rocks, 1990 - 2005 (NODC Accession 0011143)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Cape Florida, 2005 - 2006 (NODC Accession 0014185)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Iselin, 2006 - 2007 (NODC Accession 0039240)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bullard Bank, 1992 - 2005 (NODC Accession 0010426)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Cape Florida, 1996 - 2005 (NODC Accession 0002788)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Sprigger Bank, 1992 - 2006 (NODC accession 0013114)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Iselin, 2004-2006 (NODC Accession 0014271)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Long Key, 2008 - 2010 (NODC Accession 0093063)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Smith Shoal, 1998 - 2006 (NODC Accession 0014121)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Buoy, 1988 - 2004 (NODC Accession 0002616)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bullard Bank, 2005 - 2007 (NODC Accession 0039881)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Triumph Reef, 1990 - 2006 (NODC Accession 0013166)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Carysfort Reef, 2006-2010 (NODC Accession 0093022)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Grecian Rocks, 2007 - 2010 (NODC Accession 0093026)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Alligator Reef, 2007-2010 (NODC Accession 0093017)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Tennessee Reef, 2004-2006 (NODC Accession 0014272)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Long Key, 2005-2006 (NODC Accession 0014269)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

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).

Pressures on the marine environment and the changing climate of ocean biogeochemistry.

Science.gov (United States)

Rees, Andrew P

2012-12-13

The oceans are under pressure from human activities. Following 250 years of industrial activity, effects are being seen at the cellular through to regional and global scales. The change in atmospheric CO(2) from 280 ppm in pre-industrial times to 392 ppm in 2011 has contributed to the warming of the upper 700 m of the ocean by approximately 0.1°C between 1961 and 2003, to changes in sea water chemistry, which include a pH decrease of approximately 0.1, and to significant decreases in the sea water oxygen content. In parallel with these changes, the human population has been introducing an ever-increasing level of nutrients into coastal waters, which leads to eutrophication, and by 2008 had resulted in 245,000 km(2) of severely oxygen-depleted waters throughout the world. These changes are set to continue for the foreseeable future, with atmospheric CO(2) predicted to reach 430 ppm by 2030 and 750 ppm by 2100. The cycling of biogeochemical elements has proved sensitive to each of these effects, and it is proposed that synergy between stressors may compound this further. The challenge, within the next few decades, for the marine science community, is to elucidate the scope and extent that biological processes can adapt or acclimatize to a changing chemical and physical marine environment.

Two-phase convection in the high-pressure ice layer of the large icy moons: geodynamical implications

Science.gov (United States)

Kalousova, K.; Sotin, C.; Tobie, G.; Choblet, G.; Grasset, O.

2015-12-01

The H2O layers of large icy satellites such as Ganymede, Callisto, or Titan probably include a liquid water ocean sandwiched between the deep high-pressure ice layer and the outer ice I shell [1]. It has been recently suggested that the high-pressure ice layer could be decoupled from the silicate core by a salty liquid water layer [2]. However, it is not clear whether accumulation of liquids at the bottom of the high-pressure layer is possible due to positive buoyancy of water with respect to high-pressure ice. Numerical simulation of this two-phase (i.e. ice and water) problem is challenging, which explains why very few studies have self-consistently handled the presence and transport of liquids within the solid ice [e.g. 3]. While using a simplified description of water production and transport, it was recently showed in [4] that (i) a significant fraction of the high-pressure layer reaches the melting point and (ii) the melt generation and its extraction to the overlying ocean significantly influence the global thermal evolution and interior structure of the large icy moons.Here, we treat the high-pressure ice layer as a compressible mixture of solid ice and liquid water [5]. Several aspects are investigated: (i) the effect of the water formation on the vigor of solid-state convection and its influence on the amount of heat that is transferred from the silicate mantle to the ocean; (ii) the fate of liquids within the upper thermal boundary layer - whether they freeze or reach the ocean; and (iii) the effect of salts and volatile compounds (potentially released from the rocky core) on the melting/freezing processes. Investigation of these aspects will allow us to address the thermo-chemical evolution of the internal ocean which is crucial to evaluate the astrobiological potential of large icy moons. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Hussmann et al. (2007), Treatise of

Temperature and pressure data collected using drifting buoy and profiling floats from the North Atlantic Ocean in part of the IDOE/POLYMODE (International Decade of Ocean Exploration / combination of USSR POLYGON project and US MODE) from 1975-01-10 to 1981-05-31 (NODC Accession 8700121)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and pressure data were collected using drifting buoy and profiling floats from CHAIN, GILLISS, OCEANUS, and ENDEAVOR from the North Atlantic Ocean from...

Controlling Bottom Hole Flowing Pressure Within a Specific Range for Efficient Coalbed Methane Drainage

Science.gov (United States)

Zhao, Bin; Wang, Zhi-Yin; Hu, Ai-Mei; Zhai, Yu-Yang

2013-11-01

The stress state of coal surrounding a coalbed methane (CBM) production well is affected by the bottom hole flowing pressure (BHFP). The permeability of coal shows a marked change under compression. The BHFP must be restricted to a specific range to favor higher permeability in the surrounding coal and thus higher productivity of the well. A new method to determine this specific range is proposed in this paper. Coal has a rather low tensile strength, which induces tensile failure and rock disintegration. The deformation of coal samples under compression has four main stages: compaction, elastic deformation, strain hardening, and strain softening. Permeability is optimal when the coal samples are in the strain softening stage. The three critical values of BHFP, namely, p wmin, p wmid, and p wupper, which correspond to the occurrence of tensile failure, the start of strain softening, and the beginning of plastic deformation, respectively, are derived from theoretical principles. The permeability of coal is in an optimal state when the BHFP is between p wmin and p wmid. The BHFP should be confined to this specific range for the efficient drainage of CBM wells. This method was applied to field operations in three wells in the Hancheng CBM field in China. A comprehensive analysis of drainage data and of the BHFP indicates that the new method is effective and offers significant improvement to current practices.

An analytical two-flow model to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance

Science.gov (United States)

Ma, Wei-Ming

1997-06-01

An analytical two-flow model is derived from the radiative transfer equation to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance. The model utilizes unique boundary conditions, including the surface slope of the downwelling and upwelling irradiance as well as the influence of wind and bottom reflectance on simulated surface reflectance. The developed model provides a simple mathematical concept for understanding the irradiant light flux and associated processes in coastal or fresh water as well as turbid estuarine waters. The model is applied to data from the Banana River and coastal Atlantic Ocean water off the east coast of central Florida, USA. The two-flow irradiance model is capable of simulating realistic above-surface reflectance signatures under wind-roughened air-water surface given realistic input parameters including a specular flux conversion coefficient, absorption coefficient, backscattering coefficient, atmospheric visibility, bottom reflectance, and water depth. The root-mean-squared error of the calculated above-surface reflectances is approximately 3% in the Banana River and is less than 15% in coastal Atlantic Ocean off the east of Florida. Result of the subsurface reflectance sensitivity analysis indicates that the specular conversion coefficient is the most sensitive parameter in the model, followed by the beam attenuation coefficient, absorption coefficient, water depth, backscattering coefficient, specular irradiance, diffuse irradiance, bottom reflectance, and wind speed. On the other hand, result of the above-surface reflectance sensitivity analysis indicates that the wind speed is the most important parameter, followed by bottom reflectance, attenuation coefficient, water depth, conversion coefficient, specular irradiance, downwelling irradiance, absorption coefficient, and backscattering coefficient. Model results depend on the accuracy of these parameters to a large degree and

Ocean angular momentum signals in a climate model and implications for Earth rotation

Science.gov (United States)

Ponte, R. M.; Rajamony, J.; Gregory, J. M.

2002-03-01

Estimates of ocean angular momentum (OAM) provide an integrated measure of variability in ocean circulation and mass fields and can be directly related to observed changes in Earth rotation. We use output from a climate model to calculate 240 years of 3-monthly OAM values (two equatorial terms L1 and L2, related to polar motion or wobble, and axial term L3, related to length of day variations) representing the period 1860-2100. Control and forced runs permit the study of the effects of natural and anthropogenically forced climate variability on OAM. All OAM components exhibit a clear annual cycle, with large decadal modulations in amplitude, and also longer period fluctuations, all associated with natural climate variability in the model. Anthropogenically induced signals, inferred from the differences between forced and control runs, include an upward trend in L3, related to inhomogeneous ocean warming and increases in the transport of the Antarctic Circumpolar Current, and a significantly weaker seasonal cycle in L2 in the second half of the record, related primarily to changes in seasonal bottom pressure variability in the Southern Ocean and North Pacific. Variability in mass fields is in general more important to OAM signals than changes in circulation at the seasonal and longer periods analyzed. Relation of OAM signals to changes in surface atmospheric forcing are discussed. The important role of the oceans as an excitation source for the annual, Chandler and Markowitz wobbles, is confirmed. Natural climate variability in OAM and related excitation is likely to measurably affect the Earth rotation, but anthropogenically induced effects are comparatively weak.

a New Technique Based on Mini-Uas for Estimating Water and Bottom Radiance Contributions in Optically Shallow Waters

Science.gov (United States)

Montes-Hugo, M. A.; Barrado, C.; Pastor, E.

2015-08-01

The mapping of nearshore bathymetry based on spaceborne radiometers is commonly used for QC ocean colour products in littoral waters. However, the accuracy of these estimates is relatively poor with respect to those derived from Lidar systems due in part to the large uncertainties of bottom depth retrievals caused by changes on bottom reflectivity. Here, we present a method based on mini unmanned aerial vehicles (UAS) images for discriminating bottom-reflected and water radiance components by taking advantage of shadows created by different structures sitting on the bottom boundary. Aerial surveys were done with a drone Draganfly X4P during October 1 2013 in optically shallow waters of the Saint Lawrence Estuary, and during low tide. Colour images with a spatial resolution of 3 mm were obtained with an Olympus EPM-1 camera at 10 m height. Preliminary results showed an increase of the relative difference between bright and dark pixels (dP) toward the red wavelengths of the camera's receiver. This is suggesting that dP values can be potentially used as a quantitative proxy of bottom reflectivity after removing artefacts related to Fresnel reflection and bottom adjacency effects.

Major role of marine vegetation on the oceanic carbon cycle

NARCIS (Netherlands)

Duarte, C.M.; Middelburg, J.J.; Caraco, N.

2005-01-01

The carbon burial in vegetated sediments, ignored in past assessments of carbon burial in the ocean, was evaluated using a bottom-up approach derived from upscaling a compilation of published individual estimates of carbon burial in vegetated habitats (seagrass meadows, salt marshes and mangrove

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Key West Channel, 1991 - 2005 (NODC Accession 0012739)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Boca Grande Channel, 2004-2006 (NODC Accession 0014184)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Sand Key Lighthouse, 1990 - 2005 (NODC Accession 0012769)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Key West Channel, 2005 - 2007 (NODC Accession 0039986)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Sand Key Lighthouse, 2007 - 2010 (NODC Accession 0093065)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Card Sound Bridge, 2004 - 2006 (NODC Accession 0014266)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Sand Key Lighthouse, 2005 - 2007 (NODC Accession 0040080)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at 9-Ft Shoal, 2007-2010 (NODC Accession 0092549)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Ball Buoy Reef, 1990 - 1998 (NODC Accession 0002781)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bicentennial Coral Head, 1998 - 2006 (NODC Accession 0039481)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bahia Honda Bridge, 2007-2011 (NODC Accession 0093018)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Snake Creek Bridge, 1989 - 2005 (NODC accession 0013148)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Harbor Key Bank, 1992 - 1997 (NODC Accession 0013553)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Sombrero Reef Lighthouse, 1991-2005 (NODC Accession 0013726)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at 7-mile Bridge, 2005 - 2007 (NODC Accession 0039469)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at 7-mile Bridge, 2007-2010 (NODC Accession 0092548)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at 9-FT Shoal, 2005-2007 (NODC Accession 0039533)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bicentennial Coral Head, 2006 - 2007 (NODC Accession 0039817)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Boca Grande Channel, 2006 - 2007 (NODC Accession 0039818)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Snake Creek Bridge, 1989 - 2005 (NODC Accession 0013148)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Bicentennial Coral Head, 2007-2009 (NODC Accession 0090835)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Method and apparatus for disposing a radioactive waste container to submarine bottom

International Nuclear Information System (INIS)

Shibata, Kiyoshi; Yoshida, Shoichi.

1980-01-01

Purpose: To completely eliminate a danger occurred by the rolling of a hull in the ocean in a method and apparatus for disposing radioactive waste container to submarine bottom by independently handling the radioactive waste containers when loading the container in a compartment carried on a barge and sinking the containers together with the compartment to the submarine bottom at its disposing time. Method: Radioactive waste containers are carried into a compartment loaded on a barge floating completely, and the barge is then applied with external force thereto by a ship or the like and sailed to the marine disposal area. Then, water is filled in the ballast tank of the barge to submerge the barge, the compartment is floated and separated from the containers, and water is charged into the compartment to sink the compartment. (Aizawa, K.)

Ultrasonic level sensors for liquids under high pressure

Science.gov (United States)

Zuckerwar, A. J.; Mazel, D. S.; Hodges, D. Y.

1986-01-01

An ultrasonic level sensor of novel design continuously measures the level of a liquid subjected to a high pressure (up to about 40 MPa), as is sometimes required for the effective transfer of the liquid. The sensor operates as a composite resonator fabricated from a standard high-pressure plug. A flat-bottom hole is machined into the plug along its center line. An ultrasonic transducer is bonded rigidly to the interior surface of the bottom wall, while the exterior surface is in contact with the liquid. Although the bottom wall is designed to satisfy the pressure code, it is still sufficiently thin to permit ready excitation of the axisymmetric plate modes of vibration. The liquid level is measured by a conventional pulse-echo technique. A prototype sensor was tested successfully in a 2300-l water vessel at pressures up to about 37 MPa. A spectral analysis of the transmitted pulse reveals that the flexural, extensional, thickness-shear, and radial plate modes are excited into vibration, but none of these appears to be significantly affected by the pressurization of the liquid.

Out-pile test of the capsule with cone shape bottom structures

Energy Technology Data Exchange (ETDEWEB)

Choi, M. H.; Kang, Y. H.; Cho, M. S.; Choo, K. N.; Kim, B. G.; Son, J. M.; Park, S. J.; Shin, Y. T.; Oh, J. M

2004-01-01

The design modification of bottom guide structures for the instrumented capsule which is used for the irradiation test in the research reactor, HANARO is done because of the cutting trouble of the bottom guide arm's pin. The previous structure of the 3-pin arm shape is changed into one body of the cone shape. The specimens of the bottom end cap ring with three different sizes ({phi}68mm, {phi}70mm, {phi}72mm) are designed and manufactured. The out-pile test for the capsule with previous 3-pin arm and new three bottom structures of the cone shape is performed using the one-channel flow test facilities. In order to estimate the compatibility with HANARO, the structural stability and integrity of the capsule, the out-pile test such as a loading/unloading test, a pressure drop test, a thermal performance test, a displacement measurement due to a vibration and an endurance test etc. is conducted, and the outer diameter of the bottom end cap ring to meet the HANARO requirements is selected. From out-pile test results the capsule with cone shape bottom structures is evaluated as to have the structural stability and the benefit from the fluid's flow respect. Also the size satisfied various requirements among three kinds of bottom end cap rings is 70mm in diameter. It is expected that the new bottom structures of the cone shape with 70mm in diameter will be applicable to all material and special capsules which will be designed and manufactured for the purpose of irradiation tests in the future.

Temperature, pressure, and other data collected using tide gauge and CTD casts from the Northwest Atlantic Ocean in part of the IDOE/POLYMODE (International Decade of Ocean Exploration / combination of USSR POLYGON project and US MODE) from 06 October 1976 to 05 July 1977 (NODC Accession 7900243)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, pressure, and other data were collected using tide gauge and CTD casts from the Northwest Atlantic Ocean from October 6, 1976 to July 5, 1977. Data were...

Temperature, pressure, and other data collected using tide gauge and CTD casts from the Northwest Atlantic Ocean as part of the IDOE/POLYMODE (International Decade of Ocean Exploration / combination of USSR POLYGON project and US MODE) from 01 May 1977 to 31 May 1978 (NODC Accession 7900244)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, pressure, and other data were collected using tide gauge and CTD casts from the Northwest Atlantic Ocean from May 1, 1977 to May 31, 1978. Data were...

Tide Gauge Records Reveal Improved Processing of Gravity Recovery and Climate Experiment Time-Variable Mass Solutions over the Coastal Ocean

Science.gov (United States)

Piecuch, Christopher G.; Landerer, Felix W.; Ponte, Rui M.

2018-05-01

Monthly ocean bottom pressure solutions from the Gravity Recovery and Climate Experiment (GRACE), derived using surface spherical cap mass concentration (MC) blocks and spherical harmonics (SH) basis functions, are compared to tide gauge (TG) monthly averaged sea level data over 2003-2015 to evaluate improved gravimetric data processing methods near the coast. MC solutions can explain ≳ 42% of the monthly variance in TG time series over broad shelf regions and in semi-enclosed marginal seas. MC solutions also generally explain ˜5-32 % more TG data variance than SH estimates. Applying a coastline resolution improvement algorithm in the GRACE data processing leads to ˜ 31% more variance in TG records explained by the MC solution on average compared to not using this algorithm. Synthetic observations sampled from an ocean general circulation model exhibit similar patterns of correspondence between modeled TG and MC time series and differences between MC and SH time series in terms of their relationship with TG time series, suggesting that observational results here are generally consistent with expectations from ocean dynamics. This work demonstrates the improved quality of recent MC solutions compared to earlier SH estimates over the coastal ocean, and suggests that the MC solutions could be a useful tool for understanding contemporary coastal sea level variability and change.

The influence of triple bottom line on international operations management

Directory of Open Access Journals (Sweden)

Francisco Sperotto Flores

2017-12-01

Full Text Available This paper takes a triple bottom line perspective to analyze how the international operations literature integrates economic, social, and environmental issues. Additionally, it shows the main drivers of and barriers to the adoption of triple bottom line practices by companies in an international context. We conducted a literature review in English language journals which publish research of production and operations management and sustainability, resulting in a final sample of 29 papers. Results show that social and legal pressure for companies to adopt a responsible behavior prompts an isomorphic process that leads them to conduct their operations on behalf of triple bottom line goals. Behavioral differences between spin-offs in various countries caused institutions to create mechanisms that can press and change private standards through regulation and enforcement. There is room for progress in studies that seek to analyze the company’s relationships in its international experience and its multi-institutional relations.

Deep Sea Coral voucher sequence dataset - Identification of deep-sea corals collected during the 2009 - 2014 West Coast Groundfish Bottom Trawl Survey

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Data for this project resides in the West Coast Groundfish Bottom Trawl Survey Database. Deep-sea corals are often components of trawling bycatch, though their...

Large bio-geographical shifts in the north-eastern Atlantic Ocean

DEFF Research Database (Denmark)

Hátún, Hjálmar; Payne, Mark; Beaugrand, G.

2009-01-01

and persistent bottom-up bio-physical link is demonstrated using a numerical ocean general circulation model and data on four trophically connected levels in the food chain – phytoplankton, zooplankton, blue whiting, and pilot whales. The plankton data give a unique basin-scale depiction of these changes...

Increased thermohaline stratification as a possible cause for an ocean anoxic event in the Cretaceous period.

Science.gov (United States)

Erbacher, J; Huber, B T; Norris, R D; Markey, M

2001-01-18

Ocean anoxic events were periods of high carbon burial that led to drawdown of atmospheric carbon dioxide, lowering of bottom-water oxygen concentrations and, in many cases, significant biological extinction. Most ocean anoxic events are thought to be caused by high productivity and export of carbon from surface waters which is then preserved in organic-rich sediments, known as black shales. But the factors that triggered some of these events remain uncertain. Here we present stable isotope data from a mid-Cretaceous ocean anoxic event that occurred 112 Myr ago, and that point to increased thermohaline stratification as the probable cause. Ocean anoxic event 1b is associated with an increase in surface-water temperatures and runoff that led to decreased bottom-water formation and elevated carbon burial in the restricted basins of the western Tethys and North Atlantic. This event is in many ways similar to that which led to the more recent Plio-Pleistocene Mediterranean sapropels, but the greater geographical extent and longer duration (approximately 46 kyr) of ocean anoxic event 1b suggest that processes leading to such ocean anoxic events in the North Atlantic and western Tethys were able to act over a much larger region, and sequester far more carbon, than any of the Quaternary sapropels.

Large Eddy Simulations of a Bottom Boundary Layer Under a Shallow Geostrophic Front

Science.gov (United States)

Bateman, S. P.; Simeonov, J.; Calantoni, J.

2017-12-01

The unstratified surf zone and the stratified shelf waters are often separated by dynamic fronts that can strongly impact the character of the Ekman bottom boundary layer. Here, we use large eddy simulations to study the turbulent bottom boundary layer associated with a geostrophic current on a stratified shelf of uniform depth. The simulations are initialized with a spatially uniform vertical shear that is in geostrophic balance with a pressure gradient due to a linear horizontal temperature variation. Superposed on the temperature front is a stable vertical temperature gradient. As turbulence develops near the bottom, the turbulence-induced mixing gradually erodes the initial uniform temperature stratification and a well-mixed layer grows in height until the turbulence becomes fully developed. The simulations provide the spatial distribution of the turbulent dissipation and the Reynolds stresses in the fully developed boundary layer. We vary the initial linear stratification and investigate its effect on the height of the bottom boundary layer and the turbulence statistics. The results are compared to previous models and simulations of stratified bottom Ekman layers.

Major role of marine vegetation on the oceanic carbon cycle

Directory of Open Access Journals (Sweden)

C. M. Duarte

2005-01-01

Full Text Available The carbon burial in vegetated sediments, ignored in past assessments of carbon burial in the ocean, was evaluated using a bottom-up approach derived from upscaling a compilation of published individual estimates of carbon burial in vegetated habitats (seagrass meadows, salt marshes and mangrove forests to the global level and a top-down approach derived from considerations of global sediment balance and a compilation of the organic carbon content of vegeatated sediments. Up-scaling of individual burial estimates values yielded a total carbon burial in vegetated habitats of 111 Tmol C y-1. The total burial in unvegetated sediments was estimated to be 126 Tg C y-1, resulting in a bottom-up estimate of total burial in the ocean of about 244 Tg C y-1, two-fold higher than estimates of oceanic carbon burial that presently enter global carbon budgets. The organic carbon concentrations in vegetated marine sediments exceeds by 2 to 10-fold those in shelf/deltaic sediments. Top-down recalculation of ocean sediment budgets to account for these, previously neglected, organic-rich sediments, yields a top-down carbon burial estimate of 216 Tg C y-1, with vegetated coastal habitats contributing about 50%. Even though vegetated carbon burial contributes about half of the total carbon burial in the ocean, burial represents a small fraction of the net production of these ecosystems, estimated at about 3388 Tg C y-1, suggesting that bulk of the benthic net ecosystem production must support excess respiration in other compartments, such as unvegetated sediments and the coastal pelagic compartment. The total excess organic carbon available to be exported to the ocean is estimated at between 1126 to 3534 Tg C y-1, the bulk of which must be respired in the open ocean. Widespread loss of vegetated coastal habitats must have reduced carbon burial in the ocean by about 30 Tg C y-1, identifying the destruction of these ecosystems as an important loss of CO

Enhanced Open Ocean Storage of CO2 from Shelf Sea Pumping

NARCIS (Netherlands)

Thomas, H.; Bozec, Y.; Elkalay, K.; de Baar, H.J.W.

2004-01-01

Seasonal field observations show that the North Sea, a Northern European shelf sea, is highly efficient in pumping carbon dioxide fromthe atmosphere to the North Atlantic Ocean. The bottom topography–controlled stratification separates production and respiration processes in the North Sea, causing a

Ocean energy

International Nuclear Information System (INIS)

2009-01-01

There are 5 different ways of harnessing ocean energy: tides, swells, currents, osmotic pressure and deep water thermal gradients. The tidal power sector is the most mature. A single French site - The Rance tidal power station (240 MW) which was commissioned in 1966 produces 90% of the world's ocean energy. Smaller scale power stations operate around the world, 10 are operating in the European Union and 5 are being tested. Underwater generators and wave energy converters are expanding. In France a 1 km 2 sea test platform is planned for 2010. (A.C.)

Sediment movement along the U.S. east coast continental shelf-I. Estimates of bottom stress using the Grant-Madsen model and near-bottom wave and current measurements

Science.gov (United States)

Lyne, V.D.; Butman, B.; Grant, W.D.

1990-01-01

Bottom stress is calculated for several long-term time-series observations, made on the U.S. east coast continental shelf during winter, using the wave-current interaction and moveable bed models of Grant and Madsen (1979, Journal of Geophysical Research, 84, 1797-1808; 1982, Journal of Geophysical Research, 87, 469-482). The wave and current measurements were obtained by means of a bottom tripod system which measured current using a Savonius rotor and vane and waves by means of a pressure sensor. The variables were burst sampled about 10% of the time. Wave energy was reasonably resolved, although aliased by wave groupiness, and wave period was accurate to 1-2 s during large storms. Errors in current speed and direction depend on the speed of the mean current relative to the wave current. In general, errors in bottom stress caused by uncertainties in measured current speed and wave characteristics were 10-20%. During storms, the bottom stress calculated using the Grant-Madsen models exceeded stress computed from conventional drag laws by a factor of about 1.5 on average and 3 or more during storm peaks. Thus, even in water as deep as 80 m, oscillatory near-bottom currents associated with surface gravity waves of period 12 s or longer will contribute substantially to bottom stress. Given that the Grant-Madsen model is correct, parameterizations of bottom stress that do not incorporate wave effects will substantially underestimate stress and sediment transport in this region of the continental shelf.

Organic geochemistry of the early Toarcian oceanic anoxic event in Hawsker Bottoms, Yorkshire, England

Science.gov (United States)

French, K. L.; Sepúlveda, J.; Trabucho-Alexandre, J.; Gröcke, D. R.; Summons, R. E.

2014-03-01

A comprehensive organic geochemical investigation of the Hawsker Bottoms outcrop section in Yorkshire, England has provided new insights about environmental conditions leading into and during the Toarcian oceanic anoxic event (T-OAE; ∼183 Ma). Rock-Eval and molecular analyses demonstrate that the section is uniformly within the early oil window. Hydrogen index (HI), organic petrography, polycyclic aromatic hydrocarbon (PAH) distributions, and tricyclic terpane ratios mark a shift to a lower relative abundance of terrigenous organic matter supplied to the sampling locality during the onset of the T-OAE and across a lithological transition. Unlike other ancient intervals of anoxia and extinction, biomarker indices of planktonic community structure do not display major changes or anomalous values. Depositional environment and redox indicators support a shift towards more reducing conditions in the sediment porewaters and the development of a seasonally stratified water column during the T-OAE. In addition to carotenoid biomarkers for green sulfur bacteria (GSB), we report the first occurrence of okenane, a marker of purple sulfur bacteria (PSB), in marine samples younger than ∼1.64 Ga. Based on modern observations, a planktonic source of okenane's precursor, okenone, would require extremely shallow photic zone euxinia (PZE) and a highly restricted depositional environment. However, due to coastal vertical mixing, the lack of planktonic okenone production in modern marine sulfidic environments, and building evidence of okenone production in mat-dwelling Chromatiaceae, we propose a sedimentary source of okenone as an alternative. Lastly, we report the first parallel compound-specific δC13 record in marine- and terrestrial-derived biomarkers across the T-OAE. The δC13 records of short-chain n-alkanes, acyclic isoprenoids, and long-chain n-alkanes all encode negative carbon isotope excursions (CIEs), and together, they support an injection of isotopically light

Mantle Serpentinization near the Central Mariana Trench Constrained by Ocean Bottom Surface Wave Observations

Science.gov (United States)

Cai, C.; Wiens, D. A.; Lizarralde, D.; Eimer, M. O.; Shen, W.

2017-12-01

We investigate the crustal and uppermost mantle seismic structure across the Mariana trench by jointly inverting Rayleigh wave phase and group velocities from ambient noise and longer period phase velocities from Helmholtz tomography of teleseismic waveforms. We use data from a temporary deployment in 2012-2013, consisting of 7 island-based stations and 20 broadband ocean bottom seismographs, as well as data from the USGS Northern Mariana Islands Seismograph Network. To avoid any potential bias from the starting model, we use a Bayesian Monte-Carlo algorithm to invert for the azimuthally-averaged SV-wave velocity at each node. This method also allows us to apply prior constraints on crustal thickness and other parameters in a systematic way, and to derive formal estimates of velocity uncertainty. The results show the development of a low velocity zone within the incoming plate beginning about 80 km seaward of the trench axis, consistent with the onset of bending faults from bathymetry and earthquake locations. The maximum depth of the velocity anomaly increases towards the trench, and extends to about 30 km below the seafloor. The low velocities persist after the plate is subducted, as a 20-30 km thick low velocity layer with a somewhat smaller velocity reduction is imaged along the top of the slab beneath the forearc. An extremely low velocity zone is observed beneath the serpentine seamounts in the outer forearc, consistent with 40% serpentinization in the forearc mantle wedge. Azimuthal anisotropy results show trench parallel fast axis within the incoming plate at uppermost mantle depth (2%-4% anisotropy). All these observations suggest the velocity reduction in the incoming plate prior to subduction results from both serpentinized normal faults and water-filled cracks. Water is expelled from the cracks early in subduction, causing a modest increase in the velocity of the subducting mantle, and moves upward and causes serpentinization of the outer forearc

Long-term simulation of 137Cs in the Irish Sea by using ocean environment assessment system

International Nuclear Information System (INIS)

Kobayashi, Takuya; Otosaka, Shigeyoshi; Togawa, Orihiko; Hayashi, Keisuke

2007-01-01

An ocean environment assessment system that forecasts the detailed migration processes of radionuclides in the ocean has been developed. This system consists of an ocean current model and a particle random-walk model. The ocean current model is the modified Princeton Ocean Model (POM). The POM calculates tidal currents by giving tide levels at the open boundary. The particle random-walk model, SEA-GEARN, calculates the radionuclides migration in the ocean. Radionuclides that exist in the ocean are modeled in three phases, such as dissolved in seawater, adsorbed with large particulate matter (LPM) and adsorbed with active bottom sediment. The adsorption and desorption processes between the dissolved and solid phases are solved with the kinetic transfer coefficients by the stochastic method. Deposition of LPM and resuspension from bottom sediment are also considered. As model validation, the system has been applied to the Irish Sea to simulate the long-term dispersion of 137 Cs actually released from the BNFL spent nuclear fuel reprocessing plant at Sellafield in UK. Calculation results of surface dissolved 137 Cs have been compared with the observed data. The observed data are extracted from a database, Marine Information System (MARIS), which is released from the International Atomic Energy Agency's Marine Environment Laboratory (IAEA-MEL) in Monaco. The calculation well reproduces the main characteristics of migration of surface dissolved 137 Cs concentration in the Irish Sea. (author)

Rescue of Long-Tail Data from the Ocean Bottom to the Moon

Science.gov (United States)

Hsu, L.; Lehnert, K. A.; Carbotte, S. M.; Ferrini, V.; Delano, J. W.; Gill, J. B.; Tivey, M.

2013-12-01

IEDA (Integrated Earth Data Applications, www.iedadata.org), the NSF facility that operates EarthChem, the Marine Geoscience Data System, and the System for Earth Sample Registration, launched a Data Rescue Initiative in 2013 to advance preservation and re-use of valuable legacy datasets that are in danger of being lost. As part of this initiative, IEDA established a competition for Data Rescue Mini-Awards that provide modest funds to investigators to properly compile, document, and transfer legacy data sets to IEDA. Applications from late-career and near-retirement investigators were specifically encouraged. Awardees were given approximately six months to complete their data rescue activities. Three projects were awarded in 2013: (1) Geochemistry of Lunar Glasses: assembly of major element, trace element, volatile element, and isotope ratio data for lunar volcanic glasses and lunar impact glasses, (2) Geochemical and Geochronological data from Fiji, Izu-Bonin-Marianas, and Endeavor segment: assembly of published and unpublished data and metadata from large rock sample collections, and (3) Near-bottom Magnetic Data: curation and archival of 35 years of high-resolution, near-bottom magnetic field data from deeptowed platforms, submersibles, and ROVs. IEDA is working closely with the awardees to guide and support the data rescue effort and to assist with specific challenges related to outdated storage media or technology, diversity of platforms over decades of research, and the lack of established standards for data documentation. In this contribution we describe procedures and tools used for each project, summarize lessons learned and best practices, and present the final output of each data rescue project. Depending on the experiences of this first year and the availability of funds, we plan to continue the competition in future years.

Mass-induced sea level variations in the Red Sea from GRACE, steric-corrected altimetry, in situ bottom pressure records, and hydrographic observations

Science.gov (United States)

Feng, W.; Lemoine, J.-M.; Zhong, M.; Hsu, H. T.

2014-08-01

An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.

Direct observations of atmosphere - sea ice - ocean interactions during Arctic winter and spring storms

Science.gov (United States)

Graham, R. M.; Itkin, P.; Granskog, M. A.; Assmy, P.; Cohen, L.; Duarte, P.; Doble, M. J.; Fransson, A.; Fer, I.; Fernandez Mendez, M.; Frey, M. M.; Gerland, S.; Haapala, J. J.; Hudson, S. R.; Liston, G. E.; Merkouriadi, I.; Meyer, A.; Muilwijk, M.; Peterson, A.; Provost, C.; Randelhoff, A.; Rösel, A.; Spreen, G.; Steen, H.; Smedsrud, L. H.; Sundfjord, A.

2017-12-01

To study the thinner and younger sea ice that now dominates the Arctic the Norwegian Young Sea ICE expedition (N-ICE2015) was launched in the ice-covered region north of Svalbard, from January to June 2015. During this time, eight local and remote storms affected the region and rare direct observations of the atmosphere, snow, ice and ocean were conducted. Six of these winter storms passed directly over the expedition and resulted in air temperatures rising from below -30oC to near 0oC, followed by abrupt cooling. Substantial snowfall prior to the campaign had already formed a snow pack of approximately 50 cm, to which the February storms contributed an additional 6 cm. The deep snow layer effectively isolated the ice cover and prevented bottom ice growth resulting in low brine fluxes. Peak wind speeds during winter storms exceeded 20 m/s, causing strong snow re-distribution, release of sea salt aerosol and sea ice deformation. The heavy snow load caused widespread negative freeboard; during sea ice deformation events, level ice floes were flooded by sea water, and at least 6-10 cm snow-ice layer was formed. Elevated deformation rates during the most powerful winter storms damaged the ice cover permanently such that the response to wind forcing increased by 60 %. As a result of a remote storm in April deformation processes opened about 4 % of the total area into leads with open water, while a similar amount of ice was deformed into pressure ridges. The strong winds also enhanced ocean mixing and increased ocean heat fluxes three-fold in the pycnocline from 4 to 12 W/m2. Ocean heat fluxes were extremely large (over 300 W/m2) during storms in regions where the warm Atlantic inflow is located close to surface over shallow topography. This resulted in very large (5-25 cm/day) bottom ice melt and in cases flooding due to heavy snow load. Storm events increased the carbon dioxide exchange between the atmosphere and ocean but also affected the pCO2 in surface waters

The pole tide in deep oceans

Science.gov (United States)

Dickman, S. R.

1990-01-01

The fluid-dynamical theory of the pole tide is examined by describing the oceanic response to the Chandler wobble and assessing its implications for mantle anelasticity and low-frequency ocean dynamics. The Laplace tide equations accounting for bottom friction are given, and a spherical harmonic approach is delineated in which the time-independent portion of the tide height is expanded. Pole-tide height and related inertia products are linearly proportional to wobble amplitude, and the final equations are modified to account for mantle elasticity and oceanic loading. Results for pole tide effects are given for various earth models with attention to the role of boundary constraints. A dynamic effect is identified which lengthens the Chandler period by about 1 day more than static lengthening, a contribution that suggests a vigorous low-frequency response. The values derived are shown to agree with previous models that do not incorporate the effects of the pole tide.

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Pillar Coral Forest site, 2006 (NODC accession 0040039)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Bahia Honda Bridge, 2005 - 2007 (NODC Accession 0039226)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Hen and Chickens Reef, 2006 - 2007 (NODC Accession 0020554)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Hen and Chickens Reef, 1989 - 2006 (NODC Accession 0011144)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Broad Creek site, 2006 - 2007 (NODC Accession 0039880)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Broad Creek site, 2007-2009 (NODC Accession 0093020)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Key Back Reef, 2004-2006 (NODC Accession 0014270)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Bahia Honda Bridge, 1990 - 2004 (NODC Accession 0002772)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Hen and Chickens Reef, 2007 - 2011 (NODC Accession 0093027)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Laboratory Investigations in Support of Dioxide-Limestone Sequestration in the Ocean

Energy Technology Data Exchange (ETDEWEB)

Dan Golomb; Eugene Barry; David Ryan; Stephen Pennell; Carl Lawton; Peter Swett; Devinder Arora; John Hannon; Michael Woods; Huishan Duan; Tom Lawlor

2008-09-30

that the CaCO{sub 3} emulsion is slightly alkaline, not acidic. We tested the release of the CO{sub 2}-in-H{sub 2}O emulsion stabilized by pulverized limestone in the DOE National Energy Technology Laboratory High Pressure Water Tunnel Facility (HPWTF). Digital photographs showed the sinking globules in the HPWTF, confirming the concept of releasing the emulsion in the deep ocean. We modeled the release of an emulsion from the CO{sub 2} output of a 1000 MW coal-fired power plant at 500 m depth. The emulsion would typically sink several hundred meters before density equilibration with ambient seawater. The CO{sub 2} globules would rain out from the equilibrated plume toward the ocean bottom where they would disintegrate due to wave action and bottom friction. Conceptual release systems are described both for an open ocean release and a sloping seabed release of the emulsion.

Sensitivity of the regional ocean acidification and carbonate system in Puget Sound to ocean and freshwater inputs

Directory of Open Access Journals (Sweden)

Laura Bianucci

2018-03-01

Full Text Available While ocean acidification was first investigated as a global phenomenon, coastal acidification has received significant attention in recent years, as its impacts have been felt by different socio-economic sectors (e.g., high mortality of shellfish larvae in aquaculture farms. As a region that connects land and ocean, the Salish Sea (consisting of Puget Sound and the Straits of Juan de Fuca and Georgia receives inputs from many different sources (rivers, wastewater treatment plants, industrial waste treatment facilities, etc., making these coastal waters vulnerable to acidification. Moreover, the lowering of pH in the Northeast Pacific Ocean also affects the Salish Sea, as more acidic waters get transported into the bottom waters of the straits and estuaries. Here, we use a numerical ocean model of the Salish Sea to improve our understanding of the carbonate system in Puget Sound; in particular, we studied the sensitivity of carbonate variables (e.g., dissolved inorganic carbon, total alkalinity, pH, saturation state of aragonite to ocean and freshwater inputs. The model is an updated version of our FVCOM-ICM framework, with new carbonate-system and sediment modules. Sensitivity experiments altering concentrations at the open boundaries and freshwater sources indicate that not only ocean conditions entering the Strait of Juan de Fuca, but also the dilution of carbonate variables by freshwater sources, are key drivers of the carbonate system in Puget Sound.

Stresses in a submarine topography under ocean waves

Energy Technology Data Exchange (ETDEWEB)

Mei, C.C.; McTigue, D.F.

1984-09-01

The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular, the dynamic pore pressure and the combined static and dynamic effective stresses are presented.

Temperature profile and pressure data from CTD casts in the TOGA area of the Pacific Ocean from NOAA Ship DISCOVERER from 1992-09-06 to 1992-12-08 (NODC Accession 9400195)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using CTD casts from NOAA Ship DISCOVERER in the TOGA area of the Pacific Ocean from 06 September 1992 to 08...

Temperature profile and pressure data from CTD casts in the TOGA area of the Pacific Ocean from NOAA Ship DISCOVERER from 1994-05-11 to 1994-11-19 (NODC Accession 9600136)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using CTD casts from NOAA Ship DISCOVERER in the TOGA area of the Pacific Ocean from 11 May 1994 to 19 November...

Temperature profile and pressure data from CTD casts in the Northwest Atlantic Ocean from 19 April 2001 to 15 December 2001 (NODC Accession 0000370)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected from the NAVIGATION RESPONSE TEAM 2 from April 19, 2001 to December 15, 2001. Data were submitted by National...

Determining Ocean-Bottom Seismometer Orientations from the RHUM-RUM experiment from P-wave and Rayleigh wave polarizations

Science.gov (United States)

Scholz, John-Robert; Barruol, Guilhem; Fontaine, Fabrice R.; Sigloch, Karin

2016-04-01

To image the upper mantle structure beneath La Réunion hotspot, a large-scale seismic network has been deployed on land and at sea in the frame of the RHUM-RUM project (Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel). This French-German passive seismic experiment was designed to investigate and image the deep structure beneath La Réunion, from crust to core, to precise the shape and depth origin of a mantle plume, if any, and to precise the horizontal and vertical mantle flow associated to a possible plume upwelling, to its interaction with the overlying plate and with the neighboring Indian ridges. For this purpose, 57 Ocean-Bottom Seismometers (OBS) were installed around La Réunion and along the Central and Southwest Indian ridges. Broad-band instruments were deployed with the French R/V Marion Dufresne in late 2012 (cruise MD192), and recovered 13 months later by the German R/V Meteor (cruise M101). The pool of OBS was complemented by ~60 terrestrial stations, installed on different islands in the western Indian Ocean, such as La Réunion, Madagascar, Mauritius, Seychelles, Mayotte and the Îles Éparses in the Mozambique channel. The OBS installation is a free-fall down to the seafloor, where they landed in an unknown orientation. Since seismologic investigations of crustal and upper mantle structure (e.g., receiver functions) and azimuthal anisotropy (e.g., SKS-splitting and Rayleigh waves) rely on the knowledge of the correct OBS orientation with respect to the geographic reference frame, it is of importance to determine the orientations of the OBS while recording on the seafloor. In an isotropic, horizontally homogeneous and non-dipping layered globe, the misorientation of each station refers to the offset between theoretical and recorded back-azimuth angle of a passive seismic event. Using large earthquakes (MW > 5.0), it is possible to establish multiple successful measurements per station and thus to determine with good confidence the

Continuous bottom temperature measurements in strategic atreas of the Florida Reef Tract at the New Ground Shoal site, 1992 - 2006 (NODC Accession 0012845)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Boca Grande Channel, 2007 - 2008 and 2012 (NODC Accession 0093019)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Pillar Coral Forest site, 1996 - 2006 (NODC accession 0013096)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the New Ground Shoal site, 1992 - 2006 (NODC Accession 0012845)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at M/V ELPIS Restoration Site, 2007 - 2011 (NODC Accession 0093024)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the Pillar Coral Forest site, 1996 - 2006 (NODC Accession 0013096)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Spatial and temporal changes in cumulative human impacts on the world's ocean.

Science.gov (United States)

Halpern, Benjamin S; Frazier, Melanie; Potapenko, John; Casey, Kenneth S; Koenig, Kellee; Longo, Catherine; Lowndes, Julia Stewart; Rockwood, R Cotton; Selig, Elizabeth R; Selkoe, Kimberly A; Walbridge, Shaun

2015-07-14

Human pressures on the ocean are thought to be increasing globally, yet we know little about their patterns of cumulative change, which pressures are most responsible for change, and which places are experiencing the greatest increases. Managers and policymakers require such information to make strategic decisions and monitor progress towards management objectives. Here we calculate and map recent change over 5 years in cumulative impacts to marine ecosystems globally from fishing, climate change, and ocean- and land-based stressors. Nearly 66% of the ocean and 77% of national jurisdictions show increased human impact, driven mostly by climate change pressures. Five percent of the ocean is heavily impacted with increasing pressures, requiring management attention. Ten percent has very low impact with decreasing pressures. Our results provide large-scale guidance about where to prioritize management efforts and affirm the importance of addressing climate change to maintain and improve the condition of marine ecosystems.

Characterization of the Airflow from a Bottom Hung Window under Natural Ventilation

DEFF Research Database (Denmark)

Svidt, Kjeld; Heiselberg, Per; Nielsen, Peter V.

This paper describes the results of laboratory measurements of the airflow from a bottom hung window mounted near the ceiling of a ventilated room. In the laboratory set-up it was possible to control the temperature difference and the airflow rate through the window. The pressure drop through...

Stresses in a submarine topography under ocean waves

Energy Technology Data Exchange (ETDEWEB)

Mei, C.C.; McTigue, D.F.

1984-01-01

The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, to obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular the dynamic pore pressure and the combined static and dynamic effective stresses are presented. 10 references, 11 figures.

The salinity effect in a mixed layer ocean model

Science.gov (United States)

Miller, J. R.

1976-01-01

A model of the thermally mixed layer in the upper ocean as developed by Kraus and Turner and extended by Denman is further extended to investigate the effects of salinity. In the tropical and subtropical Atlantic Ocean rapid increases in salinity occur at the bottom of a uniformly mixed surface layer. The most significant effects produced by the inclusion of salinity are the reduction of the deepening rate and the corresponding change in the heating characteristics of the mixed layer. If the net surface heating is positive, but small, salinity effects must be included to determine whether the mixed layer temperature will increase or decrease. Precipitation over tropical oceans leads to the development of a shallow stable layer accompanied by a decrease in the temperature and salinity at the sea surface.

High-resolution sub-bottom seismic and sediment core records from the Chukchi Abyssal Plain reveal Quaternary glaciation impacts on the western Arctic Ocean

Science.gov (United States)

Joe, Y. J.; Seokhoon, Y.; Nam, S. I.; Polyak, L.; Niessen, F.

2017-12-01

For regional context of the Quaternary history of Arctic marine glaciations, such as glacial events in northern North America and on the Siberian and Chukchi margins, we used CHIRP sub-bottom profiles (SBP) along with sediment cores, including a 14-m long piston core ARA06-04JPC taken from the Chukchi abyssal plain during the RV Araon expedition in 2015. Based on core correlation with earlier developed Arctic Ocean stratigraphies using distribution of various sedimentary proxies, core 04JPC is estimated to extend to at least Marine Isotope Stage 13 (>0.5 Ma). The stratigraphy developed for SBP lines from the Chukchi abyssal plain to surrounding slopes can be divided into four major seismostratigraphic units (SSU 1-4). SBP records from the abyssal plain show well preserved stratification, whereas on the surrounding slopes this pattern is disrupted by lens-shaped, acoustically transparent sedimentary bodies interpreted as glaciogenic debris flow deposits. Based on the integration of sediment physical property and SBP data, we conclude that these debris flows were generated during several ice-sheet grounding events on the Chukchi and East Siberian margins, including adjacent ridges and plateaus, during the middle to late Quaternary.

Determination of intrinsic attenuation in the oceanic lithosphere-asthenosphere system

Science.gov (United States)

Takeuchi, Nozomu; Kawakatsu, Hitoshi; Shiobara, Hajime; Isse, Takehi; Sugioka, Hiroko; Ito, Aki; Utada, Hisashi

2017-12-01

We recorded P and S waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS. The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere.

Global Ocean Surface Water Partial Pressure of CO₂ Database: Measurements Performed During 1968-2007 (Version 2007)

Energy Technology Data Exchange (ETDEWEB)

Kozyr, Alex [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Carbon Dioxide Information Analysis Center

2008-09-30

More than 4.1 million measurements of surface water partial pressure of CO₂ obtained over the global oceans during 1968-2007 are listed in the Lamont-Doherty Earth Observatory (LDEO) database, which includes open ocean and coastal water measurements. The data assembled include only those measured by equilibrator-CO₂ analyzer systems and have been quality-controlled based on the stability of the system performance, the reliability of calibrations for CO₂ analysis, and the internal consistency of data. To allow re-examination of the data in the future, a number of measured parameters relevant to pCO₂ measurements are listed. The overall uncertainty for the pCO₂ values listed is estimated to be ± 2.5 µatm on the average. For simplicity and for ease of reference, this version is referred to as 2007, meaning that data collected through 31 December 2007 has been included. It is our intention to update this database annually. There are 37 new cruise/ship files in this update. In addition, some editing has been performed on existing files so this should be considered a V2007 file. Also we have added a column reporting the partial pressure of CO₂ in seawater in units of Pascals. The data presented in this database include the analyses of partial pressure of CO₂ (pCO₂), sea surface temperature (SST), sea surface salinity (SSS), pressure of the equilibration, and barometric pressure in the outside air from the ship’s observation system. The global pCO₂ data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center (CDIAC). The NDP consists of the oceanographic data files and this printed documentation, which describes the procedures and methods used to obtain the data.

Experimental Study on Peak Pressure of Shock Waves in Quasi-Shallow Water

Directory of Open Access Journals (Sweden)

Zhenxiong Wang

2015-01-01

Full Text Available Based on the similarity laws of the explosion, this research develops similarity requirements of the small-scale experiments of underwater explosions and establishes a regression model for peak pressure of underwater shock waves under experimental condition. Small-scale experiments are carried out with two types of media at the bottom of the water and for different water depths. The peak pressure of underwater shock waves at different measuring points is acquired. A formula consistent with the similarity law of explosions is obtained and an analysis of the regression precision of the formula confirms its accuracy. Significance experiment indicates that the influence of distance between measuring points and charge on peak pressure of underwater shock wave is the greatest and that of water depth is the least within the range of geometric parameters. An analysis of data from experiments with different media at the bottom of the water reveals an influence on the peak pressure, as the peak pressure of a shock wave in a body of water with a bottom soft mud and rocks is about 1.33 times that of the case where the bottom material is only soft mud.

Pressure vessel lid

International Nuclear Information System (INIS)

Schoening, J.; Elter, C.; Becker, G.; Pertiller, S.

1986-01-01

The invention concerns a lid for closing openings in reactor pressure vessels containing helium, which is made as a circular casting with hollow spaces and a flat floor and is set on the opening and kept down. It consists of helium-tight metal cast material with sufficient temperature resistance. There are at least two concentric heat resistant seals let into the bottom of the lid. The bottom is in immediate contact with the container atmosphere and has hollow spaces in its inside in the area opposite to the opening. (orig./HP) [de

Hyperspectral Imager for the Coastal Ocean (HICO): Overview, Operational Updates, and Coastal Ocean Applications

Science.gov (United States)

Davis, Curtiss O.; Kappus, Mary E.; Bowles, Jeffrey H.; Evans, Cynthia A.; Stefanov, William L.

2014-01-01

The Hyperspectral Imager for the Coastal Ocean (HICO) was built to measure in-water properties of complex coastal regions. HICO enables synoptic coverage; 100-meter spatial resolution for sampling the variability and spatial irregularity of coastal waters; and high spectral resolution to untangle the signals from chlorophyll, colored dissolved organic matter, suspended sediments and varying bottom types. HICO was built by the Naval Research Laboratory, installed on the International Space Station (ISS) in September 2009, and operated for ONR for the first three years. In 2013, NASA assumed sponsorship of operations in order to leverage HICO's ability to address their Earth monitoring mission. This has opened up access of HICO data to the broad research community. Over 8000 images are now available on NASA's Ocean Color Website (http://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sen=hi). Oregon State University's HICO website (http://hico.coas.oregonstate.edu) remains the portal for researchers to request new collections and access their requested data. We will present updates on HICO's calibration and improvements in geolocation and show examples of the use of HICO data to address issues in the coastal ocean and Great Lakes.

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract, at the M/V ELPIS Restoration Site, 2006 - 2007 (NODC Accession 0039899)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract, at the M/V ELPIS Restoration Site, 2004 - 2006 (NODC Accession 0010576)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Key West Channel, 2007 - 2010 and 2011 - 2012 (NODC Accession 0093028)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Key-Back Reef, 2008 and 2011 - 2012 (NODC Accession 0093064)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Characteristics of fin whale vocalizations recorded on instruments in the northeast Pacific Ocean

Science.gov (United States)

Weirathmueller, Maria Michelle Josephine

This thesis focuses on fin whale vocalizations recorded on ocean bottom seismometers (OBSs) in the Northeast Pacific Ocean, using data collected between 2003 and 2013. OBSs are a valuable, and largely untapped resource for the passive acoustic monitoring of large baleen whales. This dissertation is divided into three parts, each of which uses the recordings of fin whale vocalizations to better understand their calling behaviors and distributions. The first study describes the development of a technique to extract source levels of fin whale vocalizations from OBS recordings. Source levels were estimated using data collected on a network of eight OBSs in the Northeast Pacific Ocean. The acoustic pressure levels measured at the instruments were adjusted for the propagation path between the calling whales and the instruments using the call location and estimating losses along the acoustic travel path. A total of 1241 calls were used to estimate an average source level of 189 +/-5.8 dB re 1uPa 1m. This variability is largely attributed to uncertainties in the horizontal and vertical position of the fin whale at the time of each call, and the effect of these uncertainties on subsequent calculations. The second study describes a semi-automated method for obtaining horizontal ranges to vocalizing fin whales using the timing and relative amplitude of multipath arrivals. A matched filter is used to detect fin whale calls and pick the relative times and amplitudes of multipath arrivals. Ray-based propagation models are used to predict multipath times and amplitudes as function of range. Because the direct and first multiple arrivals are not always observed, three hypotheses for the paths of the observed arrivals are considered; the solution is the hypothesis and range that optimizes the fit to the data. Ray-theoretical amplitudes are not accurate and solutions are improved by determining amplitudes from the observations using a bootstrap method. Data from ocean bottom

Making sense of ocean biota: how evolution and biodiversity of land organisms differ from that of the plankton.

Science.gov (United States)

Smetacek, Victor

2012-09-01

The oceans cover 70% of the planet's surface, and their planktonic inhabitants generate about half the global primary production, thereby playing a key role in modulating planetary climate via the carbon cycle. The ocean biota have been under scientific scrutiny for well over a century, and yet our understanding of the processes driving natural selection in the pelagic environment - the open water inhabited by drifting plankton and free-swimming nekton - is still quite vague. Because of the fundamental differences in the physical environment, pelagic ecosystems function differently from the familiar terrestrial ecosystems of which we are a part. Natural selection creates biodiversity but understanding how this quality control of random mutations operates in the oceans - which traits are selected for under what circumstances and by which environmental factors, whether bottom-up or top-down - is currently a major challenge. Rapid advances in genomics are providing information, particularly in the prokaryotic realm, pertaining not only to the biodiversity inventory but also functional groups. This essay is dedicated to the poorly understood tribes of planktonic protists (unicellular eukaryotes) that feed the ocean's animals and continue to run the elemental cycles of our planet. It is an attempt at developing a conceptually coherent framework to understand the course of evolution by natural selection in the plankton and contrast it with the better-known terrestrial realm. I argue that organism interactions, in particular co-evolution between predators and prey (the arms race), play a central role in driving evolution in the pelagic realm. Understanding the evolutionary forces shaping ocean biota is a prerequisite for harnessing plankton for human purposes and also for protecting the oceanic ecosystems currently under severe stress from anthropogenic pressures.

Hydrostatic pressure mimics gravitational pressure in characean cells

Science.gov (United States)

Staves, M. P.; Wayne, R.; Leopold, A. C.

1992-01-01

Hydrostatic pressure applied to one end of a horizontal Chara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca2+ concentrations, osmotic pressure, neutral red, TEA Cl-, and the Ca2+ channel blockers nifedipine and LaCl3. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.

Buoyancy frequency profiles and internal semidiurnal tide turning depths in the oceans

NARCIS (Netherlands)

King, B.; Stone, M.; Zhang, H.P.; Gerkema, T.; Marder, M.; Scott, R.B.; Swinney, H.L.

2012-01-01

We examine the possible existence of internal gravity wave "turning depths," depths below which the local buoyancy frequency N(z) becomes smaller than the wave frequency. At a turning depth, incident gravity waves reflect rather than reaching the ocean bottom as is generally assumed. Here we

AtlanticCanyons2011: Exploration and Research of Mid-Atlantic Deepwater hard Bottom Habitats and Shipwrecks with Emphasis on Canyons and Coral Communities between 20110604 and 20110617

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This is an interagency study that focuses on the exploration and investigation of deepwater hard bottom biological communities located in the northwest Atlantic...

Temperature profile and pressure data from CTD casts from the MALCOLM BALRDIGE and other platforms from the TOGA area of Pacific Ocean from 1993-02-28 to 1997-06-27 (NODC Accession 9700222)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using CTD casts in the TOGA area of the Pacific Ocean from NOAA Ship MALCOLM BALDRIGE and other platforms from...

Seismic Site Effects from the Seafloor Motion Recorded by the Short-period Ocean Bottom Seismometers

Science.gov (United States)

Lin, J. Y.; Cheng, W. B.; Chin, S. J.; Hsu, S. K.; Dong, J. J.

2014-12-01

For decades, it has been mentioned that submarine slope failures are spatially linked to the presence of gas hydrates/gas-charged sediments. When triggered by earthquakes, oversteepen and instable sediments may prompt breakouts of the slopes containing gas hydrates and cause submarine landslides and tsunamis. Widely distributed BSRs have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In the region, large or small scale landslides were also reported based on seismic interpretations. In order to clarify the link between earthquake, landslide and the presence of gas hydrate, we evaluate the response of seafloor sediments in regard to passive dynamic loads. Horizontal-to-vertical (H/V) spectral ratios are used to characterize the local sediment response. Ambient noise as well as distant earthquakes are used as generators of the passive dynamic loads. Based on this study, we aim to characterize the site in terms of its physical properties and the local site effect produced by shallow marine sediments. The results show that the maximum H/V ratios appeared in the range of 5-10 Hz, where the horizontal amplitudes increased by an order of magnitude relative to the vertical amplitude. The stations located in the northwestern part of study area were characterized by another relatively small peak at proximately 2 Hz, which may indicates the presence of a discontinuity of sediments. For most stations, the H/V ratios estimated based on the earthquake (i.e. strong input signal) and noise (background, micro-seismic noise) records were characterized by different pattern. No distinct peak is observed for the H/V pattern calculated during earthquakes. This phenomenon may suggest that no clear sedimentary boundary exist when a stronger motion applies. Estimating H/V spectral ratios of data recorded by the seven short period OBSs (Ocean Bottom Seismometer) deployed in the southwest Taiwan

pressure distribution in a layered reservoir with gas-cap and bottom

African Journals Online (AJOL)

2012-07-02

Jul 2, 2012 ... Finally, only fluid ratios is recommended as adequate to reveal which ... pressure derivatives, interlayer cross flow, heterogeneity, reservoir characterization, pressure ... sure derivatives to thoroughly understand movement.

Dispersion of tracers by the oceanic eddy field modelling programme

International Nuclear Information System (INIS)

Richards, K.J.; O'Farrell, S.P.

1987-01-01

A numerical model has been developed to study the dispersion of tracers by the oceanic eddy field. The present study is designed to study the dispersion of particles in a mesoscale eddy field produced by the numerical model. Dispersion rates are calculated for flows above three types of topography, a flat bottom, a random collection of hills and a ridge. The presence of topography is found to significantly affect the flow. The effective diffusion coefficient of the flow near the bottom is reduced by 20% for the random topography and 60% for the ridge from that for the flat bottom case. Estimates are given of the number of float years required to obtain a given accuracy for the diffusion coefficient. At the surface a modest number of floats (order 5) are required to obtain a 50% accuracy. However at the bottom, to be within a factor of 2 of the true value for the flows considered requires respectively 26, 42 and 103 float years for the flat, random and ridge cases. (author)

Cylinder-type bottom reflector

International Nuclear Information System (INIS)

Elter, C.; Fritz, R.; Kissel, K.F.; Schoening, J.

1982-01-01

Proposal of a bottom reflector for gas-cooled nuclear reactor plants with a pebble bed of spherical fuel elements, where the horizontal forces acting from the core and the bottom reflector upon the side reflector are equally distributed. This is attained by the upper edge of the bottom reflector being placed levelly and by the angle of inclination of the recesses varying. (orig.) [de

Numerical simulation of water flow through the bottom en piece of a nuclear fuel assembly

International Nuclear Information System (INIS)

Navarro, Moyses A.; Santos, Andre A. Campagnole dos

2007-01-01

The water flow through the bottom nozzle of a nuclear fuel assembly was simulated using a commercial CFD code, CFX 10.0. Previously, simulations with a perforated plate similar to the bottom nozzle plate were performed to define the appropriate mesh refinement and turbulence model (κ-ε or SST). Subsequently, the numerical simulation was performed with the optimized mesh using the turbulence model (κ-ε in a standard bottom nozzle with some geometric simplifications. The numerical results were compared with experimental results to determine the pressure drop through the bottom nozzle in the Reynolds range from ∼10500 to ∼95000. The agreement between the numerical simulations and experimental results may be considered satisfactory. The study indicated that the CFD codes can play an important role in the development of pieces with complex geometries, optimizing the planning of the experiments and aiding in the experimental analysis. (author)

Ocean Worlds Analog Systems in the Hadal Ocean: Systematic Examination of Pressure, Food Supply, Topography, and Evolution on Hadal Life

Science.gov (United States)

Shank, T. M.; German, C.; Machado, C.; Bowen, A.; Drazen, J.; Yancey, P.; Jamieson, A.; Rowden, A.; Clark, M.; Heyl, T.; Mayor, D.; Piertney, S.; Ruhl, H.

2018-05-01

Key questions on life’s evolution are being pursued in Earth’s hadal ocean, Earth’s only analog to Europa’s ocean. A recent WHOI-JPL partnership is developing an armada of autonomous underwater drone vehicles to explore of Earth’s and Europa’s oceans.

Current, temperature, salinity, and other data from bottom instrument packages off Wrightsville Beach, North Carolina, from 02 April 1996 to 22 May 1996 (NODC Accession 0066099)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Measurements of bottom currents and waves to investigate the flow field and sediment transport in a rippled scour depression offshore of Wrightsville Beach, NC.

Analysis of NSWC Ocean EM Observatory Test Data

Science.gov (United States)

2016-09-01

computer was being moved and should not cause any problems for automated data collection. Thus the PUTTYLOG.EXE time-stamping software should be used...the sea-bottom. Could this possibly be a lightning strike hitting the water? In addition to these big glitches in the shore station data , there...Analysis of NSWC Ocean EM Observatory test data : final report J. Bradley Nelson Date: September 2016 Contract #: NICOP - N62909-15

Benthic Sampling Adjacent to the Waianae Ocean Outfall, Oahu, Hawaii, 2001-2010 (NODC Accession 0084994)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Annual surveys are undertaken to sample bottom-sediment for biological and geochemical analyses at six stations at a depth of approximately 34 m in the vicinity of...

Development of debris resistant bottom end piece

International Nuclear Information System (INIS)

Lee, Jae Kyung; Sohn, Dong Seong; Yim, Jeong Sik; Hwang, Dae Hyun; Song, Kee Nam; Oh, Dong Seok; Rhu, Ho Sik; Lee, Chang Woo; Kim, Seong Soo; Oh, Jong Myung

1993-12-01

Debris-related fuel failures have been identified as one of the major causes of fuel failures. In order to reduce the possibility of debris-related fuel failures, it is necessary to develop Debris-Resistant Bottom End Piece. For this development, mechanical strength test and pressure drop test were performed, and the test results were analyzed. And the laser cutting, laser welding and electron beam welding technology, which were the core manufacturing technology of DRBEP, were developed. Final design were performed, and the final drawing and specifications were prepared. The prototype of DRBEP was manufactured according to the developed munufacturing procedure. (Author)

Comparision of Bathymetry and Bottom Characteristics From Hyperspectral Remote Sensing Data and Shipborne Acoustic Measurements

Science.gov (United States)

McIntyre, M. L.; Naar, D. F.; Carder, K. L.; Howd, P. A.; Lewis, J. M.; Donahue, B. T.; Chen, F. R.

2002-12-01

There is growing interest in applying optical remote sensing techniques to shallow-water geological applications such as bathymetry and bottom characterization. Model inversions of hyperspectral remote-sensing reflectance imagery can provide estimates of bottom albedo and depth. This research was conducted in support of the HyCODE (Hyperspectral Coupled Ocean Dynamics Experiment) project in order to test optical sensor performance and the use of a hyperspectral remote-sensing reflectance algorithm for shallow waters in estimating bottom depths and reflectance. The objective of this project was to compare optically derived products of bottom depths and reflectance to shipborne acoustic measurements of bathymetry and backscatter. A set of three high-resolution, multibeam surveys within an 18 km by 1.5 km shore-perpendicular transect 5 km offshore of Sarasota, Florida were collected at water depths ranging from 8 m to 16 m. These products are compared to bottom depths derived from aircraft remote-sensing data collected with the AVIRIS (Airborne Visible-Infrared Imaging Spectrometer) instrument data by means of a semi-analytical remote sensing reflectance model. The pixel size of the multibeam bathymetry and AVIRIS data are 0.25 m and 10 m, respectively. When viewed at full resolution, the multibeam bathymetry data show small-scale sedimentary bedforms (wavelength ~10m, amplitude ~1m) that are not observed in the lower resolution hyperspectral bathymetry. However, model-derived bottom depths agree well with a smoothed version of the multibeam bathymetry. Depths derived from shipborne hyperspectral measurements were accurate within 13%. In areas where diver observations confirmed biological growth and bioturbation, derived bottom depths were less accurate. Acoustic backscatter corresponds well with the aircraft hyperspectral imagery and in situ measurements of bottom reflectance. Acoustic backscatter was used to define the distribution of different bottom types

Enhanced deep ocean ventilation and oxygenation with global warming

Science.gov (United States)

Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

2014-12-01

Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

Biogeochemical Reactions Under Simulated Europa Ocean Conditions

Science.gov (United States)

Amashukeli, X.; Connon, S. A.; Gleeson, D. F.; Kowalczyk, R. S.; Pappalardo, R. T.

2007-12-01

Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its surface became a distinct possibility. Moreover, understanding of Europa's potential habitability is now one of the major goals of the Europa Orbiter Flagship mission. It is likely, that in the early stages of Europa's ocean formation, moderately alkaline oceanic sulfate-carbonate species and a magnetite-silicate mantel could have participated in low-temperature biogeochemical sulfur, iron and carbon cycles facilitated by primitive organisms (Zolotov and Shock, 2004). If periodic supplies of fresh rock and sulfate-carbonate ions are available in Europa's ocean, then an exciting prospect exists that life may be present in Europa's ocean today. In our laboratory, we began the study of the plausible biogeochemical reactions under conditions appropriate to Europa's ocean using barophilic psychrophilic organisms that thrive under anaerobic conditions. In the near absence of abiotic synthetic pathways due to low Europa's temperatures, the biotic synthesis may present a viable opportunity for the formation of the organic and inorganic compounds under these extreme conditions. This work is independent of assumptions regarding hydrothermal vents at Europa's ocean floor or surface-derived oxidant sources. For our studies, we have fabricated a high-pressure (5,000 psi) reaction vessel that simulates aqueous conditions on Europa. We were also successful at reviving barophilic psychrophilic strains of Shewanella bacterium, which serve as test organisms in this investigation. Currently, facultative barophilic psychrophilic stains of Shewanella are grown in the presence of ferric food source; the strains exhibiting iron

Arctic Ocean circulation during the anoxic Eocene Azolla event

Science.gov (United States)

Speelman, Eveline; Sinninghe Damsté, Jaap; März, Christian; Brumsack, Hans; Reichart, Gert-Jan

2010-05-01

The Azolla interval, as encountered in Eocene sediments from the Arctic Ocean, is characterized by organic rich sediments ( 4wt% Corg). In general, high levels of organic matter may be caused by increased productivity, i.e. extensive growth of Azolla, and/or enhanced preservation of organic matter, or a combination of both. Anoxic (bottom) water conditions, expanded oxygen minimum zones, or increased sedimentation rates all potentially increase organic matter preservation. According to plate tectonic, bathymetric, and paleogeographic reconstructions, the Arctic Ocean was a virtually isolated shallow basin, with one possible deeper connection to the Nordic Seas represented by a still shallow Fram Strait (Jakobsson et al., 2007), hampering ventilation of the Arctic Basin. During the Azolla interval surface waters freshened, while at the same time bottom waters appear to have remained saline, indicating that the Arctic was highly stratified. The restricted ventilation and stratification in concert with ongoing export of organic matter most likely resulted in the development of anoxic conditions in the lower part of the water column. Whereas the excess precipitation over evaporation maintained the freshwater lid, sustained input of Nordic Sea water is needed to keep the deeper waters saline. To which degree the Arctic Ocean exchanged with the Nordic Seas is, however, still largely unknown. Here we present a high-resolution trace metal record (ICP-MS and ICP-OES) for the expanded Early/Middle Eocene section capturing the Azolla interval from Integrated Ocean Drilling Program (IODP) Expedition 302 (ACEX) drilled on the Lomonosov Ridge, central Arctic Ocean. Euxinic conditions throughout the interval resulted in the efficient removal of redox sensitive trace metals from the water column. Using the sedimentary trace metal record we also constrained circulation in the Arctic Ocean by assessing the relative importance of trace metal input sources (i.e. fluvial, eolian, and

Features of distribution and quality of organic matter in the bottom sediments of the Great Peter Bay (Sea of Japan)

Science.gov (United States)

Nesterova, Olga; Tregubova, Valentina; Semal, Victoria; Vasenev, Ivan

2017-04-01

The nature and distribution of organic carbon in marine waters depends on: 1) biological productivity and revenue of the autochthonous organic matter to the bottom; 2) sediment grain-size composition and conditions of dumping, which in turn depends of hydrothermic regime, topography, speed River mist and received major erosion products; 3) living conditions of the benthos (the quantity consumed of OM, gas regime of habitats, physiological capacity of heterotrophs). Autochthonous OM of phytoplankton plays a dominant role in the processes of formation of humus in aquatic conditions. Bottom sediments at different distance from the shoreline to depths from 0.5 up to 480 m of the Sea of Japan, which are formed in various conditions of facies, were selected as the objects of study. There is no clear relationships to the amount of organic matter in bottom sediments on the characteristics of the distribution and nature of living matter in the oceans and seas. This is because the process of sedimentation and fossilization of organic matter on the seabed and the ocean floor depends on many factors (currents, depth). Humus of studied bottom sediments in composition can be attributed mainly to the humic type. Nonhydrolyzing rest is 70-90%. This is characteristic of bottom sediments formed in facial types of small bays, internal coastal shelf bights and the underwater slope. At a fraction of the carbon of humic acids in organic matter, ranging from 4 to 80% of the amount of humic and fulvic acids. Fulvic acids content is much less. This is due to more favourable conservation situation of humic acids in precipitation with high content of organic matter, whereas fulvic acids in aquatic environments are more labile and almost not dumped. Despite the fact humic acids are not the most stable component (s), however, with increased content of humic acids, the mobility of organic matter and removing it from the bottom sediments are reduced. Internal shelf facies of the Great Peter Bay

Oceanic-type accretion may begin before complete continental break-up

Science.gov (United States)

Geoffroy, L.; Zalan, P. V.; Viana, A. R.

2011-12-01

Oceanic accretion is thought to be the process of oceanic crust (and lithosphere) edification through adiabatic melting of shallow convecting mantle at oceanic spreading ridges. It is usually considered as a post-breakup diagnostic process following continents rupturing. However, this is not always correct. The structure of volcanic passive margins (representing more than 50% of passive continental margins) outlines that the continental lithosphere is progressively changed into oceanic-type lithosphere during the stage of continental extension. This is clear at least, at crustal level. The continental crust is 'changed' from the earliest stages of extension into a typical -however thicker- oceanic crust with the typical oceanic magmatic layers (from top to bottom: lava flows/tuffs, sheeted dyke complexes, dominantly (sill-like) mafic intrusions in the lower crust). The Q-rich continental crust is highly extended and increases in volume (due to the magma) during the extensional process. At the continent-ocean transition there is, finally, no seismic difference between this highly transformed continental crust and the oceanic crust. Using a large range of data (including deep seismic reflection profiles), we discuss the mantle mechanisms that governs the process of mantle-assisted continental extension. We outline the large similarity between those mantle processes and those acting at purely-oceanic spreading axis and discuss the effects of the inherited continental lithosphere in the pattern of new mafic crust edification.

Dispersal from deep ocean sources: physical and related scientific processes

International Nuclear Information System (INIS)

Robinson, A.R.; Kupferman, S.L.

1985-02-01

This report presents the results of the workshop ''Dispersal from Deep Ocean Sources: Physical and Related Scientific Processes,'' together with subsequent developments and syntheses of the material discussed there. The project was undertaken to develop usable predictive descriptions of dispersal from deep oceanic sources. Relatively simple theoretical models embodying modern ocean physics were applied, and observational and experimental data bases were exploited. All known physical processes relevant to the dispersal of passive, conservative tracers were discussed, and contact points for inclusion of nonconservative processes (biological and chemical) were identified. Numerical estimates of the amplitude, space, and time scales of dispersion were made for various mechanisms that control the evolution of the dispersal as the material spreads from a bottom point source to small-, meso-, and world-ocean scales. Recommendations for additional work are given. The volume is presented as a handbook of dispersion processes. It is intended to be updated as new results become available

Calculation method of passive tracer using regional ocean modeling system (ROMS)

International Nuclear Information System (INIS)

Tubono, Takaki; Tsumune, Daisuke; Misumi, Kazuhiro; Yoshida, Yoshikatsu

2010-01-01

A dose assessments method for packages shipping radioactive materials was developed to calculate concentrations of radioactive materials discharged from the hypothetically sinking point using Regional Ocean Modeling System (ROMS). The programs of ROMS were improved for simultaneously calculating the flow fields around Japan and the concentrations discharged from several bottom points in the continental shelf. The model domain covered the northeast pacific region around Japan, 20degN-65degN, 120degE-165degE, with 1/10 degree horizontal resolution and 30 sigma-levels. The ROMS model captured main features such as Kuroshio currents, including the separation location and the Kuroshio extension, and Oyashio currents. The calculated volume transports through the main straits such as Tokara strait, Tsushima strait and Tsugaru strait were compared well to the measured or estimated that. The calculated concentrations discharged from 12 bottom points showed mixing associated with the eddies of ocean currents. This method is available to evaluate effectively the concentrations of radioactive materials only by setting the subsidence location and the concentrations and volume discharged. (author)

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the M/V Alec Owen Maitland restoration site, 2006 - 2007 (NODC Accession 0039987)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the M/V Alec Owen Maitland restoration site, 2004 - 2006 (NODC Accession 0010585)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at the M/V Alec Owen Maitland Restoration site, 2006 - 2007 (NODC Accession 0039987)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Eddy current testing system for bottom mounted instrumentation welds

OpenAIRE

Kobayashi Noriyasu; Ueno Souichi; Suganuma Naotaka; Oodake Tatsuya; Maehara Takeshi; Kasuya Takashi; Ichikawa Hiroya

2015-01-01

The capability of eddy current testing (ECT) for the bottom mounted instrumentation (BMI) weld area of reactor vessel in a pressurized water reactor was demonstrated by the developed ECT system and procedure. It is difficult to position and move the probe on the BMI weld area because the area has complexly curved surfaces. The space coordinates and the normal vectors at the scanning points were calculated as the scanning trajectory of probe based on the measured results of surface shape on th...

Scientists’ perspectives on global ocean research priorities

Directory of Open Access Journals (Sweden)

Murray Alan Rudd

2014-08-01

Full Text Available Diverse natural and social science research is needed to support policies to recover and sustain healthy oceans. While a wide variety of expert-led prioritization initiatives have identified research themes and priorities at national and regional scale, over the past several years there has also been a surge in the number of scanning exercises that have identified important environmental research questions and issues ‘from the bottom-up’. From those questions, winnowed from thousands of contributions by scientists and policy-makers around the world who participated in terrestrial, aquatic and domain-specific horizon scanning and big question exercises, I identified 657 research questions potentially important for informing decisions regarding ocean governance and sustainability. These were distilled to a short list of 67 distinctive research questions that, in an internet survey, were ranked by 2179 scientists from 94 countries. Five of the top 10 research priorities were shared by respondents globally. Despite significant differences between physical and ecological scientists’ priorities regarding specific research questions, they shared seven common priorities among their top 10. Social scientists’ priorities were, however, much different, highlighting their research focus on managerial solutions to ocean challenges and questions regarding the role of human behavior and values in attaining ocean sustainability. The results from this survey provide a comprehensive and timely assessment of current ocean research priorities among research-active scientists but highlight potential challenges in stimulating crossdisciplinary research. As ocean and coastal research necessarily becomes more transdisciplinary to address complex ocean challenges, it will be critical for scientists and research funders to understand how scientists from different disciplines and regions might collaborate and strengthen the overall evidence base for ocean

Slamming pressures on the bottom of a free-falling vertical wedge

Science.gov (United States)

Ikeda, C. M.; Judge, C. Q.

2013-11-01

High-speed planing boats are subjected to repeat impacts due to slamming, which can cause structural damage and injury to passengers. A first step in understanding and predicting the physics of a craft re-entering the water after becoming partially airborne is an experimental vertical drop test of a prismastic wedge (deadrise angle, β =20° beam, B = 300 mm; and length, L = 600 mm). The acrylic wedge was mounted to a rig allowing it to free-fall into a deep-water tank (5.2m × 5.2m × 4.2m deep) from heights 0 camera (1000 fps, resolution of 1920 × 1200 pixels) is mounted above the wedge model to record the wetted surface as the wedge descended below the free surface. The pressure measurements taken with both conventional surface pressure transducers and the pressure mapping system agree within 10% of the peak pressure values (0.7 bar, typical). Supported by the Office of Naval Research.

Nekton densities along Spartina alterniflora marsh-edge and adjacent shallow non-vegetated bottom in Carancahua Cove, Texas from 1982-03-03 to 1993-06-24 (NCEI Accession 0161172)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains nekton counts used to quantify and compare densities along Spartina alterniflora marsh-edge and adjacent shallow non-vegetated bottom in...

Bottom sample taker

Energy Technology Data Exchange (ETDEWEB)

Garbarenko, O V; Slonimskiy, L D

1982-01-01

In order to improve the quality of the samples taken during offshore exploration from benthic sediments, the proposed design of the sample taker has a device which makes it possible to regulate the depth of submersion of the core lifter. For this purpose the upper part of the core lifter has an inner delimiting ring, and within the core lifter there is a piston suspended on a cable. The position of the piston in relation to the core lifter is previously assigned depending on the compactness of the benthic sediments and is fixed by tension of the cable which is held by a clamp in the cover of the core taker housing. When lowered to the bottom, the core taker is released, and under the influence of hydrostatic pressure of sea water, it enters the sediments. The magnitude of penetration is limited by the distance between the piston and the stopping ring. The piston also guarantees better preservation of the sample when the instrument is lifted to the surface.

Reconstructing bottom water temperatures from measurements of temperature and thermal diffusivity in marine sediments

Science.gov (United States)

Miesner, F.; Lechleiter, A.; Müller, C.

2015-07-01

Continuous monitoring of oceanic bottom water temperatures is a complicated task, even in relatively easy-to-access basins like the North or Baltic seas. Here, a method to determine annual bottom water temperature variations from inverse modeling of instantaneous measurements of temperatures and sediment thermal properties is presented. This concept is similar to climate reconstructions over several thousand years from deep borehole data. However, in contrast, the presented method aims at reconstructing the recent temperature history of the last year from sediment thermal properties and temperatures from only a few meters depth. For solving the heat equation, a commonly used forward model is introduced and analyzed: knowing the bottom water temperature variations for the preceding years and the thermal properties of the sediments, the forward model determines the sediment temperature field. The bottom water temperature variation is modeled as an annual cosine defined by the mean temperature, the amplitude and a phase shift. As the forward model operator is non-linear but low-dimensional, common inversion schemes such as the Newton algorithm can be utilized. The algorithms are tested for artificial data with different noise levels and for two measured data sets: from the North Sea and from the Davis Strait. Both algorithms used show stable and satisfying results with reconstruction errors in the same magnitude as the initial data error. In particular, the artificial data sets are reproduced with accuracy within the bounds of the artificial noise level. Furthermore, the results for the measured North Sea data show small variances and resemble the bottom water temperature variations recorded from a nearby monitoring site with relative errors smaller than 1 % in all parameters.

Bottom friction models for shallow water equations: Manning’s roughness coefficient and small-scale bottom heterogeneity

Science.gov (United States)

Dyakonova, Tatyana; Khoperskov, Alexander

2018-03-01

The correct description of the surface water dynamics in the model of shallow water requires accounting for friction. To simulate a channel flow in the Chezy model the constant Manning roughness coefficient is frequently used. The Manning coefficient nM is an integral parameter which accounts for a large number of physical factors determining the flow braking. We used computational simulations in a shallow water model to determine the relationship between the Manning coefficient and the parameters of small-scale perturbations of a bottom in a long channel. Comparing the transverse water velocity profiles in the channel obtained in the models with a perturbed bottom without bottom friction and with bottom friction on a smooth bottom, we constructed the dependence of nM on the amplitude and spatial scale of perturbation of the bottom relief.

Continuous bottom temperature measurements in strategic areas of the Florida Reef Tract at Looe Key Iselin, from 2011-07-15 to 2014-08-31 (NODC Accession 0122162)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Continuous bottom temperature measurements in strategic areas of the Western Sambo Reef, Western Sambo Reef Buoy 16 and Jacquelyn L Grounding Site, 1990 - 2005 (NODC Accession 0014120)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to document bottom seawater temperature in strategic areas of the Florida Reef Tract on a continuing basis and make that information...

Contourite drift off Madeira Island (Northeast Atlantic) and implications to Cenozoic bottom-current circulation

Science.gov (United States)

Roque, Cristina; Hernández-Molina, F. Javier; Madureira, Pedro; Quartau, Rui; Magalhães, Vitor; Carrara, Gabriela; Santos de Campos, Aldino; Brandão, Filipe; Tomás Vázquez, Juan; Somoza, Luis

2017-04-01

During the last decades several works have been carried out on the morphosedimentary processes driven by bottom-currents in several continental margins and abyssal plains worldwide. However these processes still remain poorly understood on deep-water settings and particularly around oceanic islands. This study is focused on the offshore of Madeira Island (Portugal), which is located in the Northeast Atlantic at about 700 km west of NW Africa. The interpretation of a newly acquired dataset, composed of multibeam bathymetry, Parasound echosounder profiles and multichannel seismic reflection profiles, allowed to identify a giant (about 385 km long and over than 175 km wide) plastered contourite drift, called the "Madeira Drift", developing along the lower slope of the Madeira plateau. It formed on top of a major erosional unconformity that truncates the underlying pelagic deposits, which drape over faulted blocks of Cretaceous oceanic crust. The Madeira Drift is composed of three main regional seismic units showing a predominant aggradational stacking pattern, without evidence of major lateral migration thought time. Its internal configuration indicates that it was build-up by a northwards flowing deep bottom current. These characteristics suggests that an almost persistent and stable water mass has been responsible for its edification trough time. While the precise age of this contourite drift is undetermined, some chronostratigraphic constraints can be determined based upon published works regarding seafloor magnetic anomalies (e.g. Bird et al., 2007), DSDP Site 136drilling data (Hayes et al., 1978). Attending to this, we propose that the possible onset of Madeira Drift must have occurred after Late Cretaceous, within the tertiary period, and quite probably in the Late Eocene / Eocene-Oligocene transition. Based on them is commonly accepted that an enhanced proto-Antarctic Bottom Water (AABW) started to circulate at that time we considered this water mass as the

Background light measurements in the deep ocean

Energy Technology Data Exchange (ETDEWEB)

Aoki, T.; Kitamura, T.; Matsuno, S.; Mitsui, K.; Ohashi, Y.; Okada, A.; Cady, D.R.; Learned, J.G.; O' Connor, D.; Dye, S.

Ambient light intensities in the ocean at depths between 1500 m and 4700 m near Hawaii Island were measured around the one photoelectron level with 5'' diameter hemispherical photomultipliers. Measurements of count rates above variable thresholds were carried out in ship-suspended and bottom-tethered configurations. The ship-suspended rates show considerable fluctuation and their mean value decreases with depth approximately as exp (-x(m)/877). The bottomtethered rates are about an order of magnitude lower than the ship-suspended rates and show little fluctuation. The calibration of our instrument indicates an absolute flux at 4700 m depth based on the bottom-tethered measurement of 218/sub -60//sup +20/ photons/cm/sup 2/.s, which is consistent with calculated intensities due to ..beta..-decay electrons from /sup 40/K. The difference in the two cases is attributed to bioluminescence due to environmental stimulation.

Effects of the bottom boundary condition in numerical investigations of dense water cascading on a slope

Science.gov (United States)

Berntsen, Jarle; Alendal, Guttorm; Avlesen, Helge; Thiem, Øyvind

2018-05-01

The flow of dense water along continental slopes is considered. There is a large literature on the topic based on observations and laboratory experiments. In addition, there are many analytical and numerical studies of dense water flows. In particular, there is a sequence of numerical investigations using the dynamics of overflow mixing and entrainment (DOME) setup. In these papers, the sensitivity of the solutions to numerical parameters such as grid size and numerical viscosity coefficients and to the choices of methods and models is investigated. In earlier DOME studies, three different bottom boundary conditions and a range of vertical grid sizes are applied. In other parts of the literature on numerical studies of oceanic gravity currents, there are statements that appear to contradict choices made on bottom boundary conditions in some of the DOME papers. In the present study, we therefore address the effects of the bottom boundary condition and vertical resolution in numerical investigations of dense water cascading on a slope. The main finding of the present paper is that it is feasible to capture the bottom Ekman layer dynamics adequately and cost efficiently by using a terrain-following model system using a quadratic drag law with a drag coefficient computed to give near-bottom velocity profiles in agreement with the logarithmic law of the wall. Many studies of dense water flows are performed with a quadratic bottom drag law and a constant drag coefficient. It is shown that when using this bottom boundary condition, Ekman drainage will not be adequately represented. In other studies of gravity flow, a no-slip bottom boundary condition is applied. With no-slip and a very fine resolution near the seabed, the solutions are essentially equal to the solutions obtained with a quadratic drag law and a drag coefficient computed to produce velocity profiles matching the logarithmic law of the wall. However, with coarser resolution near the seabed, there may be a

Bottom-linked innovation

DEFF Research Database (Denmark)

Kristensen, Catharina Juul

2018-01-01

hitherto been paid little explicit attention, namely collaboration between middle managers and employees in innovation processes. In contrast to most studies, middle managers and employees are here both subjects of explicit investigation. The collaboration processes explored in this article are termed...... ‘bottom-linked innovation’. The empirical analysis is based on an in-depth qualitative study of bottom-linked innovation in a public frontline institution in Denmark. By combining research on employee-driven innovation and middle management, the article offers new insights into such collaborative......Employee-driven innovation is gaining ground as a strategy for developing sustainable organisations in the public and private sector. This type of innovation is characterised by active employee participation, and the bottom-up perspective is often emphasised. This article explores an issue that has...

Design and implementation of a 3D ocean virtual reality and visualization engine

Science.gov (United States)

Chen, Ge; Li, Bo; Tian, Fenglin; Ji, Pengbo; Li, Wenqing

2012-12-01

In this study, a 3D virtual reality and visualization engine for rendering the ocean, named VV-Ocean, is designed for marine applications. The design goals of VV-Ocean aim at high fidelity simulation of ocean environment, visualization of massive and multidimensional marine data, and imitation of marine lives. VV-Ocean is composed of five modules, i.e. memory management module, resources management module, scene management module, rendering process management module and interaction management module. There are three core functions in VV-Ocean: reconstructing vivid virtual ocean scenes, visualizing real data dynamically in real time, imitating and simulating marine lives intuitively. Based on VV-Ocean, we establish a sea-land integration platform which can reproduce drifting and diffusion processes of oil spilling from sea bottom to surface. Environment factors such as ocean current and wind field have been considered in this simulation. On this platform oil spilling process can be abstracted as movements of abundant oil particles. The result shows that oil particles blend with water well and the platform meets the requirement for real-time and interactive rendering. VV-Ocean can be widely used in ocean applications such as demonstrating marine operations, facilitating maritime communications, developing ocean games, reducing marine hazards, forecasting the weather over oceans, serving marine tourism, and so on. Finally, further technological improvements of VV-Ocean are discussed.

Validation of the Engineering Plant Analyzer methodology with Peach Bottom 2 stability tests

International Nuclear Information System (INIS)

Rohatgi, U.S.; Mallen, A.N.; Cheng, H.S.; Wulff, W.

1994-01-01

The Engineering Plant Analyzer (EPA) had been developed in 1984 at Brookhaven National Laboratory to simulate plant transients in boiling water reactors (BWR). Recently, the EPA with its High-Speed Interactive Plant Analyzer code for BWRs ( ppercase HIPA-BWR ) simulated for the first time oscillatory transients with large, non-linear power and flow amplitudes; transients which are centered around the March 9, 1988 instability at the LaSalle-2 BWR power plant.The EPA's capability to simulate oscillatory transients has been demonstrated first by comparing simulation results with LaSalle-2 plant data (Wulff et al., NUREG/CR-5816, BNL-NUREG-52312, Brookhaven National Laboratory, 1992). This paper presents an EPA assessment on the basis of the Peach Bottom 2 instability tests (Carmichael and Niemi, EPRI NP-564, Electric Power Research Institute, Palo Alto, CA, 1978). This assessment of the EPA appears to constitute the first validation of a time-domain reactor systems code on the basis of frequency-domain criteria, namely power spectral density, gain and phase shift of the pressure-to-power transfer function.The reactor system pressure was disturbed in the Peach Bottom 2 power plant tests, and in their EPA simulation, by a pseudo-random, binary sequence signal. The data comparison revealed that the EPA predicted for Peach Bottom tests PT1, PT2, and PT4 the gain of the power-to-pressure transfer function with the biases and standard deviations of (-10±28)%, (-1±40)% and (+28±52)%, respectively. The respective frequencies at the peak gains were predicted with the errors of +6%, +3%, and -28%. The differences between the predicted and the measured phase shift increased with increasing frequency, but stayed within the margin of experimental uncertainty. ((orig.))

PODAAC-GRGAD-20C05

Data.gov (United States)

National Aeronautics and Space Administration — FOR EXPERT USE ONLY. This dataset contains estimates of Earths ocean bottom pressure derived from the Gravity Recovery and Climate Experiment (GRACE) mission...

PODAAC-GRGAD-2WG05

Data.gov (United States)

National Aeronautics and Space Administration — FOR EXPERT USE ONLY. This dataset contains estimates of Earths ocean bottom pressure derived from the Gravity Recovery and Climate Experiment (GRACE) mission...

PODAAC-GRGAD-20J15

Data.gov (United States)

National Aeronautics and Space Administration — FOR EXPERT USE ONLY. This dataset contains estimates of Earths ocean bottom pressure derived from the Gravity Recovery and Climate Experiment (GRACE) mission...

Underway physical and meteorological data collected aboard NOAA Ship DAVID STARR JORDAN in the North Pacific from 2004-07-12 to 2004-08-11 (NODC Accession 0001682)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, pressure, conductivity, salinity, bottom depth, and other data were collected using meteorological sensors, and thermosalinograph from NOAA Ship DAVID...

Seasonality of bottom water temperature in the northern North Sea reconstructed from the oxygen isotope composition of the bivalve Arctica islandica

Science.gov (United States)

Trofimova, Tamara; Andersson, Carin; Bonitz, Fabian

2017-04-01

The seasonality of temperature changes is an important characteristic of climate. However, observational data for the ocean are only available for the last 150 year from a limited number of locations. Prior to 18th century information is only available from proxy reconstructions. The vast majority of such reconstructions depend on land-based archives, primarily from dendrochronology. Established marine proxy records for the ocean, especially at high latitudes, are both sparsely distributed and poorly resolved in time. Therefore, the identification and development of proxies for studying key ocean processes at sub-annual resolution that can extend the marine instrumental record is a clear priority in marine climate science. In this study, we have developed a record of early Holocene seasonal variability of bottom water temperature from the Viking Bank in the northern most North Sea. This area is of a particular interest since the hydrography is controlled by the inflow of Atlantic water. The reconstruction is based on the oxygen isotope composition of the growth increments in two sub-fossil shells of Arctica islandica (Bivalvia), dated to 9600-9335 cal. yr BP. By combining radiocarbon dating and sclerochronological techniques a floating chronology spanning over 200 years was constructed. Using the chronology as an age model, oxygen isotope measurements from 2 shells were combined into a 22-years long record. The results from this oxygen isotope record are compared with stable oxygen isotope profiles from modern shells to estimate changes in the mean state and seasonality between present and early Holocene. Shell-derived oxygen isotope values together with ice-volume corrected oxygen isotope values for the seawater were used to calculate bottom-water temperatures on a sub-annual time-scale. Preliminary results of the reconstructed early Holocene bottom water temperature indicate higher seasonality and lower minimum temperature compared to the present.

Turbulent heat/mass transfer at oceanic interfaces

Energy Technology Data Exchange (ETDEWEB)

Enstad, Lars Inge

2005-07-01

solver. We find that the mixed layer of the active scalar is growing in the start, but then levels out because of large density gradient at the boundary of the turbulent layer. At distinct times the turbulent intensity is suddenly increased for a short time. This is due to a build up of velocity gradients which increases the turbulent intensity when it overcomes the damping effect of the buoyancy forces. This thesis tries to gain insight in turbulence near a gas liquid interface or a density interface by using small scale modeling. Stratification is imposed (both stable and unstable), and we have also used different forcing (i.e. pressure gradient and shear stress). It is found that stratification can significantly alter the scalar transfer through the gas-liquid interface. The heat flux through the gas liquid interface in an unstable stratified channel flow do no longer obey the correlation of Komori et al. (1989) and Rashidi et al. (1991). For a shear driven flow with inward heat flux it is found that the stable stratification weakens and distorts the streamwise vorticity thought to be an important agent in the scalar transfer through the interface. We have also tried to obtain results for turbulence more in general. It is confirmed that eddy viscosity can become negative in a region near the interface in the presence of unstable stratification in a channel flow. This leaves gradient diffusion models less reliable in such flow configurations. We have also found some interesting aspects of the Reynolds stress in a shear driven flow with stable stratification. In this flow configuration the Reynolds stress is decreased by damping of the ejection events from the interface. The last article which deals with an idealized brine pool at the sea bottom, could have relevance for CO2 disposal in CO2 lakes in the deep ocean. It is very important to know how such disposal of CO2 would affect the environment near the sea bottom. This thesis deals with idealized types of flows. It

The Incredible Shrinking Cup Lab: Connecting with Ocean and Great Lakes Scientists to Investigate the Effect of Depth and Water Pressure on Polystyrene

Science.gov (United States)

Rose, Chantelle M.; Adams, Jacqueline M.; Hinchey, Elizabeth K.; Nestlerode, Janet A.; Patterson, Mark R.

2013-01-01

Pressure increases rapidly with depth in a water body. Ocean and Great Lakes scientists often use this physical feature of water as the basis of a fun pastime performed aboard research vessels around the world: the shrinking of polystyrene cups. Depending on the depth to which the cups are deployed, the results can be quite striking! Capitalizing…

June 13, 2013 U.S. East Coast Meteotsunami: Comparing a Numerical Model With Observations

Science.gov (United States)

Wang, D.; Becker, N. C.; Weinstein, S.; Whitmore, P.; Knight, W.; Kim, Y.; Bouchard, R. H.; Grissom, K.

2013-12-01

On June 13, 2013, a tsunami struck the U.S. East Coast and caused several reported injuries. This tsunami occurred after a derecho moved offshore from North America into the Atlantic Ocean. The presence of this storm, the lack of a seismic source, and the fact that tsunami arrival times at tide stations and deep ocean-bottom pressure sensors cannot be attributed to a 'point-source' suggest this tsunami was caused by atmospheric forces, i.e., a meteotsunami. In this study we attempt to reproduce the observed phenomenon using a numerical model with idealized atmospheric pressure forcing resembling the propagation of the observed barometric anomaly. The numerical model was able to capture some observed features of the tsunami at some tide stations, including the time-lag between the time of pressure jump and the time of tsunami arrival. The model also captures the response at a deep ocean-bottom pressure gauge (DART 44402), including the primary wave and the reflected wave. There are two components of the oceanic response to the propagating pressure anomaly, inverted barometer response and dynamic response. We find that the dynamic response over the deep ocean to be much smaller than the inverted barometer response. The time lag between the pressure jump and tsunami arrival at tide stations is due to the dynamic response: waves generated and/or reflected at the shelf-break propagate shoreward and amplify due to the shoaling effect. The evolution of the derecho over the deep ocean (propagation direction and intensity) is not well defined, however, because of the lack of data so the forcing used for this study is somewhat speculative. Better definition of the pressure anomaly through increased observation or high resolution atmospheric models would improve meteotsunami forecast capabilities.

Thermodynamic Equations of State for Aqueous Solutions Applied to Deep Icy Satellite and Exoplanet Oceans

Science.gov (United States)

Vance, S.; Brown, J. M.; Bollengier, O.; Journaux, B.; Sotin, C.; Choukroun, M.; Barnes, R.

2014-12-01

Supporting life in icy world or exoplanet oceans may require global seafloor chemical reactions between water and rock. Such interactions have been regarded as limited in larger icy worlds such as Ganymede and Titan, where ocean depths approach 800 km and GPa pressures (>10katm). If the oceans are composed of pure water, such conditions are consistent with the presence of dense ice phases V and VI that cover the rocky seafloor. Exoplanets with oceans can obtain pressures sufficient to generate ices VII and VIII. We have previously demonstrated temperature gradients in such oceans on the order of 20 K or more, resulting from fluid compressibility in a deep adiabatic ocean based on our experimental work. Accounting for increases in density for highly saline oceans leads to the possibility of oceans perched under and between high pressure ices. Ammonia has the opposite effect, instead decreasing ocean density, as reported by others and confirmed by our laboratory measurements in the ammonia water system. Here we report on the completed equation of state for aqueous ammonia derived from our prior measurements and optimized global b-spline fitting methods We use recent diamond anvil cell measurements for water and ammonia to extend the equation of state to 400°C and beyond 2 GPa, temperatures and pressures applicable to icy worlds and exoplanets. Densities show much less temperature dependence but comparabe high-pressure derivatives to previously published ammonia-water properties derived for application to Titan (Croft et al. 1988). Thermal expansion is in better agreement with the more self-consistent equation of state of Tillner-Roth and Friend (1998). We also describe development of a planetary NaCl equation of state using recent measurements of phase boundaries and sound speeds. We examine implications of realistic ocean-ice thermodynamics for Titan and exoplanet interiors using the methodology recently applied to Ganymede for oceans dominated by MgSO4. High

The ocean planet.

Science.gov (United States)

Hinrichsen, D

1998-01-01

The Blue Planet is 70% water, and all but 3% of it is salt water. Life on earth first evolved in the primordial soup of ancient seas, and though today's seas provide 99% of all living space on the planet, little is known about the world's oceans. However, the fact that the greatest threats to the integrity of our oceans come from land-based activities is becoming clear. Humankind is in the process of annihilating the coastal and ocean ecosystems and the wealth of biodiversity they harbor. Mounting population and development pressures have taken a grim toll on coastal and ocean resources. The trend arising from such growth is the chronic overexploitation of marine resources, whereby rapidly expanding coastal populations and the growth of cities have contributed to a rising tide of pollution in nearly all of the world's seas. This crisis is made worse by government inaction and a frustrating inability to enforce existing coastal and ocean management regulations. Such inability is mainly because concerned areas contain so many different types of regulations and involve so many levels of government, that rational planning and coordination of efforts are rendered impossible. Concerted efforts are needed by national governments and the international community to start preserving the ultimate source of all life on earth.

Seasonal variation of CaCO3 saturation state in bottom water of a biological hotspot in the Chukchi Sea, Arctic Ocean

Directory of Open Access Journals (Sweden)

M. Yamamoto-Kawai

2016-11-01

Full Text Available Distribution of calcium carbonate saturation state (Ω was observed in the Chukchi Sea in autumn 2012 and early summer 2013. Ω in bottom water ranged from 0.3 to 2.0 for aragonite and from 0.5 to 3.2 for calcite in 2012. In 2013, Ω in bottom water was 1.1–2.8 for aragonite and 1.7–4.4 for calcite. Aragonite and calcite undersaturation was found in high productivity regions in autumn 2012 but not in early summer 2013. Comparison with other parameters has indicated that biological processes – respiration and photosynthesis – are major factors controlling the regional and temporal variability of Ω. From these ship-based observations, we have obtained empirical equations to reconstruct Ω from temperature, salinity and apparent oxygen utilization. Using 2-year-round mooring data and these equations, we have reconstructed seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern Chukchi Sea. Estimated Ω was high in spring and early summer, decreased in later summer, and remained relatively low in winter. Calculations indicated a possibility that bottom water could have been undersaturated for aragonite on an intermittent basis even in the pre-industrial period, and that anthropogenic CO2 has extended the period of aragonite undersaturation to more than 2-fold longer by now.

Evaluative pressure overcomes perceptual load effects.

Science.gov (United States)

Normand, Alice; Autin, Frédérique; Croizet, Jean-Claude

2015-06-01

Perceptual load has been found to be a powerful bottom-up determinant of distractibility, with high perceptual load preventing distraction by any irrelevant information. However, when under evaluative pressure, individuals exert top-down attentional control by giving greater weight to task-relevant features, making them more distractible from task-relevant distractors. One study tested whether the top-down modulation of attention under evaluative pressure overcomes the beneficial bottom-up effect of high perceptual load on distraction. Using a response-competition task, we replicated previous findings that high levels of perceptual load suppress task-relevant distractor response interference, but only for participants in a control condition. Participants under evaluative pressure (i.e., who believed their intelligence was assessed) showed interference from task-relevant distractor at all levels of perceptual load. This research challenges the assumptions of the perceptual load theory and sheds light on a neglected determinant of distractibility: the self-relevance of the performance situation in which attentional control is solicited.

Advancing Ocean Science Through Coordination, Community Building, and Outreach

Science.gov (United States)

Benway, H. M.

2016-02-01

The US Ocean Carbon and Biogeochemistry (OCB) Program (www.us-ocb.org) is a dynamic network of scientists working across disciplines to understand the ocean's role in the global carbon cycle and how marine ecosystems and biogeochemical cycles are responding to environmental change. The OCB Project Office, which is based at the Woods Hole Oceanographic Institution (WHOI), serves as a central information hub for this network, bringing different scientific disciplines together and cultivating partnerships with complementary US and international programs to address high-priority research questions. The OCB Project Office plays multiple important support roles, such as hosting and co-sponsoring workshops, short courses, working groups, and synthesis activities on emerging research issues; engaging with relevant national and international science planning initiatives; and developing education and outreach activities and products with the goal of promoting ocean carbon science to broader audiences. Current scientific focus areas of OCB include ocean observations (shipboard, autonomous, satellite, etc.); changing ocean chemistry (acidification, expanding low-oxygen conditions, etc.); ocean carbon uptake and storage; estuarine and coastal carbon cycling; biological pump and associated biological and biogeochemical processes and carbon fluxes; and marine ecosystem response to environmental and evolutionary changes, including physiological and molecular-level responses of individual organisms, as well as shifts in community structure and function. OCB is a bottom-up organization that responds to the continually evolving priorities and needs of its network and engages marine scientists at all career stages. The scientific leadership of OCB includes a scientific steering committee and subcommittees on ocean time-series, ocean acidification, and ocean fertilization. This presentation will highlight recent OCB activities and products of interest to the ocean science community.

Phytoplankton community structure at the juncture of the Agulhas return front and subtropical front in the Indian Ocean sector of Southern Ocean: Bottom-up and top-down control

Digital Repository Service at National Institute of Oceanography (India)

Naik, R.K.; George, J.V.; Soares, M.A.; Devi, A.; Anilkumar, N.; Roy, R.; Bhaskar, P.V.; Murukesh, N.; Achuthankutty, C.T.

The juncture of the Agulhas Return Front (ARF) and Subtropical Front (STF) in the Indian Ocean sector of Southern Ocean (SO) is characterized by high mesoscale turbulence, which results in sporadic, short lived phytoplankton proliferation The biota...

The aluminum anode in deep ocean environments

International Nuclear Information System (INIS)

Schreiber, C.F.

1989-01-01

Results of field and mini-plant studies are presented for A1 + 0.045% Hg + 0.1% Si + 0.45% Zn* and A1 + 0.015% In + 0.1% Si + 3% Zn** anodes in varying depths of natural seawater. Current capacity and potential information are presented. In addition to information on anode current capacity and potential, polarization curves were obtained on both aluminum alloys using potentiostatic techniques at a simulated ocean depth of 1090 ft. (332 m). These data were compared with similarly run experiments at ocean surface pressures. As a basis of comparison, zinc anodes (U.S. Mil-A-18001H) were included as a companion alloy. Information gained on zinc is sufficient to accurately represent the behavior of this alloy. Results conclude that conditions of high pressure (and low temperature) associated with the alloys under test did not alter their galvanic behavior from that noted at the ocean surface

Near Surface Ocean Experimental Technology Workshop Proceedings Held at Naval Ocean Research and Development Activity, NSTL Station, Mississippi on 6-8 November 1979,

Science.gov (United States)

1980-02-01

have been made by Sippican Corporation of Marion, Massachusetts. An example of our use was a survey in ,June 1978 around the 2 km high Caryn Seamount ...Sound. McGraw-Hill, New York, 384 pp. 8. Wishner, K. F., 1979, The biomass and ecology of the deep-sea benthopelagic (near-bottom) zooplankton, Ph.D...COMPONENT PART NOTICE THIS PAPER IS A COMPONENT PART OF THE FOLLOWING COMPILATION REPORT: (TITLE): Near Sarface Ocean Experimental Technology Workshop

Low-Temperature Alteration of the Seafloor: Impacts on Ocean Chemistry

Science.gov (United States)

Coogan, Laurence A.; Gillis, Kathryn M.

2018-05-01

Over 50% of Earth is covered by oceanic crust, the uppermost portion of which is a high-permeability layer of basaltic lavas through which seawater continuously circulates. Fluid flow is driven by heat lost from the oceanic lithosphere; the global fluid flux is dependent on plate creation rates and the thickness and distribution of overlying sediment, which acts as a low-permeability layer impeding seawater access to the crust. Fluid-rock reactions in the crust, and global chemical fluxes, depend on the average temperature in the aquifer, the fluid flux, and the composition of seawater. The average temperature in the aquifer depends largely on bottom water temperature and, to a lesser extent, on the average seafloor sediment thickness. Feedbacks between off-axis chemical fluxes and their controls may play an important role in modulating ocean chemistry and planetary climate on long timescales, but more work is needed to quantify these feedbacks.

Three dimensional investigation of oceanic active faults. A demonstration survey

Energy Technology Data Exchange (ETDEWEB)

Nakao, Seizo; Kishimoto, Kiyoyuki; Ikehara, Ken; Kuramoto, Shinichi; Sato, Mikio [Geological Survey of Japan, Kawasaki, Kanagawa (Japan)

1999-02-01

Oceanic active faults were classified into trench and in-land types, and a bottom survey was conducted on an aim of estimation on activity of a trench type oceanic active faults. For both sides of an oceanic active fault found at high precision sonic investigations in 1996 fiscal year, it was attempted from a record remained in sediments how a fault changed by a fault motion and how long time it acted. And, construction of a data base for evaluation of the active faults was promoted by generalizing the issued publications. As a result, it was found that a method to estimate a fault activity using turbidite in success at shallow sea could not easily be received at deep sea, and that as sedimentation method in deep sea changed largely by topography and so on, the turbidite did not play always a rule of key layer. (G.K.)

Analysis of Peach Bottom turbine trip tests

International Nuclear Information System (INIS)

Cheng, H.S.; Lu, M.S.; Hsu, C.J.; Shier, W.G.; Diamond, D.J.; Levine, M.M.; Odar, F.

1979-01-01

Current interest in the analysis of turbine trip transients has been generated by the recent tests performed at the Peach Bottom (Unit 2) reactor. Three tests, simulating turbine trip transients, were performed at different initial power and coolant flow conditions. The data from these tests provide considerable information to aid qualification of computer codes that are currently used in BWR design analysis. The results are presented of an analysis of a turbine trip transient using the RELAP-3B and the BNL-TWIGL computer codes. Specific results are provided comparing the calculated reactor power and system pressures with the test data. Excellent agreement for all three test transients is evident from the comparisons

The Influence of Ice-Ocean Interactions on Europa's Overturning Circulation

Science.gov (United States)

Zhu, P.; Manucharyan, G. E.; Thompson, A. F.; Goodman, J. C.; Vance, S.

2016-12-01

Jupiter's moon Europa appears to have a global liquid ocean, which is located beneath an ice shell that covers the moon's entire surface. Linking ocean dynamics and ice-ocean interactions is crucial to understanding observed surface features on Europa as well as other satellite measurements. Ocean properties and circulation may also provide clues as to whether the moon has the potential to support extraterrestrial life through chemical transport governed by ice-ocean interactions. Previous studies have identified a Hadley cell-like overturning circulation extending from the equator to mid latitudes. However, these model simulations do not consider ice-ocean interactions. In this study, our goal is to investigate how the ocean circulation may be affected by ice. We study two ice-related processes by building idealized models. One process is horizontal convection driven by an equator-to-pole buoyancy difference due to latitudinal ice transport at the ocean surface, which is found to be much weaker than the convective overturning circulation. The second process we consider is the freshwater layer formed by ice melting at the equator. A strong buoyancy contrast between the freshwater layer and the underlying water suppresses convection and turbulent mixing, which may modify the surface heat flux from the ocean to the bottom of the ice. We find that the salinity of the ocean below the freshwater layer tends to be homogeneous both vertically and horizontally with the presence of an overturning circulation. Critical values of circulation strength constrain the freshwater layer depth, and this relationship is sensitive to the average salinity of the ocean. Further coupling of temperature and salinity of the ice and the ocean that includes mutual influences between the surface heat flux and the freshwater layer may provide additional insights into the ice-ocean feedback, and its influence on the latitudinal difference of heat transport.

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

International Nuclear Information System (INIS)

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

2017-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-01-15

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

Temperature profile and pressure data from CTD casts from NOAA Ship RONALD H. BROWN and NOAA Ship KA'IMIMOANA in the TOGA area of Pacific Ocean from 1997-08-05 to 1999-06-28 (NODC Accession 9900141)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using CTD casts in the TOGA area of Pacific Ocean from NOAA Ship RONALD H. BROWN and NOAA Ship KA'IMIMOANA from...

Transport processes near coastal ocean outfalls

Science.gov (United States)

Noble, M.A.; Sherwood, C.R.; Lee, Hooi-Ling; Xu, Jie; Dartnell, P.; Robertson, G.; Martini, M.

2001-01-01

The central Southern California Bight is an urbanized coastal ocean where complex topography and largescale atmospheric and oceanographic forcing has led to numerous sediment-distribution patterns. Two large embayments, Santa Monica and San Pedro Bays, are connected by the short, very narrow shelf off the Palos Verdes peninsula. Ocean-sewage outfalls are located in the middle of Santa Monica Bay, on the Palos Verdes shelf and at the southeastern edge of San Pedro Bay. In 1992, the US Geological Survey, together with allied agencies, began a series of programs to determine the dominant processes that transport sediment and associated pollutants near the three ocean outfalls. As part of these programs, arrays of instrumented moorings that monitor currents, waves, water clarity, water density and collect resuspended materials were deployed on the continental shelf and slope information was also collected on the sediment and contaminant distributions in the region. The data and models developed for the Palos Verdes shelf suggest that the large reservoir of DDT/DDE in the coastal ocean sediments will continue to be exhumed and transported along the shelf for a long time. On the Santa Monica shelf, very large internal waves, or bores, are generated at the shelf break. The near-bottom currents associated with these waves sweep sediments and the associated contaminants from the shelf onto the continental slope. A new program underway on the San Pedro shelf will determine if water and contaminants from a nearby ocean outfall are transported to the local beaches by coastal ocean processes. The large variety of processes found that transport sediments and contaminants in this small region of the continental margin suggest that in regions with complex topography, local processes change markedly over small spatial scales. One cannot necessarily infer that the dominant transport processes will be similar even in adjacent regions.

Influence of submarine morphology on bottom water flow across the western Ross Sea continental margin

Science.gov (United States)

Davey, F.J.; Jacobs, S.S.

2007-01-01

Multibeam sonar bathymetry documents a lack of significant channels crossing outer continental shelf and slope of the western Ross Sea. This indicates that movement of bottom water across the shelf break into the deep ocean in this area is mainly by laminar or sheet flow. Subtle, ~20 m deep and up to 1000 m wide channels extend down the continental slope, into tributary drainage patterns on the upper rise, and then major erosional submarine canyons. These down-slope channels may have been formed by episodic pulses of rapid down slope water flow, some recorded on bottom current meters, or by sub-ice melt water erosion from an icesheet grounded at the margin. Narrow, mostly linear furrows on the continental shelf thought to be caused by iceberg scouring are randomly oriented, have widths generally less than 400 m and depths less than 30m, and extend to water depths in excess of 600 m.

Measurements of bottom cores collected in the Gulf of Mexico in support of MMS 'Deepwater Program: Northern Gulf of Mexico Continental Slope Habitat and Benthic Ecology', 2000 - 2001 (NCEI Accession 0002382)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This data collection includes characteristics of bottom cores collected in support of this research program to gain better knowledge of the benthic communities of...

Relocation of earthquakes at southwestern Indian Ocean Ridge and its tectonic significance

Science.gov (United States)

Luo, W.; Zhao, M.; Haridhi, H.; Lee, C. S.; Qiu, X.; Zhang, J.

2015-12-01

The southwest Indian Ridge (SWIR) is a typical ultra-slow spreading ridge (Dick et al., 2003) and further plate boundary where the earthquakes often occurred. Due to the lack of the seismic stations in SWIR, positioning of earthquakes and micro-earthquakes is not accurate. The Ocean Bottom Seismometers (OBS) seismic experiment was carried out for the first time in the SWIR 49 ° 39 'E from Jan. to March, 2010 (Zhao et al., 2013). These deployed OBS also recorded the earthquakes' waveforms during the experiment. Two earthquakes occurred respectively in Feb. 7 and Feb. 9, 2010 with the same magnitude of 4.4 mb. These two earthquakes were relocated using the software HYPOSAT based on the spectrum analysis and band-pass (3-5 Hz) filtering and picking up the travel-times of Pn and Sn. Results of hypocentral determinations show that there location error is decreased significantly by joined OBS's recording data. This study do not only provide the experiences for the next step deploying long-term wide-band OBSs, but also deepen understanding of the structure of SWIR and clarify the nature of plate tectonic motivation. This research was granted by the Natural Science Foundation of China (41176053, 91028002, 91428204). Keywords: southwest Indian Ridge (SWIR), relocation of earthquakes, Ocean Bottom Seismometers (OBS), HYPOSAT References:[1] Dick, H. J. B., Lin J., Schouten H. 2003. An ultraslow-spreading class of ocean ridge. Nature, 426(6965): 405-412. [2] Zhao M. H., et al. 2013. Three-dimensional seismic structure of the Dragon Flag oceanic core complex at the ultraslow spreading Southwest Indian Ridge (49°39' E). Geochemistry Geophysics Geosystems, 14(10): 4544-4563.

Socio-economic impacts of ocean acidification in the Mediterranean Sea

NARCIS (Netherlands)

Rodrigues, L.; van den Bergh, J.C.J.M.; Ghermandi, A.

2013-01-01

Ocean acidification appears as another environmental pressure associated with anthropogenic emissions of carbon dioxide. This paper aims to assess the likely magnitude of this phenomenon in the Mediterranean region. This involves translating expected changes in ocean chemistry into impacts, first on

Mass-induced sea level variations in the Red Sea from steric-corrected altimetry, GRACE, in-situ bottom pressure records, and hydrographic observations

Science.gov (United States)

Feng, Wei; Lemoine, Jean-Michel; Zhong, Min; Xu, Houze

2014-05-01

An annual amplitude of ~18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from steric-corrected altimetry and the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 to 2011, which dominates the mean sea level in the region. Seawater mass variations here generally reach maximum in late January/early February. The steric component of SLV calculated from oceanographic temperature and salinity data is relatively small and peaks about seven months later than mass variations. The phase difference between the steric SLV and the mass-induced SLV indicates that when the Red Sea gains the mass from inflow water in winter, the steric SLV fall, and vice versa in summer. In-situ bottom pressure records in the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. Furthermore, we compare the horizontal water mass flux in the Red Sea from steric-corrected altimetry and GRACE with that estimated from hydrographic observations.

Tropical teleconnections via the ocean and atmosphere induced by Southern Ocean deep convective events

Science.gov (United States)

Marinov, I.; Cabre, A.; Gunn, A.; Gnanadesikan, A.

2016-12-01

The current generation (CMIP5) of Earth System Models (ESMs) shows a huge variability in their ability to represent Southern Ocean (SO) deep-ocean convection and Antarctic Bottom Water, with a preference for open-sea convection in the Weddell and Ross gyres. A long control simulation in a coarse 3o resolution ESM (the GFDL CM2Mc model) shows a highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process also happens naturally, with different frequencies and durations of convection across most CMIP5 models under preindustrial forcing (deLavergne et al, 2014). Here we assess the impact of SO deep convection and resulting sea surface temperature (SST) anomalies on the tropical atmosphere and ocean via teleconnections, with a focus on interannual to multi-decadal timescales. We combine analysis of our low-resolution coupled model with inter-model analysis across historical CMIP5 simulations. SST cooling south of 60S during non-convective decades triggers a stronger, northward shifted SH Hadley cell, which results in intensified northward cross-equatorial moist heat transport and a poleward shift in the ITCZ. Resulting correlations between the cross-equatorial atmospheric heat transport and ITCZ location are in good agreement with recent theories (e.g. Frierson et al. 2013; Donohoe et al. 2014). Lagged correlations between a SO convective index and cross-equatorial heat transports (in the atmosphere and ocean), as well as various tropical (and ENSO) climate indices are analyzed. In the ocean realm, we find that non-convective decades result in weaker AABW formation and weaker ACC but stronger Antarctic Intermediate Water (AAIW) formation, likely as a result of stronger SO westerlies (more positive SAM). The signals of AABW and AAIW are seen in the tropics on short timescales of years to decades in the temperature, heat storage and heat transport anomalies and also in deep and intermediate ocean oxygen. Most

Magma ocean formation due to giant impacts

Science.gov (United States)

Tonks, W. B.; Melosh, H. J.

1993-01-01

The thermal effects of giant impacts are studied by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, the effects of the planet's initial temperature on the generated melt volume are examined. The shock pressure required to completely melt the material is determined using the Hugoniot curve plotted in pressure-entropy space. Once the melting pressure is known, an impact melting model is used to estimate the radial distance melting occurred from the impact site. The melt region's geometry then determines the associated melt volume. The model is also used to estimate the partial melt volume. Magma ocean depths resulting from both excavated and retained melt are calculated, and the melt fraction not excavated during the formation of the crater is estimated. The fraction of a planet melted by the initial shock wave is also estimated using the model.

Open oceanic productivity changes at mid-latitudes during interglacials and its relation to the Atlantic Meridional Overturning Circulation

Science.gov (United States)

Nave, Silvia; Lebreiro, S.; Kissel, C.; Guihou, A.; Figueiredo, M. O.; Silva, T. P.; Michel, E.; Cortijo, E.; Labeyrie, L.; Voelker, A.

2010-05-01

Variations in the interactions between marine ecosystems, thermohaline circulation, external forcing and atmospheric greenhouse gases concentrations are not yet fully represented in detailed models of the glacial-interglacial transitions. Most of the research on past productivity changes has been focused so far on high-productivity areas such as upwelling areas (i.e. equatorial or coastal upwelling areas) even though those regions appraise only a little part of the ocean. Accordingly, the importance of oceanic productivity changes over glacial/interglacial cycles should be better known, as it may also play an important role on the loss of photosynthetically generated carbon as a central mechanism in the global carbon cycle. Its understanding will help quantifying the parameters needed to run comprehensive climate models, and subsequently help to better predict climate change for the near future. A high-resolution study of oceanic productivity, bottom water flow speed, surface and deep-water mass, bottom water ventilation, and terrestrial input changes during two interglacials (Holocene and Marine Isotope Stage [MIS] 5), at an open ocean site approximately 300 km west off Portugal [IMAGES core MD01-2446: 39°03'N, 12°37'W, 3547 m water depth] was conducted within the AMOCINT project (ESF-EUROCORES programme, 06-EuroMARC-FP-008). Even though siliceous productivity is expectedly low for oceanic regions, it shows a robust and consistent pattern with increased values during cold phases of MIS 5, and during the glacial stages 4 and 6 suggesting higher nutrient availability, during these periods. The same pattern is observed for MIS2 and the last deglaciation. The opal record is fully supported by the organic carbon content and to the estimated productivity using foraminifera based FA20 and SIMMAX.28 transfer functions for a near location. The benthic δ13C record suggests less North Atlantic Deep Water (NADW) coincident with periods of higher productivity. The grain

Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

Directory of Open Access Journals (Sweden)

Rohitha Weerasinghe

2017-01-01

Full Text Available Heat recovery bottoming cycles for internal combustion engines have opened new avenues for research into small steam expanders (Stobart and Weerasinghe, 2006. Dependable data for small steam expanders will allow us to predict their suitability as bottoming cycle engines and the fuel economy achieved by using them as bottoming cycles. Present paper is based on results of experiments carried out on small scale Wankel and two-stroke reciprocating engines as air expanders and as steam expanders. A test facility developed at Sussex used for measurements is comprised of a torque, power and speed measurements, electronic actuation of valves, synchronized data acquisition of pressure, and temperatures of steam and inside of the engines for steam and internal combustion cycles. Results are presented for four engine modes, namely, reciprocating engine in uniflow steam expansion mode and air expansion mode and rotary Wankel engine in steam expansion mode and air expansion mode. The air tests will provide base data for friction and motoring effects whereas steam tests will tell how effective the engines will be in this mode. Results for power, torque, and p-V diagrams are compared to determine the change in performance from air expansion mode to steam expansion mode.

The role of the complete Coriolis force in cross-equatorial transport of the Antarctic Bottom Water

Science.gov (United States)

Stewart, Andrew; Dellar, Paul

2010-05-01

We investigate the equatorial crossing of the Antarctic Bottom Water using a shallow water model that includes the complete Coriolis force. Most theoretical models of the atmosphere and ocean neglect the component of the Coriolis force associated with the horizontal component of the Earth's rotation vector, the so-called traditional approximation. This approximation is typically justified on the basis that ratio of the ocean depth to the Rossby radius of deformation is negligibly small, H-Rd ≪ 1. However, the steep topography and weak stratification in the abyssal ocean magnify the role of the non-traditional component of the Coriolis force. This is most pronounced in equatorial regions, where the traditional component of the Coriolis force is weakest and the non-traditional component is strongest. The inclusion of the complete Coriolis force gives rise to a range of very long sub-inertial waves, whose frequencies lie below the inertial frequency, in the two-layer shallow water equations. These waves have a dramatically different structure to their traditional counterparts, particularly when the stratification is weak. We focus on the flow of the Antarctic Bottom Water from the Brazil Basin in the western South Atlantic to the Guiana Basin in the western North Atlantic. In this region, the current traverses a deep channel directed westwards and very slightly northwards across the equator. Previous attempts to model this flow have struggled to explain why the cross-equatorial transport is so high, with around 2.0-2.2 Sv exiting at the northern end of the channel. We present analytical and numerical solutions of the non-traditional shallow water equations for the cross-equatorial flow of the Antarctic Bottom Water. We obtain analytical solutions by considering the steady-state flow of a single layer of shallow water through a northwesterly channel with a simple geometry. We assume zero potential vorticity, as it may be shown that fluid whose potential vorticity q

Interannual variability of surface and bottom sediment transport on the Laptev Sea shelf during summer

Directory of Open Access Journals (Sweden)

C. Wegner

2013-02-01

Full Text Available Sediment transport dynamics were studied during ice-free conditions under different atmospheric circulation regimes on the Laptev Sea shelf (Siberian Arctic. To study the interannual variability of suspended particulate matter (SPM dynamics and their coupling with the variability in surface river water distribution on the Laptev Sea shelf, detailed oceanographic, optical (turbidity and Ocean Color satellite data, and hydrochemical (nutrients, SPM, stable oxygen isotopes process studies were carried out continuously during the summers of 2007 and 2008. Thus, for the first time SPM and nutrient variations on the Laptev Sea shelf under different atmospheric forcing and the implications for the turbidity and transparency of the water column can be presented.

The data indicate a clear link between different surface distributions of riverine waters and the SPM transport dynamics within the entire water column. The summer of 2007 was dominated by shoreward winds and an eastward transport of riverine surface waters. The surface SPM concentration on the southeastern inner shelf was elevated, which led to decreased transmissivity and increased light absorption. Surface SPM concentrations in the central and northern Laptev Sea were comparatively low. However, the SPM transport and concentration within the bottom nepheloid layer increased considerably on the entire eastern shelf. The summer of 2008 was dominated by offshore winds and northward transport of the river plume. The surface SPM transport was enhanced and extended onto the mid-shelf, whereas the bottom SPM transport and concentration was diminished. This study suggests that the SPM concentration and transport, in both the surface and bottom nepheloid layers, are associated with the distribution of riverine surface waters which are linked to the atmospheric circulation patterns over the Laptev Sea and the adjacent Arctic Ocean during the open water season. A continuing trend toward

Root-Contact/Pressure-Plate Assembly For Hydroponic System

Science.gov (United States)

Morris, Carlton E.; Loretan, Philip A.; Bonsi, Conrad K.; Hill, Walter A.

1994-01-01

Hydroponic system includes growth channels equipped with rootcontact/pressure-plate assemblies. Pump and associated plumbing circulate nutrient liquid from reservoir, along bottom of growth channels, and back to reservoir. Root-contact/pressure-plate assembly in each growth channel stimulates growth of roots by applying mild contact pressure. Flat plate and plate connectors, together constitute pressure plate, free to move upward to accommodate growth of roots. System used for growing sweetpotatoes and possibly other tuber and root crops.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

Science.gov (United States)

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

Isotopes as tracers of the oceanic circulation: Results from the World Ocean Circulation Experiment

International Nuclear Information System (INIS)

Schlosser, P.; Jenkins, W.J.; Key, R.; Lupton, J.

2002-01-01

global 14 C maps with respect to the bottom water circulation in the Pacific Ocean. Although most of the presented results are preliminary, they demonstrate the potential of the WOCE tracer data set for obtaining insights into the oceanic circulation that were not possible on the basis of pre-WOCE data sets. (author)

A highly oxidized atmosphere-ocean system and oceanic molybdenum drawdown during the Paleoproterozoic

Science.gov (United States)

Goto, K. T.; Ito, T.; Suzuki, K.; Anbar, A. D.; Gordon, G. W.; Kashiwabara, T.; Takaya, Y.; Shimoda, G.; Nozaki, T.; Kiyokawa, S.; Tetteh, G. M.; Nyame, F. K.

2014-12-01

Multiple lines of evidence suggest that the first major oxidation of the atmosphere-ocean system occurred during the Paleoproterozoic. However, the course of this redox transition remains elusive. A number of large Mn deposits are distributed in Paleoproterozoic sedimentary successions. As Mn is a redox-sensitive element characterized by high redox potential, knowledge of the Mn cycle in Paleoproterozoic seawater may provide insight into redox evolution during this period. Here, we investigate the Mn cycle in Paleoproterozoic seawater based on the Re-Os and Mo isotope compositions, and the abundance of major and trace elements, in Mn-rich sedimentary rocks from the Nsuta deposit of the Birimian Supergroup, Ghana. The Mn ore is composed mainly of rhodochrosite and is distributed at the boundaries between sedimentary rocks and tholeiitic volcanic rocks. The Re-Os isochron age (2217 ± 100 Ma) we obtained was consistent with U-Pb zircon ages of the volcanic rocks. The manganophile elements, except for Mo, show no enrichment, which is similar to modern hydrothermal Mn oxides. The PAAS-normalized REE compositions show positive Ce anomaly, indicative of Ce enrichment due to the oxidation of Ce(III) by Mn(IV). These findings suggest that Mn ore formed from primary precipitation of Mn oxides from hydrothermal fluids as they were mixed with bottom seawater at ~2.2 Ga. Thus, the bottom seawater would have been sufficiently oxygenated for the precipitation of Mn oxides at ~2.2 Ga. The Nsuta ore samples exhibit slight Mo enrichment, but Mo/Mn ratios are orders of magnitude lower than those in modern hydrothermal Mn oxides. We also found that the Mo isotopes in the Nsuta ore are ~0.7‰ heavier than those in modern hydrothermal and hydrogenous Mn oxides. As Mo in hydrothermal Mn oxides is sourced primarily from seawater (Goto et al., in prep), these results may reflect smaller oceanic Mo inventory and heavier seawater Mo isotope composition at 2.2 Ga than those of present

Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

Science.gov (United States)

Goldner, A; Herold, N; Huber, M

2014-07-31

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

Physical oceanographic characteristics influencing the dispersion of dissolved tracers released at the sea floor in selected deep ocean study areas

International Nuclear Information System (INIS)

Kupferman, S.L.; Moore, D.E.

1981-02-01

Scenarios which follow the development in space and time of the concentration field of a dissolved tracer released at the sea floor are presented for a Pacific and two Atlantic study areas. The scenarios are closely tied to available data by means of simple analytical models and proceed in stages from short time and space scales in the immediate vicinity of a release point to those scales characteristic of ocean basins. The concepts of internal mixing time and residence time in the benthic mixed layer, useful for developing an intuitive feeling for the behavior of a tracer in this feature, are introduced and discussed. We also introduce the concept of domain of occupation, which is useful in drawing distinctions between mixing and stirring in the ocean. From this study it is apparent that reliable estimation of mixing will require careful consideration of the dynamics of the eddy fields in the ocean. Another area in which more information is urgently needed is in the relation of deep isopycnal structure and bottom topography to local near-bottom circulation

Oxygen (average seabed consumption) data collected using pressure gauge from the Drake Passage in part of the International Decade of Ocean Exploration / International Southern Ocean Studies / First Dynamic Response and Kinematics Experiment in the Drake Passage from 1976-02-08 to 1982-03-19 (NODC Accession 9000027)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Oxygen (average seabed consumption) data were collected using pressure gauge from the Drake Passage from February 8, 1976 to March 19, 1982. Data were submitted by...

Cavitation nuclei in water exposed to transient pressures

DEFF Research Database (Denmark)

Andersen, Anders Peter; Mørch, Knud Aage

2015-01-01

A model of skin-stabilized interfacial cavitation nuclei and their response to tensile and compressive stressing is presented. The model is evaluated in relation to experimental tensile strength results for water at rest at the bottom of an open water-filled container at atmospheric pressure...... and room temperature. These results are obtained by recording the initial growth of cavities generated by a short tensile pulse applied to the bottom of the container. It is found that the cavitation nuclei shift their tensile strength depending on their pressure history. Static pressurization...... for an extended period of time prior to testing is known to increase the tensile strength of water, but little information is available on how it is affected by compression pulses of short duration. This is addressed by imposing compression pulses of approximately 1 ms duration and a peak intensity of a few bar...

Microwave Atmospheric-Pressure Sensor

Science.gov (United States)

Flower, D. A.; Peckham, G. E.; Bradford, W. J.

1986-01-01

Report describes tests of microwave pressure sounder (MPS) for use in satellite measurements of atmospheric pressure. MPS is multifrequency radar operating between 25 and 80 GHz. Determines signal absorption over vertical path through atmosphere by measuring strength of echoes from ocean surface. MPS operates with cloud cover, and suitable for use on current meteorological satellites.

Study on collapse behavior of a square plate subjected to water pressure; Suiatsu wo ukeru kukeiban no atsukai kyodo ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Yao, T; Fujikubo, M; Mizutani, K [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

1996-04-10

Bottom plates of a hull are subjected to laterally distributing force due to in-plane compression force and water pressure in the ship`s length direction as a result of longitudinal bending in a hogging condition. Because buckling collapse of the hull bottom plates leads directly to longitudinal bending collapse of the hull bottom cross section, the hull bottom plates must have sufficient strength. The present study performs a static elastic large deflection analysis and an elasto-plastic large deflection analysis. It elucidates buckling collapse behavior of a square plate subjected to water pressure and in-plane compression load, and considers limits in application of conventional approximation analysis methods. In the case of a water pressure action, deflection components growing in excess of the buckling load do not necessarily correspond to buckling modes of the case where no water pressure is acting upon. Conventional approximation analysis methods may not be able often to pursue actual buckling phenomena. According the result of an analysis on hull bottom panels of an actual ship, the ultimate strength decreases when the water pressure is large. Compression force in the lateral direction as a result of water pressure acting on ship`s sides affected very little the ultimate strength. 3 refs., 7 figs.

Development of a non-conservative radionuclides dispersion model in the ocean and its application to surface cesium-137 dispersion in the Irish Sea

International Nuclear Information System (INIS)

Kobayashi, Takuya; Otosaka, Shigeyoshi; Togawa, Orihiko; Hayashi, Keisuke